Tilted Pixel Array Prevents Cracking in Light-Receiving Devices
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Solution Overview
Problem
Array-type light-receiving devices experience cracking due to thermal expansion coefficient differences between semiconductor materials and silicon read-out circuits, leading to reduced yields and device rigidity.
Innovation Solution
The array-type light-receiving device is designed with pixels arranged in tilted array directions relative to the cleavage direction of the semiconductor substrate, preventing cracking and improving rigidity by ensuring the array directions do not coincide with the cleavage directions, and using a specific angle relationship between the array and cleavage directions to enhance structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the array directions coincide with the cleavage directions of the semiconductor substrate, then the manufacturing process is simplified, but cracks are easily introduced along the cleavage directions during temperature cycling
Solution Approach 1:
The patent applies asymmetry by intentionally misaligning the pixel array directions with the substrate cleavage directions. Specifically, the first array direction is set at a first angle to the first cleavage direction, and the second array direction is set at a second angle to the second cleavage direction. This asymmetric arrangement prevents cracks that would naturally propagate along cleavage planes from aligning with pixel rows, thereby maintaining reliability while preserving manufacturing simplicity.
2Reliability
If the array-type light-receiving device is cooled with a thermoelectric cooler to decrease dark current, then the detector performance is improved, but cracks are introduced due to thermal expansion coefficient differences between semiconductor material and silicon read-out circuit
Solution Approach 1:
The patent uses asymmetry to decouple the thermal stress propagation paths from the pixel array structure. By setting array directions at specific angles relative to cleavage directions, the design ensures that thermal cracks propagating along cleavage planes do not coincide with pixel rows, even when temperature cycling occurs during thermoelectric cooling operation.
Solution Approach 2:
The patent applies preliminary anti-action by pre-configuring the pixel array orientation to counteract the expected thermal stress directions. Before thermal cycling occurs, the array directions are deliberately angled relative to cleavage directions, creating a geometric configuration that prevents crack formation along pixel rows during subsequent temperature cycles.
3Device complexity
If pixels are arranged in straight rows along cleavage directions, then the device structure is simpler, but the rigidity of the array-type light-receiving device is reduced
Solution Approach 1:
The patent implements asymmetry in the pixel array configuration by setting the first array direction at a first angle to the first cleavage direction and the second array direction at a second angle to the second cleavage direction. This asymmetric arrangement enhances rigidity by distributing mechanical stresses more effectively across the substrate, preventing the formation of continuous crack paths along pixel rows while maintaining a relatively simple overall array structure.
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 design effectively prevents cracking and enhances the rigidity of the array-type light-receiving device, even under temperature cycles, thereby improving yields and device reliability.
Implementation Method 1
The optical absorption layer includes a p-n junction... The impurity concentration in the diffusion concentration distribution control layer is reduced toward the optical absorption layer
Implementation Method 2
In order to decrease the dark current of a hybrid optical detector, the hybrid optical detector is cooled with a thermoelectric cooler, such as a Peltier device or a Stirling cooler
Implementation Method 3
Due to a difference between the thermal expansion coefficient of a semiconductor material of the array-type light-receiving device and the thermal expansion coefficient of a material (silicon) of the read-out circuit, a crack is introduced in the array-type light-receiving device by repeating temperature cycle
Data Source
AI summary
An array-type light-receiving device includes a semiconductor substrate having a cleavage direction; a light-receiving surface disposed on the semiconductor substrate; and a plurality of pixels two-dimensionally arranged on the light-receiving surface in a first array direction and a second array direction, each of the pixels including a staked semiconductor layer including an optical absorption layer. The first and second array directions are tilted relative to the cleavage direction of the semiconductor substrate at a predetermined angle α, as viewed from above the light-receiving surface. In addition, the first and second array directions and the cleavage direction extend along the light-receiving surface.