Heat treatment device, maintenance method for heat treatment device, and method for regenerating lamp sleeve

Abstract

To easily obtain the timing for removing granular SiOx accumulated on an inner wall of a lamp sleeve, prevent a decrease in production efficiency, and suppress an increase in power consumption required for heat treatment.SOLUTION: A heat treatment device includes a plurality of lamps 30 that heat a semiconductor substrate W, a lamp sleeve 33 that is removably arranged to surround each of the plurality of lamps and reflects light emitted by the plurality of lamps, a power source 60 that applies a lamp voltage to the plurality of lamps, a temperature detection unit 50 that detects the temperature of the semiconductor substrate, a controller 70 that controls the lamp voltage or lamp current applied to the plurality of lamps, and a warning unit 80 that issues a display or audio warning of the timing for cleaning of the lamp sleeve, and the controller causes the warning unit to issue a warning when the lamp voltage or lamp current applied to the plurality of lamps exceeds a predetermined threshold value.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a heat treatment apparatus, a maintenance method for the heat treatment apparatus, and a regenerating method for a lamp sleeve, and more particularly to a heat treatment apparatus for heat treating a semiconductor substrate by thermal energy of a lamp, a maintenance method for the heat treatment apparatus, and a regenerating method for a lamp sleeve. [Background technology]

[0002] For example, silicon wafers used as substrates for semiconductor devices are required to form a defect-free layer free of void defects called crystal originated particles (COPs) on the surface and surface layer that will become the active region of the semiconductor device. Rapid thermal processing (RTP) is known as a technology that meets this requirement.

[0003] The heat treatment equipment used for RTP (hereafter referred to as RTP equipment) is designed to rapidly heat silicon wafers to temperatures exceeding 1200°C by efficiently absorbing the light irradiated from the lamp, which is the heat source (hereafter referred to as "irradiation light"), into the silicon wafer, and to minimize energy loss.

[0004] For example, Patent Document 1 (JP 2017-11282 A) proposes a lamp sleeve that contains silver in a reflective coating that covers the periphery of the lamp in order to increase the reflectance of the light irradiated from the heat lamp (to increase the energy efficiency of the substrate being processed). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-11282 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, when heat treatment is repeatedly performed in an RTP device, a phenomenon occurs in which it is necessary to gradually increase the voltage applied to the lamp (hereinafter also referred to as "lamp voltage") in order to raise the temperature inside the chamber to a specified temperature of 1200°C or higher. As a result, there is a problem in that the power consumption required for RTP (heat treatment) gradually increases. The reason why it becomes difficult to increase the temperature of the silicon wafer is believed to be that the light irradiated from the lamp gradually becomes less able to reach the silicon wafer in proportion to the number of times the heater is operated, resulting in increased energy loss.

[0007] In order to solve this problem, the inventors of the present application conducted continuous operation of an RTP apparatus at a temperature where the maximum temperature of the silicon wafer exceeds 1200° C., and conducted extensive research to identify the cause of the change in lamp output over time. As a result, they discovered that the main cause was a decrease in reflectance due to fogging of the inner wall of the lamp sleeve arranged to enclose the heating lamp.

[0008] Furthermore, an investigation into the cause of the fogging revealed that it was caused by the accumulation of granular SiOx, and that this SiOx was generated when the glass used in the lamp jacket (lamp glass) melted due to heat from the filament.

[0009] The present invention has been made under such circumstances, and aims to easily obtain the timing for removing granular SiOx accumulated on the inner wall of the lamp sleeve, prevent a decrease in production efficiency, and suppress an increase in power consumption required for heat treatment. [Means for solving the problem]

[0010] The heat treatment apparatus of the present invention, which has been made to solve the above-mentioned problems, comprises a plurality of lamps for heating a semiconductor substrate, a lamp sleeve which is removably arranged to surround each of the plurality of lamps and reflects the light irradiated by the plurality of lamps, a power source which applies a lamp voltage to the plurality of lamps, a temperature detection unit which detects the temperature of the semiconductor substrate, a controller which controls the lamp voltage or lamp current applied to the plurality of lamps, and a warning unit which issues a visual or audio warning of the timing of cleaning of the lamp sleeve, wherein the controller controls the lamp voltage or lamp current applied to the plurality of lamps based on the temperature of the semiconductor substrate detected by the temperature detection unit, and causes the warning unit to issue a warning when the lamp voltage or lamp current applied to the plurality of lamps exceeds a predetermined threshold value. Furthermore, when the lamp voltage or lamp current applied to the multiple lamps exceeds a predetermined threshold, the controller stops applying the lamp voltage or lamp current to the lamps, and the lamp sleeve of the corresponding lamp is removed and then reattached, thereby enabling the controller to apply the lamp voltage or lamp current to the corresponding lamp.

[0011] With this configuration, the timing for removing the granular SiOx accumulated on the inner wall of the lamp sleeve can be easily obtained, and by removing the fogging caused by the accumulation of SiOx according to this timing, unnecessary chamber maintenance time is not required, and a decrease in production efficiency can be prevented. In addition, by removing the cloudiness caused by the accumulation of SiOx on the lamp sleeve, the reflectance of the irradiated light on the lamp sleeve can be restored, and the semiconductor substrate can be effectively heated to the desired temperature without increasing the lamp output, thereby suppressing an increase in power consumption required for heat treatment.

[0012] In addition, the maintenance method for a heat treatment apparatus according to the present invention, which has been devised to solve the above-mentioned problems, is characterized in that it includes the steps of controlling the lamp voltage or lamp current applied to the multiple lamps by the controller and heating the semiconductor substrate by the multiple lamps, detecting the temperature of the semiconductor substrate by the temperature detection unit and controlling the lamp voltage applied to the multiple lamps based on the temperature of the semiconductor substrate, and, when the lamp voltage or lamp current applied to the multiple lamps exceeds a predetermined threshold value, causing the warning unit to issue a display or audio warning of the timing of cleaning of a lamp sleeve that is arranged to surround each of the multiple lamps and reflects the light irradiated by the multiple lamps. In addition, after the step of issuing a warning by the warning unit using display or sound, it is desirable to have a step of removing the lamp sleeve of the corresponding lamp and cleaning the lamp sleeve using an acidic aqueous solution, and a step of attaching the cleaned lamp sleeve.

[0013] According to this method, the timing for removing the granular SiOx accumulated on the inner wall of the lamp sleeve can be easily obtained, and by removing the fogging caused by the accumulation of SiOx according to this timing, unnecessary chamber maintenance time is not required, and a decrease in production efficiency can be prevented. In addition, by removing the cloudiness caused by the accumulation of SiOx on the lamp sleeve, the reflectance of the irradiated light on the lamp sleeve can be restored, and the semiconductor substrate can be effectively heated to the desired temperature without increasing the lamp output, thereby suppressing an increase in power consumption required for heat treatment.

[0014] In addition, the lamp sleeve regeneration method of the present invention, which has been devised to solve the above-mentioned problem, is a lamp sleeve regeneration method that uses the heat treatment device maintenance method, and is characterized in that it has a step of having the controller cause the warning unit to display or sound an alarm indicating the timing for cleaning the lamp sleeve that reflects the light irradiated by the multiple lamps, and then a step of cleaning the lamp sleeve using an acidic aqueous solution. In addition, in the step of cleaning the lamp sleeve with the acidic aqueous solution, it is preferable to clean the lamp sleeve by immersing it in an HF aqueous solution having a concentration of 1% to 5% for 1 minute to 100 minutes.

[0015] According to this method, the particulate SiOx deposited on the inner wall of the lamp sleeve can be easily removed. Effect of the Invention

[0016] According to the present invention, it is possible to easily obtain the timing for removing the granular SiOx accumulated on the inner wall of the lamp sleeve, prevent a decrease in production efficiency, and suppress an increase in power consumption required for heat treatment. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a cross-sectional view that illustrates a schematic configuration of an RTP apparatus (thermal treatment apparatus) according to an embodiment of the present invention. [Diagram 2] FIG. 2 is an enlarged cross-sectional view of a halogen lamp provided in the RTP device of FIG. [Diagram 3] FIG. 3 is a flow chart showing the flow of the control method according to the present invention. [Figure 4] FIG. 4 is a micrograph showing the results of Experiment 1 of the embodiment. [Diagram 5] FIG. 5 is a graph showing the results of Experiment 3 of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The embodiment of the present invention will be described by taking as an example an RTP apparatus (thermal processing apparatus) that uses a lamp (eg, a high voltage tungsten halogen lamp) disposed within a lamp sleeve as a heat source. 1 is a cross-sectional view showing a schematic configuration of an RTP apparatus (heat treatment apparatus) 100 according to an embodiment of the present invention. The RTP apparatus 100 includes a process chamber 20 having a chamber side wall 2, a chamber bottom 4 coupled to the chamber side wall 2, and a quartz window 6 disposed over the chamber side wall 2.

[0019] The chamber sidewall 2, the chamber bottom 4, and the quartz window 6 that constitute the processing chamber 20 form a chamber 25 for heat-treating a silicon wafer W, which is a semiconductor substrate, placed therein. The RTP apparatus 100 is provided with a slit valve door (not shown) that penetrates the chamber sidewall 2 in order to transfer the silicon wafer W into the chamber 25. In this embodiment, a silicon wafer W is used as an example of the semiconductor substrate. However, the semiconductor substrate is not limited to the silicon wafer W, and may be, for example, a SiC wafer, a GaN wafer, or a wafer on which a circuit pattern is formed.

[0020] The RTP apparatus 100 also includes a gas inlet 20a formed in the chamber sidewall 2 that is connected to a gas supply 18 configured to provide one or more process gases to the chamber 25. The RTP apparatus 100 also includes a gas outlet 20b formed in the chamber sidewall 2 that is connected to a vacuum pump 21 for evacuating the chamber 25. The RTP apparatus 100 also includes a substrate support 40 that supports the silicon wafer W in the chamber 25 in the processing chamber 20. In addition, the RTP apparatus 100 also includes a rotating means (not shown) that rotates the silicon wafer W around its central axis at a predetermined speed.

[0021] The substrate support 40 includes an annular susceptor 40a that supports the outer periphery of the silicon wafer W, and a stage 40b that supports the susceptor 40a. Moreover, the temperature of the silicon wafer W in this RTP apparatus 100 is controlled using a plurality of radiation thermometers 50 (temperature detection units) embedded in the stage 40b of the substrate support unit 40. The radiation thermometers 50 are connected to a controller 70, which is a computer, and the controller 70 controls the temperature of the silicon wafer W based on temperature information of the silicon wafer W acquired by the radiation thermometers 50.

[0022] That is, the controller 70 measures the temperature at multiple points (e.g., nine points) within the substrate surface in the radial direction of the lower part of the silicon wafer W using the radiation thermometer 50, and controls the multiple halogen lamps 30 (individual ON-OFF control of each lamp, increase / decrease control of the power supply, control of the emission intensity of the emitted light, etc.) based on the measured temperatures.

[0023] The plurality of halogen lamps 30 are disposed above the quartz window 6 and configured to transmit thermal energy through the quartz window 6 toward the silicon wafer W. The plurality of halogen lamps 30 are arranged, for example, in a hexagonal pattern in a plan view. Each of the plurality of halogen lamps 60 is connected to the heating assembly base 17 for electrical connection to a power source 60.

[0024] Each halogen lamp 30 is configured, for example, as shown in Fig. 2. The halogen lamp 30 shown in Fig. 2 has a tungsten filament coil 32 disposed in lamp glass 31 made of quartz glass, and gas including halogen gas is sealed in the lamp glass 31.

[0025] The lamp glass 31 is surrounded by a cylindrical lamp sleeve 33, and the inner wall 33a of the lamp sleeve 33 is inclined so that the thermal energy emitted from the lamp glass 31 is directed downward toward the silicon wafer W. The inner wall 33a of the lamp sleeve 33 is preferably Au-plated. This is because Au plating has high heat resistance, high reflectance, and also high acid resistance. The lamp sleeve 33 is configured to be detachable from the RTP device 100, and is configured so that only the lamp sleeve 33 can be easily removed. As will be described in detail later, this configuration allows the lamp sleeve 33 to be easily cleaned, and after the lamp sleeve 33 is regenerated, it can be attached to the RTP device 100 again. A lamp voltage is applied to each halogen lamp 30 from a power source 60. The value of this lamp voltage is controlled by a controller 70. Note that the controller 70 may control a current applied to the halogen lamp 30 (hereinafter also referred to as a "lamp current") instead of the lamp voltage.

[0026] In addition, the RTP device 100 of this embodiment is equipped with a warning unit 80 for notifying the degree of contamination of the inner wall 33a of the lamp sleeve 33, for example by a screen display or an alarm sound (voice), and for encouraging cleaning of the inner wall 33a of the lamp sleeve 33. Specifically, the controller 70 issues a warning through the warning unit 80 when the lamp voltage (or lamp current) applied to the halogen lamp 30 required to raise the temperature of the silicon wafer W to a predetermined temperature (e.g., 1300°C) exceeds a predetermined threshold value.

[0027] Next, a series of operations of the thermal processing apparatus (RTP apparatus) according to the present invention will be described with reference to the flow chart of FIG. First, in the RTP apparatus 100 shown in FIG. 1, a silicon wafer W is placed in the process chamber 20 maintained at a desired initial temperature (step S1 in FIG. 3).

[0028] For example, when a silicon wafer W is heat-treated at a target temperature of 1300° C., the controller 70 determines a lamp voltage (initial setting voltage) to be applied to the corresponding halogen lamps 30, and applies the lamp voltage to each halogen lamp 30 via the power supply 60. Each halogen lamp 30 irradiates light corresponding to the supplied lamp voltage toward the silicon wafer W. This starts heating the silicon wafer W (step S2 in FIG. 3).

[0029] In each halogen lamp 30, the surface of the lamp glass 31 on which the filament coil 32 is disposed is sublimated into granular SiOx by the heat of the filament coil 32, and adheres to the inner wall 33a of the lamp sleeve 33. Therefore, when the RTP device 100 is continuously operated and heat treatment is repeated, the granular SiOx accumulates on the inner wall 33a of the lamp sleeve 33, causing clouding and reducing the heat reflection function of the lamp sleeve 33. The accumulation of SiOx on the inner wall of the lamp sleeve is noticeable in heat treatment at 1250°C or higher, so it is particularly preferable to apply this embodiment to an RTP device that performs heat treatment at a maximum reaching temperature of 1250°C or higher.

[0030] While the silicon wafer W is being heated, the radiation thermometer 50 measures the temperatures at multiple points (eg, nine points) within the substrate surface in the radial direction of the lower part of the silicon wafer W (step S3 in FIG. 3). The controller 70 measures the voltage (or current) applied to the halogen lamp 30 based on the temperature measured in step S3 (step S4 in FIG. 3), and controls the applied voltage (or current) so that the silicon wafer W reaches a desired temperature. Here, when the voltage (or current) applied to the halogen lamp 30 exceeds a predetermined threshold value (step S5 in FIG. 3), the controller 70 causes the warning unit 80 to display a warning on a screen or by sound that cleaning of the lamp sleeve 33 is necessary (step S6 in FIG. 3). In addition, the controller 70 stops the application of the lamp voltage to the halogen lamp 30 and stops the operation of the RTP device 100 (step S8 in FIG. 3).

[0031] When the warning unit 80 issues a warning, the lamp sleeve 33 may be cleaned after the operation of the RTP device 100 is stopped. That is, the lamp sleeve 33 is removed and cleaned using an acidic aqueous solution (for example, immersed in an HF aqueous solution with a concentration of 1% to 5% for 1 min to 100 min), and then the cleaned lamp sleeve 33 is attached. As a result, the controller 70 enables the application of a lamp voltage to the halogen lamp 30, and the operation of the RTP device 100 is resumed. When an HF aqueous solution is used as the acidic aqueous solution, if the concentration is less than 1%, cleaning may take a long time. Also, if the concentration exceeds 5%, the nickel body of the Au-plated lamp sleeve 33 may be damaged. Therefore, the concentration of the HF aqueous solution is preferably 1% to 5%. On the other hand, in step S5 of FIG. 3, if the voltage (or current) applied to the halogen lamp 30 does not exceed the predetermined threshold, the heat treatment of the silicon wafer W is continued until the heat treatment is completed (step S7 of FIG. 3).

[0032] As described above, according to the embodiment of the present invention, the timing for removing the granular SiOx accumulated on the inner wall 33a of the lamp sleeve 33 can be easily obtained, and by removing the fogging caused by the accumulation of SiOx according to this timing, unnecessary chamber maintenance time is not required, and a decrease in production efficiency can be prevented. In addition, by removing the cloudiness caused by the accumulation of SiOx on the inner wall 33a of the lamp sleeve 33, the reflectance of the irradiated light at the lamp sleeve 33 can be restored, and the semiconductor substrate can be effectively heated to the desired temperature without increasing the lamp output, thereby suppressing an increase in power consumption required for heat treatment.

[0033] In the above embodiment, the magnitude of the voltage supplied to the halogen lamp 30 is monitored by the controller 70, but the present invention is not limited to this. The magnitude of the current supplied to the halogen lamp 30 may be monitored, and a warning may be issued depending on whether or not the current exceeds a predetermined threshold value.

[0034] Furthermore, in the above embodiment, an example has been described in which the lamp voltage applied to the plurality of halogen lamps 30 is uniformly controlled, but the present invention is not limited to this. For example, each halogen lamp 30 may measure the temperature of each corresponding region of the silicon wafer W, and the voltage applied to each corresponding halogen lamp 30 may be controlled and monitored based on the temperature of each region. More specifically, the silicon wafer W may be divided into a number of concentric regions (regions 1, 2, ..., n) having a predetermined width in the radial direction from the center thereof, and the voltage applied to each of the corresponding halogen lamps 30 may be controlled based on the temperature of each region. EXAMPLES

[0035] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples.

[0036] (Experiment 1) In experiment 1, it was verified whether the inner wall of the lamp sleeve of the halogen lamp fogs up by continuously operating the RTP device. The RTP equipment was used to perform 100,000 continuous heat treatment processes on semiconductor silicon wafers at a heating temperature of 1,300°C. The inner wall of the lamp sleeve that had been used 100,000 times was observed by SEM / EDX. Figure 4 shows the micrograph of the observation results.

[0037] SEM observation revealed that the inner wall of the sleeve was black and cloudy, with granular deposits. EDX analysis revealed that the granular deposits were SiOx, a material made up of Si and O, which are not found in new lamp sleeves.

[0038] (Experiment 2) In experiment 2, a preferable concentration of the HF solution was examined when cleaning a lamp sleeve having SiOx attached thereto with the HF solution. In Example 1, the lamp sleeve used in Experiment 1 after continuous use was washed for 1 min with a 5% HF aqueous solution. As a result, SiOx was dissolved in HF and the cloudiness was eliminated. In addition, the inner wall of the sleeve of the washed regenerated product was observed by SEM / EDX, and it was found that SiOx was largely removed, though not completely.

[0039] In Example 2, the lamp sleeve used in Experiment 1 after continuous use was washed with a 1% HF aqueous solution and observed until SiOx was dissolved by HF and the cloudiness disappeared. As a result, it took 100 minutes for SiOx to be dissolved by HF and the cloudiness to disappear. This washing time was determined to be the maximum value in a practical range.

[0040] In Comparative Example 1, the lamp sleeve used in Experiment 1 after continuous use was washed with a 0.9% HF aqueous solution and observed until SiOx dissolved in HF and the cloudiness disappeared. As a result, it took more than 100 minutes for SiOx to dissolve in HF and the cloudiness to disappear. In other words, it was confirmed that an HF aqueous solution with a concentration of 1% or more is preferable because it takes too long to clean with an HF aqueous solution with a concentration of less than 1%.

[0041] In Comparative Example 2, the lamp sleeve after continuous use used in Experiment 1 was washed for 1 min with a 6% HF aqueous solution. As a result, SiOx was dissolved by HF and the cloudiness was eliminated, but the Au plating covering the lamp sleeve peeled off, and there was a risk of damaging the nickel body of the lamp sleeve. Therefore, it was confirmed that the concentration of the HF aqueous solution is preferably 1% or more and 5% or less, and the cleaning time (immersion time) is in the range of 1 minute or more and 100 minutes or less.

[0042] (Experiment 3) In experiment 3, the light reflectance was measured using a SolisSpec-3700DUV ultraviolet-visible-near infrared spectrophotometer (manufactured by Shimadzu Corporation) for the inner wall of the continuously used lamp sleeve (second-hand product) obtained in experiment 1, the inner wall of the lamp sleeve (recycled product) cleaned and regenerated in experiment 2, and the inner wall of a new lamp sleeve. The results are shown in the graph in Figure 5. The vertical axis of the graph in Figure 5 is the reflectance (%), and the horizontal axis is the wavelength (nm).

[0043] As shown in the graph in Figure 5, the reflectance of the inner wall of the cleaned and regenerated lamp sleeve (regenerated product) at wavelengths of 900 nm or longer, which have a large effect on heating of silicon wafers, had recovered to about 53% to 90% of that of the inner wall of the lamp sleeve (used product) that had been continuously used, meaning that although not completely, it was close to that of a new product. [Explanation of symbols]

[0044] 20 Processing Room 20a Gas inlet 20b Gas outlet 25 Chambers 30 Halogen lamp (lamp) 33 Lamp Sleeve 33a inner wall 40 Substrate support 40a Susceptor 50 Radiation thermometer (temperature detection part) 60 power supply 70 Controller 80 Warning section W Silicon wafer (semiconductor substrate)

Claims

1. a plurality of lamps for heating the semiconductor substrate; a lamp sleeve that is detachably disposed so as to surround each of the plurality of lamps and that reflects light emitted from the plurality of lamps; a power source that applies a lamp voltage to the plurality of lamps; a temperature detection unit for detecting a temperature of the semiconductor substrate; A controller for controlling a lamp voltage or a lamp current applied to the plurality of lamps; a warning unit that warns the user by display or sound when it is time to clean the lamp sleeve; The controller controls the lamp voltage or lamp current applied to the plurality of lamps based on the temperature of the semiconductor substrate detected by the temperature detection unit, and causes the warning unit to issue a warning when the lamp voltage or lamp current applied to the plurality of lamps exceeds a predetermined threshold value.

2. the controller stops application of a lamp voltage or a lamp current to the plurality of lamps when a lamp voltage or a lamp current applied to the plurality of lamps exceeds a predetermined threshold value; 2. The heat treatment apparatus according to claim 1, wherein the controller enables application of a lamp voltage or a lamp current to the corresponding lamp by removing a lamp sleeve from the corresponding lamp and then reattaching the lamp sleeve.

3. A maintenance method for a heat treatment apparatus according to claim 1, comprising the steps of: The controller a step of controlling a lamp voltage or a lamp current applied to the plurality of lamps and heating a semiconductor substrate by the plurality of lamps; detecting a temperature of the semiconductor substrate by the temperature detection unit, and controlling lamp voltages applied to the plurality of lamps based on the temperature of the semiconductor substrate; A maintenance method for a heat treatment apparatus, comprising: a step of, when the lamp voltage or lamp current applied to the plurality of lamps exceeds a predetermined threshold, having the warning unit warn by display or sound that it is time to clean the lamp sleeves, which are arranged to surround each of the plurality of lamps and reflect the light irradiated by the plurality of lamps.

4. After the step of causing the warning unit to warn using a display or a sound, removing the lamp sleeve of the lamp and cleaning the lamp sleeve with an acidic aqueous solution; 4. The method for maintaining a thermal processing apparatus according to claim 3, further comprising the step of attaching the cleaned lamp sleeve.

5. A method for regenerating a lamp sleeve using the method for maintaining a heat treatment apparatus according to claim 3, comprising the steps of: a step of causing the warning unit to warn by display or sound of the timing for cleaning the lamp sleeve that reflects the light emitted from the plurality of lamps by the controller; A method for regenerating a lamp sleeve, comprising the step of cleaning the lamp sleeve with an acidic aqueous solution.

6. In the step of cleaning the lamp sleeve with an acidic aqueous solution, 6. The method for regenerating a lamp sleeve according to claim 5, further comprising the step of immersing the lamp sleeve in an aqueous HF solution having a concentration of 1% to 5% for 1 min to 100 min for cleaning.

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