U. Glaeser

An example of the selection of CMOS IC types is given in Table 14.9 and Fig. 47.14. Six critical processes
were assumed to be responsible for the yield loss, and were accompanied by in-line yield measurements
and the consequent yield analysis. It can be seen from Table 14.9 that in this particular example, the yield
associated with p + -diffusion was much smaller than the yields of the other process steps and, therefore,
was the main cause of the wafer yield loss. It is obvious that in this example an investment in the process
of p + -diffusion would be extremely beneficial. An investment made to improve the process of p + -diffusion
© 2002 by CRC Press LLC
TABLE 47.8 Yield Predictions for Lithographic Defects
Critical Level A ci
FIGURE 47.14 Example of IC type selection.
SPPI .000259 .9939 6.98 × 10 −6
OPPI .002052 .9459 5.83 × 10 −5
SNPI .000225 .9986 1.65 × 10 −6
ONPI .002460 .9767 2.61 × 10 −5
SCON .004425 .8520 1.45 × 10 −4
OCON .001830 .9396 6.48 × 10 −5
SPOL .000954 .9668 3.69 × 10 −5
OPOL .001283 .9909 1.03 × 10 −5
SME1 .007499 .7804 1.96 × 10 −4
OME1 .006962 .9135 9.07 × 10 −5
SME2 .000384 .9809 2.15 × 10 −5
OME2 .003384 .9135 9.06 × 10 −5
Total — .4490 2.84 × 10 −4
TABLE 47.9 Yield Prediction Results
Wafer Yield Yi Critical Process Chip 1 Chip 2
1. p − -diffusion 0.952 0.884
2. p + -diffusion 0.845/0.928 ∗
0.671/0.792 ∗
3. n + -diffusion 0.966 0.897
4. Gate oxide formation 0.993 0.978
5. Photoprocess contacts 0.984 0.949
6. Photoprocess metal 0.958 0.867
Final wafer yield 0.727/0.799 ∗
0.428/0.505 ∗
Y
∗ after investment in p + -diffusion process
Yi
2
∂Yi