Recovery of electronic properties in process-damaged ferroelectrics by ...

(54) RECOVERY OF ELECTRONIC PROPERTIES IN PROCESS-DAMAGED FERROELECTRICS BY VOLTAGE-CYCLING

(75) Inventors: Vikram Joshi; Narayan Solayappan, both of Colorado Springs, CO (US); Walter Hartner; Giinther Schindler,

both of Munich (DE)

(73) Assignees: Symetrix Corporation, Colorado Springs, CO (US); Siemens Aktiengesellschaft, Munich (DE)

( * ) Notice: Under 35 U.S.C. 154(b), the term of this patent shall be extended for 0 days.

(21) Appl. No.: 09/144,297

(22) Filed: Aug. 31, 1998

(51) Int. CI.7 H01L 21/326; H01L 21/479;

H01L 21/00; H01L 21/8242

(52) U.S. CI 438/469; 438/3; 438/240

(58) Field of Search 438/396, 3, 469,

438/240; 427/130

(56) References Cited

U.S. PATENT DOCUMENTS 5,046,043 9/1991 Miller et al. .

5,337,279 * 8/1994 Gregory et al 365/201

5,372,859 * 12/1994 Thakoor 427/551

5,434,102 7/1995 Watanabe et al. .
5,487,032 1/1996 Mihara et al. .
5,508,954 4/1996 Mihara et al. .
5,519,234 5/1996 Paz de Araujo et al. .
5,523,964 6/1996 McMillan et al. .

5,525,528 6/1996 Perino et al. .

5,561,307 10/1996 Mihara et al. .

5,977,577 * 11/1999 Evans, Jr 257/295

5,990,507 * 11/1999 Mochizuki et al 257/295

FOREIGN PATENT DOCUMENTS

0 669 655 A2 8/1995 (EP) .

WO98/05074 2/1998 (WO) .

OTHER PUBLICATIONS

Al-Shareef et al., "Qualitative model for the fatigue-free behavior of SrBi2Ta209," Appl. Phys. Lett., American Institute of Physics, vol. 68 (No. 5), pp. 6910-692 (Jan. 29, 1996).

Furuya et al., "Compositional dependence of electrical characteristics of SrBi2(Tal-xNbx)209 thin-film capacitors," Journal of Applied Physics, American Institute of Physics, vol. 84 (No. 12), p. 6788-6794 (Dec. 15, 1998).

* cited by examiner

Primary Examiner—Richard Elms
Assistant Examiner—Adam Pyonin

(74) Attorney, Agent, or Firm—Duft, Graziano & Forest, PC.

(57) ABSTRACT

An integrated circuit is formed containing a metal-oxide ferroelectric thin film. An voltage-cycling recovery process is conducted to reverse the degradation of ferroelectric properties caused by hydrogen. The voltage-cycling recovery process is conducted by applying from 104 to 1011 voltage cycles with a voltage amplitude of from 1 to 15 volts. Conducting voltage-cycling at a higher temperature in the range 30-200° C. enhances recovery. Preferably the metal oxide thin film comprises layered superlattice material. Preferably the layered superlattice material comprises strontium bismuth tantalate or strontium bismuth tantalum niobate. If the integrated circuit manufacture includes a forming-gas anneal, then the voltage-cycling recovery process is performed after the forming-gas anneal. The voltagecycling recovery process obviates oxygen-recovery annealing, and it allows continued use of conventional hydrogen-rich plasma processes and forming-gas anneals without the risk of permanent damage to the ferroelectric thin film.

15 Claims, 8 Drawing Sheets