JP2010135132A - Sample stage for focused ion beam processing device, and method for making transmission type electron microscope plane-observed semiconductor thin sample - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sample stage for a focused ion beam processing device, using an easy method for inexpensively making a plane-observed semiconductor thin sample, and to provide a method using the same for making the transmission type electron microscope plane-observed semiconductor thin sample. <P>SOLUTION: The sample stage face has an inclined groove for holding a mesh on the sample stage face. With the emission of focused ion beams, a micro sample piece is cut out of a sample substrate, and separated and picked out by a microprobe, and then the mesh held in the inclined groove of the sample stage face is inclined so that the side face of the mesh is directed perpendicular to the focused ion beams. The micro sample piece adheres to the end face of the mesh so that its observed plane is directed perpendicular to the focused ion beams, and then the inclined sample stage is rotated 180° around the rotational axis. The focused ion beams are emitted to make the transmission type electron microscope plane-observed semiconductor thin sample. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a method for producing a semiconductor thin-film sample for planar observation of a transmission electron microscope (TEM) by a microsampling method using a focused ion beam processing apparatus (FIB apparatus), and more particularly, a planar surface of a semiconductor substrate or a semiconductor chip. The present invention relates to a sample stage of an FIB apparatus for producing a semiconductor thin piece sample for observation.

In order to observe a sample with a TEM, it is necessary to slice the sample to a thickness (0.1 μm or less) through which an electron beam can pass. In particular, a semiconductor substrate such as a silicon substrate (silicon wafer) is used. In recent years, it has become common to thin a semiconductor element manufactured by using an FIB apparatus. After bonding the microprobe mounted on the FIB apparatus to a large sample substrate such as a silicon wafer or a chip placed flat on the sample stage, a small sample piece with a side of several tens of μm is cut out by a focused ion beam, The micro sample piece is separated and extracted by a microprobe and bonded to the end face of a thin plate-like sample piece holding plate called a mesh placed in the same sample stage surface, and then the micro sample piece is irradiated with a focused ion beam. The thinning method is called a microsampling method. Usually, the preparation of a semiconductor thin film sample for TEM observation using an FIB apparatus is mainly aimed at the preparation of a semiconductor thin film sample for observation of a vertical section perpendicular to the main plane of the semiconductor element substrate, but was observed in a cross section parallel to the main plane. In many cases, the observation target can be accurately grasped and is suitable for the purpose of observation, and there is a great need for manufacturing a semiconductor thin film sample for observation of a cross section (hereinafter abbreviated as a plane). A method for producing a semiconductor thin-film sample for planar observation is disclosed by the microsampling method (Patent Document 1). According to the micro-sampling method described in Patent Document 1, in order to produce a semiconductor thin piece sample for planar observation, the mesh (sample piece holding plate) is turned 90 degrees in the middle of the process and bonded to the mesh. It is necessary to change the cutting direction of the minute sample piece by 90 degrees and change the longitudinal section cut to the transverse section cut. First, after attaching a microprobe to a portion to be cut out of a fine sample piece on the surface of a sample substrate such as a wafer or chip placed flat on the sample stage, a focused ion beam is irradiated to form a semiconductor thin piece sample for planar observation. A small sample piece including a region to be processed is cut out. The micro sample piece is separated and extracted from the sample substrate and transferred to the end face of a thin plate-like mesh (sample piece holding plate). At this time, since the direction of the micro sample piece cut out and bonded to the microprobe cannot be changed at this stage, the micro sample piece is bonded to the end face of the mesh erected perpendicularly to the sample stage surface in the same direction. Thereafter, when the fine sample piece is thinned by irradiating with a focused ion beam, a semiconductor thin piece sample having a longitudinal section is produced, but a semiconductor thin piece sample having a transverse section (plane) cannot be produced as it is. Therefore, as shown in the enlarged cross-sectional view of the mesh end in FIG. 10A, the direction of the thin mesh 2 is once changed to be parallel to the sample stage surface, and then the minute sample piece 5 is moved to the mesh 2. Adhere to the end face. Next, since the irradiation direction (arrow) of the focused ion beam is fixed in the direction perpendicular to the sample stage surface, the direction of the minute sample piece 5 bonded to the mesh 2 is set to 90 as shown in FIG. It is necessary to change the thickness so that the observation plane 8 indicated by the broken line is parallel to the irradiation direction (arrow) of the focused ion beam.
Japanese Patent No. 3805547

  However, a general FIB apparatus is mainly intended to produce a semiconductor thin piece sample for observing a longitudinal section as described above, and is perpendicular to the surface of a sample substrate placed horizontally on a sample stage surface. A focused ion beam is incident in the direction. When irradiating the sample substrate with the tilted focused ion beam, the sample stage is not tilted but the sample stage is tilted. In addition to the tilt angle control mechanism, the sample stage also includes an axis rotation mechanism and a position control mechanism (XY manipulator). The method of fixing the mesh to the sample stage is also premised on vertical cross section processing, so a thin mesh is sandwiched in a vertical groove provided on the sample stage surface and the mesh is held perpendicular to the sample stage surface. Yes. As a result, the irradiation direction of the focused ion beam becomes perpendicular to the observation plane of the minute sample piece adhered to the end face of the thin plate mesh. Therefore, if a minute sample piece is thinned by focused ion beam irradiation as it is, a thin piece sample having a longitudinal section is produced. In addition, the sample stage is provided with a tilt mechanism that works integrally with the base by a base attached to the lower part of the sample stage. There are many mechanisms that only tilt to about 45 to 60 degrees. Therefore, in such a device having a limited tilt angle control mechanism, as described in Patent Document 1 described above, the mesh direction is set to the tilt angle (90 degrees) necessary for the production of the semiconductor thin film sample for plane observation. I can't change it. The FIB apparatus described in Patent Document 1 having a mechanism capable of setting the mesh direction to an inclination angle of 90 degrees or more for producing a semiconductor thin-film sample for planar observation is usually very expensive. .

  The present invention has been made in view of the above-described problems, and provides a planar observation of a sample stage and a transmission electron microscope of a focused ion beam processing apparatus that enables a semiconductor thin-film sample for planar observation to be produced at low cost by a simple method. An object of the present invention is to provide a method for producing a semiconductor thin film sample.

  According to the first aspect of the present invention, in order to produce the surface on which the main surface of the semiconductor substrate sample is placed in a state of facing the focused ion beam and the semiconductor thin film sample for transmission electron microscope plane observation Further, the object of the present invention is achieved by having an inclined groove for holding a mesh for holding a micro sample piece cut out from the semiconductor substrate sample by the focused ion beam.

According to a second aspect of the present invention, the angle formed by the inclined direction of the inclined groove and the surface on which the semiconductor substrate sample is placed is 20 to 70 °. The sample stage of the focused ion beam processing apparatus.
According to the third aspect of the present invention, the sample stage of the focused ion beam processing apparatus according to the first or second aspect of the present invention is supported, and the position control of the sample stage and the tilt and rotation of the sample stage are supported. The focused ion beam apparatus according to the claims is provided with a base having the control mechanism.

  According to the invention described in claim 4, the irradiation direction of the focused ion beam is placed and fixed on the sample stage of the focused ion beam processing apparatus according to claim 1 or 2. A step of cutting a micro sample piece by irradiating a focused ion beam after attaching a microprobe to a semiconductor substrate sample having an observation plane perpendicular to the surface, and tilting the sample stage with a mesh held in an inclined groove A step of making a side surface perpendicular to the irradiation direction of the focused ion beam, and attaching the microprobe by adhering the micro sample piece having an observation plane perpendicular to the irradiation direction of the focused ion beam to an end surface of the mesh. Separating the sample stage, rotating the sample stage 180 degrees around the rotation axis, and setting the observation plane of the micro sample piece to the focused ion beam It is possible to provide a method for producing a semiconductor thin film sample for plane observation of a transmission electron microscope, which includes a step of making it parallel to the irradiation direction and a step of thinning by irradiating the focused ion beam parallel to the observation plane of the minute sample piece. .

  The sample stage of the present invention includes a sample stage surface for cutting out a small sample piece from a sample substrate flatly fixed on the sample stage with a focused ion beam, and separating and extracting with a microprobe, and oblique to the sample stage surface. An inclined groove for sandwiching the formed thin mesh (for example, 45 degrees) is provided. A micro sample piece is cut out from a sample substrate fixed on the sample stage surface in a direction perpendicular to the focused ion beam, separated and extracted, and then sandwiched in an inclined groove having an inclination angle (for example, 45 degrees) with respect to the sample stage surface. The sample stage surface is tilted (for example, 45 degrees) in the thin plate-shaped mesh so that the side surface of the mesh is in a direction perpendicular to the focused ion beam. The micro sample piece separated and extracted from the sample substrate is transferred and bonded to the end face of the mesh so that the observation plane is perpendicular to the focused ion beam. After the micro sample piece is transferred and bonded to the end face of the mesh, the tilted sample stage is rotated 180 degrees around the rotation axis. The tilt angle is adjusted (not necessary if the mesh tilt angle is 45 degrees) so that the thin mesh is oriented parallel to the focused ion beam. In this state, the observation plane of the micro sample piece and the focused ion beam are parallel to each other, so that it is easy to make the observation plane thin with the focused ion beam, and it becomes easy to produce a semiconductor thin sample for plane observation.

  According to the above-described present invention, there is provided a sample stage of a focused ion beam processing apparatus and a method for producing a semiconductor thin film sample for plane observation of a transmission electron microscope, which can produce a semiconductor thin film sample for flat observation with a simple method at low cost. can do.

  1A and 1B show a sample stage of an FIB apparatus of the present invention, in which FIG. 1A is a schematic plan view, and FIG. 1B is a cross-sectional view taken along line A-A ′ of FIG. 3 to 8 are views for explaining a method for producing a semiconductor thin film sample for TEM plane observation using the sample stage of the present invention, wherein (a) in each figure is a schematic plan view and (b) in each figure. FIG. 3 is a cross-sectional view taken along line AA ′ in FIG. FIG. 9 is related to a method for producing a semiconductor thin film sample for TEM plane observation using the sample stage of the present invention, (a) is an enlarged cross-sectional view of a micro sample piece before thinning bonded to the end of a mesh, and (b). FIG. 3 is an enlarged cross-sectional view of a semiconductor thin piece sample after thinning. FIG. 11 is a schematic perspective view of an FIB apparatus equipped with a sample stage according to the present invention.

  Hereinafter, an embodiment according to a sample stage of a focused ion beam processing apparatus of the present invention and a method for producing a planar thin film sample for observation using the sample stage will be described in detail with reference to the drawings. The present invention is not limited to the description of the examples described below unless it exceeds the gist.

  FIG. 1A is a plan view showing a sample stage according to one embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along the line A-A ′ of FIG. FIG. 2A is a plan view showing a conventional sample stage, and FIG. 2B is a cross-sectional view taken along line B-B ′ of FIG. As shown in FIG. 1, the sample stage 1 according to the present invention comprises a sample stage surface 1a, an inclined groove 1b of a thin plate-like mesh 2, and a groove width adjusting screw 1c for adjusting the width of the inclined groove 1b. As shown in FIG. 2, the conventional sample stage 101 has grooves 101b formed in a direction perpendicular to the sample stage surface 101a of the sample substrate, whereas the sample stage 1 according to the present invention is shown in FIG. In addition, the inclined groove 1b is formed obliquely with respect to the sample stage surface 1a. The angle formed by the sample stage surface 1a and the inclined groove 1b according to the present invention is the position in the XY direction of the sample stage 1 of the FIB apparatus 20 (FIG. 11) that uses the inclination of the mesh 2 sandwiched between the inclined grooves 1b. By using the control function, the tilt function, and the shaft rotation function, various tilt angles can be controlled within a range that can be controlled in a direction perpendicular to the irradiation direction of the focused ion beam 10 (arrow-FIG. 11) and in a parallel manner. can do. A particularly preferable inclination angle is 20 to 70 degrees. The width of the inclined groove 1b can be finely adjusted with a groove width adjusting screw 1c for sandwiching and fixing the thin mesh 2 (FIGS. 1 and 11). The material of the sample stage 1 is not particularly limited, although metals such as aluminum and brass are used.

The base 4 (shown in FIGS. 3 to 8) of the sample stage 1 is a part of the FIB apparatus 20 (FIG. 11), and functions for controlling the plane XY movement, the shaft rotation angle, and the tilt angle are provided on the base 4. Is transmitted to the sample stage 1 which is held and fixed to the substrate. Although the sample stage 1 is firmly fixed to the upper surface of the base 4 of the FIB apparatus 20, the sample stage 1 can be removed from the base 4.
Hereinafter, an example of a method for producing a planar thin film sample for observation using the sample stage 1 of the present invention will be described with reference to FIGS. 3A to 8A are plan views, and the irradiation direction of the focused ion beam (not shown) is from the front to the back of the drawing. FIGS. 3 to 8B are cross-sectional views taken along line AA 'of FIGS. 3 to 8A, respectively, and the irradiation direction of the focused ion beam (not shown) is from the top to the bottom of the drawings. . FIG. 9 is a view for showing a state of thinning the minute sample piece 5, and is an enlarged sectional view of a portion where the minute sample piece 5 is bonded to the end face of the mesh 2. In this case, the irradiation direction of the focused ion beam (not shown) is from the top to the bottom of the drawing.
(Sample outline)
A chip of a semiconductor device is used as the sample substrate 3, a circular through-hole is provided in the interlayer insulating film formed on the surface of the device, a predetermined semiconductor region directly under the interlayer insulating film is exposed, and the metal conductor is exposed. In order to investigate the embedded state of the metal conductor in the contact structure portion having a function of drawing out necessary electrical connection from the buried semiconductor region to the surface of the interlayer insulating film, the object is to planarly observe the contact structure portion in a ring shape.
(Outline of the sample stage of the present invention)
As shown in FIG. 3, the sample stage 1 of the present invention is made of brass and has a size of 40 mm × 30 mm × 5 mm (horizontal × vertical × thickness). When the sample stage 1 is viewed from above, there is an inclined groove 1 b that forms an angle of 45 degrees with the sample stage surface 1 a at a position 5 mm from the end of the sample stage 1. The width of the inclined groove 1b can be adjusted from 0 to 1 mm by the groove width adjusting screw 1c.
(Processing using FIB equipment)
First, as shown in FIG. 3, the sample substrate 3 is fixed to the sample stage surface 1a with a carbon tape (not shown). The mesh 2 is held between the inclined grooves 1b by tightening the groove width adjusting screw 1c. The sample stage 1 is fixed to the surface of the base 4. The base 4 is an apparatus in the FIB apparatus 20 (FIG. 11) provided with a shaft rotation and tilt control mechanism and a stage position control mechanism (not shown).

Next, as shown in FIGS. 4 and 5, a tungsten microprobe 6 is bonded to the surface of the micro sample piece 5 including the contact structure portion having the embedded metal conductor on the surface of the sample substrate 3, and then the gallium is removed from the sample substrate 3. The ion beam 10 is cut out and separated. Next, as shown in FIG. 6, the sample stage 1 is inclined 45 degrees, and the mesh 2 is made perpendicular to the irradiation direction of the focused ion beam 10. In this state, the micro sample piece 5 adhered to the microprobe 6 is adhered to the end face of the mesh 2, and the micro probe 6 and the micro sample piece 5 are separated by the gallium ion beam 10 (FIG. 7). Adhesion between the microprobe 6 and the minute sample piece 5 and between the minute sample piece 5 and the mesh 2 was performed using a platinum ion beam assisted deposition apparatus 9 shown in FIG. The fine sample piece 5 and the mesh 2 may be bonded using a tungsten ion beam assisted deposition apparatus 9 '. Thereafter, the base 4 is rotated by 180 degrees with respect to the rotation axis of the sample stage 1 shown by a broken line in FIG. 7, so that the mesh 2 is parallel to the irradiation direction of the focused ion beam 10 as shown in FIG. Is 45 degrees). Further, if necessary, the sample stage 1 is finely adjusted so that the mesh 2 is parallel to the irradiation direction of the focused ion beam 10. Then, as shown in FIG. 9B, the micro sample piece 5 is thinned to a thickness of 0.1 μm or less through which an electron beam is transmitted using a gallium ion beam 10 to obtain a semiconductor thin sample for plane observation.
(TEM observation)
After producing the semiconductor thin sample 7 for plane observation in which the micro sample piece 5 was made into a thin piece, the mesh 2 was removed from the inclined groove 1b of the sample stage 1 and set on a sample holder of a TEM (not shown), and TEM observation was performed. The planar image of the contact structure having the embedded metal conductor could be clearly observed, and the state of the embedded metal conductor and the presence or absence of voids or voids could be confirmed.

It is a sample stage of the FIB apparatus of this invention, (a) is a schematic plan view, (b) is the sectional view on the A-A 'line of (a). It is the sample stage of the conventional FIB apparatus, (a) is a schematic plan view, (b) is the BB sectional drawing of (a). It is a figure for demonstrating the preparation method of the semiconductor thin piece sample for TEM plane observation using the sample stage of this invention, (a) is a schematic plan view, (b) is the sectional view on the AA line of (a). is there. It is a figure for demonstrating the preparation method of the semiconductor thin piece sample for TEM plane observation using the sample stage of this invention, (a) is a schematic plan view, (b) is the sectional view on the AA line of (a). is there. It is a figure for demonstrating the preparation method of the semiconductor thin piece sample for TEM plane observation using the sample stage of this invention, (a) is a schematic plan view, (b) is the sectional view on the AA line of (a). is there. It is a figure for demonstrating the preparation method of the semiconductor thin piece sample for TEM plane observation using the sample stage of this invention, (a) is a schematic plan view, (b) is the sectional view on the AA line of (a). is there. It is a figure for demonstrating the preparation method of the semiconductor thin piece sample for TEM plane observation using the sample stage of this invention, (a) is a schematic plan view, (b) is the sectional view on the AA line of (a). is there. It is a figure for demonstrating the preparation method of the semiconductor thin piece sample for TEM plane observation using the sample stage of this invention, (a) is a schematic plan view, (b) is the sectional view on the AA line of (a). is there. (A) is an enlarged cross-sectional view of a micro sample piece before thinning bonded to an end of a mesh, and (b) is a thin piece according to the method for producing a semiconductor thin film sample for TEM plane observation using the sample stage of the present invention. It is an expanded sectional view of the semiconductor thin piece sample after conversion. (A) is an enlarged cross-sectional view showing the relationship between the mesh edge at the time of microsampling and the irradiation direction of the focused ion beam, and (b) is a thinned piece. It is an expanded sectional view which shows the relationship between the mesh edge part at the time, and the irradiation direction of a focused ion beam. 1 is a schematic perspective view of an FIB apparatus equipped with a sample stage according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sample stage 1a Sample stage surface 1b Inclined groove 1c Groove width adjustment screw 2 Mesh 3 Sample substrate 4 Base 5 Micro sample piece 6 Micro probe 7 Semiconductor thin film sample for plane observation 8 Observation plane 9, 9 'Ion beam assist deposition apparatus 10 Ion beam 20 FIB equipment

Claims (4)

A surface on which the main surface of the semiconductor substrate sample is placed in a state facing the focused ion beam, and a microscopic portion cut out from the semiconductor substrate sample by the focused ion beam in order to produce a semiconductor thin film sample for transmission electron microscope plane observation A sample stage of a focused ion beam processing apparatus comprising an inclined groove for holding a mesh for holding a sample piece. 2. The sample stage of the focused ion beam processing apparatus according to claim 1, wherein an angle formed by an inclination direction of the inclined groove and a surface on which the semiconductor substrate sample is placed is 20 to 70 degrees. 3. A focused ion beam apparatus comprising: a base portion that supports the sample stage of the focused ion beam processing apparatus according to claim 1 or 2 and that has a control mechanism for controlling the position of the sample stage and tilting and rotating the shaft. 3. After attaching a microprobe to a semiconductor substrate sample mounted on and fixed to the sample stage of the focused ion beam processing apparatus according to claim 1 and having an observation plane perpendicular to the ion beam irradiation direction, Irradiating a beam to cut out a minute sample piece, tilting the sample stage holding the mesh in an inclined groove to make the side surface of the mesh perpendicular to the irradiation direction of the ion beam, and an end surface of the mesh Bonding the micro sample piece having an observation plane perpendicular to the irradiation direction of the ion beam to separate the micro probe; rotating the sample stage 180 degrees about a rotation axis; and A step of making the observation plane parallel to the irradiation direction of the ion beam, the ion beam parallel to the observation plane of the micro sample piece The method for manufacturing a plain view transmission electron microscopy for the semiconductor thin sample, characterized in that it comprises a step of thinning shines.