Transparent SOI Wafer Production via Laser Periphery Cutting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for producing transparent SOI wafers face challenges with thick silicon films, as conventional bonding-and-etch-back methods risk surface damage and chipping due to differences in thermal expansion coefficients between donor and handle wafers, especially when using SOQ or SOS wafers.
Innovation Solution
A method involving bonding a silicon wafer to a transparent handle wafer, followed by a first heat treatment at 150-300°C, cutting off the unbonded periphery using a visible light laser at a specific angle, and then grinding or polishing to form a silicon film, followed by a second heat treatment at 300-500°C to enhance bonding strength and prevent chipping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the bonding-and-etch-back method is used to form a thick silicon film (greater than 1 μm), then the silicon film thickness can be achieved, but the surface of the silicon film is damaged due to increased acceleration voltage during ion implantation or chipping occurs during grinding/polishing
Solution Approach 1:
The patent applies preliminary action by performing a first heat treatment at 150-300°C before the main bonding process to enhance adhesion between the silicon wafer and handle wafer. This preliminary bonding step ensures that subsequent grinding and polishing operations do not cause chipping, as the wafer is already securely bonded. The method also performs preliminary peripheral removal before bonding to prevent edge-related defects during later processing steps.
Solution Approach 2:
The patent utilizes parameter changes by implementing a two-stage heat treatment process with different temperature ranges (150-300°C for adhesion enhancement, 300-500°C for bonding strength enhancement). This staged temperature approach allows progressive strengthening of the bond without causing thermal shock or surface damage that would occur with a single high-temperature step.
2Ease of manufacture
If wafers are bonded without sufficient heat treatment, then the bonding process can be completed, but the bonded wafer is damaged due to difference in coefficient of thermal expansion between donor wafer and handle wafer
Solution Approach 1:
The patent applies parameter changes by implementing a two-stage heat treatment process with different temperature ranges (150-300°C for adhesion enhancement, 300-500°C for bonding strength enhancement). This staged temperature approach allows progressive strengthening of the bond without causing thermal shock or surface damage that would occur with a single high-temperature step.
Solution Approach 2:
The patent applies preliminary action by performing a first heat treatment at 150-300°C before the main bonding process to enhance adhesion between the silicon wafer and handle wafer. This preliminary bonding step ensures that subsequent grinding and polishing operations do not cause chipping, as the wafer is already securely bonded. The method also performs preliminary peripheral removal before bonding to prevent edge-related defects during later processing steps.
3Manufacturing precision
If the periphery of the wafer is mechanically or chemically removed before sufficient heat treatment, then chipping can be prevented, but bonding strength is insufficient causing unnecessary portions to be removed
Solution Approach 1:
The patent applies preliminary action by performing a first heat treatment at 150-300°C before the main bonding process to enhance adhesion between the silicon wafer and handle wafer. This preliminary bonding step ensures that subsequent grinding and polishing operations do not cause chipping, as the wafer is already securely bonded. The method also performs preliminary peripheral removal before bonding to prevent edge-related defects during later processing steps.
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 method effectively prevents wafer damage and chipping, allowing for the production of high-quality transparent SOI wafers by optimizing the bonding process and thermal treatments.
Implementation Method 1
cutting off an unbonded portion of the bonded wafer by irradiating a visible light laser from a silicon wafer side of the heat-treated bonded wafer to a boundary between a bonded surface portion and an unbonded surface portion
Implementation Method 2
heat-heating the bonded wafer at a first temperature of 150 to 300°C as a first heat treatment... heat-treating the bonded wafer having the silicon film formed at a second temperature of 300 to 500°C as a second heat treatment which is higher than the first temperature
Data Source
Figure 1(A)~1(B)
Figure 2(A)~2(F)
Figure 3
AI summary
A method for producing a transparent SOI wafer by which wafer damage and chipping can be prevented is provided. The method for producing a transparent SOI wafer comprises the steps of: bonding a surface of a silicon wafer used as a donor wafer and a surface of a transparent handle wafer together to obtain a bonded wafer; heat-treating the bonded wafer at a first temperature of 150 to 300°C as a first heat treatment; cutting off an unbonded portion of the bonded wafer by irradiating a visible light laser from a silicon wafer side of the heated bonded wafer to a boundary between the bonded surface and an unbonded circumferential surface, while keeping an angle of 60 to 90° between the incident light and a radial direction of the silicon wafer; subjecting the silicon wafer of the bonded wafer having the unbonded portion cut off to grinding, polishing, or etching to form a silicon film; and heat-treating the bonded wafer having the silicon film formed at a second temperature of 300 to 500°C as a second heat treatment which is higher than the first temperature.