Recess Gate Transistor with Capture Layer for Uniform Doping
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Solution Overview
Problem
The existing recess gate structure in semiconductor devices faces challenges in achieving efficient doping of impurities, particularly in deep zones, due to penetration phenomena and decreased doping efficiency as the height of the silicon electrodes increases, which affects the short channel effect and leakage current in DRAMs.
Innovation Solution
A method involving a gate conductive layer with a capture species, such as carbon or nitrogen, is used, where the layer is doped with impurities and then diffused through annealing, ensuring efficient impurity accumulation and distribution across the recess, including deep zones, by forming a multi-layered structure with a capture species in the intermediate layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If ion beam implantation method is used to dope deep zones, then doping depth is improved, but penetration phenomenon occurs causing poor manufacturing precision
Solution Approach 1:
A capture layer is introduced as an intermediary between the silicon electrode and the deep zone. This capture layer absorbs excess impurities during ion beam implantation, preventing penetration through the silicon electrode while still allowing doping to reach deep zones. The capture layer acts as a buffer that mediates between the doping source and the target deep zone, solving the contradiction between achieving deep doping and maintaining concentration control.
2Manufacturing precision
If plasma doping method is used, then surface doping is improved, but doping efficiency decreases for deep zones
Solution Approach 1:
The doping process is segmented into two distinct phases: first, plasma doping is used to achieve high surface doping concentration; second, ion beam implantation is used to dope deep zones. The capture layer is also segmented into different regions that selectively interact with each doping method. This segmentation allows each doping technique to operate in its optimal regime without compromising the other, thereby resolving the contradiction between surface doping quality and deep zone doping efficiency.
3Reliability
If silicon electrode height is increased, then gate control is improved, but doping efficiency decreases
Solution Approach 1:
The capture layer serves as a mediator between the tall silicon electrode and the impurity source. During ion beam implantation, the capture layer intercepts and absorbs excess impurities that would otherwise penetrate through the entire silicon electrode structure. This allows the silicon electrode to maintain its necessary height for good gate control while the capture layer ensures that doping efficiency is maintained by preventing impurity loss through penetration.
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 enhances impurity doping efficiency, preventing penetration and ensuring uniform doping across the recess, thereby improving the driving performance and reducing leakage current in semiconductor devices.
Implementation Method 1
doping the gate conductive layer with an impurity, wherein the impurity is accumulated in the capture zone
Implementation Method 2
diffusing the impurity by performing annealing
Data Source
AI summary
A transistor including a recessed gate structure having improved doping characteristics and a method for forming such a transistor. The transistor includes a recess in a semiconductor substrate, where the recess is filled with a recessed gate structure including an impurity doped layer and a layer doped with a capture species. The capture species accumulates the impurity and diffuses the impurity to other layers of the recessed gate structure.