Working principle of wet etching machine

Wet etching machines (usually referring to wet etching equipment or wet etching devices) are mainstream equipment used in semiconductor manufacturing and metal processing industries.

I. Core Working Principle: Selective Chemical Etching

The working principle of a wet etching machine is based on the selective chemical etching of materials. Specifically, it uses various organic acids, inorganic acids, alkaline solutions, and bromine-based etchants (often called etchants or corrosive solutions) as wet liquids. Through the principle of permeation etching, metal or semiconductor materials are dissolved (etched) under the action of external force (chemical energy).

This selectivity is reflected in the fact that different chemical solutions have different etching rates for different materials (such as metals, oxides, nitrides, and photoresists). By carefully selecting the composition, concentration, temperature, and time of the etchant, it is possible to precisely adapt to a single film, thereby achieving highly selective etching, that is, only etching the target material layer while minimizing or completely avoiding etching the underlying material or mask layer.

II. Key Process for Achieving Precise Graphics: Photolithographic Mask Protection

In semiconductor manufacturing, wet etching is often used to generate specific patterns on Si (silicon) substrates or films. To achieve this selective area etching, photolithography is a crucial preceding step. The photoresist pattern (or hard mask) is a key tool in this process. It is coated and developed on the wafer surface, covering and protecting the surface areas that are desired to be retained, preventing these areas from being etched by the subsequent etchant. Only the areas not covered by the photoresist will be exposed to the etchant and react. In this way, precise patterns and structures can be formed on the material surface.

III. Brief Description of Typical Workflow

Pre-treatment: The wafer undergoes cleaning and drying steps to ensure a clean surface.

Coating: A uniform layer of photoresist is applied to the wafer surface.

Exposure and Development: The designed pattern is transferred to the photoresist using a stepper, and after development, a physical protective mask is formed.

Wet Etching: The wafer with the photoresist pattern is immersed in a specific etchant (or using spraying, etc.), and the reaction is carried out at precisely controlled temperature and time. The etchant penetrates the unprotected surface area, dissolving and removing the target material.

Cleaning and De-coating: After etching, the wafer is rinsed with a large amount of deionized water to thoroughly remove residual chemicals. Then, a special de-coating solution or plasma is used to remove the protective photoresist layer.

Drying and Inspection: After drying, the wafer is inspected to confirm that the pattern size, etching depth, etc., meet the requirements.

IV. Advantages of Wet Etching Process

Its advantages lie not only in its fast and uniform etching capability but also in its low cost, high output, and high reliability. This makes it particularly suitable for the production of large-size wide-strip devices. In addition, it has a good selectivity ratio, that is, it can perform targeted etching on different materials (as mentioned earlier) without affecting other parts.

V. Technological Development Trends

With continuous technological advancements, wet etching equipment is also constantly improving and innovating. Current development trends mainly include automation, improved repeatability of etching conditions under microprocessor control, point-of-use filtration control, and the development of automatic spraying equipment. These improvements make the wet etching process more efficient and stable, and reduce the influence of human factors. At the same time, it greatly reduces the generation of defects during etching (such as particles, water stains, uneven etching, etc.).

VI. Summary and Outlook

It is believed that in the future, with continuous technological advancements and innovations, the performance and efficiency of wet etching machines (equipment) will continue to improve, especially in terms of automated control, chemical management, uniformity optimization, and defect control, providing strong support for the continuous development of semiconductor manufacturing, metal processing, and other related industries. Its core principle of selective chemical etching, combined with precise photolithographic mask technology, remains an efficient and economical means of achieving specific material patterning.

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