Field-effect transistor and method for fabricating field-effect transistor

• US 8,268,666 B2
• Filed: 07/07/2010
• Issued: 09/18/2012
• Est. Priority Date: 07/09/2009
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Abe, Yukiko, Ueda, Naoyuki, Nakamura, Yuki, Sone, Yuji
• Primary Examiner(s): HO, TU TU V
• Application Number:
  US12/831,454
• Publication Number:
  US 20110006299A1
• Time in Patent Office: 804 Days
• Field of Search: 438/104, 438/149, 438/479, 257/43, 257/288, 257/347, 257/E29.296, 257/E21.461
• US Class Current: 438/104
• CPC Class Codes: H01L 21/02565 Oxide semiconducting materials not being Group 12/16 materials, e.g. ternary compounds
• CPC Class Codes: H01L 21/02631 Physical deposition at reduced pressure, e.g. MBE, sputtering, evaporation
• CPC Class Codes: H01L 29/66969 of devices having semiconductor bodies not comprising group 14 or group 13/15 materials comprising selenium or tellurium in uncombined form other than as impurities in semiconductor bodies of other materials, comprising cuprous oxide or cuprous iodide H01L21/02365
• CPC Class Codes: H01L 29/7869 having a semiconductor body comprising an oxide semiconductor material, e.g. zinc oxide, copper aluminium oxide, cadmium stannate

Abstract

A method for fabricating a field-effect transistor having a gate electrode, a source electrode, a drain electrode, and an active layer forming a channel region, the active layer having an oxide semiconductor mainly containing magnesium and indium is disclosed. The method includes a deposition step of depositing an oxide film, a patterning step of patterning the oxide film by processes including etching to obtain the active layer, and a heat-treatment step of heat-treating the obtained active layer subsequent to the patterning step.

Claims

1. A method for fabricating a field-effect transistor having a gate electrode, a source electrode, a drain electrode, and an active layer forming a channel region, the method comprising:

a deposition step of depositing an oxide film containing In₂MgO₄;

a patterning step of patterning the oxide film by processes including etching to obtain an active layer having an oxide semiconductor containing In₂MgO₄; and

a heat-treatment step of heat-treating the obtained active layer subsequent to the patterning step.

2. The method as claimed in claim 1, wherein in the heat-treatment step, a heat-treat temperature for heating the obtained active layer is equal to or higher than a deposition temperature at which the oxide film is deposited in the deposition step.

3. The method as claimed in claim 1, wherein in the heat-treatment step, a heat-treat temperature for heating the obtained active layer is equal to or higher than 200°

C.

4. The method as claimed in claim 1, wherein in the heat-treatment step, a heat-treat temperature for heating the obtained active layer is in a range of 300°

C. to 500°

C.

5. The method as claimed in claim 1, wherein in the deposition step, at least one of aluminum (Al) and gallium (Ga) is substituted for part of indium (In) in the oxide film containing In₂MgO₄.

6. The method as claimed in claim 1, wherein in the deposition step, at least one of calcium (Ca), strontium (Sr) and barium (Ba) is substituted for part of magnesium (Mg) in the oxide film containing In₂MgO₄.

7. The method as claimed in claim 1, wherein in the deposition step, the oxide film containing In₂MgO₄ is deposited such that at least part of the oxide film containing In₂MgO₄ includes a spinel structure or an olivine structure.

8. The method as claimed in claim 7, wherein in the deposition step, the oxide film containing In₂MgO₄ is deposited such that at least part of the oxide film is amorphous.

9. A method for fabricating a field-effect transistor having a gate electrode, a source electrode, a drain electrode, and an active layer forming a channel region, the active layer having an oxide semiconductor mainly containing magnesium and indium, the method comprising:

a deposition step of depositing an oxide film;

a patterning step of patterning the oxide film by processes including etching to obtain the active layer; and

a heat-treatment step of heat-treating the obtained active layer subsequent to the patterning step,

wherein in the deposition stei the oxide film containing In₂MgO₄ is deposited, and

wherein in the deposition step, at least one of aluminum (Al) and gallium (Ga) is substituted for part of indium (In) and at least one of calcium (Ca), strontium (Sr) and barium (Ba) is substituted for part of magnesium (Mg) in the oxide film containing In₂Mga₄.

10. A method for fabricating a field-effect transistor having a gate electrode, a source electrode, a drain electrode, and an active layer forming a channel region, the active layer having an oxide semiconductor mainly containing magnesium and indium, the method comprising:

a deposition step of depositing an oxide film;

a patterning step of patterning the oxide film by processes including etching to obtain the active layer; and

a heat-treatment step of heat-treating the obtained active layer subsequent to the patterning step,

wherein in the deposition step, at least one of nitrogen and fluorine is substituted for part of oxygen in the oxide film containing In₂MgO₄.