In general, semiconductor products are manufactured by performing a complex series of processes such as a process of manufacturing a pure silicon wafer, a process of forming patterns on the pure silicon wafer to fabricate semiconductor chips, an electric die sorting (EDS) process of testing electric characteristics of the semiconductor chips to determine whether the semiconductor chips are good or bad, a process of packaging good semiconductor chips, and a process of finally testing the packaged semiconductor chips.
Among chips determined to be bad through an electric characteristic test process, repairable chips are repaired while non-repairable chips are eliminated before performing an assembly process. Thus, the electric characteristic test process is significant in reducing assembly cost and enhancing a yield of a semiconductor chip fabricating process.
An apparatus for performing an EDS process includes a probe card with probe tips, which are in contact with a conductive pad provided for a test object such as a wafer to apply electric signals to the conductive pad. All ends of the probe tips must be disposed at the same height such that all the probe tips contact the pad. The probe tips protrude downwardly from the bottom of a space transformer. However, if a thickness of a space transformer 42 is not even as illustrated in FIG. 1, the ends of probe tips 46 have different heights although the space transformer 42 is disposed horizontally. For this reason, a loose contact occurs between a pad and the probe tip 46 during a test.
FIG. 2 is a cross-sectional view of a conventional probe card configured for controlling a level of the bottom of a space transformer 42. A top reinforcement member 30 is provided to a top surface of a printed circuit board (PCB) 10 and a bottom reinforcement member 20 is provided to a bottom surface thereof. The top reinforcement member 30 is a disk-shaped member, and the bottom reinforcement member 20 is a ring-shaped member. These reinforcement members 20 and 30 are fixed by means of a bolt 70. An installation member 40 is provided to the inside of the bottom reinforcement member 20. The installation member 40 includes a space transformer 42 with a probe tip 46 and a support plate 44 disposed to hold the space transformer 42. The support plate 44 is coupled with the bottom reinforcement member 20 by means of a plate spring 50. A plurality of holes 12 are formed at the top reinforcement member 30 and the PCB 10. A plurality of fine-tunable control bolts 60 are inserted into the holes 12, respectively. The insertion degree of the respective control bolts 60 is controlled to adjust a force applied to press the space transformer 42. Thus, the level of the bottom of the space transformer 42 is controlled. As illustrated in FIG. 3, a press force F1 applied from a control bolt 60 is counterpoised to a press force F2 applied from a support plate 44 to a plate spring 50 by a restoring force to fix a position of a space transformer 42. Elastic means such as a pogo pin 80 is provided between a PCB 10 and the space transformer 42 for their electric connection.
Generally, a test process is conducted while a wafer is heated. If the above-described probe card is used for a long while, the plate spring 50 is deformed to change an elastic modulus of the plate spring 50. As a result, a restoring force of the plate spring 50 is also changed to deteriorate a controlled level of the space transformer 42. Further, a number of components such as a plurality of plate springs 50, a top reinforcement member 30, and a bottom reinforcement member 50 are used to require a long time for assembling or maintaining a probe card.