Semiconductor device and method of manufacturing the same
By pre-passing a set gas through the substrate before growing the epitaxial layer to react with impurities, oxygen impurities in the SiC substrate are removed, solving the leakage problem caused by oxygen impurity diffusion and improving the performance and reliability of semiconductor devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DYNAX SEMICON
- Filing Date
- 2021-12-24
- Publication Date
- 2026-07-21
AI Technical Summary
In the prior art, oxygen impurities in the SiC substrate diffuse into the GaN epitaxial layer, leading to increased leakage current and affecting the performance of semiconductor devices.
Before growing the epitaxial layer, a set gas is pre-passed through the substrate to chemically react with impurities in the substrate to remove the impurities. For example, gallium or aluminum gas is used to react with oxygen impurities at a specific temperature and decompose them to form intermediate compounds, which are then discharged.
It effectively suppresses the diffusion of substrate impurities into the epitaxial layer, improves the performance of semiconductor devices, and in particular reduces leakage current, thereby improving the reliability and efficiency of the devices.
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Figure CN116344332B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of microelectronics technology, and in particular to a semiconductor device and a method for fabricating the same. Background Technology
[0002] Group III nitride materials possess unique advantages in realizing optoelectronic devices and high electron mobility transistors (HEMTs), and their research has undergone a long development process. Gallium nitride (GaN) semiconductor materials have significant advantages such as a large bandgap, high electron saturation drift velocity, high breakdown field strength, and high temperature resistance. Compared with first-generation semiconductor silicon and second-generation semiconductor gallium arsenide, they are more suitable for fabricating high-temperature, high-voltage, high-frequency, and high-power electronic devices, and have broad application prospects, making them a current research hotspot in the semiconductor industry.
[0003] In existing technologies, two main approaches are used to improve the crystal quality of GaN: one is to employ nucleation layer technology, and the other is to select a substrate with a lattice constant close to that of GaN. While using a substrate with a lattice constant close to GaN effectively improves crystal quality, the growth and polishing processes introduce impurities into the substrate surface. These impurities tend to diffuse from GaN into the epitaxial layer, increasing the overall impurity content and impacting the performance of the fabricated semiconductor device. For example, in SiC substrates, impurities doped into the surface include nitrogen and oxygen. During GaN epitaxial growth, oxygen impurities from the SiC substrate diffuse into the GaN epitaxial layer. Since oxygen impurities exist as donors in GaN, the increased oxygen impurities lead to increased leakage current in the GaN epitaxial layer, significantly degrading the performance of the semiconductor device. Summary of the Invention
[0004] This invention provides a semiconductor device and its fabrication method to suppress the diffusion of impurities from the substrate to the epitaxial layer and improve the performance of the semiconductor device.
[0005] In a first aspect, embodiments of the present invention provide a method for fabricating a semiconductor device, comprising:
[0006] Provide substrate;
[0007] A predetermined gas is pre-passed through the substrate to allow the predetermined gas to chemically react with impurities in the substrate, thereby removing the impurities from the substrate;
[0008] An epitaxial layer is formed on the substrate.
[0009] Optionally, the impurities in the substrate include oxygen impurities;
[0010] The set gas is a gas that reacts chemically with the oxygen impurity at a first preset temperature and decomposes at a second preset temperature.
[0011] Optionally, the set gas includes at least one of gallium or aluminum.
[0012] Optionally, the substrate can be pre-passed with a pre-set gas in a cyclic pre-pass manner.
[0013] Optionally, one cycle in the cyclic pre-circuiting includes:
[0014] A first preset temperature condition is provided, and the set gas is introduced into the surface of the substrate so that the set gas reacts chemically with impurities in the substrate to form an intermediate compound;
[0015] A second preset temperature condition and an exhaust passage are provided to allow the intermediate compound to decompose and be discharged with the exhaust gas.
[0016] Optionally, the epitaxial layer includes a nucleation layer that is in contact with the substrate;
[0017] The number of cycles in the pre-pass treatment is negatively correlated with the thickness of the nucleation layer.
[0018] Optionally, the thickness of the nucleation layer is X, the number of cycles is Y, and the preset thickness is Z;
[0019] If X > Z, then Y is a constant value;
[0020] If X ≤ Z, then Y is a decreasing function of X.
[0021] Optionally, the constant value is 1 or 2.
[0022] Optionally, the functional relationship between X and Y can be expressed as: Y = ROUND(-0.1*X + Q), where ROUND represents rounding to the nearest integer and Q is an integer.
[0023] Optionally, the value of Z can be in the range of 30nm to 40nm.
[0024] Optionally, the gas flow method for pre-passing the substrate with a set gas includes at least one of the following: constant flow rate, multi-pulse flow rate, and flow rate gradual change flow rate.
[0025] Optionally, the flow rate gradient method includes at least one of the following: flow rate increment, flow rate decrement, flow rate increment followed by decrement, and flow rate decrement followed by increment.
[0026] Optionally, the flow rate gradation method includes at least one of stepless flow rate gradation and stepped flow rate gradation.
[0027] Secondly, embodiments of the present invention also provide a semiconductor device, which is manufactured using the manufacturing method described in any embodiment of the present invention.
[0028] This invention provides a novel method for fabricating a semiconductor device, comprising: providing a substrate; pre-passing a predetermined gas through the substrate to allow the predetermined gas to chemically react with impurities in the substrate, thereby removing the impurities; and forming an epitaxial layer on the substrate. In other words, this invention reduces the impurity content in the substrate by pre-passing a predetermined gas through the substrate before growing the epitaxial layer, thereby inhibiting the diffusion of impurities from the substrate to the epitaxial layer and improving the performance of the semiconductor device. Attached Figure Description
[0029] Figure 1 A schematic flowchart illustrating a method for fabricating a semiconductor device according to an embodiment of the present invention;
[0030] Figure 2 This is a schematic diagram of the structure of a semiconductor device provided in an embodiment of the present invention;
[0031] Figure 3 This is a schematic diagram illustrating the change of the flow rate of a pre-set gas over time, provided as an embodiment of the present invention.
[0032] Figure 4 This is a schematic diagram illustrating the change of the flow rate of a pre-passed gas over time, as provided in another embodiment of the present invention.
[0033] Figure 5 A schematic diagram illustrating the change of flow rate of a pre-passed gas over time, as provided in another embodiment of the present invention;
[0034] Figure 6 A schematic diagram illustrating the change of flow rate of a pre-passed gas over time, as provided in another embodiment of the present invention;
[0035] Figure 7 A schematic diagram illustrating the change of flow rate of a pre-passed gas over time, as provided in another embodiment of the present invention;
[0036] Figure 8 A schematic diagram illustrating the change of flow rate of a pre-passed gas over time, as provided in another embodiment of the present invention;
[0037] Figure 9 This is a schematic diagram illustrating the change in the flow rate of a pre-set gas over time, as provided in another embodiment of the present invention. Detailed Implementation
[0038] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.
[0039] This invention provides a method for fabricating a semiconductor device. Figure 1 This is a schematic flowchart illustrating a method for fabricating a semiconductor device according to an embodiment of the present invention. See also... Figure 1 The method for fabricating semiconductor devices includes the following steps:
[0040] S110 provides a substrate.
[0041] The substrate material can be one or more of gallium nitride (GaN), aluminum gallium nitride (AlGaN), indium gallium nitride (InGaN), aluminum indium gallium nitride (AlInGaN), indium phosphide (InP), gallium arsenide (GaAs), silicon carbide (SiC), diamond, sapphire, germanium, and silicon, or any other material capable of growing group III nitrides. For example, the substrate material is SiC, and the impurities in the substrate include oxygen impurities and nitrogen impurities.
[0042] S120. A set gas is pre-passed through the substrate to allow the set gas to react chemically with impurities in the substrate, thereby removing the impurities from the substrate.
[0043] The set gas refers to a gas capable of chemically reacting with impurities in the substrate, and its specific characteristics can be determined based on the substrate material and the type of impurities. For example, the substrate material is SiC, the impurities in the substrate include oxygen impurities, and the set gas is a gas that chemically reacts with oxygen impurities at a first preset temperature and decomposes at a second preset temperature. This configuration facilitates the removal of oxygen impurities and prevents substances synthesized from oxygen impurities and the set gas from further affecting the performance of the epitaxial layer. For example, the set gas includes at least one of gallium or aluminum; preferably, the set gas is gallium, meaning that gallium is pre-passed through the substrate before forming the epitaxial layer. Compared to aluminum oxide, gallium oxide, formed by gallium and oxygen, requires a lower temperature to decompose, which is beneficial for the implementation of the gallium pre-passing impurity removal process.
[0044] S130, An epitaxial layer is formed on the substrate.
[0045] The epitaxial layer can be a multilayer epitaxial structure, and can include semiconductor materials based on III-V compounds.
[0046] Therefore, the embodiments of the present invention reduce the impurity content in the substrate by pre-passing a set gas through the substrate before growing the epitaxial layer, and by the set gas reacting chemically with the impurities in the substrate. This helps to suppress the diffusion of impurities from the substrate to the epitaxial layer and improves the performance of the semiconductor device.
[0047] Based on the above embodiments, optionally, the method of pre-passing the substrate with the set gas is cyclic pre-passing. Cyclic pre-passing means that the set gas can be pre-passed two or more times. This setting helps to thoroughly remove impurities from the substrate.
[0048] In one embodiment of the present invention, optionally, one cycle of the pre-pass cycle includes: providing a first preset temperature condition and introducing a set gas into the substrate surface to allow the set gas to chemically react with impurities in the substrate to form an intermediate compound; providing a second preset temperature condition and an exhaust channel to allow the intermediate compound to decompose and be discharged with the exhaust gas. The first preset temperature condition refers to the temperature condition that allows the impurities to chemically react with the set gas, and the second preset temperature condition refers to the temperature condition that allows the intermediate compound to decompose. Specifically, taking the pre-passing of gallium on a SiC substrate as an example, the first preset temperature condition is a low-temperature condition, and the second preset temperature condition is a high-temperature condition. One cycle includes: first, introducing Ga into the SiC substrate surface at a low temperature, where Ga reacts with oxygen in the SiC substrate to form gallium oxide; then, raising the temperature to a high temperature, where gallium oxide decomposes into Ga and oxygen and is discharged with the exhaust gas. This configuration simplifies the process of removing impurities from the substrate and is easy to implement.
[0049] Figure 2 This is a schematic diagram of the structure of a semiconductor device provided in an embodiment of the present invention. See also... Figure 2Based on the above embodiments, optionally, the epitaxial layer has a multilayer structure, sequentially including, from the direction of the substrate 10: a nucleation layer 21, a buffer layer 22, a channel layer 23, and a barrier layer 24. The nucleation layer 21 is in contact with the substrate 10 and influences parameters such as the crystal quality, surface morphology, and electrical properties of the heterojunction material above it. The nucleation layer 21 varies depending on the material of the substrate 10, mainly serving to match the substrate 10 material with the semiconductor material layer in the heterojunction structure. For example, the material of the nucleation layer 21 includes aluminum nitride (AlN). The buffer layer 22 serves both to bond the semiconductor material layer to be grown next and to protect the substrate 10 material from intrusion by metal ions. The material of the buffer layer 22 can be a group III nitride material such as aluminum gallium nitride (AlGaN), gallium nitride (GaN), or aluminum indium gallium nitride (AlGaInN). Preferably, the material of the buffer layer 22 is gallium nitride ((Al)GaN) with controllable aluminum content. The channel layer 23 and the barrier layer 24 above it together form a heterojunction structure. The channel layer 23 provides a channel for the movement of two-dimensional electron gas. The barrier layer 24 is located close to the channel layer 23, and the material of the barrier layer 24 can be aluminum gallium nitride (AlGaN) or aluminum indium gallium nitride (AlGaInN).
[0050] Based on the above embodiments, optionally, the epitaxial layer further includes a cap layer, which is located on the side of the barrier layer 24 away from the substrate 10. The cap layer can be made of gallium nitride (GaN), and optionally, the thickness of the cap layer is greater than 10 nm, preferably greater than 30 nm, and more preferably greater than 100 nm. The cap layer can be undoped, n-type doped, or n-type partially doped, etc. The cap layer can both stabilize the epitaxial heterojunction and prevent the diffusion of silicon atoms from the dielectric layer to p-type gallium nitride.
[0051] In the above embodiments, optionally, the number of cycles in the pre-pass treatment is negatively correlated with the thickness of the nucleation layer. The nucleation layer (e.g., AlN) reduces leakage current in semiconductor devices; the thicker the nucleation layer, the lower the leakage current. However, when the nucleation layer thickness reaches a certain level, such as 35 nm, its effect on reducing leakage current tends to saturate; that is, increasing the nucleation layer thickness can no longer further reduce the leakage current of the semiconductor device. Combining this with a pre-pass setting gas method can further reduce the leakage current of the semiconductor device. Therefore, the nucleation layer and the pre-pass setting gas method play a complementary role in suppressing leakage current in semiconductor devices. Thus, when the nucleation layer thickness is relatively thick, the number of cycles in the pre-pass treatment can be appropriately reduced; conversely, when the nucleation layer thickness is relatively thin, the number of cycles in the pre-pass treatment can be appropriately increased.
[0052] In practical applications, the number of cycles of the cyclic pre-connection process can be determined according to the thickness of the nucleation layer. Specifically, in some cases, the thickness of the nucleation layer needs to be set relatively thick. At this time, the leakage current of the semiconductor device is small, but it still does not meet the performance requirements of the semiconductor device. Correspondingly, the leakage current performance requirements of the semiconductor device can be achieved by performing the cyclic pre-connection process. In other cases, the thickness of the nucleation layer needs to be set relatively thin. At this time, the leakage current of the semiconductor device increases. Correspondingly, the increase in the leakage current of the semiconductor device can be suppressed by increasing the number of cycles of the cyclic pre-connection process.
[0053] To achieve better performance of the semiconductor device and lower cost of the manufacturing process, the inventors further studied the relationship between the thickness of the nucleation layer and the number of cycles. On the basis of the above embodiments, optionally, let the thickness of the nucleation layer be X, the number of cycles be Y, and the preset thickness be Z; if X > Z, then Y is a constant value; if X ≤ Z, then Y is a decreasing function of X. Among them, the setting of the preset thickness Z is related to the influence of the thickness of the nucleation layer on the leakage current of the semiconductor device. When the nucleation layer reaches the preset thickness Z, the effect of reducing the leakage current will tend to saturate. Exemplarily, the value range of the preset thickness Z is: 30 nm to 40 nm, preferably 35 nm. The setting of the constant value is related to the influence of pre-passing a preset gas on the substrate on the leakage current of the semiconductor device. If the thickness of the nucleation layer reaches the preset thickness Z, increasing the number of cycles beyond the set value will not significantly improve the leakage current effect. Therefore, the number of cycles is set to a constant value. Exemplarily, the constant value is 1 or 2, preferably 1. In some cases, after the thickness of the nucleation layer reaches the preset thickness Z, the leakage current suppression effects of one cycle and multiple cycles are basically the same. Therefore, one cycle is beneficial to improving the manufacturing efficiency of the semiconductor device and reducing the manufacturing cost of the semiconductor device.
[0054] Optionally, the functional relationship between X and Y is expressed as: Y = ROUND(-0.1*X + Q), where ROUND means rounding to an integer, and Q is an integer. Among them, the setting method of Q is related to the influence of pre-passing a preset gas on the substrate on the leakage current of the semiconductor device. Exemplarily, when X = 0 (that is, the nucleation layer is not set), Y = Q. That is to say, Q is the upper limit value of the number of cycles. When the number of cycles reaches Q, the effect of reducing the leakage current will tend to saturate. Even if the value of Q is increased, no better beneficial effect will be brought. For example, Q = 5. Such a setting is beneficial to ensuring the removal of substrate impurities to the greatest extent and reducing the manufacturing cost.
[0055] In the above embodiments, optionally, when 0 < X ≤ 35, Y = -0.1*X + 5, and Y is rounded to an integer; when X > 35 nm, Y = 1. Such a setting can reduce the manufacturing cost to the greatest extent on the basis of ensuring that the leakage current of the semiconductor device is small.
[0056] Based on the above embodiments, there are various methods for pre-flushing the substrate with a set gas, such as constant flow rate, multi-pulse method, and flow rate gradual variation method, which will be described in detail below. These various ventilation methods can be combined arbitrarily, and this invention does not limit them.
[0057] Figure 3 This is a schematic diagram illustrating the change in the flow rate of a pre-flowed gas over time, provided as an embodiment of the present invention. See also... Figure 3 In one embodiment of the present invention, optionally, the gas flow method for pre-passing the substrate with a set gas is a constant flow rate method. Specifically, taking gallium (Ga) pre-passing as an example, before time t1, it is the stage before Ga pre-passing, and the Ga flow rate is 0; between time t1 and t2, it is the stage of Ga pre-passing, and the Ga flow rate is the set value; after time t2, it is the stage after Ga pre-passing, and the Ga flow rate is 0.
[0058] Figure 4 This is a schematic diagram illustrating the change in the flow rate of a pre-flowed gas over time, as provided in another embodiment of the present invention. See also... Figure 4 In one embodiment of the present invention, optionally, the gas flow method for pre-passing the substrate with a set gas is a pulse method. Specifically, taking gallium (Ga) pre-passing as an example, before time t1, it is the stage before Ga pre-passing, and the Ga flow rate is 0; between time t1 and t2, it is the stage of Ga pre-passing, and the Ga flow rate jumps between 0 and the set value multiple times, in a pulsed manner; after time t2, it is the stage after Ga pre-passing, and the Ga flow rate is 0.
[0059] Figure 5 This is a schematic diagram illustrating the change in the flow rate of a pre-flowed gas over time, as provided in another embodiment of the present invention. See also... Figure 5 In one embodiment of the present invention, optionally, the gas flow method for pre-passing the substrate with a set gas is a gradually decreasing flow rate method. Specifically, taking gallium (Ga) pre-passing as an example, before time t1, which is the stage before Ga pre-passing, the Ga flow rate is 0; between time t1 and t2, which is the stage of Ga pre-passing, the Ga flow rate gradually decreases from the set value to 0, showing a decreasing flow rate; after time t2, which is the stage after Ga pre-passing, the Ga flow rate is 0.
[0060] It should be noted that the gradual change in traffic can also be achieved through methods such as... Figure 6 As shown, the flow rate increases; it can also be as follows: Figure 7 As shown, the flow rate first increases and then decreases; it can also be as follows: Figure 8 As shown, the flow rate first decreases and then increases.
[0061] It should also be noted that, in Figures 5-8 The example shown illustrates a flow rate gradient method that is stepless, i.e., a smooth gradient, and is not intended to limit the invention. In other embodiments, such as... Figure 9 As shown, the flow rate gradient method can also be set to flow rate step gradient.
[0062] This invention also provides a semiconductor device, which is manufactured using the same method as provided in any embodiment of this invention. The specific principles and effects are similar and will not be described again.
[0063] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.
Claims
1. A method for fabricating a semiconductor device, characterized in that, include: Provide substrate; The substrate is doped with impurities; A pre-passing gas is introduced into the substrate to allow the gas to chemically react with impurities in the substrate, thereby removing the impurities; wherein, the pre-passing of the pre-passing gas into the substrate is performed in a cyclic pre-passing manner. An epitaxial layer is formed on the substrate; the epitaxial layer comprises a semiconductor material based on a III-V compound; wherein the epitaxial layer includes a nucleation layer that is in contact with the substrate; the number of cycles of the pre-pass treatment is negatively correlated with the thickness of the nucleation layer; The thickness of the nucleation layer is X, the number of cycles is Y, and the preset thickness is Z; If X > Z, then Y is a constant value; If X ≤ Z, then Y is a decreasing function of X.
2. The method for fabricating a semiconductor device according to claim 1, characterized in that, The impurities in the substrate include oxygen impurities; The set gas is a gas that reacts chemically with the oxygen impurity at a first preset temperature and decomposes at a second preset temperature.
3. The method for fabricating a semiconductor device according to claim 2, characterized in that, The set gas includes at least one of gallium or aluminum.
4. The method for fabricating a semiconductor device according to claim 1, characterized in that, One of the loops in the cyclic pre-circuit includes: A first preset temperature condition is provided, and the set gas is introduced into the surface of the substrate so that the set gas reacts chemically with impurities in the substrate to form an intermediate compound; A second preset temperature condition and an exhaust passage are provided to allow the intermediate compound to decompose and be discharged with the exhaust gas.
5. The method for fabricating a semiconductor device according to claim 1, characterized in that, The functional relationship between X and Y is expressed as: Y = ROUND(-0.1*X + Q), where ROUND means rounding to the nearest integer and Q is an integer.
6. The method for fabricating a semiconductor device according to claim 5, characterized in that, The value of Z ranges from 30nm to 40nm.
7. A semiconductor device, characterized in that, It is manufactured using the manufacturing method described in any one of claims 1-6.