JPS58123474A - Circuit for measuring threshold voltage of transistor - Google Patents

Abstract

PURPOSE:To enable easy measurement of threshold voltage of a transistor in a semiconductor integrated circuit, even in a finished product, after it is sealed into a container by providing a plurality of inverter circuits into which partial voltages are inputted from a plurality of varied intermediate points of a resistance between two power sources different in the potential. CONSTITUTION:When the resistance value of a resistance 2 is set at R, intermediate terminals 3, 4 and 5 are so positioned that a resistance value between terminals 1-3, 3-4, 4-5 and 5-GND becomes R/4. When a power source +VDD is applied thereto, the output of an inverter 15, namely, an external terminal 18 moves to L if a potential 3/4 VDD at the input 3 of an enhancement transistor 12 of an inverter circuit 15 exceeds the threshold voltage thereof while it reaches H if it does not. When all outputs are L, the threshold voltage is between GND and 1/4 VDD while it is between 3/4 VDD and VDD when all outputs are H. In addition, when a terminal 18 is H and terminals 19-20 are L, the threshold voltage ranges 2/4 VDD-3/4VDD. When terminals 18 and 19 are H and a terminal 20 is L, it ranges 1/4 VDD-2/4 VDD. Thus, the threshold voltage can be measured easily even in a finished product contained in a container.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to threshold voltage measurement of transistors in semiconductor integrated circuits.

, the threshold voltages of transistors of semiconductor integrated circuits manufactured on the same univer under the same conditions are approximately equal. Therefore, conventionally, a transistor for threshold voltage measurement, whose source, drain, and gate are not connected anywhere, was provided on the semiconductor integrated circuit chip or on the chip of the semiconductor integrated circuit, and the source, drain, and gate of this transistor were connected to the outside. It is equipped with pads to make it easier to connect the measuring device, and a measuring device is connected to these using a needle-like conductor with a minute tip.
I was measuring the threshold voltage of transistors in semiconductor integrated circuits. For this reason, measuring the threshold voltage required a lot of man-hours and could not be done easily (I++'it).Also, it could not be measured unless it was in a state where it could be connected to the outside, such as a wafer or chip. There wasn't.

SUMMARY OF THE INVENTION An object of the present invention is to provide a threshold voltage measuring circuit that can easily measure the threshold voltage of a transistor in a semiconductor integrated circuit even in a finished product sealed in a container.

In the present invention, a plurality of inverter circuits are provided to input arbitrarily different intermediate points of a resistor between two power sources having different potentials, and the output portions thereof are connected to an external terminal. Therefore, when power is applied, the voltage divided by the resistors is input to the input of each inverter circuit, and the threshold value is determined by measuring the output potential of each inverter circuit at this time from the external terminal. You can know the voltage. Therefore, it becomes possible to easily measure the threshold voltage of a transistor even when the finished product is housed in a container.

Next, one embodiment of the present invention will be described using the drawings.

In Figure 1, terminals 1, 6, 7.8 are the positive power supply (VDD
), the resistor 2 is made of a diffusion layer or polycrystalline silicon. Transistors 9, 10, and 11 are depletion transistors serving as loads, and transistors 12, 13, and 14 are enhancement transistors. The inverter circuits 15.16, 17 are constructed based on transistors 6, 12.7, 13.8 and 14, respectively.

Intermediate terminals 3°4.5 of resistor 2 are inverter circuits. 1
5, 16, and 17 inputs.

Here, when the resistance value of resistor 2 is R, terminals 1-3,
The resistance value between 3-4, 4-5, 5-GND is R/4
Position intermediate terminals 3, 4.5 so that Then, when the power supply +VDD is applied, the inverter circuit 150 input 3
The potential of the input 4 of the inverter circuit 160 is 2/4 vDD, the potential of the input 5 of the inverter circuit 17 is 1/4 VDD, with respect to the threshold voltage of the enhancement transistor 12 of the inverter circuit 15. If the potential 3/4 VDD of the human power 3 exceeds it, the output of the inverter circuit 15, that is, the external terminal 18 is low (@1"
) and if it is not exceeded, it will be (“H”).

Similarly, the output of the inverter circuit 16 is connected to the external terminal 19.
, the output of the inverter circuit 17 is output to the external terminal 20. At this time, the outputs of the inverter circuits 15, 16, and 17 are output to the external terminals 18, 19, and 20, respectively, and as a result, if all outputs are @L@, then the inverter circuits 15, 1
6.17 Enforcement transistor 1
2', 13.14 are in a conductive state, so their input 3
,4. The potential of S exceeds the threshold voltage of transistors 12, 13, and 14, and the threshold voltage in this case is between GND - and -''/4 VDD.

In addition, when all outputs are 1H1, the potential of each input 3.4.5 of the inverter circuit is the transistor 2, 13.1.
This means that the threshold voltage of 4 is not exceeded, and the threshold voltage is between 3/4'/DD and VDD.

Furthermore, when terminal 18 is 1H" and terminals 19 to 20 are at Chiriso (D Ll IX pressure ti 2/4 VDD -3/4
VDD1m child 18.

The threshold voltage when 19 is @H drop and terminal 2o is @I, w is the threshold voltage Fi/4 VDD ~”/4 VDD Tona h.

Although the FiN channel MO8 has been described above, the P channel MO8 can be similarly described.

Therefore, as described above, the threshold voltage of a transistor in a semiconductor integrated circuit can be easily measured even in a finished product placed in a container.

In order to improve the inverter circuit's pB, it is possible to improve the inverter circuit by changing the value of 10 VDD, or by making the power supply l of resistor 2 in Fig. 1 a separate power supply. The measurement may be performed by changing the .

Also, if the power consumption by resistor 2 in Figure 1 cannot be ignored, it is recommended to insert a transfer gate controlled by a test signal in series with resistor 2 between power supply 1 or GND, so that it is not energized except during testing. do it.

Furthermore, when the external terminal is used also as a normal input/output terminal, it is necessary to insert a multiplexer circuit controlled by a test signal between the external terminal and the output of the inverter circuit.

Can be used for both purposes.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. 1.6, 7.8...+VDDIIIC1! li
, 2...Resistance, 3゜4.5...Resistance 2
sb, inverter circuits 15, 16.1 at any intermediate point of
7 input, 9.10, 11... Depressive transistor as load, 12゜13.14...
...Enhancement transistor, 15...
An inverter circuit consisting of 9 and 12 transistors. Agent: Patent Attorney Shinji Uchihara) −

Claims (1)

[Claims] A plurality of inverter circuits each receiving divided voltages from a plurality of different midpoints of resistors connected between two power supplies with different potentials are provided, and the outputs of the inverter circuits are connected to external terminals. A transistor threshold voltage measuring circuit characterized in that the threshold voltage of the inverter can be measured by measuring the output voltage of an external terminal.