Semiconductor Contact Plug Formation Process
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Solution Overview
Problem
The miniaturization of semiconductor devices below 60 nm leads to challenges in simultaneous photomask processes for forming drain contact plugs and high voltage device contact plugs due to differences in shape and size, requiring separate processes and increasing manufacturing costs.
Innovation Solution
A method where mask formation processes for both cell and peripheral regions are performed simultaneously, using the same material for gap-filling contact holes, simplifying the process and reducing costs by forming contact plugs from tungsten and polysilicon layers with spacers to manage critical dimensions and prevent bridging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If separate photomask processes are performed for drain contact holes and high voltage device contact holes, then each contact hole can be formed with precise dimensions, but the manufacturing process complexity and cost increase
Solution Approach 1:
The contact hole formation process is segmented into two stages: first forming all contact holes simultaneously using a single photomask process, then selectively removing contact plugs from peripheral regions using a second targeted photomask process. This segmentation allows precise control for each region type while avoiding the complexity of completely separate formation processes.
Solution Approach 2:
All contact holes (both cell and peripheral regions) are formed in advance using the same photomask process focused on drain contact hole specifications. This preliminary action enables simultaneous formation with consistent precision, and subsequent selective removal adjusts the final configuration without requiring separate initial formation processes.
2Manufacturing precision
If separate photomask processes are performed for different contact holes, then each region can be optimized, but the manufacturing time and cost increase
Solution Approach 1:
The formation of all contact holes (cell region drain contacts and peripheral region high voltage contacts) is merged into a single photomask process. By designing the mask to accommodate both contact types with different specifications, the process achieves specification compliance for both regions while reducing total process time compared to separate formation approaches.
Solution Approach 2:
All contact holes are preliminarily formed in the first photomask process with dimensions optimized for drain contacts. This preliminary formation satisfies specifications for both contact types initially, and the second selective removal process adjusts the final configuration without adding significant time penalty.
3Reliability
If different materials are used for gap-filling drain contact holes and peripheral contact holes, then each contact type can be optimized, but the process complexity and material cost increase
Solution Approach 1:
The same gap-fill material (polysilicon) is used for both drain contact holes and peripheral contact holes. This homogeneous material approach simplifies the manufacturing process by eliminating the need for separate material deposition processes, while still allowing different final contact configurations through selective removal and spacer formation.
Solution Approach 2:
Instead of using different materials from the beginning, the invention uses a uniform polysilicon gap-fill material for all contacts, then extracts (removes) the polysilicon from peripheral contact holes in a selective process. This extraction approach achieves material differentiation only where needed, simplifying the overall material process.
4Device complexity
If a single photomask process is used for both contact hole types, then process simplicity increases, but dimension precision for different contact types deteriorates
Solution Approach 1:
The photomask process is segmented into two distinct stages: first a comprehensive mask forming all contact holes with drain-contact-optimized dimensions, then a second selective mask removing specific contacts. This segmentation enables the single initial process to achieve precision for drain contacts while the second process adjusts peripheral contact dimensions.
Solution Approach 2:
Instead of directly forming different sized contacts in a single mask process, the invention inverts the approach by first forming all contacts with one specification (drain contact size) and then selectively removing material to achieve the other specification (peripheral contact size). This indirect approach maintains process simplicity while achieving dimension precision.
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 contact plug formation process, reduces manufacturing costs, and prevents bridging by using the same material for gap-filling contact holes in both regions, thereby enhancing process efficiency and reducing prime costs.
Implementation Method 1
The first insulating layer is etched using an etch process, thus forming contact holes through which junctions are exposed in the cell region and the first contact plug is exposed in the peri region
Implementation Method 2
The spacer formation process includes forming a second insulating layer over the first insulating layer and the contact holes
Data Source
AI summary
The present invention relates to a method of forming contact plugs of a semiconductor device. According to the method, a first insulating layer is formed over a semiconductor substrate in which a cell region and a peri region are defined and a first contact plug is formed in the peri region. The first insulating layer is etched using an etch process, thus forming contact holes through which junctions are exposed in the cell region and the first contact plug is exposed in the peri region. Second contact plugs are formed in the contact holes. The second contact plug formed within the contact hole of the peri region are removed using an etch process. A spacer is formed on sidewalls of the contact holes. Third contact plugs are formed within the contact holes.