TWI788998B - Target expansion rate control in an extreme ultraviolet light source - Google Patents

Target expansion rate control in an extreme ultraviolet light source Download PDF

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TWI788998B
TWI788998B TW110133390A TW110133390A TWI788998B TW I788998 B TWI788998 B TW I788998B TW 110133390 A TW110133390 A TW 110133390A TW 110133390 A TW110133390 A TW 110133390A TW I788998 B TWI788998 B TW I788998B
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target
radiation beam
target material
modified
radiation
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TW110133390A
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TW202210958A (en
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羅伯特 傑 拉法斯
丹尼爾 傑森 萊格斯
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荷蘭商Ａｓｍｌ荷蘭公司
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Priority claimed from US14/824,147 external-priority patent/US9713240B2/en
Priority claimed from US14/824,141 external-priority patent/US9820368B2/en
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05G—X-RAY TECHNIQUE
    • H05G2/00—Apparatus or processes specially adapted for producing X-rays, not involving X-ray tubes, e.g. involving generation of a plasma
    • H05G2/001—X-ray radiation generated from plasma
    • H05G2/003—X-ray radiation generated from plasma being produced from a liquid or gas
    • H05G2/005—X-ray radiation generated from plasma being produced from a liquid or gas containing a metal as principal radiation generating component
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05G—X-RAY TECHNIQUE
    • H05G2/00—Apparatus or processes specially adapted for producing X-rays, not involving X-ray tubes, e.g. involving generation of a plasma
    • H05G2/001—X-ray radiation generated from plasma
    • H05G2/008—X-ray radiation generated from plasma involving a beam of energy, e.g. laser or electron beam in the process of exciting the plasma

Abstract

A method includes providing a target material that comprises a component that emits extreme ultraviolet (EUV) light when converted to plasma; directing a first beam of radiation toward the target material to deliver energy to the target material to modify a geometric distribution of the target material to form a modified target; directing a second beam of radiation toward the modified target, the second beam of radiation converting at least part of the modified target to plasma that emits EUV light; measuring one or more characteristics associated with one or more of the target material and the modified target relative to the first beam of radiation; and controlling an amount of radiant exposure delivered to the target material from the first beam of radiation based on the one or more measured characteristics to within a predetermined range of energies.

Description

極紫外線光源中之目標擴張率控制Target dilation rate control in EUV light sources

所揭示主題係關於控制用於雷射產生電漿極紫外線光源之目標材料之擴張率。The disclosed subject matter relates to controlling the dilation rate of a target material for a laser-generated plasma EUV light source.

極紫外線(EUV)光(例如，具有為大約50奈米或更小之波長之電磁輻射(有時亦被稱作軟x射線)且包括處於大約13奈米之波長之光)可用於光微影程序中以在基板(例如，矽晶圓)中產生極小特徵。 用以產生EUV光之方法包括但未必限於運用在EUV範圍內之發射譜線而將具有一元素(例如，氙、鋰或錫)之材料轉換成電漿狀態。在一種此類方法(常常被稱為雷射產生電漿「LPP」)中，可藉由運用可被稱作驅動雷射之經放大光束來輻照目標材料(例如，呈材料之小滴、板、帶、串流或叢集之形式)而產生所需電漿。對於此程序，通常在例如真空腔室之密封容器中產生電漿，且使用各種類型之度量衡設備來監視電漿。Extreme ultraviolet (EUV) light (e.g., electromagnetic radiation having a wavelength of about 50 nanometers or less (sometimes also referred to as soft x-rays) and including light at a wavelength of about 13 nanometers) can be used for optical microscopy. In the imaging process to create extremely small features in the substrate (eg, silicon wafer). Methods for generating EUV light include, but are not necessarily limited to, converting materials with an element (eg, xenon, lithium, or tin) into a plasmonic state using emission lines in the EUV range. In one such method, often referred to as laser-produced plasma (LPP), target material (e.g., in the form of droplets, plate, strip, series or cluster) to generate the desired plasma. For this process, the plasma is typically generated in a sealed container, such as a vacuum chamber, and various types of metrology equipment are used to monitor the plasma.

在一些通用態樣中，一種方法包括：提供一目標材料，該目標材料包含當轉換成電漿時發射極紫外線(EUV)光之一組份；將一第一輻射光束導引朝向該目標材料以將能量遞送至該目標材料，以修改該目標材料之一幾何分佈以形成一經修改目標；將一第二輻射光束導引朝向該經修改目標，該第二輻射光束將該經修改目標之至少部分轉換成發射EUV光之電漿；量測相對於該第一輻射光束的與該目標材料及該經修改目標中之一或多者相關聯的一或多個特性；及基於該一或多個經量測特性將自該第一輻射光束遞送至該目標材料之放射曝光量(radiant exposure)之一量控制在一預定能量範圍內。 實施可包括以下特徵中之一或多者。舉例而言，可藉由量測該第一輻射光束之一能量來量測與該目標材料及該經修改目標中之一或多者相關聯的該一或多個特性。可藉由量測自該目標材料之一光學反射表面反射的該第一輻射光束之該能量來量測該第一輻射光束之該能量。可藉由量測導引朝向該目標材料之該第一輻射光束之一能量來量測該第一輻射光束之該能量。可藉由量測橫越垂直於該第一輻射光束之一傳播方向的一方向之一空間積分能量來量測該第一輻射光束之該能量。 可藉由使該目標材料與該第一輻射光束之涵蓋其共焦參數之一區域重疊而將該第一輻射光束導引朝向該目標材料。該共焦參數可大於1.5毫米。 可藉由量測該目標材料相對於一目標位置之一位置來量測與該目標材料及該經修改目標中之一或多者相關聯的該一或多個特性。該目標位置可與該第一輻射光束之一光束腰重合。可沿著一第一光束軸線來導引該第一輻射光束，且可沿著平行於該第一光束軸線之一方向量測該目標材料之該位置。可量測相對於收集該經發射EUV光之一收集器器件之一主焦點之該目標位置。可藉由沿著兩個或多於兩個非平行方向量測該目標材料之該位置來量測該目標材料之該位置。 可藉由在該第二輻射光束將該經修改目標之至少部分轉換成電漿之前偵測該經修改目標之一大小來量測與該目標材料及該經修改目標中之一或多者相關聯的該一或多個特性。可藉由估計該經修改目標之一擴張率來量測與該目標材料及該經修改目標中之一或多者相關聯的該一或多個特性。 可藉由控制該經修改目標之一擴張率而控制自該第一輻射光束遞送至該目標材料之該放射曝光量。 可藉由基於該一或多個經量測特性判定是否應調整該第一輻射光束之一特徵而控制自該第一輻射光束遞送至該目標材料之該放射曝光量。可在量測該一或多個特性時執行應調整該第一輻射光束之該特徵之該判定。 若判定出應調整該第一輻射光束之該特徵，則可調整該第一輻射光束之一脈衝之一能量含量及該第一輻射光束與該目標材料相互作用之一面積中的一或多者。可藉由調整該第一輻射光束之一脈寬；該第一輻射光束之該脈衝之一持續時間；及調整該第一輻射光束之該脈衝內之一平均功率來調整該第一輻射光束之該脈衝之該能量含量。 可藉由將第一輻射之脈衝導引朝向該目標材料而將該第一輻射光束導引朝向該目標材料；可藉由針對第一輻射之每一脈衝量測該一或多個特性來量測該一或多個特性；且可藉由針對第一輻射之每一脈衝判定是否應調整該特徵來判定是否應調整該第一輻射光束之該特徵。 可藉由在該經發射EUV光之至少一部分正曝光一晶圓時控制自該第一輻射光束遞送至該目標材料之該放射曝光量來控制自該第一輻射光束遞送至該目標材料的該放射曝光量。 可藉由提供目標材料之一小滴來提供該目標材料；且可藉由將該目標材料之該小滴變換成熔融金屬之一圓盤形體積來修改該目標材料之該幾何分佈。可根據一擴張率將該目標材料小滴變換成該圓盤形體積。 該方法亦可包括收集該經發射EUV光之至少一部分；及將該經收集EUV光導引朝向一晶圓以將該晶圓曝光至該EUV光。 可藉由針對導引朝向該目標材料之該第一輻射光束之每一脈衝量測至少一個特性來量測該一或多個特性。 可將該第一輻射光束導引朝向該目標材料使得該目標材料之一部分轉換成發射EUV光之電漿，且相比於自轉換自該經修改目標的該電漿發射之EUV光，自轉換自該目標材料的該電漿發射較少EUV光，且對該目標材料之主要作用為該修改該目標材料之該幾何分佈以形成該修改目標。 可藉由將該目標材料之一形狀變換成該經修改目標(其包括根據一擴張率沿著至少一個軸線來擴張該經修改目標)來修改該目標材料之該幾何分佈。可藉由控制該目標材料至該經修改目標之該擴張率而控制遞送至該目標材料之該放射曝光量。 可沿著不平行於該第二輻射光束之光軸的該至少一個軸線來擴張該經修改目標。 可藉由量測自該經修改目標反射之光子之一數目來量測與該目標材料及該經修改目標中之一或多者相關聯的該一或多個特性。可藉由依據多少光子撞擊該目標材料而量測自該經修改目標反射之光子之該數目來量測自該經修改目標反射的光子之該數目。 可藉由將第一輻射之脈衝導引朝向該目標材料而將該第一輻射光束導引朝向該目標材料；及可藉由將第二輻射之脈衝導引朝向該經修改目標而將該第二輻射光束導引朝向該經修改目標。 可藉由將該第一輻射光束導引通過一或多個光學放大器之一第一集合來導引該第一輻射光束；及可藉由將該第二輻射光束導引通過一或多個光學放大器之一第二集合來導引該第二輻射光束；其中該第一集合中之該等光學放大器中之至少一者處於該第二集合中。 可藉由量測導引朝向該目標材料之該第一輻射光束之一能量來量測與該目標材料及該經修改目標中之一或多者相關聯的該一或多個特性；且可藉由基於該經量測能量調整自該第一輻射光束導引至該目標材料之能量之一量而控制遞送至該目標材料的該放射曝光量。可藉由使該目標材料與該第一輻射光束之涵蓋其共焦參數之一區域重疊而將該第一輻射光束導引朝向該目標材料；且該共焦參數可小於或等於2毫米。 可藉由調整該第一輻射光束之一屬性而調整自該第一輻射光束導引至該目標材料之能量之該量。 可藉由調整如下各者中之一或多者而控制自該第一輻射光束遞送至該目標材料之該放射曝光量：恰好在該第一輻射光束將一能量遞送至該目標材料之前的該第一輻射光束之該能量；該目標材料之一位置；及與該第一輻射光束相互作用的該目標材料之一區。 可藉由將該第一輻射光束導引通過包括一或多個第一光學放大器的光學組件之一第一集合來導引該第一輻射光束；且可藉由將第二輻射光束導引通過包括一或多個第二光學放大器的光學組件之一第二集合來導引該第二輻射光束；其中光學組件之該第一集合與光學組件之該第二集合相異且與其分離。 在其他通用態樣中，一種裝置包括：一腔室，其界定接收一第一輻射光束之一初始目標部位及接收一第二輻射光束之一目標部位；一目標材料遞送系統，其經組態以將目標材料提供至該初始目標部位，該目標材料包含當轉換成電漿時發射極紫外線(EUV)光之一材料；一光學源，其經組態以產生該第一輻射光束及該第二輻射光束；及一光學操縱系統。該光學操縱系統經組態以：將該第一輻射光束導引朝向該初始目標部位以將能量遞送至該目標材料，以修改該目標材料之一幾何分佈以形成一經修改目標；及將該第二輻射光束導引朝向該目標部位，以將該經修改目標之至少部分轉換成發射EUV光之電漿。該裝置包括：一量測系統，其量測相對於該第一輻射光束的與該目標材料及該經修改目標中之一或多者相關聯的一或多個特性；及一控制系統，其連接至該目標材料遞送系統、該光學源、該光學操縱系統及該量測系統。該控制系統經組態以自該量測系統接收該一或多個經量測特性，且基於該一或多個經量測特性將一或多個信號發送至該光學源以控制自該第一輻射光束遞送至該目標材料的一放射曝光量。 實施可包括以下特徵中之一或多者。舉例而言，該光學操縱系統可包括一聚焦裝置，該聚焦裝置經組態以將該第一輻射光束聚焦於該初始目標部位處或附近，且將該第二輻射光束聚焦於該目標部位處或附近。 該裝置可包括一光束調整系統，其中該光束調整系統連接至該光學源及該控制系統，且該控制系統經組態以藉由將一或多個信號發送至該光束調整系統來將一或多個信號發送至該光學源以控制遞送至該目標材料之能量之量，該光束調整系統經組態以調整該光學源之一或多個特徵以藉此維持遞送至該目標材料之能量之該量。該光束調整系統可包括耦合至該第一輻射光束之一脈寬調整系統，該脈寬調整系統經組態以調整該第一輻射光束之脈衝之一脈寬。該脈寬調整系統可包括一電光調變器。 該光束調整系統可包括耦合至該第一輻射光束之一脈衝功率調整系統，該脈衝功率調整系統經組態以調整該第一輻射光束之脈衝內之一平均功率。該脈衝功率調整系統可包括一聲光調變器。 該光束調整系統可經組態以藉由將一或多個信號發送至該光束調整系統來將一或多個信號發送至該光學源以控制導引至該目標材料的能量之該量，該光束調整系統經組態以調整該光學源之一或多個特徵以藉此控制導引至該目標材料之能量之該量。 該光學源可包括該第一輻射光束傳遞通過的一或多個光學放大器之一第一集合；及該第二輻射光束傳遞通過的一或多個光學放大器之一第二集合，該第一集合中之該等光學放大器中之至少一者處於該第二集合中。該量測系統可在該第一輻射光束經導引朝向該初始目標部位時量測該第一輻射光束之一能量；且該控制系統可經組態以自該量測系統接收該經量測能量，且基於該經量測能量將一或多個信號發送至該光學源以控制自該第一輻射光束導引至該目標材料的能量之一量。 在一些通用態樣中，一種方法包括：提供一目標材料，該目標材料包括當轉換成電漿時發射極紫外線(EUV)光之一組份；將一第一輻射光束導引朝向該目標材料以將能量遞送至該目標材料，以修改該目標材料之一幾何分佈以形成一經修改目標；將一第二輻射光束導引朝向該經修改目標，該第二輻射光束將該經修改目標之至少部分轉換成發射EUV光之電漿；將自該第一輻射光束遞送至該目標材料之一放射曝光量控制在一預定放射曝光量範圍內；及藉由將自該第一輻射光束遞送至該目標材料之該放射曝光量控制在該預定放射曝光量範圍內而使自該電漿發射的該EUV光之一功率穩定。 實施可包括以下特徵中之一或多者。舉例而言，可藉由將該第一輻射光束導引通過包括一或多個第一光學放大器的光學組件之一第一集合來導引該第一輻射光束；及可藉由將該第二輻射光束導引通過包括一或多個第二光學放大器的光學組件之一第二集合來導引該第二輻射光束。光學組件之該第一集合可與光學組件之該第二集合相異且與其分離。 可藉由將該第一輻射光束導引通過一或多個光學放大器之一第一集合來導引該第一輻射光束；及可藉由將該第二輻射光束導引通過一或多個光學放大器之一第二集合來導引該第二輻射光束；其中該第一集合中之該等光學放大器中之至少一者處於該第二集合中。 可藉由提供目標材料之一小滴來提供該目標材料；且可藉由將目標材料之該小滴變換成具有一實質上平面表面的熔融金屬之一圓盤形體積來修改該目標材料之該幾何分佈。 可藉由提供目標材料之一小滴來提供該目標材料；且可藉由將目標材料之該小滴變換成熔融金屬粒子之一霧狀物形體積來修改該目標材料之該幾何分佈。 可根據一擴張率將該目標材料變換成該經修改目標。 可藉由如下操作來控制自該第一輻射光束遞送至該目標材料之該放射曝光量：量測相對於該第一輻射光束的與該目標材料及該經修改目標中之一或多者相關聯的一或多個特性；基於該一或多個經量測特性將自該第一輻射光束遞送至該目標材料之一放射曝光量維持在一預定放射曝光量範圍內。 可藉由估計該經修改目標之一擴張率而控制自該第一輻射光束遞送至該目標材料之該放射曝光量。可藉由維持該經修改目標之一擴張率而控制自該第一輻射光束遞送至該目標材料之該放射曝光量。 可藉由判定是否應調整該第一輻射光束之一特徵而控制自該第一輻射光束遞送至該目標材料之該放射曝光量。可藉由調整該第一輻射光束之每一脈衝之一能量含量，及該第一輻射光束與該目標材料相互作用之一面積中之一或多者而控制自該第一輻射光束遞送至該目標材料之該放射曝光量。可藉由調整如下各者中之一或多者來調整該第一輻射光束之每一脈衝之該能量含量：該第一輻射光束之每一脈衝之一寬度；該第一輻射光束之每一脈衝之一持續時間；及該第一輻射光束之每一脈衝之一功率。 可藉由在自該電漿發射之該EUV光之至少一部分正曝光一晶圓時使該EUV光之該功率穩定而使自該電漿發射的該EUV光之該功率穩定。 該方法亦可包括收集該經發射EUV光之至少一部分；及將該經收集EUV光導引朝向一晶圓以將該晶圓曝光至該EUV光。 可藉由將該目標材料之一形狀變換成該經修改目標(其包括根據一擴張率沿著至少一個軸線來擴張該經修改目標)來修改該目標材料之該幾何分佈。 可藉由調整該第一輻射光束之一屬性而控制自該第一輻射光束遞送至該目標材料之該放射曝光量。可藉由調整該第一輻射光束之一能量而調整該第一輻射光束之該屬性。 在其他通用態樣中，一種裝置包括：一腔室，其界定接收一第一輻射光束之一初始目標部位及接收一第二輻射光束之一目標部位；一目標材料遞送系統，其經組態以將目標材料提供至該初始目標部位，該目標材料包含當轉換成電漿時發射極紫外線(EUV)光之一材料；一光學源，其經組態以產生該第一輻射光束及該第二輻射光束；及一光學操縱系統。該光學操縱系統經組態以：將該第一輻射光束導引朝向該初始目標部位以將能量遞送至該目標材料，以修改該目標材料之一幾何分佈以形成一經修改目標；及將該第二輻射光束導引朝向該目標部位，以將該經修改目標之至少部分轉換成發射EUV光之電漿。該裝置包括一控制系統，該控制系統連接至該目標材料遞送系統、該光學源及該光學操縱系統，且經組態以將一或多個信號發送至該光學源以將自該第一輻射光束遞送至該目標材料的一放射曝光量控制在一預定放射曝光量範圍內，以藉此使自該電漿發射之EUV光之一功率穩定。 實施可包括以下特徵中之一或多者。舉例而言，該裝置亦可包括一量測系統，該量測系統量測相對於該第一輻射光束的與該目標材料及該經修改目標中之一或多者相關聯的一或多個特性，其中該控制系統連接至該量測系統。 該裝置亦可包括一光束調整系統，其中該光束調整系統連接至該光學源及該控制系統，且該控制系統經組態以藉由將一或多個信號發送至該光束調整系統來將一或多個信號發送至該光學源以控制遞送至該目標材料的該放射曝光量，該光束調整系統經組態以調整該光學源之一或多個特徵以藉此控制遞送至該目標材料的該放射曝光量。 In some general aspects, a method includes: providing a target material comprising a component that emits extreme ultraviolet (EUV) light when converted into a plasma; directing a first beam of radiation toward the target material to deliver energy to the target material to modify a geometric distribution of the target material to form a modified target; directing a second radiation beam towards the modified target, the second radiation beam will at least partially converting to a plasma that emits EUV light; measuring one or more properties associated with one or more of the target material and the modified target relative to the first radiation beam; and based on the one or more A measured characteristic controls an amount of radiant exposure delivered to the target material from the first radiation beam within a predetermined energy range. Implementations can include one or more of the following features. For example, the one or more properties associated with one or more of the target material and the modified target can be measured by measuring an energy of the first radiation beam. The energy of the first radiation beam can be measured by measuring the energy of the first radiation beam reflected from an optically reflective surface of the target material. The energy of the first radiation beam can be measured by measuring the energy of the first radiation beam directed towards the target material. The energy of the first radiation beam may be measured by measuring a spatially integrated energy across a direction perpendicular to a propagation direction of the first radiation beam. The first radiation beam may be directed towards the target material by overlapping the target material with a region of the first radiation beam encompassing its confocal parameters. The confocal parameter can be greater than 1.5 mm. The one or more properties associated with one or more of the target material and the modified target can be measured by measuring a position of the target material relative to a target location. The target location may coincide with a beam waist of the first radiation beam. The first radiation beam can be directed along a first beam axis, and the position of the target material can be measured along a direction parallel to the first beam axis. The target position can be measured relative to a main focus of a collector device that collects the emitted EUV light. The position of the target material can be measured by measuring the position of the target material along two or more non-parallel directions. Measurements related to one or more of the target material and the modified target may be measured by detecting a size of the modified target before the second radiation beam converts at least part of the modified target into plasma The one or more properties of the association. The one or more properties associated with one or more of the target material and the modified target can be measured by estimating a rate of expansion of the modified target. The radiation exposure delivered from the first radiation beam to the target material can be controlled by controlling a dilation rate of the modified target. The radiation exposure delivered from the first radiation beam to the target material can be controlled by determining whether a characteristic of the first radiation beam should be adjusted based on the one or more measured characteristics. The determination that the characteristic of the first radiation beam should be adjusted may be performed while measuring the one or more characteristics. If it is determined that the characteristic of the first radiation beam should be adjusted, one or more of an energy content of a pulse of the first radiation beam and an area where the first radiation beam interacts with the target material may be adjusted . The first radiation beam can be adjusted by adjusting the pulse width of the first radiation beam; the duration of the pulse of the first radiation beam; and adjusting an average power within the pulse of the first radiation beam. the energy content of the pulse. The first radiation beam can be directed towards the target material by directing a pulse of first radiation towards the target material; can be measured by measuring the one or more properties for each pulse of first radiation The one or more characteristics are measured; and whether the characteristic of the first radiation beam should be adjusted can be determined by determining whether the characteristic should be adjusted for each pulse of the first radiation. The radiation exposure delivered from the first radiation beam to the target material can be controlled by controlling the radiation exposure delivered from the first radiation beam to the target material while at least a portion of the emitted EUV light is exposing a wafer. radiation exposure. The target material can be provided by providing a droplet of the target material; and the geometric distribution of the target material can be modified by transforming the droplet of the target material into a disk-shaped volume of molten metal. The target material droplet can be transformed into the disk-shaped volume according to a dilation rate. The method can also include collecting at least a portion of the emitted EUV light; and directing the collected EUV light toward a wafer to expose the wafer to the EUV light. The one or more properties may be measured by measuring at least one property for each pulse of the first radiation beam directed towards the target material. The first beam of radiation may be directed toward the target material such that a portion of the target material is converted into a plasma emitting EUV light, and self-converted The plasmon from the target material emits less EUV light, and the main effect on the target material is to modify the geometric distribution of the target material to form the modified target. The geometric distribution of the target material can be modified by transforming a shape of the target material into the modified target, which includes expanding the modified target along at least one axis according to a dilation rate. The radiation exposure delivered to the target material can be controlled by controlling the dilation rate of the target material to the modified target. The modified target may be dilated along the at least one axis that is not parallel to the optical axis of the second radiation beam. The one or more properties associated with one or more of the target material and the modified target can be measured by measuring a number of photons reflected from the modified target. The number of photons reflected from the modified target can be measured by measuring the number of photons reflected from the modified target according to how many photons hit the target material. The first radiation beam can be directed towards the target material by directing pulses of first radiation towards the target material; and the second radiation beam can be directed towards the modified target by directing pulses of second radiation towards the modified target. Two radiation beams are directed towards the modified target. The first radiation beam may be directed by directing the first radiation beam through a first set of one or more optical amplifiers; and the second radiation beam may be directed by directing the second radiation beam through one or more optical amplifiers A second set of amplifiers is used to direct the second radiation beam; wherein at least one of the optical amplifiers in the first set is in the second set. the one or more properties associated with one or more of the target material and the modified target may be measured by measuring an energy of the first radiation beam directed towards the target material; and may The radiation exposure delivered to the target material is controlled by adjusting an amount of energy directed from the first radiation beam to the target material based on the measured energy. The first radiation beam may be directed towards the target material by overlapping the target material with a region of the first radiation beam encompassing its confocal parameter; and the confocal parameter may be less than or equal to 2 millimeters. The amount of energy directed from the first radiation beam to the target material can be adjusted by adjusting a property of the first radiation beam. The radiation exposure delivered to the target material from the first radiation beam can be controlled by adjusting one or more of: the radiation exposure just before the first radiation beam delivers an energy to the target material the energy of the first radiation beam; a location of the target material; and a region of the target material that interacts with the first radiation beam. The first radiation beam may be directed by directing the first radiation beam through a first set of optical components comprising one or more first optical amplifiers; and the second radiation beam may be directed by A second set of optical components comprising one or more second optical amplifiers is used to direct the second radiation beam; wherein the first set of optical components is distinct from and separate from the second set of optical components. In other general aspects, an apparatus includes: a chamber defining an initial target site receiving a first radiation beam and a target site receiving a second radiation beam; a target material delivery system configured to provide a target material to the initial target site, the target material comprising a material that emits extreme ultraviolet (EUV) light when converted into a plasma; an optical source configured to generate the first radiation beam and the second two radiation beams; and an optical steering system. The optical steering system is configured to: direct the first radiation beam toward the initial target site to deliver energy to the target material to modify a geometric distribution of the target material to form a modified target; and Two radiation beams are directed towards the target site to convert at least a portion of the modified target into a plasma emitting EUV light. The apparatus includes: a metrology system that measures one or more properties associated with one or more of the target material and the modified target relative to the first radiation beam; and a control system that Connected to the target material delivery system, the optical source, the optical manipulation system and the measurement system. The control system is configured to receive the one or more measured characteristics from the measurement system, and based on the one or more measured characteristics send one or more signals to the optical source to control the optical source from the first A radiation beam delivers a radiation exposure to the target material. Implementations can include one or more of the following features. For example, the optical steering system may include a focusing device configured to focus the first radiation beam at or near the initial target site and to focus the second radiation beam at the target site or nearby. The device may include a beam tuning system, wherein the beam tuning system is connected to the optical source and the control system, and the control system is configured to direct one or more signals to the beam tuning system by sending one or more signals to the beam tuning system Signals are sent to the optical source to control the amount of energy delivered to the target material, the beam adjustment system is configured to adjust one or more characteristics of the optical source to thereby maintain the amount of energy delivered to the target material The amount. The beam adjustment system may include a pulse width adjustment system coupled to the first radiation beam, the pulse width adjustment system configured to adjust a pulse width of pulses of the first radiation beam. The pulse width adjustment system may include an electro-optic modulator. The beam tuning system can include a pulse power tuning system coupled to the first radiation beam, the pulse power tuning system configured to tune an average power within pulses of the first radiation beam. The pulsed power modulation system may include an acoustic light modulator. The beam steering system can be configured to send one or more signals to the optical source to control the amount of energy directed to the target material by sending one or more signals to the beam steering system, the A beam adjustment system is configured to adjust one or more characteristics of the optical source to thereby control the amount of energy directed to the target material. The optical source may comprise a first set of one or more optical amplifiers through which the first radiation beam passes; and a second set of one or more optical amplifiers through which the second radiation beam passes, the first set At least one of the optical amplifiers is in the second set. the measurement system can measure an energy of the first radiation beam as the first radiation beam is directed toward the initial target site; and the control system can be configured to receive the measured from the measurement system energy, and sending one or more signals to the optical source based on the measured energy to control an amount of energy directed from the first radiation beam to the target material. In some general aspects, a method includes: providing a target material comprising a component that emits extreme ultraviolet (EUV) light when converted into a plasma; directing a first beam of radiation toward the target material to deliver energy to the target material to modify a geometric distribution of the target material to form a modified target; directing a second radiation beam towards the modified target, the second radiation beam will at least partially converting into a plasma that emits EUV light; controlling radiation exposure delivered from the first radiation beam to the target material within a predetermined range of radiation exposure; and by delivering radiation from the first radiation beam to the The radiation exposure of the target material is controlled within the predetermined radiation exposure range to stabilize a power of the EUV light emitted from the plasma. Implementations can include one or more of the following features. For example, the first radiation beam may be directed by directing the first radiation beam through a first set of optical components comprising one or more first optical amplifiers; and may be directed by the second The radiation beam steering directs the second radiation beam through a second set of optical components comprising one or more second optical amplifiers. The first set of optical components may be distinct and separate from the second set of optical components. The first radiation beam may be directed by directing the first radiation beam through a first set of one or more optical amplifiers; and the second radiation beam may be directed by directing the second radiation beam through one or more optical amplifiers A second set of amplifiers is used to direct the second radiation beam; wherein at least one of the optical amplifiers in the first set is in the second set. The target material can be provided by providing a droplet of the target material; and the target material can be modified by transforming the droplet of the target material into a disk-shaped volume of molten metal having a substantially planar surface. the geometric distribution. The target material may be provided by providing a droplet of target material; and the geometric distribution of the target material may be modified by transforming the droplet of target material into a mist-shaped volume of molten metal particles. The target material can be transformed into the modified target according to a dilation rate. The radiation exposure delivered to the target material from the first radiation beam may be controlled by measuring relative to the first radiation beam relative to one or more of the target material and the modified target maintaining a radiation exposure delivered from the first radiation beam to the target material within a predetermined radiation exposure range based on the one or more measured characteristics. The radiation exposure delivered from the first radiation beam to the target material can be controlled by estimating a dilation rate of the modified target. The radiation exposure delivered from the first radiation beam to the target material can be controlled by maintaining a dilation rate of the modified target. The radiation exposure delivered from the first radiation beam to the target material can be controlled by determining whether a characteristic of the first radiation beam should be adjusted. Delivery from the first radiation beam to the target material can be controlled by adjusting one or more of the energy content of each pulse of the first radiation beam, and the area over which the first radiation beam interacts with the target material. The radiation exposure of the target material. The energy content of each pulse of the first radiation beam can be adjusted by adjusting one or more of: the width of each pulse of the first radiation beam; the width of each pulse of the first radiation beam; a duration of pulses; and a power of each pulse of the first radiation beam. The power of the EUV light emitted from the plasma can be stabilized by stabilizing the power of the EUV light emitted from the plasma while at least a portion of the EUV light emitted from the plasma is exposing a wafer. The method can also include collecting at least a portion of the emitted EUV light; and directing the collected EUV light toward a wafer to expose the wafer to the EUV light. The geometric distribution of the target material can be modified by transforming a shape of the target material into the modified target, which includes expanding the modified target along at least one axis according to a dilation rate. The radiation exposure delivered from the first radiation beam to the target material can be controlled by adjusting a property of the first radiation beam. The property of the first radiation beam can be adjusted by adjusting an energy of the first radiation beam. In other general aspects, an apparatus includes: a chamber defining an initial target site receiving a first radiation beam and a target site receiving a second radiation beam; a target material delivery system configured to provide a target material to the initial target site, the target material comprising a material that emits extreme ultraviolet (EUV) light when converted into a plasma; an optical source configured to generate the first radiation beam and the second two radiation beams; and an optical steering system. The optical steering system is configured to: direct the first radiation beam toward the initial target site to deliver energy to the target material to modify a geometric distribution of the target material to form a modified target; and Two radiation beams are directed towards the target site to convert at least a portion of the modified target into a plasma emitting EUV light. The device includes a control system connected to the target material delivery system, the optical source, and the optical steering system, and configured to send one or more signals to the optical source to direct radiation from the first A radiation exposure delivered by the beam to the target material is controlled within a predetermined radiation exposure range, thereby stabilizing a power of EUV light emitted from the plasma. Implementations can include one or more of the following features. For example, the device may also include a metrology system that measures one or more of the components associated with one or more of the target material and the modified target relative to the first radiation beam. characteristics, wherein the control system is connected to the measurement system. The device may also include a beam tuning system, wherein the beam tuning system is connected to the optical source and the control system, and the control system is configured to direct a beam tuning system by sending one or more signals to the beam tuning system or signals are sent to the optical source to control the radiation exposure delivered to the target material, the beam adjustment system is configured to adjust one or more characteristics of the optical source to thereby control the radiation exposure delivered to the target material The radiation exposure.

揭示用於增加極紫外線(EUV)光產生之轉換效率之技術。參看圖1且如下文更詳細地論述，目標材料120與第一輻射光束110之間的相互作用造成該目標材料變形且幾何地擴張以藉此形成經修改目標121。以增加歸因於經修改目標121與第二輻射光束115之間的相互作用而自電漿轉換之可用EUV光130之量之方式來控制經修改目標121之幾何擴張率。可用EUV光130之量為可經利用以在光學裝置145處使用之EUV光130之量。因此，可用EUV光130之量可取決於若干態樣，諸如，用以利用EUV光130之光學組件之頻寬或中心波長。 經修改目標121之幾何擴張率之控制使能夠在該經修改目標121與第二輻射光束115相互作用時控制該經修改目標121之大小或幾何態樣。舉例而言，經修改目標121之幾何擴張率之調整會在該經修改目標121與第二輻射光束115相互作用時調整該經修改目標121之密度，此係因為在該經修改目標121與第二輻射光束115相互作用時該經修改目標121之密度影響由該經修改目標121吸收之輻射之總量及此輻射被吸收所遍及之範圍。隨著經修改目標121之密度增加，在某時刻EUV光130將不能夠自該經修改目標121逸出且因此可用EUV光130之量可降低。作為另一實例，經修改目標121之幾何擴張率之調整在該經修改目標121與第二輻射光束115相互作用時調整該經修改目標121之表面積。 以此方式，可藉由控制經修改目標121之擴張率而增加或控制所產生之可用EUV光130之總量。詳言之，經修改目標121之大小及其擴張率取決於自第一輻射光束110施加至目標材料120之放射曝光量，該放射曝光量為由第一輻射光束110遞送至目標材料120之區域的能量之量。因此，可藉由維持或控制每單位面積遞送至目標材料120之能量之量來維持或控制經修改目標121之擴張率。遞送至目標材料120之能量之量取決於恰好在第一輻射光束110照射於該目標材料之表面上之前該第一輻射光束110之能量。 第一輻射光束110中之脈衝之能量可藉由積分藉由快速光偵測器量測之雷射脈衝信號來判定。偵測器可為適於長波長紅外線(LWIR)輻射之光電磁(PEM)偵測器、用於量測近紅外線(IR)輻射之InGaAs二極體，或用於可見或近IR輻射之矽二極體。 經修改目標121之擴張率至少部分地取決於由目標材料120截取之第一輻射光束110之脈衝中的能量之量。在一假設基線設計中，假定目標材料120總是具有相同大小且被置放於經聚焦第一輻射光束110之腰部中。但實務上，目標材料120可具有相對於第一輻射光束110之光束腰之小但通常恆定的軸向位置偏移。若所有此等因素保持恆定，則控制經修改目標121之擴張率之一個因素為為了使第一輻射光束110之脈衝具有為幾奈秒至100奈秒之持續時間的該第一輻射光束之脈衝能量。可在第一輻射光束110之脈衝具有處於或低於100奈秒之持續時間的情況下控制經修改目標121之擴張率之另一因素為第一輻射光束110之瞬時峰值功率。若第一輻射光束110之脈衝具有較短(例如，大約數皮秒(ps))之持續時間，則其他因素可控制經修改目標121之擴張率，如下文所論述。 如圖1中所展示，光學源105 (亦被稱作驅動源或驅動雷射)用以驅動雷射產生電漿(LPP)極紫外線(EUV)光源100。該光學源105產生提供至第一目標部位111之第一輻射光束110及提供至第二目標部位116之第二輻射光束115。第一輻射光束110及第二輻射光束115可為脈衝式放大光束。 第一目標部位111自目標材料供應系統125接收諸如錫之目標材料120。第一輻射光束110與目標材料120之間的相互作用將能量遞送至目標材料120以修改或改變其形狀(例如，使其形狀變形)使得目標材料120之幾何分佈變形成經修改目標121。通常自目標材料供應系統125沿著-X方向或沿著將目標材料120置放於第一目標部位111內之方向而導引目標材料120。在第一輻射光束110將能量遞送至目標材料120以使其變形成經修改目標121之後，經修改目標121可除了沿著另一方向(諸如平行於Z方向之方向)移動以外亦可繼續沿著-X方向移動。隨著經修改目標121移動遠離第一目標部位111，其幾何分佈繼續變形直至該經修改目標121到達第二目標部位116為止。第二輻射光束115與經修改目標121之間的相互作用(在第二目標部位116處)將該經修改目標121之至少部分轉換成電漿129，該電漿發射EUV光或輻射130。集光器系統(或集光器) 135收集EUV光130且將EUV光130作為經收集EUV光140導引朝向諸如微影工具之光學裝置145。第一目標部位111及第二目標部位116以及集光器135可容納於腔室165內，腔室165提供適合於產生EUV光140之受控環境。 有可能在一些目標材料120與第一輻射光束110相互作用時將目標材料轉換成電漿，且因此此電漿有可能可發射EUV輻射。然而，第一輻射光束110之屬性經選擇及控制使得第一輻射光束110對目標材料120之主要作用為變形或修改目標材料120之幾何分佈以形成經修改目標121。 第一輻射光束110及第二輻射光束115中之每一者係由光束遞送系統150導引朝向各別目標部位111、116。光束遞送系統150可包括若干光學操縱組件152及一聚焦總成156，該聚焦總成156將第一輻射光束110或第二輻射光束115聚焦至各別第一聚焦區及第二聚焦區。第一聚焦區及第二聚焦區可分別與第一目標部位111及第二目標部位116重疊。光學組件152可包括藉由折射及/或反射而導引輻射光束110、115之光學元件，諸如透鏡及/或鏡面。光束遞送系統150亦可包括控制及/或移動光學組件152之元件。舉例而言，光束遞送系統150可包括可控制以使光學組件152內之光學元件移動之致動器。 亦參看圖2，聚焦總成156聚焦第一輻射光束110使得第一輻射光束110之直徑D1在第一聚焦區210中處於最小值。換言之，聚焦總成156使第一輻射光束110在其在第一軸向方向212上朝向第一聚焦區210傳播時會聚，該第一軸向方向212為第一輻射光束110之一般傳播方向。第一軸向方向212沿著由X-Z軸界定之平面延伸。在此實例中，第一軸向方向212平行於或接近平行於Z方向，但其可沿著相對於Z所成之一角度。在不存在目標材料120的情況下，第一輻射光束110在其在第一軸向方向212上傳播遠離第一聚焦區210時發散。 另外，聚焦總成156聚焦第二輻射光束115使得第二輻射光束115之直徑D2在第二聚焦區215中處於最小值。因此，聚焦總成使第二輻射光束115在其在第二軸向方向217上朝向第二聚焦區215傳播時會聚，該第二軸向方向217為第二輻射光束115之一般傳播方向。第二軸向方向217亦沿著由X-Z軸界定之平面延伸，且在此實例中，第二軸向方向217平行於或接近平行於Z方向。在不存在經修改目標121的情況下，第二輻射光束115在其沿著第二軸向方向217傳播遠離第二聚焦區215時發散。 如下文所論述，EUV光源100亦包括一或多個量測系統155、一控制系統160，及一光束調整系統180。控制系統160連接至光源100內之其他組件，諸如，量測系統155、光束遞送系統150、目標材料供應系統125、光束調整系統180及光學源105。量測系統155可量測光源100內之一或多個特性。舉例而言，一或多個特性可為與相對於第一輻射光束110之目標材料120或經修改目標121相關聯的特性。作為另一實例，一或多個特性可為經導引朝向目標材料120之第一輻射光束110之脈衝能量。將在下文更詳細地論述此等實例。控制系統160經組態以自量測系統接收一或多個經量測特性使得其可控制第一輻射光束110如何與目標材料120相互作用。舉例而言，控制系統160可經組態以將自第一輻射光束110遞送至目標材料120之能量之量維持在一預定能量範圍內。作為另一實例，控制系統160可經組態以控制自第一輻射光束110導引至目標材料120之能量之量。光束調整系統180為包括光學源105內之組件或包括調整光學源105內之組件以藉此控制第一輻射光束110之屬性(諸如，脈寬、脈衝能量、脈衝內之瞬時功率或脈衝內之平均功率)的組件之系統。 參看圖3A，在一些實施中，光學源105包括：第一光學放大器系統300，其包括第一輻射光束110傳遞通過之一系列一或多個光學放大器；及第二光學放大器系統305，其包括第二輻射光束115傳遞通過之一系列一或多個光學放大器。來自第一系統300之一或多個放大器可處於第二系統305中；或第二系統305中之一或多個放大器可處於第一系統300中。替代地，有可能將第一光學放大器系統300與第二光學放大器系統305完全分離。 另外，儘管不需要，光學源105仍可包括產生第一脈衝光束311之第一光產生器310及產生第二脈衝光束316之第二光產生器315。光產生器310、315可各自為(例如)雷射、諸如主控振盪器之種子雷射，或燈。可用作光產生器310、315之例示性光產生器為可在為(例如) 100 kHz之重複率下操作之Q切換、射頻(RF)泵浦、軸流、二氧化碳(CO2 )振盪器。 光學放大器系統300、305內之光學放大器各自在來自各別光產生器310、315之光束311、316傳播所沿著的各別光束路徑上含有增益介質。當激發光學放大器之增益介質時，該增益介質將光子提供至光束、放大光束311、316以產生經放大光束，經放大光束形成第一輻射光束110或第二輻射光束115。 光束311、316之波長或輻射光束110、115之波長可彼此不同，使得輻射光束110、115在其經組合於光學源105內之任何點處的情況下可彼此分離。若輻射光束110、115係由CO2 放大器產生，則第一輻射光束110可具有為10.26微米(µm)或10.207微米之波長，且第二輻射光束115可具有為10.59微米之波長。該等波長經選擇為較容易實現使用色散光學件或雙向色鏡或光束分裂器塗層進行之兩個輻射光束110、115之分離。在輻射光束110、115兩者一起傳播於同一放大器鏈中之情形(例如，光學放大器系統300之一些放大器處於光學放大器系統305中之情形)下，則相異波長可用以調整該兩個輻射光束110、115之間的相對增益(儘管該兩個輻射光束110、115橫穿過相同放大器)。 舉例而言，輻射光束110、115一旦經分離就可經操縱或聚焦至腔室165內之兩個分離部位(諸如分別為第一目標部位111及第二目標部位116)。詳言之，輻射光束110、115之分離亦使經修改目標121能夠在第一輻射光束110自第一目標部位111行進至第二目標部位116時與該第一輻射光束110相互作用之後擴張。 光學源105可包括光束路徑組合器325，光束路徑組合器325將第一輻射光束110與第二輻射光束115疊對且將該等輻射光束110、115置放於針對光學源105與光束遞送系統150之間的距離中之至少一些之同一光學路徑上。圖3B中展示例示性光束路徑組合器325。光束路徑組合器325包括一對雙向色光束分裂器340、342及一對鏡面344、346。雙向色光束分裂器340使第一輻射光束110能夠沿著通向雙向色光束分裂器342之第一路徑傳遞通過。雙向色光束分裂器340將第二輻射光束115沿著第二路徑反射，其中第二輻射光束115係自鏡面344、346反射，該等鏡面將第二輻射光束115重新導引朝向雙向色光束分裂器342。第一輻射光束110自由地通過雙向色光束分裂器342而傳遞至輸出路徑上，而第二輻射光束115自雙向色光束分裂器342反射至該輸出路徑上使得第一輻射光束110及第二輻射光束115兩者在該輸出路徑上疊對。 另外，光學源105可包括光束路徑分離器326，光束路徑分離器326將第一輻射光束110與第二輻射光束115分離使得該兩個輻射光束110、115可分離地經操縱及聚焦於腔室165內。圖3C中展示例示性光束路徑分離器326。光束路徑分離器326包括一對雙向色光束分裂器350、352及一對鏡面354、356。雙向色光束分裂器350接收該經疊對對之輻射光束110、115、將第二輻射光束115沿著第二路徑反射，且將第一輻射光束110沿著第一路徑透射朝向雙向色光束分裂器352。第一輻射光束110沿著第一路徑自由地傳遞通過雙向色光束分裂器352。第二輻射光束115自鏡面354、356反射且返回至雙向色光束分裂器352，其中其經反射至相異於第一路徑之第二路徑上。 另外，第一輻射光束110可經組態為具有比第二輻射光束115之脈衝能量更少的脈衝能量。此係因為第一輻射光束110用以修改目標材料120之幾何形狀，而第二輻射光束115用以將經修改目標121轉換成電漿129。舉例而言，第一輻射光束110之脈衝能量可小達第二輻射光束115之脈衝能量1/5至1/100。 在如圖4A及圖4B中所展示之一些實施中，光學放大器系統300或305分別包括一組三個光學放大器401、402、403及406、407、408，但可使用少至一個放大器或多於三個放大器。在一些實施中，光學放大器406、407、408中之每一者包括一增益介質，該增益介質包括CO2 ；且可在大於1000之增益下放大處於約9.1微米與約11.0微米之間且特別處於約10.6微米的波長之光。有可能以相似方式或在不同波長下操作光學放大器401、402、403。用於光學放大器系統300、305中之合適放大器及雷射可包括脈衝式雷射器件，諸如(例如)運用在相對高功率(例如，10 kW或更高)及高脈衝重複率(例如，50 kHz或更大)下操作的DC或RF激發產生處於約9.3微米或約10.6微米之輻射的脈衝式氣體放電CO2 放大器。例示性光學放大器401、402、403或406、407、408為運用無磨損氣體循環及電容性RF激發之軸流高功率CO2 雷射，諸如由康乃狄格州法明頓之TRUMPF公司生產的TruFlow CO2 雷射。 另外，儘管不需要，光學放大器系統300及305中之一或多者仍可包括分別充當前置放大器411、421之第一放大器。前置放大器411、421 (若存在)可為經擴散冷卻之CO2 雷射系統，諸如由康乃狄格州法明頓之TRUMPF公司生產的TruCoax CO2 雷射系統。 光學放大器系統300、305可包括未展示於圖4A及圖4B中的用於導引及塑形各別光束311、316之光學元件。舉例而言，光學放大器系統300、305可包括反射光學件(諸如，鏡面)、部分透射光學件(諸如，光束分裂器或部分透射鏡面)，及雙向色光束分裂器。 光學源105亦包括光學系統320，光學系統320可包括用於將光束311、316導引通過光學源105之一或多個光學件(諸如，反射光學件(諸如鏡面)、部分反射光學件及部分透射光學件(諸如光束分裂器)、折射光學件(諸如稜鏡或透鏡)、被動光學件、主動光學件等等)。 儘管光學放大器401、402、403及406、407、408被展示為分離區塊，但該等放大器401、402、403中之至少一者有可能處於光學放大器系統305中且該等放大器406、407、408中之至少一者有可能處於光學放大器系統300中。舉例而言，如圖5中所展示，放大器402、403對應於各別放大器407、408，且光學放大器系統300、305包括額外光學元件500 (諸如光束路徑組合器325)，該光學元件500用於將自放大器401、406輸出之兩個光束組合至穿過放大器402/407及放大器403/408之單一路徑中。在光學放大器系統300、305之間放大器中之至少一些與光學件重疊之此系統中，有可能使第一輻射光束110及第二輻射光束115耦合在一起使得第一輻射光束110之一或多個特性之改變可造成第二輻射光束115之一或多個特性之改變，且反之亦然。因此，變得更重要的是控制系統內之能量，諸如，第一輻射光束110之能量或遞送至目標材料120之能量。另外，光學放大器系統300、305亦包括光學元件505 (諸如光束路徑分離器326)，光學元件505用於分離自放大器403/408輸出之兩個光束110、15以使該兩個光束110、115能夠經導引至各別目標部位111、116。 目標材料120可為包括當轉換成電漿時發射EUV光之目標材料的任何材料。目標材料120可為包括目標物質及雜質(諸如，非目標粒子)之目標混合物。目標物質為可轉換成具有在EUV範圍之發射譜線之電漿狀態的物質。目標物質可為(例如)液體或熔融金屬之小滴、液體串流之一部分、固體粒子或叢集、液滴內所含有之固體粒子、目標材料之發泡體，或液體串流之一部分內所含有之固體粒子。目標物質可為(例如)水、錫、鋰、氙，或當轉換成電漿狀態時具有在EUV範圍之發射譜線的任何材料。舉例而言，目標物質可為元素錫，其可用作純錫(Sn)；用作錫化合物，例如，SnBr4 、SnBr2 、SnH4 ；用作錫合金，例如，錫-鎵合金、錫-銦合金、錫-銦-鎵合金，或此等合金之任何組合。此外，在不存在雜質之情形下，目標材料僅包括目標物質。以下之論述提供目標材料120為由諸如錫之熔融金屬製成的小滴之實例。然而，目標材料120可採取其他形式。 可藉由將熔融目標材料傳遞通過目標材料供應裝置125之噴嘴且允許目標材料120漂移至第一目標部位111中而將目標材料120提供至第一目標部位111。在一些實施中，可藉由力將目標材料120導引至第一目標部位111。 在目標材料120到達第二目標部位116之前藉由運用來自第一輻射光束110之輻射脈衝輻照目標材料120而改變或修改目標材料120之形狀(例如，使目標材料120之形狀變形)。 第一輻射光束110與目標材料120之間的相互作用造成材料自目標材料120 (及經修改目標121)之表面剝蝕，且此剝蝕提供使目標材料120變形成經修改目標121之力，該經修改目標121具有不同於目標材料120之形狀的形狀。舉例而言，目標材料120可具有相似於小滴之形狀，而經修改目標121之形狀變形使得在該經修改目標121到達第二目標部位116時其形狀更接近圓盤之形狀(諸如盤餅形狀)。經修改目標121可為未經離子化之材料(不為電漿之材料)或最低限度地經離子化之材料。經修改目標121可為(例如)液體或熔融金屬之圓盤、不具有空隙或相當大間隙之目標材料之連續片段、微離子或毫微粒子之霧狀物，或原子蒸汽之雲狀物。舉例而言，如圖2中所展示，經修改目標121在約時間T2-T1 (其可為大約數微秒(µs))之後在第二目標部位116內擴張成熔融金屬之圓盤形片件121。 另外，使材料自目標材料120 (及經修改目標121)之表面剝蝕的介於第一輻射光束110與目標材料120之間的相互作用可提供力，該力可使經修改目標121沿著Z方向獲取某一推進力或速度。經修改目標121在X方向上之擴張以及在Z方向上之所獲取速度取決於第一輻射光束110之能量，且特別取決於遞送至目標材料120 (亦即，由目標材料120截取)之能量。 舉例而言，對於恆定目標材料120大小及對於第一輻射光束110之長脈衝(長脈衝為具有幾奈秒(ns)與100奈秒之間的持續時間之脈衝)，則擴張率與第一輻射光束110之每單位面積能量(焦耳/平方公分)成線性比例。每單位面積能量亦被稱作放射曝光量或通量。放射曝光量為每單位面積由目標材料120之表面接收之放射能量，或等效地為遍及目標材料120經輻照之時間而積分的目標材料120之表面之輻照度。 作為另一實例，對於恆定目標材料120大小及對於短脈衝(具有小於幾百皮秒(ps)之持續時間之脈衝)，則擴張率與第一輻射光束110之能量之間的關係可不同。在此體系中，使較短脈衝持續時間與第一輻射光束110之強度增加相關，第一輻射光束110與目標材料120相互作用，且該第一輻射光束110表現得像衝擊波。在此體系中，擴張率主要取決於第一輻射光束110之強度I，且該強度等於第一輻射光束之能量E除以與目標材料120相互作用的第一輻射光束110之光點大小(橫截面積A)與脈衝持續時間(τ)，或I = E/(A·121之範圍之 τ)。在此皮秒-脈衝持續時間體系中，經修改目標121擴張以便形成霧狀物。 另外，經修改目標121之圓盤形狀之角度定向(相對於Z方向或X方向之角度)取決於第一輻射光束110在其撞擊目標材料120時之位置。因此，若第一輻射光束110撞擊目標材料120使得第一輻射光束110涵蓋該目標材料且第一輻射光束110之光束腰以該目標材料120為中心，則更可能的是，經修改目標121之圓盤形狀將與其平行於X方向之長軸230及其平行於Z方向之短軸235對準。 第一輻射光束110係由輻射脈衝組成，且每一脈衝可具有一持續時間。相似地，第二輻射光束115係由輻射脈衝組成，且每一脈衝可具有一持續時間。脈衝持續時間可由某一百分比高(例如，半高)寬表示，亦即，脈衝之強度為脈衝之最大強度之至少百分比的時間量。然而，其他度量可用以判定脈衝持續時間。第一輻射光束110內之脈衝之脈衝持續時間可為(例如) 30奈秒(ns)、60奈秒、130奈秒、50奈秒至250奈秒、10皮秒至200皮秒(ps)，或小於1奈秒。第一輻射光束110之能量可為(例如) 1毫焦耳(mJ)至100毫焦耳(mJ)。第一輻射光束110之波長可為(例如) 1.06微米、1微米至10.6微米、10.59微米或10.26微米。 如上文所論述，經修改目標121之擴張率取決於截取目標材料120之第一輻射光束110之放射曝光量(每單位面積能量)。因此，對於具有約60奈秒之持續時間及約50毫焦能量之第一輻射光束110之脈衝，實際放射曝光量取決於第一輻射光束110聚焦於第一聚焦區210處之嚴格程度。在一些實例中，目標材料120處之放射曝光量可為約400焦耳/平方公分至700焦耳/平方公分。然而，放射曝光量對目標材料120相對於第一輻射光束110之部位極敏感。 第二輻射光束115可被稱作主光束且其由以一重複率釋放之脈衝組成。第二輻射光束115具有足夠能量以將經修改目標121內之目標物質轉換成發射EUV光130之電漿。第一輻射光束110之脈衝及第二輻射光束115之脈衝在時間上分離一延遲時間，諸如1微秒至3微秒(μs)、1.3微秒、1微秒至2.7微秒、3微秒至4微秒，或允許經修改目標121擴張成圖2中所展示之具所要大小的圓盤形狀之任何時間量。因此，當經修改目標121在X-Y平面中擴張及伸長時，經修改目標121經歷二維擴張。 第二輻射光束115可經組態成使得其在其撞擊經修改目標121時稍微散焦。圖2中展示此散焦方案。在此狀況下，第二聚焦區215處於沿著Z方向之與經修改目標121之長軸230不同的部位；此外，第二聚焦區215在第二目標部位116外部。在此方案中，將第二聚焦區215沿著Z方向置放於經修改目標121之前。亦即，第二輻射光束115在第二輻射光束115撞擊經修改目標121之前達到聚焦(或光束腰)。其他散焦方案係可能的。舉例而言，如圖6中所展示，將第二聚焦區215沿著Z方向置放於經修改目標121之後。以此方式，第二輻射光束115在第二輻射光束115撞擊經修改目標121之後達到聚焦(或光束腰)。 再次參看圖2，經修改目標121在其自第一目標部位111移動(例如，飄移)至第二目標部位116時擴張之速率可被稱作擴張率(ER)。在第一目標部位111處，恰好在時間T1時目標材料120由第一輻射光束110撞擊之後，經修改目標121就具有沿著長軸230所截留之範圍(或長度) S1。在經修改目標121在時間T2時到達第二目標部位116時，該經修改目標121具有沿著長軸230所截留之範圍S2。擴張率為沿著長軸230所截留之經修改目標121之範圍之差(S2-S1)除以時間差(T2-T1)，因此：

Figure 02_image001
儘管經修改目標121沿著長軸230擴張，但亦有可能使經修改目標121沿著短軸235壓縮或薄化。 上文所論述之二步法途徑導致為約3%至4%之轉換效率，在該途徑中經修改目標121係藉由將第一輻射光束110與目標材料120相互作用而形成，且接著藉由將經修改目標121與第二輻射光束115相互作用而將該經修改目標121轉換成電漿。一般而言，需要增加來自光學源105之光至EUV輻射130之轉換率，此係因為過低轉換效率可需要增加光學源105需要遞送之功率之量，此情形增加操作光學源105之成本且亦增加對光源100內之所有組件之熱負荷，且可導致在容納第一目標部位111及第二目標部位116之腔室內之碎屑產生增加。轉換效率之增加可幫助符合對高容量製造工具之要求且同時將光學源功率要求保持在可接受限度內。各種參數影響轉換效率，諸如，第一輻射光束110及第二輻射光束115之波長、目標材料120，以及輻射光束110、115之脈衝形狀、能量、功率及強度。轉換效率可被定義為由EUV光130產生之EUV能量除2π立體角及圍繞用於集光器系統135以及光學裝置145中之照明及投影光學件中之任一者或兩者中的(多層)鏡面之反射率曲線之中心波長之2%頻寬，除以第二輻射光束115之輻照脈衝之能量。在一項實例中，反射率曲線之中心波長為13.5奈米(nm)。 用以增加、維持或最佳化轉換效率之一種方式應為控制EUV光130之能量或使EUV光130之能量穩定，且為了進行此操作，變得重要的是將經修改目標121之擴張率(與其他參數)維持在值之可接受範圍內。藉由維持自第一輻射光束110在目標材料120上之放射曝光量而將經修改目標121之擴張率維持在值之可接受範圍內。且，可基於與相對於第一輻射光束110之目標材料120或經修改目標121相關聯之一或多個經量測特性來維持放射曝光量。放射曝光量為每單位面積由目標材料120之表面接收之放射能量。因此，可將放射曝光量估計或近似為在目標材料120之區域在脈衝間保持恆定的情況下導引朝向該目標材料120之表面的能量之量。 存在用以將經修改目標121之擴張率維持在值之可接受範圍內之不同方法或技術。且，所使用之方法或技術可取決於與第一輻射光束110相關聯之某些屬性。轉換效率亦受到其他參數影響，諸如，目標材料120之大小或厚度、目標材料120相對於第一聚焦區210之位置，或目標材料120相對於x-y平面之角度。 可影響如何維持放射曝光量之一個屬性為第一輻射光束110之共焦參數。輻射光束之共焦參數為輻射光束之瑞立長度的兩倍，且瑞立長度為沿著輻射光束之傳播方向自腰部至橫截面面積加倍之地點之距離。參看圖2，對於輻射光束110，瑞立長度為沿著第一輻射光束110之傳播方向212自其腰部(其為D1/2)至該第一光束之橫截面加倍之地點之距離。 舉例而言，如圖7A中所展示，第一輻射光束110之共焦參數如此長使得光束腰(D1/2)容易涵蓋目標材料120，且由第一輻射光束110截取的目標材料120之表面積(其橫越X方向而量測)保持相對恆定，即使目標材料120之位置偏離光束腰D1/2之部位亦如此。舉例而言，由第一輻射光束110在部位L1處截取的目標材料120之表面積係在由第一輻射光束110在部位L2處截取的目標材料120之表面積的20%內。在此第一情境(其中由第一輻射光束110截取的目標材料120之表面積較不可能偏離平均值(相比於下文所描述之第二情境))中，可藉由維持自第一輻射光束110導引至目標材料120之能量之量來維持或控制放射曝光量及(因此)擴張率(而不必將由第一輻射光束110曝光之目標材料120之表面積計算在內)。 作為另一實例，如圖7B中所展示，第一輻射光束110之共焦參數如此短使得光束腰(D1/2)不涵蓋目標材料120，且在目標材料120之位置偏離光束腰D1/2之部位L1的情況下，由第一輻射光束110截取之目標材料120之表面積偏離平均值。舉例而言，由第一輻射光束110在部位L1處截取的目標材料120之表面積實質上不同於由第一輻射光束110在部位L2處截取的目標材料120之表面積。在由第一輻射光束110截取的目標材料120之表面積更可能偏離平均值之此第二情境中(相比於在第一情境中)，可藉由控制自第一輻射光束110遞送至目標材料120之能量之量而維持或控制放射曝光量及(因此)擴張率。為了控制放射曝光量，控制每單位面積由目標材料120之表面接收的第一輻射光束110之放射能量。因此，重要的是控制第一輻射光束110之脈衝之能量，及目標材料120截取第一輻射光束110所處的第一輻射光束110之區域。使目標材料120截取第一輻射光束110所處的第一輻射光束110之區域與由第一輻射光束110截取之目標材料120之表面相關。可影響目標材料120截取第一輻射光束110所處的第一輻射光束110之區域之另一因素為第一輻射光束110之光束腰D1/2之部位及大小之穩定性。舉例而言，若第一輻射光束110之腰部大小及位置恆定，則吾人可控制目標材料120相對於光束腰D1/2之部位。第一輻射光束110之腰部大小及位置有可能歸因於(例如)光學源105中之熱效應而改變。一般而言，變得重要的是維持第一輻射光束110中之脈衝之恆定能量且亦控制光學源105之其他態樣，使得目標材料120到達相對於光束腰D1/2之已知軸向(Z方向)位置，而關於彼位置無過多變化。 用以將經修改目標121之擴張率維持或控制在值之可接受範圍內之全部所描述方法皆使用接下來所描述的量測系統155之用途。 再次參看圖1，量測系統155量測與目標材料120、經修改目標121及第一輻射光束110中的任何一或多者相關聯之至少一個特性。舉例而言，量測系統155可量測第一輻射光束110之能量。如圖8A中所展示，例示性量測系統855A量測經導引至目標材料120之第一輻射光束110之能量。 如圖8B中所展示，例示性量測系統855B量測在第一輻射光束110與目標材料120相互作用之後自目標材料120反射的輻射860之能量。自目標材料120進行之輻射860之反射可用以判定目標材料120相對於第一輻射光束110之實際位置之部位。 在一些實施中，如圖8C中所展示，可將例示性量測系統855B置放於光學源105之光學放大器系統300內。在此實例中，量測系統855B可經置放成量測照射於光學放大器系統300內之光學元件中之一者(諸如薄膜偏光器)上或自該等光學元件中之一者反射的反射輻射860中之能量之量。自目標材料120反射之輻射860之量與遞送至目標材料120之能量之量成比例；因此，藉由量測反射輻射860，可控制或維持遞送至目標材料120之能量之量。另外，使在第一輻射光束110或反射輻射860中量測之能量之量與該光束中之光子數目相關。因此，可稱量測系統855A或855B量測各別光束中之光子之數目。另外，量測系統855B可被認為依據多少光子衝擊目標材料120而量測自目標材料120反射之光子之數目(該目標材料在其由第一輻射光束110撞擊之後就變成經修改目標121)。 量測系統855A或855B可為光電感測器，諸如，光電池陣列(例如，2×2陣列或3×3陣列)。光電池具有對待量測光之波長之敏感度，且其具有適於待量測之光脈衝之持續時間的足夠速度或頻寬。 一般而言，量測系統855A或855B可藉由量測橫越垂直於第一輻射光束110之傳播方向的方向之空間積分能量來量測輻射光束110之能量。因為可快速執行光束能量之量測，所以有可能對在第一輻射光束110中發射之每一脈衝採取一量測，且因此，該量測及控制可基於脈衝間進行。 量測系統855A、855B可為快速光偵測器，諸如，適於長波長紅外線(LWIR)輻射之光電磁(PEM)偵測器。PEM偵測器可為用於量測近紅外線輻射或可見光輻射之矽二極體，或用於量測近紅外線輻射之InGaAs二極體。第一輻射光束110中之脈衝之能量可藉由積分藉由量測系統855A、855B量測之雷射脈衝信號來判定。 參看圖9A，量測系統155可為例示性量測系統955A，其量測目標材料120相對於目標位置之位置Tpos。目標位置可處於第一輻射光束110之光束腰處。可沿著平行於第一輻射光束110之光束軸線之方向(諸如第一軸向方向212)來量測目標材料120之位置。 參看圖9B，量測系統155可為例示性量測系統955B，其量測目標材料120相對於集光器135之主焦點990之位置Tpos。此量測系統955B可包括在接近目標材料120時自目標材料120反射以量測目標材料120之位置及目標材料120相對於腔室165內之座標系統之到達時間之雷射及/或攝影機。 參看圖9C，量測系統155可為例示性量測系統955C，其在經修改目標121與第二輻射光束115相互作用之前量測處於一位置的經修改目標121之大小。舉例而言，量測系統955C可經組態以在經修改目標121處於第二目標部位116內時但在經修改目標121由第二輻射光束115撞擊之前量測經修改目標121之大小Smt。量測系統955C亦可判定經修改目標121之定向。量測系統955C可使用脈衝式背光照明器及攝影機(諸如，電荷耦合器件攝影機)之影像圖技術。 量測系統155可包括量測子系統之集合，每一子系統經設計為量測特定特性且以不同速度或取樣時間間隔量測。子系統之此集合可一起工作以提供對第一輻射光束110如何與目標材料120相互作用以形成經修改目標121的清楚瞭解。 量測系統155可包括腔室165內之複數個EUV感測器，該複數個EUV感測器用於偵測自在經修改目標121與第二輻射光束115相互作用之後由該經修改目標121產生的電漿發射之EUV能量。藉由偵測所發射之EUV能量，有可能獲得關於經修改目標121之角度或第二光束相對於第二輻射光束115之橫向偏移之資訊。 在控制系統160之控制下使用光束調整系統180以使得能夠控制遞送至目標材料120之能量(放射曝光)之量。可藉由在假定在第一輻射光束110與目標材料120相互作用之位置處該第一輻射光束110之面積恆定的情況下控制第一輻射光束110內之能量之量而控制放射曝光。光束調整系統180自控制系統160接收一或多個信號。光束調整系統180經組態以調整光學源105之一或多個特徵以維持遞送至目標材料120之能量(亦即，放射曝光)之量或控制導引至目標材料120之能量之量。因此，光束調整系統180可包括控制光學源105之特徵之一或多個致動器，該等致動器可為用於使光學源105之特徵經修改之機械、電、光學、電磁或任何合適的力器件。 在一些實施中，光束調整系統180包括耦合至第一輻射光束110之脈寬調整系統。脈寬調整系統經組態以調整第一輻射光束110之脈寬。在此實施中，脈寬調整系統可包括電光調變器，諸如，勃克爾盒。舉例而言，勃克爾盒配置於光產生器310內，且藉由開啟勃克爾盒達較短或較長時間段，由勃克爾盒透射之脈衝(及(因此)自光產生器310發射之脈衝)可經調整為較短或較長。 在其他實施中，光束調整系統180包括耦合至第一輻射光束110之脈衝功率調整系統。脈衝功率調整系統經組態以(例如)藉由調整第一輻射光束110之每一脈衝內之平均功率而調整每一脈衝之功率。在此實施中，脈衝功率調整系統可包括聲光調變器。聲光調變器可經配置成使得施加至調變器之邊緣處之壓電轉換器之RF信號的改變可變化以藉此改變自聲光調變器繞射之脈衝之功率。 在一些實施中，光束調整系統180包括耦合至第一輻射光束110之能量調整系統。該能量調整系統經組態以調整第一輻射光束110之能量。舉例而言，能量調整系統可為電可變衰減器(諸如，在0 V與半波電壓之間變化之勃克爾盒，或外部聲光調變器)。 在一些實施中，目標材料120相對於光束腰D1/2之位置或角度變化如此多使得光束調整系統180包括控制光束腰D1/2相對於第一目標部位111之部位或角度或相對於腔室165內之在腔室165之座標系統中的另一部位之部位或角度之裝置。該裝置可為聚焦總成156之部件，且其可用以沿著Z方向或沿著橫向於Z方向之方向(例如，沿著由X及Y方向界定之平面)移動光束腰。 如上文所論述，控制系統160分析自量測系統155接收之資訊，且判定如何調整第一輻射光束110之一或多個屬性以藉此控制及維持經修改目標121之擴張率。參看圖10，控制系統160可包括與光源100之其他部件介接之一或多個子控制器1000、1005、1010、1015，諸如，子控制器1000經具體組態以與光學源105介接(自光學源105接收資訊及將資訊發送至光學源105)、子控制器1005經具體組態以與量測系統155介接、子控制器1010經組態以與光束遞送系統150介接，且子控制器1015經組態以與目標材料供應系統125介接。光源100可包括圖1及圖10中未展示，但可與控制系統160介接之其他組件。舉例而言，光源100可包括診斷系統，諸如，小滴位置偵測回饋系統，及一或多個目標或小滴成像器。目標成像器提供指示小滴(例如)相對於特定位置(諸如，集光器135之主焦點990)之位置之輸出，且將此輸出提供至小滴位置偵測回饋系統，小滴位置偵測回饋系統可(例如)計算小滴位置及軌跡，自該小滴位置及軌跡可基於逐小滴地或平均地計算出小滴位置誤差。因此，小滴位置偵測回饋系統將小滴位置誤差作為輸入提供至控制系統160之子控制器。控制系統160可將(例如)雷射位置、方向及時序校正信號提供至光學源105內之可用以(例如)控制雷射時序電路之雷射控制系統，及/或提供至光束控制系統以控制光束傳送系統之經放大光束位置及塑形，以改變第一輻射光束110或第二輻射光束115之焦平面之部位及/或焦度。 目標材料遞送系統125包括目標材料遞送控制系統，目標材料遞送控制系統可操作以回應於(例如)來自控制系統160之信號以修改如由內部遞送機構釋放的目標材料120之小滴之釋放點，以校正到達所要目標部位111之小滴中的誤差。 控制系統160通常包括數位電子電路、電腦硬體、韌體及軟體中之一或多者。控制系統160亦可包括適當輸入及輸出器件1020、一或多個可程式化處理器1025，及有形地體現於機器可讀儲存器件中以供可程式化處理器執行之一或多個電腦程式產品1030。此外，子控制器(諸如子控制器1000、1005、1010、1015)中之每一者可包括其自有適當輸入及輸出器件、一或多個可程式化處理器，及有形地體現於機器可讀儲存器件中以供可程式化處理器執行之一或多個電腦程式產品。 一或多個可程式化處理器可各自執行指令程式以藉由對輸入資料進行操作且產生適當輸出來執行所要功能。通常，處理器自唯讀記憶體及/或隨機存取記憶體接收指令及資料。適合於有形地體現電腦程式指令及資料之儲存器件包括所有形式之非揮發性記憶體，包括(作為實例)半導體記憶體器件，諸如EPROM、EEPROM及快閃記憶體器件；磁碟，諸如內部硬碟及抽取式磁碟；磁光碟；以及CD-ROM磁碟。前述任一者可由經特殊設計之特殊應用積體電路(ASIC)補充或併入於經特殊設計之特殊應用積體電路(ASIC)中。 為此目的，控制系統160包括自一或多個量測系統155接收量測資料之分析程式1040。一般而言，分析程式1040執行判定如何修改或控制自第一輻射光束110遞送至目標材料120之能量或修改或控制第一輻射光束110之能量所需的所有分析，且可在基於脈衝間獲得量測資料的情況下基於脈衝間來執行此分析。 參看圖11，光源100 (在控制系統160之控制下)執行用於維持或控制經修改目標121之擴張率(ER)以藉此改良光源100之轉換效率之工序1100。光源100提供目標材料120 (1105)。舉例而言，目標材料供應系統125 (在控制系統160之控制下)可將目標材料120遞送至第一目標部位111。目標材料供應系統125可包括其自有致動系統(連接至控制系統160)及迫使目標材料通過之噴嘴，其中致動系統控制經導引通過噴嘴以產生導引朝向第一目標部位111之小滴串流的目標材料之量。 接下來，光源100將第一輻射光束110導引朝向目標材料120以將能量遞送至目標材料120，以修改目標材料120之幾何分佈以形成經修改目標121 (1110)。詳言之，將第一輻射光束110通過一或多個光學放大器之第一集合300而導引朝向目標材料120。舉例而言，光學源105可由控制系統160啟動以產生第一輻射光束110 (呈脈衝之形式)，該第一輻射光束可經導引朝向目標部位111內之目標材料120，如圖2中所展示。第一輻射光束110之焦平面(D1/2)可經組態以橫穿目標部位111。此外，在一些實施中，焦平面可與目標材料120重疊或與目標材料120之面對第一輻射光束110之邊緣重疊。可藉由(例如)將第一輻射光束110導引通過光束遞送系統150而將第一輻射光束110導引至目標材料120 (1110)，其中各種光學件可用以修改輻射110之方向或形狀或發散度使得其可與目標材料120相互作用。 可藉由使目標材料120與第一輻射光束110之涵蓋其共焦參數之區域重疊而將第一輻射光束110導引朝向目標材料120 (1110)。在一些實施中，第一輻射光束110之共焦參數可如此長使得光束腰(D1/2)容易涵蓋目標材料120，且由第一輻射光束110截取的目標材料120之表面積(其橫越X方向而量測)保持相對恆定，即使目標材料120之位置偏離光束腰D1/2之部位亦如此(如圖7A中所展示)。舉例而言，第一輻射光束110之共焦參數可大於1.5毫米。在其他實施中，第一輻射光束110之共焦參數如此短使得光束腰(D1/2)不涵蓋目標材料120，且在目標材料120之位置偏離光束腰D1/2之部位L1的情況下，由第一輻射光束110截取之目標材料120之表面積偏離相當多(如圖7B中所展示)。舉例而言，共焦參數可(例如)小於或等於2毫米。 經修改目標121將其形狀自恰好在受到第一輻射光束110影響之後的目標材料120之形狀改變成經擴張形狀，且此經擴張形狀隨著其遠離第一目標部位111飄移朝向第二目標部位116繼續變形。經修改目標121可具有自目標材料之形狀變形成具有實質上平面表面的熔融金屬之圓盤形體積之幾何分佈(諸如圖1及圖2中所展示)。根據擴張率而將經修改目標121變換成圓盤形體積。藉由根據擴張率使經修改目標121沿著至少一個軸線擴張而變換經修改目標121。舉例而言，如圖2中所展示，至少沿著大體上平行於X方向之長軸230來擴張經修改目標121。沿著不平行於第二輻射光束115之光軸(其為第二軸向方向217)之至少一個軸線來擴張經修改目標121。 儘管第一輻射光束110藉由改變目標材料120之形狀而主要與目標材料120相互作用，但有可能使第一輻射光束110以其他方式與目標材料120相互作用；舉例而言，第一輻射光束110可將目標材料120之一部分轉換成發射EUV光之電漿。然而，相比於自產生自經修改目標121的電漿發射之EUV光，自產生自目標材料120的電漿發射較少EUV光(歸因於經修改目標121與第二輻射光束115之間的後續相互作用)，且自第一輻射光束110對目標材料120之主要作用為為了形成經修改目標121進行的目標材料120之幾何分佈之修改。 光源100將第二輻射光束115導引朝向經修改目標121使得第二輻射光束將經修改目標121之至少部分轉換成發射EUV光之電漿129 (1115)。詳言之，光源100將第二輻射光束115通過一或多個光學放大器之第二集合305而導引朝向經修改目標121。舉例而言，光學源105可由控制系統160啟動以產生第二輻射光束115 (呈脈衝之形式)，該第二輻射光束可經導引朝向第二目標部位116內之經修改目標121，如圖2中所展示。第一集合300中之光學放大器中之至少一者可在第二集合305中，諸如圖5中所展示之實例。 光源100量測與相對於輻射光束110之目標材料120及經修改目標121中之一或多者相關聯的一或多個特性(例如，能量)(1120)。舉例而言，量測系統155量測在控制系統160之控制下之特性，且控制系統160自量測系統155接收量測資料。光源100基於該一或多個特性而控制在目標材料120處來自第一輻射光束110的放射曝光量(1125)。如上文所論述，放射曝光量為每單位面積自第一輻射光束110遞送至目標材料120之放射能量之量。換言之，放射曝光量為每單位面積由目標材料120之表面接收之放射能量。 在一些實施中，可量測之特性(1120)為第一輻射光束110之能量。在其他一般實施中，可量測之特性(1120)為目標材料120相對於第一輻射光束110之位置(例如，相對於第一輻射光束110之光束腰)之位置，此位置可在縱向(Z)方向上抑或在橫向於縱向方向之方向(例如，在X-Y平面中)予以判定。 可藉由量測自目標材料120之光學反射表面反射之輻射860之能量來量測第一輻射光束110之能量(諸如圖8B及圖8C中所展示)。可藉由量測自目標材料120之光學反射表面反射之輻射860橫越四個個別光電池之總強度來量測該輻射860之能量。 背向反射輻射860之總能量含量可結合關於第一輻射光束110之其他資訊而使用，以判定沿著Z方向或橫向於Z方向之方向(諸如，在X-Y平面中)在目標材料120與第一輻射光束110之光束腰之間的相對位置。或，可使用背向反射輻射860之總能量含量(連同其他資訊)以判定沿著Z方向在目標材料120與第一輻射光束之光束腰之間的相對位置。 可藉由量測導引朝向目標材料120之第一輻射光束110之能量來量測第一輻射光束110之能量(諸如圖8A中所展示)。可藉由量測橫越垂直於第一輻射光束110之傳播方向(第一軸向方向212)的方向之空間積分能量來量測第一輻射光束110之能量。 在一些實施中，可量測之特性(1120)為第一輻射光束110在其行進朝向目標材料120時之指向或方向(如圖8A中所展示)。關於指向之此資訊可用以判定目標材料120之位置與第一輻射光束110之軸線之間的疊對誤差。 在一些實施中，可量測之特性(1120)為目標材料120相對於目標位置之位置。目標位置可處於第一輻射光束110沿著Z方向之光束腰(D1/2)。可沿著平行於第一軸向方向212之方向量測目標材料120之位置。可量測相對於集光器135之主焦點990之目標位置。可沿著兩個或多於兩個非平行方向量測目標材料120之位置。 在一些實施中，可量測之特性(1120)為在第二輻射光束將經修改目標之至少部分轉換成電漿之前的經修改目標之大小。 在一些實施中，可量測之特性(1120)對應於經修改目標之擴張率之估計。 在一些實施中，可量測之特性(1120)對應於自目標材料120之光學反射表面反射的輻射860之特性(諸如圖8B及圖8C中所展示)。。此資訊可用以判定目標材料120與第一輻射光束110之光束腰之間的相對位置(例如，沿著Z方向)。可藉由使用置放於反射輻射860之路徑中的散光成像系統來判定或量測此空間特性。 在一些實施中，可量測之特性(1120)對應於相對於第一輻射光束110之角度的輻射860經導引所成之角度。此經量測角度可用以判定沿著橫向於Z方向之方向在目標材料120與第一輻射光束110之光束軸線之間的距離。 在其他實施中，可量測之特性(1120)對應於在第一輻射光束110與目標材料120相互作用之後形成的經修改目標121之空間態樣。舉例而言，可量測相對於方向(例如，在橫向於Z方向之X-Y平面中之方向)之經修改目標121之角度。關於經修改目標121之角度之此資訊可用以判定沿著橫向於Z方向之方向在目標材料120與第一輻射光束110之軸線之間的距離。作為另一實例，可在經修改目標121初次根據目標材料120與第一輻射光束110之間的相互作用而形成之後的預定或固定時間之後量測經修改目標121之大小或擴張率。關於經修改目標121之大小或擴張率之此資訊可用以在無人知曉第一輻射光束110之能量恆定的情況下判定沿著縱向方向(Z方向)在目標材料120與第一輻射光束110之光束腰之間的距離。 可針對第一輻射光束110之每一脈衝儘可能快速地量測特性(1120)。舉例而言，若量測系統155包括PEM或四重電池(4個PEM之配置)，則量測速率可與脈衝間一樣快。 另一方面，對於量測諸如目標材料120或經修改目標121之大小或擴張率之特性的量測系統155，可將攝影機用於該量測系統155，但攝影機通常慢得多，例如，攝影機可在約1赫茲至約200赫茲之速率下量測。 在一些實施中，可控制自第一輻射光束110遞送至目標材料120之放射曝光量之量(1125)以藉此控制或維持經修改目標之擴張率。在其他實施中，可藉由基於一或多個經量測特性判定是否應調整第一輻射光束110之特徵而控制自第一輻射光束110遞送至目標材料120之放射曝光量之量(1125)。因此，若判定出應調整第一輻射光束110之特徵，則(例如)可調整第一輻射光束110之脈衝之能量含量，或可調整第一輻射光束110在目標材料120之位置處之區域。可藉由調整第一輻射光束110之脈寬、第一輻射光束110之脈衝持續時間及第一輻射光束110之脈衝之平均或瞬時功率中的一或多者來調整第一輻射光束110之脈衝之能量含量。可藉由調整目標材料120與第一輻射光束110之光束腰之間的相對軸向(沿著Z方向)位置來調整與目標材料120相互作用之第一輻射光束110之區域。 在一些實施中，可針對第一輻射光束110之每一脈衝量測一或多個特性(1120)。以此方式，可針對第一輻射光束110之每一脈衝判定是否應調整第一輻射光束110之特徵。 在一些實施中，可藉由在經發射及收集之EUV光140之至少一部分正曝光微影工具之晶圓時控制自第一輻射光束110遞送至目標材料120之放射曝光量而控制該放射曝光量(例如，在放射曝光量之可接受範圍內)。 工序1100亦可包括收集自電漿發射之EUV光130之至少一部分(使用集光器135)；及將經收集EUV光140導引朝向晶圓以將晶圓曝光至EUV光140。 在一些實施中，一或多個經量測特性(1120)包括自經修改目標121反射之數個光子。可依據多少光子撞擊目標材料120而量測自經修改目標121反射之光子之數目。 如上文所論述，工序1100包括基於一或多個特性控制在目標材料120處來自第一輻射光束110的放射曝光量(1125)。舉例而言，可控制放射曝光量(1125)使得將放射曝光量維持在預定放射曝光量範圍內。放射曝光量為每單位面積自第一輻射光束110遞送至目標材料120之放射能量之量。換言之，放射曝光量為每單位面積由目標材料120之表面接收之放射能量。若控制曝光至第一輻射光束110或由第一輻射光束110截取的目標材料120之表面之單位面積(或將其維持在可接受範圍內)，則放射曝光量之此因數保持相對恆定，且有可能藉由將第一輻射光束110之能量維持在能量之可接受範圍內而控制目標材料120處之放射曝光量或維持目標材料120處之放射曝光量(1125)。存在用以將曝光至第一輻射光束110之目標材料120之表面的單位面積維持在面積之可接受範圍內之各種方式。接下來論述此等方式。 可控制在目標材料120處來自第一輻射光束110的放射曝光量(1125)使得將第一輻射光束110之脈衝能量維持(藉由使用經量測特性(1120)之回饋控制件)處於恆定位準或在可接受值之範圍內，而不管可造成能量波動之干擾。 在其他態樣中，可控制在目標材料120處來自第一輻射光束110的放射曝光量(1125)，使得藉由使用經量測特性(1120)之回饋控制件調整(例如，增加或減低)第一輻射光束110之脈衝能量，以補償目標材料120相對於第一輻射光束110之光束腰之位置在縱向(Z方向)置放上的誤差。 第一輻射光束110可為脈衝式輻射光束，使得光脈衝經導引朝向目標材料120 (1110)。相似地，第二輻射光束115可為脈衝式輻射光束使得光脈衝經導引朝向經修改目標121 (1115)。 目標材料120可為自目標材料供應系統125產生的目標材料120之小滴。以此方式，目標材料120之幾何分佈可經修改成經修改目標121，該經修改目標121變換成具有實質上平面表面的熔融金屬之圓盤形體積。根據擴張率將目標材料小滴變換成圓盤形體積。 參看圖12，藉由光源100執行工序1200 (在控制系統160之控制下)，以使由根據經修改目標121與第二輻射光束115之間的相互作用而形成的電漿129所產生之EUV光能量穩定。相似於以上之工序1100，光源100提供目標材料120 (1205)；光源100將第一輻射光束110導引朝向目標材料120以將能量遞送至目標材料120，以修改目標材料120之幾何分佈以形成經修改目標121 (1210)；且光源100將第二輻射光束115導引朝向經修改目標121使得第二輻射光束將經修改目標121之至少部分轉換成發射EUV光之電漿129 (1215)。光源100使用工序1110 (1220)控制自第一輻射光束110施加至目標材料120之放射曝光量。 藉由控制放射曝光量而使EUV光130之功率或能量穩定(1225)。由電漿129產生之EUV能量(或功率)取決於至少兩個函數，第一函數為轉換效率CE且第二函數為第二輻射光束115之能量。轉換效率為由第二輻射光束115轉換成電漿129的經修改目標121之百分比。轉換效率取決於若干變數，包括第二輻射光束115之峰值功率、經修改目標121在其與第二輻射光束115相互作用時之大小、經修改目標121相對於所要位置之位置、第二輻射光束115在其與經修改目標121相互作用時之橫向區域或大小。因為經修改目標121之位置及經修改目標121之大小取決於目標材料120如何與第一輻射光束110相互作用，所以藉由控制自第一輻射光束110施加至目標材料120之放射曝光量，吾人可控制經修改目標121之擴張率，且因此，吾人可控制此兩種因素。以此方式，可藉由控制放射曝光量而使轉換效率穩定或控制轉換效率(1220)，因此，此情形使由電漿129產生之EUV能量穩定(1225)。 亦參看圖13，在一些實施中，第一輻射光束110可由光學源105內之專用子系統1305A產生，且第二輻射光束115可由光學源105內之專用及分離子系統1305B產生，使得該等輻射光束110、115遵循在至各別第一目標部位111及第二目標部位116之道路上的兩個分離路徑。以此方式，輻射光束110、115中之每一者行進通過光束遞送系統150之各別子系統，且因此，其行進通過各別及分離光學操縱組件1352A、1352B及聚焦總成1356A、1356B。 舉例而言，子系統1305A可為基於固態增益介質之系統，而子系統1305B可為基於氣體增益介質(諸如由CO2 放大器產生之氣體增益介質)之系統。可用作子系統1305A之例示性固態增益介質包括摻鉺光纖雷射及摻釹釔鋁石榴石(Nd:YAG)雷射。在此實例中，第一輻射光束110之波長可相異於第二輻射光束115之波長。舉例而言，使用固態增益介質之第一輻射光束110之波長可為約1微米(例如，約1.06微米)，且使用氣體介質之第二輻射光束115之波長可為約10.6微米。 其他實施處於以下申請專利範圍之範疇內。Techniques for increasing conversion efficiency of extreme ultraviolet (EUV) light generation are disclosed. Referring to FIG. 1 and discussed in more detail below, the interaction between the target material 120 and the first radiation beam 110 causes the target material to deform and geometrically expand to thereby form the modified target 121 . The geometric expansion rate of the modified target 121 is controlled in a manner that increases the amount of available EUV light 130 converted from the plasma due to the interaction between the modified target 121 and the second radiation beam 115 . The amount of available EUV light 130 is the amount of EUV light 130 that can be harnessed for use at optical device 145 . Thus, the amount of available EUV light 130 may depend on several aspects, such as the bandwidth or center wavelength of the optical components used to utilize the EUV light 130 . Control of the geometric expansion rate of the modified target 121 enables control of the size or geometrical aspect of the modified target 121 as it interacts with the second radiation beam 115 . For example, an adjustment of the geometric expansion rate of the modified target 121 adjusts the density of the modified target 121 as the modified target 121 interacts with the second radiation beam 115 since the modified target 121 interacts with the second radiation beam 115 The density of the modified target 121 when the two radiation beams 115 interact affects the total amount of radiation absorbed by the modified target 121 and the area over which this radiation is absorbed. As the density of modified targets 121 increases, at some point EUV light 130 will not be able to escape from the modified targets 121 and thus the amount of available EUV light 130 may decrease. As another example, adjustment of the geometric expansion rate of the modified target 121 adjusts the surface area of the modified target 121 as the modified target 121 interacts with the second radiation beam 115 . In this way, the total amount of usable EUV light 130 produced can be increased or controlled by controlling the dilation rate of the modified target 121 . In particular, the size of the modified target 121 and its rate of dilation depend on the radiation exposure applied to the target material 120 from the first radiation beam 110, which is the area of the target material 120 delivered by the first radiation beam 110 amount of energy. Thus, the expansion rate of the modified target 121 can be maintained or controlled by maintaining or controlling the amount of energy delivered to the target material 120 per unit area. The amount of energy delivered to the target material 120 depends on the energy of the first radiation beam 110 just before the first radiation beam 110 impinges on the surface of the target material. The energy of the pulses in the first radiation beam 110 can be determined by integrating the laser pulse signal measured by the fast photodetector. Detectors can be photoelectromagnetic (PEM) detectors for long-wavelength infrared (LWIR) radiation, InGaAs diodes for measuring near-infrared (IR) radiation, or silicon for visible or near-IR radiation. diode. The dilation rate of the modified target 121 depends at least in part on the amount of energy in the pulses of the first radiation beam 110 intercepted by the target material 120 . In a hypothetical baseline design, it is assumed that the target material 120 is always the same size and is placed in the waist of the focused first radiation beam 110 . In practice, however, the target material 120 may have a small but generally constant axial position offset relative to the beam waist of the first radiation beam 110 . One factor controlling the dilation rate of the modified target 121, if all these factors are held constant, is for the pulses of the first radiation beam 110 to have a duration of a few nanoseconds to 100 nanoseconds for the pulses of the first radiation beam energy. Another factor that may control the dilation rate of the modified target 121 if the pulses of the first radiation beam 110 have a duration at or below 100 nanoseconds is the instantaneous peak power of the first radiation beam 110 . If the pulses of the first radiation beam 110 have a shorter (eg, on the order of picoseconds (ps)) duration, other factors may control the expansion rate of the modified target 121, as discussed below. As shown in FIG. 1 , an optical source 105 (also referred to as a driving source or a driving laser) is used to drive a laser produced plasma (LPP) extreme ultraviolet (EUV) light source 100 . The optical source 105 generates a first radiation beam 110 which is provided to a first target site 111 and a second radiation beam 115 which is provided to a second target site 116 . The first radiation beam 110 and the second radiation beam 115 can be pulsed amplified beams. The first target site 111 receives a target material 120 , such as tin, from a target material supply system 125 . The interaction between the first radiation beam 110 and the target material 120 delivers energy to the target material 120 to modify or change its shape (eg, deform its shape) such that the geometric distribution of the target material 120 deforms into a modified target 121 . The target material 120 is generally directed from the target material supply system 125 along the −X direction or along the direction in which the target material 120 is placed within the first target site 111 . After the first radiation beam 110 delivers energy to the target material 120 to deform it into the modified target 121, the modified target 121 may continue to move in addition to moving in another direction, such as a direction parallel to the Z direction. Move in the -X direction. As the modified target 121 moves away from the first target site 111 , its geometric distribution continues to deform until the modified target 121 reaches the second target site 116 . The interaction between the second radiation beam 115 and the modified target 121 (at the second target site 116 ) converts at least part of the modified target 121 into a plasma 129 which emits EUV light or radiation 130 . A collector system (or collector) 135 collects EUV light 130 and directs the EUV light 130 as collected EUV light 140 toward an optical device 145 such as a lithography tool. The first target site 111 and the second target site 116 and the light collector 135 may be housed within a chamber 165 that provides a controlled environment suitable for generating EUV light 140 . It is possible that some of the target material 120 is converted into a plasma when it interacts with the first radiation beam 110, and thus this plasma is likely to emit EUV radiation. However, the properties of the first radiation beam 110 are selected and controlled such that the primary effect of the first radiation beam 110 on the target material 120 is to deform or modify the geometric distribution of the target material 120 to form the modified target 121 . Each of the first radiation beam 110 and the second radiation beam 115 is directed towards a respective target site 111 , 116 by a beam delivery system 150 . The beam delivery system 150 may include a number of optical steering components 152 and a focusing assembly 156 that focuses the first radiation beam 110 or the second radiation beam 115 into respective first and second focal regions. The first focus area and the second focus area may overlap with the first target part 111 and the second target part 116 respectively. The optical assembly 152 may include optical elements, such as lenses and/or mirrors, that guide the radiation beams 110, 115 by refraction and/or reflection. The beam delivery system 150 may also include elements to control and/or move the optical assembly 152 . For example, beam delivery system 150 may include actuators controllable to move optical elements within optical assembly 152 . Referring also to FIG. 2 , the focusing assembly 156 focuses the first radiation beam 110 such that the diameter D1 of the first radiation beam 110 is at a minimum in the first focusing region 210 . In other words, the focusing assembly 156 converges the first radiation beam 110 as it propagates towards the first focusing region 210 in the first axial direction 212 , which is the general direction of propagation of the first radiation beam 110 . The first axial direction 212 extends along a plane defined by the XZ axes. In this example, the first axial direction 212 is parallel or nearly parallel to the Z direction, but it could be along an angle with respect to Z. In the absence of the target material 120 , the first radiation beam 110 diverges as it propagates away from the first focal zone 210 in the first axial direction 212 . In addition, the focusing assembly 156 focuses the second radiation beam 115 such that the diameter D2 of the second radiation beam 115 is at a minimum in the second focus region 215 . Thus, the focusing assembly converges the second radiation beam 115 as it propagates towards the second focusing region 215 in the second axial direction 217 , which is the general direction of propagation of the second radiation beam 115 . The second axial direction 217 also extends along the plane defined by the XZ axes, and in this example, the second axial direction 217 is parallel or nearly parallel to the Z direction. In the absence of the modified target 121 , the second radiation beam 115 diverges as it propagates away from the second focal zone 215 along the second axial direction 217 . As discussed below, EUV light source 100 also includes one or more metrology systems 155 , a control system 160 , and a beam adjustment system 180 . Control system 160 is connected to other components within light source 100 , such as metrology system 155 , beam delivery system 150 , target material supply system 125 , beam adjustment system 180 and optical source 105 . The metrology system 155 can measure one or more characteristics within the light source 100 . For example, the one or more properties may be properties associated with the target material 120 or the modified target 121 relative to the first radiation beam 110 . As another example, the one or more characteristics may be the pulse energy of the first radiation beam 110 directed towards the target material 120 . Such examples will be discussed in more detail below. The control system 160 is configured to receive one or more measured characteristics from the metrology system so that it can control how the first radiation beam 110 interacts with the target material 120 . For example, control system 160 may be configured to maintain the amount of energy delivered from first radiation beam 110 to target material 120 within a predetermined energy range. As another example, control system 160 may be configured to control the amount of energy directed from first radiation beam 110 to target material 120 . The beam conditioning system 180 is comprised of components within the optical source 105 or comprises components within the optical source 105 to thereby control properties of the first radiation beam 110 such as pulse width, pulse energy, instantaneous power within a pulse, or average power) of the components of the system. 3A, in some implementations, the optical source 105 includes: a first optical amplifier system 300 comprising a series of one or more optical amplifiers through which the first radiation beam 110 passes; and a second optical amplifier system 305 comprising The second radiation beam 115 is passed through a series of one or more optical amplifiers. One or more amplifiers from the first system 300 may be in the second system 305 ; or one or more amplifiers in the second system 305 may be in the first system 300 . Alternatively, it is possible to completely separate the first optical amplifier system 300 from the second optical amplifier system 305 . Additionally, although not required, the optical source 105 may include a first light generator 310 that generates a first pulsed beam 311 and a second light generator 315 that generates a second pulsed beam 316 . The light generators 310, 315 may each be, for example, a laser, a seed laser such as a master oscillator, or a lamp. Exemplary light generators that may be used as light generators 310, 315 are Q-switched, radio frequency (RF) pumped, axial flow, carbon dioxide ( CO2 ) oscillators operable at repetition rates of, for example, 100 kHz . The optical amplifiers within the optical amplifier systems 300, 305 each contain a gain medium on a respective beam path along which the beam 311, 316 from the respective light generator 310, 315 propagates. When the gain medium of the optical amplifier is excited, the gain medium provides photons to the beam, amplifying the beam 311 , 316 to produce an amplified beam which forms the first 110 or second 115 radiation beam. The wavelengths of the beams 311 , 316 or the wavelengths of the radiation beams 110 , 115 may be different from each other such that the radiation beams 110 , 115 may be separated from each other if they are combined at any point within the optical source 105 . If the radiation beams 110, 115 are generated by CO amplifiers, the first radiation beam 110 may have a wavelength of 10.26 microns (µm) or 10.207 microns, and the second radiation beam 115 may have a wavelength of 10.59 microns. These wavelengths are chosen to allow easier separation of the two radiation beams 110, 115 using dispersive optics or dichroic mirrors or beam splitter coatings. In the case where both radiation beams 110, 115 propagate together in the same amplifier chain (e.g. where some amplifiers of optical amplifier system 300 are in optical amplifier system 305), then distinct wavelengths can be used to adjust the two radiation beams 110, 115 (even though the two radiation beams 110, 115 traverse the same amplifier). For example, once separated, the radiation beams 110, 115 may be steered or focused to two separate locations within the chamber 165, such as the first target site 111 and the second target site 116, respectively. In particular, the separation of the radiation beams 110 , 115 also enables the modified target 121 to expand after the first radiation beam 110 interacts with the first radiation beam 110 as it travels from the first target site 111 to the second target site 116 . The optical source 105 may include a beam path combiner 325 that superimposes the first radiation beam 110 and the second radiation beam 115 and places the radiation beams 110, 115 in relation to the optical source 105 and the beam delivery system. At least some of the distances between 150 are on the same optical path. An exemplary beam path combiner 325 is shown in FIG. 3B. The beam path combiner 325 includes a pair of dichroic beam splitters 340 , 342 and a pair of mirrors 344 , 346 . The dichroic beam splitter 340 enables the first radiation beam 110 to pass along a first path to the dichroic beam splitter 342 . The dichroic beam splitter 340 reflects the second radiation beam 115 along a second path, wherein the second radiation beam 115 is reflected from mirrors 344, 346 which redirect the second radiation beam 115 towards the dichroic beam splitting device 342. The first radiation beam 110 passes freely through the dichroic beam splitter 342 onto the output path, while the second radiation beam 115 is reflected from the dichroic beam splitter 342 onto the output path such that the first radiation beam 110 and the second radiation Both beams 115 overlap on the output path. In addition, the optical source 105 may comprise a beam path splitter 326 that separates the first radiation beam 110 from the second radiation beam 115 such that the two radiation beams 110, 115 are separably steered and focused on the chamber Within 165. An exemplary beam path splitter 326 is shown in FIG. 3C. The beam path splitter 326 includes a pair of dichroic beam splitters 350 , 352 and a pair of mirrors 354 , 356 . The dichroic beam splitter 350 receives the superimposed pair of radiation beams 110, 115, reflects the second radiation beam 115 along a second path, and transmits the first radiation beam 110 along a first path towards the dichroic beam splitting device 352. The first radiation beam 110 freely passes through the dichroic beam splitter 352 along a first path. The second radiation beam 115 reflects from the mirrors 354, 356 and returns to the dichroic beam splitter 352, where it is reflected onto a second path different from the first path. Additionally, the first radiation beam 110 may be configured to have less pulse energy than the pulse energy of the second radiation beam 115 . This is because the first radiation beam 110 is used to modify the geometry of the target material 120 and the second radiation beam 115 is used to convert the modified target 121 into a plasma 129 . For example, the pulse energy of the first radiation beam 110 can be as small as 1/5 to 1/100 of the pulse energy of the second radiation beam 115 . In some implementations as shown in FIGS. 4A and 4B , the optical amplifier system 300 or 305 includes a set of three optical amplifiers 401, 402, 403 and 406, 407, 408, respectively, although as few as one amplifier or as many on three amplifiers. In some implementations, each of the optical amplifiers 406, 407, 408 includes a gain medium that includes CO2 ; and can amplify between about 9.1 microns and about 11.0 microns and particularly Light at a wavelength of about 10.6 microns. It is possible to operate the optical amplifiers 401, 402, 403 in a similar manner or at different wavelengths. Suitable amplifiers and lasers for use in optical amplifier systems 300, 305 may include pulsed laser devices, such as, for example, operating at relatively high power (e.g., 10 kW or higher) and high pulse repetition rate (e.g., 50 DC or RF excitation operating at kHz or greater) produces a pulsed gas discharge CO2 amplifier at radiation at about 9.3 microns or about 10.6 microns. Exemplary optical amplifiers 401, 402, 403 or 406, 407, 408 are axial flow high power CO2 lasers using wear-free gas circulation and capacitive RF excitation, such as the TruFlow® manufactured by TRUMPF Corporation of Farmington, Connecticut CO2 laser. Additionally, although not required, one or more of the optical amplifier systems 300 and 305 may include a first amplifier that acts as a preamplifier 411, 421, respectively. The preamplifiers 411, 421 (if present) may be diffusion cooled CO2 laser systems, such as the TruCoax CO2 laser system manufactured by TRUMPF Corporation of Farmington, Connecticut. The optical amplifier systems 300, 305 may include optical elements not shown in FIGS. 4A and 4B for directing and shaping the respective light beams 311, 316. For example, optical amplifier systems 300, 305 may include reflective optics such as mirrors, partially transmissive optics such as beam splitters or partially transmissive mirrors, and dichroic beam splitters. The optical source 105 also includes an optical system 320, which may include one or more optical elements for directing the light beams 311, 316 through the optical source 105, such as reflective optics such as mirrors, partially reflective optics, and Partially transmissive optics (such as beam splitters), refractive optics (such as lenses or lenses), passive optics, active optics, etc.). Although the optical amplifiers 401, 402, 403 and 406, 407, 408 are shown as separate blocks, it is possible that at least one of the amplifiers 401, 402, 403 is in the optical amplifier system 305 and that the amplifiers 406, 407 At least one of , 408 may be in the optical amplifier system 300 . For example, as shown in FIG. 5 , amplifiers 402, 403 correspond to respective amplifiers 407, 408, and optical amplifier systems 300, 305 include additional optical elements 500, such as beam path combiners 325, for In combining the two beams output from amplifiers 401, 406 into a single path through amplifiers 402/407 and amplifiers 403/408. In such a system in which at least some of the amplifiers overlap the optics between the optical amplifier systems 300, 305, it is possible to couple the first radiation beam 110 and the second radiation beam 115 together such that one or more of the first radiation beams 110 A change in one of the properties may result in a change in one or more properties of the second radiation beam 115, and vice versa. Therefore, it becomes more important to control the energy within the system, such as the energy of the first radiation beam 110 or the energy delivered to the target material 120 . In addition, the optical amplifier system 300, 305 also includes an optical element 505 (such as a beam path splitter 326) for splitting the two beams 110, 15 output from the amplifier 403/408 such that the two beams 110, 115 Can be guided to respective target sites 111 , 116 . The target material 120 may be any material including a target material that emits EUV light when converted into a plasma. Target material 120 may be a target mixture including target species and impurities such as non-target particles. The target substance is a substance that can be converted into a plasmonic state with an emission line in the EUV range. The target substance can be, for example, a droplet of liquid or molten metal, a portion of a liquid stream, a solid particle or cluster, a solid particle contained within a droplet, a foam of target material, or a portion of a liquid stream. Contains solid particles. The target species can be, for example, water, tin, lithium, xenon, or any material that has an emission line in the EUV range when converted to a plasma state. For example, the target species can be elemental tin, which can be used as pure tin (Sn); as tin compounds, such as SnBr 4 , SnBr 2 , SnH 4 ; as tin alloys, such as tin-gallium alloys, tin - Indium alloys, tin-indium-gallium alloys, or any combination of these alloys. Furthermore, the target material includes only the target substance in the absence of impurities. The following discussion provides an example where target material 120 is a droplet made of molten metal, such as tin. However, target material 120 may take other forms. Target material 120 may be provided to first target site 111 by passing molten target material through a nozzle of target material supply 125 and allowing target material 120 to drift into first target site 111 . In some implementations, the target material 120 can be guided to the first target site 111 by force. The shape of the target material 120 is changed or modified (eg, the shape of the target material 120 is deformed) by irradiating the target material 120 with radiation pulses from the first radiation beam 110 before the target material 120 reaches the second target site 116 . The interaction between first radiation beam 110 and target material 120 causes material to be ablated from the surface of target material 120 (and modified target 121), and this ablation provides the force that deforms target material 120 into modified target 121, which is modified The modified target 121 has a shape different from that of the target material 120 . For example, the target material 120 may have a shape similar to a droplet, and the modified target 121 deforms in shape so that when the modified target 121 reaches the second target site 116, its shape is closer to that of a disc (such as a disc cake). shape). The modified target 121 may be non-ionized material (material that is not plasma) or minimally ionized material. The modified target 121 can be, for example, a disk of liquid or molten metal, a continuous segment of target material with no or substantial gaps, a mist of micro-ions or nanoparticles, or a cloud of atomic vapor. For example, as shown in FIG. 2, modified target 121 expands into a disc-shaped sheet of molten metal within second target site 116 after about time T2-T1, which may be on the order of microseconds (µs). piece 121. In addition, the interaction between the first radiation beam 110 and the target material 120 that ablate material from the surface of the target material 120 (and the modified target 121) can provide a force that can cause the modified target 121 to move along the Z direction to obtain a certain propulsion or velocity. The expansion of the modified target 121 in the X direction and the acquired velocity in the Z direction depend on the energy of the first radiation beam 110 and in particular on the energy delivered to (i.e. intercepted by) the target material 120 . For example, for a constant target material 120 size and for long pulses of the first radiation beam 110 (a long pulse is a pulse with a duration between a few nanoseconds (ns) and 100 nanoseconds), the dilation rate is related to the first The energy per unit area (J/cm2) of the radiation beam 110 scales linearly. Energy per unit area is also known as radiation exposure or flux. The radiation exposure is the radiation energy received by the surface of the target material 120 per unit area, or equivalently, the irradiance of the surface of the target material 120 integrated over the time the target material 120 is irradiated. As another example, the relationship between the expansion rate and the energy of the first radiation beam 110 may be different for a constant target material 120 size and for short pulses (pulses with a duration of less than a few hundred picoseconds (ps)). In this system, a shorter pulse duration is correlated with an increase in the intensity of the first radiation beam 110, which interacts with the target material 120, and which behaves like a shock wave. In this system, the dilation rate mainly depends on the intensity I of the first radiation beam 110, and this intensity is equal to the energy E of the first radiation beam divided by the spot size of the first radiation beam 110 interacting with the target material 120 (horizontal Cross-sectional area A) and pulse duration (τ), or I = E/(τ of the range of A·121). In this picosecond-pulse duration regime, the modified target 121 expands so as to form a mist. In addition, the angular orientation (angle relative to the Z or X direction) of the disc shape of the modified target 121 depends on the position of the first radiation beam 110 when it hits the target material 120 . Therefore, if the first radiation beam 110 hits the target material 120 such that the first radiation beam 110 encompasses the target material and the beam waist of the first radiation beam 110 is centered on the target material 120, it is more likely that the modified target 121 The shape of the disk will be aligned with its major axis 230 parallel to the X direction and its minor axis 235 parallel to the Z direction. The first radiation beam 110 is composed of radiation pulses, and each pulse may have a duration. Similarly, the second radiation beam 115 is composed of radiation pulses, and each pulse may have a duration. Pulse duration may be represented by a certain percentage high (eg, half-maximum) width, ie, the amount of time the pulse's intensity is at least a percentage of the pulse's maximum intensity. However, other metrics can be used to determine pulse duration. The pulse duration of the pulses within the first radiation beam 110 can be, for example, 30 nanoseconds (ns), 60 nanoseconds, 130 nanoseconds, 50 nanoseconds to 250 nanoseconds, 10 picoseconds to 200 picoseconds (ps) , or less than 1 nanosecond. The energy of the first radiation beam 110 may be, for example, 1 millijoule (mJ) to 100 millijoule (mJ). The wavelength of the first radiation beam 110 can be, for example, 1.06 microns, 1 micron to 10.6 microns, 10.59 microns or 10.26 microns. As discussed above, the dilation rate of the modified target 121 depends on the radiation exposure (energy per unit area) of the first radiation beam 110 that intercepts the target material 120 . Thus, for a pulse of the first radiation beam 110 having a duration of about 60 nanoseconds and an energy of about 50 mJ, the actual radiation exposure depends on how tightly the first radiation beam 110 is focused at the first focal region 210 . In some examples, the radiation exposure at target material 120 may be about 400 J/cm2 to 700 J/cm2. However, the amount of radiation exposure is very sensitive to the location of the target material 120 relative to the first radiation beam 110 . The second radiation beam 115 may be referred to as the main beam and it consists of pulses released at a repetition rate. Second radiation beam 115 has sufficient energy to convert target species within modified target 121 into a plasma that emits EUV light 130 . The pulses of the first radiation beam 110 and the pulses of the second radiation beam 115 are separated in time by a delay time, such as 1 microsecond to 3 microseconds (μs), 1.3 microseconds, 1 microsecond to 2.7 microseconds, 3 microseconds to 4 microseconds, or any amount of time to allow modified target 121 to expand into the disk shape of the desired size shown in FIG. 2 . Thus, as modified target 121 expands and elongates in the XY plane, modified target 121 undergoes two-dimensional expansion. The second radiation beam 115 may be configured such that it is slightly defocused when it hits the modified target 121 . This defocusing scheme is shown in Figure 2. In this case, the second focal region 215 is at a different location along the Z direction than the long axis 230 of the modified target 121 ; moreover, the second focal region 215 is outside the second target location 116 . In this scheme, the second focal zone 215 is placed in front of the modified target 121 along the Z direction. That is, the second radiation beam 115 reaches focus (or beam waist) before the second radiation beam 115 hits the modified target 121 . Other defocusing schemes are possible. For example, as shown in FIG. 6, a second focal region 215 is placed behind the modified target 121 along the Z direction. In this way, the second radiation beam 115 reaches focus (or beam waist) after the second radiation beam 115 hits the modified target 121 . Referring again to FIG. 2 , the rate at which the modified target 121 expands as it moves (eg, drifts) from the first target site 111 to the second target site 116 may be referred to as the expansion rate (ER). At the first target site 111 , the modified target 121 has an intercepted extent (or length) S1 along the major axis 230 just after the target material 120 is impinged by the first radiation beam 110 at time T1 . When the modified target 121 reaches the second target site 116 at time T2 , the modified target 121 has a range S2 intercepted along the major axis 230 . The dilation rate is the difference in range (S2-S1) of the intercepted modified target 121 along the major axis 230 divided by the time difference (T2-T1), thus:
Figure 02_image001
While the modified target 121 expands along the major axis 230 , it is also possible to compress or thin the modified target 121 along the minor axis 235 . The two-step approach discussed above in which the modified target 121 is formed by interacting the first radiation beam 110 with the target material 120 results in a conversion efficiency of about 3% to 4%, and then by The modified target 121 is converted to plasma by interacting the modified target 121 with the second radiation beam 115 . In general, it is desirable to increase the conversion rate of light from the optical source 105 to EUV radiation 130 because too low a conversion efficiency may require increasing the amount of power that the optical source 105 needs to deliver, which increases the cost of operating the optical source 105 and It also increases the heat load on all components within the light source 100 and can lead to increased debris generation within the chamber housing the first target site 111 and the second target site 116 . The increase in conversion efficiency can help meet the requirements for high volume manufacturing tools while keeping the optical source power requirements within acceptable limits. Various parameters affect the conversion efficiency, such as the wavelength of the first radiation beam 110 and the second radiation beam 115 , the target material 120 , and the pulse shape, energy, power and intensity of the radiation beams 110 , 115 . Conversion efficiency can be defined as the EUV energy generated by EUV light 130 divided by 2π solid angle and the (multilayer ) divided by the 2% bandwidth of the central wavelength of the reflectance curve of the mirror surface by the energy of the irradiation pulse of the second radiation beam 115 . In one example, the center wavelength of the reflectance curve is 13.5 nanometers (nm). One way to increase, maintain or optimize the conversion efficiency would be to control or stabilize the energy of the EUV light 130, and in order to do this it becomes important to modify the dilation rate of the target 121 (and other parameters) are maintained within an acceptable range of values. The dilation rate of the modified target 121 is maintained within an acceptable range of values by maintaining the radiation exposure from the first radiation beam 110 on the target material 120 . Also, radiation exposure may be maintained based on one or more measured characteristics associated with the target material 120 or modified target 121 relative to the first radiation beam 110 . The radiation exposure is the radiation energy received by the surface of the target material 120 per unit area. Accordingly, the radiation exposure can be estimated or approximated as the amount of energy directed towards the surface of the target material 120 if the area of the target material 120 remains constant from pulse to pulse. There are different methods or techniques to maintain the dilation rate of the modified target 121 within an acceptable range of values. Also, the method or technique used may depend on certain properties associated with the first radiation beam 110 . The conversion efficiency is also affected by other parameters, such as the size or thickness of the target material 120, the position of the target material 120 relative to the first focal region 210, or the angle of the target material 120 relative to the xy plane. One attribute that can affect how radiation exposure is maintained is the confocal parameter of the first radiation beam 110 . The confocal parameter of the radiation beam is twice the Rayleigh length of the radiation beam, and the Rayleigh length is the distance along the direction of propagation of the radiation beam from the waist to the point where the cross-sectional area doubles. Referring to FIG. 2 , for a radiation beam 110 , the Rayleigh length is the distance along the propagation direction 212 of the first radiation beam 110 from its waist (which is D1/2 ) to the point where the cross-section of the first beam is doubled. For example, as shown in FIG. 7A, the confocal parameter of the first radiation beam 110 is so long that the beam waist (D1/2) easily covers the target material 120, and the portion of the target material 120 intercepted by the first radiation beam 110 The surface area (as measured across the X direction) remains relatively constant even though the position of the target material 120 is offset by the beam waist D1/2. For example, the surface area of the target material 120 intercepted by the first radiation beam 110 at location L1 is within 20% of the surface area of the target material 120 intercepted by the first radiation beam 110 at location L2. In this first situation (wherein the surface area of the target material 120 intercepted by the first radiation beam 110 is less likely to deviate from the mean value (compared to the second situation described below)), it can be achieved by maintaining The amount of energy 110 directed to the target material 120 is used to maintain or control the radiation exposure and, thus, the dilation rate (without taking into account the surface area of the target material 120 exposed by the first radiation beam 110). As another example, as shown in FIG. 7B , the confocal parameters of the first radiation beam 110 are so short that the beam waist ( D1/2 ) does not encompass the target material 120 and is offset from the beam waist D1 at the location of the target material 120 In the case of the portion L1 of /2, the surface area of the target material 120 intercepted by the first radiation beam 110 deviates from the average value. For example, the surface area of the target material 120 intercepted by the first radiation beam 110 at the location L1 is substantially different from the surface area of the target material 120 intercepted by the first radiation beam 110 at the location L2. In this second scenario where the surface area of the target material 120 intercepted by the first radiation beam 110 is more likely to deviate from the average (compared to the first scenario), it is possible to control the The amount of energy of 120 to maintain or control the radiation exposure and (therefore) expansion rate. In order to control the radiation exposure, the radiation energy of the first radiation beam 110 received by the surface of the target material 120 per unit area is controlled. It is therefore important to control the energy of the pulses of the first radiation beam 110 and the region of the first radiation beam 110 where the target material 120 intercepts the first radiation beam 110 . The region of the first radiation beam 110 where the target material 120 intercepts the first radiation beam 110 is related to the surface of the target material 120 intercepted by the first radiation beam 110 . Another factor that can affect the area of the first radiation beam 110 where the target material 120 intercepts the first radiation beam 110 is the stability of the location and size of the beam waist D1/2 of the first radiation beam 110 . For example, if the waist size and position of the first radiation beam 110 are constant, then one can control the position of the target material 120 relative to the beam waist D1/2. The waist size and position of the first radiation beam 110 may vary due to, for example, thermal effects in the optical source 105 . In general, it becomes important to maintain a constant energy of the pulses in the first radiation beam 110 and also to control other aspects of the optical source 105 such that the target material 120 arrives at a known axis relative to the beam waist D1/2 (Z-direction) position without much variation about that position. All described methods to maintain or control the expansion rate of the modified target 121 within an acceptable range of values use the use of the metrology system 155 described next. Referring again to FIG. 1 , metrology system 155 measures at least one characteristic associated with any one or more of target material 120 , modified target 121 , and first radiation beam 110 . For example, the measurement system 155 can measure the energy of the first radiation beam 110 . As shown in FIG. 8A , an exemplary metrology system 855A measures the energy of the first radiation beam 110 directed to the target material 120 . As shown in FIG. 8B , exemplary metrology system 855B measures the energy of radiation 860 reflected from target material 120 after first radiation beam 110 interacts with target material 120 . The reflection of the radiation 860 from the target material 120 can be used to determine the location of the actual position of the target material 120 relative to the first radiation beam 110 . In some implementations, an exemplary metrology system 855B can be placed within the optical amplifier system 300 of the optical source 105, as shown in FIG. 8C. In this example, metrology system 855B may be positioned to measure the reflection of light impinging on or reflecting off one of the optical elements within optical amplifier system 300, such as a thin film polarizer. The amount of energy in the radiation 860. The amount of radiation 860 reflected from target material 120 is proportional to the amount of energy delivered to target material 120; thus, by measuring reflected radiation 860, the amount of energy delivered to target material 120 can be controlled or maintained. Additionally, the amount of energy measured in the first radiation beam 110 or reflected radiation 860 is related to the number of photons in the beam. Accordingly, measurement system 855A or 855B may measure the number of photons in the respective beams. Additionally, the metrology system 855B may be considered to measure the number of photons reflected from the target material 120 (which becomes the modified target 121 after it is struck by the first radiation beam 110 ) in terms of how many photons impacted the target material 120 . Metrology system 855A or 855B may be a photosensor, such as an array of photocells (eg, a 2x2 array or a 3x3 array). Photocells have sensitivity to the wavelength of the light to be measured, and they have sufficient speed or bandwidth for the duration of the light pulse to be measured. In general, the measurement system 855A or 855B can measure the energy of the radiation beam 110 by measuring the spatially integrated energy across a direction perpendicular to the propagation direction of the first radiation beam 110 . Because the measurement of the beam energy can be performed quickly, it is possible to take a measurement for each pulse emitted in the first radiation beam 110, and thus the measurement and control can be performed on a pulse-to-pulse basis. Metrology systems 855A, 855B may be fast optical detectors, such as photoelectromagnetic (PEM) detectors adapted for long wavelength infrared (LWIR) radiation. The PEM detector can be a silicon diode for measuring near-infrared radiation or visible radiation, or an InGaAs diode for measuring near-infrared radiation. The energy of the pulses in the first radiation beam 110 can be determined by integrating the laser pulse signals measured by the measurement systems 855A, 855B. Referring to FIG. 9A , the metrology system 155 may be an exemplary metrology system 955A that measures the position Tpos of the target material 120 relative to the target position. The target location may be at the beam waist of the first radiation beam 110 . The position of the target material 120 may be measured along a direction parallel to the beam axis of the first radiation beam 110 , such as the first axial direction 212 . Referring to FIG. 9B , the metrology system 155 may be an exemplary metrology system 955B that measures the position Tpos of the target material 120 relative to the primary focal point 990 of the light collector 135 . The measurement system 955B may include a laser and/or a camera that reflects off the target material 120 as it approaches the target material 120 to measure the position of the target material 120 and the time of arrival of the target material 120 relative to a coordinate system within the chamber 165 . Referring to FIG. 9C , metrology system 155 may be an exemplary metrology system 955C that measures the size of modified target 121 at a location before modified target 121 interacts with second radiation beam 115 . For example, metrology system 955C may be configured to measure size Smt of modified target 121 while modified target 121 is within second target site 116 but before modified target 121 is struck by second radiation beam 115 . Metrology system 955C may also determine the orientation of modified target 121 . The metrology system 955C may use image-graphic techniques with a pulsed backlight illuminator and a camera, such as a charge-coupled device camera. Metrology system 155 may include a collection of metrology subsystems, each designed to measure a particular characteristic and at different rates or sampling intervals. This set of subsystems can work together to provide a clear understanding of how the first radiation beam 110 interacts with the target material 120 to form the modified target 121 . Metrology system 155 may include a plurality of EUV sensors within chamber 165 for detecting radiation generated by modified target 121 after it interacts with second radiation beam 115 Plasma emitted EUV energy. By detecting the emitted EUV energy it is possible to obtain information about the angle of the modified target 121 or the lateral offset of the second beam relative to the second radiation beam 115 . A beam adjustment system 180 is used under the control of the control system 160 to enable control of the amount of energy (radiation exposure) delivered to the target material 120 . Radiation exposure can be controlled by controlling the amount of energy within the first radiation beam 110 assuming a constant area of the first radiation beam 110 at the location where it interacts with the target material 120 . Beam adjustment system 180 receives one or more signals from control system 160 . Beam adjustment system 180 is configured to adjust one or more characteristics of optical source 105 to maintain or control the amount of energy delivered to target material 120 (ie, radiation exposure) to target material 120 . Thus, the beam adjustment system 180 may include one or more actuators for controlling the characteristics of the optical source 105, which may be mechanical, electrical, optical, electromagnetic or any other means for modifying the characteristics of the optical source 105. Appropriate force device. In some implementations, the beam adjustment system 180 includes a pulse width adjustment system coupled to the first radiation beam 110 . The pulse width adjustment system is configured to adjust the pulse width of the first radiation beam 110 . In this implementation, the pulse width modulation system may include an electro-optic modulator, such as a Bockel cell. For example, a Bockel cell is disposed within the light generator 310, and by turning on the Bockel cell for a shorter or longer period of time, the pulses transmitted by the Bockel cell (and thus, emitted from the light generator 310 pulse) can be adjusted to be shorter or longer. In other implementations, the beam conditioning system 180 includes a pulsed power conditioning system coupled to the first radiation beam 110 . The pulse power adjustment system is configured to adjust the power of each pulse of the first radiation beam 110, for example by adjusting the average power within each pulse. In this implementation, the pulsed power modulation system may include an acousto-optic modulator. The AOM can be configured such that a change in the RF signal applied to the piezoelectric transducer at the edge of the modulator can be varied to thereby vary the power of the pulses diffracted from the AOM. In some implementations, the beam conditioning system 180 includes an energy conditioning system coupled to the first radiation beam 110 . The energy adjustment system is configured to adjust the energy of the first radiation beam 110 . For example, the energy adjustment system may be an electrically variable attenuator such as a Bockel cell that varies between 0 V and a half-wave voltage, or an external acousto-optic modulator. In some implementations, the position or angle of the target material 120 relative to the beam waist D1/2 varies so much that the beam adjustment system 180 includes controls to control the position or angle of the beam waist D1/2 relative to the first target site 111 or relative to Means for the location or angle of another location within the chamber 165 in the coordinate system of the chamber 165. The device may be part of the focusing assembly 156, and it may be used to move the beam waist along the Z direction or along a direction transverse to the Z direction (eg, along a plane defined by the X and Y directions). As discussed above, control system 160 analyzes information received from metrology system 155 and determines how to adjust one or more properties of first radiation beam 110 to thereby control and maintain the dilation rate of modified target 121 . 10, control system 160 may include one or more sub-controllers 1000, 1005, 1010, 1015 that interface with other components of light source 100, such as sub-controller 1000 being specifically configured to interface with optical source 105 ( receiving information from and sending information to optical source 105), sub-controller 1005 specifically configured to interface with metrology system 155, sub-controller 1010 configured to interface with beam delivery system 150, and Sub-controller 1015 is configured to interface with target material supply system 125 . Light source 100 may include other components not shown in FIGS. 1 and 10 , but which may interface with control system 160 . For example, light source 100 may include a diagnostic system, such as a droplet position detection feedback system, and one or more target or droplet imagers. The target imager provides an output indicative of the position of the droplet, for example, relative to a particular location, such as the primary focus 990 of the light collector 135, and this output is provided to a droplet position detection feedback system, droplet position detection The feedback system can, for example, calculate a droplet position and trajectory from which a droplet position error can be calculated on a droplet-by-drop basis or on an average. Thus, the droplet position detection feedback system provides the droplet position error as an input to the sub-controllers of the control system 160 . Control system 160 may provide, for example, laser position, direction, and timing correction signals to a laser control system within optical source 105 that may be used, for example, to control laser timing circuitry, and/or to a beam control system to control The amplified beam position and shaping of the beam delivery system to change the location and/or power of the focal plane of the first radiation beam 110 or the second radiation beam 115 . Target material delivery system 125 includes a target material delivery control system operable to modify the release point of a droplet of target material 120 as released by the internal delivery mechanism in response to, for example, a signal from control system 160, To correct errors in the droplets reaching the desired target site 111. The control system 160 generally includes one or more of digital electronic circuits, computer hardware, firmware, and software. Control system 160 may also include suitable input and output devices 1020, one or more programmable processors 1025, and one or more computer programs tangibly embodied in a machine-readable storage device for execution by the programmable processors. Product 1030. In addition, each of the sub-controllers (such as sub-controllers 1000, 1005, 1010, 1015) may include its own appropriate input and output devices, one or more programmable processors, and tangibly embodied in the machine One or more computer program products can be executed by a programmable processor in a readable storage device. One or more programmable processors can each execute a program of instructions to perform desired functions by operating on input data and generating appropriate outputs. Typically, a processor receives instructions and data from ROM and/or RAM. Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, including, by way of example, semiconductor memory devices such as EPROM, EEPROM, and flash memory devices; magnetic disks, such as internal hard disk and removable disks; magneto-optical disks; and CD-ROM disks. Any of the foregoing may be supplemented by or incorporated in a specially designed application specific integrated circuit (ASIC). To this end, the control system 160 includes an analysis program 1040 that receives measurement data from one or more measurement systems 155 . In general, the analysis program 1040 performs all the analysis needed to determine how to modify or control the energy delivered to the target material 120 from the first radiation beam 110 or to modify or control the energy of the first radiation beam 110 and can be obtained on a pulse-by-pulse basis. This analysis is performed on a pulse-to-pulse basis in the case of measured data. Referring to FIG. 11 , light source 100 (under the control of control system 160 ) performs a process 1100 for maintaining or controlling the expansion ratio (ER) of modified target 121 to thereby improve the conversion efficiency of light source 100 . Light source 100 provides target material 120 (1105). For example, target material supply system 125 (under the control of control system 160 ) can deliver target material 120 to first target site 111 . The target material supply system 125 may include its own actuation system (connected to the control system 160) and nozzles through which the target material is forced, wherein the actuation system controls the nozzles directed through the nozzles to produce droplets directed towards the first target site 111 Amount of target material to stream. Next, light source 100 directs first radiation beam 110 toward target material 120 to deliver energy to target material 120 to modify the geometric distribution of target material 120 to form modified target 121 (1110). In particular, the first radiation beam 110 is directed towards the target material 120 through a first set 300 of one or more optical amplifiers. For example, optical source 105 can be activated by control system 160 to generate first radiation beam 110 (in pulsed form), which can be directed towards target material 120 within target site 111, as shown in FIG. exhibit. The focal plane ( D1/2 ) of the first radiation beam 110 can be configured to traverse the target site 111 . Furthermore, in some implementations, the focal plane may overlap with the target material 120 or with an edge of the target material 120 facing the first radiation beam 110 . The first radiation beam 110 can be directed to the target material 120 by, for example, directing the first radiation beam 110 through a beam delivery system 150 (1110), wherein various optics can be used to modify the direction or shape of the radiation 110 or The divergence is such that it can interact with the target material 120 . The first radiation beam 110 may be directed towards the target material 120 by overlapping the target material 120 with a region of the first radiation beam 110 encompassing its confocal parameters (1110). In some implementations, the confocal parameter of the first radiation beam 110 can be so long that the beam waist (D1/2) easily covers the target material 120, and the surface area of the target material 120 intercepted by the first radiation beam 110 (which traverses The X direction (measured) remains relatively constant even though the position of the target material 120 is offset from the beam waist D1/2 (as shown in FIG. 7A ). For example, the confocal parameter of the first radiation beam 110 may be greater than 1.5 mm. In other implementations, the confocal parameters of the first radiation beam 110 are so short that the beam waist (D1/2) does not cover the target material 120, and where the position of the target material 120 deviates from the beam waist D1/2 at the location L1 However, the surface area of the target material 120 intercepted by the first radiation beam 110 deviates considerably (as shown in FIG. 7B ). For example, confocal parameters can be, for example, less than or equal to 2 millimeters. The modified target 121 changes its shape from the shape of the target material 120 just after being affected by the first radiation beam 110 to an expanded shape, and this expanded shape drifts towards the second target site as it moves away from the first target site 111 116 continues to deform. The modified target 121 may have a geometric distribution (such as shown in FIGS. 1 and 2 ) that deforms from the shape of the target material into a disk-shaped volume of molten metal with a substantially planar surface. The modified target 121 is transformed into a disk-shaped volume according to the dilation rate. The modified object 121 is transformed by dilating the modified object 121 along at least one axis according to a dilation rate. For example, as shown in FIG. 2, the modified target 121 is dilated at least along a major axis 230 that is generally parallel to the X-direction. The modified target 121 is dilated along at least one axis that is not parallel to the optical axis of the second radiation beam 115 , which is the second axial direction 217 . Although the first radiation beam 110 primarily interacts with the target material 120 by changing the shape of the target material 120, it is possible to cause the first radiation beam 110 to interact with the target material 120 in other ways; for example, the first radiation beam 110 may convert a portion of target material 120 into a plasma that emits EUV light. However, less EUV light is emitted from the plasma generated from the target material 120 (due to the distance between the modified target 121 and the second radiation beam 115) than the EUV light emitted from the plasma generated from the modified target 121. subsequent interaction), and the main effect from the first radiation beam 110 on the target material 120 is the modification of the geometric distribution of the target material 120 in order to form the modified target 121 . The light source 100 directs the second radiation beam 115 towards the modified target 121 such that the second radiation beam converts at least a portion of the modified target 121 into a plasma 129 emitting EUV light (1115). In particular, the light source 100 directs the second radiation beam 115 towards the modified target 121 through the second set 305 of one or more optical amplifiers. For example, optical source 105 can be activated by control system 160 to generate second radiation beam 115 (in the form of pulses), which can be directed towards modified target 121 within second target site 116, as shown in FIG. shown in 2. At least one of the optical amplifiers in the first set 300 may be in the second set 305, such as the example shown in FIG. 5 . Light source 100 measures one or more properties (eg, energy) associated with one or more of target material 120 and modified target 121 relative to radiation beam 110 (1120). For example, measurement system 155 measures properties under the control of control system 160 , and control system 160 receives measurement data from measurement system 155 . The light source 100 controls radiation exposure at the target material 120 from the first radiation beam 110 based on the one or more characteristics (1125). As discussed above, radiation exposure is the amount of radiation energy delivered from the first radiation beam 110 to the target material 120 per unit area. In other words, the radiation exposure is the radiation energy received by the surface of the target material 120 per unit area. In some implementations, the measurable characteristic (1120) is the energy of the first radiation beam 110. In other general implementations, the measurable property (1120) is the position of the target material 120 relative to the position of the first radiation beam 110 (e.g., relative to the beam waist of the first radiation beam 110), which may be in the longitudinal direction Whether it is determined in the (Z) direction or in a direction transverse to the longitudinal direction (for example, in the XY plane). The energy of first radiation beam 110 may be measured by measuring the energy of radiation 860 reflected from an optically reflective surface of target material 120 (such as shown in FIGS. 8B and 8C ). The energy of the radiation 860 can be measured by measuring the total intensity of the radiation 860 reflected from the optically reflective surface of the target material 120 across the four individual photocells. The total energy content of the back-reflected radiation 860 can be used in conjunction with other information about the first radiation beam 110 to determine the distance between the target material 120 and the first radiation beam 110 along the Z direction or in a direction transverse to the Z direction, such as in the XY plane. The relative position between beam waists of a radiation beam 110 . Alternatively, the total energy content of the back-reflected radiation 860 (along with other information) may be used to determine the relative position along the Z-direction between the target material 120 and the beam waist of the first radiation beam. The energy of the first radiation beam 110 may be measured by measuring the energy of the first radiation beam 110 directed towards the target material 120 (such as shown in FIG. 8A ). The energy of the first radiation beam 110 can be measured by measuring the space-integrated energy across a direction perpendicular to the direction of propagation of the first radiation beam 110 (the first axial direction 212 ). In some implementations, the measurable characteristic (1120) is the pointing or direction of the first radiation beam 110 as it travels towards the target material 120 (as shown in Figure 8A). This information about the pointing can be used to determine the overlay error between the position of the target material 120 and the axis of the first radiation beam 110 . In some implementations, the measurable characteristic (1120) is the position of the target material 120 relative to the target location. The target location may be at the beam waist (D1/2) of the first radiation beam 110 along the Z direction. The position of the target material 120 can be measured along a direction parallel to the first axial direction 212 . The position of the target relative to the main focal point 990 of the collector 135 can be measured. The position of the target material 120 can be measured along two or more non-parallel directions. In some implementations, the measurable characteristic (1120) is a size of the modified object before the second radiation beam converts at least a portion of the modified object into plasma. In some implementations, the measurable characteristic (1120) corresponds to an estimate of the expansion rate of the modified target. In some implementations, the measurable characteristic (1120) corresponds to a characteristic of the radiation 860 reflected from the optically reflective surface of the target material 120 (such as shown in Figures 8B and 8C). . This information can be used to determine the relative position (eg, along the Z direction) between the target material 120 and the beam waist of the first radiation beam 110 . This spatial characteristic can be determined or measured by using an astigmatic imaging system placed in the path of the reflected radiation 860 . In some implementations, the measurable characteristic ( 1120 ) corresponds to the angle at which the radiation 860 is directed relative to the angle of the first radiation beam 110 . This measured angle can be used to determine the distance between the target material 120 and the beam axis of the first radiation beam 110 along a direction transverse to the Z-direction. In other implementations, the measurable property ( 1120 ) corresponds to a spatial pattern of the modified target 121 formed after the first radiation beam 110 interacts with the target material 120 . For example, the angle of the modified target 121 may be measured relative to a direction (eg, a direction in an XY plane transverse to the Z direction). This information about the angle of the modified target 121 can be used to determine the distance between the target material 120 and the axis of the first radiation beam 110 along a direction transverse to the Z-direction. As another example, the size or expansion rate of the modified target 121 may be measured after a predetermined or fixed time after the modified target 121 is first formed from the interaction between the target material 120 and the first radiation beam 110 . This information about the size or dilation rate of the modified target 121 can be used to determine the light intensity between the target material 120 and the first radiation beam 110 along the longitudinal direction (Z direction) without anyone knowing that the energy of the first radiation beam 110 is constant. The distance between the girdle. The characteristic may be measured (1120) as quickly as possible for each pulse of the first radiation beam 110. For example, if the measurement system 155 includes a PEM or a quad cell (4 PEM configuration), the measurement rate can be as fast as between pulses. On the other hand, for a metrology system 155 that measures properties such as the size or expansion rate of the target material 120 or the modified target 121, a camera can be used for the metrology system 155, but the camera is usually much slower, e.g. It can be measured at a rate of about 1 Hz to about 200 Hz. In some implementations, the amount of radiation exposure delivered from the first radiation beam 110 to the target material 120 can be controlled (1125) to thereby control or maintain the dilation rate of the modified target. In other implementations, the amount of radiation exposure delivered from the first radiation beam 110 to the target material 120 may be controlled by determining whether characteristics of the first radiation beam 110 should be adjusted based on one or more measured characteristics (1125) . Thus, if it is determined that the characteristics of the first radiation beam 110 should be adjusted, for example the energy content of the pulses of the first radiation beam 110 may be adjusted, or the area of the first radiation beam 110 at the location of the target material 120 may be adjusted. The pulse of the first radiation beam 110 can be adjusted by adjusting one or more of the pulse width of the first radiation beam 110, the pulse duration of the first radiation beam 110, and the average or instantaneous power of the pulse of the first radiation beam 110 of energy content. The area of the first radiation beam 110 that interacts with the target material 120 can be adjusted by adjusting the relative axial (along the Z-direction) position between the target material 120 and the beam waist of the first radiation beam 110 . In some implementations, one or more characteristics may be measured for each pulse of the first radiation beam 110 (1120). In this way, it can be determined for each pulse of the first radiation beam 110 whether a characteristic of the first radiation beam 110 should be adjusted. In some implementations, the radiation exposure can be controlled by controlling the amount of radiation exposure delivered from the first radiation beam 110 to the target material 120 while at least a portion of the emitted and collected EUV light 140 is exposing the wafer of the lithography tool. amount (e.g., within acceptable limits for radiation exposure). Process 1100 may also include collecting at least a portion of EUV light 130 emitted from the plasma (using concentrator 135 ); and directing collected EUV light 140 toward the wafer to expose the wafer to EUV light 140 . In some implementations, the one or more measured characteristics ( 1120 ) include a number of photons reflected from the modified target 121 . The number of photons reflected from the modified target 121 can be measured in terms of how many photons hit the target material 120 . As discussed above, process 1100 includes controlling an amount of radiation exposure at target material 120 from first radiation beam 110 based on one or more characteristics (1125). For example, the radiation exposure can be controlled (1125) such that the radiation exposure is maintained within a predetermined radiation exposure range. The radiation exposure is the amount of radiation energy delivered from the first radiation beam 110 to the target material 120 per unit area. In other words, the radiation exposure is the radiation energy received by the surface of the target material 120 per unit area. This factor of radiation exposure remains relatively constant if the unit area of the surface of the target material 120 exposed to or intercepted by the first radiation beam 110 is controlled (or maintained within an acceptable range), and It is possible to control or maintain radiation exposure at the target material 120 by maintaining the energy of the first radiation beam 110 within an acceptable range of energy (1125). There are various ways to maintain the unit area of the surface of the target material 120 exposed to the first radiation beam 110 within an acceptable range of areas. These methods are discussed next. The radiation exposure (1125) at the target material 120 from the first radiation beam 110 can be controlled such that the pulse energy of the first radiation beam 110 is maintained (by using the feedback control of the measured characteristic (1120)) at a constant position Accurate or within the range of acceptable values, regardless of interference that may cause energy fluctuations. In other aspects, the radiation exposure from the first radiation beam 110 at the target material 120 can be controlled (1125) such that it is adjusted (eg, increased or decreased) by using a feedback control of the measured characteristic (1120) The pulse energy of the first radiation beam 110 is used to compensate the position error of the target material 120 relative to the position of the beam waist of the first radiation beam 110 in the longitudinal direction (Z direction). The first radiation beam 110 may be a pulsed radiation beam such that pulses of light are directed towards the target material 120 (1110). Similarly, the second radiation beam 115 may be a pulsed radiation beam such that pulses of light are directed towards the modified target 121 (1115). Target material 120 may be a droplet of target material 120 generated from target material supply system 125 . In this way, the geometric distribution of the target material 120 can be modified into a modified target 121 transformed into a disk-shaped volume of molten metal with a substantially planar surface. The target material droplet is transformed into a disk-shaped volume according to the dilation rate. 12, process 1200 is performed by light source 100 (under the control of control system 160) so that EUV Light energy is stable. Similar to process 1100 above, the light source 100 provides the target material 120 (1205); the light source 100 directs the first radiation beam 110 towards the target material 120 to deliver energy to the target material 120 to modify the geometric distribution of the target material 120 to form the modified target 121 (1210); and the light source 100 directs the second radiation beam 115 towards the modified target 121 such that the second radiation beam converts at least part of the modified target 121 into a plasma 129 emitting EUV light (1215). Light source 100 controls the amount of radiation exposure applied from first radiation beam 110 to target material 120 using process steps 1110 (1220). The power or energy of the EUV light 130 is stabilized (1225) by controlling the radiation exposure. The EUV energy (or power) generated by the plasma 129 depends on at least two functions, the first function is the conversion efficiency CE and the second function is the energy of the second radiation beam 115 . The conversion efficiency is the percentage of modified target 121 converted into plasma 129 by second radiation beam 115 . The conversion efficiency depends on several variables including the peak power of the second radiation beam 115, the size of the modified target 121 as it interacts with the second radiation beam 115, the position of the modified target 121 relative to the desired location, the second radiation beam 115 the lateral area or size as it interacts with the modified target 121 . Since the position of the modified target 121 and the size of the modified target 121 depend on how the target material 120 interacts with the first radiation beam 110, by controlling the amount of radiation exposure applied from the first radiation beam 110 to the target material 120, we The rate of expansion of the modified target 121 can be controlled, and thus, we can control for these two factors. In this way, the conversion efficiency can be stabilized or controlled (1220) by controlling the radiation exposure, which thus stabilizes the EUV energy generated by the plasma 129 (1225). Referring also to FIG. 13 , in some implementations, the first radiation beam 110 can be generated by a dedicated subsystem 1305A within the optical source 105 and the second radiation beam 115 can be generated by a dedicated and separate subsystem 1305B within the optical source 105 such that these The radiation beams 110 , 115 follow two separate paths on the way to the respective first 111 and second 116 target sites. In this way, each of the radiation beams 110, 115 travels through a respective subsystem of the beam delivery system 150, and thus, it travels through separate and separate optical steering components 1352A, 1352B and focusing assemblies 1356A, 1356B. For example, subsystem 1305A may be a solid gain medium based system, while subsystem 1305B may be a gas gain medium based system such as that produced by a CO2 amplifier. Exemplary solid-state gain media that may be used as subsystem 1305A include Erbium-doped fiber lasers and Neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers. In this example, the wavelength of the first radiation beam 110 may be different from the wavelength of the second radiation beam 115 . For example, the wavelength of the first radiation beam 110 using a solid gain medium may be about 1 micron (eg, about 1.06 microns), and the wavelength of the second radiation beam 115 using a gaseous medium may be about 10.6 microns. Other implementations are within the scope of the following patent applications.

100:雷射產生電漿(LPP)極紫外線(EUV)光源 105:光學源 110:第一輻射光束/輻射 111:第一目標部位 115:第二輻射光束 116:第二目標部位 120:目標材料 121:經修改目標/熔融金屬之圓盤形片件 125:目標材料供應系統/目標材料遞送系統 129:電漿 130:可用極紫外線(EUV)光/輻射 135:集光器系統/集光器 140:經收集極紫外線(EUV)光 145:光學裝置 150:光束遞送系統 152:光學操縱組件 155:量測系統 156:聚焦總成 160:控制系統 165:腔室 180:光束調整系統 210:第一聚焦區 212:第一軸向方向/傳播方向 215:第二聚焦區 217:第二軸向方向 230:長軸 235:短軸 300:第一光學放大器系統/光學放大器之第一集合 305:第二光學放大器系統/光學放大器之第二集合 310:第一光產生器 311:第一脈衝光束 315:第二光產生器 316:第二脈衝光束 320:光學系統 325:光束路徑組合器 326:光束路徑分離器 340:雙向色光束分裂器 342:雙向色光束分裂器 344:鏡面 346:鏡面 350:雙向色光束分裂器 352:雙向色光束分裂器 354:鏡面 356:鏡面 401:光學放大器 402:光學放大器 403:光學放大器 406:光學放大器 407:光學放大器 408:光學放大器 411:前置放大器 421:前置放大器 500:光學元件 505:光學元件 855A:量測系統 855B:量測系統 860:背向反射輻射 955A:量測系統 955B:量測系統 955C:量測系統 990:主焦點 1000:子控制器 1005:子控制器 1010:子控制器 1015:子控制器 1020:輸入及輸出器件 1025:可程式化處理器 1030:電腦程式產品 1040:分析程式 1100:工序 1105:步驟 1110:步驟 1115:步驟 1120:步驟 1125:步驟 1200:工序 1205:步驟 1210:步驟 1215:步驟 1220:步驟 1225:步驟 1305A:專用子系統 1305B:專用及分離子系統 1352A:光學操縱組件 1352B:光學操縱組件 1356A:聚焦總成 1356B:聚焦總成 L1:部位 L2:部位100: Laser produced plasma (LPP) extreme ultraviolet (EUV) light source 105: Optical source 110: First radiation beam/radiation 111: The first target site 115: Second radiation beam 116: Second target site 120: target material 121:Modified Target/Disc-Shaped Pieces of Molten Metal 125: Target material supply system/target material delivery system 129: Plasma 130: available extreme ultraviolet (EUV) light/radiation 135: Concentrator system/concentrator 140: Harvested extreme ultraviolet (EUV) light 145: Optical device 150: beam delivery system 152: Optical manipulation components 155:Measuring system 156: Focusing assembly 160: Control system 165: chamber 180: Beam adjustment system 210: The first focus area 212: First axial direction/propagation direction 215: Second focus area 217: Second axial direction 230: long axis 235: Minor axis 300: First Optical Amplifier System/First Collection of Optical Amplifiers 305: Second Optical Amplifier System/Second Collection of Optical Amplifiers 310: the first light generator 311: The first pulse beam 315: second light generator 316: Second pulse beam 320: Optical system 325: Beam Path Combiner 326: beam path splitter 340: bidirectional color beam splitter 342: Bi-directional color beam splitter 344: mirror surface 346: mirror surface 350: bidirectional color beam splitter 352: Bi-directional color beam splitter 354: mirror surface 356: mirror surface 401: optical amplifier 402: optical amplifier 403: optical amplifier 406:Optical Amplifier 407:Optical Amplifier 408:Optical Amplifier 411: Preamplifier 421: Preamplifier 500: optical components 505: Optical components 855A: Measurement system 855B: Measurement system 860: Back Reflected Radiation 955A: Measurement system 955B: Measurement system 955C: Measurement system 990: main focus 1000: sub-controller 1005: sub-controller 1010: sub-controller 1015: sub-controller 1020: Input and output devices 1025: Programmable processor 1030: Computer program products 1040: Analysis program 1100: Process 1105:step 1110:step 1115:step 1120: Step 1125:step 1200: Process 1205: step 1210: step 1215:step 1220: step 1225:step 1305A: Dedicated Subsystem 1305B: Dedicated and separate subsystems 1352A: Optical Manipulation Assembly 1352B: Optical Manipulation Assembly 1356A: Focusing Assembly 1356B: Focusing assembly L1: part L2: parts

圖1為包括光學源之雷射產生電漿極紫外線光源的方塊圖，該光學源產生導引至目標材料之第一輻射光束及導引至經修改目標之第二輻射光束以將該經修改目標之部分轉換成發射EUV光之電漿； 圖2為展示導引至第一目標部位之第一輻射光束及導引至第二目標部位之第二輻射光束的示意圖； 圖3A為用於圖1之光源中之例示性光學源的方塊圖； 圖3B及圖3C分別為可用於圖1之光學源中之例示性光束路徑組合器及例示性光束路徑分離器的方塊圖； 圖4A及圖4B為可用於圖3A之光學源中之例示性光學放大器系統的方塊圖； 圖5為可用於圖3A之光學源中之例示性光學放大器系統的方塊圖； 圖6為展示導引至第一目標部位之第一輻射光束及導引至第二目標部位之第二輻射光束之另一實施的示意圖； 圖7A及圖7B為展示導引至第一目標部位之第一輻射光束之實施的示意圖； 圖8A至圖8C及圖9A至圖9C展示量測系統之各種實施的示意圖，量測系統量測與目標材料、經修改目標及第一輻射光束中之任何一或多者相關聯之至少一個特性； 圖10為圖1之光源之例示性控制系統的方塊圖； 圖11為藉由光源(在控制系統之控制下)執行以用於維持或控制經修改目標之擴張率(ER)以藉此改良光源之轉換效率之例示性工序的流程圖； 圖12為藉由光源執行以用於藉由控制自第一輻射光束遞送至目標材料之放射曝光量而使自電漿發射之EUV光之功率穩定的例示性工序之流程圖；及 圖13為例示性光學源及例示性光束遞送系統之方塊圖，例示性光學源產生第一輻射光束及第二輻射光束，且例示性光束遞送系統調整第一輻射光束及第二輻射光束且將該第一輻射光束及該第二輻射光束聚焦至各別第一目標部位及第二目標部位。1 is a block diagram of a laser-generated plasma EUV light source including an optical source that produces a first beam of radiation directed at a target material and a second beam of radiation directed at a modified target to produce the modified A portion of the target is converted into plasma that emits EUV light; 2 is a schematic diagram showing a first radiation beam directed to a first target site and a second radiation beam directed to a second target site; 3A is a block diagram of an exemplary optical source for use in the light source of FIG. 1; 3B and 3C are block diagrams, respectively, of an exemplary beam path combiner and an exemplary beam path splitter that may be used in the optical source of FIG. 1; 4A and 4B are block diagrams of exemplary optical amplifier systems that may be used in the optical source of FIG. 3A; 5 is a block diagram of an exemplary optical amplifier system that may be used in the optical source of FIG. 3A; 6 is a schematic diagram showing another implementation of a first radiation beam directed to a first target site and a second radiation beam directed to a second target site; 7A and 7B are schematic diagrams showing implementation of a first radiation beam directed to a first target site; 8A-8C and 9A-9C show schematic diagrams of various implementations of metrology systems that measure at least one of the components associated with any one or more of the target material, the modified target, and the first radiation beam. characteristic; 10 is a block diagram of an exemplary control system for the light source of FIG. 1; 11 is a flowchart of an exemplary process performed by the light source (under the control of the control system) for maintaining or controlling the expansion ratio (ER) of a modified target to thereby improve the conversion efficiency of the light source; 12 is a flow diagram of an exemplary process performed by a light source for stabilizing the power of EUV light emitted from a plasma by controlling the amount of radiation exposure delivered from a first radiation beam to a target material; and 13 is a block diagram of an exemplary optical source that generates a first radiation beam and a second radiation beam and an exemplary beam delivery system that conditions the first and second radiation beams and converts The first radiation beam and the second radiation beam are focused to a respective first target site and a second target site.

100:雷射產生電漿(LPP)極紫外線(EUV)光源 100: Laser produced plasma (LPP) extreme ultraviolet (EUV) light source

105:光學源 105: Optical source

110:第一輻射光束/輻射 110: First radiation beam/radiation

111:第一目標部位 111: The first target site

115:第二輻射光束 115: Second radiation beam

116:第二目標部位 116: Second target site

120:目標材料 120: target material

121:經修改目標/熔融金屬之圓盤形片件 121:Modified Target/Disc-Shaped Pieces of Molten Metal

125:目標材料供應系統/目標材料遞送系統 125: Target material supply system/target material delivery system

129:電漿 129: Plasma

130:可用極紫外線(EUV)光/輻射 130: available extreme ultraviolet (EUV) light/radiation

135:集光器系統/集光器 135: Concentrator system/concentrator

140:經收集極紫外線(EUV)光 140: Harvested extreme ultraviolet (EUV) light

145:光學裝置 145: Optical device

150:光束遞送系統 150: beam delivery system

152:光學操縱組件 152: Optical manipulation components

155:量測系統 155:Measuring system

156:聚焦總成 156: Focusing assembly

160:控制系統 160: Control system

165:腔室 165: chamber

180:光束調整系統 180: Beam adjustment system

Claims (50)

一種用於目標擴張率控制之方法，其包含：提供一目標材料，其包含當轉換成電漿時發射極紫外線(EUV)光之一組份(component)；將一第一輻射光束導引朝向該目標材料以將能量遞送至該目標材料，以修改該目標材料之一幾何分佈以形成一經修改目標；將一第二輻射光束導引朝向該經修改目標，該第二輻射光束將該經修改目標之至少部分轉換成發射EUV光之電漿；量測該經修改目標之一大小；分析該經修改目標之該經量測大小；及基於該經修改目標之該經量測大小之該分析將自該第一輻射光束遞送至該目標材料之一放射曝光量(amount of radiant exposure)控制在一預定放射曝光範圍內。 A method for target dilation rate control comprising: providing a target material comprising a component that emits extreme ultraviolet (EUV) light when converted into a plasma; directing a first beam of radiation toward the target material to deliver energy to the target material to modify a geometric distribution of the target material to form a modified target; directing a second radiation beam towards the modified target, the second radiation beam will modify the converting at least part of the target into a plasma emitting EUV light; measuring a size of the modified target; analyzing the measured size of the modified target; and the analysis based on the measured size of the modified target An amount of radiant exposure delivered to the target material from the first radiation beam is controlled within a predetermined radiation exposure range. 如請求項1之方法，其中量測該經修改目標之該大小包含使用一影像圖(shadowgraph)技術。 The method of claim 1, wherein measuring the size of the modified object comprises using a shadowgraph technique. 如請求項1之方法，其中量測該經修改目標之該大小包含在該第二輻射光束將該經修改目標之至少部分轉換成電漿之前，量測該經修改目標之該大小。 The method of claim 1, wherein measuring the size of the modified target comprises measuring the size of the modified target before the second radiation beam converts at least a portion of the modified target into plasma. 如請求項1之方法，更包含估計該經修改目標之一擴張率，其中基於該經修改目標之該經量測大小之該分析及該經修改目標之該經估計擴張率之兩者而控制自該第一輻射光束遞送至該目標材料之該放射曝光量。 The method of claim 1, further comprising estimating a rate of expansion of the modified target, wherein controlling is based on both the analysis of the measured size of the modified target and the estimated rate of expansion of the modified target The radiation exposure delivered to the target material from the first radiation beam. 如請求項1之方法，更包含量測該目標材料之該位置。 The method according to claim 1, further comprising measuring the position of the target material. 如請求項5之方法，其中該經修改目標具有一圓盤形狀，且該經修改目標之該圓盤形狀之一角度定向(angular orientation)取決於該第一輻射光束在其撞擊(strike)該目標材料時之該位置。 The method of claim 5, wherein the modified target has a disc shape, and an angular orientation of the disc shape of the modified target depends on when the first radiation beam strikes the The location of the target material. 如請求項1之方法，其中量測該經修改目標之該大小包含量測該經修改目標沿著一方向之一擴張(expanse)，其垂直於該第二輻射光束之一方向。 The method of claim 1, wherein measuring the size of the modified target comprises measuring an expansion of the modified target along a direction perpendicular to a direction of the second radiation beam. 如請求項1之方法，更包含量測該經修改目標之一定向。 The method of claim 1, further comprising measuring an orientation of the modified object. 一種用於目標擴張率控制之裝置，其包含：一腔室，其界定接收一第一輻射光束之一初始目標部位及接收一第二輻射光束之一目標部位；一目標材料遞送系統，其經組態以將目標材料提供至該初始目標部位，該目標材料包含當轉換成電漿時發射極紫外線(EUV)光之一材料； 一光學操縱(steering)系統，其經組態以：將該第一輻射光束自一光學源導引朝向該初始目標部位以將能量遞送至該目標材料，以修改該目標材料之一幾何分佈以形成一經修改目標；及將該第二輻射光束自該光學源導引朝向該目標部位，以將該經修改目標之至少部分轉換成發射EUV光之電漿；一量測系統，其經組態以量測該經修改目標之一大小；及一控制系統，其連接至該目標材料遞送系統、該光學源、該光學操縱系統及該量測系統，其中該控制系統經組態以：自該量測系統接收該經量測大小；分析該經量測大小；及基於該經量測大小之該分析將一或多個信號發送至該光學源以控制自該第一輻射光束遞送至該目標材料之一放射曝光量。 An apparatus for target dilation rate control comprising: a chamber defining an initial target site receiving a first radiation beam and a target site receiving a second radiation beam; a target material delivery system via configured to provide a target material to the initial target site, the target material comprising a material that emits extreme ultraviolet (EUV) light when converted into a plasma; an optical steering system configured to: direct the first beam of radiation from an optical source toward the initial target site to deliver energy to the target material to modify a geometric distribution of the target material to forming a modified target; and directing the second beam of radiation from the optical source towards the target site to convert at least part of the modified target into a plasma emitting EUV light; a measurement system configured to measure a size of the modified target; and a control system connected to the target material delivery system, the optical source, the optical manipulation system, and the measurement system, wherein the control system is configured to: a metrology system receives the measured size; analyzes the measured size; and sends one or more signals to the optical source based on the analysis of the measured size to control delivery from the first radiation beam to the target The radiation exposure of one of the materials. 如請求項9之裝置，其中該量測系統採用一影像圖(shadowgraph)技術。 The device according to claim 9, wherein the measurement system adopts a shadowgraph technology. 如請求項9之裝置，更包含另一量測系統經組態以量測該目標材料相對於一目標位置之一位置。 The device of claim 9, further comprising another measurement system configured to measure a position of the target material relative to a target position. 如請求項11之裝置，其中該控制系統經組態以自該另一量測系統接收該經量測位置；分析該經量測位置；及基於該經量測大小之該分 析及該經量測位置之該分析將一或多個信號發送至該光學源以控制自該第一輻射光束遞送至該目標材料的該放射曝光量。 The device of claim 11, wherein the control system is configured to receive the measured position from the other measurement system; analyze the measured position; and the score based on the measured size The analysis and the analysis of the measured positions send one or more signals to the optical source to control the radiation exposure delivered from the first radiation beam to the target material. 如請求項11之裝置，其中該另一量測系統經組態以量測該目標材料相對於該第一輻射光束之一光束腰(beam waist)之該位置。 The apparatus of claim 11, wherein the another measurement system is configured to measure the position of the target material relative to a beam waist of the first radiation beam. 如請求項9之裝置，其中該光學源包含：一第一專用子系統，其產生該第一輻射光束；一第二專用子系統，其產生該第二輻射光束，在該光學源內該第二專用子系統與該第一專用子系統分離。 The device as claimed in claim 9, wherein the optical source includes: a first dedicated subsystem that generates the first radiation beam; a second dedicated subsystem that generates the second radiation beam, the first radiation beam in the optical source A second dedicated subsystem is separate from the first dedicated subsystem. 如請求項14之裝置，更包含一光束遞送系統，每一該第一及第二輻射光束行進通過該光束遞送系統之各別子系統使得該第一及第二輻射光束遵循在至各別該第一及第二目標部位之道路(way)上的兩個分離路徑。 The device of claim 14, further comprising a beam delivery system, each of the first and second radiation beams travels through a respective subsystem of the beam delivery system such that the first and second radiation beams follow directions to the respective Two separate paths on the way of the first and second target sites. 一種用於目標擴張率控制之方法，其包含：提供一目標材料，該目標材料包含當轉換成電漿時發射極紫外線(EUV)光之一組份；將一第一輻射光束導引朝向該目標材料以將能量遞送至該目標材料，以修改該目標材料之一幾何分佈以形成一經修改目標；將一第二輻射光束導引朝向該經修改目標，該第二輻射光束 將該經修改目標之至少部分轉換成發射EUV光之電漿；量測相對於該第一輻射光束之與該目標材料及該經修改目標中之一或多者相關聯的一組明顯(distinct)特性；分析該組中的每一經量測特性，並判定該第一輻射光束如何與該目標材料交互作用以基於每一該經量測特性之該混合分析而形成該經修改目標；及基於該判定將自該第一輻射光束遞送至該目標材料之一放射曝光量控制在一預定放射曝光範圍內。 A method for target dilation rate control comprising: providing a target material comprising a component that emits extreme ultraviolet (EUV) light when converted into a plasma; directing a first radiation beam toward the target material to deliver energy to the target material to modify a geometric distribution of the target material to form a modified target; directing a second radiation beam toward the modified target, the second radiation beam converting at least a portion of the modified target into a plasma emitting EUV light; measuring a distinct set of values associated with one or more of the target material and the modified target relative to the first radiation beam ) properties; analyzing each measured property in the set and determining how the first radiation beam interacts with the target material to form the modified target based on the mixture analysis of each of the measured properties; and based on The determination controls a radiation exposure delivered to the target material from the first radiation beam within a predetermined radiation exposure range. 一種用於目標擴張率控制之裝置，其包含：一腔室，其界定接收一第一輻射光束之一初始目標部位及接收一第二輻射光束之一目標部位；一目標材料遞送系統，其經組態以將目標材料提供至該初始目標部位，該目標材料包含當轉換成電漿時發射極紫外線(EUV)光之一材料；一光學源，其經組態以產生該第一輻射光束及該第二輻射光束；一光學操縱(steering)系統，其經組態以：將該第一輻射光束導引朝向該初始目標部位以將能量遞送至該目標材料，以修改該目標材料之一幾何分佈以形成一經修改目標；及將該第二輻射光束導引朝向該目標部位，以將該經修改目標之至少部分轉換成發射EUV光之電漿； 一量測系統，其包含一組量測子系統，每一量測子系統經組態以量測相對於該第一輻射光束之與該目標材料及該經修改目標之一或多者相關聯之一特性；及一控制系統，其連接至該目標材料遞送系統、該光學源、該光學操縱系統及該量測系統，其中該控制系統經組態以：自該量測系統之該每一量測子系統接收該經量測特性；分析該經量測特性；及基於該經量測接收特性之該分析將一或多個信號發送至該光學源以控制自該第一輻射光束遞送至該目標材料之一放射曝光量。 An apparatus for target dilation rate control comprising: a chamber defining an initial target site receiving a first radiation beam and a target site receiving a second radiation beam; a target material delivery system via configured to provide a target material to the initial target site, the target material comprising a material that emits extreme ultraviolet (EUV) light when converted into a plasma; an optical source configured to generate the first radiation beam and the second radiation beam; an optical steering (steering) system configured to: direct the first radiation beam toward the initial target site to deliver energy to the target material to modify a geometry of the target material distributing to form a modified target; and directing the second beam of radiation towards the target site to convert at least part of the modified target into a plasma emitting EUV light; A metrology system comprising a set of metrology subsystems, each metrology subsystem configured to measure, relative to the first beam of radiation, associated with one or more of the target material and the modified target a characteristic; and a control system connected to the target material delivery system, the optical source, the optical manipulation system, and the measurement system, wherein the control system is configured to: from each of the measurement system a metrology subsystem receives the measured characteristic; analyzes the measured characteristic; and sends one or more signals to the optical source based on the analysis of the measured received characteristic to control delivery from the first radiation beam to The radiation exposure of one of the target materials. 一種用於目標擴張率控制之方法，其包含：提供一目標材料，該目標材料包含當轉換成電漿時發射極紫外線(EUV)光之一組份；將一第一輻射光束導引朝向該目標材料以將能量遞送至該目標材料，以修改該目標材料之一幾何分佈以形成一經修改目標；將一第二輻射光束導引朝向該經修改目標，該第二輻射光束將該經修改目標之至少部分轉換成發射EUV光之電漿；量測相對於該第一輻射光束之與該目標材料及該經修改目標之一或多者相關聯的一或多個特性；分析相對於該第一輻射光束之與該目標材料及該經修改目標之一或多者相關聯之該經量測之一或多個特性；及 基於該一或多個經量測特性之該分析控制該經修改目標之一幾何擴張率(geometric expansion rate)以增加因該經修改目標及該第二輻射光束之間的該交互作用而自該電漿轉換為該EUV光之量。 A method for target dilation rate control comprising: providing a target material comprising a component that emits extreme ultraviolet (EUV) light when converted into a plasma; directing a first radiation beam toward the target material to deliver energy to the target material to modify a geometric distribution of the target material to form a modified target; directing a second radiation beam toward the modified target, the second radiation beam to modify the modified target converting at least part of it into a plasma that emits EUV light; measuring one or more properties associated with one or more of the target material and the modified target relative to the first radiation beam; analyzing relative to the first radiation beam the measured one or more properties of a radiation beam associated with one or more of the target material and the modified target; and A geometric expansion rate of the modified target is controlled based on the analysis of the one or more measured properties to increase a rate of increase from the modified target due to the interaction between the second radiation beam. Plasma is converted to the amount of EUV light. 如請求項18之方法，其中控制該幾何擴張率在該經修改目標與該第二輻射光束交互作用之時啟動控制該經修改目標之一幾何態樣(geometric aspect)。 The method of claim 18, wherein controlling the rate of geometric expansion activates controlling a geometric aspect of the modified target when the modified target interacts with the second radiation beam. 如請求項19之方法，其中控制該經修改目標之該幾何擴張率包含調整該幾何擴張率。 The method of claim 19, wherein controlling the geometric expansion rate of the modified target comprises adjusting the geometric expansion rate. 一種用於目標擴張率控制之方法，其包含：提供一目標材料，其包含當轉換成電漿時發射極紫外線(EUV)光之一組份；使一第一輻射光束與該目標材料交互作用以將能量遞送至該目標材料，其包含修改該目標材料之一幾何分佈以形成一經修改目標；使一第二輻射光束與該經修改目標交互作用，該第二輻射光束將該經修改目標之至少部分轉換成發射EUV光之電漿；以一第一量測系統量測該經修改目標之一空間態樣(spatial aspect)及以一第二量測系統量測該經修改目標之一空間態樣；及 基於自該第一及第二量測系統之該複數個量測控制一輻射光束。 A method for target dilation rate control comprising: providing a target material comprising a component that emits extreme ultraviolet (EUV) light when converted into a plasma; interacting a first radiation beam with the target material to deliver energy to the target material, comprising modifying a geometric distribution of the target material to form a modified target; interacting a second radiation beam with the modified target, the second radiation beam forming a modified target at least partially converted into plasma emitting EUV light; measuring a spatial aspect of the modified object with a first measurement system and measuring a spatial aspect of the modified object with a second measurement system appearance; and A radiation beam is controlled based on the plurality of measurements from the first and second measurement systems. 如請求項21之方法，其中量測該經修改目標之該空間態樣包含量測該經修改目標之一大小、一位置及一定向之一或多者。 The method of claim 21, wherein measuring the spatial aspect of the modified object comprises measuring one or more of a size, a position, and an orientation of the modified object. 請求項22之方法，更包含基於該經修改目標之該經量測定向判定該目標材料與該第一輻射光束沿著一方向之一軸線之間的一距離，其橫向(transverse)於該第一輻射光束之該方向。 The method of claim 22, further comprising determining a distance between the target material and an axis of the first radiation beam along a direction transverse to the first radiation beam based on the measured direction of the modified target the direction of a radiation beam. 如請求項21之方法，其中控制該輻射光束包含控制自該第一輻射光束遞送至該目標材料之一放射曝光量。 The method of claim 21, wherein controlling the radiation beam comprises controlling a radiation exposure delivered from the first radiation beam to the target material. 如請求項21之方法，其中控制該輻射光束包含控制曝光至或截取(intercept)自該第一輻射光束之目標材料之表面之一單元面積。 The method of claim 21, wherein controlling the radiation beam comprises controlling a unit area of a surface of the target material exposed to or intercepted from the first radiation beam. 如請求項21之方法，其中量測該經修改目標之該空間態樣包含使用一影像圖技術，其包含一脈衝式背光照明器及一攝影機。 The method of claim 21, wherein measuring the spatial aspect of the modified object comprises using an image technique comprising a pulsed backlight illuminator and a camera. 如請求項21之方法，其中量測該經修改目標之該空間態樣包含在該第二輻射光束與該經修改目標交互作用之前，量測該經修改目標之該空間態樣。 The method of claim 21, wherein measuring the spatial aspect of the modified object comprises measuring the spatial aspect of the modified object before the second radiation beam interacts with the modified object. 如請求項21之方法，其中控制該輻射光束包含調整該第一輻射光束之一脈衝之一能量含量，其包含調整該脈衝之一寬度、調整該脈衝之一持續時間、及調整該脈衝內之一平均功率之一或多者。 The method of claim 21, wherein controlling the radiation beam includes adjusting the energy content of a pulse of the first radiation beam, which includes adjusting a width of the pulse, adjusting a duration of the pulse, and adjusting an energy content within the pulse. One or more of average power. 如請求項21之方法，其中修改該目標材料之該幾何分佈包含將該目標材料之一形狀變換成該經修改目標，其包括根據一擴張率沿著一目標軸線來擴張該經修改目標，該目標軸線並非平行於該第二輻射光束之一光軸。 The method of claim 21, wherein modifying the geometric distribution of the target material comprises transforming a shape of the target material into the modified target comprising expanding the modified target along a target axis according to an expansion rate, the The target axis is not parallel to an optical axis of the second radiation beam. 如請求項21之方法，其中該經修改目標具有一圓盤形狀，且該圓盤形狀之一角度定向(angular orientation)取決於該第一輻射光束與該目標材料交互作用時之一位置。 The method of claim 21, wherein the modified target has a disk shape, and an angular orientation of the disk shape depends on a position of the first radiation beam interacting with the target material. 如請求項21之方法，其中控制該輻射光束包含控制該第一輻射光束與該目標材料之間的一交互作用。 The method of claim 21, wherein controlling the radiation beam comprises controlling an interaction between the first radiation beam and the target material. 一種用於目標擴張率控制之裝置，其包含：一腔室，其界定經組態以接收一第一輻射光束之一初始目標部位及經組態以接收一第二輻射光束之一目標部位；一目標材料遞送系統，其經組態以將目標材料提供至該初始目標部位，該目標材料包含當轉換成電漿時發射極紫外線(EUV)光之一材料；一光學配置，其經組態以： 使該第一輻射光束在該初始目標部位與該目標材料交互作用以將能量遞送至該目標材料且修改該目標材料之一幾何分佈以形成一經修改目標；及使該第二輻射光束在該目標部位與該經修改目標交互作用以將該經修改目標之至少部分轉換成發射EUV光之電漿；兩個量測系統，每一量測系統經組態以量測該經修改目標之一空間態樣；及一控制系統，其連接至該目標材料遞送系統、該光學配置及該量測系統，其中該控制系統經組態以接收來自該兩個量測系統之量測資料並將一或多個信號發送至該光學配置以基於該經接收量測資料控制一輻射光束。 An apparatus for target dilation rate control comprising: a chamber defining an initial target site configured to receive a first radiation beam and a target site configured to receive a second radiation beam; a target material delivery system configured to provide target material to the initial target site, the target material comprising a material that emits extreme ultraviolet (EUV) light when converted into a plasma; an optical arrangement configured by: interacting the first radiation beam with the target material at the initial target site to deliver energy to the target material and modify a geometric distribution of the target material to form a modified target; and causing the second radiation beam at the target a site interacting with the modified target to convert at least a portion of the modified target into a plasma emitting EUV light; two measurement systems, each configured to measure a volume of the modified target Aspects; and a control system connected to the target material delivery system, the optical arrangement, and the measurement system, wherein the control system is configured to receive measurement data from the two measurement systems and convert one or Signals are sent to the optical arrangement to control a radiation beam based on the received measurement data. 如請求項32之裝置，其中每一量測系統包含一脈衝式背光照明器及一攝影機。 The device according to claim 32, wherein each measurement system includes a pulsed backlight illuminator and a camera. 如請求項33之裝置，其中該攝影機為一電荷耦合器件攝影機。 The device according to claim 33, wherein the camera is a charge-coupled device camera. 如請求項32之裝置，其中該光學配置包含一光學源經組態以產生該第一輻射光束及該第二輻射光束、及一光學操縱系統經組態以操縱該第一輻射光束朝向該初始目標部位且操縱該第二輻射光束朝向該目標部位。 The device of claim 32, wherein the optical configuration includes an optical source configured to generate the first radiation beam and the second radiation beam, and an optical steering system configured to steer the first radiation beam toward the initial target site and directing the second radiation beam towards the target site. 如請求項32之裝置，其中每一量測系統採用一影像圖技術。 The device as claimed in claim 32, wherein each measurement system uses an image technology. 如請求項32之裝置，其中該光學配置包含一光學源，其包含一第一光產生器經組態以產生該第一輻射光束及與該第一光產生器分離之一第二光產生器經組態以產生該第二輻射光束。 The device of claim 32, wherein the optical arrangement comprises an optical source comprising a first light generator configured to generate the first radiation beam and a second light generator separate from the first light generator configured to generate the second radiation beam. 一種具有目標擴張率控制之用於一極紫外線(EUV)光源之裝置，其包含：一光學配置，其經組態以使一第一輻射光束在一腔室內與一目標材料交互作用以形成一經修改目標；一第一量測系統，包含一感測器，其經組態以當該目標材料與該第一輻射光束交互作用時接收自該目標材料反射之輻射；一第二量測系統，其包含複數個量測子系統，每一量測子系統經組態以量測形成自該第一輻射光束與該目標材料之間的該交互作用之該經修改目標之一空間態樣；及與該第一量測系統及該第二量測系統通信之一控制系統，其經組態以分析來自該第一及該第二量測系統之輸出，並基於該分析傳送資訊至該光學配置。 An apparatus for an extreme ultraviolet (EUV) light source with target dilation control, comprising: an optical arrangement configured such that a first radiation beam interacts with a target material within a chamber to form an modifying the target; a first measurement system comprising a sensor configured to receive radiation reflected from the target material when the target material interacts with the first radiation beam; a second measurement system, comprising a plurality of measurement subsystems, each measurement subsystem configured to measure a spatial aspect of the modified target resulting from the interaction between the first radiation beam and the target material; and a control system in communication with the first measurement system and the second measurement system configured to analyze the output from the first and the second measurement system and transmit information to the optical arrangement based on the analysis . 如請求項38之裝置，其中該控制系統經組態以基於該分析傳送資訊至該光學配置包含維持該第一輻射光束之一能量於一可接受能量範圍內。 The device of claim 38, wherein the control system configured to transmit information to the optical arrangement based on the analysis includes maintaining an energy of the first radiation beam within an acceptable energy range. 如請求項38之裝置，其中該控制系統經組態以分析來自該第一 及該第二量測系統之輸出包含基於該分析判定是否需調整該第一輻射光束之一特性。 The device of claim 38, wherein the control system is configured to analyze And the output of the second measurement system includes determining whether a characteristic of the first radiation beam needs to be adjusted based on the analysis. 如請求項38之裝置，其中該光學配置經組態使該第一輻射光束與該目標材料交互作用以形成該經修改目標包含修改該目標材料之一幾何分佈。 The device of claim 38, wherein the optical arrangement is configured to cause the first radiation beam to interact with the target material to form the modified target comprises modifying a geometric distribution of the target material. 如請求項38之裝置，其中每一量測子系統經組態以藉由量測該經修改目標之一大小、一位置及一定向之一或多者而量測該經修改目標之該空間樣態。 The device of claim 38, wherein each measurement subsystem is configured to measure the space of the modified object by measuring one or more of a size, a position, and an orientation of the modified object state. 如請求項42之裝置，其中每一量測子系統包含一背光照明器及一攝影機。 The device according to claim 42, wherein each measurement subsystem includes a backlight illuminator and a camera. 如請求項42之裝置，其中每一量測子系統採用一影像圖技術。 The device as claimed in claim 42, wherein each measurement subsystem adopts an image technology. 如請求項38之裝置，其中該光學配置更經組態以使得該第二輻射光束與該經修改目標交互作用以將該經修改目標之至少部分轉換成發射EUV光之電漿。 The device of claim 38, wherein the optical arrangement is further configured such that the second radiation beam interacts with the modified target to convert at least part of the modified target into a plasma emitting EUV light. 如請求項38之裝置，其中該光學配置包含一光學源經組態以產生該第一輻射光束及該第二輻射光束、及一光學操縱系統經組態以操縱該第一輻射光束朝向一初始目標部位且操縱該第二輻射光束朝向一 目標部位。 The device of claim 38, wherein the optical configuration includes an optical source configured to generate the first radiation beam and the second radiation beam, and an optical steering system configured to steer the first radiation beam toward an initial target site and directing the second radiation beam toward a target site. 一種用於目標擴張率控制之方法，其包含：使一第一輻射光束在一腔室內與一目標材料交互作用以形成一經修改目標；當該經目標材料與該第一輻射光束交互作用時感測自該目標材料反射之輻射；以一第一量測子系統量測該經修改目標之一空間態樣及以一第二量測子系統量測該經修改目標之一空間態樣；分析該經感測輻射及來自該第一及第二量測子系統之輸出；及基於該分析控制該第一輻射光束。 A method for target dilation rate control comprising: interacting a first radiation beam with a target material in a chamber to form a modified target; sensing when the targeted material interacts with the first radiation beam measuring radiation reflected from the target material; measuring a spatial aspect of the modified target with a first measurement subsystem and measuring a spatial aspect of the modified target with a second measurement subsystem; analyzing the sensed radiation and outputs from the first and second measurement subsystems; and controlling the first radiation beam based on the analysis. 如請求項47之方法，其中使該第一輻射光束與該目標材料交互作用以形成該經修改目標包含修改該目標材料之一幾何分佈以形成該經修改目標。 The method of claim 47, wherein interacting the first radiation beam with the target material to form the modified target comprises modifying a geometric distribution of the target material to form the modified target. 如請求項47之方法，更包含使一第二輻射光束與該經修改目標交互作用，該第二輻射光束將該經修改目標之至少部分轉換成發射EUV光之電漿。 The method of claim 47, further comprising interacting a second radiation beam with the modified target, the second radiation beam converting at least part of the modified target into a plasma emitting EUV light. 如請求項47之方法，其中基於該分析控制該第一輻射光束包含控制該第一輻射光束之一能量及自該第一輻射光束遞送至該目標材料之一放射曝光量之一或多者。 The method of claim 47, wherein controlling the first radiation beam based on the analysis comprises controlling one or more of an energy of the first radiation beam and a radiation exposure delivered from the first radiation beam to the target material.
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