WO2019014343A1 - Spatially resolved optical emission spectroscopy (oes) in plasma processing - Google Patents
Spatially resolved optical emission spectroscopy (oes) in plasma processing Download PDFInfo
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- WO2019014343A1 WO2019014343A1 PCT/US2018/041637 US2018041637W WO2019014343A1 WO 2019014343 A1 WO2019014343 A1 WO 2019014343A1 US 2018041637 W US2018041637 W US 2018041637W WO 2019014343 A1 WO2019014343 A1 WO 2019014343A1
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- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/66—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light electrically excited, e.g. electroluminescence
- G01N21/68—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light electrically excited, e.g. electroluminescence using high frequency electric fields
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- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
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- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
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- G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
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- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
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Definitions
- the present invention relates to a method, computer method, system, and apparatus for measuring concentrations of chemical species in semiconductor plasma processing using plasma optical emission spectroscopy (OES). Specifically, it relates to determining two-dimensional distributions of plasma optical emissions from which two- dimensional distributions of chemical species concentrations can be determined. DESCRIPTION OF RELATED ART
- Production of semiconductor devices, displays, photovolfaics, etc. proceeds in a sequence of steps, each step having parameters optimized for maximum device yield.
- the chemistry of the plasma and particularly the local chemistry of the plasma, i.e. the local concentrations of various chemical species in the plasma environment proximate the substrate being processed.
- Certain species, particularly transient chemical species, such as radicals have a great influence on the plasma processing outcome, and it is known that elevated local concentrations of these species can produce areas of faster processing, which may lead to nonuniformities in the processing steps and ultimately the devices being produced.
- the chemistry of a plasma process is controlled in a direct or indirect manner through the control of a large number of process variables, such as one or more RF or microwave powers supplied to excite the plasma, the gas flows and kinds of gases supplied to the plasma processing chamber, the pressure in the plasma processing chamber, the type of substrate being processed, the pumping speed delivered to the plasma processing chamber, and many 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 chemical species of particular interest, such as radicals, is deduced from acquired optical (i.e.
- optical emission spectroscopy While the use of optical emission spectroscopy has become relatively commonplace, particularly in plasma process development, if is usually done by acquiring optical emission spectra from a single elongated volume within the plasma, inside the plasma processing chamber. The precise shape and size of this volume is determined by the optica! system used to collect the optical emission from the plasma. Such collection of the optical emission signal inherently results in averaging of the plasma optical emission spectra along the length of this elongated volume, also known as a ray, and thus all the information about local variations of the plasma optica! emission spectra, and thus also local variations of chemical species concentrations, are generally lost.
- a further application of the plasma optical emission spectroscopy technique is in determining the endpoint of a plasma processing step by monitoring the evolution of and abrupt change of chemical species present in the plasma that is associated with e.g. an etching step reaching a substrate layer of different chemical composition that the one that was etched during the etching process.
- the ability to determine the plasma processing step endpoint across the entire surface of the substrate contributes to increased device yield because of not terminating the plasma processing step prematurely.
- An aspect of the invention includes an apparatus for optical emission measurement that comprises a collection system for collecting a plasma optical emission spectra through an optical window disposed at a wall of a plasma processing chamber.
- the optical 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.
- An alternative embodiment includes a plasma optical emission measurement system that comprises 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 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 the spectrometer.
- Yet another embodiment of the invention includes a method for optical emission measurement that comprises depositing an optical window at a wail of a plasma processing chamber; providing a collection system for collecting plasma optical emission spectra through the optical window, the collection system including a mirror and a telecentric coupler; scanning a plurality of non-coincident rays across the plasma processing chamber using the mirror; collecting an optical signal from a plasma via the telecentric coupler; and directing the optical signal to a spectrometer for measuring the plasma optical emission spectra.
- FIG. 1 is a side view schematic of a plasma processing system equipped with an optical emission spectroscopy (OES) measurement system in accordance with an embodiment.
- OES optical emission spectroscopy
- FIG. 2 is a top view schematic of the plasma processing system equipped with the OES measurement system in accordance with an embodiment.
- FIG. 3 is an exemplary plasma optical emission spectrum acquired using the
- FIG. 4 is a schematic of an optical system for use in the OES measurement system, in accordance with an embodiment.
- FIG. 5 is a schematic of an optical system for use in the OES measurement system, in accordance with another embodiment.
- FIG. 6 is an expanded schematic view of an embodiment of an optical system in accordance with an embodiment
- FIG. 7 is an exemplary two-dimensional distribution of plasma optical emission measured using the OES measurement system and associated method in accordance with an embodiment.
- FIG. 8 is a schematic of an optical system for use in the OES measurement system, in accordance with another embodiment.
- FIG. 9 is an expanded schematic view of an embodiment of an optical system in accordance with another embodiment.
- FIG. 10 is a top view schematic of the plasma processing system equipped with the optical system of FIG. 8.
- FIG. 1 1 is an expanded schematic view of an embodiment of an optical system in accordance with another embodiment.
- FIG. 12 is a schematic of an optical system for use in the OES measurement system, in accordance with another embodiment.
- FIG. 13 is a schematic that shows exemplary results of reconstructed patterns of optical emission intensity.
- FIG. 14 is a flowchart that shows a method for optical emission measurement according to one example.
- substrate which represents the workpiece being processed
- terms such as semiconductor wafer, liquid crystal display (LCD) panel, light-emitting diode (LED), photovoltaic (PV) device panel, etc., the processing of all of which falls within the scope of the claimed invention.
- Fig. 1 shows an embodiment of a plasma processing system 10 equipped with a plasma optical emission spectroscopy (OES) system 15.
- Plasma processing system 10 comprises plasma processing chamber 20, inside which a substrate holder 30 is disposed, such as an electrostatic chuck, for receiving a substrate 40 to be processed.
- Radio frequency (RF) and/or microwave power is supplied to the plasma processing chamber 20 (not shown) to ignite and sustain a plasma 50 proximate the substrate 40, wherein the energetic chemical species from the plasma 50 are used to perform a plasma processing step on substrate 40.
- Processing gases are flown 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 a desired process pressure.
- Examples of plasma processing steps include plasma etching, plasma-enhanced chemical vapor deposition (PECVD), plasma-enhanced atomic layer deposition (PEALD), etc.
- PECVD plasma-enhanced chemical vapor deposition
- PEALD plasma-enh
- the plasma optical emission spectroscopy (OES) system 15 is used to acquire plasma optical emission spectra via at least one optical detector 60, which communicates the acquired plasma optical emission spectra to and is controlled by controller 80.
- Controller 80 may be a general purpose computer, and may be located proximate to plasma processing system 10, or may be located remotely, and connected via an intranet or internet connection to optical detector 60.
- Optical detector 60 has optics configured in such a way that it collects plasma optical emissions from an elongated, generally pencil-shaped volume of space 65 within the plasma 50.
- Optical access to the plasma processing chamber is provided by optical window 70.
- Optical window 70 can 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.
- the volume 65 hereinafter referred to as a "ray" 65, defines the portion of space from which the plasma optical emission spectra are collected, and the collected spectra represent an integral of contributions to the collected plasma optical emission spectrum from ail points located along and within the ray 65.
- the ray 65 is oriented substantially parallel with the surface of substrate 40 and is maintained at a small distance from the surface of substrate 40, so as to reduce optical interference from the substrate surface, yet is kept dose enough to the substrate 40 to sample the plasma chemistry proximate the substrate surface.
- Controller 80 is used to control the plasma optical emission spectroscopy system 15, and to also compute the (1 ) plasma optical intensity distribution as a function of spatial location and wavelength, and to compute (2) the spatial distribution of chemical species of interest from the computed plasma optical intensity distribution. This information can then be used for process development, plasma processing tool development, in-situ plasma process monitoring, plasma process fault detection, plasma process endpoint detection, etc.
- Fig. 1 shows one ray 85 traversing the plasma 50 located within the plasma processing chamber 20, proximate substrate 40 being processed.
- multiple rays 100 can be used to sample the plasma optical emission spectra, as shown in Fig. 2, which shows the top schematic view of the plasma processing system 10 of e.g. Fig. 1 .
- two optical detectors 60 are used to collect plasma optical emission spectra, each from 7 rays 100.
- the rays 100 need to be non-coincident such that the largest amount of spatial information is acquired from the plasma 50 above substrate 40.
- the number of rays 100 per optical detector 80 can vary from 2 to 9, and higher.
- a single optical detector 80 can be used with its associated fan of rays 100.
- a third or more optical detectors, each with an associated ray fan, may be used.
- the angle of each ray 100 is defined with respect to the centerline of its optical detector 60, as $ .
- Every point within the plasma processing chamber can be defined by its polar coordinates, i.e. , as shown in Fig. 2. [0036] As will be described in greater detail later, depending on the configuration of optical detector 60, all plasma optical emission spectra from the associated fan of rays 100 can be collected simultaneously.
- optical detector 60 with multiple optical systems and channels, allowing simultaneous collection from all rays 100.
- the plasma optical emission spectra can be acquired sequentially along rays 100 associated with an optical detector 80.
- the latter is suitable in scanning embodiments, where plasma optical emission spectra are collected as the ray 100 is scanned from one angle ⁇ to another. Understandably, this scanning and acquisition needs to occur fast enough such that rapid changes in the plasma chemistry can be detected across the entire substrate.
- Fig. 3 shows an example plasma optical emission spectrum acquired from one ray 100, at angle ⁇ , using one optical detector 60.
- intensities of wavelengths are collected, typically ranging from about 200nm to about 80Qnm.
- CCDs of typical spectrometers employed for optical emission spectroscopy have 4096 pixels spanning the wavelength range, but the number of pixels can vary as low as 256 and as high as 65536, depending on the application and required resolution of the collected spectra.
- Plasma optical emission spectra collected by optical detectors 60 from their associated fans of rays 100 are communicated to controller 80, which is used to further process the communicated data to compute the spatial distribution of plasma optical emission, and from there the spatial distribution of chemical species concentrations.
- An aspect of the present invention is an algorithm for fast calculation of the spatial distribution of plasma optical emissions for each wavelength, which allows in-situ monitoring of plasma processes, for endpoint detection, fault detection, etc.
- Fig. 4 shows an embodiment of optical detector 80 wherein a single multichannel spectrometer 310 is used to collect plasma optical emission spectra from rays 305A-E simultaneously.
- the exemplary embodiment shown here has 5 rays 305A-E, for clarify, but the number can vary from 2 to 9, and even higher than 9.
- the optical detector 60 comprises optical systems 300A-E for each ray 305A-E, ail located proximate optical window 70 mounted on the wall of plasma processing chamber 20. Rays 305A-E are arranged in a diverging manner, so as to cover the relevant portion of substrate 40 (not shown). Collected plasma optical emission spectra are fed into the multi-channel spectrometer 310 from optical systems 300A-E, via respective optical fibers 320A-E. Optical systems 300A-E will be described in greater detail later.
- the embodiment of Fig, 4 is suitable for fast diagnostics, because of its ability to collect plasma optical emission spectra simultaneously.
- FIG. 5 shows an alternative embodiment in which a single channel
- spectrometer 310 is used, and rays 305A-E are formed by a scanning mirror 400 which is controilably scanned to sweep out rays 305A-E while plasma optical emission spectra are acquired by the spectrometer 310 via a single optical system 300, which will be described in greater detail later.
- This embodiment is suitable for sequential collection of plasma optical emission spectra, and therefore is more suited for diagnostics of slower-evolving plasma processes.
- the scanning mirror 400 can be mounted and actuated by a galvanometer stage 410. Alternatively, the scanning mirror 400 may be mounted on and scanned by a stepper motor 410.
- the number of rays 305A-E here is shown as 5, but in practice it is determined by the settings in the controller software for controlling the galvanometer stage or stepper motor 410. [0041] To ensure that a precise volume of space is sampled, the optical systems 300A-E of Fig. 4 and optical system 300 of Fig. 5 need to be configured such that rays 305A-E are collimated, with as small a divergence angle as can feasibly be achieved for a given target cost of the optical system.
- optical system 300A-E also known as a telecentric coupler, has the task of collecting plasma optical emission spectra from a volume of space within the plasma 50 defined by rays 305A-E, and directing the collected plasma optical emission spectra to the end 390 of an optical fiber 320A-E, or 320, so it can be transmitted to the
- the diameter of the rays 305A-E is defined by an optional aperture 350, formed in a plate.
- other optical components such as lenses can be used to define the diameter of the rays 305A-E.
- An example ray diameter is 4.5mm but it can vary from about 1 mm to 20mm, depending on the application.
- the collected rays 305A-E are passed through a combination of collection lenses 360A and 380B which in combination with the optional aperture define the rays 305A-E.
- the numerical aperture of the collection system and rays 305A-E is generally very low, for example, approximately 0.005, and the resultant rays 305A-E are essentially collimated, with minimal divergence angle.
- optical system 300A-E or 300 is another pair of lenses, i.e. coupling lenses 370A and 370B, which serve to focus the collected optical emission spectra onto the end 390 of the optical fiber 320A-E, or 320.
- AH 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, such that the optical system 300A-E, or 300, operates satisfactorily over a large range of wavelengths, ttyyppiiccaallllyy ffrroomm 220000nnmm ttoo SSOOOOnnmm,, bbuutt iinn ssoommee ccaasseess ggooiinngg aass llooww aass 115500nnmm..
- I(r, ⁇ ) is the plasma optical emission intensify at a location (r, ⁇ ) within and along the ray 100
- w(r, ⁇ ) is the optical efficiency for collection of light from location (r, ⁇ ) by optical detector /.
- the resultant optical detector output ! represents an integral of the product of these quantities along a straight path from point A to point B on the circumference of the substrate (see Fig. 2), the contributions from plasma outside the circumference of substrate 40 being neglected in this model (this is a valid assumption because the plasma density and thus plasma light emission is generally low in these areas).
- Zernike polynomials are defined as a product of a term
- Table 1 lists the first 18 order Zernike polynomials, herein denoted using
- Fig. 7 shows an example of one such plasma optical emission intensity distribution determined with the method in accordance with an embodiment of the invention.
- FIG. 8 shows an alternative embodiment in which a single channel
- Rays 305A-E are formed by the scanning mirror 400 and a mirror system 800 which moves a center of rotation of the rays 305A-E from a location of the stepper motor 410 associated with the scanning mirror 400 to the optica! window 70 or substantially near the optical window 70 as indicated by point C in Fig. 8 (i.e., point C shows the center of rotation).
- the window dimension (i.e., upper limit) is limited by factors such as contamination, chamber UV and RF leakage, and available space at the wail of the plasma processing chamber 20.
- the window may have a rectangular shape with the large dimension in a plane corresponding to the plane of scanning of the beam. That has the advantage of minimizing the size of the window while satisfying leakage and space requirements.
- the scanning mirror 400 is controllably scanned to sweep out rays 305A-E using the stepper motor 410 while the plasma optical emission spectra are acquired by the spectrometer 310 via a single optical system 300.
- the mirror system 800 may include a transfer mirror 802 and a fold mirror 804.
- Each collected ray 305A-E or 65 i.e., optical signal from a plasma with collected ray 305 is transmitted by the transfer mirror 802 which reflects the collected ray 305 and transfers the collected ray 305 to the fold mirror 804.
- the fold mirror 804 reflects the collected ray 305 from horizontal (azimutba!) to vertical concentric and transmit the collected ray 305 to the scanning mirror 400 which reflects the collected ray 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 may be mounted proximate to the plasma processing chamber 20.
- the scanning mirror 400 As the scanning mirror 400 is swept, a high spatial resolution of the spatial distribution of chemical species concentrations is obtained.
- the scanning mirror 400 may be swept siowiy while the plasma optical emission spectra is acquired.
- the acquired plasma optical emission spectra is associated with any position between -0max°, + 0max°-
- a very precise spatial resolution may be obtained.
- FIG. 9 is an expanded schematic view of an embodiment of the optical system 300 of Fig. 8 in accordance with an embodiment.
- the optical system 300 has the task of collecting plasma optical emission spectra from a volume of space within the plasma 50 defined by collected rays 305, and directing the collected plasma optical emission spectra to the end 390 of the optical fiber 320, so it can be transmitted to the spectrometer 310 as described previously herein.
- Optical system 300 includes a teiecentric coupler with a small NA.
- the collected scanning rays sizes can vary from about 3 to 5 mm in diameter along the collection path.
- the collected ray 305 (i.e., reflected from the scanning mirror 400) is passed through a first collection lens 902. Then, the rays may be passed through a teiecentric aperture 908, for example having a diameter of 600 ⁇ . Then, two coupling lenses 904 and 906, serve to focus the collected optical emission spectra onto the end 390 of the optical fiber 320. In one example, the optical fiber 320 has a diameter of ⁇ .
- the collection system 300 may also include an optional filter positioned between the two coupling lenses 904 and 906.
- Lenses 902, 904, 906 are achromatic lenses having effective focal lengths of 30mm, 12.5mm, and 12.5mm, and diameters of 12.5mm, 6.25mm, and 6.25mm, respectively.
- the scanning mirror 400 may have a dimension of at least 10mm xl Qmm.
- the transfer mirror 802 may be a spherical mirror.
- the scanning mirror 400 and the transfer mirror 802 may have an Aluminum coating, a Silicon Monoxide (SiO) overcoat, or a multilayer film of dielectrics on top of aluminum to increase the reflectance in certain wavelength regions (e.g., UV).
- the transfer mirror's 802 radius may be between 100mm to 120mm, in one implementation, the transfer mirror's 802 radius is 109.41 1 mm.
- the transfer mirror 802 may be positioned at a distance of 68.4mm from an outer edge of the optical window 70.
- the fold mirror 804 may be positioned at a distance of 71 .5mm from the plane of the scanning mirror 400.
- Spectrometer 310 may be an ultra broadband (UBB) high resolution spectrometer with a spectral resolution of 0.4 nm and having a wavelength range between 200nm-1000nm.
- ULB ultra broadband
- Fig. 10 is a top view schematic of the plasma processing system equipped with the optical system of FIG. 8.
- the plasma processing chamber 20 may be equipped with two optical systems of FIG. 8.
- the optical system is referred to as a scanning module.
- Each scanning module may be configured to collect data from X to Y ray positions.
- each scanning module may be configured to collect data from 5 to 50 ray positions which provide better accuracy to detect events with high spatial resolution.
- one position of ray 305 is shown.
- scan angle of rays 305 may vary from - 0 max °,+9 r!iax ° (e.g., or 30°).
- Each module may include a single channel spectrometer 310, or alternatively a single spectrometer having two channels may be used for the two scanning modules. Additional scanning modules may also be used to provide higher spatial resolution.
- Optical windows 70 i.e., optical window 70 of each scanning module
- the optical windows 70 may be located on the side wail of the plasma processing chamber 20 perpendicular or substantially perpendicular to each other. Depending on the configuration of plasma processing chamber 20, the optical windows 70 may be quartz, fused silica, or sapphire depending on the application and how aggressive the chemistry of the plasma. [0063] Fig.
- FIG. 1 1 is an expanded schematic view of an embodiment of the optical system 300 of Fig. 5 or Fig. 8.
- the optical system 300 has the task of directing the reflected collected plasma optical emission spectra from the scanning mirror 400 to the end 390 of the optical fiber 320, so if can be transmitted to the spectrometer 310 as described previously herein.
- the collected ray 305 is passed through a collection lens which may be a triplet lens 1 102, for example having an effective focal length of 40mm.
- the coliected ray 305 may be passed through an optional mask aperture 1 108, for example having a diameter of 7mm.
- the mask aperture 1 108 may be positioned between the scanning mirror 400 and the triplet lens 1 102.
- the coliected ray 305 may be passed through an optional teiecentric aperture 1 1 10, for example having a diameter of 1 .20mm.
- other optica! components such as lenses can be used to define the diameter of the rays 305.
- Two coupling triplet lenses 1 104 and 1 108 serve to focus the coliected optical emission spectra onto the end 390 of the optical fiber 320.
- the coupling triplet lenses 1 104 and 1 108 may be triplet lenses having effective focal lengths of 15mm.
- the effective focal lengths of the coupling triplet lenses 1 104 and 1 106 is a function of a type and a diameter of the optical fiber 320.
- All lenses used in the system are preferably achromatic, or even
- FIG. 12 is a schematic of an alternative embodiment in which a single channel spectrometer 310 is used.
- the plasma optical emission spectra can be acquired sequentially using one or two modules.
- Each module may include a linear arc stage 1204.
- the spectrometer 310, the optical system 300, and a fold mirror 1202 are mounted on the linear arc stage 1204.
- the fold mirror 1202 is positioned to receive the collected ray 305 from the plasma processing chamber 20 and to reflect the collected ray 305 to the optical system 300.
- the linear arc stage 1204 is controllabiy scanned to sweep out collected rays 305 while the plasma optical emission spectra are acquired by the spectrometer 310 via a single optical system 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 that shown and described in Fig. 9 or Fig. 1 1 .
- the linear arc stage 1204 may have a scanning angle of 85° and a length of 183,2mm.
- the linear scanning speed may vary from 0.35m/s to 2.2m/s.
- the scanning speed may be adjusted to optimize a tradeoff between spatial resolution and speed depending on the application of the plasma optical emission spectroscopy system 15.
- optical system 300 of Figs. 8, 9, and 1 1 other optical components may be used, such as mirrors, prisms, lenses, spatial light modulators, digital micromirror devices, and the like, to steer the collected rays 305.
- the configuration and component layout of the optical system 300 of Figs. 4-8, and Figs. 8-12 do not necessary need to be as shown exactly in Figs. 4-8, and Figs. 8-12, but the collected rays 305 can be folded and steered by way of additional optical components to facilitate packaging the plasma optical emission spectroscopy system 15 into a compact packaging suitable for mounting on the wail of the plasma processing chamber 20.
- the inventors performed several experiments to reconstruct patterns of optical emission distribution and to compare the reconstructed patterns to etch patterns.
- FIG. 13 is a schematic that shows exemplary results of reconstructed patterns of optical emission intensity.
- the intensity of an emission line i.e., 522.45 nm for silicon chloride
- Fig. 13 shows a comparison between an actual etch rate and an actual distribution of the optical emission acquired by the plasma OES system 15 described herein at 522.5nm.
- Plots 1302, 1304, and 1306 show actual etching rate for various samples at 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.
- the etching uniformity may be monitored.
- the apparatus may be used during process development to monitor the etching uniformity for various plasma processing conditions without transferring the substrate to another apparatus which makes the development of various processes faster.
- the results show strong correlation between the etching thickness and the reconstructed OES distribution given by plasma etching involved species, including both reactants and products.
- the uniformity of OES distribution and Oxide etching profile follows the same trend, for example plot 1302 compared to plot 1308.
- Substrate with better etching uniformity shows lower correlation with OES distribution (e.g., plot 1306 compared to plot 1302).
- FIG. 14 is a flowchart that shows a method 1400 for optical emission measurement according to one example.
- an optical window is deposited at a wall of a plasma processing chamber (e.g. , the plasma processing chamber 20).
- a collection system is provided for collecting plasma optical emission spectra through the optical window.
- the collection system may include a mirror and a teiecentric coupler.
- the teiecentric coupler may include at least one collection lens (e.g., collection lens 360A and 360B) and at least one coupling lens (e.g., coupling lenses 904 and 906 of FIG. 9).
- a plurality of non-coincident rays is scanned across the plasma processing chamber using the mirror. The scanning may be controlled by the controller 80.
- an optical signal is collected from a plasma via the
- the optical signal is directed to a spectrometer for measuring the plasma optical emission spectra.
- a method for optical emission measurement comprising depositing an optical window at a wail of a plasma processing chamber; providing a collection system for collecting plasma optical emission spectra through the optical window, the collection system including a mirror and a teiecentric coupler; scanning a plurality of non- coincident rays across the plasma processing chamber using the mirror; collecting an optical signal from a plasma via the telecentric coupler; and directing the optical signal to a spectrometer for measuring the plasma optical emission spectra.
- the telecentric coupler further includes: an aperture disposed between the at least one collection lens and the at least coupling lens for defining a diameter of the plurality of non-coincident rays.
- the mirror system includes a transfer mirror; a fold mirror; and in which the transfer mirror is configured to transfer the collected signal to the fold mirror and the fold mirror is configured to transfer the collected signal to the mirror.
- the teiecentric coupler includes a collection triplet lens configured to collect the optical signal from the mirror; and two coupling triplet lenses configured to focus the collected signal info an end of an optical fiber coupled to the spectrometer.
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KR20130062791A (en) * | 2011-12-05 | 2013-06-13 | 삼성전자주식회사 | Plasma diagnostic apparatus and method |
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JPH10261625A (en) * | 1997-03-19 | 1998-09-29 | Olympus Optical Co Ltd | Etching termination detector for plasma etcher |
US20040026035A1 (en) * | 2000-11-28 | 2004-02-12 | Mitrovic Andrej S. | Method and apparatus for 2-d spatially resolved optical emission and absorption spectroscopy |
US20100200767A1 (en) * | 2009-02-10 | 2010-08-12 | Yi Hunjung | Optical apparatus for plasma |
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