Patent ID: 8032248

Claim:
A method for finding the correlation between prevention maintenance of a tool and the product yield of the tool, the method comprising: (a) collecting a plurality of product yield data of a plurality lots of wafers that are correspondingly formed from being processed by a plurality of tools of a production line; (b) according to the aforementioned product yield data, respectively calculating a yield gap between an average yield a predetermined days before the prevention maintenance of the tool and an average yield a predetermined days after the prevention maintenance of the tool; (c) selecting the tools that has its product yield gap greater than or equal to a predetermined yield threshold; (d) within the time frame between the predetermined days before the prevention maintenance of the tool and the predetermined days after the prevention maintenance of the tool, selecting the tools that has processed wafer lots in numbers greater than or equal to a predetermined lot count threshold; (e) finding all the product yield data generated at different time for different wafer lots from each of the tools in step (c) and step (d), and using a moving average method to magnify a curve trend that is formed by the product yield data of each tool which has been captured during the predetermined days before the prevention maintenance of the tool and the product yield data of each tool which has been captured during the predetermined days after the prevention maintenance of the tool, so as to decrease the effect of data noise to subsequent analysis; (f) displaying every one of the aforementioned magnified curve trend via a format of cumulative sum chart respectively; (g) through each of the cumulative sum chart, finding a continuous downward trend period number from the product yield data during the predetermined days before the prevention maintenance of the tool, furthermore finding a continuous upward trend period number from the product yield data during the predetermined days after the prevention maintenance, so as to find the tools that has its sum of the continuous downward trend period number and the continuous upward trend period number greater than or equal to a predetermined period threshold; and (h) for those tools that are greater than or equal to the aforementioned predetermined period threshold, sending a notification information to related workers regarding the effect between the prevention maintenance for those tools and the product yield of those tools.