テクニカルジャーナル

Our new plasma source "ISM-duo" enables the across-wafer etching rate uniformity of our uGmni etching module to be controlled. ISM-duo consists of an RF current distribution unit and two separate ICP antennas placed coaxially so as to control the spatial distribution of plasma generated in the process chamber. The RF current distribution to each antenna is performed at an arbitrary ratio without depending on process parameters such as gas type, and changing the distribution ratio does not disturb impedance matching. These features enable a stable operation of the etching rate uniformity control through the optimization of the RF current distribution ratio for various processes. ISM-duo delivers a new process tuning knob that enlarges the process window in our etching module.

We have developed the radical assist sputter epitaxy (RaSE) method to enable epitaxial growth of gallium nitride (GaN) by sputtering and the "SEGul" system for mass production. Compared to the metal organic chemical vapor deposition (MO-CVD) method, which is a common GaN film formation method, the RaSE method has the advantages of a low deposition temperature and a low material cost when forming epitaxial GaN thin films. The MO-CVD method uses organometallics and toxic gases such as NH₃ as raw materials at a formation temperature of about 1000℃. In contrast, the "RaSE" method uses common materials such as Ga, N₂, and Ar, and GaN formation can be performed at relatively low temperatures of 700℃ or lower. It can also be applied to the formation of high density n-type GaN thin films with n-type carrier density in the 1x10²⁰ cm^-3 range by using an additional sputtering source for doping. In this report, we describe the characteristics of GaN thin films formed by the RaSE method, as well as the mass production system "SEGul" which can handle up to 8-inch wafer sizes.

Organic light emitting diode (OLED) devices are applied to various displays such as smartphones, monitors, and TVs, but it is necessary to improve the cost and lifetime of such displays. Top emission type OLEDs have high light extraction efficiency but require higher transmission and lower resistance cathode electrodes, so we have developed a low damage sputtering process for these OLED devices.
Sputtering processes with high temperatures and lots of particles not only reduce device performance, but also reduce mass production yields. That is why ULVAC's sputtering process concepts for these OLED devices are "low damage," "low temperature," and "low particle."
In this paper, we analyzed the sputtering damage factor related to device performance and established a sputtering process that can reduce the damage factor. The drive voltage and efficiency of OLED devices using the low damage sputtering process was the same as that of the reference vapor deposition device, and the lifetime was more than 20% longer.

We have developed a method of micro arc oxidation treatment (VACAL®-Z) as a surface treatment for aluminum alloy used in vacuum equipment using corrosive gases, such as CVD equipment. The oxide layer formed by VACAL®-Z had a three layer structure of crystalline γ-alumina. In addition, we have devised and made possible a step processing method for treating the entire surface of large objects, such as vacuum production equipment for flat panel displays, by VACAL®-Z.

We have developed a new batch-type isotropic gas etching system that does not utilize H radicals. The isotropic gas etching process is used in semiconductor manufacturing to etch pattern structures and requires high aspect ratio etching without causing damage to the underlying layer. Our previous release, RISE-300, was a batch-type gas etching tool that utilized H radicals and was easy to handle due to the absence of highly corrosive gases like HF. However, it was difficult to control the etching distribution within each batch. In recent years, conventional processes have become insufficient to meet the performance requirements of device manufacturers. Our new batch-type isotropic gas etching process, which does not utilize H radicals, outperforms conventional methods in terms of wafer-to-wafer uniformity and step coverage. Additionally, this new process allows for precise control of etching distribution within the wafer plane.

The size of glass substrates in organic light emitting diode (OLED) vapor deposition equipment has increased, the mainstream has changed from conventional G6H devices to G8H devices, and the vapor deposition equipment itself has also become larger. Therefore, cryopumps used as high vacuums pumps will also be increased in size from 20 inches to 22 inches, and pumping speed will increase. In this paper, we introduce the history of 22-inch cryopump development and a technology that realizes both cost reduction and energy saving in a cryopump system that will be adopted in the G8H in the future.

The problem with organic light-emitting diode (OLED) displays is that their service lifetime is affected by impurities in vacuum equipment. Therefore, equipment manufacturers need to ensure the cleanliness of their equipment. We developed a technology to evaluate trace amounts of water-soluble impurities in vacuum equipment by using ion chromatography (IC). As a result, we established our own simple cleanliness evaluation technology.
By using this evaluation technology to monitor and take countermeasures against residual ions in the equipment during each process from manufacturing to delivery, we have been able to manufacture equipment with high cleanliness that meets the required quality.
In addition, we conducted device fabrication and service lifetime tests on OLED deposition equipment to evaluate the impact of equipment components on device lifetime. The evaluation of devices exposed to fluorinated resin-coated cables suggested that the factor causing service lifetime degradation was a gas containing C-F. Meanwhile, it was found that the devices can still be used as device components by reducing the amount of impurities through appropriate cleaning processes. We will contribute to further quality improvement of OLED production equipment by utilizing this technology.

When radio frequency (RF) power sources are used on both the cathode and stage sides, effective stage bias can be achieved by controlling the RF phase. We found that this can be ascertained from the voltage peak to peak (Vpp) curve at each phase position.
The number of layers in 3D-NAND flash memory is increasing, so the processed height of each layer must be reduced to maintain the total device height. The height of etch-stop layers must also be reduced, and a filling process is required for insulator materials. ULVAC had knowledge of stable RF sputtering processes, but we were not able to produce an adequate filling performance. We knew that the stage bias process used in conventional ULVAC technologies, such as high coverage ionized sputtering (HiCIS), was a good candidate for this filling process. However, it is only used for metal layers, which have lower ionized energy materials. We tried to combine both cathode and stage RF processes, but the filling performance was not stable and we could not control the RF processes together. In order to solve these issues, we found that phase control is one of the key factors to not only use matching control but also control stage bias effectiveness. Also, filling performance can be controlled by selecting the correct phase position for both the cathode and stage RF output. It makes further possibility for sputter process applications.