A method for removing residual wax from a gallium arsenide substrate surface
By using a variety of dewaxing composite solvents and specific process steps to remove wax residue from the surface of gallium arsenide substrates, the problem of poor removal effect in the prior art is solved, and the performance of gallium arsenide devices is improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- VITAL MICRO-ELECTRONICS TECH CO LTD
- Filing Date
- 2026-03-05
- Publication Date
- 2026-06-09
AI Technical Summary
Existing technologies are not effective enough in removing residual wax from gallium arsenide substrates, which affects the performance of gallium arsenide devices.
A variety of dewaxing composite solvents, including limonene, dodecane, ethylene glycol butyl ether, acetone, isopropanol, ethyl acetate, isopropanol, and cyclohexane, are used in combination with heating softening, step-by-step ultrasonication, and gradient rinsing processes to remove wax residue from the surface of gallium arsenide substrates.
It significantly improves the removal of wax from gallium arsenide substrates, enhances the performance of gallium arsenide devices, and in particular reduces the noise figure of microwave devices and the threshold current of lasers, thus extending device lifespan.
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Figure CN122180331A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of semiconductor substrate technology, and in particular relates to a method for removing residual wax from the surface of a gallium arsenide substrate. Background Technology
[0002] Compared to silicon (Si), a first-generation semiconductor material, gallium arsenide (GaAs), as a typical representative of second-generation semiconductor materials, has an electron mobility that is about 5-6 times that of silicon. This allows GaAs-based HEMTs, MESFETs, and other devices to operate at higher frequencies (up to the terahertz range) and have faster switching speeds. In addition, GaAs is a direct bandgap semiconductor, which can efficiently emit and absorb photons. Therefore, it is an ideal material for fabricating optoelectronic devices such as light-emitting diodes (LEDs), laser diodes (LDs), and solar cells, and occupies an irreplaceable position in the field of high-speed, high-frequency, optoelectronic, and microwave devices.
[0003] Gallium arsenide (GaAs) devices typically consist of a GaAs substrate and an epitaxial functional layer. The epitaxial functional layer is deposited on the GaAs substrate using processes such as metallographic vapor deposition (MOCVD). The GaAs substrate is the physical carrier of the device, and its surface and interface states significantly affect the quality of the epitaxial functional layer, thereby impacting the performance of the GaAs device. To ensure the performance of GaAs devices, extremely stringent requirements are placed on the surface and interface states of the GaAs substrate. Any minute surface defects, contamination, or lattice damage will severely scatter charge carriers, significantly degrading device performance, for example, leading to an increase in the noise figure of microwave devices. Increased output power or increased threshold current and shortened lifespan of the laser can lead to problems. However, to obtain gallium arsenide substrates with ultra-flat polished surfaces, processes such as slicing, grinding, mechanical polishing, and chemical mechanical polishing (CMP) are usually required. In the polishing process, high-purity waxes such as paraffin wax, microcrystalline wax, or special synthetic waxes are used to temporarily bond the substrate to the base. Therefore, after the polishing process is completed, how to thoroughly and without damage remove these wax residues becomes a key and extremely challenging aspect to ensure the surface and interface state of the gallium arsenide substrate and the performance of gallium arsenide devices.
[0004] However, the current process of removing residual wax from gallium arsenide substrates after polishing and other processes is not effective enough, and the amount of residual wax is relatively large. It is necessary to develop new wax removal processes to ensure the quality of gallium arsenide substrates. Summary of the Invention
[0005] In view of this, this application provides a method for removing residual wax from the surface of a gallium arsenide substrate, which solves the technical problem that the existing technology is not effective enough in removing residual wax from gallium arsenide substrates.
[0006] The first aspect of this application provides a method for removing residual wax from the surface of a gallium arsenide substrate, comprising the following steps:
[0007] Preparation steps of the first dewaxing composite solvent: Mix limonene, dodecane and ethylene glycol butyl ether to obtain the first dewaxing composite solvent;
[0008] The preparation steps of the second dewaxing composite solvent are as follows: Acetone, isopropanol and ethyl acetate are mixed to obtain the second dewaxing composite solvent;
[0009] Preparation steps of the third dewaxing composite solvent: Mix isopropanol and cyclohexane to obtain the third dewaxing composite solvent;
[0010] The heating and softening dewaxing process involves immersing a polished gallium arsenide substrate with wax in a first dewaxing composite solvent heated to 40-60°C to obtain a heated and softened gallium arsenide substrate.
[0011] The steps of stepped ultrasonic dewaxing are as follows: The gallium arsenide substrate that has been heated and softened by dewaxing is placed in a second dewaxing composite solvent and subjected to stepped ultrasonic dewaxing with increasing power to obtain a gallium arsenide substrate with stepped ultrasonic dewaxing.
[0012] Solvent replacement and dewaxing steps: The gallium arsenide substrate that has undergone stepped ultrasonic dewaxing is sequentially placed in the third dewaxing composite solvent and anhydrous ethanol for rinsing, and then dried to obtain a polished gallium arsenide wafer.
[0013] Preferably, the first dewaxing composite solvent comprises, by volume, 4-8 parts limonene, 2-4 parts dodecane, and 0.5-2 parts ethylene glycol butyl ether.
[0014] Preferably, the second dewaxing composite solvent comprises, by volume, 3-7 parts acetone, 2-6 parts isopropanol, and 0.5-2 parts ethyl acetate.
[0015] Preferably, the third dewaxing composite solvent comprises, by volume, 5-10 parts isopropanol and 1-3 parts cyclohexane.
[0016] Preferably, the soaking time is 5 to 15 minutes.
[0017] Preferably, the stepwise ultrasound with increasing power is sequentially applied at power levels of 0.2~0.4 W / cm². 2 The first stage of ultrasound was performed at a power of 0.3~0.6W / cm. 2 Perform a second stage of ultrasound; and the ultrasound power in the second stage is greater than that in the first stage.
[0018] Preferably, the duration of the first stage of ultrasound is 1 to 5 minutes, and the ultrasound power of the second stage is 1 to 5 minutes.
[0019] Preferably, the rinsing method is overflow rinsing and / or spray rinsing at a rotation speed of 5~10 rpm for 0.5~2 minutes.
[0020] Preferably, the drying method is to introduce nitrogen gas at a rate of 1-10 L / min and dry for 1-5 min.
[0021] Preferably, the anhydrous ethanol has a water content of less than 50 ppm.
[0022] The second aspect of this application provides a gallium arsenide polished wafer, which is prepared by the method for removing residual wax from the surface of a gallium arsenide substrate as described in the first aspect.
[0023] A third aspect of this application provides a gallium arsenide device, including a gallium arsenide polished wafer and an epitaxial functional layer, wherein the gallium arsenide polished wafer is selected from the gallium arsenide polished wafer described in the second aspect.
[0024] Compared with the prior art, the method for removing residual wax from the surface of a gallium arsenide substrate provided in this application has at least the following beneficial effects:
[0025] This application provides a method for removing residual wax from the surface of a gallium arsenide substrate. It introduces a series of wax-removing composite solvents, including a "first wax-removing composite solvent," a "second wax-removing composite solvent," and a "third wax-removing composite solvent." These solvents utilize various properties, such as high-boiling-point wax-removing solvents with good wax solubility, wax-removing solvents that can act as swelling agents, ethyl acetate that dissolves polar residues, and solvents with low surface tension and low boiling points. Combined with process steps such as "heat softening," "stepped ultrasonication," and "gradient rinsing," the method improves the removal of residual wax from the gallium arsenide substrate, thereby enhancing the performance of subsequent gallium arsenide device fabrication. Attached Figure Description
[0026] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0027] Figure 1 This is a schematic flowchart of a method for removing residual wax from the surface of a gallium arsenide substrate, provided in Embodiment 1 of this application. Detailed Implementation
[0028] This application provides a method for removing residual wax from the surface of a gallium arsenide substrate, which solves the technical problem that the existing technology is not effective enough in removing residual wax from gallium arsenide substrates.
[0029] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0030] Example 1
[0031] This embodiment provides a method for removing residual wax from the surface of a gallium arsenide substrate, the process flow diagram of which is shown below. Figure 1 As shown, the process includes the preparation steps of the dewaxing composite solvent, the dewaxing step of the gallium arsenide substrate, and the post-processing steps.
[0032] The preparation steps of the dewaxing composite solvent include:
[0033] Weigh D-limonene, dodecane, and ethylene glycol butyl ether according to a volume ratio of 6:3:1, and stir the weighed D-limonene, dodecane, and ethylene glycol butyl ether evenly to obtain the first dewaxing composite solvent.
[0034] Acetone, isopropanol, and ethyl acetate were weighed according to a volume ratio of 5:4:1, and the weighed acetone, isopropanol, and ethyl acetate were stirred and mixed evenly to obtain the second dewaxing composite solvent.
[0035] Weigh isopropanol and cyclohexane at a volume ratio of 8:2, and stir them evenly to obtain the third dewaxing composite solvent.
[0036] The dewaxing process for gallium arsenide substrates includes:
[0037] After heating the first dewaxing composite solvent to 45°C, the polished waxed gallium arsenide substrate was immersed in the heated first dewaxing composite solvent for 8 minutes to obtain a heated and softened dewaxing gallium arsenide substrate.
[0038] The heated and softened gallium arsenide substrate was transferred to a second dewaxing composite solvent at room temperature and subjected to step-wise ultrasonication with increasing power to obtain a step-wise ultrasonically dewaxed gallium arsenide substrate. The first stage of the step-wise ultrasonication with increasing power was at 0.3 W / cm². 2 The first stage involved ultrasonication for 2 minutes at a temperature of 25℃, followed by a second stage at 0.5 W / cm². 2 Sonicate for 2 minutes at a process temperature of 30℃;
[0039] The gallium arsenide substrate dewaxed by step ultrasonic was first placed in the third dewaxing composite solvent at room temperature for 1 minute for overflow rinsing, and then placed in anhydrous ethanol (water content <50ppm) at room temperature for 1 minute for overflow rinsing. During the rinsing process, the gallium arsenide substrate dewaxed by step ultrasonic was rotated at a speed of 8 rpm to obtain the rinsed gallium arsenide substrate.
[0040] Post-processing steps include:
[0041] The rinsed gallium arsenide substrate was placed in a sealed drying chamber, and nitrogen gas at a flow rate of 8 L / min was introduced sequentially for drying at 35°C for 1 min, nitrogen gas at a flow rate of 4 L / min was introduced for drying at 25°C for 2 min, and nitrogen gas at a flow rate of 2 L / min was introduced for drying at 20°C for 1 min, to obtain a gallium arsenide polished wafer.
[0042] Comparative Example 1
[0043] This comparative example provides a method for removing residual wax from the surface of a gallium arsenide substrate, including a wax removal step and a post-treatment step.
[0044] The dewaxing process for gallium arsenide substrates includes:
[0045] Waxed gallium arsenide substrates polished in the same batch as those used in Example 1 were immersed in xylene dewaxing solvent heated to 70°C for 15 minutes.
[0046] Post-processing steps include:
[0047] The dewaxed gallium arsenide substrate was placed in a sealed drying chamber, and nitrogen gas at a flow rate of 8 L / min was introduced sequentially for drying at 35°C for 1 min, nitrogen gas at a flow rate of 4 L / min was introduced for drying at 25°C for 2 min, and nitrogen gas at a flow rate of 2 L / min was introduced for drying at 20°C for 1 min, to obtain a gallium arsenide polished wafer.
[0048] Comparative Example 2
[0049] This comparative example provides a method for removing residual wax from the surface of a gallium arsenide substrate, including a wax removal composite solvent preparation step, a gallium arsenide substrate wax removal step, and a post-treatment step.
[0050] The preparation steps of the dewaxing composite solvent include:
[0051] Weigh D-limonene, dodecane, and ethylene glycol butyl ether according to a volume ratio of 6:3:1, and stir the weighed D-limonene, dodecane, and ethylene glycol butyl ether evenly to obtain the first dewaxing composite solvent.
[0052] Acetone, isopropanol, and ethyl acetate were weighed according to a volume ratio of 5:4:1, and the weighed acetone, isopropanol, and ethyl acetate were stirred and mixed evenly to obtain the second dewaxing composite solvent.
[0053] Weigh isopropanol and cyclohexane at a volume ratio of 8:2, and stir them evenly to obtain the third dewaxing composite solvent.
[0054] The dewaxing process for gallium arsenide substrates includes:
[0055] After heating the first dewaxing composite solvent to 45°C, the waxed gallium arsenide substrate polished in the same batch as the waxed gallium arsenide substrate used in Example 1 was immersed in the heated first dewaxing composite solvent for 8 minutes to obtain a heat-softened dewaxing gallium arsenide substrate.
[0056] The gallium arsenide substrate, after being heated and softened to remove wax, was transferred to a second dewaxing composite solvent at room temperature and subjected to ultrasonication at a power of 0.4 W / cm². 2 The time was 4 minutes, and gallium arsenide substrates were obtained after ultrasonic dewaxing.
[0057] The gallium arsenide substrate that has been dewaxed by ultrasound was placed in a third dewaxing composite solvent at room temperature for overflow rinsing for 2 minutes. During the rinsing process, the gallium arsenide substrate was rotated at a speed of 8 rpm to obtain the rinsed gallium arsenide substrate.
[0058] Post-processing steps include:
[0059] The rinsed gallium arsenide substrate was placed in a sealed drying chamber, and nitrogen gas at a flow rate of 8 L / min was introduced sequentially for drying at 35°C for 1 min, nitrogen gas at a flow rate of 4 L / min was introduced for drying at 25°C for 2 min, and nitrogen gas at a flow rate of 2 L / min was introduced for drying at 20°C for 1 min, to obtain a gallium arsenide polished wafer.
[0060] Comparative Example 3
[0061] This comparative example provides a method for removing residual wax from the surface of a gallium arsenide substrate, including a wax removal step and a post-treatment step.
[0062] The dewaxing process for gallium arsenide substrates includes:
[0063] After heating the xylene dewaxing solvent to 45°C, the waxed gallium arsenide substrate polished in the same batch as the waxed gallium arsenide substrate used in Example 1 was immersed in the heated xylene dewaxing solvent for 8 minutes to obtain a heated and softened dewaxing gallium arsenide substrate.
[0064] The heated and softened gallium arsenide substrate was transferred to a xylene dewaxing solvent at room temperature and subjected to step-wise ultrasonication with increasing power to obtain a step-wise ultrasonically dewaxed gallium arsenide substrate. The first stage of the step-wise ultrasonication with increasing power was at 0.3 W / cm². 2 The first stage involved ultrasonication for 2 minutes at a temperature of 25℃, followed by a second stage at 0.5 W / cm². 2 Sonicate for 2 minutes at a process temperature of 30℃;
[0065] The gallium arsenide substrate dewaxed by step ultrasonication was first rinsed in xylene dewaxing solvent at room temperature for 1 minute, and then rinsed in anhydrous ethanol (water content <50ppm) at room temperature for 1 minute. During the rinsing process, the gallium arsenide substrate dewaxed by step ultrasonication was rotated at a speed of 8 rpm to obtain the rinsed gallium arsenide substrate.
[0066] Post-processing steps include:
[0067] The dewaxed gallium arsenide substrate was placed in a sealed drying chamber, and nitrogen gas at a flow rate of 8 L / min was introduced sequentially for drying at 35°C for 1 min, nitrogen gas at a flow rate of 4 L / min was introduced for drying at 25°C for 2 min, and nitrogen gas at a flow rate of 2 L / min was introduced for drying at 20°C for 1 min, to obtain a gallium arsenide polished wafer.
[0068] Experimental Example 1
[0069] This experimental example tests the effectiveness of the methods for removing residual wax from gallium arsenide substrates provided in Example 1 and Comparative Examples 1-3.
[0070] The testing process for removing residual wax from gallium arsenide substrates includes:
[0071] Prepare a batch of polished waxed gallium arsenide substrates from the same batch as the waxed gallium arsenide substrate used in Example 1 as gallium arsenide substrate sample 1, a polished gallium arsenide sheet prepared in Example 1 as gallium arsenide substrate sample 2, a polished gallium arsenide sheet prepared in Comparative Example 1 as gallium arsenide substrate sample 3, a polished gallium arsenide sheet prepared in Comparative Example 2 as gallium arsenide substrate sample 4, and a polished gallium arsenide sheet prepared in Comparative Example 3 as gallium arsenide substrate sample 5.
[0072] X-ray photoelectron spectroscopy (XPS) was used to detect the residual carbon C1s (At%) on the surface of gallium arsenide substrate samples 1-5, and the test results are shown in Table 1.
[0073] Table 1: Test results of residual carbon on the surface of gallium arsenide substrate samples 1-5
[0074]
[0075] As shown in Table 1, the waxed gallium arsenide substrates polished in the same batch as those used in Example 1, before the removal of residual wax on the surface using the removal methods provided in Example 1 or Comparative Examples 1-3, i.e., gallium arsenide substrate sample 1, showed an extremely strong carbon signal detected by X-ray photoelectron spectroscopy. This indicates that during the polishing process, due to the need to temporarily adhere the gallium arsenide substrate to the substrate, a large amount of wax remained on the surface of the gallium arsenide substrate. Compared with gallium arsenide substrate sample 1, the carbon signal of gallium arsenide substrate sample 2 dropped to near background levels, indicating that the residual wax on the surface was completely removed by the substrate. This is because in the method for removing residual wax on the surface of the gallium arsenide substrate provided in Example 1, the first dewaxing composite solvent used has good solubility for wax and high boiling points, such as limonene and long-chain alkanes, which can soften and initially dissolve most of the wax layer during heating. Meanwhile, ethylene glycol butyl ether can act as a swelling agent to penetrate into the wax layer and reduce its... The adhesion, namely the good solubility and high boiling point of the first dewaxing composite solvent, after heating, works synergistically with the dewaxing solvent that can act as a swelling agent, so that the main body of the wax layer remaining on the surface of the gallium arsenide substrate is dissolved. The second dewaxing composite solvent used has better volatility and extremely high purity of acetone and isopropanol. In addition, it also contains ethyl acetate, which has the solubility for polar residues, and step-by-step ultrasound. The cavitation effect of ultrasound can be used to effectively remove stubborn wax residues attached to the micro-depressions on the surface of the gallium arsenide substrate. The third dewaxing composite solvent used contains solvents with low surface tension and low boiling point, such as isopropanol, cyclohexane, and anhydrous ethanol. These solvents can replace the solvents with high surface tension remaining in the previous dewaxing composite solvents and remove the last trace contaminants. At the same time, the low surface tension solvent reduces the formation of water stain-like spots during drying and is conducive to subsequent drying, resulting in a cleaner gallium arsenide polished wafer.
[0076] Table 1 also shows that compared with gallium arsenide substrate sample 2, the carbon signal of gallium arsenide substrate sample 3 is significantly stronger, indicating that using xylene as a single dewaxing solvent is not effective enough in removing residual wax from the gallium arsenide substrate. Compared with gallium arsenide substrate sample 3, the carbon signal of gallium arsenide substrate sample 5 is reduced, indicating that although the dewaxing solvent used in gallium arsenide substrate sample 5 is similar to that used in gallium arsenide substrate sample 3, the use of processes such as "heat softening", "stepped ultrasonic", and "gradient rinsing" improves the effect of removing residual wax from the gallium arsenide substrate. At the same time, compared with gallium arsenide substrate sample 3, the carbon signal of gallium arsenide substrate sample 4 is reduced, indicating that although the dewaxing process of gallium arsenide substrate sample 4 is similar to that of gallium arsenide substrate sample 3, the use of "first dewaxing composite solvent", "second dewaxing composite solvent", and "third dewaxing composite solvent" improves the effect of removing residual wax from the gallium arsenide substrate.
[0077] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.
Claims
1. A method for removing residual wax from the surface of a gallium arsenide substrate, characterized in that, Includes the following steps: Limonene, dodecane, and ethylene glycol butyl ether are mixed to obtain the first dewaxing composite solvent; Acetone, isopropanol and ethyl acetate are mixed to obtain a second dewaxing composite solvent; Isopropanol and cyclohexane are mixed to obtain the third dewaxing composite solvent; The polished gallium arsenide substrate with wax is sequentially immersed in a first dewaxing composite solvent heated to 40-60°C, subjected to step-wise ultrasonic treatment with increasing power in a second dewaxing composite solvent, rinsed in a third dewaxing composite solvent, rinsed in anhydrous ethanol, and dried to obtain a polished gallium arsenide wafer.
2. The method for removing residual wax from the surface of a gallium arsenide substrate according to claim 1, characterized in that, The first dewaxing composite solvent comprises, by volume, 4-8 parts limonene, 2-4 parts dodecane, and 0.5-2 parts ethylene glycol butyl ether.
3. The method for removing residual wax from the surface of a gallium arsenide substrate according to claim 1, characterized in that, The second dewaxing composite solvent comprises, by volume, 3-7 parts acetone, 2-6 parts isopropanol, and 0.5-2 parts ethyl acetate.
4. The method for removing residual wax from the surface of a gallium arsenide substrate according to claim 1, characterized in that, The third dewaxing composite solvent comprises, by volume, 5-10 parts isopropanol and 1-3 parts cyclohexane.
5. The method for removing residual wax from the surface of a gallium arsenide substrate according to claim 1, characterized in that, The soaking time is 5-15 minutes.
6. The method for removing residual wax from the surface of a gallium arsenide substrate according to claim 1, characterized in that, The stepped ultrasound with increasing power is described as follows: power ranges from 0.2 to 0.4 W / cm². 2 The first stage of ultrasound was performed at a power of 0.3~0.6W / cm. 2 Perform a second stage of ultrasound; and the ultrasound power in the second stage is greater than that in the first stage.
7. The method for removing residual wax from the surface of a gallium arsenide substrate according to claim 1, characterized in that, The rinsing method is to use overflow rinsing and / or spray rinsing at a speed of 5-10 rpm for 0.5-2 minutes.
8. The method for removing residual wax from the surface of a gallium arsenide substrate according to claim 1, characterized in that, The drying method involves introducing nitrogen gas at a rate of 1-10 L / min for 1-5 minutes.
9. A gallium arsenide polished wafer, characterized in that, It is prepared by the method for removing residual wax from the surface of a gallium arsenide substrate as described in any one of claims 1-8.
10. A gallium arsenide device, characterized in that, The gallium arsenide polishing wafer used is selected from the gallium arsenide polishing wafer described in claim 9.