Ultrasonic bond testing of semiconductor devices

• US 4,366,713 A
• Filed: 03/25/1981
• Issued: 01/04/1983
• Est. Priority Date: 03/25/1981
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Gilmore, Robert S., Glascock, Homer H. II, Webster, Harold F.
• Primary Examiner(s): Kreitman, Stephen A.
• Application Number:
  US06/247,199
• Time in Patent Office: 650 Days
• Field of Search: 73/618, 73/620, 73/624, 73/582, 73/588, 73/600
• US Class Current: 73/618
• CPC Class Codes: G01N 2291/015 Attenuation, scattering
• CPC Class Codes: G01N 2291/0231 Composite or layered materials
• CPC Class Codes: G01N 2291/0237 Thin materials, e.g. paper, membranes, thin films
• CPC Class Codes: G01N 2291/102 one emitter, one receiver
• CPC Class Codes: G01N 29/11 by measuring attenuation of acoustic waves
• CPC Class Codes: G01N 29/221 Arrangements for directing or focusing the acoustical waves electronic orientation or focusing G01N29/262; sound directing or focusing G10K11/26; mechanical steering of sound transducers or their beams G10K11/35
• CPC Class Codes: G01N 29/223 Supports, positioning or alignment in fixed situation mounting transducers per se G10K11/004
• CPC Class Codes: G01N 29/225 Supports, positioning or alignment in moving situation

Abstract

The bond between a structured copper heat sink member and a semiconductor wafer is inspected for voids and unbonds by a focused ultrasonic pulse transmission method. The small focused spot of ultrasound is transmitted along the structured copper strands and is attenuated in the lateral direction. The absence of a received pulse or a significantly reduced amplitude signal, as the assembled device is scanned with acoustic pulses, indicate flaws in the bond.

Claims

1. The method of testing an assembled semiconductor device for unbonded areas in the bond between a metal layer on a semiconductor wafer and a structured copper heat sink member which has substantially parallel closely packed strands of copper, comprising the steps of:

scanning said assembled device with pulses of ultrasound which are incident on one surface thereof and are transmitted along said copper strands and highly attenuated in the lateral direction, and pass through said bond and metal layer and said semiconductor wafer without significant lateral spreading;

detecting the ultrasound pulses that are transmitted to the other surface of said assembled device and producing received electrical signals; and

processing and displaying said received signals such that a high amplitude signal designates a good bond and a low amplitude or no signal designates voids and unbonded areas in the bond of said structured copper member to the semiconductor wafer metal layer.

2. The method of claim 1 wherein said pulses of ultrasound have a frequency of about 5 MHz and the bond testing is performed in a water bath.

3. The method of claim 1 wherein said pulses of ultrasound are focused to a small spot and are incident on the ends of a bundle of said copper strands.

4. The method of claim 1 wherein said pulses of ultrasound are generated by a focused transmitting transducer and the transmitted pulses are detected by an unfocused receiving transducer.

5. The method of testing an assembled semiconductor device for voids and unbonded areas in the bonds above and below metal layers on a semiconductor wafer to structured copper heat sink members which have substantially parallel closely packed strands of copper, comprising the steps of:

scanning said assembled device in a water bath with pulses of ultrasound which are focused to a small spot at the end of a bundle of copper strands of one structured copper member and are transmitted along said copper strands and highly attenuated in the lateral direction, and pass through said bonds and metal layers and said semiconductor wafer without significant lateral spreading;

detecting the ultrasound pulses that are transmitted through said assembled device and generating received electrical signals; and

producing a bond interface image in which high amplitude received signals designate a good bond and low amplitude or no received signals designate a defective bond.

6. The method of claim 5 wherein said received signals are peak detected and said bond interface image has shades of gray.

7. The method of claim 5 wherein said assembled device is scanned with a scanning aocustic microscope having a focused transmitting transducer and an unfocused receiving transducer on a common axis.

8. The method of claim 7 wherein the frequency of said pulses of ultrasound is about 5 MHz.

9. The method of claim 8 wherein said bond interface image has shades of gray depending on the received signal amplitude.

10. The method of testing an assembled semiconductor device for voids and unbonds in the bond of a metal layer on a semiconductor wafer to a structured copper heat sink member which has substantially parallel closely packed strands of copper, comprising the steps of:

scanning said assembled device relative to a doubly focused acoustic system having focused transmitting and receiving transducers on a common axis;

exciting said transmitting transducer to generate pulses of ultrasound that are focused to a small spot approximately at one surface of said assembled device and are transmitted along said strands of copper and highly attenuated in the lateral direction, and pass through said bond and metal layer and said semiconductor layer without significant lateral spreading;

the transmitted ultrasound pulses being focused onto said receiving transducer which produces received electrical signals; and

processing and mapping said received signals to produce a bond interface image in which high amplitude received signals designate a good bond and low amplitude or no received signals designate voids and unbonds.