JPH0750129B2 - Potential measuring method and device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and apparatus for measuring a wiring potential of a semiconductor integrated circuit element using laser light.

[Conventional technology]

With the recent progress in miniaturization and large scale of semiconductor integrated circuit elements, in order to check the operation of the semiconductor integrated circuit elements in the development stage and analyze the failure of defective products, the wiring inside the semiconductor integrated circuit elements in operation is being checked. The importance of methods and devices for accurately and simply measuring potential states has been increasing.
As this method, a potential measuring method using an electron beam tester method has been well known. In this method, while operating a semiconductor integrated circuit element in a scanning electron microscope (SEM), the wiring is irradiated with an electron beam in synchronization with the operation, and an operation waveform and a voltage contrast image are obtained. For example, by Nakamura in 1985 of Nikkei Microdevice Magazine.
In the December issue of the year, commentary articles are described on pages 72 to 75.

[Problems to be Solved by the Invention]

The potential measuring method and apparatus using the electron beam tester method have the following problems. First, since it is essential to hold the sample in the vacuum chamber in order to irradiate the semiconductor integrated circuit device with the electron beam, the apparatus becomes large and expensive due to evacuation or the like. Further, since the semiconductor integrated circuit element is in a vacuum, the temperature of the element is likely to rise due to heat generation of the element, which makes it difficult to operate the semiconductor integrated circuit element in a room temperature atmosphere which is a normal operating condition of these semiconductor integrated circuit elements. In addition, it is necessary to minimize the irradiation dose in order to avoid charge-up due to the electron beam. Therefore, when measuring the potential of thin wiring under the insulating film, it is necessary to obtain a potential contrast image with a high S / N ratio. Has the drawback that it becomes difficult.

The object of the present invention is to enable measurement in the atmosphere and to make the device configuration simple and inexpensive, as compared to the conventional electron beam tester potential measuring method and device, and even with the potential of deep wiring under the insulating film. An object of the present invention is to provide an excellent potential measuring method and device capable of measuring with a high S / N ratio.

[Means for Solving the Problems]

The present invention relates to a potential measuring method for measuring a potential state of a wiring in a semiconductor integrated circuit device, wherein a transparent electrode is closely attached to a surface of the semiconductor integrated circuit device via a phosphor layer in which molecules are oriented by application of an electric field. Then, with the potential of the transparent electrode held at the reference potential of the semiconductor integrated circuit element, an electrical test pattern is applied to the semiconductor integrated circuit element, and pulsed laser light synchronized with the repetition frequency of the electrical test pattern, The phosphor is irradiated through the transparent electrode, and the intensity of the fluorescence emitted from the phosphor is measured.

A first potential measuring device of the present invention for carrying out this method includes: a test pattern generating unit for operating a semiconductor integrated circuit device; and a transparent presser having a transparent electrode in contact with the surface of the semiconductor integrated circuit device via a thin phosphor layer. An optical system for observing the surface of the semiconductor integrated circuit device through the plate and the holding plate, focusing the pulsed laser light on the phosphor immediately above a specific wiring location, and guiding the fluorescence emitted from the laser light irradiation part. The system is characterized by having a system, a photodetector for receiving the fluorescence guided by the optical system, and a waveform observation unit for monitoring the output intensity of the photodetector.

A second potential measuring device of the present invention comprises: a test pattern generating unit for operating a semiconductor integrated circuit element; a transparent holding plate having a transparent electrode in contact with the surface of the semiconductor integrated circuit element through a thin phosphor layer; Through the plate, observe the surface of the semiconductor integrated circuit device with a TV camera, and simultaneously irradiate the phosphors on multiple wiring points with pulsed laser light at the same time, and at the imaging position the fluorescent pattern generated from the laser light irradiation part. An optical system for receiving light by the arranged photodetector array, and an image processing unit for superimposing and displaying the output signal of the television camera for observing the surface and the output of the photodetector array are provided.

[Action]

The principle of the present invention utilizes the phenomenon that when fluorescent molecules that cause molecular orientation due to an electric field are irradiated with excitation light from the direction in which the electric field is applied, the intensity of fluorescence generated changes according to the degree of orientation of the fluorescent molecules due to the electric field. Then, the potential of the wiring of the semiconductor integrated circuit element is measured. For this purpose, a thin phosphor layer is provided between the surface of the semiconductor integrated circuit element and the holding plate having the transparent electrode, and the transparent electrode and the transparent electrode are arranged so that an electric potential is applied between the transparent electrode and the wiring of the semiconductor integrated circuit element. The reference voltage terminal of the semiconductor integrated circuit device is connected in advance, and the electric signal of the test pattern is applied to the semiconductor integrated circuit device.

In this state, laser light oscillating at the excitation wavelength of the phosphor is
The wiring part on the semiconductor integrated circuit is irradiated through the transparent electrode, and the intensity of the fluorescence generated from the phosphor layer is measured. Fourth
The figure shows the relationship between the intensity of the electric field applied to the phosphor and the intensity of the fluorescence. Generally, when an electric field is applied to a fluorescent molecule, the fluorescent molecule tends to align in the direction of the electric dipole moment of the fluorescent molecule. The response time of this orientation is as short as about 1 ns. When the fluorescent molecules are aligned in the direction of the electric field, the transition moment is often oriented in the alignment direction, so
For the laser light incident from the same direction, the electric field component of the laser light necessary to excite the fluorescent molecule disappears,
Excitation of the fluorescent molecule ceases to occur, resulting in a decrease in fluorescence intensity as the electric field increases.

In the present invention, since the potential of the wiring is measured by utilizing the difference in the orientation of the fluorescent molecules due to the electric field, there is an advantage that the measurement can be performed in the atmosphere without the need for vacuum and the potential can be measured in a non-contact manner. .

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a potential measuring device which is an embodiment of the present invention. This potential measuring device includes a holder 3 for holding a semiconductor integrated circuit element 8 and a semiconductor integrated circuit element 8
The test pattern generating unit 5 for operating the semiconductor integrated circuit device, the transparent holding plate 7 having the transparent electrode 1 in contact with the surface of the semiconductor integrated circuit device via the thin phosphor layer 2, and the surface of the semiconductor integrated circuit device are observed through the holding plate. At the same time, the pulsed laser light is focused on the phosphor 2 directly above the specific wiring location,
Further, an optical system for guiding the fluorescence generated from the laser light irradiation section to the photodetector 15, and an XY stage 4 for moving the irradiation position of the laser light on the surface of the semiconductor integrated circuit element.
And a waveform observation unit for monitoring the output intensity of the photodetector 15.

The optical system includes a laser light source 12, an illumination light source 13, a first half mirror 11, a second half mirror 10, a lens 6, a dichroic mirror 14, a filter 17, a television camera 9, and a television receiver 18.
It is composed by.

The waveform observation unit is composed of an oscilloscope 16.

The semiconductor integrated circuit element 8 is connected to the XY via the holder 3.
It is fixed to stage 4. A phosphor 2 is thinly applied to the surface of the semiconductor integrated circuit element 8, and a pressing plate 7 is provided on the semiconductor integrated circuit element 8 in close contact with the transparent electrode 1 on the lower side. Phosphor 2 is obtained by dissolving acridine red, a laser dye, in ethyl alcohol.
After the solution is dropped onto the semiconductor integrated circuit element 8, the holding plate 7 is pressed onto the semiconductor integrated circuit element 8 to have a thickness of about 5 μm. The transparent electrode 1 is connected to the ground terminal of the semiconductor integrated circuit element 8.

The semiconductor integrated circuit element 8 is driven by the test pattern generation unit 5. Above the holding plate 7, light from a laser light source 12 including an Ar laser for exciting the phosphor 2 on the semiconductor integrated circuit element 8 and a pulse modulator, and an illumination light source.
There is a first half mirror 11 that synthesizes the light from 13 and reflects the light synthesized by the first half mirror 11 to form a lens 6
A second half mirror that guides the fluorescent light from the phosphor 2 and the reflected light of the illumination light from the surface of the semiconductor integrated circuit element, a lens 6 that condenses the irradiation light and the laser light, and a second half mirror. A dichroic mirror 14 for separating reflected light and fluorescent light passing through 10 is provided.

The light from the illumination light source 13 illuminates the surface of the semiconductor integrated circuit element 8 as in a normal microscope. The reflected light from the illumination light is reflected by the dichroic mirror 14, and the filter 17
Then, the excitation light and the fluorescence are removed, the television camera 9 receives the light, and the television receiver 18 can observe the surface wiring shape.

Fluorescence from the phosphor 2 passes through a dichroic mirror 14 that transmits light having a fluorescence wavelength, is converted into an electric signal by a photodetector 15, and a time-varying waveform of signal intensity is observed by an oscilloscope 16. .

The illumination laser light can be supplied with a signal from the test pattern generation unit 5 to the laser light source 12 so that a short pulsed light synchronized with the clock cycle of the test pattern generation unit 5 can be generated. For this purpose, the test pattern generating unit 5 can supply a signal to the oscilloscope 16.

In the potential measuring device having the above configuration, the laser light is emitted from the phosphor 2 immediately above the specific wiring portion on the semiconductor integrated circuit element 8.
To selectively irradiate. The pulse width of the laser light is 2 ns, and the repetition frequency is the same as the clock frequency 20 MHz of the semiconductor integrated circuit element 8 used. The time response speed in this potential measurement method is determined by the orientation speed of the phosphor 2 and the pulse width of the irradiation laser pulse, and is estimated to be about 2 ns in this configuration.

FIGS. 2 (a) and 2 (b) show the configuration shown in FIG. 1 when the clock signal wiring of the semiconductor integrated circuit element 8 is irradiated with the above pulsed laser light and the phase of the clock is used as a parameter. The relationship between the peak intensity of the pulsed fluorescence waveform generated by each pulsed laser light irradiation and the potential of the wiring is shown. When the potential of the clock signal wiring is high, a strong electric field is applied between the transparent electrode 1 and the wiring, so that the phosphor 2 is oriented, and as a result, the fluorescence intensity becomes weak. On the contrary, when the potential of the clock signal wiring is low, the orientation of the phosphor 2 does not occur and the fluorescence intensity increases.

In the present embodiment, unlike the electron beam tester method in which reflected electrons from the wiring portion are directly captured, the orientation of the produced phosphor is measured by the electric field produced on the surface of the semiconductor integrated circuit element 8. Even if there is a thick insulating film of about 5 μm, which is about the same as the thickness of the body, the electric field strength generated between the wiring and the transparent electrode is weakened to at most about 1/2 of that without the insulating film. The potential of the wiring could be measured with a high S / N ratio even in the film. Further, no vacuum is required, and the image is not disturbed due to charge-up. Further, since the potential can be measured in a non-contact manner, there is an advantage that the semiconductor integrated circuit element 8 is less likely to be damaged.

FIG. 3 is a schematic configuration diagram of another embodiment of the present invention.
In this potential measuring device, a holder 3 for holding a semiconductor integrated circuit element 8, a test pattern generating unit 5 for operating the semiconductor integrated circuit element 8, and a transparent layer which is in contact with the surface of the semiconductor integrated circuit element via a thin phosphor layer 2 are provided. A transparent holding plate 7 having an electrode 1 and the surface of the semiconductor integrated circuit element are observed through the holding plate, and at the same time, the phosphors 2 on a plurality of wiring points are collectively irradiated with laser light and the laser light irradiation is performed. Microchannel plate (MC), which is a photodetector array in which the fluorescence pattern generated from
P) 19, an optical system for receiving light, an image processing unit 20 for superimposing and displaying the output signal of the television camera 9 for observing the surface and the output of the photodetector array, and a semiconductor integrated circuit element for indicating the irradiation position of laser light. XY for moving on the surface of
And stage 4.

The optical system includes a laser light source 12, an illumination light source 13, a first half mirror 11, a second half mirror 10, a lens 6, a dichroic mirror 14, a filter 17, and a television camera 9.

The difference from the embodiment of FIG. 1 is that the excitation light from the laser light source 12 is radiated over a plurality of wirings of the semiconductor integrated circuit element 8 and the emission pattern of the generated fluorescence. A microchannel plate (MCP) 19, which is a photodetector array, is arranged at the image forming position,
Another point is that the image processing unit 20 is provided, which can superimpose and display the image of the television camera 9 and the image from the MCP 19.

According to this configuration, there is an advantage that the potentials of a plurality of wirings can be simultaneously observed by irradiating the one-shot pulse laser light. Further, it is also possible to accumulate each image when the laser light is irradiated at a timing different in phase with respect to the clock signal in the image processing unit 20 and accumulate the temporal change in the potential of each wiring and then display it. There are advantages such as

In each of the embodiments of the present invention described above, the case where the dye dissolved in the solution is used as the phosphor is described, but other solid fluorescent materials that can be arranged by an electric field may be used. In that case, a thin phosphor can be directly formed on the semiconductor integrated circuit element, and then the transparent electrode can be vapor-deposited to form a structure, which brings about an advantage that the substrate can be easily handled.

〔The invention's effect〕

As described above, according to the present invention, it is possible to measure the potential of the wiring in a non-contact manner while operating the semiconductor integrated circuit element in the air, and there is no fear of charge-up, and the high S There is an advantage that the potential of the wiring can be measured by the / N ratio. Further, there is an advantage that the vacuum pumping system is unnecessary and the device configuration is simple, and the device can be made inexpensive.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention, FIG. 2 is a diagram showing a relationship between fluorescence intensity and wiring potential in the embodiment of FIG. 1, and FIG. 4 is a schematic configuration diagram of the embodiment of FIG. 4, and FIG. 4 is a diagram for explaining the measurement principle of the present invention. 1 ... Transparent electrode 2 ... Phosphor 3 ... Holder 4 ... XY stage 5 ... Test pattern generation unit 6 ... Lens 7 ... Holding plate 8 ... Semiconductor integrated circuit element 9 ... TV camera 10 ...... Second half mirror 11 …… First half mirror 12 …… Laser light source 13 …… Illumination light source 14 …… Dichroic mirror 15 …… Photodetector 16 …… Oscilloscope 17 …… Filter 18 …… TV receiver 19 …… MCP 20 …… Image processing unit

Claims (3)

[Claims] 1. A potential measuring method for measuring a potential state of a wiring in a semiconductor integrated circuit device, comprising: a transparent electrode is adhered to a surface of the semiconductor integrated circuit device through a phosphor layer in which molecules are oriented by application of an electric field. In this state, the electric potential of the transparent electrode is maintained at the reference potential of the semiconductor integrated circuit element, an electric test pattern is applied to the semiconductor integrated circuit element, and pulsed laser light synchronized with the repetition frequency of the electric test pattern is applied. A method for measuring potential, which comprises irradiating a phosphor through a transparent electrode and measuring the intensity of fluorescence emitted from the phosphor. 2. A test pattern generating unit for operating a semiconductor integrated circuit device, a transparent holding plate having a transparent electrode in contact with the surface of the semiconductor integrated circuit device via a thin phosphor layer, and a semiconductor integrated circuit through the holding plate. An optical system for observing the device surface, focusing the pulsed laser light on the phosphor immediately above a specific wiring location, and guiding the fluorescence emitted from the laser light irradiation part, and this optical system. An electric potential measuring device comprising: a photodetector that receives fluorescence; and a waveform observation unit that monitors the output intensity of the photodetector. 3. A test pattern generating unit for operating a semiconductor integrated circuit device, a transparent holding plate having a transparent electrode in contact with the surface of the semiconductor integrated circuit device via a thin phosphor layer, and a semiconductor integrated circuit through the holding plate. A photodetector array that observes the element surface with a TV camera, irradiates the phosphors on a plurality of wiring locations with pulsed laser light all at once, and arranges the fluorescence pattern generated from the laser light irradiation part at the imaging position. 2. An electric potential measuring device, comprising: an optical system for receiving light by an optical system; and an image processing unit for superimposing and displaying an output signal of the television camera for observing the surface and an output of the photodetector array.