4324T5 五、杳明說明⑴ 本發明係有關於一種增進光學系統（optical system) 單向（single direction)頻寬（bandwidth)之裝置，特別 有關於一種用於半導體微影製程之增進光學系統單向頻寬 之裝置。 在製作積體電路裝置時，微影技街 (photolithography)為主要的製程之一，一般而言，微影 技術包括製作光罩（mask)、光阻層之塗佈（c〇at);曝光 (exposure)，及顯影液去除光阻（ph〇t〇resist)等。其中 ’配合蝕刻步驟可移轉圖案至晶圓表面。4324T5 V. 杳 明 ⑴ This invention relates to a device that enhances the single direction bandwidth of an optical system, and particularly relates to a method that enhances the unidirectional optical system used in semiconductor lithography processes. Bandwidth device. In the fabrication of integrated circuit devices, photolithography is one of the main processes. Generally speaking, photolithography includes the production of masks and photoresist layers (coat); exposure (exposure), and removal of photoresist by the developer. Among them, the pattern can be transferred to the wafer surface with the etching step.
然而隨著積體電路尺寸逐漸的縮小化，光罩之圖案也 趨於密集，因此除了繼續尋找波長更短之光源外，對於光 學系統（optical system)的解析度要求也隨之增加。但由 於現仃OAI (off-axis illumination)系統之曝光裝置的解 析度（resolution)係決定於截止頻率（cut_〇ff frequency )，而截止頻率則受光學系統光瞳（pupU)的控制，因此， 對於解析度的增進有相當的限制。 ’本發明在不改變光學系統的光曈（卿⑴ ，形下，可籍減低Fy方向的解析度來增加ρχ方向的解析 度0 其中’依據本發明提出 之曝光裝置，包括：一光源 光鏡；一第一光栅，置於— 用以將來自第一聚光鏡之光 焦面上；一第二光柵，與第 之—種增進光學系統單向頻寬 ’用以發射一光束至一第一聚 光罩之前並旋轉一既定角度， 束繞射到一第二聚光鏡系之後 —光柵之圖案相同，用以將來However, as the size of the integrated circuit is gradually reduced, the pattern of the photomask also tends to be dense. Therefore, in addition to continuing to find light sources with shorter wavelengths, the resolution requirements for the optical system have also increased. However, since the resolution of the exposure device of the OAI (off-axis illumination) system is determined by the cutoff frequency (cut_off frequency), and the cutoff frequency is controlled by the optical system pupil (pupU), so There are considerable restrictions on the improvement of resolution. 'In the present invention, without changing the optical axis of the optical system, the resolution in the Fy direction can be increased by reducing the resolution in the Fy direction. Wherein, the exposure device according to the present invention includes: a light source light mirror A first grating placed on-for focusing the light from the first condenser lens; a second grating and first-a kind of enhancing the unidirectional bandwidth of the optical system 'for emitting a light beam to a first condenser Before the reticle and rotated a predetermined angle, the beam is diffracted behind a second condenser lens system-the pattern of the grating is the same for future use
4324 75 五、發明說明（2) 自^二聚光鏡系之光束繞射至一單方向濾波器，形成一具 有單方向頻寬之光束以成像至一晶圓表面。其中，由於通 過單方向遽波器面之光束之頻譜可得頻寬較寬之影像，因 此在單方向上可獲得較佳之解析度。 為讓本發明之上述和其他目的、特徵、和優點能更明 顯易懂，下文特舉一較佳實施例，並配合所附圖式，作詳 細說明如下： 圖式簡單說明 第1圖為傳統0AI光學系統之曝光裝置示意圖。 第2圖為本發明之一實施例中，光學系統之曝光裝置 示意圖。 第3A至3F圖為依據弟2A圖之曝光裝置產生之Fx_Fy方 向頻譜圖。 [符號說明] 12、120〜聚光鏡；16、160〜物鏡；14、140〜光罩；18 、180〜晶圓；130、150〜光柵；17〇〜傅立葉轉換透鏡；19〇 ~低通濃波！§'，1 9 5 ~早方向ί慮波器。 實施例 為方便說明起見，在此係先說明傳統ΟΑΙ系統（of f-axis illumination)之曝光裝置，如第1圖所示。 一般而言，在製造高度積體化電路如64M位元以上之 動態隨機存取記憶體（DRAM)時，可以選擇KrF激化雷射光 源5及採用0 AI系統之曝光裝置2 0，其中，來自光源之光係 受光圈（aperture)之中心區域遮斷（intercepted)且入射4324 75 V. Description of the invention (2) The beam from the ^ 2 condenser lens system is diffracted to a unidirectional filter to form a beam with a unidirectional bandwidth for imaging onto a wafer surface. Among them, since a wide bandwidth image can be obtained through the spectrum of the light beam on the unidirectional waver surface, a better resolution can be obtained in one direction. In order to make the above and other objects, features, and advantages of the present invention more comprehensible, a preferred embodiment is given below in conjunction with the accompanying drawings to make a detailed description as follows: The drawings briefly illustrate that FIG. 1 is traditional Schematic diagram of the exposure device of the 0AI optical system. Fig. 2 is a schematic diagram of an exposure device of an optical system in an embodiment of the present invention. Figures 3A to 3F are Fx_Fy direction spectrum charts generated by the exposure device according to Figure 2A. [Symbols] 12, 120 ~ condenser lens; 16, 160 ~ objective lens; 14, 140 ~ reticle; 18, 180 ~ wafer; 130, 150 ~ grating; 170 ~ Fourier conversion lens; 19 ~ low pass concentrated wave !! § ', 1 9 5 ~ Early wave filter. EXAMPLES For the convenience of explanation, the exposure device of the conventional OA system (of f-axis illumination) is described first, as shown in FIG. 1. Generally speaking, when manufacturing highly integrated circuits such as dynamic random access memory (DRAM) of 64M bits or more, KrF laser source 5 and exposure device 20 using 0 AI system can be selected. Among them, from The light of the light source is intercepted and incident by the central area of the aperture
432475 五 '發明說明（3) 到聚光鏡（condenser lens)12 的外圈區域（outer region) ，接著由聚光鏡12以一既定傾斜角度將光入射到具有圖案 之光罩14.表面’此時，會產生兩道由光罩14產生之繞射（ diffracted)光束，亦即0階繞射光束（0-0RDER)和屬於高 頻範圍之Η階繞射光束（ + 131;-0Κ])ΕΚ)藉物鏡16而聚焦於晶 圓1 8表面’其中’部份屬於高頻範圍之+1階繞射光束 ( + lst-0RDER)則被偏離於物鏡16之外d 然而隨著積體電路尺寸逐漸的縮小化，光罩之圖案也 趨於密集’亦即在光罩圖案之空間頻率（spatial frequency)提高下’屬於高頻範圍之繞射光束的偏離角度 加大’當大部份屬於高頻範圍之繞射光束被偏離於物鏡16 之外時’光學系統的解析度將趨於降低。 為解決前述問題’本發明之實施例在不改變光學系統 的光曈（pupi 1)情形下，可藉減低Fy方向的解析度來增加 Fx方向的解析度。 請配合第3A至第3F圖之Fx-Fy方向頻譜圖參閱第2圖之 一種增進光學系統單向頻寬之曝光裝置。 首先依據第2圖之曝光裝置，係包括一光源7，例如選 擇KrF激化雷射光源以發射一光束至第一聚光鏡 (condenser lenS)12〇。一第一光柵 13〇，置於一光罩 14〇 之前並旋轉一既定角度¥，用以將來自第一聚光鏡12〇之光 束繞射到第二聚光鏡系（condenser lens)1 6〇之後焦面（ b = ck focal plane)，其中，第二聚光鏡系16()係包括兩個 聚光鏡，基本上為構成一成像系統。接著，一第二光柵432475 Five 'invention description (3) to the outer region of the condenser lens 12, and then the condenser lens 12 incident light at a predetermined inclination angle to the patterned mask 14. Surface' At this time, it will Generate two diffracted beams generated by the mask 14, that is, a 0-order diffracted beam (0-0RDER) and a Η-order diffracted beam (+ 131; -0Κ]) ΕΚ) borrowed from the high frequency range The objective lens 16 and the +1 order diffraction beam (+ lst-0RDER) focused on the surface of the wafer 1 8 in the high frequency range are deviated from the objective lens 16d. However, as the integrated circuit size gradually increases, Reduced, the pattern of the mask also tends to be denser, that is, with the increase of the spatial frequency of the mask pattern, 'the deviation angle of the diffraction beam belonging to the high frequency range is increased', when most of it belongs to the high frequency range When the diffracted beam is deviated from the objective lens 16, the resolution of the optical system tends to decrease. To solve the foregoing problem, the embodiment of the present invention can increase the resolution in the Fx direction by reducing the resolution in the Fy direction without changing the pupi 1 of the optical system. Please refer to FIG. 2 for an exposure device for improving the unidirectional bandwidth of the optical system in conjunction with the Fx-Fy direction spectrum charts of FIGS. 3A to 3F. First, the exposure device according to FIG. 2 includes a light source 7, for example, a KrF laser source is selected to emit a light beam to a first condenser lens 12. A first grating 13 ° is placed in front of a mask 14 ° and rotated by a predetermined angle ¥ to diffract the light beam from the first condenser lens 120 to the focal surface of the second condenser lens 1660. (B = ck focal plane), wherein the second condenser lens system 16 () system includes two condenser lenses, which basically constitute an imaging system. Next, a second grating
4 3 24 7' δ 五、發明說明（4) 150，與第一光柵130之圖案相同，其用以將來自第二聚光 鏡系1 60之光束繞射至一Fx方向濾波器丨95，形成—具有Fx 方向頻寬之光束以成像至一晶圓1 8 〇表面。 其申，睛參閱第3A圖之光罩圖案的頻譜（freqUenCy spectrum)，由於光罩140之圖案趨於密集，而在一般情形 下’X方向上之圖案也遠較y方向上之圖案複雜，因此，光 罩14G在頻域上之Fx-Fy方向上之分佈係如所示。 此外’請參閱第3B圖之第一光柵130的頻譜。由於第 一光柵130被旋轉一既定角度w ’因此，第—光柵13〇 χ -Fy方向上之頻域分佈係如頻譜信號、fa2、fa3所示。 另’假定第一光柵130之狹縫圖案具有間格距離為d, 光罩140頻域分佈寬度為fw ’則第一光栅之狹缝圖案之間 格距離d可依據光罩之頻域分佈決定，如下式所示。 da λ X (1/fw)； d為狹縫圖案之間格距離； fw為光罩頻域分佈寬度； λ為光源波長。 其次’請參閱第3C圖’其顯示一由第—光栅130調制 (modulated)之光罩140的頻譜，其在Fx — Fy方向上之頻域 分佈係如頻譜信號fbl、fb2、fb3所示。 請參閱第3D圖，其顯示光束依序通過第一光柵13〇、 光罩140、及第二聚光鏡系16〇時，受到第二聚光鏡系16〇 之光瞳（pupil)影響’屬於高頻範圍之光束將無法通過， 因此’只有部份頻譜可以通過第二聚光鏡系丨6 〇，其在頻4 3 24 7 'δ V. Description of the invention (4) 150, the same pattern as the first grating 130, is used to diffract the light beam from the second condenser lens system 1 60 to an Fx direction filter 丨 95, forming- A light beam with a bandwidth in the Fx direction is imaged onto a 180 ° surface of a wafer. In its application, please refer to the freqUenCy spectrum of the mask pattern in FIG. 3A. Since the pattern of the mask 140 tends to be dense, the pattern in the 'X direction is generally more complicated than the pattern in the y direction. Therefore, the distribution of the mask 14G in the Fx-Fy direction in the frequency domain is as shown. In addition, please refer to the spectrum of the first grating 130 in FIG. 3B. Since the first grating 130 is rotated by a predetermined angle w ', the frequency domain distribution in the direction of the first grating 13 × χ-Fy is shown as the spectrum signal, fa2, fa3. In addition, 'assuming that the slit pattern of the first grating 130 has a grid distance of d and the mask 140 frequency domain distribution width is fw', the grid distance d between the slit patterns of the first grating can be determined according to the frequency domain distribution of the mask. As shown below. da λ X (1 / fw); d is the grid distance between the slit patterns; fw is the width of the mask frequency domain distribution; λ is the wavelength of the light source. Secondly, please refer to FIG. 3C, which shows a frequency spectrum of the mask 140 modulated by the first grating 130, and its frequency domain distribution in the Fx-Fy direction is shown by the spectrum signals fbl, fb2, and fb3. Please refer to FIG. 3D, which shows that when the light beam sequentially passes through the first grating 13o, the mask 140, and the second condenser lens system 160, it is affected by the pupil of the second condenser lens system 160, which belongs to the high frequency range. The beam will not pass through, so 'only part of the spectrum can pass through the second condenser system.
432475432475
域Fx-Fy方向上之分佈係如頻譜信號fcl、fc2、fc3所示。 其中，其頻譜如下式所示。The distribution in the domain Fx-Fy direction is shown by the spectrum signals fcl, fc2, and fc3. The frequency spectrum is shown in the following formula.
Fc=F(M1)^F(MASK)X PUPILFc = F (M1) ^ F (MASK) X PUPIL
Fc為頻譜； F(M1)為第一光栅之頻譜； *為捲積； F(MASK)為光罩之頻譜； X為乘積； PUPIL為第二聚光鏡系之光瞳。 請參閱第3E圖’其顯示於光束通過第二聚光鏡系，16〇 後，再以一相同於第一光柵圖案之第二光柵150調制，形 成一將原有高頻範圍之影像恢復之頻譜，其在Fx-Fy方向 上之頻域分佈係如頻譜信號f d 1、f d 2、f d 3、f d 4、f d 5所 示，其中’在Fx方向上之頻譜信號fd3即為光束之原影像 頻譜。 其他之頻譜信號fdl、fd2、fd4、fd5則透過第3F圖之 單方向濾波器1 9 5濾除’其中，單方向濾波器1 9 5包括一傅 立葉轉換（fourier transform)透鏡170，及一低通濾波器 (low pass filter)190，其設置於傅立葉轉換（f0Urier transform)透鏡170之後，其中，低通濾波器（low pass fil ter )190為一沿Fx方向上由兩片不透光板320、340構成 之矩形透光孔360 ’而透過傅立葉轉換透鏡17〇及低通濾波 器1 90可以濾除在頻域上不必要之頻譜信號f dl、fd2、fd4 、fd5，因此通過矩形透光孔360之光束於Fx方向之頻譜信Fc is the frequency spectrum; F (M1) is the frequency spectrum of the first grating; * is convolution; F (MASK) is the frequency spectrum of the mask; X is the product; PUPIL is the pupil of the second condenser system. Please refer to FIG. 3E, which shows that the light beam passes through the second condenser lens system. After 160, it is modulated with a second grating 150 that is the same as the first grating pattern to form a spectrum that restores the original high frequency range image. Its frequency domain distribution in the Fx-Fy direction is shown in the spectrum signals fd 1, fd 2, fd 3, fd 4, fd 5, where 'the spectrum signal fd3 in the Fx direction is the original image spectrum of the beam. The other spectral signals fdl, fd2, fd4, and fd5 are filtered by the one-way filter 195 of FIG. 3F. Among them, the one-way filter 195 includes a Fourier transform lens 170, and a low A low pass filter 190 is disposed behind the F0Urier transform lens 170, where the low pass filter 190 is a two opaque plate 320 along the Fx direction The rectangular light-transmitting holes 360 ′ formed by 340 and 340 can be filtered through the Fourier transform lens 170 and the low-pass filter 1 90 to remove unnecessary spectral signals f dl, fd2, fd4, and fd5 in the frequency domain. Spectrum signal of the beam of hole 360 in the Fx direction
432475 五、發明說明（6) 號fd3可得頻寬較寬之影像，因此在Fx方向上可獲得較佳 之解析度。 雖然本發明已以一較佳實施例揭露如下，然其並非用 以限定本發明，任何熟習此技藝者，在不脫離本發明之精 神和範圍内，當可做些許之更動與潤飾，因此本發明之保 護範圍當視後附之申請專利範圍所界定者為準。432475 V. Description of the invention (6) fd3 can obtain a wide bandwidth image, so better resolution can be obtained in the Fx direction. Although the present invention has been disclosed in the following with a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make some modifications and retouching without departing from the spirit and scope of the present invention. The scope of protection of the invention shall be determined by the scope of the attached patent application.