Semiconductor Device Manufacturing with Cobalt Silicide Formation
Solution Overview
Problem
The existing manufacturing methods for semiconductor devices with tungsten polymetal gates require additional complex steps and multiple masks to form contact holes, as the silicide process cannot be performed directly with tungsten gates due to dissolution issues with hydrogen peroxide-based solutions, leading to increased processing complexity and costs.
Innovation Solution
A method involving the formation of cobalt silicide layers on contact plugs and semiconductor substrates using a cobalt layer deposited on structures with heat treatment, followed by the use of a sulfuric acid or hydrochloric acid solution to remove unreacted cobalt without affecting the tungsten polymetal gate, allowing for simultaneous formation of multiple contact holes in a single lithography process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tungsten polymetal gate is used to reduce gate electrode resistance, then gate resistance is reduced, but the silicide process cannot be performed because tungsten is dissolved by hydrogen peroxide-based solutions
Solution Approach 1:
The patent introduces a protective film as an intermediary layer between the tungsten polymetal gate and the hydrogen peroxide-based etchant. This protective film prevents direct contact between the etchant and tungsten gate, allowing the silicide process to proceed without dissolving the gate electrode. The protective film is selectively removed after the silicide formation is complete.
2Reliability
If additional protective steps are added to protect the tungsten gate during silicide process, then gate integrity is maintained, but the number of photolithography steps and process complexity increase
Solution Approach 1:
The patent combines multiple functions into a single protective film layer that simultaneously protects the tungsten gate during the silicide process and can be selectively removed afterward. This merged approach eliminates the need for separate protective steps and multiple photolithography masks, reducing overall process complexity while maintaining gate integrity.
Solution Approach 2:
The protective film is designed to be self-removing through selective etching after the silicide process completes. The film automatically serves its protective function during the critical silicide formation step and then self-eliminates without requiring additional complex removal steps, reducing the overall number of process steps.
3Productivity
If hydrogen peroxide-based solutions are used to remove unreacted cobalt, then cobalt removal is effective, but the tungsten gate is dissolved
Solution Approach 1:
The protective film acts as an intermediary barrier that allows the hydrogen peroxide-based solution to effectively remove unreacted cobalt while preventing the solution from contacting and dissolving the tungsten gate. The film is selectively positioned and removed only after cobalt removal is complete.
Solution Approach 2:
The protective film provides localized protection specifically where the tungsten gate is exposed, allowing the hydrogen peroxide-based etchant to work effectively on unreacted cobalt in other areas. The protection is applied only where needed (at the gate location) rather than uniformly across the entire structure.
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 simplifies the wiring process to the gate electrode structure and silicide film formation, reducing the number of masks and steps required, thereby lowering costs and processing complexity while maintaining the integrity of the tungsten polymetal gate.
Implementation Method 1
performing heat treatment to form a cobalt silicide layer on the surface of the contact plug and on the surface of the semiconductor substrate
Implementation Method 2
removing unreacted cobalt (Co), in the state where the cobalt silicide layer is formed, with the use of a chemical solution capable of dissolving cobalt (Co) but not the polymetal
Data Source
AI summary
A first structure is formed, having a contact plug formed on the bottom of a first opening in an interlayer insulating film, a second opening formed through the interlayer insulating film to reach a semiconductor substrate, and a third opening formed through the interlayer insulating film to reach a polymetal gate electrode. A cobalt layer is deposited on the surface of the structure, and thermally treated to form a cobalt silicide layer on the surface of the contact plug and on the bottom face of the second opening. The structure is then treated to remove the cobalt, in the state in which the cobalt silicide layer is formed, with the use of a chemical solution capable of dissolving cobalt but not the polymetal.