According to the materials, there are terms like dummy wafer, test wafer, and production wafer used in wafer fabs. What are the respective functions of these different types of wafers?
01
Dummy Wafers
The literal translation of “dummy” is “fake” or “simulated,” so dummy wafer can also be called a fake wafer. Typically, it has no patterns or only a few layers of patterns. Main applications include:
- Used for debugging and calibrating semiconductor equipment to ensure the equipment is in optimal condition before actual production.
- Used for testing and optimizing when introducing a new process or adjusting an existing one, to reduce risks to mass production wafers.
02
Test Wafers
A test wafer (also known as an engineering wafer) goes through a complete process flow and contains various patterns and structures.
Main functions:
- During the introduction of a new chip product, test wafers are used to verify and optimize the manufacturing process to eventually achieve mass production.
- When process issues occur in mass production wafers, DOE experiments are conducted on test wafers to improve the process.
03
Production Wafers
Production wafers are used to manufacture semiconductor devices for customer delivery. They undergo strict quality control during production to ensure the final product meets customer requirements.
- Dummy Wafer: Usually made of wafer-like materials but without any circuit elements. Mainly used as fillers or support during certain process steps to help maintain balance and stability of production equipment.
- Test Wafer: Used to test equipment performance and product quality during the production process. Usually contains standard test structures or devices. Used to verify equipment function, inspect the process, and ensure products meet specifications.
- Production Wafer: Refers to actual wafers used for mass production of chips or other electronic components. These contain complete circuit designs and structures and become the final product after processing.
04
Why distinguish these types of wafers?
Mainly due to considerations of cost and criticality. Cost/criticality: production wafer > test wafer > dummy wafer. Production wafers are shipped to customers and are the economic lifeline of the company, so it’s essential to complete their production with high quality and efficiency. The process parameters and workflows are relatively fixed, and any changes must ensure 100% safety. Therefore, lower-cost and more flexible dummy wafers and engineering wafers are used to avoid wasting production wafers.
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