110. The thickness of In film 121 and In film 122 is, for example, from 2 μm to 15 μm.

Next, as shown in FIG. 11, a sputtering of an oxide containing In, for example, In₂O₃(indium oxide), is performed. As a result, an oxide film 131 containing In is formed on the surface of In film 121. An oxide film 132 containing In is formed on the surface of In film 122. An oxide film 133 containing In is formed on the surface of In film 123. Oxide film 131, oxide film 132, and oxide film 133 are, for example, In₂O₃films.

When oxide film 131, oxide film 132, and oxide film 133 are formed by a sputtering such as a reactive sputtering, for example, a structure illustrated in FIG. 10 is placed in a film forming chamber. An internal pressure of the film forming chamber is 3×10⁻⁶Torr. An In₂O₃sintered material is used as a target material. A mixture gas of Ar (argon) gas and O₂gas is supplied into the film forming chamber. A partial pressure of the O₂gas is 1×10⁻⁴Torr. A total pressure of the mixture gas is 5×10⁻³Torr. A target voltage is 2 kV. A power density is from 3.2 W/cm²to 4.8 W/cm². A film forming speed is set to 0.13 nm/see to 0.23 nm/sec.

A method of forming oxide film 131 and oxide film 132 is not limited to a sputtering. Oxide films 131 and 132 may be formed by a vacuum evaporation, a thermal oxidation, a natural oxidation, or an wet treatment. As described above, oxide film 131 and oxide film 132 may be formed by various methods.

When oxide film 131 and oxide film 132 are formed by a vacuum evaporation, for example, a structure shown in FIG. 10 is placed in the film forming chamber. An internal pressure of the film forming chamber is 2×10⁻⁵Torr. In₂O₃powder is used as an evaporation source, and a temperature of substrate 10 is set to 100° C. A film forming speed is set to 0.2 nm/sec to 0.3 nm/sec.

Next, as shown in FIG. 12, photoresist film 110 is removed. As photoresist film 110 is removed, In film 123 and oxide film 133 are also removed. As shown in FIGS. 12 and 13, a remaining In film 121 forms an In bump 101. A remaining In film 122 forms an In bump 102. In this manner, In bump 101 and In bump 102 are formed by a lift-off method. A surface of In bump 101 is covered with oxide film 131. A surface of In bump 102 is covered with oxide film 132. In bump 101 and In bump 102 are examples of first bumps. Each of oxide film 131 and oxide film 132 is an example of a first oxide films.

Photoresist film 110 can be removed by dissolution using, for example, an organic solvent such as acetone or a so-called resist remover solution such as N-methylpyrrolidone (NMP). For example, photoresist film 110 can be removed by immersing the structure shown in FIG. 11 in acetone or NMP at a temperature of 60° C. or less and holding it for about 24 hours. When oxide film 131 and oxide film 132 are formed, photoresist film 110 may be kept in a high temperature environment and may be solidified or carbonized. In this case, photoresist film 110 may be removed by O₂ashing, for example.

In this manner, In bump 101 and In bump 102 are formed as first bumps containing In. Oxide film 131 is formed as an oxide film containing In on the surface of In bump 101. Oxide film 132 is formed as an oxide film containing In on the surface of In bump 102.

Next, a method of forming a second bump containing In and a method of forming an oxide film containing In on the surface of the second bump will be described. FIGS. 14 to 20 are cross-sectional views illustrating a method of forming a second bump and an oxide film according to the first embodiment.

First, as shown in FIG. 14, a readout circuit substrate (ROIC) 200 is prepared. Readout circuit substrate 200 includes a wiring substrate 20, a plurality of pixel electrodes 250, and a common electrode 260. The plurality of pixel electrodes 250 and common electrode 260 are arranged on one surface of wiring substrate 20. Pixel electrode 250 is connected to p-electrode 150, and common electrode 260 is connected to wiring electrode 160. Readout circuit substrate 200 is an example of a circuit substrate. Readout circuit substrate 200 has a second main surface 200a on a side of wiring substrate 20 on which pixel electrode 250 and common electrode 260 are provide. Pixel electrode 250 and common electrode 260 are arranged on second main surface 200a.

Next, as shown in FIG. 15, a photoresist film 210 is formed. Photoresist film 210 is formed on wiring substrate 20, pixel electrode 250, and common electrode 260 by coating.

Next, as shown in FIG. 16, an opening portion 211 and an opening portion 212 are formed. Opening portion 211 exposing pixel electrode 250 and opening portion 212 exposing common electrode 260 are formed on photoresist film 210 by exposing and developing photoresist film 210.

Next, as shown in FIG. 17, an EB evaporation of In is performed. As a result, an In film 221 is formed on pixel electrode 250 inside opening portion 211. An In film 222 is formed on common electrode 260 inside opening portion 212. An In film 223 is formed on photoresist film 210.

Next, as shown in FIG. 18, a sputtering of an oxide containing In, for example, In₂O₃, is performed. As a result, an oxide film 231 containing In is formed on the surface of In film 221. An oxide film 232 containing In is formed on the surface of In film 222. An oxide film 233 containing In is formed on the surface of In film 223. Oxide film 231, oxide film 232, and oxide film 233 are, for example, In₂O₃films. Oxide film 231 and oxide film 232 can be formed under conditions similar to those of oxide film 131 and oxide film 132.

Next, as shown in FIG. 19, photoresist film 210 is removed. As photoresist film 210 is removed, In film 223 and oxide film 233 are also removed. Photoresist film 210 may be removed under the same conditions as photoresist film 110. As shown in FIGS. 19 and 20, a remaining In film 221 forms an In bump 201. A remaining In film 222 forms an In bump 202. In this manner, In bump 201 and In bump 202 are formed by a lift-off method. The surface of In bump