The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 04, 1992
Filed:
Aug. 14, 1990
Toshihiko Nakata, Hiratsuka, JP;
Yukio Kembo, Yokohama, JP;
Tsuguo Sawada, Tokyo, JP;
Takehiko Kitamori, Ushiku, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
A method and apparatus are disclosed for detection of surface defects and internal defect information of a sample, such as a semiconductor device, using the photoacoustic effect. Operationally, an intensity-modulated laser beam is provided having a predetermined desired frequency. The intensity-modulated laser beam is focused on the sample thereby inducing said photoacoustic effect inside the sample which is detected in two-dimensional directions of the sample so as to compose a two-dimensional photoacoustic image of the excited sample. Surface and internal information of the sample is then extracted from the two-dimensional photoacoustic image and an inverse filtering factor is in turn computed on the basis of a thermal impulse response of the particular sample for compensating degradation of the resolution of the actual photoacoustic image obtained. Lastly, the computed inverse filtering factor is then applied to the detected photoacoustic image to arrive at an image having greatly improved resolution.