T-gates are required for the manufacture of high-quality transistors. Allresist optimised several three-layer systems for this particular application and designed both universal developers for a single development step, as well as individual developers which are suitable to develop each one of the three layers specifically.
Resist T-gate structure (PMMA/PMMAcoMA/PMMA)
Three-layer structure with PMMA and copolymer after development
The already well-established three-layer structure „PMMA 950k (AR-P 679.03) as bottom, copolymer (AR-P 617.08) as intermediate, and PMMA 50k (AR-P 639.04) as top layer” can be developed after irradiation with standard developers AR 600-55 and AR 600-50. Disadvantageous however is that the developer has to be switched during the development process. We thus aimed our research at the development of a mixture which should ideally be able to develop all layers in a defined manner, sufficiently high quality, and also low dark erosion. Special developer X AR 600-55/1 is now optimised for this application, being suitable for the development of AR-P 617 as well as for PMMA, and can thus be used as universal developer for two- or three-layer processes. The degree of the undercut is easily controlled the exposure dose.
Three-layer structure with PMMA and CSAR 62
In the second structural composition „PMMA 950k (AR-P 679.03) bottom, copolymer (AR-P 617.08) as intermediate, CSAR 62 (AR-P 6200.09) on top“, each layer is developed individually with a specific developer. The additional effort of multiple development steps is outweighed by the advantages of an exact adjustment of the desired profiles and by a large process window of the single steps.
These two – in however different ways – optimised development processes motivated us to choose the three-layer system developers for T-gates as resists of the month. More detailed results will be presented in the next AR NEWS and on the website of Allresist. Should you be particularly interested in a certain product, we will be glad to provide all required information also in a personal conversation.