KR20200019258A - Spatially resolved optical emission spectroscopy (OES) in plasma processing - Google Patents

Abstract

Methods, systems, and apparatus for optical emission measurements are disclosed. The apparatus includes a collection system for collecting plasma optical emission spectra through an optical window disposed in the wall of the plasma processing chamber. The optics includes a mirror configured to scan a plurality of non-matching light rays across the plasma processing chamber; And a telecentric coupler for collecting the optical signal from the plasma and directing the optical signal to a spectrometer for measuring plasma optical emission spectra.

Description

Spatially resolved optical emission spectroscopy (OES) in plasma processing

Cross Reference to Related Applications

This application claims priority to US patent application Ser. No. 15 / 648,035, filed July 12, 2017, entitled "SPATIALLY RESOLVED OPTICAL EMISSION SPECTROSCOPY (OES) IN PLASMA PROCESSING" (reference number TTI-247), The entire contents of which are incorporated herein by reference. Additionally, this application is hereby incorporated by reference to US Patent Application No. 14 / 530,164 entitled "SPATIALLY RESOLVED OPTICAL EMISSION SPECTROSCOPY (OES) IN PLASMA PROCESSING", filed Oct. 31, 2014 (reference number TTI-242). Which is incorporated herein by reference in its entirety and filed on November 1, 2013, entitled "SPATIALLY RESOLVED OPTICAL EMISSION SPECTROSCOPY (OES) IN PLASMA ETCHING" (reference number TTI-242PROV). It is based on 61 / 898,975 and claims its interests and priorities.

The present invention relates to methods, computer methods, systems, and apparatus for measuring concentrations of chemical species in semiconductor plasma processing using plasma optical emission spectroscopy (OES). In particular, the present invention relates to determining two-dimensional distributions of plasma optical emissions from which two-dimensional distributions of species concentrations can be determined.

The creation of semiconductor devices, displays, photovoltaic proceeds in a sequence of steps, each step having parameters optimized for maximum device yield. In plasma processing, among the controlled parameters, the chemistry of the plasma, in particular the local chemistry of the plasma, ie the local concentrations of various species in the plasma environment adjacent to the substrate being processed yields. ) Is strongly affected. Certain species, in particular transient species such as radicals, have a large impact on plasma processing performance, and elevated local concentrations of these species can create areas of faster processing, which It may lead to processing steps and non-uniformities in the ultimately generated devices.

The chemistry of the plasma process may include one or more RF or microwave powers supplied to excite the plasma, gas flows and types of gases supplied to the plasma processing chamber, pressure in the plasma processing chamber, It is controlled in a direct or indirect manner through the control of a large number of process variables such as type, pumping speed delivered to the plasma processing chamber, and more. Optical emission spectroscopy (OES) has proven itself as a useful tool for process development and monitoring in plasma processing. In optical emission spectroscopy, the presence and concentrations of certain species of interest, such as radicals, are inferred from the acquired optical (ie, light) emission spectra of the plasma, where the intensities and ratios of certain spectral lines Are correlated to concentrations of species. A detailed description of the technique can be found, for example, in G. Selwyn, "Optical Diagnostic Techniques for Plasma Processing", AVS Press, 1993 and will not be repeated here for brevity.

The use of optical emission spectroscopy has become relatively common, especially in plasma process development, but it is usually done by acquiring optical emission spectra from a single elongated volume in the plasma, inside the plasma processing chamber. The precise shape and size of this volume is determined by the optical system used to collect the optical emission from the plasma. This collection of optical emission signals essentially results in the averaging of the plasma optical emission spectra along the length of this elongated volume, also known as a ray, and thus local fluctuations in the plasma optical emission spectra, and Thus, also, all information about local variations in species concentrations is generally lost.

In the development of plasma processes, and indeed in the development of new and improved plasma processing systems, it is useful to know the two-dimensional distribution of the species of interest on the substrate being processed, and thus in system design and / or process parameters. The changes in can be done, for example, to minimize variations in processing performance across the substrate. Further applications of the plasma optical emission spectroscopy technique are, for example, by monitoring the evolution and abrupt changes of species present in the plasma associated with the etching step reaching a substrate layer of a different chemical composition than was etched during the etching process. In determining the endpoint of the plasma processing step. The ability to determine the plasma processing step endpoint across the entire surface of the substrate contributes to increased device yield due to not terminating the plasma processing step early.

One widely used in other fields of technology, such as X-ray tomography, to determine the spatial distribution of a variable from known integrated measurements along a number of light rays traversing an area of interest. 'S technique is tomographic inversion using Abel transform or Radon transfrom. However, effectively, this technique is not practical for large amounts of semiconductor processing tools that have limited optical access to the plasma through one or a small number of windows or optical ports built into the plasma processing chamber wall. Requires the acquired data, i.e. a large number of rays. Tomographic techniques are also generally very computationally intensive. Local fluctuations in species concentrations are generally smooth in nature, without any sharp gradients in the radial direction, and without much sharper gradients in the circumferential (ie azimuthal) direction. Was also found. Thus, a simple, fast and relatively low cost plasma optical emission spectroscopy capable of obtaining two-dimensional distributions of plasma optical emission spectra without the overhead involved in tomographic approaches to OES measurements. It would be advantageous to have the technique and system.

In particular, the variations in the circumferential direction may be small, but the variations do not exist as some conventional techniques assume, and an ideal technique and system should still be able to reliably capture these variations.

Aspects of the invention include an apparatus for optical emission measurement that includes a collection system for collecting plasma optical emission spectra through an optical window disposed in a wall of the plasma processing chamber. The collection system includes a mirror configured to scan a plurality of non-coincident rays across the plasma processing chamber; And a telecentric coupler for collecting the optical signal from the plasma and directing the optical signal to a spectrometer for measuring plasma optical emission spectra.

Alternative embodiments include a plasma processing chamber; An optical window disposed on the wall of the plasma processing chamber; A collection system for collecting plasma optical emission spectra through the optical window; A plasma optical emission measurement system including a spectrometer coupled to a collection system for measuring plasma optical emission spectra. The collection system includes a mirror configured to scan a plurality of non-matching light rays across the plasma processing chamber, and a telecentric combiner for collecting the optical signal from the plasma and directing the optical signal to the spectrometer.

Yet another embodiment of the invention includes depositing an optical window in a wall of a plasma processing chamber; Providing a collection system for collecting plasma optical emission spectra through an optical window, the collection system comprising a mirror and a telecentric combiner; Scanning a plurality of non-matching light rays across the plasma processing chamber using a mirror; Collecting an optical signal from the plasma via a telecentric coupler; And directing the optical signal to a spectrometer for measuring plasma optical emission spectra.

Many more complete recognition of the invention and its ancillary advantages will be readily apparent with reference to the following detailed description, particularly when considered in conjunction with the accompanying drawings:
1 is a side schematic view of a plasma processing system with an optical emission spectroscopy (OES) measurement system, according to an embodiment.
2 is a top schematic view of a plasma processing system with an OES measurement system, in accordance with an embodiment.
3 is an exemplary plasma optical emission spectrum acquired using an OES measurement system, according to an embodiment.
4 is a schematic diagram of an optical system for use in an OES measurement system, according to an embodiment.
5 is a schematic diagram of an optical system for use in an OES measurement system, according to another embodiment.
6 is an enlarged schematic diagram of an embodiment of an optical system, according to an embodiment.
7 is an exemplary two-dimensional distribution of plasma optical emission measured using an OES measurement system and associated method, according to an embodiment.
8 is a schematic diagram of an optical system for use in an OES measurement system, according to another embodiment.
9 is an enlarged schematic diagram of an embodiment of an optical system, according to another embodiment.
FIG. 10 is a top schematic view of a plasma processing system with the optical system of FIG. 8.
11 is an enlarged schematic diagram of an embodiment of an optical system, according to another embodiment.
12 is a schematic diagram of an optical system for use in an OES measurement system, according to another embodiment.
13 is a schematic diagram illustrating exemplary results of reconstructed patterns of optical emission intensity.
14 is a flowchart illustrating a method for optical emission measurement, according to one example.

In the following description, specific geometries of the plasma optical emission spectroscopy (OES) system, and various components and processes, are intended to facilitate a thorough understanding of the invention and for purposes of explanation and not limitation. Specific details such as the descriptions are described. However, it should be understood that the invention may be practiced in other embodiments that depart from these specific details.

In the description that follows, the term substrate representing the workpiece being processed includes a semiconductor wafer, a liquid crystal display (LCD) panel, a light-emitting diode (LED), a photovoltaic (PV) device panel. And the like, and the like, and processing of all of them falls within the scope of the claimed invention.

Reference throughout this specification to "one embodiment" or "an embodiment" is provided that certain features, structures, materials, or properties described in connection with the embodiment are included in at least one embodiment of the invention. It does not indicate that they are present in every embodiment. Accordingly, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily referring to the same embodiment of the invention. In addition, certain features, structures, materials, or properties may be combined in any suitable manner in one or more embodiments.

Various operations will be described in turn as multiple individual operations, in a manner that is most helpful in understanding the invention. However, the order of description should not be construed as to imply that these operations are necessarily order dependent. In particular, these operations need not be performed in the order of presentation. Operations described may be performed in a different order than the described embodiment. Various additional operations may be performed and / or described operations may be omitted in additional embodiments.

1 illustrates an embodiment of a plasma processing system 10 having a plasma optical emission spectroscopy (OES) system 15. The plasma processing system 10 includes a plasma processing chamber 20 in which a substrate holder 30, such as an electrostatic chuck, is placed therein for receiving a substrate 40 to be processed. do. Radio frequency (RF) and / or microwave power is supplied (not shown) to the plasma processing chamber 20 to ignite and sustain the plasma 50 adjacent the substrate 40. Here, highly reactive species from the plasma 50 are used to perform the plasma processing step on the substrate 40. Processing gases are flowed into the plasma processing chamber 20 (not shown) and a pumping system is provided (not shown) to maintain a vacuum in the plasma processing chamber 20 at the desired process pressure. Examples of plasma processing steps include plasma etching, plasma-enhanced chemical vapor deposition (PECVD), plasma-enhanced atomic layer deposition (PEALD), and the like. The systems and methods described herein are applicable to any kind of plasma processing.

Plasma optical emission spectroscopy (OES) system 15 is used to communicate the acquired plasma optical emission spectra and to obtain plasma optical emission spectra through at least one optical detector 60 controlled by the controller 80. do. The controller 80 may be a general purpose computer, may be located adjacent to the plasma processing system 10, or may be located remotely, and connect to the optical detector 60 via an intranet or internet connection. May be

Optical detector 60 has optics configured in such a way that optical detector 60 collects plasma optical emissions from an elongate, generally pencil-shaped volume of space 65 in plasma 50. Optical access to the plasma processing chamber is provided by the optical window 70. The optical window 70 may comprise a material such as glass, quartz, fused silica, or sapphire, depending on the application and how aggressive the chemistry of the plasma 50 is. . Volume 65, hereinafter referred to as “light” 65, defines a portion of the space in which plasma optical emission spectra are collected therefrom, with the collected spectra being located along and within ray 65. Express the integral of the contributions to the collected plasma optical emission spectra from the points. Note that, depending on the geometry and configuration of the optical detector 60, the contributions of each point in the ray 65 are not the same, but weighted and governed by the optical efficiency (which will be discussed in more detail later). Should be. In a typical configuration, the light rays 65 are oriented substantially parallel to the surface of the substrate 40 and maintained at a small distance from the surface of the substrate 40 to reduce optical interference from the substrate surface, but adjacent to the substrate surface. It is kept close enough to the substrate 40 to sample the plasma chemistry.

The controller 80 controls the plasma optical emission spectroscopy system 15, as mentioned previously, and also (1) calculates the plasma optical intensity distribution as a function of spatial position and wavelength, and calculates the calculated plasma optical intensity From the distribution (2) it is used to calculate the spatial distribution of the species of interest. This information can then be used for process development, plasma processing tool development, in-situ plasma process monitoring, plasma process error detection, plasma process endpoint detection, and the like.

으로서, 그 광학적 검출기(60)의 중심선에 대하여 정의된다. 플라즈마 프로세싱 챔버 내의 매 포인트는 도 2에서 도시된 바와 같이, 그 극 좌표(polar coordinate)들, 즉,

에 의해 정의될 수 있다.1 shows one ray 85 traversing a plasma 50 located in a plasma processing chamber 20 adjacent to the substrate 40 being processed. In an embodiment of the invention, multiple light rays 100 may be used to sample plasma optical emission spectra, for example, as shown in FIG. 2, which shows a top schematic view of the plasma processing system 10 of FIG. 1. have. In the example embodiment of FIG. 2, two optical detectors 60 are used to collect plasma optical emission spectra, each of which is from seven rays 100. Rays 100 need to be non-matched such that the greatest amount of spatial information is obtained from plasma 50 over substrate 40. The number of light rays 100 per optical detector 80 can vary from 2 to 9 and higher. Also, in another embodiment where optical access is provided to the plasma processing chamber 20 only by a single optical window 70, a single optical detector 80 is associated with its associated fan of rays 100. Can be used. Alternatively, third or more optical detectors, each having an associated light fan, may be used. The angle of each ray 100

As for the center line of the optical detector 60 is defined. Every point in the plasma processing chamber has its polar coordinates, ie, as shown in FIG.

Can be defined by

로부터 또 다른 것으로 주사될 때에 수집된다. 이해가능하게도, 이 주사 및 취득은 플라즈마 화학작용에서의 신속한 변화들이 전체 기판에 걸쳐 검출될 수 있도록 충분히 고속으로 발생할 필요가 있다.As described in more detail below, depending on the configuration of the optical detector 60, all plasma optical emission spectra from the associated fan of the rays 100 may be collected simultaneously. This is suitable for embodiments of optical detector 60 having multiple optics and channels, allowing simultaneous collection from all light rays 100. Alternatively, the plasma optical emission spectra can be acquired sequentially along the rays 100 associated with the optical detector 80. The latter is suitable in scanning embodiments, where the plasma optical emission spectra are in one angle of the light ray 100.

Collected when injected from one to another. Understandably, this scanning and acquisition needs to occur at a sufficiently high speed so that rapid changes in plasma chemistry can be detected across the entire substrate.

에서, 하나의 광선(100)으로부터 취득된 일 예의 플라즈마 광학적 방출 스펙트럼을 도시한다. 스펙트럼에서는, 전형적으로, 약 200 nm로부터 약 800 nm까지의 범위인 파장들의 세기들이 수집된다. 광학적 방출 스펙트로스코피를 위하여 채용된 전형적인 스펙트로미터들의 CCD들은 파장 범위에 걸쳐 이어지는 4096 개의 픽셀들을 가지지만, 픽셀들의 수는 응용 및 수집된 스펙트럼들의 요구된 해상도에 따라, 256만큼 낮게 그리고 65536만큼 높게 변동될 수 있다.3 shows the angle using one optical detector 60.

Shows an example plasma optical emission spectrum acquired from one ray 100. In the spectrum, intensities of wavelengths that typically range from about 200 nm to about 800 nm are collected. Typical spectrometers CCDs employed for optical emission spectroscopy have 4096 pixels spanning the wavelength range, but the number of pixels may vary as low as 256 and as high as 65536, depending on the application and the required resolution of the collected spectra. Can be.

Plasma optical emission spectra collected by optical detectors 60 from their associated fans of rays 100 are communicated to controller 80, which further processes the communicated data, thereby causing plasma optical emission. And the spatial distribution of chemical species concentrations therefrom. Aspects of the present invention are algorithms for fast computation of the spatial distribution of plasma optical emissions for each wavelength, allowing in-situ monitoring of plasma processes for endpoint detection, error detection, and the like.

4 shows an embodiment of an optical detector 80 in which a single multichannel spectrometer 310 is used to collect plasma optical emission spectra from light rays 305A-305E simultaneously. The example embodiment shown here has five rays 305A through 305E for clarity, but the number may vary from 2 to 9 and higher than nine. Optical detector 60 includes optical systems 300A-300E for each light ray 305A-305E, all located adjacent to optical window 70 mounted on the wall of plasma processing chamber 20. Rays 305A-305E are arranged in a diverging manner to cover the relevant portion of substrate 40 (not shown). The collected plasma optical emission spectra are fed from the optical systems 300A through 300E to the multi-channel spectrometer 310 through the individual optical fibers 320A through 320E. The optical systems 300A to 300E will be described in more detail later. The embodiment of FIG. 4 is suitable for high speed diagnostics because of its ability to simultaneously collect plasma optical emission spectra.

5 shows an alternative embodiment in which a single channel spectrometer 310 is used, with light rays 305A-305E being controllably scanned to sweep out light rays 305A-305E. While formed by the scanning mirror 400, the plasma optical emission spectra are acquired by the spectrometer 310 through a single optical system 300, which will be described in more detail later. This embodiment is suitable for the sequential collection of plasma optical emission spectra and therefore more suitable for the diagnosis of slower-evolving plasma processes. The scanning mirror 400 may be mounted and actuated by a galvanometer stage 410. Alternatively, scan mirror 400 may be mounted on stepper motor 410 and may be scanned by stepper motor 410. The number of rays 305A-305E here is shown as 5, but in practice, the number is determined by the settings in the controller software for controlling the galvanometer stage or stepper motor 410.

In order to ensure that a precise volume of space is sampled, the optics 300A-300E of FIG. 4 and the optics 300 of FIG. 5 have light beams 305A-305E for a given target cost of the optics. It needs to be configured to collimate with a small divergence angle as can be achievably achieved.

An exemplary embodiment of the optical systems 300A-300E, and 300 is shown in FIG. 6. Optics 300A-300E, also known as a telecentric combiner, collect plasma optical emission spectra from the volume of space in plasma 50 defined by light rays 305A-305E, and the plasma optical emission spectra are shown in FIG. It has a task to direct the collected plasma optical emission spectra to the ends 390 of the optical fibers 320A-320E, or 320 so that they can be transmitted to the spectrometers 310 of the embodiments of FIG. The diameter of the rays 305A-305E is defined by an optional aperture 350 formed in the plate. In an alternative embodiment, other optical components, such as lenses, may be used to define the diameter of the light rays 305A-305E. An example light beam diameter is 4.5 mm, but depending on the application, the light beam diameter may vary from about 1 mm to 20 mm. Collected light rays 305A through 305E, in combination with an optional opening, pass through a combination of collection lenses 360A and 380B that define light rays 305A through 305E. The numerical aperture of the collection system and light rays 305A-305E is generally very low, for example approximately 0.005, and the resulting light rays 305A-305E are essentially collimated with a minimum divergence angle. . On the other end of the optics 300A to 300E, or 300, another pair of lenses, ie, a combination that acts to focus the collected optical emission spectra onto the ends 390 of the optical fibers 320A to 320E, or 320. There are coupling lenses 370A and 370B. All the lenses used in the system are preferably achromatic or even apochromatic for more demanding applications, which ensures that the focal length of each lens does not vary with wavelength (300A-300E, or 300) typically operates satisfactorily on a large range of wavelengths, from 200 nm to 800 nm, but in some cases as low as 150 nm. For better performance in the ultraviolet part of the spectrum, i.e. 350 nm or less, UV-grade materials should be used for all optical components.

을 아는 것이 중요하다. 광학적 효율

은 광선(305A 내지 305E) 내의 주어진 위치로부터 광섬유 단부(390)까지의 광의 결합의 효율을 결정하기 위하여, 광학적 설계 소프트웨어를 이용하여 시뮬레이션에 의해, 또는 교정된 광원들을 이용하고 교정된 광원들을 광선들(305A 내지 305E)에 걸쳐 그리고 광선들(305A 내지 305E)을 따라 이동시키는 실험에 의해 결정될 수 있다. 광학적 효율들

은 플라즈마 광학적 방출들의 공간적 분포를 결정하기 위한 알고리즘에서 이용될 것이다.For every optical hardware configuration, optical efficiency is a weighting factor that is applied to all points in the light rays 305A to 305E from which the plasma optical emission spectra are obtained.

It is important to know. Optical efficiency

In order to determine the efficiency of the coupling of light from a given position in the silver rays 305A to 305E to the optical fiber end 390, the light sources are calibrated by simulation using optical design software or by using calibrated light sources Can be determined by experiments moving across 305A-305E and along light rays 305A-305E. Optical efficiencies

Will be used in the algorithm for determining the spatial distribution of plasma optical emissions.

개의 측정된 파장들

의 각각에 대한, 플라즈마 광학적 방출의 2 차원 세기 분포의 결정이다.As previously mentioned, the operation of the plasma optical emission spectroscopy (OES) system 15

Measured wavelengths

For each of is a determination of the two-dimensional intensity distribution of the plasma optical emission.

에 의해 수학적으로 나타내어지는 광선에 대하여, 수집된 광학적 검출기 출력

은 다음으로서 정의될 수 있고,Each ray 100, index of FIG. 2

Collected optical detector output for light rays mathematically represented by

Can be defined as

은 광선(100) 내에서의 그리고 광선(100)을 따르는 위치

에서의 플라즈마 광학적 방출 세기이고,

은 광학적 검출기

에 의해 위치

로부터의 광의 수집을 위한 광학적 효율이다. 결과적인 광학적 검출기 출력

은 기판(도 2 참조)의 원주 상의 포인트 A로부터 포인트 B까지의 직선 경로를 따르는 이 수량들의 곱셈(product)의 적분을 표현하고, 기판(40)의 원주 외부의 플라즈마로부터의 기여분들은 이 모델에서 무시된다(이것은 플라즈마 밀도 및 이에 따른 플라즈마 광 방출이 이 에어리어들에서 일반적으로 낮기 때문에 유효한 가정임).here,

Position within and along ray 100

Plasma optical emission intensity at

Silver optical detector

By location

Optical efficiency for the collection of light from. Resultant optical detector output

Represents the integral of the product of these quantities along a straight path from point A on the circumference of the substrate (see FIG. 2) to point B, the contributions from the plasma outside the circumference of the substrate 40 Is ignored (this is a valid assumption because the plasma density and thus plasma light emission are generally low in these areas).

개의 광학적 검출기들 및 광선들, 또는 대안적으로, 광선들(100)의

개의 주사된 포지션(position)들을 갖는 플라즈마 광학적 방출 스펙트로스코피 시스템(15)에서는,

개의 측정된 파장들

의 각각에 대한

개의 수집된 세기들이 있다. 그러므로, 하나의 파장

에서의 플라즈마 광학적 방출의 공간적 분포를 재구성하기 위하여,

개의 파라미터들을 갖는 함수 형태가 가정되어야 한다. 한정된 수

개의 파라미터들이 주어지면, 플라즈마 광학적 방출의 분포에 대한 기저 함수들의 판단력 있는 선택이 행해져야 할 필요가 있다. 선택된 기저 함수들은 이들이 기판(40)에 걸쳐 플라즈마 방출의 원주 변동들을 만족스럽게 재현할 수 있기 위하여, 방사상 좌표

및 또한, 원주 좌표

양자와 함께 변동될 필요가 있다.

Optical detectors and light rays, or alternatively, light rays 100

In the plasma optical emission spectroscopy system 15 with two scanned positions,

Measured wavelengths

For each of

There are two collected centuries. Therefore, one wavelength

To reconstruct the spatial distribution of plasma optical emission in

A function type with 2 parameters should be assumed. A limited number

Given two parameters, a judgmental choice of basis functions for the distribution of plasma optical emission needs to be made. The selected basis functions are radial coordinates so that they can satisfactorily reproduce the circumferential variations in plasma emission across the substrate 40.

And also circumferential coordinates

It needs to be varied with both.

이다. 제르니케 다항식들은 방사상 좌표

에 종속적인 항 및 원주 좌표

에 종속적인 항의 곱셈으로서 정의되고, 즉,One class of basis functions particularly well suited to this task is the Zernike polynomials.

to be. Zernike polynomials are radial coordinates

Term and circumference coordinates dependent on

Is defined as the multiplication of terms that depend on

를 이용하여 본원에서 나타내어진 최초 18 차수 제르니케 다항식(first 18 order Zernike polynomial)들을 열거한다.Table 1 shows commonly used mathematical notation

Enumerate the first 18 order Zernike polynomials represented herein.

In general, as in the case of Zernike polynomials, other basis functions can be selected in this application as long as the other basis functions are orthogonal and their derivatives are continuous on the unit circle. However, Zernike polynomials are preferred in this application because of the property that a relatively small number of terms can be used to account for fairly complex variations in the function of both radial and circumferential polar coordinates.

을 수집된 검출기 출력으로 치환하는 것은 다음으로 귀착되고,Zernike polynomials

Substituting for the collected detector output results in

은 매 기저 함수, 즉, 제르니케 다항식 차수와 연관된 맞춤 파라미터들이다.here,

Are the custom parameters associated with each basis function, ie the Zernike polynomial order.

은 선택된 기저 함수들, 맞춤 파라미터들, 및 광학적 효율의 측면에서 정의되므로,

의 맞춤 파라미터들

을 결정하는 문제는 다음을 최소화하는 것, 즉, 최소 제곱 문제를 푸는 것으로 축소되고,Collected Detector Output

Is defined in terms of selected basis functions, fitting parameters, and optical efficiency,

Custom parameters

The problem of determining is reduced to minimizing the following: solving the least squares problem,

or

은 광선

에서의 측정된 플라즈마 광학적 스펙트럼들 세기들을 표현한다. 이 최소화 알고리즘은

개의 측정된 파장들

의 각각에 대하여 반복될 필요가 있다. 이 최소 제곱 문제를 풀기 위한 많은 방법들이 당해 분야에서 알려져 있다. 최소 제곱 문제의 치수는 상대적으로 작으므로, 최소 제곱 문제는 플라즈마 광학적 방출 스펙트럼들이 측정되는 시간에 있어서의 각각의 순간에 대하여, 모든 파장들에 대해 효율적으로 풀릴 수 있고; 또한, 이러한 계산들은 급속하게 연속으로 반복될 수 있어서, 큰 수들

개의 파장들에 대한 플라즈마 광학적 방출들의 급속하게 진화하는 2 차원 분포들의 결정을 가능하게 할 수 있다. 이것들로부터, 누군가는 그 다음으로, 종점 검출, 오류 검출, 프로세스 개발, 프로세싱 도구 개발 등을 위하여 이용될 수 있는, 기판(40)에 걸친 화학종들 농도들의 시간-진화하는 2 차원 분포들을 결정할 수 있다.here,

Silver rays

Represent the measured plasma optical spectra intensities at. This minimization algorithm

Measured wavelengths

It needs to be repeated for each of. Many methods are known in the art to solve this least squares problem. Since the dimension of the least squares problem is relatively small, the least squares problem can be solved efficiently for all wavelengths, for each instant in time at which the plasma optical emission spectra are measured; Also, these calculations can be repeated in rapid succession, so that large numbers

It may be possible to determine the rapidly evolving two-dimensional distributions of plasma optical emissions for two wavelengths. From these, one can then determine time-evolving two-dimensional distributions of species concentrations across the substrate 40, which can then be used for endpoint detection, error detection, process development, processing tool development, and the like. have.

에도 불구하고, 플라즈마 광학적 방출 세기에서의 양자의 방사상 및 원주 변동들의 양호한 캡처를 명확하게 도시한다.7 shows an example of one such plasma optical emission intensity distribution determined by a method according to an embodiment of the invention. The distribution shown shows a relatively low number of terms,

Nevertheless, it clearly shows a good capture of both radial and circumferential variations in plasma optical emission intensity.

= 25°)에 걸쳐 광선들(305A 내지 305E)을 스윕 아웃하기 위하여 전형적으로 작고(즉, 직경에 있어서 1 인치), 광선들(305A 내지 305E)은 광학적 윈도우(70)에서 최소 편위(minimal excursion)를 가진다. 그러므로, 광선들(305A 내지 305E)의 회전의 중심은 광학적 윈도우(70)의 실질적으로 근처 또는 광학적 윈도우(70)에 있도록 구성된다. 본원에서 설명된 구성을 이용하면, 68.5 mm x 8 mm 또는 더 큰 것의 치수를 가지는 윈도우를 이용하는 것이 가능하다. 윈도우 치수(즉, 상한)는 오염, 챔버 UV 및 RF 누설, 및 플라즈마 프로세싱 챔버(20)의 벽에서의 이용가능한 공간과 같은 인자들에 의해 제한된다. 하나의 구현예에서, 윈도우는 빔의 주사의 평면에 대응하는 평면에서 큰 치수를 갖는 직사각형 형상을 가질 수도 있다. 그것은 누설 및 공간 요건들을 만족시키면서 윈도우의 크기를 최소화하는 장점을 가진다.8 illustrates an alternative embodiment in which a single channel spectrometer 310 is used. Light rays 305A through 305E are arranged in the optical window 70, or FIG. 3, from the position of the scan mirror 400 and the stepper motor 410 associated with the scan mirror 400 with the center of rotation of the lights 305A through 305E. It is formed by a mirror system 800 that moves substantially near the optical window 70 as indicated by point C at point 8 (point C shows the center of rotation). The optical window 70 thus corresponds to the angle of the central axis of the plasma 50 (eg, the plasma processing chamber 20).

= 25 °) and are typically small (ie 1 inch in diameter) to sweep out rays 305A through 305E, and rays 305A through 305E are minimal excursion in optical window 70 ) Therefore, the center of rotation of the rays 305A-305E is configured to be substantially near or in the optical window 70 of the optical window 70. Using the configuration described herein, it is possible to use windows having dimensions of 68.5 mm x 8 mm or larger. Window dimensions (ie, upper limit) are limited by factors such as contamination, chamber UV and RF leakage, and available space in the walls of the plasma processing chamber 20. In one implementation, the window may have a rectangular shape with large dimensions in a plane corresponding to the plane of scanning of the beam. It has the advantage of minimizing the size of the window while satisfying leakage and space requirements.

Scanning mirror 400 is controllably scanned to sweep out rays 305A to 305E using stepper motor 410, while plasma optical emission spectra are spectrometer 310 through single optic 300 Is obtained by

Mirror system 800 may include a transfer mirror 802 and a fold mirror 804. Each collected rays 305A through 305E, or 65 (ie, an optical signal from a plasma having the collected rays 305) reflects the collected rays 305 and folds the collected rays 305 into a fold mirror. Transmitted by transmission mirror 802 to transmit to 804. The fold mirror 804 reflects the collected light rays 305 from the horizontal (azimuth angle) to the vertical concentric circles and transmits the collected light rays 305 to the scan mirror 400, which scan mirror 400 collects the light rays 305 ) Is reflected by the optical system 300. The mirror system 800 and the optical system 300 are stationary. The mirror system 800, the scanning mirror 400, the optical system 300, and the spectrometer 310 may be mounted adjacent to the plasma processing chamber 20.

°, +

° 사이의 임의의 포지션과 연관된다. 이에 따라, 본원에서 설명된 주사 셋업을 이용하면, 매우 정밀한 공간적 해상도가 획득될 수 있다.When the scanning mirror 400 is swept, a high spatial resolution of the spatial distribution of species concentrations is obtained. For example, the scanning mirror 400 may be slowly swept while the plasma optical emission spectra are acquired. The acquired plasma optical emission spectra are −

°, +

Associated with any position between °. Thus, using the scan setup described herein, very precise spatial resolution can be obtained.

9 is an enlarged schematic diagram of an embodiment of the optical system 300 of FIG. 8, according to an embodiment. Optical system 300 collects plasma optical emission spectra from the volume of space in plasma 50 defined by collected light rays 305, and the plasma optical emission spectra are spectrometers (as previously described herein). It has the task of directing the collected plasma optical emission spectra to the end 390 of the optical fiber 320 so that it can be transmitted to 310. Optical system 300 includes a telecentric coupler having a small NA. The collected scan rays sizes can vary from about 3 to 5 mm in diameter along the collection path.

의 직경을 가지는 텔레센트릭 개구부(908)를 통과하게 될 수도 있다. 그 다음으로, 2 개의 결합 렌즈들(904 및 906)은 수집된 광학적 방출 스펙트럼들을 광섬유(320)의 단부(390) 상으로 포커싱하도록 작용한다. 하나의 예에서, 광섬유(320)는 600

의 직경을 가진다. 수집 시스템(300)은 또한, 2 개의 결합 렌즈들(904 및 906) 사이에 위치결정된 임의적인 필터를 포함할 수도 있다.The collected light rays 305 (ie, reflected from the scanning mirror 400) pass through the first collecting lens 902. Next, the rays are, for example, 600

It may be passed through a telecentric opening 908 having a diameter of. Next, the two coupling lenses 904 and 906 act to focus the collected optical emission spectra onto the end 390 of the optical fiber 320. In one example, optical fiber 320 is 600

Has a diameter of. Acquisition system 300 may also include an optional filter positioned between two coupling lenses 904 and 906.

The numerical aperture of the collection system 300 is very low, for example 0.005. Lenses 902, 904, and 906 are achromatic lenses having effective focal lengths of 30 mm, 12.5 mm, and 12.5 mm, respectively, and diameters of 12.5 mm, 6.25 mm, and 6.25 mm.

Referring again to FIG. 8, the scan mirror 400 may have a dimension of at least 10 mm × 10 mm. The transmission mirror 802 may be a spherical mirror. Scanning mirror 400 and transmission mirror 802 may be coated with an aluminum coating, silicon monoxide (SiO) overcoat, or aluminum to increase reflectance in certain wavelength regions (eg, UV). It may have a multilayer film of dielectrics on top. The radius of the transmission mirror 802 may be between 100 mm and 120 mm. In one implementation, the radius of the transmission mirror 802 is 109.411 mm. The transmission mirror 802 may be positioned at a distance of 68.4 mm from the outer edge of the optical window 70. Fold mirror 804 may be positioned at a distance of 71.5 mm from the plane of scan mirror 400.

The spectrometer 310 may be an ultra broadband (UBB) high resolution spectrometer having a spatial resolution of 0.4 nm and having a wavelength range between 200 nm and 1000 nm.

°로부터 +

°(예컨대,

= 25° 또는 30°)로 변동될 수도 있다. 스펙트로미터들(310)로부터의 데이터는 2 차원(2D) OES 세기 분포를 획득하기 위하여 본원에서 이전에 설명된 바와 같이 프로세싱된다. 각각의 모듈은 단일 채널 스펙트로미터(310)를 포함할 수도 있거나, 대안적으로, 2 개의 채널들을 가지는 단일 스펙트로미터는 2 개의 주사 모듈들을 위하여 이용될 수도 있다. 추가적인 주사 모듈들은 또한, 더 높은 공간적 해상도를 제공하기 위하여 이용될 수도 있다. 광학적 윈도우들(70)(즉, 각각의 주사 모듈의 광학적 윈도우(70))은 서로에 대해 수직이거나 실질적으로 수직인 플라즈마 프로세싱 챔버(20)의 측벽 상에서 위치될 수도 있다. 플라즈마 프로세싱 챔버(20)의 구성에 따라서는, 광학적 윈도우들(70)은 응용 및 플라즈마 화학작용이 얼마나 공격적인지에 따라 석영, 용융된 실리카, 또는 사파이어일 수도 있다.FIG. 10 is a top schematic view of a plasma processing system with the optical system of FIG. 8. The plasma processing chamber 20 may have two optical systems of FIG. 8. The optics are referred to as the scanning module. Each scanning module may be configured to collect data from X to Y light positions. In one implementation, each scanning module may be configured to collect data from five to fifty ray positions providing better accuracy for detecting events with high spatial resolution. In FIG. 10, one position of light ray 305 is shown. As previously described herein, the scanning angle of the rays 305 is −

From +

° (e.g.,

= 25 ° or 30 °). Data from spectrometers 310 are processed as previously described herein to obtain a two dimensional (2D) OES intensity distribution. Each module may include a single channel spectrometer 310, or alternatively, a single spectrometer with two channels may be used for two scanning modules. Additional scanning modules may also be used to provide higher spatial resolution. Optical windows 70 (ie, optical window 70 of each scanning module) may be located on the sidewall of plasma processing chamber 20 that is perpendicular or substantially perpendicular to each other. Depending on the configuration of the plasma processing chamber 20, the optical windows 70 may be quartz, fused silica, or sapphire, depending on the application and how aggressive the plasma chemistry is.

11 is an enlarged schematic diagram of an embodiment of the optical system 300 of FIG. 5 or 8. The optics 300 may reflect the collected collected plasma optical emission spectra from the scanning module 400 to the end of the optical fiber 320 such that the plasma optical emission spectra may be transmitted to the spectrometer 310 as previously described herein. 390 has a task to direct. Collected light rays 305 pass through a collecting lens, which may be, for example, a triplet lens 1102 having an effective focal length of 40 mm. The collected light rays 305 may be passed through an optional mask opening 1108 having a diameter of, for example, 7 mm. The mask opening 1108 may be positioned between the scanning mirror 400 and the triple lens 1102. The collected rays 305 may then be passed through an optional telecentric opening 1110 having a diameter of, for example, 1.20 mm. In alternative embodiments, other optical components, such as lenses, may be used to define the diameter of the light rays 305.

The two combined triple lenses 1104 and 1108 act to focus the collected optical emission spectra onto the end 390 of the optical fiber 320. In one implementation, the combined triple lenses 1104 and 1108 may be triple lenses having effective focal lengths of 15 mm. The effective focal lengths of the combined triple lenses 1104 and 1106 are a function of the type and diameter of the optical fiber 320.

All the lenses used in the system are preferably achromatic or even apochromatic for more demanding applications, which ensures that the focal length of each lens does not vary with wavelength, so that the optics 300A to 300E, or 300 typically operates satisfactorily on a large range of wavelengths from 200 nm to 1000 nm, but in some cases as low as 150 nm. For better performance at the UV part of the spectrum, i.e. 350 nm or less, UV-grade materials such as quartz, fused silica, Calcium fluoride (CaF 2) are used for all optical components.

12 is a schematic diagram of an alternative embodiment in which a single channel spectrometer 310 is used. Plasma optical emission spectra can be acquired sequentially using one or two modules. Each module may include a linear arc stage 1204. Spectrometer 310, optics 300, and fold mirror 1202 are mounted on linear arc stage 1204. Fold mirror 1202 is positioned to receive the light rays 305 collected from the plasma processing chamber 20 and to reflect the collected light rays 305 to the optical system 300. The linear arc stage 1204 is controllably scanned to sweep out the collected rays 305, while the plasma optical emission spectra are acquired by the spectrometer 310 through a single optic 300. The linear arc stage 1204 may be controlled via the controller 80. Point C in FIG. 12 indicates the center of rotation of the linear arc stage 1204. The single optical system 300 may be one shown and described in FIG. 9 or FIG. In one implementation, the linear arc stage 1204 may have a scan angle of 85 ° and a length of 163.2 mm. The linear scan speed may vary from 0.35 m / s to 2.2 m / s. Accordingly, the scanning speed may be adjusted to optimize the tradeoff between spatial resolution and speed, depending on the application of the plasma optical emission spectroscopy system 15.

In further embodiments of the optical system 300 of FIGS. 8, 9, and 11, mirrors, prisms, lenses, spatial light modulators, to steer the collected light rays 305, Other optical components, such as digital micromirror devices, may be used. The configuration and component layout of the optical system 300 of FIGS. 4-8 and 8-12 need not necessarily be exactly as shown in FIGS. 4-8 and 8-12, but the collected light rays. 305 may be folded and steered through additional optical components to facilitate packaging the plasma optical emission spectroscopy system 15 into a compact packaging suitable for mounting on the wall of the plasma processing chamber 20. .

The inventors have performed several experiments to reconstruct the patterns of the optical emission distribution and to compare the reconstructed patterns with etch patterns.

13 is a schematic diagram illustrating exemplary results of reconstructed patterns of optical emission intensity. The intensity of the emission line (ie 522.45 nm for silicon chloride) ultimately indicates the concentration of silicon chloride (SiCl) associated with the intensity of local etching on the substrate 40. FIG. 13 shows a comparison between the actual distribution of optical emission and the actual etch rate obtained by the plasma OES system 15 described herein at 522.5 nm. Plots 1302, 1304, and 1306 show actual etch rates for various samples in various plasma processing conditions. Plots 1308, 1310, and 1312 show the reconstructed optical emission distribution for the samples associated with plots 1302, 1304, and 1306, respectively.

Using the apparatus and methodologies described herein, etch uniformity may be monitored. For example, the apparatus may be used during process development to monitor the etch uniformity for various plasma processing conditions without transferring the substrate to another apparatus that speeds up the development of the various processes.

The results show a strong correlation between the etch thickness and the given reconstructed OES distribution by plasma etching involved species including both reactants and products. The uniformity of the OES distribution and the oxide etch profile follows the same trend, for example, when comparing plot 1308 to plot 1302. Substrates with better etch uniformity show lower correlation with the OES distribution (eg, chart 106 is compared to chart 1302).

14 is a flowchart illustrating a method 1400 for optical emission measurement, according to one example. At 1402, an optical window is deposited in a plasma processing chamber (eg, a wall of the plasma processing chamber 20. At 1404, a collection system is provided for collecting plasma optical emission spectra through the optical window. The telecentric combiner may comprise at least one collecting lens (eg, collection lenses 360A and 360B) and at least one combining lens (eg, coupling lenses 904 and 906 of FIG. 9). A plurality of non-matching light rays are scanned across the plasma processing chamber using a mirror at 1406. Scanning may be controlled by the controller 80. At 1408, the optical signal is tele Collected from the plasma via a centric coupler .. At 1410, an optical signal is used to measure plasma optical emission spectra. It is directed to the spectrometer.

Those skilled in the art will appreciate that many modifications and variations are possible in view of the above teachings. Those skilled in the art will recognize various equivalent combinations and permutations for the various components shown in the figures, and therefore, the scope of the invention is not to be described in this detailed description, but rather by the claims appended to the detailed description. It is intended to be limited.

The above disclosure also encompasses the embodiments listed below.

(1) a method for optical emission measurement, comprising depositing an optical window at a wall of a plasma processing chamber; Providing a collection system for collecting plasma optical emission spectra through an optical window, the collection system comprising a mirror and a telecentric combiner; Scanning a plurality of non-matching light rays across the plasma processing chamber using a mirror; Collecting an optical signal from the plasma via a telecentric coupler; And directing the optical signal to a spectrometer for measuring plasma optical emission spectra.

(2) The method of feature (1), wherein the telecentric coupler comprises at least one collecting lens; And at least one coupling lens.

(3) The method of feature (2), wherein the at least one collecting lens or the at least one combining lens is achromatic lenses.

(4) The method of feature (2), wherein the telecentric combiner further comprises an opening disposed between the at least one collecting lens and at least the combining lens for defining a diameter of the plurality of non-matching light rays. .

(5) The method of any of features (1) to (4), wherein the mirror is a scanning mirror.

(6) The method of feature (5), wherein the scanning mirror is mounted on a galvanometer scanning stage and scanned by a galvanometer scanning stage.

(7) The method of feature (5), wherein the scanning mirror is mounted on the stepper motor and scanned by the stepper motor.

(8) The method of feature (5), wherein the collection system further comprises a mirror system for shifting the center of rotation of the plurality of non-matching light rays into or near the optical window.

(9) The method of feature (8), wherein the mirror system comprises a transfer mirror; A fold mirror; The transmit mirror is configured to transmit the collected signal to the fold mirror, and the fold mirror is configured to transmit the collected signal to the mirror.

(10) The method of feature (1), wherein the telecentric combiner comprises: a collecting triplet lens configured to collect optical signals from the mirror; And two coupling triple lenses configured to focus the collected signal onto an end of the optical fiber coupled to the spectrometer.

(11) The method of feature (1), further comprising collecting plasma optical emission spectra through a second optical window disposed in the wall of the plasma processing chamber using the second collection system. The central axis of the second optical window is perpendicular to the central axis of the optical window.

(12) The method of feature (1), wherein the collection system is configured such that the linear arc stage holding the mirror, the telecentric combiner, and the spectrometer-the linear arc stage move radially with respect to the central axis of the optical window, Causing the plurality of non-matching light rays to scan across the plasma processing chamber.

(13) The method of feature (12), wherein the mirror is a fold mirror.

(14) The method of any one of features (1) through (13), wherein the plurality of non-matching light rays are scanned at 25 ° of the central axis of the optical window across the plasma processing chamber.

(15) The method of any one of features (1) to (14), wherein the spectrometer is an ultra-wideband high resolution spectrometer.

(16) The method of any one of features (1) to (15), wherein the collection system has a low numerical aperture.

(17) The method of any one of features (1) to (14), wherein the optical signal is collected from 21 non-matching light rays.

Claims (20)

Apparatus for optical emission measurement,
A collection system for collecting plasma optical emission spectra through an optical window disposed in a wall of the plasma processing chamber, the collection system comprising:
A mirror configured to scan a plurality of non-coincident rays across the plasma processing chamber; And
And a telecentric coupler for collecting the optical signal from the plasma and directing the optical signal to a spectrometer for measuring the plasma optical emission spectra. The method of claim 1,
The telecentric combiner,
At least one collection lens; And
An apparatus for optical emission measurement, comprising at least one coupling lens. The method of claim 2,
The at least one collecting lens or the at least one combining lens is an achromatic lens. The method of claim 2,
The telecentric combiner,
And an opening disposed between the at least one collecting lens and the at least one coupling lens to define a diameter of the plurality of non-matching light rays. The method of claim 1,
And the mirror is a scanning mirror. The method of claim 5, wherein
And the scanning mirror is mounted on a galvanometer scanning stage and scanned by the galvanometer scanning stage. The method of claim 5, wherein
And the scanning mirror is mounted on a stepper motor and scanned by the stepper motor. The method of claim 5, wherein
The collection system,
And a mirror system for shifting a center of rotation of the plurality of non-matching light rays to or near the optical window. The method of claim 8, wherein the mirror system,
Transfer mirror;
A fold mirror;
The transmission mirror is configured to transmit the collected optical signal to the fold mirror, and the fold mirror is configured to transmit the collected optical signal to the mirror. The method of claim 1,
The telecentric combiner,
A collection triplet lens configured to collect the optical signal from the mirror; And
And two coupling triple lenses configured to focus the collected optical signal onto an end of an optical fiber coupled to the spectrometer. The method of claim 1,
And a second collection system for collecting the plasma optical emission spectra through a second optical window disposed in the wall of the plasma processing chamber, the second optical window perpendicular to a central axis of the optical window. Apparatus for optical emission measurement, having a central axis. The method of claim 1,
The collection system,
And a linear arc stage holding the mirror, the telecentric coupler, and the spectrometer, the linear arc stage configured to move radially with respect to the central axis of the optical window, And cause a plurality of non-matching light rays to be scanned across the plasma processing chamber. The method of claim 12,
And the mirror is a fold mirror. The method of claim 1,
And the plurality of non-matching light rays are scanned at 25 ° of the central axis of the optical window across the plasma processing chamber. The method of claim 1,
Wherein the spectrometer is an ultra-wideband high resolution spectrometer. The method of claim 1,
And the collection system has a low numerical aperture. The apparatus of claim 1, wherein the optical signal is collected from 21 non-matching light rays. A system for plasma processing,
A plasma processing chamber;
An optical window disposed on a wall of the plasma processing chamber;
A collection system for collecting plasma optical emission spectra through the optical window;
A spectrometer coupled to the collection system for measuring the plasma optical emission spectra;
The collection system,
A mirror configured to scan a plurality of non-matched rays across the plasma processing chamber; And
And a telecentric coupler for collecting the optical signal from the plasma and directing the optical signal to the spectrometer. As a method for optical emission measurement,
Placing an optical window in a wall of the plasma processing chamber;
Providing a collection system for collecting plasma optical emission spectra through the optical window, the collection system comprising a mirror and a telecentric combiner;
Scanning a plurality of non-matching light rays across the plasma processing chamber using the mirror;
Collecting an optical signal from a plasma through the telecentric coupler; And
Directing the optical signal to a spectrometer for measuring the plasma optical emission spectra. The method of claim 19,
Shifting a center of rotation of the plurality of non-matching light rays to or near the optical window using a mirror system, the mirror system including at least a transmission mirror and a fold mirror , Method for optical emission measurement.

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