WO2020142451A1

WO2020142451A1 - Monitoring process wall depositions and coatings

Info

Publication number: WO2020142451A1
Application number: PCT/US2019/068981
Authority: WO
Inventors: Luc Albarede; Cristian Siladie; Lingyan Ruan
Original assignee: Lam Research Corporation
Priority date: 2018-12-31
Filing date: 2019-12-30
Publication date: 2020-07-09
Also published as: TW202041697A

Abstract

Various embodiments include apparatuses and methods using the apparatus. In one embodiment, the apparatus includes an adsorption sensor having a light source, and at least a first transparent-window and a second transparent-window mounted on substantially opposing walls in a process chamber through which radiation from the light source traverses. The first windows are selected to be substantially transparent at one or more wavelengths emitted by the light source. A light-source detector is configured to receive radiation transmitted through the second transparent-window and provide an intensity level of the received radiation that includes transmission losses through the first transparent-window and the second transparent-window due to adsorbed films on the windows. Other apparatuses and systems are disclosed.

Description

MONITORING PROCESS WALL DEPOSITIONS AND COATINGS CLAIM OF PRIORITY

[0000] This application claims the priority benefit to U.S. Patent Application Serial No.62/786,984, filed on 31 December 2018, and entitled "MONITORING PROCESS WALL DEPOSITIONS AND COATINGS," which is incorporated by reference herein in its entirety. TECHNICAL FIELD

[0001] The subject matter disclosed herein relates to equipment used in the semiconductor and allied industries. More specifically, the disclosed subject matter relates to an apparatus to determine a level at which previously-deposited films and other residues have been removed from interior walls of a process chamber. In particular, the disclosed subject matter relates to an apparatus used for endpoint determination of wafer- less plasma cleaning methods for the substantial removal of the films and other residues on the interior walls, or other components, inside the process chamber. BACKGROUND

[0002] A continuing trend for smaller device-geometries for

semiconductor devices is creating increased difficulty in maintaining the uniformity, accuracy, and precision of critical dimensions (CDs) of the devices. The semiconductor and related industries have realized that it has become increasingly important that a cleanliness level of surfaces (e.g., interior walls) inside processing chambers (e.g., deposition chambers and etch chambers) be at a consistent cleanliness-level to reduce or eliminate wafer-to-wafer, or even across wafer, variability with regard to critical dimensions. As is known to a person of ordinary skill in the art, many of the processes carried out within the processing chambers leave films, residues, particulates, and other contaminants on the interior surfaces of processing chambers. [0003] Additionally, an increasing buildup of the contaminants can cause an inconsistent chamber-conditioning environment, which can impact various processing operations. Since the buildup of contaminants increases with each processing operation, each successive processing operation fails to initiate with the same chamber conditions. Accordingly, the change in starting conditions for each successive processing operation causes a variation that eventually exceeds acceptable limits, resulting in etch-rate drifts, critical-dimension drifts, profile drifts, and other deleterious effects. [0004] One attempt to solve these issues has been to run cleaning processes on the process chamber between processing operations.

However, these cleaning processes do not have an automated endpoint determination. Consequently, each cleaning process is run for a specified length of time. Running the cleaning process in a timed mode typically results in a significantly longer run time than necessary to ensure the processing chamber is clean, rather than risk the chamber being under- cleaned. Significantly, this over-clean mode may also result in a

degradation of chamber components, which in turn decreases a lifetime of the components, and increases the cost of replacement components. [0005] Formerly, the cleaning processes relied on plasma cleans for cleaning plasma-based process chambers by placing a wafer in the process chamber to cover the electrostatic chuck (e.g., lower electrode). However, it has become more common to do wafer-less process chamber cleans. This has led to the use of a wafer-less auto clean (WAC) process. The WAC process has conventionally used a composite one-step recipe focused on the removal of all chamber deposition byproducts involving a mixture of etchant gases for the removal of, for example, both silicon-based byproducts and carbon-based byproducts. However, a composite WAC recipe for both silicon and carbon byproduct removal suffers from lower removal rates of both silicon-based and carbon-based deposition byproducts. Additionally, cleaning compounds (e.g., aluminum fluoride, AlF₃) left behind in the one-step recipe could adversely impact later- performed etch operations. [0006] Another contemporaneous technology to monitor interior process chamber walls is based on using experimental "coupons" placed within the process chamber. These coupons are inserted at different locations inside the chamber to check the deposition level and clean capability of the chamber. Productivity engineers then run long experiments using the coupons to define optimal parameters for a particular film and state of the process chamber wall. In addition to the lengthy testing procedures required, the process chamber must be opened and closed multiple times with repeated multiple tests, both of which add to the lengthy testing requirements using coupons. [0007] In yet another contemporaneous technology, experiments have been performed using infrared-attenuated total reflection (IR ATR) techniques to monitor optically a level of cleanliness within the process chamber. However, these types of measurements are heavily invasive and require a significant modification of the process chamber. [0008] Therefore, given the above-mentioned problems, in one embodiment, the disclosed subject matter provides a light source to irradiate or illuminate a window situated within the process chamber to monitor the absorbance of the light source on deposits and/or coatings formed on the window. The level of absorbance is related to the thickness of the deposit/film. In other embodiments, the absorbance level for a given film and/or process can be saved to a database and applied to similar process chambers manufactured without the window and light source. [0009] The information described in this section is provided to offer the skilled artisan a context for the following disclosed subject matter and should not be considered as admitted prior art. BRIEF DESCRIPTION OF THE FIGURES

[00010] FIG. 1A shows an adsorption sensor to monitor wall deposits in substantially real time. FIG. 1A is depicted as three-dimensional cutaway view of a portion of a process chamber having lateral ports through which light can be transmitted across the process chamber to determine adsorption of films on walls of the process chamber; [00011] FIG.1B shows a cross-sectional two-dimensional view of the adsorption sensor shown as a three-dimensional cutaway view in FIG.1A; [00012] FIG. 2A shows an exemplary embodiment of a light source that may be used as the light source for FIG.1A and FIG. 1B; [00013] FIG. 2B shows an exemplary embodiment of a detector that may be used as the detector for FIG. 1A and FIG.1B; [00014] FIG. 2C is a top view of a portion of a process chamber showing the light source and the detector of FIGS.2A and 2B, respectively; [00015] FIG. 3A shows another embodiment of an adsorption sensor to monitor wall deposits in a process chamber in substantially real time. The adsorption sensor is used to determine absorbance of films on the process wall using a broadband light source with a first spectrometer used as a detector and a second spectrometer used to monitor any variability in the broadband light source; [00016] FIG. 3B shows yet another embodiment of an adsorption sensor used to determine absorbance of films on the process wall using a broadband light source with a first spectrometer and a second

spectrometer and a first-surface mirror to improve a lower limit of detection; [00017] FIG. 4 shows a graph of the absorbance spectrum across a range of light-source wavelengths with isopropyl alcohol (IPA) injected on the on the windows as a test; [00018] FIG. 5 shows a graph of the absorbance spectrum across a range of light source wavelengths with various flowrates of trifluoromethane (CHF3) and Argon (Ar) gases flowing in the process chamber at 400 millitorr (mT); [00019] FIG. 6 shows a graph of adsorption of CHF₃ as a function of the ratio of CHF3 in a CHF3 to Ar mixture; [00020] FIG. 7 shows a graph of the absorbance spectrum across a range of light source wavelengths with various deposition times of a silicon dioxide (SiO₂) coating on the walls of the process chamber; [00021] FIG. 8 shows a graph of adsorption of SiO2 as a function of the coating time; [00022] FIG. 9 shows a flowchart of operations in an embodiment in using various forms of an adsorption sensor described herein to determine or create a wafer-less auto clean (WAC) endpoint time in accordance with various embodiments of the disclosed subject matter; and [00023] FIG.10 shows a simplified block diagram of a machine in an example form of a computing system within which a set of instructions for causing the machine to perform any one or more of the methodologies and operations discussed herein may be executed.

DETAILED DESCRIPTION

[00024] The disclosed subject matter will now be described in detail with reference to a few general and specific embodiments as illustrated in various ones of the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the disclosed subject matter. It will be apparent, however, to one skilled in the art, that the disclosed subject matter may be practiced without some or all of these specific details. In other instances, well-known process steps or structures have not been described in detail so as not to obscure the disclosed subject matter. [00025] As noted above, both etch processes and deposition processes can leave films, residues, particulates, and other contaminants on surfaces (e.g., interior walls) within a process chamber. Typical species deposited on chamber walls include, for example, silicon (Si) byproducts, CxFy polymers, silicon dioxide (SiO2), various types of silicon chloride (SiClx), and other species. As is known to a person of ordinary skill in the art, a WAC cleaning process employed will depend on the type of byproduct to be removed from the process chamber walls. [00026] For example, in the case of Si byproducts, a WAC cleaning method may begin by flowing an etchant process gas with a fluorine- containing compound, generally of the formula X_yF_z. A fluorine-containing compound is optimized to remove silicon and silicon compounds. Then, a first plasma is formed from the etchant process-gas to perform a silicon- based cleaning step. [00027] In the case of carbon-containing contaminants, a WAC cleaning method may begin by flowing an etchant process gas with an oxygen- containing compound; the oxygen-containing compound being optimized to remove carbon and carbon compounds. Then, a first plasma is formed from the etchant process-gas to perform a carbon-based cleaning step. [00028] However, as will be recognized by a person of ordinary skill in the art, each of these cleaning methods have numerous variables involved (e.g., flow rates of the etchant gases, concentrations and partial pressures of the etchant gases, plasma power, plasma frequency, etc.). Therefore, a consistent approach to WAC cleaning processes is needed and is disclosed herein. [00029] In an exemplary embodiment, a transmission spectrometer is constructed to include two lateral ports that are formed into walls of a process chamber. One side of the chamber has a light source placed on an outer portion (outside of the process chamber) of the first lateral port and a detector is placed on an outer portion of the second lateral port. A light (radiation) path generated by the light source traverses through the process chamber, being transmitted through the two transparent windows placed within the lateral ports. The windows are selected to comprise a material that is transparent at a wavelength or range of wavelengths provided by the light source. [00030] In other exemplary embodiments, an arrangement using a light source, a transmission spectrometer, and one or more first-surface mirrors is constructed to produce multiple passes of the radiation traversing the process chamber, thereby increasing a sensitivity level of the

spectrometer. The sensitivity of the spectrometer using the multiple-paths is increased since the radiation path (e.g., light beam) traverses the chamber and the windows multiple times. The absorbance of the deposits on the windows is therefore multiplying. Consequently, a limit of detection of the deposited films increases. As a result, even very thin films are detectable. [00031] In various embodiments, the disclosed subject matter provides a light source to irradiate or illuminate a window situated within the process chamber to monitor the absorbance of the light source on deposits, films, and/or coatings formed on the window. The level of absorbance is related to the thickness of the deposit/coating. In other embodiments, the absorbance level for a given film and/or process can be saved to a database and applied to similar process chambers manufactured without the windows, light-source detector, and light source. The disclosed subject matter can be applied to various types of process chambers including etch chambers and deposition chambers and include monitoring deposits on substrates (e.g., on Si wafers). [00032] In the various embodiments, the main targets include detection of SixOy oxide, CxFy polymer, and SixCly types of molecule. However, moisture on the windows (e.g., windows 105, 107 of FIG. 1A, below) can also be monitored (e.g., the presence of moisture on the window including H₂O, OH band when the chamber is at start-up after maintenance). [00033] As used herein, the terms "deposits," "films," "coatings,"

"particulates," and "residues" may all be used, singly or in various combinations, to refer to various types of unwanted contamination that has accumulated on interior walls (and other surfaces) within a process chamber. [00034] Further, as is known to a person of ordinary skill in the art, "adsorption" refers to a surface phenomenon in which adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solids forms on a surface (e.g., the interior portions of chamber walls and the windows used to construct portions of the spectrometer). The adsorption process therefore creates a film of the adsorbate on a surface of a material. "Absorption" is a measure of the capacity of a substance to absorb light of a specified wavelength, as discussed in greater detail herein. Absorption is equal to the common logarithm of the reciprocal of transmittance of the substance. [00035] With reference now to FIG.1A, an adsorption sensor to monitor wall deposits in substantially real time is shown. FIG. 1A is depicted as three-dimensional cutaway view of a portion of a process chamber 100 having lateral ports through which light can be transmitted across the process chamber 100 to determine adsorption of films on walls of the process chamber. [00036] The portion of the process chamber 100 of FIG.1A is shown to include a light source 101, a light-source detector 103, a first transparent- window 105, and a second transparent-window 107. In a specific exemplary embodiment, the adsorption sensor of FIG. 1A is configured as a transmission infrared spectrometer as the light source 101 transmits radiation (e.g., a beam of light) through the first transparent-window 105, and onto and through the second transparent-window 107. A level of the radiation that is transmitted through both windows (a level of the radiation that is not absorbed, scattered, or otherwise "blocked" by films, particulates and/or residues formed on a portion of the windows that is interior to the process chamber) is then detected by the light-source detector 103. In embodiments, since the light-source detector detects an intensity of a received signal as a function of multiple wavelengths of radiation, the light-source detector 103 may be considered to be a spectrometer. [00037] The additional portions of FIG. 1A are shown and described for completeness but are not necessarily directly relevant to the disclosed subject matter. The portion of a process chamber 100 of FIG.1A is also shown to include portions of chamber walls 109 (or, alternatively, a liner placed or otherwise formed on an interior wall of the process chamber). An opening 111 through which various substrate types (not shown but may include, e.g., silicon wafers) may enter the process chamber. The substrate may then be placed on, for example, an electrostatic chuck (not shown but known to a person of ordinary skill in the art) prior to processing operations beginning on the substrate. Once the substrate is placed on a suitable substrate held within the process chamber, a process-chamber door (not shown) may close off the opening 111 so that processing operations (e.g., starting with a vacuum pump-down) of the process chamber. [00038] In various embodiments, the light source 101 may comprise various types of lasers. Typically, the disclosed subject matter may use the transmission and absorption of various regions of infrared (IR)

wavelengths through the two windows shown in FIG.1A. For example, depending upon the type of material to be detected, various embodiments of the disclosed subject matter can use short-wavelength IR up to far- wavelength IR radiation transmitted by the light source 101 (e.g., in this IR range, wavelengths of less than about 1 µm to greater than about 250 µm). However, upon reading and understanding the disclosed subject matter, a person of ordinary skill in the art will readily recognize that additional wavelengths may be used as well. For example, depending on the types of films, particulates, and residues to be detected, radiation sources in the near-IR or even into the visible light spectrum and ultraviolet may be used as well. Further, longer wavelengths in the far- wavelength IR or beyond may also be used. [00039] The light source 101 is transmitted through the first

transparent-window 105 and detected by the light-source detector 103 after being transmitted through the second transparent-window 107. In one embodiment, the second transparent-window 107 is formed within a wall of the process chamber substantially opposite the first transparent- window 105. As films, particulates, residues, and other contaminants ("films" for brevity) begin to adsorb or form onto an interior portion of the windows, a level of absorption of the transmitted radiation by the film increases (and transmission through the windows 105, 107 decreases). Concomitantly, an overall signal-level detected by the light-source detector 103 decreases. [00040] Consequently, the disclosed subject matter can determine a relative thickness of films that have been adsorbed onto the two windows 105, 107 based on a change in the detected radiation level. As more material (e.g., films) are adsorbed or otherwise formed on the two windows, a level of absorption of the incident radiation (at a given wavelength) from the light source 101 (e.g., the laser) increases as well. From this level of absorption of the incident radiation, a determination can be made of the WAC process time needed to restore the windows, and consequently the interior of the process chamber walls, back to a clean condition. This determination of the WAC process time needed is discussed in more detail with reference to FIG.9, below. [00041] In a specific exemplary embodiment, a quantum cascade laser (QCL, a semiconductor laser) is used as the light source 101. As noted above, the first transparent-window 105 and the second transparent- window 107 comprise one or more materials that are transparent or substantially transparent at a wavelength or wavelength range of interest. For example, depending upon a particular type of QCL device,

wavelengths as short as about 2.5 µm up to about 250 µm are produced by the QCL device and one or more materials at least partially transparent to radiation in this range of wavelengths is selected to form the windows 105, 107. If a frequency-selective element is included (not shown in FIG.1A) and coupled to the QCL, the emission of the QCL can be selectable within the wavelength range to a single wavelength. The selected wavelength is also tunable. [00042] Sources for QCL that emit in the mid- to far-infrared portion of the electromagnetic spectrum include, for example, Pranalytica Inc.; 1101 Colorado Avenue; Santa Monica, California, United States; and Block Engineering of Spectra Optics, Inc.; 132 Turnpike Road; Southborough, Massachusetts, United States. Each of these companies produces QCL devices operable in wavelength ranges of about 3.5 Ǎm to about 12.5 Ǎm. Typical operating parameters for one of the QCL devices selected are given in Table I, below

Table I [00043] In other embodiments, a carbon dioxide (CO2) or other substantially-monochromatic laser emitting in the IR range may be selected as well. As is known to a person of ordinary skill in the art, CO2 lasers emit a wavelength of about 9 µm to about 12 µm (with principal wavelengths of about 9.4 µm and about 10.6 µm). Upon reading and understanding the disclosed subject matter, a person of ordinary skill in the art will recognize that other laser types may also be employed. For example, a distributed feedback laser (DFB laser) may be used in place of or in addition to the QCL or the CO₂ laser. In general, a monochromatic wavelength may provide for a faster scan speed with a similar level of sensitivity as a broadband light-source. However, the monochromatic wavelength may not be equally adept to the broadband light-source when considering a wide range of possible adsorbent species. Additionally, other non-laser sources for the light source 101 are discussed below with reference to FIGS.3A and 3B. [00044] In a specific exemplary embodiment that utilizes a QCL or other IR-emitting laser for the light source 101, the first transparent-window 105 and the second transparent-window 107 each comprise zinc selenide (ZnSe). ZnSe is known in the art to be highly transmissive at various IR wavelengths (e.g., from about 0.45 µm to about 21.5 µm). [00045] In various embodiments, the ZnSe windows may be coated with various films or film combinations to reduce or eliminate corrosion of the window elements. Such coatings include, for example, yttrium oxide (Y₂O₃) and yttrium oxyfluoride (YOF). A person of ordinary skill in the art will recognize that, depending upon a given process, other coatings may be used instead of or in addition to these coatings. Upon reading and understanding the disclosed subject matter, a skilled artisan will further recognize that a "sticking coefficient" of the adsorbed material onto the windows may be different from the sticking coefficient of the walls of the process chamber. Also, the sticking coefficient of the windows may different with a coating as compared to no coating being on the windows. However, each of these effects may be considered and calibrated as noted below with reference to FIG. 9. [00046] In various embodiments, the light-source detector 103 may be selected from any type of detector known in the art to be able to detect the wavelength ranges emitted by the light source 101. In a specific exemplary embodiment that utilizes a QCL or other IR-emitting laser for the light source 101, the light-source detector 103 may be a mercury cadmium telluride (HgCdTe or MCT) detector. MCT detectors are generally sensitive in a mid-IR spectral range of wavelengths. In general, an MCT detector allows both control of a gain amplifier as well as selection of a bandwidth of a spectral-detection range. Sources for an MCT detector include Vigo System S.A.; Poznaęska street 129/133 05-850; Oİarów, Mazowiecki, Warsaw, Poland; and Thorlabs Inc.; 56 Sparta Avenue;

Newton, New Jersey, United States. [00047] FIG. 1B shows a cross-sectional two-dimensional view 130 of the adsorption sensor shown as a three-dimensional cutaway view in FIG.1A. The cross-sectional two-dimensional view 130 is Section A-A as indicated by the section markings in FIG.1A. FIG.1B is shown to include a cross- sectional view of a process chamber 131, an adjustable iris 133 located in an output path of the light source 101, as well as components of the light- source detector 103. In an exemplary embodiment, the light-source detector 103 comprises a collimated mirror 103A and a detector component 103B (e.g., the MCT detector described above). In this exemplary embodiment, the collimated mirror collects radiation transmitted through the second transparent-window 107 and collimates the collected radiation to redirect the radiation into the detector component 103B. As is known to a person of ordinary skill in the art, a collimated beam of radiation has substantially parallel rays that will spread minimally as the radiation propagates to the detector component 103B. [00048] The adjustable iris 133 is typically a mechanical device having a diaphragm with a variable opening at its center, through which the light or radiation is directed. The variable opening is an adjustable aperture to prevent saturation of the light-source detector 103. If the light source 101 is too powerful, the adjustable iris 133 may be closed down (e.g., an open area of the adjustable iris 133 is reduced) to prevent the saturation. Also, as material is adsorbed onto the windows, the adjustable iris 133 may be opened throughout the WAC cleaning process as need to maintain a desired signal-to-noise ratio (SNR). [00049] In other embodiments, and depending upon a wavelength or range of wavelengths chosen for the light source 101, the adjustable iris 133 may comprise a series of one or more discrete neutral-density filters that can be place in an output path of the light source 101 to prevent saturation of the light-source detector. In this embodiment, the SNR is still selectable depending on a transmission density or number of neutral- density filters placed in the radiation path from the light source 101. [00050] The collimated mirror 103A may comprise a spherical or parabolic mirror (the shape being considered with regard to the first surface of the mirror) to collimate the collected radiation. The collimated mirror 103A is generally a first-surface mirror to reduce or eliminate refraction and double-reflection effects from the substrate (generally comprising glass) upon which a reflective material is coated. As is known to a person of ordinary skill in the art, the reflective coating is typically applied by a vacuum deposition process to maintain uniformity of the coating over the glass substrate as well as minimize surface roughness of the coating (thereby reducing or eliminating diffuse scattering of the collected radiation). Common coating materials include, for example, silver (Ag), aluminum (Al), and gold (Au). When the light source 101 comprises an IR source, a gold coating is generally applied to the glass substrate as gold is especially reflective in the IR portions of the spectrum. [00051] FIG. 2A shows an exemplary embodiment of a light source 201 that may be used as the light source 101 for FIG. 1A and FIG.1B. The light source 201 is mounted to an outer portion of the process chamber (e.g., see the process chamber 131 of FIG.1B or the process chamber 205 of FIG.2C, below). In this embodiment, the light source 201 is an IR QCL laser having a tunable range of wavelengths from about 8 µm to about 10 µm. In other embodiments, the light source 201 may be the same as or similar to the light source 101 of FIGS.1A and 1B. [00052] FIG. 2B shows an exemplary embodiment of a detector 203 that may be used as the light-source detector 103 for FIG.1A and FIG.1B. In this embodiment, the detector 203 is an MCT detector mounted at approximately 90° from the direction of radiation traversal across the process chamber (see FIG.1B and FIG.2C). A 90° focusing mirror (e.g., collimating spherical or parabolic mirror) is used to direct collected radiation into the detector 203. In other embodiments, the detector 203 may be the same as or similar to the light-source detector 103 of FIGS.1A and 1B. [00053] FIG. 2C is a top view of a portion of a process chamber 205 showing the light source 201 and the detector 203 of FIGS.2A and 2B, respectively. As indicated in FIG.2C, the light source 201 and the detector 203 are mounted on substantially opposite sides of the process chamber 205. [00054] FIG. 3A shows another embodiment of an adsorption sensor 300 to monitor wall deposits in a process chamber 311 in substantially real time. The adsorption sensor 300 is used to determine absorbance of films on the process wall using a broadband light-source 301. A first

spectrometer 305 is used as a detector and a second spectrometer 303 is used to monitor any variability in the broadband light-source 301. A displayed or reported output of the first spectrometer 305 is adjusted by a level of output of the broadband light-source 301, as detected by the second spectrometer 303, to account for any variability detected in the broadband light-source 301. A person of ordinary skill in the art understands how to apply such an adjustment. The adsorption sensor 300 is also shown to include a first transparent-window 390, and a second transparent-window 307. [00055] The broadband light-source 301 may be selected to include any type of source that has a sufficient intensity and a wavelength range that can be transmitted through films that are expected to be adsorbed on the windows 307, 309. In a specific exemplary embodiment, a Xenon (Xe) lamp may be used as the broadband light-source 301. The Xe lamp has a wavelength range of approximately 200 nm to 1100 nm (covering a range from middle ultraviolet (UV) to near IR). A xenon arc-lamp is a specialized type of gas-discharge lamp produces light by passing electricity through ionized xenon gas at high pressure. The Xe lamp may not be as repeatable as a laser source as disclosed above with reference to FIGS.1A and 1B. However, the Xe lamp covers a larger range of wavelengths and therefore may be more suitable for certain film types. [00056] The first spectrometer 305 and the second spectrometer 303 may each comprise various types of optical spectrometer known in the art. In various embodiments, the spectrometers 303, 305 may be the same as or identical to one another. In other exemplary embodiments, the

spectrometers 303, 305 may comprised different types of spectrometer and/or an optical detector. In certain exemplary embodiments, the spectrometers 303, 305 may comprise an optical detector if an intensity of the light as a function of wavelength is not required. In this exemplary embodiment, the detector simply integrates all radiation received from the broadband light-source 301 and displays an intensity value (e.g., a voltage level) as a single quantity. [00057] In a specific exemplary embodiment, the adsorption sensor 300 of FIG. 3A is configured as a transmission ultraviolet-to-infrared spectrometer as the broadband light-source 301 transmits radiation (e.g., a beam of light) through the first transparent-window 309, and onto and through the second transparent-window 307. A level of the radiation that is transmitted through both windows (a level of the radiation that is not absorbed, scattered, or otherwise "blocked" by films, particulates and/or residues formed on a portion of the windows that is interior to the process chamber 311) is then detected by the broadband light-source 301. [00058] The first transparent-window 309 and the second transparent- window 307 comprise one or more materials that are transparent or substantially transparent at a wavelength or wavelength range of interest. For example, depending upon a particular type of broadband light-source 301 used, wavelengths as short as about 200 nm up to about 1100 nm are produced by the broadband light-source 301. One or more materials at least partially transparent to radiation in this range of wavelengths is selected to form the windows 307, 309. [00059] Similar to the description provided above with reference to FIGS.1A and 1B, the broadband light-source 301 is transmitted through the first transparent-window 309 and detected by the first spectrometer 305 after being transmitted through the second transparent-window 307. In one embodiment, the second transparent-window 307 is formed within a wall of the process chamber 311 substantially opposite the first transparent-window 309. As films, particulates, residues, and other contaminants ("films" for brevity) begin to adsorb or form onto an interior portion of the windows, a level of absorption of the transmitted radiation by the film increases. Concomitantly, an overall signal-level detected by the first spectrometer 305 decreases. [00060] FIG. 3B shows yet another embodiment of an adsorption sensor 330 used to determine absorbance of films on walls of a process chamber 311 using a broadband light-source 301 with a first spectrometer 305, a second spectrometer 303, and a first-surface mirror 313 to improve a lower limit of detection. The broadband light-source 301 may be similar to or the same as the broadband light-source 301 used in the embodiment of FIG. 3A. Similarly, each of the windows 307, 309 and the spectrometers 303, 305 may be the same as or similar to the windows 309, 307 and the spectrometers 303, 305, respectively, of FIG.3A. [00061] However, unlike the first spectrometer 305 of FIG.1A that collects radiation that is transmitted through the second transparent- window 307, the first spectrometer 305 of FIG.3B collects radiation that is reflected from the first-surface mirror 313 after being transmitted through the second transparent-window 307. The reflected radiation then traverses the process chamber 311 back through the first transparent- window 309 and is detected by the first spectrometer 305. Consequently, an overall level of sensitivity of films on the windows 307, 309 is increased over the sensitivity level of the adsorption sensor 300 of FIG.3A. A reason for the increase is due to the radiated beam from the broadband light- source 301 traversing each of the windows 307, 309 twice; once on an original beam path and a second time on the reflected beam path. The adsorption sensor 300 of FIG. 3A uses only a single pass based on the original beam path. Although not shown explicitly, a person of ordinary skill in the art, upon reading and understanding the disclosed subject matter, will readily understand and recognize that more than one of the first-surface mirror 313 and more than one of the second transparent- window 307 may be placed in various locations around a periphery of the process chamber 311 so as to further increase the number of reflected radiation passes that may be used to increase the sensitivity of the adsorption sensor 330 even further than when using a single first-surface mirror 313. [00062] The first-surface mirror 313 may comprise a planar, spherical, or parabolic mirror (the shape being considered with regard to the first surface of the mirror) to reflect radiation transmitted through the second transparent-window 307. The shape will be dependent on a shape of the second transparent-window 307 to which the first-surface mirror is coupled (e.g., the portion of the second transparent-window 307 not facing the process chamber 311, the "outer face"). Therefore, the shape of the first-surface mirror may be concave if the shape of the outer face of second transparent-window 307 is convex and planar if the outer face of second transparent-window 307 is planar. [00063] The first-surface mirror 313 may comprise a solid material (e.g., aluminum, gold, or silver) or have a reflective material coated on at least the first surface of a substrate (generally comprising glass). As is known to a person of ordinary skill in the art, the reflective coating is typically applied by a vacuum deposition process to maintain uniformity of the coating over the glass substrate as well as minimize surface roughness of the coating (thereby reducing or eliminating diffuse scattering of the collected radiation). Common coating materials include, for example, silver (Ag), aluminum (Al), and gold (Au) depending on a level of reflectivity for a given range of wavelengths. [00064] With reference now to FIG.4, a graph 400 of the absorbance spectrum across a range of light-source wavelengths with isopropyl alcohol (IPA) injected on the on the windows as a test is shown. The graph 400 shows a voltage level produced by a detector (e.g., the light-source detector 103 of FIGS.1A and 1B), as a function of wavelength. [00065] In this embodiment, IPA was injected onto interior portions of the windows (e.g., the windows 105,107 of FIG. 1A) prior to pump-down of the process chamber. IPA comprises alcohol (having a hydroxyl functional- group, OH) and water. Water has a large absorbance-spectrum while alcohol has a relatively smaller, peak-absorbance spectrum. [00066] As is indicated by the graph 400, a first line 401 indicates the voltage as a function of wavelength prior to any IPA being injected on the windows. A second line 403 indicates voltage as a function of wavelength after IPA was injected on the windows. The second line 403 indicates a significant drop in the voltage intensity for the radiation detected, which also indicates a significant increase of adsorption of the IPA on the windows (thus reducing transmission of the radiation through the windows). A line 405 indicates voltage intensity for the radiation detected has again increased, near the first line 401 for any IPA being injected. Therefore, after the IPA is removed from the windows (e.g., by

evaporation), the transmission of radiation through the windows is nearly at the same intensity of voltage level as prior to the IPA being injected (e.g., clean windows). [00067] FIG. 5 shows a graph 500 of the absorbance spectrum across a range of light source wavelengths with various flowrates (flowrates are shown in units of standard cubic centimeters per minute (sccm)) of trifluoromethane (CHF3) and Argon (Ar) gases flowing in the process chamber at 400 millitorr (mT). A first line 517 indicates a baseline spectrum with only Ar flowing in the process chamber at a pressure of 400 mT. A total volumetric flowrate of CHF3 and Ar was chosen (500 sccm) to keep the total flowrate constant for each of the tests (all run at a process chamber pressure of 400 mT). A person of ordinary skill in the art will recognize that lines 501, 501, . .. , 515 (lowest-level line through highest- level line) indicate an increasing level of transmission with a reduced level of CHF3 flowing in the process chamber. For example, with 500 sccm of CHF3 flowing in the process chamber and no Ar flow, an output voltage level from the detector is near 0 volts at a wavelength of between 8.6 µm and 8.8 µm, as indicated by line 501. With only 12.5 sccm of CHF₃ flowing in the process chamber and 487.5 sccm of Ar flowing in the process chamber, an output voltage level from the detector is near 0.25 volts at a wavelength of between 8.6 µm and 8.8 µm, as indicated by line 515. The graph 500 therefore confirms an ability of the absorbance sensor to distinctly detect various levels of CHF₃ gas flowing in the process chamber. [00068] FIG. 6 shows a graph 600 of adsorption of CHF3 as a function of the ratio of CHF₃ in a CHF₃-to-Ar mixture. The graph 600 indicates that linearity is fairly consistent. Additional tests (results not shown) indicated that tests are repeatable down to a pressure of about 50 mT. Further, low pressures can be used by increasing the number of light passes in the process chamber by using first-surface mirrors to reflect the radiation as described above. Overall, the absorption is linear with the number of passes. Consequently, the adsorption sensor can also be used to calibrate gas flow within the process chamber. By mixing different gas flows at constant pressure, a gas which has absorbance for the incident-radiation wavelength can be calibrated with one which does not have absorbance in the same wavelength range. [00069] FIG. 7 shows a graph 700 of the absorbance spectrum across a range of light source wavelengths with various deposition times of a silicon dioxide (SiO₂) coating on the walls of the process chamber. An assumption is made that an adsorbed level of SiO2 on the windows (e.g., windows 105, 107 of FIG. 1A) is the same as the level of SiO2 adsorbed on the interior walls of the process chamber. Generally, films adsorbed to the windows should have the same level of SiO₂ as is adsorbed onto the walls but there may be a slight difference due to the "sticky coefficient" between the windows and the walls due to temperature and material differences. However, any differences can be calibrated by running an initial coupon test as is known to a person of ordinary skill in the art. [00070] With continuing reference to FIG. 7, a baseline scan line 703 was run with no SiO2 being deposited. Only Ar gas was flowing at 500 sccm with the process chamber pressure set to 400 mT. A number of other tests were run with SiO₂ being deposited at various times including 25 sec (indicated by line 705), 125 sec (indicated by line 707), 225 sec (indicated by line 709), and 325 sec (indicated by line 711). A scan was taken after each level of deposition time across the 8.2 µm to 10 µm IR spectrum. As can be seen readily in the graph 700, an indicated voltage level from the detector (e.g., the light-source detector 103 of FIG.1A) decreases with an increasing SiO₂ deposition time. Consequently, the transmission of radiation through the windows (e.g., windows 105, 107 of FIG.1A) decreases with an increased level of adsorption onto the windows. [00071] After the SiO2 deposition test was completed, a post clean of the process chamber was performed using a nitrogen trifluoride (NF₃) process step to clean the interior of the process chamber, including the windows. As is indicated by line 701, the transmission of radiation is actually slightly higher than the baseline scan line 703. [00072] FIG. 8 shows a graph 800 of adsorption of SiO2 as a function of the coating time. As indicated by the graph 800, the absorbance for different time exposures to the deposition step indicates that film thickness is linear with time. The graph 800 shows absorbance of the radiation versus time. Consequently, the time can be converted directly to thickness and, similarly, the absorbance can be converted to a thickness value. The window sticky coefficient can be calibrated to any other material and a gain and/or offset can be applied to adjust the value to a different material. Consequently, the results can be saved from an instrumented tool (e.g., one that has the disclosed adsorption sensor) to a similar model and type of tool, operating on the same set of parameters, that is not instrumented. A high-level calibration procedure is shown and described in detail with reference to FIG.9, below. [00073] Therefore, a production engineer can use an instrumented process chamber to optimize film deposition step(s) and their related cleaning step(s) to ensure that all or nearly all of the film(s) are removed from the interior walls of the process chamber. A level of absorbance and its related calibrated thickness can be added to a data log (e.g., that may be converted to a process recipe) and the related WAC process can be used with a user interface to monitor in substantially real time. Any upper or lower limits, or a threshold value, can be used to make an endpoint call or display or sound an alarm or warning. [00074] Referring now to FIG.9, a flowchart 900 of operations in an embodiment in using various forms of an adsorption sensor described herein to determine or create a wafer-less auto clean (WAC) endpoint time in accordance with various embodiments of the disclosed subject matter is shown. Although not shown explicitly, upon reading and understanding the disclosed subject matter, a person of ordinary skill in the art could construct a similar flowchart to monitor an endpoint detection for depositing or etching a given film. [00075] At operation 901, the spectrometer (e.g., the adsorption sensors of FIGS.1A through 3B, or various combinations thereof) is configured for a particular wavelength or range of wavelengths. The wavelength may be selected based on various factors discussed herein such as film type (or gas type for flow/concentration calibrations), pressure of the process chamber, plasma power, frequency, and other factors known to a person of ordinary skill in the art that affect deposition characteristics. At operation 903, a determination is made whether a database (e.g., including a process recipe) already exists for cleaning the film type of interest. If the database and process recipe already exist, the process recipe is loaded into the deposition (or etch) tool. [00076] If a database exists, one or more databases for the parameters of interest are selected at operation 905. At operation 907, a determination is made of cleaning type (e.g., chemicals needed, plasma power, process chamber pressure, etc.) and length of time to run the WAC operation for a given film type and thickness. [00077] At operation 909, the WAC process is performed for the first (or only) film type. At operation 911, a determination is made whether other film types are present that may need different WAC cleaning techniques or processes. If the end-user selects at operation 911 that other film types are present that need to also be cleaned, the flowchart 900 loops back to operation 907 to add to the process for other film types. [00078] With continuing reference to FIG.9, note that, in various embodiments, many of the process parameters and operations in operation 905 through operation 911 may already be included as a part of a loadable, process recipe that has been previously stored in the database. [00079] Back at operation 903, if a determination is made that no database exists, either a new database can be created and stored, or a new WAC process is performed. At operation 913, WAC monitoring for each film type is monitored in accordance with operations described above. The WAC process is run, at operation 915, for each film type under

consideration. At operation 917 a threshold signal (e.g., a "clean signal") is determined for a clean process chamber for each film type. [00080] At operation 919, a determination is made whether to save the WAC database (e.g., a process recipe for cleaning a particular film). If a determination is made to save the WAC data, then the WAC data are saved for each film type at operation 921. A determination is made at operation 923 whether additional film types are to be considered. If there are additional film types to be considered, then the flowchart 900 loops back to operation 915 to add to the process for other film types. [00081] If a determination is made not to save the WAC data to a database at operation 919, then a determination is made at operation 923 whether additional film types are to be considered at operation 923. If there are additional film types to be considered, then the flowchart 900 loops back to operation 915 to add to the process for other film types. [00082] As will be recognized by a person of ordinary skill in the art, each of these cleaning methods have numerous variables involved (e.g., flow rates of the etchant gases, concentrations and partial pressures of the etchant gases, plasma power, plasma frequency, etc.). Therefore, the flowchart 900 of FIG. 9 merely provides a high-level overview to determine or create a wafer-less auto clean (WAC) endpoint time in accordance with various embodiments of the disclosed subject matter. As will also be recognizable to the skilled artisan, databases created and saved by an instrumented deposition or etch process tool (e.g., one that has the disclosed adsorption sensor) can be used by a similar model and type of tool, operating on the same set of parameters, that is not instrumented. Consequently, a process tool manufacturer or an R&D facility for a semiconductor device manufacturer, may use one instrumented tool and provide databases and/or process recipes for other tools operating under similar conditions. Each of these databases may be saved as process recipes, or saved as a loadable program (e.g., on a computer readable medium) that can be executed by a processor within a process tool, as shown and described with reference to FIG.10. [00083] FIG. 10 is a block diagram illustrating components of a machine 1000, according to some embodiments, able to read instructions from a machine-readable medium (e.g., a non-transitory machine-readable medium, a machine-readable storage medium, a computer-readable storage medium, or any suitable combination thereof) and perform any one or more of the methodologies discussed herein. Specifically, FIG.10 shows a diagrammatic representation of the machine 1000 in the example form of a computer system and within which instructions 1023 (e.g., software, a program, an application, an applet, an app, or other executable code) for causing the machine 1000 to perform any one or more of the methodologies discussed herein may be executed. In various embodiments, the machine 1000 may partially comprise a controller within a process tool. [00084] In alternative embodiments, the machine 1000 operates as a standalone device or may be connected (e.g., networked) to other machines. In a networked deployment, the machine 1000 may operate in the capacity of a server machine or a client machine in a server-client network environment, or as a peer machine in a peer-to-peer (or distributed) network environment. The machine 1000 may be a server computer, a client computer, a personal computer (PC), a tablet computer, a laptop computer, a netbook, a set-top box (STB), a personal digital assistant (PDA), a cellular telephone, a smartphone, a web appliance, a network router, a network switch, a network bridge, or any machine capable of executing the instructions 1023, sequentially or otherwise, that specify actions to be taken by that machine. Further, while only a single machine is illustrated, the term "machine" shall also be taken to include a collection of machines that individually or jointly execute the instructions 1023 to perform any one or more of the methodologies discussed herein. [00085] The machine 1000 includes a processor 1001 (e.g., a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a radio- frequency integrated circuit (RFIC), or any suitable combination thereof), a main memory 1003, and a static memory 1005, which are configured to communicate with each other via a bus 1007. The processor 1001 may contain microcircuits that are configurable, temporarily or permanently, by some or all of the instructions 1023 such that the processor 1001 is configurable to perform any one or more of the methodologies described herein, in whole or in part. For example, a set of one or more microcircuits of the processor 1001 may be configurable to execute one or more modules (e.g., software modules) described herein. [00086] The machine 1000 may further include a graphics display 1009 (e.g., a plasma display panel (PDP), a light emitting diode (LED) display, a liquid crystal display (LCD), a projector, or a cathode ray tube (CRT)). The machine 1000 may also include an alpha-numeric input device 1011 (e.g., a keyboard), a cursor control device 1013 (e.g., a mouse, a touchpad, a trackball, a joystick, a motion sensor, or other pointing instrument), a storage unit 1015, a signal generation device 1017 (e.g., a speaker), and a network interface device 1019. [00087] The storage unit 1015 includes a machine-readable medium 1021 (e.g., a tangible and/or non-transitory machine-readable storage medium) on which is stored the instructions 1023 embodying any one or more of the methodologies or functions described herein. The instructions 1023 may also reside, completely or at least partially, within the main memory 1003, within the processor 1001 (e.g., within the processor#s cache memory), or both, during execution thereof by the machine 1000.

Accordingly, the main memory 1003 and the processor 1001 may be considered as machine-readable media (e.g., tangible and/or non- transitory machine-readable media). The instructions 1023 may be transmitted or received over a network 1025 via the network interface device 1019. For example, the network interface device 1019 may communicate the instructions 1023 using any one or more transfer protocols (e.g., hypertext transfer protocol (HTTP)). [00088] In some embodiments, the machine 1000 may be a portable computing device, such as a smart phone or tablet computer, and have one or more additional input components (e.g., sensors or gauges). Examples of such additional input components include an image input component (e.g., one or more cameras), an audio input component (e.g., a microphone), a direction input component (e.g., a compass), a location input component (e.g., a global positioning system (GPS) receiver), an orientation

component (e.g., a gyroscope), a motion detection component (e.g., one or more accelerometers), an altitude detection component (e.g., an altimeter), and a gas detection component (e.g., a gas sensor). Inputs harvested by any one or more of these input components may be accessible and available for use by any of the modules or process tools described herein. [00089] As used herein, the term "memory" refers to a machine-readable medium able to store data temporarily or permanently and may be taken to include, but not be limited to, random-access memory (RAM), read-only memory (ROM), buffer memory, flash memory, and cache memory. While the machine-readable medium 1021 is shown in an embodiment to be a single medium, the term "machine-readable medium" should be taken to include a single medium or multiple media (e.g., a centralized or distributed database, or associated caches and servers) able to store instructions. The term "machine-readable medium" shall also be taken to include any medium, or combination of multiple media, that is capable of storing instructions for execution by a machine (e.g., the machine 1000), such that the instructions, when executed by one or more processors of the machine (e.g., the processor 1001), cause the machine to perform any one or more of the methodologies described herein. Accordingly, a "machine- readable medium" refers to a single storage apparatus or device, as well as "cloud-based" storage systems or storage networks that include multiple storage apparatus or devices. The term "machine-readable medium" shall accordingly be taken to include, but not be limited to, one or more tangible (e.g., non-transitory) data repositories in the form of a solid-state memory, an optical medium, a magnetic medium, or any suitable combination thereof. [00090] Furthermore, the machine-readable medium is non-transitory in that it does not embody a propagating signal. However, labeling the tangible machine-readable medium as "non-transitory" should not be construed to mean that the medium is incapable of movement $ the medium should be considered as being transportable from one physical location to another. Additionally, since the machine-readable medium is tangible, the medium may be considered to be a machine-readable device. [00091] The instructions 1023 may further be transmitted or received over a network 1025 (e.g., a communications network) using a

transmission medium via the network interface device 1019 and utilizing any one of a number of well-known transfer protocols (e.g., HTTP).

Examples of communication networks include a local area network (LAN), a wide area network (WAN), the Internet, mobile telephone networks, POTS networks, and wireless data networks (e.g., WiFi and WiMAX networks). The term "transmission medium" shall be taken to include any intangible medium that is capable of storing, encoding, or carrying instructions for execution by the machine, and includes digital or analog communications signals or other intangible medium to facilitate communication of such software. [00092] Throughout this specification, plural instances may implement components, operations, or structures described as a single instance.

Although individual operations of one or more methods are illustrated and described as separate operations, one or more of the individual operations may be performed concurrently, and nothing requires that the operations be performed in the order illustrated. Structures and functionality presented as separate components in example configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements fall within the scope of the subject matter herein. [00093] Certain embodiments are described herein as including logic or a number of components, modules, or mechanisms. Modules may constitute either software modules (e.g., code embodied on a machine-readable medium or in a transmission signal) or hardware modules within a process tool. A "hardware module" is a tangible unit capable of performing certain operations and may be configured or arranged in a certain physical manner. In various embodiments, one or more computer systems (e.g., a standalone computer system, a client computer system, or a server computer system) or one or more hardware modules of a computer system (e.g., a processor or a group of processors) may be configured by software (e.g., an application or application portion) as a hardware module that operates to perform certain operations as described herein. [00094] In some embodiments, a hardware module may be implemented mechanically, electronically, or any suitable combination thereof. For example, a hardware module may include dedicated circuitry or logic that is permanently configured to perform certain operations. For example, a hardware module may be a special-purpose processor, such as a field programmable gate array (FPGA) or an ASIC. A hardware module may also include programmable logic or circuitry that is temporarily configured by software to perform certain operations. For example, a hardware module may include software encompassed within a general-purpose processor or other programmable processor. It will be appreciated that the decision to implement a hardware module mechanically, in dedicated and permanently configured circuitry, or in temporarily configured circuitry (e.g., configured by software) may be driven by cost and time

considerations. [00095] Accordingly, the phrase "hardware module" should be

understood to encompass a tangible entity, be that an entity that is physically constructed, permanently configured (e.g., hardwired), or temporarily configured (e.g., programmed) to operate in a certain manner or to perform certain operations described herein. As used herein,

"hardware-implemented module" refers to a hardware module.

Considering embodiments in which hardware modules are temporarily configured (e.g., programmed), each of the hardware modules need not be configured or instantiated at any one instance in time. For example, where a hardware module comprises a general-purpose processor configured by software to become a special-purpose processor, the general-purpose processor may be configured as respectively different special-purpose processors (e.g., comprising different hardware modules) at different times. Software may accordingly configure a processor, for example, to constitute a particular hardware-module at one instance of time and to constitute a different hardware module at a different instance of time. [00096] Hardware modules can provide information to, and receive information from, other hardware modules. Accordingly, the described hardware modules may be regarded as being communicatively coupled. Where multiple hardware modules exist contemporaneously,

communications may be achieved through signal transmission (e.g., over appropriate circuits and buses) between or among two or more of the hardware modules. In embodiments in which multiple hardware modules are configured or instantiated at different times, communications between such hardware modules may be achieved, for example, through the storage and retrieval of information in memory structures to which the multiple hardware modules have access. For example, one hardware module may perform an operation and store the output of that operation in a memory device to which it is communicatively coupled. A further hardware module may then, at a later time, access the memory device to retrieve and process the stored output. Hardware modules may also initiate

communications with input or output devices, and can operate on a resource (e.g., a collection of information). [00097] The various operations of exemplary methods described herein may be performed, at least partially, by one or more processors that are temporarily configured (e.g., by software) or permanently configured to perform the relevant operations. Whether temporarily or permanently configured, such processors may constitute processor-implemented modules that operate to perform one or more operations or functions described herein. As used herein, "processor-implemented module" refers to a hardware module implemented using one or more processors. [00098] Similarly, the methods described herein may be at least partially processor-implemented, a processor being an example of hardware. For example, at least some of the operations of a method may be performed by one or more processors or processor-implemented modules. Moreover, the one or more processors may also operate to support performance of the relevant operations in a "cloud computing" environment or as a "software as a service" (SaaS). For example, at least some of the operations may be performed by a group of computers (as examples of machines including processors), with these operations being accessible via a network (e.g., the Internet) and via one or more appropriate interfaces (e.g., an application program interface (API)). [00099] The performance of certain of the operations may be distributed among the one or more processors, not only residing within a single machine, but deployed across a number of machines. In some

embodiments, the one or more processors or processor-implemented modules may be located in a single geographic location (e.g., within a fabrication environment, an office environment, or a server farm). In other embodiments, the one or more processors or processor-implemented modules may be distributed across a number of geographic locations. [000100] Overall, the disclosed subject matter contained herein describes or relates generally to operations of "tools" in a semiconductor fabrication environment (fab). Such tools can include various types of deposition (including plasma-based tools such as ALD (atomic layer deposition), CVD (chemical vapor deposition), PECVD (plasma-enhanced CVD), etc.) and etching tools (e.g., reactive-ion etching (RIE) tools), as well as various types of thermal furnaces (e.g., such as rapid thermal annealing and oxidation), ion implantation, and a variety of other process and metrology tools found in various fabs and known to a person of ordinary skill in the art. However, the disclosed subject matter is not limited to semiconductor environments and can be used in a number of machine-tool environments such as robotic assembly, manufacturing, and machining environments (e.g., those including physical vapor deposition (PVD tools)). Upon reading and understanding the disclosure provided herein, a person of ordinary skill in the art will recognize that various embodiments of the disclosed subject matter may be used with other types of process tools. [000101] As used herein, the term "or" may be construed in an inclusive or exclusive sense. Further, other embodiments will be understood by a person of ordinary skill in the art upon reading and understanding the disclosure provided. Further, upon reading and understanding the disclosure provided herein, the person of ordinary skill in the art will readily understand that various combinations of the techniques and examples provided herein may all be applied in various combinations. [000102] Although various embodiments are discussed separately, these separate embodiments are not intended to be considered as independent techniques or designs. As indicated above, each of the various portions may be inter-related and each may be used separately or in combination with other embodiments discussed herein. For example, although various embodiments of methods, operations, and processes have been described, these methods, operations, and processes may be used either separately or in various combinations. [000103] Consequently, many modifications and variations can be made, as will be apparent to a person of ordinary skill in the art upon reading and understanding the disclosure provided herein. Functionally equivalent methods and devices within the scope of the disclosure, in addition to those enumerated herein, will be apparent to the skilled artisan from the foregoing descriptions. Portions and features of some embodiments may be included in, or substituted for, those of others. Such modifications and variations are intended to fall within a scope of the appended claims. Therefore, the present disclosure is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. [000104] The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. The abstract is submitted with the understanding that it will not be used to interpret or limit the claims. In addition, in the foregoing Detailed Description, it may be seen that various features may be grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as limiting the claims. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment.

Claims

CLAIMS What is claimed is: 1. An adsorption sensor, comprising:

a light source;

at least a first transparent-window and a second transparent-window mounted on substantially opposing walls in a process chamber such that radiation from the light source traverses each of the first transparent-window and the second transparent-window, the first transparent-window and the second transparent-window being selected to be substantially transparent at one or more wavelengths of radiation emitted by the light source; and

a light-source detector configured to receive radiation transmitted through the first transparent-window and the second transparent-window and provide an intensity level of the received radiation that includes transmission losses through the first transparent-window and the second transparent-window due to adsorbed films on the windows.

2. The adsorption sensor of claim 1, wherein the adsorption sensor is

configured to determine a relative thickness of films that have been adsorbed onto the first transparent-window and the second transparent-window based on a change in the intensity level of the received radiation.

3. The adsorption sensor of claim 1, wherein the light source is configured to transmit at least one wavelength of radiation selected from a wavelength range from short-wavelength infrared (IR) up to far- wavelength IR radiation.

4. The adsorption sensor of claim 1, wherein the light source is configured to transmit at least one wavelength of radiation selected from a wavelength range from a near-infrared (IR) range, a visible light range, and an ultraviolet range.

5. The adsorption sensor of claim 1, wherein the light source is a quantum cascade laser (QCL).

6. The adsorption sensor of claim 5, further comprising a frequency- selective element configured to select an emission wavelength of the QCL to a single wavelength.

7. The adsorption sensor of claim 1, wherein the light source is a Xenon lamp.

8. The adsorption sensor of claim 1, wherein the light source is a

substantially-monochromatic laser emitting in the infrared (IR) range.

9. The adsorption sensor of claim 1, wherein the first transparent-window and the second transparent-window each comprise zinc selenide (ZnSe).

10. The adsorption sensor of claim 1, wherein each of the first

transparent-window and the second transparent-window is coated on at least one surface with at least one film selected from films including yttrium oxide (Y₂O₃) and yttrium oxyfluoride (YOF).

11. The adsorption sensor of claim 1, wherein the light-source detector comprises a mercury cadmium telluride (HgCdTe) detector.

12. The adsorption sensor of claim 1, wherein the adsorption sensor is configured to detect at least one type of molecule selected from molecules including Si_xO_y oxides, C_xF_y polymers, and Si_xCl_y compounds.

13. An adsorption sensor, comprising:

a light source;

at least one transparent window having a first face proximate to the light source and an opposing second face such that radiation from the light source is to traverse through both the first face and the opposing second face, the at least one transparent window being selected to be substantially transparent at one or more wavelengths emitted by the light source;

a first detector mounted proximate to the at least one transparent window proximate to the first face of the at least one transparent window; and

a first-surface mirror to reflect radiation received from the light source through the at least one transparent window to the first detector, the reflected radiation to traverse the at least one transparent window at least once prior to being received by the first detector, the at least one transparent window and the first-surface mirror being mounted on substantially opposing walls in a process chamber.

14. The adsorption sensor of claim 13, wherein the reflected radiation from the first-surface mirror is to traverse the process chamber back through the at least one transparent window and to be detected by the first detector.

15. The adsorption sensor of claim 13, further comprising a second transparent-window mounted between the first-surface mirror and the at least one transparent window to protect the first-surface mirror from chemicals inside the process chamber.

16. The adsorption sensor of claim 13, wherein the first-surface mirror comprises a solid material selected from at least one material including aluminum, gold, and silver.

17. The adsorption sensor of claim 13, wherein the first-surface mirror comprises a reflective material coated on at least a first surface of a substrate that faces the light source.

18. The adsorption sensor of claim 13, wherein the light source is a

broadband light-source.

19. The adsorption sensor of claim 13, further comprising a second

detector to monitor directly variability from the light source.

20. The adsorption sensor of either one of claim 13 or claim 19, wherein the first detector and the second detector each comprises a spectrometer.

21. An adsorption sensor, comprising:

a light source;

a first transparent-window and a second transparent-window mounted on substantially opposing walls in a process chamber such that radiation from the light source traverses the process chamber and each of the first transparent-window and the second transparent- window, the first transparent-window and the second transparent- window being selected to be substantially transparent at one or more wavelengths emitted by the light source;

a first light-source detector configured to monitor a radiation output directly from the light source; and

a second light-source detector configured to receive radiation transmitted through both the first transparent-window and the second transparent-window and provide an intensity level of the received radiation that includes transmission losses through the first transparent-window and the second transparent-window due to adsorbed films on the windows.

22. The adsorption sensor of claim 21, wherein the first light-source

detector and the second light-source detector each comprises a spectrometer.

23. The adsorption sensor of claim 21, wherein the light source is a

broadband light-source configured to produce radiation in wavelengths from about 200 nm up to about 1100 nm.

24. The adsorption sensor of claim 23, wherein the broadband light-source comprises a Xenon lamp.

25. The adsorption sensor of claim 21, wherein the light source is a substantially-monochromatic laser emitting radiation in the infrared (IR) range.