Patent Application
20070069745
1. Field of the Invention
The present invention relates to a probe card for integrated circuits, and more particularly, to a probe card for integrated circuits which uses ultrasonic energy to vibrate a probe pin of the probe card to scratch a dielectric layer on a pad of the integrated circuit so as to decrease the contact resistance between the probe pin and the pad.
2. Description of the Related Art
Generally, it is necessary to test electrical properties of integrated circuit devices on the wafer level to verify that the integrated circuit device satisfies the product specification. Integrated circuit devices with all electrical properties satisfying specifications are selected to continue through the subsequent packaging process, while other devices are discarded to avoid additional packaging cost. Another electrical property test is performed on the integrated circuit device after the packaging process is completed to sieve out unsatisfactory devices so as to increase product yield. In other words, the integrated circuit device undergoes several tests during the manufacturing process.
As the semiconductor fabrication technique proceeds into the nanometer scale, the line width and the pitch shrink correspondingly, which results in RC-delay effect due to an increased conductor resistance and capacitance between conductors. RC-delay has many negative influences such as a decreased signal propagation speed, an increased cross talk noise and power consumption, wherein the decreased signal propagation speed is the most serious one. To reduce the RC-delay effect, researchers use porous low-k dielectric material to prepare the dielectric structure between conductors in the advanced integrated circuit fabrication process.
Conventional dielectric material such as silicon dioxide possesses higher mechanical properties to sustain the applied force as the probe pin 12 is overdriven. But, the porous low-k dielectric material used in the advanced integrated circuit fabrication process possesses lower mechanical properties, which can not sustain the applied force as the probe pin 12 is overdriven above 70 micrometers. Consequently, piercing the hard dielectric layer 24 by overdriving the probe pin 12 may cause the porous low-k dielectric material below the pad 22 to collapse due to unsustainable force applied by the probe pin 12. This destroys the dielectric structure between conductors and the integrated circuit device 20 fails or is damaged.
In addition, contaminants such as oxide fragment adhere to the probe pin 12 when the probe card 10 is used to perform electrical tests of the integrated circuit device 20. An on-line cleaning process may be performed to remove the contaminants from the probe pin 12 by brushing the probe pin 12 on a cleaning pad of the test machine. However, the cleaning process is controlled by the test machine and requires a length of time, reducing efficiency. Further, the conventional cleaning process can not completely remove all contaminants, and some contaminants may remain on the probe pin 12. More particularly, the brushing movement of the cleaning process often damages the probe pin 12. An off-line cleaning process may be performed by dipping the probe pin 12 into a cleaning solution to remove the contaminants from the probe pin 12 according to the prior art.
The objective of the present invention is to provide a probe card for integrated circuits which uses ultrasonic energy to vibrate a probe pin of the probe card to scratch a dielectric layer on a pad of the integrated circuit so as to decrease the contact resistance between the probe pin and the pad, and method for cleaning the probe pin by the ultrasonic energy.
In order to achieve the above-mentioned objective and avoid the problems of the prior art, one embodiment of the present invention discloses a probe card comprising a first substrate, at least one probe pin positioned on the first substrate, and an ultrasonic generator positioned on the first substrate to generate ultrasonic energy to vibrate the probe pin. The ultrasonic generator may be positioned on a second substrate, which can be assembled to the first substrate when the probe card is used to perform electrical tests. In addition, the ultrasonic generator and its power supply may be incorporated in a test head of a test machine, and the ultrasonic generator can acquire operation power from a power supply of the test head to generate the ultrasonic energy to vibrate the probe pin when the test head is docked to the probe card.
When the probe pin contacts a pad of an integrated circuit device under test, the ultrasonic generator can emit the ultrasonic energy to vibrate the probe pin so as to form a recess on a dielectric layer on the pad, and the probe pin is then pressed downward to contact the pad through the recess with low overdrive forming a signal path. Preferably, the ultrasonic energy can vibrate the probe pin in an XYZ 3-dimensional manner. In addition, the ultrasonic energy may vibrate the probe pin to brush the surface of the pad or scratch the dielectric layer on the surface of the pad when the probe pin contacts the surface of the pad of the integrated circuit device, with the ultrasonic energy preferably vibrating the probe pin in an XY 2-dimensional manner. Consequently, the contact resistance between the probe pin and the pad can be decreased due to improved contact between the probe pin and the pad with the dielectric removed.
In short, the embodiment of the present invention uses ultrasonic energy to vibrate the probe pin to form the recess and then presses the probe pin downward to contract the surface of the pad with low overdrive, or to vibrate the probe pin to brush the surface of the pad to decrease the contact resistance by increasing the contact between the probe pin and the pad. In addition, contaminants such as oxide fragment adhere to the probe pin when the probe card is used to perform electrical tests of the integrated circuit device, and ultrasonic energy can be used to vibrate the probe pin to remove any adhered contaminants from the probe pin.
Conventional technique must overdrive the probe pin continuously to scratch the dielectric layer on the surface of the pad, which is likely to result in a sliding probe pin or in collapse of the porous low-k dielectric material below the pad under high probe pressure, causing the dielectric structure between conductors to be damaged. Conversely, when the probe pin contacts the surface of the pad, the embodiment of the present invention uses ultrasonic energy to vibrate the probe pin to form the recess and then with low overdrive causing the probe pin to contract the pad, forming the signal path. Since the recess can automatically locate the position of the probe pin to avoid the occurrence of the sliding probe, the pad can be contacted precisely.
In addition, the probe pin can scratch the dielectric layer without overdriving the probe pin since the ultrasonic energy vibrates the probe pin to form the recess before the probe pin is pressed downward to scratch the dielectric layer at the precise location of the recess. Consequently, the present invention can prevent the porous low-k dielectric material below the pad from collapsing to maintain the dielectric structure between conductors since the probe pin can scratch the dielectric layer on the pad without overdriving.
Further, ultrasonic energy may be used to vibrate the probe pin to brush the surface of the pad to clear the dielectric layer on the pad. The probe pin then contacts the pad of the integrated circuit device, and the contact resistance can be decreased as a result of improved contact between the probe pin and the pad. In addition, ultrasonic energy can also be used to vibrate the probe pin to remove contaminants during tests.
The objectives and advantages of the present invention will become apparent upon reading the following description and upon reference to the accompanying drawings in which:
Preferably, after the probe pin 36 contacts the pad 22 of the integrated circuit device 20 and the probe pin 36 is then overdriven downward a small distance, the ultrasonic generator 40 is activated to emit ultrasonic energy to form the recess 26. The duration, operation power, and vibration type of the ultrasonic energy depend on the type of the probe pin 32, the pad 22, and the dielectric layer 24. Consequently, the operation parameter of the ultrasonic generator 40 can be determined according to experimental results or a standard set of reference preset parameters.
Referring back to
Generally speaking, a tiny point of contact is formed between the probe pin 36 and the pad 22 by simply overdriving the probe pin 36 downward, and the contact resistance is higher. To decrease the contact resistance, the present invention can activate the ultrasonic generator 40 as the probe pin 36 contacts the pad 22 to generate ultrasonic energy to vibrate the probe pin 36 in an XY 2-dimensional manner so as to scratch the dielectric layer 24 and remove oxide fragments between the probe pin 36 and the pad 22. As a result, the contact resistance can be decreased due to improved contact between the probe pin 36 and pad 22. Even with no dielectric layer 24 on the surface of the pad 22, the ultrasonic energy can be used to vibrate the probe pin 36 in XY 2-dimensional manner so as to brush the surface of the pad 22 removing any interface impurities or particles. Consequently, the contact resistance can also be decreased since there is improved contact between the probe pin 36 and pad 22.
As an alternative to the conventional technique for cleaning the probe pin, the present invention can be used to clean the probe pin 36 by placing the probe pin 36 on a cleaning pad when the probe card 30 is assembled on the probe station and then activating the ultrasonic generator 40 to emit ultrasonic energy, thereby vibrating the probe pin 36 on the cleaning pad in a reciprocating manner to remove adhered contaminants. The present invention can perform the on-line cleaning process for the probe pin 36 during intervals between actual electrical tests. Since ultrasonic energy vibrates the probe pin 36 in a reciprocating manner, adhered contaminants can be effectively removed without damaging the probe pin 36. In addition, when the probe card 30 is not used to perform electrical tests, the ultrasonic generator 40 can emit ultrasonic energy to vibrate the probe pin 36 to remove adhered contaminants, thereby performing the cleaning process off-line. In short, the present invention can perform the on-line and off-line cleaning processes for the probe pin 36 more effectively than could the prior art.
Conventional technique must overdrive the probe pin continuously to scratch the dielectric layer on the surface of the pad, which is likely to result in a sliding probe pin or in collapse of the porous low-k dielectric material below the pad, resulting in damage to the dielectric structure between conductors. In the present embodiment, conversely, when the probe pin contacts the surface of the pad, ultrasonic energy is used to vibrate the probe pin to form the recess and then presses the probe pin downward to scratch the dielectric layer to form the signal path. Since the recess can automatically locate the position of the probe pin to avoid the occurrence of the sliding probe, the dielectric layer can be scratched precisely.
In addition, the probe pin can scratch the dielectric layer with minimal or without overdriving the probe pin since the ultrasonic energy vibrates the probe pin to form the recess before the probe pin is overdriven downward to contact the pad at the precise location of the recess. Consequently, the present invention can prevent the porous low-k dielectric material below the pad from collapsing to maintain the dielectric structure between conductors since the probe pin can scratch the dielectric layer on the pad with minimum or with no overdrive.
Ultrasonic energy may be used to vibrate the probe pin to brush the surface of the pad or the dielectric layer on the pad when the probe pin contacts the pad of the integrated circuit device, and the contact resistance can be decreased due to improved contact between the probe pin and the pad. In addition, ultrasonic energy can also be used to vibrate the probe pin to remove contaminants.
The above-described embodiments of the present invention are intended to be illustrative only. Numerous alternative embodiments may be devised by those skilled in the art without departing from the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 094133675 | Sep 2005 | TW | national |
