A method for producing a single-crystal thin film with low defects

Abstract

The application provides a preparation method of a single crystal thin film with low defects, and at least comprises the following steps: step S1, providing a substrate and placing the substrate in a reaction cavity; the pressure in the reaction cavity is less than 20 tor, and the process temperature of the substrate is lower than 900 DEG C; step S2, introducing a first deposition gas into the reaction cavity to form an N-type single crystal thin film on the surface of the substrate; the first deposition gas comprises a raw material gas and an N-type doping gas; step S3, switching to introduce a second deposition gas into the reaction cavity to form a P-type single crystal thin film on the surface of the N-type single crystal thin film; the second deposition gas comprises a raw material gas and a P-type doping gas; and the raw material gas is a silicon source precursor or a germanium source precursor. The preparation method can reduce the defects of the single crystal thin film and improve the film quality.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor manufacturing technology, and specifically relates to a method for preparing a low-defect single-crystal thin film. Background Technology

[0002] Epitaxial growth is a technique for growing a single-crystal material with specific properties on a single-crystal substrate, and it is widely used in semiconductor device manufacturing. Epitaxially growing a single-crystal epitaxial layer with the same crystal orientation as the wafer surface can be used to manufacture semiconductor device structures, such as source / drain regions of complementary metal-oxide-semiconductor (CMOS), epitaxial wafers, photoelectric conversion sensors, and photovoltaic solar cells.

[0003] Currently, gases such as silane, dichlorosilane, germanane, diborane, phosphine, and arsine are commonly used to generate a doped epitaxial layer on the silicon surface. Typically, the growth of epitaxial wafers (containing one or more single-crystal thin films) requires high temperatures (above 1000℃) and high pressures, with HCl added for selective epitaxial growth. HCl, as an additive for selective epitaxial growth, primarily functions to: 1) etch amorphous regions to remove the epitaxial layer grown in these regions, achieving selective growth; and 2) control the growth rate by adjusting the chemical activity of the reactants, ensuring uniform growth of the single-crystal thin film. Generally, when growing NP single-crystal thin films on a substrate surface, under high temperature and high pressure conditions, arsine or phosphine are first introduced into silane or dichlorosilane to form an N-type single-crystal thin film, followed by the introduction of diborane to form a P-type single-crystal thin film. The steps are reversed to form a PN single-crystal thin film.

[0004] However, while high temperature and high pressure can achieve high growth rates in the growth of NP / PN single crystal thin films, the resulting films suffer from poor quality and numerous defects, affecting subsequent applications and significantly limiting further improvements in semiconductor device performance. Therefore, a new technological solution is urgently needed to address these issues and meet the evolving needs of the semiconductor industry. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a low-defect single-crystal thin film. Under low temperature and low pressure conditions, a large flow rate of deposition gas is introduced into a high-quality substrate to form a single-crystal thin film, thereby reducing film defects and improving film quality.

[0006] To achieve the above objectives, the present invention provides a method for preparing a low-defect single-crystal thin film, comprising at least the following steps:

[0007] Step S1: Provide a substrate and place the substrate in a reaction chamber; the pressure in the reaction chamber is less than 20 tor and the process temperature of the substrate is less than 900°C;

[0008] Step S2: A first deposition gas is introduced into the reaction chamber to form an N-type single crystal thin film on the substrate surface; the first deposition gas includes a raw material gas and an N-type dopant gas.

[0009] Step S3: Switch the flow of a second deposition gas into the reaction chamber to form a P-type single crystal film on the surface of the N-type single crystal film; the second deposition gas includes a raw material gas and a P-type doping gas; the raw material gas is a silicon source precursor or a germanium source precursor.

[0010] Optionally, the pressure inside the reaction chamber is 10 tor-20 tor.

[0011] Optionally, the substrate processing temperature is 500℃-900℃.

[0012] Optionally, the raw material gas is any one of silane, dichlorosilane, and germanane.

[0013] Optionally, the N-type doping gas is arsine or phosphine; the P-type doping gas is diborane.

[0014] Optionally, the flow rates of both the first and second deposition gases are 10 sccm to 1000 sccm.

[0015] Optionally, the flow rate of the N-type doped gas is 20%-30% of the flow rate of the first deposited gas, and the flow rate of the P-type doped gas is 20%-30% of the flow rate of the second deposited gas.

[0016] Alternatively, the method for forming a single-crystal thin film is chemical vapor deposition or physical vapor deposition.

[0017] Optionally, prior to step S1, the substrate may be subjected to an etching process to form a natural oxide layer.

[0018] Optionally, prior to step S1, the substrate may undergo a hydrogen deep treatment.

[0019] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:

[0020] 1) At a temperature below 900℃ and a pressure below 20tor, a high flow rate of first deposition gas (raw material gas and arsine or phosphine that can provide free electrons) is first introduced into a high-quality substrate to form an N-type single crystal film. Then, a high flow rate of second deposition gas (raw material gas and diborane that can provide holes) is introduced to form a P-type single crystal film, thus obtaining an NP single crystal film with a highly ordered crystal structure. On the one hand, the pre-cleaned substrate possesses high quality; its surface is very smooth and undamaged, which facilitates uniform film growth. Furthermore, its lattice coefficient matches the epitaxial layer's lattice coefficient well, reducing defects caused by lattice mismatch and improving film quality. On the other hand, high flow rates of the first and second deposition gases improve gas distribution uniformity and increase reaction rates, contributing to the formation of a uniform film and allowing less time for defects to form during growth, thus reducing defects. Moreover, at low temperatures, the film growth process is closer to thermodynamic equilibrium, with lower thermal energy of atoms or molecules, weakened diffusion capabilities, and more ordered migration and bonding on the substrate surface, reducing lattice mismatch and dislocations caused by excessive diffusion. At low pressure, the reactant concentration is lower, and the reaction rate is relatively slower, allowing more time for reactants to find suitable adsorption sites on the substrate surface, thereby reducing defects caused by rapid growth. Therefore, under low-temperature and low-pressure conditions, using a high flow rate of deposition gases with a specific mixing ratio to epitaxially grow single-crystal films on a high-quality substrate can result in high-quality, virtually defect-free single-crystal films.

[0021] 2) In addition, under the above process conditions, the diffusion, adsorption and reaction processes of reactant molecules are relatively slow and stable, and they tend to react on specific crystal surfaces. The growth of the thin film itself has a certain selectivity. Therefore, the present invention does not require the addition of HCl for selective epitaxial growth, which is simple to operate, has less reaction time and lower cost. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the NP single-crystal thin film of the present invention.

[0023] Figure 2 This is a flowchart of the method for preparing the low-defect single-crystal thin film of the present invention.

[0024] Figure 3 These are comparative diagrams of the NP single-crystal thin films of the comparative examples and embodiments of the present invention; wherein, a is the NP single-crystal thin film of the comparative example, and b is the NP single-crystal thin film of the embodiment.

[0025] Attached image labels:

[0026] Substrate 10

[0027] N-type single crystal thin film 20

[0028] P-type single crystal thin film 30. 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] As mentioned in the background, although high temperature (above 1000℃) and high pressure can achieve a high growth rate when growing NP / PN single crystal thin films on the substrate surface, the film quality is poor and there are more defects, which affects the subsequent application in semiconductor devices.

[0033] To reduce film defects and improve film quality, this invention involves first introducing a high-flow-rate first deposition gas (raw material gas and arsine or phosphine that can provide free electrons) into a high-quality substrate at a temperature below 900°C and a pressure below 20 Tor to form an N-type single-crystal film. Then, a high-flow-rate second deposition gas (raw material gas and diborane that can provide holes) is introduced to form a P-type single-crystal film, thus obtaining an NP single-crystal film with a highly ordered crystal structure. Furthermore, the preparation process does not require the addition of HCl for selective epitaxial growth. This single-crystal film exhibits high quality and few defects, and its structure is as follows: Figure 1 As shown, it includes a substrate 10, an N-type single-crystal thin film 20, and a P-type single-crystal thin film 30. Specifically, the present invention provides a method for preparing a low-defect single-crystal thin film, the process of which is as follows: Figure 2As shown, it includes at least the following steps:

[0034] Step S1: Provide a substrate and place the substrate in a reaction chamber; the pressure in the reaction chamber is less than 20 Tor and the process temperature of the substrate is less than 900°C.

[0035] The substrate 10 is of high quality. "High quality" as used herein refers to the strict control of surface particle defects, resulting in a very smooth, undamaged surface that contributes to uniform film growth. Furthermore, the high-quality substrate 10 has a high lattice constant matching degree with the epitaxial layer, reducing defects caused by lattice mismatch and thus improving film quality. To obtain a high-quality substrate 10, its surface needs to be cleaned before placing it in the reaction chamber. For example, the native oxide layer on the substrate 10 surface can be etched and cleaned using plasma (such as ammonia or fluorine-containing gases), or the oxide layer on the substrate 10 surface can be effectively reduced at high temperature in a hydrogen atmosphere to remove residual impurities, thereby providing a clean surface for subsequent film deposition. After the surface of substrate 10 is cleaned, it is placed in the reaction chamber. The pressure inside the reaction chamber is less than 20 Tor, and the process temperature of substrate 10 is below 900°C. Compared with traditional high temperature (above 1000°C) and high pressure, at low temperature, the growth process of the thin film is closer to the thermodynamic equilibrium state. The thermal energy of atoms or molecules is lower, the diffusion ability is weakened, and the migration and bonding on the surface of substrate 10 are more orderly, reducing lattice mismatch and dislocations caused by excessive diffusion. However, the temperature cannot be too low, otherwise the starting energy required for growth will not be provided. At low pressure, the concentration of reactants is lower, the reaction rate is relatively slow, and the reactants have more time to find suitable adsorption sites on the surface of substrate 10, thereby reducing defects caused by rapid growth.

[0036] In some embodiments, the pressure inside the reaction chamber is 10 tor-20 tor, and the substrate process temperature is 500°C-900°C.

[0037] Step S2: A first deposition gas is introduced into the reaction chamber to form an N-type single crystal thin film on the substrate surface; the first deposition gas includes a raw material gas and an N-type dopant gas.

[0038] A raw material gas and an N-type dopant gas are introduced into the reaction chamber to form an N-type single-crystal thin film 20 on the surface of a high-quality substrate 10. In some embodiments, the raw material gas is any one of silane, dichlorosilane, or germanane, and the N-type dopant gas is arsine or phosphine. The total flow rate of the raw material gas and the N-type dopant gas is 10 sccm-1000 sccm, and the flow rate of the N-type dopant gas is 20%-30% of the total flow rate. During the deposition process, when arsine or phosphine is incorporated into the silicon lattice, the pentavalent arsenic or phosphorus elements can provide additional electrons, significantly increasing the concentration of free electrons in the silicon lattice, thereby enabling the formation of the N-type single-crystal thin film 20.

[0039] Step S3: Switch the flow of a second deposition gas into the reaction chamber to form a P-type single crystal film on the surface of the N-type single crystal film; the second deposition gas includes a raw material gas and a P-type doping gas; the raw material gas is a silicon source precursor or a germanium source precursor.

[0040] A second deposition gas, comprising a raw material gas and a P-type dopant gas, is introduced into the reaction chamber to form a P-type single-crystal thin film 30 on the surface of the N-type single-crystal thin film 20. In some embodiments, the raw material gas is a silicon source precursor or a germanium source precursor, specifically any one of silane, dichlorosilane, or germanane; the P-type dopant gas is diborane; the total flow rate of the raw material gas and the P-type dopant gas is 10 sccm-1000 sccm, and the flow rate of the P-type dopant gas is 20%-30% of the total flow rate. During the deposition process, when diborane is incorporated into the silicon lattice, the trivalent boron element provides holes, significantly increasing the hole concentration in the silicon lattice, thereby enabling the formation of the P-type single-crystal thin film 30. It is understood that the N-type dopant gas and the P-type dopant gas increase the concentration of charge carriers (free electrons or holes) in the silicon lattice, thereby improving the conductivity of the thin film and reducing its resistivity.

[0041] In some embodiments, the method for forming the single-crystal thin film is chemical vapor deposition or physical vapor deposition.

[0042] In this embodiment, a first deposition gas and a second deposition gas are sequentially introduced into a high-quality substrate 10. The flow rates of both the first and second deposition gases are relatively high, which improves the uniformity of gas distribution and ensures consistent reactant concentrations across the surface of the substrate 10. This contributes to the formation of a uniform thin film. Simultaneously, increasing the reactant concentration enhances the reaction rate, allowing less time for defects to form during film growth, thereby reducing defects. Therefore, under low-temperature and low-pressure conditions, by introducing a large flow rate of deposition gas with a specific mixing ratio into the high-quality substrate 10, a single-crystal thin film with fewer defects and higher quality can be obtained. Furthermore, under these process conditions, the diffusion, adsorption, and reaction processes of reactant molecules are relatively slow and stable, tending to react on specific crystal surfaces. The film growth itself already exhibits a certain degree of selectivity. Therefore, this embodiment does not require the addition of HCl for selective epitaxial growth, simplifying the operation, reducing reaction time, and lowering costs. However, it is worth noting that in this embodiment, even if HCl is added, it will not affect film growth; on the contrary, it will be more conducive to the formation of a single-crystal thin film.

[0043] In this embodiment, if a PN single-crystal thin film needs to be formed, a second deposition gas is first introduced into the reaction chamber to form a P-type single-crystal thin film 30 on the surface of the substrate 10. Then, a first deposition gas is introduced into the reaction chamber to form an N-type single-crystal thin film 20 on the surface of the P-type single-crystal thin film 30. The order of steps S2 and S3 is not limited in this invention.

[0044] Comparative Example

[0045] A substrate is provided and placed inside a reaction chamber; the pressure inside the reaction chamber is 100 Tor, and the substrate's processing temperature is 1100 °C. Dichlorosilane and arsine are introduced into the reaction chamber to form an N-type single-crystal thin film on the substrate surface. The total flow rate of dichlorosilane and arsine is 500 sccm, and the flow rate of arsine is 125 sccm. Dichlorosilane and diborane are then introduced into the reaction chamber to form a P-type single-crystal thin film on the N-type single-crystal thin film. The total flow rate of dichlorosilane and diborane is 500 sccm, and the flow rate of diborane is 125 sccm. The NP single-crystal thin film obtained using this comparative method is as follows: Figure 3 As shown in Figure 'a', the dots in the circles represent defects. It can be seen that the film has many defects and is of poor quality.

[0046] Example

[0047] A high-quality substrate is provided and placed inside a reaction chamber. The pressure inside the reaction chamber is 10 Tor, and the substrate processing temperature is 800°C. Dichlorosilane and arsine are introduced into the reaction chamber to form an N-type single-crystal thin film on the substrate surface. The total flow rate of dichlorosilane and arsine is 1000 sccm, and the flow rate of arsine is 250 sccm. Dichlorosilane and diborane are then introduced into the reaction chamber to form a P-type single-crystal thin film on the surface of the N-type single-crystal thin film. The total flow rate of dichlorosilane and diborane is 1000 sccm, and the flow rate of diborane is 250 sccm. The NP single-crystal thin film obtained using the method of this embodiment is as follows: Figure 3 As shown in b, the dots in the circle represent defects. It can be seen that the film has almost no defects and is of high quality.

[0048] In summary, this invention, at temperatures below 900°C and pressures below 20 tor, first introduces a high-flow-rate first deposition gas into a high-quality substrate to form an N-type single-crystal thin film, and then introduces a high-flow-rate second deposition gas to form a P-type single-crystal thin film, thus obtaining an NP single-crystal thin film with a highly ordered crystal structure. On one hand, the pre-cleaned substrate has high quality; the surface of a high-quality substrate is very flat, undamaged, and its lattice coefficient matches the lattice coefficient of the epitaxial layer well, reducing defects caused by lattice mismatch and improving film quality. On the other hand, the high flow rates of the first and second deposition gases improve gas distribution uniformity and increase the reaction rate, contributing to the formation of a uniform thin film and allowing less time for defects to form during film growth, thereby reducing defects. Furthermore, at low temperatures, the film growth process is closer to thermodynamic equilibrium; the thermal energy of atoms or molecules is lower, diffusion ability is weakened, and migration and bonding on the substrate surface are more ordered, reducing lattice mismatch and dislocations caused by excessive diffusion. At low pressures, the concentration of reactants is lower, the reaction rate is relatively slower, and reactants have more time to find suitable adsorption sites on the substrate surface, thereby reducing defects caused by rapid growth. Therefore, under low temperature and low pressure conditions, by introducing a large flow rate of deposition gas with a certain mixing ratio into a high-quality substrate to epitaxially grow single-crystal thin films, high-quality single-crystal thin films with almost no defects can be obtained. Furthermore, under the above process conditions, the diffusion, adsorption, and reaction processes of reactant molecules are relatively slow and stable, tending to occur on specific crystal surfaces. The film growth itself already exhibits a certain degree of selectivity. Therefore, this invention does not require the addition of HCl for selective epitaxial growth, simplifying the operation, reducing reaction time, and lowering costs.

[0049] 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 method for preparing a low-defect single-crystal thin film, characterized in that, Include at least the following steps: Step S1: Provide a substrate and place the substrate in a reaction chamber; the pressure in the reaction chamber is less than 20 tor and the process temperature of the substrate is less than 900°C; Step S2: A first deposition gas is introduced into the reaction chamber to form an N-type single crystal thin film on the substrate surface; the first deposition gas includes a raw material gas and an N-type dopant gas. Step S3: Switch the flow of a second deposition gas into the reaction chamber to form a P-type single crystal film on the surface of the N-type single crystal film; the second deposition gas includes a raw material gas and a P-type doping gas; the raw material gas is a silicon source precursor or a germanium source precursor.

2. The method as described in claim 1, characterized in that, The pressure inside the reaction chamber is 10 to 20 tor.

3. The method as described in claim 1, characterized in that, The substrate processing temperature is 500℃-900℃.

4. The method as described in claim 1, characterized in that, The raw material gas is any one of silane, dichlorosilane, and germanane.

5. The method as described in claim 1, characterized in that, The N-type doping gas is arsine or phosphine; the P-type doping gas is diborane.

6. The method as described in claim 1, characterized in that, The flow rates of the first and second deposition gases are both 10 sccm-1000 sccm.

7. The method as described in claim 6, characterized in that, The flow rate of the N-type doped gas is 20%-30% of the flow rate of the first deposited gas, and the flow rate of the P-type doped gas is 20%-30% of the flow rate of the second deposited gas.

8. The method as described in claim 1, characterized in that, The methods for forming single-crystal thin films are chemical vapor deposition or physical vapor deposition.

9. The method as described in claim 1, characterized in that, Prior to step S1, the substrate is further subjected to an etching process to form a natural oxide layer.

10. The method as described in claim 1, characterized in that, Prior to step S1, the substrate is subjected to a hydrogen deep treatment.

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