JP3321614B2 - Manufacturing method of electric field measurement probe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of irradiating a laser beam to an electro-optic material whose birefringence changes according to an electric field.
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric field measurement probe used for testing a circuit of an integrated circuit, which measures an electric field generated by the operation of the integrated circuit and tests the circuit, and a method of manufacturing the same.

[0002]

2. Description of the Related Art As a means for evaluating and testing an integrated circuit in a non-contact manner, there is known a method in which an electro-optical material is used for a sensor for measuring an electric field. That is, it utilizes the property of the electro-optic material that the birefringence is changed by the electric field. When the electro-optical material is irradiated with laser light, the phases of the vibration components in two orthogonal directions of the irradiated light, that is, the polarization state change according to the magnitude of the electric field.

Normally, this change in polarization can be converted into a change in the intensity of laser light by passing through a polarizing plate set to a certain appropriate axial direction. If a pulse wave is used as the laser light, a time-varying electric field, that is, a time change of an electric signal can be measured with a resolution corresponding to a pulse width. This is called electro-optic sampling. FIG. 4 is a configuration diagram showing the configuration of the above-described electro-optic sampling. In the figure, reference numeral 41 denotes an electric field measurement probe used for measurement, in which a chip 42 made of the above-described electro-optical material is fixed to a tip of a support 43 made of quartz or the like, and a reflection made of a dielectric multilayer film is attached to the tip. Membrane 44
Are formed.

The tip of the electric field measuring probe 41 is arranged close to a predetermined distance on the wiring 46 of the integrated circuit 45 to be measured, and the chip 42 is irradiated with the laser beam 48 via the support 43. Then, a leakage electric field 47 from the wiring 46 is measured based on a change in light reflected by the reflection film 44. This is the most versatile measurement method and is generally called the external probe method. As a material of the chip 42, a crystal such as GaAs, CdTe, LiTaO ₃ , or KTP is typically used.

Here, an outline of a method of manufacturing an electric field measuring probe used in the external probe method will be described. First, after the above-mentioned crystal is polished on both sides to an appropriate thickness of about 100 to 500 μm, it is fixed to the tip of a rod-shaped support. Next, a reflective film having a high reflectance by a dielectric multilayer film is formed on the crystal surface by a vapor deposition method or the like. And, in order to make this tip thin, the tip part is several tens to several tens.
It is polished into a 00 μm square pyramid.

FIG. 5 is a perspective view showing the structure of the electric field measuring probe, and the reflective film 4 is polished on both sides to a predetermined thickness.
4 is a chip 42 made of an electro-optical crystal formed on the surface
Are processed into a pyramid-shaped rectangle and arranged at the tip of the support 43. Here, in the figure, reference numeral 51 denotes a chipped portion generated at the end of the tip 42 when the tip is polished.
Chipping 52 is the peeling of the reflection film 44 generated at the end of the chip 42. In addition, what cut | disconnected the front-end | tip into the conical shape of the same magnitude | size is also used.

[0007]

Conventionally, the above-mentioned configuration has the following problems.
First, as a first problem, there is a low manufacturing throughput. Electro-optical materials (crystals) such as GaAs and LiTaO ₃ originally have strong anisotropy, and are susceptible to chipping and chipping when processed into small pieces by polishing or cutting.
It is difficult to finish a desired size with high accuracy.

In addition, when a dielectric multilayer film (reflection film) is formed on the crystal surface during processing, the crystal is often peeled off due to chipping or chipping of the crystal. Since the adhesion strength of the dielectric thin film to GaAs or LiTaO ₃ is extremely low, more advanced technology is required for polishing and cutting. For this reason, the current situation is that the electric field measurement probes are hand-made one by one. For example, when polishing is performed so that the tip is in the state shown in FIG.
Since one side is polished one by one, it takes a considerable amount of production time.

Next, as a second problem, there is a problem that the life is short for repeated use. This is mainly due to the peeling of the reflection film made of the dielectric multilayer film. In the external probe method, the tip of an electric field measurement probe may be applied to a circuit to be measured in order to increase measurement sensitivity. Also, in order to set a certain distance between the electric field measurement probe and the integrated circuit to be measured, the electric field measurement probe is often used after being lifted by a predetermined distance after being applied to the circuit.

However, as described above, the chip 42
(FIG. 5) is subjected to mechanical processing, so that stress is added. For this reason, the adhesive strength between the reflective film 44 made of a dielectric multilayer film and the chip 42 is weakened.
In this state, as described above, as the number of times of contact with the circuit surface to be measured increases, the dielectric formed from the periphery of the chip 42 which is most likely to be peeled off due to chipping / chipping 51 (FIG. 5). In many cases, the film peels and the peeling 52 increases. Even if only a few layers on the surface of the dielectric multilayer film are peeled off, the reflectivity is greatly reduced, causing a decrease in measurement sensitivity and making it unusable.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to increase the productivity of an electric field measuring probe and extend its life.

[0012]

Means for Solving the Problems] method of forming a field measuring up <br/> lobe of the invention, the step of polishing both surfaces of a substrate made of electro-optic material which changes its birefringence by the electric field, the substrate
Apply photoresist on the main surface of the
Polished by selectively irradiating light on the
Forming a resist pattern on the main surface
The substrate is etched using the
A process of forming a convex portion on the main surface of the plate and a resist pattern
Removing the substrate and etching the substrate surface and protrusions
A step of forming a reflective film made of a dielectric so as to cover, a step of separating a chip centering on the protrusion from the substrate, and a tip of a support through which light is transmitted so that the surface on which the protrusion is not formed contacts. And a step of fixing the chip. In addition, electric light whose birefringence changes depending on the electric field
Polishing both sides of a substrate made of
Forming a reflective film made of a dielectric on the main surface of a damaged substrate
And apply photoresist on the main surface of the substrate.
By selectively irradiating light on the photoresist and developing it,
Forming a resist pattern on the reflective film;
Etch the reflective film and substrate using the pattern as a mask
Forming convex portions on the main surface of the substrate by
Separating the chip from the substrate
Support tip that allows light to pass through so that untouched surfaces touch
Characterized by chromatic and fixing the chip.

[0013]

[Function] Without making the tip of the support body too thin,
The tip of a chip made of an electro-optical material used directly for measurement can be miniaturized.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. FIG. 1 is a perspective view showing a configuration of an electric field measuring probe according to the present invention. In the figure, reference numeral 1 denotes a protrusion 1a having a square shape with several sides of several tens of μm and a height of about 10 μm.
Are formed in the center of the electro-optic crystal chip, 2 is a reflection film made of a dielectric multilayer film formed on the surface of the electro-optic crystal chip 1, and 3 is an electro-optic crystal chip 1 made of quartz or the like attached to the tip. Support. In this embodiment, the bonding surface between the electro-optic crystal chip 1 and the support 3 constituting the electric field measuring probe is different from the conventional one.
mm or more.

Hereinafter, a method of manufacturing the electric field measuring probe of the first embodiment will be described. First, FIG.
As shown in FIG. 2, the main surface of the substrate 21 made of an electro-optic crystal whose both sides are polished to a thickness of about 100 to 500 μm is several tens μm on a side by photolithography.
A substantially square resist pattern 22 is formed. Next, the substrate 21 is etched by about 10 μm using the resist pattern 22 as a mask. This etching includes chemical etching, reactive ion etching, E
It may be performed by an etching technique such as sputter etching using CR plasma. The size of the substrate 21 is
Considering the ease of handling during the process, it is preferably at least several mm or more.

Next, as shown in FIG. 2B, the resist pattern 22 is removed by ashing, etc.
It is assumed that the convex portion 23 is formed above. Then, FIG.
As shown in (c), a dielectric multilayer film is formed thereon by a vapor deposition method or the like to form a reflective film 24 having a high reflectance.
Next, as shown in FIG. 2D, the substrate 21 is cut into a square shape with the projection 23 as a center by using a dicing saw or the like, and an electro-optic crystal chip 25 is formed.

Then, this electro-optic crystal chip 25 is
A support such as quartz (not shown, but similar to the support 3 in FIG. 1) whose front end is processed in advance is fixed to the front end with an optical adhesive, and is used for electric field measurement as shown in FIG. The probe is completed. The tip of this support is sized to fit the electro-optic crystal chip 25. The reference numerals 1, 1a, and 2 in FIG.
5, 23, and 24. As described above, according to this embodiment, the electro-optic crystal chip 25 is cut out. However, the portion functioning as the tip of the electric field measurement probe is the convex portion 23, and this portion has nothing. Since no stress is applied, the problem of cutting out does not affect the characteristics, and the adhesion strength of the reflection film 24 does not deteriorate.

Embodiment 2 FIG. By the way, in the above embodiment, as shown in FIGS. 2A to 2C, the reflection film 24 is formed after the projection 23 is formed, but the present invention is not limited to this. FIG. 3 is a sectional view showing a method for manufacturing an electric field measurement probe according to a second embodiment of the present invention. Less than,
A manufacturing method according to the second embodiment will be described. First, as shown in FIG.
On the main surface of a substrate 31 made of an electro-optic crystal having a thickness of about 500 μm, a dielectric multilayer film is formed by a vapor deposition method or the like to form a reflective film 32 having a high reflectance.

Next, a square resist pattern 33 having a side of about several tens of μm is formed thereon by photolithography (FIG. 3B), and using this as a mask, the substrate 31 is etched by about 10 μm. Protruding part 34
Is formed (FIG. 3C). This etching may be performed by an etching technique such as chemical etching, reactive ion etching, or sputter etching using ECR plasma. Next, after removing the resist pattern 33 by ashing or the like, as shown in FIG.
Using a dicing saw or the like, the substrate 31 is cut into a square shape with the projection 34 as the center, and an electro-optic crystal chip 35 is formed.

Then, similarly to the above embodiment, if this electro-optic crystal chip 35 is fixed to the tip of a support (not shown) made of quartz or the like, the tip of which has been processed in advance, with an optical adhesive, The electric field measurement probe is completed. Also in the case of this embodiment, when cutting out the electro-optic crystal chip 35, the portion functioning as the tip of the electric field measurement probe is the convex portion 34, and the problem at the time of cutting out does not affect.
Deterioration of the adhesion strength of the reflection film 32 does not occur. In addition,
In the second embodiment, in the electro-optic crystal chip 35, the reflection film 32 is formed only on the upper surface of the convex portion 34. Unlike the first embodiment, the reflective film 32 is not formed on the side surface of the convex portion 34. There is no problem as a measurement probe.

In the above embodiment, the electro-optic crystal chip is cut out with a dicing saw.
It is not limited to this. For example, in a state where a substrate made of an electro-optical crystal is fixed on a protective glass plate or the like,
What is necessary is just to show as follows. First, the reflective film and the convex portions are formed as described above, and thereafter, a resist pattern is formed by photolithography or the like so as to cover a region used as an electro-optic crystal chip.

Then, after etching the substrate up to the glass plate using this as a mask, the resist pattern is removed, and an electro-optic crystal chip is formed in the same manner as in the above embodiment. By doing so, it is possible to form the electro-optic crystal chip with almost no stress due to machining, without causing foreign matter adhesion failure due to cutting or the like. In the above embodiment, a non-reflective coating may be applied to the bonding surface of the electro-optic crystal chip with the support. Laser reflection at this interface due to the difference in the refractive index between the electro-optic crystal chip and the support can be reduced.

[0023]

As described above, according to the present invention, a chip made of an electro-optical material having a convex portion having a reflective film formed on the surface thereof is arranged at the tip of the support. Therefore, the tip for use in the measurement of the electric field measurement probe does not chip or chip.
Further, no stress is applied to the tip portion by machining, and the adhesion strength of the reflection film is not degraded.
This has the effect of extending the life.

According to the present invention, the projections are formed by photolithography.
This has the effect that the tip of the probe for electric field measurement can be accurately processed to a size on the order of μm.
Since the chip can be formed at the wafer level in the same manner as in the manufacturing process of a semiconductor device such as an LSI, the processing of the tip of the electric field measurement probe, which has been conventionally performed one by one, requires, for example, 1000 or more. You can do it all at once.

[Brief description of the drawings]

FIG. 1 is a perspective view showing the configuration of an electric field measurement probe according to the present invention.

FIG. 2 is a cross-sectional view for describing a method for manufacturing the electric field measurement probe of the first embodiment.

FIG. 3 is a cross-sectional view illustrating a method for manufacturing an electric field measurement probe according to a second embodiment of the present invention.

FIG. 4 is a configuration diagram showing a configuration of electro-optic sampling.

FIG. 5 is a perspective view showing a configuration of a conventional electric field measurement probe.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electro-optic crystal chip, 1a ... Convex part, 2 ... Reflection film, 3
... support.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G01R 31/28 G01R 1/06-1/073 G01R 19/00 H01L 21/64-21/66

Claims (2)

(57) [Claims] 1. An electric light whose birefringence changes according to an electric field.
Polishing both sides of a substrate made of a chemical material ; applying a photoresist to a main surface of the substrate;
By selectively irradiating light on the photoresist and developing it,
Form a resist pattern on the main surface of the polished substrate
And etching the substrate using the resist pattern as a mask.
Forming a protrusion on the main surface of the substrate by etching , removing the resist pattern, and inviting the cover to cover the surface of the substrate and the protrusion after etching.
Forming a reflective film made of an electric conductor, and separating a chip centering on the convex portion from the substrate.
The light is transmitted so that the surface on which the convex portions are not formed is in contact.
Having a the step of securing the tip to the support tip over to
Field method for manufacturing a measuring probe, characterized in that that. A step of polishing both surfaces of a substrate made of electro-optical material birefringence is changed by 2. A field, a pre-Symbol polished reflecting film made of dielectric on the main surface of the substrate
Forming a photoresist and applying a photoresist to the main surface of the substrate.
By selectively irradiating light on the photoresist and developing it,
Forming a resist pattern on the reflective film, the reflective film and the resist pattern as a mask;
Etching the substrate to form protrusions on the main surface of the substrate
And a step of separating the chip around the protrusion from the substrate; and fixing the chip to the tip of a support that transmits light so that a surface on which the protrusion is not formed contacts. A method for manufacturing an electric field measurement probe, comprising: