Optical wall and plasma-facing sensor process sensor

Abstract

Embodiments disclosed herein include an optical sensor system for use in a plasma processing tool. In one embodiment, the optical sensor system includes an optically transparent body having a first surface and a second surface facing in a direction away from the first surface. In one embodiment, the optically transparent body further includes a third surface recessed from the second surface. In one embodiment, the optical sensor system further includes a target above the third surface; and a first reflector to optically couple the first surface to the target.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. non-provisional patent application No. 16 / 682,616, filed on November 13, 2019, which is hereby incorporated by reference in its entirety.

[0003] background

[0004] Embodiments relate to the field of semiconductor manufacturing, and more particularly, to systems and methods for providing in-situ optical sensors for monitoring chamber surface conditions and chamber processing parameters.

[0005] Description of related technologies

[0006] Changes in chamber surfaces affect various processing parameters. For example, redeposition of etch byproducts on chamber walls can change the etch rate of a given process. Consequently, as substrates are processed in the chamber, the etch rate (or other process parameters) can vary and lead to non-uniform processing between substrates.

[0007] To account for changes in processing conditions, optical emission spectroscopy (OES) has been implemented in processing chambers. OES involves monitoring the emission spectrum of the plasma in the chamber. A window is positioned along the chamber wall, and the emission spectrum can be passed through the window along an optical path to a sensor outside the chamber. As the plasma spectrum changes, a qualitative analysis of the processing operation can be inferred. Specifically, OES is useful for determining when the endpoint of the processing operation has been met. To provide optimal measurements, the window is designed to prevent deposition along the optical path. Furthermore, while endpoint analysis is possible, there is currently no process for performing quantitative analysis using existing OES systems. Summary of the Invention

[0008] Embodiments disclosed herein include an optical sensor system for use in a plasma processing tool. In one embodiment, the optical sensor system includes an optically transparent body having a first surface and a second surface facing away from the first surface. In one embodiment, the optically transparent body further includes a third surface recessed from the second surface. In one embodiment, the optical sensor system further includes a target above the third surface and a first reflector optically coupling the first surface to the target.

[0009] Embodiments disclosed herein can also include an optical sensor. In an embodiment, the optical sensor includes an optically transparent body. In an embodiment, the optically transparent body includes: a first surface; a second surface opposite the first surface; and a third surface recessed into the second surface. In an embodiment, the optical sensor further includes: a target above the third surface; a first reflector embedded in the optically transparent body; and a second reflector embedded in the optically transparent body. In an embodiment, the optical sensor further includes: a light source optically coupled to the optically transparent body; and an optical detector optically coupled to the optically transparent body.

[0010] Embodiments disclosed herein can also include a plasma processing chamber. In an embodiment, the plasma processing chamber includes: an optical sensing system through a wall of the plasma processing chamber. The optical sensing system includes: a lens and an optically transparent body adjacent to the lens. In an embodiment, the optically transparent body includes: a first surface facing the lens; a second surface opposite the first surface; and a third surface recessed into the second surface, wherein the third surface faces a center of the processing chamber. In an embodiment, the optical sensing system further includes: a target above the third surface; and a first reflector embedded in the optically transparent body. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a cross-sectional view of a processing tool having an optical sensor system according to an embodiment.

[0012] Figure 2A is a cross-sectional view of an optical sensor system having a recessed target and reflector according to an embodiment.

[0013] Figure 2B is a cross-sectional view of an optical sensor system having a recessed target according to an embodiment, wherein an optical path passes through the recessed target.

[0014] Figure 2C is a cross-sectional view of an optical sensor system having a target according to an embodiment, wherein an optical path reflects off a backside surface of the target.

[0015] Figure 2D is a cross-sectional view of an optical sensor system having an optically transparent body including a reflective coating according to an embodiment.

[0016] Figure 2E is a cross-sectional view of an optical sensor system having an optically transparent body including a lens surface according to an embodiment.

[0017] Figure 3 is a cross-sectional view of an optical sensor system having a coating above a target according to an embodiment.

[0018] Figure 4A is a cross-sectional view of an optical sensor system having a prism for reflecting light to an optical detector, according to an embodiment.

[0019] Figure 4B is a cross-sectional view of an optical sensor system having a filter, according to an embodiment.

[0020] Figure 5 is a cross-sectional plan view of a chamber having an array of optical sensor systems, according to an embodiment.

[0021] Figure 6 is a block diagram illustrating an exemplary computer system that can be used with an optical sensor having an optical path through a chamber wall, according to an embodiment. DETAILED DESCRIPTION

[0022] The systems and methods described herein include optical sensors for in-situ monitoring of chamber conditions and / or process conditions in a chamber. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments. It will be apparent, however, to one skilled in the art that the embodiments can be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail in order not to unnecessarily obscure the embodiments. Also, it is to be understood that the various embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale.

[0023] As described above, currently available optical emission spectroscopy (OES) systems can provide qualitative measurements to achieve functions such as endpointing, but are currently unable to provide precise quantitative measurements. Process parameters such as etch rate cannot be directly measured using existing OES systems. Accordingly, the embodiments disclosed herein include optical sensor systems that measure a reference signal and plasma emission spectra. For example, the reference signal starts at a light source, passes through a chamber wall, and reflects off of a target surface in the chamber and back toward the sensor. Since the reference signal and the emission spectra pass within the same optical sensor system, the reference signal can be used to determine losses attributable to the optical path without having to open the chamber and disrupt operations. This allows for accurate and quantitative measurements of the emission spectra. Accordingly, calibrated plasma emission spectra can be used to determine process parameters such as etch rate.

[0024] Further, while currently available OES systems are designed to prevent deposition along the optical path, embodiments disclosed herein include a target exposed to the processing environment. In some embodiments, the target can be selected to substantially match the interior surfaces of the chamber. Additionally, the target can be oriented to face the plasma. This ensures that the target experiences substantially the same environmental conditions as the chamber surfaces. As such, deposition on the target is substantially similar to the deposition seen on the interior surfaces of the chamber. The target interacts with the photons emitted by the source and thus can be used to determine properties of the deposited film or the conversion of the wall material. For example, the absorption of portions of the photon spectrum can be correlated to specific material composition and / or film thickness.

[0025] Accordingly, embodiments disclosed herein allow for quantitative in-situ measurements of processing conditions, substrate conditions, and / or chamber conditions. Since embodiments disclosed herein provide quantitative measurements, embodiments can allow for chamber matching measurements (i.e., comparing individual processes performed in different chambers). In some embodiments, a single optical sensor can be included in the processing chamber. Other embodiments can include an array of optical sensors positioned around the perimeter of the processing chamber. Such embodiments can allow for obtaining chamber uniformity data (e.g., plasma uniformity, chamber surface uniformity, substrate uniformity, etc.). Further, these embodiments can also provide an indication of chamber anomalies (e.g., chamber drift).

[0026] Referring now to Figure 1 , a cross-sectional view of a processing tool 100 is shown in accordance with an embodiment. In an embodiment, the processing tool 100 includes a chamber 105. For example, the chamber 105 can be suitable for low pressure processing operations. In one embodiment, the processing operations can include generating a plasma 107 in the chamber 105. In an embodiment, a substrate support 108 is in the chamber 105. The substrate support 108 can be a chuck (e.g., an electrostatic chuck, a vacuum chuck, or the like) or any other suitable support on which one or more substrates can be placed during processing.

[0027] In an embodiment, the processing tool 100 can include an in-situ optical sensor 120. The in-situ optical sensor 120 penetrates a surface of the chamber 105 such that a first portion of the optical sensor 120 is inside the chamber 105 and a second portion of the optical sensor is outside the chamber 105. In an embodiment, the optical sensor 120 is illustrated as penetrating a sidewall of the chamber 105. However, it should be understood that the optical sensor 120 can be positioned to penetrate any surface of the chamber 105.

[0028] In the illustrated embodiment, a single optical sensor 120 is shown. However, it should be understood that embodiments are not limited to such a configuration and more than one optical sensor 120 can be included in the processing tool 100. Further, the optical sensor 120 need only pass through a single optical opening (i.e., window) of the chamber 105. As will be described in greater detail below, the optical path includes a target 121 that passes through the same opening along the optical path that reflects photons from the source 137 back. For example, the optical path along can include one or more reflectors 123. This is in contrast to existing systems that require an optical path that spans the space of the chamber 105 and require at least two optical openings through the chamber.

[0029] In one embodiment, the target 121 is oriented so that the target 121 faces the interior of the chamber 105. Orienting the target 121 so that the target 121 faces the interior of the chamber 105 allows the surface of the target 121 to be modified in substantially the same manner as the interior surfaces of the chamber are modified during processing operations. For example, byproducts that are deposited onto the interior surfaces of the chamber 105 can also be deposited onto the target 121. Further, such an orientation of the target 121 will expose the target to substantially the same ion and / or electron bombardment as the interior surfaces of the chamber 105. Accordingly, the chemical reactions on the target 121 are substantially similar to the chemical reactions on the interior surfaces of the chamber 105. In a particular embodiment, the target 121 can include the same material as the interior surfaces of the chamber 105. Accordingly, it can be assumed that changes to the surface of the target 121 substantially match changes to the interior surfaces of the chamber 105. In this manner, chamber surface monitoring can be performed by the optical sensor 120.

[0030] In another embodiment, the target 121 can include a grating. The grating can be fabricated so that the grating provides a known wavelength-dependent diffraction angle of incident light. As the grating is altered (e.g., by deposition, material removal, or material transformation), the changes to the target can be detected as a change in intensity received at the optical detector and can be used as an additional mechanism for monitoring chamber conditions.

[0031] In one embodiment, the optical sensor 120 includes a housing. In one embodiment, the housing can include a first housing 124 and a second housing 122. In one embodiment, the first housing 124 can be fastened to the second housing 122 using any suitable fastener. In other embodiments, the housing can be a single structure. That is, the first housing 124 and the second housing 122 can be combined into a single structure. Further, although a first housing 124 and a second housing 122 are disclosed, it should be understood that the housing can include any number of components that are coupled together.

[0032] In one embodiment, the first housing 124 can secure an optically transparent body 126 through the chamber 105 into the interior of the chamber 105. In one embodiment, the optically transparent body 126 can be quartz, sapphire, or the like. The optically transparent body 126 allows photons from the plasma 107 to enter the optical sensor 120. Additionally, light from the source 137 can propagate through the optically transparent body 126 and reflect off of the one or more reflectors 123 and the target 121.

[0033] In some embodiments, a lens 125 is secured between the first housing 124 and the second housing 122. The lens 125 is positioned along the optical path between the source 137 and the target 121 so as to focus photons passing along the optical path. In some embodiments, the lens 125 can be part of a seal that closes an opening through the chamber 105. For example, an O-ring or the like (not shown) can be seated against a surface of the lens 125 that faces the chamber 105.

[0034] In one embodiment, the optical sensor 120 can further include a source 137 and an optical detector 138. The source 137 and the optical detector 138 can be optically coupled to the optical path. For example, a fiber optic cable 132 can extend from the second housing 122. In one embodiment, the fiber optic cable 132 can include a splitter 134 that branches into a fiber optic cable 135 to the source 137 and a fiber optic cable 136 to the optical detector 138.

[0035] In one embodiment, the source 137 can be any suitable source for propagating photons along the optical path. In particular, embodiments include a high precision source 137. The high precision source 137 provides a known electromagnetic spectrum or specific wavelengths and intensities that can be used as a reference baseline for calibrating measurements using the optical sensor 120. In one embodiment, the source 137 can be a single wavelength source. For example, the source 137 can be a laser or a light emitting diode (LED). In other embodiments, the source 137 can be a broadband light source. For example, the source 137 can be an arc flash lamp (e.g., a xenon flash lamp).

[0036] In one embodiment, the optical detector 138 can be any suitable sensor for detecting photons. In one embodiment, the optical detector 138 can include a spectrometer. For example, the spectrometer can have a charge-coupled device (CCD) array. In other embodiments, the optical detector 138 can have photodiodes that are sensitive to specific wavelengths of photons.

[0037] Referring now toFigure 2A , according to one embodiment, shows a cross-sectional view of an optical sensor 220. In one embodiment, the optical sensor 220 includes a first housing 224 and a second housing 222. The first housing 224 can secure an optically transparent body 226 extending through the chamber wall 205. In one embodiment, the optically transparent body 226 includes a first surface 251 and a second surface 252 opposite the first surface 251. In one embodiment, a third surface 253 of the optically transparent body 226 is recessed from the second surface 252.

[0038] In one embodiment, the target 221 is disposed above the third surface 253. In some embodiments, the target 221 can comprise the same material as the interior surfaces of the chamber 205. In one embodiment, the target 221 is exposed to the interior of the processing chamber.

[0039] In one embodiment, the first reflector 223 A and the second reflector 223 B Embedded in the optically transparent body 226. The reflector 223 A and 223 B Embedded in the optically transparent body 226, it prevents the environment in the chamber from causing the reflector 223 to A and 223 B First reflector 223 A and the second reflector 223 B Can be positioned between the second surface 252 and the third surface 253. Figure 2A In the specific embodiment shown in FIG. A and the second reflector 223 B Located at the corners of the optically transparent body 226. In one embodiment, the reflector 223 A and 223 B It can be any suitable reflector. For example, reflector 223 A and 223 B It may be a mirrored surface, a grating, or any other structure suitable for changing the path of light.

[0040] In one embodiment, the optical path may pass through the optical sensor 220. Figure 2A The optical path is represented by a plurality of ray traces 241-244. The optical path is from the optical cable 232 to the first reflector 223. A The optical path starts from the first reflector 223 A The ray 242 reflected off and continues to the target 221. That is, the first reflector 223 A It can be considered as optically coupled to the target 221. In one embodiment, the optical path is reflected off the target 221 to the second reflector 223.B That is, the second reflector 223 B It can be considered as optically coupled to the target 221. In one embodiment, the optical path is from the second reflector 223 B Ray 244 reflects off and continues to optical cable 232 .

[0041] like Figure 2A As shown in FIG, rays 242 and 243 can propagate through portions of optically transparent body 226 and through portions of the interior of chamber 205. That is, ray 242 begins inside optically transparent body 226 and exits optically transparent body 226 (through the sidewalls) before reaching target 221. Similarly, ray 243 begins outside optically transparent body 226 and exits second reflector 223 before reaching target 221. B 2. The target 221 may be positioned outside the optically transparent body 226. This allows the target 221 to be exposed to substantially the same environmental conditions as the interior surfaces of the chamber 205.

[0042] In one embodiment, photons 245 from the processing environment inside chamber 205 can pass through the sidewalls of optically transparent body 226 and into optically transparent body 226. In one embodiment, photons 245 pass through optically transparent body 226 and enter optical cable 232. The illustration of photons 245 shows them bending without contacting any reflective surfaces. However, this is for illustration only, and it should be understood that photons 245 can reflect off of any number of surfaces before reaching optical cable 232.

[0043] In one embodiment, the optical sensor 220 may further include a lens 225. In one embodiment, the lens can be used to focus photons (e.g., ray 241, ray 244, or ray 245) passing through the optical sensor 220. In one embodiment, the optical sensor 220 may be adjacent to a first surface 251 of the optically transparent body 226. As shown, the first surface 251 conforms to the shape of the lens 225. In other embodiments, the first surface 251 may be a substantially flat surface.

[0044] Now refer to Figure 2B , shows a cross-sectional view of an optical sensor 220 according to another embodiment. In one embodiment, in addition to the reflector 223 A and 223 B In addition to the positioning, Figure 2B The optical sensor 220 in FIG. Figure 2A In addition, the third surface 253 of the depression may have a Figure 2A The recessed third surface 253 has a different configuration.

[0045] As shown, the recessed third surface 253 causes only a single protrusion of the optically transparent body 226 to extend beyond the target 221. In an embodiment, the first reflector 223 A may be positioned in the protrusion of the optically transparent body 226. That is, the first reflector 223 A may be positioned between the second surface 252 and the third surface 253. In an embodiment, the second reflector 223 B may be positioned between the third surface 253 and the first surface 251.

[0046] The change in position of the second reflector 223 B causes the optical path through the optically transparent body 226 to differ. As shown, the first ray 241 passes through the optically transparent body 226 and intersects the first reflector 223 A . Subsequently, the reflected second ray 242 A passes outside the optically transparent body 226 and intersects the target 221. In an embodiment, the optical path continues through the target 221. That is, a portion of the second ray 242 A passes through the target 221 back into the optically transparent body 226 (i.e., the third ray 242 B ). The third ray 242 B intersects the second reflector 223 B . A portion of the second ray 242 A may reflect off the target 221 (i.e., the fourth ray 242 C ). In an embodiment, the optical path then continues with the fifth ray 243 which continues to the optical cable 232.

[0047] Such an optical path differs from the optical path in Figure 2A in that the optical path passes through the target 221. Accordingly, as the target 221 changes (e.g., due to deposition of material, etching of material, or the like), the intensity of the ray 242 B and / or the wavelength of the ray 242 B changes.

[0048] Referring now to Figure 2C , a cross-sectional view of an optical sensor 220 is shown, according to another embodiment. In Figure 2C , the target 221 is positioned above the second surface 252. That is, in some embodiments, there is no recessed third surface. In such embodiments, the optical path remains within the optically transparent body 226. For example, the first ray 241 passes through the optically transparent body 226 and intersects the backside surface of the target 221. A portion (i.e., the ray 242 B ) passes through the target 221, and a portion (i.e., the ray 242A ) back to the optical cable 232. Similar to the embodiments in Figure 2B , as the target 221 changes (e.g., due to deposition of material, etching of material, or the like), the intensity of the rays 242 A and / or the wavelength of the rays 242 A changes. However, the embodiments in Figure 2C differ from the embodiments in Figure 2B in that, Figure 2B the light of interest in Figure 2C is light that is reflected off of the target 221.

[0049] Reference is now made to Figure 2D , which illustrates a cross-sectional view of an optical sensor 220, according to another embodiment. In one embodiment, the optical sensor 220 in Figure 2D is generally similar to the optical sensor 220 in Figure 2A , except that it includes an additional reflector. Specifically, Figure 2D the embodiment illustrated in includes a reflector 261 around the perimeter of a portion of the optically transparent body 226. For example, the reflector 261 can cover the surface of the optically transparent body 226 that is within the chamber opening and is encircled by the housing 224. Such a reflector can increase the amount of light from the rays 245 that is extracted from the processing environment.

[0050] Reference is now made to Figure 2E , which illustrates a cross-sectional view of an optical sensor 220, according to another embodiment. In addition to the removal of the discrete lens 225, Figure 2E the optical sensor 220 in Figure 2A is generally similar to the optical sensor 220 in Figure 2E . That is, the embodiments disclosed herein can include optical sensors 220 that do not include a focusing lens. In other embodiments (as illustrated in ), the optically transparent body 226 can include a first surface 251 that is shaped to provide a lens. Accordingly, the optically transparent body 226 can have an integrated lens.

[0051] Reference is now made to Figure 3 , which illustrates a cross-sectional view depicting the use of an optical sensor 320, according to an embodiment. In one embodiment, the optical sensor 320 can be generally similar to any of the optical sensors 220 described above. In a particular embodiment, the optical sensor 320 is generally similar to the optical sensor 220 in Figure 2AThat is, the optical sensor 320 may include a first housing 324, a second housing 322, a lens 325, and an optically transparent body 326. The optical sensor 320 may be inserted through a hole in the chamber 305.

[0052] In one embodiment, the optically transparent body 326 may include a first surface 351, a second surface 352, and a concave third surface 353. In one embodiment, the first reflector 323 A and the second reflector 323 B The target 321 may be positioned between the third surface 353 and the second surface 352. In one embodiment, the target 321 may be disposed above the third surface 353. The target 321 may comprise substantially the same material as the interior surface of the chamber 305.

[0053] In one embodiment, a film 306 may be disposed over the surface of chamber 305 and over the surface of target 321. Film 306 may be a byproduct of a processing operation performed in chamber 305. For example, film 306 may be a redeposition of a byproduct of an etching process. In embodiments where the surface of target 321 and the interior surface of chamber 305 are the same material, film 306 on target 321 will represent film 306 on the interior surface of chamber 305. Specifically, because target 321 faces the interior of chamber 305, target 321 will be subject to substantially the same processing environment as the chamber surface (e.g., substantially the same ion and / or electron bombardment as the interior surface of chamber 305).

[0054] In one embodiment, the film 306 can be optically measured using the sensor 320. For example, light from a source (not shown) can travel along an optical path that intersects the film 306 above the target 321 before reaching an optical detector (not shown). The light source and the optical detector can be optically coupled to the optical sensor 320 via an optical cable 332. In one embodiment, rays 341-344 depict the same patterns as described above with respect to the target. Figure 2A The optical paths described are generally similar to the optical paths of FIG.

[0055] Because the source emits photons with a known spectrum and intensity, measurements of ray 344 by the optical detector prior to deposition of film 306 provide a baseline of losses along the optical path. Such measurements may be referred to herein as reference signal measurements. Accordingly, the difference between the measured results (e.g., spectrum and intensity) of ray 344 and the known spectrum and intensity of the source provides a measure of the losses inherent in optical sensor 320. Accordingly, the known losses can be used to calibrate subsequently acquired signals.

[0056] Optical sensor 320 can be used to determine one or more characteristics of film 306. In one embodiment, reflected radiation 344 can be measured to find differences relative to a reference signal measurement. For example, after deposition of film 306, a decrease in a particular wavelength of reflected radiation 344 (relative to the reference signal measurement) can be used to determine what material constitutes film 306. Specifically, certain materials will preferentially absorb portions of the reference signal spectrum. Accordingly, identifying portions of reflected radiation 344 where the intensity is reduced allows the composition of film 306 to be determined. Additionally, changes to reflected radiation 344 after deposition of film 306 can also identify the thickness of the film.

[0057] Additionally, the sensor can sense photons emitted by the plasma. For example, plasma signal 345 can pass through the sidewalls of optically transparent body 326 and propagate along an optical path to an optical detector (not shown). Measurements of plasma signal 345 can then be corrected by adding back known losses inherent to optical sensor 320. In this manner, a quantitative measurement of photons emitted by the plasma can be provided.

[0058] Now refer to Figure 4A , a cross-sectional view of an optical sensor 420 is shown according to another embodiment. Figure 4A The optical sensor 420 and Figure 2A The optical sensor 220 in FIG. 4 is substantially similar, except that the source 437 and the optical detector 438 are integrated directly into the second housing 422. For example, the ray 441 may pass through the prism 439 and the lens 425 toward the reflector 423. A and 423 B and target 421, and the reflected radiation 444 and plasma signal 445 can be redirected by prism 439 toward optical detector 438. Accordingly, optical coupling of source 437 and optical detector 438 to the optical path can be implemented without fiber optic cables. Such an embodiment can also provide a more compact optical sensor 420.

[0059] Now refer to Figure 4B , shows a cross-sectional view of an optical sensor 420 according to another embodiment. In addition to positioning a filter 447 along the optical path, Figure 4B The optical sensor 420 and Figure 2A Filter 447 is substantially similar to optical sensor 220 in FIG. In one embodiment, filter 447 can provide a specific passband to improve the signal-to-noise ratio and enhance the performance of the optical sensor. In one embodiment, filter 447 is positioned between lens 425 and the sensor (not shown). In other words, filter 447 is positioned outside the chamber space to be protected from the processing environment.

[0060] Now refer toFigure 5 A plan view cross-sectional view of a processing tool 500 is shown in accordance with an embodiment. In an embodiment, the processing tool 500 can include a chamber 505. A substrate support 508 (e.g., a chuck or the like) can be located within the chamber 505. In an embodiment, a plurality of optical sensors 520 A -520 E are arranged in an array around a perimeter of the chamber 505. The optical sensors 520 A -520 E may be generally similar to one or more of the optical sensors described above. In the illustrated embodiment, five optical sensors 520 A -520 E are shown. However, it should be understood that any number of optical sensors 520 can be included in the processing tool 500. The use of a plurality of optical sensors 520 allows uniformity data to be obtained. For example, plasma uniformity and / or wall condition uniformity can be obtained. In addition, chamber drift can also be determined.

[0061] Reference is now made to Figure 6 A block diagram of an exemplary computer system 660 of a processing tool is shown in accordance with an embodiment. In an embodiment, the computer system 660 is coupled to a processing tool and controls processing in the processing tool. The computer system 660 can be connected, e.g., networked, to other machines in a Local Area Network (LAN), an intranet, an extranet, or the Internet. The computer system 660 can operate in the capacity of a server or a client machine in a client-server network environment, or as a peer machine in a peer-to-peer (or distributed) network environment. The computer system 660 can be a personal computer (PC), a tablet computer, a set-top box (STB), a Personal Digital Assistant (PDA), a cellular telephone, a web appliance, a server, a network router, switch or bridge, or any machine capable of executing a set of instructions (sequential or otherwise) that specify actions to be taken by that machine. Further, while only a single machine is illustrated for the computer system 660, the term "machine" shall also be taken to include any collection of machines (e.g., computers) that individually or jointly execute a set, or multiple sets, of instructions to perform any one or more of the methodologies discussed herein.

[0062] The computer system 660 can include a computer program product, or software 622, having a non-transitory machine-readable medium 624 with instructions 626 stored on it, which can be used to program a computer system 660 (or other electronic devices) to perform a process according to embodiments. A machine-readable medium 624 includes any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computer). For example, a machine-readable medium 624 includes a machine- (e.g., a computer-) readable storage medium (e.g., read only memory ("ROM"), random access memory ("RAM"), magnetic disk storage media, optical storage media, flash memory devices, etc.), a machine- (e.g., a computer-) readable transmission medium (electrical, optical, acoustical or other form of propagated signals (e.g., infrared signals, digital signals, etc.)), etc.

[0063] In one embodiment, the computer system 660 includes a system processor 602, a main memory 604 (e.g., read-only memory (ROM), flash memory, dynamic random access memory (DRAM) such as synchronous DRAM (SDRAM), Rambus DRAM (RDRAM), etc.), a static memory 606 (e.g., flash memory, static random access memory (SRAM), etc.), and a secondary memory 618 (e.g., a data storage device), which communicate with each other via a bus 630.

[0064] The system processor 602 represents one or more general-purpose processing devices such as a microsystem processor, central processing unit, or the like. More particularly, the system processor can be a complex instruction set computing (CISC) microsystem processor, reduced instruction set computing (RISC) microsystem processor, very long instruction word (VLIW) microsystem processor, system processor implementing other instruction sets, or system processors implementing a combination of instruction sets. The system processor 602 can also be one or more special-purpose processing devices such as an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a digital signal system processor (DSP), network system processor, or the like. The system processor 602 is configured to execute the processing logic 626 for performing the operations described herein.

[0065] The computer system 660 can further include a system network interface device 608 to communicate with other devices or machines over a network. The computer system 660 can also include a video display unit 610 (e.g., a liquid crystal display (LCD), a light emitting diode display (LED), or a cathode ray tube (CRT)), an alphanumeric input device 612 (e.g., a keyboard), a cursor control device 614 (e.g., a mouse), and a signal generation device 616 (e.g., a speaker).

[0066] The secondary memory 618 can include a machine-storage medium 631 (or more specifically a computer-readable storage medium) on which is stored one or more sets of instructions (e.g., software 622) embodying any one or more of the methodologies or functions described herein. The software 622 can also reside, completely or at least partially, within the main memory 604 and / or within the system processor 602 during execution thereof by the computer system 660, the main memory 604 and the system processor 602 also constituting machine-readable storage media. The software 622 can further be transmitted or received over a network 620 via the network interface device 608. In one embodiment, the network interface device 608 can operate using RF coupling, optical coupling, acoustic coupling, or inductive coupling.

[0067] While the machine-storage medium 631 is shown in an example embodiment to be a single medium, the phrase "machine-readable storage medium" should be taken to include a single medium or multiple media (e.g., a centralized or distributed database, and / or associated caches and servers) that store the one or more sets of instructions. The phrase "machine-readable storage medium" shall also be taken to include any medium that is capable of storing or encoding a set of instructions for execution by the machine and that cause the machine to perform any one or more of the methodologies. The phrase "machine-readable storage medium" shall accordingly be taken to include, but not be limited to, solid-state memories, and optical and magnetic media.

[0068] In the foregoing specification, specific exemplary embodiments have been described. It is evident, however, that various modifications can be made thereto without departing from the scope of the appended claims. Accordingly, the specification and drawings are to be regarded as illustrative in nature rather than restrictive.

Claims

1. An optical sensor system comprising: an optically transparent body having a first surface and a second surface facing away from the first surface, wherein the optically transparent body further comprises a third surface recessed from the second surface; a target above the third surface; a first reflector optically coupling the first surface to the target; and a second reflector optically coupling the first surface to the target, wherein: The first reflector and the second reflector are between the second surface and the third surface; or The first reflector is between the second surface and the third surface, and the second reflector is between the first surface and the third surface. 2 . The optical sensor system of claim 1 , wherein the first reflector and the second reflector are embedded in the optically transparent body. The optical sensor system of claim 1 , wherein the optical path passes through the target.

4. The optical sensor system of claim 1 , further comprising: case; and A lens is within the housing, wherein the lens is adjacent to the first surface of the optically transparent body.

5. The optical sensor system of claim 1, wherein the first surface of the optically transparent body is a lens.

6. The optical sensor system of claim 1 , further comprising: a light source optically coupled to the optically transparent body; and An optical detector is optically coupled to the optically transparent body. The optical sensor system of claim 6 , wherein the light source is a single wavelength source or a broadband light source.

8. The optical sensor system of claim 6, wherein the optical detector is a single wavelength detector or a spectrometer.

9. An optical sensor comprising: An optically transparent body, wherein the optically transparent body comprises: a first surface; a second surface opposite to the first surface; and a third surface recessed into said second surface; a target above the third surface; a first reflector embedded in the optically transparent body; a second reflector embedded in the optically transparent body; a light source optically coupled to the optically transparent body; and an optical detector optically coupled to the optically transparent body, wherein: The first reflector and the second reflector are positioned between the second surface and the third surface; or The first reflector is between the second surface and the third surface, and the second reflector is between the first surface and the third surface.

10. The optical sensor of claim 9, wherein the optically transparent body comprises glass or sapphire. The optical sensor of claim 9 , wherein the first reflector is a mirror.

12. The optical sensor of claim 9, wherein one or both of the first reflector and the target comprises a grating.

13. A plasma processing chamber comprising: an optical sensing system extending through a wall of the plasma processing chamber, wherein the optical sensing system comprises: lens; an optically transparent body adjacent to the lens, wherein the optically transparent body comprises: a first surface facing the lens; a second surface opposite to the first surface; and a third surface recessed into the second surface, wherein the third surface faces a center of the processing chamber; a target above the third surface; a first reflector embedded in the optically transparent body; and A second reflector is embedded in the optically transparent body, wherein: The first reflector and the second reflector are positioned between the second surface and the third surface; or The first reflector is between the second surface and the third surface, and the second reflector is between the first surface and the third surface.

14. The plasma processing chamber of claim 13, wherein the optical sensing system is configured to provide plasma conditions, wall conditions, substrate conditions, or any combination thereof.

15. The plasma processing chamber of claim 13, further comprising a plurality of optical sensing systems.

16. The plasma processing chamber of claim 13, further comprising: a light source optically coupled to the optically transparent body; and An optical detector is optically coupled to the optically transparent body.

17. The plasma processing chamber of claim 13, wherein the target is external to the optically transparent body and within the plasma processing chamber.

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