In-line statistical process control and feedback for VLSI integrated circuit manufacturing

Abstract

A number of quality control and yield improvement techniques are used in the H P Fort Collins IC wafer fabrication line. Four of these are described, with examples of how each has improved quality and yield. (1) Silicon wafer measurements obtained from the vendor or made at incoming inspection are correlated with device parameters and chip yield.( 2 ) Control charts on the manufacturing line are generated on-line. from monitor wafer data entered by operators, giving immediate feedback. In addition, a daily summary report lists any chart out of control. In certain instances it is necessary to improve the process ca ability of an operation. A feedback technique is u s e f t o do this for operations which have a predictable systematic drift. (3) Individual wafer positions in critical operations are automatically recorded throughout the fabrication line. This greatly facilitates correlation of input to out ut parameters and pinpoints the root cause of levice parameter, or chip yield fluctuations. (4ThC$d correlation of the myriad of data obtained throughout the fabrication and wafer test areas is done with a common data base and tools which transform the raw data into an optimum form for analysis.

On the use of wafer positional and spatial pattern analysis to identify process marginality and to de-convolute counterintuitive experimental results

“…Wafer positional analysis (or wafer-level tracking) was first reported in the 1990's [1], [2], and has since been widely used [3], [4].…”

An Electronics Division Retrospective (1952-2002) and Future Opportunities in the Twenty-First Century

“…264 Significant improvements were observed in MOS, 263 bipolar, 265 and CPU ICs. 266 Louis Parrillo and colleagues described the integrated benefits of detailed attention to optimizing the response of the silicon wafer to the full suite of bipolar fabrication processes beyond just gettering, in order to achieve optimal IC performance. 265 The development of quantitative gettering processes and models were especially helpful in gaining insight into the microphysical processes operative, although continuous refinements ensure this will remain an active area of research.…”

Fault isolation during semiconductor manufacturing using automated discovery from wafer tracking databases

“…It was included in the prototype because we think it will be useful for other classes of queries. Figure 4 shows an example taken from Scher [1] showing how trel~ds in wafer tracking data can enable fault diagnosis. This figure shows the difference between threshold voltage at the top of the wafer and at the bottom of the wafer, plotted versus wafer position in the furnace at a key step in formlng a transistor; namely gate oxidation.…”