JP4483957B2 - Sample preparation device - Google Patents

Description

The present invention uses a transmission electron microscope (hereinafter abbreviated as TEM) and a scanning electron microscope (hereinafter abbreviated as SEM) from the surface of a semiconductor wafer, magnetic head or the like on which a fine structure is formed. The present invention relates to a sample preparation method and a sample preparation device for processing and collecting a sample piece having a fine dimension necessary for observation using a focused ion beam (hereinafter abbreviated as FIB).

For example, ECG Kirk et al.
Microscopy of Semiconducting Materials 1989, Institute of Physics No.1
00, pages 501-506.

This prior art will be described with reference to FIG. Approximately 3 x 0.1 x 0.5 mm (wafer thickness) by dicing the strip-shaped pellet 102 (sample) from the wafer 101 to be observed
To cut out (pellet cutting step). Next, the strip-shaped pellet 102 is fixed to the end surface of the semicircular metal plate 103 (pellet fixing step). In this state, the thickness is 100 nm by FIB
It is processed into a thin film to the extent (pellet molding process). This is illustrated as a strip-shaped pellet 102 '. Then, the semicircular metal plate 103 is manually set on the TEM observation holder 104 (sample setting step), and TEM observation is performed.
Proceedings Microscopy of Semiconducting Materials 1989, Institute of Physics No.100, p.501-506

First, in the above-described prior art, it may be necessary to perform a long process of 3 to 5 hours from the pellet cutting process to the completion of the sample setting process. In addition, pellets and semicircular metal plates are very small, and skill is required to handle them manually, which increases the cost for sample preparation.

In order to solve this problem, the present invention simplifies a series of sample preparation processes and provides a sample preparation apparatus and method capable of automating most of the preparation work, thereby reducing time and cost. It is aimed.

In order to achieve the above object, the following measures are taken in the present invention. A sample preparation apparatus according to the present invention includes an FIB, a secondary electron detector, a deposition gas source, a sample moving mechanism, a sample piece probe for collecting a sample piece, and a sample piece probe in a sample processing chamber. The sample piece probe holder and the sample piece probe moving mechanism which can be attached and detached, and the observation sample holder and the observation sample holder moving mechanism on which the sample piece probe alone is mounted are provided.

Next, a sample preparation method using the components of the sample preparation apparatus will be described. A series of steps for sample preparation according to the present invention includes a marking step in which a processing target position is marked on the original sample with a laser or the like, and a sample piece probe previously installed in an observation sample holder in a sample processing chamber is observed by visual field observation by FIB. , Sample piece probe holding step for changing to a sample piece probe holder, sample piece forming step for forming a sample piece from an original sample into a desired shape, sample piece probe contact step for bringing the tip of the sample piece probe into contact with the formed sample piece , Sample piece connection process of sample piece and sample piece probe tip by irradiation of focused ion beam and deposition gas, sample piece separation process of separating sample piece and original sample by irradiation of focused ion beam, for observation of sample piece probe This is performed by a sample piece probe transfer process of transferring to the sample holder 10.

In addition, in the sample preparation method as described above, when preparing a sample for TEM observation, in addition to the above steps, the sample piece is placed in the center of the sample piece between the sample piece separation step and the sample piece probe transfer step. By irradiating the focused ion beam, a thin wall portion forming step of forming a thin wall portion having a thickness of about 100 nm is added.

According to the present invention, it is possible to perform a consistent sample preparation process in a vacuum environment in a sample processing chamber with little manual intervention for handling a series of minute sample pieces, which saves time and cost compared to the conventional method. In addition, the possibility of contamination and damage to the observation sample surface can be eliminated.

1 and 2 are schematic views showing a basic configuration of a sample preparation apparatus according to the present invention.
In FIG. 1, a sample processing chamber 1 having an evacuation function includes a focused ion beam (FIB) irradiation optical system 2 and a secondary electron detector 3 for processing a sample piece and observing an image of the vicinity of the processed portion, and a focusing point. A deposition gas source 4 for forming a deposition film in the ion beam irradiation area, an original sample 5 is installed, a sample moving mechanism 6 for giving a relative displacement with respect to the ion beam, and a sample piece are collected. Sample piece probe 7
A sample piece probe holder 8 and a sample piece probe moving mechanism 9 to which the sample piece probe 7 can be attached and detached, and an observation sample holder 10 and an observation sample holder moving mechanism 11 for mounting the sample piece probe 7 alone are installed. .

In FIG. 2, the sample piece probe 7 is configured by integrally connecting a chuck plate 12 serving as a connecting portion with the sample piece probe holder 8, an inclined spacer 13, and a cantilever 14 holding the sample piece 15. Is done. Where the cantilever
14 needs to have a clearance angle of 15 to 20 ° with the chuck plate 12 by the inclined spacer 13. This is because when the electron beam of TEM is irradiated vertically on the drawing,
This is because the sample probe 7 must also be installed vertically, and the cantilever 14 prevents the transmission electron beam from being scattered unless there is an appropriate clearance angle.

Next, the 1st sample preparation method by the component of said sample preparation apparatus is demonstrated. 3, 4 and 5 are diagrams showing an outline of the first sample preparation method according to the present invention.

FIG. 3 (a) shows a method of forming the sample piece 15 with a focused ion beam. First, a processing target position is marked on the original sample 5 with a laser or the like in advance (marking step, not shown). On the other hand, as shown in FIG.
1, the sample piece probe 7 installed in the observation sample holder 10 in advance is transferred to the sample piece probe holder 8 by visual field observation using a focused ion beam (sample piece probe changing step). Here, the movement for positioning the sample piece probe holder 8 and the observation sample holder 10 is performed by the sample piece probe moving mechanism 9 and the observation sample holder moving mechanism 11 of FIG.

The original sample 5 is transported to the sample processing chamber 1, and the marking position and the beam position are aligned by the sample moving mechanism 6. Next, by irradiation with a focused ion beam, a hatched region is originally formed in a hatched region by a combination of a rectangular vertical processing unit and an inclined processing unit as shown in a plan view of the processing unit enlarged in a circle in FIG. Sample 5 is removed. In the case of this tilting process, the sample moving mechanism 6 is tilted. As a result, the sample pieces 15 connected in a cantilevered state can be formed (sample piece forming step).

FIG. 3 (b) shows the cantilever 14 when the sample piece probe 7 is brought close to the sample piece 15 after molding.
The state which made the front-end | tip contact is shown. In this approach, the sample piece 15 is fixed at the center of the field of view, and the approach and contact are performed by three-dimensional precision movement of the sample piece probe moving mechanism 9. The tip of the cantilever 14 is shaped so that it can be brought into contact with the surface of the original sample 5 across both ends of the sample piece 15 and the vertical processing portion. This is because when the contact end of the cantilever 14 comes into contact with the original sample 5, it is supported by the surface of the original sample 5, and the sample piece 15 in the cantilever state is pressed down too much so that the cantilevered portion is not damaged. Yes (sample piece probe contact step).

FIG. 4A shows a method of connecting the contact end of the cantilever 14 and the sample piece 15 and separating the sample piece 15 from the original sample 5. Cantilever 14 focused ion beam irradiation area
Is set to an area (black circle indicating portion) extending over the contact end of the sample piece 15 and the sample piece 15. Then, for example, hexacarbonyl tungsten (W (CO
₆ ) The deposition gas such as ₆ ) is irradiated and a tungsten film is formed on the contact end and the sample piece 15 to connect them (sample piece connecting step).

Next, the cantilever portion is removed by irradiation with a focused ion beam to separate the sample piece 15 from the original sample 5 (sample piece separation step).

Next, as shown in FIG. 5, the sample piece probe 7 held by the sample piece probe holder 8 is transferred to the observation sample holder 10 by visual field observation using a focused ion beam (sample piece probe transfer step).

In the sample preparation method as described above, when preparing a sample for TEM observation, in addition to the above steps, a sample piece separation step and a sample piece probe transfer step are performed as shown in FIG.
As shown in (b), the central portion of the sample piece 15 is irradiated with a focused ion beam to form a thin wall portion having a thickness of about 100 nm (thin wall portion forming step).

The sample preparation apparatus and sample preparation method described above are for wafers (6 to 12 inches in size).
This is suitable when a relatively large original sample is placed on the sample moving mechanism to create a sample piece. However, when a relatively small original sample such as a tip (about 5 mm square) is handled, the explanation is given below. It is effective to perform a sample preparation method using a sample preparation device.

FIG. 6 is a schematic diagram showing the basic configuration of the second sample preparation apparatus according to the present invention. FIG.
In the sample processing chamber 1 having a vacuum evacuation function, a focused ion beam (FIB) irradiation optical system 2 and a secondary electron detector 3 for processing a sample piece and observing an image in the vicinity of the processed portion, a focused ion beam A deposition gas source 4 for forming a deposition film in the irradiation region, a sample piece probe 7 for collecting a sample piece 15, a sample piece probe holder 8 and a sample piece to which the sample piece probe 7 can be attached and detached Probe moving mechanism
9, an observation sample holder 16 on which the sample piece probe 7 alone and the original sample 17 are mounted, and an observation sample holder moving mechanism 18 are installed.

Next, a second sample preparation method using the constituent elements of the second sample preparation apparatus described above is the first.
This will be described with reference to FIG. A processing target position is marked on the original sample 17 with a laser or the like in advance (marking step), and the original sample 17 is placed in the observation sample holder 16 together with the sample piece probe 7 and then introduced into the sample processing chamber 1.

Next, as shown in FIG. 7 (a), the sample piece probe 7 placed on the observation sample holder 16 is observed by visual field observation using a focused ion beam, and then the sample piece probe holder 8 is used.
(Sample piece probe change process). Here, the movement for alignment of the sample piece probe holder 8 and the observation sample holder 16 is performed by the sample piece probe moving mechanism 9 and the observation sample holder moving mechanism 18 of FIG.

Next, the marking position and the beam position of the original sample 17 installed on the observation sample holder 16 are matched by the observation sample holder moving mechanism 18. Hereinafter, the sample piece forming step, the sample piece probe contacting step, the sample piece connecting step, and the sample piece separating step are performed on the observation sample holder 16 as shown in FIG. This is the same as the sample preparation method.

Next, as shown in FIG. 7C, the sample piece probe 7 held by the sample piece probe holder 8 is transferred to the observation sample holder 16 by visual field observation using a focused ion beam (sample piece probe transfer). Process).

Even in the second sample preparation method as described above, when preparing a sample for TEM observation, in addition to the above-described steps, the sample piece separation step and the sample piece probe transfer step are performed as shown in FIG. ), A thin wall portion having a thickness of about 100 nm is formed by irradiating the central portion of the sample piece 15 with a focused ion beam (thin wall portion forming step).

By the way, in the sample piece probe contact step in the first sample preparation method and the second sample preparation method, it is possible to relatively accurately align the tip of the sample piece probe 7 by visual field observation. Since it is difficult to obtain position information in the vertical direction, it is difficult to make accurate contact.

Therefore, in addition to visual field observation, it is desirable to provide means for detecting that the tip of the sample piece probe 7 is in contact with the surface of the original sample 5 or 17.

FIG. 8 is a diagram showing an example of means for detecting contact of the tip of the sample piece probe. First
As shown in FIG. 8 (a), a piezoelectric element 23 is installed on the back surface of the sample piece probe holder 8, and the ultrasonic vibration in the resonance state of the sample piece probe holder 8 is applied by the piezoelectric element 23 as shown in FIG. The contact detection can be performed by measuring the disturbance of the resonance state due to the contact of the tip of 7.

Further, as shown in FIG. 8 (b), the sample piece probe holder 8 generated by the contact is provided.
The elastic deformation is detected by touching a strain gauge 25 on the back surface of the sample piece probe holder 8 and measuring a change in resistance.

Further, in FIG. 8, as a means for the sample piece probe holder 8 to hold the sample piece probe 7 in the first and second sample preparation apparatuses according to the present invention, aluminum nitride or the like is used as an insulating film on the surface of the sample piece probe holder 8 and Johnson. A bipolar electrostatic chuck 24 that generates an attracting force due to the Labebeck force is formed.

Now, it is a method of handling the observation sample holder 10 and the observation sample holder 16 of the first and second sample preparation apparatuses described above. The observation sample holder must be exchanged for each processing, but this is the sample. It is not efficient in terms of time to exchange the processing chamber 1 in the atmospheric state every time. In order to improve this, it is necessary to provide the observation sample holder moving mechanism with an air lock structure so that the sample processing chamber is not exposed to the atmosphere when the observation sample holder is inserted and removed.

Hereinafter, although the means itself is publicly known, how to perform the air lock of the observation sample holder will be described with reference to FIG. This air lock structure is configured by including a vacuum pump 22 as means for evacuating the space between the front shaft seal 21, the rear shaft seal 20, the shutoff valve 19, the front shaft seal 21, and the rear shaft seal 20. here,
For example, when the observation sample holder 16 is inserted, the shutoff valve 19 is closed in contact with the rear shaft seal 20 when the observation sample holder 16 passes through the front shaft seal 21.

Further, since the space between the front shaft seal 21 and the rear shaft seal 20 is evacuated, the sample processing chamber 1 can maintain a vacuum state. Next, at the stage where the observation sample holder 16 passes through the rear shaft seal 20, the passage portion of the observation sample holder 16 is already in a vacuum state by the front shaft seal 21, so even if the shutoff valve 19 is opened, Sample processing chamber 1
Can maintain a vacuum state. Conversely, when the observation sample holder 16 is extracted, the same vacuum can be maintained, so that the sample processing chamber 1 is not exposed to the atmosphere.

Schematic which shows the basic composition of the 1st sample preparation apparatus by this invention. The principal part schematic which shows the basic composition of the 1st sample preparation apparatus by this invention. Explanatory drawing which shows the 1st sample preparation method by this invention. Explanatory drawing which shows the 1st sample preparation method by this invention. The perspective view which shows the 1st sample preparation method by this invention. Schematic which shows the basic composition of the 2nd sample preparation apparatus by this invention. The perspective view which shows the 2nd sample preparation method by this invention. The side view which showed the means of contact detection of the front-end | tip of the sample piece probe by this invention. Explanatory drawing of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Sample processing chamber, 2 ... Focused ion beam irradiation optical system, 3 ... Secondary electron detector, 4 ... Deposition gas source 4, 5 ... Original sample, 6 ... Sample moving mechanism, 7 ... Sample piece probe, 8 ... Sample piece probe holder, 9 ... Sample piece probe moving mechanism, 10 ... Sample holder for observation, 11
... Observation sample holder moving mechanism, 12 ... Chuck plate, 13 ... Inclined spacer, 14 ...
Cantilever, 15 ... sample piece, 16 ... observation sample holder, 17 ... original sample, 18 ... observation sample holder moving mechanism, 19 ... shutoff valve, 20 ... rear shaft seal, 21 ... front shaft seal, 22 ... vacuum pump, 23 ... piezoelectric element, 24 ... electrostatic chuck, 25 ... strain gauge, 101 ... wafer, 1
02 ... Strip pellet, 103 ... Semicircular metal plate, 104 ... Holder for TEM observation.

Claims (9)

A sample processing chamber having a vacuum exhaust function;
A sample moving mechanism for placing a sample installed in the sample processing chamber;
A focused ion beam irradiation optical system for irradiating the sample with a focused ion beam;
A sample piece probe with a strain gauge for collecting a sample piece from the sample in the sample processing chamber;
A sample piece probe moving mechanism for moving the sample piece probe in the optical axis direction of the focused ion beam irradiation system in the sample processing chamber ;
An observation sample holder installed in the sample processing chamber and holding the sample piece collected via the sample piece probe;
An observation sample holder moving mechanism having a structure for moving the position of the observation sample holder and performing the movement without exposing the sample processing chamber to the atmosphere when the observation sample holder is inserted and removed. The sample preparation apparatus characterized by the above-mentioned. A sample preparation device capable of irradiating a sample with a focused ion beam and preparing a sample piece for observation with a transmission electron microscope or a scanning electron microscope in a sample processing apparatus,
A focused ion beam irradiation optical system for irradiating the sample with the focused ion beam;
A sample moving mechanism for placing the sample;
A sample processing chamber having a vacuum exhaust function,
The sample processing chamber is
A sample piece probe with a strain gauge for collecting the sample piece from the sample in the sample processing chamber;
A movable observation sample holder to which the sample piece can be transferred via the sample piece probe is further provided in the sample processing chamber,
The sample preparation apparatus, wherein the observation sample holder has a structure that can be inserted and removed without exposing the sample processing chamber to the atmosphere . In the sample preparation device according to claim 1 or 2,
The sample preparation apparatus according to claim 1, wherein the strain gauge is arranged to face the focused ion beam irradiation optical system of the sample piece probe . In the sample preparation device according to claim 1 or 2,
A sample preparation device , wherein the strain gauge detects that the sample piece probe is in contact with the sample. In the sample preparation device according to claim 4,
It is detected by measuring the resistance change of the strain gauge that the contact is detected . In the sample preparation device according to claim 1,
The sample piece probe moving mechanism has a structure capable of moving in three orthogonal directions with the optical axis direction as one axis . In the sample preparation device according to claim 1 or 2,
The sample preparation apparatus , wherein the sample is a wafer . In the sample preparation device according to claim 1 or 2,
Furthermore, the sample preparation apparatus further comprises an observation sample holder disposed in the sample processing chamber for holding the sample piece collected via the sample piece probe . In the sample preparation device according to claim 8,
The sample preparation apparatus , wherein the observation sample holder includes an air lock structure .

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