Tungsten Layer Grain Control via Segmented CVD
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current semiconductor manufacturing processes face challenges in controlling the grain size of tungsten layers, leading to rough surfaces and performance issues during subsequent processes like dicing, due to continuous grain growth and uneven surfaces.
Innovation Solution
A two-step CVD process is employed to form tungsten layers, with a treatment process between the steps to inhibit grain growth by introducing suitable gases or radicals, transforming the top tungsten layer into amorphous tungsten, thereby maintaining a smaller grain size and preventing oversized grains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single tungsten layer is deposited using conventional CVD process, then the tungsten layer can be formed to fill the opening, but the grain size continuously increases with film thickness resulting in rough surface
Solution Approach 1:
The single tungsten layer deposition process is segmented into two separate deposition steps, creating a first tungsten layer and a second tungsten layer. This segmentation allows independent control of grain growth in each layer, preventing continuous grain size increase through the entire thickness and thereby improving surface smoothness.
Solution Approach 2:
The first tungsten layer is deposited with controlled grain growth, and then a treatment process is performed preliminarily before depositing the second tungsten layer. This preliminary treatment prevents oversized grain formation in the subsequent layer, ensuring the final surface remains smooth.
2Volume of moving object
If the tungsten layer thickness is increased to fill larger openings, then the filling capability is improved, but the grain size over increases causing rough surface and performance issues
Solution Approach 1:
The thick tungsten layer is segmented into multiple thinner sub-layers (first and second tungsten layers), each deposited separately. This allows the total thickness to be increased for filling larger openings while each individual layer maintains controlled, smaller grain sizes, preventing surface roughness.
Solution Approach 2:
The deposition process uses periodic action by alternating between deposition steps and treatment processes. This periodic intervention resets or controls grain growth at each stage, enabling thick layer formation without continuous grain size increase that would cause rough surfaces.
3Productivity
If conventional single-step CVD is used for tungsten deposition, then the process is simple and fast, but grain growth cannot be controlled leading to oversized grains and rough surfaces
Solution Approach 1:
The deposition process is segmented into multiple steps with treatment processes in between, which controls grain growth while maintaining overall productivity. The segmented approach allows faster deposition rates in each step without sacrificing grain size control, as the treatment processes are brief interventions rather than lengthy slow-downs.
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 improves the surface smoothness and performance of semiconductor devices by preventing oversized grain growth, reducing the impact on subsequent processes such as dicing and enhancing overall element performance.
Implementation Method 1
a treatment process is performed between two stepped tungsten depositing processes, to interact with the original grain growth of the tungsten layer
Implementation Method 2
to interfere with the original crystallization, and to transfer the grain growth of tungsten thereof into amorphous tungsten
Implementation Method 3
the top tungsten layer deposited on the bottom tungsten layer may be recrystallized to obtain a relative smaller grain size
Implementation Method 4
The present invention utilizes a two-step CVD process to form two tungsten layers
Data Source
AI summary
A semiconductor device includes a substrate, a dielectric layer, a first tungsten layer, an interface layer and a second tungsten layer. The dielectric layer is disposed on the substrate and has a first opening and a second opening larger than the first opening. The first tungsten layer is filled in the first opening and is disposed in the second opening. The second tungsten layer is disposed on the first tungsten layer in the second opening, wherein the second tungsten layer has a grain size gradually increased from a bottom surface to a top surface. The interface layer is disposed between the first tungsten layer and the second tungsten layer, wherein the interface layer comprises a nitrogen containing layer. The present invention further includes a method of forming a semiconductor device.