Die Attach Film Isolation Structure for Leakage-Free Die Dicing
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Solution Overview
Problem
Existing methods for separating semiconductor dies from a wafer, such as laser and mechanical dicing, fail to completely separate devices due to issues like incomplete cutting through metallization layers, leading to reduced yields and potential short circuits from semiconductor scrap material.
Innovation Solution
A method involving a partially cut die attach film layer and an uncut die attach film layer is used, where the partially cut layer is formed by a sawing operation that does not fully cut through the die attach film, and the uncut layer isolates the die pad, preventing semiconductor chips from forming shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If laser dicing is used to separate semiconductor devices, then the dicing operation can be performed without cutting through metallization and dielectric layers, but incomplete separation of semiconductor devices occurs reducing yields
Solution Approach 1:
The patent segments the die attach film into two distinct layers: a partially cut layer that allows laser penetration and an uncut layer that provides isolation. This segmentation enables the laser to cut through the first layer while the second layer remains intact to prevent chip formation, thus resolving the contradiction between ease of manufacture and separation completeness.
Solution Approach 2:
The uncut die attach film layer acts as an intermediary barrier between the semiconductor device and the substrate. This intermediary layer prevents direct contact and potential short circuits caused by chips, while still allowing the laser to perform its cutting function in the lower layer, thereby maintaining both manufacturing ease and device separation reliability.
2Reliability
If mechanical dicing with a saw is used to completely separate semiconductor devices, then complete separation is achieved, but chipping occurs at the backside of the wafer where die attach film is attached
Solution Approach 1:
The die attach film is segmented into a partially cut layer and an uncut layer. The partially cut layer allows the mechanical saw to cut through and achieve complete separation, while the uncut layer remains intact to prevent chipping at the wafer backside, thus resolving the contradiction between separation completeness and chip formation.
Solution Approach 2:
The uncut die attach film layer serves as a protective cushion layer that absorbs the mechanical stress and prevents chip formation during the dicing operation. This prior cushioning protects the wafer backside from damage while allowing complete separation to occur, addressing the contradiction between reliability and harmful factors.
3Reliability
If the die attach film is completely cut through during dicing, then complete separation is achieved, but semiconductor chips can become lodged in the die attach film and extend through to form current leakage paths
Solution Approach 1:
The die attach film is divided into a partially cut layer that enables complete separation and an uncut layer that acts as a barrier. This segmentation ensures that while devices are completely separated, the uncut layer prevents chips from extending through to form current leakage paths, resolving the contradiction between separation completeness and prevention of harmful factors.
Solution Approach 2:
The patent converts the potential harm of complete cutting (which could allow chips to form leakage paths) into a benefit by using the cut surface of the partially cut layer as a controlled interface. The uncut layer then utilizes this interface to trap chips safely, converting what could be a harmful situation into a controlled and beneficial isolation mechanism.
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 effectively prevents current leakage by containing semiconductor chips away from the die pad, ensuring complete separation and reducing the risk of short circuits during the dicing process.
Implementation Method 1
a sawing operation that does not fully cut through the die attach film
Implementation Method 2
the uncut die attach film layer isolates the die pad, preventing semiconductor chips from forming shorts
Implementation Method 3
a laser is focused at a depth beneath a surface of the semiconductor wafer in a scribe lane, and a stress area is created by application of laser energy
Implementation Method 4
the dicing tape can be expanded on a stretching table. As the dicing tape stretches the semiconductor device die are separated from one another along the cuts in the scribe lanes
Data Source
AI summary
In a described example, an apparatus includes: a semiconductor die having a device side surface and an opposing backside surface, the backside surface mounted to a die pad of a lead frame using a die attach film; bond pads overlying the device side surface of the semiconductor die; bond wires electrically coupling the bond pads to leads of the lead frame spaced from the die pad; and mold compound covering the semiconductor die, the bond wires, and portions of the lead frame, where portions of the leads are exposed from the mold compound to form terminals of the packaged semiconductor device. The die attach film has a partially cut die attach film layer with a cut side edge normal to the backside surface, and the die attach film has an uncut die attach film layer with a torn side edge normal to the backside surface.