A method for forming an epitaxial layer

Abstract

The present invention relates to a method for forming an epitaxial layer, comprising the following steps: S1, providing a substrate; placing the substrate in a chamber of an epitaxial device, the epitaxial device comprising a chamber, a first air inlet, an exhaust port, and inner and outer lamp groups, the inner and outer lamp groups being used to heat the substrate, the first air inlet and the exhaust port being respectively positioned on opposite sides of the chamber; S2, introducing a process gas into the chamber along a first direction through the first air inlet to perform an epitaxial process; wherein the process gas comprises a first silicon source and a second silicon source different from the first silicon source. The present invention improves the uniformity of the silicon epitaxial layer by controlling the flow rates of the two silicon source process gases and optimizing the power ratio of the inner and outer lamp groups.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing, and in particular to a method for forming an epitaxial layer. Background Art

[0002] Currently, silicon wafers, as the most important semiconductor material, play an irreplaceable role in the information industry. However, they have disadvantages such as low carrier mobility and slow device speed. Other materials need to be epitaxially grown to solve this problem. Among them, silicon germanium is the most common epitaxial material.

[0003] However, stress within the SiGe epitaxial layer is prone to relaxation, necessitating the overlay of a second layer of silicon on top of the SiGe epitaxial layer for protection and subsequent processing. Due to the limited heating lamps used in epitaxial equipment, uniformity of the silicon epitaxial layer has been a persistent problem. Summary of the Invention

[0004] In order to solve the problem of uniformity of silicon epitaxial layer, the present invention proposes a method for forming epitaxial layer, comprising the following steps:

[0005] S1. Providing a substrate; placing the substrate in a cavity of an epitaxial device, wherein the epitaxial device comprises a cavity, a first air inlet, an exhaust port, and inner and outer lamp groups, wherein the inner and outer lamp groups are used to heat the substrate, and the first air inlet and the exhaust port are respectively placed on opposite sides of the cavity;

[0006] S2, introducing a process gas into the cavity along a first direction through a first gas inlet member to perform an epitaxial process;

[0007] The process gas includes a first silicon source and a second silicon source different from the first silicon source.

[0008] Preferably, the first silicon source includes silicon and hydrogen; and the second silicon source includes silicon and at least one of fluorine and chlorine.

[0009] Further, the first silicon source includes at least one of SiH4, Si2H6, and Si3H8.

[0010] Further, the second silicon source includes at least one of SiHCl 3 , SiH 2 Cl 2 , and SiCl 4 .

[0011] As a preferred example, the first air inlet member includes at least two air inlet channels, and the at least two air inlet channels are horizontally arranged and parallel to the plane where the substrate is located.

[0012] As a preferred example, each of the air inlet channels supplies process gas independently of each other, and each air inlet channel independently controls the flow rate of the process gas.

[0013] As a preferred example, in step S2, the uniformity of forming the epitaxial layer in the epitaxial process is adjusted by adjusting the flow ratio of the first silicon source and the second silicon source in different gas inlet channels.

[0014] As a preferred example, in step S2, a first silicon source and a second silicon source are introduced into the air inlet channel of the first air inlet member; wherein, the flow rate of the first silicon source in different air inlet channels decreases from the center to the edge, and the flow rate of the second silicon source in different air inlet channels increases from the center to the edge.

[0015] As a preferred example, in step S2, the first silicon source and the second silicon source are introduced into the air inlet channel of the first air inlet member; wherein, the air inlet channel located at the edge of the first air inlet member only introduces the second silicon source, and the flow rate of the first silicon source in different air inlet channels decreases from the center to the edge, and the flow rate of the second silicon source in different air inlet channels increases from the center to the edge.

[0016] As a preferred example, the epitaxial equipment also includes a second air inlet member, which is arranged in the plane where the first air inlet member is located. In step S2, a second silicon source is introduced into the cavity along a second direction through the second air inlet member, and the second direction forms an angle with the first direction, and the angle is greater than 30°.

[0017] As a preferred example, the inner and outer lamp groups are arranged above and / or below the cavity, and the inner and outer lamp groups are arranged in concentric circles; in step S2, the uniformity of the epitaxial layer formed in the epitaxial process is adjusted by adjusting the power ratio of the inner and outer lamp groups.

[0018] As a preferred example, the power proportion of the external light group ranges from 55% to 90%.

[0019] As a preferred example, in step S2, the first silicon source and the second silicon source are introduced into the air inlet channel of the first air inlet member, and the flow ratio of the first silicon source to the second silicon source is 0.1:1-10:1.

[0020] Furthermore, the process temperature of the epitaxial process is 550°C-850°C.

[0021] Furthermore, the process gas also includes a germanium source and a carrier gas, the germanium source is germane, and the carrier is hydrogen or helium.

[0022] The present invention controls the flow rates of the two silicon source gases so that the two silicon source process gases in the cavity complement each other in space, thereby improving the uniformity of the silicon epitaxial layer; and optimizes the power ratio of the inner and outer lamp groups so that the power ratio of the outer lamp group is 55%-90%. The temperature sensitivity of the epitaxial layer is formed by the silicon source process gas, thereby improving the uniformity of the silicon epitaxial layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of the structure of the epitaxial device provided by the present invention;

[0024] Figure 2 This is a schematic structural diagram of an air intake component according to an embodiment of the present invention;

[0025] Figure 3 A schematic structural diagram of an air intake member according to another embodiment of the present invention;

[0026] Figure 4 Partial diagram of the thickness of epitaxial layers formed by different silicon sources of the present invention;

[0027] Figure 5 Flow chart of preparing epitaxial layer of the present invention. DETAILED DESCRIPTION

[0028] The following is a further detailed description of a method for forming an epitaxial layer proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the drawings are in a very simplified form and use non-precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In order to make the purposes, features and advantages of the present invention more obvious and easy to understand, please refer to the accompanying drawings. It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no technical significance. Any modification of the structure, change in the proportional relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the efficacy and purpose that can be achieved by the present invention.

[0029] like Figure 1Figure 1 is a schematic structural diagram of an epitaxial growth apparatus according to an embodiment of the present invention. The epitaxial growth apparatus includes a chamber formed by an upper dome 101, a lower dome 108, an upper liner 102, a lower liner 111, an upper flange 104, and a lower flange 107. The upper dome 101, the lower dome 108, the upper liner 102, and the lower liner 111 are all made of quartz. A susceptor 105 for supporting a substrate W is disposed within the chamber. Below the susceptor 105 are a rotating support shaft 110, a support bracket, and pins. The rotating support shaft 110 supports the rotation and elevation of the susceptor 105. The support bracket supports the pins when the rotating support shaft 110 descends, thereby separating the substrate W from the susceptor 105 during transfer. A first gas inlet 113 and a gas outlet 106 are provided on the side of the chamber. The first gas inlet 113 is connected to the gas inlet line 112 and is used to introduce process gas 114. The process gas 114 is deposited on the surface of the substrate W through heat to form an epitaxial layer. Finally, the used process gas is discharged from the gas outlet 106. Preheating rings 115 are also provided around the base 105 to preheat the process gas 114 entering the chamber.

[0030] Heating lamp groups 109 are installed at both the top and bottom of the chamber. These groups use infrared radiation to provide heat energy within the chamber. The power of these groups can be controlled to adjust the process temperature within the chamber. The heating lamp group 109 located at the top of the chamber comprises an inner group and an outer group. Both groups are arranged concentrically in a circular pattern, forming independently controlled groups. The inner group projects onto the inner ring of the base 105, while the outer group projects onto the outer ring. The center and edge temperatures of the substrate W can be adjusted by varying the power ratio of the inner and outer groups. The top and bottom of the chamber are also equipped with thermometers 103, respectively, for monitoring the temperature of the substrate W and near the base 105. Similarly, the heating lamp group 109 located at the bottom of the chamber can have the same arrangement as the heating lamp group 109 located at the top. Research has found that the silicon epitaxial layers formed by different silicon source process gases exhibit distinct characteristics, with the thickness distribution of these layers exhibiting certain patterns. Furthermore, different silicon source process gases respond differently to temperature, meaning that the uniformity of the silicon epitaxial layers formed by the same silicon source at different power ratios between the inner and outer lamp groups varies. Based on these two influencing factors, the uniformity of the silicon epitaxial layer can be improved by optimizing the composition and spatial distribution of the silicon source, as well as optimizing the temperature distribution near the substrate.

[0031] like Figure 5 As shown, based on the above Figure 1 The present invention provides a method for forming an epitaxial layer of the epitaxial device. The uniformity of the silicon epitaxial layer prepared by the method is greatly improved. The method comprises the following steps:

[0032] S1. Provide a substrate; place the substrate in a cavity of an epitaxial device, wherein the epitaxial device includes a cavity, a first air inlet 113, an exhaust port 106, and inner and outer lamp groups, wherein the inner and outer lamp groups are used to heat the substrate, and the first air inlet 113 and the exhaust port 106 are respectively placed on opposite sides of the cavity;

[0033] S2. Introduce a process gas into the chamber along a first direction through the first gas inlet member 113 to perform an epitaxial process; wherein the process gas includes a first silicon source and a second silicon source different from the first silicon source.

[0034] In this example, the first silicon source includes silicon and hydrogen; the second silicon source includes silicon and at least one of fluorine and chlorine.

[0035] Further, the first silicon source includes at least one of SiH4, Si2H6, and Si3H8.

[0036] Further, the second silicon source includes at least one of SiHCl 3 , SiH 2 Cl 2 , and SiCl 4 .

[0037] like Figure 2 The figure shows a top view of a first gas inlet component 113 of an epitaxial device proposed by the present invention. The first gas inlet component 113 of the epitaxial device includes at least two gas inlet channels 1131, which are arranged horizontally and parallel to the plane where the substrate is located. Each of the gas inlet channels 1131 supplies process gas independently of each other, and each gas inlet channel 1131 independently controls the flow rate of the process gas. Each gas inlet channel 1131 can independently introduce different silicon source process gases and independently control the flow rate of each silicon source process gas. The silicon source process gas in the gas inlet channel flows into the cavity in a first direction for epitaxial growth. For example, Figure 2 Taking the uppermost inlet channel 1131 (based on the direction of the drawing) as an example, a first silicon source and a second silicon source are respectively introduced into the inlet channel 1131. The flow rates of the first silicon source and the second silicon source are independently adjustable in the inlet channel 1131. The number of inlet channels 1131 can be set according to actual conditions. In this example, eight inlet channels 1131 are provided. Optionally, the number of inlet channels 1131 can be 5-12.

[0038] Figure 4 Figure 2 shows the thickness distribution of epitaxial layers formed on substrates with different silicon sources under the same process conditions. Figure 4 It can be found that: when only the first silicon source (SiH4 in the experiment) is used as the process gas, the epitaxial layer formed on the diameter of the substrate has a distribution characteristic of being thick in the middle and thin at the edge, while when only the second silicon source (SiH2Cl2 in the experiment) is used as the process gas, the epitaxial layer formed on the diameter of the substrate has a distribution characteristic of being thin in the middle and thick at the edge; Figure 5 The method shown in FIG. 1 is to simultaneously introduce SiH2Cl2+SiH4 into each gas inlet channel 1131 as process gases, and in each gas inlet channel 1131, the ratio of the flow rate of SiH2Cl2 to the flow rate of SiH4 is the same, and an epitaxial layer with a relatively uniform thickness distribution on the diameter of the substrate can be obtained (see FIG. 2 ). Figure 4 Although the overall uniformity of the curve is improved, the thickness of the epitaxial layer is still reduced at the center of the substrate (i.e., the position of 0 mm on the curve), and the thickness of the epitaxial layer is also reduced at the edge of the substrate (i.e., the position of ±150 mm on the curve). In this regard, the present invention proposes multiple preferred examples to improve the uniformity of the silicon epitaxial layer.

[0039] In step S2, the first silicon source and the second silicon source in each inlet channel 1131 are mixed to form process gases with different concentration ratios, and the concentration ratios can be adjusted by flow rate. The ratio of the two silicon source process gases is controlled by flow rate to form gas complementarity in different areas of the chamber. Specifically, the attached Figure 2 The first air intake member is shown.

[0040] Optionally, in step S2, a first silicon source and a second silicon source are introduced into the inlet channel 1131 of the first inlet member; wherein the flow rate of the first silicon source in different inlet channels 1131 decreases from the center O to the edge E, and the flow rate of the second silicon source in different inlet channels 1131 increases from the center to the edge. According to the characteristics of the epitaxial layer formed by the above-mentioned two silicon source process gases, this method introduces more of the second silicon source into the inlet channel 1131 near the edge of the substrate, and introduces more of the first silicon source into the inlet channel 1131 near the center of the substrate. The two silicon sources complement each other in space, and the first silicon source and the second silicon source have higher concentrations at the center and edge of the substrate, respectively. The two have complementary advantages in thickness, thereby forming thicker epitaxial layers at both the edge and center of the substrate, compensating for the disadvantage of uneven thickness of the epitaxial layer, and thereby preparing an epitaxial layer with better uniformity. Under certain process conditions, experiments have shown that although the proportion of the second silicon source in the edge inlet channel 1131 is very high, the thickness of the epitaxial layer at the edge is still relatively thin, and the purpose of making the epitaxial layer at the edge uniform cannot be achieved.

[0041] To this end, in step S2, a first silicon source and a second silicon source are introduced into the inlet channels 1131 of the first inlet member. The inlet channels 1131 at the edge of the first inlet member only receive the second silicon source, and the flow rate of the first silicon source decreases from the center to the edge of each inlet channel 1131, while the flow rate of the second silicon source increases from the center to the edge. In this case, the first silicon source is not introduced into the inlet channels 1131 at the edge of the first inlet member. In this example, since a larger amount of the second silicon source is introduced at the edge, complementing the first silicon source, the thickness of the epitaxial layer at the edge is maintained.

[0042] To further improve the uniformity of the epitaxial layer edge, as Figure 3 The figure shows another top view of the first gas inlet of an epitaxial device proposed in the present invention. The epitaxial device not only includes the first gas inlet 113 in the above-mentioned epitaxial device, but also has a second gas inlet 121. The process gas can not only flow into the cavity in a first direction through the first gas inlet, but also flow into the cavity in a second direction through the second gas inlet. The cross-flow of process gas in two directions can make the spatial distribution of process gas in the cavity more uniform, thereby preparing an epitaxial layer with better uniformity. An angle β is formed between the first direction and the second direction, and the angle β is greater than 30°. Preferably, the angle β is 90°. Based on the improved gas inlet, a second silicon source is also introduced into the cavity through the second gas inlet, and the first gas inlet is used to make the silicon source process gases in the cavity cross each other, thereby obtaining a better gas distribution, thereby obtaining a silicon epitaxial layer with better uniformity, and improving the uniformity of the edge.

[0043] Optionally, the method further includes adjusting the power of the inner and outer lamp groups, and adjusting the power ratio of the inner and outer lamp groups to adjust the uniformity of the epitaxial layer formed in the epitaxial process.

[0044] Preferably, the ratio of the power of the outer lamp group to the total power (i.e., the sum of the power of the inner and outer lamp groups) of the heating lamp group at the top of the chamber (or the heating lamp group at the bottom of the chamber) is in the range of 55%-90%. Due to the increased power of the outer lamp group, the deposition rate at the edge is increased, further improving the uniformity of the edge.

[0045] Furthermore, in the first preferred embodiment, the first silicon source and the second silicon source are introduced into the air inlet channel of the first air inlet member, and in the same air inlet channel, the flow ratio of the first silicon source to the second silicon source is 0.1:1-10:1.

[0046] Furthermore, the process temperature of the epitaxial process in the above embodiment is 550°C-850°C.

[0047] Furthermore, the process gas in the above embodiment also includes a germanium source and a carrier gas, the germanium source is germane, and the carrier is hydrogen or helium.

[0048] In summary, the present invention controls the flow rates of the two silicon source gases so that the two silicon source process gases in the cavity form complementary advantages in space, thereby improving the uniformity of the silicon epitaxial layer; and optimizes the power ratio of the inner and outer lamp groups so that the power ratio of the outer lamp group is 55%-90%, and utilizes the silicon source process gas to form the temperature sensitivity of the epitaxial layer, thereby improving the uniformity of the silicon epitaxial layer.

[0049] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description is not intended to limit the present invention. After reading the above description, various modifications and substitutions of the present invention will become apparent to those skilled in the art. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for forming an epitaxial layer, characterized in that: The following steps are involved: S1. Provide a substrate; place the substrate in a cavity of an epitaxial growth device, wherein the epitaxial growth device includes a cavity, a first air inlet, an exhaust port, and inner and outer lamp assemblies, wherein the inner and outer lamp assemblies are used to heat the substrate, and the first air inlet and the exhaust port are respectively placed on opposite sides of the cavity; the first air inlet includes at least two air inlet channels, and the at least two air inlet channels are arranged horizontally and parallel to the plane where the substrate is located; S2, introducing a process gas into the cavity along a first direction through an inlet channel of the first inlet member to perform an epitaxial process; In which, the process gas includes a first silicon source and a second silicon source different from the first silicon source; the uniformity of forming the epitaxial layer in the epitaxial process is adjusted by adjusting the flow ratio of the first silicon source and the second silicon source in different air inlet channels; the flow rate of the first silicon source in different air inlet channels decreases from the center to the edge, and the flow rate of the second silicon source in different air inlet channels increases from the center to the edge.

2. The method for forming an epitaxial layer according to claim 1, wherein: The first silicon source includes silicon and hydrogen; the second silicon source includes silicon and at least one of fluorine and chlorine.

3. The method for forming an epitaxial layer according to claim 2, wherein: The first silicon source includes at least one of SiH4, Si2H6, and Si3H8.

4. The method for forming an epitaxial layer according to claim 2, wherein: The second silicon source includes at least one of SiHCl 3 , SiH 2 Cl 2 , and SiCl 4 .

5. The method for forming an epitaxial layer according to claim 1, wherein: Each of the air inlet channels supplies process gas independently of each other, and each air inlet channel independently controls the flow rate of the process gas.

6. The method for forming an epitaxial layer according to claim 1, wherein: In step S2 , the gas inlet channel located at the edge of the first gas inlet member only allows the second silicon source to flow in.

7. The method for forming an epitaxial layer according to claim 6, wherein: The epitaxial device also includes a second air inlet member, which is arranged in the plane where the first air inlet member is located. In step S2, a second silicon source is introduced into the cavity along a second direction through the second air inlet member. The second direction forms an angle with the first direction, and the angle is greater than 30°.

8. The method for forming an epitaxial layer according to claim 6, wherein: The inner and outer lamp groups are arranged above and / or below the cavity, and the inner and outer lamp groups are arranged in concentric circles; in step S2, the uniformity of the epitaxial layer formed in the epitaxial process is adjusted by adjusting the power ratio of the inner and outer lamp groups.

9. The method for forming an epitaxial layer according to claim 8, wherein: The power proportion of the external light group ranges from 55% to 90%.

10. The method for forming an epitaxial layer according to claim 1, wherein: In step S2, the flow ratio of the first silicon source to the second silicon source is 0.1:1-10:

1.

11. The method for forming an epitaxial layer according to claim 1, wherein: The process temperature of the epitaxial process is 550°C-850°C.

12. The method for forming an epitaxial layer according to claim 1, wherein: The process gas further includes a germanium source and a carrier gas. The germanium source is germane, and the carrier gas is hydrogen or helium.

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