Semiconductor Wafer CMP Slurry for Surface Unevenness Reduction
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Solution Overview
Problem
Conventional methods for semiconductor substrate fabrication face challenges in reducing surface unevenness caused by surface protrusions and voids, which lead to reduced fabrication yield and unreliable device performance due to issues like unbonded areas and stress on the GaN wafer during the wafer bonding process.
Innovation Solution
A method involving a first slurry with diamond particles, capable of mechanically removing a portion of the deposited and protective layers to create an intermediate surface, followed by additional dielectric layer deposition and polishing steps to achieve a smoother bonding surface, utilizing a second slurry without diamond particles for further surface refinement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional SiO2 slurry is used for CMP to remove surface protrusions, then the deposited SiO2 layer can be removed, but the surface protrusions made of III-nitride and Si based materials cannot be effectively removed
Solution Approach 1:
The patent changes the hardness parameter of the slurry particles from conventional soft SiO2 particles to hard diamond particles. This parameter change enables the slurry to mechanically remove both the deposited SiO2 layer and the harder surface protrusions made of III-nitride and Si based materials, achieving effective surface flatness improvement and reliable bonding quality simultaneously
Solution Approach 2:
The patent uses a composite slurry system combining diamond particles with SiO2 binder. The diamond particles provide the necessary hardness to remove both the deposited layer and surface protrusions, while the SiO2 binder provides chemical affinity for selective removal. This composite approach resolves the contradiction by combining materials with complementary properties
2Manufacturing precision
If multiple iterations of SiO2 deposition and CMP process are applied to reduce surface protrusions, then surface flatness can be improved, but the process time and complexity increase significantly
Solution Approach 1:
The patent changes the removal mechanism parameter from chemical-mechanical polishing with soft particles to mechanical abrasion with hard diamond particles. This single parameter change enables one-step removal of surface protrusions that would otherwise require multiple iterative deposition-CMP cycles, significantly reducing process time while maintaining surface flatness improvement
Solution Approach 2:
The patent extracts the diamond particles from the conventional SiO2 slurry formulation. This extraction of the key functional component (hard abrasive particles) creates a specialized slurry that directly addresses surface protrusions in a single step, eliminating the need for repeated iterative processes and reducing overall process cycle time
3Reliability
If a thick SiO2 layer is deposited to cover surface protrusions for bonding, then bonding quality can be improved, but additional stress on the GaN wafer increases
Solution Approach 1:
The patent converts the harmful surface protrusions into removable features by using diamond particle slurry. Instead of depositing thick SiO2 to cover the protrusions (which creates stress), the hard particles mechanically remove the protrusions themselves. This converts the problem of surface unevenness into a direct removal solution, achieving reliable bonding without the stress penalty of thick dielectric layers
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 reduces surface imperfections, enhancing the bonding quality and reducing yield loss by creating a more even and strong bond between semiconductor layers, while minimizing additional stress on the wafer and reducing the need for multiple iterations of deposition and polishing.
Implementation Method 1
removing a portion of a deposited layer and a protective layer thereon using a first slurry to provide an intermediate surface, the first slurry including particles with a hardness level the same as or exceeding that of the deposited layer
Implementation Method 2
SiO2 is deposited conformably by a PECVD process on the GaN-on-Si wafer
Data Source
AI summary
Disclosed is a method of reducing surface unevenness of a semiconductor wafer (100). In a preferred embodiment, the method comprises: removing a portion of a deposited layer and a protective layer thereon using a first slurry to provide an intermediate surface (1123). In the described embodiment, the deposited layer includes an epitaxial layer (112) and the protective layer includes a first dielectric layer (113). The first slurry includes particles with a hardness level the same as or exceeding that of the epitaxial layer (112). A slurry for use in wafer fabrication for reducing surface unevenness of a semiconductor wafer is also disclosed.