JPH0234423B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device attached to a scanning electron microscope, etc., and particularly relates to a device attached to a scanning electron microscope, etc. The present invention relates to a tilt amplification display device for a sample image, which is capable of detecting and displaying whether or not the sample image is tilted.

In a conventional scanning electron microscope, as shown in FIG. 1, an electron beam (charged particle beam) 2 emitted from an electron gun 1 is focused by a focusing lens 3, and the focused electron beam 2 along the Z direction is focused. the deflection coil 4,
The electron beam 2 is deflected in the X direction and the Y direction at 5, and the deflected electron beam 2 is scanned over a sample (IC pattern, etc.) 7 while being focused by an objective lens 6.

The secondary electrons from the sample 7 are detected by the secondary electron detection device D, and the sample image is displayed on the CRT 8 as a display device. (See Fig. 2) The deflection coils 4 and 5 receive sawtooth wave signals SX and SX for deflecting the electron beam 2 in the X and Y directions.
SY is supplied.

These sawtooth wave signals SX, SY are output from the X-direction sawtooth wave generation circuit 9 and the Y-direction sawtooth wave generation circuit 10 by converting the signals VX, VY into a variable magnification attenuator 1.
1 and 12, respectively, and the adjusted signals A _X and _AY are amplified by amplifiers (Amp) 13 and 14.

In this way, the deflection coil 4, the X-direction sawtooth wave generating circuit 9, the variable magnification attenuator 11, and the amplifier 13 constitute the X-direction deflection member DX.

Similarly, the deflection coil 5, the Y-direction sawtooth wave generating circuit 10, the variable magnification attenuator 12, and the amplifier 14 constitute the Y-direction deflection member DY.

Note that the magnification M _H in the X direction and the magnification M _V in the Y direction are changed in conjunction with each other by the magnification interlock command unit 16, and are the same magnification M.

By the way, in such a conventional device, sample 7
Before observing the sample 7, the sample 7 is positioned in a predetermined reference state.

That is, as shown in FIG. 2, the coordinates x, indicated by the cross-shaped reference mark MK placed on the sample 7,
By matching y with X and Y, the display coordinates of the sample image 15 are
The angle of inclination θ ₁ from Y is set to zero. (See FIG. 3) Note that this tilt correction is performed by rotating a sample moving table (not shown) on the lower surface of the sample 7 about the Z direction.

However, with such a tilt display means in a conventional scanning electron microscope, there is a problem that when the tilt of the reference mark MK shown on the CRT 8 is small, this tilt cannot be detected with the naked eye, and the accuracy is low. It is a low tilt display means.

On the other hand, with other tilt display means in conventional scanning electron microscopes, as shown in FIG. and display coordinates X, Y
After roughly matching the values, move the sample moving table to observe area A of sample 7 (see Figure 5), then move the sample moving table linearly in the x direction to observe area B. Observe. (See Figure 6.) Along with this movement, the image of the straight line SL changes.
If you move in the Y direction on the CRT8, you will find that there is a tilt, and the angle of tilt θ ₂ can _be calculated by the following _formula : Calculated by

θ ₂ ⁼ tan ^-1 ₍ l _Y / _l Then _, from tanθ ₂ ⁼ _{l Y /} l _X = (1/M)・L/ _l 1)/(1×10 ^-5 ) = 100 [mm]. That is, it is necessary to measure two points on the sample 7 with an interval of 100 [mm].

As described above, other conventional tilt display means have the problem that tilt cannot be detected unless two locations widely separated in the X direction are observed, and that sufficient detection accuracy cannot be obtained.

Further, there are problems in that the inclination cannot be detected in the same field of view, and as a result, the inclination cannot be detected in a short period of time, and that measurement errors are accumulated.

The present invention aims to solve these problems, and by amplifying the tilt of the sample image, the tilt can be observed quickly and accurately within the same field of view of a display device, and the tilt can be clearly displayed. It is an object of the present invention to provide a tilt amplification display device for a sample image, which is capable of displaying a sample image.

For this reason, the sample image tilt amplification display device of the present invention includes an X-direction deflection member that can deflect the charged particle beam in the X direction, and a Y
a Y-direction deflection member capable of deflecting the sample in the Y-direction, and a display device for displaying the sample;
In order to amplify the tilt of the sample image projected on the display device from the display coordinates on the display device, the magnification of at least one of the X-direction deflection member and the Y-direction deflection member can be controlled to increase or decrease. It is characterized by the addition of a magnification adjustment section.

Hereinafter, a sample image tilt amplification display device as an embodiment of the present invention will be explained with reference to the drawings. FIG. 7 is an overall configuration diagram thereof, and FIG. 8 is a plane showing the relationship between the display coordinates and the tilt of the sample image. Figure, No. 9, 1
1 and 13 are schematic diagrams showing the scanning area, and FIGS. 10, 12, and 14 are explanatory diagrams showing sample images on the display device. In addition, in FIGS. 7 to 14, the same reference numerals as in FIGS. 1 to 6 indicate substantially similar parts.

As shown in FIG. 7, in this embodiment as well, an electron beam (charged particle beam) 2 emitted from an electron gun 1 of a scanning electron microscope is focused by a focusing lens 3,
This focused electron beam 2 along the Z direction is deflected in the X and Y directions by deflection coils 4 and 5, and the deflected electron beam 2 is scanned over a sample (IC pattern, etc.) 7 via an objective lens 6. I'm starting to do that.

The secondary electrons from the sample 7 are detected by a secondary electron detection device D, and a sample image 15 is displayed on a CRT 8 as a display device. (See Fig. 8) Sawtooth wave signals SX and SX for deflecting the electron beam 2 in the X and Y directions are supplied to the deflection coils 4 and 5.
SY is supplied.

This sawtooth wave signal SX is generated by adjusting the magnification of the signal VU from the X direction sawtooth wave generation circuit 9 with a variable magnification attenuator 11, and further by adjusting the magnification of the signal VU from _{the X} direction sawtooth wave generation circuit 9.
is amplified by an amplifier (Amp) 13.

In addition, the sawtooth wave signal SY is transmitted through the changeover switch 17.
When is on the side a in FIG.
2, and the adjusted signal A _Y is further amplified by an amplifier (Amp) 14.

At this time, the magnification in the X direction M _H and the magnification in the Y direction M _V
and have the same magnification, and are changed in conjunction with each other by the magnification interlock command section 16.

When the changeover switch 17 is on the b side in Fig. 7,
The sawtooth wave signal SY is generated by the Y direction sawtooth wave generation circuit 1.
It is produced by adjusting the magnification of the signal VY from 0 through the Y-direction magnification variable attenuator 18 and by the magnification variable attenuator 12, and further amplifying the adjusted signal A _Y with the amplifier 14.

At this time, the magnification in the X direction M _H and the magnification in the Y direction M _Y
is set to a constant ratio (M _V /M _H ) by the Y-direction magnification variable attenuator 18.

In this way, the deflection coil 4, the X-direction sawtooth wave generating circuit 9, the variable magnification attenuator 11, and the amplifier 13 constitute the X-direction deflection member DX.

Similarly, the Y-direction deflection member DY is composed of the deflection coil 5, the Y-direction sawtooth wave generation circuit 10, the variable magnification attenuator 12, the Y-direction variable attenuator 18, the changeover switch 17, and the amplifier 14.

By setting the magnification of the sawtooth wave signal SY to a value different from the magnification of the sawtooth wave signal SX in this way,
The magnification M _V in the X direction can be different from the magnification M _H in the X direction.

Since the sample image tilt amplification display device of the present invention is constructed as described above, the changeover switch 17 is
side, as shown in Figure 9, when scanning the sample 7 over a range of horizontal length _{h and vertical length v, the magnification M H in} the The magnification ratio (M _V /M _H ) is 1.

At this time, the cross-shaped reference mark MK on sample 7
On a CRT8 with horizontal length H and vertical length V,
It is displayed as _shown in Fig. 10, and the angle _of inclination α (=
θ ₃ ) is as follows.

α=θ _{3 = tan} ^-1 (L _{Y1 /} It is calculated as follows.

When this magnification ratio (M _V /M _H ) is 1, the accuracy on the CRT 8 is limited to 1 [mm] as described above, and the tilt can be corrected up to this accuracy limit.

Next, when the changeover switch 17 is switched to the b side and the Y-direction variable magnification attenuator 18 is set to, for example, 2x, the scanning area C of the sample 7 is shrunk by 1/2 in the Y-direction, as shown in FIG. Since the vertical length is (v/2), the magnification ratio (M _V /M _H ) is 2.

At this time, the cross-shaped reference mark MK on sample 7
is displayed on the CRT 8 as shown in FIG. 12, and the angle α' of the inclination on the CRT 8 from the horizontal length L _X and vertical length L _Y2 of the sample image 15 is as follows.

α′=tan ⁻¹ (L _Y2 /L _X ) Also, the actual angle of inclination θ ₃ on the sample 7 is as follows.

θ ₃ = tan ^-1 {(M _H /M _V )・L _Y2 /L _X } In this way, the length in the Y direction on the CRT8
L _Y2 becomes 2L _Y1 . In other words, the CRT of sample image 15
Since the tilt from the display coordinate X on the CRT8 can be amplified, the measurement accuracy in the Y direction on the CRT8 can be increased by 2
It will be doubled.

Next, install the attenuator 17 for variable magnification in the Y direction.
When set to 10 times, the scanning area C of sample 7 is
As shown in FIG. 3, it is further shrunk in the Y direction, the vertical length becomes (v/10), and the magnification ratio (M _V /M _H ) becomes 10.

At this time, the cross-shaped reference mark MK on sample 7
is displayed on the CRT 8 as shown in Figure 14, and is calculated from the horizontal length L _X and vertical length L _Y3 of the sample image 15.
The angle of inclination α″ on the CRT 8 is as follows.

α″=tan ⁻¹ (L _Y3 /L _X ) Furthermore, the actual angle of inclination θ ₃ on the sample 7 is as follows.

θ ₃ = tan ^-1 {(M _H /M _V )・L _Y3 /L _X } In this way, the length in the Y direction on the CRT8
Since L _Y3 becomes 10L _Y1 (also in this case, the inclination of the sample image 15 can be amplified), the measurement accuracy in the Y direction on the CRT 8 becomes 10 times.

This magnification ratio (M _V /M _H ) is 1, 2,
It can be set to values other than 10. For example, when the magnification in the X direction M _H = 30 and the magnification in the Y direction M _V = 30000, that is, the magnification ratio (M _V /M _H ) = 1000, the CRT8
When the measurement accuracy in the Y direction above is 1 [mm], tanθ ₃ = 1 × 10 ^-5 without changing the field of view.
It is possible to observe the slope of Furthermore, at this time
The length L _X of the CRT8 in the X direction is 100 [mm].

Furthermore, by increasing the magnification ratio (M _V /M _H ), it is possible to accurately display and measure the tilt. It is also possible to reduce the size with higher precision.

Furthermore, in addition to increasing the magnification in one of the X direction and the Y direction, it is also possible to use a magnification that decreases the other.

As the magnification adjustment section, in addition to the one provided with the attenuator 18 for varying the magnification in the Y direction as described above, it may also be provided with an attenuator for varying the X direction magnification in the X direction. The magnification M _H in the direction can be made larger than the magnification M _V in the Y direction.

Further, the magnification adjustment section may be configured to independently give command values for the X-direction magnification and Y-direction magnification of the magnification interlocking command section 16 of the variable magnification attenuators 11 and 12; The configuration is such that it can be switched between an independent state and an independent state.

As described in detail above, according to the sample image tilt amplification display device of the present invention, at least one of the X-direction deflection member and the Y-direction deflection member is provided with a magnification adjustment section that can control increase/decrease in magnification. With the simple structure of This has the advantage of being simple and quick to operate, and also reduces errors associated with detecting inclinations.

Further, by combining the device of the present invention with a tilt correction means, it becomes possible to detect the reference mark and automatically correct the tilt.

[Brief explanation of drawings]

Figures 1 to 3 show a tilting display device in a conventional scanning electron microscope. Figure 1 is a diagram of its overall configuration, and Figures 2 and 3 are explanatory diagrams showing a sample image on the display device. , Figures 4 to 6 show tilt display means in other conventional scanning electron microscopes. Figure 4 is a plan view showing the relationship between the display coordinates and the tilt, and Figures 5 and 6 both show the tilt display means. FIG. 7 is an explanatory diagram showing a sample image on a display device;
Figure 14 shows a sample image tilt amplification display device in a scanning electron microscope as an embodiment of the present invention, Figure 7 is its overall configuration, and Figure 8 shows its display coordinates and sample image tilt. FIGS. 9, 11, and 13 are all schematic diagrams showing the scanning area, and each of FIGS. 10, 12, and 14 is an explanatory diagram showing the sample image on the display device. 1... Electron gun, 2... Electron beam (charged particle beam),
3... Focusing lens, 4, 5... Deflection coil, 6... Objective lens, 7... Sample, 8... CRT as a display device,
9... X direction sawtooth wave generation circuit, 10... Y direction sawtooth wave generation circuit, 11, 12... Attenuator for variable magnification, 13, 14... Amplifier, 15... Sample image, 16
...Magnification interlocking command unit, 17...Selector switch, 18...
Attenuator for variable magnification in the Y direction as a magnification adjustment unit, C...scanning area, D...secondary electron detection device, DX
...X direction deflection member, DY...Y direction deflection member, MK
...Reference mark.

Claims (1)

[Claims] 1 An X-direction deflection member capable of deflecting the charged particle beam in the X direction in order to scan the charged particle beam on the sample;
a Y-direction deflection member capable of deflecting the sample in the Y-direction, and a display device for displaying the sample;
In order to amplify the tilt of the sample image projected on the display from the display coordinates on the display, at least one of the X-direction deflection member and the Y-direction deflection member is provided with a magnification that can increase or decrease the magnification. A tilt amplification display device for a sample image, characterized in that an adjustment section is attached.