Optical coupling for testing integrated circuits

• US 7,042,563 B2
• Filed: 01/24/2005
• Issued: 05/09/2006
• Est. Priority Date: 12/21/2000
• Status: Expired due to Term

• Current Assignee: DCG Systems Incorporated (Thermo Fisher Scientific Incorporated)
• Original Assignee: Credence Systems Corporation (COHU Incorporated)
• Inventors: Kasapi, Steven, Wilsher, Kenneth R.
• Primary Examiner(s): Rosenberger, Richard A.
• Application Number:
  US11/042,288
• Publication Number:
  US 20050128471A1
• Time in Patent Office: 470 Days
• Field of Search: 356/237.1, 324/752, 324/753
• US Class Current: 356/237.1
• CPC Class Codes: G01R 31/311 of integrated circuits G01R31/31728 takes precedence
• CPC Class Codes: G01R 31/31905 Interface with the device under test [DUT], e.g. arrangements between the test head and the DUT, mechanical aspects, fixture

Abstract

A method and system of testing integrated circuits (IC) via optical coupling. The optical system includes an optical fiber, fixture and focusing element. In addition, channels are provided in the fixture mounted on the integrated circuit to accommodate the optical system. The fixture acts as a heat sink. As such, one or more photosensitive elements/targets on the integrated circuit are probed using light that is brought to a focus on each target site. The light causes latching of data into the integrated circuit (which is operating under influence of a test program) and formation of a test pattern output from the integrated circuit that is used to confirm proper functioning of the IC.

Claims

1. An optical test system for testing a device under test comprising:

a fixture attached to an integrated circuit under test;

an optical fiber held within said fixture and optically connected at its proximal end to a light source having a beam of light, wherein said optical fiber is held by said fixture in optical alignment with said device under test;

means for retrieving the latched data from said device under test;

an output device for reporting the retrieved latch data in a format that enables analysis of the device under test; and

a computing device configured to receive the retrieved latch data and determine the functionality of the device under test.

2. The optical test system of claim 1 wherein said fixture acts as a heat sink for said device under test.

3. The optical test system of claim 1 wherein said light source is a laser.

4. The optical test system of claim 1 wherein said focusing element is a computer-generated holographic optical element (CG-HOE).

5. The optical test system of claim 1 wherein said focusing element is a zone-plate.

6. The optical test system of claim 1 wherein said focusing element is a lens.

7. The optical test system of claim 1 further comprising one or more lenses located in combination with said focusing element to focus said light onto a photosensitive target on said device under test.

8. A method of testing a device under test having an operating integrated circuit on a fixture comprising the acts of:

obtaining a fixture defining a hole;

inserting an optical fiber into a hole defined in said fixture;

applying light from a light source to a proximal end of said fiber;

focusing said light as it exits a distal end of said fiber onto a photosensitive element of said integrated circuit thereby to cause latching of data into said integrated circuit;

relaying the latched data from said integrated circuit to an output device; and

analyzing the relayed data to determine the functioning of the device under test.

9. The method of claim 8 further comprising the act of capturing light at a proximal end of said fiber reflected by said element.

10. The method of claim 9 further comprising the act of analyzing said reflected light for proper focusing of said light onto said element.

11. The method of claim 9 further comprising the act of analyzing said reflected light to determine whether said light is correctly coupled into said fiber.

12. The method of claim 8 where said fixture performs the function of a heat sink for said device under test.