JPH09298226A - Test device for semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a test device which is capable of checking even the base of a deep hole such as a contact hole provided to a semiconductor device of IG bit class by a method wherein the test device is capable of controlling the orientation of a semiconductor substrate toward an ion beam by the displacement of a piezoelectric device. SOLUTION: A specimen holder holds a specimen 1, and an ion source emits an ion beam which serves as a probe. The support leg 21 of the specimen holder equipped with a precision orientation control mechanism is formed of a piezoelectric device or the like and composed of three legs. The three support legs are made to extend from the apexes of a regular triangle on a lower plate 23 to support an upper plate 22. Pawls 24 which press down the specimen 1 are provided to the upper plate 22. Therefore, when a voltage is applied to the support leg 21 formed of piezoelectric devices, the support leg 21 has such a function that it extends or shrinks to an accuracy of the order of 10nm or so, so that the orientation of the specimen 1 can be optionally determined by controlling the three legs of piezoelectric devices separately.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates directly to the holes formed in a semiconductor substrate or the like by microfabrication, in particular, impurities in contact holes of about 0.1 .mu.m and aspect ratio 10 of highly integrated circuits of 1 Gbit class. The present invention relates to a semiconductor inspection device suitable for analytical analysis.

[0002]

2. Description of the Related Art When a substance is irradiated with an ion beam, it is scattered near the surface of the substance according to the principle of elastic scattering and has a kinetic energy corresponding to the mass number of the substance. For example, 3.0K
When helium ions accelerated to eV are scattered by silicon, 180 ° scattered helium is 1.7 KeV,
It is 0.8 KeV when scattered by carbon. Therefore,
The elemental composition of a substance can be known by irradiating an unknown substance with an ion beam and examining the kinetic energy of scattered ions. An apparatus shown in FIG. 4 has been proposed as an inspection apparatus that directly analyzes impurities and the like in holes formed by fine processing on a semiconductor substrate or the like by applying such a principle. In this device, the ion source 3
The ion beam from the substrate is chopped by the chopping deflector 6 which operates by the pulse signal output from the pulse generator 12, and then accelerated to a predetermined speed through the ion acceleration electrode 4, and the semiconductor substrate 1 held by the sample holder 2 Irradiate the surface of. At this time, the incident position of the ion beam is changed via the scanning electrode 5 which is operated by the voltage from the ion beam scanning power source 10. Secondary electrons generated by being excited on the surface of the semiconductor substrate are detected by the secondary electron detector 8, and the detection signal is sent to the ion beam scanning power source 10 and the CRT display 14 which is tuned and controlled by the synchronizing circuit 15. A secondary electron image is formed, and a desired hole is searched from the secondary electron image. Next, the bottom of the hole is focused and irradiated with an ion beam to scatter the ions and neutral atoms in the hole. These ions and neutral atoms are detected by the ion / neutral atom detector 7, and the detection signal is sent to the time digital converter 13. Since the start signal is input from the pulse generator 12 to the time digital converter 13, the time-digital converter 13 converts the time from the start signal reception to the detection signal reception into a digital signal, and the control computer Transfer to 16. This operation is repeated for each pulse of the pulse generator 12, and the control computer 16
The elemental composition on the surface of the sample 1 can be analyzed by adding in.

[0003]

The conventional device as described above has a problem as shown in FIG. In the figure, 1-1 is a hole formed on the surface of the sample 1, 1-2 is an impurity at the bottom of the hole to be analyzed. Trajectories of scattered ions and neutral atoms are mainly classified into three types b1 to b3. FIG. 5 (a)
Since the scattered ions following the locus b1 in (1) receive only one scattering, they fly in the ion state. Therefore, the locus b1 has no particular problem and is scattered at the hole bottom,
It is directly taken into the detection unit. On the other hand, the locus b2
Is scattered at the bottom of the hole, but is scattered again on the side surface and undergoes multiple scattering, so that the ions are neutralized and taken into the detector. In this case, since the kinetic energy is lost again at the time of scattering on the side surface, the characteristic composition cannot be determined. As the depth of the hole increases, the number of scattered ions and neutral atoms that follow the locus b2 increases, which makes it difficult to determine the composition of the hole bottom. In addition, as shown in FIG. 5B, when the surface of the sample 1 is slightly tilted with respect to the ion beam, the locus b3 is scattered by the side surface and the ion beam cannot reach the bottom of the hole. As the hole depth increases, it tends to increase with a slight inclination of the sample 1 surface.

In particular, with the recent demand for high integration, it is necessary to inspect impurities and the like in contact holes in 1 Gbit class semiconductor devices. The contact holes have an aspect ratio of about 0.1 μm. Because of the size, first, unless the azimuth angle of the sample holder with respect to the ion beam is precisely adjusted, the trajectories b2 and b3 increase, and the backscattered ions cannot be accurately measured. Secondly, based on the backscattered ions on the locus b1, neutral atoms and the like generated on the loci b2 and b3 must be blocked in order to perform accurate sample analysis.

Conventionally, a goniometer is generally used as a mechanism for changing the direction of the sample surface with respect to the incident direction of the ion beam. However, the angle at which the ion / neutral atom detector scatters (the angle formed by the arrows a and b) ) Is about 2.9 °, it is necessary to control the azimuth angle with an accuracy of about 0.03 ° to obtain sufficient accuracy for a contact hole (about 0.1 μm, aspect ratio 10). The direction control accuracy cannot meet the first request. Further, in order to answer the above second request, b1
It is necessary to selectively trap backscattered ions based on.

Therefore, in order to solve the above problems, the first object of the present invention is to provide a semiconductor inspection device capable of inspecting even the bottom of a deep hole such as a contact hole in a 1 Gbit class semiconductor device. Has an aim. A second object of the present invention is to provide a semiconductor inspection apparatus capable of performing accurate sample analysis based on the backscattered ions on the locus b1.

[0007]

According to the present invention, a secondary electron image is detected by irradiating an ion beam on the surface of a semiconductor substrate in a vacuum chamber and changing the incident position of the ion beam to detect excited secondary electrons. , A desired hole is searched from the secondary electron image, the bottom of the hole is irradiated with an ion beam to scatter ions and neutral atoms in the hole, and these ions and neutral atoms are ionized. A device for performing elemental composition analysis in a hole by detecting with a neutral atom detector, comprising a sample holding part having a mechanism for holding a semiconductor substrate and controlling an azimuth angle with respect to an ion beam. In the semiconductor inspection device, the piezoelectric element that expands and contracts according to the applied voltage is used as the displacement support portion and the azimuth angle with respect to the ion beam can be controlled. By utilizing the position, in which it is possible to control the azimuth angle with respect to the ion beam. Incidentally, the piezoelectric element has a function of expanding and contracting with an accuracy of about 10 nm when a voltage is applied. Therefore, the ion beam can be guided to the bottom of the hole even for the contact hole (about 0.1 μm, aspect ratio 10) in order to give precise azimuth adjustment to the sample holder.

It is preferable that the supporting portion is composed of three piezoelectric element supporting legs that determine the sample holding surface. Therefore, 3
By controlling each piezoelectric element individually, the azimuth angle of the sample with respect to the ion beam can be freely determined. When the distance between the piezoelectric elements is set to about 20 mm, the azimuth angle can be accurate to about 0.03 °. You will have control. As described above, the angle (angle formed by arrows a and b) scattered in the direction of the ion / neutral detector is about 2.9 °,
Sufficient precision for contact holes (about 1 μm, aspect ratio 10).

If an electrode capable of trapping scattered ions is provided between the sample holder and the ion / neutral atom detector, the energy amount of only the ion / neutral atom and that of the neutral atom can be obtained. Can be obtained, the influence of the neutral atom on the measurement accuracy can be eliminated, and the analysis in the hole can be performed accurately. Normally, the ion / neutral atom discrimination electrode is composed of three electrodes, and when all the electrodes are grounded, neither ions nor neutral atoms are affected by flight. On the other hand, when the sample-side electrode and detector-side electrode are grounded and a negative potential is applied only to the center electrode, passing neutral atoms are not affected, but the ions are attracted to the center mesh electrode and Unable to reach the neutral atom detector. That is, it is possible to distinguish between the ion + neutral atom and the neutral atom by applying a voltage to the central electrode.
Therefore, the ion and the neutral atom can be easily discriminated by simply subtracting these differences later. As described above, the ions that have been scattered multiple times are neutralized,
The composition at the bottom of the hole can be accurately detected by performing composition analysis using only ions. It is said that the appropriate voltage for the central electrode is about 0.8 times the voltage for the acceleration electrode.

By arranging a semiconductor manufacturing apparatus in the vacuum chamber and connecting it to the semiconductor inspection apparatus, it is possible to carry out semiconductor manufacturing while searching for real-time semiconductor surface properties. Examples of the semiconductor manufacturing apparatus include an etching apparatus and a sputtering apparatus that are performed in a vacuum space, and the semiconductor inspection apparatus can be used as a monitor during processing.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a layout diagram and a block diagram of a control electric circuit of a semiconductor inspection apparatus of the present invention in which a secondary electron detector and a time-of-flight ion scattering spectrometer are combined. Reference numeral 1 is a sample to be measured such as a semiconductor substrate, in which fine holes are formed on the surface. Usually, the holes have a diameter of about 0.3 μm and a depth of about 0.2 μm. The hole has a diameter of about 0.1 μm and an aspect ratio of about 10. Two
Is a sample holder for holding the sample 1. Reference numeral 3 is an ion source for generating an ion beam used as a probe, 4 is an accelerating electrode for accelerating and focusing the generated ions, and 5 is a scanning electrode for scanning the surface of the sample 1 with the ions. Further, 6 is a chopping deflector which makes the ions generated in the ion source 3 into pulses and sends them to the accelerating electrode 4 side. 7 is an ion / neutral atom detector equipped with a function of detecting ions scattered by the sample and neutral atoms neutralized at the time of scattering, and at the same time outputting a pulse signal, 8 is the ion scattered by the surface of the sample 1. The secondary electrons generated at the same time,
It is a secondary electron detector having a function of outputting an electric signal according to its intensity.

A block diagram of a main control system is shown within a dotted line 9 and 10 is a power supply circuit for the scan electrode 5 and 11 is a power supply circuit for the acceleration electrode 4. 12 is a chopping deflector 6
Numeral 13 is a time-digital converter for measuring the time from the generation of pulsed ions to the detection of ions and neutral atoms by the ion / neutral atom detector 7. Reference numeral 14 denotes a CRT (Cathode Ray Tube) display for visualizing a secondary electron image by the secondary electron detector 8.
Reference numeral 5 is a synchronizing circuit for adjusting the display cycle of the CRT display 14 and the cycle of the ion beam scanning power source 10. Reference numeral 16 represents a control computer. The arrow a indicates the ion beam with which the sample 1 is irradiated, the arrow b indicates the trajectory of ions and neutral atoms that are scattered by the sample 1 and enter the ion / neutral atom detector 7, and the arrow c indicates the secondary electron detector. 8 shows the trajectories of the secondary electrons incident on No. 8 respectively.

Usually, the sample 1 and the ion / neutral atom detector 7
Since the distance between them is about 100 cm and the distance between the arrow a and the ion / neutral atom detector 7 is about 5 cm, the angle formed by the arrows a and b is 2.9 °. Therefore, the scattering angle of scattered ions and neutral atoms is about 180 °.

In the present invention, the sample holder 2 further includes a precision azimuth adjusting mechanism 17 and an ion / neutral atom discrimination electrode 18.
It has. FIG. 2 shows a configuration diagram of the sample holder 2 provided with the precise azimuth angle adjusting mechanism 17, and FIG.
(B) shows a cross section indicated by a dotted line II '. Reference numeral 21 is a support leg of the sample holding unit, which is composed of a piezoelectric element such as a piezo. The number of the support legs 21 is three, and the upper legs 22 are supported by projecting from the positions of the apexes of the equilateral triangle of the lower plate 23.
A claw 24 for holding the sample 1 is provided on the upper plate 22. Therefore, the support leg 2 including the piezoelectric element
1 has a function of expanding and contracting with an accuracy of about 10 nm when a voltage is applied. Therefore, if the supporting legs 21 composed of three piezoelectric elements are individually controlled as shown in FIG. 3, the azimuth angle of the sample 1 can be freely set. For example, when the distance between the support legs 21 is set to about 20 mm, the azimuth angle control can be performed with an accuracy of about 0.03 °. As described above, the angle of scattering in the direction of the ion / neutral atom detector 7 (arrows a, b
Since the angle formed by the angle is about 2.9 °, sufficient accuracy is achieved.

The ion / neutral atom discriminating electrode 18 is an electrode of three mesh plates and is a sample side electrode 18-1 and 18-2.
The central electrode and the detector-side electrode 18-3. 19 is a power supply circuit for the ion / neutral atom discrimination electrode 18,
Reference numeral 20 is a power supply circuit for the sample holder 17. When all the electrodes of the ion / neutral atom discrimination electrode 18 are grounded, neither ions nor neutral atoms are affected by flight. On the other hand, the sample side electrode 18-1, the detector side electrode 18
-3 is grounded and a negative potential is applied only to the central electrode 18-2, the passing neutral atoms are not affected, but the ions are attracted to the central mesh electrode and the ion / neutral atom detector 7 Can't reach. That is, the central electrode 18-2
It is possible to distinguish between ion + neutral atoms and neutral atoms by applying a voltage to. Therefore, the ion and the neutral atom can be easily discriminated by simply subtracting these differences later. As described above, the ions scattered a plurality of times are neutralized, so that the composition at the hole bottom can be accurately detected by performing the composition analysis using only the ions.
The voltage of the central electrode 18-2 is preferably about 0.8 times the voltage of the acceleration electrode 4. For example, when the voltage applied to the acceleration electrode 4 is 3.0 kV, the voltage of the central electrode 18-2 is about 2.4 kV.

The composition analysis in the hole is performed by the following procedures A to F. A) Surface observation The surface of the sample 1 is scanned with an ion beam, and secondary electrons excited by the ion beam are detected by the secondary electron detector 8,
Output as an electric signal to the CRT display 14. C
The RT display 14 outputs the luminance signal on the CRT. Since the display cycle of the CRT display 14 and the scanning cycle of the ion beam are adjusted by the synchronizing circuit 15, the secondary electron image is visualized on the CRT. B) Hole search and scanning voltage fixing A desired hole is searched for in the secondary electron image, and the scanning voltage is fixed at the hole position. C) Azimuth Adjustment Further, when the azimuth of the sample 1 does not match the ion beam, the sample holder 2 is adjusted by the precision azimuth adjusting mechanism 17. D) Repeated Adjustment The procedures A to C are repeated until the azimuth angle of the sample 1 matches the ion beam. E) In-hole analysis (ion + neutral atom detection) Without operating the ion / neutral atom selection electrode, the hole is intensively irradiated with an ion beam, and composition analysis is started by scattered ions and neutral atoms. F) In-hole analysis (neutral atom detection) Ion and neutral atom selective electrodes are operated to start composition analysis by neutral atoms. The kinetic energy of scattered ions can be calculated by measuring the flight time until the ions emitted from the ion source 3 are scattered on the surface of the sample 1 and reach the ion / neutral detector 7. The pulse generator 12 outputs an ion generation signal to the chopping deflector 6 and simultaneously outputs a measurement start signal to the time-digital converter 13. The ion / neutral atom detector 7 outputs a detection signal to the time-digital converter 13 as soon as ions and neutral atoms arrive. Since the start signal is input from the pulse generator 12 to the time digital converter 13, the time-digital converter 13 converts the time from the start signal reception to the detection signal reception into a digital signal, and the control computer Transfer to 16. By repeating this operation for each pulse of the pulse generator 12 and adding them by the control computer 16, the elemental composition in the holes can be analyzed.

Embodiment 2 FIG. 3 is a layout diagram and a block diagram of a control electric circuit showing an embodiment of the present invention, and the same reference numerals in the drawing denote the same members as those in FIGS. Reference numeral 25 denotes an etching electrode, which forms the upper plate 22 of the sample holding part 2 and the electrode part of the parallel plate type plasma etching apparatus. Also, 26
Is a high frequency power supply circuit for etching. Reference numeral 27 indicates the sample holder 17 together with the sample 1 at the operating position p of the etching apparatus.
1 is a carrying device for carrying between the semiconductor inspection device unit 1 and the operating position p2.

In the semiconductor inspection apparatus configured as described above, the etching processing is performed in the etching apparatus section at the position p1. Then, the transport device 27 is operated to position the sample 1 at the position p.
Then, the semiconductor inspection device unit performs the in-hole analysis according to the procedure described in the first embodiment. When the analysis result shows that the etching process is incomplete, the sample 1 can be quickly returned to the position p1 and the etching process can be performed again. That is, since it is possible to repeatedly perform processing and analysis in the same device, it is possible to use the semiconductor inspection device as a monitor during processing and perform real-time manufacturing control.

Although only the etching apparatus is described in the above example, it may be connected to other semiconductor manufacturing apparatus such as a sputtering apparatus and an ashing apparatus.

[0020]

As is apparent from the above description, according to the present invention, the semiconductor inspection apparatus has the precise azimuth adjusting mechanism in which the displacement mechanism is composed of the piezoelectric element in the sample holding portion.
Even a fine contact hole in a G-bit class highly integrated circuit board can be accurately controlled to guide the ion beam to the hole bottom, and composition analysis of the hole bottom deeper than in the past can be performed. Further, by disposing an electrode between the sample 1 and the ion / neutral atom detector 7, the ion and the neutral atom can be discriminated from each other, so that the analysis in the hole can be performed more accurately than before. . Further, if the apparatus configured as described above is connected to a semiconductor manufacturing apparatus such as an etching apparatus and a sputtering apparatus in the same vacuum chamber, it can be utilized as a monitor during the process and real-time manufacturing control can be performed.

[Brief description of drawings]

FIG. 1 is a schematic view showing a first embodiment according to the present invention.

FIG. 2 is a configuration diagram of a sample holding mechanism according to the present invention.

FIG. 3 is a schematic diagram showing a second embodiment according to the present invention.

FIG. 4 is a schematic diagram of a conventional semiconductor inspection device.

FIG. 5 is a conceptual diagram for explaining a problem of a conventional semiconductor inspection device.

[Explanation of symbols]

1 sample 1-1 hole formed on sample 1 surface 1-2 impurities at hole bottom 2 sample holder 3 ion source 4 accelerating electrode 5 scan electrode 6 chopping deflector 7 ion, neutral atom detector 8 2 Next electron detector 10 Scan electrode power supply circuit 11 Accelerating electrode power supply circuit 12 Pulse generator 13 Time-to-digital converter 14 CRT display 15 Synchronous circuit 16 Control computer 17 Precision azimuth adjustment mechanism 18 Ion / neutral atom identification electrode 18-1 Sample-side electrode, 18-2 Central electrode, 18
-3 Detector side electrode 19 Power source for ion / neutral atom discrimination electrode 20 Power source for precise control of azimuth angle 21 Piezoelectric element 22 Upper plate 23 Lower plate a Ion irradiated on sample b Ion scattered on sample 1, medium Trajectory of neutral atom b1 Neutral atom that is scattered at the bottom of the hole b1 and directly enters the detector b2 Trajectory of neutral atom b2 that is scattered at the bottom of the hole and again scattered at the side of the hole and incident on the detector 7 b3 Trajectory of ions and neutral atoms scattered on the side surface of the hole and directly incident on the detector c Trajectory of secondary electrons generated at the same time as ion beam scattering p1 Etching processing operation position p2 Analysis processing operation position

Claims (6)

[Claims] 1. A secondary electron image is formed by irradiating an ion beam on the surface of a semiconductor substrate in a vacuum chamber and changing the incident position of the ion beam to detect excited secondary electrons to form a secondary electron image. A desired hole is searched from the image, the bottom of the hole is irradiated with an ion beam to scatter ions and neutral atoms in the hole, and these ions and neutral atoms are detected by an ion / neutral atom detector. A device for performing elemental composition analysis in a hole, which has a sample holding part having a mechanism for holding a semiconductor substrate and controlling an azimuth angle with respect to an ion beam, and the sample holding part uses a piezoelectric element as a displacement supporting part. An inspection apparatus for semiconductors, wherein the azimuth angle of the sample holder with respect to the ion beam can be controlled by the displacement of the piezoelectric element. 2. The semiconductor inspection apparatus according to claim 1, wherein the supporting portion is composed of three piezoelectric element supporting legs that determine a holding surface of the sample holding portion. 3. The semiconductor inspection apparatus according to claim 1, wherein an electrode capable of capturing backscattered ions is provided between the sample holder and the ion / neutral atom detector. 4. The electrode is composed of three electrodes, and is switched between a state in which all the electrodes are grounded and a state in which the sample-side electrode and the detector-side electrode are grounded and a negative potential is applied only to the central electrode. The semiconductor inspection apparatus according to claim 3, which is possible. 5. A high-performance integrated circuit of about 1 Gbit class of about 0.1.
The semiconductor inspection apparatus according to claim 1, which is capable of inspecting the inside of a contact hole having a micrometer or less and an aspect ratio of 10 or more. 6. A semiconductor manufacturing apparatus is arranged in the vacuum chamber and is connected to the semiconductor inspection apparatus according to any one of claims 1 to 4, for inspecting a semiconductor device manufactured by the manufacturing apparatus. , A semiconductor inspection device characterized by being used as a monitor.