A polishing solution for improving the surface quality of monocrystalline indium antimonide

Abstract

The application discloses a polishing liquid for improving the surface quality of single crystal indium antimonide, and the polishing liquid comprises the following components: abrasive with a mass percentage of 10-20%, oxidizing agent with a mass percentage of 1-2.5%, and complexing agent with a mass percentage of 0.2-2.5%; and the pH value of the polishing system is 3-5. The abrasive is silicon dioxide; the oxidizing agent is hydrogen peroxide; and the complexing agent is citric acid or phosphoric acid. The application realizes the removal rate of indium antimonide of 1202.82 nm / min and 565.33 nm / min, and the surface roughness of 0.17 nm and 0.28 nm. After the surface of the single crystal indium antimonide material is treated by the polishing liquid, the surface roughness (Sq) is less than 1 nm, and the polishing liquid is green and environment-friendly.

Description

Technical Field

[0001] This invention belongs to the field of chemical mechanical polishing for ultra-precision machining, specifically relating to a polishing slurry for preparing high surface quality single-crystal indium antimonide semiconductor materials and its preparation method. Background Technology

[0002] Indium antimonide (InSb) materials possess narrow band gap (0.17 eV at room temperature) and extremely high electron mobility (78,000 cm⁻¹ at room temperature). 2 Its (V•s) characteristic gives it a core position in the mid-infrared field. Indium antimonide materials have wide applications in detection and imaging, military and defense, aerospace and remote sensing, novel electronics and optoelectronics, optical communication and integrated photonics. The wide range of applications of indium antimonide materials has led to a large demand for high-quality single-crystal indium antimonide. Chemical mechanical polishing (CMP) technology, as a technique for achieving global planarization, is widely used in the ultra-precision machining of various materials. However, CMP technology for single-crystal indium antimonide materials is still under development.

[0003] Polishing slurry is a key consumable affecting surface quality in the chemical mechanical polishing (CMP) technology for monocrystalline indium antimonide. Because monocrystalline indium antimonide has low hardness (Knoop hardness 223 HK, Mohs hardness 4) and is brittle, abrasives with high hardness, such as alumina (Knoop hardness 2,000 HK, Mohs hardness 9), can cause significant damage to its surface. Silica (Knoop hardness approximately 666 HK, Mohs hardness 6), with its even lower hardness and commonly used polishing slurry abrasive, offers advantages such as low cost and good polished surface quality. Therefore, using silica as the abrasive for polishing monocrystalline indium antimonide not only satisfies the necessary mechanical action but also better protects the material's surface.

[0004] Patent CN201510014588, "A Chemical Polishing Method for Indium Antimonide Wafers," discloses a chemical polishing method for indium antimonide wafers. This method involves placing a polishing disk with the indium antimonide wafer adhering to it upside down in a tank containing a 0.005%~10% bromomethanol chemical polishing solution. This method can significantly reduce the surface roughness of the indium antimonide wafer and remove surface damage. However, the bromomethanol used in this method may cause the material surface to become antimony-rich, i.e., the antimony element ratio increases. It may also change the electronic structure of the material surface, increasing surface leakage current. Furthermore, the polishing solution is toxic and volatile, and its waste liquid also contains bromine and methanol. After this chemical polishing, the surface roughness was optimized from 6.692 nm to 6.443 nm.

[0005] Patent CN202011141093, "A Polishing Method for Indium Antimonide Single Wafers," discloses a method that first performs laser polishing followed by chemical mechanical polishing. This method uses aluminum sol or silica sol as the abrasive in the chemical mechanical polishing slurry, and ammonia or sodium hypochlorite as the oxidant. Through the chemical action of the prepared polishing slurry and the mechanical action of the polishing equipment, a scratch-free surface finish is achieved on the wafer, with a surface roughness of 0.3 nm. However, because laser polishing can cause thermal damage to the material, and ammonia and sodium hypochlorite can volatilize and produce toxic gases such as ammonia, chlorine, and hydrogen chloride, the waste liquid requires special treatment to avoid potential environmental pollution. Summary of the Invention

[0006] The purpose of this invention is to obtain a high-quality surface finish on monocrystalline indium antimonide materials by providing a polishing slurry with a simple composition and high surface quality. This polishing slurry uses silica sol as its basic component, which has low hardness, uniform particle size distribution, and is easy to clean afterward. Furthermore, the silica abrasive is non-toxic and non-polluting. Hydrogen peroxide is used as the oxidant, which is easy to mix with the polishing slurry and produces good polished surface quality. The oxidation rate of hydrogen peroxide varies under different pH values. The complexing agent, in addition to complexing the metal ions generated during polishing, also acts as a pH adjuster, providing a specific environment for polishing monocrystalline indium antimonide, controlling the material removal rate, and avoiding the introduction of other impurity ions. A soft polishing pad is used in conjunction with larger-particle-size silica sol on the equipment, harmonizing the surface quality and removal rate of the material.

[0007] The solution to the technical problem of this invention is: A polishing slurry for improving the surface quality of single-crystal indium antimonide, the slurry comprising: an abrasive mass percentage concentration of 10-20%, an oxidant mass percentage of 1-2.5%, and a complexing agent mass percentage of 0.2-2.5%; The pH value of the polishing system is 3~5.

[0008] The abrasive is silicon dioxide; the oxidant is hydrogen peroxide; The complexing agent is citric acid or phosphoric acid; when the complexing agent is citric acid, its concentration in the polishing solution is 0.5-2.5%; when it is phosphoric acid, its concentration is 0.2-1%. The silica has a particle size of 80~130 nm; The method for preparing the polishing slurry used to improve the surface quality of single-crystal indium antimonide includes the following steps: Step S1: According to the material ratio of the target polishing slurry, take the silica sol stock solution into the container; The concentration of the silica sol stock solution was 30 wt.%~60 wt.%; Step S2: Then add the hydrogen peroxide solution to the container from step S1; The concentration of the hydrogen peroxide solution was 20 wt.%~40 wt.%. Step S3: Add deionized water to the container from step S2; Step S4: Stir the mixture from step S3; Step S5: Add the complexing agent to the solution and stir the mixture until homogeneous. The pH of the resulting solution is 3-5.

[0009] The method for applying the polishing slurry to improve the surface quality of single-crystal indium antimonide is used for chemical mechanical polishing of single-crystal indium antimonide surfaces.

[0010] The conditions for chemical mechanical polishing are: The polishing machine model is Rui Xuan SSP-500, the polishing pad model is TF7836, the polishing time is 10 min, the polishing pressure is 4.53 psi, the polishing fluid flow rate is 40 ml / min, the polishing head speed is 50 r / min, and the polishing disc speed is 50 r / min.

[0011] The essential features of this invention are: This invention achieves a simple and effective planarization of indium antimonide single-crystal surfaces using a polishing slurry composed of silica sol and hydrogen peroxide. Under acidic conditions, the oxidation rate of indium antimonide surfaces and the removal rate of oxidation products by hydrogen peroxide are both improved. After indium antimonide is oxidized to Sb₂O₃ and In₂O₃, it further transforms into Sb. 3+ Sb 5+ and In 3+ Secondly, due to the low hardness and brittleness of indium antimonide, a larger particle size silica sol and a softer polishing pad were used in the polishing process. Unlike traditional methods that use small-particle abrasives to avoid scratches, the larger particle size silica sol and the softer polishing pad used in this invention achieve a better combination.

[0012] Citric acid or phosphoric acid was used as a complexing agent in the polishing solution: the citrate ions from the ionization of citric acid reacted with In... 3+ and Sb 3+ A complexation reaction occurs, forming soluble indium citrate [In(C6H5O7)] and antimony citrate [Sb(C6H5O7)] complexes. These complexes have good water solubility, thus being effectively removed from the polished surface; similarly, phosphate ions (mainly H2PO4) undergo a complexation reaction to form soluble indium citrate [In(C6H5O7)] and antimony citrate [Sb(C6H5O7)] complexes. - and HPO4 2- ) and In 3+ and Sb 3+ Formation of soluble phosphate complexes (e.g., [In(H2PO4)]) 2+[Sb(HPO4)] + These complexes also exhibit good water solubility, promoting the effective removal of polishing products. The clever use of citric acid or phosphoric acid also functions as a pH adjuster, providing an acidic environment to the polishing solution without introducing other pH adjusters.

[0013] Furthermore, the flexible material of the polishing pad provides support and acts as a buffer and self-adaptive mechanism for the abrasive particles. Larger abrasive particles achieve a good balance between rolling friction and cutting removal under the elastic support of the polishing pad, and the larger silica sol particles can also accommodate more polishing fluid components. Thus, a balance between high efficiency and low damage is achieved for single-crystal indium antimonide materials.

[0014] The beneficial effects of this invention are: This invention provides a polishing slurry exhibiting high removal rate and surface quality for single-crystal indium antimonide. The slurry maintains a stable pH within the range of 3-5, and hydrogen peroxide is used as the oxidant. Under acidic conditions, hydrogen peroxide enhances its oxidizing power against indium antimonide. The oxidation products of indium antimonide are dissolved and abraded by the combined action of the polishing slurry environment and the polishing pad. The low hardness of silica, when combined with a soft polishing pad, further protects the surface of indium antimonide. During a 10-minute polishing process, this invention achieved indium antimonide removal rates of 1202.82 nm / min and 565.33 nm / min, with surface roughnesses of 0.17 nm and 0.28 nm, respectively. The surface roughness (Sq) of the single-crystal indium antimonide material after polishing with this slurry is less than 1 nm, and the slurry components are environmentally friendly. Attached Figure Description

[0015] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the preparation process of the polishing slurry used in this invention to improve the removal rate and surface quality of single-crystal indium antimonide; Figure 2 The image shows the microstructure of polished single-crystal indium antimonide corresponding to Example 1.

[0016] Figure 3 This is the surface of a single-crystal indium antimonide crystal in Example 5 without polishing using a soft polishing pad. The image shows the surface field of view with a side length of 2560 μm under a laser confocal microscope.

[0017] Figure 4 This is the surface of indium antimonide over-oxidized in Example 6. Over-oxidation marks are visible along the polishing direction in the figure.

[0018] Figure 5 The bar chart shows the effect of adding phosphoric acid, citric acid, sulfuric acid, hydrochloric acid, and no additives on the Zeta potential of silica sol and the line graph shows the effect on the dispersion of silica sol. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0020] Please see Figure 1 This invention provides a polishing slurry for improving the surface quality of single-crystal indium antimonide, comprising the following steps: Step S1: Take m1 of silica sol stock solution into a container at a mass percentage of 10-20%.

[0021] Step S2: Take m2 of hydrogen peroxide solution and add it to the container from step S1, according to a mass percentage of 1-2.5%. Step S3: Add m3 of deionized water to the container from step S2; Step S4: Use a tool to stir the mixture from step S3 until it is homogeneous; Step S5: Adjust the pH of the liquid to a suitable level using citric acid or phosphoric acid solution. Then stir the mixture thoroughly.

[0022] In step S1 of the present invention, the silica sol stock solution (particle size 80~130 nm) m1 is 150~200 g; In step S2 of the present invention, the hydrogen peroxide solution m2 is 15~25 g; In step S3 of the present invention, the mass m3 of the deionized water is 180~220 g; In step S5 of this invention, the additive is a prepared solution of approximately 50 wt.% citric acid or 20 wt.% phosphoric acid. Ultimately, the pH of the polishing solution is 3-5.

[0023] Example 1: Prepare 400 ml of polishing solution Add 180 g of finished silica sol (sol concentration 40%, particle size 80~130 nm) to a clean container, then add 20 g of finished 30 wt.% hydrogen peroxide solution; then weigh out 200 g of deionized water and add it to the container. Stir the mixture thoroughly using a tool; then monitor the pH of the mixture using a pH meter, and add 13.5 ml of the prepared 50 wt.% citric acid solution to obtain 400 ml of polishing solution with a pH of 3. The polishing machine used was a domestic Rui Xuan SSP-500; the polishing pad was a TF7836 (made of damping cloth); the process conditions were: polishing time 10 min, polishing pressure 4.53 psi, polishing fluid flow rate 40 ml / min, polishing head speed 50 r / min, and polishing disc speed 50 r / min; chemical mechanical polishing was performed on single-crystal indium antimonide material with a side length of 12 mm; after polishing, the indium antimonide was cleaned with deionized water and dried; its surface morphology and surface roughness (Sq) were tested using an Agilent 5600LS atomic force microscope manufactured by Agilent Technologies, France.

[0024] Example 2: Prepare 400 ml of polishing solution The other steps are the same as in Example 1, except that 7.5 ml of a 50 wt.% citric acid solution is used, and the pH of the resulting solution is 4. Example 3: Prepare 400 ml of polishing solution The other steps are the same as in Example 1, except that 5 ml of a 20 wt.% phosphoric acid solution is used, and the pH of the resulting solution is 3. Example 4: Prepare 400 ml of polishing solution The other steps are the same as in Example 1, except that 4.5 ml of a 20 wt.% phosphoric acid solution is used, and the pH of the resulting solution is 4. Example 5: Prepare 400 ml of polishing solution The other steps are the same as in Example 1, except that a polyurethane polishing pad was used for comparison. Example 6: The other steps are the same as in Example 1, except that a 50 wt.% citric acid solution is used, and the pH of the resulting solution is approximately 2. Example 7: The other steps are the same as in Example 1, except that the prepared polishing solution without added oxidant and complexing agent is divided into 5 equal portions, and then, in sequence, untreated, phosphoric acid, citric acid, sulfuric acid, and hydrochloric acid are added. After standing for 24 hours, the Zeta potential and dispersibility of each solution are tested. The test results are shown in the accompanying drawings. Figure 5 .

[0025] Table 1 Comparison of removal rate and surface roughness among different embodiments

[0026] For Example 5, Appendix Figure 3The scratches on the polished surface of single-crystal indium antimonide are shown. It can be seen that using the polyurethane polishing pad in Example 5 causes damage to the material surface, while Examples 1, 2, 3, and 4 do not have this problem. For Example 6, see Appendix Figure 4 The image shows excessive oxidation of the surface of the single-crystal indium antimonide material after polishing experiments; the dark oxidation area can be seen along the direction of the polishing motion. Examples 1, 2, 3, and 4 did not have this problem because of the appropriate pH range.

[0027] Appendix corresponding to Example 7 Figure 5 The effects of adding phosphoric acid, citric acid, sulfuric acid, hydrochloric acid and no addition were compared in the silica sol. It can be found that the addition of citric acid or phosphoric acid further reduced the dispersion of particle size in the abrasive while ensuring a good zeta potential value.

[0028] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

[0029] Matters not covered in this invention are common knowledge.

Claims

1. A polishing slurry for improving the surface quality of single-crystal indium antimonide, characterized in that, The polishing slurry comprises: an abrasive concentration of 10-20% by mass, an oxidant concentration of 1-2.5% by mass, and a complexing agent concentration of 0.2-2.5% by mass. The pH value of the polishing system is 3~5; The abrasive is silicon dioxide; the oxidant is hydrogen peroxide; The complexing agent is citric acid or phosphoric acid.

2. The polishing slurry for improving the surface quality of single-crystal indium antimonide as described in claim 1, characterized in that, When the complexing agent is citric acid, its concentration in the polishing solution is 0.5-2.5%; when it is phosphoric acid, the concentration is 0.2-1%.

3. The polishing slurry for improving the surface quality of single-crystal indium antimonide as described in claim 1, characterized in that, The silicon dioxide has a particle size of 80~130 nm.

4. The method for preparing the polishing slurry for improving the surface quality of single-crystal indium antimonide as used in claim 1, characterized in that, Includes the following steps: Step S1: According to the material ratio of the target polishing slurry, take the silica sol stock solution into the container; The concentration of the silica sol stock solution was 30 wt.%~60 wt.%; Step S2: Then add the hydrogen peroxide solution to the container from step S1; The concentration of the hydrogen peroxide solution was 20 wt.%~40 wt.%. Step S3: Add deionized water to the container from step S2; Step S4: Stir the mixture from step S3; Step S5: Add the complexing agent to the solution and stir the mixture until homogeneous. The pH of the resulting solution is 3-5.

5. The application method of the polishing slurry for improving the surface quality of single-crystal indium antimonide as described in claim 1, characterized in that, Used for chemical mechanical polishing of single-crystal indium antimonide surfaces.

6. The application method of the polishing slurry for improving the surface quality of single-crystal indium antimonide as described in claim 5, characterized in that, The polishing machine model is Rui Xuan SSP-500, the polishing pad model is TF7836, the polishing time is 10 min, the polishing pressure is 4.53 psi, the polishing fluid flow rate is 40 ml / min, the polishing head speed is 50 r / min, and the polishing disc speed is 50 r / min.

Images