JPH09236640A - Laser microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a laser microscope provided with a sample holder with no possibility of breakage even by a large sample. SOLUTION: In a holder 20, an opening 22 of relatively large diameter is made on the central part, and a transparent plate 23, of acrylic resin, etc., which transmits laser beam is engaged in the opening 22, and the rear surface of a sample 1 is brought into contact with the surfaces of holder 20 and transparent plate 22. The sample 1 is set on the holder 20, and a groove 24 is exhausted through an exhaust pipe and an exhaust hole 25, so that the sample 1 is vacuum- chucked to the holder 20. After this, a manipulator is operated for bringing an electrode into contact with an optional part of the sample 1, and the rear surface of the sample 1 is irradiated with the laser beam through the transparent plate 23, for observation of an OBIC(optical beam induced current). At this time, though an electrode 6 is pressed against the observation paint of the sample 1, since the rear surface of sample 1 is adheres to the surface of transparent plate 23 and holder 20, the sample 1 is prevented front accident of cracking.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an OBIC (Optical Bea
A laser microscope suitable for measuring am Induced Current).

[0002]

2. Description of the Related Art Observing an OBIC image using a laser microscope is practiced. Here, the OBIC will be briefly described. When irradiating a semiconductor with light, if the band gap energy (BG) is lower than the energy of incident light, a pair of electron and hole is generated. This carrier pair flows out by diffusion even if there is no electric field when the distance between the extraction electrodes is shorter than 2 to 3 times the Debye length (about 1 μm). In other cases, the carriers recombine and disappear. However, when there is an electric field (due to the open end potential of the PN junction or an external electric field), these carriers drift and flow out. This is O
It is BIC.

The OBIC image is obtained by, for example, scanning a certain area of a semiconductor device with a laser beam, detecting the OBIC in a portion irradiated with the laser beam, and outputting the OBIC signal to a cathode ray tube synchronized with the scanning of the laser beam by a brightness modulation signal. It can be obtained by supplying as. When observing the OBIC image, an electrode from the manipulator is brought into contact with the electrode on the semiconductor device in order to supply an electric field to the measurement location and detect the OBIC electrode.

[0004]

In recent years, semiconductor devices have become more three-dimensional and higher in density, and, for example, other wiring has come to be arranged on an element or the like directly provided on a silicon wafer. In such a device, when it is desired to observe an OBIC image of an element or the like directly provided on a silicon wafer, since other wirings are arranged above the laser beam, it is impossible to irradiate the portion to be observed. Therefore, a laser beam having a long wavelength of 1000 μm or more that passes through silicon is used, and this laser beam is emitted from the back surface of the device so as to pass through the silicon substrate and irradiate a target element or the like.

In the case of irradiating the above-mentioned laser beam from the back surface of the device, the electrodes required for OBIC observation are on the front surface of the device, and when a conventional manipulator is used, the front surface of the device is inevitably faced up. The optical system for irradiating the laser beam is arranged below the device.

By the way, a silicon substrate as a sample is placed on a sample holder, and the silicon substrate is fixed to the holder by means such as a vacuum chuck. When irradiating the laser beam from the back surface described above, it is necessary to introduce the laser beam from under the holder, and therefore the holder is provided with a relatively large opening for covering the observation region of the silicon substrate.

The size of the silicon substrate tends to increase year by year, and it is now necessary to prepare a sample holder corresponding to a size of 8 inches. As the size of the silicon substrate increases, the silicon substrate becomes more susceptible to cracking. If the electrodes are pressed from the surface of the silicon substrate with a manipulator, the load will cause the silicon substrate to crack. The silicon substrate on which the device is formed is expensive, and if the silicon substrate is damaged during observation, the loss is large. Further, the broken pieces of the silicon substrate fall on the lower optical system, and the subsequent cleaning of the optical system is troublesome.

The present invention has been made in view of the above points, and an object of the present invention is to realize a laser microscope equipped with a sample holder that does not cause a risk of breakage even for a large sample.

[0009]

A laser microscope according to the present invention is provided with a manipulator which is provided on the surface of a sample and operates electrodes for voltage application and OBIC detection to a specific portion of the sample, and a laser beam from the back surface of the sample. An optical system for irradiating and a holder for holding the sample are provided, and at least a portion of the holder through which the laser light passes is formed of a transparent plate.

In the present invention, the sample is placed on a transparent plate,
The back surface of the sample is irradiated with laser light through a transparent plate.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a basic configuration of a laser microscope for OBIC observation in which a laser beam is irradiated from the back surface of a sample and a manipulator is attached to the front surface of the sample. In the figure, 1 is a sample, and in this sample 1, many devices are arranged on a silicon substrate.

The back surface of the sample 1 is irradiated with the laser light from the He-Ne laser device 2 through the XY scanning mechanism 3 and the objective lens 4. That is, the laser light L
Is radiated on the back surface of the sample 1 after being finely focused by the objective lens 4, and the narrowed laser light is scanned by the XY scanning mechanism 3 in a predetermined region on the back surface of the sample 1.

A pair of manipulators 5 is provided on the surface of the sample 1.
Is arranged, and the tip of the electrode 6 of the manipulator 5 is in contact with the electrode of the device on the surface of the sample 1.
The other end of each of the electrodes 6 of the pair of manipulators 5 is
The power supply circuit 7 and the OBIC detection circuit 27 are respectively connected, and a voltage is applied from the power supply circuit 7 to the electrodes of the device of the sample 1 via the electrodes 6.

The OBIC generated as a result of applying a voltage to a predetermined portion of the device of the sample 1 is amplified by the amplifier 28 via the OBIC detection circuit 27 and supplied to the computer 8. The computer 8 supplies the OBIC signal to the cathode ray tube 9 together with the scanning signal supplied to the XY scanning mechanism 3. The operation of such a configuration will now be described.

With the above structure, the electrode 6 at the tip of the manipulator 5 is brought into contact with a specific electrode in the observation region of the OBIC image of the sample 1, and a voltage is applied between the specific electrodes. Further, the laser light from the laser device 2 is narrowed down by the objective lens 4 to irradiate the back surface of the sample 1. The laser light passes through the silicon substrate portion of the sample 1 and is applied to an element or the like provided on the surface of the silicon substrate.

OB is emitted from the element or the like irradiated with the laser beam L.
An IC is obtained, and this OBIC signal is an OBIC detection circuit 2
After being amplified in the amplifier 28 via 7, it is supplied to the computer 8. Here, the laser light L with which the sample 1 is irradiated is scanned by the XY scanning mechanism 3 controlled by the computer 8, and the predetermined region of the sample 1 is scanned with the laser light L.

As a result, the OBI obtained through the electrode 6
The C signals are sequentially obtained from the portion of the sample 1 irradiated with the laser light. By supplying this OBIC signal as a brightness modulation signal to the cathode ray tube 9 synchronized with the scanning signal by the XY scanning mechanism 3, the cathode ray tube 9 is provided with
An OBIC image of the scanning region of the laser light L is obtained.

When irradiating the laser beam for excitation from the back surface of the sample 1 described above, the manipulator 5 and the electrode 6 are arranged on the surface of the sample 1. Further, a large number of devices are arranged on the sample 1, and the sample 1 must be moved in the XY directions in order to observe an OBIC image of a predetermined region of a different device. When moving the sample 1, it is necessary to move only the sample without moving the positions of the manipulator 5 and the objective lens 4.

FIG. 2 shows an example of a mechanism for moving only the sample, and the same or similar components as in FIG. 1 are designated by the same reference numerals. In FIG. 2, the sample 1 is placed on the X-direction moving stage 10. The X-direction moving stage 10 is guided by the rails 12 provided on the Y-direction moving stage 11 and moved in the X direction (the left-right direction on the paper surface). Although there is a drive mechanism in the X direction, it is omitted from the drawing.

The Y-direction moving stage 11 is guided by rails 14 provided on the base 13 and moved in the Y-direction (perpendicular to the paper surface). Reference numeral 15 is a drive shaft for moving the Y-direction moving stage 11, and its movement in the axial direction is restricted. A male screw is cut on the outer periphery of the drive shaft 15 and is screwed with a female screw on the Y-direction moving stage 11 side. Then, the drive shaft 15 is rotated by a motor (not shown) to move the Y-direction moving stage 11 in the Y-direction (not shown, but the X-direction moving stage 10 is also moved by a similar mechanism. It has become). An objective lens 4 is arranged below the sample 1 on the base 13. The X-direction moving stage 1
The 0, Y-direction moving stage 11 is provided with an objective lens 4 and an opening for passing a laser beam.

A pair of manipulators 5 is arranged on the surface side of the sample 1, and an electrode 6 from the manipulator 5 is provided.
The position adjustment between the tip of the and the specific portion of the sample 1 is performed by the manipulator 5. Manipulator 5
Is fixed on the manipulator base 16, but the manipulator base 16 is placed on the X-direction moving stage 10. The manipulator stand 16 is provided with an opening for bringing the electrode 6 into contact with the sample 1.

At the end of the base 13, a plurality of lifting mechanisms 1 are provided.
7 are provided. The elevating mechanism 17 is composed of a cylinder and a piston, and the mounting table 18 on the upper part of the elevating mechanism 17 pushes the manipulator table 16 upward to lift the manipulator table 16 when the elevating mechanism 17 rises.
Separated from the directional movement stage 10. The operation of such a configuration will now be described.

The state of FIG. 2 shows the arrangement for observing an OBIC image for a specific device of the sample 1. When the observation of a specific device is completed in this state and the OBIC image of another device is observed, first, the elevating mechanism 17 is driven to move the mounting table 18 to the upper part and push the manipulator table 16 upward. As a result, the manipulator stand 1
6 is separated from the X-direction moving stage 10, and the electrode 6 at the tip of the manipulator 5 is separated from the sample 1 by a predetermined distance.

FIG. 3 shows a state in which the elevating mechanism 17 is driven and the manipulator base 16 is pushed upward. In this state, the X-direction moving stage 10 and the Y-direction moving stage 1
1 is moved and an arbitrary device is arranged at the observation position above the objective lens 3. After that, the lifting mechanism 17 is driven,
The mounting table 18 is lowered, the manipulator table 16 is mounted on the X-direction moving stage 10, and the tip of the electrode 6 of the manipulator 5 is brought into contact with a predetermined portion of the device to be observed. This state is shown in FIG. The manipulator 5 may be operated in order to surely bring the tip of the electrode 6 of the manipulator 5 into contact with a predetermined portion of the device.

FIG. 4 shows a manipulator base 16 and a holder 20 for holding the sample 1 such as a silicon substrate. The holder 20 is placed on the X-direction moving stage 10. FIG. 5 is a perspective view showing the holder 20 and the sample 1, and a handle 21 is attached to the holder 20. This handle 2
The holder 20 is attached to the stage 10 by grasping 1 or separated from the stage 10.

FIG. 6 is a cross-sectional view showing a state where the holder 20 and the sample 1 are joined. The holder 20 has an opening 22 having a relatively large diameter in the center thereof, and the opening 22 is made of an acrylic resin or the like. A transparent plate 23 that transmits laser light is fitted therein. The surface of the holder 20 and the surface of the transparent plate 23 have the same height, and the back surface of the sample 1 is in surface contact with the surfaces of the holder 20 and the transparent plate 23. A ring-shaped groove 24 for an air chuck is provided on the surface of the holder 20. The outer diameter of the groove 24 is smaller than the outer diameter of the sample 1, and the space inside the groove 24 communicates with an exhaust hole 25, which is connected to a vacuum pump (not shown) via an exhaust pipe 26. It is connected.

With the above-described structure, the sample 1 is set on the holder 20, and the holder 20 is placed on the X-direction moving stage 10.
Is placed. At this time, the sample 1 is vacuum-chucked to the holder 20 by exhausting the inside of the groove 24 through the exhaust pipe 26 and the exhaust hole 25. After that, the manipulator 5 is operated to bring the electrode 6 into contact with an arbitrary portion of the sample 1, and the laser light is transmitted through the transparent plate 23 to irradiate the back surface of the sample 1 with OB.
The IC image is observed. At this time, at the observation point of the sample 1,
The electrode 6 is pressed, but the back surface of the sample 1 is the transparent plate 23.
Since it is in close contact with the surface of the holder 20
Accidents such as cracks are prevented.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, acrylic resin is used as the transparent plate, but other materials other than acrylic resin can be used as long as they are transparent to laser light. Further, the vacuum chuck is not essential as a means for chucking the sample on the holder. Furthermore, although a part of the holder is made of a transparent material, the entire holder may be made of a transparent plate.

[0029]

As described above, according to the present invention, the sample is placed on the transparent plate, and the rear surface of the sample is irradiated with the laser beam through the transparent plate. Even if the electrodes or the like are pressed, the sample does not break, and there is no risk of damaging the expensive sample. Further, when the sample is broken, the troublesome work of cleaning the optical system arranged below the sample does not occur.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of a laser microscope for observing an OBIC image.

FIG. 2 is a diagram showing a sample portion of a laser microscope according to the present invention.

FIG. 3 is a diagram showing a state in which a manipulator is raised from the state shown in FIG.

FIG. 4 is a perspective view showing a manipulator base, a sample, a holder and the like.

FIG. 5 is a perspective view showing a holder and a sample.

FIG. 6 is a cross-sectional view showing a bonded state of a holder and a sample.

[Explanation of symbols]

 1 sample 2 laser 3 scanning mechanism 4 objective lens 5 manipulator 6 electrode 7 power supply circuit 8 computer 9 cathode ray tube 10 X-direction moving stage 11 Y-direction moving stage 12 rail 13 base 14 rail 15 drive axis 16 manipulator stand 17 lifting mechanism 18 mounting Table 20 Holder 21 Handle 22 Opening 23 Transparent plate 24 Groove 25 Exhaust hole 26 Exhaust pipe 27 OBIC detection circuit 28 Amplifier

Claims (2)

[Claims] 1. A manipulator provided on the surface of a sample, which operates an electrode for applying a voltage to a specific portion of the sample and detecting OBIC, an optical system for irradiating a laser beam from the back surface of the sample, and a sample holding device. A laser microscope having a holder and a transparent plate at least a portion of the holder that allows laser light to pass therethrough. 2. The laser microscope according to claim 1, wherein the holder is provided with an opening through which laser light passes, and a transparent plate is fitted into this opening.