Dichroic mirror and short-pass optical filter for in-situ reflection measurement

Abstract

Embodiments of the present disclosure generally relate to devices and systems for in situ film growth rate monitoring, and include a system for monitoring film growth on a substrate, the system including a light source, a collimator, a dichroic mirror, and an optical filter, all of which are in optical communication along and along a propagation path. The propagation path is split into a first sub-path and a second sub-path at the dichroic mirror. The first sub-path is directed to a pyrometer and the second sub-path is directed to a spectrometer.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to an epitaxial chamber integrated with in-situ reflectometry for real-time process monitoring. Background Art

[0002] Measurement of the film thickness of a processed substrate can be used in relation to a processing operation. Generally, after a processing operation, the film thickness measurement is performed outside the processing chamber in which the substrate to be processed is processed. Such measurement determination may be inefficient and result in reduced throughput because substrates that do not meet specifications may not be used, and multiple processing iterations may be required to obtain a measurement that meets specifications.

[0003] In addition, it is difficult to perform film thickness measurement inside the processing chamber and during the processing operation because the processing equipment inside the processing chamber may interfere with the measurement equipment, thereby hindering measurement accuracy. For example, the heat emitted by a heating lamp may interfere with the measurement equipment. As another example, during processing, materials may accumulate on the window in the processing chamber, interfering with measurement accuracy.

[0004] Therefore, there is a need for improved apparatuses, systems, and methods to facilitate in-situ and real-time measurement operations. Summary of the Invention

[0005] Embodiments of the present disclosure generally relate to apparatuses, systems, and methods for real-time in-situ reflectometry monitoring for semiconductor processing, monitoring the thickness of a film on a substrate during a substrate processing operation in which a film is deposited on the substrate. The thickness is monitored while the substrate processing operation is being performed.

[0006] In one embodiment, a system for monitoring film growth on a substrate, suitable for semiconductor processing, the system includes a light source for guiding light along a propagation path; a collimator in optical communication with the light source along the propagation path; a dichroic mirror disposed along the propagation path between the collimator and an optical tube; a pyrometer in optical communication with the dichroic mirror along a first propagation sub-path downstream of the dichroic mirror; a spectrometer in optical communication with the dichroic mirror along a second propagation sub-path downstream of the dichroic mirror; and a filter disposed along the propagation path between the light source and the spectrometer.

[0007] In another embodiment, a system for monitoring film growth on a substrate, suitable for semiconductor processing, the system includes: a light source disposed at a first end of a propagation path; an optical tube disposed along the propagation path and in optical communication with a collimator; a dichroic mirror in optical communication with the light source; a pyrometer in optical communication with the dichroic mirror along a first propagation sub-path of the propagation path downstream of the dichroic mirror; a spectrometer in optical communication with the dichroic mirror along a second propagation sub-path of the propagation path downstream of the dichroic mirror; and a filter disposed along the propagation path between the light source and the spectrometer.

[0008] In another embodiment, a system for monitoring film growth on a substrate, suitable for semiconductor processing, the system comprising: a processing chamber including: a susceptor; a preheating ring surrounding the susceptor; an upper window; a lower window; and an in-situ reflectometry system positioned near the upper window, the in-situ reflectometry system comprising: a light source for guiding light along a propagation path; a collimator in optical communication with the light source along the propagation path; a dichroic mirror disposed along the propagation path between the collimator and an optical tube; a pyrometer in optical communication with the dichroic mirror along a first propagation sub-path downstream of the dichroic mirror; a spectrometer in optical communication with the dichroic mirror along a second propagation sub-path downstream of the dichroic mirror; and a filter disposed along the propagation path between the light source and the spectrometer. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] To understand the above features of the present disclosure in detail, reference may be made to the embodiments for a more specific description of the present disclosure briefly outlined above, some of which are shown in the drawings. However, it should be noted that the drawings only show exemplary embodiments and should not be considered as a limitation of the scope, as the present disclosure may allow other equally effective embodiments.

[0010] Figure 1 Schematic cross-sectional view of a system having an in-situ reflectometry system for processing a substrate according to one embodiment.

[0011] Figure 2A According to one embodiment Figure 1 Partial schematic cross-sectional view of the in-situ reflectometry (In-Situ Reflectometry, ISR) system of the system shown in

[0012] Figure 2B According to some embodiments Figure 1 Partial schematic cross-sectional view of the in-situ reflectometry (ISR) system of the system shown in

[0013] Figure 3 According to one embodiment Figure 1 Partial cross-sectional view of the in-situ reflectometry system shown in

[0014] Figure 4 Cross-sectional view of a short-pass filter adapter plate according to one embodiment.

[0015] Figure 5 Schematic block diagram of a method for calibrating an in-situ reflectometry susceptor according to one embodiment.

[0016] For ease of understanding, wherever possible, the same reference numerals are used to indicate the same elements common to the figures. It is contemplated that elements and features of one embodiment may be advantageously incorporated in other embodiments without further recitation. Detailed Description

[0017] Embodiments of the present disclosure generally relate to an epitaxial chamber integrating in-situ reflectometry for real-time process monitoring in a process chamber such as an epitaxial chamber. Specifically, unlike chemical vapor deposition (CVD), metrology is not commonly used in epitaxial chambers due to problems arising from the directional cross-flow on the substrate surface during epitaxial deposition. The CVD process deposits material uniformly perpendicular to the main plane of the substrate, consistent with metrology-based sensors, while epitaxial deposition deposits material perpendicular to the sensors and has historically caused problems with real-time film thickness analysis. During processing, light from the substrate is monitored as material is deposited on the substrate. The light is collected and analyzed by a spectrometer, a computing device, and / or other light measurement devices to facilitate determination of substrate properties such as thin film thickness, thin film deposition rate, thin film optical properties, and / or Ge concentration within the film. Multiple measurements, such as thin film thickness, thin film deposition rate, and / or substrate temperature, may be made simultaneously using one or more measurement devices.

[0018] Figure 1 FIG. 101 is a schematic cross-sectional view of a system 101 for processing a substrate according to one embodiment. System 101 includes a process chamber 100. Process chamber 100 may be an epitaxial deposition chamber and may be used as part of a cluster tool. Process chamber 100 is configured to grow an epitaxial film on a substrate such as substrate 150. The substrate has a substrate surface on which material is grown or deposited during the epitaxial process. Process chamber 100 generates a cross-flow of precursors (e.g., process gases) on the top surface of substrate 150 during processing. System 101 uses process chamber 100 configured to perform epitaxial deposition operations on substrate 150. Aspects and advantages of the present disclosure may be used in other substrate processing operations such as in chemical vapor deposition (CVD) chambers, atomic layer deposition (ALD) chambers, physical vapor deposition (PVD) chambers, etch chambers, ion implantation chambers, oxidation chambers, and / or other processing chambers.

[0019] The process chamber 100 includes an upper housing module 102, a lower housing module 104, a chamber body assembly 106, a susceptor assembly 124, a lower window 120, and an upper window 122. The upper housing module 102 may also be a lid or part of a process chamber lid 102. The susceptor assembly 124 is disposed between the susceptor assembly 124 and the lower housing module 104. The lower window 120 is disposed between the susceptor assembly 124 and the lower housing module 104. The upper window 122 is disposed between the susceptor assembly 124 and the upper housing module 102.

[0020] The upper housing module 102 is disposed above the susceptor assembly 124 and is configured to heat a substrate, such as substrate 150, disposed on the susceptor assembly 124. The upper housing module 102 includes an upper module body 126 and a plurality of lamp holes 128 that are formed through the upper module body 126. Each of the lamp holes 128 includes an upper lamp 130 disposed therein. Each of the upper lamps 130 is coupled to a lamp socket 129. Each lamp socket 129 supports an upper lamp 130 and electrically couples each upper lamp 130 to a power source (not shown). Each lamp 129 is fixed within the hole 128 in a generally vertical orientation. As described herein, the generally vertical orientation of the upper lamps 130 is generally perpendicular to the substrate support surface of the susceptor assembly 124. However, other orientations are also contemplated. The vertical orientation of the upper lamps 130 need not be perpendicular to the substrate support surface and may be at an angle of about 30° to about 150° relative to the substrate support surface 153 of the susceptor assembly 124. The angle relative to the substrate support surface 153 may be about 45° to about 135°, such as an angle of about 70° to about 110° relative to the substrate support surface 153.

[0021] The upper housing module 102 includes a pyrometer channel 131 (e.g., a light pipe). The pyrometer channel 131 may be centered within the upper housing module 102. The upper housing module 102 may also include at least a preheat ring (PHR) 161, a PHR sensor 221, and a PHR sensor channel 219 (as Figure 2A and Figure 2B shown) to measure the film thickness on a preselected specimen 151 (e.g., formed of SiC) on the PHR 161, which specimen may provide reference information regarding the process on the substrate 150. Similar sensors may be used in conjunction with a pyrometer for dome applications or may be implemented without a pyrometer (not shown) to measure parameters at the edge of the substrate. The PHR sensor 221 allows the use of the reflected signal from the PHR specimen 151 without rotational or wobbling interference since the PHR 161 is static. By providing a reference of known value, the correlation established between the substrate and the known PHR specimen 151 thickness can be used for manufacturing process control on multiple substrates including substrates with unknown patterning.

[0022] The pyrometer channel 131 passes through the upper module body 126 and extends from the first (e.g., lower) surface 114 of the upper module body to the second (e.g., upper) surface of the upper module body 126. The pyrometer channel 131 is configured to allow light to travel between the surface of the substrate 150 and the in-situ reflectance measurement (ISR) system 185. The PHR sensor channel (such as Figure 2A and Figure 2B shown) 219 passes through the upper module body 126 and extends from the first surface 114 of the upper module body to the second surface of the upper module body 126. The PHR sensor channel 219 is configured to allow light 229 to travel between the surface of the test piece 151 or the surface of the substrate 150 and the ISR system 185. The reflected signal from the PHR test piece 151 can also be directed and collected at a right angle or other adaptable angle based on the suitability of the hardware integration. The ISR system 185 includes a housing 103, and one or more optical elements are accommodated in the housing to facilitate the processing of optical signals.

[0023] An upper gas chamber 180 is defined between the bottom surface of the upper module body 126 and the upper window 122. A heated gas is supplied to the upper gas chamber 180. A heated gas exhaust channel 142 is also provided to pass through the upper module body 126. The heated gas exhaust channel 142 is coupled to a heated exhaust pump 140. The heated exhaust pump 140 removes gas from the upper gas chamber 180.

[0024] The lower housing module 104 is disposed below the base assembly 124 and is configured to heat the bottom side of the substrate 150 disposed on the base assembly 124. The lower housing module 104 includes a lower module body 182 and a plurality of lamp holes 186, and these lamp holes 186 are arranged to pass through the lower module body 182. Each of these lamp holes 186 includes a lower lamp 188 disposed therein. Each of the lower lamps 188 is disposed in a substantially vertical orientation and is coupled to a lamp socket 184. Each lamp socket 184 supports a lower lamp 188 and electrically couples each lower lamp 188 to a power source. As described herein, the substantially vertical orientation of the lower lamp 188 is described with respect to the substrate support surface 153 of the base assembly 124. It is contemplated that the lamp orientation may not be substantially vertical, such as at an angle of about 30° to about 150° with respect to the substrate support surface 153. The angle with respect to the substrate support surface 153 may be about 45° to about 135°, such as an angle with respect to the substrate support surface 153 of about 70° to about 110°.

[0025] During a substrate processing operation, the upper lamp 130 is energized to generate radiant energy (e.g., heat) and direct the radiant energy towards the substrate 150 and the base 157. During a substrate processing operation, the lower lamp 188 is powered to generate radiant energy directed upward towards the substrate 150 and the base 157.

[0026] The lower lamp module 104 includes a base shaft passage 195 and a pyrometer passage 192. The support shaft 155 of the base assembly 124 is disposed through the base shaft passage 195. The base shaft passage 195 is disposed to centrally pass through the lower module body 182. The base shaft passage 195 allows the support shaft 155 of the base assembly 124 and a portion of the lower window 120 to pass through the lower module body 182.

[0027] The pyrometer passage 192 is disposed through the lower module body 182 outside the base shaft passage 195 so that a lower pyrometer 190 (such as a scanning pyrometer) can measure the temperature of the bottom surface of the substrate 150 or the bottom surface of the base 157 of the base assembly 124. The lower pyrometer 190 is disposed below the lower module body 182 and adjacent to the pyrometer passage 192. The pyrometer passage 192 extends from the bottom surface of the lower module body 182 to the top surface of the lower module body 182.

[0028] The upper chamber space 111 is part of the process space 110 in which the substrate 150 is processed and one or more process gases are injected. The lower chamber space 113 is the part of the process space 110 where the substrate 150 is loaded onto (or removed from) the base assembly 124. The upper chamber space 111 can also be understood as the space located above the base 157 when the base assembly 124 is in the processing position. The base assembly 124 is shown in Figure 1 a lower position (e.g., the loading position of the substrate 150). The lower chamber space 113 is understood as the space located below the base 157 of the base assembly 124 when the base assembly 124 is in the processing position. The processing position is such a position where the substrate 150 is set flush with or above the horizontal plane 125.

[0029] The upper cooling ring 118 and the lower cooling ring 112 are disposed on opposite sides of the chamber body assembly 106. The upper cooling ring 118 is disposed on top of the injection ring 116 and is configured to cool the injection ring 116. The lower cooling ring 112 is disposed below the injection ring 116. The upper cooling ring 118 includes coolant channels 146 disposed therethrough. The coolant circulated through the coolant channels 146 can include water, oil, or other fluids. The lower cooling ring 112 includes coolant channels 148 disposed therethrough. The coolant circulated through the coolant channels 148 is similar to the coolant circulated through the coolant channels 146 of the upper cooling ring 118. The upper cooling ring 118 and the lower cooling ring 112 can help to fix the injection ring 116 in place. The upper cooling ring 118 can partially support the upper lamp module 102, while the lower cooling ring 112 can partially support the lower lamp module 104.

[0030] The temperature of the injection ring 116 can be reduced by using the upper cooling ring 118 and the lower cooling ring 112, without the need to provide additional cooling channels through the injection ring 116. Using the upper cooling ring 118 and the lower cooling ring 112 reduces the production cost of the injection ring 116, which can be replaced more frequently than the upper cooling ring 118 and the lower cooling ring 112. The present disclosure contemplates that the injection ring 116 may include one or more additional cooling channels formed therein.

[0031] One or more gas injectors 108 are provided through one or more openings within the injection ring 116 to supply gas, such as process gas, to the process space 110. The present disclosure contemplates that multiple gas injectors may be provided through the injection ring 116. The gas injectors may be positioned at an angle greater than about 5° with respect to the X-Y plane of the substrate 150, such as forming an angle greater than about 10° with the X-Y plane. Each injector is fluidly coupled to one or more process gas supply sources, such as a first process gas supply source and / or a second process gas supply source. In some embodiments, only the first process gas supply source is used. In some embodiments where the first process gas supply source and the second process gas supply source are used, there may be two gas outlets within each gas injector. According to some embodiments that may be combined with other embodiments, the first process gas supply source is process gas, and the second process gas supply source is a cleaning gas. The cleaning gas may be used to clean the features of the ISR system 185 within the process space 110 and / or the features of the reflectometer system within the process space 110.

[0032] The upper window 122 is disposed between the injection ring 116 and the upper housing module 102. The upper window 122 is an optically transparent window such that the radiant energy generated by the upper lamp module 102 can pass therethrough. The upper window 122 is formed of a quartz or glass material. The upper window 122 is dome-shaped and may be referred to as the upper dome, although a planar window is also contemplated. The outer edge of the upper window 122 forms one or more peripheral supports 172. The peripheral supports 172 are thicker than the central portion of the upper window 122. The peripheral supports 172 are disposed on top of the injection ring 116. The peripheral supports 172 are connected to the central portion of the upper window 122. The peripheral supports 172 are optically opaque and may be formed of opaque quartz.

[0033] The lower window 120 is disposed between the base assembly 124 and the lower housing module 104. The lower window 120 is an optically transparent window through which radiant energy generated by the lower lamp module 104 can pass. The lower window 120 is formed of quartz or glass material. The lower window 120 may be dome-shaped and may be referred to as the lower dome, although a planar lower window 120 is also contemplated. The outer edge of the lower window 120 forms a peripheral support 170. The peripheral support 170 is thicker than the central portion of the lower window 120. The peripheral support 170 is connected to the central portion of the lower window 120.

[0034] Various gaskets and heaters are disposed inside the chamber body assembly 106 and within the process space 110. As Figure 1 shown, there are an upper gasket 156 and a lower gasket 154 disposed within the chamber body assembly 106. The upper gasket 156 is disposed above the lower gasket 154 and inside the injection ring 116. The upper gasket 156 and the lower gasket 154 are configured to be coupled together and / or the upper gasket 156 is supported on the lower gasket 154. The upper gasket 156 and the lower gasket 154 are configured to shield the inner surface of the injection ring 116 from the process gas within the process space 110. The upper gasket 156 and the lower gasket 154 are further used to reduce heat loss from the process space 110 to the injection ring 116. The reduced heat loss improves the heating uniformity of the substrate 150 and enables more uniform deposition on the substrate 150 during processing operations (e.g., epitaxial deposition operations). The preheat ring (PHR) 161 is supported on the protrusion 160 of the lower gasket 154. The PHR 161 and the edge of the substrate are located within the radially outward region of the process space 110.

[0035] The upper heater 158 and the lower heater 152 are also disposed within the chamber body assembly 106 and the process space 110. As Figure 1 shown, the upper heater 158 is disposed between the upper gasket 156 and the injection ring 116, while the lower heater 152 is disposed between the lower gaskets 154. Both the upper heater 158 and the lower heater 152 are disposed inside the chamber body assembly 106 to be able to heat the substrate 150 more uniformly when the substrate 150 is located within the process chamber 100. The upper heater 158 and the lower heater 152 reduce heat loss from the walls of the chamber body assembly 106 and create a more uniform temperature distribution around the process space 110. Both the upper heater 158 and the lower heater 152 can be configured to have a heated fluid flowing through them or can be resistance heaters. The upper heater 158 and the lower heater 152 are further shaped to accommodate openings through the injection ring 116, such as the substrate loading port.

[0036] The susceptor assembly 124 is disposed within the process chamber 110 and configured to support the substrate 150 during processing. The controller 196 is configured to rotate the susceptor assembly 124 and the substrate 150 during substrate processing operations. The susceptor assembly 124 includes a planar substrate support surface 153 for supporting the substrate 150 and a shaft 155 that extends through a portion of the lower window 120 and the lower lamp module 104. The susceptor assembly 124 is coupled to a motion assembly 194. The motion assembly 194 includes, for example, one or more motors or actuators. The motion assembly 194 is coupled to the controller 196 for causing at least rotation (stepped or continuous) about a central axis A, vertical movement of the susceptor assembly 124, angular tilt of the susceptor assembly, or other movement. The controller 196 may report the characteristics of the susceptor assembly 124 to the spectrometer and may at least indicate that the light source 244 flashes. According to some embodiments, the rotation assembly controller 196 may receive and store data.

[0037] Figure 2A For the Figure 1 Partial schematic cross-sectional view of the ISR system 185 of the system 101 shown in. The ISR system 185 also includes a light source 244, a collimator 215, a sensor 245, a pyrometer 207, one or more preheat ring sensors 221 (two are shown), and a dichroic mirror 205 coupled to or disposed above the upper housing module 102. The ISR system 185 facilitates measuring one or more properties of the substrate 150 (and / or a thin film disposed thereon). Example properties include temperature, thin film growth rate, thin film thickness, thin film optical properties, and / or Ge concentration within the film.

[0038] The light source 244 is configured to generate light 241. For example, the light source 244 can be a flash lamp capable of generating full-spectrum or partial-spectrum light. In one example, the wavelength of the generated spectrum is between about 200 nm and about 4 microns, such as 200 nm to about 800 nm and / or 3 microns to 4 microns. Full-spectrum light allows for a wide range of optical signals for analysis, however, in other embodiments, the light source can be restricted to light of a specific wavelength or a specific range of light wavelengths to complete the analysis. The light source 244 can be controlled by the controller 196. The light source 244 is in optical communication with the collimator 215 and directs the light 241 to the collimator 215 based on the instructions of the controller 196. Optical communication includes connection by an optical fiber cable, but other optical transmission modes are also contemplated. The travel path of the light from the light source 244 can be referred to as the propagation path. The collimated light 243 exits the collimator 215 and travels through the pyrometer channel 131. The pyrometer channel 131 can be made of any material capable of transmitting light of a predetermined wavelength, for example, sapphire. The pyrometer channel 131 directs the collimated light 243 to the surface of the substrate 150 (or the thin film thereon) to facilitate measurement of one or more properties of the substrate 150 (or the thin film thereon). In addition to or as an alternative to the measurement of the substrate 150, it is contemplated that the surface of the pedestal, the surface of the specimen on the PHR 161 (or other surface) can be measured. For example, the substrate, the surface of the pedestal, or the surface of the specimen can be measured to establish an initial data set for wobble calibration metrics. As used herein, thin film and substrate or specimen can be used interchangeably unless the specification explicitly excludes one or the other.

[0039] Collimated light 243 is reflected from a target measurement surface, such as substrate 150, and returns as reflected light 227. The reflected light 227 returns through pyrometer channel 131. The reflected light 227 exits pyrometer channel 131 and travels along the path of travel of the reflected light 227 to dichroic mirror 205 that is aligned with pyrometer path 131. According to some embodiments, dichroic mirror 205 is a transparent material with a dielectric coating. The dielectric coating can include, but is not limited to, magnesium fluoride, tantalum pentoxide, and titanium dioxide. Dichroic mirror 205 reflects light of certain wavelengths but allows other selected specific wavelengths to pass through. The wavelength range directed to sensor 245 can be between about 100 nm and about 1000 nm, such as in the range of 200 nm to 800 nm, such as in the range of 200 nm to 400 nm, and such as in the range of 400 nm to 800 nm. Dichroic mirror 205 enables the use of multiple light-based sensors by directing light of a first desired range to one sensor while the remaining light wavelengths are sent to at least one other sensor. Thus, ISR system 185 provides a compact measurement system that allows for more sensors to be included in a smaller footprint. Dichroic mirror 205 is arranged or oriented such that the angle of incidence A1 is between about 30° and about 60°, such as in the range of 35° to 55°, with the plane being approximately perpendicular to the longitudinal axis of pyrometer channel 131. However, other angles of incidence are also contemplated.

[0040] According to Figure 2A, the light reflected from the dichroic mirror 205 is transmitted along the optical path 211 to the pyrometer 207. According to some embodiments, only light wavelengths between approximately 1.0 μm and approximately 6.0 μm, such as between approximately 3.0 μm and approximately 4.0 μm, travel along the optical path 211 to the pyrometer 207. As described above, the properties of the dichroic mirror 205 are selected to transmit or reflect light within a specified wavelength range. The light 247 that is allowed to pass through the dichroic mirror 205 is collimated by the collimator 215. The collimated light 213 is directed to the sensor 245. For example, the sensor 245 can be a spectrometer, i.e., a spectrometer configured to measure wavelength-resolved intensity. The sensor 245 can additionally include a grating, optical lenses, a filter 421, and / or a linear array photodiode detector. The filter 421 can be a short-pass filter for limiting noise from the lamp 128, or a dielectric filter. A dielectric filter includes any thin-film-based filter capable of preventing light of a specific wavelength from passing through. Although the filter 421 is described as part of the sensor 245, it is contemplated that the filter can be located elsewhere. For example, the filter 421 can be part of the dichroic mirror 205. The filter 421 is configured to allow only light of a specific wavelength to pass through. In one example, the filter 421 allows only light with a wavelength below 550 nm to pass through to reduce the optical signal noise from the lamp in the processing chamber, thereby improving the measurement accuracy. It is contemplated that the filter 421 can be placed in any optical path, which includes the light reflected from the substrate 150 (e.g., the reflected light 227, reflected to the sensor 245) (e.g., the reflected light 247 from the dichroic mirror 205) (e.g., the collimated light 243). In one example, the filter 421 is an integral component of the sensor 245, but in other examples, the filter 421 is a separate component of the sensor 245. According to some embodiments, the filter 421 is not included in the path, thereby reducing the cost, complexity, and footprint of the ISR system 185. It should be noted that although the embodiments described herein may include the filter 421 and / or the dichroic mirror 205, both the filter 421 and the mirror 205 are optional and can be excluded from any of the embodiments or embodiments described herein because benefits can be obtained without them.

[0041] The pyrometer 207, one or more PHR sensors 221, and the sensor 245 can be connected to the controller 196 to facilitate its control and / or operation. The controller 196 can store information, data, algorithms, or other control parameters for performing the actions described herein. The controller 196 includes a central processing unit (CPU), a memory containing instructions, and support circuitry for the CPU. The controller 196 controls various items directly or through other computers and / or controllers. In one or more embodiments, the controller 196 is communicatively coupled to a dedicated controller, and the controller 196 serves as a central controller.

[0042] The controller 196 includes a computer processor (e.g., a CPU) for controlling various substrate processing chambers and equipment, and a sub-processor thereon or therein. The memory or non-transitory computer-readable medium is one or more of random access memory (RAM), dynamic random access memory (DRAM), static RAM (SRAM), and synchronous dynamic RAM (SDRAM (e.g., DDR1, DDR2, DDR3, DDR3L, LPDDR3, DDR4, LPDDR4, and the like)), read only memory (ROM), floppy disk, hard disk, flash drive, or any other form of local or remote digital memory. The support circuitry of the controller 196 is coupled to the CPU for supporting the CPU. The support circuitry includes cache memory, power supply, frequency circuitry, input / output circuitry and subsystems, and the like. Operating parameters and instructions are stored in the memory as software routines that are executed or called to configure the controller 196 into a dedicated controller for controlling the operation of the system 101 described herein. The controller 196 is configured to perform any of the operations described herein. The instructions stored in the memory, when executed, cause one or more of the operations described herein to be performed.

[0043] The ISR system 185 may optionally include one or more PHR sensors 221 that are positioned to receive data indicative of the properties of the preheat ring of the system 101. Each PHR sensor 221 is configured to be in line (e.g., vertically and / or optically aligned) with a PHR sensor channel 219. The PHR sensor 221 is a channel of a spectrometer or a multi-channel spectrometer that is configured to measure the properties of the preheat ring (PHR), such as the PHR 161 (as Figure 1 shown). In one example, each PHR sensor 221 is configured to read a reference material within or on the PHR 161 for use as a film thickness reference. For example, the reference material may be a crystalline specimen with known properties. Each PHR sensor channel 219 extends between the bottom surface and the top surface of the upper module body 126. In such examples, the PHR sensor channels are vertically aligned (and / or pointed) at the PHR 161 (as Figure 1As shown). The PHR sensor channel 219 can be sealed at its upper and lower ends by a material (such as quartz or sapphire) capable of transmitting light 229. In another embodiment, each PHR sensor channel 219 includes an optical fiber cable disposed thereon. It is contemplated that sensors similar to the PHR sensor 221 can be used on the system 101 alone or in combination with a pyrometer to analyze the substrate edge to measure the film thickness and other properties of the substrate edge as well as the temperature of the surface.

[0044] In addition, since the perimeter of the substrate 150 is close to the preheat ring 161, the preheat ring sensor 221 allows the estimation of the film thickness at the perimeter of the substrate 150. Thus, when deposition occurs on the preheat ring 161 during processing, the preheat ring sensor 221 can determine the thickness of the film on the preheat ring sensor. This thickness is an estimate of the deposited film thickness at the edge of the substrate 150. Thus, using the measurement through the pyrometer channel 131, the film thickness at the center of the substrate 150 can be determined, while using the measurement from the annular sensor 221, the film thickness at the edge of the substrate 150 can be determined. Thus, the center-to-edge uniformity of the deposited film can be determined and, if necessary, corrected in-situ. It is contemplated that the center-to-edge uniformity can be corrected by changing one or more process parameters during the deposition process. If a sensor similar to the PHR sensor 221 is used on the system 101 to observe the substrate edge position, the edge film thickness of the substrate 150 can also be directly measured.

[0045] During processing, light from the light source 244 is used to determine the film thickness and / or the film thickness deposition rate. The light is guided from the light source 244 (e.g., by an optical fiber cable) to the collimator 215. The collimator 215 directs the light to the surface to be measured (e.g., the substrate 150). The light is reflected from this surface as reflected light. The reflected light from the measurement surface of the substrate 150 contributes to the measurement of the film thickness (film thickness growth rate and / or film composition concentration, such as Ge). The reflected signal travels back to the dichroic mirror and is split into multiple paths (e.g., propagation sub-paths). The first propagation sub-path directs the reflected light to the pyrometer 207, while the second propagation sub-path directs the reflected light to the collimator 215 and then to the sensor 245. The true reflectance of the light intensity collected by the sensor 245 is analyzed and compared with a film model, for example, using a non-linear fitting equation or other empirically derived equations (Fresnel equations) to determine the film thickness.

[0046] In one example, a film thickness model is empirically derived by obtaining absorption / reflection data of light at a predetermined wavelength for various films of multiple film thicknesses. The data can be collected under process conditions that approximate those process conditions of a predetermined process recipe to be used for processing future substrates, such as the process recipe for which the model will be used. The data is then fit to an equation, such as a non-linear equation. The intensity of the light received by the analysis sensor 245 (e.g., the true reflectance of the light reflected from the measurement specimen) is analyzed, and the empirically derived equation is fit to determine the film thickness. In other words, the amount of light reflected from the surface of the substrate 150 changes as the thickness of the film on the surface of the substrate 150 changes. This data and / or equation can also account for other optical properties of the film, such as the refractive index and extinction coefficient, to improve the measurement accuracy. In one example, the film thickness model is derived from the apparatus and / or method used in U.S. Patent No. 10,281,261, which is incorporated herein by reference.

[0047] Figure 2B is a partial schematic cross-sectional view of the system shown in accordance with some embodiments Figure 1 as shown. Figure 2B Similar to Figure 2A however, the pyrometer 207 receives the light 211 passing through the dichroic mirror 205, and the collimator 215 receives the light 247 reflected from the dichroic mirror 205. The collimator 215 can then collimate the light 247 from the dichroic mirror 205. The sensor 245 can then receive the collimated light 213. According to some embodiments that can be combined with other embodiments, the collimator 215 can receive and collimate the reflected light 227 from the substrate before the dichroic mirror 205. In such embodiments, the dichroic mirror 205 receives the collimated light. As Figure 2B shown, the pyrometer 207 is located above the mirror housing 103, and the reflected light 227 has a shorter path to the pyrometer 207.

[0048] The measured light intensity of the collimated light 213 is used to determine the film thickness and / or growth rate of the film deposited on the surface of the substrate 150. For example, depending on the composition and optical properties of the particular material being measured, a lower light intensity can indicate a larger film thickness (since more light is absorbed), while a higher light intensity can indicate a smaller film thickness (since more light is reflected), or vice versa.

[0049] The thickness of the deposited film on the surface of the substrate 150 affects the light intensity of the collimated light 213 received by the sensor 245, such that a change in the light intensity can represent a change in the thickness of the deposited film on the surface of the substrate 150. In one or more instances, the measurement spectrum of the returned collimated light 213 can be filtered to provide a value indicative of the measured light intensity only within a selected wavelength range. This wavelength range is beneficial because radiation from a lamp (e.g., the upper lamp 130) is filtered out to improve the measurement accuracy at the sensor 245. The optical filter 421 can be used to block a portion of the reflected light 227, which portion of the reflected light includes light having wavelengths outside the selected wavelength range. For example, this can occur when light from the upper lamp 130 (or other lamp) is directed into the pyrometer channel 131, such as by reflection from one or more internal chamber surfaces. Unintended light can otherwise affect the measurement results at the sensor 245, and thus, filtering out the unintended wavelengths improves the measurement accuracy. In one or more instances, the selected wavelength range can exclude infrared light in order to reduce the effect of background infrared lamp radiation. In one non-limiting instance, the light generated by the light source 244 has wavelengths in the range of from about 200 nm to about 780 nm, such as from about 200 nm to about 500 nm, or from 200 nm to about 400 nm, or from about 500 nm to about 700 nm. The upper lamp 130 (or other lamp within the chamber), however, can be an infrared lamp. In such instances, the filter 421 filters out (limits passage of) light in the infrared wavelength range (IR-A, IR-B, and / or IR-C), such as light having wavelengths from 780 nm to 1.3 microns. Thus, the sensor 245 receives only the light generated by the light source 244, thereby improving the measurement accuracy of the light reflected from the surface of the substrate 150. In another instance, the filter 421 filters out light at 500 nm or greater, such as at 550 nm or greater, because signal degradation at high temperatures (e.g., 200 degrees Celsius and above, such as 600 degrees Celsius and below) begins to occur in the range of 500 nm to 550 nm, and the degradation occurs at wavelengths above it. The embodiments disclosed herein reduce interference from infrared lamp radiation, which increases the signal-to-noise ratio of the light sensor 245 for more precise film growth measurements.

[0050] The sensor 245 is used to in-situ monitor the film growth rate in the process chamber 100 and monitor in real-time during substrate processing. Compared to conventional methods, in-situ monitoring improves throughput because thickness measurements can be made without removing the substrate from the process chamber. In one instance, which can be combined with other instances, the light intensity of the returned collimated light 213 is monitored continuously throughout the substrate processing or at predetermined intervals throughout the substrate processing. Once the desired film thickness is reached, the deposition process is stopped. The substrate 150 can then be removed from the process chamber 100, or further processing can be performed within the process chamber 100 according to the process recipe.

[0051] Figure 3 Partial cross-sectional view of the ISR system 185 shown in Figure 1 FIG. 1. The mirror housing 103 includes a top plate 395 coupled to a side wall 396. The top plate 395 includes a hole 397 adjacent to the collimator 215, and the side wall 396 includes a hole 398 therein adjacent to the pyrometer 207. The pyrometer 207 and the collimator 215 are coupled to the mirror housing 103. The mirror housing 103 is made of a metal alloy such as aluminum-containing alloy or steel, and houses a dichroic mirror 205 therein. The mirror housing 103 is coupled to a cooling plate 375. The cooling plate 375 is designed to maintain the mirror housing 103 at a predetermined temperature to increase the lifespan of the mirror housing 103 and its components. Additionally or alternatively, in the case where the dichroic mirror 205 has different optical properties at different temperatures, the cooling plate 375 maintains the dichroic mirror 205 within a temperature range of predetermined optical properties. The cooling plate 375 includes one or more coolant channels 399 formed therein, and these coolant channels are coupled to a cooling system. The cooling plate 375 is also made of a metal alloy such as aluminum-containing alloy or steel. The cooling plate 375 includes a hole 363 formed therein adjacent to the pyrometer channel 131. The cooling plate 375 is located between the mirror housing 103 and the upper housing module 102 to reduce heat transfer from the upper housing module 102 to the mirror housing 103. The mirror housing 103 may include a mirror mounting plate 379 disposed therein for supporting the dichroic mirror 205. The mirror mounting plate 379 holds the dichroic mirror 205 in a predetermined orientation and position, such as an incident angle A1 (as Figure 2A shown in FIG. 2). In one example, the mirror mounting plate 379 is coupled to the mirror housing 103, but other support configurations are also contemplated. The mirror mounting plate 379 facilitates the correct positioning of the dichroic mirror 205 without obstructing the light propagation path. In addition, the mirror mounting plate 379 facilitates the easy removal of the dichroic mirror 205 for replacement or cleaning.

[0052] Figure 4 Cross-sectional view of the mirror mounting plate 379 according to one embodiment. The mirror mounting plate 379 is formed of a metal, ceramic, or polymer material, and includes a recess 403 formed therein adjacent to a hole 401. The dichroic mirror 205 is disposed in the recess 403 and is fixed by an adhesive, mechanical fit, or a mechanical fastener such as a tab. The recess 403 may be inclined at an angle A2 with respect to a first surface 405 of the mirror mounting plate 379. The angle A2 can be used for fine adjustment of the dichroic mirror 205. The angle A2 can be about 0° to about 10° with respect to the first surface 405, such as an angle of about 0.1° to about 5° with respect to the first surface 405.

[0053] Conceivably, a mounting plate similar to mounting plate 379 may also be used to support filter 421 within the propagation path of the light generated by light source 244. In such instances, the filter may be a circular optical element configured to filter (remove) light of a selected wavelength. Similarly, the mounting plate for the filter aids in improving the positioning of filter 421, as well as improving the removal of filter 421 for replacement or cleaning.

[0054] Figure 5 Schematic block diagram of method 500 for calibrating the rotation of base assembly 124. Base assembly 124 includes base 157. Figure 1 And Figure 2A Method 500 is described for purposes of explanation, but conceivably, method 500 may be used with Figure 1 systems other than system 101. It is further contemplated that controller 196 may direct or otherwise control one or more aspects of method 500. Method 500 takes into account the wobbling of base 157 while using in-situ reflectometry. For example, during processing, base assembly 124 (as Figure 1 shown) and thus substrate 150 thereon rotate during processing to facilitate uniform deposition. However, due to mechanical tolerances or other factors, base assembly 124 wobbles about the longitudinal (e.g., central) axis of support shaft 155. During rotation, the wobbling of support shaft 155 causes in-plane wobbling of base 157 and substrate 150 thereon. The in-plane wobbling inadvertently changes the distance of the propagation path between sensors (e.g., sensor 245, pyrometer 207, and preheat ring sensor 221) within the system and the test specimen (e.g., substrate 150 and preheat ring 161 and / or specimens thereon). The change in the distance of the propagation path may affect measurement accuracy and thus film thickness measurement accuracy. However, method 500 mitigates the reduced measurement accuracy due to the wobbling of base assembly 124.

[0055] Method 500 utilizes a reference substrate to determine and account for the wobbling. Method 500 begins at operation 502, where base assembly 124 and the reference substrate thereon are rotated. The reference substrate is a substrate having known physical properties, such as surface reflectivity and optical properties, e.g., refractive index and extinction coefficient. Controller 196 rotates base assembly 124 in a continuous or stepwise manner.

[0056] In operation 504, the light source 244 directs light along a propagation path to the surface of the reference substrate. The light from the light source 244 is provided at a known intensity and wavelength (or wavelength range), such as the range or wavelength measured by the sensor 245. The light from the light source 244 is provided at a defined angular position of the base assembly 124. Operation 504 also includes recording the angular position of the base assembly 124 when light is provided from the light source 244. Thus, the association between the angular position of the base assembly 124 and the light used to measure the reference substrate can be derived later, as described below. It is contemplated that the light from the light source 244 can be triggered by a controller command or in response to a physical trigger (e.g., a contact switch).

[0057] The angular position of the base assembly 124 can be determined by rotating the base assembly 124 using an actuator with a known angular position (e.g., using a stepper encoder). Additionally or alternatively, the angular position of the base assembly 124 can be determined using an optical signal. In such instances, the shaft 155 of the base assembly 124 can include a reflector on a portion thereof. When the shaft 155 rotates, an optical signal can be provided to the reflector by a sensor and an optical signal can be received from the reflector to determine the angular position of the shaft 155. It is contemplated that other methods of determining the angular position can be used, such as using a stepper motor with steps of known angular distance. In another example, the base assembly 124 can be rotated at a constant specified rate while a phased encoder provides data related to the angular position of the base assembly 124 to the controller 196. The controller 196 causes the light from the light source 244 to be directed to the substrate at a predetermined interval, and the controller 196 associates each data spectrum collected by the sensor 245 with the known angular position of the base assembly 124. In such instances, a trigger for initiating the propagation of light from the light source 244 can be omitted, thus simplifying the hardware and reducing costs.

[0058] Operation 506 includes collecting the reflected light 227 from the reference substrate. A sensor 245, such as a spectrometer, receives the reflected light 227. The sensor converts the received light into spectral data. In operation 508, the sensor 245 sends the spectral data to the controller 196. In operation 510, the controller 196 associates the received spectral data with the angular position of the base assembly 124. Since the thickness of the reference substrate is known, inconsistent spectral data (e.g., showing a thickness variation deviating from the known value of the reference substrate) can be attributed to the wobbling of the base assembly 124. The controller 196 can determine a correction factor for each angular position of the base assembly 124 to account for the wobbling. Thus, when the sensor 245 receives data during the processing of a non-reference substrate, the correction factor is applied to the received measurements to account for the substrate wobbling and variations caused by the rotating member, thereby improving the accuracy of the film thickness measurement.

[0059] In operation 512, the combination of angular position and spectral data is used to create a data set as a reference for in-situ reflectometry. This data set is stored in controller 196. It is contemplated that the data set can be updated at predetermined intervals, such as when performing preventive maintenance in system 101. In some aspects, machine learning or artificial intelligence can be applied to improve the collection and application of the data set to achieve improved thin film measurements.

[0060] The present disclosure contemplates that operations 502-512 of method 500 can be repeated one or more times to improve the collection and application of data that correlates the angular position of base component 124 with the received optical signal. According to some embodiments that can be combined with other embodiments, operations 502-512 are repeated on a second substrate (such as a different reference substrate) to confirm and / or further refine a previously determined correction factor.

[0061] During substrate processing, each measurement by sensor 245 is corrected according to the methods described above. Additionally or alternatively, other methods can be employed during substrate processing to account for the wobbling of the base component. In one example, measurements are made at the same specified angular position and only at that angular position, thereby improving consistency. In another example, the measured values can be averaged, or in yet another embodiment, the measured values can be plotted and a trend line or other function can be applied to account for the deviation caused by wobbling. In the case where the wobbling produces a sine curve, for each wavelength in the spectrum, a cosine function can be fit to the data, where:

[0062]

[0063] A = amplitude, f = frequency (Hz), R ave = average signal level.

[0064] In other examples, it is contemplated to omit method 500 from the processing of the substrate. In such examples, correction for wobbling may not be applied. In other examples, the measurements can be normalized to reduce errors attributable to problems with movement caused at least by rotation, machining tolerances, manufacturing limitations, material properties, system wear, and other possible sources of error.

[0065] The operations of 500 can also be accomplished by an algorithm that uses time to determine the angular position of base component 124. In some embodiments, the operation of an existing process chamber can be modified where two controllers are used to operate sensor 245 to measure the angular position of base 157. The angular position of base 157 can be determined by a position sensor or by a computer algorithm that uses a variable (such as time).

[0066] Benefits of the present disclosure include in-situ and real-time film growth measurement operations, precise film growth monitoring, increased signal-to-noise ratio, use of reduced optical wavelengths, increased measurement resolution, increased efficiency and throughput, reduced machine downtime, and reduced costs. Determining film thickness or growth rate includes measuring a plurality of light intensity values of reflected light over one or more time intervals. These light intensity values are associated with reference data or physical models based on the Fresnel electromagnetic wave reflection equation to determine the growth rate over one or more time intervals. The growth rate can correspond to the change in light intensity over one or more time intervals. The growth rate over a certain time interval can be used to determine the film thickness. The film thickness data can be used to improve the process. For example, if the growth rate is too high or too low, one or more process parameters can be adjusted to correct the growth rate to a target growth rate. The one or more process parameters can include: the flow rate of the process gas, the power supplied to the upper lamp and / or the lower lamp, the processing temperature of the substrate, the operation time for performing the substrate processing operation, and / or the processing pressure in the process space 110.

[0067] It is contemplated that one or more aspects disclosed herein can be combined. For example, one or more aspects, features, components, and / or properties of the system 101, the process chamber 100, and the ISR system 185 can be combined. Additionally, it is contemplated that one or more aspects disclosed herein can include some or all of the above benefits.

[0068] In addition to monitoring film growth rate, film thickness, film composition concentration, and temperature, aspects of the present disclosure can be used to monitor film composition. For example, within a SiGe film, the refractive index and extinction coefficient vary with the change in germanium concentration. Therefore, the change in the refractive index of the extinction coefficient measured by the sensor 245 can indicate the change in film composition during SiGe formation. Once determined, the process conditions can be adjusted to promote the desired film composition. Although this specific embodiment is described in relation to a SiGe film, it is contemplated that aspects of the present disclosure can also be applied to other films of other compositions.

[0069] The present disclosure achieves unexpected results because we believe that measuring film growth during processing in the process space 110 of the processing chamber would involve inaccuracies due to heating the substrate using light from the upper dome and the lower dome and / or the self-lamp illumination. The present disclosure achieves the above benefits compared to the operation of measuring the film on the substrate after the substrate has been processed and removed from the process chamber.

[0070] The present disclosure contemplates that terms such as "coupling / couple / coupled" may include, but are not limited to, welding, interference fit, and / or fastening, such as by using bolts, threaded connections, pins, and / or screws. The present disclosure contemplates that terms such as "couples / coupling / couple / coupled" may include, but are not limited to, being integrally formed. The present disclosure contemplates that terms such as "couples / coupling / couple / coupled" may include, but are not limited to, direct coupling and / or indirect coupling. The present disclosure contemplates that terms such as "couples / coupling / couple / coupled" may include operative couplings such as electrical coupling and / or fluid coupling.

[0071] The present disclosure contemplates that terms such as "send / sending", "transmit", "direct", and "reflect" light may include, but are not limited to, incident light, collimated light, light in an optical cable, light in an optical fiber, full-spectrum light, and / or light having a filtered wavelength. The present disclosure contemplates that terms such as "transparent" and / or "opaque" may include, but are not limited to, the properties of materials that allow light to pass through completely and / or partially.

[0072] Although the foregoing relates to embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from its basic scope. The present disclosure also contemplates that one or more aspects of the embodiments described herein may replace one or more of the other aspects described. The scope of the present disclosure is determined by the following claims of invention.

Claims

1. A system for monitoring film growth on a substrate, the system being applicable to semiconductor processing, the system comprising: a light source for guiding light along a propagation path; a collimator in optical communication with the light source along the propagation path; a dichroic mirror disposed along the propagation path between the collimator and an optical tube; a pyrometer in optical communication with the dichroic mirror along a first propagation sub-path downstream of the dichroic mirror; a spectrometer in optical communication with the dichroic mirror along a second propagation sub-path downstream of the dichroic mirror; and a filter for filtering light wavelengths within a predetermined range, the filter being disposed along the propagation path between the light source and the spectrometer.

2. The system according to claim 1, wherein the filter is disposed along the propagation path between the dichroic mirror and the spectrometer.

3. The system according to claim 2, wherein the filter comprises a dielectric material selected to prevent transmission of wavelengths greater than about 500 nm.

4. The system according to claim 1, wherein the collimator is disposed along the propagation path between the light source and the dichroic mirror.

5. The system according to claim 1, wherein the collimator is disposed along the propagation path between the dichroic mirror and the spectrometer.

6. A system for monitoring film growth on a substrate, the system being applicable to semiconductor processing, the system comprising: a light source disposed at a first end of a propagation path; an optical tube disposed along the propagation path and in optical communication with a collimator; a dichroic mirror in optical communication with the light source; a pyrometer in optical communication with the dichroic mirror along a first propagation sub-path of the propagation path downstream of the dichroic mirror; a spectrometer in optical communication with the dichroic mirror along a second propagation sub-path of the propagation path downstream of the dichroic mirror; and a filter disposed along the propagation path between the light source and the spectrometer.

7. The system according to claim 6, wherein the light source is a flash lamp.

8. The system according to claim 6, wherein the first propagation sub-path is an optical path reflected from the dichroic mirror to the pyrometer, and the second propagation sub-path is an optical path passing through the dichroic mirror to the spectrometer.

9. The system according to claim 6, wherein the dichroic mirror is configured to guide light wavelengths between about 200 nm and about 800 nm along the second propagation sub-path.

10. The system according to claim 6, wherein the dichroic mirror is disposed along the propagation path at an incident angle between about 40° and about 50°.

11. The system according to claim 6, wherein the dichroic mirror is configured to guide light wavelengths between about 3.0 μm and about 4.0 μm along the first propagation sub-path.

12. The system according to claim 11, wherein the dichroic mirror is configured to guide wavelengths between about 200 nm and about 800 nm along the second propagation sub-path.

13. The system according to claim 6, wherein the filter comprises a dielectric coating that only allows light with a wavelength below 550 nm to pass through.

14. The system according to claim 6, the system further comprising: a mirror housing, wherein the mirror housing is coupled to a cooling plate.

15. A system for monitoring film growth on a substrate, the system being suitable for semiconductor processing, the system comprising: a processing chamber, the processing chamber including: a pedestal; a preheating ring surrounding the pedestal; and an upper window; and a lower window; and an in-situ reflectometry system positioned near the upper window, the in-situ reflectometry system comprising: a light source for guiding light along a propagation path; a collimator in optical communication with the light source along the propagation path; a dichroic mirror disposed along the propagation path between the collimator and an optical tube; a pyrometer in optical communication with the dichroic mirror along a first propagation sub-path downstream of the dichroic mirror; a spectrometer in optical communication with the dichroic mirror along a second propagation sub-path downstream of the dichroic mirror; and a filter disposed along the propagation path between the light source and the spectrometer.

16. The system according to claim 15, the system further comprising a mounting plate that supports the dichroic mirror, wherein the mounting plate sets the dichroic mirror along the propagation path at an incident angle between about 40° and about 50°.

17. The system according to claim 15, wherein the first propagation sub-path is for light reflected by the dichroic mirror to the pyrometer, and the second propagation sub-path is for light that passes through the dichroic mirror to the spectrometer.

18. The system according to claim 15, wherein the filter prevents transmission of wavelengths greater than about 550 nm.

19. The system according to claim 15, wherein the dichroic mirror is configured to guide wavelengths between about 3.0 μm and about 4.0 μm along the first propagation sub-path.

20. The system according to claim 19, wherein the dichroic mirror is configured to guide wavelengths between about 200 nm and about 800 nm along the second propagation sub-path.

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