JPH0618636A - Device test method and tester using ion beam - Google Patents

Abstract

PURPOSE:To prevent the intrusion of a beam into a sample and to realize the test of a device such as an IC at a high speed in high accuracy by casting an ion beam on the conductor layer of the device, into which an operating voltage is supplied, and forming an image corresponding to the amount of the generated secondary electrons. CONSTITUTION:A bias is applied on a sample IC 14 with an AC power supply 4 and a DC power supply 5, and the IC 14 is driven. Under this state, an ion beam is cast, and scanning is performed in the directions of X and Y by using an X-Y scanning-signal generator 9, a controller 10 and an amplifier 11. Channel electrons 3 are positively charged. The secondary electrons, which are generated from the sample 14 by the casting of the ion beam 15, are collected and detected. The detected signal of the secondary electrons is amplified, and the scanning image of the ion beam 15 is obtained on a video monitor 12. As a result, the brightness corresponding to the voltage of the conductor layer of the device (the metal wiring layer of aluminum or the like, polycide wiring and the like) appears. The operating state of the device can be found based on the brightness pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device test method using an ion beam and a device tester using an ion beam.

[0002]

2. Description of the Related Art With the progress of miniaturization of electrically operated devices such as ICs and liquid crystals, wirings are processed at a submicron level whose line width is 1 μm or less, and device failure analysis is performed. Even in the case of (internal operation state test, etc.), the conventional typical method of applying the probe needle to the pin of the device cannot be used. Therefore, in recent years, an electron beam tester (hereinafter, referred to as EBT) has begun to be used as an apparatus for measuring the operating state inside a minute device such as an IC and performing failure analysis.

EBT is a scanning electron microscope (SEM) IC
The basic principle of irradiating a sample with an electron beam and detecting secondary electrons obtained from it is the same as that of SEM, but SEM detects the detection signal. In contrast to obtaining an image of the sample surface (or cross section) based on, the EBT irradiates the wiring (conductor layer) in the state where a voltage is generated by applying a DC or AC bias with an electron beam, 2 of that wiring
The difference is that secondary electrons are detected, the wiring pattern is reproduced, and the voltage distribution in the wiring is detected from the light-dark distribution of the reproduced pattern. That is, the EBT is a device that performs electrical inspection, not visual observation (inspection).

In order to test a device by EBT, it is necessary to scan an electron beam focused on the line width level of the wiring along the wiring. In order to perform such high-precision control of the electron beam, it is originally desirable to use a high-resolution scanning electron microscope having an accelerating voltage of about 20 to 30 KV. However, when such a high acceleration voltage is used, since the diameter of the electrons is small, the electrons penetrate into the wiring layer by about 1.5 μm, and also diffuse in the lateral direction due to irregular reflection. Cannot be used. That is, the penetration of electrons into the wiring layer fluctuates the potential distribution of the wiring to prevent accurate voltage measurement, and the lateral spread due to diffused reflection causes secondary electron emission from the adjacent wiring other than the target. And becomes a factor that gives a detection error.

Therefore, in practice, the accelerating voltage of the scanning electron microscope is adjusted to a low value of 1 to 3 KV, which is used exclusively for EBT.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
There are the following problems. (1) Even if the accelerating voltage is lowered, it is not possible to completely prevent the electron beam from penetrating the sample (wiring), and inevitably the charge-up of the sample due to the penetrating electrons occurs. Therefore, a certain detection error will occur.

(2) Further, the focusing function of the electron beam is lowered by reducing the acceleration voltage. The electron beam with reduced focusing power is distorted in the wiring (or near the wiring) due to the influence of the potential fluctuation due to the penetrating electrons described in the item (1), and the state of secondary electron generation is changed, or the Fine (0.5 micron or less) wiring causes new problems such as not exactly hitting the target. (3) Therefore, in consideration of the recent reality of the rapid integration of devices such as ICs, the EBT cannot sufficiently cope with future miniaturization of devices.

The present invention has been made based on such a consideration, and an object thereof is to prevent a beam from penetrating into a sample as much as possible and realize a device test with high acceleration and high resolution.

[0009]

[Means for Solving the Problems]

(1) In the device testing method of the present invention, a voltage is generated in a conductor layer of the device by driving the device by supplying an operating voltage, and in this state, the conductor layer of the device is irradiated with an ion beam, and the conductor layer is irradiated. The amount of secondary electrons generated from the detector is detected, an image corresponding to the detected amount of secondary electrons is formed, and the voltage state of the conductor layer is detected from the brightness pattern of this image or the change in the detected amount of secondary electrons. , The operating state of the device is inspected. (2) A gallium ion beam or the like is used as the ion beam.

(3) The device tester of the present invention comprises an ion beam generating means for generating an accelerated ion beam, a sample stage on which a sample to be irradiated with the ion beam is placed, and a vacuum chamber surrounding the sample stage. And a secondary electron detection means for detecting secondary electrons generated from the sample as a result of ion beam irradiation, and a bias supply means for supplying a DC or AC bias to the sample. . (4) The ion beam is accelerated in the range of 10 KV to 35 KV.

[0011]

[Action]

(1) Ions are composed of nuclei and electrons, and unlike electrons, have a size on the order of several Å, so at an accelerating voltage of 10 to 35 KV, they are reflected by the polar surface of the sample and do not penetrate deeply into the sample like an electron beam. . Therefore, it is not necessary to be careful of this intrusion and keep the beam acceleration voltage low.
In the V accelerating voltage region, the optimum level can be set relatively freely. As a result, a clear bright and dark pattern image can be obtained, and the detection resolution (inspection accuracy) can be improved, especially in the voltage distribution measurement of a fine wiring pattern, as compared with the case of using the electron beam. (2) The type of ion is not particularly limited as long as it is easy to handle and causes no harmful effects, but from the viewpoint of easy ion generation in the ion source, a low melting point and low vapor pressure is preferable. Well, an ion beam of a Group 3 element such as Ga or In is preferable.

(3) The device is not limited as in the case of using an electron beam in setting the acceleration voltage, and it is not necessary to make delicate adjustments to make the scanning microscope dedicated to the tester. The one for cross-section observation can be used as it is. Therefore, it is easy to use and much more economical. (4) 10K which could not be used with the electron beam
Since a high acceleration range of V to 35 KV can be used, a clear bright and dark pattern can be obtained.

[0013]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a diagram showing the configuration of an embodiment (IC tester) of the device tester of the present invention. (Device configuration)

In the figure, reference numeral 1 denotes an ion beam,
An ion column for focusing, and 2 a vacuum chamber. Reference numeral 3 is a channel electron (2
Secondary electron detector), 4 is an AC power supply, and 5 is a DC power supply.
Reference numeral 6 is an ion pump for evacuating the column, 7 is a turbo pump for exhausting the inside of the vacuum chamber, 8
Is an amplifier that amplifies the channel electron 3 signal,
Reference numeral 9 is a signal generator for scanning the beam in the XY direction, 10 is a controller for the signal of the generator 9, 11 is an amplifier for generating a voltage for scanning the actual beam in the XY direction, and 12 is 2 A video monitor for obtaining a next electron image (scanning image), 13 is a sample stand, 14 is an IC (sample) to be measured, and 15 is a gallium ion beam. Reference numeral 30 is a gas unit for blowing a platinum compound gas onto the sample, and 31 is a platinum compound gas (trimethylcyclopentadienylplatinum). These 30, 31 are provided for IC repair (repair).

(Operation of the device) IC (14) as a sample
Then, a bias is applied from the AC power source 4 and the DC power source 5 to drive the IC. In this state, the ion beam 15 is irradiated onto the sample, and this ion beam is referred to by reference numerals 9 and 1.
Scan in the X and Y directions using the configuration of 0 and 11.

The channel electron 3 is positively charged, and the secondary electron generated from the sample 14 by the irradiation of the ion beam is attracted and detected. The detection signal of the secondary electrons is amplified to obtain an ion beam scanning image on the video monitor 12. (Principle of Testing Devices such as IC) FIG. 2 is a diagram showing the principle of testing devices by ion beam scanning. In the figure, reference numeral 16 is an aluminum wiring of 0V, 15 is an aluminum wiring biased to 5V, and 20 is a grounded substrate.

When the focused ion beam 15a is incident on the aluminum wiring 16 of 0 V, unlike the case of the electron beam, the focused ion beam 15a is reflected on the surface without penetrating deeply into the sample, and from there, the secondary electrons are several times as many as the number of electrons of the ion beam. Electron is generated,
This is captured by the secondary electron detector and becomes a detection signal.

On the other hand, with respect to the aluminum wiring 17 of 5V, a considerable number of secondary electrons generated by irradiation of the focused ion beam 15b is caught by the electric force line 19 due to the bias of 5V and is detected by the secondary electron detector. Do not reach That is, even if the target is made of the same material, the higher the voltage of the target is, the more secondary electrons are captured,
The amount of electrons detected by the secondary electron detector is reduced. As a result, when secondary electrons are detected while scanning the ion beam in the X and Y directions and an image is drawn on the monitor, it corresponds to the voltage of the conductor layer of the device (metal wiring layer such as aluminum or polycide wiring). Light and dark appear. The operating state of the device can be known from this bright / dark pattern.

(Experimental Results) The present inventor obtained an aluminum wiring image of an IC by using an ion beam with an accelerating voltage of 25 KV. An example is shown in FIG. In this example, a fixed bias was applied to the aluminum wiring, and a clear image was obtained without being affected by the SiO ₂ film. Si
Since the O ₂ film is charged to a predetermined bias as soon as it is irradiated with the ion beam, an unstable pattern due to a change in bias is not seen.

FIG. 4 shows another example. When an AC bias was applied to the IC to periodically change the voltage of the internal aluminum wiring, a striped pattern was obtained only in the portion where the voltage changed. The image was clear and these proved that the ion beam tester (FIBT) was indeed fully usable.

[0021]

As described above, according to the present invention, the following effects can be obtained. (1) The ion beam is reflected on the extreme surface of the sample and does not penetrate deeply into the sample like the electron beam. Therefore, the optimum level can be set relatively freely in the high acceleration voltage range, and a clear bright-dark pattern image can be obtained especially when measuring the voltage distribution of a fine wiring pattern compared to the case of using an electron beam. Therefore, the detection resolution (inspection accuracy) can be improved.

(2) As an apparatus, there is no limitation as in the case of using an electron beam in setting an acceleration voltage, and it is not necessary to make delicate adjustments for making a scanning microscope tester special, and an ordinary device (IC (For liquid crystal, etc.) and those for observing the cross section can be used as they are. As a result, after detecting a defective portion by using it as an ion beam (IB) tester, unnecessary wiring is cut, or an ion beam is irradiated while various metal compound gases are flown to selectively select a necessary portion. Metal wiring can be added and devices such as ICs can be repaired continuously in the same chamber.

(3) With these, the present and future I
It is possible to establish an operation test inside the device that is sufficiently applicable to the miniaturization of a device such as C.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a device tester of the present invention.

FIG. 2 is a diagram showing a device testing principle by ion beam scanning.

FIG. 3: I by an ion beam obtained by an experiment
Aluminum wiring for C (device) (fixed bias)
Is a statue of.

[Fig. 4] I by an ion beam obtained by an experiment.
Aluminum wiring for C (device) (AC bias)
Is a statue of.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ion column 2 vacuum chamber 3 secondary electron detector 4 AC power supply 5 DC power supply 6 ion pump 7 turbo pump 8, 11 amplifier 9 XY scanning signal generator 10 controller 12 video monitor 13 sample stand 14 sample (such as IC) Micro device) 15 Ion beam 30 Gas supply unit 31 Trimethyl metacyclopentadienyl platinum

Claims (2)

[Claims] 1. A device in which a voltage is generated in a conductor layer of a device, the conductor layer of the device is irradiated with an ion beam in this state, the amount of secondary electrons generated from the conductor layer is detected, and the secondary electron is detected. An ion beam characterized by forming an image according to the detection amount, and detecting the voltage state of the conductor layer from the bright / dark pattern of the image or the change of the secondary electron detection amount to inspect the operating state of the device. Device test method using the. 2. An ion beam generating means for generating an accelerated ion beam, a sample stage on which a sample to be irradiated with the ion beam is placed, a vacuum chamber surrounding the sample stage, and as a result of the ion beam irradiation. A device tester using an ion beam, comprising: a secondary electron detection means for detecting secondary electrons generated from the sample; and a bias supply means for supplying a DC or AC bias to the sample.