KR19990010733A - Threshold Voltage Measurement Circuit Using Input Protection Transistor - Google Patents

Abstract

The present invention discloses a threshold voltage measurement circuit using an input protection transistor. This threshold voltage measuring circuit includes a transistor having a source connected to an input, a gate connected to a power supply voltage, and a drain connected to ground, a voltage source and a current source connected between the input and the ground, and one side is connected between the input and the voltage source, and the other side is a transistor. And a connecting means connected to a gate of the circuit to supply a gate voltage from a voltage source, and the gate voltage turns on the transistor, thereby measuring a threshold voltage according to a current change between a source and a drain of the transistor.

Description

Threshold Voltage Measurement Circuit Using Input Protection Transistor

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to testing of semiconductor devices, and more particularly to a threshold voltage measurement circuit using an input protection transistor.

As semiconductor products become more integrated and multifunctional, methods for evaluating them are also evolving. However, in many semiconductor products, in-parameters are evaluated by sampling only a small amount of wafers at the time of manufacture and production, and the flow of execution is determined based on them. And evaluation of the product is not easy.

That is, in the case of sampled DC parameters, it is possible to evaluate the whole lot, but it is not possible to extract the actual data of the individual products. Therefore, if the threshold voltage, which is one of the main characteristics of CMOS products, can be obtained from individual products, it can be a useful method for inferring the characteristics of process and unit products.

SUMMARY OF THE INVENTION An object of the present invention is to provide a threshold voltage measuring circuit using an input protection transistor that facilitates the characteristic evaluation of a predetermined semiconductor device by measuring the threshold voltage of the input protection transistor of the predetermined semiconductor device.

1 is a circuit diagram of a semiconductor device input stage having a pull-up transistor for input protection.

2 is a circuit diagram of a semiconductor device input stage having a pull-down transistor for input protection.

3 is a detailed view of the pad metal of the concave-convex shown in FIG. 1 or 2.

4 is a view for explaining a threshold voltage measuring circuit using an input protection transistor according to the present invention.

In order to achieve the above object, the threshold voltage measuring circuit using an input protection transistor according to the present invention, a transistor having a source connected to the input, a gate connected to the power supply voltage and a drain connected to ground, a voltage source connected between the input and ground and A current source and one side is connected between an input and a voltage source, and the other side is connected to a gate of the transistor, and has a connecting means for supplying a gate voltage from the voltage source, wherein the gate voltage turns on the transistor, thereby providing a current between the source and the drain of the transistor. The threshold voltage according to the change is measured.

Hereinafter, the configuration and operation of a threshold voltage measuring circuit using an input protection transistor according to the present invention will be described with reference to the accompanying drawings.

In the case of products with dynamic logic, the characteristics of the product change sensitively even with a small change in the threshold voltage. For example, in most CMOS products, a pull-up or pull-down resistor is inserted to protect the input from noise-induced malfunctions, usually using transistors.

Threshold voltage measurement using pull-up or pull-down transistors for input protection not only checks the in-parameters on the actual chip, but also provides important data for failure analysis, as well as for each chip particularly sensitive to threshold voltages among in-parameters. If the threshold voltage can be measured at, then managing this measurement can contribute to ensuring stable product characteristics.

As a representative example, dynamic logic products are particularly sensitive to light or humidity. This is because the level of the threshold voltage is not properly controlled. Therefore, when the influence of the surrounding environment acts as a noise and affects the power, it causes a malfunction of the product. It can be said to be large.

In the present invention, a method of measuring a threshold voltage of a pull-up or pull-down transistor placed at an input or output terminal using a dummy pad is shown.

1 is a circuit diagram of a semiconductor device input stage with a pull-up transistor for input protection, and FIG. 2 is a circuit diagram of a semiconductor device input stage with a pull-down transistor for input protection.

In the circuit shown in FIG. 1, the input applied to the internal logic unit 100 through the input terminal INPUT operates as a pull-up resistor when the power supply voltage VDD is applied to the transistor M12 by the pad metal 102. It is controlled by the transistor M11. In addition, in the circuit shown in FIG. 2, the input applied to the internal logic unit 200 through the input terminal INPUT operates as a pull-down resistor when the ground VSS is applied to the transistor M21 by the pad metal 202. Controlled by the transistor M22. For reference, FIG. 3 shows a detailed view of the pad metal with irregularities, and the minimum spacing may be, for example, 5 μm.

When the pull-up or pull-down transistors M12 or M22 shown in FIGS. 1 and 2 are externally controlled and their threshold voltages are measured, they may be used as analysis data of a corresponding product, thereby predicting characteristics of the product. In addition, by managing the measurement data, that is, the threshold voltage during mass production test, it is possible to secure stable characteristics for individual chips and to play a role of improving quality.

4 is a view illustrating a threshold voltage measurement circuit using an input protection transistor according to the present invention, a source connected to an input through an input terminal INPUT, a drain connected to a gate connected to a power supply voltage VDD, and a ground VSS. Transistor M42 having a voltage, a voltage source and a current source connected between the input and the ground (VSS) and one side is connected between the input and the voltage source, the other side is connected to the gate of the transistor to supply a gate voltage (Vg) from the voltage source 404. Here, the gate voltage Vg turns on the transistor M42 so that the threshold voltage according to the current change between the source and the drain of the transistor M42 is measured.

As shown in FIG. 4, when the ground VSS is applied to the transistor M41 by the pad metal 402, the transistor M42, which acts as a pull-up resistor, is composed of an NMOS transistor, and the gate thereof is a dummy. The pad-in connection 404 is connected to the source of the transistor M41.

First, in order to measure the threshold voltage, as shown in FIG. 2, a padded metal 402 of unevenness, which is floating, is connected with a probe. In addition, after connecting a voltage source and an ammeter between the input terminal INPUT and ground (VSS), a threshold voltage measurement of a known general transistor is performed. That is, after the transistor M42 is turned on by increasing the gate voltage of the transistor M42 and the applied voltage of the source together, the threshold voltage is extracted by measuring the current change between the source and the drain.

As a method of measuring voltage, 1 ~ 4μA method, gm MAX method, etc. are used, and at this time, a measuring instrument such as a DC parameter analyzer is used.

Since the impedance of the internal logic unit 400 viewed from the input terminal INPUT is very large, it can be said that all actual current and voltage characteristics occur in the input protection transistor M42.

As described above, the threshold voltage measuring circuit using the input protection transistor according to the present invention has an advantage of facilitating the evaluation of characteristics of the predetermined semiconductor device by measuring the threshold voltage of the input protection transistor of the predetermined semiconductor device.

Claims (1)

A transistor having a source coupled to the input, a gate coupled to the supply voltage, and a drain coupled to ground; A voltage source and a current source connected between the input and the ground; And a connecting means connected at one side between the input and the voltage source and connected at another side to a gate of the transistor to supply a gate voltage from the voltage source, wherein the gate voltage turns on the transistor, thereby A threshold voltage measurement circuit using an input protection transistor, characterized in that the threshold voltage according to the current change between the source and the drain is measured.