LDMOS Substrate Current Blocking via Reverse-Biased Diode
Solution Overview
Problem
LDMOS transistor devices experience performance degradation due to unwanted electric current flowing into the substrate when operating in inductive load mode, affecting thermal and frequency stability.
Innovation Solution
Incorporating a diode, such as a Schottky diode, in a reverse series connection with the PN junction to block electric current flow into the substrate, using a metal-containing element like metal silicide, positioned between the diode and the substrate, and surrounded by the gate and body electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the drain electrode is used as a pickup region electrically connected to an inductive load, then the LDMOS device can be used in an inductive load mode, but a large electric current undesirably flows into the P-type substrate when a negative pulse is applied
Solution Approach 1:
An N-type well is introduced as an intermediary element between the drain electrode and the P-type substrate. This N-type well forms a PN junction with the P-type substrate and creates a reverse-biased diode connection that blocks unwanted current flow into the substrate while allowing the drain to function in inductive load mode.
Solution Approach 2:
The unwanted current flow path into the P-type substrate is extracted and blocked by creating a separate N-type well region. The drain electrode is electrically connected to the N-type well rather than directly to the P-type substrate, separating the useful inductive load function from the harmful current leakage path.
2Power
If the LDMOS device operates in inductive load mode without current blocking, then the device can handle power amplification, but thermal stability and frequency stability deteriorate due to current flowing into the substrate
Solution Approach 1:
The N-type well acts as a mediator that enables power amplification in inductive load mode while preventing thermal and frequency instability. By forming a reverse-biased diode with the P-type substrate, it blocks current flow that would cause thermal heating and frequency drift, thus maintaining stability while preserving power handling capability.
3Device complexity
If no additional structure is added to block current, then the device structure remains simple, but the performance is adversely affected by current flowing into the substrate
Solution Approach 1:
A single N-type well is introduced as a minimal intermediary structure to block unwanted current flow. This addition maintains relative structural simplicity while significantly improving device reliability and performance by preventing current leakage into the substrate during inductive load operation.
Solution Approach 2:
The device structure is segmented by introducing the N-type well as a separate functional region between the drain and substrate. This segmentation allows the drain to maintain its inductive load functionality while the N-type well independently handles the current blocking function, improving reliability without excessive complexity.
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
Effectively prevents large electric currents from flowing into the substrate, ensuring proper operation and desirable performance of the semiconductor device by maintaining thermal and frequency stability.
Implementation Method 1
a diode component configured to form a diode together with (or in cooperation with) the second-type well. The diode may be electrically connected to the PN junction in a reverse (or reverse-bias) series connection
Data Source
AI summary
A semiconductor device may include a first-type substrate. The semiconductor device may further include a second-type well configured to form a PN junction with the first-type substrate. The semiconductor device may further include a diode component configured to form a diode with the second-type well. The diode may be connected to the PN junction in a reverse series connection. The second-type may be N-type if the first-type is P-type, and wherein the second-type may be P-type if the first-type is N-type.