【World Express】FLOSFIA and JSR Progress Toward Practical use of the World's First P-type Semiconductor, Iridium Gallium Oxide -- Development of New Iridium-Based Film Formation Materials for Mass Production Creates A Solution for Realizing the Ultimate SEMI Ecology™

    (FLOSFIA) and JSR Corporation (JSR) announced today they have jointly developed a new iridium-based film deposition material as a solution for mass production of iridium gallium oxide (alpha-(IrGa)₂O₃). This is the world’s first P-type power semiconductor developed by FLOSFIA for use in combination with corundum-type gallium oxide (alpha-Ga₂O₃). The use of this material allows for mass production in industrial applications as well as the expression of P-type characteristics, which is the most important characteristic of iridium gallium oxide.

    In the industrial application of iridium gallium oxide, there were the following three problems in mass production:
① Iridium acetylacetonate (Ir(acac)₃), a known source of iridium, is poorly soluble in water and has a slow crystal growth rate of less than 1/10 of that of gallium oxide, resulting in a lack of productivity.
② The coverage during crystal growth is poor, making it difficult to form a uniform film inside the trench.
③ Due to the poor filling efficiency inside the trench, a large amount of iridium-based film formation material is required for one film formation.

    Given the iridium element has never been mass-produced as a semiconductor and the raw materials available are limited, it was necessary to develop a completely new iridium-based film forming material. The newly developed material achieves a high-speed crystal growth rate of more than 10 times higher than the conventional material, improves coverage inside trenches (see Fig.1), and reduces the use of iridium-based film deposition materials. As a result, the possibility of mass production application of iridium gallium oxide as a new P-type semiconductor in devices has dramatically increased, making significant progress toward the realization of FLOSFIA's goal of SEMI ecology^TM. Iridium gallium oxide used in combination with gallium oxide was successfully demonstrated in a JBS structure. Iridium gallium oxide is an ultra-wide bandgap semiconductor with an extremely large bandgap of approximately 5 eV and a high hole concentration of 1 x 10¹⁹cm^-3, expecting its applicability to a wide-range of device designs assuming high-electric fields. This provides a solution for mass producibility by enabling early application to a wide range of power converters, including inverters used in the frequency range below 100 kHz.

The results of our study are as follows

    We aimed to apply iridium gallium oxide to a JBS structure that is supposed to be embedded in a trench structure (Fig.2). After fabricating a trench structure in part of the gallium oxide n^- layer, we embedded the iridium gallium oxide. At this time, we used FLOSFIA's proprietary MIST DRY^TM method for crystal growth but used a new iridium-based film formation material that we jointly developed as an iridium source in the solution. By using this new material, we confirmed the growth rate is more than 10 times higher than the conventional one. Cross-sectional observation of this trench structure by SEM confirmed the film thickness distribution of iridium gallium oxide was uniform and the film was formed with good coverage (Fig.3).

    The JBS structure based on the results of this research will be applied from the second-generation diode of FLOSFIA's GaO^TM series of corundum-type gallium oxide (alpha-Ga₂O₃) power devices. In addition to inverters and a wide range of other power converters used in the frequency range below 100 kHz, iridium gallium oxide will be applied to transistors such as MOSFET and IGBT. Examples of power converters include commercial power supplies such as AC adapters, robotic drive circuits, electric vehicles, white goods such as air conditioners and refrigerators, and solar cell power conditioners. The adoption of GaO^TM power devices will challenge the limitations of miniaturization and cost reduction of the entire power converter . Depending on the type of equipment, for example, the degree of miniaturization of power converters can reach several 1/10, and the cost reduction is expected to reach 50% of the total power converters (estimated by FLOSFIA).