JP3617236B2 - Leak current detection method and leak current detection apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a leak detection method for detecting a defect that generates a leak current in a circuit chip, for example, a semiconductor device, and specifying the position thereof, and a leak detection device suitable for using the method.
[0002]
One of the failures of semiconductor devices is accompanied by a defect in which leakage current increases more than normal. In order to analyze such a failure, it is necessary to accurately detect the leak position in the chip. Furthermore, since a slight leak current causes a failure in a semiconductor device composed of fine elements with low power consumption, high-accuracy leak detection that can detect even a small amount of leak current is required. Therefore, there is a demand for a leak detection method and a leak detection apparatus that can detect a minute increase in leak current and accurately specify the position of the leak.
[0003]
[Prior art]
Conventionally, a method using a phase transition of liquid crystal has been widely used as a method for detecting a leak of a circuit chip. In this method, a circuit is operated by applying liquid crystal on a circuit chip, for example, a semiconductor chip. At this time, if there is a defect with a leak current in the chip, the liquid crystal temperature rises locally due to heat generated by the leak current, and a liquid crystal phase transition region is formed in the vicinity of the leak position. By detecting this phase transition region and specifying the position, the position can be specified as a leak position.
[0004]
In such a conventional leak detection method using the phase transition of the liquid crystal, the temperature of the liquid crystal applied on the chip needs to be precisely maintained just below the phase transition temperature in order to increase the detection sensitivity of the leak current. . If the liquid crystal holding temperature is low, a very small temperature rise due to a small amount of leakage current cannot be detected, and the detection sensitivity deteriorates. In addition, if there is a distribution of the holding temperature in the chip surface or temporal variation, the detection sensitivity changes depending on the location or time, so that it is difficult to accurately identify a minute leak position.
[0005]
However, there are various types of circuit chips to be inspected, for example, in a chip state or in a package. Therefore, the liquid crystal temperature control mechanism is designed for each mode by adapting the heat generation and heat insulation members such as a heater or a thermostat to the chip mode. For this reason, when many types of chips are to be inspected, the heating device becomes complicated because the heat generating and heat insulating members are replaced. In addition, it is difficult to raise the temperature of a large area chip uniformly without causing temperature distribution. In particular, different types of packages have different temperature distributions. For this reason, improvement in accuracy of leak detection sensitivity has been limited.
[0006]
[Problems to be solved by the invention]
As described above, the conventional leak detection method using the phase transition of the liquid crystal has a drawback that a complicated heating device capable of generating heat and exchanging the heat insulating member is required to inspect various chips. In addition, it is difficult to raise the in-plane temperature of the chip uniformly, and there is a problem that the accuracy of leak detection sensitivity is limited.
[0007]
The present invention locally heats the liquid crystal coated on the chip to form a high temperature region heated to a temperature just below the phase transition temperature moving on the chip, and whether or not there is a phase transition region in the high temperature region. Leak detection method and leak detection apparatus with high leak detection accuracy by avoiding deterioration of leak detection accuracy due to temperature distribution or temperature fluctuation of liquid crystal that occurs when the entire surface of the chip is held at a uniform temperature. The purpose is to provide.
[0008]
[Means for Solving the Problems]
FIG. 1 is a perspective view of an embodiment of the present invention and shows a main part of a leak detection apparatus. FIG. 2 is an enlarged plan view of an embodiment of the present invention, showing the positional relationship between the phase transition region formed in the liquid crystal applied to the chip surface and the main part of the heater of the leak detection apparatus of FIG. .
[0009]
Referring to FIGS. 1 and 2, the first configuration of the present invention for solving the above-described problem is that the liquid crystal is applied on the circuit chip 1 and the phase transition is caused by the heat generated by the leakage current in the chip 1. In the leak detection method of detecting the liquid crystal phase transition region 22 and specifying the leak position 23, the liquid crystal is locally heated and moved to move locally within the chip 1 surface. Forming a high temperature region 21 formed on the liquid crystal, and detecting the phase transition region 22 in the high temperature region 21; and
The second configuration is the leak detection method of the first configuration, in which the high temperature region 21 is held in such a manner that the front end is in contact with the surface of the liquid crystal and the rear end is connected to the heater 2b. It is characterized by being formed by being heated by the heating needle 2a, and
The third configuration includes 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 leakage current in the chip 1, and the phase transition region 22 on the chip 1. In a leak detection apparatus comprising a means for specifying a position, the liquid crystal is locally heated and moved in the heating position so that a high-temperature region 21 that moves in the liquid crystal surface coated on the chip 1 is provided. Comprising a heater 2 to be formed, and a phase transition detector 10 for detecting a phase transition region 22 in the high temperature region 21; and
The fourth configuration is a means for detecting the phase transition region 22 in which the liquid crystal applied on the circuit chip 1 has undergone phase transition due to heat generated by the leakage current in the chip 1 and the position of the phase transition region on the chip. In a leak detection apparatus comprising a means for specifying, a heater 2 that locally heats the liquid crystal applied on the chip 1 to form a high temperature region 21 in the liquid crystal, and a phase in the high temperature region 21 A phase transition detector 10 for detecting a transition region 22 and an XY table that holds the chip 1 and moves the chip 1 in parallel to the surface of the chip 1 to move the high temperature region 21. And as
A fifth configuration is the leak detection device of the third or fourth configuration, wherein the heater 2 is held so that the front end is in contact with the surface of the liquid crystal and the rear end is connected to the heater 2b. Characterized in that it comprises a conductor heating needle 2a, and
The sixth configuration is the leak detection device of the third, fourth or fifth configuration, in which the temperature sensor 3 for detecting the temperature of the high temperature region 21 and the temperature of the heater 2 by the output of the temperature sensor 3 are set. A temperature controller that controls and keeps the temperature of the high temperature region 21 constant is provided.
[0010]
In the first configuration of the present invention, referring to FIG. 1 and FIG. 2, the liquid crystal 10 applied on the chip 1 is locally heated so that a partial region of the liquid crystal 10 becomes a high temperature region 21 of high temperature. . The heating position moves, and the high temperature region 21 moves within the surface of the chip 1. Further, the moving high temperature region 21 is observed by the phase transition detector 10 to detect the phase transition region 22 formed in the high temperature region 21. 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.
[0011]
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 can be precisely controlled. In addition, since the temperature of the moving high temperature region 21 is controlled in real time, it is easy to maintain a constant temperature at an arbitrary position on the chip 1, compared with the conventional method in which the entire chip is heated to a constant temperature. The temperature distribution in the chip surface is small. Therefore, the leak current can be detected with high sensitivity. In particular, the temperature distribution in a chip can be reduced even for a chip housed in an arbitrary package. Further, in this configuration, it is sufficient to heat a minute area, and it is not necessary to uniformly heat the entire chip. Therefore, the leak device using this configuration has a simple mechanism.
[0012]
In the second configuration of the present invention, in order to form the high temperature region 21, the tip of the heating needle 2a made of a good heat conductor that is heated with the rear end connected to the heater 2b is brought into contact with the surface of the liquid crystal 10. And the liquid crystal 10 is locally heated. In this configuration, since the temperature control of the high temperature region 21 can be performed by controlling the temperature of the heater 2b, the temperature control can be accurately performed with a simple device.
[0013]
The third configuration relates to a leak detection apparatus using the leak detection method of the first configuration. The third configuration includes a heater 2 that locally heats the liquid crystal 10 applied on the chip 1 while moving. The heater 2 is realized by, for example, 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. Further, the phase transition region 22 generated in the high temperature region 21 formed in the liquid crystal 10 by the heater 2 is detected by the phase transition detector 10, for example, the deflection microscope 10a. The phase transition detector 10 only needs to be able to detect the phase transition region 22 in the high temperature region 21 and may be one that moves with the heater 2 by observing the high temperature region 21 or may be fixed to observe the entire surface of the liquid crystal 10. .
[0014]
The fourth configuration relates to another leak detection apparatus using the leak detection method of the first configuration. The fourth configuration includes a heater 2 that locally heats the liquid crystal 10 applied on the chip 1 to form a high temperature region 21 and an XY table 4 that holds and moves the chip 1. Accordingly, the high temperature region 21 moves on the chip surface as the chip 1 moves. The phase transition region 22 generated in the high temperature region 21 is detected by the phase transition detector 10 that monitors the inside of the high temperature region 21, and the leak position 23 on the chip 1 is specified from the position of the XY table 4 at the time of detection.
[0015]
In the fifth configuration, the heater 2 is provided with a good heat conductor heating needle 2a which is held such that the front end is in contact with the surface of the liquid crystal 10 and the rear end is connected to the heater 2b. In the apparatus of this configuration, precise temperature control of the high temperature region 21 is performed by a simple temperature control device, as in the second method.
[0016]
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 for detecting the temperature of the high temperature region 21, and the temperature of the heater 2 by controlling the temperature sensor 3 output, A temperature controller (not shown) that keeps the temperature of the high temperature region 21 constant is provided. The temperature sensor 3 is realized by a sensor capable of measuring the temperature of the high-temperature region 21 having a very 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 immediately below the phase transition temperature, and leakage detection can be performed. Sensitivity is increased.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below with reference to an embodiment in which the present invention is applied to a semiconductor chip leak detection apparatus.
[0018]
In the leak detection apparatus according to this embodiment, referring to FIG. 1, an XY table 4 on which a sample table 5 is placed is fixed on a base 7. The sample table 5 has a rotation mechanism around three axes, and can hold the upper surface of the chip 1 parallel to the moving surface of the XY table. The chip 1 to be inspected is a semiconductor chip that is exposed on the package base 6 by removing the upper surface of the package of the integrated circuit, and is placed on the sample table 5 together with the package base. Further, a deflection microscope 10 a as a phase transition detector 10 is fixed to the support column 8 above the chip 1.
[0019]
Further, a support column 8 is suspended from a base 7 beside the XY table 4, and an operation box 11 for moving and finely adjusting the two arms 9 is guided and supported by the support 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, the heater 2 has a linear heater 2b at the tip, and a heating needle 2a made of a fine heat conductor, for example, a copper thin wire having a diameter of 10 μm, is joined to the center of the heater 2b. The temperature sensor 3 is composed of a thin thermocouple 3a.
[0020]
In detecting the 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, the chip 1 is placed on the sample table 5 with the bottom surface of the package base 6 in close contact, and the sample table 5 is finely adjusted so that the surface of the chip 1 becomes the moving surface of the 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.
[0021]
Next, the tips of the heater 2 and the temperature sensor 3 are moved within the field of view of the deflection microscope 10a, and the tips of the heater 2 and the temperature sensor 3 are moved to the surface of the liquid crystal 10 while the XY table 4 is moved, for example, in the X direction. To touch. Next, the heater 2b input power of the heater 2 is controlled through a temperature controller (not shown) so that the output of the temperature sensor 3 is directly 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 μm becomes a high temperature region 21 immediately below the phase transition temperature centering on the surface of the liquid crystal 10 contacting the tip of the heater 2, that is, the tip of the heating needle 2 a. . The thermocouple 3a for measuring the temperature of the high temperature region 21 is held close to the heating needle 2a, for example, within 10 μm.
[0022]
The deflection microscope 10a adjusts the deflection plate so that a dark field is obtained in a state where no liquid crystal is applied, and monitors the inside of the high temperature region 21. When the XY table 4 is scanned and the leak position 23 enters the high temperature region 21, a phase transition region 22 is formed around the leak position 23 and is observed as a black spot by the deflection microscope 10a. The leak position 23 can be easily determined from the center position of the phase transition region 22 in the field of view of the deflection microscope 10a and the position of the XY table.
[0023]
【The invention's effect】
As described above, according to the present invention, in order to heat the temperature of the liquid crystal, the liquid crystal is locally and scanned and heated to form a high-temperature region having a very small area. Since the temperature change in the high-temperature region in the chip surface can be reduced, the leak current can be detected with high accuracy, which greatly contributes to the improvement of semiconductor device failure analysis technology.
[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.
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 Strut 9 Arm 10 Phase transition detector (10a microscope)
11 Operation box 21 High temperature region 22 Phase transition region 23 Leak position

Claims (6)

In a leakage current detection method for applying a liquid crystal on a circuit chip and detecting a phase transition region of the liquid crystal that has undergone phase transition due to heat generated by the leakage current in the chip to identify a leakage position,
A step of locally heating a part of the liquid crystal and moving the heating position to form a locally heated high temperature region moving in the chip surface in the liquid crystal;
And a step of detecting the phase transition region in the high temperature region. The leak detection method according to claim 1,
The high temperature region is formed by holding the tip of the liquid crystal in contact with the surface of the liquid crystal and heating the back end by a heating needle of a good heat conductor connected to the heater. Detection method. Leakage current comprising: means for detecting a phase transition region in which the liquid crystal applied on the circuit chip has undergone phase transition due to heat generation due to leakage current in the chip; and means for identifying the position of the phase transition region on the chip In the detection device,
A heater by moving the heating position with locally heating a portion of the liquid crystal, to form a high temperature region to move the liquid crystal plane coated on the chip,
A leak current detection device comprising: a phase transition detector for detecting a phase transition region in the high temperature region. Leakage current comprising: means for detecting a phase transition region in which the liquid crystal applied on the circuit chip has undergone phase transition due to heat generation due to leakage current in the chip; and means for identifying the position of the phase transition region on the chip In the detection device,
A heater for locally heating a part of the liquid crystal applied on the chip to form a high temperature region in the liquid crystal;
A phase transition detector for detecting a phase transition region in the high temperature region;
An apparatus for detecting leakage current, comprising: an XY table that holds the chip and moves the chip parallel to the surface of the chip to move the high temperature region. In the leak current detection device according to claim 3 or 4,
The leak current detecting device, wherein the heater includes a heating needle of a good heat conductor that is held such that a front end thereof is in contact with the surface of the liquid crystal and a rear end is connected to a heater. The leak current detection device according to claim 3, 4 or 5,
A temperature sensor for detecting the temperature of the high temperature region;
A leak current detection device comprising a temperature controller for controlling the temperature of the heater by the output of the temperature sensor and maintaining the temperature in the high temperature region constant.

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