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Question 33.3: Yield in Wafer Processing A silicon wafer with a diameter of...

Yield in Wafer Processing

A silicon wafer with a diameter of 200 mm is processed over a circular area whose diameter = 190 mm. The chips to be fabricated are square with 10 mm on a side. From previous experience, the density of point defects in the surface area is 0.002 defects/cm² . Determine an estimate of the number of good chips using the Bose–Einstein yield computation.

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Using Equation (33.3) ,

n_c =0.34(\frac{D_w}{L_c})^{2.25}  (33.3)

n_c= 0.34(190/10)^{2.25} = 0.34(19)^{2.25} = 256 chips
Processable wafer area A =π(190)²/ 4 = 28,353 mm² = 283.53 cm²

Y_m =\frac{1}{1+283.53(0.002)}=\frac{1}{1+0.567} = 0.638 = 63.8% yield

Number of good chips = 0.638(256) = 163.4 rounded down to 163 good chips

Related Answered Questions

Question: 33.2

Rent ’ s Rule The 18-mm square chips in Example 33.1 are microprocessors with a processable area of 17 mm by 17 mm. The density of circuits within each chip ’ s processable area is 500 circuits per mm² . Determine the number of (a) internal circuits that can be placed on each chip and (b) input/ ...

Verified Answer:

(a) The processable area of each chip = (17)² = 28...
Question: 33.1

Number of Chips on a Wafer A 200-mm-diameter silicon wafer has a processable area of diameter = 190 mm. The IC chips to be fabricated on the wafer surface are square with 18 mm on a side. How many IC chips can be placed on the wafer? ...

Verified Answer:

n_c=0.34(\frac{190}{18})^{2.25}=0.34(10.56)...