HEMT Gate Insulator Stack for High-k Diffusion Control
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Solution Overview
Problem
Conventional high electron mobility transistors (HEMTs) with a channel layer on a barrier layer face difficulties in improving electrical characteristics when using high dielectric constant films as gate insulating films due to atom diffusion during heat treatment.
Innovation Solution
Incorporating a silicon nitride film with a higher relative dielectric constant than the silicon nitride film, positioned between the high dielectric constant film and the channel layer, reduces atom diffusion and enhances electrical characteristics by providing a barrier layer with nitrogen polarity and a gate electrode on the dielectric film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a high dielectric constant film is used as the gate insulating film of the HEMT, then the capacitance is increased, but atom diffusion occurs during heat treatment which deteriorates electrical characteristics
Solution Approach 1:
A silicon nitride film is introduced as an intermediary layer between the high dielectric constant film and the channel layer. This intermediate silicon nitride film acts as a diffusion barrier that prevents atom diffusion during heat treatment, while allowing the high dielectric constant film to maintain its capacitance-enhancing function.
Solution Approach 2:
The gate insulating film is constructed as a composite structure combining a high dielectric constant film and a silicon nitride film. This composite configuration leverages the high capacitance of the high dielectric constant material while utilizing the diffusion-barrier properties of silicon nitride to protect electrical characteristics.
2Quantity of substance
If a high dielectric constant film is deposited and heat treated, then the relative dielectric constant is increased, but atom diffusion into the film occurs which reduces electrical characteristics
Solution Approach 1:
The silicon nitride film serves as a protective intermediary that blocks atom diffusion during the heat treatment process. This allows the high dielectric constant film to undergo heat treatment and achieve its desired dielectric constant without suffering from atom diffusion-induced deterioration.
Solution Approach 2:
The silicon nitride film is formed in advance before the high dielectric constant film is deposited and heat treated. This preliminary formation of the diffusion barrier ensures that when heat treatment occurs, atoms cannot diffuse into the high dielectric constant film, preserving electrical characteristics while allowing the dielectric constant to be optimized.
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 configuration allows for a large drain current and improved electrical characteristics by reducing atom diffusion and adjusting capacitance, thereby stabilizing two-dimensional electron gas concentration.
Implementation Method 1
it was found that, in a case where a silicon nitride film is present between the high dielectric constant film and the channel layer, the diffusion of the atoms composing the channel layer is reduced
Implementation Method 2
a dielectric film provided on the silicon nitride film; and a gate electrode provided on the dielectric film, wherein a relative dielectric constant of the dielectric film is higher than a relative dielectric constant of the silicon nitride film
Data Source
AI summary
A semiconductor device includes a barrier layer having an upper surface with a nitrogen polarity, a channel layer having an upper surface with a nitrogen polarity, provided on the barrier layer, a silicon nitride film provided on the channel layer, a dielectric film provided on the silicon nitride film, and a gate electrode provided on the dielectric film. A relative dielectric constant of the dielectric film is higher than a relative dielectric constant of the silicon nitride film.