Scanning photoinduced current analyzer capable of detecting photoinduced current in nonbiased specimen

• US 5,952,837 A
• Filed: 08/29/1997
• Issued: 09/14/1999
• Est. Priority Date: 07/18/1995
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Koyama, Tohru
• Primary Examiner(s): Nguyen, Vinh P.
• Application Number:
  US08/921,254
• Time in Patent Office: 746 Days
• Field of Search: 324/71.3, 324/73.1, 324/158.1, 324/752, 324/765, 324/769, 324/750, 438/14, 438/17, 438/18, 257/40, 257/48, 356/400, 356/401, 348/126
• US Class Current: 324/754.23
• CPC Class Codes: G01R 31/311 of integrated circuits G01R31/31728 takes precedence

Abstract

A sample to be measured having a semiconductor integrated circuit having interconnection lines is set on a scanning photoinduced current analyzer with one end of the interconnection line being open and the other end connected through a current amplifier to the ground. When a laser beam falls on part having a comparatively low thermal conductivity, such as a part having a void, of the interconnection line while the interconnection line is scanned with the laser beam, temperature distribution in the interconnection line changes at the part. The change in temperature distribution produces spontaneous thermoelectromotive force by the Seebeck effect to induce a current. The current amplifier amplifies the induced current, and then an image date converter converts the amplified current into image information in synchronism with the scanning operation of the laser beam. Since the photoinduced current can be measured without supplying a bias current to the sample to be measured, a current image corresponding to the photoinduced current can be formed to determine the position of a void even if the sample to be measured has a high resistance.

Claims

1. A scanning photoinduced current analyzer capable of detecting photoinduced current induced in a sample to be measured when the sample to be measured is scanned with a focused laser beam, said scanning photoinduced current analyzer comprising:

a laser light source that emits the laser beam;

scanning means for controlling the laser beam to scan a region specified by a first control signal;

focusing means for focusing the laser beam on the sample to be measured;

control means that provides the first control signal;

a source of reference potential for supplying a first potential;

current amplifying means connected between the source of reference potential and one end of the sample to be measured, an opposite end of the sample being open, to amplify the current flowing through the sample to be measured and to provide a signal corresponding to the amplified current;

image converting means for converting the output signal of the current amplifying means into image information in synchronism with the scanning operation of the laser beam and for providing the image information; and

image output means for reconstructing an image represented by the image information.

2. A scanning photoinduced current analyzer according to claim 1, further comprising image forming means for forming an image of the reflected light reflected from the sample to be measured and supplying image forming information to the image converting means,

said image converting means including switching means for selectively establishing a first state in which the image information is supplied to the image output means or a second state in which the image forming information is supplied to the image output means, according to a second control signal, wherein

said control means provides the second control signal.

3. A scanning photoinduced current analyzer according to claim 1, further comprising a resistor connected to the open other end of the sample to be measured.

4. A scanning photoinduced current analyzer according to claim 1, further comprising a capacitor connected between the open end of the sample to be measured and the source of reference potential.

5. A scanning photoinduced current analyzer according to claim 1, said scanning means further including scanning speed varying means for varying the scanning speed of the laser beam.

6. A scanning photoinduced current analyzer according to claim 1, wherein, when the sample to be measured includes a semiconductor, the wavelength of the laser beam emitted by the laser light source is longer than a wavelength corresponding to the band gap energy of the semiconductor.