High-permittivity thin film capacitor for a semiconductor integrated circuit and a fabrication method thereof

• US 5,882,946 A
• Filed: 04/26/1995
• Issued: 03/16/1999
• Est. Priority Date: 07/27/1994
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Otani, Seigen
• Primary Examiner(s): TSAI, H JEY
• Application Number:
  US08/429,169
• Time in Patent Office: 1,420 Days
• Field of Search: 437/60, 437/52, 437/919
• US Class Current: 438/240
• CPC Class Codes: H01L 27/0605 integrated circuits made of compound material, e.g. AIIIBV
• CPC Class Codes: H01L 28/56 the dielectric comprising two or more layers, e.g. comprising buffer layers, seed layers, gradient layers

Abstract

A semiconductor integrated circuit integrating a high-permittivity thin film capacitor of strontium titanate on the same semiconductor chip, the thin film capacitor consisting of a pair of electrodes and essentially crystalline strontium titanate film therebetween which has a thin surface layer where concentration of titanium is higher than that of the rest of the crystalline strontium titanate film. In one embodiment according to the present invention, a thin film capacitor was fabricated by depositing a 200 nm thick film of strontium titanate at a temperature of 300° C. on a 10 nm thick amorphous titanium oxide film which eventually became the thin surface layer, and subsequent annealing of 250° C. for 30 min in an oxidation atmosphere. A structure and processes realized a thin film capacitor having a dielectric constant of 100 and leakage current density of 4×10^-7 A/cm² without degrading characteristics of transistors already fabricated in the same semiconductor chip.

Claims

1. A method of fabricating a capacitor having a pair of electrodes and a high-permittivity thin film therebetween comprising the steps of:

forming an amorphous layer of titanium oxide TiO_x (0<

X<

2) on a conducting layer for one of the electrodes; and

forming a layer essentially consisting of strontium titanate (SrTiO₃) subsequently on the amorphous layer of titanium oxide.

2. A method of fabricating a capacitor according to claim 1, wherein the amorphous layer of titanium oxide TiO_x (0<

X<

2) is thinner than 30 nm thick.

3. A method of fabricating a capacitor according to claim 1, wherein the amorphous layer of titanium oxide TiO_x (0<

X<

2) is formed at a temperature below 220°

C.

4. A method of fabricating a capacitor according to claim 1, wherein the layer essentially consisting of titanium oxide strontium (SrTiO₃) is formed at a temperature below 350°

C.

5. A method of fabricating a capacitor according to claim 1, further comprising the step of annealing the amorphous layer of titanium oxide TiO_x (0<

X<

2) and the layer essentially consisting of strontium titanate (SrTiO₃) in an oxidation atmosphere.

6. A method of fabricating a semiconductor device having a semiconductor integrated circuit essentially formed in a semiconductor substrate and a capacitor consisting a pair of electrodes and a high-permittivity thin film therebetween formed on the semiconductor substrate comprising the steps of:

forming an amorphous layer of titanium oxide TiO_x (0<

X<

2) on a conducting layer for one of the electrodes formed on an insulated surface of the semiconductor substrate by keeping a substrate temperature below 220°

C.;

forming a layer essentially consisting of strontium titanate (SrTiO₃) subsequently on the amorphous layer of titanium oxide keeping the substrate temperature between 250°

C. and 350°

C. before the amorphous layer of titanium oxide is crystallized; and

annealing the amorphous layer of titanium oxide and the layer essentially consisting of strontium titanate in an oxidation atmosphere keeping the substrate temperature below 300°

C. so that the amorphous layer of titanium oxide is transformed into a layer having a composition of Sr_1-x Ti_x O₃ (0<

X <

1).

7. A method of fabricating a semiconductor device having a semiconductor integrated circuit essentially formed in a semiconductor substrate and a capacitor consisting a pair of electrodes and a high-permittivity thin film therebetween formed on the semiconductor substrate comprising the steps of:

forming an amorphous layer of strontium titanium oxide on a conducting layer for one of the electrodes formed on an insulated surface of the semiconductor substrate by keeping a substrate temperature below 220°

C.;

forming a layer essentially consisting of strontium titanate (SrTiO₃) subsequently on the amorphous layer of titanium oxide keeping the substrate temperature between 250°

C. and 350°

C. before the amorphous layer of titanium oxide is crystallized; and

annealing the amorphous layer of strontium titanium oxide and the layer essentially consisting of strontium titanate in an oxidation atmosphere keeping the substrate temperature below 300°

C. so that the amorphous layer of strontium titanium oxide is transformed into a layer of a crystalline strontium titanate.