US3885158A

US3885158A - Specimen block and specimen block holder

Info

Publication number: US3885158A
Application number: US408836A
Authority: US
Inventors: Richard Edward Flutie; Richard William Belcher
Original assignee: Harris Corp
Current assignee: Harris Corp
Priority date: 1973-10-23
Filing date: 1973-10-23
Publication date: 1975-05-20
Anticipated expiration: 1992-05-20

Abstract

A specimen block which supports a specimen during inspection by both an optical and a scanning electron microscope, and further supports the specimen during a coating operation to enhance secondary electron and X-ray emission, has a planar base and an inclined surface upon which the specimen is to be mounted. During inspection by the scanning electron microscope, the specimen block is held by a standard specimen block holder and the specimen is held at the angle of the inclined surfaces with respect to the base of the holder. During the optical inspection and coating operations, the specimen block is held by a special holder having obliquely bored holes into which the specimen block will fit to compensate for the inclined surface and hold the specimen parallel to the base of the holder. In an alternate mode, the special holder can be used to hold a standard specimen block so that its specimen is at an angle with respect to the holder''s base, for inspection by a scanning electron microscope.

Description

United States Patent 1 Flutie et al.

[ SPECIMEN BLOCK AND SPECIMEN BLOCK HOLDER [75] Inventors: Richard Edward Flutie, Melbourne Beach; Richard William Belcher, lndialantic, both of Fla.

[73] Assignee: Harris Corporation, Cleveland,

Ohio

22 Filed: Oct. 23, 1973 21 Appl. No.: 408,836

Primary Examiner-James W. Lawrence Assistant Examiner-C. E. Church Attorney, Agent, or Firm-Fidelman, Wolffe & Leltner [11] 3,885,158 [451 May 20, 1975 [5 7] ABSTRACT A specimen block which supports a specimen during inspection by both an optical and a scanning electron microscope, and further supports the specimen during a coating operation to enhance secondary electron and X-ray emission, has a planar base and an inclined surface upon which the specimen is to be mounted. During inspection by the scanning electron microscope, the specimen block is held by a standard specimen block holder and the specimen is held at the angle of the inclined surfaces with respect to the base of the holder. During the optical inspection and coating operations, the specimen block is held by a special holder having obliquely bored holes into which the specimen block will fit to compensate for the inclined surface and hold the specimen parallel to the base of the holder. In an alternate mode, the special holder can be used to hold a standard specimen block so that its specimen is at an angle with respect to the holder's base, for inspection by a scanning electron microscope.

11 Claims, 7 Drawing Figures PMENTEU HAY 2 0 I975 SHEET 1 [IF 2 Ew QEW SPECIMEN BLOCK AND SPECIMEN BLOCK HOLDER BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to devices for holding specimens for examination with both optical and scanning electron microscopes and for holding specimens during coating operations and relates more particularly to devices for holding specimens at a desired angle of tilt for inspection with scanning electron microscopes and for holding specimens in a horizontal position for inspection with optical microscopes and during coating operations.

2. Prior Art In the manufacture of miniature electronic components, it is necessary to closely examine a manufactured specimen to determine if the specimen meets various design criteria. In the course of this examination, several commercially available instruments, such as optical microscopes, scanning electron microscopes and X-ray spectrometers are utilized. Because of the structural design of these various instruments, it is necessary to hold the specimen in two different positions during the examination process. For example, it is well known that when examining a specimen with a scanning electron microscope, it is desirable to tilt the specimen with respect to the path of incoming electrons to increase electron emission and facilitate detection of the emitted electrons. To accomplish this tilting, various adjustable platforms have been developed. These prior art adjustable tilting platforms are of a relatively complex construction and as a result are costly to manufacture and purchase and somewhat timeconsuming to operate.

Before examining a specimen with a scanning electron microscope, it is a common practice to coat the specimen with a uniform layer of metal to increase Secondary electron emission and thus allow higher resolution inspection. When performing this coating operation, it is desirable to hold the specimen in a flat rotating plane to achieve a uniform coating of metal.

Likewise, whenexamining a specimen with an optical microscope, due to the construction of most commercially available models, it is desirable to hold the specimen in a plane parallel to the base of the microscope.

SUMMARY OF THE INVENTION Briefly, the invention provides a specimen block for holding a specimen in a selected plane for inspection with both an optical and a scanning electron microscope and for use in specimen coating operations, which specimen block is in the shape of a cylinder havmg a first planar base surface and having a second planar specimen surface forming the selected plane, inclined at an acute angle with respect to the first planar base surface. The specimen is mounted on the inclined planar specimen surface of the specimen block. The invention further provides a specimen block holder for holding a standard specimen block at an angle for use n a scanning electron microscope and for holding the nventive specimen block in a selected position for use in optical microscopes and for use in specimen coating operations, which specimen block holder comprises a body having a planar base surface and having at least one cavity extending downward into a portion of the body at an acute angle with respect to the planar base surface. The invention further contemplates the insertion of the inventive specimen block into the cavity in the specimen block holder in such a manner that the inclined planar specimen mounting surface on the specimen block will be parallel to the planar base surface of the specimen block holder and the insertion of a standard specimen block into the cavity to incline its planar specimen mounting surface with respect to the planar base of the specimen block holder.

OBJECTS OF THE INVENTION An object of the present invention is the provision of a novel specimen block which is capable of being inserted into both a standard specimen block holder and a novel specimen block holder of the present invention.

Another object of the present invention is the provision of a novel specimen block which is capable of holding a mounted specimen at a selected angle of tilt when the specimen is being inspected by a scanning electron microscope.

A further object of the present invention is the provision of a novel specimen block which is capable of effectively extending the range of tilt of a standard tilting platform.

A further object of the present invention is the provision of a novel specimen block holder capable of bold ing the novel specimen block of the present invention at a selected angle of tilt to compensate for the angle of tilt built into the novel specimen block and thus hold the specimen in a horizontal position for examination with an optical microscope and for coating operations.

Yet another object of the present invention is the provision of a novel specimen block holder capable of holding a standard specimen block at a specified angle of tilt when the specimen is being inspected by a scanning electron microscope.

Another object of the present invention is the provision of a novel specimen block for holding a specimen in a selected plane which is simple, inexpensive to manufacture, and easy to use.

A still further object of the present invention is the provision of a novel specimen block holder for holding a specimen block in a selected position which is simple, inexpensive to manufacture, and easy to use.

Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram of the cross-section of an electron optical system, specimen chamber and X-ray spectrometer;

FIG. 2 is a side view of a specimen block holder constructed in accordance with the present invention;

FIG. 3 is a top view of the specimen block holder of FIG. 2;

FIG. 4 is a front view of the specimen block holder of FIG. 2 including a partial cutaway and a side view of a specimen block constructed in accordance with the present invention;

FIG. 5 shows the specimen block of FIG. 4 held by a standard specimen block holder;

FIG. 6 shows a standard specimen block held by a standard specimen block holder;

FIG. 7 shows a standard specimen block held by the specimen block holder of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to facilitate a better understanding of the invention, it will be helpful to consider the environment in which the invention is to be used. FIG. 1 shows a diagram of the cross-section of a prior art electron optical system, specimen chamber and X-ray spectrometer, manufactured by Japan Electron Optics Laboratory Co., Ltd. The components of the scanning microscope, generally indicated at 10, are a high voltage input cable 12, an electron gun 13, an anode 14, a gate valve 15, a condenser lens 16, a pole piece 17 and an objective lens 18. A detector 11 is provided to measure electron emission. The unit further includes an X-ray spectrom eter l9 and an optical microscope 20. A specimen stage 22 is situated at the base of the unit and supports a standard specimen block holder 50. The present invention is used in conjunction with, and as, a substitute for, the specimen block holder 50.

Thus, it is evident from FIG. 1 that a stream of electrons emitted by the gun 13 follows a vertical path to the anode 14, through the valve 15, and the lenses l6 and 18 to a specimen (not shown) held in the holder 50. Since the electron emission detector 11 is positioned off to the side of the microscope 10, it is well known that tilting the specimen with respect to the incoming vertical stream of electrons improves secondary electron collection by deflecting the emitted electrons in the direction of the detector. On the other hand, since the optical microscope 20 can be positioned directly over the specimen holder 50, it is most desirable to hold a specimen in a horizontal position when inspecting the specimen with the optical microscope 20.

With reference to FIGS. 2, 3, 4 and 5, the invention will be described in detail. A specimen 60, which is ready for inspection, is mounted on the surface 41 of a specimen block 40. The specimen block 40 may be formed of any metal, e.g., cast aluminum, or any other material suitable for use in electron and X-ray environments, and is illustrated as a partially truncated right circular cylinder. The plane of truncation creates a specimen mounting surface 41 on specimen block 40 and forms an acute angle a with respect to the planar base 42 of specimen block 40. The angle a is preferably 60, but may lie in the range of to 80. The specimen block may take other shapes as long as it has a planar base and a planar inclined specimen mounting surface.

After the specimen 60 has been mounted on planar specimen mounting surface 41, it is desirable to inspect the specimen with an optical microscope. Because of the characteristics of most commercially available optical microscopes, the specimen 60 should be held in a horizontal position. Thus, the present invention further provides a specimen block holder 30 to hold the specimen block 40 in such a manner as to place the planar specimen mounting surface 41 in a horizontal plane. The specimen block holder 30 is a solid block or body and may be formed of any metal, e.g., cast aluminum, or any other material suitable for use in electron and and X-ray environments. The body contains two

cavities

31 and 32 which are formed by drilling holes of circular cross-section about linear axes 33 and 34, respectively, into the top of the specimen block holder 30 at an angle B with respect to the planar base 35 of specimen block holder 30. The angle B is preferably 30, but may lie in the range of 10 to 60. It should be noted, however, that angles a and B must be complementary in order to hold the specimen 60 in a horizontal plane. The specimen block holder 30 is illustrated as containing two

cavities

31 and 32 so that two specimen blocks may be held simultaneously; however, the number of cavities in the specimen block holder is purely a function of space limitations and more could be added if space were available.

Subsequent to optical inspection of the specimen 60, but before examination with a scanning electron microscope, it is desirable to coat the specimen with a thin layer of metal, such as gold, having a thickness on the order of 200 angstroms to increase secondary electron emission and to improve X-ray emission if an X-ray spectrometer is used. To produce a uniform metal coating, it is once again desirable to hold the specimen block 40 in such a manner as to place the planar specimen mounting surface 41 in a horizontal plane. Thus, for the coating operation, the specimen block 40 is held by the specimen block holder 30. After coating, the specimen 60 may again be examined with an optical microscope and maintained in a horizontal position.

For examination with a scanning electron microscope as explained in connection with FIG. 1, it is helpful to tilt the specimen with respect to the path of incident electrons 25. Thus, with the present invention, the specimen block 40 is held in a vertical position and the planar specimen mounting surface 41 becomes the tilted surface. For examination with a scanning electron microscope, the specimen block 40 is held by a standard specimen block holder 50, well known in the prior art, which holds a specimen block in a vertical position. The planar specimen mounting surface 41 is thus tilted with respect to the path of incident electrons 25 by the angle [3. The specimen block is prevented from rotating by tightening a set screw 52.

It is also possible to utilize the specimen block 40, when held by the specimen block holder 50, in conjunction with a standard tilting stage such as the stage symbolically indicated at 22. Thus, if the stage 22 were capable of being tilted 45, the tilting range could be extended to 45+a by utilizing the specimen block 40 in conjunction with the stage 22.

Thus, it is apparent that the use of the specimen block and specimen block holder of the present invention greatly facilitates optical microscope inspection and insures more uniform metal coatings of a specimen by holding the specimen in a horizontal position. The present invention further saves time in the inspection of a specimen since the specimen may remain mounted on the specimen block throughout the entire operation. The specimen block need only be moved once and that is from the specimen block holder 30 to the standard holder 50.

With reference to FIGS. 6 and 7, an alternate embodiment of the invention will be described. A specimen 61, which is to be inspected, is mounted on surface 71 of a standard specimen block which is in the shape of a right circular cylinder. The specimen mounting surface 71 is the top of the cylinder and is parallel to the base surface 72. As discussed earlier, for optical microscope inspection, the specimen 61 should be held in a horizontal position. Thus, a standard specimen block holder 50 has been used to hold the standard specimen block 70 for optical inspection of the specimen 61. Furthermore, when coating the specimen 61 with a thin layer of metal as discussed in connection with FIGS. 2-5, the specimen 6] should be maintained in a horizontal plane and as a result the specimen block 70 is again held by a standard specimen block holder 50. To this point, what has been described is illustrated in FIG. 6 and is part of the prior art and comprises no part of the present invention.

For examination of the specimen 61 with a scanning electron microscope, it is necessary to tilt the specimen 61 with respect to the path of incident electrons. Known methods of tilting the specimen 61 frequently involved remounting the specimen 61 on a special device or the use of relatively complex and expensive tilting platforms. However, by utilizing the specimen block holder 30 of the present invention, the specimen block 70 need merely be transferred from the standard holder 50 to one of the

cavities

31 or 32 in the specimen block holder 30. The specimen mounting surface 71 is thus tilted with respect to the path of incident electrons 25 by the angle ,6.

Some standard specimen blocks may be too short to be held by the specimen block holder 30. Thus, it is important to select a block of sufficient height to be securely held by the holder 30.

Therefore, it is apparent that the use of the specimen block holder of the present invention further greatly facilitates scanning electron microscope inspection of a specimen mounted on a standard specimen block.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention. For example, the specimen block 40 need not be shaped as a right circular cylinder, but may assume any convenient shape that will keep the specimen mounting surface in the desired position. Likewise, the cavities in the specimen block holder 30 need not be of circular cross-section but may be of any shape capable of holding a specimen block in a desired position. Additionally, the

cavities

31 and 32 may include a keying or locking mechanism to prevent relative movement between the specimen block and the specimen block holder. Furthermore, the specimen block holder 30 need not be in the shape of a rectangular parallelepiped as illustrated, but may take on any shape that will hold a specimen block in the desired position. it is therefore aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A specimen block holder and a specimen block for holding a specimen in a selected plane for use in optical microscopes and for use in specimen coating operations comprising:

a block holder having a first planar base surface for resting said holder on a supporting surface;

at least one cavity extending downward into a portion of said holder, said cavity having a linear axis which forms a first acute angle with respect to said first planar base surface and;

a cylindrical specimen block having a second planar base surface, and a third planar specimen mounting surface inclined at a second acute angle with respect to said second planar base surface to form said selected plane said cylindrical block extending into said cavity and resting therein in such a manner that said third planar specimen mounting surface is substantially parallel to said first planar base surface. 2. A specimen block holder and a specimen block as set forth in claim 1 wherein said first acute angle is between l0 and and said second acute angle is the complement of said first acute angle.

3. A specimen block holder and a specimen block as set forth in claim 2 wherein said first acute angle is 30 and said second acute angle is 60.

4. A specimen block holder and a specimen block as set forth in claim 1 wherein said cylindrical specimen block is a truncated right circular cylinder with said third planar specimen mounting surface forming the plane of truncation.

5. A specimen block holder and a specimen block as set forth in claim 1 wherein the cross-section of said cavity taken perpendicular to said linear axis is circular.

6. A specimen block holder and a specimen block as set forth in claim 5 having a second cavity extending into a portion of said holder in a direction opposite to that of said first cavity, said second cavity having a second linear axis which forms a third acute angle with respect to said first planar base surface.

7. A specimen block holder and a specimen block as set forth in claim 6 wherein said third acute angle is equal to said first acute angle.

8. A specimen block holder and a specimen block as set forth in claim 7 wherein said cross-section of said second cavity taken perpendicular to said second linear axis is circular.

9. A specimen block holder and a specimen block as set forth in claim 1 wherein said specimen block holder and said specimen block are made of an opaque material.

10. A specimen block holder and a specimen block as set forth in claim 9 wherein said opaque material is aluminum.

11. In a microscope including a specimen stage the improvement comprising:

a specimen block holder and a cylindrical specimen block for holding a specimen in a selected plane;

said specimen block holder having a first planar base surface, said first planar base surface being positioned to rest on said specimen stage;

a first cavity extending downward into a portion of said holder, said cavity having a linear axis which forms a first acute angle with respect to said first planar base surface;

a second cavity extending downward into a portion of said holder in a direction opposite to that of said first cavity, said second cavity having a second linear axis which forms a second acute angle with respect to said first planar surface; and

said cylindrical specimen block having a second planar base surface, and a third planar specimen mounting surface inclined at a third acute angle with respect to said second planar base surface to form said selected plane, said cylindrical block extending into one of said first and second cavities and resting therein in such a manner that said third planar specimen mounting surface is substantially parallel to said first planar base surface.

i l l i l

Claims

1. A specimen block holder and a specimen block for holding a specimen in a selected plane for use in optical microscopes and for use in specimen coating operations comprising: a block holder having a first planar base surface for resting said holder on a supporting surface; at least one cavity extending downward into a portion of said holder, said cavity having a linear axis which forms a first acute angle with respect to said first planar base surface and; a cylindrical specimen block having a second planar base surface, and a third planar specimen mounting surface inclined at a second acute angle with respect to said second planar base surface to form said selected plane said cylindrical block extending into said cavity and resting therein in such a manner that said third planar specimen mounting surface is substantially parallel to said first planar base surface.

2. A specimen block holder and a specimen block as set forth in claim 1 wherein said first acute angle is between 10* and 60* and said second acute angle is the complement of said first acute angle.

3. A specimen block holder and a specimen block as set forth in claim 2 wherein said first acute angle is 30* and said second acute angle is 60*.

11. In a microscope including a specimen stage the improvement comprising: a specimen block holder and a cylindrical specimen block for holding a specimen in a selected plane; said specimen block holder having a first planar base surface, said first planar base surface being positioned to rest on said specimen stage; a first cavity extending downward into a portion of said holder, said cavity having a linear axis which forms a first acute angle with respect to said first planar base surface; a second cavity extending downward into a portion of said holder in a direction opposite to that of said first cavity, said second cavity having a second linear axis which forms a second acute angle with respect to said first planar surface; and said cylindrical specimen block having a second planar base surface, and a third planar specimen mounting surface inclined at a third acute angle with respect to said second planar base surface to form said selected plane, said cylindrical block extending into one of said first and second cavities and resting therein in such a manner that said third planar specimen mounting surface is substantially parallel to said first planar base surface.