System and method for improved optical signal detection

Abstract

To provide an optical signal detection system which can be used for improved monitoring of a semiconductor process and has improved spectral resolution and signal-to-noise.SOLUTION: The improved spectral resolution may be associated with improved spectral discrimination where narrow portions of the spectral bandwidth are monitored individually. In one example, an apparatus comprises (1) an optical interface configured to receive an optical signal, (2) a narrow bandpass filter configured to transmit a portion of the received optical signal, and (3) an optical etalon in series with the narrow bandpass filter configured to further filter the received optical signal, wherein: Wherein the combination of the passband of the bandpass filter and the passband of the optical etalon is configured to provide an optical bandwidth of less than 1. 0nm for the optical signal, and (4) a multi-pixel optical sensor configured to collect the filtered optical signal essentially simultaneously.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 670,232, filed July 12, 2024 by Andrew Kueny and entitled "System and Method for Improved Optical Signal Detection," which is commonly assigned and incorporated herein by reference in its entirety.

[0002] FIELD OF THE DISCLOSURE The present disclosure relates generally to optical measurement systems and methods of use, and more particularly to systems and methods for improved resolution and signal-to-noise monitoring of optical emissions from semiconductor processes. [Background technology]

[0003] Optical monitoring of semiconductor processes is a well-established method for controlling processes such as etching, deposition, chemical-mechanical polishing, and implantation. Optical emission spectroscopy (OES) and interferometric endpoint (IEP) are two basic types of operational modes for data collection. In OES applications, light emitted from a process, typically from a plasma, is collected and analyzed to identify and track changes in atomic and molecular species that indicate the state or progress of the process being monitored. In IEP applications, interference patterns of light reflected from a wafer are analyzed and used to indicate the state or progress of the process being monitored. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 7,049,156 Summary of the Invention

[0005] In one aspect, the present disclosure provides an optical signal detection system. In one example, the optical signal detection system includes: (1) an optical interface configured to receive an optical signal; (2) a narrow bandpass filter configured to transmit a portion of the received optical signal; (3) an optical etalon in series with the narrow bandpass filter configured to further filter the received optical signal, wherein a combination of the passband of the bandpass filter and the passband of the optical etalon is configured to provide an optical bandwidth of less than 1.0 nm for the optical signal; and (4) a multi-pixel photosensor configured to essentially simultaneously collect the filtered optical signal.

[0006] In another aspect, a semiconductor process control system is disclosed. In one example, the semiconductor process control system includes: (1) a processing tool configured to perform a semiconductor manufacturing process that generates an optical signal; (2) an optical interface configured to receive the optical signal; (3) a narrow bandpass filter configured to transmit a portion of the received optical signal; (4) an optical etalon in series with the narrow bandpass filter configured to further filter the received optical signal, wherein a combination of the passband of the bandpass filter and the passband of the optical etalon provides an optical bandwidth of less than 1.0 nm for the optical signal; and (5) a multi-pixel photosensor configured to essentially simultaneously collect the filtered optical signal.

[0007] In yet another aspect, a method of controlling a semiconductor processing system is disclosed. In one example, the method includes: (1) generating an optical signal in a processing chamber of the semiconductor processing system; (2) receiving the optical signal at an optical interface; (3) filtering the received optical signal using a narrow bandpass filter that transmits a portion of the received optical signal; (4) further filtering the received optical signal using an optical etalon in series with the narrow bandpass filter, where a combination of the passband of the bandpass filter and the passband of the optical etalon provides an optical bandwidth of less than 1.0 nm for the optical signal; and (5) essentially simultaneously collecting the filtered optical signal using a multi-pixel photosensor.

[0008] Reference is now made to the following descriptions taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram of a system for monitoring and / or controlling the state of a plasma or non-plasma process in a semiconductor process tool using OES and / or IEP. [Figure 2] FIG. 1 is a plot of the optical emission spectrum with a typical resolution of approximately 1 nm. [Figure 3] FIG. 3 is a plot of a portion of the spectrum of FIG. 2. [Figure 4] FIG. 1 is a plot of a portion of a spectrum showing the presence of various emission lines that can be used for process monitoring. [Figure 5] FIG. 1 is a plot of a portion of a spectrum with enhanced resolution showing various emission lines that may be used for process monitoring. [Figure 6] 1 is a schematic diagram of a proposed optical signal detection system with improved resolution and signal-to-noise characteristics. [Figure 7]1A and 1B are plots of portions of example transmission curves for an etalon and a bandpass filter, respectively, showing the relative wavelength position, transmission, and spectral bandwidth of each component. [Figure 8] FIG. 1 is a block diagram of a proposed optical signal detection system with improved resolution and signal-to-noise characteristics. [Figure 9] 1 is a flow diagram of a method for controlling a semiconductor process system using an optical signal detection system. DETAILED DESCRIPTION OF THE INVENTION

[0010] In the following description, reference is made to the accompanying drawings, which form a part hereof, and in which are shown, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it should be understood that other embodiments may be utilized. It should also be understood that structural, procedural, and system changes may be made without departing from the spirit and scope of the invention. Therefore, the following description should not be taken in a limiting sense. For clarity of illustration, like features shown in the accompanying drawings are designated with like reference numerals, and similar features as shown in alternative embodiments in the drawings are designated with like reference numerals. Other features of the present invention will become apparent from the accompanying drawings and the following detailed description. It should be noted that, for clarity of illustration, some elements in the drawings may not be drawn to scale.

[0011] The constant advancements in semiconductor processes, toward faster processes, smaller feature sizes, more complex structures, and larger wafers, place significant demands on process monitoring technology. For example, higher data rates are required to accurately monitor much faster etch rates on extremely thin layers, such as those in fin field-effect transistor (FINFET) and three-dimensional NAND (3D NAND) structures, where changes of a few angstroms (a few atomic layers) are significant. In many cases, both OES and IEP methodologies require wider optical bandwidths, higher resolution, and better signal-to-noise to help detect small changes in reflectivity, optical emission, or both. As process equipment becomes more complex and, itself, more expensive, cost and packaging size are also under constant pressure. These processing demands are driving the need for improved capabilities in optical monitoring of semiconductor processes.

[0012] The increasing complexity of process chemistries, along with the reduction of process open areas, is also driving advances in process monitoring systems, most of which require improved signal-to-noise and signal detection performance. While improvements can be realized with better-performing electronic components such as A / D converters, power supplies, and higher NEP sensors, the usefulness of process control information can remain limited. Accordingly, the present disclosure provides an optical signal detection system with improved spectral resolution and signal-to-noise that can be used for improved monitoring of semiconductor processes. In the present disclosure, improved spectral resolution can be associated with improved spectral discrimination, where narrow portions of spectral bandwidths are individually monitored. The present disclosure includes at least one embodiment of an improved optical signal detection system that combines a predetermined process-specific wavelength range, high optical throughput, very high wavelength resolution / discrimination, improved out-of-band light rejection, and enhanced signal-to-noise characteristics to provide improved process control instrumentation.

[0013] With particular regard to monitoring and evaluating the state of a semiconductor process within a process tool, FIG. 1 illustrates a block diagram of a process system 100 that utilizes an OES and / or an IEP to monitor and / or control the state of a plasma or non-plasma process within a semiconductor process tool 110. The semiconductor process tool 110, or simply process tool 110, generally encloses a wafer 120 and possibly a process plasma 130 within a typically partially evacuated volume of a processing chamber 135 that may contain various process gases. The process tool 110 may include one or more optical interfaces, or simply interfaces 140, 141, and 142, that enable viewing within the processing chamber 135 at various positions and orientations for receiving optical signals. The interfaces 140, 141, and 142 may include multiple types of optical elements, such as, but not limited to, optical filters, lenses, windows, apertures, optical fibers, etc.

[0014] For IEP applications, a light source 150 can be connected to the interface 140 directly or via a fiber optic cable assembly 153. As shown in this configuration, the interface 140 is oriented perpendicular to the surface of the wafer 120 and is often centered relative to the wafer 120. Light from the light source 150 can enter the interior volume of the process chamber 135 in the form of a collimated beam 155. The beam 155 reflected from the wafer 120 can be received again by the interface 140. In a typical application, the interface 140 can be an optical collimator. After being received by the interface 140, the light can be transmitted via a fiber optic cable assembly 157 to an optical signal detection system 160 for detection and conversion to a digital signal. The light can include light provided and detected and can include, for example, a wavelength range from deep ultraviolet (DUV) to near-infrared (NIR). The wavelength of interest can be selected from any subrange of the wavelength range. For larger substrates, or when understanding wafer non-uniformity is a concern, additional optical interfaces (not shown in FIG. 1 ) oriented perpendicular to the wafer 120 may be used. The semiconductor processing tool 110 may also include additional optical interfaces positioned at various locations for other monitoring options.

[0015] For OES applications, interface 142 may be oriented to collect optical emissions from plasma 130. Interface 142 may simply be a sight glass or may additionally include other optics, such as lenses, mirrors, and optical wavelength filters. A fiber optic cable assembly 159 may direct any collected light, also referred to as an optical signal, to optical signal detection system 160 for detection and conversion to a digital signal. Optical signal detection system 160 may also be directly coupled to interface 142 and / or processing tool 110 via a free-space optical assembly without the use of an interconnecting fiber optic cable assembly 159. Multiple interfaces may be used separately or in parallel to collect optical signals related to OES. For example, as shown in FIG. 1, interface 141 may be positioned to collect emissions from near the surface of wafer 120, while interface 142 may be positioned to view the bulk of plasma 130. Although not shown, interface 141 may be coupled to an optical signal detection system 160 either directly or via a fiber optic cable assembly (not shown).

[0016] After detection and conversion of the received optical signal by the optical signal detection system 160 to an analog electrical signal, the analog electrical signal is typically amplified and digitized within a subsystem of the optical signal detection system 160 and passed to the signal processor 170. The signal processor 170 may be, for example, an industrial PC, PLC, or other system, which uses one or more algorithms to produce an output 180, such as an analog or digital control value representing the intensity of a particular wavelength or the ratio of two wavelength bands. Instead of a separate device, the signal processor 170 may alternatively be integrated with the optical signal detection system 160. The signal processor 170 may use an OES algorithm that analyzes the optical emission intensity signal at a predetermined wavelength to determine trend parameters related to the state of the process and can be used to assess conditions, such as endpoint detection, etch depth, etc. For IEP applications, the signal processor 170 may use an algorithm that analyzes a broadband portion of the spectrum to determine film thickness. See, for example, U.S. Patent No. 7,049,156, "System and Method for In-Situ Monitoring and Control of Film Thickness and Trench Depth," which is incorporated herein by reference. Output 180 can be transmitted to process tool 110 via communication link 185 to monitor and / or modify the production process occurring in processing chamber 135 of process tool 110.

[0017] The components of FIG. 1 shown and described are simplified for convenience and are commonly known. In addition to their general functionality, optical signal detection system 160, signal processor 170, or a combination of both, may also be configured to identify steady and transient optical and non-optical signals and process those signals according to the methods and / or features disclosed herein. Thus, optical signal detection system 160 or signal processor 170 may include algorithms, processing power, and / or logic for identifying and processing optical signals and time trends extracted therefrom. The algorithms, processing power, and / or logic may be in the form of hardware, software, firmware, or any combination thereof. The algorithms, processing power, and / or logic may reside within a single computing device or may be distributed across multiple devices, such as optical signal detection system 160 and signal processor 170.

[0018] Optical signal detection system 160 may be an optical signal detection system configured to provide discrimination and detection of a specific spectral bandwidth associated with the emission of a desired species. Accordingly, optical signal detection system 160 may provide / include improved spectral discrimination and signal-to-noise characteristics suitable for observing process control transitions where individual, unique emissions of a desired species are present and require improved detection. For example, optical signal detection system 160 may be an optical signal detection system such as optical signal detection system 600 of FIG. 6. Optical signal detection system 160 may provide an improved signal-to-noise ratio for a specific narrow-bandwidth portion of the spectrum of interest. As discussed herein in connection with FIG. 8, optical signal detection system 160 may include, in addition to optical detection system 600, electronics for converting the collected and filtered optical signal from analog to digital format. Instead of being included in optical signal detection system 160, the electronics may be part of signal processor 170.

[0019] 2-5 show plots of optical emission spectra that demonstrate how the spectral resolution and signal-to-noise of an emission spectrum can affect the type and amount of information that can be obtained and used for process control. It should be understood that the examples described herein are not specific to any particular spectral emission of any particular atomic or molecular species, and that similar discussions may be applicable to other atomic or molecular species where similar resolution and signal-to-noise requirements exist and / or are required. The plots in FIGS. 2-5 have an x-axis of wavelength in nanometers and a y-axis on an arbitrary scale of signal numbers.

[0020] FIG. 2 is a plot of an example optical emission spectrum 200 with a typical resolution of approximately 1 nm. The optical emission spectrum 200 represents an optical signal as received from a processing tool, such as processing tool 110. The optical emission spectrum 200 includes a combination of background signals, such as ambient light, emissions from process gases in a processing chamber, such as processing chamber 135, and the emission to be monitored. The emission or wavelength to be monitored is the emission identified and designated for controlling a process in the processing chamber. As an example of a process, monitoring of an emission spectrum including spectral lines 210 near 250 nm is used. As shown in FIG. 2, these particular spectral emission lines 210, which provide an example of emission for monitoring, are not easily observed, and observation of the emission lines is hindered by several aspects of spectrum 200. These aspects include the presence of large molecular spectral features near 250 nm and limited signal-to-noise of the desired emission due to low signal level, relatively low spectral resolution / discrimination, and the inherent low concentration and / or excitation of species in the observed plasma.

[0021] FIG. 3 is a plot of an enlarged and localized portion 300 of the spectrum 200 of FIG. 2 near 250 nm, which is essentially featureless with respect to emission lines w1, w2, and w3, which are examples of monitored spectral lines 210, and is indicated by wavelength locations 310, 320, and 330, respectively. The most notable feature of spectrum 200 is a tail of spectral features near 250 nm that results in a large background signal at wavelengths 310, 320, and 330 of interest for monitoring species of interest. This large background signal complicates the observation and detection of species of interest at the expected wavelengths 310, 320, and 330 because it involves a proportionally large noise level (approximately the square root of the background signal), a relatively much larger utilization of the dynamic range of the observation sensor, and any fluctuations / changes in the background signal may mask the much smaller expected emission signal and degrade the quality of the observation.

[0022] FIG. 4 is a plot of a portion of spectrum 400 covering the same spectral range as FIG. 3 and illustrating the presence of various emission lines that can be used for process monitoring of desired species at expected mission line wavelengths. Emission lines w1, w2, and w3, indicated by wavelength locations 410, 420, and 430, respectively, provide various representations of various emission signals of interest at indicated wavelengths above a large background. Emission lines 410, 420, and 430 provide examples of emission lines 310, 320, and 330 in FIG. 3. Emission line w1 at location 410 is indicated by an inflection in the background signal. Emission line w2 at location 420 is indicated by a small, broad peak above the background signal. Emission line w3 at location 430 is essentially unobservable except as an inflection in the background signal. While emission line w2 at wavelength location 420 is observable, the relatively low spectral resolution, large background, and resulting low signal-to-noise inhibit robust control using the signal corresponding to w2. The ability to use emission lines w1 and w3 is further greatly hindered by the extremely low expression of these signals relative to the background signal.

[0023] FIG. 5 is a plot of a portion of spectrum 500 covering the same spectral range as FIG. 3 but with significantly increased resolution showing various emission lines that can be used for process monitoring. FIG. 5 provides an example of a portion of an optical spectrum that may be incident on optical signal detection system 600 of FIG. 6, for example. Due to the increased wavelength resolution, emission line w1 at location 510 is now indicated by a small, narrow peak above the background signal with a signal-to-noise ratio of approximately 1:1 or less. Similarly, emission line w2 at location 520 is indicated by a small, narrow peak above the background signal with a signal-to-noise ratio of approximately 3:1 or less. The peak at 520 may be much less than 1 nm wide. Emission line w3 generally remains unresolved, and emission lines 510 and 520 provide examples of emission lines 410 and 420 of FIG. 4. Spectrum 500 also includes a non-resolved peak near 263 nm, e.g., unmonitored emission.

[0024] While the plots above show spectrally resolved data from a spectrometer, it should be understood that these plots are presented to aid in the clear communication of spectral resolution / discrimination and signal-to-noise issues for small signals. Small signals are signals that are difficult to observe due to minimal signal-to-noise variation or minimal amplitude difference compared to the local background signal, for example. For example, as shown in Figures 2-5, the large spectral feature near 250 nm is much larger in amplitude than the feature at the wavelength of interest. For certain monitoring applications, spectrally resolved broadband data may not be required to achieve robust process control. For example, in the present exemplary case, the process monitoring condition may call for a signal transition in emission line intensity from a stable higher level to a stable lower level, or vice versa. This type of signal transition may simply require the identification and detection of a specific narrow spectral bandwidth associated with one or more of the desired species' emissions and may not require a comparison of emission intensities across multiple species or a wider bandwidth. Each narrowband wavelength range of interest may correspond to a specific chemical component of a semiconductor process element or molecule, such as one used as a dopant.

[0025] Accordingly, FIG. 6 is a schematic diagram of an example optical signal detection system 600 constructed in accordance with the principles of the present disclosure. Optical signal detection system 600 provides improved spectral discrimination, narrow bandwidth (high spectral resolution), high optical throughput, and signal-to-noise characteristics suitable for observing the presence of individual characteristic emissions of desired species and process control transitions desirable for use in process control applications. Optical signal detection system 600 includes an optical interface, represented by source plane 610, configured to receive optical signals generally indicated by light rays 605 from source plane 610, which may define a free-space optical interface, such as interfaces 140, 141, and 142 of FIG. 1. Source plane 610 may be defined with a large clear aperture (field of view), such as having a 1" diameter, to provide large light gathering power. Alternatively, the field of view may be limited to a smaller diameter, such as 1 / 4", as limited by the design of a processing tool, such as processing tool 110 of FIG. 1, or to specifically limit the field of view to a localized region of available optical signals, such as those emitted from a plasma in a processing chamber, such as processing chamber 135. Alternatively, the source surface 610 may be configured to be attached to a fiber optic cable assembly interface including one or more optical fibers. The received optical signal may then be transmitted through a narrow bandpass filter 620 and an etalon 625 to determine and identify the spectral bandwidth and provide, for example, an optical bandwidth of less than 1.0 nm for the optical signal. The etalon 625 may be, for example, an air-insulating etalon having a free spectral range of approximately 1 nm or less, a finesse of 5 or 10 or more, a resonance / peak bandwidth of less than 0.5 nm or less than 0.1 nm, and a peak transmittance of approximately 70%. The etalon 625 may be provided, for example, by Light Machinery of Canada. The bandpass filter 620 may be useful in the system 600 to suppress sidebands of the etalon 625. The narrow bandpass filter 620 may have a bandwidth of approximately 10 nm or less, in which case the center wavelength of the etalon (or one of the resonant frequencies of the etalon) and the center wavelength of the bandpass filter are approximately equivalent.Bandpass filter 620 may be available, for example, from Edmund Optics. Optical signal detection system 600 also includes a lens 630, a field stop 640, and a sensor 650.

[0026] FIG. 7 is a plot 700 of portions of transmission curves 710 and 720 for an etalon and bandpass filter, such as etalon 625 and bandpass filter 620, respectively, showing the relative wavelength position, transmittance, and spectral bandwidth of each component. One or more of bandpass filter 620 or etalon 625 may be adjustable or replaceable for selection of various wavelengths. Thus, various signals of interest may be monitored and processed, for example, to control a semiconductor process within the chamber. Signal processor 170 may be configured, for example, to process received digital signals corresponding to the received, collected, converted, and filtered optical signals to generate controls for the semiconductor process. Signal processor 170, or another processor such as that described in connection with FIG. 8, may also be used to automate the control or replacement of elements of optical signal detection system 600, such as temperature control of the resonant center wavelength of etalon 625, replacement of bandpass filter 620, and control of signal collection by sensor 650.

[0027] After wavelength discrimination by the combination of bandpass filter 620 and etalon 625, the optical signal may be passed through lens 630 to provide re-imaging of the source plane via field stop 640. Lens 630 may be, for example, a 25 mm diameter fused silica lens with a 100 mm focal length and a 10 mm clear aperture. Lens 630 may also include an anti-reflection coating or a bandwidth control coating to further assist in wavelength discrimination and removal of undesired wavelengths. An appropriate bandwidth control coating on lens 630 can complement the function of bandpass filter 620 or replace it. After apertureing through field stop 640, the optical signal may be collected onto the active surface of multi-pixel sensor 650. Sensor 650 may be, for example, an S16101 back-illuminated active pixel sensor provided by Hamamatsu Photonics of Hamamatsu, Japan. Sensor 650 may include a two-dimensional array of pixels, such as 1280 x 1024 pixels for S16101, or fewer (i.e., 100 x 100) or more (i.e., 2048 x 2048) pixels, depending on the desired detection area or expected signal-to-noise response. Optical signal detection system 600 as described can provide a nominal bandwidth of approximately 0.3 nm or less and a maximum signal-to-noise ratio of 150,000. This is achieved by simultaneous optical signal collection and averaging across approximately 1.3 million pixels of multi-pixel sensor 650 (considering the S16101 sensor option). Each of the pixels of sensor 650 can receive the same or essentially the same optical signal.

[0028] The physical size of the components of optical signal detection system 600 is such that it allows a large amount of light to be detected by sensor 650. The diameters of the various components of optical signal detection system 600 may depend, for example, on which components are the limiting components in terms of the amount of light passing therethrough. The diameter of lens 630 and / or the diameter of another one of the components of optical detection system 600, such as aperture 640, may be 1 inch. Components of optical signal detection system 600, such as elements 610, 620, 625, 630, and 640, may have or provide a field of view of, for example, 1 / 4 inch to 1 inch. The field of view may be based on the physical size of sensor 650 to ensure that sufficient optical signal is received by sensor 650 for processing. The separated light beams at sensor 650 represent various angles of view at source 610.

[0029] 8 is a block diagram of an example optical signal detection system 800 constructed in accordance with the principles of the present disclosure. Optical signal detection system 800 has improved resolution and signal-to-noise characteristics in accordance with the present disclosure. Optical signal detection system 800 can incorporate the systems, features, and methods disclosed herein to advantage for measuring, characterizing, analyzing, and processing optical signals from semiconductor processes, and can be associated with optical signal detection system 160 and signal processor 170 of FIG. 1 and optical signal detection system 600 of FIG. 6.

[0030] Optical signal detection system 800 may be enclosed in housing 810 and may include optical interface 840 for receiving optical signals from external optical system 830, such as interfaces 141 and 142 of FIG. 1, or via fiber optic cable assembly 157 or 159, and following integration and conversion, may transmit data, such as output 180 of FIG. 1, to external system 820, which may also be used to control optical signal detection system 800, for example, by selecting an operating mode or controlling the integration timing as defined herein.

[0031] The optical interface 840 may be a subminiature assembly (SMA) or ferrule connector (FC) fiber optic connector, or other opto-mechanical interface, such as a free-space interface. Additional optical components 845, such as slits, lenses, filters, etalons, and gratings, shape, guide, identify, and color-separate the received optical signals and send them to the multi-pixel sensor 850 for integration and conversion.

[0032] Low-level functionality of multi-pixel sensor 850 may be controlled by elements such as FPGA 860 and processor 870. Following optical-to-electrical conversion, the analog signal may be sent to A / D converter 880 for conversion from an electrical analog signal to an electrical digital signal, which may then be stored in memory 890 for immediate or later use and transmission, such as to external system 820 (see signal processor 170 in FIG. 1 ). While some interfaces and relationships are indicated by arrows, not all interactions and control relationships are shown in FIG. 8 . Spectral data may be collected, stored, and / or acted upon, for example, in / by one or more of memory / storage 890, FPGA 860, processor 870, and / or external system 820. Memory / storage 890, FPGA 860, processor 870, and / or external system 820 provide examples where processing power, logic, and / or operational instructions corresponding to algorithms for processing optical signals disclosed herein may be stored. The optical signal detection system 800 also includes a power supply 895, which may be a conventional AC or DC power supply.

[0033] As described above, optical signal detection system 800 may be associated with optical signal detection system 160. Optical signal detection system 800 may also correspond to optical signal detection system 600 of FIG. 6. For example, optical interface 840 may correspond to source surface 610, optical components 845 may correspond to bandpass filter 620, etalon 625, and lens 630, and sensor 850 may correspond to sensor 650. One or more combinations of A / D 880, memory / storage 890, FPGA 860, processor 870, or external system 820 may correspond to electronic devices for analog-to-digital processing.

[0034] FIG. 9 is a flow diagram of an example method 900 for controlling a semiconductor processing system using an optical signal detection system as described herein. Method 900 begins in step 910, in which an optical signal is generated. The optical signal may be generated, for example, from a plasma, such as plasma 130 in chamber 135 of FIG. 1. The generated optical signal may include radiation from a species of interest for controlling a semiconductor process occurring in chamber 135. Next, in step 920, the optical signal may be received via an optical interface, such as interface 142 of FIG. 1, source surface 610 of FIG. 6, or external optics 830 of FIG. 8. Subsequently, in step 930, the received optical signal may be filtered via a filter and etalon, such as those described in connection with FIG. 6, that transmits a predetermined portion of the bandwidth of the received optical signal. Next, during step 940, the filtered optical signal may be collected essentially simultaneously via illumination onto active pixels of a multi-pixel sensor, such as sensor 650 of FIG. 6. Essentially simultaneous acquisition may include predetermining or predefining timing, gating, and integration times for the multi-pixel sensor to maintain temporal correlation between individual pixels of the multi-pixel sensor and the signals derived therefrom. Integration times may be defined, for example, to be long enough to utilize the dynamic range of the pixels, sensors, and associated conversion and processing systems, yet short enough to maintain sufficient temporal resolution to detect changes in the derived signals. These integration times may range from less than a second to several minutes. Some individual pixels of the multi-pixel sensor may not be illuminated to provide a reference or background signal for other signals derived from illuminated pixels.

[0035] Then, in step 950, the collected optical signals may be converted from analog to digital format using an A / D converter connected to the multi-pixel sensor, such as converter 880 of FIG. 8 . Following conversion, in step 960, the converted, collected, and filtered optical signals may be further processed to obtain a desired signal-to-noise level, such as or exceeding 10,000:1, or to provide an output signal useful for controlling the process being monitored. All or a portion of the signals received from multiple pixels of the multi-pixel sensor may be processed individually or together. Processing may be performed, for example, by signal processor 170 of FIG. 1 or by FPGA 860 or processor 870 of FIG. 8 . At the end of method 900, in step 970, an output signal, such as output 180 of FIG. 1 , may be provided by a subsystem, such as signal processor 170 of FIG. 1 , or by FPGA 860 or processor 870 of FIG. 8 , to a secondary system, such as a semiconductor processing system controller, to direct control of the process from which the original optical signals originated.

[0036] Some of the disclosed embodiments may relate to computer storage products including non-transitory computer-readable media bearing program code for performing various computer-implemented operations, embodying portions of an apparatus, device, or performing steps of the methods described herein. As used herein, non-transitory refers to all computer-readable media, excluding transitory propagating signals. Examples of non-transitory computer-readable media include, but are not limited to, magnetic media such as hard disks, floppy disks, and magnetic tape; optical media such as CD-ROM disks; magneto-optical media such as floptical disks; and hardware devices specially configured to store and execute program code, such as ROM and RAM devices. Examples of program code include both machine code, such as produced by a compiler, and files containing higher-level code that can be executed by a computer using an interpreter. Configured or configured to means, for example, designed, constructed, or programmed with the necessary logic, algorithms, processing instructions, and / or characteristics to perform a task.

[0037] These and other modifications may be made to the optical measurement systems and subsystems described herein without departing from the scope of the present specification. For example, while some examples have been described in connection with semiconductor wafer processing equipment, it will be understood that the optical measurement systems described herein may be adapted for other types of processing equipment, such as roll-to-roll thin film processing, solar cell fabrication, or any application where high-precision optical measurements may be required. Furthermore, while some embodiments discussed herein describe the use of a single optical analysis device, it should be understood that multiple optical analysis devices with known relative sensitivities may be utilized. Furthermore, while the term "wafer" is used herein in describing aspects of the present invention, it should be understood that other types of workpieces may be used, including quartz plates, phase-shift masks, LED substrates, and other non-semiconductor processing-related substrates, as well as solid workpieces, gas workpieces, and liquid workpieces.

[0038] The exemplary embodiments described herein have been chosen and described in order to best explain the principles and practical applications of the present invention and to enable others skilled in the art to understand the present invention in various embodiments with various modifications as suited to the particular uses intended. The particular embodiments described herein are in no way intended to limit the scope of the present invention, as the present invention can be practiced in various modifications and environments without departing from the scope and spirit of the present invention. Therefore, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features described herein.

[0039] The flowcharts and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that in some alternative implementations, the functions noted in the blocks may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may possibly be executed in the reverse order, depending on the functionality involved. It should also be noted that each block of the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, may be implemented by a dedicated hardware-based system that performs the specified functions or acts, or a combination of dedicated hardware and computer instructions.

[0040] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that when the terms "comprises" and / or "comprising" are used herein, they specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0041] As will be appreciated by those skilled in the art, the present invention may be embodied as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, microcode, etc.), or an embodiment combining software and hardware aspects, generally referred to herein as "circuits" or "modules." Furthermore, the present invention may take the form of a computer program product on a computer-usable storage medium having computer-usable program code embodied in the medium.

[0042] Various aspects of the present disclosure may be claimed, including the devices, systems, and methods disclosed herein. Aspects disclosed herein and described in the Summary of the Invention include the following:

[0043] A. An optical signal detection system comprising: (1) an optical interface configured to receive an optical signal; (2) a narrow bandpass filter configured to transmit a portion of the received optical signal; (3) an optical etalon in series with the narrow bandpass filter configured to further filter the received optical signal, wherein the combination of the passband of the bandpass filter and the passband of the optical etalon is configured to provide an optical bandwidth of less than 1.0 nm for the optical signal; and (4) a multi-pixel optical sensor configured to essentially simultaneously collect the filtered optical signal.

[0044] B. A semiconductor process control system including: (1) a processing tool configured to perform a semiconductor manufacturing process that generates an optical signal; (2) an optical interface configured to receive the optical signal; (3) a narrow bandpass filter configured to transmit a portion of the received optical signal; (4) an optical etalon in series with the narrow bandpass filter configured to further filter the received optical signal, wherein a combination of the passband of the bandpass filter and the passband of the optical etalon provides an optical bandwidth of less than 1.0 nm for the optical signal; and (5) a multi-pixel optical sensor configured to essentially simultaneously collect the filtered optical signal.

[0045] C. A method of controlling a semiconductor processing system, comprising: (1) generating an optical signal within a processing chamber of a semiconductor processing system; (2) receiving the optical signal at an optical interface; (3) filtering the received optical signal using a narrow bandpass filter that transmits a portion of the received optical signal; (4) further filtering the received optical signal using an optical etalon in series with the narrow bandpass filter, wherein a combination of the passband of the bandpass filter and the passband of the optical etalon provides an optical bandwidth of less than 1.0 nm for the optical signal; and (5) essentially simultaneously collecting the filtered optical signal using a multi-pixel optical sensor.

[0046] Each of aspects A, B, and C can have one or more of the following additional elements in combination: Element 1: The optical interface comprises at least one of a fiber optic interface and a free-space interface. Element 2: The bandpass filter has an optical passband width of 10 nm or less. Element 3: The etalon has a free spectral range of 1 nm or less. Element 4: Further comprising electronics for converting the collected and filtered optical signal from analog to digital form. Element 5: Further comprising a processor for processing the converted collected and filtered optical signal to produce an output signal. Element 6: The output signal is provided to a secondary system for use as a control signal for a semiconductor process in which the optical signal occurs. Element 7: The output signal is processed to obtain a signal-to-noise ratio of 10,000 or greater. Element 8: The field of view of one or more of the optical interface, narrow bandpass filter, or optical etalon is in the range of ¼ inch to 1 inch in diameter. Element 9: The optical interface comprises at least one of a fiber optic interface and a free-space interface. Element 10: The narrow bandpass filter has an optical passband width of 10 nm or less. Element 11: The optical etalon has a free spectral range of 1 nm or less. Element 12: Further comprising electronics for converting the collected and filtered optical signal from analog form to digital form. Element 13: Further comprising a processor for processing the converted collected and filtered optical signal to produce an output signal. Element 14: The output signal is provided to a processing tool for use as a control signal for a semiconductor manufacturing process. Element 15: The output signal is processed to obtain a signal-to-noise ratio of 10,000 or greater. Element 16: The field of view of one or more of the optical interface, narrow bandpass filter, or optical etalon is in the range of 1 / 4 inch to 1 inch in diameter. Element 17: Further comprising converting the collected and filtered optical signal from analog form to digital form, processing the converted collected and filtered optical signal to produce an output signal, and providing the output signal to a semiconductor processing system for use as a control signal for the process in which the optical signal occurs.

Claims

1. an optical interface configured to receive an optical signal; a narrow bandpass filter configured to transmit a portion of the received optical signal; an optical etalon in series with the narrow bandpass filter configured to further filter the received optical signal, the combination of the passband of the bandpass filter and the passband of the optical etalon configured to provide an optical bandwidth of less than 1.0 nm for the optical signal; a multi-pixel photosensor configured to collect the filtered light signals essentially simultaneously; An optical signal detection system comprising:

2. The optical signal detection system of claim 1 , wherein the optical interface comprises at least one of a fiber optic interface and a free space interface.

3. 10. The optical signal detection system of claim 1, wherein the bandpass filter has an optical passband width of 10 nm or less.

4. 10. The optical signal detection system of claim 1, wherein the etalon has a free spectral range of 1 nm or less.

5. 10. The optical signal detection system of claim 1, further comprising electronics for converting the collected and filtered optical signals from analog to digital format.

6. 6. The optical signal detection system of claim 5, further comprising a processor for processing the converted, collected and filtered optical signal to produce an output signal.

7. 7. The optical signal detection system of claim 6, wherein the output signal is provided to a secondary system for use as a control signal for a semiconductor process in which the optical signal occurs.

8. 7. The optical signal detection system of claim 6, wherein the output signal is processed to obtain a signal-to-noise ratio of 10,000 or greater.

9. 10. The optical signal detection system of claim 1, wherein the field of view of one or more of the optical interface, the narrow bandpass filter, or the optical etalon is within the range of 1 / 4 inch to 1 inch in diameter.

10. a processing tool configured to perform a semiconductor manufacturing process that generates an optical signal; an optical interface configured to receive the optical signal; a narrow bandpass filter configured to transmit a portion of the received optical signal; an optical etalon in series with the narrow bandpass filter configured to further filter the received optical signal, wherein the combination of the passband of the bandpass filter and the passband of the optical etalon provides an optical bandwidth of less than 1.0 nm for the optical signal; a multi-pixel photosensor configured to collect the filtered light signals essentially simultaneously; A semiconductor processing control system comprising:

11. 11. The semiconductor process control system of claim 10, wherein the optical interface comprises at least one of a fiber optic interface and a free space interface.

12. 11. The semiconductor process control system of claim 10, wherein said narrow bandpass filter has an optical passband width of 10 nm or less.

13. 11. The semiconductor process control system of claim 10, wherein the optical etalon has a free spectral range of 1 nm or less.

14. 11. The semiconductor process control system of claim 10, further comprising electronics for converting the collected and filtered optical signals from analog to digital format.

15. 15. The semiconductor process control system of claim 14, further comprising a processor for processing the converted, collected and filtered optical signal to produce an output signal.

16. 16. The semiconductor process control system of claim 15, wherein the output signal is provided to the processing tool for use as a control signal for the semiconductor manufacturing process.

17. 16. The semiconductor process control system of claim 15, wherein the output signal is processed to obtain a signal-to-noise ratio of 10,000 or greater.

18. 11. The semiconductor processing control system of claim 10, wherein the field of view of one or more of the optical interface, the narrow bandpass filter, or the optical etalon is in the range of 1 / 4 inch to 1 inch in diameter.

19. generating an optical signal within a processing chamber of a semiconductor processing system; receiving the optical signal at an optical interface; filtering the received optical signal using a narrow bandpass filter that transmits a portion of the received optical signal; further filtering the received optical signal using an optical etalon in series with the narrow bandpass filter, wherein a combination of the passband of the bandpass filter and the passband of the optical etalon provides an optical bandwidth of less than 1.0 nm for the optical signal; collecting said filtered light signals essentially simultaneously using a multi-pixel light sensor; 1. A method for controlling a semiconductor processing system, comprising:

20. converting the collected and filtered optical signal from analog to digital form; processing the converted, collected and filtered optical signal to produce an output signal; providing said output signal to said semiconductor processing system for use as a control signal for a process in which said optical signal occurs; 20. The method of controlling a semiconductor processing system of claim 19, further comprising:

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