Semiconductor structure and forming method thereof

Abstract

The invention discloses a semiconductor structure and a forming method thereof, the semiconductor structure comprises a reactor and a substrate, the reactor comprises a reaction area, a first gas distribution cavity and a second gas distribution cavity, the first gas distribution cavity and the second gas distribution cavity are communicated with the reaction area, a first reaction gas is introduced into the reaction area through the first gas distribution cavity, and a second reaction gas is introduced into the second gas distribution cavity through the second gas distribution cavity; second reaction gas is introduced into the reaction area through the second gas distribution cavity, and P-type layer growth is carried out on the substrate through the first reaction gas and the second reaction gas; the first reaction gas at least comprises a V-group precursor and a first carrier gas, and the second reaction gas at least comprises a P-type doping precursor, a III-group precursor and a second carrier gas. By adjusting the relative flow velocity or relative density of the second carrier gas relative to the first reaction gas, the transmission speed of the second reaction gas is higher, the transmission direction is not easy to change, the doping concentration of the P-type doping ions in the P-type layer is improved, the doping is more uniform, and the performance of the semiconductor device is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor manufacturing, and in particular to a semiconductor structure and a forming method thereof. Background Art

[0002] III-V compound semiconductors are widely used in the manufacture of optoelectronic devices, power electronics and radio frequency devices due to their semiconductor properties such as large bandgap, wide direct bandgap (high photoelectric conversion efficiency), high electron mobility and high temperature resistance. In order to realize the functions of these devices, one of the very important processes is P-type doped epitaxial growth. In the P-type doped epitaxial growth process, the P-type doped precursor and the III-group precursor are mixed and then enter the reactor to react with the V-group precursor to obtain a P-type doped III-V compound semiconductor.

[0003] At present, the commonly used P-type doping precursor is bismuth magnesium, however, since bismuth magnesium and group V are prone to pre-reaction before reaching the substrate, it affects its doping efficiency and doping uniformity, and ultimately affects the performance of the device. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of low doping efficiency and uneven doping of P-type doping precursors in III-V compound semiconductors, improve the semiconductor structure formation method, achieve effective transportation of P-type doping precursors and doping uniformity, and thus improve the performance of the device.

[0005] In order to achieve the above-mentioned object, the present invention provides a method for forming a semiconductor structure, comprising: providing a reactor, the reactor comprising a reaction area and a gas shower head located at the top of the reaction area, the gas shower head comprising a first gas distribution chamber and a second gas distribution chamber stacked up and down, the first gas distribution chamber and the second gas distribution chamber are respectively connected to the reaction area; providing a substrate, placed in the reaction area; introducing a first reaction gas into the reaction area through the first gas distribution chamber, and introducing a second reaction gas into the reaction area through the second gas distribution chamber, the first reaction gas and the second reaction gas growing a P-type layer on the substrate; wherein the first reaction gas at least comprises Containing a group V precursor and a first carrier gas, the first reaction gas outputted from the first gas distribution chamber has a first density and a first flow rate, the second reaction gas at least comprises a P-type doping precursor, a group III precursor and a second carrier gas, the P-type doping precursor is used to provide P-type doping ions, the second carrier gas outputted from the second gas distribution chamber has a second density and a second flow rate, the second density is greater than the first density, the second flow rate is greater than the first flow rate, the ratio of the second density to the first density is the relative density of the second carrier gas, and the ratio of the second flow rate to the first flow rate is the relative flow rate of the second carrier gas; by adjusting the relative flow rate or relative density of the second carrier gas, the doping concentration of the P-type doping ions in the P-type layer is increased.

[0006] Optionally, the relative flow rate or relative density of the second carrier gas is adjusted so that the doping concentration of the doping precursor in the P-type layer is increased by more than 10 times.

[0007] Optionally, when the relative density is 170%, the relationship between the resistance of the P-type layer and the relative flow rate of the second carrier gas is: y=3.652x 2 -28.37x+56.27, the relationship between the relative flow rate of the holes in the P-type layer and the second carrier gas is: y=(8E+16)x+(6E+14).

[0008] Optionally, the relative flow rate of the second carrier gas is 1.5 to 5 times.

[0009] Optionally, the relative flow rate of the second carrier gas is 3 to 4.3 times.

[0010] Optionally, when the relative flow rate is 354%, the relationship between the resistance of the P-type layer and the relative density of the second carrier gas is: y=4.092x 2 -16.38x+17.17, the relationship between the relative density of holes in the P-type layer and the second carrier gas is: y=(2E+17)x-(5E+16).

[0011] Optionally, the relative density of the second carrier gas is 1.0 to 5.0 times.

[0012] Optionally, the relative density of the second carrier gas is 1.5 to 2.3 times.

[0013] Optionally, the first carrier gas includes: hydrogen.

[0014] Optionally, the first carrier gas also includes: nitrogen.

[0015] Optionally, the second carrier gas includes nitrogen.

[0016] Optionally, the second carrier gas also includes: hydrogen.

[0017] Optionally, the second gas distribution chamber is isolated into an inner chamber and an outer chamber so as to independently adjust the relative flow rate or relative density of the second carrier gas passing through the inner chamber and the outer chamber.

[0018] Optionally, the Group III precursor includes at least any one of a gallium source precursor, a boron source precursor, an aluminum source precursor, and an indium source precursor, or any combination of multiple thereof.

[0019] Optionally, the Group V precursor contains at least a nitrogen source precursor; the nitrogen source precursor is hydrogen nitride.

[0020] Optionally, the P-type doping precursor is bismuthocene magnesium.

[0021] The present invention also provides a semiconductor structure, comprising at least:

[0022] substrate;

[0023] A P-type layer is formed on the substrate and is prepared by any one of the above-mentioned methods for forming a semiconductor structure.

[0024] Optionally, the composition of the P-type layer is In x Ga y Al 1-x-y N represents, where 0≤x≤1, 0≤y≤1, 0≤x+y≤1.

[0025] Optionally, the P-type layer is any one of GaN, AlGaN or InAlGaN.

[0026] Compared with the prior art, the beneficial effects of the technical solution of the present invention include at least:

[0027] (1) The present invention reduces the pre-reaction between the P-type doping precursor and the Group V precursor and prevents the generation of intermediate by-products by adjusting the relative flow rate or relative density of the second carrier gas. Therefore, the doping concentration of the doped ions in the P-type layer is increased by up to 10 times, and the effective transportation and uniform distribution of the doped ions in the P-type layer can be achieved, thereby improving the performance of the device.

[0028] (2) Furthermore, the gas shower head of the present invention comprises a first gas distribution chamber and a second gas distribution chamber stacked one above the other, wherein the second gas distribution chamber is located above the first gas distribution chamber, so that the group V precursor in the first gas distribution chamber located below can receive more heat radiation from the heating component inside the chamber, which is beneficial to the decomposition of the group V precursor and improves the utilization efficiency; wherein the second gas distribution chamber is divided into an inner chamber and an outer chamber, and the present invention further differentially adjusts the relative flow rate or relative density of the second carrier gas introduced into the inner chamber and the outer chamber, so that the inner chamber and the outer chamber have different flow rates and densities, which can compensate for the uneven doping defect caused by the pre-reaction of the P-type doping precursor with the group V precursor, thereby realizing the radial doping uniformity adjustment of the doped ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a flow chart of a method for forming a semiconductor structure.

[0030] Figure 2 It is a schematic diagram of a semiconductor structure forming device of the present invention.

[0031] Figure 3 It is a schematic diagram showing the relationship between the relative flow rate of the second carrier gas and the doping efficiency of magnesium in the P-type layer when the relative density of the second carrier gas is kept unchanged in the semiconductor forming method of the present invention.

[0032] Figure 4 It is a schematic diagram showing the relationship between the relative density of the second carrier gas and the doping efficiency of magnesium in the P-type layer when the relative flow rate of the second carrier gas is kept unchanged in the semiconductor forming method of the present invention.

[0033] Among them, 1-first gas distribution chamber, 2-second gas distribution chamber, 3-reaction area, 4-substrate, 5-isolation wall, 6-gas shower head. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0035] The meanings of the terms "on," "over," and "over" should be interpreted in the broadest manner, so that "on" means not only "directly on" something, but also includes being on something with other intervening features or layers therebetween, and "over" or "over" means not only being "on" or "over" something, but also includes being "on" or "over" something with no other intervening features or layers therebetween (i.e., directly on something).

[0036] The terms "forming" or "disposing" are used hereinafter to describe the act of applying a material layer to a substrate. These terms are intended to describe any feasible layer formation technique, including but not limited to thermal growth, sputtering, evaporation, chemical vapor deposition, epitaxial growth, electroplating, etc.

[0037] III-V semiconductor materials include compounds containing an element from the "III" group of the periodic table and another element from the "V" group of the periodic table. For example, the III group elements may include boron, aluminum, gallium, indium, etc., and the V group elements may include nitrogen, phosphorus, arsenic, antimony, etc. III-V semiconductor materials, such as gallium nitride (GaN), indium nitride (InN), aluminum nitride (AlN), etc., are usually obtained by epitaxial growth on an underlying substrate using a vapor phase growth method such as an organic metal vapor phase growth method, a molecular beam vapor phase growth method, and a hydride vapor phase growth method. Taking the organic metal vapor phase growth method as an example, the III-V compound semiconductor MOCVD (metal organic chemical vapor deposition) reactor has a group III gas distribution chamber and a group V gas distribution chamber. The P-type doping precursor is usually mixed with the group III precursor and enters the group III gas distribution chamber through the group III precursor pipe. The group V precursor enters the group V gas distribution chamber through the group V precursor pipe. The P-type doping precursor, the group III precursor, and the group V precursor enter the reaction area to perform epitaxial growth of the P-type layer on the underlying substrate.

[0038] Since the P-type doping precursor has a strong activity, once the P-type doping precursor, the III-group precursor, and the V-group precursor are respectively ejected from the gas shower head into the reaction area, before reaching the substrate, the P-type doping precursor is very likely to pre-react with the V-group precursor to generate intermediate by-products. The pre-reaction will consume the P-type doping precursor, thereby reducing the amount of the P-type doping precursor reaching the substrate, thereby reducing the doping efficiency of the P-type doping precursor on the substrate.

[0039] To solve this technical problem, the present invention adopts at least one of the following technical solutions:

[0040] 1) By adjusting the relative flow rate of the second carrier gas introduced into the second gas distribution chamber, the flow rate of the second reaction gas is made greater than the flow rate of the first reaction gas, so that the transmission speed of the second reaction gas in the second gas distribution chamber is faster, the diffusion of doped ions in the reaction area is reduced, and the collision and contact between the doped ions and the Group V precursor are avoided, thereby reducing the occurrence of pre-reaction.

[0041] 2) By adjusting the relative density of the second carrier gas introduced into the second gas distribution chamber, the density of the second reaction gas is made greater than the density of the first reaction gas. When the second reaction gas enters the reaction area, it is not easy to collide with other molecules or to change direction after colliding with other molecules. As a result, the transmission direction of the second reaction gas in the second gas distribution chamber is not easy to change, so that more P-type doped ions can reach the surface of the substrate.

[0042] The present invention reduces the pre-reaction between the P-type doping precursor and the Group V precursor and reduces the generation of intermediate by-products through the method of adjusting the relative flow rate or relative density of the second carrier gas, thereby improving the doping efficiency of the P-type doping precursor and making the P-type layer of the formed semiconductor structure more uniformly doped.

[0043] In order to make the above-mentioned objects, features and beneficial effects of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0044] Figure 1 It is a flow chart of a method for forming a semiconductor structure of the present invention.

[0045] like Figure 1 As shown, the present invention provides a method for forming a semiconductor structure, comprising:

[0046] Step S1: providing a reactor, wherein the reactor comprises a reaction area and a gas shower head located at the top of the reaction area, wherein the gas shower head comprises a first gas distribution chamber and a second gas distribution chamber stacked up and down, and the first gas distribution chamber and the second gas distribution chamber are respectively connected to the reaction area.

[0047] The purpose of the first gas distribution chamber and the second gas distribution chamber being respectively connected to the reaction area is to introduce the first reaction gas and the second reaction gas into the reaction area through the first gas distribution chamber and the second gas distribution chamber respectively, so as to avoid the first reaction gas and the second reaction gas from pre-reacting in the gas shower head, thereby generating intermediate by-products.

[0048] In some embodiments, in order to further achieve effective transport of P-type doping precursors, the transmission distance between the gas shower head at the top of the reaction area and the upper surface of the substrate is 30 mm to 90 mm to prevent the transmission distance from being too long, causing the first reaction gas and the second reaction gas to pre-react before reaching the substrate, thereby increasing the generation of intermediate by-products and affecting the doping of the P-type doping precursor.

[0049] Step S2: providing a substrate and placing it in the reaction area.

[0050] The substrate may be selected from any one of a silicon substrate, a silicon carbide substrate, and a gallium nitride substrate.

[0051] Step S3: introducing a first reaction gas into the reaction area through the first gas distribution chamber, and introducing a second reaction gas into the reaction area through the second gas distribution chamber, wherein the first reaction gas and the second reaction gas react on the substrate to form a P-type layer.

[0052] Among them, the first reaction gas at least includes a Group V precursor and a first carrier gas, the first reaction gas output by the first gas distribution chamber has a first density and a first flow rate, the second reaction gas at least includes a P-type doping precursor, a Group III precursor and a second carrier gas, the P-type doping precursor is used to provide P-type doping ions, the second carrier gas output by the second gas distribution chamber has a second density and a second flow rate, the second density is greater than the first density, the second flow rate is greater than the first flow rate, the ratio of the second density to the first density is the relative density of the second carrier gas, and the ratio of the second flow rate to the first flow rate is the relative flow rate of the second carrier gas; by adjusting the relative flow rate or relative density of the second carrier gas, the doping concentration of the P-type doping ions in the P-type layer is increased.

[0053] The purpose of this step is to make the first reaction gas and the second reaction gas react on the substrate to grow a P-type layer. In order to prevent the V-group precursor from pre-reacting with the P-type doping precursor and the III-group precursor in the gas distribution chamber in advance, the present invention introduces the first reaction gas and the second reaction gas through the first gas distribution chamber and the second gas distribution chamber respectively.

[0054] In order to increase the doping concentration, in some embodiments, by adjusting the relative flow rate of the second carrier gas in the second reaction gas, the flow rate of the second reaction gas is greater than the flow rate of the first reaction gas, and the transmission speed of the second reaction gas is faster, thereby reducing the pre-reaction of the P-type doping precursor and the V-group precursor before reaching the substrate. In other embodiments, the relative density of the second carrier gas in the second reaction gas can be adjusted so that the density of the second reaction gas is greater than the density of the first reaction gas, so the transmission direction of the second reaction gas is not easy to change, thereby reducing the pre-reaction of the P-type doping precursor and the V-group precursor before reaching the substrate. The first reaction gas and the second reaction gas grow a P-type layer on the substrate, reducing the pre-reaction, so that more P-type doping precursors reach the surface of the substrate, thereby helping to increase the doping concentration of P-type doping ions in the P-type layer.

[0055] When the size of the substrate is large, when the reaction gas is introduced into the substrate in the reaction area through the gas shower head, the gas distribution corresponding to the edge part of the substrate and the central part of the substrate will be different. In particular, when the reaction gas is extracted with the vacuum pump, the gas distribution at the edge part of the substrate may be different from that at the central part of the substrate. The different gas distributions at different parts of the substrate surface will lead to uneven doping of the doping precursor on the substrate surface. When the difference in gas flow rate or density between the central area and the edge area of ​​the gas distribution cavity is large, a sudden change in gas flow rate or density will occur at the gas shower head, which will cause a sudden change in the processing effect of the substrate below, and then cause uneven gas to react on the substrate, seriously affecting the uniformity of doping and the quality and efficiency of substrate processing. To solve this technical problem, in some embodiments of the present invention, the second gas distribution cavity is divided into an inner cavity and an outer cavity, the inner cavity corresponds to the central area of ​​the second gas distribution cavity, and the outer cavity corresponds to the edge area surrounding the periphery of the central area. The inner cavity is arranged relative to the central part of the substrate in the reaction area, and the outer cavity is arranged relative to the edge part of the substrate in the reaction area.

[0056] In order to achieve radial doping uniformity adjustment of doped ions, the flow rate and density of the gas passing through the inner cavity and the outer cavity of the second gas distribution cavity can be differentially adjusted. When the flow rate difference between the gas passing through the inner cavity and the outer cavity is large, the flow rate difference between the two can be reduced by adjusting the flow rate of the second carrier gas respectively introduced into the inner cavity and the outer cavity; or, when the density difference between the gas passing through the inner cavity and the outer cavity is large, the density difference between the two can be reduced by adjusting the flow rate of nitrogen and hydrogen in the second carrier gas respectively introduced into the inner cavity and the outer cavity. Therefore, the present invention can avoid uneven gas spraying onto the substrate due to large differences in gas flow rate or density in different regions when the gas passing through the inner cavity and the outer cavity is sprayed out from the shower head through a differentiated adjustment method.

[0057] The III group precursor is an organic metal salt. In some embodiments, the III group precursor includes at least one of a gallium source precursor, a boron source precursor, an aluminum source precursor, and an indium source precursor, or any combination of any multiple thereof. The gallium source precursor includes at least one of trimethyl gallium, triethyl gallium, diethyl gallium chloride, and isotopic gallium hydride compounds, or any combination of any multiple thereof; the boron source precursor includes at least one of trimethyl boron and triethyl boron, or any combination of any one or more thereof; the aluminum source precursor includes at least one of trimethyl aluminum and triethyl aluminum, or any combination of any one or more thereof; the indium source precursor includes at least one of trimethyl indium and triethyl indium, or any combination of any one or more thereof.

[0058] In order to facilitate the adjustment of relative flow rate and relative density, the present invention also includes a carrier gas. The carrier gas does not react with the reaction gas, and the carrier gas of the present invention is used to disperse the reaction gas. In the present invention, the carrier gas contains at least two gases with a large difference in density. For example, the carrier gas can be nitrogen or hydrogen. When a larger relative density is required, the flow rate of nitrogen in the second carrier gas can be increased. When a smaller relative density is required, the flow rate of hydrogen in the second carrier gas can be increased. In some embodiments, the first carrier gas is used to pass the V group precursor into the first gas distribution chamber. The first carrier gas can be any one of hydrogen and nitrogen, or a mixture of hydrogen and nitrogen. In some embodiments, the second carrier gas is used to pass the III group precursor and the P-type doping precursor into the second gas distribution chamber. The second carrier gas can be any one of nitrogen and hydrogen, or a mixture of nitrogen and hydrogen.

[0059] The second reaction gas of the present invention at least includes a P-type doping precursor, a group III precursor, and a second carrier gas. Since the amount of the group III precursor is relatively small, usually not exceeding 1000 sccm, when the P-type layer is grown, the P-type doping precursor and the group III precursor are mainly introduced into the second gas distribution chamber through the second carrier gas. Therefore, the present invention changes the relative flow rate or relative density of the second reaction gas by adjusting the relative flow rate or relative density of the second carrier gas, so that the second reaction gas transmission speed is faster and the transmission direction is not easy to change, thereby making the doping of doping ions in the P-type layer more uniform.

[0060] In order to prevent the reaction gas from being high-energy ions and causing damage to the thin film on the surface of the substrate, in some embodiments, the first reaction gas and the second reaction gas are both saturated steam, and the gas molecules are thermally decomposed at high temperature to generate clusters, which are respectively introduced into the first gas distribution cavity and the second gas distribution cavity in the form of saturated steam, and diffused to the substrate surface through the first carrier gas and the second carrier gas for growth.

[0061] In some embodiments, the P-type layer may include a P-type doped aluminum nitride layer, a P-type doped gallium nitride layer, or other suitable P-type doped III-V compound materials. The P-type doping precursor in the P-type doped III-V compound material may include bismuth magnesium (Cp 2 Mg), magnesium or other suitable P-type doping precursors. In the following embodiments of the present invention, the P-type doping precursors are all dicyclopentadienyl magnesium.

[0062] Figure 2 It is a schematic diagram of a semiconductor structure forming device of the present invention.

[0063] like Figure 2As shown, a semiconductor structure forming device of the present invention comprises at least one reactor. The reactor comprises a reaction area 3 and a gas shower head 6 located at the top of the reaction area 3, the gas shower head 6 comprises a first gas distribution chamber 1 and a second gas distribution chamber 2 stacked up and down, the second gas distribution chamber 2 is located above the first gas distribution chamber 1, and the first gas distribution chamber 1 and the second gas distribution chamber 2 are respectively connected to the reaction area 3. The second gas distribution chamber 2 is divided into an inner chamber and an outer chamber by two isolation walls 5. A substrate 4 is placed at the bottom of the reaction area 3. The transmission distance between the gas shower head 6 at the top of the reaction area 3 and the substrate 4 at the bottom of the reaction area 3 is 30 mm to 90 mm.

[0064] The working principle of a semiconductor structure forming device of the present invention is as follows:

[0065] A substrate 4 to be processed is placed at the bottom of the reaction area 3, and a purge gas is introduced to purge the substrate 4; a first reaction gas is introduced into the first gas distribution chamber 1, and a second reaction gas is introduced into the second gas distribution chamber 2, the relative density of the second carrier gas in the second reaction gas is kept unchanged, and the relative flow rate of the second carrier gas introduced is adjusted so that the relative flow rate of the second carrier gas is greater than the relative flow rate of the first reaction gas; or, the relative flow rate of the second carrier gas in the second reaction gas is kept unchanged, and the nitrogen flow rate or the hydrogen flow rate in the second carrier gas introduced is adjusted so that the relative density of the second carrier gas is greater than the relative density of the first reaction gas.

[0066] Further, the relative flow rates of the second carrier gas introduced into the inner cavity and the outer cavity are adjusted respectively, so that the gases introduced into the inner cavity and the outer cavity have different flow rates, or the nitrogen flow rate or hydrogen flow rate in the second carrier gas introduced into the inner cavity and the outer cavity is adjusted respectively, so that the gases introduced into the inner cavity and the outer cavity have different densities. The first reaction gas and the second reaction gas are respectively sprayed out by the gas shower head 6 and transmitted to the substrate 4 for growth of the P-type layer.

[0067] The present invention also provides a semiconductor structure, comprising a substrate, a semiconductor layer formed on the substrate, and a semiconductor layer having a general formula In x Ga y Al 1-x-y A III-V compound semiconductor having a stacked structure of compound semiconductor crystal layers represented by N (wherein 0≤x≤1, 0≤y≤1, 0≤x+y≤1).

[0068] In some embodiments, the III-V compound semiconductor layer (P-type layer) may include GaN, AlGaN, InAlGaN, or other suitable III-V compound semiconductor materials.

[0069] Example 1

[0070] This embodiment provides a method for forming a semiconductor structure, comprising the following steps:

[0071] Step S1: providing a reactor for forming a semiconductor structure, the reactor comprising a reaction area and a plurality of gas shower heads located on the top of the reaction area, the gas shower heads comprising a first gas distribution cavity and a second gas distribution cavity stacked up and down, the first gas distribution cavity and the second gas distribution cavity being respectively connected to the reaction area;

[0072] Step S2: providing a silicon substrate, placing the silicon substrate at the bottom of the reaction area, and introducing a purge gas to purge the silicon substrate at the bottom of the reaction area;

[0073] Step S3: Using hydrogen and nitrogen as the first carrier gas, under the action of the first carrier gas, keep the V group precursor ammonia gas continuously passing into the first gas distribution chamber through the V group precursor pipeline, and the first carrier gas and ammonia gas constitute the first reaction gas. Pass bismuth magnesium through the bismuth magnesium precursor pipeline, pass trimethyl gallium through the III group precursor pipeline, and after bismuth magnesium and trimethyl gallium are mixed, use nitrogen and hydrogen as the second carrier gas, under the action of the second carrier gas, keep bismuth magnesium and trimethyl gallium continuously passing into the second gas distribution chamber, and the second carrier gas, bismuth magnesium, and trimethyl gallium constitute the second reaction gas. The flow rate of each component gas is shown in Table 1, wherein hydride represents the first carrier gas leading to the first gas distribution chamber, the inner cavity carrier gas represents the second carrier gas leading to the inner cavity of the second gas distribution chamber, and the outer cavity carrier gas represents the second carrier gas leading to the outer cavity of the second gas distribution chamber.

[0074] A P-type layer is grown on a silicon substrate using a metal organic chemical vapor deposition epitaxial growth method, and the mass flow meters of nitrogen and hydrogen are used to set the respective flow rates, thereby adjusting the relative flow rate and relative density. When the relative density of the second carrier gas is fixed at 1.7 times, the flow rate of the first reaction gas introduced into the first gas distribution chamber is kept unchanged, and the flow rate of the second carrier gas introduced into the second gas distribution chamber is adjusted so that the flow rate of the second carrier gas increases from 3 times to 3.5 times and 4.3 times relative to the flow rate of the first reaction gas. Until the required growth thickness is reached, stop introducing the gas into the first gas distribution chamber and the second gas distribution chamber.

[0075] Table 1 Gas flow rate, relative flow rate and relative density of each component

[0076]

[0077] (Slm and sccm are the units of gas flow rate. 1 slm means that a gas with a volume of 1 liter flows under standard conditions every minute. 1000 sccm is equivalent to 1 slm.)

[0078] like Figure 3 As shown in the figure, when the relative density is 1.7 times, as the flow rate of the second carrier gas increases from 3 times to 3.5 times and 4.3 times relative to the flow rate of the first reaction gas, the hole concentration of P-type gallium nitride continues to rise and the resistance continues to decrease, indicating that the doping efficiency of magnesium has been improved. At this time, the relationship between the resistance of the P-type layer and the relative flow rate of the second carrier gas is y=3.652x 2 -28.37x+56.27: (wherein the x coordinate represents the relative flow rate of the second carrier gas, and the y coordinate on the left represents the resistance of the P-type layer), the relationship between the holes in the P-type layer and the relative flow rate of the second carrier gas is y=(8E+16)x+(6E+14) (wherein the x coordinate represents the relative flow rate of the second carrier gas, and the y coordinate on the right represents the hole concentration in the P-type layer). It can be seen that when the relative density of the second carrier gas is kept unchanged, the doping concentration and doping efficiency of magnesium in the P-type layer can be improved by adjusting the relative flow rate of the second carrier gas.

[0079] Example 2

[0080] This embodiment provides a method for forming a semiconductor structure, comprising the following steps:

[0081] The step different from that of Example 1 is that in step S3, the mass flow meters of nitrogen and hydrogen are used to set the respective flow rates, thereby adjusting the relative flow rate and relative density. When the relative flow rate of the second carrier gas is fixed at 3.54 times, the density of the first reaction gas introduced into the first gas distribution chamber is kept unchanged, and the flow rates of nitrogen and hydrogen in the second carrier gas introduced into the second gas distribution chamber are adjusted, so that the density of the second carrier gas increases from 1.5 times to 2.3 times relative to the density of the first reaction gas.

[0082] like Figure 4 As shown in the figure, when the relative flow rate is 3.54 times, as the density of the second carrier gas increases from 1.5 times to 2.3 times relative to the density of the first reaction gas, the hole concentration of P-type gallium nitride continues to rise and the resistance continues to decrease, indicating that the doping efficiency of magnesium has been improved. At this time, the relationship between the resistance of the P-type layer and the relative density of the second carrier gas is: y = 4.092x 2 -16.38x+17.17 (wherein the x coordinate represents the relative density of the second carrier gas, and the y coordinate on the left represents the resistance of the P-type layer), the relationship between the relative density of the holes in the P-type layer and the second carrier gas is: y=(2E+17)x-(5E+16) (wherein the x coordinate represents the relative density of the second carrier gas, and the y coordinate on the right represents the hole concentration in the P-type layer). It can be seen that when the relative flow rate of the second carrier gas is kept unchanged, the doping concentration and doping efficiency of magnesium in the P-type layer can be improved by adjusting the relative density of the second carrier gas.

[0083] In summary, a method for forming a semiconductor structure of the present invention maintains the relative density of the second carrier gas unchanged by adjusting the relative flow rate of the second carrier gas relative to the first reaction gas, or maintains the relative flow rate of the second carrier gas unchanged by adjusting the relative density of the second carrier gas relative to the first reaction gas. Furthermore, the gas distribution cavity can be divided into different chambers, and the radial doping uniformity can be adjusted by differentially adjusting the relative flow rate or relative density of the gas, so that the doping concentration of magnesium in the P-type layer is significantly improved, the doping efficiency of magnesium is improved, the doping is more uniform, and the performance of the semiconductor device is improved.

[0084] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A method for forming a semiconductor structure, characterized in that: include: A reactor is provided, the reactor comprising a reaction area and a gas shower head located on the top of the reaction area, the gas shower head comprising a first gas distribution cavity and a second gas distribution cavity stacked up and down, the first gas distribution cavity and the second gas distribution cavity are respectively connected to the reaction area; Providing a substrate, and placing it in the reaction area; A first reaction gas is introduced into the reaction region through the first gas distribution cavity, and a second reaction gas is introduced into the reaction region through the second gas distribution cavity, wherein the first reaction gas and the second reaction gas grow a P-type layer on the substrate; Wherein, the first reaction gas at least comprises a group V precursor and a first carrier gas, the first reaction gas outputted from the first gas distribution chamber has a first density and a first flow rate, the second reaction gas at least comprises a P-type doping precursor, a group III precursor and a second carrier gas, the P-type doping precursor is used to provide P-type doping ions, the second carrier gas outputted from the second gas distribution chamber has a second density and a second flow rate, the second density is greater than the first density, the second flow rate is greater than the first flow rate, the ratio of the second density to the first density is the relative density of the second carrier gas, and the ratio of the second flow rate to the first flow rate is the relative flow rate of the second carrier gas; By adjusting the relative flow rate or relative density of the second carrier gas, the doping concentration of the P-type doping ions in the P-type layer is increased.

2. The method for forming a semiconductor structure according to claim 1, wherein: The relative flow rate or relative density of the second carrier gas is adjusted so that the doping concentration of the doping precursor in the P-type layer is increased by more than 10 times.

3. The method for forming a semiconductor structure according to claim 1, wherein: When the relative density is 170%, the relationship between the resistance of the P-type layer and the relative flow rate of the second carrier gas is: y = 3.652x 2 -28.37x+56.27, the relationship between the relative flow rate of the holes in the P-type layer and the second carrier gas is: y=(8E+16)x+(6E+14).

4. The method for forming a semiconductor structure according to claim 3, wherein: The relative flow rate of the second carrier gas is 1.5 to 5 times.

5. The method for forming a semiconductor structure according to claim 4, wherein: The relative flow rate of the second carrier gas is 3 to 4.3 times.

6. The method for forming a semiconductor structure according to claim 1, wherein: When the relative flow rate is 354%, the relationship between the resistance of the P-type layer and the relative density of the second carrier gas is: y = 4.092x 2 -16.38x+17.17, the relationship between the relative density of holes in the P-type layer and the second carrier gas is: y=(2E+17)x-(5E+16).

7. The method for forming a semiconductor structure according to claim 6, wherein: The relative density of the second carrier gas is 1.0 to 5.0 times.

8. The method for forming a semiconductor structure according to claim 7, wherein: The relative density of the second carrier gas is 1.5 to 2.3 times.

9. The method for forming a semiconductor structure according to claim 1, wherein: The first carrier gas includes hydrogen.

10. The method for forming a semiconductor structure according to claim 9, wherein: The first carrier gas also includes nitrogen.

11. The method for forming a semiconductor structure according to claim 1, wherein: The second carrier gas includes nitrogen.

12. The method for forming a semiconductor structure according to claim 11, wherein: The second carrier gas also includes: hydrogen.

13. The method for forming a semiconductor structure according to claim 1, wherein: The second gas distribution chamber is separated into an inner chamber and an outer chamber so as to independently adjust the relative flow rate or relative density of the second carrier gas passing through the inner chamber and the outer chamber.

14. The method for forming a semiconductor structure according to claim 1, wherein: The group III precursor includes at least any one of a gallium source precursor, a boron source precursor, an aluminum source precursor, and an indium source precursor, or any combination of multiple thereof.

15. The method for forming a semiconductor structure according to claim 1, wherein: The group V precursor at least includes a nitrogen source precursor; the nitrogen source precursor is hydrogen nitride.

16. The method for forming a semiconductor structure according to claim 1, wherein: The P-type doping precursor is bismuthocene magnesium.

17. A semiconductor structure, characterized in that: At least: substrate; A P-type layer, wherein the P-type layer is formed on the substrate, and the P-type layer is prepared by the method for forming a semiconductor structure according to any one of claims 1 to 16.

18. The semiconductor structure according to claim 17, wherein: The composition of the P-type layer is In x Ga y Al 1-x-y N represents, where 0≤x≤1, 0≤y≤1, 0≤x+y≤1.

19. The semiconductor structure according to claim 18, wherein: The P-type layer is any one of GaN, AlGaN or InAlGaN.

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