Stacked Substrate Structure for Low-Damage Laser Cleavage
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Solution Overview
Problem
The separation of a support substrate in semiconductor devices can cause lattice defects and damage to the semiconductor substrate due to thermal expansion during the cleavage process, which limits the reusability of the support substrate.
Innovation Solution
A stacked substrate design is employed, featuring a semiconductor substrate with a phosphorus-doped polysilicon layer and a thinner insulating layer, which absorbs laser energy to thermally expand and cleave, minimizing heat transfer to the semiconductor substrate, thereby reducing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the support substrate is thermally expanded by laser irradiation to separate it from the semiconductor substrate, then the support substrate can be cleaved and separated, but lattice defects and damage occur in the support substrate
Solution Approach 1:
A sacrificial insulating layer is introduced as an intermediary between the support substrate and the semiconductor substrate. This layer absorbs the thermal expansion stress and serves as a sacrificial element that protects the support substrate from direct damage during laser-induced separation, enabling clean cleavage while preserving the support substrate for reuse
Solution Approach 2:
The thermal conductivity parameter of the insulating layer is specifically controlled to be lower than that of the support substrate. This parameter difference creates a thermal gradient during laser irradiation that confines thermal expansion to the insulating layer, preventing heat transfer to the support substrate and avoiding lattice defects
2Object-affected harmful factors
If a thick insulating layer is used to protect the support substrate, then damage is reduced, but the support substrate cannot be effectively separated
Solution Approach 1:
The insulating layer thickness and thermal conductivity are optimized to specific ranges. The thickness is controlled to be sufficient to absorb thermal expansion (preventing direct contact damage) but not so thick as to prevent effective stress transmission for cleavage. The thermal conductivity is specifically lowered to confine thermal effects while maintaining mechanical coupling for separation
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 allows for efficient separation of the support substrate with reduced damage to the semiconductor substrate, enabling its reuse and maintaining device integrity.
Implementation Method 1
a phosphorus-doped polysilicon layer and a thinner insulating layer, which absorbs laser energy to thermally expand and cleave
Implementation Method 2
the support substrate on the insulating layer side is thermally expanded by irradiation with a laser beam or the like
Data Source
AI summary
A stacked substrate of an embodiment is a stacked substrate for separating a semiconductor substrate using thermal expansion by a laser beam, the stacked substrate including the semiconductor substrate, a first insulating layer disposed above the semiconductor substrate, and a polysilicon layer that is disposed in contact with the first insulating layer, a thickness of the polysilicon layer being larger than a thickness of the first insulating layer in a direction perpendicular to a surface of the semiconductor substrate, and the polysilicon layer being doped with phosphorus.