Silicon Carbide Die Singulation by Multi-Pass Stealth Dicing
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Solution Overview
Problem
Existing methods for singulating semiconductor die from silicon carbide substrates are inefficient and difficult due to the extreme hardness of silicon carbide, leading to slow dicing and unpredictable results, especially when attempting to produce die that can pass reliability tests.
Innovation Solution
A stealth dicing process involving focused laser irradiation to create modified regions within the substrate, followed by breaking along these regions using an anvil and tape expansion to separate die, optimizing parameters such as laser power, focal points, and scan speeds specific to silicon carbide substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional dicing methods are used on silicon carbide substrates, then the process is simple and equipment is readily available, but the dicing speed is extremely slow and results are unpredictable
Solution Approach 1:
The laser irradiates the silicon carbide substrate in advance to create modified regions along the die streets before breaking occurs. This preliminary modification of the material structure enables subsequent easy separation along predetermined paths, transforming the hard-to-cut silicon carbide into a material that can be efficiently singulated.
Solution Approach 2:
The patent replaces traditional mechanical dicing methods with a combination of laser irradiation and controlled breaking. Instead of using mechanical saws or dicing blades that struggle with silicon carbide's extreme hardness, the process uses laser energy to modify the material and then applies mechanical breaking force that easily separates along the modified regions.
2Manufacturing precision
If multiple laser passes are used to create modified regions at different depths, then singulation precision is improved, but processing time increases
Solution Approach 1:
The laser irradiation process is divided into multiple passes, each targeting different depth regions within the substrate. The first pass creates modified regions at a first depth range, the second pass targets a second depth range, and so on. This segmentation of the modification process ensures complete penetration and uniform modified regions throughout the substrate thickness, enabling precise breaking along the entire die street length.
Solution Approach 2:
The laser applies periodic irradiation through multiple passes at different depths rather than attempting to modify the entire thickness in a single continuous action. This periodic application of laser energy at different focal points ensures thorough modification throughout the substrate while maintaining controlled processing parameters for each pass.
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 process allows for efficient and repeatable singulation of silicon carbide die that can be included in packages passing reliability tests, increasing wafer and unit processing rates while reducing die street width, and minimizing yield losses and lateral cracking.
Implementation Method 1
irradiating the silicon carbide substrate in an X-direction with a laser beam focused at a first focal point a first distance into the thickness
Implementation Method 2
irradiating the silicon carbide substrate in the X-direction with the laser beam focused at a second focal point a second distance into the thickness
Data Source
AI summary
Implementations of a method of singulating silicon carbide may include providing a silicon carbide substrate including a thickness; in a plurality of X-direction die streets, irradiating the silicon carbide substrate with a laser beam at a focal point a depth into the thickness in a predetermined number of X-passes, each X-pass having a different laser spot diameter; and in a plurality of Y-direction die streets, irradiating the silicon carbide substrate in a Y-direction with the laser beam at a focal point a depth into the thickness in a predetermined number of Y-passes, each Y-pass having a different laser spot diameter. The method may include breaking the silicon carbide substrate first in the Y-direction and then in the X-direction using an anvil; and expanding a tape coupled to the silicon carbide substrate to separate a plurality of die from the silicon carbide substrate.