Semiconductor Pressure Sensor Exposed Alignment Mark
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Solution Overview
Problem
Conventional semiconductor pressure sensor manufacturing methods face challenges such as increased production costs, reduced pressure measuring accuracy, and metal contamination due to the complexity of alignment mark formation and the difficulty in maintaining the desired diaphragm thickness, which affects the reliability of gauge resistors.
Innovation Solution
A semiconductor pressure sensor design where the first substrate has a concave portion and an exposed alignment mark, while the second substrate has a diaphragm and gauge resistors, preventing metal contamination and allowing for accurate alignment and grinding without the need for IR aligners, thus improving registration accuracy and reducing production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an IR aligner is used to recognize the first alignment mark, then registration can be performed, but capital investment efficiency decreases and unit cost per process increases
Solution Approach 1:
The patent replaces the expensive IR aligner with a conventional stepper that uses visible light alignment marks. The alignment mark structure is designed to be simple and inexpensive, consisting of protrusions and recesses that can be formed using standard photolithography processes already present in the manufacturing line, eliminating the need for costly specialized equipment
Solution Approach 2:
The patent changes the alignment mark from an invisible IR-reflective pattern to a visible light-absorbing or -reflecting pattern using standard photolithographic materials. The alignment mark is formed with a photoresist pattern that can be visually detected by conventional stepper equipment, making the alignment process accessible with standard equipment rather than requiring rare and expensive IR-capable steppers
2Ease of manufacture
If the second silicon substrate is ground to form the diaphragm, then the diaphragm is formed, but the thickness varies significantly and pressure measuring accuracy is reduced
Solution Approach 1:
The patent performs preliminary formation of the diaphragm by selectively removing the second silicon substrate in the region corresponding to the concave portion before bonding with the first substrate. This preliminary diaphragm formation, combined with subsequent controlled grinding, ensures more uniform thickness. The preliminary action establishes the basic diaphragm structure and alignment, making the final thickness control more predictable and uniform
Solution Approach 2:
The patent implements a feedback mechanism where the alignment mark position and the concave portion depth are used to control the grinding process. The alignment mark ensures precise positioning of the diaphragm relative to the concave portion, and the known concave portion depth provides a reference for controlling the amount of grinding needed to achieve the desired diaphragm thickness, thereby improving thickness uniformity
3Measurement precision
If the first alignment mark is formed to pass through the second silicon substrate, then alignment can be performed, but etching time and cost increase
Solution Approach 1:
The patent uses partial action by forming the alignment mark only in the first substrate rather than etching through the entire thickness of the second substrate. The alignment mark protrusions and recesses are formed at a limited depth in the first substrate, which is sufficient for accurate alignment when viewed through the transparent or semi-transparent structure, eliminating the need for deep through-etching of the second substrate
Solution Approach 2:
The patent changes the alignment mark from a deep vertical through-hole structure to a surface-level protrusion and recess pattern that can be detected in the lateral dimension. The alignment mark is formed as a planar pattern of protrusions and recesses on the bonding surface of the first substrate, allowing alignment to be performed in the lateral plane rather than requiring deep vertical etching through the second substrate
Data Source
AI summary
A semiconductor pressure sensor includes a first substrate having a concave portion and an alignment mark at a main surface thereof, and a second substrate formed on the main surface of the first substrate and having a diaphragm provided to cover a space inside the concave portion of the first substrate and a gauge resistor provided on the diaphragm. The alignment mark is provided to be exposed from the second substrate. Accordingly, it is possible to obtain a semiconductor pressure sensor and a method of manufacturing the same with reduced production costs and with improved pressure measuring accuracy.