A method for p-type doping of semiconductor materials grown by MOCVD

Abstract

This invention discloses a method for P-type doping of semiconductor materials grown by MOCVD, which involves performing P-type doping and N-type doping in steps during the growth of indium gallium arsenide or indium phosphide epitaxial layers. The doping method of this invention can effectively suppress the diffusion effect of zinc doping. At the same time, due to the high temperature used for doping, high material quality can be obtained. The process is simple and low-cost.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more specifically to a method for P-type doping of semiconductor materials grown by MOCVD. Background Technology

[0002] When indium gallium arsenide (IGaAs) and indium phosphide (IPP) semiconductor materials are used as intermediate layers in devices and require P-type doping, P-type doping is typically achieved directly by introducing MO sources such as carbon tetrabromide, magnesium thiocene, or diethylzinc during the MOCVD (Metal-Organic Chemical Vapor Deposition) growth process. However, when IGaAs and IPP require P-type doping at the top layer of the device, there are more doping methods available. Doping can be performed directly with MO sources during MOCVD growth, or P-type doping can be achieved using a diffusion furnace or ion implanter after growth.

[0003] Using carbon sources for P-type doping of gallium arsenide and indium phosphide is suitable for low-temperature MOCVD processes (450-570℃) and has no diffusion issues. However, as the temperature increases and the V / III ratio increases, the carrier concentration of P-type doping decreases significantly, and even N-type doping may occur. Therefore, in MOCVD growth of gallium arsenide and indium phosphide, the P-type doping concentration is usually increased by lowering the temperature and V / III ratio. However, this operation significantly reduces the crystal quality of the material, thus affecting the overall device performance. Magnesium and iron, as doping sources, exhibit diffusion effects and leave magnesium or iron residues in the reaction chamber, causing a memory effect that affects the background concentration during the growth of other structures. Considering all factors, the industry generally uses zinc as a doping source. Although it has diffusion effects, it does not exhibit the memory effect of magnesium and iron, which has a more severe impact on the reaction chamber cavity. How to solve these technical problems is a research direction that those skilled in the art are dedicated to. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for P-type doping of semiconductor materials grown by MOCVD.

[0005] To achieve the above objectives, the technical solution adopted by this invention is: a method for P-type doping of semiconductor materials grown by MOCVD, comprising the following steps:

[0006] 1) The substrate is placed in the reaction chamber, and an epitaxial layer is grown on the substrate using the MOCVD method at a temperature of 550℃-650℃;

[0007] 2) P-type doping is performed during the growth of indium gallium arsenide or indium phosphide epitaxial layers. The specific steps are as follows:

[0008] 21) Introduce a group III metal source and a group V nitrogen source, and simultaneously introduce a carbon source. The V / III ratio should be between 10 and 150, and the carbon source flow rate should be controlled at 1e. -5-9e -4 Moles per minute, lasting 2-5 seconds;

[0009] 22) Turn off the three metal sources for 1-2 seconds;

[0010] 23) Reopen the group III metal source and repeat steps 21) and 22) for 3-10 cycles;

[0011] 3) N-type doping is performed during the growth of indium gallium arsenide or indium phosphide epitaxial layers.

[0012] 31) Turn on the N-type doped source;

[0013] 32) After 3-5 seconds, turn off the N-type doped source, turn on the group III metal source and group V nitrogen source, turn on the zinc source, and control the zinc source flow rate at 1e. -5 -9e -5 Moles per minute, lasting 5-20 seconds;

[0014] 33) Turn off the zinc source for 1-2 seconds;

[0015] 4) Repeat steps 32) and 33) until the indium gallium arsenide or indium phosphide epitaxial layer reaches the target thickness;

[0016] 5) Turn off the zinc source and N-type doping source, then turn off the group III metal source. Under the protection of the group V nitrogen source, heat to 550℃-650℃, turn on the group III metal source and zinc source, and continue to grow for 8-20 minutes. Turn off the zinc source, anneal in situ, and then cool to room temperature.

[0017] In one specific implementation, the group III metal source uses at least one of trimethylindium and trimethylgallium.

[0018] In one specific implementation, the carbon source is at least one of carbon tetrabromide and carbon tetrachloride.

[0019] In one specific implementation, the zinc source is diethylzinc.

[0020] In one specific implementation, the N-type doping source in step 31) is a carbon source or silane, ethylsilane. When a carbon source is used, the flow rate of the carbon source is controlled at 1e. -5 -2e -5 Moles per minute.

[0021] As one specific implementation, the growth rate of the indium gallium arsenide or indium phosphide epitaxial layer is 1-5 angstroms / second.

[0022] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: The present invention performs P-type doping by introducing a carbon source under high temperature conditions, controlling the V / III ratio, and then performing an on-off-on cycle operation of the carbon source. Then, a zinc source is introduced, and the insertion of the N-type recombination region is performed by switching the zinc source on and off to complete the doping step. The entire process can effectively suppress the diffusion effect of zinc doping. At the same time, due to the high temperature used in the doping process, high material quality can be obtained. For example, if the top layer of the device structure grown by MOCVD needs to be P-type doped, the corresponding P-type doping can be completed by combining the method of the present invention, without the need for diffusion furnace ion implantation and other equipment, which can reduce the process difficulty and cost. Attached Figure Description

[0023] Appendix Figure 1 This is the electrochemical CV test result for Example 1;

[0024] Appendix Figure 2 The image shows the electrochemical CV test results for Comparative Example 1. Detailed Implementation

[0025] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0026] Example 1

[0027] A method for p-type doping of semiconductor materials grown by MOCVD includes the following steps:

[0028] 1) The substrate is placed in the reaction chamber, and the temperature of the reaction chamber is raised to 550°C using MOCVD to grow an epitaxial layer on the substrate;

[0029] 2) P-type doping is performed during InGaAs growth. The specific steps are as follows:

[0030] 21) The V / III ratio is 114. Simultaneously, the first channel of trimethylindium / trimethylgallium / arsenane is introduced for epitaxial film growth (where the molar ratio of trimethylindium / trimethylgallium is 2:3), and carbon tetrabromide is introduced at a flow rate of 4e. -4 Moles per minute, lasting 5 seconds: The introduction of carbon affects the incorporation efficiency of indium and gallium.

[0031] 22) Turn off the indium and gallium sources for 2 seconds;

[0032] 23) Turn on the indium and gallium sources again and repeat steps 21) and 22) for 10 cycles;

[0033] 3) N-type doping is performed during the growth of indium gallium arsenide or indium phosphide epitaxial layers.

[0034] 31) Turn off the first group III metal source, turn on carbon tetrabromide, and adjust the flow rate to 2e -5 moles per minute;

[0035] 32) After 5 seconds, turn off the carbon source and turn on the trimethylindium / trimethylgallium (trimethylindium / trimethylgallium molar ratio is 2:3), then introduce diethylzinc at a flow rate controlled at 1.3e. -5 Moles per minute, lasting 10 seconds;

[0036] 33) Turn off the zinc source for 1 second;

[0037] 4) Repeat steps 32) and 33) for 8 cycles until the cumulative growth of the indium gallium arsenide or indium phosphide epitaxial layer reaches 350 nm;

[0038] 5) Turn off carbon tetrabromide and diethylzinc for 1 minute to interrupt doping, then turn off trimethylindium / trimethylgallium. Under nitrogen protection, heat to 650℃ and stabilize. Then introduce trimethylindium / trimethylgallium (molar ratio of 9:11) at a flow rate of 2.5e. -5 The flow rate was 3.2 e mol / min for 8 minutes, then the diethylzinc was turned off for 1 minute. -5 moles / minute, duration 8 minutes at 350 nm, final electrochemical CV test results as follows: Figure 1 As shown, a significant decrease in concentration was observed at the end.

[0039] Comparative Example 1

[0040] First, the reaction chamber temperature is raised to 650℃. During InGaAs growth, the V / III ratio is 114, and trimethylindium / trimethylgallium / arsine is simultaneously introduced for epitaxial film growth (where the molar ratio of trimethylindium / trimethylgallium is 9:11). Diethylzinc is introduced at a flow rate of 1.1 e. -5 The process was carried out at a flow rate of mol / min for 10 minutes until the InGaAs epitaxial layer grew to 430 nm. Doping was then interrupted by turning off diethylzinc for 2 minutes, followed by a diethylzinc flow rate of 2e⁻¹. -5 Moles per minute were maintained at the InGaAs epitaxial layer thickness of 430 nm for 10 minutes. Doping was then interrupted by turning off diethylzinc for 2 minutes, and the diethylzinc flow rate was adjusted to 4e. -5 The InGaAs epitaxial layer thickness was maintained at 430 nm for 10 minutes at a rate of moles per minute. The final electrochemical CV test results are attached. Figure 2 As shown, the diffusion phenomenon is quite obvious at the end of each layer. However, the interruption time of doping between each layer in Example 1 is shorter than that in the comparative example, but the diffusion phenomenon in the last layer is weaker. This means that the carbon doping composite operation in Example 1 has a significant effect of weakening the diffusion effect.

[0041] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for P-type doping of a semiconductor material grown by MOCVD, characterized in that, The method comprises the following steps: 1) placing the substrate in a reaction chamber, and growing an epitaxial layer on the substrate at a temperature of 550-650°C by MOCVD; 2) performing P-type doping during the growth of the indium gallium arsenide or indium phosphide epitaxial layer, and the specific steps are as follows: 21) Pass the trimethyl source and arsine, while passing carbon tetrabromide, the ratio of V / III is between 10-150, the flow of carbon tetrabromide is controlled at 1e -5 -9e -4 moles / minute, for 2-5 seconds; 22) turning off the group III metal source for 1-2 seconds; 23) turning on the group III metal source again, and repeating steps 21) and 22) for 3-10 cycles; 3) performing N-type doping during the growth of the indium gallium arsenide or indium phosphide epitaxial layer, 31) Open the carbon tetrabromide, flow controlled at 1e -5 -2e -5 moles / minute; 32) After 3-5 seconds, turn off carbon tetra-bromide, turn on tri-metal source and arsine, turn on zinc source, control the flow of zinc source at 1e -5 -9e -5 Moles / minute for 5-20 seconds; 33) turning off the zinc source for 1-2 seconds; 4) repeating steps 32) and 33) until the indium gallium arsenide or indium phosphide epitaxial layer reaches a target thickness; 5) turning off the zinc source and carbon tetrabromide, then turning off the group III metal source, and then heating to 550-650°C under nitrogen protection, and then continuously growing for 8-20 minutes by turning on the group III metal source and the zinc source, then turning off the zinc source, and then cooling to room temperature after in-situ annealing, wherein the zinc source is diethyl zinc.

2. The method of claim 1, wherein the MOCVD-grown semiconductor material is P-type doped. The group III metal source uses at least one of trimethyl indium and trimethyl gallium.

3. The method of claim 1, wherein the P-type doping is performed by MOCVD growth. The growth rate of the indium gallium arsenide or indium phosphide epitaxial layer is 1-5 angstroms per second.

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