JPH0812229B2 - Potential measuring method and device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention utilizes laser light to
The present invention relates to a method and a device for measuring a wiring potential of a semiconductor circuit.

[0002]

2. Description of the Related Art In semiconductor circuits such as circuit boards using semiconductors in recent years, the need for circuit operation check and failure analysis has become more and more intense as the degree of integration increases. In such application of circuit analysis, it is strongly required as a measurement method to be able to measure the wiring potential in the circuit in a non-contact manner in order to minimize the influence on the circuit element and to perform the measurement easily. ing.

Among them, as a potential measuring method utilizing a laser beam, a method utilizing a change in the intensity of a fluorescent substance by applying an electric field has been reported in Japanese Patent Laid-Open No. 2-298871. According to this method, a phosphor is applied to the surface of the semiconductor circuit element, and in the state where the transparent electrode is formed on the phosphor, while irradiating the phosphor with laser light, an electric signal is applied to the wiring,
By observing the change in fluorescence intensity from the phosphor, it is possible to measure the wiring potential, and, compared with the potential measurement method using an electron beam, since a vacuum device is unnecessary, the device configuration can be simple and inexpensive, and It has been reported that the wiring potential can be measured with a high S / N ratio.

[0004]

However, in the method utilizing fluorescence, the time resolution of measurement is limited by the lifetime of fluorescence, so that the time resolution in real time is at most 2.
There is a drawback that the limit is about ns. Further, since the excitation wavelength of the phosphor used is limited to the substantially visible red region, it is difficult to use an inexpensive semiconductor laser, and the entire device becomes large and expensive.

The object of the present invention is to improve the response speed and the selection range of the excitation light source, which are the drawbacks of the conventional method for measuring the wiring potential based on the change of the fluorescence intensity, and are high. An object of the present invention is to provide an excellent potential measuring method and device capable of measuring a wiring potential with an S / N ratio.

[0006]

According to the present invention, there is provided a potential measuring method for measuring a potential state of wiring of a semiconductor circuit, in which a plate-shaped sensor including a voltage sensitive medium is arranged in proximity to the surface of the semiconductor circuit. Then, irradiate the sensor with laser light,
It is characterized in that the potential of the wiring on the substrate is measured by separating the second harmonic generated from the sensor and measuring the intensity thereof.

The present invention also relates to a potential measuring device for measuring the potential state of wiring of a semiconductor circuit, wherein a plate-shaped sensor which is arranged close to the surface of the semiconductor circuit and which contains a voltage-sensitive medium, and a laser for this sensor. It is characterized by comprising an irradiation optical system for irradiating light and detecting the generated second harmonic light, and a means for measuring the intensity of the detected second harmonic light.

[0008]

The principle of the present invention is that, in the absence of an electric field, due to the symmetry of the molecular structure, it is not SHG (second harmonic) active, and the dipole moment of the molecule is biased by the application of an electric field, causing SH
This is to measure the wiring potential by using a potential-sensitive medium having G activity as a sensor and measuring the SHG light generated by laser light irradiation separately from the incident laser light.

According to the present invention, the time response of the electric field measurement is
Since the SHG response has a high-speed response of ps or less, it is limited by the time in which the bias of the dipole moment of the voltage-sensitive medium is generated. Normally, it is expected that the bias of the dipole moment is sufficiently ps. It Further, the detection sensitivity is that SHG generation does not occur without application of an electric field, so that the received SHG light does not include a bias-like optical component, and fluorescence does not exist when an electric field is applied and when an electric field is applied as in the fluorescence method. It is not necessary to extract the signal from the difference in intensity. As a result, S
There is an advantage that the / N ratio can be made extremely high.

Further, the only limiting factor of the wavelength of the laser light source used is that there is no absorption of the voltage-sensitive medium at the fundamental wavelength and the wavelength of the SHG light. When a voltage-sensitive dye used for electrical pulse response measurement is used, its absorption wavelength is in the red region, so a near-infrared semiconductor laser capable of high-speed modulation is used as the excitation source, and SHG in the blue region is used as a microchannel plate. A configuration for observing can be applied, and in this case, a highly sensitive and inexpensive light source / detector combination can be realized, and a highly practical device can be configured.

[0011]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic view of an example of a potential measuring device for carrying out the method of the present invention. This potential measuring device includes a holder 3 for holding a semiconductor circuit 2, a test pattern generating unit 5 for generating a test signal for operating the semiconductor circuit 2, and an oscilloscope 1 for observing the waveform of SHG light.
2, the sensor 1 placed on the semiconductor circuit, and the sensor 1
An irradiation optical system that irradiates a laser beam for observing the potential of the sensor 1 and at the same time observes the position of the sensor 1 and detects the generated SHG light, and moves the irradiation position of the laser beam on the surface of the semiconductor circuit 2. XY stage 4 for

The irradiation optical system includes a laser light source 14 for supplying semiconductor laser light, an illumination light source 13, and a first half mirror 15 for combining laser light with light from the illumination light source 13.
The semiconductor circuit 2 has a second half mirror 7 that reflects the combined light and an objective lens 6 that is arranged in the reflected light optical path. The second half mirror 7 is used to separate the SHG light generated by the sensor 1 from the excitation light (laser light). Laser light source 14
Is a semiconductor laser having a wavelength of 0.8 μm. The irradiation optical system further includes a dichroic mirror 8, a photodetector 11, a filter 9, a camera 10, and a TV 25. Sensor 1
The SHG light generated in 1 passes through the lens 6 and the second half mirror 7, and also passes through the dichroic mirror 8 that selectively passes the SHG light, and is a photodetector composed of a photomultiplier tube with a response time of 0.4 ns. It is incident on 11. The output of the photodetector 11 is connected to the oscilloscope 12, and the oscilloscope 12 receives the timing signal from the test pattern generation unit 5.
It is configured to take the trigger of. The light reflected by the dichroic mirror 8 is converted into an electric signal by the camera 10 after the incident laser light is removed by the filter 9, and the wiring shape of the semiconductor circuit can be observed by the TV 25.

FIG. 2 is a schematic diagram showing the structure of the sensor 1.
The sensor 1 includes a transparent conductive film (ITO) 18, a film layer 17 having a thickness of 10 μm in which a styryl dye, which is a voltage-sensitive dye, is dispersed in a polymer, and 90% or more of generated SHG light are reflected under the glass plate 19 in this order. The high-reflection film 20 that returns the incident light to the optical path is laminated. Below the four ends of the sensor 1, a height of 10 is provided in order to keep a constant distance from the semiconductor circuit.
A μm spacer 16 is provided. The size of the sensor 1 can be covered over the entire wiring potential measurement point.
× 3 cm. The lead wire 1 from the ITO film 18
Reference numeral 8'is connected to the ground terminal of the semiconductor circuit 2 and is configured to effectively apply an electric field between the wiring of the semiconductor circuit 2 and the ITO film. Examples of the voltage-sensitive dye include cyanine dyes, merocyanine dyes, rhodamine dyes, and oxonol dyes.

An actual operation of the electric potential measuring device having the above-mentioned structure will be described. The XY stage is moved so that the irradiation position of the laser light from the laser light source 14 becomes a desired potential measurement position on the semiconductor circuit 2. Next, while irradiating laser light, a test signal is supplied from the test pattern generation unit 5 to the semiconductor circuit 2, the generated SHG light is detected by the photodetector 11, and the time-varying waveform of the SHG light is observed by the oscilloscope 12. To do. Rising 1ns, pulse width 2n
s, a clock pulse with a repetitive frequency of 160 MHz was observed, and the same rise time as the clock pulse 1
An SHG output waveform following an electric pulse of ns was obtained, and a high-speed time response could be confirmed. Also, in real-time waveform observation, the noise level is as low as 5 mV, which is sufficiently high with respect to the normal semiconductor circuit operating amplitude of 5 V.
The / N ratio was obtained.

In the above-mentioned embodiments, the example of observing the time waveform of one point of the wiring on the semiconductor circuit has been described, but the light emitted from the laser light source 14 is collectively radiated over a plurality of wirings, It goes without saying that it is possible to form an image of the generated SHG light on a surface type photodetector such as a microchannel plate and measure the potential distribution image on the wiring at a specific time timing.

FIG. 3 is a diagram showing the structure of a sensor unit in another embodiment in which the method of holding the sensor unit according to the present invention is different. In FIG. 3, the sensor 1 is held by the vertical movement mechanism 21 that projects from the support base 22, and can be kept in a state of being floated close to the semiconductor circuit 2. The height can be adjusted by detecting the contact between the semiconductor circuit 2 and the sensor 1 by the piezoelectric sensor 23 provided below the vertical movement mechanism 21 and attaching the vertical movement mechanism 21 to the position 10 μm above the contact height. This is done by moving the motor 24. According to this method, since there is no contact between the semiconductor circuit and the sensor during measurement, there is an advantage that the position of the sensor can be moved to an arbitrary position on the surface of the semiconductor circuit, and a wide measurement site can be taken.

It is needless to say that the present invention can be applied to a potential sensitive medium used in the sensor section, such as a crystalline organic molecule in which the symmetry of the electric dipole moment peculiar to the molecule is easily broken by the electric field.

[0019]

According to the present invention, the actual response time is as short as ns or less, and the change in signal strength due to the presence or absence of an electric field is large. Therefore, a minute potential change can be detected with high sensitivity. Since there are few restrictions on the combination of a potential sensitive medium and a potential sensitive medium, there is an advantage that an inexpensive light source or detector can be used, and as a result, a potential measuring method and device capable of providing a highly practical and inexpensive device can be obtained. To be

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a configuration of a sensor unit according to the present invention.

FIG. 3 is a schematic diagram showing a second configuration of the sensor unit according to the present invention.

[Explanation of symbols]

 1 Sensor 2 Semiconductor Circuit 3 Holder 4 XY Stage 5 Test Pattern Generation Unit 6 Lens 7 Second Half Mirror 8 Dichroic Mirror 9 Filter 10 Camera 11 Photodetector 12 Oscilloscope 13 Illumination Light Source 14 Laser Light Source 15 First Half Mirror 16 Spacer 17 Film Layer 18 ITO 19 Glass Plate 20 High Reflection Film 21 Vertical Movement Mechanism 22 Support Stand 23 Piezoelectric Sensor 24 Motor 25 TV

Claims (4)

[Claims] 1. A potential measuring method for measuring a potential state of wiring of a semiconductor circuit, wherein a laser beam is applied to the sensor in a state where a plate-shaped sensor containing a voltage sensitive medium is arranged in proximity to the surface of the semiconductor circuit. Then, the potential of the wiring on the substrate is measured by separating the second harmonic generated from the sensor and measuring its intensity. 2. The potential measuring method according to claim 1, wherein a film in which a voltage-sensitive dye is dispersed in a polymer is used as the voltage-sensitive medium. 3. A potential measuring device for measuring a potential state of a wiring of a semiconductor circuit, comprising: a plate-shaped sensor which is arranged close to the surface of the semiconductor circuit and which contains a voltage-sensitive medium; An electric potential measuring device comprising: an irradiation optical system for detecting the generated second harmonic light; and means for measuring the intensity of the detected second harmonic light. 4. The sensor comprises a glass substrate, a transparent conductive film formed on the glass substrate, a film layer formed on the transparent conductive film and serving as the voltage-sensitive medium, and a film layer formed on the film layer. 4. The potential measuring device according to claim 3, further comprising: a highly reflective film that returns the formed and generated second harmonic to the incident light optical path of the laser light.