Solid Body Layer Separation via Thermal Stress and Defect Guidance
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Solution Overview
Problem
Current methods for producing thin wafers, such as those used in microelectronic and photovoltaic technology, result in significant material loss and thickness variations, making them costly and unsuitable for many applications, while alternative methods like ion implantation are expensive and complex.
Innovation Solution
A method involving the introduction of defects in a solid body to determine detachment planes, followed by the application of heat to generate mechanical stresses for controlled separation of layers, allowing for the production of wafers with reduced thickness variations and minimal material waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional sawing methods are used to produce thin wafers, then the separation process is simple and straightforward, but significant material loss occurs (kerf loss of almost 50%)
Solution Approach 1:
The patent changes the physical state and temperature parameters of the polymer layer to induce stress. By cooling the polymer layer below its glass transition temperature, the material becomes brittle and generates sufficient stress to propagate cracks along the detachment plane, enabling kerf-free separation without complex mechanical sawing equipment
Solution Approach 2:
The patent utilizes the glass transition phase change of the polymer layer. By cooling the polymer below its glass transition temperature, it transitions from a rubbery state to a glassy state, dramatically increasing its elastic modulus and enabling it to generate the necessary stress for crack propagation and wafer separation
2Stress or pressure
If polymer layers with high thermal expansion coefficient are used to induce stress, then sufficient stress can be generated for separation, but strong wafer bending occurs making controlled separation difficult and causing thickness variations
Solution Approach 1:
The patent introduces localized defects at specific positions within the solid body to serve as crack initiation sites. By controlling where defects are introduced, the crack propagation can be guided along a predetermined detachment plane, preventing uncontrolled bending and ensuring uniform wafer thickness during separation
Solution Approach 2:
The patent performs preliminary defect introduction into the solid body before the stress-induced separation process. These pre-introduced defects act as nucleation sites that guide crack propagation along the desired detachment plane, ensuring controlled separation and preventing unwanted wafer bending during the subsequent stress application
3Manufacturing precision
If ion implantation method is used to produce detachment planes, then precise control over separation is achieved, but the process becomes extremely costly and complex
Solution Approach 1:
The patent replaces expensive ion implantation equipment with a simple defect introduction mechanism that can be implemented using conventional manufacturing techniques. The defect introduction process uses affordable methods such as mechanical scratching, chemical etching, or laser marking, eliminating the need for costly ion cannons while achieving comparable precision in detachment plane formation
Solution Approach 2:
The patent replaces the complex ion implantation process with a simpler mechanical or chemical defect introduction method. Instead of using high-energy ion beams to create detachment planes, the invention uses straightforward mechanical scratching, chemical etching, or thermal field application to introduce defects that guide crack propagation, dramatically simplifying the equipment required
4Loss of substance
If polymer layer is used for stress induction, then kerf-free separation is achieved, but undesirable oscillations occur during break propagation leading to thickness variations
Solution Approach 1:
The patent introduces localized defects at specific positions within the solid body to serve as crack initiation sites. By controlling where defects are introduced, the crack propagation can be guided along a predetermined detachment plane, preventing uncontrolled bending and ensuring uniform wafer thickness during separation
Solution Approach 2:
The patent uses introduced defects as intermediary elements that mediate between the applied stress and the crack propagation. These defects act as controlled nucleation sites that guide the break front along the desired path, preventing oscillations and ensuring smooth, uniform separation without the thickness variations caused by uncontrolled crack behavior
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
Enables the inexpensive production of wafers with even thickness and reduced total thickness variation, improving the efficiency and cost-effectiveness of wafer production while allowing for precise control over the separation process.
Implementation Method 1
The polymer layer has a thermal expansion coefficient that is higher by approximately two orders of magnitude in comparison to the workpiece. Moreover, by utilising a glass transition a relatively high elasticity modulus can be achieved in the polymer layer so that sufficiently large stresses can be induced in the polymer layer workpiece layer system by cooling
Implementation Method 2
by utilising a glass transition a relatively high elasticity modulus can be achieved in the polymer layer so that sufficiently large stresses can be induced in the polymer layer workpiece layer system by cooling
Data Source
AI summary
Providing a solid body to be split into a number of layers of solid material, introducing or generating defects in the solid body in order to determine a first detachment plane (8) along which a first layer of solid material is separated from the solid body, providing a receiving layer for holding the layer of solid material on the solid body, applying heat to the receiving layer in order to generate, in particular mechanically, stresses in the solid body, due to the stresses a crack propagating in the solid body along the detachment plane, which crack separates the first layer of solid material from the solid body, then providing a second receiving layer for holding another layer of solid material on the solid body reduced by the first layer of solid material, introducing or generating defects in the solid body in order to determine a second detachment plane (9) along which a second layer of solid material is separated from the solid body, applying heat to the second receiving layer in order to generate, in particular mechanically, stresses in the solid body, due to the stresses a crack propagating in the solid body along the second detachment plane, which crack separates the second layer of solid material from the solid body.