Method for manufacturing epitaxial silicon wafers and epitaxial growth apparatus

Abstract

Even when using a low-resistivity silicon substrate doped with a high concentration of dopant, the substrate temperature during the epitaxial growth process is stably controlled. [Solution] The method for manufacturing an epitaxial wafer according to the present invention involves placing 1.8 × 10 in a chamber 10. 19 atoms / cm 3 The process includes a substrate introduction step of introducing a silicon substrate W having the above-mentioned dopant concentrations, a heating step of heating the silicon substrate W to a target temperature, and an epitaxial growth step of supplying a mixed gas containing a source gas and a carrier gas into the chamber 10 while maintaining the silicon substrate W at the target temperature to grow an epitaxial film on the main surface of the silicon substrate W. The epitaxial growth step involves PID control of the output of the heater 20 based on the temperature detected by an upper pyrometer 22A installed above the silicon substrate W, and lowering the sensitivity of the proportional control of the PID control compared to before the start of the epitaxial growth step.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing epitaxial silicon wafers and an epitaxial growth apparatus, and more particularly to temperature control during the epitaxial growth process. [Background technology]

[0002] Epitaxial silicon wafers are widely used as substrate materials for semiconductor devices. Epitaxial silicon wafers are formed by depositing a single-crystal film (epitaxial film) on the main surface of a bulk silicon substrate. Due to their high crystal integrity, it is possible to manufacture high-quality and reliable semiconductor devices. In particular, when the dopant concentration is 5 × 10⁻¹⁶, 19 atoms / cm 3 Epitaxial wafers using the low-resistance substrates described above are essential for reducing the power consumption of low-voltage power MOSFETs used in power supply systems for personal computers and smartphones.

[0003] Epitaxial silicon wafers are manufactured by setting a silicon substrate in the chamber of an epitaxial growth apparatus, and then supplying a silicon source gas such as trichlorosilane together with a carrier gas and a dopant gas to grow a single-crystal silicon film in the vapor phase on the main surface of the wafer. Regarding the manufacturing method of epitaxial silicon wafers, for example, Patent Document 1 describes that when manufacturing an epitaxial wafer by forming an epitaxial film on the surface of a silicon substrate, the lamp output is PID controlled so that the surface temperature of the silicon substrate detected by the upper pyrometer reaches a desired temperature.

[0004] Furthermore, Patent Document 2 contains 5 × 10 19 atoms / cm 3In the method for manufacturing an epitaxial wafer using a phosphorus-doped, low-resistivity silicon substrate, it is described that, in order to suppress the occurrence of stacking faults, the epitaxial layer is grown on the silicon substrate at a temperature of 1040°C or higher and 1130°C or lower, and at a growth rate of 2 μm / min or lower. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-174807 [Patent Document 2] Japanese Patent Publication No. 2017-195273 [Overview of the project] [Problems that the invention aims to solve]

[0006] During the epitaxial growth process, the temperature of the silicon substrate is kept constant by PID control of the ramp output based on the temperature detected by the upper and lower pyrometers. Conventionally, when controlling the temperature during epitaxial growth, the sensitivity of the proportional control in the PID control was increased, and the amount of adjustment by the ramp output was increased to enhance temperature controllability and adjust the substrate temperature.

[0007] However, when manufacturing epitaxial wafers using low-resistivity silicon substrates highly doped with dopants such as phosphorus, the temperature detected by the upper pyrometer hunts during the epitaxial growth process. This causes large fluctuations in the ramp output, leading to unstable temperature control of the silicon substrate.

[0008] The present invention has been made in view of the above circumstances, and the object of the present invention is to provide a method for manufacturing an epitaxial silicon wafer and an epitaxial growth apparatus that can stably control the substrate temperature during the epitaxial growth process even when a silicon substrate doped with a high concentration of dopant is used. [[Means for Solving the Problems]]

[0009] In order to solve the above-mentioned problems, the inventors of the present application conducted intensive studies, and as a result, found that the reason why the temperature control of a silicon substrate becomes unstable is that even when the actual temperature of the silicon substrate does not change, the temperature detected by an upper pyrometer fluctuates due to the influence of dopants in the silicon substrate, causing excessive temperature control to act.

[0010] The present invention is based on such technical findings, and the method for manufacturing an epitaxial silicon wafer according to the present invention comprises placing 1.8×10 19 atoms / cm 3 a substrate introduction step of introducing a silicon substrate having the above dopant concentration into a chamber of a single-wafer epitaxial growth apparatus; a temperature raising step of heating the silicon substrate with a heater to raise the temperature to a target temperature; and an epitaxial growth step of supplying a mixed gas containing a source gas and a carrier gas into the chamber while maintaining the silicon substrate at the target temperature to grow an epitaxial film on the main surface of the silicon substrate, wherein in the epitaxial growth step, the output of the heater is PID-controlled based on the temperature detected by an upper pyrometer installed above the silicon substrate, and the sensitivity of proportional control of the PID control is made lower than that before the start of the epitaxial growth step.

[0011] According to the present invention, when PID-controlling the temperature of a silicon substrate during an epitaxial growth process, the sensitivity of proportional control of the PID control is lowered, so excessive temperature control can be suppressed, and the temperature of the silicon substrate can be stably controlled.

[0012] In the present invention, the heating step controls the output of the heater using PID control based on both the temperature detected by the upper pyrometer and the temperature detected by the lower pyrometer installed below the silicon substrate, and sets the proportional gain of the PID control to a first value. The epitaxial growth step sets the proportional gain of the PID control to a second value smaller than the first value, preferably 0.07 to 0.5 times the first value. This makes it possible to stabilize the substrate temperature by suppressing fluctuations in the heater output during the epitaxial growth process.

[0013] In the present invention, it is preferable that the epitaxial growth step increases the sensitivity of the integral control of the PID control compared to before the start of the epitaxial growth step. In this case, it is preferable that the heating step sets the integral gain in the PID control to a third value, and the epitaxial growth step sets the integral gain in the PID control to a fourth value greater than the third value, and that the fourth value is greater than six times the third value. This compensates for the insufficient control caused by reducing the proportional gain, and enables further optimization of the PID control of the heater output.

[0014] In the present invention, it is preferable to change the PID control conditions when the temperature detected by the upper pyrometer has exceeded the target temperature due to overshoot and reached the peak temperature, and then returned to the target temperature. This allows the PID control conditions to be changed at an appropriate timing.

[0015] A method for manufacturing an epitaxial silicon wafer according to the present invention further comprises, after the temperature raising step and before the epitaxial growth step, a hydrogen baking step of removing a surface oxide film by heat-treating the silicon substrate in a hydrogen atmosphere, wherein in the hydrogen baking step, the output of the heater may be PID-controlled based on the temperature detected by the upper pyrometer and the temperature detected by the lower pyrometer, and the proportional gain of the PID control may be maintained at the first value. This enables stabilization of the heater output even during hydrogen baking.

[0016] In the present invention, the concentration of the dopant is 3.6×10 19 ~1.18×10 20 atoms / cm 3 The effect of the present invention is remarkable when manufacturing an epitaxial silicon wafer using a silicon substrate doped with a high concentration of dopant, because hunting of the temperature detected by the upper pyrometer becomes significant during the epitaxial growth process.

[0017] Furthermore, the epitaxial growth apparatus according to the present invention comprises a chamber, a susceptor supporting a silicon substrate within the chamber, a heater for heating the silicon substrate, an upper pyrometer positioned above the center of the susceptor and measuring the temperature of the upper surface of the silicon substrate on the susceptor, a lower pyrometer positioned below the center of the susceptor and measuring the temperature of the lower surface of the susceptor, and a control unit that PID-controls the output of the heater based on the temperature detected by the upper pyrometer, or by both the upper and lower pyrometers, wherein the control unit controls the upper pyrometer The method is characterized by sequentially performing a heating step in which the silicon substrate is heated by the heater to a target temperature based on both the detected temperature of the lower pyrometer and the detected temperature of the lower pyrometer, and an epitaxial growth step in which a mixed gas containing a source gas and a carrier gas is supplied into the chamber to grow an epitaxial film on the main surface of the silicon substrate while maintaining the silicon substrate at the target temperature based on the detected temperature of the upper pyrometer, and by lowering the sensitivity of the proportional control of the PID control during the epitaxial growth step compared to before the start of the epitaxial growth step.

[0018] According to the present invention, when controlling the temperature of a silicon substrate using PID control during the epitaxial growth process, the sensitivity of the proportional control of the PID control is reduced, thereby suppressing excessive temperature control and enabling stable control of the silicon substrate temperature.

[0019] The epitaxial growth apparatus according to the present invention comprises a lower pyrometer installed below the susceptor for measuring the temperature of the lower surface of the susceptor, and the control unit preferably sets the proportional gain of the PID control to a first value in the heating step and sets the proportional gain of the PID control to a second value smaller than the first value in the epitaxial growth step. Furthermore, the heater preferably includes a plurality of upper lamps arranged in a ring shape above the chamber and a plurality of lower lamps arranged in a ring shape below the chamber. [Effects of the Invention]

[0020] Thus, according to the present invention, it is possible to provide a method for manufacturing an epitaxial silicon wafer and an epitaxial growth apparatus that can stably control the substrate temperature during the epitaxial growth process even when using a silicon substrate doped with a high concentration of dopant. [Brief explanation of the drawing]

[0021] [Figure 1] Figure 1 is a schematic cross-sectional view showing the configuration of an epitaxial growth apparatus used in the manufacture of epitaxial silicon wafers. [Figure 2] Figure 2 is a flowchart showing the manufacturing process of an epitaxial silicon wafer. [Figure 3] Figures 3(a) and 3(b) are graphs showing measured values ​​during the epitaxial growth process, where Figure 3(a) shows the center temperature of the silicon substrate measured by the upper pyrometer, and Figure 3(b) shows the heater output (ramp output). [Figure 4] Figures 4(a) and 4(b) are graphs showing measured values ​​during the epitaxial growth process before and after optimization of the PID control conditions. Figure 4(a) shows the center temperature of the silicon substrate measured by the upper pyrometer, and Figure 4(b) shows the heater output (ramp output). [Modes for carrying out the invention]

[0022] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings.

[0023] Figure 1 is a schematic cross-sectional view showing the configuration of an epitaxial growth apparatus used in the manufacture of epitaxial silicon wafers.

[0024] As shown in Figure 1, the epitaxial growth apparatus 1 is a single-wafer type apparatus that processes silicon substrates one by one, and comprises a chamber 10 in which the silicon substrate W is housed, a susceptor 12 that horizontally supports the silicon substrate W from the bottom side within the chamber 10, a support shaft 14 that rotatably supports the susceptor 12, a plurality of upper lamps 20A that heat the silicon substrate W from above, a plurality of lower lamps 20B that heat the silicon substrate W from below, an upper pyrometer 22A positioned above the chamber 10 to measure the temperature of the upper surface of the silicon substrate W, and a lower pyrometer 22B positioned below the chamber 10 to measure the temperature of the lower surface of the susceptor 12. The predetermined directions in the epitaxial growth apparatus 1 are determined based on its normal operating conditions, "up" means the direction from the bottom surface to the top surface of the silicon substrate W placed horizontally within the apparatus, and "down" means the direction from the top surface to the bottom surface of the silicon substrate W.

[0025] Chamber 10 comprises an upper dome 11A, a lower dome 11B, and a dome mounting body 11C for attaching them. The dome mounting body 11C is made of stainless steel, while the upper dome 11A and lower dome 11B are made of transparent quartz material that does not block radiant heat from the heat source. The upper dome 11A and lower dome 11B are detachably fixed to the dome mounting body 11C, and during maintenance, they are removed from the dome mounting body 11C to perform maintenance work such as removing silicon by-products adhering to the inner surface. The inside of Chamber 10, sandwiched between the upper dome 11A and the lower dome 11B, is a sealed space.

[0026] A gas supply port 16 is provided on one side of the chamber 10, and a gas outlet 18 is provided on the opposite side. A mixed gas of source gas, carrier gas, and dopant gas is supplied into the chamber 10 from the gas supply port 16 and exhausted from the gas outlet 18. A baffle and a flow straightening member are provided at the gas supply port 16 to control the flow of the mixed gas.

[0027] The susceptor 12 is a disc-shaped component made of carbon graphite with a SiC coating on its surface. A circular recess (counterbored portion) is formed on the upper surface of the susceptor 12 to stably hold the silicon substrate W. The susceptor 12 also has three through holes, and a lift pin is inserted into each of the three through holes. The lift pins are simultaneously driven up and down by a lift pin lifting mechanism located below the susceptor 12. As a result, the lift pins can support the silicon substrate W placed on the susceptor in a way that allows for free movement up and down.

[0028] The upper and lower lamps consist of halogen lamps or infrared lamps. Multiple upper lamps are arranged in a ring shape above the chamber 10, and multiple lower lamps are arranged in a ring shape below the chamber 10. Multiple upper lamps 20A and multiple lower lamps 20B constitute a heater 20 that heats the silicon substrate W in the chamber 10 from above and below. The output of the heater 20 is PID controlled based on the temperature detected by at least one of the upper pyrometer 22A and the lower pyrometer 22B.

[0029] The upper pyrometer 22A is located outside the chamber 10 and directly above the center of the susceptor 12. The upper pyrometer 22A measures the center temperature of the upper surface of the silicon substrate W placed on the susceptor 12.

[0030] The lower pyrometer 22B is located outside the chamber 10 and is positioned diagonally downward when viewed from the center of the susceptor 12. The lower pyrometer 22B measures the central temperature of the lower surface of the susceptor 12.

[0031] The control unit 30 controls the operation of each part. For example, the control unit 30 controls the output of the heater 20 based on the temperature detected by at least one of the upper pyrometer 22A and the lower pyrometer 22B. The control unit 30 also controls the flow rate and supply time of the source gas and dopant gas.

[0032] In the production of epitaxial silicon wafers using the epitaxial growth apparatus 1 described above, after placing the silicon substrate W on the susceptor 12, the silicon substrate W is heated to a predetermined temperature, and a mixed gas containing the source gas is supplied from the gas supply port 16 while exhausting gas from the gas outlet 18. The mixed gas flows from the gas supply port 16 into the upper space of the chamber 10. The silicon substrate W is heated by the heater 20, and as the source gas flows in a laminar flow state along the surface of the heated silicon substrate W, epitaxial growth occurs on the silicon substrate W, and an epitaxial film is formed.

[0033] Next, a method for manufacturing epitaxial silicon wafers using the epitaxial growth apparatus 1 will be described.

[0034] Figure 2 is a flowchart showing the manufacturing process of an epitaxial silicon wafer.

[0035] As shown in Figure 2, in the manufacturing of epitaxial silicon wafers, a silicon substrate W is first prepared (step S1). A low-resistivity CZ silicon wafer doped with a high concentration of dopants is used as the silicon substrate W. The dopant species is not particularly limited, but the dopant in an n-type silicon substrate is preferably phosphorus (P) or arsenic (As). The dopant species in a p-type silicon substrate is preferably boron (B). The dopant concentration is 1.8 × 10⁻¹⁶. 19 atoms / cm 3 That is all, 3.6 × 10 19 ~1.18×10 20 atoms / cm 3 This is preferable. In an epitaxial growth process using such a low-resistivity silicon substrate W, the temperature detected by the upper pyrometer 22A fluctuates significantly even though the actual temperature of the substrate hardly changes, making the substrate temperature control unstable. Therefore, the temperature control according to the present invention is necessary.

[0036] Next, the inside of the chamber 10 is heated with the heater 20 to set a predetermined input temperature (for example, 700 degrees Celsius), and then the silicon substrate W is introduced into the chamber 10 (step S2). The silicon substrate W is set on the susceptor 12 inside the chamber 10.

[0037] Next, the temperature of the silicon substrate W in the chamber 10 is raised to the target temperature required for epitaxial growth (epitaxial growth temperature) (steps S3 to S5). The target temperature is preferably 1100 to 1130°C, and the heating rate is preferably 7 to 12°C / second. Immediately after the start of the heating step, the heater output is kept constant, and PID control of the heater output is started partway through the heating step once a certain amount of heating has progressed.

[0038] During the temperature rise step, the PID control receives feedback from the temperatures detected by the upper pyrometer 22A and the lower pyrometer 22B, and the PID control conditions at this time are proportional gain k p1 The (first value) is set to a relatively higher value than during the epitaxial growth process. This is because the proportional gain k of the PID control in the heating step p1 This is because reducing k increases the overshoot after reaching the target temperature, thus increasing the risk of slip dislocations. There is also the issue of so-called autodoping, where dopants in the silicon substrate migrate into the epitaxial film. Proportional gain k p1 By setting this value to a sufficiently large value, it is possible to suppress overshoot when the substrate temperature rises.

[0039] Subsequently, the PID control conditions for the heater 20 are changed (step S6). Specifically, PID control is performed based on the temperature detected by the upper pyrometer 22A, and the sensitivity of the proportional control in the PID control is reduced. The changed proportional gain k p2 (The second value) is the proportional gain k before the change. p1 It is preferable that the value is 0.07 to 0.5 times the (first value). For example, the proportional gain k before the change. p1 Set to 1.4kW / ℃, and the changed proportional gain k p2 This can be set to 0.1 to 0.7 kW / ℃.

[0040] When changing the PID control conditions, the sensitivity of the integral control may be changed along with the sensitivity of the proportional control. For example, the changed proportional gain k p2 (Second value) Proportional gain k before modification p1 Make it smaller than (the first value), and also change the integral gain k i2 (The fourth value) represents the integral gain k before the change. i1 Make it greater than (the third value). In this case, the modified integral gain k i2 (The fourth value) represents the integral gain k before the change. i1 It is preferable that the value is greater than six times the (third value). This compensates for the lack of control caused by reducing the proportional gain, and enables further optimization of the PID control of the heater 20 output.

[0041] The PID control conditions are changed after the substrate temperature reaches the target temperature and before the epitaxial growth process begins. In this case, the PID control conditions may be changed when the temperature detected by the upper pyrometer 22A first reaches the target temperature, or when the temperature detected by the upper pyrometer 22A exceeds the target temperature due to overshoot, reaches a peak temperature, and then returns to the target temperature.

[0042] Next, a hydrogen bake is performed to remove the surface oxide film of the silicon substrate W (step S7). In the hydrogen bake step, hydrogen gas is introduced into the chamber 10, which is maintained at a target temperature, and the silicon substrate W is heat-treated in a hydrogen atmosphere. The heat treatment time can be 40 to 50 seconds.

[0043] Subsequently, the epitaxial growth process is initiated (step S8). In the epitaxial growth step, a mixed gas of source gas, dopant gas, and carrier gas is introduced into the chamber 10. The mixed gas flows into the upper space of the chamber 10 and flows laminarly along the surface of the silicon substrate W, thereby growing an epitaxial film on the surface of the silicon substrate W.

[0044] During the hydrogen bake step and the epitaxial growth step, the surface temperature of the silicon substrate W is maintained at the target temperature by PID control of the heater output based on the temperature detected by the upper pyrometer 22A. The modified PID control conditions are applied to the PID control of the heater output, namely, the proportional gain k p The value is set to be smaller than before, and the integral gain k is also set as needed. i This setting is increased compared to before the change. Therefore, it is possible to prevent the heater output from hunting.

[0045] At the end of the epitaxial growth step, PID control of the heater output is terminated (step S9). Then, the heater output is reduced to lower the temperature inside the chamber 10 to a predetermined extraction temperature (e.g., 800°C) (step S10). Subsequently, the atmospheric gas inside the chamber 10 is evacuated and replaced with air, and then the silicon substrate W is removed from inside the chamber 10 (step S11). This completes the series of epitaxial growth processes.

[0046] If the same PID control conditions are applied continuously from the time the silicon substrate W is introduced into the chamber 10 until the end of the epitaxial growth process, the high concentration of dopants contained in the silicon substrate W will cause hunting of the detection temperature of the upper pyrometer 22A, resulting in fluctuations in the heater output and large temperature fluctuations of the silicon substrate W during epitaxial growth. These temperature fluctuations lead to fluctuations in the amount of dopant taken up in the epitaxial film, resulting in variations in dopant concentration. However, as in this embodiment, if two-stage PID control is implemented, changing the PID control conditions before and after the start of the epitaxial growth step, and the proportional gain of the PID control during the epitaxial growth step is made smaller than before the start of the epitaxial growth step, fluctuations in the heater output can be suppressed.

[0047] As described above, in the method for manufacturing an epitaxial silicon wafer according to this embodiment, when the output of the heater 20 is PID controlled based on the temperature detected by the upper pyrometer 22A to bring the temperature of the silicon substrate W closer to the target temperature, the sensitivity of the proportional control of the PID control during the epitaxial growth step is made smaller than before the start of the epitaxial growth step. This suppresses excessive control of the output of the heater 20 based on the temperature detected by the upper pyrometer 22A, and enables stable control of the temperature of the silicon substrate W.

[0048] Although preferred embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the above embodiments, and various modifications are possible without departing from the spirit of the invention, and these modifications are also included within the scope of the present invention.

[0049] For example, in the above embodiment, the PID control conditions are changed in two stages, but they may be set to three or more stages. [Examples]

[0050] A 300mm diameter epitaxial silicon wafer was manufactured using a single-wafer epitaxial growth system (Centura Epi) from APPLIED MATERIALS. The silicon substrate used was 1.07 × 10⁶. 15 ~1.79 × 10 15 atoms / cm 3 Boron-doped p-wafer, 1.23 × 10⁻¹⁶ 19 ~8.50×10 19 atoms / cm 3 Boron-doped p++ wafers, 8.90 x 10⁻¹⁶ 19 ~1.18×10 20 atoms / cm 3 Three types of n+++ wafers doped with high concentrations of phosphorus were used. The specifications for the epitaxial film were a target thickness of 4.0 ± 0.1 μm and a target resistivity of 10.0 ± Ωcm.

[0051] In the production of an epitaxial silicon wafer, a silicon substrate is introduced into a chamber maintained at a loading temperature of about 700°C, and the substrate temperature is raised to a target temperature of 1100°C at a heating rate of 8°C / sec. Then, after performing hydrogen baking for about 50 seconds, a mixed reaction gas obtained by diluting SiHCl₃, which is a silicon source, with hydrogen gas is supplied into the chamber to perform an epitaxial growth process for about 6 minutes. No dopant gas was supplied in order to unify the state of the epitaxial layer.

[0052] Temperature control during the production process of the epitaxial silicon wafer was performed in accordance with a preset temperature control recipe. It was also performed by performing PID control on the outputs of a plurality of upper lamps and a plurality of lower lamps based on the temperature detected by an upper pyrometer. In the production of the epitaxial silicon wafer, the PID control conditions were kept constant from the middle of the temperature raising process until the end of the epitaxial growth process. Specifically, the proportional gain k of PID control p was set to 1.4kW / °C, and the integral gain k i was set to 6kW / °C, and the derivative gain k d was set to 0kW / °C.

[0053] Figures 3(a) and 3(b) are graphs showing measurement values during the epitaxial growth process, wherein Figure 3(a) shows the central temperature of a silicon substrate (wafer) measured by an upper pyrometer, and Figure 3(b) shows the heater output (lamp output), respectively.

[0054] As shown in Figure 3(a), continuous fluctuation occurred in the temperature detected by the upper pyrometer during the epitaxial growth process. The fluctuation range of temperature depended on the dopant concentration of the silicon substrate, and increased in the order of p- < p++ < n+++. The maximum fluctuation range of the temperature of the n+++ wafer was about ±12°C. In addition, the fluctuation of the temperature detected by the upper pyrometer converged as the epitaxial growth process progressed, and completely converged approximately 225 seconds after the start of the process.

[0055] As shown in Fig. 3(b), continuous fluctuations were also observed in the heater output during the epitaxial growth process. The fluctuation range of temperature depends on the dopant concentration of the silicon substrate, and increased in the order of p- < p++ < n+++. The maximum fluctuation range of the heater output for the n+++ wafer was about ±10 kW.

[0056] From the above results, it was found that the higher the dopant concentration in the silicon substrate, the greater the fluctuation of the temperature detected by the upper pyrometer, and the heater output also fluctuates along with the fluctuation of the temperature detected by the upper pyrometer.

[0057] In consideration of the above evaluation results, an epitaxial silicon wafer was produced according to an example using an n+++ wafer. In the production of the epitaxial silicon wafer according to the example, the PID control conditions were changed before and after the start of the epitaxial growth process. Specifically, in the temperature raising step before the start of the epitaxial growth process, the proportional gain k of the PID control p was set to 1.4 kW / °C, and the integral gain k i was set to 6 kW / °C, and the differential gain k d was set to 0 kW / °C. In addition, for temperature control during the epitaxial growth process, the proportional gain k of the PID control p was set to 0.1 kW / °C, the integral gain k i was 40 kW / °C, and the differential gain k d was set to 0 kW / °C. That is, the sensitivity of proportional control in PID control was reduced, and the adjustment amount of the heater output accompanying fluctuations in the temperature detected by the upper pyrometer was reduced. Contrary to reducing the proportional gain, the integral gain was slightly increased to ensure the balance of the entire control.

[0058] Figs. 4(a) and 4(b) are graphs showing measurement values during the epitaxial growth process before and after optimization of PID control conditions, wherein Fig. 4(a) shows the wafer center temperature measured by the upper pyrometer, and Fig. 4(b) shows the heater output (lamp output), respectively.

[0059] As shown in Figure 4(a), the fluctuation range due to wafer center temperature hunting in the comparative example was ±7.5°C, while the fluctuation range due to wafer center temperature hunting in the example was ±6.0°C. In other words, no significant change was observed in wafer center temperature hunting even when the PID control conditions were changed.

[0060] On the other hand, as shown in Figure 4(b) and Table 1, the fluctuation range due to heater output hunting in the comparative example was 25.11 kW, while the fluctuation range of heater output in Example 1 was 4.41 kW. In other words, it was found that by using two-stage PID control, which involves changing the PID control conditions before and after the start of the epitaxial growth process and weakening the sensitivity of the proportional control after the change compared to before, the hunting of the epitaxial growth temperature can be suppressed, and the controllability of the heater output during the epitaxial growth process can be significantly improved.

[0061] Next, two-stage PID control was applied, and the proportional gain of the PID control during the epitaxial growth process was changed to 0.4 kW / °C and 0.7 kW / °C, respectively. Epitaxial silicon wafers were then manufactured according to Examples 2 and 3 under the same conditions as Example 1. Subsequently, the fluctuation range of the heater output during the epitaxial growth process was evaluated. As shown in Table 1, the fluctuation range of the heater output in Example 2 was 4.44 kW, and the fluctuation range of the heater output in Example 3 was 8.49 kW. In other words, it was confirmed that even with a proportional gain of 0.7 kW / °C for PID control, there is an effect in suppressing the hunting of the epitaxial growth temperature.

[0062] [Table 1] [Industrial applicability]

[0063] By using epitaxial wafers manufactured using the manufacturing method of this invention, it is possible to contribute to lowering the power consumption of low-voltage power MOSFETs. This contributes to reducing energy consumption and improving energy efficiency. [Explanation of Symbols]

[0064] 1. Epitaxial growth apparatus 10 chambers 11A Upper dome 11B Lower Dome 11C Dome Mounting Body 12 Susceptors 14 Support shaft 16 Gas supply port 18 Gas outlet 20 Heaters 20A Upper Lamp 20B Lower Lamp 22A Upper Pyrometer 22B Lower pyrometer W Silicon substrate (silicon wafer)

Claims

1. 1.8 × 10 in the chamber of a single-leaf epitaxial growth apparatus １９ atoms / cm ３ A substrate introduction step involves introducing a silicon substrate having the above dopant concentrations, A heating step in which the silicon substrate is heated with a heater to raise the temperature to a target temperature, The system includes an epitaxial growth step in which an epitaxial film is grown on the main surface of the silicon substrate by supplying a mixed gas containing a source gas and a carrier gas into the chamber while maintaining the silicon substrate at the target temperature. A method for manufacturing an epitaxial silicon wafer, characterized in that the epitaxial growth step involves PID control of the output of the heater based on the temperature detected by an upper pyrometer installed above the silicon substrate, and the sensitivity of the proportional control of the PID control is lower than that before the start of the epitaxial growth step.

2. The heating step involves PID-controlled control of the heater output based on both the temperature detected by the upper pyrometer and the temperature detected by the lower pyrometer located below the silicon substrate, and setting the proportional gain of the PID control to a first value. The epitaxial growth step involves setting the proportional gain of the PID control to a second value smaller than the first value. The method for manufacturing an epitaxial silicon wafer according to claim 1, wherein the second value is 0.07 to 0.5 times the first value.

3. The method for manufacturing an epitaxial silicon wafer according to claim 1, wherein the epitaxial growth step increases the sensitivity of the integral control of the PID control to a level higher than that before the start of the epitaxial growth step.

4. The aforementioned temperature-raising step sets the integral gain in the PID control to a third value, The epitaxial growth step involves setting the integral gain in the PID control to a fourth value that is greater than the third value, The method for manufacturing an epitaxial silicon wafer according to claim 2, wherein the fourth value is greater than six times the third value.

5. The method for manufacturing an epitaxial silicon wafer according to claim 1, wherein the PID control conditions are changed when the temperature detected by the upper pyrometer exceeds the target temperature due to overshoot and reaches a peak temperature, and then returns to the target temperature.

6. The following steps, after the heating step and before the epitaxial growth step, are further included: a hydrogen bake step in which the silicon substrate is heat-treated in a hydrogen atmosphere to remove the surface oxide film. The method for manufacturing an epitaxial silicon wafer according to claim 2, wherein the hydrogen bake step involves PID control of the output of the heater based on the temperature detected by the upper pyrometer and the temperature detected by the lower pyrometer, and maintaining the proportional gain of the PID control at the first value.

7. The concentration of the dopant is 3.6 × 10 １９ ~1.18 x 10 ２０ atoms / cm ３ The method for manufacturing an epitaxial silicon wafer according to claim 1.

8. Chamber and A susceptor supporting a silicon substrate within the chamber, A heater for heating the silicon substrate, An upper pyrometer positioned above the center of the susceptor and measuring the temperature of the upper surface of the silicon substrate on the susceptor, A lower pyrometer is positioned below the center of the susceptor and measures the temperature of the lower surface of the susceptor, The system includes a control unit that performs PID control of the heater output based on the temperature detected by the upper pyrometer, or by both the upper pyrometer and the lower pyrometer, The control unit sequentially performs a heating step of heating the silicon substrate with the heater to a target temperature based on both the temperature detected by the upper pyrometer and the temperature detected by the lower pyrometer, and an epitaxial growth step of supplying a mixed gas containing a source gas and a carrier gas into the chamber while maintaining the silicon substrate at the target temperature based on the temperature detected by the upper pyrometer to grow an epitaxial film on the main surface of the silicon substrate, and is characterized in that the sensitivity of the proportional control of the PID control during the epitaxial growth step is lower than before the start of the epitaxial growth step.

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