An epitaxial apparatus cooling system and method

Abstract

This invention discloses a cooling system and method for epitaxial wafers. The system includes: a heating module configured to radiate heat to the epitaxial wafer at different heating powers; and a control module configured to send a control signal to the heating module to control the power of the heating module so that the temperature difference is less than the preset threshold when the temperature difference between the measured temperatures of the upper and lower surfaces of the epitaxial wafer exceeds a preset threshold. By ensuring that the temperature difference between the measured temperatures of the upper and lower surfaces of the epitaxial wafer remains within a reasonable range through the control module and the heating module, the edge stress of the epitaxial wafer is effectively reduced, resulting in an epitaxial wafer that meets process requirements.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing, and more particularly to a cooling system and method for epitaxial equipment. Background Technology

[0002] In the semiconductor field, silicon wafers are generally the raw material for integrated circuits. Among them, epitaxial wafers are widely used in highly integrated IC components and MOS processes due to their characteristics such as fewer surface defects and controllable resistivity. Circuits and electronic components need to be fabricated on epitaxial wafers, with different applications such as PMOS, NMOS, and CMOS in MOS type and saturated and unsaturated types in bipolar. As integrated circuit design moves towards lighter, thinner, shorter, smaller, and more energy-efficient designs, mobile communications, information appliances, and other products are all striving to save energy consumption, which continuously increases the requirements for epitaxial wafer products.

[0003] During epitaxial growth, numerous defects can occur on the epitaxial layer, including dislocations, stacking faults, deposited foreign matter, and defects caused by oxidation. In a broader sense, defects also include impurities such as oxygen, carbon, and heavy metals, as well as point defects such as atomic vacancies and interstitial atoms. The presence of some of these defects can directly affect the performance of the semiconductor. The various defects in the epitaxial layer are not only related to the substrate quality and surface condition, but also closely related to the epitaxial growth process itself. For example, during the cooling process after epitaxial growth, rapid cooling should be avoided, otherwise, large temperature gradients will induce slip dislocations in the epitaxial layer. Summary of the Invention

[0004] In view of this, embodiments of the present invention aim to provide an apparatus and method for a cooling system of an epitaxial device; capable of dynamically adjusting the heating power of the heating module during the cooling process of the epitaxial wafer to ensure that the temperature difference between the upper and lower surfaces of the epitaxial wafer is within a reasonable range, thereby avoiding the generation of slip defects.

[0005] The technical solution of this invention is implemented as follows:

[0006] In a first aspect, embodiments of the present invention provide a cooling system for an epitaxial device, the system comprising:

[0007] A heating module is configured to radiate heat to the epitaxial wafer at different heating powers; a control module is configured to send a control signal to the heating module to control the power of the heating module so that the temperature difference is less than the preset threshold when the temperature difference between the measured temperature of the upper surface and the measured temperature of the lower surface of the epitaxial wafer is greater than a preset threshold.

[0008] In a second aspect, embodiments of the present invention provide a cooling method for an epitaxial device, the cooling method comprising:

[0009] After the epitaxial wafer completes epitaxial deposition, the heating power is set according to the measured temperature of the upper surface and the measured temperature of the lower surface of the epitaxial wafer to reduce the temperature of the epitaxial wafer; when the temperature difference between the measured temperature of the upper surface and the measured temperature of the lower surface is greater than a preset threshold, the control module sends a control signal to the heating module; the heating module changes the heating power so that the temperature difference is less than the preset threshold; the above cooling process is repeated until the epitaxial wafer completes the cooling process.

[0010] This invention provides a cooling system and method for an epitaxial wafer. A temperature detection module acquires the measured temperatures of the upper and lower surfaces of the epitaxial wafer. A control module sends a control signal to a heating module based on the temperature difference between the upper and lower surfaces of the epitaxial wafer. The heating module then adjusts its heating power to reduce the temperature difference, thereby reducing the internal stress at the edges of the epitaxial wafer, lowering the risk of slip defects, and enhancing the quality of the epitaxial wafer. Attached Figure Description

[0011] Figure 1 A schematic diagram of an apparatus for fabricating epitaxial silicon wafers using the atmospheric pressure epitaxial deposition method in the prior art;

[0012] Figure 2 For use of the attached Figure 1 Temperature curves of the device used to cool the epitaxial wafer;

[0013] Figure 3 This is a schematic diagram of an apparatus for preparing epitaxial silicon wafers by atmospheric pressure epitaxial deposition, which has a cooling system provided in an embodiment of the present invention.

[0014] Figure 4 For use of the attached Figure 3 Temperature curves of the device used to cool the epitaxial wafer;

[0015] Figure 5 This is a schematic flowchart of a cooling method provided in an embodiment of the present invention. Detailed Implementation

[0016] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0017] Epitaxial growth via the SiHCI3 (SiCI4) hydrogen (H2) reduction method is typically performed at high temperatures of 1100-1250℃. During cooling, thermal stress can occur to varying degrees due to uneven thermal field distribution and poor contact between the substrate and the silicon wafer. Thermal stress can cause plastic deformation of the material. If relative slip occurs between portions on opposite sides of a crystal plane, dislocations form at the boundary between the slipped and unslipped portions, potentially creating steps on the surface at the 1-10 nm scale. A schematic diagram of an apparatus for preparing epitaxial silicon wafers using atmospheric pressure epitaxial deposition is attached. Figure 1 As shown, a high-purity graphite base 1 is placed in the epitaxial silicon wafer growth chamber. The upper and lower walls of this growth chamber are made of transparent and high-temperature resistant quartz material, referred to as the upper and lower quartz domes 2. The epitaxial wafer is placed on the graphite base 1, and infrared lamps 3 and 4 are used for rapid heating to provide the heat required for the epitaxial reaction. During the cooling process after epitaxial growth is completed, a low fixed power is set for infrared lamps 3 and 4 to begin lowering the temperature of the epitaxial wafer. See Appendix. Figure 1 Infrared lamp 3, located above the epitaxial wafer, directly irradiates the upper surface of the epitaxial wafer to heat it. However, infrared lamp 4, located below the graphite base 1, irradiates the lower surface of the graphite base 1. Heat can only reach the lower surface of the epitaxial wafer through conduction via the graphite base 1. This results in a significant temperature difference during cooling due to the different heat absorption efficiencies of the upper and lower surfaces of the epitaxial wafer, as shown in the attached diagram. Figure 2 As shown, due to the different heating methods on the upper and lower surfaces of the epitaxial wafer, the temperature of the lower surface of the epitaxial wafer is lower than that of the upper surface for most of the time during the cooling process. This results in uneven heat distribution, increases the internal stress at the edge of the epitaxial wafer, and causes the silicon single crystal structure to be damaged under internal stress, resulting in slip defects.

[0018] Therefore, in response to the aforementioned technical problems, and based on the idea of ​​reducing the temperature difference between the upper and lower surfaces of the epitaxial wafer during cooling, thereby reducing the internal stress at the edges of the epitaxial wafer and avoiding slip defects to obtain a single-crystal silicon epitaxial wafer with a perfect crystal structure, this invention proposes a cooling system 100 for an apparatus capable of preparing epitaxial silicon wafers using the atmospheric pressure epitaxial deposition method. (See attached diagram.) Figure 3 The cooling system includes a heating module 10, a control module (not shown), a graphite base 1, and a temperature detection module (not shown). The temperature detection module acquires the measured temperatures of the upper and lower surfaces of the epitaxial wafer located on the graphite base 1. The control module sends a control signal to the heating module based on the temperature difference between the upper and lower surfaces of the epitaxial wafer. The heating module 10 then adjusts its heating power to reduce the temperature difference, thereby reducing the internal stress at the edges of the epitaxial wafer, lowering the risk of slip defects, and improving the quality of the epitaxial wafer.

[0019] Heating module 10 is used to provide heat to the epitaxial reaction in different heating power ways, see appendix. Figure 3 The heating module includes a first heating unit 5 and a second heating unit 6. The first heating unit 5 is positioned above the epitaxial wafer and directly transfers heat to the upper surface of the epitaxial wafer via thermal radiation. The second heating unit 6 is positioned below the epitaxial wafer and also transfers heat to the lower surface of the epitaxial wafer via thermal radiation. Furthermore, the first heating unit 5 and the second heating unit 6 consist of two or more halogen lamps to ensure more uniform heat transfer to the epitaxial wafer. The first heating unit 5 and the second heating unit 6 can adjust their power to reduce the heat received by the epitaxial wafer, thereby lowering its temperature. During the cooling process after epitaxial growth, compared to the set power of the heating module during epitaxial growth, the power of both the first heating unit 5 and the second heating unit 6 is reduced to lower the temperatures of the upper and lower surfaces of the epitaxial wafer, respectively.

[0020] See appendix Figure 3 Throughout the entire epitaxial growth process, the epitaxial wafer is horizontally placed on a graphite substrate 1, which is made of high-purity graphite and has good thermal conductivity. The upper surface of the epitaxial wafer on the graphite substrate 1 is directly irradiated by the first heating unit 5, and the second heating unit 6 is used to transfer heat to the lower surface of the epitaxial wafer. That is, the second heating unit directly irradiates the lower surface of the graphite substrate 1. After receiving heat, the graphite substrate 1 transfers the heat to the epitaxial wafer through direct contact. Therefore, the temperature of the lower surface of the graphite substrate 1 can well characterize the temperature of the lower surface of the epitaxial wafer.

[0021] The different heat transfer methods mentioned above lead to inconsistent temperatures on the upper and lower surfaces of the epitaxial wafer during cooling, easily causing temperature differences and slip defects. The cooling system also includes a control module that calculates the temperature difference between the upper and lower surfaces of the epitaxial wafer based on the measured temperatures of the upper and lower surfaces. This control module has a preset threshold for this temperature difference, which can be set according to actual production needs and modified based on different production processes and product requirements. The control module compares the temperature difference with the preset threshold. When the temperature difference is less than the preset threshold, it indicates that the measured temperatures of the upper and lower surfaces of the epitaxial wafer are within a reasonable range, and cooling at this temperature will not cause excessive stress within the epitaxial wafer. When the temperature difference is greater than the preset threshold, it indicates that the measured temperatures of the upper and lower surfaces of the epitaxial wafer exceed a reasonable range, and cooling at this temperature will cause excessive stress within the epitaxial wafer, resulting in slip defects. Therefore, when the temperature difference exceeds the preset threshold, the control module sends a first control signal to the first heating unit 5 and / or a second control signal to the second control unit. The first heating unit 5 and the second heating unit 6 in the heating module start to control their own heating power. Due to the different heat transfer methods, the measured temperature of the upper surface of the epitaxial wafer is often higher than that of the lower surface. Therefore, the first heating unit 5 reduces its own heating power to reduce the temperature of the upper surface of the epitaxial wafer, and the second heating unit 6 increases its own heating power to increase the temperature of the lower surface of the epitaxial wafer. Consequently, the temperature difference between the measured temperature of the upper surface and the measured temperature of the lower surface of the epitaxial wafer decreases, so that the temperature of the epitaxial wafer cooling process meets the process requirements.

[0022] The cooling system also includes a temperature detection module configured to measure the temperature of the upper surface of the epitaxial wafer to obtain the upper surface measurement temperature, and to measure the temperature of the lower surface of the epitaxial wafer to obtain the lower surface measurement temperature. The temperature detection module can be implemented using devices such as an infrared temperature measuring instrument or a temperature sensor.

[0023] Through append Figure 3 The apparatus for preparing epitaxial silicon wafers using atmospheric pressure epitaxial deposition with the cooling system shown herein includes a cooling process for the epitaxial wafer. This process may include reducing the power of the first and second heating units. Subsequently, a temperature detection module measures the upper and lower surface temperatures. A control module calculates the temperature difference between the upper and lower surfaces of the epitaxial wafer based on these temperatures and compares the temperature difference with a preset threshold. When the temperature difference exceeds the preset threshold, the control module sends control signals to the first and second heating units, causing them to adjust their power accordingly. This changes the upper and / or lower surface temperatures of the epitaxial wafer, reducing the temperature difference and ensuring the cooling process meets process requirements. The final temperature curve is shown in the attached figure. Figure 4 As shown. See appendix. Figure 5 This illustrates a cooling method for an epitaxial device provided by an embodiment of the present invention, which can be applied to epitaxial devices. Figure 3 The apparatus shown is for fabricating epitaxial silicon wafers using atmospheric pressure epitaxial deposition with the cooling system. The cooling method includes the following steps:

[0024] After the epitaxial deposition is completed, the heating power is set according to the measured temperature of the upper surface and the measured temperature of the lower surface of the epitaxial wafer to reduce the temperature of the epitaxial wafer;

[0025] When the temperature difference between the measured temperature of the upper surface and the measured temperature of the lower surface is greater than the preset threshold, the control module sends a control signal to the heating module.

[0026] The heating module adjusts its heating power to make the temperature difference less than the preset threshold.

[0027] Repeat the above cooling process until the epitaxial wafer has completed the cooling process.

[0028] Through append Figure 5 The technical solution shown in this invention enables the control module to monitor the temperature difference between the upper and lower surfaces of the epitaxial wafer, thereby constantly adjusting the heating power of the heating module to prevent slippage defects during the cooling process. Further, changing the heating module power to ensure the temperature difference is less than a preset threshold specifically includes:

[0029] Increase the heating power of the second heating unit to slow down the rate of temperature decrease on the lower surface of the silicon wafer, and / or decrease the heating power of the first heating unit to accelerate the rate of temperature decrease on the upper surface of the silicon wafer, until the temperature difference is less than a preset threshold.

[0030] In order to optimize the one-step cooling in the prior art into the segmented cooling based on temperature difference proposed in this invention, the operator can adjust the preset threshold according to the actual processing requirements. By changing the preset value, the number of times the trigger control module sends control signals to the heating module is changed, so as to repeat the above cooling process multiple times. Preferably, the above cooling process can be repeated at least twice.

[0031] To address the technical problem proposed in this invention, based on the idea of ​​reducing the temperature difference between the upper and lower surfaces of the epitaxial wafer during the cooling process, thereby reducing the internal stress at the edge of the epitaxial wafer and avoiding slip defects to obtain a single-crystal silicon epitaxial wafer with a perfect crystal structure, this invention proposes to control the heating module through a temperature detection module and a control module so that the temperature difference between the upper and lower surfaces of the epitaxial wafer is within an acceptable and reasonable range, thus obtaining an epitaxial wafer that meets the process requirements.

[0032] It should be noted that the technical solutions described in the embodiments of the present invention can be combined arbitrarily without conflict.

[0033] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A cooling system for epitaxial equipment, characterized in that, The system includes: A heating module configured to radiate heat to the epitaxial wafer at different heating powers; A control module is configured to send a control signal to the heating module to control the power of the heating module so that the temperature difference is less than the preset threshold when the temperature difference between the measured temperature of the upper surface and the measured temperature of the lower surface of the epitaxial wafer is greater than a preset threshold. The preset threshold is configured to trigger the control module to send the control signal to the heating module at least twice. The cooling system further includes a graphite base for supporting the epitaxial wafer, and the temperature of the lower surface of the graphite base is used to characterize the temperature of the lower surface of the epitaxial wafer.

2. The cooling system according to claim 1, characterized in that, The cooling system also includes a temperature detection module configured to obtain the upper surface temperature by measuring the upper surface temperature of the epitaxial wafer and to obtain the lower surface temperature by measuring the lower surface temperature of the graphite substrate.

3. The cooling system according to claim 2, characterized in that, The heating module includes a first heating unit arranged above the graphite base and a second heating unit arranged below the graphite base.

4. The cooling system according to claim 3, characterized in that, Both the first heating unit and the second heating unit consist of two or more halogen lamps.

5. The cooling system according to claim 3, characterized in that, The control module is configured to send a first control signal to the first heating unit to reduce power and lower the upper surface temperature of the epitaxial wafer, and / or send a second control signal to the second heating unit to increase power and raise the lower surface temperature of the epitaxial wafer.

6. A cooling method for an epitaxial device, said cooling method being applied to the epitaxial device cooling system according to any one of claims 1-4, characterized in that, The cooling method includes: After the epitaxial deposition is completed, the heating power is set according to the measured temperature of the upper surface and the measured temperature of the lower surface of the epitaxial wafer to reduce the temperature of the epitaxial wafer; When the temperature difference between the measured temperature of the upper surface and the measured temperature of the lower surface is greater than a preset threshold, the control module sends a control signal to the heating module. The heating module changes the heating power so that the temperature difference is less than the preset threshold. Repeat the above cooling process until the epitaxial wafer has completed the cooling process.

7. The method for cooling an epitaxial device according to claim 6, characterized in that, The heating module changes its power to make the temperature difference less than the preset threshold, specifically including: The heating power of the first heating unit arranged above the graphite base is reduced to accelerate the temperature decrease rate of the upper surface of the epitaxial wafer, and / or the heating power of the second heating unit arranged below the graphite base is increased to slow down the temperature decrease rate of the lower surface of the epitaxial wafer, until the temperature difference is less than the preset threshold.

8. The cooling method for epitaxial equipment according to claim 6, characterized in that, The method further includes: The preset threshold is set according to process requirements so that the above cooling process can be repeated at least twice.

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