The present invention generally relates to contactors, and especially to a contactor making a contact to electronic components such as a large-scale integrated circuit and a contact process that uses such a contactor.
In recent years, the development of production technology in the field of semiconductor substrate is remarkable. Associated with this, interconnection patterns of large-scale integrated circuits are miniaturized, and along with this, the terminals of large-scale integrated circuits are also miniaturized. Further, the number of the terminals used in an LSI is increasing with remarkable rate.
The demand of miniaturization and high-density mounting is acute especially in the apparatuses that use a large-scale integrated circuit. For example, the number of mobile apparatuses (cellular phones, mobile personal computers, video integrated cameras etc.), in which downsizing is demanded, or high-performance computers in which the distance between adjacent LSIs has to be minimized for guaranteeing high speed operation, is increasing rapidly.
The foregoing demand also affects on the shipment mode of LSIs. Thus, the cases are increasing for shipping unpackaged LSI chips while guaranteeing the operability thereof as known as KGD (Known Good Die), or shipping the LSIs in the form of CSP (Chip Size Package), which is a small-sized package having the size of a chip.
From these circumstances, there is a need of a contactor capable of making a contact with a large number of miniature pin terminals with certainty for testing the LSIs.
Also, from the viewpoint of efficient test of LSIs, there is emerging a need of full test, in which all the tests such as final test (FT) or burn-in (BI) test are conducted for each of the LSIs in the state of wafer, before the wafer is divided into individual LSI chips. By using the full test in the state of wafer, following effects are expected.
First, the efficiency of handling is improved as compared with the case of conducting the testing on separate chips. When the size of the chips is different, it should be noted that the compatibility of the handling equipment used for the testing is lost. In the case the testing is conducted in the state of wafer, on the other hand, it becomes possible to convey the wafers of standard outer size one after another. Further, it becomes possible to control the defect information in the form of wafer map.
In the case the art of wafer-level CSP, which is subjected to intensive research and development in recent years, is used, it is potentially possible to conduct the entire process steps from the wafer process up to the assembling step in the form of the wafer. Thus, if it becomes possible to realize the test process in the state of wafer, the entire steps from the wafer process to the packaging process (assembling process) can be conducted in the state of the wafer, and the efficiency of production of LSI chips would be improved significantly.
However, as noted before, it has been difficult to realize a conductor that can contact the terminals of plural LSIs on a wafer or the terminals of entire LSIs on the wafer, in view of miniaturization of individual LSIs and hence the terminals thereof, and further in view of increasing number of the terminals.
Hereinafter, typical examples of conventional contactors (probe cards or sockets) will be summarized.
(1) Needle Type Mechanical Probe
A needle type mechanical probe has a construction of disposing a plurality of needles formed of a tungsten wire and the like on a contactor substrate of an insulating material in correspondence to respective terminals of the LSIs to be tested. Generally, a cantilever structure has been used in which the needles are provided so as to extend obliquely over the LSI wafer. Further, there is a proposal of disposing needles in a vertical direction to the terminals of the tested LSIs, by providing resiliency to the needles.
(2) Membrane Type Probe
A membrane type probe has a structure of a film circuit having a metal projection (referred to hereinafter as “bump”) for the contact electrode of the probe.
(3) Anisotropic Conductive Rubber
An anisotropic conductive rubber uses an elastic rubber as an insulating base material and has a structure in which a conductive material that extends only in the thickness direction of the rubber base material such as a metal wire is incorporated.
Further, the Japanese Laid-Open Patent Application 10-111316 official gazette discloses a contactor in which an end part of the wire, extending out from an edge of a substrate, is used for a connection terminal that makes a contact with the semiconductor device to be tested and the terminals extending at the other edge of the substrate is used for the measurement terminal.
On the other hand, the abovementioned needle type mechanical probe has problems such as:
a) High cost of forming a large number of needles or pins individually;
b) Limitation in the precision of the needle tip due to the construction in which a large number of needles are arranged individually; and
c) Restriction imposed on the arrangement of the needles in view of the oblique arrangement of the needles.
Thus, it has been difficult to use a needle type mechanical probe for the contactor that makes a contact with plural LSIs at the same time.
Further, the abovementioned membrane type probe has the problems as summarized below.
a) Individual contact electrodes cannot move freely
Because the contact electrode is connected to a polyimide layer forming the insulating substrate, the movable range of the individual electrode is limited. Also, in view of the fact that the contact electrode is formed of a metal bump of a hard metal that lacks flexibility, there arises a problem in that a defective contact may be caused in the case there exists a change of height between the bump electrodes.
b) High Cost
The bump constituting a contact electrode is generally formed by plating a metal. Thus, it takes time for forming a bump and the cost is inevitably increased.
Furthermore, the anisotropic conductive rubber has problems summarized as below.
a) Limited Lifetime
In the case it is used at high temperatures, in particular (it should be noted that the BI test is carried out usually at the temperature of 125° C. or more), the rubber part undergoes plastic deformation, and it can be used for only a dozens of time at best.
b) It cannot be used for the case of narrow electrode pitch.
Because it is difficult to incorporate a conductive material into a rubber, the pitch of 200-150 μm is thought as being a practical limit.
Also, the contactor disclosed in the Japanese Laid-Open Patent Application 10-111316 official gazette has a disadvantage in that it is difficult to achieve a contact for all the electrode terminals in the case there exists a variation of height in the electrode terminals of the semiconductor device to be tested, in view of insufficient stroke of the contactor terminal in the longitudinal direction. Further, there can be a possibility that sufficient contact cannot be achieved in the case the thermal expansion coefficient of the semiconductor device to be tested is different from that of the base material of the contactor as a result of displacement caused at the time of the high temperature test such as in the case of the burn-in test.
Thus, the conventional contactors have the problems summarized as follows.
1) Insufficient stroke of the contactor contact terminals
Thus, in such a conventional contactor having insufficient stroke (elastic deformation) for the contact part, a sufficient contact is achieved only when it is caused to make a contact with an aluminum pad on a wafer, in which the variation of the height is relatively small, or in the case it is used for a narrow area of the wafer. However, in the case of a wafer level CSP or molded packages formed by a simultaneous molding process, the terminals or balls on the package generally have a large variation of height, and it becomes difficult to achieve a sufficient contact by using such a conventional contactor having a small stroke or elastic deformation in the contact part. This problem becomes especially serious in the case the contactor is used to make a simultaneous contact with a thin wafer, which tends to have a warp. It should be noted that the warp of a wafer tends to increase when the thickness of the chip is reduced.
2) Positional deviation by the difference of the thermal expansion coefficient
The LSI wafer to be tested is generally formed of silicon (Si). It should be noted that the coefficient of linear thermal expansion is about 3 ppm in the case of silicon, while in the case of an insulated substrate used for the contactor such as a resin, the value of the coefficient of linear thermal expansion becomes several ten ppm (13˜30 ppm, for example). Thus, even in the case the contactor is contacting properly at ordinary temperatures, the location of the contactor may be deviated due to the difference of the coefficient of linear thermal expansion when it is used at a high temperature as in the case of a BI test. In an extreme case, the contactor may miss the intended terminal or make a contact with a terminal next to the intended terminal. Further, a similar problem occurs also in the case of the wafer level CSP or packages molded by a simultaneous molding process, in view of the fact that the coefficient of linear thermal expansion is different between the insulated substrate material and the package material such as seal resin. In the case polyimide is used for the insulating substrate, for example, the linear thermal expansion coefficient takes a value of about 13 ppm and there can occur a displacement as much as 100 μm at the peripheral part of an 8-inch wafer, which has a diameter of about 100 mm, when it is heated to 125° C., even in the case the contactor is aligned properly at ordinary temperature.