Dual-Depth STI Structure via Sacrificial Oxide Selective Etching
Solution Overview
Problem
Conventional dual-depth shallow trench isolation (STI) structures in semiconductor manufacturing require a two-step etching process and two trench defining masks, which increases time and cost.
Innovation Solution
A one-step etching process with etching selectivity between a sacrificial SiO2 layer and the Si substrate is employed to create a dual-depth STI structure using only one trench defining mask, allowing for both deeper and shallower STI structures to be formed simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a two-step etching process with two trench defining masks is used to manufacture dual-depth STI structure, then the isolation performance for different device regions is improved, but the manufacturing time and process complexity increase
Solution Approach 1:
The patent combines two separate etching processes and two trench defining masks into a single etching process using one trench defining mask. The key is forming a sacrificial oxide layer that enables selective etching to create both deep and shallow trenches simultaneously, thereby reducing manufacturing steps and time while maintaining the required isolation performance for different device regions.
Solution Approach 2:
The sacrificial oxide layer is formed in advance on the substrate before the main etching process. This preliminary layer serves as a depth control mechanism during etching, allowing the formation of trenches at different depths in a single step. The sacrificial layer is subsequently removed to complete the dual-depth STI structure, eliminating the need for multiple masking steps.
2Manufacturing precision
If a two-step etching process with two trench defining masks is used to manufacture dual-depth STI structure, then the isolation performance for different device regions is improved, but the process complexity increases
Solution Approach 1:
The patent merges multiple process steps (two etching processes, two masking steps) into a single integrated process. By using one trench defining mask combined with the sacrificial oxide layer, the process complexity is significantly reduced while still achieving the dual-depth STI structure required for different device regions with appropriate isolation performance.
Solution Approach 2:
The sacrificial oxide layer acts as an intermediary element that enables the single-step formation of dual-depth trenches. This intermediate layer provides the necessary depth differentiation during etching without requiring multiple masks, thereby simplifying the overall process while maintaining manufacturing precision for different isolation requirements.
3Productivity
If a one-step etching process with sacrificial oxide layer is used to manufacture dual-depth STI structure, then the manufacturing time and cost are reduced, but the etching selectivity control becomes more critical
Solution Approach 1:
The patent utilizes etching selectivity parameters between the sacrificial oxide layer and the silicon substrate to achieve depth control in a single etching step. By carefully controlling the etching conditions and exploiting the differential etch rates, the process achieves both deep and shallow trenches simultaneously, maintaining manufacturing precision while improving productivity.
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 method reduces manufacturing time and cost by enabling the production of semiconductor devices with dual-depth STI structures using a single mask, improving efficiency and reducing the complexity of the manufacturing process.
Implementation Method 1
A one-step etching process with etching selectivity between a sacrificial SiO2 layer and the Si substrate is employed
Implementation Method 2
A chemical-mechanical polishing (CMP) process is performed until the sacrificial oxide layer is removed
Data Source
AI summary
A method for manufacturing a semiconductor device is provided and comprises steps as follows. A Si substrate is provided. The Si substrate includes a first region and a second region. A sacrificial oxide layer is formed on the substrate with respect to the first region. A sacrificial nitride layer is conformally formed on the sacrificial oxide layer and on the substrate with respect to the second region. A photoresist layer is coated over the sacrificial nitride layer. A shallow trench isolation (STI) mask is provided. The STI mask has at least one first STI pattern and at least one second STI pattern to be transferred to the Si substrate to form at least one first trench and at least one second trench in the substrate. A STI oxide layer is deposited. A chemical-mechanical polishing (CMP) process is performed until the sacrificial oxide layer is removed.