JPS5943733Y2 - semiconductor equipment - Google Patents

Description

[Detailed Description of the Invention] The present invention is applicable to characteristic testing of semiconductor wafers during the manufacturing process of semiconductor devices by applying current during operation of completed semiconductor devices, especially when the meter reading of the testing device is connected to Kelvin. , relates to a structure of a semiconductor device that can be completely adapted.

As is well known, semiconductor devices such as transistors are made using thin semiconductor wafers, which are processed through various processing steps such as impurity diffusion, and a large number of semiconductor elements are formed. As shown in FIG. 1B, a semiconductor wafer 1
For each of the upper semiconductor elements 2゜2..., a probe 3゜3, which is energized for characteristic inspection, is pressed against each electrode E, B of the semiconductor element 2, for example, a transistor, and connected to the probes 3, 3. Tester T is used to check whether the voltage/current characteristics are good or bad.

If the semiconductor element 20 is defective, a defective mark is placed on the surface of the semiconductor element 20.

Next, the semiconductor wafer 1 is cut along the device partition boundaries to pelletize the semiconductor devices 2, 2, . . . .

The pellets of semiconductor elements 2 are soldered and fixed to a predetermined substrate while excluding the marked defective products.

The electrode C for external connection on the back side of the pellet is electrically connected to the board by soldering to the board, and the electrodes E and B for external connection on the front side are connected to external lead wires by bonding predetermined lead wires. electrically connected to.

Thereafter, it is packaged in a predetermined package and manufactured as a single semiconductor device.

Therefore, the characteristics inspection of the semiconductor elements 2 carried out in the state of the semiconductor wafer 1 described above can detect any defective semiconductor elements at an early stage and prevent the defective semiconductor elements 2 from being used in subsequent processing steps. It is intended to do so.

By the way, the above characteristic inspection is performed on the semiconductor wafer 1 on which elements have been formed before it is pelletized, which poses a problem in workability. Conventionally, it has been carried out only on simple check items using a small current, and it has not been possible to conduct a complete inspection. This is generally carried out after the semiconductor element is completed as a semiconductor device.

For this reason. During the subsequent inspection, some products were found to be defective.

However, in recent years, in order to improve manufacturing yields, the characteristics inspection using large currents during actual use, which was conventionally performed after the semiconductor device has been completed, has been changed to
It is carried out when the situation is as follows.

For this purpose, a large current and high voltage must be applied to the semiconductor element 2.

However, when testing the characteristics of the semiconductor wafer 1, there is a problem that there is contact resistance between this electrode and the prober probes 3, 3, etc. that are in contact with it. A drop occurs, making the measurement inaccurate.

Therefore, in order to solve this problem, the Kelvin connection of meter reading 3.3 is used.

This Kelvin connection is a method in which a total of two meter readings are brought into contact with one electrode, a forcing meter reading F that flows a driving current, and a sensing meter reading S that detects the potential of that electrode. A schematic diagram is shown in FIG.

In this figure 2, Ro is the resistance R1゜R2v R3e that exists between the two electrodes E and C. R4 is the resistance that exists between the two sets of meter readings, forcing F and sensing S, and electrodes E and C, respectively. It is contact resistance.

With this Kelvin connection, a predetermined high voltage and large current ■ is caused to flow through the resistance Ro between the electrodes E and C from forcings F and F.
When measuring the voltage V between sensing S and S at that time, the contact resistance R1? Since almost no current flows through R3, this voltage V allows the voltage drop V between the electrodes E and C to be detected without error.

By measuring with the Kelvin connection in this manner, measurement errors due to contact resistance between the meter reading and the electrode can be removed.

However, in the case of semiconductor element pellets of power transistors, in which electrodes for external connection of the emitter E and base B are formed on the front surface, and electrodes for external connection of the collector C are formed on the entire back surface, the semiconductor wafer 1 When testing the characteristics in this state, only the emitter E and the base B, which are electrodes on the front side, can be connected in Kelvin.

When trying to measure such a semiconductor element using a large test current using a Kelvin connection, the results are shown in Figures 3B and 4, which are enlarged views of circle N in Figure 3A.
As shown in the figure, two prober probes S and F are brought into contact with the electrodes E and B on the front side of the semiconductor wafer 1 using the Kelvin connection. Connection is made via the vacuum suction chuck top 5 of the stage 4, which also serves as a mounting table.

That is, each semiconductor element 2゜2...the electrode C on the back surface is
The electrode C is formed integrally over the entire back surface of the semiconductor wafer 1, and since this electrode C comes into contact with the chuck dog 5, the lead wire 6 from the tester T is connected to the chuck top 5 itself.

The illustrated chuck top 5 is of a two-part type, and a lead wire 6.6 (however, an electrically common lead wire) is connected to each of the two parts.

Now, when attempting to perform a characteristic test using such a connection method, the contact resistance between the electrode C on the back side and the chuck top 5 becomes a problem.

Since this contact resistance is distributed over the entire back surface of the semiconductor wafer 1, the lateral resistance varies greatly depending on the position of the semiconductor element 2 on the semiconductor wafer 1, and the lateral resistance can be measured. The directness will be different.

For example, when measuring the VCE (SAT) of a transistor,
The measured value VCE (SAT) of the semiconductor elements 2, 2... is the 6th lateral resistance taken in the direction of the X-X line in FIG.
As shown in the figure, it changes between the center and the periphery.

For this reason, even if an attempt is made to test the characteristics of a semiconductor element by applying a large current to the chuck top 5, in which the lateral resistance intervenes, using the chuck top 5 as a characteristic testing terminal, accurate measured values cannot be obtained.

Therefore, in view of the above-mentioned drawbacks of the conventional technology, the present invention is an improvement thereof, and examples thereof will be described below.

In other words, the present invention is a semiconductor element that is formed in large numbers on a semiconductor wafer at one time and later divided into pellets to produce a semiconductor device.The surface of the semiconductor element is provided with electrodes for external connection, and the wafer is mounted on the back surface of the semiconductor element. In a device that is provided with an electrode for external connection that comes into contact with a characteristic test terminal that also serves as a mounting stand, the same electrode as the electrode for external connection on the back side is also provided on the front side as a sensing pad 1, as shown in Figure 1. It is.

The reason why the sensing pad 7 only needs to have a small area is that the electrodes E and B on the surface of the semiconductor element 2 are large because it is necessary to bond leads for external extraction. This is suitable for situations where the extra space available for installation is small.

As shown in FIG. 8, each probe of a prober is brought into contact with the semiconductor element 2 provided with the sensing pad 7 in this manner.

That is, the electrodes E and B for external connection on the surface of the semiconductor element 2
Since the sensing S and forcing F can be connected to the electrode C for external connection on the back surface of the semiconductor element 2 via the chuck top 5, the sensing hat 7 on the surface of the semiconductor element 2 can be connected to the electrode C for external connection on the back surface of the semiconductor element 2. Only one sensing S is brought into contact with the sensor.

Since a perfect Kelvin connection can be constructed by the above connection, the characteristic measurement by the tester T can completely eliminate measurement errors as shown in FIG. 6, which occur in the conventional means.

Therefore, it becomes possible to completely inspect the characteristics of the semiconductor element in the state of the semiconductor chip, and it becomes possible to reliably detect and eliminate defective pellets.

Therefore, defective pellets are not mixed into the processing step after the semiconductor wafer characteristics inspection, and the manufacturing yield of semiconductor devices is improved.

Note that in the above embodiments, a transistor is used as an example of a semiconductor device, but the same can be applied to other semiconductor devices, such as a diode.

In order to provide the sensing pad, it may be formed at a location on the surface of the semiconductor element using a predetermined photolithographic processing technique, either simultaneously with other processing steps or separately.

As explained above, according to the present invention, by providing the same t-pole as the external connection electrode on the back side as a sensing pad on the front side of the semiconductor element, the characteristic test conducted in the semiconductor wafer state can be completed. This can now be done with a wall Kelvin connection.

Therefore, defective semiconductor devices can be removed early in the semiconductor wafer state, and the yield of semiconductor device manufacturing can be improved.

[Brief explanation of the drawing]

FIGS. 1A and 1B are a plan view of a semiconductor wafer and an enlarged plan view of essential parts to explain conventional characteristic testing of semiconductor elements, FIG. 2 is a principle diagram explaining Kelvin connection, and FIGS. 3A and 3B are
B is a diagram explaining characteristic measurement by conventional means using Kelvin connection, FIG. 4 is a side view showing the connection state on a semiconductor wafer, FIG. 5 is a top view of the chuck top in contact with the wafer, and FIG. 6 7 is a characteristic curve diagram showing how the measured VCE (SAT) of a transistor changes with respect to fluctuations in lateral resistance along line X-X in FIG. The figure is an enlarged top view of a semiconductor device showing an embodiment of the present invention, and FIG. 8 is a top view showing the contact state of a meter when a Kelvin connection is made to the semiconductor device of FIG. 7. 1...Semiconductor wafer, 2...Semiconductor element, 5...Chuck top, 1...Sensing pad, E...Semiconductor element surface Electrode (emitter), B... Electrode (base) on the surface of the semiconductor element, C... Electrode (collector) on the back surface of the semiconductor element, S... Sensing, F... ...Forcing, T...Tester.

Claims (1)

[Scope of utility model registration request] In a semiconductor wafer in which an electrode for external connection is provided on the surface of the semiconductor element and also an electrode for external connection is provided on the back side of the semiconductor wafer 1, the same electrode as the electrode for external connection on the back side is also provided on the front side. A semiconductor device characterized by being provided as a sensing pad.