Wafer Grinding Thermal Deformation Control
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Solution Overview
Problem
Conventional wafer grinding methods struggle to achieve uniform thickness due to thermal deformation of the chuck table during processing, particularly when aiming for in-plane thickness differences of 0.1 μm or thinner, as the tilt adjustment between the chuck table and grindstone is insufficient to maintain uniformity.
Innovation Solution
A wafer grinding apparatus and method that includes a chuck table with a conical holding surface, a table rotation mechanism, a grinding unit, a lifting/lowering mechanism, a thickness measuring instrument, and a jetting nozzle for applying cold or warm water to the wafer, allowing for controlled contraction or swelling of the wafer to achieve uniform thickness by adjusting the grinding amount based on measured thickness variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If tilt adjustment between chuck table and grindstone is used to maintain uniform thickness, then manufacturing precision is improved, but thermal deformation of the chuck table causes the thickness uniformity to deteriorate during processing
Solution Approach 1:
The invention changes the physical state of the wafer by controlling its temperature through heating or cooling. By adjusting the temperature parameter, the wafer undergoes thermal expansion or contraction to compensate for thickness variations caused by chuck table deformation, thereby maintaining uniform thickness during grinding
Solution Approach 2:
The invention applies preliminary heating or cooling to the wafer before grinding to induce thermal expansion or contraction that counteracts the expected thickness variations. This preliminary anti-action compensates for the detrimental effects of chuck table thermal deformation before the grinding process begins
2Productivity
If the chuck table accumulates processing heat, then the processing continues, but thermal deformation increases and causes thickness non-uniformity
Solution Approach 1:
The invention implements continuous temperature control of the wafer during the entire grinding process. By continuously heating or cooling the wafer, the system maintains the wafer at the appropriate temperature throughout processing, preventing thickness variations even as the chuck table accumulates heat over extended operation
Solution Approach 2:
The invention dynamically adjusts the temperature parameter of the wafer during continuous processing. By changing the temperature to induce thermal expansion or contraction, the system compensates for cumulative thermal deformation effects, allowing continuous operation 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
The method effectively reduces in-plane thickness differences by using water jetting to adjust the grinding amount, ensuring the wafer achieves uniform thickness across its surface after processing, even when thermally deformed, by heating or cooling specific areas to match the thickness of other areas.
Implementation Method 1
at least a portion of the wafer is caused to contract or swell in a ring shape by a rotation operation of the chuck table by the table rotation mechanism and the cold water or the warm water jetted from the jetting nozzle
Implementation Method 2
grinding the wafer by a lower surface of an annular grindstone that is caused to come into contact with a radial portion of the wafer
Data Source
AI summary
A wafer grinding method includes a first grinding step of grinding a first wafer for testing held on a chuck table to a finishing thickness, a thickness measuring step of measuring, at a plurality of locations in a radial direction, a thickness of the first wafer ground in the first grinding step, a nozzle positioning step of positioning a jetting nozzle directly above a portion of the first wafer having a thickness that is one of the thicknesses of the first wafer measured at the plurality of locations in the thickness measuring step and that is either greater or smaller than a reference thickness set beforehand, and a second grinding step of grinding a second wafer that is next held on the chuck table, while jetting cold water or warm water from the jetting nozzle to the second wafer.