Grass Defect Removal in Patterned Cavity Etching
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Solution Overview
Problem
During deep reactive ion etching (DRIE) processing, 'grass' defects – thin spikes of silicon or semiconductor material – often form and are difficult to remove, especially in double etch procedures where the etch chemistry cannot be adjusted to eliminate them.
Innovation Solution
A method involving a semiconductor substrate with a pattern of trenches and mesas, where an oxide layer is formed and etched to remove the 'grass' defects, using a combination of deep reactive ion etching and buffered oxide etch techniques to recess the pattern and eliminate unwanted material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If deep reactive ion etching (DRIE) processing is used to form cavities and patterns in semiconductor substrates, then the desired cavity structures are formed, but 'grass' defects (thin spikes of silicon or semiconductor material) are generated on the sidewalls and free surfaces
Solution Approach 1:
A sacrificial oxide layer is deposited as an intermediary material that selectively covers the grass defects on mesa sidewalls and free surfaces. This oxide layer acts as a mediator that can be easily removed through buffered oxide etch (BOE) treatment, thereby eliminating the grass defects without affecting the underlying semiconductor structure. The oxide layer is applied after cavity formation and pattern recessing, allowing it to target and encapsulate the grass formations for subsequent removal.
2Object-generated harmful factors
If etch chemistry is adjusted to attempt to eliminate grass defects, then the grass formation may be reduced, but the desired cavity and pattern structures cannot be properly formed
Solution Approach 1:
The sacrificial oxide layer is deposited in advance as a protective coating before the grass defects become problematic. By applying the oxide layer after cavity formation but before final pattern completion, the method proactively prevents grass defects from interfering with subsequent processing steps. This preliminary action allows the etch chemistry to be optimized for cavity formation without concern for grass defects, which are then removed in a controlled manner using BOE treatment.
3Object-generated harmful factors
If additional processing steps are added to remove grass defects, then the grass defects are eliminated, but the manufacturing process complexity increases
Solution Approach 1:
The method changes the chemical parameters of the processing environment by introducing buffered oxide etch (BOE) treatment as a dedicated grass removal step. This parameter change allows selective removal of the sacrificial oxide layer and embedded grass defects without affecting the semiconductor substrate or other processings. The BOE treatment uses specific chemical composition and concentration parameters to achieve selective etching, thereby eliminating grass defects through a controlled chemical process rather than mechanical or physical means.
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
Effectively removes 'grass' defects by recessing the pattern in the cavity and using an oxide layer to target and eliminate the unwanted material, improving the quality of semiconductor devices in double etch procedures.
Implementation Method 1
forming an oxide layer in the cavity and on the sidewalls and free surfaces of the plurality of mesas
Implementation Method 2
etching the oxide layer to remove the oxide layer from the free surfaces of the plurality of mesas and at least a portion of the sidewalls of the plurality of mesas
Data Source
AI summary
A method of manufacturing a semiconductor device includes providing a first semiconductor substrate having a first main surface and an opposing second main surface, and forming a pattern into the first semiconductor substrate. The pattern includes a plurality of trenches defining a plurality of mesas. Each of the plurality of mesas has sidewalls and a free surface formed by material of the first semiconductor substrate. The method further includes forming a cavity in the first semiconductor substrate such that the pattern is recessed in the cavity, forming an oxide layer in the cavity and on the sidewalls and free surfaces of the plurality of mesas, and etching the oxide layer to remove the oxide layer from the free surfaces of the plurality of mesas and at least a portion of the sidewalls of the plurality of mesas.