JPH06118107A - Production of electric field sensor - Google Patents

Abstract

PURPOSE:To make the surface of an electric field sensor for testing an integrated circuit by electro-optical sampling uniform and clean and to detect the vertical electric field in the integrated circuit. CONSTITUTION:A polymer film 1 is formed on a silicon substrate 3 whose surface is treated with a silane coupling agent and a support material 2 is formed on the polymer film 1. High voltage is applied across the silicon substrate 3 and the support material 2 while the support material 2 is heated to temp. equal to or higher than the transition point of the polymer film 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electric field sensor for testing a circuit of an integrated circuit.

[0002]

2. Description of the Related Art As a means for contactless evaluation and testing of an integrated circuit (IC), a method using an electro-optical material as a sensor for measuring an electric field is known. That is, it utilizes the property of a material that the birefringence changes depending on the electric field. When this material is irradiated with laser light, the phase difference between the vibration components in two orthogonal directions of the irradiated light depends on the magnitude of the electric field. That is, the polarization state changes. Usually, this polarization change can be converted into a laser light intensity change by passing through a polarizing plate set in a certain suitable axial direction. If a pulse wave is used for the laser light, a time-varying electric field, that is, a time-varying electric signal flowing through the electrodes of the IC can be measured with a resolution equivalent to the pulse width. This is called electro-optic sampling. There is. Above all, as shown in FIG. 4, a thin plate-shaped electro-optical material 5 is attached to an integrated circuit chip 6 to be measured, and a leakage electric field from the metal wiring 7 of the circuit is coupled to the material, so that a change in the strength of this electric field is caused. The most versatile and simple method is to detect the polarization change of the reflected light of the corresponding laser light 8.

In recent years, as such an electro-optical material, an organic nonlinear optical polymer (hereinafter referred to as a poled polymer) has been attracting attention in terms of sensitivity, disturbance, responsiveness, etc., and active research has been advanced. Conventionally, as an electric field sensor using this poled polymer, one having a structure shown in FIG. 5 or 6 has been representative (for example, Electronics Lett.
ers, Vol.27, No.11pp932-934,1991, Applied Physics Let
ters, Vol.59, No.10, pp.1159-1161 1991). In FIG. 5, a poled polymer is applied to a flexible polyimide film 9 as a supporting material to form a polymer film 1, and then the electrode 4 is sandwiched under an environmental temperature higher than the glass transition temperature of the polymer film 1. It is created by polarization treatment by applying a high electric field. On the other hand, in FIG. 6, after the poled polymer is applied on the glass substrate 10 to form the polymer film 1, the metal thin film electrode 4a is formed thereon. Then, at the glass transition temperature or higher, an electric field is applied between the thin film electrodes 4a to similarly perform polarization treatment, and thereafter the metal electrode is removed by etching or the like. The sensor above
Both are used by sticking the polymer film 1 side toward the integrated circuit.

[0004]

The above-mentioned problems have been encountered in the prior art because of the above-mentioned problems.
First, the surface of the sensor that is attached to the surface of the integrated circuit is susceptible to damage such as dirt and irregularities during the manufacturing process. In the method of FIG. 5, when the electrode 4 is sandwiched and an electric field is applied, the surface irregularities of the electrode 4 may be transferred to the surface of the polymer film 1. Normally, when an electric field is applied, the temperature of the polymer film is raised above the glass transition point, so that the polymer film is in a fairly soft state and is easily affected by the surface of the pressure-bonded electrode.

Further, in the method of FIG. 6, in order to apply to a more general integrated circuit, it is necessary to remove the electrode by wet or dry etching after the polarization treatment, but the metal thin film cannot be completely removed, There is a high possibility that the polymer surface will be damaged and produce irregularities.
If there is such unevenness, when irradiated with laser light,
Light is diffused, the amount of reflected light is reduced, and the sensitivity is reduced. Further, since the amount of reflected light changes depending on the measurement point, it becomes difficult to compare data obtained at different measurement points. Furthermore, if the distance between the measured integrated circuit and the polymer film changes spatially due to this unevenness, the amount of the signal electric field that couples to the polymer film changes, so comparison of the data obtained at different measurement points as above. Becomes difficult.

As a second problem, in the method of applying a high voltage as shown in FIG. 6, polarization treatment is performed perpendicularly to the polymer film surface in the vicinity of the electrodes, and between the electrodes is performed in parallel with the polymer film. The local non-uniformity of the polarization direction may occur. That is, the polymer film near the electrodes detects a vertical electric field perpendicular to the integrated circuit substrate by the electric field in the integrated circuit, while the area between the electrodes detects a lateral electric field. In the measurement of a general integrated circuit, it is indispensable to detect only the electric field in the vertical direction in order to obtain the spatial resolution, and in the manufacturing by the method of FIG. 6, only a part of the manufactured sensor region can be used.

The present invention has been made in order to solve the above problems, and in an electric field sensor for circuit testing of an integrated circuit by electro-optical sampling, its surface is clean without unevenness, and the integrated circuit is clean. The purpose is to be able to detect the longitudinal electric field inside.

[0008]

According to the present invention, there is provided a process of forming a functional film containing an organic polymer material having a large second-order nonlinear performance on a substrate having conductivity and a flat surface, and a step of forming the functional film on the functional film. The step of forming a supporting material for holding the functional film as a film, and heating the substrate on which the functional film and the supporting material are formed to a temperature not lower than the glass transition point of the functional film, and applying a high direct current between the supporting material and the substrate. A step of applying a voltage to polarize the functional film in the vertical direction. Further, it is characterized in that the functional film is formed on a substrate whose surface is treated so that the functional film is easily peeled off.

[0009]

The electric field sensor can be manufactured while the surface in contact with the object to be measured is clean and flat.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 to 3 are explanatory views showing an embodiment of the present invention. In the figure, 1 is a polymer film made of the material shown in the following chemical formula 2 synthesized by dispersing and binding the azo compound which is the organic nonlinear optical material shown in the following chemical formula 1 to an acrylic ester resin which is a polymer material, Reference numeral 2 is a support material made of acrylic resin, 3 is a silicon substrate surface-treated with a silane coupling material, and 4 is an electrode plate made of a metal plate to which a high voltage is applied.

[0011]

[Chemical 1]

[0012]

[Chemical 2]

The above-mentioned organic nonlinear optical material is not limited to the azo compound shown in Chemical formula 1, but any material having a large second-order optical nonlinear performance such as methylnitroamine (MNA) may be used.

Next, a method of manufacturing the electric field sensor will be described. First, as shown in FIG. 1, a polymer film 1 having a thickness of about 20 μm and a support material 2 having a thickness of 20 to 3 are formed on a silicon substrate 3.
It is formed by uniformly applying a spin coat method to a thickness of about 0 μm. Next, as shown in FIG. 2, the silicon substrate 3 on which the film of the polymer film 1 and the support material 2 is formed is sandwiched by the electrode plates 4, and these are heated to a temperature not lower than the glass transition point of the polymer film 120. Heat to 150 ° C and apply 2 to electrode 4.
The polymer film 1 is polarized by applying a DC voltage of 000V. This DC voltage corresponds to 50 to 100 V per 1 μm of the thickness of the polymer film 1. The polarization process is terminated by freezing the polarization state by applying a DC voltage and then stopping the heating and leaving it at room temperature while keeping the voltage applied. Finally, the polymer film 1 and the base material 2 that have been polarized are peeled from the silicon substrate 3 to form an electric field sensor.

The electric field sensor is cut into an appropriate size, attached to an integrated circuit chip to be measured, and irradiated with laser light to evaluate and test the integrated circuit chip. The laser light is spot-irradiated on the wiring electrode to be measured of the integrated circuit chip. The birefringence of the vertically polarized polymer film is sensitive to changes in the vertical electric field due to the electrodes of the integrated circuit chip. By detecting the polarization change of the reflected light of the laser light, it is possible to evaluate and test the electric signal in the integrated circuit chip. As a method of sticking this electric field sensor to the integrated circuit chip, for example, an ultraviolet curable resin is applied to the surface of the polymer film, and this is placed on the integrated circuit chip, and positioning is performed while holding the top with glass or the like. Then, ultraviolet rays are radiated through the glass to cure and fix the ultraviolet curable resin.

Although the DC voltage applied for the polarization treatment is applied by the electrode plate 4 in the above embodiment, the present invention is not limited to this, and instead of the silicon substrate 3, a thin glass film is formed on a smooth glass substrate. A polymer film and a support material may be formed on the vapor-deposited material, and a metal film may be formed on the support material by vapor deposition to use these as electrodes. As a result, the electrode to which a voltage is applied and the support material are in closer contact with each other, and the electric field can be more uniformly and effectively applied to the polymer film, and the sensitivity can be expected to be improved and the sensitivity can be made uniform. . The electrode deposited on the support material may be removed by etching after the polarization treatment. Compared to the case where an electrode is formed on the surface of a polymer film which is a non-linear optical material as in the conventional example shown in FIG. 6, the remaining electrode or the damage to the surface of the support material due to etching is not a major problem in measurement. I won't.

After the polarization treatment, a solid transparent substrate such as plastic or glass may be attached to the support material with an adhesive and the electric field sensor may be peeled off from the substrate. Since the soft electric field sensor is supported by the hard transparent substrate, the electric field sensor can be easily handled, and the work of attaching the electric field sensor to the integrated circuit chip that is the object to be measured becomes easy.
In addition, by supporting the electric field sensor with such a solid transparent substrate, when fixing the electric field sensor to the integrated circuit chip, it is possible to integrate the electric field sensor through an optical oil (such as immersion oil) without using an adhesive. Just put it on the circuit chip,
It is possible to provide a uniform minute gap between the polymer film surface of the electric field sensor and the circuit surface of the integrated circuit chip.

[0018]

As described above, according to the present invention, the electric field sensor for integrated circuit testing by electro-optical sampling, which has a smooth and clean surface and can detect the electric field in the vertical direction in all regions. Is obtained. Therefore, the scattering of light on the film surface of the electric field sensor is eliminated, the adhesiveness with the circuit to be measured is improved, and the electric field of the electrode of the circuit is efficiently coupled to this electric field sensor, so that the sensitivity is improved. There is. Further, since the spatially uniform sensitivity is obtained, it is possible to compare the measurement results at different measurement points.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a cross section of a product in the process of a manufacturing method according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the cross section of the product in the process of the manufacturing method which is one embodiment of the present invention, following FIG.

FIG. 3 is a cross-sectional view showing the cross section of the product which is in the process of being manufactured, which is one embodiment of the present invention, following FIG. 2;

FIG. 4 is a cross-sectional view showing a test state of an electric signal on a metal wiring of an integrated circuit by an electric field sensor.

FIG. 5 is a cross-sectional view showing a state in the middle of manufacturing a conventional electric field sensor.

FIG. 6 is a cross-sectional view showing a state in the process of manufacturing a conventional electric field sensor.

[Explanation of symbols]

 1 polymer film 2 support 3 silicon substrate 4 electrode

Claims (2)

[Claims] 1. A step of forming a functional film containing an organic polymer material having a large second-order nonlinear performance on a substrate having conductivity and a flat surface, and holding the functional film as a film on the functional film. A step of forming a transparent support material for, the substrate on which the functional film and the support material is formed is heated to a temperature not lower than the glass transition point of the functional film, and a high DC voltage is applied between the support material and the substrate. And a step of vertically polarizing the functional film. 2. The method for manufacturing an electric field sensor according to claim 1, further comprising the step of forming the functional film on the substrate whose surface is subjected to a treatment for facilitating peeling of the functional film. Manufacturing method of electric field sensor.