Temperature Measurement System for Millisecond Annealing System

Abstract

A temperature measurement system for a millisecond annealing system is provided. In one exemplary embodiment, the system may include: a far-infrared temperature sensor configured to obtain one or more temperature measurements of a substrate in a millisecond annealing system at a processing temperature less than about 450 °C, the millisecond annealing system including a processing chamber having a wafer platen that divides the processing chamber into a top chamber and a bottom chamber; and a processing circuit configured to process the measurements from the temperature sensor to determine the temperature of the substrate at a temperature less than about 450 °C.

Description

[0001] This disclosure is a divisional application of a PCT application titled "Pre-heat Processes for Millisecond Anneal System", with a filing date of December 13, 2016, an international application number of PCT / US2016 / 066341, and a national application number of 201680054053.9.

[0002] Priority Claim

[0003] Accordingly, this application claims the benefit of priority of U.S. Provisional Application Serial No. 62 / 272,811, titled "Pre-heat Processes for Millisecond Anneal System", filed on December 30, 2015, which is incorporated herein by reference. Technical Field

[0004] This disclosure generally relates to a heat treatment chamber, and more particularly to a millisecond annealing heat treatment chamber for processing substrates such as semiconductor substrates. Background Art

[0005] Millisecond annealing systems can be used for semiconductor processing of ultra-rapid heat treatment of substrates such as silicon wafers. In semiconductor processing, rapid thermal processing can be used as an annealing step for repairing implantation damage, improving the quality of deposited layers, improving the quality of layer interfaces, activating dopants, and achieving other purposes while controlling the diffusion of dopants.

[0006] Millisecond or ultra-rapid temperature processing of a semiconductor substrate can be achieved by using intense and brief light exposure to heat the entire top surface of the substrate at a rate that can exceed 10 4 °C per second. Rapid heating of only one surface of the substrate can create a large temperature gradient across the thickness of the substrate while the bulk of the substrate remains at the temperature prior to light exposure. Thus, the bulk of the substrate acts as a heat sink, resulting in a rapid cooling rate of the top surface. Summary of the Invention

[0007] Aspects and advantages of embodiments of the present disclosure will be set forth in part in the following description, or may be learned from the description, or may be learned by practice of the embodiments.

[0008] One exemplary aspect of the present disclosure is a pre-heat method for a millisecond annealing system. The pre-heat method includes placing a substrate on a wafer support plate in a processing chamber of the millisecond annealing system. The processing chamber is divided into a top chamber and a bottom chamber. The method includes obtaining one or more temperature measurements of the wafer support plate using a temperature sensor. The method includes applying a pre-heat recipe to heat the wafer support plate based at least in part on the one or more temperature measurements of the wafer support plate.

[0009] Another exemplary aspect of the present disclosure relates to a temperature measurement system for a millisecond annealing system. The temperature measurement system includes a far-infrared temperature sensor configured to obtain one or more temperature measurements of a semiconductor substrate in a millisecond annealing system at a process temperature less than about 450 °C. The millisecond annealing system can include a processing chamber having a wafer platen. The wafer platen can divide the processing chamber into a top chamber and a bottom chamber. The temperature measurement system can include a processing circuit configured to process the measurements from the temperature sensor to determine the temperature of the semiconductor substrate at a temperature less than about 450 °C.

[0010] Yet another exemplary aspect of the present disclosure relates to a preheating method for a millisecond annealing system. The preheating method includes obtaining one or more temperature measurements from a temperature sensor in a field of view of a wafer support plate in a millisecond annealing system. The millisecond annealing system has a processing chamber divided into a top processing chamber and a bottom processing chamber. The method includes applying a pulsed preheating regime to heat the wafer support plate in the millisecond annealing system based at least in part on the one or more temperature measurements. During application of the pulsed heating regime, no substrate is located on the wafer support plate.

[0011] Variations and modifications can be made to the exemplary aspects of the present disclosure.

[0012] Other exemplary aspects of the present disclosure relate to systems, methods, apparatuses, and processes for heat treating a semiconductor substrate.

[0013] These and other features, aspects, and advantages of the various embodiments will become better understood with reference to the following description and the appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and, together with the description, serve to explain the relevant principles. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] A detailed discussion of embodiments for a person of ordinary skill in the art is set forth in the specification with reference to the drawings, in which:

[0015] Figure 1 An exemplary millisecond annealing heating curve in accordance with an exemplary embodiment of the present disclosure is depicted;

[0016] Figure 2 An exemplary perspective view of a portion of an exemplary millisecond annealing system in accordance with an exemplary embodiment of the present disclosure is depicted;

[0017] Figure 3 An exploded view of an exemplary millisecond annealing system in accordance with an exemplary embodiment of the present disclosure is depicted;

[0018] Figure 4 A cross-sectional view of an exemplary millisecond annealing system in accordance with an exemplary embodiment of the present disclosure is depicted;

[0019] Figure 5 Shows a perspective view of an exemplary lamp used in a millisecond annealing system according to an exemplary embodiment of the present disclosure;

[0020] Figure 6 Shows an exemplary edge reflector used in a wafer platen of a millisecond annealing system according to an exemplary embodiment of the present disclosure;

[0021] Figure 7 Shows an exemplary reflector that can be used in a millisecond annealing system according to an exemplary embodiment of the present disclosure;

[0022] Figure 8 Shows an exemplary arc lamp that can be used in a millisecond annealing system according to an exemplary embodiment of the present disclosure;

[0023] Figures 9 to 10 Shows the operation of an exemplary arc lamp according to an exemplary embodiment of the present disclosure;

[0024] Figure 11 Shows a cross-sectional view of an exemplary electrode according to an exemplary embodiment of the present disclosure;

[0025] Figure 12 Shows an exemplary closed-loop system for supplying water and gas (e.g., argon) to an exemplary arc lamp used in a millisecond annealing system according to an exemplary embodiment of the present disclosure;

[0026] Figure 13 Shows an exemplary temperature measurement system for a millisecond annealing system according to an exemplary embodiment of the present disclosure;

[0027] Figure 14 Shows an exemplary millisecond annealing system according to an exemplary embodiment of the present disclosure having a tungsten halogen lamp for heating a semiconductor substrate to an intermediate temperature;

[0028] Figure 15 Shows a flowchart of an exemplary method according to an exemplary embodiment of the present disclosure;

[0029] Figure 16 Shows an exemplary processing chamber according to an exemplary embodiment of the present disclosure having a pyrometer temperature sensor configured to determine the temperature of a wafer support plate;

[0030] Figure 17 Shows a typical thermal emission spectrum associated with a wafer support plate made of quartz;

[0031] Figure 18 Shows a graphical representation of the wafer support plate temperature distribution due to relaxation according to an exemplary embodiment of the present disclosure;

[0032] Figure 19 depicts a flowchart of an exemplary method according to an exemplary embodiment of the present disclosure;

[0033] Figure 20 depicts an exemplary pulse preheating regime according to an exemplary embodiment of the present disclosure;

[0034] Figure 21 depicts an exemplary pulse preheating regime according to an exemplary embodiment of the present disclosure; and

[0035] Figure 22 depicts an exemplary millisecond annealing system with a far-infrared temperature sensor according to an exemplary embodiment of the present disclosure. DETAILED DESCRIPTION

[0036] Reference will now be made in detail to embodiments, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explaining the embodiments, not limiting the present disclosure. In fact, it will be apparent to those skilled in the art that various modifications and changes can be made to the embodiments without departing from the scope or spirit of the present disclosure. For example, features shown or described as part of one embodiment can be used with another embodiment to yield yet another embodiment. Accordingly, it is intended that aspects of the present disclosure cover such modifications and changes.

[0037] Overview

[0038] Exemplary aspects of the present disclosure relate to a preheating method for a millisecond annealing system to reduce the impact on a first substrate (e.g., a silicon wafer) during millisecond heat treatment of the substrate. For purposes of illustration and discussion, aspects of the present disclosure are discussed with reference to a "wafer" or semiconductor wafer. Using the disclosure provided herein, one of ordinary skill in the art will understand that the exemplary aspects of the present disclosure can be used in conjunction with any workpiece, semiconductor substrate, or other suitable substrate. Additionally, the term "about" when used in conjunction with a numerical value is intended to mean within 10% of that numerical value.

[0039] Millisecond or ultra-fast heat treatment of a semiconductor wafer can be achieved using intense and brief light exposure (e.g., a "flash") to heat the entire top surface of the wafer at a rate that can exceed 10 4 °C per second. A typical heat treatment cycle can include: (a) loading a cold semiconductor substrate into the chamber; (b) purging the chamber with, for example, nitrogen (atmospheric pressure); (c) heating the semiconductor substrate to an intermediate temperature T i ; (d) millisecond heating by flash exposure of the top surface of the semiconductor substrate while the body of the wafer remains at T i; (e) rapid cooling by conduction cooling through the top surface of the semiconductor substrate, wherein the body of the semiconductor substrate is a heat sink that is conductively coupled; (f) slow cooling of the body of the semiconductor substrate by thermal radiation and convection, wherein the processing gas at atmospheric pressure is used as the coolant; and (g) transporting the semiconductor substrate back to the cassette.

[0040] The exact parameters of the processing steps in the heat treatment cycle (e.g., duration, temperature set point, heating rate, etc.) can be specified in the process regime. The process regime can be edited and modified by the user. The regime can be executed by one or more electronic system controllers at runtime. The controller can include one or more processors and one or more storage devices. The storage device can store the regime as computer-readable instructions that, when executed by one or more processors, cause the controller to implement the regime.

[0041] The system can have multiple predefined regimes stored in one or more storage devices. The type of application or heat treatment can determine which regime to execute. The semiconductor substrate can be loaded onto the system through a FOUP (Front Opening Unified Pods), which includes a cassette that can accommodate, for example, 25 semiconductor substrates or other suitable input mechanisms. A physical group of 25 semiconductor substrates can constitute a "lot" or "batch" of semiconductor substrates. Typically, the same process regime is used to process a batch. If there is no interruption between processing batches using the same regime, the system can be said to be operating in a continuous mode.

[0042] As discussed in detail below, the processing chamber in which such a processing cycle is performed can include: (1) a wafer support plate made of, for example, quartz glass; (2) chamber walls made of highly reflective water-cooled aluminum plates; (3) a top water window and a bottom water window made of water-cooled quartz plates that are transparent to heating light. Except for the wafer support plate, all components of the chamber can be actively cooled and can maintain a constant temperature throughout the heat treatment method of the semiconductor substrate. In some embodiments, the wafer support plate is not actively cooled.

[0043] When starting from a cold system, each heat treatment cycle heats the wafer support plate while heating the semiconductor substrate and cools the wafer support plate during the cooling phase of the cycle. Since the heating phase is typically more dominant than the cooling phase, the average temperature of the plate increases with each cycle until it reaches the equilibrium temperature. Before reaching the equilibrium temperature, each semiconductor substrate undergoing heat treatment encounters a different thermal radiation background, which affects the thermal budget of the processing method and thus the processing result. To achieve good repeatability, the cold processing chamber may need to be preheated to the equilibrium temperature. This can be accomplished by performing the process regime on a plurality of preheating dummy wafers. For example, six preheating dummy wafers can be used for this purpose and can be run before the first batch is being processed. When the system is operating in continuous mode, no preheating dummy wafers are required since the wafer support plate is automatically maintained at the equilibrium temperature.

[0044] The disadvantage of the dummy wafers is that preheating dummy wafers are required and the preheating cycle takes a significant amount of processing time. This is especially true when the system cannot be maintained in continuous mode or when multiple applications that each require a different equilibrium temperature of the wafer support plate need to be run. Therefore, the preheating dummy wafers may have to be run between batches.

[0045] Exemplary aspects of the present disclosure are directed to reducing the preheating processing time and / or reducing the number of dummy wafers for preheating the processing chamber to the equilibrium temperature. In this way, the operating efficiency of the millisecond annealing system can be improved.

[0046] For example, one exemplary embodiment relates to a preheating method for a millisecond annealing system. The method can include placing a substrate on a wafer support plate in a processing chamber of the millisecond annealing system. The processing chamber can be divided into a top chamber and a bottom chamber. The method can include obtaining one or more temperature measurements of the wafer support plate using a temperature sensor; and applying a preheating regime to heat the wafer support plate at least partially based on the one or more temperature measurements of the wafer support plate.

[0047] Variations and modifications can be made to this exemplary embodiment. For example, in some embodiments, the wafer support plate can be a quartz material. In some embodiments, the substrate can include a dummy semiconductor substrate.

[0048] In some embodiments, applying a preheating regime to heat the wafer support plate at least partially based on the one or more temperature measurements of the wafer support plate can include applying a preheating regime to heat the wafer support plate until the temperature of the wafer support plate reaches a preset temperature. When the wafer support plate reaches the preset temperature, the method can include: stopping the preheating regime; and applying a process regime to a second substrate in the processing chamber. The process regime is different from the preheating regime.

[0049] In some embodiments, a preheat regime specifies heating a wafer support plate and a substrate using one or more continuous mode lamps located near a bottom processing chamber in a millisecond annealing system. The one or more continuous mode lamps are controlled based at least in part on one or more temperature measurements of the wafer support plate.

[0050] In some embodiments, the temperature sensor can include a pyrometer that measures temperature associated with wavelengths greater than about 4 μm. In some embodiments, the temperature sensor is located in the bottom chamber and has a field of view of the wafer support plate without being blocked by the water window of the millisecond annealing system.

[0051] Another exemplary embodiment of the present disclosure relates to a temperature measurement system for a millisecond annealing system. The temperature measurement system can include a far-infrared temperature sensor configured to obtain one or more temperature measurements of a semiconductor substrate in a millisecond annealing system at a processing temperature less than about 450 °C (e.g., less than about 300 °C, e.g., less than about 250 °C). The millisecond annealing system can include a processing chamber having a wafer platen. The wafer platen can divide the processing chamber into a top chamber and a bottom chamber. The temperature measurement system can include a processing circuit configured to process the measurements from the temperature sensor to determine the temperature of the semiconductor substrate at a temperature less than about 450 °C (e.g., less than about 300 °C, e.g., less than about 250 °C).

[0052] In some embodiments, the far-infrared temperature sensor includes a pyrometer associated with a spectral range of about 8 μm to about 14 μm. In some embodiments, the far-infrared temperature sensor is mounted at a corner of the top chamber of the millisecond annealing system. The far-infrared temperature sensor can be unblocked by the water window of the millisecond annealing system.

[0053] In some embodiments, the temperature measurement system further includes a second temperature sensor configured to measure the temperature of the wafer support plate in the millisecond annealing system. The second temperature sensor can be located in the bottom processing chamber and has a field of view of the wafer support plate.

[0054] Another exemplary embodiment of the present disclosure relates to a preheat method for a millisecond annealing system. The preheat method can include obtaining one or more temperature measurements from a temperature sensor having a field of view of a wafer support plate in a millisecond annealing system. The millisecond annealing system can have a processing chamber divided into a top processing chamber and a bottom processing chamber. The method includes applying a pulsed preheat regime to heat the wafer support plate in the millisecond annealing system based at least in part on the one or more temperature measurements. During application of the pulsed heating regime, no substrate is located on the wafer support plate. In some embodiments, the wafer support plate is a quartz material.

[0055] In some embodiments, applying a pulsed preheat regime to heat a wafer support plate based at least in part on the temperature of the wafer support plate includes applying a preheat regime to heat the wafer support plate until the temperature of the wafer support plate reaches a preset temperature. When the wafer support plate reaches the preset temperature, the method may include: stopping the preheat regime; and applying a process regime to a second substrate in the processing chamber. The process regime is different from the preheat regime.

[0056] In some embodiments, the pulsed preheat regime may specify a plurality of heating light pulses. In some embodiments, the temperature sensor may include a pyrometer having a measured temperature value associated with a wavelength greater than about 4 μm.

[0057] Exemplary millisecond annealing system

[0058] An exemplary millisecond annealing system may be configured to provide a strong and brief light exposure to heat the top surface of a wafer at a rate exceeding, for example, about 10 4 °C per second. Figure 1 An exemplary temperature profile 100 of a semiconductor substrate achieved using a millisecond annealing system is depicted. As Figure 1 shown, during the ramp-up phase 102, the bulk of the semiconductor substrate (e.g., a silicon wafer) is heated to an intermediate temperature T i . The intermediate temperature may be in the range of about 450 °C to about 900 °C. When the intermediate temperature T i is reached, the top side of the semiconductor substrate may be exposed to a very brief and intense flash, causing a heating rate of up to about 10 4 °C per second. Window 110 shows the temperature profile of the semiconductor substrate during the brief and intense flash. Curve 112 represents the rapid heating of the top surface of the semiconductor substrate during the flash exposure. Curve 116 depicts the temperature of the remainder or bulk of the semiconductor substrate during the flash exposure. Curve 114 represents the rapid cooling caused by the cooling conduction of the top surface of the semiconductor substrate by the bulk of the semiconductor substrate acting as a heat sink. The bulk of the semiconductor substrate acts as a heat sink, creating a high top-side cooling rate for the substrate. Curve 104 represents the slow cooling of the bulk of the semiconductor substrate by thermal radiation and convection, where the process gas acts as a coolant.

[0059] An exemplary millisecond annealing system may include a plurality of arc lamps (e.g., four argon arc lamps) as light sources for a strong millisecond-long exposure — a so-called "flash" — of the top surface of a semiconductor substrate. The flash may be applied to the semiconductor substrate when the substrate has been heated to an intermediate temperature (e.g., about 450 °C to about 900 °C). A plurality of continuous-mode arc lamps (e.g., two argon arc lamps) may be used to heat the semiconductor substrate to the intermediate temperature. In some embodiments, heating the semiconductor substrate to the intermediate temperature is achieved by heating the entire bulk of the wafer at a ramp rate through the bottom surface of the semiconductor substrate.

[0060] Figures 2 to 5 illustrates aspects of an exemplary millisecond annealing system 80 in accordance with an exemplary embodiment of the present disclosure. As Figures 2 to 4 shown, the millisecond annealing system 80 may include a processing chamber 200. The processing chamber 200 may be divided into a top chamber 202 and a bottom chamber 204 by a wafer platen 210. A semiconductor substrate 60 (e.g., a silicon wafer) may be supported by support pins 212 (e.g., quartz support pins) mounted to a wafer support plate 214 (e.g., a quartz glass plate inserted into the wafer platen 210).

[0061] As Figure 2 and Figure 4 shown, the millisecond annealing system 80 may include a plurality of arc lamps 220 (e.g., four argon arc lamps) arranged adjacent to the top chamber 202 as a light source for intense millisecond-long exposure of the top surface of the semiconductor substrate 60 - a so-called "flash". The flash may be applied to the semiconductor substrate when the substrate has been heated to an intermediate temperature (e.g., from about 450 °C to about 900 °C).

[0062] A plurality of continuous mode arc lamps 240 (e.g., two argon arc lamps) located adjacent to the bottom chamber 204 may be used to heat the semiconductor substrate 60 to the intermediate temperature. In some embodiments, heating the semiconductor substrate 60 to the intermediate temperature is achieved by heating the entire body of the semiconductor substrate 60 from the bottom chamber 204 at a ramp rate through the bottom surface of the semiconductor substrate.

[0063] As Figure 3 shown, light for heating the semiconductor substrate 60 from the bottom arc lamps 240 (e.g., for heating the semiconductor substrate to the intermediate temperature) and from the top arc lamps 220 (e.g., for providing millisecond heating by the flash) may enter the processing chamber 200 through a water window 260 (e.g., a water-cooled quartz glass window). In some embodiments, the water window 260 may include a sandwich structure: a water layer of about 4 mm thick is sandwiched between two quartz glass plates, and the water layer circulates between the glass plates to cool the quartz plates and provide a filter for wavelengths above about 1400 nanometers.

[0064] Also as Figure 3 illustrated, the processing chamber wall 250 may include a mirror 270 for reflecting the heating light. The mirror 270 may be, for example, a water-cooled polished aluminum panel. In some embodiments, the body of the arc lamp used in the millisecond annealing system may include a reflector for lamp irradiation. For example, Figure 5FIG. 0 depicts a perspective view of a top lamp array 220 and a bottom lamp array 240 that can be used in a millisecond annealing system 200. As shown, the body of each lamp array 220 and 240 can include a reflector 262 for reflecting heating light. These reflectors 262 can form part of the reflective surface of the processing chamber 200 of the millisecond annealing system 80.

[0065] The temperature uniformity of a semiconductor substrate can be controlled by manipulating the light density falling on different regions of the semiconductor substrate. In some embodiments, the uniformity adjustment can be achieved by changing the reflectivity of the small reflectors to the main reflector and / or by using edge reflectors mounted around the wafer on the wafer support plane.

[0066] For example, the edge reflector can be used to redirect the light from the bottom lamp 240 to the edge of the semiconductor substrate 60. As an example, Figure 6 FIG. 8 depicts an exemplary edge reflector 264 that forms a part of the wafer plate 210 that can be used to direct the light from the bottom lamp 240 to the edge of the semiconductor substrate 60. The edge reflector 264 can be mounted to the wafer plate 210 and can surround or at least partially surround the semiconductor substrate 60.

[0067] In some embodiments, additional reflectors can also be mounted on the chamber wall near the wafer plate 210. Figure 7 FIG. 13 depicts an exemplary reflector that can be mounted to the processing chamber wall and can be used as a mirror for heating light. More specifically, Figure 7 FIG. 15 shows an exemplary wedge reflector 272 mounted to the lower chamber wall 254. Figure 7 Also illustrated is the reflective element 274 of the reflector 270 mounted to the upper chamber wall 252. The uniformity of the processing of the semiconductor substrate 60 can be adjusted by changing the reflectivity of the wedge reflector 272 and / or other reflective elements (such as the reflective element 274) in the processing chamber 200.

[0068] Figures 8 to 11 FIG. 21 depicts aspects of an exemplary upper arc lamp 220 that can be used as a source of intense millisecond-long exposure for the top surface of the semiconductor substrate 60. For example, Figure 8Depicts a cross-sectional view of an exemplary arc lamp 220. The arc lamp 220 can be, for example, an open flow arc lamp, where pressurized argon gas (or other suitable gas) is converted into high-pressure plasma during an arc discharge. The arc discharge occurs in a quartz tube 225 between a negatively charged cathode 222 and a spaced-apart positively charged anode 230 (e.g., spaced apart by about 300 mm). Once the voltage between the cathode 222 and the anode 230 reaches the breakdown voltage of argon (e.g., about 30 kV) or the breakdown voltage of other suitable gas, a stable low-inductance plasma is formed, and the stable low-inductance plasma emits light in the visible and UV ranges of the electromagnetic spectrum. As Figure 9 shown, the lamp can include a lamp reflector 262, which can be used to reflect light provided by the lamp for processing the semiconductor substrate 60.

[0069] Figure 10 and Figure 11 Depicts aspects of an exemplary operation of the arc lamp 220 in a millisecond annealing system 80 according to an exemplary embodiment of the present disclosure. More specifically, the plasma 226 is contained within the quartz tube 225, and the quartz tube 225 is internally water-cooled by a water wall 228. The water wall 228 is injected at the cathode end of the lamp 200 at a high flow rate and discharged at the anode end. The same is true for the argon gas 229, which also enters the lamp 220 at the cathode end and is discharged from the anode end. The water forming the water wall 228 is injected perpendicular to the lamp axis, such that centrifugal action creates a water vortex. Thus, a channel for the argon gas 229 is formed along the centerline of the lamp. The argon gas column 229 rotates in the same direction as the water wall 228. Once the plasma 226 is formed, the water wall 228 protects the quartz tube 225 and confines the plasma 226 to the central axis. Only the water wall 228 and the electrodes (cathode 230 and anode 222) are in direct contact with the high-energy plasma 226.

[0070] Figure 11 Depicts a cross-sectional view of an exemplary electrode (e.g., cathode 230) used in conjunction with an arc lamp according to an exemplary embodiment of the present disclosure. Figure 11 Depicts the cathode 230. However, a similar configuration can be used for the anode 222.

[0071] In some embodiments, when the electrodes are subjected to high thermal loads, one or more electrodes can each include a tip 232. The tip can be made of tungsten. The tip can be coupled to and / or fused to a water-cooled copper heat sink 234. The copper heat sink 234 can include at least a portion of an internal cooling system of the electrode (e.g., one or more water-cooled channels 236). The electrode can also include a brass base 235 having water-cooled channels 236 to provide circulation of water or other fluid and cooling of the electrode.

[0072] The arc lamp used in an exemplary millisecond annealing system according to aspects of the present disclosure can be an open flow system for water and argon. However, for reasons of maintenance, in some embodiments, both media can be circulated in a closed loop system.

[0073] Figure 12 An exemplary closed loop system 300 is depicted. The exemplary closed loop system 300 is used to supply the water and argon required to operate an open flow argon arc lamp used in a millisecond annealing system according to an exemplary embodiment of the present disclosure.

[0074] More specifically, high purity water 302 and argon 304 are supplied to the lamp 220. The high purity water 302 is used for the water wall and for cooling the electrodes. Exiting the lamp is a gas / water mixture 306. This water / gas mixture 306 is separated by a separator 310 into gas-free water 302 and dry argon 304 before it can be re-supplied to the inlet of the lamp 220. To create the required pressure drop across the lamp 220, the gas / water mixture 306 is pumped by means of a water-driven ejector pump 320.

[0075] A high power electric pump 330 provides the water pressure to drive the water wall in the lamp 220, the cooling water for the lamp electrodes, and the motive flow of the ejector pump 320. The separator 310 downstream of the ejector pump 320 can be used to extract the liquid and gas phases from the mixture (argon). The argon is further dried in a coalescing filter 340 before it re-enters the lamp 220. Additional argon can be supplied from an argon source 350 if needed.

[0076] The water passes through one or more particle filters 350 to remove particles sputtered into the water by the electric arc. Ionic contaminants are removed by ion exchange resin. A portion of the water flows through a mixed bed ion exchange filter 370. The inlet valve 372 to the ion exchange bypass 370 can be controlled by the water resistivity. If the water resistivity drops below a lower limit value, the valve 372 opens, and when the water resistivity reaches an upper limit value, the valve 372 closes. The system can include an activated carbon filter bypass circuit 380 in which a portion of the water can be additionally filtered to remove organic contaminants. To maintain the water temperature, the water can be passed through a heat exchanger 390.

[0077] A millisecond annealing system according to an exemplary embodiment of the present disclosure can include the ability to independently measure the temperature of two surfaces (e.g., a top surface and a bottom surface) of a semiconductor substrate. Figure 13 An exemplary temperature measurement system 150 for a millisecond annealing system 200 is depicted.

[0078] Figure 13A simplified representation of a millisecond annealing system 200 is shown. The temperatures on both sides of the semiconductor substrate 60 can be independently measured by temperature sensors, such as temperature sensor 152 and temperature sensor 154. Temperature sensor 152 can measure the temperature of the top surface of the semiconductor substrate 60. Temperature sensor 154 can measure the bottom surface of the semiconductor substrate 60. In some embodiments, a narrowband pyrometric sensor having a measurement wavelength of about 1400 nm can be used as temperature sensor 152 and / or temperature sensor 154 to measure the temperature of, for example, the central region of the semiconductor substrate 60. In some embodiments, temperature sensors 152 and 154 can be ultra-fast radiometers (UFRs) with a sampling rate high enough to resolve the millisecond temperature spikes caused by flash heating.

[0079] The readings of temperature sensors 152 and 154 can be emissivity compensated. As Figure 13 shown, the emissivity compensation scheme can include a diagnostic flash 156, a reference temperature sensor 158, and temperature sensors 152 and 154 configured to measure the temperatures of the top and bottom surfaces of the semiconductor wafer. The diagnostic heating and measurement can be used with the diagnostic flash 156 (e.g., a test flash). The measurements from the reference temperature sensor 158 can be used for emissivity compensation of temperature sensors 152 and 154.

[0080] In some embodiments, the millisecond annealing system 200 can include a water window. The water window can provide a filter that suppresses lamp radiation in the measurement bands of temperature sensors 152 and 154, such that temperature sensors 152 and 154 measure only the irradiation from the semiconductor substrate.

[0081] The readings of temperature sensors 152 and 154 can be provided to the processor circuit 160. The processor circuit 160 can be located within the housing of the millisecond annealing system 200, but alternatively, the processor circuit 160 can be located remotely from the millisecond annealing system 200. If desired, the various functions described herein can be performed by a single processor circuit, or by other combinations of local and / or remote processor circuits.

[0082] As will be discussed in detail below, the temperature measurement system can include other temperature sensors, such as temperature sensors (e.g., as Figure 16 shown) configured to obtain one or more temperature measurements of the wafer support plate and / or far-infrared temperature sensors (e.g., as Figure 22As shown). The processor circuit 160 can be configured to process the measurements obtained from the temperature sensor to determine the temperature of the semiconductor substrate and / or the wafer support plate.

[0083] An alternative source for heating the semiconductor substrate to an intermediate temperature T i can be an array of tungsten-halogen lamps located in the bottom processing chamber. For example, for a total power of 250 kW, two consecutive-mode arc lamps can each have an electrical power of 125 kW. An array of 40 tungsten-halogen lamps each having 6 kW can provide the same power. Figure 14 depicts an exemplary millisecond annealing system having tungsten-halogen lamps 245 for heating the semiconductor substrate 60 to an intermediate temperature T i . The advantage of heating with halogen lamps is economy. Tungsten-halogen lamps can be cheaper and can have a longer service life. In addition, tungsten-halogen lamps only require electrical connection and do not require expensive water cooling and water treatment units.

[0084] Exemplary preheating method for chamber preconditioning

[0085] According to an exemplary aspect of the present disclosure, by using a wafer support plate temperature measurement system to determine when the equilibrium temperature is reached, the time and number of preheating dummy wafers required for the preheating chamber can be reduced. For example, in some embodiments, the wafer support plate can be heated by applying heat to a dummy wafer with a special preheating regime. Once the wafer support plate temperature reaches the desired temperature, the preheating regime execution can be stopped, and the process regime execution of the first device wafer in the wafer batch can be started.

[0086] Figure 15 depicts a flowchart of an example method (400) according to an exemplary embodiment of the present disclosure. The method (400) can be implemented in a millisecond annealing system such as one of the exemplary millisecond annealing systems discussed with reference to Figures 1 to 14 . Figure 15 depicts steps performed in a specific order for illustration and discussion purposes. Using the disclosure provided herein, one of ordinary skill in the art will understand that the various steps of any method or process described herein can be modified, adjusted, extended, omitted, and / or rearranged in various ways without departing from the scope of the present disclosure.

[0087] At (402), the method includes placing a semiconductor substrate on a wafer support plate in a processing chamber of a millisecond annealing system. For example, a dummy wafer can be placed on the wafer support plate 214 in the processing chamber 200 as shown in Figures 2 to 4 . The semiconductor substrate can be supported by support pins. The wafer support plate can be made of quartz material. For example, the wafer support plate can be a quartz glass plate.

[0088] At (404), the method can include using a temperature sensor to obtain one or more temperature measurements of the wafer support plate. Figure 16 FIG. Figure 16 depicts an exemplary processing chamber 80 according to an exemplary embodiment of the present disclosure having a temperature sensor 162 (e.g., a quartz pyrometer) configured to determine the temperature of a wafer support plate 214. As shown, the temperature sensor 162 is mounted at the bottom of the processing chamber at one of the corners of the bottom chamber 204 such that the field of view of the temperature sensor 162 is not blocked by the semiconductor substrate 60 and the water window 260. In some embodiments, the temperature sensor 162 can be directed to the center of the wafer support plate 214.

[0089] In some embodiments, the temperature sensor 162 can be a pyrometer having a measurement wavelength with a transmission cutoff greater than that of quartz (e.g., greater than about 4 μm). For example, Figure 17 FIG. Figure 17 depicts a typical thermal emission spectrum 502 associated with a wafer support plate made of quartz. As shown, beyond about 4 μm, the quartz of the support plate is opaque and emits thermal radiation. The thermal radiation can be measured by the temperature sensor 162 for temperature measurement to determine the temperature of the wafer support plate.

[0090] At Figure 15 (406), the method can include determining whether the temperature of the wafer support plate has reached a threshold temperature (e.g., a preset temperature). The threshold temperature can be associated with the equilibrium temperature of the wafer support plate. If the temperature of the wafer support plate has not reached the threshold temperature (e.g., is not greater than or equal to the threshold temperature), then method (400) can include applying a preheat regime to heat the wafer support plate and the semiconductor substrate (e.g., a dummy wafer), as Figure 15 shown in (408). In some embodiments, the preheat regime can use only continuous mode lamps to heat a dummy wafer placed on the wafer support plate. In some embodiments, the lamps can operate in a closed loop control, where the semiconductor substrate temperature and / or the wafer support plate temperature are used as control inputs.

[0091] In some embodiments, the heating cycle of the preheat regime can include one or more combinations of soak and spike wafer temperature set points, and flash heating using flash lamps. In some embodiments, the heating cycle does not use a closed loop mode. Instead, the continuous mode lamps operate in an open loop manner at a fixed power value. In some embodiments, the heating cycle of the preheat regime includes a cooling stage prior to the heating stage to improve the starting temperature consistency and thus improve the repeatability of the preconditioning.

[0092] If the temperature of the wafer support plate has reached a threshold temperature, method (400) may include stopping the preheating regime (410). Method (400) may then include loading a device semiconductor substrate for processing (412) and applying a process regime to perform a heat treatment on the semiconductor substrate (414). The process regime may be different from the preheating regime and may include a regime for processing a device semiconductor substrate from among a plurality of semiconductor substrates.

[0093] Exemplary pseudo-wafer-free preheating method

[0094] According to an exemplary aspect of the present disclosure, a preheating method that does not require a preheating dummy wafer can be implemented. The wafer support plate may be made of quartz, which is not easily heated by light due to its optical properties. In a millisecond annealing system according to an exemplary embodiment of the present disclosure, an arc lamp (e.g., an argon arc lamp) may be used to process a semiconductor substrate. The lamp radiation emitted from the lamp may mainly include light having a wavelength less than 1.5 μm, which is the wavelength range transmitted by the water window. In other rapid thermal processing systems, the light source may be a tungsten halogen lamp at about 3000 K, where the peak of the spectrum is at about 1 μm. Quartz glass may be transparent to light up to about 2 μm, where the transmission coefficient is greater than about 90%. Therefore, the heating rate of the wafer support plate by directly absorbing the light from the arc lamp is small.

[0095] In a preheating method using a preheating dummy wafer, such as Figure 15 the method shown, this difficulty can be avoided. In these exemplary embodiments, light is mainly used to heat the semiconductor substrate, which is a good absorber of light in the UV to near-infrared region (e.g., from about 0.2 μm to about 1 μm). Since the dummy wafer re-emits light in a wavelength range determined by its temperature (Planck's law), the short-wavelength light of the heating source is converted into the long-wavelength range. For example, a semiconductor substrate at 1000 °C emits almost all of its radiation in a wavelength range greater than about 2 μm, which is easily absorbed by the quartz material. Therefore, the quartz wafer support plate is indirectly heated by the secondary radiation from the semiconductor substrate.

[0096] According to an exemplary embodiment of the present disclosure, a method is provided for heating a highly transparent quartz of a wafer support plate by light without the need for the presence of a semiconductor substrate. The method may utilize the same principle as Figure 15 the method of. For example, the wafer support plate temperature is measured by a quartz pyrometer sensor, for example. A preheating regime may be applied until the temperature of the wafer support plate reaches a threshold temperature (e.g., a temperature related to the equilibrium temperature of the wafer support plate).

[0097] In a system where the heating source is a halogen lamp, the sensor signal contains not only radiation from the wafer support plate but also radiation from the light source itself. Therefore, the temperature of the wafer support plate can only be accurately measured when the lamp is off.

[0098] In some applications, small pieces of silicon are part of the chamber. These small pieces of silicon remain in the chamber even when there is no semiconductor substrate in the chamber. In addition to the quartz material of the wafer support plate, these silicon pieces are good absorbers of light and do not actively cool, so they can quickly reach the melting point temperature. The same is true for every other material (e.g., rubber pads) such as quartz that has a high light absorption rate and a low melting point. Therefore, the maximum allowable heating power can be determined by the materials in the chamber.

[0099] Another difficulty in directly heating a quartz plate is that the thermal conductivity of quartz is very small. Therefore, when heating without a semiconductor substrate, the temperature distribution of the quartz plate is different from the static situation of a semiconductor substrate. The temperature distribution mainly presents the shape of the heating source. It is a circular pattern in the case of secondary heating through a semiconductor substrate. It is a stripe pattern in the case of direct heating through a linear heating source (e.g., arc lamp and tungsten halogen lamp).

[0100] The preheating method according to an exemplary aspect of the present disclosure can overcome this difficulty by using relaxation caused by cooling, and the temperature distribution becomes stable over time through relaxation. For example, Figure 19 A graphical representation of the temperature distribution of the wafer support plate with relaxation is depicted. As shown, through heat conduction, during the cooling of the wafer support plate, the stripe heat pattern formed by the lamp array is averaged. More specifically, curve 504 represents the temperature of the wafer support plate as a function of the position on the wafer support plate at the first time t1. Curve 506 represents the temperature of the wafer support plate as a function of the position on the wafer support plate at the second time t2. Curve 506 represents the temperature of the wafer support plate as a function of the position on the wafer support plate at the third time t3. Curve 508 represents the temperature of the wafer support plate as a function of the position on the wafer support plate at the third time t4. As shown, as time goes from t1 to t4, the temperature distribution of the wafer support plate approaches the average temperature 512 on the wafer support plate.

[0101] The time required for the temperature distribution to be uniform is determined by the thermal conductivity of the material and the temperature difference. This can be seen in Fourier's law of heat conduction (in one-dimensional form for simplicity):

[0102]

[0103] Q x : Heat flux density

[0104] k: Thermal conductivity of the material

[0105] dT / dx: Temperature gradient

[0106] The transparent quartz material of the heated wafer support plate can be based on an isothermal chamber. In an equilibrium state, the substrate to be heated assumes the temperature of the isothermal chamber wall, and the temperature distribution can be uniform. In a first-order approximation, the millisecond annealing system according to an exemplary embodiment of the present disclosure can be an isothermal chamber due to the highly reflective chamber wall. Given enough time, any material, regardless of its optical properties, will assume the temperature of the heating source. In other words, since the heating light is trapped in the reflective box of the chamber, it passes through the wafer support plate multiple times, absorbing, for example, 10% of the light each time it passes through. Eventually, all the light is absorbed, and the wafer support plate reaches an equilibrium temperature. In an empty processing chamber without a semiconductor substrate to be processed, the main absorber can be the quartz of the wafer support plate.

[0107] Exemplary aspects of the present disclosure relate to shortening the time required to reach the equilibrium temperature to a few minutes. To achieve this, the lamp can be operated in a pulsed manner. The heating power of each pulse can be much higher than the heating power required to reach the equilibrium temperature in the non-pulsed case (overheating). Between heating pulses, the temperature distribution can relax through heat diffusion. Due to the high thermal gradient, the time required for relaxation is much shorter than in the non-pulsed case. After multiple pulses, the wafer support plate can reach an average, uniform temperature.

[0108] Figure 19 A flowchart of an exemplary method (600) according to an exemplary embodiment of the present disclosure is depicted. Method (600) can be implemented in a millisecond annealing system such as one of the exemplary millisecond annealing systems discussed with reference to Figures 1 to 14 one of the exemplary millisecond annealing systems discussed. Figure 19 The steps depicted are performed in a specific order for purposes of illustration and discussion. Using the disclosures provided herein, a person of ordinary skill in the art will understand that the various steps of any method or process described herein can be modified, adjusted, extended, omitted, and / or rearranged in various ways without departing from the scope of the disclosure. Method (600) can be performed without a semiconductor substrate being located on the wafer support plate.

[0109] At (602), the method can include obtaining one or more temperature measurements of the wafer support plate using a temperature sensor. For example, the temperature measurement of the wafer support plate can be obtained from Figure 16 the temperature sensor 162.

[0110] At Figure 19At (604), the method may include determining whether the temperature of the wafer support plate has reached a threshold temperature (e.g., a preset temperature). The threshold temperature may be associated with the equilibrium temperature of the wafer support plate. If the temperature of the wafer support plate has not reached the threshold temperature (e.g., is not greater than or equal to the threshold temperature), then method (600) may include applying a pulsed preheating regime as shown in Figure 19 (606) to heat the wafer support plate.

[0111] Figure 20 FIG. depicts a graphical representation of an exemplary pulsed preheating regime that accelerates the time required for the wafer support plate to reach equilibrium temperature and a uniform temperature distribution. More specifically, curve 520 represents the pulsed heating of a lamp implementing a pulsed preheating regime in accordance with an exemplary aspect of the present disclosure. Curve 522 represents the temperature of the wafer support plate in response to the pulsed heating of the lamp. In some exemplary embodiments, the heating power of the pulses is such that the thermal load specification of the chamber is not exceeded. The number of pulses may be between 10 and 100, and the total time of the preheating cycle is 3 to 4 minutes.

[0112] In some embodiments, the pulsed heating may be controlled at least in part based on temperature measurements of a temperature sensor (e.g., a pyrometer) configured to measure the temperature of the wafer support plate. Since the temperature sensor signal is also affected by the light and only measures a small area on the wafer support plate, the temperature sensor signal may not be equal to the average wafer plate temperature. In some embodiments, the lamp power is cut off when the temperature sensor signal reaches an upper limit and turned on when the quartz pyrometer reaches a lower limit.

[0113] For example, Figure 20 FIG. depicts an exemplary pulsed preheating of a wafer support plate based on temperature measurements of the wafer support plate by a temperature sensor in accordance with an exemplary embodiment of the present disclosure. Curve 540 represents the pulsed heating of a lamp implementing a pulsed preheating regime in accordance with an exemplary aspect of the present disclosure. As shown, if the signal 550 from the temperature sensor reaches the upper limit 552, the pulsed heating is turned off. When the signal 550 from the temperature sensor reaches the lower limit 554, the pulsed heating is turned on. After several cycles, an approximately uniform average temperature represented by curve 560 across the entire wafer support plate is achieved.

[0114] In some embodiments, the time to reach equilibrium temperature may be shortened by "overheating" with a constant power and turned off when the temperature sensor signal reaches the target temperature. Compared to non-pulsed overheating, the pulsed overheating method may have several advantages. For example, the average temperature may be independent of the duration of the preheating cycle or the number of pulses. Additionally, the pulsed preheating method may also work in cases where the quartz temperature sensor signal is affected by parasitic signals.

[0115] Referring to Figure 19, if the temperature of the wafer support plate has reached a threshold temperature, method (600) may include stopping the preheating regime (610). Method (600) may then include loading a device semiconductor substrate for processing (612) and applying a process regime for heat treating the semiconductor substrate (614). The process regime may be different from the preheating regime and may include a regime for processing the device semiconductor substrate from among a plurality of semiconductor substrates.

[0116] Exemplary low-temperature control using temperature sensor measurements of a wafer support plate

[0117] Another exemplary aspect of the present disclosure relates to reducing the minimum intermediate temperature at which a millisecond annealing system can operate by using a far-infrared temperature sensor. As described above, typical temperature sensors for measuring the temperature of a semiconductor substrate during heat treatment include UFRs. UFRs typically use a wavelength of 1.45 μm to determine the temperature of the semiconductor substrate. At this wavelength, lightly doped silicon is transparent at temperatures below about 450°C. Thus, UFR temperature sensors cannot be used to measure temperatures below 450°C.

[0118] According to an exemplary embodiment of the present disclosure, a far-infrared temperature sensor (e.g., a quartz pyrometer temperature sensor) may be used to measure the temperature of a semiconductor substrate. The sensor may have a far-infrared spectral range of from about 8 μm to about 14 μm, which is in the range where silicon has a non-zero emissivity at low temperatures and can pick up the radiation signal.

[0119] In some embodiments, the far-infrared temperature sensor may be mounted in a corner of the top chamber of the millisecond annealing system such that its field of view is not blocked by the water window. For example, Figure 22 depicts an exemplary position of a far-infrared temperature sensor 164 in a corner of the top chamber 202 of a millisecond annealing system 80 according to an exemplary embodiment of the present disclosure. The temperature sensor 164 may have a field of view of the substrate 60 mounted in the processing chamber without being blocked by the water window.

[0120] In some embodiments, the sensor is mounted on the bottom half-chamber and directly measures the temperature of the wafer support plate that is thermally coupled to the silicon wafer. The advantage of measuring the wafer support plate rather than directly measuring the semiconductor substrate is that the wafer emissivity depends on the device pattern and can vary, while the emissivity of a quartz wafer support plate is constant.

[0121] Although the subject matter of the present invention has been described in detail with respect to specific exemplary embodiments thereof, it should be understood that those skilled in the art can readily arrive at modifications, variations, and equivalents of such embodiments upon attaining an understanding of the foregoing. Accordingly, the scope of the present disclosure is by way of example and not by way of limitation, and the subject matter disclosure does not exclude inclusion of such modifications, variations, and / or additions to the subject matter that would be obvious to one of ordinary skill in the art.

Claims

1. A temperature measurement system for a millisecond annealing system, the temperature measurement system comprising: A first far-infrared temperature sensor configured to obtain one or more temperature measurement values of a substrate in a millisecond annealing system at a processing temperature of less than 450 °C, the millisecond annealing system comprising a processing chamber having a wafer platen that divides the processing chamber into a top chamber and a bottom chamber, wherein the first far-infrared temperature sensor comprises a pyrometer associated with a spectral range of 8 μm to 14 μm, the pyrometer being configured to obtain a temperature measurement value of the substrate at a temperature below 450 °C; A second far-infrared temperature sensor configured to obtain one or more temperature measurement values of a substrate in a millisecond annealing system at a processing temperature of less than 450 °C, wherein the second far-infrared temperature sensor comprises a pyrometer associated with a spectral range of 8 μm to 14 μm; A diagnostic flash and reference temperature sensor, wherein the measurement value from the reference temperature sensor can be used as emissivity compensation for the first far-infrared temperature sensor and / or the second far-infrared temperature sensor; And A processing circuit configured to process the measurement values from the first far-infrared temperature sensor, the second far-infrared temperature sensor, and / or the reference temperature sensor to determine the temperature of the substrate at a temperature of less than 450 °C.

2. The temperature measurement system according to claim 1, wherein, The first far-infrared temperature sensor is mounted in a corner of the top chamber of the millisecond annealing system.

3. The temperature measurement system according to claim 2, wherein, The first far-infrared temperature sensor is not blocked by the water window of the millisecond annealing system.

4. The temperature measurement system according to claim 1, wherein the second far-infrared temperature sensor is configured to measure the temperature of a wafer support plate in the millisecond annealing system, the second far-infrared temperature sensor being located in the bottom processing chamber and having a field of view of the wafer support plate.

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