JPH0968558A - Semiconductor device and inspection method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the internal potential of a semiconductor substrate without increasing the external terminal of a semiconductor device. SOLUTION: A resistance 3 set to such value as to be not more than input leakage current value specified by a standard is connected between an input terminal 1 and an internal power line 10. Voltage is applied so that a current does not flow to the input terminal 1, and the voltage at that time is measured to detect internal potential with high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a method of testing the same, and more particularly to a circuit capable of measuring a bias voltage in a predetermined region of a semiconductor substrate at an external terminal and a method of measuring the bias voltage.

[0002]

2. Description of the Related Art Measuring a step-down circuit in a semiconductor substrate, a substrate potential, etc. is a dynamic random
It is important in evaluating the characteristics of access memory.

FIG. 7 showing an example of a conventional simple circuit for externally detecting the internal potential such as the substrate potential of such a semiconductor substrate.
Referring to FIG. 3, the internal power supply generation circuit 33 of the semiconductor substrate covered with the package supplies the internal power supply generation circuit 33 to the external terminal 3 outside the package.
1 is derived by wiring and the voltage of the external terminal 31 is measured by a tester or the like. In this case, the number of terminals 31 dedicated to measurement increases according to the number of circuits 33 to be measured.

If there are no vacant terminals in the standardized number of external terminals of the semiconductor device, it is not possible to add terminals dedicated to measurement, and the number of terminals is forcibly increased and the terminal pitch is changed. Then, a new problem arises in that the printed wiring prepared on the user side cannot be used.

Referring to FIG. 8 disclosed in Japanese Patent Application Laid-Open No. 2-132384, which does not need to increase the number of terminals, a substrate voltage internally generated due to a back bias of the semiconductor substrate 48 and the like. In order to indirectly detect VBB, cells 44, 45, 46, and each cell and substrate 48.
One diode, two diodes 47 connected in series, and three diodes 47 connected in series are prepared.

According to this solution, a potential increased from the substrate voltage VBB by an integral multiple of the forward voltage of the diode 47 is applied to one end of each cell. Cell 44, cell 4
5, 5 and 6 are set to have different states (logic value 1 or 0) with a certain threshold value of the voltage applied from the voltage VBB as a boundary. That is, digitized data is obtained according to the magnitude of the voltage VBB, and the value of the voltage VBB is estimated by reading the state of this cell from the outside.

However, since the resolution within the forward voltage of one diode cannot be provided, the substrate voltage VBB cannot be detected with high accuracy, and the cells 44, 45, 46, the diode 47, etc. are not formed properly. In this case, the substrate voltage VBB becomes defective, and there is a problem that the reliability in inspection is low. In particular, even in each cell alone, the decrease in reliability in this respect cannot be ignored because it is composed of six elements. Further, in addition to the cell and the diode, a circuit for reading out the digitized data to the outside is required, which causes a problem that the scale becomes large.

[0008]

In view of the above-mentioned various problems, the present invention has the following problems. (1) To make it possible to detect the potential of a predetermined region of a semiconductor substrate with high accuracy and reliability by using an external terminal. (2) To be able to be used as other terminals without adding a dedicated terminal for measurement. That is, it is not necessary to change the number of terminals or the terminal pitch of the semiconductor device. (3) The circuit that outputs the potential of the predetermined region to the terminal has an extremely simple configuration.

[0009]

According to a solution of the present invention, in a semiconductor device, a terminal electrically connected to each region of a semiconductor substrate covered with a package is led out of the package. The predetermined region and the terminal are electrically connected via a resistor so that the internal potential applied to the predetermined region of the semiconductor substrate can be measured.

In particular, the resistance value of the resistor is adjusted so as to be equal to or less than the leak current value defined by the standard of the terminal.

Further, it is characterized in that the internal potential is a substrate potential of the semiconductor substrate.

Further, in particular, the input of the buffer or the output of the three-state buffer is connected to the terminal.

A first semiconductor device inspection method according to the present invention is
The internal potential is estimated by measuring the voltage of the power source in the previous period when the current applied from the external power source to the terminal stops flowing.

The second semiconductor device inspection method of the present invention is characterized in that the internal potential is calculated from the voltage value of the terminal and the voltage value applied to the terminal via a resistor.

According to the solution of the present invention, the internal potential is
Since it is simply led to the terminal via a resistor, the function of the conventional terminal part is not impaired, and the internal potential can be accurately detected, which allows it to be used as a conventional input / output terminal. Become.

According to the first inspection method of the present invention, since the external power supply voltage at the time when current stops flowing is detected, the internal potential can be accurately measured, and according to the second inspection method. Since it is not necessary to adjust the voltage of the external power supply for each measurement only by calculating the internal potential from both voltage values, the inspection work can be performed more quickly.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 showing a first embodiment of the present invention, this semiconductor device is provided with an input terminal 1 serving as an external lead outside the package and is formed on a semiconductor substrate inside the package. The input terminal 1 is connected to the input of the input first stage 2 formed by the buffer circuit, and the power supply line 10 to which the potential of the predetermined region of the internal power supply generation circuit formed on the semiconductor substrate is applied is connected via the predetermined resistor 3. And is connected between the input terminal 1 and the input first stage 2.

The internal power supply generation circuit 4 has a function of generating a voltage necessary for the circuit in a predetermined region in the semiconductor substrate based on a power supply voltage input from the outside. It is a circuit that oscillates, boosts this oscillation output, and then rectifies it to obtain a high voltage necessary for the circuit. When there are a plurality of circuits 4, a corresponding number of input terminals 1, input first stage 2, resistors 3, power supply line 1
0 is prepared for each.

The resistor 3 is preferably formed in the semiconductor substrate, but separately from the semiconductor substrate, the resistor 3 is formed as a single unit.
It may be incorporated in the package.

The input terminal 1 serving as an external lead is electrically connected to a pad on the semiconductor substrate through an internal lead, directly or via a bonding wire, but not shown.

The input terminal 1 is, for example, a lead to which a data signal is input, and is usually provided with a plurality of leads. Using this terminal 1, the potential of the power supply line 10 is detected. No data signal or the like is applied during potential detection. Here, the input impedance of the first stage 2 is extremely large, and is a value larger than the resistance 3 by one digit or more.

The specified leak current value of the input terminal 1 is set to 1
Assuming that the input impedance of the input first stage 2 is infinite and the voltage applied to the resistor 3 is 5 V at the maximum, the resistance value of the resistor 3 is set to 500 KΩ or more.
The input leakage current value can be 10 μA or less.

Referring to FIG. 4, which shows one measuring system in the case of measuring the potential of the power supply line 10 in this circuit, an external power supply 17 for arbitrarily varying the voltage value and a connection between the external power supply 17 and the input terminal 1 are connected. An ammeter 20 for operating and a voltmeter 19 for measuring the voltage value of the external power supply 17 are prepared. Although not shown, the ground terminals of the external power supply 17 and the voltmeter 19 are commonly connected to the semiconductor device under test and the ground terminal.

Referring to the flowchart of FIG. 6 showing the actual measurement procedure, first, the voltage of the external power supply 17 is appropriately applied to the input terminal 1, and then the current value is measured by the ammeter 20. It is determined whether the current is flowing in either direction, and if it is flowing, the voltage is varied to adjust the current so that it does not flow. When the current stops flowing, the voltage of the external power supply 17 at that time becomes equal to the internal potential of the circuit 4, so that the voltmeter 19
You can measure immediately by reading the display.

Here, since the voltage value when the current stops flowing in the ammeter 20 is measured, there is no concern that the measurement accuracy will be deteriorated by the voltage drop caused by the internal resistance of the ammeter 20 and the resistor 3. There are advantages. The overall measurement accuracy in this case mainly depends on the measurement accuracy of the voltmeter 19 and the ammeter 20.

If the measured voltage value is within the permissible value, it is recognized as a non-defective product, and if it is outside the permissible value, it is discarded as a defective product or only the circuit to which the voltage of the power supply line 10 is applied. It is used by utilizing other circuits without using it.

As described above, according to the internal potential detecting circuit and the detecting method thereof of this embodiment, in the semiconductor device having a plurality of input terminals or a combination of input and output terminals, the internal power supply or the internal signal line is provided. And the input terminal or the input / output combined terminal with a resistor set to a value that is equal to or less than the input current value specified in the standard. By applying a voltage so that no current flows and measuring the potential at that time, the potential of the internal power supply or the internal signal line can be accurately detected.

Referring to FIG. 2 showing a second embodiment of the present invention, in this embodiment, the potential of the signal line 11 commonly used by the internal circuits 8 and 9 is input via a resistor 7. It is common to the first embodiment described above except that the measurement is performed at the terminal 5.

Referring to FIG. 3 showing a third embodiment of the present invention, an input / output terminal 16 to which a resistor 15 for detection is connected, and an input / output terminal connected to the input / output terminal 16 are provided. The third embodiment is common to the first embodiment described above except that the three-state buffers 12 and 18 are provided.

The buffers 12 and 18 are respectively provided with control terminals 13 and 14 for bringing the outputs into a high impedance state.

Prior to the measurement, the buffer 12 is set to a high impedance state. If there is a concern about oscillation due to positive feedback, the buffer 18 is also placed in a high impedance state.

The measuring procedure in this case is the same as in the case of the first embodiment described above.

In the first, second and third embodiments described above, the measurement system using the voltmeter 19 and the ammeter 20 shown in FIG. 4 has been described, but the measurement system shown in FIG. 5 is also used. It is also possible to measure the internal potential.

In FIG. 5, in this measuring system, the voltmeter 19 is connected to the terminal 1, and the external power source 17 is connected via the resistor 21.
Is connected. Here, the external power supply 17 does not need to be adjusted for each measurement as shown in FIG. 6, and the resistance value of the resistor 21 is the same as the resistance value of the resistor 3 or 7 or 17, and the element is used. The measured internal voltage in this case is (2 · VI-V0)
It is immediately obtained by calculating the simple formula for Here, VI is the voltage value of the voltmeter 19, and V0 is the voltage value of the external power supply.

According to this embodiment, there is an advantage that it is not necessary to adjust the external power supply 17.

[0036]

As described above, according to the present invention, since the dual-purpose terminal to which the resistor is connected can be provided and the internal potential can be measured with the dual-purpose terminal, it is not necessary to newly provide a dedicated terminal. , And without the need to add a large-scale circuit,
All the above-mentioned issues have been achieved.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a second embodiment.

FIG. 3 is a circuit diagram showing a third embodiment.

FIG. 4 is a circuit diagram showing one measurement system of each embodiment of the present invention.

FIG. 5 is a circuit diagram showing another measurement system according to each embodiment of the present invention.

FIG. 6 is a flowchart showing the operation of one measurement system.

FIG. 7 is a circuit diagram for detecting a conventional internal potential.

FIG. 8 is a circuit diagram for detecting an internal potential using a conventional memory cell.

[Explanation of symbols]

 1,5 Input terminal 2,6 Input first stage 3,7,15,21 Resistance 4,33 Internal power supply generation circuit 8,9 Internal circuit 10 Power supply line 11 Signal line 12,18 Three-state buffer 13,14 High impedance control terminal 16 Input / output terminal 17 External power supply 19 Voltmeter 20 Ammeter 31 Output terminal 44, 45, 46 Cell 47 Diode 48 Substrate

Claims (7)

[Claims] 1. In a semiconductor device in which terminals electrically connected to respective regions of a semiconductor substrate covered by a package are led out of the package, an internal potential applied to a predetermined region of the semiconductor substrate. So that you can measure
A semiconductor device, wherein the predetermined region and the terminal are electrically connected via a resistor. 2. The semiconductor device according to claim 1, wherein the resistance value of the resistor is adjusted to be equal to or less than a leakage current value defined by the standard of the terminal. 3. The semiconductor device according to claim 2, wherein the resistance value of the resistor is 500 KΩ or more. 4. The semiconductor device according to claim 1, wherein the internal potential is a substrate potential of the semiconductor substrate. 5. The semiconductor device according to claim 1, wherein an input of a buffer or an output of a three-state buffer is connected to the terminal. 6. The method of inspecting a semiconductor device according to claim 1, wherein the internal potential is estimated by measuring a voltage of the power supply when a current applied to the terminal from an external power supply stops flowing. A characteristic semiconductor device inspection method. 7. The method of inspecting a semiconductor device according to claim 1, wherein the internal potential is calculated from a voltage value of the terminal and a voltage value applied to the terminal via a resistor. Method for inspecting semiconductor device.