Wire Saw Wafer Slicing with Thermal Roller Position Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional wire saw methods for separating slices, such as lap slicing and grind slicing, face limitations in achieving precise plane-parallelism and flatness of wafers, particularly in the semiconductor industry, due to inherent limitations in controlling the relative positions of the wire frame and workpiece during cutting processes.
Innovation Solution
The method involves using a wire saw with a wire gate made of moving wire sections and an adjusting device, where the wire guide rollers are mounted between fixed and floating bearings. The method includes tempering the fixed bearings with a cooling liquid based on a temperature profile correlated with the cutting depth to adjust the floating bearing's displacement, and simultaneously displacing the workpiece along its axis using an actuator, to minimize shape deviations. This approach combines wire guide temperature control (WGTC) and ingot positioning control (IPC) to achieve precise axial displacement and shape correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional wire saw methods (lap slicing or grind slicing) are used, then the basic separation function is achieved, but the plane-parallelism and flatness of wafers cannot be precisely controlled
Solution Approach 1:
The patent applies parameter changes by controlling the temperature of the fixed bearing through cooling liquid flow rate adjustments. This thermal parameter change causes controlled thermal expansion/contraction of the fixed bearing, which in turn adjusts the axial position of the wire guide roller to compensate for shape deviations in the workpiece, thereby improving wafer plane-parallelism and flatness
Solution Approach 2:
The patent replaces direct mechanical adjustment mechanisms with a thermal field-based adjustment system. Instead of using complex mechanical actuators to position the wire guide roller, the system uses temperature-controlled thermal expansion of the fixed bearing to achieve precise positional control, simplifying the mechanical structure while improving control precision
2Manufacturing precision
If the position of wire guide rollers is kept fixed relative to the workpiece, then the control system is simple, but shape deviations cannot be corrected
Solution Approach 1:
The patent implements feedback control by measuring the shape deviation of the workpiece (such as bow or curvature) and using this information to adjust the cooling liquid flow rate to the fixed bearing. The feedback loop continuously monitors workpiece shape and dynamically adjusts the wire guide roller position through thermal control to compensate for detected deviations, ensuring high shape accuracy
Solution Approach 2:
The system dynamically changes the temperature parameter of the fixed bearing based on measured shape deviations. By adjusting the cooling liquid flow rate, the system varies the thermal state of the fixed bearing, which translates to axial position adjustments of the wire guide roller that counteract the measured shape deviations in real-time
3Manufacturing precision
If thermal control of fixed bearing is used to displace wire guide rollers, then low-frequency shape deviations are corrected, but response time is comparatively slow
Solution Approach 1:
The patent merges two different control mechanisms: thermal control of the fixed bearing for low-frequency, large-amplitude shape deviations, and mechanical actuation of the floating bearing for high-frequency, small-amplitude corrections. This combined approach leverages the strengths of both systems to achieve comprehensive shape control across different frequency ranges
Solution Approach 2:
The control system is segmented into two independent control paths: one controlling the fixed bearing temperature for low-frequency deviations, and another controlling the floating bearing position for high-frequency deviations. This segmentation allows each subsystem to operate in its optimal performance range without interfering with the other
4Manufacturing precision
If axial displacement of wire guide rollers is increased to correct shape deviations, then flatness improves, but the range and amplitude of displacement are limited
Solution Approach 1:
The patent combines the displacement effects of two independent control mechanisms: thermal expansion of the fixed bearing and mechanical actuation of the floating bearing. By merging these two displacement sources, the system achieves a greater total displacement range and amplitude than either mechanism could provide alone, enabling correction of larger shape deviations while maintaining precision
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 significantly improves the amplitude and range of displacement of the wire guide rollers relative to the workpiece, allowing for greater control over shape deviations, with WGTC addressing low-frequency deviations and IPC handling high-frequency ones, resulting in improved flatness and plane-parallelism of the separated discs.
Implementation Method 1
tempering the fixed bearing with a cooling liquid
Implementation Method 2
a thermal increase or decrease in length of the wire guide roller is brought about until the measured change in position of the reference surface is balanced again
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A method for cutting a plurality of discs from workpieces (4) using a wire saw during a sequence of cutting operations subdivided into initial cuts and subsequent cuts, wherein the wire saw comprises a wire frame (2) made of moving wire segments of a saw wire (3) and a positioning device (12), and the wire frame (2) is clamped in a plane between two wire guide rollers (1), each of the two wire guide rollers (1) being mounted between a fixed bearing (5) and a floating bearing (6). The method comprises, during each of the cutting operations, feeding the respective workpiece (4) through the wire frame (2) by means of the positioning device (12) along a feeding direction perpendicular to a workpiece axis and perpendicular to the plane of the wire frame (2) in the presence of a working fluid and hard materials that act abrasively on the workpiece (4).characterized by the following during each of the cutting operations: feeding the workpiece (4) through the wire screen (2) while simultaneously axially displacing the floating bearings (6) by tempering the fixed bearings (5) with a cooling fluid according to a specified temperature profile, which specifies the temperature of the cooling fluid as a function of a cutting depth and correlates with a first correction profile, which specifies the displacement of the floating bearings (6) as a function of the cutting depth; and feeding the workpiece (4) through the wire screen (2) while simultaneously displacing the workpiece (4) along the workpiece axis by means of an adjusting element (15) according to a second correction profile, which specifies the displacement of the workpiece (4), wherein the first and second correction profiles are directed against a form deviation; and determining the form deviation during each of the cutting operations and/or before each of the cutting operations.