Semiconductor Recess Etching for Smooth Vertical Sidewalls
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The semiconductor industry faces challenges in forming deep recesses such as trenches in semiconductor substrates with desired shapes and profiles, as existing methods result in rough and inclined sidewalls, leading to undesirable signal transmission losses when optical fibers are accommodated.
Innovation Solution
A method involving the formation of a mask, a protection layer, and alternating anisotropic and isotropic etching processes to create a recessed portion with uniform and consistent concaves on the sidewall, ensuring the sidewall is substantially perpendicular to the bottom surface, and maintaining a controlled depth within 160 μm to 400 μm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional etching methods are used to form deep recesses, then the etching depth can be achieved, but the sidewalls become rough and inclined
Solution Approach 1:
The etching process is segmented into multiple alternating steps of anisotropic and isotropic etching. Each cycle creates a portion of the final recessed structure, with the anisotropic etching providing vertical depth and the isotropic etching smoothing the sidewalls. This segmentation allows achievement of both deep etching and smooth perpendicular sidewalls that would be impossible in a single continuous process.
2Length of stationary object
If deep holes or trenches are fabricated using existing methods, then the required depth is achieved, but the sidewall profile becomes rough and inclined
Solution Approach 1:
The method employs periodic alternation between anisotropic and isotropic etching processes. The anisotropic etching step advances the recessed portion depth while creating slightly inclined sidewalls, followed by an isotropic etching step that smooths the sidewalls to be substantially perpendicular. This periodic action repeats for multiple cycles, each contributing to the final deep recessed structure with the desired smooth perpendicular sidewall profile.
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 achieves a higher etching rate and smoother, more uniform sidewalls, enhancing signal transmission efficiency by maintaining the sidewall's verticality and consistency, thereby improving the accommodation of optical fibers in semiconductor devices.
Implementation Method 1
performing a first etching process to remove the protection layer on the at least one surface of the substrate exposed by the mask; and performing a second etching process to remove the protection layer on the at least one sidewall of the mask and to etch the substrate to form the recessed portion
Data Source
AI summary
A recessed portion in a semiconductor substrate and a method of forming the same are provided. The method comprises: forming a mask on the semiconductor substrate; forming a protection layer on a top surface of the mask and on at least one sidewall of the mask, and on at least one surface of the semiconductor substrate exposed by the mask; performing a first etching process to remove the protection layer on the top surface of the mask and on a bottom surface of the semiconductor substrate exposed by the mask; and performing a second etching process to remove the remaining protection layer and to etch the semiconductor substrate to form the recessed portion. In this way, a recessed portion with relatively smooth and vertical sidewalls can be realized.