Bosch Deep Trench Etching With Oxide Steps for High Aspect Ratios
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Solution Overview
Problem
Traditional Bosch processes for deep silicon etching face challenges in achieving high aspect ratio trenches due to increased lateral etching at the top regions of the trench, resulting in uneven sidewall widths and reduced aspect ratios.
Innovation Solution
Incorporating an oxidation operation at various stages of the Bosch process to reduce lateral etching at the top regions of the trench, forming an oxide layer on the sidewalls and bottom surface, and repeatedly cycling through etching and deposition processes with polymer liner formation to achieve trenches with higher aspect ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If traditional Bosch process is used for deep silicon etching, then etching depth can be achieved, but lateral etching increases at top regions resulting in uneven sidewall widths and reduced aspect ratios
Solution Approach 1:
The patent applies local quality by forming an oxide layer specifically at the top region of the trench sidewalls through selective oxidation. This oxide layer is then removed only from the top region, creating a localized modification that compensates for the excessive lateral etching at that specific location. The result is uniform sidewall width throughout the trench depth, resolving the contradiction between achieving deep etching and maintaining sidewall width uniformity.
2Length of stationary object
If etching cycles are increased to achieve higher aspect ratio trenches, then trench depth increases, but lateral etching at top regions worsens the aspect ratio
Solution Approach 1:
The patent applies preliminary anti-action by performing selective oxidation to form an oxide layer at the top region before the lateral etching problem occurs. This oxide layer acts as a temporary protective structure that prevents excessive lateral etching during the etching cycles. By anticipating and counteracting the lateral etching issue in advance, the method enables achievement of higher aspect ratios without the detrimental widening at the top region.
3Manufacturing precision
If oxidation operation is added to reduce lateral etching, then sidewall width uniformity improves, but process complexity increases
Solution Approach 1:
The patent uses an oxide layer as an intermediary substance to achieve uniform sidewall widths. The oxide layer is formed through oxidation, serves as a protective mediator during etching to prevent lateral etching at the top region, and is subsequently removed. This intermediary approach resolves the contradiction by providing a simple yet effective mechanism to control sidewall dimensions without requiring complex process equipment or multiple specialized steps.
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
The method effectively reduces lateral etching at the top regions, resulting in trenches with more uniform sidewall widths and higher aspect ratios, suitable for applications like decoupling capacitors, MEMS devices, and DRAM.
Implementation Method 1
Incorporating an oxidation operation at various stages of the Bosch process to reduce lateral etching at the top regions of the trench, forming an oxide layer on the sidewalls and bottom surface
Implementation Method 2
repeatedly cycling through etching and deposition processes with polymer liner formation
Data Source
AI summary
Some embodiments pertain to a semiconductor device. The semiconductor device includes a semiconductor substrate including a trench extending downward into an upper surface of the semiconductor substrate. The trench includes a bottom surface and a plurality of scallops along sidewalls of the trench. An oxide layer lines the bottom surface and the sidewalls of the trench. The oxide layer has varying thicknesses along the sidewalls of the trench at different depths. The varying thicknesses step down at discrete increments as a depth into the trench increases.