BiCMOS Spacer Layer CD-Uniformity Improvment

The bad CD uniformity of BiCMOS spacer layer in photo process were discussed. For spacer CDU bad, the main problem was analyzed in detail and got the solution finally. The solution of this problem has been implement successfully and increase the yield.Details are as follows:1. The CD Uniformity problem in BiCMOS Photo processCD uniformity is very key in PH process.Bad CD uniformity will impact Each process and lost product yield.2. The theory of CD uniformity and its bad impactThe CD uniformity means that the average distribution of measured CD values of the entire chip-chip or inter chip.The representation of the CD uniformity as:The average of five measured CD values X=(X1+X2+X3+X4+X5)/5,CD uniformity=(X max-X min)/2X×100﹪.Smaller CD uniformity better wafer process quality and better process capability.If the bad CDU occured in litho process ,the product need to redo once or several times, which makes the cost increase. And affect product yield, product defects, such products must scrap, lost production and costs, and even affect the ship, causing huge losses.3. The control method of CD uniformityAccording to impact factors to the CD uniformity,under the cost control found out the best method to resolve this issue . From the many data collected by experiment the CD uniformity of BiCMOS spacer layer can be reached 0.5%. This not only reduces costs and improves yields. This study is to optimize uniformity of line width provides a good reference and direction.