Thermocompression Bonding Sheet Planarization for Clean Chip Support
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Solution Overview
Problem
In the process of fabricating device chips, residues of the adhesive layer from the tape used in thermocompression bonding can remain on the chips, leading to failures, and the lack of close contact between the workpiece and the sheet with projections and depressions results in inadequate support and contamination during processing.
Innovation Solution
A method involving thermocompression bonding a sheet with no adhesive layer at the device region to the workpiece, using a flat plate to planarize the sheet and ensure close contact, while heating and applying external force to fill the spaces between the workpiece and sheet, allowing for precise imaging and processing without chip separation or contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a tape with adhesive layer is used to bond the workpiece, then the workpiece can be held and processed, but residues of the adhesive layer remain on the device chips causing failures
Solution Approach 1:
The adhesive layer is extracted and removed from the sheet, leaving only the non-adhesive protective layer that contacts the device region. This eliminates the source of adhesive residues while maintaining the sheet's ability to protect and support the workpiece during processing.
Solution Approach 2:
The sheet is functionally segmented into different regions: the device region with no adhesive layer for clean contact, and the outer peripheral margin region with adhesive layer for bonding to the frame. This segmentation allows the adhesive to be positioned only where needed for structural purposes.
2Reliability
If a sheet with no adhesive layer is used at the device region, then adhesive residues are prevented, but spaces are formed between the sheet and workpiece at depressions causing inadequate support
Solution Approach 1:
The sheet undergoes thermocompression bonding where temperature and pressure parameters are changed to soften the sheet material, allowing it to deform and fill the depression spaces on the workpiece surface, thereby providing adequate support while maintaining clean contact at the device region.
Solution Approach 2:
The sheet is pre-formed with a thickness greater than the depth of depressions before bonding. This preliminary preparation ensures that when the sheet is bonded to the workpiece, it can naturally fill the depression spaces and provide uniform support across the entire device region.
3Ease of operation
If spaces are formed between the sheet and workpiece, then the sheet cannot be brought into close contact, but cutting fluid penetrates into the spaces causing contamination
Solution Approach 1:
Thermocompression bonding applies heat and pressure to change the physical state of the sheet material, making it pliable enough to conform to the workpiece surface topology. This eliminates spaces where cutting fluid could penetrate, preventing contamination while allowing the sheet to maintain close contact throughout the device region.
4Strength
If the sheet is brought into close contact with the workpiece, then support is improved, but steps are generated on the sheet side that simulate projections and depressions of the workpiece
Solution Approach 1:
The thermocompression bonding process applies controlled heat and pressure that soften the sheet material, allowing it to conform to the workpiece surface. The resulting steps on the sheet's rear surface are acceptable because they do not interfere with the primary function of close contact support, and the sheet's front surface remains in intimate contact with the workpiece.
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 prevents adhesive residues, ensures firm contact between the workpiece and sheet, reducing chip and crack formation, and maintains cleanliness by eliminating spaces for debris penetration during processing.
Implementation Method 1
heating the sheet and applying an external force to the stack
Implementation Method 2
the sheet is heated and softened, and a predetermined external force is applied to the sheet and the workpiece
Implementation Method 3
a predetermined external force is applied to the sheet and the workpiece
Implementation Method 4
applying an external force to the stack
Implementation Method 5
a device to enable imaging of the front side of the workpiece from below through the holding table
Data Source
AI summary
A thermocompression bonding method for thermocompression bonding a sheet to a workpiece, where the method includes a stacking step of placing the sheet between a flat plate and the workpiece to form a stack in which the sheet is held between the workpiece and an entire surface of the flat plate and a thermocompression bonding step of thermocompression bonding the sheet to the workpiece while planarizing the sheet with the flat plate by heating the sheet and applying an external force to the stack, after performing the stacking step.