Wafer Backside Recess for Penetrating Electrode Exposure
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Solution Overview
Problem
The manufacturing of semiconductor chips with penetrating electrodes faces challenges in handling and processing due to wafer thinning, which leads to fragility and increased yield loss, and existing methods struggle to form insulating films around exposed electrodes without covering the electrode tops, causing conduction failures.
Innovation Solution
A method involving protective tape application, selective grinding to create a recessed area on the wafer backside, plasma etching to expose electrodes, and resin coating followed by cutting to form a flat insulating film around the electrodes, ensuring wafer rigidity and preventing conduction failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the semiconductor wafer is thinned by grinding the back-side surface to expose penetrating electrodes, then the electrodes can be exposed for secure electrical connection, but the wafer becomes too thin to handle, leading to cracking and reduced yield
Solution Approach 1:
The wafer back surface is divided into two regions: a ground recessed part where electrodes are exposed, and an unground outer peripheral marginal region that maintains original thickness for strength. This segmentation allows simultaneous achievement of electrode exposure and wafer strength maintenance.
Solution Approach 2:
Different regions of the wafer back surface are given different properties: the central device formation region is ground to expose electrodes, while the outer peripheral marginal region is left unground to maintain structural strength. Each region has optimized quality for its specific function.
2Productivity
If spin coating technique is used to form insulating film on the back side of the wafer, then the resin can be applied efficiently, but the resin flows over the electrodes and covers them, causing conduction failure
Solution Approach 1:
The wafer back surface is pre-ground to create a recessed part before applying the insulating resin. This preliminary action creates a geometric structure that prevents resin flow from covering the electrodes, ensuring electrode exposure is maintained throughout the coating process.
Solution Approach 2:
The recessed part structure creates different local conditions: the resin is contained within the recessed area away from electrode tops, while the outer peripheral region remains elevated. This local geometric differentiation ensures proper resin distribution without electrode coverage.
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 enhances wafer handling and processing, reduces yield loss by maintaining wafer rigidity, and ensures secure electrical connections by forming insulating films around the electrodes, thereby improving productivity and yield.
Implementation Method 1
the back-side surface of the wafer is ground so that a recessed part is formed on the back side
Implementation Method 2
the back-side surface is subjected to plasma etching or the like so that a small thickness thereof is removed
Data Source
AI summary
A method of machining a wafer in which, at the time of grinding the back-side surface of the wafer, only a back-side surface region corresponding to a device formation region where semiconductor chips are formed is thinned by grinding, to form a recessed part on the back side of the wafer. An annular projected part surrounding the recessed part is utilized to secure rigidity of the wafer. Next, the recessed part is etched to cause metallic electrodes to project from the bottom surface of the recessed part, thereby forming a back-side electrode parts, then an insulating film is formed in the recessed part, and the insulating film and end surfaces of the back-side electrode parts are cut.