Improvements in process yields for a 200 mm wafer fabricator

IBM's 200 mm wafer fabricator in Essex Junction, Vermont, Like other semiconductor manufacturers, periodically experienced production losses due to wafers scrapped in process or at final wafer test. Efforts to increase yield by the use of traditional top-down management techniques such as executive directives and problem solving by management with little input from hands-on employees did not result in any sustainable improvement. To remedy the situation, IBM turned to it's employees and their knowledge of the product and the processes used to manufacture that product. Two self-directed work teams, which eventually merged into a single unit, were formed and given responsibility for improving process and electrical test yields. A three-pronged approach to improving process yields was put in place that included in-depth team meetings that discovered reasons why wafers were scrapped and drove activity to fix the problems, stimulated preventive actions through systematic investigation and improvement of process controls for every process area, and created focus on process control and yield problems through an incentive program. This program is still in use today. In-depth team reviews are conducted for all wafers stopped in process because of quality screens. These reviews are attended by team members and representatives from every manufacturing department holding wafers that might be defective. Information from these meetings is shared with a subset of the team that works directly with toolset teams (reactive ion etching, wet cleans, oxidations and diffusions, etc.), to improve preventive measures. Actions taken to prevent process problems are developed from working meetings with every toolset team. Teams are rewarded through an incentive program based on attaining team targets, as well as goals for overall fabricator process yield. This work team approach has resulted in an eighty percent reduction in the scrap rate of wafers in process and at wafer-level functional test.