Wafer corrosion process and corrosion method

Abstract

The invention provides a wafer corrosion process and a corrosion method. The wafer corrosion process comprises the following steps: sequentially adding pure water, HNO3, HF and Hac into a polyethylene container containing a catalyst according to a ratio of 175: 120: 130: 70; according to the invention, pure water, HNO, HF and HAc are added in a specific volume ratio formula, AgNO is added as a catalyst, a corrosive liquid system with moderate reaction activity and stable synergistic effect of all components is formed, the addition of HAc effectively adjusts the oxidation-reduction potential and surface tension of the solution, the corrosion resistance of the solution is improved, and the corrosion resistance of the solution is improved. The corrosion reaction is mild and uniform, uniform oxidation of the silicon surface is promoted by the catalyst AgNO, and too fast local reaction is avoided.

Description

A wafer etching process and etching method Technical Field

[0001] This invention relates to the field of semiconductors, and more particularly to a wafer etching process and etching method. Background Technology

[0002] Wafer mica sheets are commonly used test or temporary support structures in semiconductor research and development, materials analysis, and microelectromechanical systems (MEMS) processes. They are usually covered with silicon thin films or patterned silicon structures. In order to observe their microstructure, measure their thickness, or perform failure analysis, chemical wet etching techniques are often used to selectively remove silicon material in specific areas, thereby clearly exposing the target layer or interface.

[0003] Currently, the industry commonly uses a mixed acid solution based on nitric acid and hydrofluoric acid for wet etching of mica wafers. However, the etching rate of conventional formulas is too fast and difficult to control precisely, which can easily lead to "over-etching", that is, etching beyond the target area, damaging the fine structure or mica substrate, and affecting the accuracy of observation results. Due to the violent etching reaction, uneven etching is easily generated on the wafer surface, forming a rough surface or etching pits, resulting in blurred pattern outlines and unclear boundaries. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the defects of the existing technology. The present invention proposes a wafer etching process and etching method.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a wafer etching process and etching method, comprising: adding pure water, HNO3, HF and Hac in a ratio of 175:120:130:70 to a polyethylene container containing a catalyst; stirring and shaking slowly, and after standing for 50 minutes, an etching solution is prepared for etching a single wafer.

[0006] Preferably, the catalyst is AgNO3.

[0007] Preferably, 2.1g of AgNO3 is added in equal proportion.

[0008] A wafer etching method includes the aforementioned wafer etching process, wherein a mica wafer is placed in a prepared etching solution and agitated within the solution; when dense bubbles are generated, the mica wafer is removed and rinsed with pure water; the rinsed mica wafer is then placed back into the etching solution for reaction, and when dense bubbles are generated, it is removed and rinsed with pure water, repeating this process until all silicon wafer outlines appear; the mica wafer is then removed, and an appropriate amount of Hac is added to the etching solution in a proportional ratio; the mica wafer is then placed back into the etching solution for reaction, and when dense bubbles are generated, it is removed and rinsed with pure water, repeating this process until all silicon wafer outlines appear; the etching contaminants and etching solution are then cleaned with pure water; the wafer etching is thus completed.

[0009] Preferably, the equiproportional Hac is 50 ml.

[0010] Preferably, the wafer mica sheet is moved by clamps.

[0011] Preferably, the clip is made of polyethylene.

[0012] Compared with the prior art, the beneficial effects of the present invention include: by using a specific volume ratio of pure water, HNO3, HF and HAc, and adding AgNO3 as a catalyst, a corrosion liquid system with moderate reactivity and stable synergistic effect of each component is formed. The addition of HAc effectively regulates the redox potential and surface tension of the solution, making the corrosion reaction mild and uniform. The catalyst AgNO3 promotes uniform oxidation of the silicon surface and avoids excessively rapid local reactions. Attached Figure Description

[0013] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts. Specifically: Figure 1 schematically shows a wafer etching process according to an embodiment of the present invention. Detailed Implementation

[0014] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0015] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0016] This invention provides a chemical wet etching process and method for etching mica wafers. The core of this process lies in providing a stable and controllable etching solution formulation and a step-by-step etching method. By mixing pure water, nitric acid (HNO3), hydrofluoric acid (HF), and glacial acetic acid (HAc) in specific proportions and adding silver nitrate (AgNO3) as a catalyst, an etching solution with suitable etching rate and selectivity is prepared. During the etching process, a "etch-rinse-re-etch" cycle is adopted, and the reaction progress is judged by observing the generation of bubbles. Finally, the activity of the etching solution is adjusted by adding glacial acetic acid to ensure that all silicon wafers are completely and clearly etched and exposed, while avoiding over-etching or uneven etching. The use of polyethylene tools can effectively prevent metal contamination and acid corrosion.

[0017] Example 1 According to an embodiment of the present invention, as shown in Figure 1, the preparation of the corrosive solution involves a clean polyethylene container. Polyethylene has excellent acid resistance and chemical stability, which can ensure the purity of the corrosive solution and avoid metal ion contamination.

[0018] First, add silver nitrate (AgNO3) as a catalyst to the polyethylene container. In a typical embodiment, the amount of AgNO3 added is 2.1 grams. This catalyst can effectively promote the redox reaction of silicon, making the corrosion reaction more uniform and controllable. According to the volume ratio of pure water:HNO3:HF:HAc = 175:120:130:70, add the measured pure water, HNO3, HF and HAc to the polyethylene container in sequence. This order of addition must be strictly followed, that is, add pure water first as a matrix, and then add acid, which helps to ensure safe operation and uniform mixing.

[0019] Cover the container and slowly stir and shake it to ensure that all components are fully mixed and the catalyst is dissolved. Then, let the prepared corrosion solution stand at room temperature for 50 minutes. This aging process allows all components of the corrosion solution to fully react and reach a stable state, resulting in corrosion performance with good reproducibility.

[0020] Example 2, Initial etching cycle of wafer etching operation: Use a polyethylene clamp (corrosion-proof and pollution-proof) to hold the mica wafer to be processed and immerse it in the etching solution prepared in step one.

[0021] Gently and slowly oscillate the mica wafer in the etching solution to ensure that the etching solution can evenly contact its surface and remove reaction products, preventing localized corrosion stagnation.

[0022] Closely observe the wafer surface. When dense, fine bubbles begin to appear on the wafer surface (this is a phenomenon of gas generation from the oxidation reaction of silicon with mixed acid, a direct sign of the corrosion process), immediately remove the wafer mica sheet using polyethylene clips.

[0023] The removed mica wafer was quickly placed under running pure water for thorough rinsing to completely stop the current corrosion reaction and remove any residual corrosion liquid and preliminary reaction products from the surface.

[0024] Repeat the etching cycle: Put the cleaned mica wafer back into the etching solution and repeat the above steps of oscillation, observation (waiting for dense bubbles to form), removal, and rinsing with pure water.

[0025] This "etch-rinse" process needs to be repeated multiple times. Each cycle will etch away a certain thickness of silicon layer. This process is observed under a microscope or with the naked eye until the silicon material in a certain area (usually at the edge or defect) of the wafer mica sheet is etched away, and the outline of the underlying mica begins to be revealed. The goal of this stage is to initially expose the silicon wafer pattern.

[0026] Acid replenishment and final etching: Once most of the silicon wafer outline has appeared, remove the mica wafer from the etching solution and temporarily place it in pure water.

[0027] Add HAc to the existing etching solution. The amount added should be determined based on the proportion of HAc in the initial preparation. In one embodiment, the amount added is 50 ml. Adding HAc can adjust the redox potential and surface wettability of the etching solution, which helps to remove the remaining silicon more finely and thoroughly in the later stages of etching, especially in areas where the reactivity may be reduced.

[0028] The mica wafer was then placed back into the etching solution replenished with HAc, and the cycle of oscillation, bubble observation, removal, and rinsing was repeated.

[0029] Repeat this process until all the silicon wafer structures that need to be revealed on the mica wafer are clearly and completely etched out, and the mica substrate is fully exposed.

[0030] Final cleaning: After etching is complete, the wafer mica sheet is rinsed thoroughly with a large amount of pure water for a long time to ensure that all etching products (such as silicates, fluorosilicate complexes, etc.) and residual etching solution are completely removed.

[0031] After cleaning, the mica wafer can be dried with nitrogen or air-dried naturally. At this point, the wafer etching process is complete and the wafer can be used for subsequent observation or analysis.

[0032] Using the above-described specific implementation method, uniform and controllable chemical etching of the silicon layer on the mica wafer can be achieved. The step-by-step cyclic etching method combined with the observation of reaction phenomena (bubbles) avoids the problems of over-etching or drilling caused by a single long-term etching. By adding glacial acetic acid midway, the activity of the etching solution in the final stage of the process is effectively maintained and adjusted, ensuring the integrity and clarity of the pattern transfer. The entire process is simple to operate, has good reproducibility, and is suitable for the pretreatment and structural analysis of wafer samples in the laboratory and in small-batch production.

[0033] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0034] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A wafer etching process, characterized in that, include: Pure water, HNO3, HF, and Hac were added sequentially to a polyethylene container containing the catalyst in a ratio of 175:120:130:

70. After slow stirring and shaking, and standing for 50 minutes, an etching solution was prepared for etching single wafers.

2. The wafer etching process according to claim 1, characterized in that, The catalyst is AgNO3.

3. The wafer etching process according to claim 2, characterized in that, 2.1g of AgNO3 was added in equal proportion.

4. A wafer etching method, comprising the wafer etching process according to any one of claims 1-3, characterized in that, Place the mica wafer into the prepared etching solution and agitate it. When dense bubbles are generated, remove the mica wafer and rinse it with pure water. Place the rinsed mica wafer back into the etching solution to react. When dense bubbles are generated, remove it and rinse with pure water. Repeat this process until all silicon wafer outlines appear. Remove the mica wafer and add an appropriate amount of Hac to the etching solution. Place the mica wafer back into the etching solution to react. When dense bubbles are generated, remove it and rinse with pure water. Repeat this process until all silicon wafer outlines appear. Rinse thoroughly with pure water to remove etching contaminants and the etching solution. The wafer etching is now complete.

5. The wafer etching process and method according to claim 4, characterized in that, The equiproportional Hac is 50ml.

6. The wafer etching process and method according to claim 4, characterized in that, The wafer mica sheet is moved by clamps.

7. The wafer etching process and method according to claim 6, characterized in that, The clip is made of polyethylene.

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