JPH02198347A - Apparatus for analyzing defect in semiconductor - Google Patents

Abstract

PURPOSE:To improve defect analyzing efficiency and detecting accuracy by using a unitary system of associated devices for heating the surface of a specimen pattern, detecting infrared rays, lighting and sensing images with visible light, synthesizing the images, and displaying the visible/infrared-ray image. CONSTITUTION:A main optical axis is formed of a plurality of lenses and half mirrors over a specimen stage on which a specimen 1 is mounted. The half mirrors 4, 6, 7 and 8 have mechanisms which are associated with infrared-ray detection, laser, visible light and naked-eye view. A TV camera 17 is provided at the end of the main optical axis. The camera 17 is connected to an image synthesizing circuit 18 and a display device 19. All of them are controlled with a central processing unit 20. When a current is conducted through the specimen 1, detected infrared-ray level signal, two-dimensional temperature information and a visible light image are obtained. The results of the processing are displayed on the device 19. The defective part wherein a logic pattern is formed randomly can be pointed out.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a technology for analyzing failures in semiconductor circuits, and in particular to a technology that is effective in accurately detecting failures caused by disconnections, short circuits, etc. in semiconductor circuit patterns. .

[Conventional technology]

Conventionally, various testers have been used to detect defective locations such as disconnections and short circuits in semiconductor circuit patterns. Such testers include, for example, one that scans the surface on which a semiconductor circuit is formed with a laser beam and processes it using a laser beam diffraction pattern spatial filter method, and one that processes the photocurrent generated by beam irradiation into a visual image so that it can be displayed as an image. There are also methods that measure the power supply current by flowing power generated by a program power supply to a semiconductor circuit.

Among the technologies related to such defect detection, the technology using the filter method is disclosed in, for example, Japanese Patent Application Laid-open No. 11710/1983.
It is described in Publication No. 6.

[Problem to be solved by the invention]

However, with testers such as those mentioned above, there is no problem when the location of a defective bit can be directly detected using an address, such as in a memory, but when the circuit is randomly arranged, such as in a logic pattern, it is difficult to identify the defective location. is difficult.

Logic circuits are ASIC (integrated circuits for specific applications: Ap
plication Spe=ificIntegr
There is an increasing demand for products such as C1rcuts and the like, and there is a tendency for higher yields to be required.Therefore, there is a need to efficiently analyze and take countermeasures against defects.

In addition to pointing out defective locations, we also evaluate the temperature characteristics of circuit patterns in detail as patterns become finer.
Although it is necessary to improve the reliability of I, conventional testers do not take into account the measurement of temperature distribution in minute portions of circuit patterns that occur during electrical transient conditions.

An object of the present invention is to provide a technology that can solve the problems of the prior art and can effectively identify defective locations such as disconnections and short circuits in semiconductor logic patterns, or defective contact resistance locations in circuit patterns. It's about doing.

The above objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[Means to solve the problem]

A brief overview of typical inventions disclosed in this application is as follows.

That is, a heating means for heating a patterned surface of a sample, an infrared detection means for detecting infrared rays emitted by the heating means, an illumination means for irradiating the patterned surface with visible light, and a heating means for heating the patterned surface illuminated by the illumination means. an image capturing means for capturing an image; an image synthesizing means for superimposing a visible light image obtained by the image capturing means and an infrared image obtained by processing an output signal of the infrared detecting means; and displaying a synthesized image by the image synthesizing means. A display means for displaying the information is provided.

[For production]

According to the above-mentioned means, when the sample is energized or irradiated with laser light, the defective part is heated and infrared rays are emitted when the sample is energized, and the temperature of the defective part is increased when the laser light is irradiated, causing a difference in the heat conduction distribution. let By detecting this infrared ray in each minute area, measuring its two-dimensional distribution to create an infrared image, and displaying a visible light image superimposed on this infrared image, it is possible to point out defective areas.

〔Example〕

FIG. 1 is a block diagram showing the main configuration of an embodiment of a semiconductor failure analysis device according to the present invention.

The sample 1 is placed on a sample stage 2, and a lens 3, a half mirror 4, a lens 5, half mirrors 6, 7, 8, and a lens 9 are sequentially arranged in a straight line above the sample stage 2. , forming the main optical axis.

A lens lO is disposed on the reflection optical axis of the half mirror 40, and a chopper 1 is provided on the extension of the optical axis to open and close the optical path.
1 is provided. Further, a lens 12 is disposed on the incident optical axis perpendicular to the main optical axis of the half mirror 6, and a rotatable galvano mirror 13 is disposed on an extension of the optical axis. A laser generator 14 is installed on the galvano mirror 13 so as to be able to irradiate it with a laser beam.

A light source 15 using a lamp is installed on the half mirror 7 so as to be able to irradiate the sample 1 with visible light.

Furthermore, a lens is placed on the optical path reflected by the half mirror 8 so that the light reflected from the sample 1 by the light source 15 can be observed.
6 are arranged.

In addition, the reflected image when the sample 1 is illuminated by the light source 15 is
A television camera 17 is provided so as to be able to take images through an optical system consisting of lenses 3 to 9. The television camera 17 is connected to an image synthesis circuit 18 for superimposing an image obtained by visible light and an image obtained by infrared rays, and further displays the superimposed image output from the image synthesis circuit 18. In order to do this, a display device 19 using a CRT (cathode ray tube) or the like is connected to the image synthesis circuit 18.

Sample stage 2, galvanometer mirror 13, laser generator li! !
14, a central processing unit (
Central ProcessingUnit
:hereinafter referred to as CPU) is used.

The output port of the CPU 20 includes an operation input unit 21 equipped with keys for inputting various commands, a sample stage control unit 22 for controlling the movement of the sample stage 2, and a galvanometer mirror.
13, a laser power supply section 24 for driving the laser generator 14, and a light source 1.
A lamp control section 25 that controls turning on and off of the sample 5, and a signal power supply section 26 that is used to energize the sample 1 when the laser generator 14 is not used are connected. Further, a signal system circuit is connected to the human power port of the CPU 20. This signal system circuit includes an image memory 27 that stores a detection signal from an infrared detector 29 (described later) as temperature information, and an analog/digital (A/D) converter 2 that digitizes a detection signal from the infrared detection system.
8, each connected to an input port.

The infrared detection system includes an infrared detector 29 arranged after the chopper 11, an amplifier 30 that amplifies the signal from each cell of this infrared detector 29 to a predetermined level, and each amplifier 30.
a sample-and-hold (S/H) circuit 31 that samples and holds the output signals of the multiple sample-and-hold circuits 31, a multiplexer 32 that sequentially selects and outputs the output signals of the plurality of sample-and-hold circuits 31, and an analog signal output from the multiplexer 32. A/D converter 28 that converts digital signals
It consists of The infrared detector 29 detects infrared rays emitted from the pattern of the sample 1 pixel by pixel and causes the CPU 20 to store it in the image memory 27 as secondary temperature information, for example, an array type sensor is used.

Next, the operation of the embodiment with the above configuration will be explained with reference to FIGS. 2 and 3.

FIG. 2 is a simple circuit example taken to explain failure analysis according to the present invention, and FIG. 3 is a semiconductor circuit pattern corresponding to this circuit. As shown in Figure 2, this circuit consists of the base B of an NPN transistor and the input terminal X.
A resistor R1 is connected between the collector C and the terminal 2, and a resistor R2 is connected between the collector C and the terminal 2. Further, the emitter E of the transistor is connected to the terminal Y. In such a circuit, as shown in FIG. 2, there is a contact failure in the resistor R2 (more specifically, as shown in FIG. 4, the resistor R2 and the terminal Z are in contact with each other through a small contact area). The case will be explained below.

During inspection, the sample 1 is placed on the sample stage 2, and the CPU 2
0, the signal power supply unit 26 is driven and the sample 1 is energized. Due to this energization, Joule heat is generated in the resistor R2,
A temperature difference occurs between the surrounding parts. At this time, chopper 1
1 is a sample/hold circuit 31 .1 under the control of the CPU 20 . The optical path is opened and closed in synchronization with the operation timing of the multiplexer 32 and the A/D converter 28. The light that has passed through the chopper 11 reaches a large number of cells of the infrared detector 29, and a detection signal corresponding to the infrared level of the sample 1 is output. The detection signal is output for each cell corresponding to each minute detection area, and the output signal of each cell is amplified by each amplifier 30 and then sampled at a predetermined timing.
Hold, output selection, and A/D conversion are performed by sample and hold circuit 31, multiplexer 32, and A/D converter 28. The output signal of the A/D converter 28 is taken into the CPU 20, and the CPU 20 uses the coordinates of the sample stage 2 (which can be obtained from the sample stage control section 22) and the pixel information from the A/D converter 28 to calculate the two-dimensional A temperature information image is created and stored in the image memory 27.

Next, the CPU 20 drives the lamp control section 25 to turn on the light source 15. That light is half mirror 7,6
, lens 5, half mirror 4, and lens 3 in order to reach the sample 1. The reflected light travels straight through the optical system toward the lens 9, and is captured as a visible light image by the television camera 17 (at this time, the operator
(The more branched light can be observed through the lens 16). The image information obtained by the television camera 17 is superimposed on a two-dimensional temperature information image already stored in the image memory 27. This image is in the form of a temperature information image projected onto a visible light image, and is displayed on the display device 19. In this case, the portion of the resistor R2 in which the contact failure as shown in FIG. 4 occurs is shown as an infrared image on the image, so that the operator can easily confirm the defective location. In particular, by superimposing a normal visible light image on an infrared image, it becomes extremely easy to identify defective locations with the naked eye.

On the other hand, instead of generating infrared rays by energizing the sample l using the signal power supply unit 26, infrared rays can also be generated by irradiating laser light from the laser generator 14. That is, under the control of the CPU 20, the laser power supply unit 24 is driven, the laser generator 14 is operated (at this time, the signal power supply unit 26 is in an inoperable state), and a laser beam is generated.

The laser beam generated by the laser generator 14 is
It reaches the sample 1 via the galvanometer mirror 13, lens 12, half mirror 6, lens 5, half mirror 4, and lens 3. The laser beam irradiated onto the sample 1 heats the surface of the sample 1, but at this time, the temperature at the failed location increases. At this time, the galvanometer mirror 13 rotates, and the laser beam scans the sample 1 from one side to the other.

The infrared light from the sample 1 passes through the lens 3, half mirror 4, lens 10, and chopper 11, and reaches the infrared detector 2.
9, and a detection signal corresponding to the amount of infrared rays of the sample 1 is outputted from each output terminal of the infrared detector 29. This infrared light image is finally output from the A/D converter 28, and its output signal is taken into the CPU 20.

The CPU 20 creates a two-dimensional temperature information image from the coordinates of the sample stage 2 (which can be obtained from the sample stage control unit 22) and pixel information from the A/D converter 28, and stores this in the image memory 27. do.

Next, the CPU 20 drives the lamp control section 25 to turn on the light fi15. That light is half mirror 7,
6, the sample 1 is reached through the lens 5, the half mirror 4, and the lens 3 in this order. The reflected light travels straight through the optical system toward the lens 9, and is captured by the television camera 17 as a visible light image. The image information captured by the television camera 17 is superimposed on a two-dimensional temperature information image already stored in the image memory 27. This superimposed image is displayed on the display group [19], and the portion of the resistor R2 where the contact failure occurs is shown as an infrared image on the image. Therefore, the operator can easily confirm the defective location.

In particular, by using laser light, contact (adhesiveness) between patterns, cavities within the patterns, etc. can be effectively detected.

Although the invention made by the present invention has been specifically explained based on Examples above, it goes without saying that the present invention is not limited to the above-mentioned Examples and can be modified in various ways without departing from the gist thereof. .

〔Effect of the invention〕

Among the inventions disclosed in this application, the effects obtained by typical inventions are briefly described below.

That is, a heating means for heating a patterned surface of a sample, an infrared detection means for detecting infrared rays emitted by the heating means, an illumination means for irradiating the patterned surface with visible light, and a heating means for heating the patterned surface illuminated by the illumination means. an image capturing means for capturing an image; an image synthesizing means for superimposing a visible light image obtained by the image capturing means and an infrared image obtained by processing an output signal of the infrared detecting means; and displaying a synthesized image by the image synthesizing means. Since the display means is provided, it becomes possible to determine the state of electrical continuity, the state of contact resistance, etc. from the temperature distribution on the sample.

As a result, it becomes possible to point out defective locations even in devices in which logic patterns are randomly formed, such as LSI logic, and detection accuracy can be improved. Furthermore, by improving the efficiency of failure analysis, countermeasures against failure detection can be taken accurately, and reliability can also be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the main configuration of an embodiment of a semiconductor failure analysis device according to the present invention, FIG. 2 is a circuit diagram of a simple circuit example used to explain failure analysis according to the present invention, and FIG. is a semiconductor circuit pattern diagram corresponding to the circuit of FIG. 2, and FIG. 4 is an enlarged pattern diagram showing details of defective locations in the pattern of FIG. 3. DESCRIPTION OF SYMBOLS 1... Sample, 2... Sample stage, 14... Laser generator, 15... Light source, 17... Television camera, 18
...Image synthesis circuit, 19...Display device, 2
0...CPU, 26...Signal type S section, 27...Image memory, 29...Infrared detector, 31...Sample/hold circuit, 32...Multiplexer.

Claims (1)

[Scope of Claims] 1. A heating means for heating a patterned surface of a sample, an infrared detection means for detecting infrared rays emitted by the heating means, an illumination means for irradiating the patterned surface with visible light, and an illumination device for illuminating the patterned surface by the illumination means. an image capturing means for capturing an image of the patterned surface; an image synthesizing means for superimposing a visible light image obtained by the image capturing means and an infrared image obtained by processing an output signal of the infrared detecting means; 1. A semiconductor failure analysis apparatus, comprising display means for displaying a composite image produced by the means. 2. The semiconductor failure analysis apparatus according to claim 1, wherein the heating means includes a laser beam generating means for irradiating a patterned surface of the sample with a laser beam. 3. The semiconductor failure analysis apparatus according to claim 1, wherein the heating means includes power supply means for applying electricity to the sample.