Ultra-Thin MOSFET Substrates Using Structural Support Coating
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Solution Overview
Problem
Current methods for producing ultra-thin substrates for vertical metal oxide field effect transistors (MOSFETs) often result in wafer breakage and high production costs, as they require grinding and cutting techniques that waste silicon and risk damaging the wafer.
Innovation Solution
A process involving a structural support coating over the gate and source pads, followed by back-side processing to thin the silicon layer, and subsequent removal of the coating to expose the pads, allowing for the wafer to be ground to less than 50 μm thickness without breaking, while maintaining low drain-source on resistance (RDS(on)) values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If grinding and cutting techniques are used to produce ultra-thin substrates, then substrate thickness is reduced, but wafer breakage and silicon waste increase
Solution Approach 1:
The patent applies preliminary action by forming the structural support coating on the wafer surface before the thinning process. This coating is deposited in advance to provide mechanical support during subsequent grinding and cutting operations, preventing wafer breakage while enabling ultra-thin substrate production
Solution Approach 2:
The structural support coating acts as an intermediary element between the grinding tools and the wafer substrate. This intermediate layer absorbs mechanical stresses during processing, protecting the fragile ultra-thin substrate from damage while allowing the thinning process to proceed
2Length of moving object
If traditional grinding methods are used to thin the wafer, then substrate thickness is reduced, but production costs increase due to multiple processing steps
Solution Approach 1:
The structural support coating is formed beforehand using a single deposition process that provides both structural support and a planar surface. This preliminary action consolidates multiple functions into one step, reducing the number of subsequent processing steps needed and lowering overall production costs
Solution Approach 2:
The structural support coating serves multiple functions simultaneously: it provides mechanical support during thinning, creates a planar surface for subsequent processing, and acts as a protective layer. This multi-functionality eliminates the need for separate processing steps, reducing manufacturing complexity and cost
3Manufacturing precision
If the wafer is ground to ultra-thin thickness, then RDS(on) values are reduced, but the wafer may break into pieces during processing
Solution Approach 1:
The structural support coating is applied before the wafer is ground to ultra-thin thickness. This preliminary protective layer maintains wafer strength during the thinning process, preventing breakage while allowing the substrate to be reduced to the thinness required for low RDS(on) values
Solution Approach 2:
The structural support coating serves as an intermediary that protects the wafer during thinning operations. It distributes mechanical stresses evenly across the wafer surface, preventing stress concentration that would cause breakage, while allowing the substrate to be ground to the precise thickness needed for optimal electrical performance
Data Source
AI summary
A method comprising: molding a structural support coating over the gate pad and source pad at the front side of a wafer; back-side processing the wafer to remove a portion of a silicon layer so that the silicon layer has a post-process thickness, wherein the post-process thickness is less than the pre-process thickness; and removing the structural support coating at the front side of the wafer sufficiently to expose the gate pad and source pad. An electronic device comprising: a silicon layer less than 50 μm thick and defining a back side of the electronic device, a metal layer on the silicon layer, wherein the metal layer defines a front side of the electronic device, wherein the metal layer has a source pad and a gate pad; and a structural support coating between the source pad and the gate pad.