Pixel Separation Trench Layout to Prevent Sensor Substrate Cracks
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Solution Overview
Problem
The manufacturing process of sensor devices with semiconductor substrates and pixel separation trenches is prone to crack generation due to heat treatment, which can lead to substrate damage and performance issues.
Innovation Solution
The sensor device incorporates a semiconductor substrate with pixel separation trenches formed in directions different from the crystal cleavage directions, and includes insulation films and metal films with embedded heat expansion materials to equalize thermal expansion and reduce stress, as well as a wetting film configuration to prevent void formation in the metal film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If heat treatment such as annealing is performed on the semiconductor substrate with pixel separation trenches, then the manufacturing process can be completed and light absorbing/reflecting films can be formed in the trenches, but heat shrink of the semiconductor substrate may generate cracks from the vicinity of the trenches
Solution Approach 1:
The patent changes the orientation parameter of the pixel separation trenches, forming them in directions different from the cleavage directions of the semiconductor substrate crystals. This parameter change prevents cracks from propagating along the trenches during heat treatment, as the trench orientation no longer aligns with the preferred crack propagation paths of the crystal structure.
Solution Approach 2:
The patent employs a composite structure by forming light absorbing materials or light reflecting materials within the pixel separation trenches. This composite configuration serves multiple functions: it provides optical isolation between pixels while the specific trench orientation prevents heat-induced cracking during subsequent annealing processes.
2Manufacturing precision
If pixel separation trenches are formed to separate pixels and reduce light leakage, then optical performance is improved, but the trenches become stress concentration points that facilitate crack generation during heat treatment
Solution Approach 1:
The patent changes the directional parameter of the pixel separation trenches, orienting them at angles different from the crystal cleavage directions. This parameter modification maintains the effectiveness of pixel separation and light leakage reduction while simultaneously preventing the trenches from acting as stress concentration points that would facilitate crack propagation during thermal processing.
3Reliability
If insulation films are formed on the trenches to prevent contact during manufacturing, then process reliability is improved, but additional manufacturing steps and film layers increase process complexity
Solution Approach 1:
The patent changes the primary parameter from film layer configuration to trench orientation. By forming pixel separation trenches in directions different from crystal cleavage directions, the substrate itself becomes more resistant to cracking during heat treatment, thereby achieving manufacturing reliability without requiring additional insulation films or increasing process complexity.
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 configuration effectively prevents crack generation during heat treatment, enhances light collection performance, and ensures reliable pixel separation and light shielding functions.
Implementation Method 1
This heat treatment causes a heat shrink of the semiconductor substrate, and may generate a crack from a vicinity of the trench according to the heat shrink
Implementation Method 2
The first insulation film is formed such that the trench has an opening on a first surface side. The second insulation film is formed across an upper part of the opening of the trench
Implementation Method 3
A similar heat expansion material that has a heat expansion characteristic similar to a heat expansion characteristic of a material constituting the semiconductor substrate is embedded inside the metal film
Data Source
AI summary
A sensor device according to the present technology includes a semiconductor substrate that includes a plurality of photoelectric conversion elements arranged for each pixel and a pixel separation portion having a trench formed between pixels to separate the pixels. The pixel separation portion of the semiconductor substrate is formed in directions different from cleavage directions of crystals of the semiconductor substrate.