Metal Field Plate Contact in LDMOS for Drift Region Resistance
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Solution Overview
Problem
LDMOS transistors face limitations in achieving high output power with sufficient drain to source breakdown voltage and maximum power gain frequency, particularly in RF power amplifiers, due to challenges in doping profile creation and electric field resistance.
Innovation Solution
A transistor structure with a metal field plate contact extending into a shallow trench isolation structure, which improves performance by attracting electrons and reducing resistance in the drift region, thereby enhancing transconductance, breakdown voltage, and reducing leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional LDMOS transistor structures are used, then manufacturing processes are simpler, but transconductance is lower and resistance is higher
Solution Approach 1:
The patent extends the gate contact vertically into the shallow trench isolation structure, transitioning from a planar contact to a three-dimensional structure. This vertical extension into the STI region creates an additional dimensional pathway for electron attraction, enhancing transconductance without requiring changes to the horizontal device layout or additional processing steps.
Solution Approach 2:
The metal field plate contact acts as an intermediary element between the gate structure and the drift region. By extending into the STI structure, it mediates the electric field distribution and attracts electrons into the drift region, improving carrier concentration and transconductance without directly modifying the semiconductor substrate or doping profiles.
2Strength
If conventional LDMOS transistor structures are used, then device structure is simpler, but breakdown voltage is insufficient
Solution Approach 1:
The vertical extension of the contact into the STI structure creates an additional dimensional control mechanism for the electric field. This allows the field distribution to be optimized in the vertical dimension, enhancing the electric field resistance and breakdown voltage capability of the device.
Solution Approach 2:
The patent modifies the electrical parameters of the drift region by using the extended contact to attract electrons, changing the carrier concentration and electric field distribution. This parameter change in the drift region directly improves the breakdown voltage without requiring changes to the substrate doping or device geometry.
3Reliability
If conventional LDMOS transistor structures are used, then manufacturing is simpler, but resistance in drift region is higher
Solution Approach 1:
The metal field plate contact serves as an intermediary that attracts electrons into the drift region, increasing the carrier concentration. This reduces the resistance in the drift region by providing additional charge carriers without requiring changes to the doping profile or substrate material.
Solution Approach 2:
The extended contact changes the electrical parameters of the drift region by attracting electrons, thereby increasing carrier concentration and reducing resistance. This parameter modification occurs without altering the physical structure of the drift region itself, maintaining manufacturing simplicity.
4Reliability
If conventional LDMOS transistor structures are used, then leakage is higher, but device structure is simpler
Solution Approach 1:
The metal field plate contact extending into the STI structure acts as an intermediary that modifies the electric field distribution at the interface between the drift region and STI. This reduces leakage by controlling the field concentration and preventing excessive field-induced carrier generation at the isolation interface.
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 metal field plate contact structure effectively improves transconductance, reduces resistance, and increases breakdown voltage, addressing the limitations of existing LDMOS transistors in RF power amplifiers.
Implementation Method 1
the metal field plate provides improved performance of the LDMOS by attracting electrons and reducing resistance in the drift region
Implementation Method 2
attracting electrons and reducing resistance in the drift region, thereby enhancing transconductance, breakdown voltage, and reducing leakage
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to a transistor with a metal field plate contact and methods of manufacture. The structure includes: a gate structure (14) on a semiconductor substrate (12); a shallow trench isolation structure (18) within the semiconductor substrate; and a contact (22) extending from the gate structure and into the shallow trench isolation structure.