Using a test site for the rapid introduction of 32-kb bipolar RAM

The authors describe the introduction of a 32-kb bipolar RAM. The introduction started with a preliminary phase, using an exploratory test site, followed by a more conventional product test site. Both the cell layout and processing were optimized with an exploratory test site in the early manufacturing cycle. The exploratory test site has yield test structures with different ground rules and cell layouts side by side. The yield detractors and product yields are continuously monitored in the manufacturing line with a product test site in order to enhance defect learning. A number of product test sites are distributed on the product wafer. The test site has the same ground rules as the product. The test-site-aided product introduction doubled the defect learning rate