Nitride Recess Gate Structure Using Polarity Inversion Wet Etching
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Solution Overview
Problem
Achieving a recess gate structure in nitride semiconductors is challenging due to the lack of suitable etchants for wet etching and the damage caused by dry etching, which degrades device characteristics and hinders the establishment of a selective etching technique for uniformity and reproducibility.
Innovation Solution
A semiconductor device and manufacturing method that includes forming a polarity inversion layer of AlN with Group-V polarity on a nitride semiconductor layer, allowing for the formation of a recess gate structure using selective wet etching that minimizes device damage and ensures accurate groove depth control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If dry etching with plasma is used to etch nitride semiconductor layer, then etching can be performed, but crystal damage occurs causing degradation of device characteristics
Solution Approach 1:
The patent changes the chemical parameters of the etching process by using a specific wet etchant composition (ammonium fluoride and hydrofluoric acid in specific ratios) instead of conventional dry etching plasma conditions, thereby achieving etching without crystal damage
Solution Approach 2:
The patent replaces the physical/mechanical dry etching process with a chemical wet etching process, substituting plasma-based physical removal with solution-based chemical dissolution to avoid mechanical damage to the crystal structure
2Reliability
If wet etching is used to etch nitride semiconductor layer, then no crystal damage occurs, but suitable etchant is unavailable making wet etching virtually impossible
Solution Approach 1:
The patent introduces an intermediary substance (ammonium fluoride) that facilitates the etching of nitride semiconductor by converting the chemically inert nitride surface into a form that can be selectively removed, thereby enabling wet etching where none was previously possible
Solution Approach 2:
The patent modifies the chemical environment by introducing specific pH-adjusting agents and chelating agents in the etchant formulation, changing the chemical parameters to enable selective etching of nitride semiconductor layers
3Ease of manufacture
If conventional etching methods are used, then etching can be performed, but selective etching technique is not established hindering uniformity and reproducibility
Solution Approach 1:
The patent achieves selective etching by creating local quality differences through the polarity inversion layer, which has different etching characteristics than the surrounding nitride semiconductor regions, enabling precise and uniform groove formation only where needed
Solution Approach 2:
The patent establishes a controlled etching process where the etchant selectively interacts with the polarity inversion layer, providing inherent feedback control that stops etching automatically when the groove reaches the desired depth, ensuring uniformity and reproducibility
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
Facilitates the easy realization of a recess gate structure in nitride semiconductors by reducing processing damage and ensuring consistent groove formation, thereby maintaining device characteristics and threshold voltage stability.
Implementation Method 1
the polarity inversion layer is a layer made by nitriding aluminum oxide
Implementation Method 2
a first semiconductor layer formed on the substrate and made of a first nitride semiconductor epitaxially grown in a positive direction along the c-axis
Data Source
Figure 1A~1C
Figure 1D~1F
Figure 1G~1I
AI summary
A first semiconductor layer (102) is formed on a substrate (101) by crystal growth of a first nitride semiconductor in a direction along a c-axis. A second semiconductor layer (103) made of a second nitride semiconductor having a band-gap energy larger than that of the first nitride semiconductor is formed on the first semiconductor layer (102). A polarity inversion layer (104) made of AlN and having a Group-V polar surface on a partial region on the second semiconductor layer (103) is formed.