Semiconductor Process Single Photomask Dual Work Function Metal Gate
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Solution Overview
Problem
The conventional semiconductor process for forming dual work function metal gates in CMOS devices requires two photomasks, which complicates the integration and control processes, leading to increased costs and potential short circuits due to scoring at the junction of the photomasks.
Innovation Solution
A semiconductor process that uses a single photomask to form layers of different depths by partially filling a sacrificed material in recesses and performing an etching process to remove the metal layer in one recess while reserving it in the other, thereby simplifying the process and avoiding scoring and short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If two photomasks are used to remove work function metal layer in NMOS and PMOS recesses separately, then selective removal of metal layers is achieved, but process complexity increases and scoring at photomask junction causes short circuits
Solution Approach 1:
A sacrificial material layer is introduced as an intermediary between the metal layer and the etching process. This sacrificial layer selectively protects the metal in PMOS recesses during etching, enabling precise selective removal without requiring multiple photomasks. The sacrificial material serves as a mediator that translates the single photomask pattern into differential metal removal across NMOS and PMOS regions.
Solution Approach 2:
The sacrificial material is deposited and patterned in advance before the metal layer formation and etching steps. This preliminary action creates a protective mask that remains during subsequent processing, allowing the metal layer to be selectively removed only where needed without requiring complex multi-step photomasking procedures.
2Manufacturing precision
If two photomasks are used for forming metal layers in different recesses, then selective metal layer formation is achieved, but potential short circuits occur due to scoring at photomask junction
Solution Approach 1:
The sacrificial material acts as a protective intermediary that prevents etching of the metal layer in regions where it should be retained. By placing the sacrificial material selectively in PMOS recesses before metal deposition and etching, the method ensures that metal is removed only in NMOS recesses, eliminating the risk of short circuits at photomask junctions that plagues multi-photomask approaches.
3Manufacturing precision
If conventional dual photomask process is used, then work function metal layers are formed in both recesses, but process cost and complexity increase
Solution Approach 1:
The sacrificial material serves as a cost-effective intermediary that replaces the need for a second photomask and associated alignment procedures. By using a simple deposition and patterning step to create the sacrificial layer, the process achieves the same selective metal formation function as a dual photomask system would, but with significantly reduced complexity and lower material costs.
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 semiconductor process by eliminating the need for two photomasks, preventing scoring and short circuits, and allows for precise control of the metal layer height, improving trench filling and reducing complexity in metal gate fabrication.
Implementation Method 1
An etching process is performed to remove the remaining metal layer in the first recess and reserve the remaining metal layer in the second recess
Data Source
AI summary
A semiconductor process includes the following steps. An interdielectric layer is formed on a substrate and the interdielectric layer has a first recess and a second recess. A metal layer is formed to cover the surface of the interdielectric layer, the first recess and the second recess. Partially fills a sacrificed material into the first recess and the second recess so that a portion of the metal layer in each of the recesses is respectively covered. The uncovered metal layer in each of the recesses is removed. The sacrificed material is removed. An etching process is performed to remove the remaining metal layer in the first recess and reserve the remaining metal layer in the second recess.