Back Face Gettering Layer for Semiconductor Chip Thinning
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Solution Overview
Problem
In semiconductor manufacturing, heavy-metal contamination during the second-half process, particularly in multi-chip packages, leads to defects in gate insulation films and reduced device yield due to the loss or thinning of gettering layers formed in the first-half process.
Innovation Solution
A semiconductor chip with a gettering layer formed on its back face, achieved by mechanically grinding the back face using a silica material to create a damaged layer, which effectively traps heavy metals during the second-half process, even when the chip thickness is reduced to 100 μm or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the wafer thickness is thinned to raise integration degree in multi-chip packages, then the device integration is improved, but the gettering layer is lost or thinned causing heavy-metal contamination
Solution Approach 1:
A gettering layer is formed on the back face of the semiconductor chip before the chip is thinned to 100 μm or less. This preliminary formation of the gettering layer ensures that even after thinning, the gettering function remains effective in trapping heavy metals during the second-half process, thus preventing contamination while achieving high integration.
Solution Approach 2:
Instead of forming the gettering layer inside the bulk of the wafer (three-dimensional positioning), the invention places the gettering layer on the back face surface (two-dimensional positioning). This dimensional change allows the gettering layer to remain effective even after the chip is thinned, as it is positioned at the surface where heavy metals would contact the chip during assembly.
2Reliability
If a gettering layer is formed inside or on the back face of the wafer in the first-half process, then heavy-metal contamination is prevented, but the gettering layer is lost or thinned when the wafer is thinned in the second-half process
Solution Approach 1:
The gettering layer is formed on the back face before the thinning process occurs. By establishing this protective layer in advance, the invention ensures that the gettering function is preserved even after subsequent thinning operations reduce the chip thickness to 100 μm or less.
Solution Approach 2:
The invention uses a thin film gettering layer on the back face that is specifically designed to remain effective even after the bulk material is thinned. This thin film approach allows the gettering function to be maintained with minimal material, preventing both loss of the gettering layer and heavy-metal contamination.
3Volume of moving object
If the chip thickness is reduced to 100 μm or less to raise integration degree, then device integration is improved, but heavy-metal contamination occurs due to loss of gettering layer
Solution Approach 1:
The gettering layer is formed on the back face before the chip is thinned to 100 μm or less. This preliminary formation ensures that the gettering function is already in place to trap heavy metals during the second-half process, preventing contamination while achieving the desired thin chip thickness for high integration.
Solution Approach 2:
The invention positions the gettering layer on the back face surface rather than within the bulk, changing from a three-dimensional to two-dimensional positioning. This allows the chip to be thinned to 100 μm or less while the surface-level gettering layer remains effective at trapping heavy metals during assembly operations.
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 approach significantly reduces device defects and improves yield by effectively gettering heavy metals, lowering the percentage of defective devices from 61% to 0.7% and maintaining the integrity of the gate insulation film.
Implementation Method 1
a gettering layer is formed on the back face of a semiconductor chip by mechanically grinding the back face of the semiconductor chip using a silica material to form a damaged layer
Implementation Method 2
mechanically grinding the back face of the semiconductor chip using a silica material to form a damaged layer
Data Source
AI summary
In a semiconductor chip A wherein an element layer 2 having transistors and the like is formed on the front face, and the back face is joined to an underlying member, such as a package substrate, the thickness T is made 100 μm or less, and thereafter, a gettering layer 3 is formed on the back face of the semiconductor chip A. The gettering layer 3 is formed, for example, by polishing the back face of said semiconductor chip A using a polishing machine. Thereby, the yield of devices can be improved in the step for assembling the package.