Trench Gate Semiconductor Device Dummy Gate Screening
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for evaluating the reliability of dummy gate insulator films in trench gate semiconductor devices are inadequate, leading to increased market failure rates due to potential short-circuits in metal wires and inability to apply voltage to dummy gate insulator films during screening, which affects the breakdown voltage and parasitic capacitance.
Innovation Solution
A fabrication method that includes forming trench gate structures with both active and dummy trench gate structures, where the dummy gate electrode is short-circuited to an electrode pad after screening, allowing for the application of a predetermined voltage to evaluate the dummy gate insulator film reliability and reducing the market failure rate by identifying faulty chips during the fabrication process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the dummy gate electrode is short-circuited to the emitter electrode to prevent parasitic capacitance increase, then the switching loss is reduced, but the reliability of the dummy gate insulator film cannot be evaluated during screening
Solution Approach 1:
The patent applies preliminary action by performing the voltage application test to the dummy gate insulator film before the dummy gate electrode is short-circuited to the emitter electrode. The screening process is executed at an intermediate stage where the dummy gate electrode is still electrically isolated, allowing reliability evaluation to be conducted prior to the short-circuiting operation that would prevent subsequent testing.
Solution Approach 2:
The patent segments the fabrication process into distinct stages: first forming the dummy gate structure with isolated electrode, then performing screening tests, and finally short-circuiting the dummy gate electrode. This segmentation allows the reliability evaluation to be performed as a separate step before the electrical connection is made, resolving the contradiction between early short-circuiting for performance and late testing for reliability.
2Reliability
If voltage is applied to the dummy gate insulator film for reliability screening, then the breakdown voltage can be measured, but the dummy gate electrode must remain electrically isolated from the emitter electrode
Solution Approach 1:
The patent performs the voltage application test to evaluate dummy gate insulator film reliability before the dummy gate electrode is short-circuited to the emitter electrode. This preliminary screening approach allows the insulator film to be tested while still electrically accessible, avoiding the need for complex post-short-circuit testing arrangements.
3Reliability
If the number of trench MOS cells is reduced to increase the interval between cells, then the parasitic thyristor latch-up is prevented, but the electric field concentration increases at the trench bottom and breakdown voltage decreases
Solution Approach 1:
The patent introduces dummy gate structures as intermediary elements between the active trench MOS cells. These dummy gates serve as electrical buffers that prevent parasitic thyristor latch-up by providing alternative current paths and reducing electric field concentration at the trench bottoms of active cells, thereby maintaining breakdown voltage without requiring increased spacing between functional cells.
4Ease of manufacture
If conventional screening is performed with the dummy gate electrode short-circuited to the emitter electrode, then the fabrication process is simplified, but no voltage can be applied to the dummy gate insulator film for reliability evaluation
Solution Approach 1:
The patent performs the reliability screening of the dummy gate insulator film before the dummy gate electrode is short-circuited to the emitter electrode. This preliminary action allows voltage to be applied to the insulator film for breakdown voltage measurement while the electrode remains electrically isolated, enabling reliability evaluation without complicating the subsequent short-circuiting step.
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 method enables effective evaluation of dummy gate insulator film reliability and reduces market failure rates by ensuring the dummy gate electrode is properly short-circuited, thereby maintaining the breakdown voltage and reducing parasitic capacitance, resulting in a more reliable semiconductor device.
Implementation Method 1
screening is executed to evaluate the reliability of the gate insulator film by applying a predetermined voltage to the gate insulator film of the trench side wall
Implementation Method 2
the reliability of the dummy gate insulator film cannot be measured
Data Source
AI summary
A semiconductor device that includes a plurality of trench gate structures each having a gate electrode extending in a depth direction of an element, the plurality of trench gate structures including first trench gate structures respectively contributing to control of the element and second trench gate structures respectively not contributing to the control of the element, the semiconductor device including an electrode portion having a potential other than a gate potential, and an electrode pad that is disposed on a front face of a semiconductor substrate, wherein the electrode pad is used as a terminal to apply a predetermined voltage to gate insulator films, in screening that is executed by applying the predetermined voltage to the gate insulator films respectively in contact with the gate electrode connected to the electrode pad and that is executed before the electrode pad is short-circuited to the electrode portion.