Support-Layer Processing of Thin Wide Band Gap Wafers
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Solution Overview
Problem
Thin semiconductor wafers with a thickness of less than 250 μm often exhibit wafer bow or warp, making it difficult to process them fully automatically due to limitations in existing equipment, and there is a need for methods to efficiently reuse and process wide band gap semiconductor wafers.
Innovation Solution
A method involving the deposition of a non-monocrystalline support layer on the back side of a wide band gap semiconductor wafer, followed by the deposition of an epitaxial layer on the front side, allowing for the splitting of the wafer to create device wafers and remaining wafers with controlled thickness and thermal expansion coefficients, enabling further processing and reuse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a thin wide band gap semiconductor wafer is processed, then the manufacturing cost is reduced and material utilization is improved, but the wafer exhibits bow or warp making it difficult to handle automatically
Solution Approach 1:
A non-monocrystalline support layer is deposited on the back side of the thin wide band gap semiconductor wafer to serve as a mechanical support structure. This intermediary layer provides the necessary rigidity for automatic handling while allowing the front side to maintain its thin profile for device fabrication. The support layer acts as a mediator between the thin functional layer and the handling requirements.
Solution Approach 2:
The wafer structure becomes a composite system consisting of a thin monocrystalline wide band gap semiconductor layer on the front side and a non-monocrystalline support layer on the back side. This composite structure combines the electrical properties of the monocrystalline layer with the mechanical support properties of the non-monocrystalline layer, resolving the contradiction between thinness and handleability.
2Ease of operation
If a non-monocrystalline support layer is deposited on the back side, then the mechanical support and handleability are improved, but the thermal expansion mismatch may cause stress
Solution Approach 1:
The thermal expansion coefficient of the non-monocrystalline support layer is carefully selected and controlled to be within 5% of the monocrystalline wide band gap semiconductor layer. By adjusting this critical parameter, the support layer provides mechanical strength while minimizing thermal stress during processing, thus resolving the contradiction between handleability and thermal compatibility.
3Productivity
If the wafer is split to obtain thin wafers, then the productivity is improved through reuse, but the equipment capability is exceeded due to wafer bow
Solution Approach 1:
The non-monocrystalline support layer is deposited on the back side of the wafer before the splitting process. This preliminary action ensures that even after splitting into thin wafers, the resulting wafers maintain sufficient mechanical strength and flatness to be processed by standard equipment, thus enabling wafer reuse without requiring specialized equipment.
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 approach allows for the efficient handling and processing of thin wide band gap semiconductor wafers by increasing their thickness, providing mechanical support, and reducing manufacturing costs through the use of a non-monocrystalline support layer, while maintaining thermal compatibility with the monocrystalline layer, thus overcoming the limitations of existing technologies.
Implementation Method 1
A non-monocrystalline support layer is deposited at a back side of a wide band gap semiconductor wafer
Implementation Method 2
an epitaxial layer is deposited at a front side of the wide band gap semiconductor wafer
Implementation Method 3
The method comprises splitting the wide band gap semiconductor wafer along a splitting region
Implementation Method 4
A thermal expansion coefficient of the non-monocrystalline support layer differs from a thermal expansion coefficient of the monocrystalline wide band gap semiconductor layer by at most 5%
Data Source
AI summary
A method for processing a wide band gap semiconductor wafer includes: depositing a support layer including semiconductor material at a back side of a wide band gap semiconductor wafer, the wide band gap semiconductor wafer having a band gap larger than the band gap of silicon; depositing an epitaxial layer at a front side of the wide band gap semiconductor wafer; and splitting the wide band gap semiconductor wafer along a splitting region to obtain a device wafer comprising at least a part of the epitaxial layer, and a remaining wafer comprising the support layer.