Laser Marking Warped Semiconductor Wafers Using Translucent Tape
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Solution Overview
Problem
Semiconductor wafers with high warpage pose challenges for laser-marking systems, leading to vacuum errors, reduced yield, and increased manufacturing costs due to difficulties in maintaining a seal and degrading resolution on uneven surfaces.
Innovation Solution
Applying tape over solder bumps on the active surface of semiconductor wafers, grinding the backside to reduce thickness, and laser-marking through the tape to stabilize the wafer during processing, followed by tape removal post-marking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser-marking is performed on wafers with high warpage, then manufacturing process continues, but vacuum seal cannot be maintained and resolution degrades
Solution Approach 1:
A carrier wafer is introduced as an intermediary substrate to support the bumped wafer during laser-marking. The carrier wafer provides a flat, vacuum-compatible surface while the bumped wafer remains positioned above it, allowing the laser to mark through the carrier material without compromising vacuum seal or marking resolution.
Solution Approach 2:
The solution transitions from attempting to mark the warped wafer surface directly to marking through a flat carrier wafer in a different dimensional configuration. This allows the laser beam to traverse a uniform path length and maintain focus while the bumped wafer retains itsWarped state for subsequent processing.
2Productivity
If laser-marking is performed on wafers with high warpage, then manufacturing process continues, but marking resolution degrades
Solution Approach 1:
The carrier wafer serves as a mediator that provides a flat marking surface, allowing high-resolution laser-marking to be achieved while the bumped wafer maintains its original warped configuration for subsequent assembly processes.
Solution Approach 2:
The marking is effectively copied onto the carrier wafer rather than directly onto the bumped wafer surface. This optical copying approach allows precise marking to be achieved on a flat surface while the actual bumped wafer remains unchanged for its intended function.
3Stability of the object's composition
If tape is applied over solder bumps to reduce warpage, then wafer stability improves, but tape must be removed after processing
Solution Approach 1:
Tape is applied in advance to the bumped wafer surface to stabilize it during the laser-marking process. This preliminary action prevents warpage-related issues during marking, and the tape is subsequently removed as a simple final step, adding minimal complexity to achieve significant process improvement.
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 allows for effective laser-marking of warped wafers by reducing warpage and improving resolution, enabling the laser-marking system to maintain a vacuum and enhance processing efficiency, thereby reducing manufacturing costs and increasing yield.
Implementation Method 1
laser-marking the backside of the semiconductor wafer
Implementation Method 2
grinding a backside of the semiconductor wafer, opposite the active surface, to reduce wafer thickness
Data Source
AI summary
A method of laser-marking a semiconductor device involves providing a semiconductor wafer having a plurality of solder bumps formed on contact pads disposed on its active surface. The solder bumps have a diameter of about 250-280 μm. A backgrinding tape is applied over the solder bumps. The tape is translucent to optical images. A backside of the semiconductor wafer, opposite the active surface, undergoes grinding to reduce wafer thickness. The backside of the semiconductor wafer is laser-marked while the tape remains applied to the solder bumps. The laser-marking system including an optical recognition device, control system, and laser. The optical recognition device reads patterns on the active surface through the tape to control the laser. The tape reduces wafer warpage during laser-marking to about 0.3-0.5 mm. The tape is removed after laser-marking the backside of the semiconductor wafer.