JP2000149845A - Holding method for specimen, holding device for specimen and charged particle beam device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To relieve turbulence of an electric field in the end part of a semiconductor wafer, by applying the same voltage to a specimen and a conductive plate having almost the same height as the surface of the specimen and also a gap of not more than a specific value from the end surface of the specimen, when the specimen is placed on an elevating pin penetrating through a holding device, the specimen is then placed on a supporting pedestal provided in a holding device by lowering the elevating pin and the specimen is held by the holding device. SOLUTION: In a transition process from the atmospheric pressure to a vacuum, conductive plates 33a, 33b and fixing holding pins 24a, 24b sandwich a movement holding pin 24c and a wafer 22. The conductive plates 33a, 33b are electrically connected to a holder 21. In addition, they are connected to the wafer 22 through the movement holding pin 24c, a third conductive plate 33c is fixed as well as electrically connected to the holder 21 outside the fixing holding pins 24a, 24b, and it surrounds the entire periphery of the wafer 22 together with the conductive plates 33a, 33b. The surface height of the conductive plates 33a, 33b, 33c is almost same as the surface of the wafer 22, and a gap between the outer rim of the wafer 22 and the plate is kept not more than 0.5 mm under a closed condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for holding a sample,
The present invention relates to a sample holding device and a charged particle beam device.

[0002]

2. Description of the Related Art An apparatus for processing a semiconductor wafer using a charged particle beam or an apparatus for inspecting a circuit pattern on a semiconductor wafer has an apparatus for holding a workpiece or a semiconductor wafer to be inspected. .

An example of such an apparatus is an electron beam measuring machine. This measures the width and position of a circuit pattern formed on a semiconductor wafer, and uses an electron beam as a charged particle beam, and consists of an electron beam probe, an image processing device, a sample stage with a laser length measuring device, etc. Have been. In this electron beam measuring machine, a voltage is applied to a semiconductor wafer to measure the width and position of a circuit pattern with desired accuracy and resolution without damaging elements of the circuit pattern by the electron beam. Is controlled. The application of this voltage is called retarding. This technology is disclosed, for example, in Japanese Patent Application Laid-Open Nos.
No. 58703.

By the way, an electric field is generated in the space above the semiconductor wafer due to the retarding. The electric field is not uniform near the edge of the semiconductor wafer but is disturbed. As a result, the trajectory of the electron beam is bent irregularly. It has been difficult to accurately measure the position of the circuit pattern near the edge of the semiconductor wafer. The influence of the disturbance of the electric field may occur not only in the electron beam length measuring device but also in an apparatus employing retarding using a charged particle beam. The above prior art does not disclose the electric field disturbance at the edge of the semiconductor wafer.

A sample holding device is used for fixing a semiconductor wafer as a sample to the above charged particle beam device. The voltage for retarding is applied to the sample by the holding device. Done through.

The structure of the sample holding device has been devised in various ways, and for example, Japanese Patent Application Laid-Open No. 60-167245 discloses that
A configuration is described in which a semiconductor wafer is reliably held by a holder that operates in a vacuum. However, there is no countermeasure for the electric field disturbance at the edge of the semiconductor wafer caused by the retarding from the sample holding device side.

[0007]

SUMMARY OF THE INVENTION The present invention focuses on applying a voltage for retarding to a sample through a sample holding device, and can reduce the above-described electric field disturbance at the edge of a semiconductor wafer. An object of the present invention is to provide an easy sample holding method, a sample holding device, and a charged particle beam device.

[0008]

Means for Solving the Problems The present invention has the following arrangement to solve the above-mentioned problems.

In the method of holding a sample, the sample is placed on an elevating pin that penetrates the holding device, and the elevating pin is lowered to place the sample on a support provided on the holding device. When the sample is held by the holding device, The same voltage is applied to the conductor plate and the specimen, which are substantially the same height as the surface of the specimen and have a gap of 0.5 mm or less from the end face of the specimen.

[0010] In the sample holding device, the lifting pin for loading the sample penetrates, and the lifting pin descends, and the support table on which the sample is mounted is substantially the same height as the surface of the sample when the sample is mounted on the support table. The gap with the end face of the sample is not more than 0.5 mm, and has a conductor plate to which the same voltage as that of the sample is applied.

In the charged particle beam apparatus, a retarding voltage supply device for supplying a retarding voltage to the sample when the sample is irradiated with the charged particle beam, an elevating pin for mounting the sample penetrates, and the elevating pin is lowered. The height of the support is approximately the same as the surface of the sample when the sample is mounted on the support, and the gap between the support and the end surface of the sample is 0.
And a conductive plate to which the same voltage as that of the sample is applied.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view schematically showing the configuration of an electron beam measuring machine. In FIG. 1, a wafer 1 as a sample is carried out of a carrier 2 by an RΘZ driving type transfer robot 3 whose arm rotates and ascends, is carried into a air lock chamber 4 through a gate 5, and is transferred onto a holder 6. Will be posted. Next, the gate 5 is closed, the valve 7 is opened, and the air lock chamber 4 is evacuated by the pump 8. The inside of the work chamber 10 partitioned by the gate 9 is constantly evacuated, and after the degree of vacuum in both chambers approaches,
The gate 9 is opened, the holder 6 on which the wafer 1 is mounted is loaded and transferred onto the stage 11 in the work chamber 10, and the loading of the wafer 1 into the measurement environment is completed.

Next, the stage 11 moves so that the first pattern to be measured on the wafer 1 is located below the electron optical system device 12, and after the stage 11 stops, the wafer to which the retarding voltage is applied is applied. The electron beam 14 is incident toward 1. The position of the stage 11 is measured by the laser interferometer 13, and the movement is controlled by the position information.

The emitted secondary electrons 15 are guided to a detector 16 and detected. By scanning with the electron beam 14, a signal of a scanning area including the first pattern is taken into the EB probe image processing control unit 105. In the image processing, the coordinates of the center of the first pattern are measured from addition and subtraction of the deviation from the center of the first pattern obtained by the signal processing to the reference coordinates and the measurement coordinates corresponding to the position of the stage (or wafer). You. Next, the second pattern is measured in the same manner, and the pitch of both patterns is calculated based on the difference between the center of the first pattern and the center of the second pattern.

After a predetermined series of measurements have been performed on the wafer 1, the holder 6 is transported to the airlock chamber 4 and the wafer 1 is further transported to the carrier 2 in the reverse order to carry out the wafer 1. Subsequently, the next wafer 1 is sequentially measured in the same manner.

The above controls are performed by the wafer transfer control unit 101,
The processing is executed by the cooperation of the holder transfer control unit 102, the evacuation control unit 103, the stage drive position measurement control unit 104, the EB probe image processing control unit 105, and the central processing unit 100 that controls them.

A first embodiment of the present invention is shown in FIGS.

FIG. 2 is a top view of the mechanical holding type holder 21 as viewed from above, and FIG. 3 is a view showing the conductor plates 33a and 33b shown in FIG.
4 and FIG. 5 are sectional views taken along the line AA of FIG.

In FIG. 3, a wafer 2 is placed on a holder 21.
The support bases 23a, 23b and 23c for supporting the bottom surface of the wafer 2 are fixed, and fixed holding pins 24a and 24a for fixing the wafer 22 corresponding to the end face or the end face notch of the wafer 22.
The transferred wafer 22 is positioned and held in the horizontal direction (XYΘ direction) in cooperation with the movement holding pins 24c that are attached with the wafer 24 and act to sandwich the wafer 22 therebetween.

Here, the movable holding pin 24c is attached to a driven lever 26 swingably guided by a fulcrum 25, and the driven lever 26 is driven by a compression spring 28 provided on a drive lever 27 similarly swingably guided. The bellows 30 filled with atmospheric pressure gas which is pressed against the pin 29 and expands and contracts in response to a vacuum or atmospheric pressure state in the air lock chamber 4 shown in FIG.
4c operates so as to sandwich (ie, close) the wafer 22 and open at atmospheric pressure.

Further, the drive lever 27 has slopes 31a, 3a.
1b, corresponding to the driven pins 34a, 34b provided on the bottom surfaces of the conductor plates 33a, 33b swingably guided by the fulcrums 32a, 32b, respectively, and tension springs 35a, 35b.
b, the conductor plates 33a and 33b urged in the closing direction.
Are driven to close in vacuum and open in atmospheric pressure.

In the process of shifting from atmospheric pressure to vacuum,
The conductor plates 33a and 33b are fixed to the holding pins 24a and 24b.
Then, the movable holding pins 24c sandwiching the wafer 22 are closed so as to follow, and thereafter, the conductor plates 33a and 33b and the fixed holding pins 24a and 24b sandwich the movable holding pins 24c and the wafer 22.

Here, the conductor plates 33a and 33b are connected to a spring hook 36 fixed to the holder 21 and tension springs 35a and 35b.
5b, it is electrically connected to the holder 21 and further connected to the wafer 22 via the moving holding pins 24c. On the other hand, the other end of the wafer 22 has fixed holding pins 24a,
24b, the third conductor plate 33 is connected to the outside of the fixed holding pins 24a, 24b.
c is fixed to the holder 21 also for electrical connection, and surrounds the entire periphery of the wafer 22 together with the conductor plates 33a and 33b.

The conductor plates 33a, 33b, and 33c have substantially the same surface height as the surface of the wafer 22, and have a gap between the outer edge of the wafer 22 in a closed state of 0.5 mm or less. According to experiments by the inventors described later, when the height is 200 micrometers or less, there is an effect of alleviating disturbance of the electric field.

The surface heights of the fixed holding pins 24a, 24b, the movable holding pins 24c, and the fulcrums 32a, 32b are also close to the surface of the wafer 22, and the retarding voltage applied from the bottom surface of the holder 21 on the stage 11 This helps to alleviate the disturbance of the electric field around the surface of the wafer 22 due to the above.

Next, the transfer and transfer of the wafer 22 will be described. When the wafer 22 is loaded, the air lock chamber 4 shown in FIG.
Also, the conductor plates 33a, 33b and the moving holding pins 24c of the holder 21 shown in FIG. 4 are opened, and the lifting pins 38a, 38b, 38c provided above the lifting drive unit 37 shown in FIG. Waiting in a rising state. A hand 39 indicated by a broken line in FIG. 4 is a part of the transfer robot 3 shown in FIG. 1, and includes elevating pins 38a, 38b, 38c.
Are arranged so as not to interfere with the hand 39.

As shown in FIG. 4, the wafer 22 is
9, the wafer 39 is conveyed onto the elevating pins 38a, 38b, and 38c that pass through the holder 21 through the gate 5 shown in FIG.
After being placed on the a, 38b, 38c, the hand 39 retreats out of the gate 5, and the wafer 22 is supported on the support tables 23a, 23b, 2 while the elevating pins 38a, 38b, 38c are descending.
3c. Thus, the wafer 22
Are fixed holding pins 24a, as shown in FIG. 2 or FIG.
24b, it is placed in the inscribed circle of the movement holding pin 24c. The unloading of the wafer 22 is performed in the reverse order.

The effects of the first embodiment of the present invention described above will be described below.

1. Since the wafer is held on the support table integrated with the holder, the wafer is stably held. 2. The wafer has a holding pin on the end face, a robot hand on the back side,
Since it is only in contact with the support, the possibility of foreign matter adhesion is reduced, and the amount of foreign matter attached can be reduced.

3. Even if the diameter of the wafer varies, the conductor plate is positioned with the movable holding pin interposed therebetween, so that the gap between the outer edge of the wafer and the conductor plate can be reduced to 0.5 mm or less.

4. Since the configuration is simple as described above, it is easy to manufacture the actual device and to secure the reliability of the operation of each unit.

A second embodiment of the present invention is shown in FIGS.

FIG. 6 is a top view of the electrostatic suction type holder 41 as viewed from above, and FIGS. 7 and 8 are longitudinal sectional views of FIG.

In FIG. 7, a wafer 2 is placed on a holder 41.
Electrostatic chuck 42 holding electrostatic chuck 2 while also serving as a support base
And a conductor plate 43 fixed to the holder 41 so as to surround the wafer 22. On the stage 11, the retarding voltage Er applies the electrostatic chuck voltage Es to the conductor plate 43.
Is applied to the holder 41.

The air lock chamber 4 is provided with a lifting drive 37 shown in FIG.
The lifting pins 38a, 38b, 3
The wafer 22 is moved up and down by driving 8c.

The wafer 22 loaded and lifted by the hand 39 shown by the broken line in FIG. 8 on the elevating pins 38a, 38b, 38c is replaced with the positioning by the holding pins on the holder in the first embodiment. The wafer is positioned at an XYΘ position that is concentric with the opening of the conductor plate 43 that is opened so as to surround the wafer 22 by a centering type wafer positioning device 44 that is arranged at a position that does not compete with the hand 39 above the holder 41. The pins 38a, 38b, and 38c are lowered so that the conductor plate 43 is placed on the electrostatic chuck 42 with the centers of the openings of the conductor plate 43 aligned. And the electrostatic chuck voltage E
By applying s, the wafer 22 is held by the holder 41 and measurement is performed.

The difference between the height of the conductor plate 43 and the height of the wafer 22 is set to 200 μm or less, and the gap is set to 0.5 mm or less, as in the first embodiment of the present invention.

If a notch or an orientation flat provided on the wafer 22 is detected,
The rotational position of the wafer 22 is determined by the pattern wafer positioning device 4
It is also possible to correct by 4.

The effects of the second embodiment of the present invention described above will be described below.

1. Even if the diameter of the wafer varies, the centering is performed by the wafer positioning device, so that the gap between the outer edge of the wafer and the conductive plate can be reduced to 0.5 mm or less.

2. By detecting the rotation of the wafer and feeding back to the Θ drive of the wafer positioning device, the rotation with respect to the stage coordinate axis can be corrected.

In the first and second embodiments of the present invention, the case where the sample holding apparatus and the sample holding method according to the present invention are applied to an electron beam length measuring machine has been described. When applied to an inspection apparatus that detects a defect in a pattern by comparing a pattern on a wafer with a pattern having the same shape at a position further away from the wafer, the accuracy of inspection of a semiconductor chip formed at a portion close to the edge of the wafer And the cause of the defect can be easily found, which contributes to the improvement of the yield. Further, even when used in a semiconductor wafer processing apparatus, a measuring apparatus other than the above-described embodiment, and an inspection apparatus, processing, measurement, and inspection can be performed up to the end of the sample.

The effect of alleviating the disturbance of the electric field according to the embodiment described above will be described.

FIG. 9 shows that the conductor plate 33 is
The electric field distribution diagram based on the result of the electric field simulation when the protrusions a, 33b, 33c, and 43 are higher than the wafer 22 by 1 mm is shown. Equipotential line 5 indicating the state of the electric field
A place where the density of 0 is not uniform is a place where the electric field is disturbed. The gradient shield electrode 51 has the same potential as the wafer 22 so as not to generate a potential gradient on the surface of the wafer 22. Further, for the purpose of simulation, the wafer 22 is supported on the supports 23a, 23b and 23 as in the embodiment of the present invention.
It does not have a structure mounted on c. FIG.
9A shows a case where the irradiation position of the electron beam 14 is 5 mm away from the protrusion, and FIG. 9B shows a case where the irradiation position of the electron beam 14 is 10 mm away from the protrusion.

When comparing FIG. 9A and FIG. 9B,
In the case of (a), that is, in the case where the protrusion is closer to the electron beam 14 than in the case of (b), the electric field fluctuates. In the range of 5 mm from the protrusion, the electric field fluctuates, and it is expected that the irradiation position of the electron beam 14 is likely to be disturbed.

FIG. 10 shows an electric field distribution diagram based on the result of the electric field simulation when the periphery of the edge of the wafer 22 is a space. The wafer 22 is placed on an electrostatic chuck 42. FIG. 10A shows a case where the irradiation position of the electron beam 14 is 5 mm from the edge of the wafer 22.
Is a case where the irradiation position of the electron beam 14 is 10 mm from the edge of the wafer 22.

Comparing FIG. 10A and FIG. 10B,
The variation of the equipotential lines 50 is larger in the case of (a) than in (b), that is, as the irradiation position of the electron beam 14 is closer to the end of the wafer 22, and the irradiation position of the electron beam 14 is more likely to be disturbed. It is expected that. Therefore, it is understood that providing a large space at the end of the wafer 22 must be avoided.

When a projection or a low space with a height is provided outside the edge of the wafer 22, the range in which the irradiation position of the electron beam 14 is not disturbed may be at least 10 mm inside from the edge of the wafer 22. all right.

Referring to the electric field distribution diagram based on the results of the electric field simulation described above, in order to prevent the fluctuation of the electric field at the end of the wafer 22 and to prevent the influence on the irradiation position of the electron beam 14, the conductor plates 33a, 33b , 33c, 43 wafer 22
It has been found that it is effective to make the periphery of the edge of the same height as the surface of the wafer 22.

The height of the wafer 22 and the conductor plate 33
It is difficult to make the height dimensions of a, 33b, 33c, and 43 completely the same due to errors in machining and assembly, but according to experiments by the inventors, the end surface of wafer 22 And the conductor plates 33a, 33b, 33c, 43 have a height difference of 2
It was found that the effect on the irradiation position of the electron beam 14 was almost negligible if it was not more than 00 micrometers.

The wafer 22 and the conductor plates 33a, 33
A gap is formed between b, 33c and 43. According to experiments by the inventors, it has been found that if this gap is 0.5 mm or less, the effect on the irradiation position of the electron beam 14 can be almost ignored.

The configuration of the present invention may be as follows.

1. In a charged particle beam apparatus for processing or inspecting a sample by irradiating a charged particle beam, a support for supporting the sample on the bottom, and when loading the sample on the support, the sample is supported on the bottom. Lifting / lowering drive means configured to avoid interference with the outer edge of the sample, so that the same voltage as the sample is applied at substantially the same height as the surface of the sample and surrounds the outer edge of the sample. A charged particle beam apparatus, comprising: a sample holding device including a plurality of openable and closable conductor plates.

2. In a charged particle beam apparatus that performs processing or inspection of a sample by irradiating a charged particle beam, an electrostatic chuck that holds the sample on a bottom surface, and when loading the sample onto the electrostatic chuck, the sample is placed on the bottom surface. Supported by, lifting and lowering drive means configured to avoid interference with the outer edge of the sample, and means for positioning the sample in the horizontal direction before the loading,
The sample holding device having a plurality of conductive plates that are substantially the same height as the surface of the sample, are applied with the same voltage as the sample, and can be opened and closed so as to surround an outer edge of the sample. A charged particle beam device characterized by the above-mentioned.

[0055]

As described above, according to the present invention, it is possible to provide a sample holding method, a sample holding apparatus, and a charged particle beam apparatus which can easily carry out the disturbance of the electric field at the edge of the semiconductor wafer. Can be.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional view schematically showing the configuration of an electron beam length measuring device.

FIG. 2 is a top view of a mechanical holding type holder.

FIG. 3 is a top view in which a part of the conductor plate shown in FIG. 2 is cut away.

FIG. 4 is a sectional view taken along the line AA of FIG. 2;

FIG. 5 is a sectional view taken along the line AA in FIG. 2;

FIG. 6 is a top view of an electrostatic chuck type holder.

FIG. 7 is a longitudinal sectional view of FIG. 6;

FIG. 8 is a longitudinal sectional view of FIG. 6;

FIG. 9 is an electric field distribution diagram showing a result of an electric field distribution simulation of a longitudinal section on a wafer surface.

FIG. 10 is an electric field distribution diagram showing a result of an electric field distribution simulation of a vertical section on a wafer surface.

[Explanation of symbols]

1, 22, wafers, 6, 21, 41 holders, 14 electron beams, 23a, 23b, 23c support bases, 24a, 24
b: fixed holding pin, 24c: movable holding pin, 33a, 3
3b, 33c, 43 ... conductor plate, 37 ... lifting drive unit, 38
a, 38b, 38c: lifting pins, 42: electrostatic chuck,
44 ... wafer positioning device.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masayuki Otsuka 882-Momo, Oaza-shi, Hitachinaka-shi, Ibaraki Pref. Inside the Measuring Instruments Division, Hitachi, Ltd. F-term in Hitachi Instruments Measuring Instruments Division (reference) 5C001 AA01 CC04 CC08

Claims (7)

[Claims] 1. A method for holding a sample of a charged particle beam apparatus for performing processing, inspection, etc. by irradiating the sample with a charged particle beam, wherein the sample is placed on an elevating pin penetrating a holding device for holding the sample. The sample is placed on the support provided on the holding device by lowering the pin, and when the sample is held by the holding device, the height is substantially the same as the surface of the sample, and the gap between the sample and the end surface of the sample is A method for holding a sample, wherein the same voltage is applied to the conductor plate and the sample, which are 0.5 mm or less. 2. The method according to claim 1, wherein a difference in height between the conductor plate and the sample is 200 μm or less. 3. The holding plate according to claim 1, wherein a fixed holding pin and a moving holding pin provided on the holding device restrain horizontal movement of the sample, and the conductor plate is divided, and a part of the conductive plate is divided. A method for holding a sample, wherein the sample is moved in conjunction with the movement of a movable holding pin. 4. A sample holding device of a charged particle beam apparatus for performing processing, inspection, and the like by irradiating a charged particle beam to a sample, wherein an elevating pin for mounting the sample penetrates, and the elevating pin descends to lower the sample. And a height substantially equal to the surface of the sample when the sample is mounted on the support, and a gap between the sample and an end surface of the sample is 0.
A sample holding device comprising: a conductive plate to which a voltage equal to or less than 5 mm is applied to the sample. 5. The sample holding device according to claim 4, wherein a difference in height between the conductor plate and the sample is 200 μm or less. 6. The apparatus according to claim 4, further comprising a fixed holding pin and a movable holding pin for restraining the sample from moving in the horizontal direction, wherein the conductor plate is divided, and a part of the conductive plate is used for movement of the movable holding pin. A sample holding device that moves in conjunction with the sample. 7. A charged particle beam apparatus for irradiating a sample with a charged particle beam to perform processing, inspection, and the like, wherein, when irradiating the sample with the charged particle beam, a voltage for retarding the charged particle beam is reduced. A retarding voltage supply device for supplying the sample, an elevating pin for mounting the sample penetrates, the elevating pin descends, and a support base for mounting the sample, and the support table when the sample is mounted on the support table. A sample holding device having a height substantially equal to the surface of the sample, a gap between the end surface of the sample being 0.5 mm or less, and a conductor plate to which the same voltage as that of the sample is applied. Charged particle beam device.