JPH0338855A - Inspection of height of protrusion for wiring - Google Patents

Abstract

PURPOSE:To inspect a height of a protrusion for wiring without damaging the protrusion for wiring by a method wherein a leakage of an induction signal from the protrusion for wiring is detected by bringing a probe close to the protrusion for wiring. CONSTITUTION:When an induction signal is applied to an object 11 to be inspected, a leakage flux is generated from the object 11 to be inspected; a magnitude of this leakage flux corresponds to a distance from a generation source. Consequently, if the leakage flux from a protrusion 13 for wiring is detected when a probe 14 is brought close to the protrusion 13 for wiring up to a prescribed height position, a height of the protrusion 13 for wiring can be detected from a magnitude of the detected leakage flux regarding in which position the height is situated with reference to a height position of the probe 14. Thereby, the height can be decided without damaging the protrusion 13 for wiring.

Description

[Detailed description of the invention] [Industrial application field]

This invention can be applied, for example, to T A B (Tape Auto
The present invention relates to a method for inspecting the height of a wiring protrusion on an object to be inspected, such as a wafer, which is bonded using tape automated bonding (tape automated bonding) technology.

[Conventional technology]

As semiconductor ICs become more dense and highly integrated, it is expected that wiring pads or wiring pitches of 100p or less will be required. With such narrow pitch wiring, it is no longer possible to electrically connect the semiconductor chip and the outer case of the package or socket using bonding wires that have been commonly used in the past. Therefore, a tape carrier method has been proposed as an alternative to such a wire bonding method, and a narrow pitch wiring technology called TAB technology, which will be explained below, has been proposed as a mounting technology for the tape carrier method (for example, the Industrial Research Association (Refer to the 1985 separate issue of the published magazine "Electronic Tariff"). That is, in this TAB technology, as shown in FIG.
A bump 2 of ~25 corals is formed (=I). Then, a connection protrusion 3 made of, for example, gold (Au) is provided on this bump 2. Then, prepare a tape 5 made of a flexible film on which a lead pattern 4 made of copper foil as shown in FIG. 3 is formed by, for example, laminating, etching, lithography, etc. In FIG. 4B is an outer lead for connection to the outer case, and 4C is a test pad to which a test probe pin is connected.The tape 5 has the lead pattern 4 as described above. A plurality of , are formed at a predetermined repeating pitch.
The tape 5 is transferred and one of the lead patterns 4 is transferred.
is brought over the semiconductor chip placed on the mounting table, and the ends of the lead patterns 4 on the semiconductor chip 1 side, that is, the inner leads 4A, are aligned with the bumps 2 of the semiconductor chip 1. In this state, when thermocompression is bonded, the gold protrusions 3 on the bumps 2 of the semiconductor chip melt, and the bumps 2 of the semiconductor chip 1, that is, the electrodes, and the inner leads 4A of the lead pattern 4 of the film 5 are electrically connected. and fixed. Thereafter, the next semiconductor chip is placed on the mounting table, and the tape is transferred to bring the next stack pattern 4 onto the semiconductor chip 2, and the same operation as above is performed. The above operations are then repeated. Further, the end portion of the lead pattern 4 of the tape 5 on the outer case 6 side of the package, that is, the outer lead 4B, and a wiring protrusion such as a bump provided on the outer case 6 are connected in the same manner. Note that the gold protrusion 3 attached on the bump 2 is attached to the tape 5.
This is for fixing to the lead pattern 4 of the tape 5, but it may also be attached to the lead pattern 4 side of the tape 5.

[Problem to be solved by the invention]

By the way, as explained above, since the plurality of bumps on the semiconductor chip 1 and the lead pattern 4 on the tape 5 are connected at the same time, the height of the bumps 2 on the semiconductor chip is
If the lead pattern 4 is different as shown in FIG.
There will be places where the bumps 2 and 2 are not connected, and there is a risk that the packaged finished product will be defective. For this reason, it is preferable that the height of the bump 2 is constant; however, at present, when trying to form a bump with a height of, for example, 15 squares, an error of ±5p occurs. Therefore, in order to avoid defects in the finished product after bonding, the bump height of each chip is inspected before bonding, for example at the wafer stage, to avoid defects in the finished product after bonding. Preferably, chips can be eliminated. A method for testing the height of bumps is to prepare a probe for each bump, touch it to the bump, test for electrical continuity, and detect bumps with no continuity. Conceivable. However, when the probe is brought into contact with the bump in this way, a certain amount of needle pressure (load), for example, about 1.0 g, is applied to the terminal in order to reduce the contact resistance.
Therefore, there are drawbacks such as damage to the wiring protrusion such as the bump 2, which becomes a hindrance when connecting the wiring protrusion and the lead. In view of the above points, it is an object of the present invention to enable the height of a wiring protrusion to be inspected without damaging the wiring protrusion.

[Means to solve the problem]

The wiring protrusion height inspection method according to the present invention applies a guidance signal to an object to be inspected on which a wiring protrusion is arranged, and prepares a probe corresponding to the position of the wiring protrusion. , By bringing the probe close to the wiring protrusion, the leakage of the guidance signal from the wiring protrusion is detected, and depending on the size of the detected leakage, 1. Detect height.

[Effect]

When an induction signal is applied to an object to be inspected, leakage magnetic flux is generated from the object to be inspected. The magnitude of this leakage magnetic flux corresponds to the distance from the source. Therefore, if the leakage magnetic flux from each wiring protrusion is detected when the probe is brought close to the wiring protrusion to a specified height position, the magnitude of the detected leakage flux can be determined from the wiring protrusion. It is possible to detect the position of the height relative to the height position of the probe.

【Example】

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for inspecting the height of wiring protrusions according to the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an example of a height inspection apparatus to which the method according to the present invention is applied, and 11 is a semiconductor wafer as an example of an object to be inspected. This semiconductor tool 11 is placed on a probe stage 2. Although a large number of semiconductor chips are formed on this semiconductor wafer 11,
As is clear from FIG. 3, each chip is provided with a plurality of humps 13 as wiring protrusions along its four sides. In this example, the height of this bump 13 is, for example, 1.5. Although it is attached so that it becomes lff+, as mentioned above, an error of, for example, ±5 corals occurs. On the other hand, probe terminals 4 having probes corresponding to each bump 13 are provided at a pitch corresponding to the arrangement pitch of the bumps 13. The probe terminal 14 is connected to a plurality of bumps 13 on the chip of the wafer 1 on the substrate 15.
Each bump 1 with the number and arrangement pitch corresponding to each of
It can be formed by depositing a plurality of conductors such as copper foils 16 corresponding to each of No. 3 and using the tip of each copper foil 16 as a probe, for example. Therefore, in this case, although not shown in the figure, as many copper foils 16 as there are bumps on one chip are provided independently. The end of each copper foil of the probe terminal 14 opposite to the end that becomes the probe is connected to a detection amplifier 17 (this detection amplifier 17 is also a probe, that is, a bump 13
(the number of terminals provided is equal to the number of terminals). Further, an oscillator 18 is provided, from which an induced AC signal SA of, for example, about 1.0 MHz is supplied to the entire semiconductor wafer 1, and this induced AC signal SA is supplied to each of the plurality of detection amplifiers 17. is supplied to the other input terminal of The outputs of the plurality of detection amplifiers 17 are each supplied to a detection circuit] 9 and detected, and the detection output is supplied to one input terminal of a comparison circuit 20. The other input terminal of this comparison circuit 20 is supplied with a threshold value. In this example, the variable resistor 21 is adjusted so that this threshold value is equal to the voltage obtained at the output of the detection circuit 19 when the probe approaches the bump 13, for example, to R1. . In the above configuration, when the induced alternating current signal SA is supplied from the oscillator 8 to the semiconductor wafer 11, leakage (leakage magnetic flux) of the induced alternating current signal SA occurs from the surface of the wafer 11. Leakage can be detected by each probe of the probe terminal 14. If the probe is now in contact with the bump 13, the probe will receive the induced AC signal SA supplied to the semiconductor wafer 11.
Signals having approximately the same phase and level are obtained, and this signal is supplied to one input terminal of the detection amplifier 17 through the copper foil 16. The other input terminal of the detection amplifier 17 receives an induced AC signal SA.
is supplied, the output of the detection amplifier 17 at this time is extremely small. On the other hand, when the probe is away from the bump 13 and is not in contact with it, the probe receives a signal whose level is smaller than the induced AC signal SA supplied to the semiconductor wafer 11 by an amount corresponding to the distance from the bump. Therefore, the detection amplifier 1
7, an output corresponding to the level of the difference between the two is obtained. The output of the detection amplifier 17 is detected by a detection circuit 19, and the detected output is compared with a threshold value by a comparison circuit 20. As described above, in this example, the threshold value is adjusted to the magnitude of the detection output of the leakage signal when the distance between the bump 13 and the probe is 1 p. Therefore, if the probe is in contact with the bump 13 or the distance between the probe and the bump 13 is less than 1μ,
Since the output of the detection circuit 19 is smaller than the threshold value, the output of the comparison circuit 20 becomes, for example, "0", and it is therefore determined that the probe and the bump 13 are in contact in this example. On the other hand, when the distance between the probe and the bump 13 becomes larger than one circle, the output of the detection circuit 19 becomes larger than the threshold value, so the output of the comparison circuit 20 becomes "1".
It is determined that the probe is not in contact with the bump. A method for inspecting the height of the bump 13 using the apparatus configured as above will be described below. In this example, a case will be explained in which a chip whose height of the bump 13 is within a range of 15 μ±1 µm is determined to be a good product, and a chip outside this range is determined to be a defective product. This inspection is performed sequentially after each chip of the semiconductor wafer 11. First, the probe terminal 14 is brought to the chip position to be inspected. Next, the bump on the chip]3 height position 17. The probe of the probe terminal 14 is brought close to the position corresponding to a+, and the output of each comparison circuit 2o at this time is monitored. At this time, the height of the bump 13 where the probe corresponding to the comparison circuit 20 whose judgment output is "0" is located is at least 16p or more, and the comparison circuit 20 whose judgment output is "1" The height of the bump 13 on which the probe corresponding to the probe is located is at least 16μ or less. Therefore, at this height position of 17p, the output of the comparator circuit 20 has rO
If there is a bump with a height of 16s1 or more, that chip is marked as defective, for example, because a bump with a height of 16s1 or more exists on that chip. Next, the probe end T-14 is brought close to a position corresponding to the height position 15 centimeters of the bump [3] on the chip, and the output of each comparison circuit 20 at this time is monitored. At this time, the height of the bump where the probe corresponding to the comparison circuit 20 corresponding to the comparison circuit 20 whose judgment output is rOJ is located is at least 14p, and the comparison circuit 20 whose judgment output is "1". The height of bump] 3, where the probe corresponding to Saga 16
Since a bump that is greater than or equal to p will be present on the chip, the chip is marked, for example, as defective. Through the above inspection process, the height of the bump 13 is 1.5R.
Only chips of 1±] fly can be determined to be good. In this case, the probe only needs to be able to detect leakage magnetic flux. Since there is no need to apply high pressure to the probe, the probe will not damage the probe if it comes into contact with the probe. As described above, only chips with the same bump height can be selected, so if these chips are bonded using TAB technology, the lead pattern and the bumps will be well connected without creating any defective parts. It is something that Note that in the case of bonding using the TAB technique, it is sufficient that the heights of the humps are the same, so it is not necessary to have the same heights as described above. Therefore, the probe terminal is brought closer to the bumps one by one, for example, by one coral pitch, and when all the height judgment outputs from the comparison circuit corresponding to each bump simultaneously go from rlJ to rOJ, it is determined that the chip is a good chip. You can do it like this. In the above example, the height of the bump itself was inspected, but the bump with the gold protrusion for connection attached is considered to be a wiring protrusion, and the height of this is inspected. Needless to say, the present invention can also be applied to such cases. Further, the wiring protrusion is not limited to the bumps as in the above example, but the present invention can also be applied to wiring bands and various other wiring protrusions, for example. Note that the frequency of the induced alternating current signal is preferably determined in consideration of the speed of the semiconductor device and the like. By the way, in this case, if the induced signal is used as a DC signal, the problem of contact resistance increases, measurement errors occur, and some terminals are insulated (for example, the gate I is turned off when DC bias is applied). ), which may result in the signal not being detected. On the other hand, if the induced alternating current signal is used, the leakage magnetic field can be detected satisfactorily without causing the above-mentioned drawbacks. In addition, unlike conventional probe needles, the probe terminal does not need to make a specific contact with the bump or inject current for testing, so it can be used not only for the probe terminal mentioned above. Various configurations can be used, such as those used as needles. Further, the tip of the probe may be flat and the same size as the tip of the bump to make it easier to pick up the leakage magnetic field, in short, it should have a shape that makes it easier to pick up the leakage magnetic flux. That's fine. Further, in the second example, the guidance signal is applied only to the entire semiconductor wafer, but the guidance signal may be applied to the entire stage on which the semiconductor wafer is placed. Furthermore, the object to be inspected is not limited to semiconductor wafers, but the present invention can also be applied to various wiring boards. Also,
Instead of inspecting a plurality of wiring protrusions at the same time as in the above example, they may be inspected one by one or a predetermined number at a time. Furthermore, the application of the induced AC signal and the determination of the height can also be performed using an ordinary IC tester.

【Effect of the invention】

As explained above, according to the present invention, the height of the wiring protrusion is inspected by applying the induction signal to the object to be inspected and detecting the leakage of the induction signal from the wiring protrusion. can do. Moreover, since it is only necessary to detect leakage of the induced signal, there is no need for the probe terminal to contact the wiring protrusion by applying a large needle pressure to reduce contact resistance. height can be determined without causing damage to the

[Brief explanation of drawings]

FIG. 1 is a diagram showing essential parts of an example of a height inspection device used in the wiring protrusion inspection method according to the present invention, and FIGS. 2 and 3 are diagrams for explaining an example of a bonding technique. ,
FIG. 4 is a diagram for explaining problems with the bonding technology. 11: Semiconductor wafer 14; Probe terminal 17; Detection amplifier 18; AC signal oscillator 20; Judgment circuit

Claims (1)

[Scope of Claims] A guidance signal is applied to the object to be inspected on which the wiring protrusion is provided, and a probe corresponding to the position of the wiring protrusion is prepared, and the probe is applied to the wiring protrusion. A leakage of the guidance signal from the wiring protrusion is detected by approaching the wiring protrusion, and the height of the wiring protrusion is detected based on the size of the detected leakage. A height inspection method for wiring protrusions.