(19)

(11)

EP 0 324 020 A1

(12)

(43) Date of publication: 19.07.1989 Bulletin 1989/29 (21) Application number: 88906932.0 (22) Date of filing: 22.07.1988

(51) International Patent Classification (IPC):  H01L 21/ 76( . ) H01L 21/ 762( . ) (86) International application number: PCT/GB1988/000597 (87) International publication number: WO 1989/001236 (09.02.1989 Gazette 1989/04)

(84) Designated Contracting States: AT BE CH DE FR GB IT LI LU NL SE (30) Priority: 24.07.1987 GB 19870017612 (71) Applicant: PLESSEY OVERSEAS LIMITED Ilford Essex IG1 4AQ (GB)	(72) Inventor: DUNCAN, Shane Kingsthorpe Northampton (GB) (74) Representative: Lupton, Frederick  The Plessey Company plc Intellectual Property Dept. Vicarage Lane Ilford, Essex IG1 4AQ Ilford, Essex IG1 4AQ (GB)