Backside Etching Alignment in MEMS Opening Structures
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Solution Overview
Problem
Current methods for manufacturing microelectromechanical systems (MEMS) and semiconductor elements face challenges in precisely positioning and transferring deep openings or trenches from the backside of a substrate to the frontside, leading to misalignment, tilting, and shape changes, which can result in defective devices like silicon microphones and loudspeakers.
Innovation Solution
A method involving the formation of a patterned hard mask within the substrate near the front side, allowing for precise alignment and etching of openings using a patterned mask that serves as both an etch stop and a mask for forming the second opening, thereby maintaining the intended shape and position with high precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If deep openings are etched from the backside of the substrate to the front side, then the openings can be formed in the substrate, but the relative positioning of the backside mask with respect to front side structures becomes imprecise
Solution Approach 1:
The etching process is divided into two separate stages: first etching from the backside to a predetermined depth (stopping before reaching the front side), then etching from the front side to complete the opening. This segmentation allows each etching operation to be precisely controlled and aligned independently, solving the positioning precision problem that arises when etching deep openings in a single step from the backside.
Solution Approach 2:
The backside mask is positioned and the first etching is performed to a predetermined depth before the front side processing begins. This preliminary action establishes a precise reference point and partial structure that guides subsequent front side etching, ensuring accurate final positioning of the opening relative to front side structures.
2Manufacturing precision
If plasma or wet-chemical etching is used to form deep openings, then the etching process can reach the front side, but the shape of the openings changes during the transfer from back side to front side
Solution Approach 1:
The etching process is divided into two separate stages: first etching from the backside to a predetermined depth, then etching from the front side to complete the opening. This segmentation allows each etching operation to be precisely controlled and aligned independently, solving the positioning precision problem that arises when etching deep openings in a single step from the backside.
Solution Approach 2:
Different etching parameters (etching depth, etching direction, mask positioning) are used in the two etching stages. The first etching from the backside uses parameters optimized for that direction and depth, while the second etching from the front side uses parameters optimized for completing the opening with precise shape control, thereby maintaining shape accuracy throughout the process.
3Device complexity
If a single mask is used on the backside for etching deep openings, then the process is simple, but the positioning and shape transfer to the front side becomes inaccurate
Solution Approach 1:
The masking process is segmented into two independent masking operations: applying a backside mask for the first etching, then applying a front side mask for the second etching. This segmentation allows each mask to be independently positioned and optimized for its specific etching operation, achieving high alignment accuracy while keeping each individual masking step relatively simple.
Solution Approach 2:
The backside mask is applied and the first etching is performed to a predetermined depth before the front side mask is applied. This preliminary action establishes a precise reference point and partial structure that guides subsequent front side masking and etching, ensuring accurate final positioning of the opening relative to front side structures.
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 approach ensures accurate positioning and shape preservation of structures on the front side of the substrate, reducing defects and improving the robustness and functionality of devices like silicon microphones by minimizing tilting and shape changes during the etching process.
Implementation Method 1
forming a patterned mask over a first side of a carrier; forming a first opening in the carrier from a second side of the carrier opposite the first side of the carrier to at least partially expose a surface of the patterned mask; and forming a second opening in the material from the second side of the carrier using the patterned mask as a mask
Implementation Method 2
forming material over the first side of the carrier covering at least a portion of the carrier
Implementation Method 3
limitations in etching processes like plasma and wet-chemical etching
Implementation Method 4
limitations in etching processes like plasma and wet-chemical etching
Data Source
AI summary
A method for manufacturing an opening structure is provided. The method may include: forming a patterned mask over a first side of a carrier; forming material over the first side of the carrier covering at least a portion of the carrier; forming a first opening in the carrier from a second side of the carrier opposite the first side of the carrier to at least partially expose a surface of the patterned mask; and forming a second opening in the material from the second side of the carrier using the patterned mask as a mask.