JPH10239404A - Detecting method of leak current, and leak current detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the leak detecting sensitivity by uniformly raising the liquid crystal temperature on the whole surface of a chip just below a phase transition temperature. SOLUTION: A liquid crystal 20 applied onto a chip is locally heated with scanning to form a high-temperature area having a minute area moved on the chip, and a phase transfer area 22 caused by leak current within this high- temperature area is detected. The temperature control of the minute are can be precisely performed with a small heat constant. Since the high-temperature area 21 is temperature-controlled with scanning, the temperature distribution within the chip can be minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects a defect that causes a leakage current in a circuit chip, for example, a semiconductor device,
The present invention relates to a leak detection method for specifying the position and a leak detection device suitable for using the method.

[0002] One of the failures of a semiconductor device involves a defect in which a leak current increases more than normal. In order to analyze such a failure, it is necessary to accurately detect a leak position in the chip. Further, in a semiconductor device composed of fine and low-power-consumption elements, a slight leak current causes a failure, so that a high-precision leak detection capable of detecting a minute leak current is required. Therefore, there is a need for a leak detection method and a leak detection device that can detect a small increase in the leak current and accurately specify the position of the leak.

[0003]

2. Description of the Related Art Conventionally, a method utilizing phase transition of liquid crystal has been widely used as a method for detecting leaks of a circuit chip. In this method, a liquid crystal is applied on a circuit chip, for example, a semiconductor chip to operate the circuit. At this time, if a defect accompanied by a leak current exists in the chip, the heat generated by the leak current locally raises the liquid crystal temperature and forms a phase transition region of the liquid crystal near the leak position. By detecting this phase transition region and specifying the position, the position can be specified as a leak position.

In the above-described conventional leak detection method utilizing the phase transition of liquid crystal, the temperature of the liquid crystal applied on the chip is precisely maintained just below the phase transition temperature in order to enhance the detection sensitivity of the leak current. There is a need. If the holding temperature of the liquid crystal is low, it is not possible to detect a small temperature rise caused by a small leak current, and the detection sensitivity is degraded. In addition, if there is a distribution of the holding temperature in the chip surface or a variation with time, the detection sensitivity changes depending on the location or time, so that it is difficult to accurately specify a minute leak position.

[0005] However, there are various types of circuit chips to be tested, such as those in a chip state or those housed in a package. Therefore, the control mechanism of the liquid crystal temperature has been designed for each mode by adapting the heat generation and heat insulating member such as a heater or a thermostat to the mode of the chip. For this reason, when many types of chips are to be inspected, the heating device becomes complicated because the heat generation and the heat insulating members are replaced. Further, it is difficult to uniformly increase the temperature of a chip having a large area without causing a temperature distribution. In particular, different types of packages have different temperature distributions. This limits the accuracy of leak detection sensitivity.

[0006]

As described above, the conventional leak detection method utilizing the phase transition of liquid crystal requires a complicated heating device capable of exchanging heat and a heat insulating member in order to inspect various chips. Had the disadvantage of doing so. Also,
It is difficult to uniformly increase the in-plane temperature of the chip, and the accuracy of leak detection sensitivity is limited.

According to the present invention, a liquid crystal applied on a chip is locally heated to form a high temperature region heated to a temperature just below a phase transition temperature moving on the chip, and a phase transition in the high temperature region is performed. By detecting the presence or absence of a region, it is possible to avoid a deterioration in leak detection accuracy due to a temperature distribution or temperature fluctuation of the liquid crystal which occurs when the entire surface of the chip is maintained at a uniform temperature, and a leak detection method having high leak detection accuracy. An object of the present invention is to provide a leak detection device.

[0008]

FIG. 1 is a perspective view of an embodiment of the present invention, showing a main part of a leak detecting device. FIG. 2 is an enlarged plan view of an embodiment of the present invention, showing a phase transition region formed in a liquid crystal applied to a chip surface and FIG.
3 shows a positional relationship with a main part of a heater of the leak detection device.

Referring to FIGS. 1 and 2, a first configuration of the present invention for solving the above-mentioned problem is to apply a liquid crystal on a circuit chip 1 and generate a phase by a heat generated by a leak current in the chip 1. In a leak detection method for detecting a phase transition region 22 of the transferred liquid crystal and specifying a leak position 23, the liquid crystal is locally heated and the heated position is moved to move in the surface of the chip 1. Forming a thermally heated high-temperature region 21 in the liquid crystal; and detecting the phase transition region 22 in the high-temperature region 21. In the leak detection method of the first configuration, the high-temperature region 21 is held so that the front end is in contact with the surface of the liquid crystal, and the rear end is heated by the heating needle 2a of a good heat conductor connected to the heater 2b. Characterized by being formed The third configuration is a means for detecting a phase transition region 22 in which the liquid crystal applied on the circuit chip 1 has undergone phase transition due to heat generated by a leak current in the chip 1, and means for detecting the phase transition region 22. A means for specifying a position on the chip 1, wherein the liquid crystal is locally heated and the heated position is moved to move within the liquid crystal plane applied on the chip 1. A heater 2 for forming a high-temperature region 21 which changes, and a phase-change region 2 in the high-temperature region 21.
And a fourth configuration is characterized in that the liquid crystal applied on the circuit chip 1 is subjected to phase transition due to heat generated by a leak current in the chip 1. The liquid crystal applied on the chip 1 is locally heated by a leak detection device including a means for detecting the phase transition region 22 and a means for specifying the position of the phase transition region on the chip. A heater 2 for forming a high-temperature region 21 in the liquid crystal, a phase transition detector 10 for detecting a phase transition region 22 in the high-temperature region 21, and holding the chip 1. And an XY table for moving the high-temperature region 21 by moving the heater in parallel with the heater. The fifth configuration is the leak detection device according to the third or fourth configuration. 2 so that the tip touches the surface of the liquid crystal A heating needle 2a of a good heat conductor held at the rear end connected to the heater 2b is provided, and the sixth configuration is characterized by a leakage of the third, fourth or fifth configuration. In the detection device, a temperature sensor 3 for detecting the temperature of the high-temperature region 21 and the temperature of the heater 2 controlled by the output of the temperature sensor 3 to obtain the high-temperature region 21
And a temperature controller that keeps the temperature constant.

In the first embodiment of the present invention, referring to FIGS. 1 and 2, the liquid crystal 10 applied on the chip 1 is locally heated so that a partial area of the liquid crystal 10 is heated to a high temperature area. Make it 21. The heating position moves, and the high-temperature region 21 moves within the surface of the chip 1. Further, the inside of the moving high-temperature region 21 is observed by the phase transition detector 10 and the high-temperature region 21 is observed.
The phase transition region 22 formed inside is detected. Note that the temperature of the high-temperature region 21 needs to be lower than the phase transition temperature of the liquid crystal 10, and is preferably close to the phase transition temperature from the viewpoint of increasing the detection sensitivity.

In this configuration, since the high-temperature region 21 is formed by locally heating a minute region on the chip, the time constant of the temperature control system is small, and the temperature of the high-temperature region 21 must be precisely controlled. Can be. In addition, the moving high-temperature region 21
Since the temperature of the chip is controlled in real time, it is easy to maintain a constant temperature at an arbitrary position on the chip 1, and the temperature distribution in the chip surface is higher than the conventional method of raising the temperature of the entire chip to a constant temperature. Is small. Therefore, the leak current can be detected with high sensitivity. In particular, the temperature distribution in the chip can be reduced for a chip housed in an arbitrary package. In addition, in this configuration, heating of a minute area is sufficient, and it is not necessary to uniformly heat the entire chip. Therefore, the mechanism of the leak device using this configuration is simplified.

In the second configuration of the present invention, in order to form the high temperature region 21, the rear end of the heating needle 2a, which is connected to the heater 2b and is made of a good heat conductor and is heated, is connected to the liquid crystal 10
The liquid crystal 10 is locally heated while being held in contact with the surface. In this configuration, since the temperature of the high-temperature region 21 can be controlled by controlling the temperature of the heater 2b, the temperature can be controlled accurately with a simple device.

A third configuration relates to a leak detection device using the leak detection method of the first configuration. The third configuration includes a heater 2 for locally heating the liquid crystal 10 applied on the chip 1 while moving. Such a heater 2
For example, it is realized by a light beam scanning mechanism or a mechanism that scans the heating needle 2a by bringing the tip of the heating needle 2a heated to a high temperature into contact with the liquid crystal surface. The phase transition region 22 generated in the high-temperature region 21 formed in the liquid crystal 10 by the heater 2 is used as a phase transition detector 10, for example, a deflection microscope 10a.
Is detected by The phase transition detector 10 only needs to detect the phase transition region 22 in the high temperature region 21.
It may be one that moves together with the heater 2 while observing 1 or one that is fixed to observe the entire surface of the liquid crystal 10.

The fourth configuration relates to another leak detection device utilizing the leak detection method of the first configuration. The fourth configuration includes a heater 2 for locally heating the liquid crystal 10 applied on the chip 1 to form a high-temperature region 21 and an XY table 4 for holding and moving the chip 1. Therefore, the high-temperature region 21 moves on the chip surface as the chip 1 moves. Phase transition region 22 generated in high temperature region 21
Is detected by the phase transition detector 10 monitoring the inside of the high-temperature region 21 and the chip 1 is detected from the position of the XY table 4 at the time of detection.
The upper leak position 23 is specified.

In the fifth configuration, the heater 2 is provided so that the front end is held in contact with the surface of the liquid crystal 10 and the rear end is provided with a heating needle 2a of a good heat conductor connected to the heater 2b. . In the device of this configuration, similar to the second method, precise temperature control of the high-temperature region 21 is performed by a simple temperature control device.

The sixth configuration relates to the temperature control of the high-temperature region 21 in each of the above-described configurations. The temperature sensor 3 detects the temperature of the high-temperature region 21, and the temperature of the heater 2 is controlled by the output of the temperature sensor 3. A temperature controller (not shown) for keeping the temperature of the high-temperature region 21 constant. The temperature sensor 3 is realized by a sensor capable of measuring the temperature of the high-temperature region 21 having a small area, for example, a thermocouple 3a in contact with the liquid crystal 10 surface. By providing such a temperature sensor 3 and a temperature controller, the temperature of the high-temperature region 21 can be precisely controlled, so that the temperature of the high-temperature region 21 can be stably maintained just below the phase transition temperature, and leak detection can be performed. Sensitivity increases.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment in which the present invention is applied to a semiconductor chip leak detecting device.

The leak detecting device according to this embodiment is
Referring to FIG. 1, an XY table 4 on which a sample table 5 is placed is fixed on a base 7. Sample table 5
Has a rotation mechanism around three axes, and X
It can be held parallel to the moving surface of the Y table. The chip 1 to be inspected is a semiconductor chip in which the upper surface of the package of the integrated circuit is removed and is exposed on the package table 6, and is mounted on the sample table 5 together with the package table. Further, a phase transition detector 1 is provided above the chip 1.
As 0, the deflection microscope 10a is fixed to the column 8.

A column 8 is suspended from a base 7 on the side of the XY table 4 and an operation box 11 for finely adjusting the two arms 9 by moving the two arms 9 is guided and supported by the column 8. The heater 2 is attached to the tip of one arm 9, and the temperature sensor 3 is attached to the tip of the other arm 9. Referring to FIG. 2, a heater 2 has a linear heater 2b at its tip.
In the center of the heater 2b, a heating needle 2a made of a fine heat conductor such as a copper thin wire having a diameter of 10 μm is joined. The temperature sensor 3 is composed of a thin thermocouple 3a.

In detecting a leak, first, the lid of the package of the semiconductor device is removed, the chip 1 fixed on the package base 6 is exposed, and liquid crystal is applied to the upper surface of the chip 1. Next, referring to FIG. 1, chip 1 is placed on sample table 5 with the bottom surface of package base 6 closely contacted, and sample table 5 is finely adjusted so that chip 1 surface is moved to the moving surface of XY table 4. Hold in parallel. Next, a probe of an IC tester (not shown) that supplies power to the terminals of the chip 1 and inputs and outputs necessary signals is connected.

Next, the tips of the heater 2 and the temperature sensor 3 are moved into the field of view of the deflection microscope 10a, and the tips of the heater 2 and the temperature sensor 3 are moved while the XY table 4 is moved, for example, in the X direction. It contacts the surface of the liquid crystal 10. Next, the input power of the heater 2b of the heater 2 is controlled through a temperature controller (not shown) so that the output of the temperature sensor 3 becomes just below the phase transition temperature of the liquid crystal 10. At this time, referring to FIG. 2, for example, a range of a radius of 30 microns around the surface of the liquid crystal 10 in contact with the tip of the heater 2, that is, the tip of the heating needle 2a is the high-temperature region 21 immediately below the phase transition temperature. . The thermocouple 3a for measuring the temperature of the high-temperature region 21 includes a heating needle 2a
, For example, within 10 μm.

The deflection microscope 10a adjusts the deflection plate so as to provide a dark field with no liquid crystal applied, and monitors the inside of the high temperature area 21. When the XY table 4 is scanned and a leak position 23 enters the high-temperature region 21, a phase transition region 22 is formed around the leak position 23 and observed as a black spot by the deflection microscope 10a. The leak position 23 is defined by the center position of the phase transition region 22 in the field of view of the deflection microscope 10a and the X position.
It can be easily determined from the position of the Y table.

[0023]

As described above, according to the present invention, in order to heat the liquid crystal, the liquid crystal is locally scanned and heated to form a high-temperature area with a small area. In addition, since a temperature change in a high-temperature region in a chip surface can be reduced, a leak current can be detected with high accuracy, which greatly contributes to improvement of a failure analysis technique of a semiconductor device.

[Brief description of the drawings]

FIG. 1 is a perspective view of an embodiment of the present invention.

FIG. 2 is an enlarged plan view of an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 chip 2 heater 2a heating needle 2b heater 2c joint 3 temperature sensor (3a temperature sensor) 4 XY table 5 sample table 6 package base 7 base 8 support 9 arm 10 phase transition detector (10a microscope) 11 operation box 21 High temperature region 22 Phase transition region 23 Leak position

Claims (6)

[Claims] 1. A method for detecting a leak current, comprising: applying a liquid crystal on a circuit chip, detecting a phase transition region of the liquid crystal which has undergone phase transition due to heat generated by the leak current in the chip, and specifying a leak position. Locally heating and moving the heating position to form a locally heated high temperature region moving in the chip plane in the liquid crystal, and detecting the phase transition region in the high temperature region And detecting the leakage current. 2. The leak detecting method according to claim 1, wherein said high-temperature region is held such that a front end thereof is in contact with a surface of said liquid crystal, and a rear end of said high-temperature conductor is connected to a heater. A method for detecting a leak current, characterized in that the method is formed by heating by a method. 3. A means for detecting a phase transition area in which liquid crystal applied on a circuit chip has undergone a phase transition due to heat generated by a leak current in the chip, and means for specifying a position of the phase transition area on the chip. A heater for locally heating the liquid crystal and moving the heating position to form a high-temperature region moving within the liquid crystal surface applied on the chip; and A phase transition detector for detecting a phase transition region in a high-temperature region. 4. A means for detecting a phase transition area in which liquid crystal applied on a circuit chip has undergone phase transition due to heat generated by a leak current in the chip, and means for specifying a position of the phase transition area on the chip. A heater for locally heating the liquid crystal applied on the chip to form a high-temperature region in the liquid crystal, and a phase transition for detecting a phase transition region in the high-temperature region. A leak current detecting device, comprising: a detector; and an XY table that holds the chip, moves the chip in parallel with the chip surface, and moves the high-temperature region. 5. The leak current detecting device according to claim 3, wherein the heater is held so that a front end thereof is in contact with a surface of the liquid crystal, and a rear end of the heater is connected to a heater. A leak current detection device comprising a heating needle. 6. The leak current detecting device according to claim 3, wherein a temperature sensor for detecting a temperature in the high temperature region, and a temperature of the heater controlled by an output of the temperature sensor, the temperature of the heater being controlled by the temperature sensor. A leak current detecting device comprising a temperature controller for keeping a temperature of a region constant.