Trench Gate MOSFET Sacrificial Layer Thermal Oxidation
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Solution Overview
Problem
Conventional trench gate MOSFET manufacturing processes face challenges in controlling the depth of the doped region due to top edge deformation caused by thermal oxidation, leading to instability and significant height differences in the doped region, especially in short channel devices.
Innovation Solution
A method involving the formation of a trench gate MOSFET with a sacrificial layer and a nitrogen-containing hard mask layer to protect the top corner of the trench during thermal oxidation, maintaining a substantially right angle and preventing deformation, allowing for uniform depth control of the doped region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermal oxidation process is used to form an interlayer insulating layer, then the insulating layer can be effectively formed, but the top edge of the trench is severely deformed and over-expanded, causing significant height difference in the subsequently formed doped region
Solution Approach 1:
A sacrificial layer is formed on the sidewall of the upper portion of the trench before the thermal oxidation process. This sacrificial layer protects the top edge of the trench from deformation during subsequent thermal oxidation, preventing over-expansion and maintaining uniform depth control of the doped region.
Solution Approach 2:
The sacrificial layer acts as an intermediary protective structure between the trench top edge and the thermal oxidation process. It absorbs the harmful thermal effects and physical stress, preventing direct damage to the trench geometry while allowing the necessary thermal oxidation to proceed for insulating layer formation.
2Ease of manufacture
If the top edge of the trench is allowed to deform during thermal oxidation, then the thermal oxidation process can be completed, but the contour difference of the doped region increases, reducing process stability
Solution Approach 1:
The sacrificial layer is prepared in advance on the trench sidewall to preemptively protect against top edge deformation during thermal oxidation, ensuring both process completion and contour uniformity.
Solution Approach 2:
The sacrificial layer is selectively applied only to the upper portion sidewall of the trench where deformation occurs, providing localized protection without interfering with the overall thermal oxidation process or other regions of the structure.
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 improves process stability by maintaining a uniform depth of the doped region and preventing top edge deformation, enhancing the consistency and reliability of the transistor.
Implementation Method 1
An interlayer insulating layer is formed on the first conductive layer by a thermal oxidation process when the sacrificial layer and the hard mask layer are present
Data Source
AI summary
Provided is a method of forming a trench gate MOSFET. A hard mask layer is formed on a substrate. The substrate is partially removed by using the hard mask layer as a mask, so as to form a trench in the substrate. A first insulating layer and a first conductive layer are formed in the lower portion of the trench. A sacrificial layer is formed on the side surface of the upper portion of the trench, and the sacrificial layer is connected to the hard mask layer. An interlayer insulating layer is formed on the first conductive layer by a thermal oxidation process when the sacrificial layer and the hard mask layer are present. A second insulating layer and a second conductive layer are formed in the upper portion of the trench. A trench gate MOSFET is further provided.