Copper-based catalytic polishing solution for diamond polishing and preparation method

Abstract

The invention discloses a copper-based catalytic polishing solution for diamond polishing and a preparation method thereof. The copper-based catalytic polishing solution comprises the following components in percentage by mass: 2-50% of a diamond abrasive; 0.01 to 10% of copper powder; 0.01 to 20% of hydrogen peroxide; 0.01 to 10 percent of alkaline pH (Potential of Hydrogen) regulator; 0.01-10% of a dispersant; and the balance of water. The invention further provides a method for using the polishing solution. The diamond is chemically and mechanically polished under the conditions of room temperature, low load and low rotating speed. According to the oxidation system, through the synergistic effect of the copper powder and H2O2 under the alkaline condition, atomic-scale smoothness of the diamond surface can be achieved within a short time, and the oxidation system has the advantages of being efficient, low in damage, stable in system and low in cost.

Description

Technical Field

[0001] This invention belongs to the field of ultra-hard and brittle material processing technology, and in particular relates to a copper-based catalytic polishing fluid for diamond polishing and its preparation method. Background Technology

[0002] Diamond, with its ultra-high hardness, excellent thermal conductivity, and chemical stability, is widely used in high-end fields such as semiconductor devices and precision tools. However, its extreme physicochemical properties make chemical mechanical polishing (CMP) a core technological bottleneck for surface planarization. Traditional diamond CMP processes rely on high loads and high rotation speeds to overcome the material's inertia, resulting in low polishing efficiency, easy formation of micro-scratches and other damage on the surface, and significantly increased equipment wear and process costs, making it difficult to meet the requirements for preparing atomically smooth surfaces.

[0003] In the existing technology, relevant research has been carried out on the oxidation system for diamond CMP, but there is still room for improvement. For example, although the diamond polishing slurry disclosed in patent CN119307184A clearly contains a "catalyst" component (specifically one or more of copper oxide, chromium oxide, titanium dioxide, and cerium oxide), its mechanism of action is to assist in the graphitization of iron powder, and the system is acidic / neutral, still requiring polishing under high load. Patent CN116875195B constructs a multi-component catalytic system, using ferric sulfate solution to catalyze the decomposition of H2O2 to generate hydroxyl radicals (·OH), while introducing nano-cerium oxide to assist in catalysis and polishing. Although it can obtain a smooth surface with Sa=0.135 nm, the system is complex, pH control is demanding (requiring acidity), and the catalyst itself is not copper powder.

[0004] Through in-depth analysis of existing technologies, the applicant recognizes that none of the existing technologies have revealed a core composition for a polishing slurry that can simultaneously achieve efficient chemical etching and low mechanical damage in a simple and stable system. In particular, no publicly available technology demonstrates that using a single component of copper powder and hydrogen peroxide synergistically under a specific alkaline environment can achieve highly efficient polishing of atomically smooth diamond surfaces under low load and low rotation speed. Catalysts in existing technologies are either metal oxides, require acidic conditions to function, or need complex combinations with other metal components. These systems often suffer from problems such as large pH fluctuations, easy component agglomeration, narrow process windows, or the need for high load assistance. Therefore, there is an urgent need in the field for a novel oxidation system that is simple in composition, highly efficient in catalysis, stable in oxidation, and suitable for low-damage polishing processes. Summary of the Invention

[0005] In view of this, the present invention aims to provide a copper-based catalytic polishing slurry for diamond polishing and its preparation method, in order to solve at least one technical problem in the prior art. This polishing slurry, through its unique component design, can rapidly obtain an atomically smooth diamond surface under polishing conditions of room temperature, low load, and low rotation speed.

[0006] This invention also provides a method for using the polishing slurry to perform chemical mechanical polishing on diamond under room temperature, low load, and low rotation speed conditions. This oxidation system, through the synergistic effect of copper powder and H₂O₂ under alkaline conditions, can achieve atomic-level smoothness on the diamond surface in a short time, offering advantages such as high efficiency, low damage, system stability, and low cost.

[0007] To achieve the above objectives, the technical solution of the present invention is implemented as follows: A copper-based catalytic polishing slurry for diamond polishing comprises the following components by mass percentage: Diamond abrasive 2-50%; Copper powder 0.01-10%; Hydrogen peroxide 0.01-20%; Alkaline pH adjuster 0.01-10%; Dispersant 0.01-10%; The remainder is water.

[0008] Furthermore, the particle size of the diamond abrasive is 50-1000 nm.

[0009] Furthermore, the copper powder has a particle size of 0.1-5000 nm, preferably 0.1-3000 nm.

[0010] Furthermore, the content of copper powder is 0.01-8%.

[0011] Furthermore, the hydrogen peroxide content is 0.01-10%.

[0012] Furthermore, the dispersant is acetylenic diol polyether, and the content of the dispersant is 0.01-10%.

[0013] Furthermore, the alkaline pH adjuster is KOH, and the content of the alkaline pH adjuster is 0.01-5%.

[0014] Furthermore, the pH value of the copper-based catalytic polishing solution used for diamond polishing is 8.0-10.5.

[0015] The preparation method of the copper-based catalytic polishing fluid for diamond polishing includes the following steps: adding copper powder and acetylenic diol polyether to a diamond aqueous solution and then ultrasonically dispersing them, then adding hydrogen peroxide and stirring, and finally adjusting the pH to 8.0-10.5 with an alkaline pH adjuster.

[0016] A method for chemical mechanical polishing of diamond, using the aforementioned polishing slurry, at room temperature, at a concentration of 0.01-10 kg / cm². 2 The diamond surface was polished using a grooveless polyurethane polishing pad under a load of 1-1200 rpm for a polishing time of 0.25-100 h.

[0017] Compared with existing technologies, the copper-based catalytic polishing fluid for diamond polishing and its preparation method described in this invention have the following advantages: This application demonstrates strong system innovation. This invention is the first to construct a synergistic oxidation system centered on "copper powder-H2O2-alkaline environment." Under alkaline conditions, copper powder can stably and efficiently catalyze the production of ·OH from H2O2, while simultaneously selectively oxidizing the diamond surface to generate an easily removable soft layer. The alkaline environment inhibits the deactivation of the copper powder, achieving a perfect balance between chemical action and subsequent mechanical removal.

[0018] The polishing effect of this application is excellent. This system is free from the dependence on high load and high speed. It can achieve atomic-level smoothness (Ra≤0.1nm) of diamond surface in a short time (e.g., within 1.5 h) under mild mechanical conditions (low load and low speed), which significantly reduces the risk of surface / subsurface damage and improves the processing yield.

[0019] The system described in this application is stable and inexpensive. The polishing slurry system has simple components, low raw material costs, stable pH environment, good oxidation durability, and is not easily degraded due to placement or storage, thus showing good prospects for industrial scale-up applications. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is the AFM image after polishing in Embodiment 1 of the present invention; Figure 2 This is the AFM image after polishing in Embodiment 2 of the present invention; Figure 3 This is the AFM image after polishing in Embodiment 3 of the present invention; Figure 4 This is the AFM image of Comparative Example 1 after polishing according to the present invention; Figure 5 This is the AFM image of Comparative Example 2 after polishing according to the present invention; Figure 6 This is the AFM image of Comparative Example 3 after polishing according to the present invention; Figure 7The image shown is the AFM image of Comparative Example 4 after polishing. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0022] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] To provide a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below. However, those skilled in the art should understand that these are merely illustrative examples, and various changes or modifications can be made to this embodiment without departing from the principle and essence of the invention. The scope of protection of the present invention is limited only by the appended claims.

[0024] Example 1 A 20% aqueous solution of 500 nm diamond was prepared by adding 0.1% 50 nm copper powder and 1% acetylation glycol polyether to a 20% aqueous solution of 500 nm diamond, followed by ultrasonic dispersion. Then, 1.2% H₂O₂ was added and stirred. Finally, the pH was adjusted to 9.6 with KOH. The diamond sheet was then subjected to a polishing solution with a load of 2 kg / cm². 2 Chemical mechanical polishing was performed at a rotation speed of 60 rpm, using grooveless polyurethane as the polishing pad, for 1.5 h. After polishing, an atomically smooth surface was achieved with an Ra value of 0.0632 nm. Figure 1 ).

[0025] Example 2 A 20% aqueous solution of 500 nm diamond was prepared by adding 0.1% 100 nm copper powder and 1% acetylation glycol polyether to a 500 nm diamond solution, followed by ultrasonic dispersion. Then, 1.2% H₂O₂ was added and stirred. Finally, the pH was adjusted to 9.6 with KOH. The diamond sheet was then subjected to a polishing solution with a load of 2 kg / cm². 2 Chemical mechanical polishing was performed at a rotation speed of 60 rpm, using grooveless polyurethane as the polishing pad, for 1.5 h. The resulting Ra value was 0.111 nm. Figure 2 ).

[0026] Example 3 A 20% aqueous solution of 500 nm diamond was prepared by adding 0.1% 500 nm copper powder and 1% acetylation glycol polyether to a 20% aqueous solution of 500 nm diamond, followed by ultrasonic dispersion. Then, 1.2% H₂O₂ was added and stirred. Finally, the pH was adjusted to 9.6 with KOH. The diamond sheet was then subjected to a polishing solution with a load of 2 kg / cm². 2 Chemical mechanical polishing was performed at a rotation speed of 60 rpm, using grooveless polyurethane as the polishing pad, for 1.5 h. The resulting Ra value was 0.148 nm. Figure 3 ).

[0027] Comparative Example 1 A 20% aqueous solution of 500 nm diamond was prepared by adding 0.2% 50 nm copper powder and 1% acetylation glycol polyether to a 20% aqueous solution of 500 nm diamond, followed by ultrasonic dispersion. Then, 1.2% H₂O₂ was added and stirred. Finally, the pH was adjusted to 9.6 with KOH. The diamond sheet was then subjected to a polishing solution with a load of 2 kg / cm². 2 Chemical mechanical polishing was performed at a rotation speed of 60 rpm, using grooveless polyurethane as the polishing pad, for 1.5 hours. The resulting surface achieved atomic-level smoothness with an Ra value of 0.0856 nm. Figure 4 ).

[0028] Comparative Example 2 A 20% aqueous solution of 500 nm diamond was prepared by adding 0.1% 50 nm CuO and 1% acetylation glycol polyether, followed by ultrasonic dispersion. Then, 1.2% H₂O₂ was added and stirred. Finally, the pH was adjusted to 9.6 with KOH. The diamond sheet was then subjected to a polishing solution with a load of 2 kg / cm². 2 Chemical mechanical polishing was performed at a rotation speed of 60 rpm, using grooveless polyurethane as the polishing pad, for 1.5 h. The resulting Ra value was 0.423 nm. Figure 5 ).

[0029] Comparative Example 3 A 20% aqueous solution of 500 nm diamond was prepared by adding 0.1% 50 nm Cu₂O and 1% acetylation diol polyether to a 20% aqueous solution of 500 nm diamond, followed by ultrasonic dispersion. Then, 1.2% H₂O₂ was added and stirred. Finally, the pH was adjusted to 9.6 with KOH. The diamond sheet was then subjected to a polishing solution with a load of 2 kg / cm². 2 Chemical mechanical polishing was performed at a rotation speed of 60 rpm, using grooveless polyurethane as the polishing pad, for 1.5 h. The resulting Ra value was 0.405 nm. Figure 6 ).

[0030] Comparative Example 4 A 20% aqueous solution of 500 nm diamond was prepared by adding 0.1% 50 nm copper powder and 1% acetylation glycol polyether, followed by ultrasonic dispersion. Then, 1.2% H₂O₂ was added and stirred. Finally, the pH was adjusted to 3.0 with an inorganic acid. The diamond sheet was then subjected to a polishing solution with a load of 2 kg / cm². 2 Chemical mechanical polishing was performed at a rotation speed of 60 rpm, using grooveless polyurethane as the polishing pad, for 1.5 h. The resulting Ra value was 0.444 nm. Figure 7 ).

[0031] The results of Examples 1-3, as shown in Table 1, indicate that polishing diamond with copper powder of different particle sizes yielded the best surface quality when the copper powder particle size was 50 nm, achieving an atomically smooth surface within 1.5 h. Examples 1-3 demonstrate that excellent polishing effects can be achieved with copper powder particle sizes ranging from 0.1 to 3000 nm, particularly in the nanoscale range (e.g., 50-500 nm), with 50 nm being the optimal size. The results of Comparative Example 1 and Example 1 show that Example 1 (0.1% 50 nm Cu) achieved the best surface quality (Ra = 0.0632 nm). While Comparative Example 1 (0.2% 50 nm Cu) also achieved atomically smoothness, the surface roughness increased. This may be because excessively high copper powder content easily leads to particle agglomeration, affecting the uniformity of dispersion in the polishing solution and the stable performance of catalytic efficiency. The above results indicate that there is an optimal range for the content of copper powder, and more is not necessarily better. Considering both the polishing effect and the stability of the system, the preferred content of copper powder is 0.01%-1%. A comparison of the results of Comparative Examples 2-3 and Example 1 shows that, compared to Example 1 which used copper powder for chemical mechanical polishing, Comparative Examples 2 and 3 used CuO and Cu2O with the same particle size and addition amount, respectively. However, after 1.5 h of CMP, they did not achieve an atomically smooth surface, resulting in poor surface quality with Ra values ​​of 0.423 and 0.405 nm, respectively. A comparison of the results of Comparative Example 4 and Example 1 shows that, compared to Example 1 which used copper powder for chemical mechanical polishing under alkaline conditions, Comparative Example 4, which used copper powder for chemical mechanical polishing of diamond under acidic conditions, had a Ra value of 0.444 nm, indicating poor surface quality. These results fully demonstrate that the oxidation system composed of copper powder and H2O2 under the alkaline conditions described in this invention can achieve atomically smooth diamond surfaces rapidly and efficiently under low load and low rotation speed.

[0032] Table 1. Comparison of the effects of Examples 1-3 and Comparative Examples 1-4; Diamond solution Copper powder / copper compound Copper particle size dispersant pH adjuster pH <![CDATA[H2O2]]> Surface roughness Ra after polishing Example 1 20% 500 nm 0.1% copper powder 50 nm 1% Acetylene glycol polyether KOH 9.6 1.2% 0.0632 nm Example 2 20% 500 nm 0.1% copper powder 100 nm 1% Acetylene glycol polyether KOH 9.6 1.2% 0.111 nm Example 3 20% 500 nm 0.1% copper powder 500 nm 1% Acetylene glycol polyether KOH 9.6 1.2% 0.148 nm Comparative Example 1 20% 500 nm 0.2% copper powder 50 nm 1% Acetylene glycol polyether KOH 9.6 1.2% 0.0856 nm Comparative Example 2 20% 500 nm 0.1% CuO (copper oxide) 50 nm 1% Acetylene glycol polyether KOH 9.6 1.2% 0.423 nm Comparative Example 3 20% 500 nm <![CDATA[0.1% Cu2O (cuprous oxide)]]> 50 nm 1% Acetylene glycol polyether KOH 9.6 1.2% 0.405 nm Comparative Example 4 20% 500 nm 0.1% copper powder 50 nm 1% Acetylene glycol polyether Inorganic acids 3.0 1.2% 0.444 nm Comparative Example 4 shows that even with the use of copper powder and H2O2, a smooth surface cannot be obtained under acidic conditions, proving that the alkaline environment of the present invention is a necessary condition for achieving atomic-level smoothness, rather than a conventional choice in the art.

[0033] In summary, the processing method provided by this invention overcomes the problems of poor surface quality caused by the extremely high hardness and chemical inertness of diamond in the prior art.

[0034] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A copper-based catalytic polishing slurry for diamond polishing, characterized in that: The following components are included by mass percentage: Diamond abrasive 2-50%; Copper powder 0.01-10%; Hydrogen peroxide 0.01-20%; Alkaline pH adjuster 0.01-10%; Dispersant 0.01-10%; The remainder is water.

2. The copper-based catalytic polishing slurry for diamond polishing according to claim 1, characterized in that: The diamond abrasive has a particle size of 50-1000 nm.

3. The copper-based catalytic polishing slurry for diamond polishing according to claim 1, characterized in that: The copper powder has a particle size of 0.1-5000 nm.

4. The polishing fluid according to claim 1 or 3, characterized in that: The copper powder content is 0.01-8%.

5. The copper-based catalytic polishing slurry for diamond polishing according to claim 1, characterized in that: The hydrogen peroxide content is 0.01-10%.

6. The copper-based catalytic polishing slurry for diamond polishing according to claim 1, characterized in that: The dispersant is acetylenic glycol polyether, and the content of the dispersant is 0.01-10%.

7. The copper-based catalytic polishing slurry for diamond polishing according to claim 1, characterized in that: The alkaline pH adjuster is KOH, and the content of the alkaline pH adjuster is 0.01-5%.

8. The copper-based catalytic polishing slurry for diamond polishing according to claim 1, characterized in that: The pH value of the copper-based catalytic polishing solution used for diamond polishing is 8.0-10.

5.

9. A method for preparing a copper-based catalytic polishing slurry for diamond polishing according to claims 1-8, characterized in that: The process includes the following steps: diamond abrasive is placed in an aqueous solution to obtain a diamond aqueous solution; copper powder and acetylenol polyether are added to the diamond aqueous solution and then ultrasonically dispersed; hydrogen peroxide is then added and stirred; and the pH is adjusted to 8.0-10.5 with an alkaline pH adjuster.

10. A method for chemical mechanical polishing of diamond, characterized in that, Using the polishing solution according to any one of claims 1 to 8, at room temperature, at a concentration of 0.01-10 kg / cm³ 2 The diamond surface was polished using a grooveless polyurethane polishing pad under a load of 1-1200 rpm for a polishing time of 0.25-100 h.

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