Bonded Wafer Top Silicon Oxidation for SOI Thickness Uniformity
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Solution Overview
Problem
The challenge of achieving uniform thickness of thin films on larger silicon-on-insulator (SOI) wafers, particularly 12-inch wafers, due to non-uniform temperature distribution leading to unsatisfactory thickness uniformity of the top silicon layer, which affects integrated circuit fabrication yield.
Innovation Solution
A method involving two furnace oxidation processes with complementary thickness profiles followed by wet etching to form and remove oxide layers on the top silicon layer, ensuring uniformity by counteracting thickness variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wet oxidation process is used dominantly for thinning the top silicon layer, then throughput is improved, but thickness uniformity deteriorates
Solution Approach 1:
The single oxidation process is segmented into two distinct oxidation steps: a first oxidation step that forms an initial oxide layer, and a second oxidation step that forms a final oxide layer. Each step uses different oxidation conditions (dry/wet ratios, temperatures, durations) to create complementary thickness profiles that, when combined, achieve both high throughput and excellent thickness uniformity.
Solution Approach 2:
The patent systematically changes multiple oxidation parameters including temperature, oxidation atmosphere composition (dry vs wet ratio), oxidation duration, and oxygen flow rates between the two oxidation steps. These parameter changes enable the creation of oxide layers with complementary thickness distributions that compensate for each other's non-uniformities.
2Device complexity
If furnace oxidation is used for contactless thinning, then manufacturing complexity is reduced, but thickness uniformity deteriorates due to non-uniform temperature distribution
Solution Approach 1:
The furnace oxidation process is divided into two sequential oxidation steps, each with tailored parameters. The first oxidation step uses one set of temperature and atmosphere conditions, while the second step uses different conditions to create complementary thickness profiles, thereby achieving uniform thinning without complex equipment.
Solution Approach 2:
The oxidation process is applied periodically in two distinct phases rather than continuously in a single phase. This periodic application with varying parameters allows the system to correct thickness non-uniformities between steps while maintaining the simplicity of furnace-based processing.
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
The method achieves a top silicon layer with improved thickness uniformity, reducing variations to less than 0.2%, enhancing the yield of integrated circuits by ensuring uniform thinning.
Implementation Method 1
performing a first furnace oxidation process and a second furnace oxidation process on the top silicon layer, a first oxide layer is formed on a surface of the top silicon layer by the first furnace oxidation process and a second oxide layer is formed on the surface of the top silicon layer by the second furnace oxidation process
Implementation Method 2
the first furnace oxidation process and the second furnace oxidation process followed by respective wet etching processes for removing the first oxide layer and the second oxide layer
Data Source
AI summary
The present invention provides a method for sacrificed oxidation of a top silicon layer in a bonded wafer, including: providing the bonded wafer, which includes a substrate layer, the top silicon layer and an insulating buried oxide layer; and performing first and second furnace oxidation processes on the top silicon layer. A first oxide layer is formed on the surface of the top silicon layer, and a second oxide layer is formed on the surface of the top silicon layer as a result of the second furnace oxidation process. The first and second oxide layers have complementary thickness profiles on a top surface of the top silicon layer, and the first and second furnace oxidation processes are followed by respective wet etching processes for removing the first and second oxide layers. With the present invention, the top silicon layer can be thinned, and its thickness uniformity can be improved.