Thin film semiconductor device containing polycrystalline Si-Ge alloy and method for producing thereof

• US 6,521,909 B2
• Filed: 02/23/2001
• Issued: 02/18/2003
• Est. Priority Date: 02/01/2001
• Status: Expired due to Term

• Current Assignee: Panasonic Liquid Crystal Display Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Hitachi, Ltd.
• Inventors: Shiba, Takeo, Hatano, Mutsuko, Park, Seong-Kee, Yamaguchi, Shinya
• Primary Examiner(s): Sherry, Michael
• Assistant Examiner(s): Sarkar, Asok Kumar
• Application Number:
  US09/790,545
• Publication Number:
  US 20020102823A1
• Time in Patent Office: 725 Days
• Field of Search: 257/19, 257/347-354, 438/141, 438/142, 438/149, 438/150, 438/164, 438/166, 438/168, 438/172, 438/311, 438/312, 438/796, 438/798, 438/933
• US Class Current: 257/19
• CPC Class Codes: H01L 29/66757 Lateral single gate single channel transistors with non-inverted structure, i.e. the channel layer is formed before the gate
• CPC Class Codes: H01L 29/78675 with normal-type structure, e.g. with top gate
• CPC Class Codes: H01L 29/78684 having a semiconductor body comprising semiconductor materials of Group IV not being silicon, or alloys including an element of the group IV, e.g. Ge, SiN alloys, SiC alloys H01L29/7869 takes precedence
• CPC Class Codes: H01L 29/78696 characterised by the structure of the channel, e.g. multichannel, transverse or longitudinal shape, length or width, doping structure, or the overlap or alignment between the channel and the gate, the source or the drain, or the contacting structure of the channel H01L29/78612 takes precedence; transistors having a drain offset region or a lightly doped drain [LDD] H01L29/78621
• CPC Class Codes: Y10S 438/933 Germanium or silicon or Ge-Si on III-V

Abstract

A high performance thin film transistor is provided containing polycrystalline Si-Ge alloy. The TFT has a crystal structure restraining both current scattering in a grain boundary and surface roughness by introduction of Ge into Si. This permits realizing an image display device having high performance and a large area at low cost.

Claims

1. A thin film transistor device comprising:

(a) an insulator substrate;

(b) a poly-crystalline thin film formed on said insulator substrate; and

(c) a transistor including a source, a drain, a channel, and a gate formed on said poly-crystalline thin film,

wherein said poly-crystalline thin film in a channel part of said transistor is comprised of a silicon-germanium poly-crystalline Si_1-xGe_x in which a Ge concentration x is 0<

x<

1, and a Ge concentration x in the poly-crystalline thin film is larger in a grain boundary than a portion where a Ge concentration in an interior crystal grain of the poly-crystalline thin film becomes a minimum value.

2. A thin film transistor device as set forth in claim 1, wherein a thickness of said poly-crystalline thin film is 10-100 nm, a ratio x of a Ge concentration in a portion where a Ge concentration is the minimum value in an interior grain of crystal forming said poly-crystalline thin film is 0<

x≦

0.3, a ratio x of a Ge concentration in a grain boundary is 0.1<

x≦

1.0, and a ratio x of the Ge concentration is larger in the grain boundary than in a central part of the interior crystal grain.

3. A thin film transistor device as set forth in claim 1, wherein said poly-crystalline Si_1-xGe_x has surface roughness thereof in the grain boundary being equal to or less than 30 nm.

4. A thin film transistor device as set forth in claim 1, wherein a main current carried in a channel part of said transistor is a positive hole.

5. A thin film transistor device comprising:

(a) an insulator substrate;

(b) a poly-crystalline Si_1-xGe_x thin film formed on said insulator substrate in which a Ge concentration x is 0<

x<

1; and

(c) a circuit part formed by integrating a plurality of pieces of transistors including sources, drains, channels, and gates formed on said poly-crystalline Si_1-xGe_x thin film,

wherein, said circuit part is comprised of CMOS type transistors including a mixture of p type transistors and n type transistors, and at least one of said p type transistors is comprised of the transistor as set forth in claim 1.

6. A thin film transistor device comprising:

(a) an insulator substrate;

(b) a poly-crystalline thin film formed on said insulator substrate; and

(c) a transistor including a source, a drain, a channel, and a gate formed on said poly-crystalline thin film,

wherein said poly-crystalline thin film in a channel part of said transistor has a {110}-oriented crystal surface, and wherein an average lattice constant in a grain boundary is larger than an average lattice constant in an interior crystal grain part of the poly-crystalline thin film.