Micro-etching liquid for removing PVD (Physical Vapor Deposition) titanium layer oxide on diamond surface and use method thereof

Abstract

The invention relates to a micro-etching solution for removing PVD titanium layer oxides on a diamond surface and a use method thereof, and provides a unique micro-etching solution formula in order to solve the problems that in the prior art, the titanium surface oxide layer removal process is complex, the cost is high, and the environment is prone to being polluted. The titanium layer component cannot be excessively corroded due to too high reaction rate, the removal process is safe and controllable, and meanwhile, the good binding force of the titanium layer and the diamond substrate is kept.

Description

Technical Field

[0001] The invention relates to a micro-etching liquid for removing oxides of a PVD titanium layer on a diamond surface and a use method thereof, belonging to a micro-etching treatment liquid for a metallized titanium-plated layer on a diamond film surface in a semiconductor heat sink material. Background Art

[0002] In order to achieve the goal of green and low carbon, in the past few years, the semiconductor industry has been constantly pursuing more efficient and powerful semiconductor devices. At the same time, the demand for reducing the impact of thermal effects on the performance of semiconductor materials is also increasing, which puts higher requirements on the thermal conductivity of heat sink materials. Traditional heat sinks are usually made of copper, red copper, aluminum, aluminum nitride, etc. Their thermal conductivity and thermal expansion coefficient are far from meeting the current development of integrated circuits and chip technology. Diamond has become an ideal heat dissipation material due to its extremely high thermal conductivity and thermal stability. Its thermal conductivity can reach 2000 W / m·K, which is five times that of copper and ten times that of aluminum. This means that diamond heat sinks can achieve efficient thermal conductivity and heat dissipation.

[0003] The connection technology between diamond and semiconductor devices is the key to achieving effective thermal management. At present, there are still technical challenges in the connection method, interface thermal resistance and long-term stability of diamond and semiconductor devices. To achieve a good connection, welding is generally used. In order to meet the welding requirements, the diamond surface must be metallized. In recent years, domestic and foreign scholars have conducted extensive and in-depth research on diamond surface modification technology. Among them, the use of physical vapor deposition (PVD) to plate titanium on the diamond surface has achieved good results. The PVD coating is generally a nano-scale coating. Titanium is a metal with very active chemical properties. When the temperature is ≥600℃, the △G of the chemical reaction between Ti and C is ≤0, indicating that Ti and C can react spontaneously at high temperature. The generated TiC can not only inhibit the thermal damage of diamond, reduce the interface stress between diamond / substrate, and improve the bonding strength, but also reduce the interface thermal resistance between diamond / substrate and improve the thermal conductivity of the material. The titanium layer is very easy to oxidize, forming a highly dense oxide layer on the surface, which affects the subsequent welding performance of the diamond heat sink. There are generally three ways to remove the titanium oxide layer: mechanical removal, chemical removal, and electrochemical removal. Mechanical removal generally uses tools such as sandpaper, grinding wheels, and brushes to remove it, which can easily damage the titanium surface and is not suitable for PVD nano-scale titanium layers; electrochemical removal is difficult to accurately control the amount of removal and requires professional equipment and technical support; chemical removal generally uses molten alkaline solution or a mixed acid made of nitric acid and hydrofluoric acid to remove the titanium oxide layer. During alkaline washing, the molten alkaline solution will react with the oxide on the surface. In addition, the temperature of the molten alkaline solution itself is relatively high, and the alkali melting will boil violently or even explode. At the same time, titanium / titanium alloys are also easy to burn in molten alkaline solution; and the nitric acid and hydrofluoric acid pickling process will cause titanium / titanium alloys to absorb hydrogen and cause hydrogen embrittlement. In the later stage, vacuum annealing must be carried out to remove hydrogen, and wastewater and waste gas will also be generated, causing environmental pollution. Summary of the invention

[0004] The present invention provides a unique micro-etching liquid formula, which can effectively remove the oxide layer of the PVD titanium layer on the diamond surface, will not cause excessive corrosion of the titanium layer parts due to too fast a reaction rate, ensures that the removal process is safe and controllable, and at the same time maintains good bonding between the titanium layer and the diamond substrate, and is used to solve the problems of complex titanium surface oxide layer removal process, high cost, and easy environmental pollution in the prior art.

[0005] The micro-etching solution is composed of an oxidant, an alkali, a corrosion inhibitor and a solvent. Calculated by weight, it contains 3% to 6% of the oxidant, 1% to 2% of the alkali, 0.1% to 2% of the corrosion inhibitor, and the balance is the solvent.

[0006] The oxidant used is potassium permanganate, sodium hypochlorite, hydrogen peroxide, etc. The oxidant can react with titanium oxide to generate peroxymetatitanic acid, which can effectively destroy the structure of the titanium oxide layer without damaging the diamond substrate.

[0007] Alkali such as sodium hydroxide and potassium hydroxide are used to convert free titanium ions into titanium hydroxide. Titanium hydroxide is easy to generate metatitanic acid and thus promotes the process of converting titanium oxide into peroxymetatitanic acid. Alkali solution is also used to adjust the pH value of the solution to keep the reaction environment stable.

[0008] Corrosion inhibitors are polyphosphates or organic phosphonates, which can prevent excessive corrosion and protect the surface of the titanium layer.

[0009] Deionized water is used as the solvent to ensure that no impurities are introduced and to facilitate the dilution and cleaning of the micro-etching solution.

[0010] Through this formula, the precise removal of PVD titanium layer oxides is achieved while taking into account environmental protection and economic benefits. Based on this formula, the proportion of each component can be adjusted according to actual needs to further optimize the performance of the micro-etching solution. For example, for titanium layer oxides of different thicknesses, the oxidant concentration is appropriately increased within the range of 3%-6% by weight to increase the reaction rate; while maintaining environmental protection requirements, the amount of alkali is reasonably reduced to reduce wastewater treatment costs.

[0011] In addition, in order to further optimize the processing effect, the present invention also provides a method for using the micro-etching solution.

[0012] In specific applications, the method for using the micro-etching liquid of the present invention includes the steps of pretreatment, micro-etching, cleaning and post-treatment. During the implementation process, the uniformity and stability of the treatment effect are effectively ensured by strictly controlling the process parameters of each step, such as temperature, time and stirring speed of the micro-etching liquid.

[0013] Specifically, the steps include: First, pretreatment ensures that the titanium layer surface is free of impurities such as oil, attachments, etc. It can be cleaned with a degreasing agent under ultrasonic conditions; Second, immerse the titanium layer parts in the micro-etching solution, control the temperature of the micro-etching solution to 50-60°C, control the processing time to 1-3 minutes, and maintain the stirring rate of the micro-etching solution at 80-100r / min to achieve the best effect; Third, take out the parts and clean them with deionized water to thoroughly remove the residual micro-etching solution; Fourth, post-treatment is to carry out rust prevention or surface activation according to special application requirements. This method not only improves the controllability of the micro-etching process, but also helps to achieve large-scale and automated production, opening up a new development direction for titanium layer processing technology.

[0014] Compared with the prior art, the present invention has the following advantages and effects: 1) The key components of the micro-etching solution can accurately control the reaction rate, ensuring that the removal process is safe and controllable; 2) It is used to solve the problems of complex process, high cost and easy environmental pollution in the removal of titanium surface oxide layer in the existing technology; 3) It improves the controllability of the micro-etching process and helps to achieve large-scale and automated production, opening up a new development direction for titanium layer processing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The following are the effects of observing the micro-etching of the PVD titanium layer using a metallographic microscope, including: a. a diamond sheet with oxidized PVD titanium layer on the surface; b. a diamond sheet effect after mixed acid treatment in comparative example 1; c. a diamond sheet effect after mixed acid treatment in comparative example 1; Figure 2 The effect diagram of the diamond sheet after micro-etching for 1 minute in Example 1-5 (from left to right are Examples 1-5 respectively); Figure 3 Effect diagram of diamond sheets after micro-etching treatment in Examples 1-5 after baking (from left to right are Examples 1-5); Figure 4 Effect diagram of the diamond sheet after being treated with micro-etching solution for 2 minutes in Example 1-5 (from left to right are Examples 1-5 respectively). DETAILED DESCRIPTION

[0016] Example 1 a. Weigh the proportion of sodium hydroxide and deionized water by mass, the mass fractions are 1% and 95.9%, respectively, dissolve the sodium hydroxide in deionized water, and stir and mix using a magnetic stirrer; b. Add potassium permanganate powder to the above solution in a mass fraction of 3%, and stir and mix evenly using a magnetic stirrer; c. Add phosphonic acid (salt) in a proportion of 0.1% by mass to the above stirring and mixing system, and stir and mix evenly using a magnetic stirrer.

[0017] Example 2 a. Weigh the proportion of potassium hydroxide and deionized water by mass, the mass fractions are 1.5% and 94%, respectively, dissolve potassium hydroxide in deionized water, and stir and mix using a magnetic stirrer; b. Add 4% sodium hypochlorite liquid to the above solution and stir to mix evenly using a magnetic stirrer; c. Add mercaptobenzothiazole in a proportion of 0.5% by mass to the above stirring and mixing system, and stir and mix evenly using a magnetic stirrer.

[0018] Example 3 a. Weigh the proportion of lithium hydroxide and deionized water by mass, the mass fractions are 2% and 92.5%, respectively, dissolve lithium hydroxide in deionized water, and stir and mix using a magnetic stirrer; b. Add 5% by mass of hydrogen peroxide liquid to the above solution and stir and mix evenly using a magnetic stirrer; c. Add benzotriazole in a proportion of 0.5% by mass to the above stirring and mixing system, and stir and mix evenly using a magnetic stirrer.

[0019] Example 4 a. Weigh the proportion of sodium hydroxide and deionized water by mass, the mass fractions are 1.5% and 90.5%, respectively, dissolve the sodium hydroxide in deionized water, and stir and mix using a magnetic stirrer; b. Add 6% sodium hypochlorite liquid to the above solution and stir to mix evenly using a magnetic stirrer; c. Add 2% by weight of sulfonated lignin to the above-mentioned stirring and mixing system, and stir and mix evenly using a magnetic stirrer.

[0020] Example 5 a. Weigh the proportion of potassium hydroxide and deionized water by mass, the mass fractions are 1.5% and 91.5%, respectively, dissolve potassium hydroxide in deionized water, and stir and mix using a magnetic stirrer; b. Add potassium permanganate powder to the above solution in a mass fraction of 5.5%, and stir and mix evenly using a magnetic stirrer; c. Add 1.5% by mass of phosphine carboxylic acid to the above stirring and mixing system, and stir and mix evenly using a magnetic stirrer.

[0021] Place 500 ml of the micro-etching solution prepared in Examples 1-5 above in a constant temperature water bath, control the temperature at about 60°C, perform magnetic stirring, and maintain the stirring rate at 90 r / min. First, place the diamond sheet with a PVD titanium layer on the surface in a neutral degreasing solution and clean it under ultrasonic conditions for 5 minutes to remove oil stains and surface attachments. Then, wash it with deionized water for 2 minutes and immerse it in the above micro-etching solution. The treatment time is about 1 minute. Then, take out the diamond sheet and rinse it with deionized water. Use a metallographic microscope to observe the micro-etching of the PVD titanium layer. The effect is as follows: Figure 2 As shown (from left to right are Examples 1-5), the PVD titanium oxide film on the surface of the diamond sheet treated with the micro-etching solution is removed, showing uniform micro-etching marks.

[0022] The samples treated with the above micro-etching solution were baked at 320℃ for 5 minutes and observed using a metallographic microscope. Figure 3As shown (from left to right are Examples 1-5), the titanium layer did not peel off, which proves that the bonding force between the titanium layer and the diamond substrate is good and the bonding force between the titanium layer and the diamond substrate is not destroyed.

[0023] The treatment time in the micro-etching solution was extended to 2 minutes. As shown in the effect diagram 4, the etching was slightly deepened, but still showed a uniform etching state, which proved that the prepared micro-etching solution had an excellent micro-etching effect. Comparative Example 1 is to remove the titanium oxide layer by using a mixed acid prepared by nitric acid and hydrofluoric acid with weight fractions of 8.5% and 6% respectively, and immerse the diamond sheet with PVD titanium layer on the surface in the mixed acid at room temperature for the same time. Figure 1 The following are the renderings of the micro-etching of the PVD titanium layer observed using a metallographic microscope, including: a. a diamond sheet with an oxidized PVD titanium layer on the surface; b. the rendering of the diamond sheet after mixed acid treatment in comparative example 1, where the treatment time was extended to 2 minutes and the titanium layer was excessively etched in some areas, exposing the diamond substrate; c. the rendering of the diamond sheet after mixed acid treatment for 1 minute in comparative example 1, where it can be seen that the PVD titanium layer on the surface of the diamond sheet treated with mixed acid has obvious pits and uneven etching, indicating that the micro-etching effect of the mixed acid treatment method on the PVD titanium layer is not as ideal as the prepared micro-etching solution.

Claims

1. A micro-etching solution for removing oxide from PVD titanium layer on diamond surface, characterized in that: Calculated by weight, the micro-etching solution includes 3% to 6% of an oxidant, 1% to 2% of an alkali, 0.1% to 2% of a corrosion inhibitor, and the balance of a solvent.

2. A micro-etching solution for removing an oxide layer on a PVD titanium layer on a diamond surface as claimed in claim 1, characterized in that: The oxidant is one or more of potassium permanganate, sodium hypochlorite or hydrogen peroxide.

3. A micro-etching solution for removing an oxide layer on a PVD titanium layer on a diamond surface as claimed in claim 1, characterized in that: The alkali is sodium hydroxide and / or potassium hydroxide.

4. A micro-etching solution for removing an oxide layer on a PVD titanium layer on a diamond surface as claimed in claim 1, characterized in that: The corrosion inhibitor is selected from polyphosphates or organic phosphonates.

5. The micro-etching solution for removing the oxide layer on the PVD titanium layer on the diamond surface as claimed in claim 1, characterized in that: The solvent is deionized water.

6. A method for removing oxides from a PVD titanium layer on a diamond surface using a micro-etching solution as claimed in any one of claims 1 to 5, characterized in that: The method comprises the following steps: First, pre-treat and clean the surface of the titanium layer; Second, immerse the component in the micro-etching solution, control the temperature of the micro-etching solution to 50-60°C, control the processing time to 1-3 minutes, and maintain the stirring rate of the micro-etching solution at 80-100r / min; Third, remove the components and clean the residual micro-etching solution with deionized water.

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