Resist Process for Improved Photo Throughput of Small Etched Via Holes
Original Publication Date: 1985-Apr-01
Included in the Prior Art Database: 2005-Feb-18
This process utilizes a modified image reversal process, MIRP"*", over- sized mask images, with under-exposure to achieve very small via hole dimensions in thick resist and high photo throughput. As is graphically shown in the figure, the standard, positive resist process requires longer exposure time as photoresist thickness increases. Thus, it can be seen that thinner resist is required to achieve reliable hole opening, as hole size decreases. The MIRP process allows reliable hole opening even when the hole diameter equals the resist thickness. This is achieved by using under-sized mask images and shorter exposure time, as shown in the figure. As much as a factor of two has been realized in photo exposure throughput, compared with the standard process.