JPH03254055A - Electron microscope - Google Patents

Abstract

PURPOSE:To accomplish wide range combinations of parallel motion amount with inclining motion amount by calculating the maximum possible motion amount from the situation of other motion amount when a certain specified motion amount is to be varied relative to the parallel motion and inclining motion of a gonio-stage, and thereupon admitting a movement within the limit thus obtained. CONSTITUTION:A drive command system 8 receives externally a command about parallel motion or inclining motion to be made by a gonio-stage 5, and sends the command to a computational processing system 7. This processing system 7 stores in memory the parallel motion amount and inclining motion amount of the gonio-stage 5 at the current time. When a motion command is received from the drive command system 8, the processing system calculates the limit value for movability and transmits only motion commands within this limit to a drive system 6, which implements the commands. This allows setting of the motion limit while correlation between the x, y parallel motion and theta, psi inclining motion are taken into consideration, so that any desired combination of the x, y, theta, psi motion amounts can be achieved within the extent in which the gonio-stage does not touch an objective stop.

Description

[Detailed description of the invention] [Industrial application field] The present invention involves transmitting an electron beam through a sample to determine its crystal structure.

This invention relates to electron microscopes and similar devices for obtaining information on composition, chemical bonding states, etc.

[Conventional technology]

In an electron microscope equipped with an analysis function that uses characteristic X-rays generated when an electron beam passes through a sample, a side-entry goniometer stage is used to hold the sample in the path of the electron beam. Common. The sample mounted on the goniometer stage is held approximately at the center of a gap forming section called the pole piece of the objective lens. FIG. 2 is a sectional view viewed from the goniometer stage insertion direction for explaining this situation. A sample holder 14 of a goniometer stage is inserted into the center of a gap 13 formed by parts 11 and 1.2 of the objective lens pole piece. In addition to this, an objective diaphragm 15 is inserted into the gap 13.

The position and orientation of the sample with respect to the electron beam 16 can be changed by changing the position and orientation of the electron beam 14. - For example, if 14 is tilted, if the tilt is too large, 14 and 15 will come into contact with each other in the tilted state of the goniometer stage shown at 14', and the objective aperture will be damaged. For this reason, it is necessary to set the movable range of the goniometer stage to prevent it from coming into contact with the parts within the mirror.

FIG. 3 is a diagram illustrating the structure of the side entry type goniometer stage and the mechanisms for translation and tilting. The vicinity of the tip of the main shaft 20 is a flat portion 21, and an X-axis 22 is set in the direction of the center line of the main shaft.

21 is equipped with a tilter 24 that can rotate about a y-axis 23 perpendicular to the x-axis 22, and a sample 25 is attached to 24. The slight movement of the main shaft 20 can give the sample 25 translation in the X and y directions, the rotation of the main shaft 20 can give a tilt θ around the X axis, and the tilt of the tilter 24 can give the sample 25 a translational movement around the A slope T can be provided. Note that the xy plane is always parallel to the 2nd flat part.

In other words, it is assumed that the direction of the y-axis changes depending on the inclination around the x-axis.

In a side-entry type goniometer stage, this can be done by changing the position and orientation of the sample relative to the electron beam using the mechanism explained in Figure 3, but if the amount of movement exceeds a certain limit, the objective as explained in Figure 2 will change. This will cause damage to the aperture. As a countermeasure for this, it is necessary to set limit values for all of the translational movement amounts in the x and y directions and the inclination movement amounts in θ and T, and to apply an interlock to prevent movement beyond these limits.

As this type of interlock method, Japanese Patent Application Laid-Open No. 59-1
A method of detecting the risk of contact by an interference member has been devised, as described in No. 46145. This is achieved by providing a fixed interference member that represents the internal structure of the mirror sample chamber and a moving interference member that represents the amount of movement of the goniometer stage. This method detects the movement limit of the goniometer stage through electrical or mechanical contact of moving interference members and applies an interlock.

[Problem to be solved by the invention]

The above-mentioned conventional technology was devised with the assumption that it would be used in scanning electron microscopes that detect reflected electrons, and no consideration was given to its practical application in extremely limited spaces such as in electron microscopes that detect transmitted electrons. do not have.

In other words, since there is a wide space inside the mirror body of a scanning electron microscope, there is ample room to incorporate a mechanism that links the movement of the goniometer stage and the movement of the movable interference member. In contrast, in a transmission electron microscope, a thin rod-shaped goniometer stage is inserted into the electron lens, and it is extremely difficult to attach an interlocking mechanism between the goniometer stage and the movable interference member that operates sufficiently stably. It is. Even if it were to be realized, the side-entry goniometer stage would be large-scale, making it susceptible to external vibrations, which would impair the performance of the electron microscope itself.

Therefore, in order to avoid the disadvantages of increasing the size, a simplified application can be considered. This is a method that assigns one set of fixed and moving interference members to each of .With this method, X+'l+θ.

It is sufficient to install fixed interference members corresponding to positive and negative movement limit values and a movable interference member that moves between the fixed interference members at appropriate positions of each drive unit of the T, and large cities do not arise. However, in this case, X.

Since individual fixed limit values are provided for each of y, θ, and (P), it must be within a range that does not cause contact between the goniometer stage and objective aperture even if x, y, θ, and ψ all reach their limit values at the same time. It has the disadvantage that it cannot be used.

Due to the recent demand for higher resolution for electron microscopes,
The shortcomings of the simplified applied interlocks of the prior art described above have become significant.

The resolution improves as the wavelength of the electron beam becomes shorter, and the resolution improves as the magnetic field of the objective lens becomes stronger. In order to strengthen the magnetic field of the objective lens, it is necessary to narrow the gap between the pole pieces, which reduces the range of movement of the goniometer stage.
In an electron microscope with an electron beam accelerating voltage of 30OkV class, the wavelength is short, so the gap between the pole pieces does not narrow much even with higher resolution, but in the 200kV class, the effect of the gap being caught is large. In the conventional limit value setting method, x and y are ±1 mm and θ for a device with a resolution of 1.4 nm.

Although T could be moved within a range of ±20', in a 1.0 nm resolution device, Xry is limited to a range of ±1 m, and θ and T are limited to a range of ±10'.

As an example, assume that in a 1.0 nm resolution device, the amount of movement of the sample is set to x=y=Q, 5 nm, θ=20@ψ=5°. Although the goniometer stage and the objective aperture do not come into contact with each other even with this setting, such a setting cannot be achieved in a 1.0 nm resolution device due to the function of an interlock. In other words, with conventional interlock technology,
Movement is only allowed within a part of the originally movable ranges of X, y, θ, and ψ, which causes inconvenience to the user.

An object of the present invention is to provide an interlocking means that operates while taking into consideration relative movement amounts of each of x, y, θ, and (P) without relying on the conventional contact method of interference members. Free x, y, and θ within the range where the stage and objective aperture do not come into contact.

The object of the present invention is to provide an electron microscope that realizes the combination of In particular, the electron microscope of the present invention is advantageous for analyzing crystalline substances.

[Means to solve the problem]

In order to achieve the above objective, each time we try to change any of the displacements of x, y, θ, ψ, we try to change it under the condition that the other displacements are kept at their current values. A movement limit value for only the amount of movement was calculated, and the structure was designed to allow movement within this limit value.

[Effect]

The present invention will be described in detail with reference to FIG. 1 showing the overall configuration of an embodiment described later. A side entry type goniometer 5 for holding the sample 4 in the path of the electron beam in the mirror body 2 through which the electron beam passes from the electron beam source 1 to the detection section 3 is driven by a drive system 6. It is controlled by an arithmetic processing system 7 and a drive instruction system 8. The drive system 6 has the role of causing the goniometer stage 5 to perform translational movement and tilting movement, and is composed of power generation means such as a motor and power transmission means. The drive instruction system 8 has the role of receiving from the outside commands for translational movement or tilting movement to be performed by the goniometer stage 5, and transmitting them to the arithmetic processing system 7. The method of receiving commands from outside is by one person using a knob.
Direct input using input means such as buttons, levers, pedals, etc., or instruction transfer from a programmed computer. The arithmetic processing system 7 includes memory elements, arithmetic elements, l!
@Input means for receiving commands from the motion instruction system 8 and the drive system 6
It consists of a means of transmitting commands to. The arithmetic processing system 7 stores the translational and tilting amounts of the goniometer stage 5 at the current time. When a movement command is received from the drive instruction system 8, a movement limit value is calculated, and only movement commands within this range are transmitted to the drive system 6 and executed. If you do this,
Translation of y3/, θ.

Since the movement limit can be set while considering the relative relationship of the tilt movement of T, a free combination of the movement amounts of X H'l Hθ and T can be realized within a range where the goniometer stage does not come into contact with the objective aperture or the like.

〔Example〕

Hereinafter, five embodiments of the present invention will be described. The construction drawing is a basic structural diagram of this embodiment. The goniometer stage 5 holds the sample 4 in the path of the electron beam in the mirror body 2 of the electron microscope, and performs translational movement in the Xr'j direction, θ, CP with respect to the sample 4 as shown in FIG. It has a structure that allows for tilt movement. These movements are executed by the power of the electric motor of the drive system 6. The drive instruction system 8 is a part that inputs the cleavage movement to be given to the goniometer stage, and is used to input the lateral movement to be applied to the goniometer stage.

A translational movement command of X+'l+Y is input, and tilting movement commands of θ, 10, 'f, +'P are inputted using another joystick. The arithmetic processing system 7 is composed of a 32-bit personal computer, an interface for receiving commands from the drive instruction system 8, and means for turning on and off the power to the motor of the drive system 6.

4 and 5 are diagrams defining a position coordinate system and diagrams showing coordinate monitor points provided on the gonio stage, in order to explain the method of controlling the translation and tilting movement of the gonio stage in this embodiment. Apart from the y-axis and y-axis that define the translational direction shown in FIG. 3, an orthogonal coordinate system is set as shown in FIG. 4 to represent the position of the goniometer stage within the mirror body.

Two axes 33 are set parallel to the direction of movement 31 of the electronic mirror, an X-axis 33 is set in the direction of the main axis of the goniometer stage, and the remaining Y-axes are set so as to form a right-handed coordinate system. The X-axis and Y-axis coincide with the X-axis and y-axis in FIG. 3 when the amount of movement of the goniometer stage is zero. In order to prevent the goniometer stage from coming into contact with other parts above and below it within the gap between the pole pieces due to translational and tilting movements, the Z coordinate of any part of the goniometer stage is determined by the structure ± l Z - ax l You just have to make sure you don't exceed that. The eight corner portions a - h of the tilter 24 in FIG. The coordinates of four points Ω~0 above and below the y-axis 23 of the section 24 are monitored for each translation and tilt operation, and the two coordinates of each point are controlled so as not to exceed ±IZ-axl.

Generally, the relationship between the alignment of the trinomial vector a representing a coordinate point and the trinomial vector a' representing the new coordinates resulting from the tilt movement operation is as follows, where A is a 3-by-3 matrix, A a = a '
It is expressed as If this relationship is applied to the coordinate system of this embodiment, the current X, Y, Z coordinates and θ.

A is uniquely determined by which movement operation of ±X, ±y, ±θ, and ±r is applied under T. Also, a is the current X,
Since these are the Y and Z coordinates themselves, a'= can be solved using simple algebra, and the range of this Z coordinate component is ±lz
, a, l or less.

In this embodiment, the arithmetic processing system 7 stores the x, y, and z coordinates of each point a-h, Q-0, and the values of the inclination angles θ and T.
Furthermore, matrix calculations are executed for each translation and tilt command, and a=
When all Z coordinates of h and Qo are less than ±1z-awl, the drive system 7 is caused to move the goniometer stage.

In the case of this embodiment, if the movable range setting of the conventional technology is set,
Translation of r'/ is within ±1mm, inclination of θ and ψ is ±10°
However, according to the movement restriction method of the present invention described in this embodiment, as an example, x=y=±0.511I11.
θ=±15°, ψ=±7° (θ.

Therefore, it is possible to realize a combination of movement amounts (any combination of + and - is possible), and this combination was not possible with the prior art.

According to this embodiment, it is possible to provide an electron microscope that achieves a range of combinations of movement amounts that cannot be achieved with conventional movement restriction methods, without causing damage to mirror components caused by the goniostage.

〔Effect of the invention〕

According to the present invention, instead of setting fixed upper limits for the translational and tilting movements of the goniometer stage within the mirror body of an electron microscope, when changing a certain amount of movement, it is possible to Since the maximum possible amount of movement is calculated and movement within that range is allowed, it is possible to realize combinations of translational and tilting amounts over a wide range.

[Brief explanation of drawings]

Figure 1 is a basic configuration diagram of an embodiment of the present invention, Figure 2 is a diagram showing the inside of the electron microscope near the sample holding part of the goniometer stage, and Figure 3 is a diagram of the side entry goniometer stage. FIG. 4 is an explanatory diagram of the structure and translation and tilting mechanism. FIG. 4 is an explanatory diagram of the XYZ orthogonal coordinate system provided for controlling the goniometer stage in an embodiment of the present invention. FIG. FIG. 3 is a diagram showing coordinate position monitor points provided for controlling the goniometer stage. 1. Electron beam source, 2. Mirror body of electron microscope, 3. Electron beam detection unit, 5. Side entry goniometer stage, 6. Drive system, 7. Arithmetic processing. System, 8・
... Drive indication system, 11.12... Part of the objective lens pole piece, Step 3... Gap between pole pieces, Step 4.
... Sample holding part of the goniometer stage, 15... Objective aperture, 20... Main shaft of the goniometer stage, 21... Flat part at the tip of the main shaft, 22... X axis, 23... Y axis, 24
・・・Slope 22 Fig. Fig. Fig. 7 Mu Fig. den + Brocade δ phrase

Claims (1)

[Claims] 1. In a device that detects an electron beam transmitted through a sample, the sample is held in the path of the electron beam by a side-entry goniometer stage, and the goniometer stage has orthogonal coordinates set in an arbitrary plane that is not parallel to the electron beam. A drive system for translating the system in the x and y directions and tilting the sample around the x and y axes, a drive instruction system that receives translation or tilt drive commands from the outside, and an arithmetic processing system. An electron microscope characterized in that the arithmetic processing system sets a limit value for translation or inclination each time the drive instruction system receives a drive command, and causes the drive system to execute driving within this range.