TW201920917A - Spatially resolved optical emission spectroscopy (OES) in plasma processing - Google Patents

Abstract

Disclosed is a method, system, and apparatus for optical emission measurement. The apparatus includes a collection system for collecting a plasma optical emission spectra through an optical window disposed at a wall of a 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 an optical signal from a plasma and directing the optical signal to a spectrometer for measuring the plasma optical emission spectra.

Description

Spatially resolved light emission spectroscopy in plasma processing

The invention relates to a method, a computer method, a system, and a device for measuring the concentration of chemical species in a semiconductor plasma treatment by using plasma optical emission spectroscopy (OES). Specifically, the present invention relates to determining a two-dimensional distribution of plasma light emission, from which a two-dimensional distribution of chemical species concentration can be determined. [Cross Reference of Related Applications]

This application is a partial continuation of US Patent Application No. 14 / 530,164, filed on October 31, 2014 and entitled "SPATIALLY RESOLVED OPTICAL EMISSION SPECTROSCOPY (OES) IN PLASMA PROCESSING" (reference number TTI-242). It is hereby introduced by reference to the entire contents of the case, which is based on the United States filed on November 1, 2013, named "SPATIALLY RESOLVED OPTICAL EMISSION SPECTROSCOPY (OES) IN PLASMA ETCHING" (reference number TTI-242PROV) Provisional Patent Application No. 61 / 898,975 and claims its rights and priority.

The production of semiconductor elements, displays, solar cells, etc. is performed in a series of steps, each of which has parameters optimized for maximum element yield. In the plasma treatment, the chemical properties of the plasma are those that strongly influence the yield among the controlled parameters, especially the local plasma chemical properties in the plasma environment near the substrate being treated, that is, the local concentrations of various chemical species . Certain species (especially transient chemical species such as free radicals) have a significant impact on the plasma treatment results, and it is known that higher local concentrations of these species may result in faster processing areas, which may be in the processing step In the end, unevenness is caused in the produced components.

The chemical nature of the plasma process is controlled directly or indirectly through the control of many process variables, such as one or more radio frequency (RF) or microwave power supplied to stimulate the plasma , The gas flow and gas type supplied to the plasma processing chamber, the pressure in the plasma processing chamber, the type of substrate being processed, the pumping rate to the plasma processing chamber, and many more variables. Optical emission spectroscopy (OES) has proven to be a useful tool in process development and monitoring of plasma processing. In light emission spectroscopy, the presence and concentration of certain chemical species (such as free radicals) that are of particular interest can be deduced from the optical (i.e., light) emission spectrum of the obtained plasma, and the intensity of some of the spectral lines and The ratio is related to the concentration of the chemical species. A detailed description of this technique is available in, for example, "Optical Diagnostic Techniques for Plasma Processing, AVS Press, 1993" by G. Selwyn, and is not repeated here for the sake of brevity.

Although the use of light emission spectroscopy has become relatively common, especially in the development of the plasma process inside the plasma processing chamber, light emission spectroscopy is usually accomplished by obtaining light emission spectra from a single narrow volume inside the plasma. . The exact shape and size of this volume is determined by the optical system used to collect light emission from the plasma. The collection of this light emission signal essentially causes the plasma light emission spectrum to be equally divided along the length of this narrow volume (also known as rays). Therefore, the local variation of the plasma light emission spectrum and the local variation of the concentration of chemical species All information was largely lost.

In the development of the plasma process, and in fact even in the development of new and improved plasma processing systems, it is useful to know the two-dimensional distribution of the chemical species of interest above the substrate being processed, for example, to make a system design. And / or changes in process parameters to minimize variations in processing results across the substrate. A further application of the plasma optical emission spectroscopy technique is to determine the end point of the plasma processing step by monitoring the evolution and discontinuous changes of the chemical species present in the plasma. The evolution and discontinuous changes are related to, for example, the An etching step is related to the chemical composition of the substrate layer being different from the chemical composition being etched during the etching process. The ability to determine the termination point of the plasma processing step over the entire substrate surface contributes to improved component yield, because the plasma processing step does not terminate prematurely.

A technique that is widely used in other technological fields (such as X-ray tomography) to determine the spatial distribution of a variable by a known integral measurement method along a plurality of rays traversing a region of interest. Tomographic inversion. However, in order to obtain effective results, this technology requires a large amount of data acquisition, that is, a large number of rays, which is impractical in semiconductor processing equipment with a limited plasma light channel, where the plasma light channel passes through Embedded in one or a few light windows or ports of the plasma processing chamber wall. Tomography is also often a very computationally intensive technique. We have also discovered that the local differences in the concentration of chemical species have the essence of a generally smooth change, and that there is no discontinuous gradient in either radial or even circumferential direction (ie, azimuth direction). Therefore, there is a simple, fast, and relatively low-cost technique for plasma light emission spectroscopy that can obtain a two-dimensional distribution of plasma light emission spectrum without the operational burden involved in the tomography method of OES measurement method and The system will be very advantageous.

The most obvious is that, as some prior art believes, although the variation in the circumferential direction may be small, it is not non-existent, and the ideal technology and system must still be able to obtain such variation.

One aspect of the present invention includes a device for measuring light emission. The device includes a collection system for collecting a plasma light emission spectrum through a light window provided in a wall portion of the plasma processing chamber. The collection system includes a mirror configured to scan a plurality of non-coinciding rays across the plasma processing chamber; and a telecentric coupler for collecting an optical signal from the plasma and guiding the optical signal Go to a spectrometer to measure the plasma light emission spectrum.

Another embodiment includes a plasma light emission measurement system including a plasma processing chamber; a light window disposed on a wall portion of the plasma processing chamber; and a collection system for transmitting through the plasma processing chamber. The light window collects the plasma light emission spectrum; a spectrometer coupled to the collection system is used to measure the plasma light emission spectrum. The collecting system includes a mirror configured to scan a plurality of non-coinciding rays across the plasma processing chamber, and a telecentric coupler for collecting an optical signal from the plasma and guiding the optical signal To the spectrometer.

Yet another embodiment of the present invention includes a method for measuring light emission, which includes setting a light window in a wall portion of a plasma processing chamber; and providing a collection system to collect the plasma through the light window. Light emission spectrum, the collection system includes a mirror and a telecentric coupler; use the mirror to scan a plurality of non-coincident rays that traverse the plasma processing chamber; collect an optical signal from the plasma through the telecentric coupler; and The optical signal is guided to a spectrometer to measure the plasma optical emission spectrum.

In the following description, specific details are listed to promote a thorough understanding of the present invention and for the purpose of explanation rather than limitation-for example, the specific geometric appearance of the plasma optical emission spectroscopy (OES) system and description of various components and procedures . It should be understood, of course, that the invention may be practiced in other embodiments that depart from these specific details.

In the following description, the terms "substrate" and the terms such as semiconductor wafers, liquid crystal display (LCD) panels, light emitting diodes (LEDs), and solar (PV) element control boards may be used interchangeably. Use, the treatment of all these items falls within the scope of the claimed invention.

Reference throughout this specification to "an embodiment" or "an embodiment" means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention, but is not It is represented in each embodiment. Thus, appearances of the words "in an embodiment" or "in an embodiment" throughout this specification do not necessarily mean the same embodiment of the invention. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments.

The various operations are described as a plurality of discrete sequential operations in a manner that is most helpful in understanding the invention. However, the order of description should not be understood as a metaphor that such operations must depend on this order. In particular, these operations need not be performed in the order in which they are presented. The operations described may be performed in a different order than the described embodiments. Various additional operations may be performed and / or the operations illustrated may be omitted in additional embodiments.

FIG. 1 shows an embodiment of a plasma processing system 10 equipped with a plasma optical emission spectroscopy (OES) system 15. The plasma processing system 10 includes a plasma processing chamber 20, and a substrate holder 30 (for example, an electrostatic clamp) for receiving a substrate 40 to be processed is disposed inside the plasma processing chamber 20. Radio frequency (RF) and / or microwave power (not shown) are supplied to the plasma processing chamber 20 to excite and maintain the plasma 50 near the substrate 40, where high-energy chemical species from the plasma 50 are used to A plasma treatment step is performed on 40. The processing gas (not shown) flows into the plasma processing chamber 20, and a pump system (not shown) is provided to maintain the vacuum state in the plasma processing chamber 20 at the required process pressure. Examples of plasma processing steps include plasma etching, plasma-assisted chemical vapor deposition (PECVD), plasma-assisted atomic layer deposition (PEALD), and the like. The systems and methods described herein are applicable to any type of plasma treatment.

The plasma optical emission spectrum (OES) system 15 is used to obtain the plasma optical emission spectrum through at least one photodetector 60. The photodetector 60 transmits the obtained plasma optical emission spectrum to the controller 80 and controls it. . The controller 80 may be a general-purpose computer, and may be located near or remote from the plasma processing system 10 and connected to the light detector 60 via an internal network or an Internet connection.

The photodetector 60 has an optical element, and the optical element is provided in such a manner that the photodetector 60 can collect the plasma light emission from a narrow, approximately pen-shaped volume 65 in the plasma 50. The light channel of the plasma processing chamber is provided by a light window 70. Depending on the application and the degree of chemical aggressiveness of the plasma 50, the light window 70 may include materials such as glass, quartz, fused silica, or sapphire. The volume 65, which is hereinafter referred to as "ray" 65, defines a portion of the space in which the plasma light emission spectrum is collected, and the collected spectrum represents electricity collected from all spatial points located along and inside the ray 65 Integration of the contribution of the plasma light emission spectrum. It should be noted that depending on the geometry and structure of the light detector 60, the contribution of each spatial point in the range of the ray 65 will not be equal, but will be weighted by the light efficiency (discussed in more detail later) And influence. In a typical structure, the ray 65 is positioned in a direction substantially parallel to the surface of the substrate 40 and maintains a slight distance from the surface of the substrate 40 to reduce optical interference from the surface of the substrate. However, it still needs to be kept close enough to the substrate 40 to face the Sampling was performed near the substrate's plasma chemistry.

As mentioned earlier, the controller 80 is used to control the plasma light emission spectrum system 15, and is also used to: (1) calculate the plasma light intensity distribution as a function of spatial position and wavelength, and (2) from The calculated plasma light intensity distribution calculates the spatial distribution of the chemical species of interest. This information can be used later for process development, development of plasma processing equipment, in-situ monitoring of the plasma process, detection of plasma process errors, detection of plasma process termination points, and so on.

FIG. 1 shows a ray 65 traversing a plasma 50 located inside the plasma processing chamber 20 and adjacent to the substrate 40 to be processed. In an embodiment of the present invention, the plurality of rays 100 can be used to sample the plasma light emission spectrum, as shown in FIG. 2, which shows a schematic top view of the plasma processing system 10 of FIG. 1, for example. In the exemplary embodiment of FIG. 2, two light detectors 60 are used to collect plasma light emission spectra from seven rays 100. The ray 100 must be non-overlapping so as to obtain the maximum amount of spatial information from the plasma 50 above the substrate 40. The number of rays 100 per light detector 60 can be changed from 2 to 9, or higher. Furthermore, in another embodiment in which the light channel of the plasma processing chamber 20 is provided by a single light window 70, a single light detector 60 may be used with the fan-shaped rays 100 associated therewith. Alternatively, a third or more light detectors each having a ray fan shape associated therewith may be used. The angle of each ray 100 with respect to the center line of its light detector 60 is defined as θ _i . Each point inside the plasma processing chamber can be defined by its polar coordinates (ie (r, θ)), as shown in FIG. 2.

As will be explained in more detail later, depending on the configuration of the photodetector 60, all plasma light emission spectra from the relevant fan 100 fan shape can be collected simultaneously. This is applicable to the embodiment of the light detector 60 having a plurality of optical systems and channels and allowing synchronous reception of light from all rays 100. Alternatively, the plasma light emission spectrum may be sequentially acquired along the ray 100 associated with the light detector 60. The latter method is applicable to a scanning embodiment in which the plasma light emission spectrum is collected as the ray 100 is scanned from one angle θ _i to another angle. Understandably, this scanning and acquisition must occur fast enough to enable rapid changes in the plasma chemistry of the entire substrate to be detected.

FIG. 3 shows an exemplary plasma light emission spectrum obtained from a ray 100 using a light detector 60 at an angle θ _i . In this spectrum, light intensities of M wavelengths are collected, and the wavelength range thereof is usually from about 200 nm to about 800 nm. The charge-coupled element (CCD) of a general spectrometer used in light emission spectroscopy has 4096 pixels in this wavelength range, but depending on the resolution required for the application and collected spectrum, the number of pixels can be as low as 256 and as high as 65536 range.

The plasma light emission spectrum collected by the photodetector 60 from its associated ray 100 sector is transmitted to the controller 80, which is used to further process the transmitted data to calculate the spatial distribution of the plasma light emission, and then From this, the spatial distribution of the concentration of chemical species was calculated. One aspect of the present invention is an algorithm for quickly calculating the spatial distribution of plasma light emission at various wavelengths. This algorithm can provide on-site monitoring of the plasma process for termination point detection, error detection, and the like.

FIG. 4 shows an embodiment of the photodetector 60, in which a single multi-channel spectrometer 310 is used to collect plasma light emission spectra from the rays 305A-E simultaneously. For the sake of clarity, the example embodiment presented here has five rays 305A-E, but the number can vary from 2 to 9, or even higher than 9. The photodetector 60 includes optical systems 300A-E for each of the rays 305A-E, and all are located adjacent to a light window 70 mounted on the wall of the plasma processing chamber 20. The rays 305A-E are arranged in a radial pattern so as to cover relevant portions of the substrate 40 (not shown). The collected plasma light emission spectra enter the multi-channel spectrometer 310 from the optical systems 300A-E through the respective optical fibers 320A-E. The optical systems 300A-E will be described in more detail later. Due to the capability of "synchronous collection of plasma light emission spectrum" in the embodiment of FIG. 4, this embodiment is suitable for rapid judgment.

FIG. 5 shows another alternative embodiment using a single-channel spectrometer 310, and when the plasma light emission spectrum is obtained by the spectrometer 310 through a single optical system 300, the rays 305A-E are controlled to sweep the rays 305A The -E scanning mirror 400 is formed, which will be described in more detail later. This embodiment is suitable for the sequential collection of the plasma light emission spectrum, and therefore, it is more suitable for the slower-evolving plasma process judgment. The scanning mirror 400 can be mounted on and actuated on a galvanometer table 410. Alternatively, the scanning mirror 400 may be mounted on the stepping motor 410 and scanned by it. The number of rays 305A-E is shown here as 5, but in reality this number is determined by the settings of the controller software used to control the galvanometer table or stepper motor 410.

In order to ensure that a precise volume of space is sampled and tested, the optical systems 300A-E of FIG. 4 and the optical system 300 of FIG. 5 need to be set so that the rays 305A-E are collimated, which has a predetermined target cost for the optical system The smallest divergence angle that can be achieved.

Exemplary embodiments of the optical systems 300A-E and 300 are shown in FIG. 6. The optical system 300A-E (also known as a telecentric coupler) is responsible for collecting the plasma light emission spectrum from the plasma volume within the range of the plasma 50 and defined by the rays 305A-E, and guiding the collected plasma light emission Spectral to the task of port 390 of the fiber 320A-E or 320, so the collected plasma light emission spectrum can be sent to the spectrometer 310 in the embodiment of FIG. 4 or FIG. The diameters of the rays 305A-E are defined by optional holes 350 formed in the plate. In another alternative embodiment, other optical elements such as lenses may be used to define the diameter of the rays 305A-E. An example beam diameter is 4.5 mm, but it can vary from about 1 mm to 20 mm depending on the application. The collected rays 305A-E pass through the combination of the light-receiving lenses 360A and 360B, and the combination of these lenses and the optional hole defines the rays 305A-E. The numerical aperture of the light-receiving system for rays 305A-E is usually very low, for example about 0.005, and the resulting rays 305A-E are substantially collimated light with a minimum divergence angle. At the other end of the optical system 300A-E or 300 is another pair of lenses, namely coupling lenses 370A and 370B. These coupling lenses 370A and 370B are used to focus the collected light emission spectrum onto the optical fibers 320A-E or 320. On port 390. All lenses used in this system are preferably achromatic, or even apochromatic for more severe applications, which ensure that the focal length of each lens does not change with wavelength, making the optical system 300A-E or 300 Works well over a wide range of wavelengths (usually from 200nm to 800nm, but in some cases as low as 150nm). For better operation in the ultraviolet (UV) portion of the spectrum (ie below 350 nm), UV-grade materials should be used for all optical components.

For each optical hardware configuration, it is important to know the light efficiency w applicable to the weight coefficients of all position points in the range of rays 305A-E. The plasma light emission spectrum is obtained from rays 305A-E. The light efficiency w may be determined by simulation using optical design software, or may be determined by experiments that use calibrated light sources and move the calibrated light sources through and along the rays 305A-E to determine the self-rays 305A-E. Optical coupling efficiency to a fiber port 390 at a given location inside. The light efficiency w will be used for the algorithm used to determine the spatial distribution of plasma light emission.

As mentioned earlier, the task of the plasma light emission (OES) system 15 is to determine the two-dimensional intensity distribution of the plasma light emission for each of the M measured wavelengths l.

For each ray 100 (rays mathematically labeled by subscript i) of FIG. 2, the collected light detector output Can be defined as: among them Is within and along the ray On the plasma light emission intensity, while Represents the self-position of the light detector i Light collection of light efficiency. Resulting photodetector output The integral value representing the product of these quantities along the straight path from point A to point B on the substrate's circumference (see Figure 2). The influence of the plasma from the periphery of the substrate 40 is ignored in this model (this is a reasonable assumption Because the plasma density (and therefore plasma light emission) in these areas is usually weak).

In a plasma light emission spectroscopy system 15 having N light detectors and rays, or N scanning positions of rays 100, there are N collected intensities for each of the M measured wavelengths λ. Therefore, in order to reconstruct the spatial distribution of plasma light emission at a wavelength λ, it is necessary to assume a function form with N parameters. Given a limited number of parameters N, a prudent selection of the basis function used for the plasma light emission distribution is required. The selected basis function must be changed with both the radial coordinate r and the circumferential coordinate θ, so that it can well reproduce the changes in the circumferential direction of the plasma radiation around the substrate 40.

The set of basis functions particularly suitable for this task is the Zernike polynomial . Zernike polynomials are dependent on the path coordinates One term and dependent on circular coordinates Defined by the product of one term, that is,

Table 1 lists the first 18 orders of Zernike polynomials, and common mathematical symbols are used here. Means. Table 1: Zernike polynomials First 18 steps

In general, other basis functions can also be selected for this application, as long as they are orthogonal like the Zernike polynomial in this case and as long as their differentials are continuous throughout the unit circle. However, the Zernike polynomial "because a relatively small number of terms can be used to describe the function of the relatively complex changes in polar coordinates (both radial and circumferential)", so the Zernike polynomial is better in this application.

Zernike polynomial Substitute the collected detector output Where a _p is a fitting parameter associated with each basis function (ie, the order of the Zernike polynomial).

Since the collected detector output D _i is defined according to the selected basis function, fitting parameters and light efficiency, the problem of determining the fitting parameter a _p of D _i can be simplified to minimize the following equation, which is to solve the least square The problem: or among them Represents the plasma spectral intensity measured at ray i. The algorithm for this minimization problem needs to be repeated for each of the M measured wavelengths λ. There are many methods known in the art for solving this least squares problem. Because the dimension of the least square problem is relatively small, this problem can be solved in time and efficiently for all wavelengths at the moment when each plasma light emission spectrum is measured; and further, this calculation can be repeated quickly and successively. The fast evolution of the two-dimensional distribution of plasma light emission is realized with a large number of M kinds of wavelengths. As a result, the time evolution of the two-dimensional distribution of the chemical species concentration across the substrate 40 can be determined, which can be used for termination point detection, error detection, process development, processing equipment development, and so on.

FIG. 7 shows an example of a plasma light emission intensity distribution measured by a method according to an embodiment of the present invention. Although it is a relatively small number of terms (N = 18), the plotted map clearly shows a good record of changes in plasma light emission intensity in both radial and circumferential directions.

FIG. 8 shows another embodiment using a single-channel spectrometer 310. The rays 305A-E are formed by a scanning mirror 400 and a mirror system 800, wherein the mirror system 800 moves the rotation center of the rays 305A-E from the position of the stepping motor 410 associated with the scanning mirror 400 to the light window 70 or substantially near the light window 70, as shown by point C in FIG. 8 (that is, point C shows the center of rotation). The light window 70 is usually small (one inch in diameter), so in order to sweep the rays 305A-E across the plasma 50 (for example, the angle θ _max = 25 ° of the central axis of the plasma processing chamber 20), Rays 305A-E at light window 70 have a minimum offset. Therefore, the center of rotation of the rays 305A-E is configured to be substantially close to or positioned at the light window 70. With the configuration described herein, it is possible to use a window portion having a size of 68.5 mm × 8 mm or more. The size (upper limit) of the window portion is limited by, for example, the following factors: pollution, chamber UV and RF leakage, and available space at the wall portion of the plasma processing chamber 20. In an embodiment, the window portion may have a rectangular shape, and a large size in a plane thereof corresponds to a scanning plane of the beam. This has the advantage of minimizing the size of the window while meeting leakage and space requirements.

The scanning mirror 400 scans in a controlled manner using a stepping motor 410 to sweep the rays 305A-E, and the spectrometer 310 obtains a plasma light emission spectrum through a single optical system 300.

The mirror system 800 may include a transmission mirror 802 and a folding mirror 804. Each of the collected rays 305A-E or 65 (that is, the optical signal collected from the plasma through the collected rays 305) is transmitted by the transmission mirror 802, which reflects the collected rays 305 and collects The rays 305 are transmitted to the folding mirror 804. The folding mirror 804 reflects the collected rays 305 from horizontal (azimuth direction) to vertical concentric, and transmits the collected rays 305 to the scanning mirror 400, and the scanning mirror 400 reflects the collected rays 305 to 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 can be installed near the plasma processing chamber 20.

When the scanning mirror 400 is swept, a spatial distribution of the chemical species concentration with a high spatial resolution is obtained. For example, the scanning mirror 400 can be slowly scanned while obtaining a plasma light emission spectrum. The obtained plasma light emission spectrum is related to any position between -θ _max ° and + θ _max °. Therefore, with the scanning configuration described in this article, a fairly accurate spatial resolution can be obtained.

FIG. 9 is a schematic development view of an embodiment of the optical system 300 of FIG. 8 according to the embodiment. The optical system 300 is responsible for collecting the plasma light emission spectrum from the volume of the plasma 50 within the space volume defined by the collected rays 305, and guiding the collected plasma light emission spectrum to the port 390 of the optical fiber 320 Task, so the collected plasma light emission spectrum can be sent to the spectrometer 310 previously described herein. The optical system 300 includes a telecentric coupler having a small numerical aperture. The collected scanning ray size can vary in diameter from about 3 mm to 5 mm along the collection path.

The collected rays 305 (reflected from the scanning mirror 400) pass through the first light-receiving lens 902. Then, the rays can be passed through the telecentric hole 908 (for example, having a diameter of 600 μm). Then, two coupling lenses 904 and 906 are used to focus the collected light emission spectrum on the port 390 of the optical fiber 320. In one example, the optical fiber 320 has a diameter of 600 μm. The optical system 300 may also include optional filters positioned between the two coupling lenses 904 and 906.

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

Referring back to FIG. 8, the scanning mirror 400 may have a size of at least 10 mm × 10 mm. The transmission mirror 802 may be a spherical mirror. The scanning mirror 400 and the transmission mirror 802 may have an aluminum coating, a silicon oxide (SiO) protective film, or a dielectric multilayer film over aluminum to increase the reflectance in certain wavelength regions (such as UV). The radius of the transmission mirror 802 may be between 100 mm and 120 mm. In one embodiment, the radius of the transmission mirror 802 is 109.411 mm. The transmission mirror 802 can be positioned at a distance of 68.4 mm from the outer edge of the light window 70. The folding mirror 804 can be positioned at a distance of 71.5 mm from the plane of the scanning mirror 400.

The spectrometer 310 may be an ultra-wideband (UBB) high-resolution spectrometer having a spectral resolution of 0.4 nm and a wavelength range of 200 nm to 1000 nm.

FIG. 10 is a schematic plan view of a plasma processing system equipped with the optical system of FIG. 8. FIG. The plasma processing chamber 20 may be equipped with two optical systems of FIG. 8. This optical system is called a scanning module. Each scanning module can be configured to collect data from X to Y ray positions. In one embodiment, each scanning module may be configured to collect data from 5 to 50 ray positions that provide better accuracy to detect events with high spatial resolution. In FIG. 10, a position of one of the rays 305 is shown. As described earlier herein, the scan angle of the ray 305 may vary between -θ _max ° to + θ _max ° (eg, θ _max = 25 ° or 30 °). The data from the spectrometer 310 was processed as previously described herein to obtain a two-dimensional (2D) OES intensity distribution. Each module may include a single-channel spectrometer 310, or a single spectrometer with two channels may be used for two scanning modules. Additional scanning modules can also be used to provide higher spatial resolution. The light window 70 (that is, the light window 70 of each scanning module) may be located on the sidewalls of the plasma processing chamber 20 that are perpendicular or substantially perpendicular to each other. Depending on the configuration of the plasma processing chamber 20, the light window 70 may be quartz, fused silica or sapphire, depending on the application and the degree of chemical aggressiveness of the plasma.

FIG. 11 is a schematic development view of an embodiment of the optical system 300 of FIG. 5 or FIG. 8. The optical system 300 is responsible for directing the reflected collected plasma light emission spectrum from the scanning mirror 400 to the port 390 of the optical fiber 320, so the collected plasma light emission spectrum can be sent to the previously described herein. Spectrometer 310. The collected rays 305 are passed through a light-receiving lens, which may be a triplet lens 1102 (for example, having an effective focal length of 40 mm). The collected rays 305 can be passed through an optional cover hole 1108 (for example, having a diameter of 7 mm). The cover hole 1108 can be positioned between the scanning mirror 400 and the triplet lens 1102. Next, the collected rays 305 can be passed through an optional telecentric hole 1110 (for example, having a diameter of 1.20 mm). In another embodiment, other optical elements such as lenses may be used to define the diameter of the ray 305.

Two coupling triplets 1104 and 1106 are used to focus the collected light emission spectrum on the port 390 of the optical fiber 320. In an embodiment, the coupling triplet lenses 1104 and 1106 may be triplet lenses having an effective focal length of 15 mm. The effective focal length of the coupled triplet lenses 1104 and 1106 is a function of the type and diameter of the fiber 320.

All lenses used in this system are preferably achromatic, or even apochromatic for more severe applications, which ensure that the focal length of each lens does not change with wavelength, making the optical system 300A-E or 300 Works well over a wide range of wavelengths (usually from 200nm to 800nm, but in some cases as low as 150nm). For better operation in the ultraviolet (UV) part of the spectrum (ie below 350 nm), UV-grade materials such as quartz, fused silica, calcium fluoride (CaF2) should be used for all optical components.

FIG. 12 is a schematic diagram of another embodiment using a single-channel spectrometer 310. One or two modules can be used sequentially to obtain the plasma light emission spectrum. Each module may include a line arc table 1204. The spectrometer 310, the optical system 300, and the folding mirror 1202 are mounted on the arc table 1204. The folding mirror 1202 is positioned to receive the collected rays 305 from the plasma processing chamber 20 and reflect the collected rays 305 to the optical system 300. The arc stage 1204 scans in a controlled manner to sweep the collected rays 305, and the spectrometer 310 obtains a plasma light emission spectrum through a single optical system 300. The wire arc table 1204 can be controlled via the controller 80. Point C in FIG. 12 shows the center of rotation of the line arc table 1204. The single optical system 300 may be the single optical system shown and described in FIG. 9 or FIG. 11. In one embodiment, the arc table 1204 may have a scanning angle of 85 ° and a length of 163.2 mm. The line scan speed can vary from 0.35m / s to 2.2m / s. Therefore, according to the application of the plasma light emission spectrum system 15, the scanning speed can be adjusted to optimize the trade-off between the spatial resolution and the speed.

In further embodiments of the optical system 300 of FIGS. 6, 9, and 11, other optical elements (such as mirrors, chirps, lenses, spatial light modulators, digital micromirror devices, etc.) can be used to collect the Ray 305 turns. The configuration and component arrangement of the optical system 300 of FIGS. 4 to 6 and FIGS. 8 to 12 do not necessarily need to be exactly as shown in FIGS. 4 to 6 and 8 to 12, but the collected rays can be collected by additional optical elements. 305 is folded and turned to facilitate the installation of the plasma light emission spectrometer system 15 in a compact package suitable for installation on the wall portion of the plasma processing chamber 20.

The inventors conducted several experiments to reconstruct a pattern of light emission distribution, and compared the reconstructed pattern with an etched pattern.

FIG. 13 is a schematic diagram showing an exemplary result of a reconstructed pattern of light emission intensity. The intensity of the radiation (ie, 522.45 nm of silicon chloride) shows the concentration of silicon chloride (SiCl), and the concentration of silicon chloride (SiCl) is related to the intensity of local etching on the substrate 40. FIG. 13 shows a comparison between the actual etch rate and the actual distribution of light emission 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 under various plasma processing conditions. Plots 1308, 1310, and 1312 each show reconstructed light emission distributions of samples related to plots 1302, 1304, and 1306.

The equipment and methods described herein can be used to monitor etch uniformity. For example, the device can be used during process development to monitor etch uniformity under various plasma processing conditions without having to transfer the substrate to another device, which makes the development of various processes faster.

The results show a strong correlation between the etch thickness and the reconstructed OES distribution of species involved in plasma etching, including both reactants and products. The uniformity of the OES distribution follows the same trend as the oxide etch profile, such as drawing 1302 compared to drawing 1308. Substrates with better etch uniformity appear to have a lower correlation with the OES distribution (e.g., drawing 1306 compared to drawing 1302).

FIG. 14 is a flowchart illustrating a light emission measurement method 1400 according to an example. At 1402, a light window is provided in a wall portion of a processing chamber (e.g., plasma processing chamber 20). At 1404, a collection system is provided to collect the plasma light emission spectrum through a light window. The collection system may include a mirror and a telecentric coupler. The telecentric coupler may include at least one light-receiving lens (for example, light-receiving lenses 360A and 360B) and at least one coupling lens (for example, coupling lenses 904 and 906 of FIG. 9). At 1406, a mirror is used to scan a plurality of non- coincident rays across the plasma processing chamber. The scan can be controlled by the controller 80. At 1408, an optical signal is collected from the plasma through a telecentric coupler. In step 1410, the optical signal is directed to a spectrometer to measure a plasma light emission spectrum.

Persons familiar with related technologies can observe that many improvements and changes are feasible based on the above teachings. Those skilled in the relevant art will understand equivalent combinations and substitutions of various elements shown in the figures. Therefore, the scope of the invention is not intended to be limited by this detailed description, but is only limited by the scope of the patent application appended hereto.

The above disclosure also includes the following embodiments.

(1) A method for measuring light emission, which includes setting a light window in a wall portion of a plasma processing chamber; and providing a collection system to collect the plasma light emission spectrum through the light window, the collection The system includes a mirror and a telecentric coupler; using the mirror to scan a plurality of non- coincident rays across the plasma processing chamber; collecting an optical signal from the plasma through the telecentric coupler; and guiding the optical signal Go to a spectrometer to measure the plasma light emission spectrum.

(2) The method according to feature (1), wherein the telecentric coupler includes at least one light-receiving lens; and at least one coupling lens.

(3) The method according to feature (2), wherein the at least one light-receiving lens or the at least one coupling lens is an achromatic lens.

(4) The method according to feature (2), wherein the telecentric coupler further comprises: a hole provided between the at least one light-receiving lens and the at least one coupling lens to define a diameter of the plurality of non-coincident rays .

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

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

(7) The method according to the feature (5), wherein the scanning mirror is mounted on a stepping motor and scanned by the stepping motor.

(8) The method according to feature (5), wherein the collecting system further includes a mirror system for moving the rotation center of the plurality of non-coinciding rays to the light window or near the light window.

(9) The method according to feature (8), wherein the mirror system includes a transmitting mirror; a folding mirror; and wherein the transmitting mirror is configured to transmit the collected signal to the folding mirror, and the folding mirror is configured To transmit the collected signal to the mirror.

(10) The method according to feature (1), wherein the telecentric coupler includes a light-receiving triplet lens configured to collect the optical signal from the mirror; and two coupling triplet lenses configured to cause The collected signal is focused into a port of an optical fiber coupled to the spectrometer.

(11) The method according to feature (1), further comprising using a second collection system to collect the plasma light emission spectrum through a second light window provided in the wall portion of the plasma processing chamber. The central axis of the second light window is perpendicular to the central axis of the light window.

(12) The method according to feature (1), wherein the collecting system further includes a linear arc stage, which holds the mirror, the telecentric coupler, and the spectrometer, and the linear arc stage is arranged relative to the center of the light window Axis and radial movement such that the plurality of non-coincident ray scans across the plasma processing chamber.

(13) The method according to feature (12), wherein the mirror is a folding mirror.

(14) The method according to any one of features (1) to (13), wherein the plurality of non-coincident rays scan a central axis of the light window at 25 ° across the plasma processing chamber.

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

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

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

10‧‧‧ Plasma treatment system

15‧‧‧ Plasma Light Emission Spectroscopy (OES) System

20‧‧‧ Plasma processing chamber

30‧‧‧ substrate holder

40‧‧‧ substrate

50‧‧‧ Plasma

60‧‧‧light detector

65‧‧‧ space

70‧‧‧light window

80‧‧‧controller

100‧‧‧ rays

300‧‧‧ Optical System

300A-E‧‧‧Optical System

305‧‧‧ray

305A-E‧‧‧ray

310‧‧‧ Spectrometer

320‧‧‧ Optical Fiber

320A-E‧‧‧Optical Fiber

350‧‧‧optional hole

360A‧‧‧Receiving lens

360B‧‧‧Receiving lens

370A‧‧‧Coupling lens

370B‧‧‧Coupling lens

390‧‧‧port

400‧‧‧scanning mirror

410‧‧‧galvanometer table / stepper motor

800‧‧‧mirror system

802‧‧‧ Telescope

804‧‧‧Folding mirror

902‧‧‧The first light receiving lens

904‧‧‧Coupling lens

906‧‧‧Coupling lens

908‧‧‧Telecentric hole

1102‧‧‧ triple lens

1104‧‧‧Coupling triplet lens

1106‧‧‧Coupling triplet lens

1108‧‧‧Cover

1110‧‧‧ Telecentric hole

1202‧‧‧Folding mirror

1204‧‧‧Line arc platform

1302‧‧‧Drawing

1304‧‧‧Drawing

1306‧‧‧Drawing

1308‧‧‧Drawing

1310‧‧‧Drawing

1312‧‧‧Drawing

1400‧‧‧Method

1402‧‧‧ Operation

1404‧‧‧operation

1406‧‧‧ Operation

1408‧‧‧operation

1410‧‧‧ Operation

With reference to the detailed description that follows, especially when considered in conjunction with the attached drawings, the more complete knowledge of the present invention and its many accompanying advantages become apparent and readily apparent. In the drawings:

According to an embodiment, FIG. 1 is a schematic side view of a plasma processing system equipped with an optical emission spectroscopy (OES) measurement system.

According to an embodiment, FIG. 2 is a schematic top view of a plasma processing system equipped with an OES measurement system.

According to an embodiment, FIG. 3 is an exemplary plasma light emission spectrum obtained using an OES measurement system.

According to an embodiment, FIG. 4 is a schematic diagram of an optical system used in an OES measurement system.

According to another embodiment, FIG. 5 is a schematic diagram of an optical system for an OES measurement system.

FIG. 6 is a schematic development view of an embodiment of an optical system according to an embodiment.

According to an embodiment, FIG. 7 is an exemplary plasma light emission two-dimensional distribution measured using an OES measurement system and related methods.

According to another embodiment, FIG. 8 is a schematic diagram of an optical system for an OES measurement system.

According to another embodiment, FIG. 9 is a schematic development view of an embodiment of an optical system.

FIG. 10 is a schematic plan view of a plasma processing system equipped with the optical system of FIG. 8. FIG.

According to another embodiment, FIG. 11 is a schematic development view of an embodiment of an optical system.

According to another embodiment, FIG. 12 is a schematic diagram of an optical system for an OES measurement system.

FIG. 13 is a schematic diagram showing an example result of a reconstructed pattern of light emission intensity.

According to an example, FIG. 14 is a flowchart showing a method for measuring light emission.

Claims (20)

A device for measuring light emission, the device comprising: a collection system for collecting plasma light emission spectrum through a light window provided on a wall portion of a plasma processing chamber, the collection system comprising: a mirror , Which is configured to scan a plurality of non-coinciding rays across the plasma processing chamber; and a telecentric coupler for collecting a light signal from the plasma and directing the light signal to a spectrometer to measure the electricity Plasma light emission spectrum. For example, the apparatus for light emission measurement according to item 1 of the patent application scope, wherein the telecentric coupler includes: at least one light-receiving lens; and at least one coupling lens. For example, the apparatus for light emission measurement according to item 2 of the application, wherein the at least one light-receiving lens or the at least one coupling lens is an achromatic lens. For example, the device for measuring light emission of item 2 of the patent application scope, wherein the telecentric coupler further includes: a hole, which is disposed between the at least one light-receiving lens and the at least one coupling lens to define the The diameter of multiple non-coincident rays. For example, the device for measuring light emission of the scope of the patent application, wherein the mirror is a scanning mirror. For example, the apparatus for optical emission measurement according to item 5 of the application, wherein the scanning mirror is installed on a galvanometer scanning table and scanned by the galvanometer scanning table. For example, the apparatus for light emission measurement according to item 5 of the application, wherein the scanning mirror is mounted on a stepping motor and scanned by the stepping motor. For example, the device for light emission measurement according to item 5 of the patent application, wherein the collection system further includes: a mirror system for moving the rotation center of the plurality of non-coincident rays to the light window or the vicinity of the light window. For example, the apparatus for measuring light emission in the scope of patent application No. 8 wherein the mirror system includes: a transmitting mirror; a folding mirror; and wherein the transmitting mirror is configured to transmit the collected optical signals to the folding lens. And the folding mirror is configured to transmit the collected optical signals to the mirror. For example, the device for optical emission measurement according to item 1 of the patent application scope, wherein the telecentric coupler includes: a light-receiving triplet lens configured to collect the optical signal from the mirror; and two coupling triplets A lens configured to focus the collected optical signal into a port of an optical fiber coupled to the spectrometer. For example, the device for light emission measurement according to the scope of patent application No. 1 further includes: a second collection system for collecting the electricity through a second light window provided in the wall portion of the plasma processing chamber The plasma light emission spectrum has a central axis perpendicular to a central axis of the optical window. For example, the apparatus for light emission measurement according to the first patent application scope, wherein the collection system further includes: a linear arc stage, which holds the mirror, the telecentric coupler, and the spectrometer, and the linear arc stage is configured to The radial movement relative to the central axis of the light window causes the plurality of non-coincident rays to scan across the plasma processing chamber. For example, the device for light emission measurement according to item 12 of the application, wherein the mirror is a folding mirror. For example, the apparatus for light emission measurement in the first scope of the patent application, wherein the plurality of non-overlapping rays scan the central axis of the light window at 25 ° across the plasma processing chamber. For example, the device for light emission measurement in the first scope of the patent application, wherein the spectrometer is an ultra-wideband high-resolution spectrometer. For example, the apparatus for light emission measurement according to the first patent application range, wherein the collection system has a low numerical aperture. For example, the device for light emission measurement in the first scope of the patent application, wherein the optical signal is collected from 21 non-overlapping rays. A system for plasma processing includes: a plasma processing chamber; a light window disposed on a wall portion of the plasma processing chamber; a collection system for collecting electricity through the light window Plasma light emission spectrum; a spectrometer coupled to the collection system for measuring the plasma light emission spectrum; and wherein the collection system includes a mirror configured to scan across the plasma processing chamber A plurality of non-coincident rays and a telecentric coupler are used to collect an optical signal from the plasma and guide the optical signal to the spectrometer. A method for measuring light emission, comprising: setting a light window on a wall portion of a plasma processing chamber; providing a collection system for collecting plasma light emission spectrum through the light window, the collection system comprising A mirror and a telecentric coupler; using the mirror to scan a plurality of non-coincident rays crossing the plasma processing chamber; collecting an optical signal from the plasma through the telecentric coupler; and guiding the optical signal to a Spectrometer to measure the plasma light emission spectrum. For example, the method for measuring light emission according to item 19 of the patent application scope further includes: using a mirror system to move the rotation center of the plurality of non-coincident rays to the light window or near the light window, and the mirror system includes at least one Telescope and a folding mirror.