Polymer Hybrid Wafer Splitting for Kerf-Free Thickness Control
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Solution Overview
Problem
Current wafer production methods, such as sawing or tearing, result in significant material loss and surface damage, leading to inefficiencies and increased costs, particularly in the production of silicon wafers for solar cells, where up to 50% of the material is lost as 'kerf loss, and wafers often exhibit thickness fluctuations and surface damage that hinder further processing.
Innovation Solution
A polymer hybrid material comprising a polymer matrix, a metal filler, and core-shell polymer particles is used to generate thermal stresses for splitting wafers without kerf loss, with the filler accelerating polymer detachment and improving adhesion and thermal conductivity, allowing for faster and more controlled separation with reduced damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional sawing or tearing processes are used to produce wafers from ingots, then wafers can be manufactured, but significant material loss occurs (up to 50% kerf loss) and surface damage is caused
Solution Approach 1:
The patent replaces the conventional mechanical sawing or tearing process with a thermal splitting process. A polymer layer with high thermal expansion coefficient is applied to the workpiece, and through controlled cooling, thermal stresses are generated that cause the material to split along the desired wafer thickness without mechanical contact, thereby eliminating kerf loss and surface damage
Solution Approach 2:
The patent exploits the thermal expansion properties of materials, specifically using a polymer layer with a coefficient of thermal expansion approximately two orders of magnitude higher than the workpiece. By cooling the polymer-workpiece system, thermal contraction differences generate sufficient stresses to enable wafer separation without material loss
2Object-affected harmful factors
If conventional sawing processes are used, then wafers can be produced, but surface damage occurs requiring additional treatment steps
Solution Approach 1:
The patent replaces mechanical cutting with thermal stress-induced splitting, which inherently avoids surface damage since no mechanical contact or cutting edges are involved in the separation process
Solution Approach 2:
The patent converts the typically harmful thermal expansion differences between materials into a beneficial force. The large thermal expansion coefficient mismatch between the polymer layer and workpiece, which could cause stress and damage, is instead exploited to generate controlled thermal stresses that enable clean, damage-free wafer separation
3Loss of substance
If polymer layers are used to generate thermal stresses for wafer separation, then kerf-free wafering is achieved, but strong wafer curvature occurs making controlled separation difficult and causing thickness fluctuations
Solution Approach 1:
The patent uses a composite structure consisting of a polymer layer with specific properties (high thermal expansion coefficient, appropriate glass transition temperature) applied to the workpiece. This composite system enables controlled thermal stress generation while the polymer's mechanical properties can be tuned to minimize excessive curvature and improve thickness uniformity
Solution Approach 2:
The patent optimizes key parameters of the polymer layer, including its coefficient of thermal expansion, glass transition temperature, and thickness, to achieve the desired balance between generating sufficient thermal stresses for separation and minimizing excessive wafer curvature. By carefully selecting and adjusting these parameters, the process achieves both kerf-free separation and improved thickness control
4Force
If polymer layers with high thermal expansion coefficients are used, then thermal stresses can be generated for wafer separation, but the polymer adheres strongly to the wafer making removal difficult and causing curvature
Solution Approach 1:
The patent carefully selects polymers with specific glass transition temperatures and thermal expansion coefficients that enable sufficient thermal stress generation for wafer separation while allowing easier polymer removal. The glass transition temperature is particularly critical, as it affects the polymer's mechanical properties and adhesion characteristics at different temperatures
Solution Approach 2:
The patent applies the polymer layer with controlled local properties, including varying thickness and composition, to optimize both the thermal stress generation and the subsequent polymer removal. The polymer layer's properties are tailored to provide sufficient adhesion during the splitting process while facilitating easier removal afterward
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 enhances the overall yield by minimizing material loss and surface damage, achieving precise thickness control and improved mechanical properties, thus reducing production costs and increasing the quality of the wafers produced.
Implementation Method 1
the polymer layer has a coefficient of thermal expansion that is approximately two orders of magnitude higher than that of the workpiece. In addition, by exploiting a glass transition, a relatively high modulus of elasticity 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
One of the fillers consists of at least one metal and causes improved thermal conductivity within the polymer hybrid material
Implementation Method 3
by exploiting a glass transition, a relatively high modulus of elasticity 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
Figure 1A~1C
Figure 2A~2C
Figure 3A~4
AI summary
The invention relates to a polymer hybrid material, to a film comprising the polymer hybrid material, to the use of the polymer hybrid material, to a splitting method using the polymer hybrid material, and to a method for producing the polymer hybrid material. The aim of the invention is to provide the possibility of increasing the total yield, i.e. the efficiency with respect to the raw materials used and other resources such as energy and workforce, of a splitting method. According to the invention, this is provided by a polymer hybrid material for use in a splitting method, wherein at least two solid-body sections are produced from a solid-body starting material. The polymer hybrid material according to the invention comprises a polymer matrix and a first filler and a second filler embedded into the polymer matrix.