Pad Oxide Thickness Strategy for Simpler Shallow Trench Isolation
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Solution Overview
Problem
The existing embedded high-voltage technology for semiconductor manufacturing is complex due to the need to remove and re-grow pad oxide layers after the P-type high-voltage ion well thermal drive-in process, complicating the process steps.
Innovation Solution
A method involving forming a first pad oxide layer with a specific thickness, followed by a nitride hard mask layer, and then thermally growing a second pad oxide layer with a greater thickness, which is thinned post-implantation, allowing for a simplified trench isolation process without re-growing pad oxide layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the oxide liner layer is completely removed after annealing the ion well and a new pad oxide layer is formed, then the high-voltage device area can be properly prepared, but the manufacturing process becomes more complex with additional steps
Solution Approach 1:
A second pad oxide layer is thermally grown on the substrate within the high-voltage device area before ion well formation. This preliminary action ensures that the oxide layer is already in place to protect the substrate during subsequent ion implantation, eliminating the need to remove and re-grow the oxide layer after annealing.
Solution Approach 2:
The patent applies different oxide layer thicknesses to different device areas. The second pad oxide layer in the high-voltage device area has a greater thickness than the first pad oxide layer in the low-voltage device area. This local differentiation allows the high-voltage area to maintain its oxide layer during ion implantation while keeping the overall process simple.
2Ease of manufacture
If the pad oxide layer is removed completely after ion well annealing, then the substrate is prepared for trench isolation, but additional processing steps are required to re-grow the pad oxide layer
Solution Approach 1:
The second pad oxide layer is thermally grown in advance before ion well formation and annealing. This preliminary formation allows the oxide layer to serve as a protective barrier during the entire ion well processing sequence, including annealing, eliminating the need for post-annealing oxide re-growth and reducing total processing time.
Solution Approach 2:
The patent changes the thickness parameter of the pad oxide layer in the high-voltage device area by thermally growing a second pad oxide layer with greater thickness. This parameter change ensures the oxide layer survives the ion implantation process intact, avoiding the need for removal and re-growth steps.
3Reliability
If a thicker pad oxide layer is used in the high-voltage device area, then the substrate is better protected during ion implantation, but the oxide layer requires additional thinning steps
Solution Approach 1:
The patent implements local quality by having the second pad oxide layer with greater thickness only in the high-voltage device area where ion implantation occurs, while the first pad oxide layer in the low-voltage device area maintains a thinner profile. This localized thickness differentiation provides targeted protection where needed without unnecessarily complicating other areas.
Solution Approach 2:
The thickness parameter of the pad oxide layer is changed through thermal growth to create a thicker second pad oxide layer in the high-voltage device area. This parameter change provides enhanced protection during ion implantation, and the subsequent thinning to a controlled third thickness prepares the structure for trench isolation without requiring complete removal and re-growth.
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
Simplifies the semiconductor manufacturing process by eliminating the need to remove and re-grow pad oxide layers, thereby reducing complexity and streamlining the production steps.
Implementation Method 1
A second pad oxide layer is thermally grown on the substrate within the second device region
Data Source
AI summary
The present invention uses the thinned second pad oxide layer as the pad oxide layer for the subsequent shallow trench isolation process. Therefore, it is not necessary to remove the entire pad oxide layer on the substrate surface after the P-type high-voltage ion well thermal drive-in process. The subsequent step of re-growing the pad oxide layer is omitted, thereby simplifying the process complexity.