Concurrent Shallow and Deep Trench Formation via Single Mask Etching
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Solution Overview
Problem
The conventional method for forming trenches and trench isolation in semiconductor manufacture is complex, time-consuming, and costly due to the separate formation of shallow and deep trenches requiring multiple etching, liner oxidation, gap-filling, and densification steps, as well as the need for a reverse mask and subsequent dry etching processes.
Innovation Solution
A method that forms shallow and deep trenches concurrently by using a substrate with defined areas, a pad layer, and a hard mask, where patterned photoresist layers are used to etch the substrate and form trenches, followed by oxide liner deposition and densification, eliminating the need for a reverse mask and reducing the number of processing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shallow trenches and deep trenches are formed separately in different stages, then the trench isolation structures can be completed, but the manufacturing process becomes complicated and time-consuming
Solution Approach 1:
The patent combines the formation of shallow trenches and deep trenches into a single integrated process. A first photoresist pattern defines both shallow trench regions and deep trench regions, allowing simultaneous etching of both trench types through the same mask layer, thereby reducing process steps and complexity while ensuring reliable trench isolation structure completion
2Manufacturing precision
If separate etching steps are used for shallow trenches and deep trenches, then precise trench formation is achieved, but the manufacturing cycle time increases
Solution Approach 1:
The patent segments the trench formation process by using different photoresist patterns applied to the same mask layer. The first photoresist pattern defines shallow trench openings, while the second photoresist pattern defines deep trench openings. Both patterns are etched simultaneously through the mask layer in a single etching step, achieving precise trench formation for both types while reducing cycle time compared to separate etching steps
3Reliability
If a reverse mask is used to remove oxide layer in the second area, then the loading effect during CMP is avoided, but additional manufacturing cost and process steps are incurred
Solution Approach 1:
The patent applies preliminary action by forming the second photoresist pattern on the mask layer before the CMP process. This pattern protects the deep trench regions during CMP, preventing loading effects and ensuring uniform polishing in shallow trench areas. The photoresist pattern is removed after CMP, eliminating the need for additional reverse mask fabrication and reducing manufacturing cost while maintaining CMP reliability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This integrated method simplifies the process, reduces manufacturing costs, and shortens cycle time by allowing concurrent formation of trench oxide liners, requiring fewer gap-filling, densification, and CMP processes, thereby improving efficiency and cost-effectiveness.
Implementation Method 1
forming a first patterned photoresist layer on the hard mask, the first patterned photoresist layer having a first opening in the first area and a second opening in the second area
Implementation Method 2
etching the hard mask, the pad layer and the substrate through the first opening and the second opening, thereby forming a first shallow trench and a second shallow trench
Implementation Method 3
forming a first oxide liner and a second oxide liner on a surface of the first shallow trench and a surface of the deep trench
Data Source
AI summary
A method for forming trench isolation on a substrate includes providing a substrate having thereon a pad layer and a hard mask; forming a first shallow trench in a first area and a second trench in a second area on the substrate; forming a resist layer covering the first area while exposing the second area; etching the second shallow trench to form a deep trench; forming oxide liner within the first shallow trench and the deep trench; and filling the shallow trench and the deep trench with an oxide layer.