Sacrificial Structure for Deep Trench Dielectric Liner Patterning
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Solution Overview
Problem
In the formation of semiconductor structures for MEMS devices, deep trench openings pose challenges due to incomplete exposure of photoresist material, leading to unremoved portions of the hard mask dielectric liner, which hinders the etching process.
Innovation Solution
A method involving the formation of a sacrificial structure within the opening, using a dielectric layer and a sacrificial material, where the sacrificial structure is used as an etch mask to remove portions of the dielectric layer, allowing for precise patterning and exposure of the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If photolithographic process is performed to pattern the hard mask dielectric liner, then the hard mask dielectric liner can be patterned, but the photoresist material cannot be fully exposed at the bottoms or corners of the deep trench openings
Solution Approach 1:
A sacrificial structure is introduced as an intermediary element between the photoresist and the hard mask dielectric liner. This sacrificial structure extends into the deep trench opening and provides a surface that can be effectively exposed by the photolithographic process. The sacrificial structure acts as a mediator that enables complete pattern transfer while maintaining reliability in the exposure process.
Solution Approach 2:
The sacrificial structure is formed in advance before the photolithographic patterning step. By preliminarily placing this structure at the bottom of the deep trench opening, the patent ensures that the photoresist can be fully exposed during the subsequent photolithography process, preventing the exposure incompleteness problem that would otherwise occur.
2Ease of manufacture
If deep trench openings are formed in the substrate, then the MEMS device structures can be created, but the photoresist residues remain at the bottom and corners of the openings
Solution Approach 1:
The patent converts the harmful effect of deep trench geometry (which causes photoresist accumulation) into a beneficial process feature. The sacrificial structure is deliberately placed in the deep trench opening, and its removal after patterning cleanly eliminates photoresist residues. The deep trench geometry, which initially causes problems, becomes compatible with the sacrificial structure approach that ensures complete clearing of photoresist materials.
Solution Approach 2:
The sacrificial structure is temporarily introduced and then completely removed after serving its purpose. This temporary structure enables the patterning process to proceed without photoresist residues, and its subsequent removal leaves the opening clean and ready for the next fabrication step, effectively discarding the sacrificial material after it has fulfilled its function.
3Reliability
If the photoresist material is not fully exposed, then the etching process cannot remove the intended portions of the hard mask dielectric liner
Solution Approach 1:
The sacrificial structure serves as an intermediary that enables effective etching. By providing a surface that can be fully exposed during photolithography, the sacrificial structure ensures that the etching process receives complete pattern information. This intermediary element mediates between the photolithography exposure and the subsequent etching process, ensuring that the etching can effectively remove the intended portions of the hard mask dielectric liner with high precision.
Data Source
AI summary
A method of forming a semiconductor structure includes forming an opening in a substrate. A dielectric layer is formed and substantially conformal to the opening. A sacrificial structure is formed within the opening, covering a portion of the dielectric layer. A portion of the dielectric layer is removed by using the sacrificial structure as an etch mask layer. The sacrificial structure is removed.