A pure germanium epitaxy process for a wafer

Abstract

The application discloses a wafer pure germanium epitaxy process, which is carried out in an epitaxy chamber containing a graphite member, and comprises the following steps: at a first temperature T1, a silicon source gas is introduced to grow a polysilicon layer on the surface of the graphite member; at a second temperature T2, a germanium source gas is introduced to grow a pure germanium isolation layer on the inner wall of the epitaxy chamber and the surface of the polysilicon layer; a wafer is placed on the graphite member with the polysilicon layer and the pure germanium isolation layer grown on the surface in sequence, a germanium source gas is introduced to epitaxially grow a pure germanium layer on the surface of the wafer; wherein the first temperature T1 is 800-1050 DEG C, and the second temperature T2 is 300-700 DEG C. The process avoids the generation of by-products, and guarantees the long-term stability of the pure germanium epitaxy process and the high product yield.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more specifically to a pure germanium epitaxial process for wafers. Background Technology

[0002] With the development of silicon photonics technology, pure germanium materials are increasingly widely used in devices such as photodetectors due to their high carrier mobility and compatibility with silicon processes. In the manufacturing process of silicon photonic devices, pure germanium epitaxial growth is a crucial step, and the quality of the epitaxial film determines the final photoelectric performance of the device. During the epitaxial process, residues inevitably accumulate in the epitaxial chamber. To ensure the stability and repeatability of the process, the chamber must be cleaned to remove these residues and restore its cleanliness.

[0003] However, existing methods for cleaning residues in epitaxial chambers typically employ high-temperature etching. While this method is suitable for traditional single-crystal silicon, polycrystalline silicon, or germanium-silicon epitaxial processes, it has limitations when applied to pure germanium epitaxial processes for silicon photonics devices. Firstly, the residues within the epitaxial chamber include germanium and non-germanium residues. The non-germanium residues are difficult to remove completely, and any remaining residues can interfere with subsequent pure germanium epitaxial processes, resulting in insufficient purity of the grown germanium film and thus affecting device performance. Secondly, since germanium has a melting point of approximately 937.4 degrees Celsius, traditional high-temperature conditions can cause the germanium residues on the chamber components to melt. The molten liquid germanium reacts with the graphite components within the chamber, generating byproducts and causing carbon precipitation, thereby damaging the graphite components. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of incomplete removal of non-germanium residues during the cleaning of pure germanium epitaxial chambers in the prior art, and component wear caused by the reaction of molten germanium with graphite parts at high temperatures, thereby improving the growth purity of pure germanium films and extending the service life of graphite parts.

[0005] To achieve the above objectives, the present invention provides a pure germanium epitaxial process for wafers. The pure germanium epitaxial process is performed in an epitaxial chamber, which contains a plurality of graphite elements, each including a base. The pure germanium epitaxial process includes: S201. Perform a polycrystalline silicon layer growth process to grow a polycrystalline silicon layer on the surface of the plurality of graphite parts; the process temperature of the polycrystalline silicon layer growth process is a first temperature T1, and the process gas of the polycrystalline silicon layer growth process includes a silicon source gas. S202. Perform a pure germanium isolation layer growth process to grow a pure germanium isolation layer on the inner wall of the epitaxial chamber and on the surface of the polycrystalline silicon layer; the process temperature of the pure germanium isolation layer growth process is a second temperature T2, and the process gas of the pure germanium isolation layer growth process includes germanium source gas. S203. Place the wafer on a substrate on which a polycrystalline silicon layer and a pure germanium isolation layer are sequentially grown on the surface, introduce germanium source gas, and epitaxially grow a pure germanium layer on the surface of the wafer. Wherein, the first temperature T1 is 800℃~1050℃, and the second temperature T2 is 300℃~700℃.

[0006] Optionally, before step S201, the method further includes: S101. Perform a germanium removal process by introducing an etching gas with a first flow rate H1 into the epitaxial chamber to remove germanium from the epitaxial chamber; the germanium removal process is performed as the temperature in the epitaxial chamber rises from a third temperature T3 to the first temperature T1. S102. Perform a polysilicon removal process by introducing an etching gas with a flow rate increasing from a second flow rate H2 to a first flow rate H1 into the epitaxial chamber to remove the polysilicon in the epitaxial chamber; the process temperature of the polysilicon removal process is the first temperature T1.

[0007] Optionally, the third temperature T3 is 300℃~700℃, and the third temperature T3 may be the same as or different from the second temperature T2.

[0008] Optionally, the first temperature T1 is 900℃~960℃.

[0009] Optionally, the first flow rate H1 is 15slm~50slm, and the second flow rate H2 is 5slm~15slm.

[0010] Optionally, the silicon source gas comprises any one or more of dichlorosilane, silane, and methylsilane.

[0011] Optionally, the germanium source gas includes any one or more of germanane, germanium tetrachloride, and germanium dichloride.

[0012] Optionally, the flow rate of the silicon source gas is 50 sccm to 1500 sccm.

[0013] Optionally, the flow rate of the germanium source gas is 50 sccm to 500 sccm.

[0014] Optionally, the etching gas is a chlorine-containing gas.

[0015] Optionally, steps S101, S102, S201, S202, S203, and S204 are executed N times in a loop, where N is an integer greater than 0.

[0016] Optionally, the plurality of graphite components further include a preheating ring and a pin, wherein: The base is disposed within the epitaxial cavity and is used to support the wafer; The preheating ring is arranged around the periphery of the base; The pin is movably inserted through the base.

[0017] Optionally, the graphite component includes a graphite substrate and a silicon carbide coating formed on the surface of the graphite substrate.

[0018] Compared to the prior art, the beneficial effects of the present invention include at least the following: (1) In this invention, a polysilicon layer and a pure germanium isolation layer are grown sequentially on the substrate of the epitaxial chamber as a composite protective layer. On the one hand, this ensures that even when a small amount of germanium melts due to small temperature fluctuations, the molten germanium is isolated by the polysilicon layer, avoiding direct contact with the silicon carbide coating on the substrate, thus fundamentally avoiding the generation of by-products and protecting the substrate. On the other hand, after depositing the pure germanium isolation layer on the substrate, it ensures that when the subsequent wafer is transferred into the epitaxial chamber for pure germanium epitaxial growth, the germanium concentration in the epitaxial chamber reaches 99.9%, providing a pure and stable chamber environment for the subsequent wafer epitaxial growth, thereby ensuring the film quality of the epitaxial pure germanium process. Furthermore, in this invention, a cleaning and etching process is performed on the epitaxial chamber before and after the wafer epitaxial growth process to remove the original polysilicon layer and pure germanium isolation layer attached to the inner wall of the epitaxial chamber and the surface of the substrate, so that a new composite protective layer can be grown after the cleaning and etching process, thereby ensuring the long-term stability and high product yield of the pure germanium epitaxial process.

[0019] (2) In the cleaning etching process of the present invention, etching begins during the heating stage, which can remove most of the pure germanium isolation layer before the temperature reaches or is slightly above the melting point of germanium, greatly reducing the risk of the pure germanium isolation layer melting as a whole; then, etching gas is introduced by linearly increasing the flow rate to ensure that the remaining pure germanium isolation layer and polysilicon layer are completely removed. The linear increase in the flow rate of the etching gas can adjust the residence time and distribution of the etching gas in the epitaxial chamber, ensuring the comprehensiveness and uniformity of cleaning of complex chamber structures (such as the base edge and near the air inlet), completely removing the pure germanium isolation layer and polysilicon layer in the previous process, and providing a stable environment for subsequent high-quality wafer epitaxial growth. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating the reaction between molten germanium residue and graphite components to generate byproducts during the cleaning of a pure germanium epitaxial chamber using existing technology.

[0021] Figure 2 This is a schematic diagram of the structure of the epitaxial device provided in an embodiment of the present invention.

[0022] Figure 3 This is a flowchart of a wafer pure germanium epitaxial process provided in an embodiment of the present invention.

[0023] Figure 4 This is a schematic diagram of a structure in which a polycrystalline silicon layer and a pure germanium isolation layer are formed on a substrate, as provided in an embodiment of the present invention.

[0024] Figure 5 This is a schematic diagram illustrating the temperature change over time in the epitaxial reaction chamber in an embodiment of the present invention.

[0025] Figure 6 This is a schematic diagram illustrating the change of etching gas flow rate over time in an embodiment of the present invention.

[0026] Figure 7 This is a schematic diagram illustrating the change in dichlorosilane flow rate over time in an embodiment of the present invention.

[0027] Figure 8 This is a schematic diagram illustrating the change of germane flow rate over time in an embodiment of the present invention.

[0028] Attached image labels: 1-Graphite component, 11-Graphite substrate, 12-Silicon carbide coating, 3-Polycrystalline silicon layer, 4-Pure germanium isolation layer, 100-Epitaxy equipment, 102-Inlet pipe, 103-Exhaust pipe, 106-Heating component, 108-Thermometer, 110-Gas injection insert, 112-Wall, 114-Upper liner, 116-Lower liner, 118-Upper dome, 120-Lower dome, 122-Base, 123-Upper flange, 124-Lower flange, 125-Quartz rotating support, 126-Quartz support assembly, 128-Pin, 130-Wafer, 132-Preheating ring, 134-Exhaust insert. Detailed Implementation

[0029] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] In the description of this invention, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0031] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0032] It should be noted that the accompanying drawings are all in a very simplified form and use non-precise ratios, and are only used to facilitate and clearly illustrate the purpose of this invention.

[0033] like Figure 1 As shown, when cleaning the pure germanium epitaxial chamber using the existing cleaning etching process, the molten germanium reacts with the graphite substrate and preheating ring of the epitaxial chamber to generate grayish-white jet-like germanium-silicon compounds, which leads to carbon precipitation and complex byproducts.

[0034] To address the aforementioned technical problems, this invention provides a pure germanium epitaxial growth process for wafers. Before pure germanium epitaxial growth, silicon source gas and germanium source gas are sequentially introduced into the epitaxial chamber. A composite protective layer comprising a polycrystalline silicon layer and a pure germanium isolation layer is grown on the surface of a graphite component. This composite protective layer not only prevents molten germanium from contacting the graphite component to avoid byproduct formation but also creates a high-purity germanium environment during the epitaxial growth of the pure germanium layer, improving the purity of the pure germanium film grown on the wafer. Furthermore, after the previous process cycle ends and before the next process cycle begins, the residual pure germanium isolation layer and polycrystalline silicon layer from the previous process cycle are removed, thereby ensuring the cleanliness of the epitaxial growth interface and the consistency of film performance across batches of wafers.

[0035] like Figure 2 As shown, Figure 2This is a schematic diagram of an epitaxial device provided by the present invention. This schematic diagram is for illustrative purposes only and does not constitute a sole limitation on the specific structure of the epitaxial device. The epitaxial device 100 includes an epitaxial chamber, a base 122, a pin 128, an air inlet pipe 102, a gas injection plug 110, a heating assembly 106, a thermometer 108, a rotating support assembly, an air outlet plug 134, and an exhaust pipe 103. The epitaxial chamber includes a wall 112, an upper inner liner 114, a lower inner liner 116, an upper dome 118, a lower dome 120, an upper flange 123, and a lower flange 124. The upper inner liner 114 and the lower inner liner 116 are both annular transparent quartz rings and are disposed inside the annular wall 112. The upper dome 118 and the lower dome 120 are approximately circular quartz rings. The upper inner liner 114 is disposed on the lower inner liner 124. Above the lower liner 116, a gas inlet and an opposite gas outlet are provided on the side of the liner for the entry and exit of process gases. The upper dome 118 is located above the upper liner 114 and is fixed above the wall 112 by the upper flange 123. The lower dome 120 is located below the lower liner 116 and is fixed below the wall 112 by the lower flange 124. The heating assembly 106 is located above and below the epitaxial chamber. The emitted infrared light can penetrate the upper dome 118 and the lower dome 120 to enter the upper and lower parts of the reaction chamber, providing heating energy to the epitaxial chamber. The base 122 is horizontally located in the epitaxial chamber to support the wafer 130 to be processed. The pin 128 is movably located on the base 122. The rotating support assembly, used to support and rotate the base 122, includes a quartz support assembly 126 and a quartz rotating support 125, with the quartz rotating support 125 coaxially arranged with the quartz support assembly 126. The temperature sensor 108 is positioned above and below the epitaxial chamber to monitor the temperature near the wafer 130. The epitaxial device 100 further includes a preheating ring 132, which is disposed around the base 122 and is used to preheat the process gas entering the epitaxial chamber. The gas inlet pipe 102 is connected to the gas inlet through the gas injection plug 110 and is used to introduce the process gas into the epitaxial chamber. The gas injection plug 110 is inserted into the gap of the wall portion 112 in the gas inlet direction. The heating component 106 heats and decomposes the process gas and deposits it on the surface of the wafer 130, thereby forming an epitaxial layer on the wafer 130. The gas outlet plug 134 is inserted into the gap of the wall portion 112 in the gas outlet direction and is connected to the exhaust pipe 103 to discharge the process waste gas from the epitaxial chamber.

[0036] At least one of the base 122, preheating ring 132, and pin 128 in the epitaxial apparatus 100 of the present invention is a graphite element, wherein the graphite element comprises a graphite substrate and a silicon carbide coating formed on the surface of the graphite substrate. A pure germanium wafer epitaxial process provided by the present invention is performed in the aforementioned epitaxial apparatus 100, and will be described in detail below: like Figures 3-8 As shown, the pure germanium epitaxial process of the present invention includes: S201. Perform a polycrystalline silicon layer growth process to grow a polycrystalline silicon layer 3 on the surface of the plurality of graphite parts 1; the process temperature of the polycrystalline silicon layer growth process is a first temperature T1, and the process gas of the polycrystalline silicon layer growth process includes silicon source gas.

[0037] To prevent direct contact between the subsequently molten germanium and the graphite part 1, this invention first grows a polycrystalline silicon layer 3 on the surface of the graphite part 1. A silicon source gas, comprising any one or more of dichlorosilane, silane, and methylsilane, is then introduced into the epitaxial chamber. Figure 7 As shown, taking dichlorosilane (DCS, chemical formula SiH2Cl2) as an example, at a first temperature T1 of 800℃~1050℃, dichlorosilane dissociates into silicon, hydrogen, and chlorine. Silicon is deposited on the surface of the graphite component 1 to form a polycrystalline silicon layer 3, while hydrogen and chlorine are discharged from the epitaxial chamber in a gaseous state. In some embodiments, the flow rate D1 of the silicon source gas is 50 sccm~1500 sccm.

[0038] It is understandable that even if the temperature of the epitaxial chamber reaches the melting point of germanium and germanium melts, the polycrystalline silicon layer 3 can act as an isolation layer, preventing the molten germanium from directly contacting the graphite component 1, thereby preventing the formation of byproducts due to the reaction between the two, fundamentally avoiding the formation of byproducts and protecting the graphite component 1.

[0039] S202. Perform a pure germanium isolation layer growth process to grow a pure germanium isolation layer 4 on the inner wall of the epitaxial chamber and on the surface of the polycrystalline silicon layer 3; the process temperature of the pure germanium isolation layer growth process is a second temperature T2, and the process gas of the pure germanium isolation layer growth process includes germanium source gas.

[0040] Before depositing a pure germanium isolation layer 4 on the surface of the polycrystalline silicon layer 3, to prevent defects such as relaxation dislocations from forming in the pure germanium isolation layer 4, it is usually necessary to lower the temperature within the epitaxial chamber, specifically from 800℃~1050℃ in the first temperature T1 to 300℃~700℃ in the second temperature T2. During pure germanium epitaxial growth, atomic mobility increases exponentially at high temperatures. The compressive stress generated by the lattice mismatch between silicon and germanium cannot be retained as elastic strain and will rapidly nucleate mismatch dislocations at the interface. Simultaneously, the thermal mismatch tensile stress from cooling after high-temperature growth will further trigger dislocation generation. The stress is released through plastic relaxation, ultimately forming high-density relaxation dislocations and other defects. Therefore, cooling the epitaxial chamber before pure germanium epitaxial growth significantly suppresses atomic mobility at low temperatures, almost eliminating the formation of relaxation dislocations and other defects.

[0041] Before pure germanium epitaxial growth, a pure germanium isolation layer 4 is grown on the inner wall of the epitaxial chamber and on the surface of the polycrystalline silicon layer 3. This significantly increases the germanium concentration within the epitaxial chamber and also acts as an isolation layer during the subsequent pure germanium epitaxial growth process, preventing impurities from entering the pure germanium layer and thus improving the quality of the film layer grown subsequently. Figure 8 As shown, a germanium source gas with a flow rate G1 of 50 sccm to 500 sccm is introduced into the epitaxial chamber. The germanium source gas contains any one or more of germanane, germanium tetrachloride, and germanium dichloride. At a second temperature T2 of 300℃ to 700℃, a pure germanium isolation layer 4 is pre-deposited on the surface of the graphite component 1, which can achieve a germanium concentration of over 99.9% in the epitaxial chamber. During the deposition of the pure germanium isolation layer 4, germanium atoms are fully adsorbed onto the surfaces of the reaction chamber walls, substrate, and other components of the epitaxial chamber, filling the active adsorption sites on the chamber surface. This prevents excessive adsorption and consumption of the gaseous germanium source by the chamber walls during subsequent pure germanium epitaxial growth, thereby maintaining a stable and higher effective germanium concentration in the chamber. This ensures a sufficient supply of germanium atoms and a uniform gas phase distribution during epitaxial growth, reducing problems such as uneven growth rate and film discontinuity caused by insufficient germanium source.

[0042] S203. Place the wafer on a graphite piece 1 (base 122) on which a polycrystalline silicon layer 3 and a pure germanium isolation layer 4 are sequentially grown on the surface, introduce germanium source gas, and epitaxially grow a pure germanium layer on the surface of the wafer.

[0043] After the composite protective layer consisting of a polycrystalline silicon layer 3 and a pure germanium isolation layer 4 is grown on the surface of the graphite component 1, the wafer is placed on the graphite component 1 (here, graphite component 1 refers to the base 122), and a pure germanium epitaxial growth process is performed in the epitaxial chamber. A germanium source gas is introduced into the epitaxial chamber. The germanium source gas contains any one or more of germanane, germanium tetrachloride, and germanium dichloride. Taking germanane as an example, germanane undergoes high-temperature thermal decomposition on the wafer surface, dissociating to generate germanium atoms and hydrogen gas. The germanium atoms are adsorbed and bonded at the wafer lattice sites, growing oriented along the wafer crystal orientation to form a pure germanium layer. The hydrogen gas is desorbed in a gaseous state and removed. In some embodiments, the flow rate G1 of the germanium source gas is 50 sccm to 500 sccm.

[0044] In some embodiments, to remove the original polycrystalline silicon layer 3 and pure germanium isolation layer 4 adhering to the inner wall of the epitaxial cavity and the surface of the substrate in order to grow a new composite protective layer, a cleaning etching process is included before step S201. This cleaning etching process includes: S101. During the process of the temperature in the epitaxial cavity rising from the third temperature T3 to the first temperature T1, an etching gas with a first flow rate H1 is introduced into the epitaxial cavity to remove germanium from the epitaxial cavity.

[0045] In the cleaning etching process of this invention, an etching gas is first introduced into the epitaxial chamber to etch germanium. The etching gas is a chlorine-containing gas (such as chlorine, hydrogen chloride, etc.). After the chlorine-containing gas undergoes a redox reaction with germanium, volatile germanium chlorides (mainly germanium tetrachloride and germanium dichloride) are generated, thereby removing germanium. When the etching gas is introduced, the temperature in the epitaxial chamber is raised, that is, gradually raised from 300℃~700℃ at the third temperature T3 to 800℃~1050℃ at the first temperature T1. The first flow rate H1 of the etching gas is 15slm~50slm. Since the melting point of germanium is approximately 937℃, etching begins during the heating stage, which can remove most of the pure germanium isolation layer 4 before the temperature reaches or slightly exceeds the melting point of germanium, avoiding the risk of the pure germanium isolation layer 4 melting completely. Furthermore, even if the temperature within the epitaxial chamber rises slightly above the melting point of germanium, causing a small amount of germanium to melt, the presence of a polycrystalline silicon layer 3 beneath the pure germanium isolation layer 4 isolates the molten germanium, preventing direct contact with the silicon carbide coating 12 on the substrate. This avoids a reaction between the two, preventing the formation of byproducts. In some embodiments, the first temperature T1 is 900℃~960℃. The third temperature T3 may be the same as or different from the second temperature T2.

[0046] S102. Maintain the temperature inside the epitaxial chamber at the first temperature T1, and introduce an etching gas with a flow rate increasing from the second flow rate H2 to the first flow rate H1 into the epitaxial chamber to remove the polysilicon inside the epitaxial chamber.

[0047] After etching away most of the pure germanium isolation layer 4, chlorine-containing gas is continuously introduced into the epitaxial chamber to etch the polysilicon and residual germanium. The chlorine-containing gas undergoes a redox reaction with the polysilicon, generating volatile silicon chlorides (mainly silicon tetrachloride), thereby removing the silicon. During polysilicon etching, the temperature within the epitaxial chamber is 800℃~1050℃, and the flow rate of the etching gas gradually increases from 5slm~15slm of the second flow rate H2 to 15slm~50slm of the first flow rate H1. By linearly increasing the flow rate of the etching gas, the flow field, pressure field, and gas residence time within the epitaxial chamber can be gradually altered through a flow gradient: Initially, at low flow rates, the etching gas velocity is slow and diffusion is stable, effectively covering near-field areas such as the inlet and ensuring sufficient reaction between the etching gas and residues. As the flow rate increases linearly, the pressure gradient and gas volume within the epitaxial chamber gradually increase, breaking down flow field dead zones at the base edge and chamber corners, allowing the etching gas to penetrate complex structures and accelerating the removal of etching products. The entire etching process avoids abrupt changes in flow rate, enabling the distribution and residence time of the etching gas in different areas of the chamber to adapt to the cleaning requirements of various structures. This solves the problems of insufficient near-field cleaning and lack of gas access at long distances under fixed flow rates, while also ensuring the uniformity of the etching gas and reaction rate, thus achieving comprehensive and uniform cleaning of complex chamber structures.

[0048] After the above-described cleaning and etching process, the original pure germanium isolation layer 4 and polysilicon layer 3 adhering to the inner wall of the epitaxial cavity and the surface of the substrate from the previous process are completely removed. It is understood that the cleaning and etching process of this invention can be performed both before and after the wafer epitaxial growth process. On the one hand, it provides a clean cavity environment for epitaxial growth. On the other hand, after the cleaning and etching process, a new composite protective layer can be regrown, thereby ensuring the long-term stability and high product yield of the pure germanium epitaxial process. Repeating steps S101, S102, S201, S202, and S203 several times can provide a clean and stable cavity environment before the pure germanium epitaxial process, and also ensure that the composite protective layer in the epitaxial cavity before the pure germanium epitaxial process is stable and controllable, thereby ensuring the long-term stability and high product yield of the pure germanium epitaxial process.

[0049] In summary, this invention performs a pure germanium epitaxial process within an epitaxial chamber containing a graphite element. The process includes growing a polysilicon layer on the surface of the graphite element at a first temperature T1, and after cooling the epitaxial chamber, growing a pure germanium isolation layer on the inner wall of the epitaxial chamber and on the surface of the polysilicon layer at a second temperature T2. The composite protective layer formed on the surface of the graphite element, containing the polysilicon layer and the pure germanium isolation layer, protects the graphite element and prevents subsequent germanium melting from directly contacting the graphite element and generating byproducts. After the composite protective layer is formed on the surface of the graphite element, the wafer is placed on the graphite element (here, the graphite element is a substrate) for the pure germanium epitaxial process, significantly increasing the germanium concentration within the chamber and thus ensuring the quality of the epitaxial pure germanium film. Furthermore, cleaning and etching processes are performed before and after epitaxial growth to remove the pure germanium isolation layer and polysilicon layer from the previous process, ensuring the long-term stability and high product yield of the pure germanium epitaxial process.

[0050] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A pure germanium epitaxial process for a wafer, wherein the pure germanium epitaxial process is performed in an epitaxial chamber, the epitaxial chamber being provided with a plurality of graphite elements, the plurality of graphite elements including a base, characterized in that, The pure germanium epitaxial process includes: S201. Perform a polycrystalline silicon layer growth process to grow a polycrystalline silicon layer on the surface of the plurality of graphite parts; the process temperature of the polycrystalline silicon layer growth process is a first temperature T1, and the process gas of the polycrystalline silicon layer growth process includes a silicon source gas. S202. Perform a pure germanium isolation layer growth process to grow a pure germanium isolation layer on the inner wall of the epitaxial chamber and on the surface of the polycrystalline silicon layer; the process temperature of the pure germanium isolation layer growth process is a second temperature T2, and the process gas of the pure germanium isolation layer growth process includes germanium source gas. S203. Place the wafer on a substrate on which a polycrystalline silicon layer and a pure germanium isolation layer are sequentially grown on the surface, introduce germanium source gas, and epitaxially grow a pure germanium layer on the surface of the wafer. Wherein, the first temperature T1 is 800℃~1050℃, and the second temperature T2 is 300℃~700℃.

2. The pure germanium epitaxial process as described in claim 1, characterized in that, Before step S201, the method further includes: S101. Perform a germanium removal process by introducing an etching gas with a first flow rate H1 into the epitaxial chamber to remove germanium from the epitaxial chamber; the germanium removal process is performed as the temperature in the epitaxial chamber rises from a third temperature T3 to the first temperature T1. S102. Perform a polysilicon removal process by introducing an etching gas with a flow rate increasing from a second flow rate H2 to a first flow rate H1 into the epitaxial chamber to remove the polysilicon in the epitaxial chamber; the process temperature of the polysilicon removal process is the first temperature T1.

3. The pure germanium epitaxial process as described in claim 2, characterized in that, The third temperature T3 is 300℃~700℃, and the third temperature T3 may be the same as or different from the second temperature T2.

4. The pure germanium epitaxial process as described in claim 2, characterized in that, The first temperature T1 is 900℃~960℃.

5. The pure germanium epitaxial process as described in claim 2, characterized in that, The first flow rate H1 is 15slm~50slm, and the second flow rate H2 is 5slm~15slm.

6. The pure germanium epitaxial process as described in claim 1, characterized in that, The silicon source gas includes any one or more of dichlorosilane, silane, and methylsilane.

7. The pure germanium epitaxial process as described in claim 1, characterized in that, The germanium source gas includes any one or more of germanane, germanium tetrachloride, and germanium dichloride.

8. The pure germanium epitaxial process as described in claim 1, characterized in that, The flow rate of the silicon source gas is 50 sccm to 1500 sccm.

9. The pure germanium epitaxial process as described in claim 1, characterized in that, The flow rate of the germanium source gas is 50 sccm to 500 sccm.

10. The pure germanium epitaxial process as described in claim 1, characterized in that, The etching gas is a chlorine-containing gas.

11. The pure germanium epitaxial process as described in claim 2, characterized in that, Steps S101, S102, S201, S202, and S203 are executed repeatedly N times, where N is an integer greater than 0.

12. The pure germanium epitaxial process as described in claim 1, characterized in that, The plurality of graphite components further include a preheating ring and a pin, wherein: The base is disposed within the epitaxial cavity and is used to support the wafer; The preheating ring is arranged around the periphery of the base; The pin is movably inserted through the base.

13. The pure germanium epitaxial process as described in claim 12, characterized in that, The graphite component comprises a graphite matrix and a silicon carbide coating formed on the surface of the graphite matrix.

Images