JP6487294B2 - Compound charged particle beam system - Google Patents

Description

  The present invention relates to a composite charged particle beam apparatus in which a plurality of charged particle beam apparatuses are integrated.

  2. Description of the Related Art In recent years, with the miniaturization of semiconductor device patterns, the importance of techniques for observing and evaluating specific minute portions of a semiconductor device with a transmission electron microscope (TEM: Transmission Electron Microscope) is increasing. A focused ion beam (FIB) apparatus is widely used to prepare such a sample that becomes a specific minute portion. However, the sample preparation by FIB is performed with a thickness of several nanometers to several tens of nanometers on the surface of the specimen. nm is altered. This altered layer is referred to as a damaged layer. As the thickness required for the thinned sample decreases, the ratio of the damaged layer to the total thickness of the sample relatively increases, which hinders TEM observation. Therefore, a method for removing the damaged layer on the surface of the thinned sample for TEM observation is required.

  In Patent Document 1, as a solution to the above situation, for example, a method of irradiating an ion beam having an ion species of an element having low chemical activity such as argon with a low acceleration voltage of several kilovolts or less is proposed. In order to perform the damage removal process reliably and efficiently, the axis of the FIB column and the axis of the scanning electron microscope are substantially perpendicular to the eucentric tilt axis of the sample stage, and the FIB column It is disclosed in Patent Document 2 that it is effective to arrange the axis, the axis of the gas ion beam column, and the eucentric tilt axis in a practical relationship in one plane. Thus, it is possible to irradiate the gas ion beam at a shallow angle by tilting the sample surface processed by FIB by an appropriate angle, and the sample surface being processed can be observed with a scanning electron microscope.

JP-A-10-212227 JP 2007-164992 A

  However, in the apparatus disclosed in Patent Document 2, since the scanning electron microscope is arranged so as to be sandwiched between the sample and the focused ion beam column, there is a problem in that the distance between the scanning electron microscope and the sample cannot be shortened. is there. In general, the scanning electron microscope tends to improve the observation capability as the distance from the sample is shorter. Improving the observation capability of a scanning electron microscope is a very important issue in order to reliably produce an extremely thin film sample having a very fine structure.

  The present invention has been made in view of such circumstances, and its purpose is to produce a thinned sample for TEM observation with a focused ion beam device and to damage the surface of the sample with a gas ion beam device with a low acceleration voltage. An object of the present invention is to provide a composite charged particle beam apparatus in which a distance between an electron microscope and a sample can be arranged short in order to observe a state of a sliced sample with high resolution in a series of steps in an apparatus for removing a layer.

In order to achieve the above object, the present invention provides the following means.
A compound charged particle beam apparatus according to the present invention includes a focused ion beam column that irradiates a focused ion beam to thin a sample, and a gas ion that irradiates a gas ion beam having a low acceleration voltage for removing a damaged layer of the sample. A beam column and a scanning electron microscope column for irradiating an electron beam for observing a thinned sample formed while thinning the sample with the focused ion beam from a vertical direction are arranged.

  A composite charged particle beam apparatus according to the present invention includes a focused ion beam column, a scanning electron microscope column, and a gas ion beam column with a low acceleration voltage, and a beam irradiation axis of the focused ion beam column includes: The beam irradiation axis of the scanning electron microscope tube is substantially orthogonal, the beam irradiation axis of the gas ion beam column is arranged to intersect the beam irradiation axis of the scanning electron microscope tube at an angle smaller than 90 degrees, and the scanning An angle formed by the beam irradiation axis of the electron microscope column and the beam irradiation axis of the gas ion beam column is a line segment obtained by projecting the beam irradiation axis of the gas ion beam column onto a plane perpendicular to the axis of the scanning electron microscope column. Each of the focused ion beam, electron beam, and gas beam is mounted on the sample stage so that the angle formed by the beam irradiation axis of the gas ion beam column is larger than the angle formed by the sample. A step of thinning the sample with the focused ion beam and removing a damaged layer of the thinned sample with a gas ion beam having a low acceleration voltage. It is characterized in that the measurement is performed while observing the sample from the vertical direction with the scanning electron microscope tube.

  According to the present invention, a thinned sample is produced by a focused ion beam device while observing the state of a thinned sample for TEM observation by shortening the distance between the electron microscope and the sample, and a gas ion beam having a low acceleration voltage is produced. An apparatus capable of performing a series of steps for removing a damaged layer on the sample surface with the apparatus is realized, and a thinned sample for TEM observation for observing a minute structure can be reliably produced.

1 is a perspective view of a composite charged particle beam apparatus according to the present invention. (A) Configuration diagram of a surface having an irradiation axis of a focused ion beam column and an irradiation axis of a gas ion beam column, (b) an irradiation axis and scanning of the focused ion beam column of the composite charged particle beam apparatus according to the present invention. It is a block diagram of the surface which has the irradiation axis | shaft of an electron microscope. It is a block diagram of the composite charged particle beam apparatus which concerns on this invention. It is a layout view of a conventional composite charged particle beam apparatus.

  Hereinafter, embodiments of the composite charged particle beam apparatus according to the present invention will be described. The description of the present embodiment is an exemplification, and the configuration of the present invention is not limited to the following description.

<Embodiment 1>
FIG. 1 is a diagram illustrating an embodiment of the present invention. The sample 4 is arranged using a sample stage so that the thickness direction in which the sample 4 is thinned becomes a direction parallel to the axis 8 of the scanning electron microscope. The sample placement method is such that there is no protrusion in the thickness direction of the sample 4. The scanning electron microscope 2 is arranged with respect to the surface of the sample 4 so that the axis 8 of the scanning electron microscope is vertical. Further, the focused ion beam column 1 is arranged so that the axis 7 of the focused ion beam column intersects the axis 8 of the scanning electron microscope at a right angle at the position of the sample 4. With such an arrangement, the distance 10 between the sample and the scanning electron microscope can be significantly reduced as compared with the configuration of the conventional apparatus shown in FIG. Accordingly, the size of the sample that can be processed by the apparatus is limited. However, since a thin sample for a TEM sample is generally smaller than a disk having a diameter of 3 mm, it is not a great limitation.

  FIG. 2A is a configuration diagram of a surface having the axis 8 of the focused ion beam column and the axis 9 of the gas ion beam column of the composite charged particle beam apparatus of FIG. FIG. 2B is a configuration diagram of a surface having the axis 8 of the focused ion beam column and the axis 8 of the scanning electron microscope of the composite charged particle beam apparatus of FIG. Since the scanning electron microscope 2 is arranged without being sandwiched between the focused ion beam column 1 and the sample 4, the distance between the tip of the scanning electron microscope 2 and the sample 4 is determined based on the tip of the focused ion beam column 1 or the gas ion beam mirror. It can be made shorter than the tip of the tube 3.

  FIG. 3 is a configuration diagram of the composite charged particle beam apparatus. A focused ion beam 21 from the focused ion beam column 1, an electron beam 22 from the scanning electron microscope 2, and a gaseous ion beam 23 from the gaseous ion beam column 3 are arranged at positions where the sample 4 can be irradiated. The sample 4 is attached to the sample stage 24 in the sample chamber 30. Further, a secondary electron detector 26 that detects secondary electrons generated from the sample 4 and a transmission electron detector 25 that detects transmission electrons irradiated from the scanning electron microscope 2 and transmitted through the sample 4 are provided. Detection signals detected by the respective detectors are sent to the control unit 27 and combined with the beam scanning signal, an observation image is formed. The observation image is displayed on the display unit 28.

  The sample 4 is processed into a thin piece shape using the focused ion beam column 1. A damaged layer is formed on the surface of the sample 4 at the time when the thinning by the focused ion beam 21 is completed. In order to remove the damaged layer, the gas ion beam 23 having an acceleration voltage of 1 kV is irradiated using the gas ion beam column 3. In many cases, a rare gas is used as a gas to be ionized, and argon is used in this example. In the conventional example, the irradiation angle of the gaseous ion beam is adjusted by rotating the sample. However, in the configuration according to the present invention, since the angle 6 formed by the axis of the scanning electron microscope and the axis of the gas ion beam column is small, it is difficult to rotate the sample 4 greatly. The gas ion beam column 3 is disposed at the position.

  Next, a method for determining the mounting angle will be described below. Since it is desired to observe the change of the surface irradiated with the gas ion beam 23 with the scanning electron microscope 1, the angle 6 formed by the axis of the scanning electron microscope and the axis of the gas ion beam column needs to be smaller than 90 degrees. Furthermore, it is necessary to select and attach an angle range in which the trajectory of the gaseous ion beam 23 is not blocked by the tip of the scanning electron microscope 2. If the incident angle of the gas ion beam 23 is too large with respect to the irradiation surface, the smoothness of the surface of the sample 4 is impaired. Conversely, if the angle is too shallow, it takes too much time to remove the damaged layer on the surface. Therefore, the angle 6 formed by the axis of the scanning electron microscope and the axis of the gas ion beam column is preferably 60 degrees or more and 88 degrees or less. In this example, the angle 6 formed by the axis of the scanning electron microscope and the axis of the gas ion beam column is 60 degrees. For the above reasons, the gas ion beam column 3 has at least an angle 6 formed by the axis of the scanning electron microscope and the axis of the gas ion beam column. The axis of the gas ion beam column and the axis of the gas ion beam column are scanned by the scanning electron microscope. It is preferable to arrange such that it is larger than the angle 12 formed by the line segment projected on the plane perpendicular to the axis.

  All the steps up to here can be performed while observing very minute changes and structures because the distance 10 between the sample and the scanning electron microscope can be used at a short distance that is optimal for the scanning electron microscope 2. The challenge has been achieved.

<Embodiment 2>
In the first embodiment, the incident angle of the gaseous ion beam 23 with respect to the sample 4 is fixed, but in practice, it may be necessary to adjust it according to the characteristics of the sample. In such a case, the first tilting mechanism 31 that holds the sample 4 near the intersection of both the axis 7 of the focused ion beam column and the axis 8 of the scanning electron microscope and tilts the sample by the axis orthogonal to both is provided. By providing the sample stage 24, the incident angle of the gaseous ion beam 23 with respect to the sample 4 can be adjusted. Since tilting the sample 4 greatly affects the observation ability of the scanning electron microscope 2, it is desirable that the practical incident angle can be controlled within a relatively small tilt angle range. In such a case, the angle in a practical range can be controlled with a relatively small inclination by attaching the gas ion beam column 3 with an angle in advance as described in the first embodiment. . As an example, when the gas ion beam column 3 and the focused ion beam column 1 are viewed from the direction of the scanning electron microscope 2, they have an angle of 60 degrees, and the axis of the scanning electron microscope and the axis of the gas ion beam column are If the formed angle 6 is 70 degrees, the incident angle can be controlled within a range of approximately 11 degrees to 29 degrees with an inclination of ± 10 degrees.
Thereby, it is possible to control the incident angle of the gaseous ion beam 23 while maintaining the advantages described in the first embodiment.

<Embodiment 3>
For the same purpose as in the second embodiment, the sample 4 is held near the intersection of the beam of the focused ion beam column 1 and the scanning electron microscope 2, and the sample is tilted by a rotation axis parallel to the axis of the focused ion beam column 1. By providing the sample stage 24 with the second tilt mechanism 32 to be performed, the incident angle of the gaseous ion beam can be controlled. As an example, when the gas ion beam column 3 and the focused ion beam column 1 are viewed from the direction of the scanning electron microscope 2, they have an angle of 30 degrees, and the axis of the scanning electron microscope and the axis of the gas ion beam column are If the formed angle 6 is 70 degrees, the incident angle can be controlled within a range of approximately 11 degrees to 29 degrees with an inclination of ± 10 degrees.

<Embodiment 4>
It is also preferable to provide a plurality of gas ion beam column 3. In general, when the sample 4 is composed of a plurality of materials, the etching rate of the sample surface by the gaseous ion beam 23 is not the same. When a part of the material that does not easily progress in etching is included, a part where etching progresses slowly is formed as if a line is drawn behind the material that is difficult to scrape when viewed from the incident direction of the gas ion beam 23. Therefore, such a phenomenon can be suppressed by providing a plurality of gas ion beam column 3 and irradiating the gas ion beam from a plurality of directions. Also in this example, the subject of this invention can be achieved by arrange | positioning the gaseous ion beam column 3 within the range of the conditions mentioned above.

DESCRIPTION OF SYMBOLS 1 ... Focusing ion beam column 2 ... Scanning electron microscope 3 ... Gas ion beam column 4 ... Sample 5 ... The angle which the axis | shaft of a scanning electron microscope and the axis | shaft of a focused ion beam column 6 ... Axis of a scanning electron microscope and gas ion Angle formed by the axis of the beam column 7 ... axis of the focused ion beam column 8 ... axis of the scanning electron microscope 9 ... axis of the gas ion beam 10 ... distance between the sample and the scanning electron microscope 11 ... the axis of the gas ion beam column Line segment projected on a plane perpendicular to the axis of the scanning electron microscope 12 ... Angle formed by a line segment projected on the plane perpendicular to the axis of the scanning electron microscope with the axis of the gas ion beam column and the axis of the gas ion beam column 21 ... focused ion beam 22 ... electron beam 23 ... gaseous ion beam 24 ... sample stage 25 ... transmission electron detector 26 ... secondary electron detector 27 ... control unit 28 ... display unit 30 ... sample chamber 31 ... first tilt mechanism 32 ... Second tilting mechanism

Claims (2)

A focused ion beam column that irradiates the focused ion beam to thin the sample;
A gas ion beam column for irradiating a gas ion beam with a low acceleration voltage for removing a damaged layer of the sample;
A scanning electron microscope tube for irradiating an electron beam for observing a thinned sample formed while thinning the sample with the focused ion beam from a vertical direction;
A sample stage for holding the sample near the intersection of the beam irradiation axis of the focused ion beam column and the beam irradiation axis of the scanning electron microscope tube;
The beam irradiation axis of the focused ion beam column is substantially orthogonal to the beam irradiation axis of the scanning electron microscope tube,
The beam irradiation axis of the gas ion beam column is arranged to intersect with the beam irradiation axis of the scanning electron microscope column at an angle smaller than 90 degrees,
The sample stage, by the focused ion beam column substantially parallel to the rotation axis and the beam irradiation axis of, e Bei a tilting mechanism for tilting said specimen,
The tilting mechanism has a diameter smaller than the diameter of the focused ion beam column . A sample is placed near the intersection of a focused ion beam column, a scanning electron microscope tube, a low acceleration voltage gas ion beam column, a beam irradiation axis of the focused ion beam column and a beam irradiation axis of the scanning electron microscope column. A sample stage to hold,
The beam irradiation axis of the focused ion beam column is substantially orthogonal to the beam irradiation axis of the scanning electron microscope tube,
The beam irradiation axis of the gas ion beam column is arranged to intersect the beam irradiation axis of the scanning electron microscope tube at an angle smaller than 90 degrees, and the beam irradiation axis of the scanning electron microscope tube and the gas ion beam mirror An angle formed by the beam irradiation axis of the tube is formed by a line segment obtained by projecting the beam irradiation axis of the gas ion beam column onto a plane perpendicular to the axis of the scanning electron microscope tube and the beam irradiation axis of the gas ion beam column. A charged particle beam apparatus in which each of a focused ion beam, an electron beam, and a gas beam is arranged at a position where the sample attached to the sample stage can be irradiated so as to be larger than an angle,
The step of thinning the sample with the focused ion beam and removing the damaged layer of the thinned sample with a gas ion beam of low acceleration voltage is performed while observing the thinned sample from the vertical direction with the scanning electron microscope tube. ,
The sample stage, by the focused ion beam column substantially parallel to the rotation axis and the beam irradiation axis of, e Bei a tilting mechanism for tilting said specimen,
The tilting mechanism has a diameter smaller than the diameter of the focused ion beam column .

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