What Is Wafer Acceptance Test (WAT)? Why Do I Need WAT?

Wafer Acceptance Test (WAT), also known as wafer acceptance test or Process Control Monitor (PCM), is a critical test step in the semiconductor manufacturing process.

WAT definition and timing of execution

WAT is a series of tests performed at the final stage of wafer manufacturing to assess its electrical parameters by measuring specific test structures on the wafer. These test structures are not used for actual chip functions, but are specifically designed to detect and monitor all aspects of the manufacturing process. Typically, these tests are performed at the end of the wafer manufacturing process and before final chip packaging and quality inspection.

Purpose of WAT

Process verification and quality control: The primary purpose of WAT is to verify that the semiconductor manufacturing process is performed according to established technical specifications, ensuring that the circuit on the wafer meets the expected electrical properties. This is an important step in ensuring product quality and reliability.

Line Monitoring: By analyzing WAT data, engineers can monitor and evaluate the operating status of the line. This includes the detection of equipment performance deviations, changes in process conditions, etc., so that process parameters can be adjusted in time to optimize the production process.

Trend analysis and early warning: Data provided by WAT supports early identification and early warning of possible problems in the production process. For example, if a particular electrical parameter shows an abnormal trend, it can be investigated and intervened quickly to avoid even greater production losses.

Quality Credentials and customer trust: WAT results are often used as part of the wafer delivery quality credentials to help customers trust the quality of the product. This is particularly important in the semiconductor industry, where the performance of the final product is directly affected by the quality of the wafer.

Why do we value WAT?

In the highly competitive semiconductor industry, yield optimization and cost control are key to business success. WAT not only helps ensure that each batch of wafers meets quality standards, it also optimizes the production process through accurate data feedback and improves overall yield. This directly affects the cost effectiveness of products and the economic benefits of enterprises.