Bipolar Transistor Trench Structure for Current Gain Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current bipolar transistors in CMOS integrated circuits face limitations in current gain due to the small emitter region and topographically uneven regions caused by the front-layer multi-step cleaning and etching process, leading to poor stability and limited current gain range.
Innovation Solution
A trench structure is introduced in the bipolar transistor manufacturing process, where a shallow trench isolation structure defines active areas, and a salicide block dielectric is deposited within the trench to form a metal silicide block structure, eliminating uneven topography and enhancing current gain stability by preventing metal silicide and electrode formation in the trench region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional process leaves an SAB layer at the emitter to increase current gain, then the current gain of the bipolar transistor is improved, but the area available for the SAB region is limited, greatly limiting the rate of increase in current gain
Solution Approach 1:
The patent transitions from a planar SAB layer to a three-dimensional trench structure. By etching a trench into the emitter region and filling it with salicide block dielectric material, the SAB structure extends vertically into the substrate, increasing the effective SAB region volume without occupying additional lateral area. This dimensional transition allows for greater current gain enhancement within the same footprint.
Solution Approach 2:
The trench structure nests the salicide block dielectric material within the etched trench in the emitter region. This nested configuration allows the SAB structure to be embedded within the existing emitter geometry, maximizing the use of available space while providing enhanced current gain control through the vertical trench structure.
2Ease of manufacture
If a front-layer multi-step cleaning and etching process is used, then the emitter region is prepared for subsequent processing, but topographically uneven regions are formed, affecting SAB region area and electric field distribution, resulting in poor stability of current gain
Solution Approach 1:
The patent performs a preliminary trench etching step before the front-layer multi-step cleaning and etching process. By pre-defining the trench boundaries and depth, subsequent processing steps can proceed without creating topographically uneven regions that would affect SAB region uniformity. The preliminary action establishes a controlled geometry that maintains current gain stability throughout subsequent manufacturing steps.
Solution Approach 2:
The trench structure creates a localized region with distinct properties within the emitter. The salicide block dielectric material is selectively placed in the trench, providing enhanced SAB functionality in that specific location while maintaining uniform processing conditions across the rest of the emitter region. This local modification improves current gain stability without compromising overall manufacturability.
3Area of stationary object
If the emitter region area is limited, then the transistor fits within the required footprint, but the rate of increase in current gain is greatly limited
Solution Approach 1:
The patent resolves the area limitation by transitioning to a vertical trench structure. The SAB region extends downward into the substrate along the trench depth, increasing the effective SAB volume without increasing the lateral emitter footprint. This allows current gain to be enhanced while maintaining the required transistor footprint.
Solution Approach 2:
The patent uses a composite structure combining the semiconductor substrate, etched trench, and salicide block dielectric material. This composite trench structure provides enhanced current gain control within the limited emitter area by utilizing the vertical dimension and the specific electrical properties of the salicide block dielectric material filled within the trench.
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 trench structure increases the current gain range and stability of the bipolar transistor, allowing for greater control over current gain through adjustable trench dimensions, thereby overcoming the limitations of prior art designs.
Implementation Method 1
a salicide block dielectric is deposited within the trench to form a metal silicide block structure
Data Source
AI summary
The present disclosure relates to a semiconductor structure and a manufacturing process therefor. Provided is a method for manufacturing a bipolar transistor with a trench structure, including providing a semiconductor substrate; fabricating a shallow trench isolation structure to define a device active area; forming an N-type well and a P-type well in the active area to define a first region, a second region and a third region of the bipolar transistor; etching a portion, adjacent to the shallow trench isolation structure, in the first region to form a trench; performing ion implantation to form an emitter, a base and a collector of the bipolar transistor; forming a salicide block structure in the trench; and forming a metal electrode of the bipolar transistor, wherein the emitter is formed in the first region. The present disclosure further provides a bipolar transistor with a trench structure.