Die Singulation via Offset Trench Etching
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Solution Overview
Problem
Conventional saw cutting for singulating semiconductor devices from wafers is limited by the need for wide spacing, generates debris, restricts device shape to rectangular or square, and is time-consuming, making it inefficient for producing a high yield of devices with arbitrary shapes and minimizing contamination.
Innovation Solution
A method involving etching trenches from opposite sides of the semiconductor wafer with a portion of one trench laterally offset from the other, allowing the oxide layer between them to be etched away for singulation, which can be done in parallel without a handle wafer, using Deep Reactive Ion Etching and hydrofluoric acid, and includes a release fixture for supporting the singulated die.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If saw cutting is used to singulate die from semiconductor wafer, then die can be separated into individual devices, but wide spacing (street) is required between adjacent devices which limits the number of devices per wafer
Solution Approach 1:
The patent replaces the mechanical saw cutting system with a chemical etching system. Instead of using a physical saw blade that requires wide spacing for operation, the invention uses chemical etchants to remove material and create separation trenches. This substitution allows die to be singulated with minimal spacing between them, as the chemical process can access and etch material in narrow regions that would be inaccessible to mechanical saws.
Solution Approach 2:
The patent introduces a vertical dimension to the singulation process by etching trenches from both the top and bottom surfaces of the wafer simultaneously. This dual-sided approach allows the trenches to meet in the middle, creating complete separation without requiring large lateral spacing. The vertical etching paths enable die separation in a way that conserves horizontal wafer area, thereby increasing device density.
2Productivity
If saw cutting is used to singulate die, then die can be separated, but debris is generated which can contaminate devices or become lodged in MEMS devices or microfluidic devices
Solution Approach 1:
The patent replaces the mechanical saw cutting process with a chemical etching process. Instead of mechanically removing material with a saw blade that generates particulate debris, the invention uses chemical reactions to dissolve and remove material. This chemical approach eliminates the generation of solid debris that would contaminate devices, as the etching process converts solid material into soluble compounds that can be flushed away by liquid etchants.
Solution Approach 2:
The patent introduces liquid etchants as an intermediary medium to perform the separation function. These liquid chemicals serve as the active agent that removes material and creates separation trenches without generating solid debris. The etchants act as a mediator between the wafer and the separation process, enabling clean removal of material that would otherwise become contaminating particulates in a mechanical process.
3Productivity
If saw cutting is used to singulate die, then die can be separated, but the process is time-consuming as each cut must be carefully aligned and performed serially
Solution Approach 1:
The patent performs preliminary actions by forming trenches from both the top and bottom surfaces of the wafer simultaneously before the trenches meet in the middle. This parallel approach allows multiple separation paths to be created at the same time, rather than sequentially. The preliminary formation of trenches from both sides enables simultaneous progress on multiple die separations, dramatically reducing the total time required compared to serial saw cutting operations.
Solution Approach 2:
The patent segments the singulation process into two independent parallel operations: top-side trench formation and bottom-side trench formation. By dividing the overall separation task into these two concurrent segments that can be performed simultaneously, the process achieves parallelism. This segmentation allows the use of multiple etching tools or multiple etching zones on the same tool to work at the same time, reducing total processing time compared to sequential operations.
4Ease of manufacture
If saw cutting is used to singulate die, then die can be separated, but the device shape is restricted to square or rectangular
Solution Approach 1:
The patent changes the fundamental parameter of how separation is achieved - from mechanical cutting along straight lines to chemical etching that can follow arbitrary patterns. By changing from a mechanical process constrained by linear motion to a chemical process that can be patterned using photolithography, the invention enables creation of die with any shape. The etching parameters (pattern design, etch rate, etch depth) can be adjusted to create complex geometries that would be impossible with saw cutting.
Solution Approach 2:
The patent replaces the mechanical saw cutting system with a chemical etching system that uses patterned masks and liquid etchants. This substitution removes the geometric constraints of mechanical cutting (straight lines only) and enables arbitrary shape creation through photolithographic patterning. The chemical process can precisely follow any designed contour, allowing die of any shape to be created without the limitations of mechanical toolpaths.
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 allows for simultaneous singulation of multiple die with arbitrary shapes, reduces handling and contamination, increases yield and performance, and eliminates the need for adhesives and additional cleaning steps, while enabling the release of MEMS devices at the same time as singulation.
Implementation Method 1
a method for singulating one or more die from a semiconductor substrate by etching
Implementation Method 2
etching away the oxide layer between the trenches and thereby singulating the die from the semiconductor substrate
Data Source
AI summary
A method is disclosed for singulating die from a semiconductor substrate (e.g. a semiconductor-on-insulator substrate or a bulk silicon substrate) containing an oxide layer (e.g. silicon dioxide or a silicate glass) and one or more semiconductor layers (e.g. monocrystalline or polycrystalline silicon) located above the oxide layer. The method etches trenches through the substrate and through each semiconductor layer about the die being singulated, with the trenches being offset from each other around at least a part of the die so that the oxide layer between the trenches holds the substrate and die together. The trenches can be anisotropically etched using a Deep Reactive Ion Etching (DRIE) process. After the trenches are etched, the oxide layer between the trenches can be etched away with an HF etchant to singulate the die. A release fixture can be located near one side of the substrate to receive the singulated die.