Sintered Tungsten Target for Low-Particle Sputtering
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Solution Overview
Problem
Conventional tungsten target production methods result in significant particle generation during sputtering, leading to reduced yield and film quality, with unsatisfactory control over crystal grain size and pore distribution, and involve cumbersome processes like hot isostatic pressing that hinder productivity.
Innovation Solution
A tungsten target with a relative density of 99% or higher, controlled pore size and distribution, and precise Vickers hardness, produced by hot pressing tungsten powder at 1,400° C. to 1,500° C. followed by hot isostatic pressing at 1,800° C. to 1,850° C., using powders with narrow particle size distribution and low impurity content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional hot isostatic pressing is used to produce tungsten target, then relative density can be improved, but manufacturing complexity and time consumption increase significantly
Solution Approach 1:
The patent applies preliminary action by conducting hot pressing treatment before hot isostatic pressing. The hot pressing step pre-densifies the tungsten powder compact, creating a more uniform green body that requires less severe HIP conditions to achieve the target 95% relative density. This preliminary densification reduces the complexity and time of the subsequent HIP process while ensuring consistent density throughout the target.
Solution Approach 2:
The patent optimizes specific process parameters: hot pressing at 1,700°C to 2,000°C with controlled pressure, followed by HIP at 1,700°C to 1,850°C. By precisely controlling temperature ranges, pressure conditions, and holding times for each step, the process achieves 95% relative density with reduced overall process complexity compared to conventional single-stage HIP methods.
2Productivity
If crystal grain size is reduced to prevent particle generation, then film yield improves, but manufacturing precision of grain size uniformity becomes difficult to control
Solution Approach 1:
The patent controls crystal grain size by optimizing the hot pressing temperature (1,700°C to 2,000°C) and holding time, followed by HIP treatment at 1,700°C to 1,850°C. These parameter combinations promote uniform grain growth while maintaining small grain dimensions (10 μm to 300 μm), ensuring both high film yield through particle suppression and consistent grain size distribution throughout the target.
Solution Approach 2:
The patent adds 0.01 wt% to 1 wt% molybdenum to the tungsten powder before sintering. Molybdenum acts as a grain growth inhibitor during the hot pressing and HIP processes, enabling the formation of fine, uniform crystal grains (10 μm to 300 μm) while maintaining high density. This composite approach suppresses particle generation during sputtering and ensures uniform erosion characteristics.
3Productivity
If molybdenum is added to tungsten powder to prevent particle generation, then film yield improves, but manufacturing precision of composition control becomes more challenging
Solution Approach 1:
The patent specifies precise molybdenum addition ranges (0.01 wt% to 1 wt%) and controls the powder mixing process to achieve uniform distribution. This controlled composition, combined with optimized hot pressing temperature (1,700°C to 2,000°C) and HIP conditions, ensures that molybdenum effectively suppresses particle generation during sputtering while maintaining consistent compositional uniformity throughout the target.
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 method significantly reduces particle generation, ensuring high-quality tungsten film formation with consistent yield and productivity, by minimizing pores and controlling grain size and hardness variations.
Implementation Method 1
hot pressing a tungsten powder at 1,400° C. to 1,500° C.
Implementation Method 2
sintering the pressed product through hot isostatic pressing at 1,800° C. to 1,850° C.
Data Source
AI summary
To provide a tungsten target in which provision of pores which may cause generation of particles is suppressed, and the size and distribution profile of the pores can be controlled at high precision, and a method for producing the tungsten target. The tungsten target is formed of a sintered product of a tungsten powder. The target has a relative density of 99% or higher, and the number of pores having a size of 0.01 μm2 or more and less than 0.2 μm2 is 20 or less; the number of pores having a size of 0.2 μm2 or more and less than 1.8 μm2 is 5 or less; and the number of pores having a size of 1.8 μm2 or more is 1 or less, when the target is observed in an observation field of 0.15 mm2.