Vacuum activated backside contact

• US 6,091,257 A
• Filed: 02/26/1998
• Issued: 07/18/2000
• Est. Priority Date: 02/26/1998
• Status: Expired due to Term

• Current Assignee: Keithley Instruments, Inc.
• Original Assignee: Keithley Instruments, Inc.
• Inventors: Kleefstra, Meindert J., Verkuil, Roger L.
• Primary Examiner(s): Ballato, Josie
• Assistant Examiner(s): Sundaram, T. R.
• Application Number:
  US09/032,496
• Time in Patent Office: 873 Days
• Field of Search: 324/754, 324/755, 324/758, 324/760, 324/765, 324/757
• US Class Current: 324/754.1
• CPC Class Codes: G01R 31/2886 Features relating to contacting the IC under test, e.g. probe heads; chucks G01R31/2865 takes precedence, test connections, e.g. test sockets, or probes per se, G01R1/04 or G01R1/06

Abstract

An apparatus for making and verifying electrical contact with the backside of a semiconductor wafer having a bulk portion covered with an insulating layer of oxide includes a contact probe, a wafer chuck having at least one probe vacuum groove and a probe aperture and a probe cylinder having a low pressure and a high pressure portion. The low pressure portion communicates with the probe vacuum groove and the probe aperture. The apparatus further includes a piston movably located between the low pressure and high pressure portions. The contact probe is attached to the piston and adapted to be protrudable from the probe aperture. The groove, aperture and low pressure portion are adapted to form a low pressure chamber with the wafer. The probe is urgeable to pierce the oxide and make electrical contact with the bulk portion of the wafer. The apparatus further includes a time-varying voltage source connectable between the chuck and the probe, and a current measuring device for measuring a current between the chuck and the probe. The probe is in electrical contact with the wafer if the current corresponds at least to a capacitive coupling between the chuck and the wafer.

Claims

1. An apparatus for making and verifying electrical contact with the backside of a semiconductor wafer having a bulk portion covered with an insulating layer of oxide, said apparatus comprising:

a contact probe;

a wafer chuck having at least one probe vacuum groove and a probe aperture;

a probe cylinder having a low pressure and a high pressure portion, said low pressure portion communicating with said probe vacuum groove and said probe aperture;

a piston movably located between said low pressure and high pressure portions, said contact probe being attached to said piston and adapted to be protrudable from said probe aperture, wherein said groove, aperture and low pressure portion are adapted to form a low pressure chamber with said wafer whereby said probe is urgeable to pierce said oxide and make electrical contact with the bulk portion of said wafer;

a time-varying voltage source connectable between said chuck and said probe; and

a current measuring device for measuring a current between said chuck and said probe, said probe being in electrical contact with said wafer if said current corresponds at least to a capacitive coupling between said chuck and said wafer.

2. An apparatus according to claim 1, further comprising a pressure regulator, said regulator being controllable to provide a progressively greater force on said contact probe until said electrical contact is established between said bulk portion and said contact probe.

3. A method for making and verifying electrical contact with the backside of a semiconductor wafer having a bulk portion covered with an insulating layer of oxide, said method comprising:

providing a contact probe;

providing a wafer chuck having at least one probe vacuum groove and a probe aperture;

providing a probe cylinder having a low pressure and a high pressure portion, said low pressure portion communicating with said probe vacuum groove and said probe aperture;

providing a piston movably located between said low pressure and high pressure portions, said contact probe being attached to said piston and adapted to be protrudable from said probe aperture, wherein said groove, aperture and low pressure portion are adapted to form a low pressure chamber with said wafer whereby said probe is urgeable to pierce said oxide and make electrical contact with the bulk portion of said wafer;

applying a pressure differential to said low pressure chamber to urge said probe into contact with said wafer, said pressure differential being variable to provide a variable force on said contact probe;

applying a varying voltage between said chuck and said probe; and

measuring a current resulting from said varying voltage, said probe being in electrical contact with said bulk portion if said current corresponds at least to a capacitive coupling between said chuck and said wafer, said variable force being progressively increased until said electrical contact is established.