Vacuum-Sealed Sensor Package Using Anodic Bonding and Pad Sealing
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Solution Overview
Problem
Existing sensor apparatuses face challenges in easily and reliably sealing sensors, particularly in maintaining a vacuum atmosphere and preventing leakage.
Innovation Solution
A sensor apparatus design involving a semiconductor substrate with an oxide layer and a glass substrate with metal films on through holes, utilizing anodic bonding to create a sealed space with a through hole sealed by a pad portion, ensuring the thickness and distance ratios enhance sealing efficacy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional sealing methods are used, then the sealing process is simple, but the reliability of sealing is insufficient and leakage risk increases
Solution Approach 1:
The sealing structure is divided into multiple functional segments: the glass substrate forms the primary sealing boundary, while the pad portion creates a secondary sealing layer at the through-hole opening. This segmentation allows each component to contribute to sealing reliability independently, ensuring that even if one sealing mechanism is compromised, the other maintains the vacuum atmosphere.
Solution Approach 2:
The invention employs composite material structures where a metal film is deposited on the glass substrate, and a metal pad portion is formed at the through-hole opening. This combination of glass and metal materials provides both chemical stability (glass) and mechanical sealing strength (metal), thereby enhancing overall sealing reliability without significantly increasing structural complexity.
2Reliability
If the pad portion is positioned close to the through hole, then the sealing structure is compact, but the sealing reliability is reduced
Solution Approach 1:
The pad portion is extended not only in the planar direction but also in the thickness direction of the glass substrate. By making the pad portion protrude from the lower surface of the glass substrate by a distance greater than the through-hole diameter, the sealing mechanism transitions from a two-dimensional planar seal to a three-dimensional overlapping seal, thereby enhancing sealing reliability without excessive area occupation.
3Reliability
If a metal film is added to the through hole side wall, then the sealing reliability is improved, but the manufacturing complexity increases
Solution Approach 1:
The metal film formation process is merged with the existing through-hole fabrication process. The metal film is deposited on the inner circumferential surface of the through hole during the same manufacturing sequence, combining two functions (through-hole creation and metal film deposition) into a unified manufacturing flow, thereby minimizing the increase in manufacturing complexity.
4Reliability
If the sum of pad portion thickness and extension portion thickness is made larger than sealed space height, then the sealing reliability is enhanced, but the device complexity increases
Solution Approach 1:
The pad portion is designed to protrude from the lower surface of the glass substrate before final assembly, creating a preliminary sealing barrier that prevents potential leakage paths. This preliminary action ensures that even during assembly variations or thermal expansion, the sealing integrity is maintained, thereby enhancing reliability without requiring complex additional 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
The design achieves reliable sealing of sensors, maintaining a vacuum atmosphere, and reduces the risk of leakage by effectively bonding the substrates, thus enhancing the sensor's operational integrity.
Implementation Method 1
utilizing anodic bonding to create a sealed space
Data Source
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AI summary
Provided is a sensor apparatus including a semiconductor substrate, a glass substrate, a physical quantity sensor, and a pad portion electrically connected to the physical quantity sensor, in which a concave portion provided to at least one of the semiconductor substrate or the glass substrate is sealed by bonding a first bonding portion in the glass substrate to a second bonding portion in the semiconductor substrate, the physical quantity sensor and the pad portion are arranged in a sealed space sealed by the semiconductor substrate and the glass substrate, and the glass substrate has, in the first bonding portion, a cation depletion layer with a cation concentration less than a cation concentration of the glass substrate.