Development of magnetron sputtering titanium target is reviewed

- Dec 05, 2018-

Development of magnetron sputtering titanium target is reviewed

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Rotatable Sputtering Target

As an important functional thin film material in the field of electronic information, high purity titanium is in rapid demand with the rapid development of China's IC, plane display, solar energy and other industries. Magnetron sputtering technology (PVD) is one of the key technologies for preparing thin film materials, and high-purity titanium sputtering target material is the key consumable material in magnetron sputtering technology, which has a broad market application prospect. Titanium target material as high value-added coating material, in such aspects as chemical purity, organizational performance has strict requirements, high technical content, the processing difficulty is big, the target material manufacturing enterprises in our country started relatively late in the field of high-end target material manufacturing, relatively backward in terms of basic raw material purity, preparation techniques such as control target, the core technology of molding technology in and abroad also has certain gap. Aiming at the downstream high-end applications, the development of high-performance titanium sputtering target material is an important measure to realize the independent research and development of key materials in electronic information manufacturing industry and promote the high-end transformation and upgrading of titanium industry.

 High Purity Planar Sputtering Target

Application and performance requirements of titanium target


Magnetron sputtering Ti target material is mainly used in electronics and information industry, such as integrated circuit, plane display screen and decoration coating field of home decoration automobile industry, such as glass decoration coating and hub decoration coating. Ti target material requirements of different industries are also very different, mainly including: purity, microstructure, welding performance, dimensional accuracy and several aspects, the specific index requirements are as follows:

1) Purity: non-integrated circuit: 99.9%; Integrated circuit for: 99.995%, 99.99%.

2) Microstructure: unintegrated circuit: average grain less than 100 microns; Integrated circuit: the average grain is less than 30 microns, the average ultrafine grain is less than 10 microns

3) Welding performance: non-integrated circuit: brazing, monomer; Integrated circuit for: monomer, brazing, diffusion welding

4) Dimensional accuracy: for non-integrated circuits: 0.1mm; For non-integrated circuits: 0.01mm.

1.1 Ti target material for integrated circuit

Ti target material purity of integrated circuit is mainly greater than 99.995% and above, and currently it mainly depends on imports. In 2013, China's integrated circuit industry achieved a sales revenue of 250.8 billion yuan and an import volume of 231.3 billion us dollars, becoming the largest import commodity of China for the first time. In 2014, the sales revenue of the integrated circuit industry was 267.2 billion yuan, and the import volume still reached 217.6 billion us dollars. The target material for integrated circuit occupies a large share in the global target material market.

 Multi-arc Target

Ti target materials: the production of high-purity Ti is mainly concentrated in the United States, Japan and other countries, such as Honeywell of the United States, toho of Japan and Osaka titanium industry of Japan. Since 2010, Beijing nonferrous metal research institute, zunyi titanium industry and ningbo chuangrun have successively launched domestic high-purity Ti products, but the stability of products still needs to be improved.


Ti: structure of target material development early foundry profit space is large, the main use of 100 ~ 150 mm magnetron sputtering machine, and small power, sputtering film thicker, the chip size is larger, single performance of target material can satisfy the use requirement of the machine at that time, the integrated circuit with Ti target material mainly from 100 ~ 150 mm monomer and combination of target, such as the typical type 3180, type 3290 target material, etc. The second stage, according to Moore's law development, chip, narrow linewidth, foundry mainly use 150 ~ 200 mm sputtering machine, in order to improve the profit space, the machine of the sputtering power increase, this requires that the size of target increase, while keeping the high thermal conductivity, low prices and a certain strength, this period Ti target material by aluminum alloy backplane diffusion welding and brazing of copper alloy backboard two structures is given priority to, such as the typical TN, TTN type, type Endura5500 target material, etc. In the third stage, with the development of integrated circuit, chip line width becomes narrower. At this time, chip foundering factories mainly use 200 ~ 300mm sputtering machines. In order to further increase profit space, sputtering power of the machines increases, which requires the size of target material to be increased, while maintaining high thermal conductivity and sufficient intensity. In this period, Ti target is mainly welded with copper alloy back plate, such as the mainstream SIP type target.


Ti target material processing and manufacturing aspects: early market at home and abroad, by the United States, Japan and other large manufacturers monopoly target material, after 2000 years of domestic manufacturing industry gradually into the target market, low end target to start importing high purity Ti raw material processing, in recent years by the rapid development of domestic Ti target material manufacturing enterprises, the market share gradually expanded to Taiwan, Europe and the United States and other markets, such as YouYan million gold and Jiang Feng electronic two enterprise focus target material manufacturing for many years. Domestic target manufacturing enterprises are also developing target materials jointly with domestic magnetron sputtering machine manufacturers to promote the development of domestic integrated circuit magnetron sputtering industry.


1.2 Ti target material for plane display


Flat panel displays include: liquid crystal display (LCD), plasma display (PDP), field luminescence display (e-l), field emission display (FED).


At present, the LCD market is the largest in the flat panel display market with a share of more than 90%. LCD is believed to be the most application prospect of flat-panel display device, it greatly expands the application range of monitor, the notebook computer monitors, desktop computer monitor, high-definition LCD TV and mobile communication, all kinds of new type LCD products are hitting the people living habits, and promote the rapid development of information industry of the world. Tft-lcd technology is a kind of technology that combines microelectronics technology and liquid crystal technology skillfully. At present, it has become the mainstream technology of plane display, which is divided into al-mo, al-ti, cu-mo and other processes.


The thin film of planar display is mostly formed by sputtering. Al, Cu, Ti, Mo and other targets are the main metal targets for plane display at present. The purity of Ti targets for plane display is more than 99.9%. This raw material can be made in China. Tft-lcd6 generation line USES flat Ti target material with large size, copper alloy water-cooled back plate target material is used in the structure, and CLP panda is applied.


At present, the world's highest generation line independently built by China -- hefei 10.5 generation line mainly produces large-size ultra-high definition liquid crystal display (uhd), with a design capacity of 90,000 glass substrates per month. The size of glass substrates is 3,370x2,940mm, with a total investment of 40 billion yuan. It will be put into production in the second quarter of 2018.


2. Magnetron sputtering Ti target preparation technology


Ti raw material preparation technology and methods of target material according to the production process can be divided into (hereinafter referred to as EB billet) and vacuum electron beam melting billet from electricity arc furnace smelting grey (hereinafter referred to as (VAR) billet) two kinds big, in the process of preparation of target material, in addition to strictly control the material purity, density, grain size and crystal orientation, the condition of heat treatment process, the subsequent forming process will need to be strictly controlled, to ensure the quality of the target material.


For the raw materials of high purity Ti, the impurity elements with high melting point in Ti matrix are usually removed by melt electrolysis, and then further purified by vacuum electron beam melting. Vacuum electron beam smelting is to use high-energy electron beam bombardment on the metal surface, and then the temperature gradually increases until the metal melts. The elements with high vapor pressure will be the first to evaporate, and the elements with low vapor pressure will remain in the melt. The greater the difference between the impurity elements and the vapor pressure of the matrix, the better the purification effect will be. However, the advantage of vacuum refining after melting is that impurity elements in Ti matrix can be removed without introducing other impurities. Therefore, when 99.99% electrolytic Ti is electrolyzed by electron beam smelting in a high vacuum environment (10-4 above), impurity elements (Fe, Co, Cu) with a saturation vapor pressure higher than the saturation vapor pressure of Ti element itself (Fe, Co, Cu) in the raw material will be given priority to wave, so as to reduce the content of impurities in the matrix and achieve the purpose of purification. The high purity metal Ti with 99.995 + purity can be obtained by combining the two methods.


For the raw materials with purity of 99.9% Ti, grade 0 sponge Ti is mostly used to be smelted by vacuum consumable electric arc furnace, and then the blank is opened by hot forging to form small-size blank. Ti metal raw material of the preparation of the two methods through the thermal mechanical deformation control its entire sputtering surface microstructure is consistent, then machined, binding, cleaning and packaging process into the preparation of integrated circuit with magnetron sputtering Ti, target material for 300 mm machine is used for special high Ti target material, in advance of sputtering target material surface before packing and sputtering reduce installed on the sputtering machine is used to Burn the target time of target (Burn - ingtime).


Ti target material preparation method of integrated circuit has complex technology and relatively high cost.


3. Technical requirements for Ti target materials


In order to ensure the quality of deposited film, the quality of target material must be strictly controlled. After a lot of practice, the main factors influencing the quality of Ti target material include purity, average grain size, crystal orientation and structure uniformity, geometric shape and size, etc.


3.1 Purity


The purity of Ti target material has a great influence on the properties of sputtering films.

The higher the purity of Ti target material, the less impurity element particles in sputtering Ti film, resulting in better film properties, including corrosion resistance, electrical and optical properties. However, in practical applications, the purity requirements of Ti target materials for different applications are different. For example, the general decoration coating with Ti target material purity requirements are not demanding, and integrated circuit, display body and other fields with Ti target material purity requirements are much higher. As the cathode source in sputtering, the impurity elements and pore inclusions are the main pollution sources. The stomatal inclusions will be basically removed in the process of ingot nondestructive flaw detection. The unremoved stomatal inclusions will produce tip discharge phenomenon (Arcing) during sputtering, and then affect the quality of the thin film. However, impurity element content can only be reflected in the results of whole-element analysis. The lower the total impurity content is, the higher the purity of Ti target material will be. Early domestic not high purity titanium sputtering target materials, is reference to the domestic and foreign Ti target material manufacturing company, after 2013 standard issued by the YS/T893-2013 electronic film with high purity titanium sputtering target materials, regulations three purity Ti target material single impurity content and total impurity content different demands, this standard is gradually standardize busy Ti purity of target market demand.


3.2 average grain size


Generally, Ti target material is of polycrystalline structure, with grain size ranging from micron to millimeter. Sputtering rate of small-size grain target is faster than that of coarse grain target, and the thickness distribution of sputtering deposited film is more uniform for targets with small difference in grain size on sputtering surface. It is found that if the grain size of titanium target is controlled below 100 microns, and the change of grain size is kept within 20%, the quality of sputtering films can be greatly improved. The average grain sizes of Ti targets to be used in integrated circuits are generally required to be less than 30 microns, and the average grain sizes to be less than 10 microns.


3.3 crystallization orientation


Metal Ti is a densely arranged hexagonal structure. Since it is easy for Ti target atoms to be preferentially sputtered along the direction of the most closely arranged hexagonal atoms during sputtering, the sputtering rate can be increased by changing the crystal structure of the target material to achieve the highest sputtering rate. At present, the crystal family of Ti target sputtering surface {1013} of most integrated circuits is more than 60%, the grain orientation of target materials produced by different manufacturers is slightly different, and the crystal direction of Ti target also has a great influence on the thickness uniformity of sputtering film. The film size of plane display and decoration coating is relatively thick, so the grain orientation requirement of Ti target material is relatively low.


3.4 uniformity of structure


Structure uniformity is also one of the important indexes to evaluate the quality of target material. For Ti target, not only the sputtering plane of target material, but also the normal direction composition, grain orientation and average grain size uniformity on the sputtering plane are required. Only in this way can Ti film with uniform thickness, reliable quality and consistent grain size be obtained at the same time within the service life of Ti target material.


3.5 geometric shape and size


It is mainly reflected in machining precision and quality, such as machining size, surface flatness, roughness, etc. If the Angle deviation of the mounting hole is too large, it cannot be installed correctly; Small thickness will affect the service life of the target; The size of sealing surface and sealing groove is too rough, which will lead to vacuum problems after the target material is installed and lead to water leakage. Target sputtering surface roughening treatment can make the surface of the target material is full of rich convex tips, under the effect of tip effect, the potential of these convex tips will be greatly improved, thus breakdown media discharge, but too large convex sputtering quality and stability is adverse.


3.6 welding bonding

At present about Ti/Al dissimilar metal diffusion welding research paper more, usually for high melting point of titanium and diffusion welding of low melting point of aluminum material, mainly based on one-way or two-way pressure or vacuum diffusion bonding technology of hot isostatic pressing technology was adopted to realize titanium, aluminum metal materials of high pressure in low temperature direct diffusion bonding. Ti/Cu and Cu alloy welding domestic manufacturers have many applications, but few research papers.


4. Prospect of Ti target materials


Global target manufacturing bases are rapidly gathering in Asia. With the rapid development of domestic high-tech industries such as semiconductor integrated circuit, plane display and decorative coating, China's target material market is expanding day by day, and has gradually become one of the world's largest demand areas for thin film target material, which provides opportunities and challenges for the development of China's target material manufacturing industry.


In recent years, in the integrated circuit industry funds, national science and technology major projects (01, 02, 03) and local funds, team leads, the integrated circuit industry investment is a big heat, according to statistics, only 2015, 2016 two years, the domestic has declared under construction or planning to start wafer production line is up to 44, 300 of them mm18 article, article 200 mm20, 6 150 mm. Driven by the huge market demand, the target material industry is bound to attract the attention and attention of relevant scientific research institutes and enterprises in China, and have invested human, material and financial resources in the research and development and production of magnetic-controlled splash target.


Ti target material, as a unique branch of target material field, has been applied in both semiconductor Al process and Cu process, and has been widely used in LCD industry and decorative coating industry. At present, Ti target material r&d and production bases are mainly concentrated in Beijing, guangdong, jiangsu, zhejiang, gansu and other places. Due to the raw material purity of target, the limitation of production equipment and technology research and development technology, Ti target material manufacturing industry in our country is still in the early stage, the domestic Ti target material production enterprise belongs to the quality and the basic technical threshold is low, the traditional processing method, on price to win the low level of sputtering target materials producers, or profit limited OEM factory. Single small production scale, variety, technology also is not stable, so far, China (including Taiwan), only a few company specialized in the production of target material, such as YouYan million gold, Jiang Feng electronic enterprise, production of Ti target material far far cannot satisfy the needs of the development of the market, a large number of Ti target material still need to import from abroad, raw materials of high purity metal Ti target material have breakthrough, but most still have to rely on imports.


Ti target material, as a kind of material with special purpose, has strong application purpose and clear application background. Metallurgical purification technology separated from metal Ti, EB vacuum smelting technology, Ti ingot nondestructive flaw detection technology, impurity analysis technology of high purity Ti, preparation technology of Ti target, sputtering machine preparation technology, sputtering technology and thin film performance test technology simply studying Ti target itself has no significance. The r&d and production of Ti target material and its subsequent application improvement involve an entire industrial chain from upstream raw materials to mid-stream equipment manufacturers and target material manufacturers, and downstream Ti target coating chip application. The relationship between Ti target material properties and sputtering film properties is not only conducive to obtaining film properties that meet application requirements, but also to better use of target material, giving full play to its role and promoting the development of target material industry.


Is currently in the IC industry in mainland China booming stage, the opportunities and challenges coexist, if you can't seize the opportunity to target material manufacturing, film manufacturing and testing equipment, the gap between our country and international level will be bigger and bigger, not only unable to regain the foreign occupation of the domestic market, more can't participate in the international market competition.