Oriented GaN Sputtering Target for Low-Oxygen Uniform Films
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Solution Overview
Problem
Sputtering targets made from gallium nitride face issues such as oxidation, low density, incorporation of impurities like oxygen, uneven erosion, and fragility, which affect the quality and longevity of the sputtered film.
Innovation Solution
A gallium nitride-based sputtering target composed of monocrystalline grains oriented with their c-axes normal to the surface, with a total oxygen concentration of 150 mass ppm or lower and oxygen concentrations in the grains measured at 2×10^17 cm^-3 or higher, enhancing film quality and target durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a sintered body composed of gallium nitride powder is used as a sputtering target, then the target can be easily manufactured, but the surface is susceptible to oxidation and oxygen is discharged during sputtering initiation
Solution Approach 1:
The invention changes the fundamental parameter of the target structure from sintered polycrystalline to oriented polycrystalline with c-axis alignment. This structural parameter change reduces oxygen discharge during sputtering while maintaining manufacturability through a controlled growth process rather than simple sintering.
Solution Approach 2:
The invention creates a composite structure where multiple small monocrystalline grains are oriented and aggregated to form an oriented polycrystalline body. This composite approach combines the low oxygen discharge characteristic of single crystals with the manufacturing advantages of polycrystalline materials.
2Ease of manufacture
If a sintered body composed of gallium nitride powder is used as a sputtering target, then the target can be easily manufactured, but the density of the target is low due to spaces between sintered grains
Solution Approach 1:
The invention changes the density parameter by transforming the target from a sintered structure with inter-granular spaces to an oriented polycrystalline structure where grains are tightly packed and oriented with c-axes normal to the surface, eliminating voids and increasing density.
3Volume of stationary object
If a polycrystalline body is formed by hydride vapor phase deposition method, then a high density target can be obtained, but impurities such as oxygen are incorporated
Solution Approach 1:
The invention changes the crystalline orientation parameter by ensuring c-axis orientation of all grains normal to the surface. This orientation parameter change reduces oxygen incorporation during growth while maintaining high density, solving both problems simultaneously through controlled directional growth.
4Volume of stationary object
If a polycrystalline gallium nitride is synthesized by CVPR method, then a high density at low oxygen concentration is obtained, but the crystal is not orientated and quality is not uniform
Solution Approach 1:
The invention introduces asymmetry in grain orientation by aligning all c-axes normal to the surface, creating a preferred orientation. This asymmetric orientation arrangement ensures uniform quality and suppresses erosion during sputtering while maintaining the high density achieved by CVPR method.
Solution Approach 2:
The invention applies local quality by ensuring each grain has its c-axis oriented normal to the surface, creating uniform local properties throughout the material. This local orientation control results in overall quality uniformity and consistent sputtering performance.
5Object-generated harmful factors
If a gallium nitride single crystal substrate is used as a sputtering target, then the oxygen concentration is low, but fracture easily occurs during sputtering and film-forming rate is very low
Solution Approach 1:
The invention segments the single crystal structure into multiple small monocrystalline grains, each with c-axis orientation. This segmentation into oriented polycrystalline structure reduces fracture risk while maintaining low oxygen concentration, as the multiple grains distribute stress more effectively than a single large crystal.
Solution Approach 2:
The invention creates a composite structure where multiple oriented monocrystalline grains form an oriented polycrystalline body. This composite approach combines the low oxygen concentration advantage of single crystals with the fracture resistance of polycrystalline structures.
6Object-generated harmful factors
If a gallium nitride single crystal substrate is used as a sputtering target, then the oxygen concentration is low, but the film-forming rate is very low
Solution Approach 1:
The invention segments the single crystal into multiple oriented grains, creating an oriented polycrystalline structure that maintains low oxygen concentration while improving film-forming rate through increased active sputtering surface area and more favorable grain orientation for material ejection.
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 solution results in a stable, low-oxygen gallium nitride film with improved uniformity and extended target life by suppressing uneven erosion and fracture during sputtering.
Implementation Method 1
a gallium nitride-based crystalline body comprising a plurality of gallium nitride-based monocrystalline grains whose c-axes are orientated in a direction normal to a predetermined surface
Implementation Method 2
Sputtering method is listed as a technique for forming a gallium nitride thin film. According to the sputtering method, it has been studied to use a sputtering target composed of, for example, gallium nitride as a raw material
Data Source
AI summary
A sputtering target includes a gallium nitride-based crystalline body composed of a plurality of gallium nitride-based monocrystalline grains whose c-axes are orientated in a direction normal to a predetermined surface. The gallium nitride-based crystalline body has a total oxygen concentration of 150 mass ppm or lower, and the gallium nitride-based monocrystalline grains have oxygen concentrations of 2×1017 cm−3 or higher measured by dynamic SIMS method.