MOCVD (Metal Organic Chemical Vapor Deposition) reaction chamber compound pretreatment method based on magnesium coating and aeration air

Abstract

The invention discloses an MOCVD (Metal Organic Chemical Vapor Deposition) reaction chamber reset pretreatment method based on a magnesium coating and aeration air, and aims to solve the technical problems of long false plating time required by reset and low brightness of an epitaxial wafer of a first furnace due to the fact that parts in a reaction chamber adsorb impurities after furnace disassembly and maintenance of MOCVD equipment. The method comprises the following core steps: firstly, introducing magnesium source gas into a maintained reaction cavity at a high temperature, so that magnesium atoms are adsorbed and permeated into micropores in the surfaces of components such as a graphite disc and the like; then, the temperature is reduced, air or other oxygen-containing gas is actively introduced into the reaction cavity, the adsorbed magnesium is promoted to react with oxygen, a compact and stable magnesium oxide passivation layer is generated in situ, and therefore residual impurities are effectively blocked. By adopting the method for pretreatment, the machine reset time can be remarkably shortened, the waste of an expensive MO source is greatly reduced, and the brightness of the first furnace epitaxial product after maintenance can reach the mass production standard.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a pretreatment method for MOCVD reaction chamber reprocessing based on magnesium coating and aeration air. Background Technology

[0002] MOCVD technology is a core process for preparing compound semiconductor materials such as LEDs and power devices. During the operation of MOCVD equipment, in order to ensure the quality of epitaxial wafers, it is necessary to perform preventive maintenance on the reaction chamber regularly, which is commonly referred to as "furnace disassembly".

[0003] During furnace dismantling, the reaction chamber is opened, and core components such as graphite disks and flow channels are directly exposed to the air in the cleanroom, inevitably adsorbing a large amount of water vapor, oxygen, and other impurities. In addition, even after replacing graphite parts or cleaning them, a large amount of adsorbed impurities remain on their surface and in their internal micropores.

[0004] In existing technologies, the following two methods are typically used to restore a machine to its growth state (i.e., "machine recovery") after preventative maintenance: 1. Prolonged high-temperature baking: This method uses high temperatures to desorb and extract impurities. However, it is inefficient and difficult to completely remove impurities from deep pores.

[0005] 2. Multi-furnace sham plating: This method involves growing multiple furnaces of unofficial products, using the deposited AlN or GaN layers to cover impurities. While effective, this method requires expensive MO sources such as trimethylgallium (TMGa) and trimethylaluminum (TMAl), and consumes valuable machine production time, resulting in extremely high production costs and reduced equipment uptime.

[0006] Typically, the first batch of standard products after preventative maintenance often suffers from low brightness or uneven wavelength due to impurity release, requiring several growth cycles to stabilize. This has become a major bottleneck restricting production line efficiency. Summary of the Invention

[0007] The purpose of this invention is to provide a pretreatment method for re-running an MOCVD reaction chamber based on magnesium coating and aeration air, which can quickly and cost-effectively seal residual impurities in the reaction chamber, significantly shorten the re-running time after preventive maintenance, and improve the yield of the first batch of epitaxial products.

[0008] To achieve the above objectives, this invention provides a pretreatment method for MOCVD reaction chamber restoration based on magnesium coating and aeration air, used to restore epitaxial growth conditions after MOCVD equipment has undergone furnace dismantling and maintenance. The method includes the following steps: Step S1: After maintenance and vacuuming of the MOCVD reaction chamber, heat the reaction chamber to the first temperature and introduce magnesium source gas into the reaction chamber to form a magnesium adsorption layer on the surface of the components inside the reaction chamber. Step S2: Stop the supply of magnesium source gas, adjust the temperature of the reaction chamber to the second temperature, and introduce oxygen-containing gas into the reaction chamber to allow the magnesium adsorption layer to react with oxygen and form a magnesium oxide passivation layer on the surface of the component. Step S3: Evacuate the reaction chamber to remove residual gas.

[0009] In step S2, the oxygen-containing gas is air, dry clean air, or a mixture of oxygen and an inert gas.

[0010] Step S2 specifically includes: filling the reaction chamber from a vacuum state to a normal pressure state and maintaining it for a predetermined time.

[0011] The characteristic is that step S2 and step S3 are alternately repeated at least once.

[0012] The first temperature ranges from 500°C to 1100°C; the second temperature ranges from 200°C to 500°C.

[0013] The first temperature is preferably 1000℃, and the second temperature is preferably 350℃.

[0014] In step S1, ammonia gas (NH3) is simultaneously introduced into the reaction chamber; the magnesium source gas is magnesia (Cp2Mg).

[0015] The internal components of the reaction chamber include a graphite disk, a spray head, and an inner wall of the reaction chamber; the magnesium oxide passivation layer covers the microporous surface of the components.

[0016] The beneficial effects of this invention are as follows: 1. Low cost: It utilizes the reaction between oxygen in the air and magnesium to achieve impurity blocking without consuming expensive Ga or Al sources.

[0017] 2. High efficiency: The MgO layer forms quickly and is dense, which can effectively prevent deep impurities from escaping during the subsequent high-temperature growth process, so that the first batch of products after preventive maintenance can reach the brightness standard for mass production.

[0018] 3. Good stability: MgO has a high melting point and stable chemical properties. As a passivation layer, it is not easily decomposed, ensuring the stability of continuous production. Attached Figure Description

[0019] Figure 1 This is a comparison chart of the brightness recovery trend after the furnace was disassembled and restarted in Embodiment 1 of the present invention.

[0020] Figure 2 This is a comparison chart of the brightness recovery trend after the furnace was disassembled and restarted in Embodiment 2 of the present invention. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to embodiments. It should be noted that the following embodiments are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0022] Example 1

[0023] This embodiment mainly focuses on MOCVD equipment for conventional LED epitaxial growth.

[0024] 1. Furnace dismantling and preparation: Complete the preventive maintenance of the machine (replace the graphite disk, clean the spray head, etc.), close the reaction chamber door, and evacuate to a pressure of <0.5 torr.

[0025] 2. Magnesium adsorption: The temperature of the reaction chamber was increased to 1000℃.

[0026] The carrier gas H2, ammonia (NH3), and magnesium source (Cp2Mg) are introduced.

[0027] The magnesium source flow rate is set to 2000 sccm-6000 sccm.

[0028] The processing time is kept at approximately 8-20 hours to ensure that magnesium atoms fully penetrate the surface layer and shallow micropores of the graphite disk.

[0029] 3. Oxidation passivation: Stop the flow of the MO source and heating, and allow the temperature of the reaction chamber to cool down naturally or with assistance to 350°C.

[0030] Key step: Open the vacuum breaking valve or dedicated air inlet line to introduce cleanroom air into the cavity until the cavity pressure reaches atmospheric pressure (approximately 760 Torr).

[0031] Maintain this state for 30-60 minutes. During this time, the magnesium adsorbed on the high-temperature surface reacts rapidly with oxygen in the air to form a dense MgO layer, locking in the impurities in the lower layer.

[0032] 4. Post-processing: The reaction chamber was evacuated again to remove the air from the chamber.

[0033] The temperature is raised to the growth temperature, and formal epitaxial growth begins.

[0034] After completing the reaction chamber pretreatment and performing furnace disassembly and re-engineering using the method described in Example 1, the white photoelectric performance of the re-engineered epitaxial wafer was tested under the same epitaxial structure and test conditions, and compared with a baseline process that did not use the method of this invention. The test results are shown in Table 1.

[0035] Table 1 index base This experiment difference IV1(mW) 226.87 229.21 1.03% Vf1(v) 3.139 3.124 -0.47% LOP1 YIELD (%) 99.42 99.45 0.03% IV1: Luminous intensity / brightness indicators of epitaxial wafers under specified test current Vf1: Forward voltage of the epitaxial wafer at a specified current. Luminous efficacy: the light output efficiency per unit of electrical power. LOP1 YIELD: Yield percentage that meets specifications such as brightness and luminous efficacy. As can be seen from Table 1, the luminescence intensity of the epitaxial wafer is significantly improved after adopting the method of the present invention, while the forward voltage decreases slightly and the yield remains stable. This indicates that the method effectively improves the luminescence performance of the epitaxial wafer after furnace disassembly and re-industry without introducing additional electrical performance degradation.

[0036] Figure 1 The comparison results of "brightness recovery trend after furnace dismantling and restarting" in Example 1 are shown.

[0037] The core comparison is between this invention and existing technology. The blue curve (method of this invention): represents the machine performance after the "magnesium coating + air aeration" pretreatment.

[0038] Red curve (existing technology): Represents the performance of machines using traditional methods (such as simple high-temperature baking or ordinary plating).

[0039] Horizontal axis (1-5): Represents the production batches (batch 1 to batch 5) after maintenance (furnace dismantling).

[0040] Vertical axis (226.0-233.0): Represents the brightness index (IV value) of the epitaxial wafer.

[0041] Summarize: Figure 1 This demonstrates that the method of this patent can significantly shorten the machine rework time and avoid the waste of the previous technology, where the first few batches of products had low brightness and required expensive MO sources for multiple batches of sham plating.

[0042] Example 2

[0043] This embodiment is applicable to scenarios where the graphite disk has a long service life, many surface pores, or is heavily contaminated.

[0044] The difference from Example 1 is that a pressure cycling mechanism is introduced in the "oxidation passivation" stage to enhance the penetration of oxidizing gases.

[0045] The specific steps are as follows: 1. Magnesium adsorption: Same as in Example 1, but when Cp2Mg is introduced, the chamber pressure can be appropriately increased to 300-600 torr to utilize high pressure to assist magnesium atom diffusion.

[0046] 2. Cyclic oxidation: Cool down to the 300℃-400℃ range.

[0047] First inflation: Inflate to atmospheric pressure and maintain for 10 minutes.

[0048] First evacuation: Evacuate to a vacuum of <0.5 torr.

[0049] Second inflation: Inflate again to normal pressure and maintain for 10 minutes.

[0050] Repeat the above "inflate-hold-evacuate" process 3-5 times.

[0051] Mechanism explanation: Through repeated pressure fluctuations, a "breathing" effect is generated, which helps to transport oxidizing gases to deeper pores to react with magnesium, while carrying out volatile byproducts generated in the reaction.

[0052] After completing the reaction chamber pretreatment and performing furnace disassembly and re-engineering using the method in Example 2, the white photoelectric performance of the re-engineered epitaxial wafer was tested under the same epitaxial structure and the same test conditions, and compared with the baseline process that did not use this method. The results are shown in Table 2.

[0053] Table 2 index base This experiment difference IV1(mW) 222.57 226.98 1.98% Vf1(V) 3.139 3.127 -0.38% LOP1 YIELD (%) 99.05 99.30 0.25% As can be seen from Table 2, this embodiment can also improve the luminescence performance of the epitaxial wafer after furnace dismantling and reactivation to a certain extent. The luminescence intensity is improved, the forward voltage is slightly reduced, and the yield remains stable, indicating that the pressure cycling mechanism has a positive effect on reducing residual contaminants in the cavity.

[0054] Figure 2 Example 2: Comparison of brightness recovery trends in specific high-difficulty scenarios.

[0055] Where: Horizontal axis (1-5): represents the first 5 furnace epitaxial growths performed after machine maintenance (furnace dismantling).

[0056] Vertical axis (222.5 - 227.0): Represents the brightness index (IV) of the epitaxial wafer; the higher the value, the better.

[0057] Blue broken line (method of the present invention): Corresponds to the process of Example 2, that is, on the basis of magnesium coating, a "pressure cycle (breathing)" oxidation step is added.

[0058] Red broken line (existing technology): corresponds to the baseline process that does not use this method.

[0059] Figure 2 illustrates that even when equipment components are in poor condition (such as graphite disks with many pores and heavy dirt), this magnesium treatment method with "pressure circulation" can still restore production faster and achieve higher brightness than traditional methods.

[0060] Example 3

[0061] This embodiment aims to further reduce the cost of rework and is suitable for scenarios with slightly lower purity requirements or routine small-scale maintenance.

[0062] 1. Magnesium adsorption: The heating temperature is set to 600℃-800℃.

[0063] The magnesium source flow rate is set to 2000 sccm-4000 sccm.

[0064] The processing time was extended to 10-20 hours to compensate for the decrease in diffusion rate caused by the lower temperature.

[0065] 2. Oxidation passivation: The temperature dropped to 200℃.

[0066] Introduce an oxygen-containing gas mixture (e.g., 20% O2 + 80% N2), with the flow rate controlled at 8000-10000 sccm and the pressure maintained at 500-700 torr.

[0067] Compared to directly introducing oxygen into the atmosphere, controlling oxygen concentration and pressure can prevent the risk of particle shedding caused by excessive local oxidation.

Claims

1. A pretreatment method for restoring an MOCVD reaction chamber based on magnesium coating and aeration air, used to restore epitaxial growth conditions after dismantling and maintenance of an MOCVD equipment, characterized in that... The method includes the following steps: Step S1: After maintenance and vacuuming of the MOCVD reaction chamber, heat the reaction chamber to the first temperature and introduce magnesium source gas into the reaction chamber to form a magnesium adsorption layer on the surface of the components inside the reaction chamber. Step S2: Stop the supply of magnesium source gas, adjust the temperature of the reaction chamber to the second temperature, and introduce oxygen-containing gas into the reaction chamber to allow the magnesium adsorption layer to react with oxygen and form a magnesium oxide passivation layer on the surface of the component. Step S3: Evacuate the reaction chamber to remove residual gas.

2. The method as described in claim 1, characterized in that, In step S2, the oxygen-containing gas is air, dry clean air, or a mixture of oxygen and an inert gas.

3. The method as described in claim 1, characterized in that, Step S2 specifically includes: filling the reaction chamber from a vacuum state to a normal pressure state and maintaining it for a predetermined time.

4. The method as described in claim 1, characterized in that, Step S2 and step S3 are repeated alternately at least once.

5. The method as described in claim 1, characterized in that, The first temperature ranges from 500°C to 1100°C; the second temperature ranges from 200°C to 500°C.

6. The method as described in claim 5, characterized in that, The first temperature is 1000℃, and the second temperature is 350℃.

7. The method as described in claim 1, characterized in that, In step S1, ammonia gas is simultaneously introduced into the reaction chamber; the magnesium source gas is magnesia-ceramsite.

8. The method as described in claim 1, characterized in that, The internal components of the reaction chamber include a graphite disk, a spray head, and an inner wall of the reaction chamber; the magnesium oxide passivation layer covers the microporous surface of the components.

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