Multi-layer Metal Contacts for Semiconductor Overlay Control
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Solution Overview
Problem
The difference in hole size between those extending to doped regions and those extending to gate electrodes in semiconductor integrated circuits complicates pattern design and critical dimension control, leading to overlay budget and dimension control issues.
Innovation Solution
A method for forming multi-layer metal contacts, where a first-layer contact is formed extending to the doped region and a second-layer contact is formed extending through a second dielectric layer to the first-layer contact, allowing for separate processes and reducing the critical dimension difference between the two types of holes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If holes are formed to extend to doped regions and gate electrodes in the same process, then the manufacturing process is simpler, but the critical dimension control and overlay budget are compromised due to different hole sizes
Solution Approach 1:
The contact formation process is divided into two separate stages: first forming contacts to doped regions, then forming contacts to gate electrodes. This segmentation allows each contact type to be optimized independently, resolving the contradiction between process simplicity and precision by trading a single complex process for two simpler, more controllable processes.
Solution Approach 2:
The first-layer contacts to doped regions are formed in advance before the second-layer contacts to gate electrodes. This preliminary action establishes a foundation that enables better overlay control and critical dimension management for subsequent contact formation, as the first contacts serve as reference structures for the second patterning step.
2Reliability
If holes extending to doped regions are made wider at the top to accommodate depth variations, then manufacturing variability is reduced, but the critical dimension difference between doped region holes and gate holes increases
Solution Approach 1:
The patent segments the contact formation into two distinct patterning operations, allowing each to have its own optimized critical dimensions. The first patterning creates contacts with dimensions suitable for doped region access, while the second patterning creates contacts with dimensions optimized for gate electrode access, eliminating the need to compromise either contact type's dimensions.
Solution Approach 2:
Different contact holes are given different local qualities through separate formation processes. Contacts to doped regions have one set of dimensional characteristics optimized for their deeper location, while contacts to gate electrodes have another set of dimensional characteristics optimized for their shallower location, allowing each to perform its function reliably.
Data Source
AI summary
A method for forming metal contacts within a semiconductor device includes forming a first-layer contact into a first dielectric layer that surrounds at least one gate electrode, the first-layer contact extending to a doped region of an underlying substrate. The method further includes forming a second dielectric layer over the first dielectric layer and forming a second-layer contact extending through the second dielectric layer to the first-layer contact.