Process for making masks with structures in the submicron range
First Claim
1. A process for making a structure including features in the submicron dimension range comprising the steps of:
- a) providing a substrate;
b) forming a first layer of material on said substrate;
c) forming a mesa including at least one vertical surface on a selected region of said first layer;
d) forming a second layer of material over said mesa and the uncovered portions of said first layer, said second layer forming a sidewall over each vertical surface of said mesa;
e) forming a planarizing layer on said second layer, said planarizing layer leaving uncovered the top of said second layer on said mesa;
f) forming a mask on said second and planarizing layers, said mask leaving uncovered the top of a sidewall;
g) removing the uncovered sidewall with an isotropic etchant to form a first pattern defining a submicron dimension;
h) transferring said first pattern to said first insulting layer;
i) removing said mask, planarizing layer, second layer, and mesa to leave said first layer defining said first pattern;
j) photolithographically defining a second pattern on said first layer;
k) transferring said second pattern to said first layer; and
transferring said first and second patterns from said first layer into said silicon substrate.
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Abstract
In the course of the process for making masks with structures in the submicrometer range, initially structures of photoresist or polymer material with horizontal and substantially vertical sidewalls are produced on a silicon substrate covered with an oxide layer. This is followed by a layer of silicon nitride which is deposited by LPCVD. The resultant structure is planarized with a photoresist which is etched back until the start of the vertical edges of the sidewall coating formed by the nitride layer is bared on the photoresist structures. In a photolithographic step, a trimming mask is produced on the surface of the nitride layer and the planarizing resist. The bared regions of the nitride layer are then removed by isotropic etching. The dimensions A-B of the openings defined after removal of the nitride layer from the vertical surfaces of the photoresist structures are transferred to the oxide layer by anisotropic etching. Concurrently with these structures of minimum line width, registration marks are generated which allow the adjustment necessary for a further photolithographic step to be carried out with maximum accuracy. After removal of the trimming mask, the planarizing resist, the photoresist structures and the remainder of the nitride layer, structures with coarser line widths are defined in a further photolithographic step, which are also transferred to the oxide layer. Using the oxide layer as a mask, trenches of the desired depth are produced in the silicon substrate by anisotropic etching. The mask is thinned by anisotropic etching, and the oxide layers are removed from the front and the back side by wet etching.
30 Citations
14 Claims
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1. A process for making a structure including features in the submicron dimension range comprising the steps of:
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a) providing a substrate; b) forming a first layer of material on said substrate; c) forming a mesa including at least one vertical surface on a selected region of said first layer; d) forming a second layer of material over said mesa and the uncovered portions of said first layer, said second layer forming a sidewall over each vertical surface of said mesa; e) forming a planarizing layer on said second layer, said planarizing layer leaving uncovered the top of said second layer on said mesa; f) forming a mask on said second and planarizing layers, said mask leaving uncovered the top of a sidewall; g) removing the uncovered sidewall with an isotropic etchant to form a first pattern defining a submicron dimension; h) transferring said first pattern to said first insulting layer; i) removing said mask, planarizing layer, second layer, and mesa to leave said first layer defining said first pattern; j) photolithographically defining a second pattern on said first layer; k) transferring said second pattern to said first layer; and transferring said first and second patterns from said first layer into said silicon substrate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification