Bulb-shaped Trench Buried Bit Line Isolation
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Solution Overview
Problem
The existing methods for manufacturing semiconductor devices with vertical transistors face challenges in preventing electric shorts between buried bit lines and word lines due to difficulties in accurately controlling the etching process during the damascene word line formation.
Innovation Solution
A method is developed to form a buried bit line separated from the surrounding gate by a specific interval, using a doped polysilicon layer, and involving a series of etching and deposition steps to create a bulb-type trench and a separate buried bit line, ensuring a distance of 500 Å to 2000 Å from the bottom portion of the surrounding gate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the etching process is performed with an exact etching target during the damascene word line process, then the damascene word line can be formed higher than the bottom portion of the surrounding gate, but it is difficult to adjust the etching target with excessive etching potentially causing an electric short between the buried bit line and the word line
Solution Approach 1:
The patent applies preliminary action by forming a protective film (such as a spacer or insulating layer) on the buried bit line before the damascene word line etching process. This protective layer is deposited in advance to prevent the etching process from exposing the buried bit line, thereby eliminating the risk of electric short while still allowing precise etching control for the word line formation.
Solution Approach 2:
The patent implements beforehand cushioning by introducing a protective film that acts as a buffer between the etching process and the buried bit line. This cushioning layer absorbs the potential harm of excessive etching, ensuring that even if the etching target is not perfectly controlled, the buried bit line remains protected and no electric short occurs.
2Area of stationary object
If the buried bit line is formed closer to the surrounding gate to improve integration, then the device area is reduced, but the risk of electric short between the buried bit line and word line increases
Solution Approach 1:
The patent introduces an intermediary protective film between the buried bit line and the etching process. This mediator allows the buried bit line to be positioned closer to the surrounding gate for better integration while still preventing electric short by blocking the etching process from exposing the bit line, thus resolving the contradiction between compact design and reliability.
3Manufacturing precision
If the etching process is performed to form the word line at the exact target depth, then the manufacturing precision is improved, but any deviation causes excessive etching and potential electric short
Solution Approach 1:
The patent applies beforehand cushioning by depositing a protective film on the buried bit line before the etching process. This cushioning layer tolerates variations in etching depth, allowing the etching process to proceed without risking exposure of the buried bit line even if the etching depth control deviates from the target, thus reducing the harmful effects of imprecise etching.
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 effectively prevents electric shorts between the buried bit line and the word line, allowing for precise control and improved device characteristics by maintaining a defined separation, enhancing the integration and performance of semiconductor devices.
Implementation Method 1
forming a bit line material film in the bulb-type trench
Implementation Method 2
The buried bit line is obtained by ion-implantation into the semiconductor substrate between the surrounding gates
Data Source
AI summary
A method for manufacturing a semiconductor device includes forming a bulb-type trench separated from a surrounding gate and forming a buried bit line in the bulb-type trench, thereby preventing electric short of a word line and the buried bit line. A semiconductor device includes a vertical pillar formed over a semiconductor substrate, a surrounding gate formed outside the vertical pillar, and a buried bit line separated from the surrounding gate.