A method and apparatus for epitaxial growth of silicon wafers

Abstract

Embodiments of the present invention disclose a method and apparatus for epitaxial growth of a silicon wafer, the method comprising: a first step of placing the silicon wafer on a disc-shaped susceptor inside a reaction chamber; a second step of delivering etching gas into the reaction chamber through a gas inlet to etch the silicon wafer, wherein the gas inlet is located radially outside the susceptor and the susceptor is at a first height level with the gas inlet; and a third step of delivering silicon source gas into the reaction chamber through the gas inlet to grow an epitaxial layer on the surface of the silicon wafer.

Description

Technical Field

[0001] This invention relates to silicon wafer epitaxial growth technology in the semiconductor field, and more particularly to a method and apparatus for silicon wafer epitaxial growth. Background Technology

[0002] Epitaxial growth of silicon wafers is a crucial process in semiconductor chip manufacturing. This process involves growing a single-crystal silicon thin film with the same crystal orientation—the epitaxial layer—on a polished silicon wafer under specific conditions, thus obtaining an epitaxial silicon wafer. Epitaxial silicon wafers are widely used in the production of high-performance semiconductor devices due to their favorable crystal structure, lower defect density, and excellent conductivity. Epitaxial growth of silicon wafers mainly includes vacuum epitaxial deposition, chemical vapor deposition (CVD), and liquid phase epitaxial deposition, with CVD being the most widely used. Unless otherwise specified, the epitaxial growth mentioned in this invention refers to epitaxial growth achieved through chemical vapor deposition.

[0003] In a conventional epitaxial growth process, the silicon source gas that enables the silicon wafer to grow epitaxially usually contacts the radial edge region of the silicon wafer first or earliest, resulting in a larger thickness of the epitaxial layer grown in this region. This affects the thickness uniformity of the epitaxial layer and thus the surface flatness of the final epitaxial silicon wafer.

[0004] With the continuous development of semiconductor manufacturing processes, the requirements for the thickness uniformity of epitaxial layers and the surface flatness of epitaxial silicon wafers are becoming increasingly stringent. Epitaxial silicon wafers obtained through conventional epitaxial growth methods often cannot meet these higher requirements. Summary of the Invention

[0005] To address the aforementioned technical problems, embodiments of the present invention aim to provide a method and apparatus for epitaxial growth of silicon wafers, which can improve the flatness of the epitaxial silicon wafer with an epitaxial layer obtained after epitaxial growth.

[0006] The technical solution of this invention is implemented as follows: In a first aspect, embodiments of the present invention provide a method for epitaxial growth of a silicon wafer, the method comprising: The first step is to place the silicon wafer on a disc-shaped base inside the reaction chamber; A second step involves delivering etching gas into the reaction chamber via an air inlet to etch the silicon wafer, wherein the air inlet is located radially outward of the base and the base is at a first height flush with the air inlet; The third step involves delivering silicon source gas through the gas inlet into the reaction chamber to grow an epitaxial layer on the surface of the silicon wafer.

[0007] In a second aspect, embodiments of the present invention provide an apparatus for epitaxial growth of silicon wafers, the apparatus comprising: An epitaxial reaction apparatus, comprising: a bell jar enclosing a reaction chamber; a disk-shaped base inside the reaction chamber configured to support the silicon wafer; and an inlet configured to deliver reaction gas into the reaction chamber, wherein the inlet is located radially outward of the base and the base is at a first height flush with the inlet. An etching gas supply device is configured to deliver etching gas to the reaction chamber via the gas inlet for etching the silicon wafer; A silicon source gas supply device is configured to supply silicon source gas into the reaction chamber via the gas inlet after the etching gas supply device supplies etching gas into the reaction chamber to grow an epitaxial layer on the surface of the silicon wafer.

[0008] This invention provides a method and apparatus for epitaxial growth of silicon wafers. Before delivering silicon source gas to the reaction chamber to grow an epitaxial layer on the surface of the silicon wafer, etching gas is first introduced into the reaction chamber to etch the silicon wafer, thereby reducing the thickness of the region where a thick epitaxial layer will grow during the epitaxial growth process. This improves the flatness of the final epitaxial silicon wafer after a thicker epitaxial layer is subsequently grown in that region. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of an existing epitaxial reaction apparatus; Figure 2 This is a schematic diagram illustrating the relationship between different positions along the diameter of the silicon wafer and the thickness of the epitaxial layer in a conventional method. Figure 3 This is a schematic diagram illustrating the surface flatness of an epitaxial silicon wafer using conventional methods. Figure 4 This is a schematic diagram of a method for epitaxial growth of silicon wafers provided in an embodiment of the present invention; Figure 5 This is a schematic diagram showing the etching gas flowing across the surface of a silicon wafer in the method provided in this embodiment of the invention; Figure 6 For Figure 5 A schematic diagram showing the relationship between different positions along the diameter of the silicon wafer and the removal thickness when the etching gas is delivered in the manner shown. Figure 7 This is a schematic diagram showing the flow of silicon source gas across the surface of the silicon wafer after the base is lowered in the method provided in this embodiment of the invention. Figure 8 This is a comparison diagram of the epitaxial layer thickness before and after the base is lowered; Figure 9 A schematic diagram illustrating the repeatability of the method provided in the embodiments of the present invention; Figure 10 This is a schematic diagram of an apparatus for epitaxial growth of silicon wafers provided in an embodiment of the present invention. Detailed Implementation

[0010] 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.

[0011] See Figure 1 The diagram illustrates a conventional epitaxial reaction apparatus 110A. This apparatus 110A may include: The bell jar 111A encloses the reaction chamber RC, in which Figure 1 The upper bell jar 111A-1 and the lower bell jar 111A-2 are shown in the figure; The disk-shaped base 112A inside the reaction chamber RC is configured to support the polished silicon wafer W. The base support frame 114A is used to support the base 112A and drive the base 112A to rotate around the central axis XA of the device 110A at a certain speed during epitaxial growth. Since the wafer W is supported by the base 112A, the wafer W rotates together with the base 112A around the central axis XA. Inlet 113A is configured to supply reaction gases, such as silicon source gas and carrier gas, into the reaction chamber RC. Figure 1 As shown by the arrow at the air inlet 113A, the air inlet 113A is located radially outside the base 112A and the base 112A is at the same height as the air inlet 113A. Exhaust port 115A is used to discharge the reaction exhaust gas from the reaction chamber RC, such as in... Figure 1 The arrow at exhaust port 115A is shown in the middle; Multiple heating bulbs 116A are disposed around the upper bell jar 111A-1 and the lower bell jar 111A-2 and are used to provide a high-temperature environment in the reaction chamber RC through the upper bell jar 111A-1 and the lower bell jar 111A-2.

[0012] In the conventional epitaxial growth process, due to the aforementioned positional relationship between the gas inlet 113A and the base 112A, the silicon source gas delivered to the reaction chamber RC via the gas inlet 113A first contacts the radial edge region of the polished silicon wafer W, resulting in a larger thickness of the epitaxial layer grown in this region. Specifically, see... Figure 2 , Figure 2Taking the growth of a 3μm epitaxial layer on a 300mm diameter silicon wafer as an example, the epitaxial layer thickness at 35 points along the diameter direction of the silicon wafer in a conventional epitaxial growth method is shown, where the horizontal axis represents the diameter of the silicon wafer and the vertical axis represents the epitaxial layer thickness. From Figure 2 As can be seen, the epitaxial layer thickness in the central region of the silicon wafer remains around 3 μm, while the thickness in the edge region, such as at a location 148 mm from the center of the wafer, reaches 3.096 μm. This thicker epitaxial layer in the edge region affects the flatness of the epitaxial silicon wafer. See also... Figure 3 , Figure 3 Taking a 300mm diameter silicon wafer as an example, the surface flatness of the epitaxial silicon wafer in conventional epitaxial growth methods is illustrated by the Site Front Quotient Range (SFQR) values ​​of different regions of the wafer. Specifically, the wafer is divided into 324 site regions using 26mm × 8mm local sites, and the SFQR value of each site region is obtained. A higher SFQR value indicates poorer flatness in that site region. Figure 3 It can be seen that the areas with larger site values ​​are mainly concentrated in the edge region of the silicon wafer, or in other words, for this epitaxial silicon wafer, the areas with poor flatness are mainly concentrated in the radial edge region of the silicon wafer.

[0013] To improve the flatness of epitaxial silicon wafers with epitaxial layers obtained after epitaxial growth, see [reference needed]. Figure 4 This invention provides a method for epitaxial growth of silicon wafers, the method comprising: The first step S101 is to place the silicon wafer on a disk-shaped base inside the reaction chamber; The second step S102 involves delivering etching gas into the reaction chamber via an air inlet to etch the silicon wafer, wherein the air inlet is located radially outward of the base and the base is at a first height flush with the air inlet. The third step S103 involves delivering silicon source gas to the reaction chamber via the gas inlet to grow an epitaxial layer on the surface of the silicon wafer.

[0014] The method provided in the embodiments of the present invention can be utilized as follows: Figure 1 The epitaxial growth apparatus 100A shown in the figure can be implemented, or in other words, the reaction chamber, base, and air inlet involved in the method can be Figure 1 The epitaxial growth apparatus 100A shown includes a reaction chamber RC, a base 112A, and an air inlet 113A. For example, this can be achieved using an epitaxial reaction apparatus of the 300mm Epi Centura model from Applied Materials.

[0015] For the etching of the silicon wafer surface in step S102 above, see [link to relevant documentation]. Figure 5 It shows the process of etching gas flowing across the silicon wafer surface after being delivered to the reaction chamber, such as... Figure 5 As shown, due to the airflow direction and cavity structure, the etching gas has a stronger etching effect on the edge of the silicon wafer. See also... Figure 6 , Figure 6 Using a 300mm diameter silicon wafer as an example, the following is illustrated: Figure 5 The image shows the removal thickness at 35 points along the diameter of the silicon wafer when the etching gas is delivered in the manner shown. The horizontal axis represents the diameter of the silicon wafer, and the vertical axis represents the removal thickness. From... Figure 6 It is evident that the silicon wafer is etched to its greatest thickness in the radial edge regions, specifically the areas 145mm to 148mm from the radial center and -145mm to -148mm from the radial center. In other words, the amount of etching is greatest in the radial edge regions. On the other hand, as mentioned earlier, the epitaxial layer grown at the radial edge of the silicon wafer is thicker. Therefore, a thicker epitaxial layer is grown on a thinner region of the silicon wafer; or, by thinning the silicon wafer at the radial edge, the thicker epitaxial layer outside the radial edge is compensated for, thereby improving the surface flatness of the final epitaxial wafer, which includes both the silicon wafer and the epitaxial layer.

[0016] Preferably, the etching gas can be hydrogen chloride (HCl) gas.

[0017] Preferably, the flow rate of the hydrogen chloride gas can be from 0.5 slm to 2 slm, where slm is a flow rate unit, which means the volume in cubic centimeters per minute flowing under conditions of 1 atmosphere and 25 degrees Celsius, and the delivery time can be from 10 s to 30 s.

[0018] Preferably, the silicon source gas can be trichlorosilane (TCS) gas, or it can be silicon, dichlorosilane, tetrachlorosilane, etc. Preferably, the flow rate of trichlorosilane can be 10 slm to 20 slm.

[0019] In a preferred embodiment of the invention, the method further includes a fourth step between the second and third steps: lowering the base so that the base is at a second height below the first height. The purpose of this fourth step is to improve the thickness uniformity of the epitaxial layer grown on the silicon wafer. Specifically, see... Figure 7 , Figure 7 It shows the base being removed from Figure 5 The image shows the silicon source gas flowing across the silicon wafer surface after descending a certain distance from the indicated position and being transported to the reaction chamber. Figure 7As shown, when the base descends a certain distance, it hinders the contact between the silicon source gas delivered to the reaction chamber and the edge region of the silicon wafer to some extent. This results in a reduction in the thickness of the epitaxial layer grown in the radial edge region of the silicon wafer compared to conventional growth methods. Specifically, see... Figure 8 , Figure 8 A comparison diagram of the epitaxial layer thickness before and after the base is lowered is shown, where the horizontal and vertical axes have the same meaning as... Figure 2 The same applies in the middle, and curve C8-1 is... Figure 2 The curves shown are for comparison; curve C8-2 represents the thickness of the epitaxial layer grown in the method provided by this embodiment of the invention when the base is at a second height below the first height. From Figure 8 It is evident that by first lowering the base a certain distance from its initial position flush with the gas inlet, and then supplying silicon source gas into the reaction chamber, the steepness of the epitaxial layer thickness at the silicon wafer edge is significantly improved. Specifically, for example, at a position 148 mm from the center of the silicon wafer, the thickness of the grown epitaxial layer decreases from 3.096 μm to 3.027 μm. In other words, the difference between the thickness of the epitaxial layer grown at the edge and at the center is reduced. Figure 8 The data shown in the figure can be used to calculate that the uniformity of the epitaxial layer thickness was improved from 1.72% to 0.74%, thereby improving the thickness uniformity of the epitaxial layer.

[0020] Etching the silicon wafer and growing the epitaxial layer on its surface both require a high-temperature environment, and the silicon wafer itself needs to reach a certain temperature. Therefore, in a preferred embodiment of the present invention, the method may further include a fifth step of preheating the silicon wafer between the first and second steps. Preferably, the silicon wafer can be preheated in a hydrogen atmosphere. Preferably, the heating rate of the silicon wafer can be maintained at 6.5-8.5℃ / s. This heating rate is to ensure that the silicon wafer does not deform due to rapid heating while meeting certain production efficiency requirements, and to prevent the generation of crystal defects such as slip lines. Preferably, the silicon wafer can be heated to 1050℃-1150℃.

[0021] The polished silicon wafer surface contains natural oxides and organic matter, which can affect the subsequent growth of epitaxial layers or degrade the quality of the grown epitaxial layers. Therefore, in a preferred embodiment of the present invention, the method may further include a sixth step between the fifth step and the second step: baking the silicon wafer in a hydrogen atmosphere. In one example, hydrogen can be introduced into the reaction chamber through the gas inlet to react with the natural oxides and organic matter on the silicon wafer surface at a high temperature, thereby removing these impurities and preventing them from affecting the subsequent epitaxial growth process. Preferably, the baking temperature of the silicon wafer can be 950℃-1250℃, and the baking time can be 10s-30s.

[0022] In a preferred embodiment of the present invention, the method may further include a seventh step between the second step and the third step, in which hydrogen gas is used to purge the reaction chamber through the inlet to remove the etching gas from the reaction chamber.

[0023] Regarding the distance between the first and second heights of the substrate, or the distance the substrate needs to descend, if the descent distance is too large, the silicon source gas delivered to the reaction chamber will not easily contact the silicon wafer surface, reducing the epitaxial growth rate and wasting the silicon source gas. On the other hand, if the descent distance is too small, the thickness of the epitaxial layer grown in the edge region of the silicon wafer cannot be sufficiently reduced, and the uniformity of the epitaxial layer thickness cannot be adequately improved. Therefore, in a preferred embodiment of the present invention, the distance between the first and second heights is 0.5 mm to 2 mm, or in other words, compared to etching the silicon wafer, the substrate descends by 0.5 mm to 2 mm for epitaxial growth. This descent distance ensures both the epitaxial growth rate and the uniformity of the grown epitaxial layer thickness.

[0024] In one example, the method for epitaxial growth of silicon wafers provided in this embodiment of the invention can be performed according to the parameters shown in Table 1 below. 　 Step ① Step ② Step ③ Step 4 Step 5 Step 6 name Silicon wafer loading heating H2 baking HCL surface etching Blowing Thin film deposition H2 flow rate (slm) 50 50 50 50 50 50 HCL flow rate (slm) 0 0 0 1 0 0 TCS traffic (slm) 0 0 0 0 0 15 Reaction chamber temperature (°C) 750 7.5℃ / s 1130 1130 1130 1130 Base height (mm) 0 0 0 0 -1 -1

[0025] Table 1 To verify the repeatability or reproducibility of the method provided in the embodiments of the present invention, see [link to relevant documentation]. Figure 9 The graph shown in the figure represents the number of silicon wafers produced consecutively on the horizontal axis and the difference between the maximum local flatness values ​​SFQRmax and Delta SFQR on the vertical axis. Curve C9-1 represents the curve corresponding to the conventional method, and curve C9-2 represents the curve corresponding to the method provided in the embodiment of the present invention. Figure 9As can be seen, with the continuous production of silicon wafers, DeltaSFQR continuously increases and local flatness deteriorates when using conventional methods. However, when using the method provided in this embodiment of the invention, the DeltaSFQR value remains stable at around 0, indicating that the method provided in this embodiment of the invention is effective and has good repeatability.

[0026] See Figure 10 This invention also provides an apparatus 100 for epitaxial growth of silicon wafer W, the apparatus 100 including: As in Figure 10 The epitaxial reaction apparatus 110, outlined by a dashed box, includes a bell jar 111 enclosing a reaction chamber RC. Figure 10 The diagram shows an upper bell jar 111-1 and a lower bell jar 111-2; a disk-shaped base 112 inside the reaction chamber RC, the base 112 being configured to support the silicon wafer W; and an air inlet 113 configured to supply reactive gases into the reaction chamber RC, as shown in... Figure 10 As shown by the arrow at the air inlet 113, the air inlet 113 is located radially outside the base 112 and the base 112 is at a first height flush with the air inlet 113; An etching gas supply device 120 is configured to deliver etching gas to the reaction chamber RC via the gas inlet 113 to etch the silicon wafer W; A silicon source gas supply device 130 is configured to supply silicon source gas to the reaction chamber RC via the gas inlet 113 after the etching gas supply device 120 supplies etching gas to the reaction chamber RC, so as to grow an epitaxial layer on the surface of the silicon wafer W.

[0027] As in Figure 10 As shown in the image, with Figure 1 Similar to the existing epitaxial reaction apparatus 110A shown in the figure, the aforementioned epitaxial reaction apparatus 110 may further include: The base support frame 114 is used to support the base 112 and drive the base 112 to rotate at a certain speed around the central axis X of the device 110 during epitaxial growth. Since the silicon wafer W is supported by the base 112, the silicon wafer W rotates together with the base 10 around the central axis X. Exhaust port 115, which is used to discharge reaction exhaust gas from reaction chamber RC, such as in Figure 10 The arrow at exhaust port 115 is shown in the middle; Multiple heating bulbs 116 are disposed around the upper bell jar 111-1 and the lower bell jar 111-2 and are used to provide a high-temperature environment in the reaction chamber RC through the upper bell jar 111-1 and the lower bell jar 111-2.

[0028] In a preferred embodiment of the present invention, see Figure 10 The epitaxial reaction apparatus 110 may further include a drive mechanism 117 configured to lower the base 112 (e.g., in...). Figure 10 (As shown by the downward arrow at the base 112) so that the base 112 is at a second height below the first height, so that the thickness of the epitaxial layer grown on the silicon wafer W is more uniform, as described in detail above.

[0029] As in Figure 10 As shown, the drive mechanism 117 can be mounted on the base support frame 114, lowering the base 112 carried by the base support frame 114 by lowering the base support frame 114. Specifically, although not shown in the drawings, it is understood that the drive mechanism 117 may include, for example, a motor, a lead screw, and a lead screw nut cooperating with the lead screw, wherein the lead screw is fixedly connected to the base support frame 114, the lead screw nut is configured to remain fixed in the vertical direction, and the motor causes a relative rotational motion between the lead screw and the lead screw nut, which can be converted into a downward movement of the lead screw, thereby achieving the lowering of the base 112.

[0030] It should be noted that the technical solutions described in the embodiments of the present invention can be combined arbitrarily without conflict.

[0031] 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 method for epitaxial growth of a silicon wafer, characterized by, include: The first step is to place the silicon wafer on a disc-shaped base inside the reaction chamber; A second step involves delivering etching gas into the reaction chamber via an air inlet to etch the silicon wafer, wherein the air inlet is located radially outward of the base and the base is at a first height flush with the air inlet; The third step involves delivering silicon source gas through the gas inlet into the reaction chamber to grow an epitaxial layer on the surface of the silicon wafer. The second step is used to etch a larger amount of material into the radial edge region of the silicon wafer than into other regions. The third step is used to grow an epitaxial layer on the radial edge region of the silicon wafer that is thicker than the epitaxial layer grown on the other regions.

2. The method according to claim 1, characterized in that, The method further includes a fourth step between the second and third steps, which involves lowering the base to a second height below the first height.

3. The method according to claim 1, characterized in that, The method further includes a fifth step of preheating the silicon wafer between the first step and the second step.

4. The method according to claim 3, characterized in that, The method further includes a sixth step between the fifth step and the second step: baking the silicon wafer in a hydrogen atmosphere.

5. The method according to claim 1, characterized in that, The method further includes a seventh step between the second and third steps, in which hydrogen gas is used to purge the reaction chamber through the inlet to remove the etching gas from the reaction chamber.

6. The method according to claim 2, characterized in that, The distance between the first height and the second height is 0.5 mm to 2 mm.

7. The method according to claim 1, characterized in that, The etching gas is hydrogen chloride gas.

8. The method according to claim 7, characterized in that, The flow rate of the hydrogen chloride gas is 0.5 slm to 2 slm, and the delivery time is 10 s to 30 s.

9. An apparatus for epitaxial growth of silicon wafers, characterized in that, include: An epitaxial reaction apparatus, comprising: a bell jar enclosing a reaction chamber; a disk-shaped base inside the reaction chamber configured to support the silicon wafer; and an inlet configured to deliver reaction gas into the reaction chamber, wherein the inlet is located radially outward of the base and the base is at a first height flush with the inlet. An etching gas supply device is configured to deliver etching gas to the reaction chamber via the gas inlet to etch a greater amount of the radial edge region of the silicon wafer than other regions; A silicon source gas supply device is configured to supply silicon source gas to the reaction chamber via the gas inlet after the etching gas supply device supplies etching gas to the reaction chamber, so as to grow an epitaxial layer on the radial edge region of the silicon wafer with a thickness greater than that of the epitaxial layer grown on the other regions.

10. The device according to claim 9, characterized in that, The epitaxial reaction apparatus further includes a drive mechanism configured to lower the base so that the base is at a second height below the first height.

Images