Protective Layer Prevents Cracks in Step-Shaped Cavity Etching
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Solution Overview
Problem
Current manufacturing processes for MEMS microphones using wet etching techniques, such as the BOE process, often result in crack formation in step-shaped silicon nitride layers, affecting the reliability of the device.
Innovation Solution
A method involving the formation of a protective layer on step-shaped portions of the multilayer film, followed by a capping layer with a step-shaped inner surface, which protects the inner surface during the etching process, preventing crack formation and improving device reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wet etching (BOE process) is used to remove silicon oxide to form a cavity, then the cavity structure can be formed, but cracks will be formed in the step-shaped silicon nitride layer, significantly affecting device reliability
Solution Approach 1:
A protective layer is formed on the step-shaped silicon nitride layer before the wet etching process. This preliminary protective coating prevents the etchant from directly attacking the silicon nitride at the step edges, thereby preventing crack formation while still allowing the cavity to be formed through the protective layer via through-holes
Solution Approach 2:
The protective layer acts as an intermediary between the wet etchant and the silicon nitride layer. It mediates the etching process by allowing controlled removal of silicon oxide through through-holes while protecting the silicon nitride step edges from direct etchant exposure that would cause cracking
2Strength
If a step-shaped silicon nitride layer is formed to support the cavity structure, then good corrosion resistance is achieved, but the density of silicon nitride growth is low in the step, making it easily removed and causing cracks
Solution Approach 1:
The protective layer is specifically applied to the step-shaped portions of the silicon nitride layer where the density is low and cracks are most likely to form. This local protection strategy targets the vulnerable areas without affecting the overall corrosion resistance properties of the silicon nitride layer
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 prevents cracks in the capping layer during the etching process, enhancing the reliability and performance of MEMS microphones by ensuring a crack-free silicon nitride layer.
Implementation Method 1
forming a protective layer on the step-shaped inner surface of the capping layer... the protective layer protects the inner surface during the etching process, preventing crack formation
Implementation Method 2
Current process techniques for manufacturing MEMS microphones employ wet etching, e.g., using a buffered oxide etch (BOE) process, to remove the silicon oxide (SiO2) to form a cavity
Data Source
AI summary
A method for manufacturing a semiconductor device includes providing a semiconductor substrate including a substrate and a multilayer film having a step-shaped portion on the substrate; forming a protective layer covering the step-shaped portion of the multilayer film; forming a capping layer having a plurality of steps on the protective layer covering the semiconductor substrate; and removing at least one layer of the multilayer film to form a cavity that is defined by the capping layer and a remaining multilayer film that has the at least one layer removed. The thus formed semiconductor device does not have cracks in the steps of the capping layer when performing an etch process, thereby improving the performance of the semiconductor device.