What are the application fields of the target
As we all know, the technical development trend of target materials is closely related to the development trend of thin film technology in the downstream application industry. With the technical improvement of thin film products or components in the application industry, the target technology should also change. Such as Ic manufacturer. In recent years, we are committed to the development of low-resistivity copper wiring. It is expected that the original aluminum film will be greatly replaced in the next few years. In this way, the development of the copper target and the required barrier layer target material will not be delayed. In addition, in recent years, flat panel displays (FPD) have largely replaced computer monitors and televisions, which were originally based on cathode ray tubes (CRT). It will also greatly increase the technology and market demand for ITO targets. Also in terms of storage technology. The demand for high-density, large-capacity hard drives and high-density rewritable optical discs continues to increase. All these have led to changes in the application industry's demand for target materials. Below we will separately introduce the main application areas of targets and the development trends of targets in these areas.
Microelectronics
In all application industries, the semiconductor industry has strict requirements on the quality of target sputtering films. Now a 12-inch (300 socket) silicon wafer has been manufactured. However, the width of the interconnection lines is decreasing. The requirements of silicon wafer manufacturers for targets are large size, high purity, low segregation and fine grains, which requires the manufactured targets to have a better microstructure. The crystalline particle diameter and uniformity of the target have been considered to be the key factors affecting the film deposition rate. In addition, the purity of the film is closely related to the purity of the target. In the past, copper targets with a purity of 99.995% (4N5) may be able to meet the needs of semiconductor manufacturers for the 0.35pm process, but they cannot meet the current 0.25um process requirements. For 0.18um technology or even 0.13m process, the required target purity will be required to reach 5 or more than 6N. Compared with aluminum, copper has higher resistance to electromigration and lower resistivity, which can satisfy! The conductor technology needs sub-micron wiring below 0.25um, but it brings up other problems: the adhesion strength between copper and organic dielectric materials is low. And it is easy to react, causing the copper interconnection of the chip to be corroded and disconnected during use. In order to solve the above problems, it is necessary to provide a barrier layer between the copper and the dielectric layer. The barrier layer material generally uses metals and their compounds with high melting point and high resistivity. Therefore, the thickness of the barrier layer is required to be less than 50 nm, and the adhesion performance to copper and dielectric materials is good. The barrier layer materials of copper interconnection and aluminum interconnection are different. Need to develop new target materials. The target materials for the barrier layer of copper interconnection include Ta, W, TaSi, WSi, etc. But Ta and W are both refractory metals. It is relatively difficult to produce. Nowadays, Taiwan gold such as molybdenum and chromium is being studied as an alternative material.
For display
Flat-panel displays (FPD) have greatly impacted the computer monitor and TV markets, which are dominated by cathode ray tubes (CRT), and will also drive the technology and market demand for ITO targets. There are two types of iTO targets today. One is to use nano-state indium oxide and tin oxide powder to be mixed and sintered, and the other is to use an indium tin alloy target. Indium tin alloy targets can be produced by DC reactive sputtering to produce ITO films, but the surface of the target will be oxidized to affect the sputtering rate, and it is not easy to obtain large-sized metal targets. Nowadays, various methods are generally adopted to produce ITO targets, using L}IRF reactive sputtering coating. It has a fast deposition rate. And it can control the film thickness, high conductivity, good film consistency, and strong adhesion to the substrate. However, it is difficult to make the target material because indium oxide and tin oxide are not easily sintered together. Generally, ZrO2, Bi2O3, CeO, etc. are used as sintering additives, and a target material with a density of 93% to 98% of the theoretical value can be obtained. The performance of the ITO film formed in this way is closely related to the additive. Japanese scientists use Bizo as an additive. Bi2O3 melts at 820Cr, and the excess part of the sintering temperature has been volatilized at a sintering temperature of l500°C. In this way, a relatively pure ITO target can be obtained under liquid-phase sintering conditions. Moreover, the required oxide raw materials are not necessarily nanoparticles, which can simplify the preliminary process. The resistivity of the ITO film obtained from Caichuan's target material reached 8.1×10n-cm, which was close to the resistivity of a pure ITO film. The sizes of FPD and conductive glass are quite hot, and the width of conductive glass can even reach 3133 mm. In order to improve the utilization rate of target materials, ITO targets of different shapes, such as cylindrical, have been developed. In 2000, the National Development Planning Commission and the Ministry of Science and Technology included ITO large-scale targets in the "Guide to Current Priority Information Industry Fields".
For storage
In terms of storage technology, the development of high-density, high-capacity hard disks requires a large number of giant magnetoresistive film materials. CoF~Cu multilayer composite film is a widely used giant magnetoresistive film structure today. The TbFeCo alloy target material required for magneto-optical disks is still being further developed. Magneto-optical disks manufactured with it have the characteristics of large storage capacity, long life, and repeated non-contact erasing and writing. The magneto-optical disk developed today has a layered composite film structure of TbFeCo/Ta and TbFeCo/Al. The Kerr rotation angle of the TbFeCo/AI structure reaches 58, while the TbFeCofFa can be close to 0.8. After research, it is found that the target material with low magnetic permeability has high AC partial discharge voltage l withstand electric strength.
Phase change memory (PCM) based on germanium antimony telluride shows significant commercialization potential and is an alternative memory technology for NOR-type flash memory and some DRAM markets. However, it exists on the road to achieve faster scaling down One of the challenges is the lack of a fully enclosed unit that can further reduce the reset current. Reducing the reset current can reduce the power consumption of the memory, extend the battery life and increase the data bandwidth, which are very important features for the current data-centric, highly portable consumer devices.
