Contact Plug Barrier Structure to Prevent WF6 Etching Voids
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Solution Overview
Problem
Conventional methods for forming contact plugs in semiconductor devices result in barrier metal segmentation, leading to etching defects and increased contact resistance due to the penetration of WF6 gas through segmentation points, causing the titanium film to be etched and voids to form between the interlayer insulating film and the titanium nitride film.
Innovation Solution
A semiconductor device structure where the titanium nitride film is deposited thickly to maintain its upper surface position higher than the semiconductor substrate surface after rapid thermal annealing, ensuring the barrier metal remains intact and preventing WF6 gas penetration, thereby embedding tungsten films effectively without segmentation and voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a titanium film and titanium nitride film are sequentially stacked as barrier metal by sputtering or CVD method, then the barrier metal structure is formed, but the barrier metal segments and cracks during rapid thermal annealing, allowing WF6 gas to penetrate through segmentation points and etch the titanium film
Solution Approach 1:
The patent applies preliminary action by forming a recess in the semiconductor substrate at the contact hole bottom before depositing the barrier metal. This recess structure pre-compensates for the volume reduction of the titanium film during silicidation, preventing the barrier metal from cracking and segmenting during rapid thermal annealing. The recess ensures that the titanium nitride film remains intact and continues to protect the titanium film from WF6 gas penetration.
2Reliability
If the titanium film is converted into silicide by rapid thermal annealing, then electrical connectivity is improved, but the titanium nitride film moves downward and the barrier metal cracks and segments
Solution Approach 1:
The recess is formed in advance to accommodate the downward movement of the titanium nitride film during rapid thermal annealing. This preliminary structural preparation allows the titanium film to convert to silicide and improve electrical connectivity without causing the barrier metal to crack or segment, as the recess provides the necessary volume compensation.
Solution Approach 2:
The patent applies local quality by creating a recess specifically at the bottom of the contact hole where the titanium film will undergo silicidation. This localized structural modification ensures that the volume reduction during silicide formation is accommodated only where needed, preventing cracking and segmentation while maintaining the integrity of the barrier metal in other regions.
3Productivity
If the barrier metal segments and cracks, then WF6 gas penetrates through segmentation points and etches the titanium film, but additional processes like introducing SiH4 gas are required to prevent etching
Solution Approach 1:
The recess is formed in advance to prevent barrier metal segmentation, which in turn prevents WF6 gas from penetrating and etching the titanium film. This preliminary structural preparation eliminates the need for additional protective process steps such as introducing SiH4 gas, thereby maintaining high manufacturing throughput without increasing process complexity.
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
Prevents embedding defects and ensures reliable electrical connectivity by maintaining the barrier metal's integrity, enhancing throughput by eliminating the need for additional processes like introducing SiH4 gas.
Implementation Method 1
the titanium film is converted into a silicide by rapid thermal annealing, thereby forming a titanium silicide film
Implementation Method 2
a tungsten film is embedded in the contact hole on the barrier metal by a CVD method
Data Source
AI summary
A semiconductor device, having: a substrate having a main surface with a recess; a device structure at the main surface; an interlayer insulating film covering the device structure; a contact hole penetrating through the interlayer insulating film to expose a portion of the device structure, the contact hole having a bottom configured by the recess; a barrier metal, including a titanium film provided along the side wall of the contact hole, and a titanium nitride film stacked on the titanium film and formed at the bottom of the contact hole; a titanium silicide film provided along an inner wall of the recess; a tungsten film provided on the barrier metal; and a metal electrode provided on the interlayer insulating film and the tungsten film. An upper surface of the titanium nitride film on the bottom of the contact hole is closer to the metal electrode than is the main surface.