Tungsten-Assisted Through-Substrate Etching for Low-k Protection
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Solution Overview
Problem
Current etching technologies for high-aspect ratio semiconductor structures, such as through-silicon vias (TSVs), often cause damage to low-k materials due to the use of aggressive etch gases, leading to undesirable secondary effects like material degradation.
Innovation Solution
Introduce tungsten hexafluoride (WF6) as an additive to the etch gas during the etching process, forming a tungsten nitride passivation layer on the sidewalls to protect low-k materials from damage during aggressive etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If aggressive etch gases are used for deep etching high-aspect ratio structures, then etch rate and aspect ratio are improved, but material damage to low-k materials occurs
Solution Approach 1:
A protective layer is introduced as an intermediary between the aggressive etch gas and the low-k materials. This protective layer selectively protects the low-k materials from etch gas damage while allowing the etch process to proceed through other layers at high rates, thus enabling high-aspect ratio etching without material damage
Solution Approach 2:
The patent applies different etch gas compositions or protective measures to different regions of the substrate. Specifically, areas with low-k materials receive enhanced protection compared to other regions, allowing aggressive etching where safe and protective conditions where vulnerable materials exist
2Shape
If aggressive etch gases are used for deep etching, then aspect ratio is improved, but adjacent materials are damaged
Solution Approach 1:
The protective layer serves as a mediator that enables the formation of high-aspect ratio structures by shielding adjacent vulnerable materials from the harmful effects of aggressive etch gases, allowing the etch front to progress vertically without lateral damage
3Length of stationary object
If corrosive etch gases are used for through-substrate etching, then etching depth is improved, but low-k materials are damaged
Solution Approach 1:
The protective layer is positioned between the corrosive etch gas and the low-k materials, enabling deep through-substrate etching while preventing the corrosive gas from directly contacting and damaging the low-k material regions
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 WF6 enables higher aspect ratio etches with reduced material damage, allowing for cleaner vertical sidewalls and improved etch profiles, enhancing the formation of TSVs without compromising the integrity of low-k materials.
Implementation Method 1
exposing the nitride layer to an etch gas including tungsten; and extending, with an etch process, the opening through the semiconductor substrate
Implementation Method 2
forming a tungsten nitride passivation layer on the sidewalls to protect low-k materials from damage during aggressive etching
Implementation Method 3
extending, with an etch process, the opening through the semiconductor substrate
Data Source
AI summary
A process for adding tungsten during through-substrate etching includes forming a nitride layer over a semiconductor substrate, forming a mask layer over the nitride layer, creating an opening through the mask layer and the nitride layer, exposing the nitride layer to an etch gas comprising tungsten, and extending, with an etch process, the opening through the semiconductor substrate.