Conductive Wafer Backside Layer for Clean Electrostatic Clamping
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Solution Overview
Problem
Electrostatic clamping of wafers during photonic integrated circuit fabrication can cause electrostatic damage and contamination, leading to reduced performance, reliability, and increased fabrication costs.
Innovation Solution
A non-metallic, electrically conductive layer is applied to the underside of the wafer, which reduces or prevents electrostatic damage and contamination by mitigating interactions between the electrical field and processing techniques like dry etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If electrostatic clamping is used to support the wafer during fabrication, then the wafer can be held securely during processing, but electrostatic damage and contamination occur that reduce performance and reliability
Solution Approach 1:
A non-metallic electrically conductive layer is introduced as an intermediary between the electrostatic chuck and the wafer. This layer mediates the electrostatic clamping force while protecting the wafer from direct exposure to the electrical field, thereby preventing electrostatic damage and contamination during dry etching and plasma processing.
Solution Approach 2:
The patent converts the potentially harmful electrical field into a beneficial protective mechanism. The conductive layer, when biased at a suitable potential, creates a protective electrical environment that shields the wafer from damaging electrostatic interactions while still allowing secure clamping.
2Reliability
If a metallic layer is used for electrostatic clamping, then electrostatic damage is reduced, but contamination occurs during etching that requires layer replacement
Solution Approach 1:
The patent changes the material parameter from metallic to non-metallic electrically conductive material. This parameter change maintains electrical conductivity for electrostatic clamping while eliminating the contamination issue associated with metallic materials during etching processes, thereby removing the need for layer replacement.
Solution Approach 2:
The solution employs a composite approach by using a non-metallic material that possesses electrical conductivity properties typically associated with metals. This composite material combines the benefits of electrical conductivity for clamping with the chemical inertness needed to resist etching contamination.
3Object-affected harmful factors
If the layer is replaced to remove contamination, then cleanliness is improved, but fabrication time increases due to un-clamping and re-clamping
Solution Approach 1:
The patent employs a disposable sacrificial layer that is intentionally designed to be consumed or damaged during processing. This layer protects the underlying wafer and circuit structures from contamination and damage, and is removed in a single final step rather than requiring multiple interruptions for replacement.
Solution Approach 2:
The conductive layer is applied in advance as a preliminary protective measure before the fabrication process begins. This preliminary action prevents contamination and damage throughout the entire fabrication sequence, eliminating the need for intermediate replacements and maintaining continuous production.
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
The use of a non-metallic layer enhances the performance, reliability, and reproducibility of photonic integrated circuits by minimizing electrostatic damage and contamination, while also reducing the need for layer replacement and associated disruptions in the fabrication process.
Implementation Method 1
A layer is provided on a first surface (e.g., of an underside) of the wafer. The layer is non-metallic, electrically conductive, and for electrostatically clamping to an electrostatic chuck.
Implementation Method 2
A non-metallic, electrically conductive layer is applied to the underside of the wafer, which reduces or prevents electrostatic damage and contamination by mitigating interactions between the electrical field and processing techniques like dry etching.
Data Source
AI summary
A method comprising: providing an electrically-insulative wafer comprising a first surface, and a second surface for processing; and providing a layer on the first surface. The layer is non-metallic, electrically-conductive, and for electrostatically clamping to an electrostatic chuck.