Backside Contact Structure With Bottle-Neck Profile for Stable Metal Filling
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Solution Overview
Problem
Conventional backside contact structures in semiconductor devices face issues with metal filling due to poor profile geometry, leading to overfilling and connectivity problems, and laser annealing can cause electron migration by hitting silicon oxide areas.
Innovation Solution
A novel backside contact structure is formed with a bottle-neck shaped geometry, featuring a first portion with a positive slope and a second portion with a constant diameter, using a liner with specific regions of Ta and Ti silicide, and a wet recess process is employed to remove the placeholder before Si removal, improving the profile and preventing metal overfilling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the placeholder is removed during Si removal, then the backside contact structure is formed, but the placeholder recess causes poor profile and metal filling issues
Solution Approach 1:
The placeholder is removed in advance using a wet recess process before the backside Si layer is removed. This preliminary removal prevents the placeholder from causing profile degradation during Si removal, thereby avoiding metal filling issues while maintaining manufacturing efficiency
2Reliability
If laser annealing is used to process the backside contact structure, then the structure is formed, but the laser passes through silicon oxide and hits the BEOL layer causing electron migration
Solution Approach 1:
A liner structure comprising multiple material layers (Ta/Ti silicide, Ti/TiN, and Ta/Ti silicide) is introduced as an intermediary between the laser annealing process and the BEOL layer. This liner absorbs or blocks the laser energy, preventing it from passing through the silicon oxide and hitting the BEOL layer, thereby eliminating electron migration while maintaining the reliability of the backside contact structure formation
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 improved backside contact structure enhances metal filling properties and reduces the risk of electron migration, ensuring better connectivity and stability in semiconductor devices.
Implementation Method 1
the placeholder is removed in advance using a wet recess process
Implementation Method 2
the first portion and the second portion include a liner
Implementation Method 3
when laser annealing is used, the laser can pass through some areas that have silicon oxide
Data Source
Figure 1A~1C
Figure 2
Figure 3A
AI summary
A system and a method are disclosed for forming a bottle-neck shaped backside contact structure in a semiconductor device, wherein the bottle-neck shaped backside contact structure has a first side partially within the first source/drain structure, a second side contacting a backside power rail, and a liner extending from the first side to the backside power rail. The liner includes a first region comprised of either a Ta silicide liner or a Ti silicide liner, a second region comprised of a Ti/TiN liner and a third region comprised of either a Ta silicide liner or a Ti silicide liner. The backside contact structure includes a first portion having a positive slope and a second portion, adjacent to the first portion, having no slope.