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New Technology Presentation Meetings of AIST (September 20)


Kogakuin University New Technology Presentation Meetings
High transparent oxide film was discovered as alternative of ITO

December 4, 2018, “Kogakuin University New Technology Presentation Meetings” was held in JST. In this here, an oral presentation by Dr. Aikawa is picked up.

The research group has researched doping technology of dopants with different ion radius as semiconductor for TFT in the past. This new oxide material was discovered in the process of this R & D. This technology is based on ion radius and Lewis acid density of dopant material, which is doped into In2O3 host material. If a dopant with small ion radius is doped, scattering cross-section becomes to be little, as a result, carrier mobility is increased. On the other hand, if Lewis acid density is high, carrier mobility is increased because of increase of shielding effect.

Dopant ion
Ion radius (nm)
Lewis acid density
  Oxygen binding dissociation energy (kJ/mol)
B3+
0.027
10.709
  809
W6+
0.06
3.158
  720
Si4+
0.04
8.096
  799
Sn4+
0.069
1.617
  528
Zn2+
0.074
0.656
  250

Table 1. Property of dopant ion1)
Therefore, various dopant materials were estimated as table 1. As a result, B3++ was desirable as dopant material because of superior ion radius and Lewis acid density respectively. And also, it has excellent oxygen binding dissociation energy property. It means that chemical resistance is superior.

Figure 1 shows comparison of light transmission. Light transmission of B3+ doped In2O3 film was high compared to that of the conventional ITO (In2O3-SnO2). By contrast, specific resistance was higher such as 1.7×10-3Ω･cm than that of ITO film (7×10-4Ω･cm) in as-deposition state after RF sputtering deposition. However, if deposited film is annealed after deposition, specific resistance is expected to be lowered.

Figure 1. Comparison of light transmission1)
Furthermore, wet-etching ratio of this film was almost same as that of ITO film in the wet-etching process using a conventional etchant for ITO. Of course, residual dross was not observed. This is reason why 3+ is solved into In2O3 at solid state.

As you can image easily, this new film can be deposited and wet-etched by conventional process for ITO. For this reason, if basic characteristic is widely authorized, it may be used as alternative material of ITO in near future.

Reference
1)Aikawa：New transparent oxide conductor due to replacing ITO, Kogakuin University New Technology Presentation Meetings!, pp.17-20 (2018.12)
※This title is translated arbitrarily by Stella News Site because of without English edition of presentation material.

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