High purification of high purity
tungsten materials for semiconductor applications
High purity tungsten powder is the preparation of high purity tungsten and tungsten alloy raw materials, the basis of the target material for preparation of high purity and super pure tungsten powder, general selection with "U" and "Th" low secondary ammonium tungstate As raw materials, through precipitation separation, solvent extraction, separation, ion exchange separation and chemical methods, such As removal of secondary ammonium tungstate As the most impurities in raw material, such As, P, Si, etc.; The purified high purity ammonium paratungstate powder was prepared by calcination, reduction and other processes. The high purity tungsten can be purified by electron beam melting, regional melting, vacuum degassing and other physical purification processes to further remove the impurities in the metal tungsten and get higher purity high purity tungsten materials. During the production of high purity W, the workshop should be kept highly clean to reduce impurities in the product.
The determination of trace elements in high purity tungsten is an important criterion to evaluate the properties of high purity tungsten. With the improvement of material purity, the amount and sensitivity of the elements measured by the traditional spectral analysis and neutron analysis can not meet the requirements of the analysis of high purity tungsten powder for semiconductor, while mass spectrometry plays an increasingly important role in the detection of trace impurities in high purity tungsten powder. In the process of preparing high purity
tungsten target material, the purity of high purity tungsten powder can be analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Glow discharge mass spectrometry (GDMS) is usually used to analyze the final high purity tungsten target products.
Preparation method of high purity tungsten alloy target material
At present, W-Ti and W-Si are the most widely used tungsten alloy targets. Since tungsten alloy materials have strong brittleness and are not suitable for rolling process, tungsten alloy targets are mainly prepared by hot pressing and hot isostatic pressing, among which hot pressing includes vacuum hot pressing and inert gas hot pressing.
In addition to purity and density, the precise control of microstructure and phase structure is one of the most important factors affecting the properties of tungsten alloy. The less the content of β(
Titanium,tungsten) phase in the target material of W-Ti alloy, the less the number of film particles produced after sputtering coating, so the content of β(Ti,W) phase in the target material of W-Ti alloy should be reduced as far as possible, or even contain no.
Preparation method of high purity tungsten target material
High purity tungsten metal targets used in semiconductor industry are usually prepared by hot isostatic pressing.
At present, high purity tungsten and tungsten alloy have been widely used in semiconductor integrated circuit manufacturing as gate electrode, shielding metal, diffusion barrier layer, etc., and become indispensable key base materials. With the increasing integration of semiconductor chips, refractory tungsten metal is expected to become the next generation of semiconductor wiring metal materials, so as to obtain a wider range of applications.
High purity tungsten and tungsten alloy target materials with fine and uniform grain structure and high density can be prepared by hot pressing and hot isostatic pressing. Therefore, it is still the mainstream method for preparing high purity tungsten and tungsten alloy target materials for semiconductor applications. The tungsten target with high purity and high density can be prepared by the process of powder metallurgy and pressure processing, but there is still a certain gap between the tungsten target prepared by hot isostatic pressing and the grain size and grain structure uniformity control.
In recent years, our country in a semiconductor with high purity tungsten and tungsten alloy preparation technology research has made great progress, there emerged a group of engaging in developing and manufacturing high purity semiconductor material research institutions and production enterprises, part of the high pure tungsten and tungsten alloy material has application in batches, but in the product specifications and quality of the defects in the aspects of stability, As a result, domestic manufacturers of semiconductor tungsten target materials are in an inferior position in the international competition. Therefore, it is necessary to further strengthen the relevant basic research work and equipment investment, overcome the key technical barriers for the preparation of high-purity tungsten target materials, and make China occupy a certain right of discourse in the manufacturing field of high-purity tungsten target materials for semiconductor use.
