Laser Separation of Solid-Phase Bonded Wafer Support Substrate
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Solution Overview
Problem
The challenge lies in processing semiconductor wafers without substantial cracking, especially when wafer thickness is below a certain limit, leading to increased warp and crystal defects during high-temperature processing, and existing methods for separating support substrates from solid-phase bonded wafers are not efficient, resulting in material wastage and high costs.
Innovation Solution
A method involving the formation of a breaking layer using laser light with a wavelength that can pass through the wafer, focused on the solid-phase bonding interface, to facilitate easy separation of the support substrate, along with steps for bonding interface separation, allowing for wafer processing without cracking and reducing material loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a thin wafer is used in the initial stage of processing, then manufacturing efficiency is improved, but wafer cracking increases due to stress caused by heat
Solution Approach 1:
A support substrate is introduced as an intermediary element bonded to the back surface of the thin wafer. This support substrate provides mechanical strength and thermal stability during high-temperature processing, preventing wafer cracking while allowing the thin wafer to be used from the initial stage, thereby improving manufacturing efficiency
Solution Approach 2:
The support substrate is bonded to the wafer back surface before any processing steps are performed. This preliminary reinforcement allows the thin wafer to withstand subsequent high-temperature processing without cracking, enabling the use of thin wafers from the very beginning of the manufacturing process
2Reliability
If a thick wafer is used in the initial stage to prevent cracking, then wafer reliability is improved, but material wastage increases due to excessive thickness removal
Solution Approach 1:
The support substrate serves as a temporary reinforcement that allows thin wafers to be used without cracking. Since the support substrate is removed after processing, only the minimal necessary material is removed from the wafer itself, significantly reducing material wastage compared to starting with thick wafers
Solution Approach 2:
The wafer thickness parameter is optimized to be thin (avoiding material wastage) while the support substrate provides the necessary mechanical and thermal parameters for crack prevention during processing
3Strength
If solid-phase bonding is used to bond support substrate to wafer, then bonding strength is improved, but separation difficulty increases
Solution Approach 1:
The bonding interface is segmented into two functional zones: a large-area bonding region for strong adhesion during processing, and a peripheral breaking layer region for easy separation. This segmentation allows the bonded structure to be strong during use but easily separable when needed
Solution Approach 2:
Different regions of the bonding interface have different properties: the central bonding area has high bond strength for structural integrity, while the peripheral region has reduced bond strength (breaking layer) designed for controlled separation, achieving both strong bonding and easy separation
4Ease of manufacture
If laser light is focused on the bonding interface to form a breaking layer, then separation ease is improved, but energy consumption increases
Solution Approach 1:
The laser energy is extracted and concentrated only at the peripheral bonding interface region where the breaking layer is formed, rather than heating the entire wafer or bonding interface. This localized energy application achieves separation ease while minimizing overall energy consumption
Solution Approach 2:
The mechanical separation process is replaced by optical field action (laser irradiation) that selectively forms a breaking layer at the bonding interface, reducing the energy required compared to mechanical force application
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 enables the use of thinner wafers in the initial stages of processing, reducing the risk of cracking, material wastage, and costs by allowing for effective separation of support substrates, thus improving the efficiency and cost-effectiveness of semiconductor device manufacturing.
Implementation Method 1
irradiating the Si wafer with laser light which uses light with a wavelength which can pass through the Si wafer and which is focused on a solid-phase bonding interface
Implementation Method 2
laser light which uses light with a wavelength which can pass through the Si wafer and which is focused on a solid-phase bonding interface
Data Source
AI summary
A method is disclosed for separating a support substrate from a solid-phase bonded wafer which includes a Si wafer and support substrate solid-phase bonded to back surface of the Si wafer. The method includes a step of irradiating the Si wafer with laser light with a wavelength which passes through the Si wafer and is focused on a solid-phase bonding interface between the Si wafer and support substrate to form a breaking layer in at least part of an outer circumferential portion of the solid-phase bonding interface, a step of separating the breaking layer; and a step of separating the solid-phase bonding interface. The method is capable of using a Si thin wafer without substantial wafer cracking at an initial stage where the wafer is inputted to a wafer process, capable of separating a support substrate from the Si thin wafer easily, and capable of reducing the wafer cost.