Wafer Die Singulation via Backside Etching and Sacrificial Layer Release
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Solution Overview
Problem
Conventional saw cutting for singulating semiconductor devices from wafers is inefficient, limiting device density, generating debris, and restricting device shape and size, while being time-consuming and costly.
Innovation Solution
A method involving etching trenches into the wafer from the backside, attaching a handle wafer, and partially or completely etching a sacrificial layer to release the die, with a retainer forming a frame to retain and package the singulated die, allowing for parallel processing and various post-processing options.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If saw cutting is used to singulate die from wafer, then individual devices can be separated, but device density is limited due to required spacing between adjacent devices
Solution Approach 1:
The patent extracts the sacrificial layer (e.g., silicon dioxide) from between the devices through etching, allowing devices to be separated without requiring permanent spacing. The sacrificial layer is removed via chemical etching processes, enabling devices to be packed closely together while maintaining separability.
Solution Approach 2:
The patent introduces a sacrificial layer as an intermediary material that temporarily occupies the space between devices during fabrication. This layer can be selectively removed through etching, enabling device separation without requiring permanent streets or spacing, thus increasing device density.
2Reliability
If saw cutting is used to singulate die, then devices can be separated, but debris is generated which contaminates devices or lodges in MEMS devices
Solution Approach 1:
The patent replaces the mechanical saw cutting process with a chemical etching process. Instead of using a physical saw blade that generates debris, the sacrificial layer is removed through chemical reactions (e.g., HF etching of silicon dioxide), which produces no particulate debris and maintains device cleanliness.
3Productivity
If saw cutting is used to singulate die, then devices can be separated, but processing time is increased due to serial cutting operation
Solution Approach 1:
The patent segments the wafer into individual devices by etching trenches through the sacrificial layer at multiple locations simultaneously. This allows parallel processing where multiple devices are separated at the same time rather than sequentially, dramatically increasing singulation speed and productivity.
Solution Approach 2:
The sacrificial layer is deposited and patterned in advance during the fabrication process, creating pre-defined separation paths. This preliminary action enables subsequent rapid etching-based singulation without requiring time-consuming alignment and cutting operations for each device.
4Adaptability or versatility
If saw cutting is used to singulate die, then devices can be separated, but device shape is restricted to square or rectangular
Solution Approach 1:
The patent changes the singulation method from mechanical cutting to chemical etching, which allows for flexible trench profiles and device shapes. The etching process can create curved, irregular, or custom-shaped device boundaries that are not constrained by the linear paths required for saw cutting, enabling greater design freedom.
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 increases device density, reduces debris and handling costs, enables non-standard device shapes, and improves yield by allowing simultaneous singulation of all die on a wafer, facilitating post-processing and efficient packaging.
Implementation Method 1
etching one or more trenches into the wafer from a backside thereof
Implementation Method 2
a sacrificial layer (e.g. comprising silicon dioxide or a silicate glass) on the device side of the wafer is partially or completely etched away to finish the singulation process
Data Source
AI summary
A method is disclosed for singulating die from a substrate having a sacrificial layer and one or more device layers, with a retainer being formed in the device layer(s) and anchored to the substrate. Deep Reactive Ion Etching (DRIE) etching of a trench through the substrate from the bottom side defines a shape for each die. A handle wafer is then attached to the bottom side of the substrate, and the sacrificial layer is etched to singulate the die and to form a frame from the retainer and the substrate. The frame and handle wafer, which retain the singulated die in place, can be attached together with a clamp or a clip and to form a package for the singulated die. One or more stops can be formed from the device layer(s) to limit a sliding motion of the singulated die.