JPH09283073A - Ion beam radiating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply observe and machine a sample with high accuracy of sub- microns by combining a focusing ion optical system and a cofocal optical microscope fitted in parallel with it, and making a specific correction. SOLUTION: An ion beam radiating system constituted of an ion beam radiating mechanism focusing and radiating the ions 4 extracted from an ion source 2 to a sample 9 on a multi-dimensional movable mechanism 11 and two- dimensionally scanning 7, 8 the radiation position and a secondary particle detecting mechanism applying mark-machining at multiple positions on the sample 9 via this radiation, detecting 13 the secondary particles 12 generated from the marks, and forming a secondary particle image 15 from the detection signals and a different image observing system (cofocal optical microscope) 29 are combined. The marks machined by the focused ion beam are used as the normal coordinates to make the coordinate transformation between different optical systems as a mechanism adjusting and superimposing the different images containing the position information of the machined portions below the surface unobservable by the secondary particle image 15 and the secondary particle image 15.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an ion beam irradiation apparatus.

[0002]

2. Description of the Related Art A conventional optical observation apparatus combined with an optical microscope uses an optical microscope for machining positioning as shown in, for example, Japanese Utility Model Publication No. 59-10687. The optical microscope has a low magnification, the optical axis of the optical microscope and the optical axis of the optical observation device have a deviation of the order of 100 μm, and the resolution is poor and the device is used for measuring the processing position. Not not.

[0003]

Conventionally, a focused ion beam apparatus has been put to practical use for circuit correction and failure analysis of a semiconductor device.
Since the interlayer insulating film on the wiring is being flattened, the lowermost layer Al wiring information cannot be obtained by a scanning ion microscope for observing surface irregularities. Since the interlayer insulating film on the second layer Al wiring is also flattened, almost no information on the second layer Al wiring can be obtained. Further, there is a possibility that even the observation of the uppermost layer Al wiring will be difficult in the future because the planarization will be further advanced in the future.

Further, as semiconductor integration progresses, the minimum line width of the device is less than submicron, and further the lamination progresses, and the thickness direction of the device is about 10 μm. In the future, this tendency will be further advanced, and it will not be possible to observe with an ordinary optical microscope over a depth direction of 10 μm with an image resolution on the order of submicrons.

When a confocal optical microscope is used in the focused ion beam apparatus, information on the lowermost Al wiring can be obtained. However, since the focused ion image and the confocal optical microscope image have different image magnifications, rotations, and distortions, the distortion between the focused ion image and the confocal optical microscope image is corrected in order to perform processing positioning in the confocal optical microscope image. It is necessary.

[0006]

Since an insulating film and a protective film of a semiconductor device are optically transparent, even a submicron lowermost layer Al wiring can be observed by using a confocal optical microscope. . Furthermore, if the image integration is performed from the bottom layer to the surface of the device, even if the line width is submicron, the bottom layer Al wiring and the top Al wiring can be observed as the same image as a clear image. In addition, the processing positioning is performed by performing the mark processing with the focused ion beam, then obtaining the processing position using the confocal microscope, and measuring the distance from the mark to the processing position with the confocal optical microscope. If the focused ion image is processed based on the distance from the measured mark, the bottom layer Al
Can also be processed. Further, in order to improve the processing positioning accuracy, it is necessary to calibrate magnification, rotation, and distortion between different optical systems, but according to this method, it is possible to perform easily and quickly with high accuracy.

Means for solving the problems of the present invention are as follows.

[0008] 1. A desired processing position is searched for using a heterogeneous optical system (confocal optical microscope) mounted in parallel with the focused ion beam device.

[0009] 2. The processing position determined by the different optical system is moved to the focused ion beam. The mark is processed (Xi, Yi) i = 0 to 4 (for example, the four corners and the center of a quadrangle) with a focused ion beam. This processing position (Xi, Yi) is processed by the coordinate system of the deflector of the focused ion beam device, and since the cross-section processing is also performed by the focused ion beam device, the coordinate system of the focused ion beam device is used as the reference coordinate. . For this reason,
It is considered that the signals (si, ti) i = 0 to 4 given to the deflector and the deflection amount (Xi, Yi) i = 0 to 4 are equal. That is,
si = Xi, ti = Yi; i = 0-4.

3. Move the mark to the different optical system. A mark processed by a focused ion beam is displayed on an observation workstation by using a heterogeneous optical system.

4. Five points (xi, yi) i = 0 to 4 are measured for each mark position from the image on the workstation.

Next, when data of (Sj = sj-s0, Tj = tj-t0) j = 1 to 4 is given to the deflection plate of the focused ion beam apparatus, the actual deflection distance (coordinates) becomes (uj
= Xj-x0, vj = yj-y0) j = 1 to 4 is converted.

5. Therefore, the coordinates ((u
i, vi) i = 0 to 3: measurement position) is the coordinate of the focused ion beam optical system ((Si, ti) i = 0 to 3: processing position)
To the conversion formula below.

That is, assuming i = 0 to 3

[0015]

Equation 3 ui = Si + a1Si + a2Ti + a3SiTi + a0 (Equation 3)

[0016]

Equation 4 vi = Ti + b1Si + b2Ti + b3SiTi + b0 (Equation 4)

The equations 3 and 4 are solved by a control computer to obtain the conversion coefficients a0 to a3 and b0 to b3.

Next, data (u, v) is given and the corresponding (S, T) is obtained. This is ui, vi,
Equations 3 and 4 are solved for a Si and a Ti from a0 to a3 and b0 to b3 to obtain.

6. The processing location (u0, v0) is searched for in the different optical image displayed on the workstation, and the processing area (Δu, Δv) is set.

[7] FIG. Move the mark towards the focused ion beam. The focused ion beam image is taken into the workstation and the center mark position (X, Y) is measured.

8.5. Conversion coefficients a0 to a3, b obtained in
Processing position (S (u0) + X, T (v0) + Y) in the focused ion beam (coordinates) by using 0 to b3 and Equations 1 and 2
Is calculated and the corresponding processing location is displayed on the focused ion beam image.

9. Set machining parameters and perform machining.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A focused ion beam apparatus conventionally used for processing a semiconductor by using a focused ion beam is provided from an ion source 2 accelerated by an ion acceleration voltage controller 1 as shown in FIG. The ion beam 4 extracted by the ion source controller 3 is focused by controlling the electrostatic lens 6 by the lens controller 5. The focused ion beam is two-dimensionally scanned by the deflector 8 which is scanned by the scanning signal from the deflect controller 7. On the other hand, the sample 9 processed by the ion beam is X
-Y (plane movement), Z (height movement), R (rotation movement),
5-axis stage 11 with 5-axis control 10 of T (tilt movement)
Held on. When a certain area on the processed sample is two-dimensionally scanned by the ion beam, 2
Secondary particles 12 are generated. The secondary particles are detected by the secondary particle detector 13, and the brightness modulation signal corresponding to the number of the secondary particles is synchronized with the deflecting signal of the deflector to be displayed on the CRT 15 by the detector controller 14 and the device control computer. 16
When controlled by, a scanning ion microscope (SIM) is obtained according to the same principle as a scanning electron microscope (SEM). The focused ion beam device observes the surface of the processed sample with this scanning ion microscope, determines the processing position, and processes the sample.

In addition, XY, Z, which holds the processed sample,
A 5-axis stage having R and T moving mechanisms is controlled by a stage controller. Naturally, the sample chamber in which the stage is present is covered with a vacuum chamber for processing with an ion beam, and is kept at a vacuum degree of 1 × 10 ⁻³ Pa by a vacuum pump. The surface plate holding the entire vacuum chamber is mounted on the air support in order to eliminate vibration of the entire system.

With this device, for example, gallium (G
a) When the ion beam is focused to a beam diameter of <0.1 μm and a contact hole of a semiconductor device of <0.5 μm is cut, the processing position accuracy can be set to <0.1 μm. Objects to be processed by the processing apparatus include semiconductor devices and semiconductor exposure masks.

A cross section of the semiconductor device is, for example, as shown in FIG. 2, from the bottom, a Si substrate 17, an SIO ₂ interlayer insulating film 18, a lowermost layer Al wiring 19, an interlayer insulating film 18, a second layer Al wiring 20, an interlayer insulating film. Film 18, uppermost Al wiring 2
1, the passivation film 22.

In recent years, the semiconductor device has hitherto been lowermost layer A.
Since the interlayer insulating film on the 1-wiring is being flattened, information on the lowermost Al wiring cannot be obtained by a scanning ion microscope for observing surface irregularities. Even the observation of the second layer Al wiring is likely to be difficult. Furthermore, semiconductor devices have become more integrated and stacked, wiring widths and contact holes have reached submicrons, and device thicknesses have also become 10 μm.

Under these circumstances, a semiconductor device using a focused ion beam cannot be processed as an extension of the conventional technique, and a new processing technique is needed. Therefore, in the present invention, a confocal optical microscope is used because the insulating film in the semiconductor device shown in FIG. 2 is optically transparent. As a result, the bottom layer Al of> 10 μm from the surface
It is possible to observe even the wiring. Further, by changing the focus of the confocal optical microscope from the lowermost wiring to the surface and displaying the integrated image at that time, an image having a submicron image resolution can be displayed over 10 μm in the depth direction of the semiconductor device. it can. Therefore, by observing with a confocal optical microscope and performing processing positioning with a scanning ion microscope, it becomes possible to process the lowermost Al wiring.

As shown in FIG. 3, the apparatus of the present invention has a confocal optical microscope 29 including a laser 24, a beam split 25, an objective lens 26, a camera 27, a memory and a controller 28 in addition to the conventional focused ion beam. It is mounted so that the inside of the sample chamber can be observed parallel to the beam. In the confocal optical microscope, the light generated from the light source is once converged by the intermediate lens, passes through the glass plate forming the partition wall between the atmosphere and the vacuum chamber, and is converged on the sample by the objective lens to form an image. The confocal optical microscope is mounted so that this image forming point coincides with the (reference) image forming height of the ion beam.

In the present invention, the image composed of the information from the confocal optical microscope means a pattern that exists below (inside) the surface of the mark and the device and does not appear as surface irregularities of the mark. The secondary particle (SIM) image means a pattern appearing as marks and device surface irregularities in the present invention.

In the present invention, a desired processing position is obtained by a confocal optical microscope, the processing position is moved to a beam irradiation position of a focused ion beam, a mark is processed by a focused ion beam device, and the position is again set by the confocal optical microscope. Is moved to measure the distance between the mark and the desired processing position, and further the position is moved to the focused ion beam device, and the SIM image is used to focus the ion beam at the position of the measurement result from the mark. To process. However, in the above method, many steps are involved and it is necessary to automate the process. In addition, a dimensional error occurs due to the influence of the distortion, rotation, and magnification difference of the optical system between different optical systems, which makes it impossible to process the target location with submicron accuracy. In order to overcome these problems, the present invention is characterized in that it is configured to provide a simple method capable of controlling processing with submicron accuracy.

The means for solving the above-mentioned object is carried out by the following procedure using the symbols shown in FIG.

1. A desired processing position is searched for using a heterogeneous optical system (confocal optical microscope) mounted in parallel with the focused ion beam device.

2. The processing position determined by the different optical system is moved to the focused ion beam. The mark is processed (Xi, Yi) i = 0 to 4 (for example, the four corners and the center of a quadrangle) with a focused ion beam. This processing position (Xi, Yi) is processed by the coordinate system of the deflector of the focused ion beam device, and since the cross-section processing is also performed by the focused ion beam device, the coordinate system of the focused ion beam device is used as the reference coordinate. Therefore, it is an object of the present invention to accurately convert the coordinate system of the heterogeneous optical system into the coordinate system of the focused ion beam device in order to achieve submicron accuracy. Therefore, the signals (si, ti) i = 0 to 4 given to the deflector and the deflection amount (Xi, Yi) i =
Consider that 0 to 4 are equal. That is, si = Xi, ti =
Yi; i = 0 to 4.

3. Move the mark to the different optical system. A mark processed by a focused ion beam is displayed on an observation workstation by using a heterogeneous optical system.

4. Five points (xi, yi) i = 0 to 4 are measured from the image on the workstation at each mark position (center). This measurement is performed by detecting the edge of the mark from the image on the workstation (automatic measurement).

The next thing to be done is to find a method for aligning the coordinate system of the different optical system with the coordinate system of the focused ion beam apparatus.

This is because when the data of (Sj = sj-s0, Tj = tj-t0) j = 1 to 4 is given to the deflection plate of the focused ion beam apparatus, the actual deflection distance (coordinates) is (uj
= Xj-x0, vj = yj-y0) It means that j = 1 to 4 is converted.

5. Therefore, the coordinates ((u
i, vi) i = 0 to 3: measurement position) is the coordinate of the focused ion beam optical system ((Si, ti) i = 0 to 3: processing position)
To the conversion formula below.

That is, assuming i = 0 to 3

[0041]

Ui = Si + a1Si + a2Ti + a3SiTi + a0 (Equation 5)

[0042]

[Equation 6] vi = Ti + b1Si + b2Ti + b3SiTi + b0 (Equation 6)

When Mathematical expression 5 is displayed in matrix, ((s
(0, t0) is the deflection center and s0 = 0, t0 = 0)

[0044]

(Equation 7)

It becomes Similarly, the number 2 can be displayed in a matrix.

These equations 5 and 6 are solved by a control computer to obtain the conversion coefficients a0 to a3 and b0 to b3.

What we want to do next is to find the position of the focused ion beam that coincides with the position determined by the different optical system, that is, give the data (u, v) and correspond to it (S, T).

This is ui, vi, a0-a3, b0
Equations 1 and 2 can be solved and obtained from b3 for Si and Ti.

6. The processing location (u0, v0) is searched for in the different optical image displayed on the workstation, and the processing area (Δu, Δv) is set.

7. Move the mark towards the focused ion beam. The focused ion beam image is taken into the workstation and the center mark position (X, Y) is measured. This measurement is performed by detecting the edge of the mark from the image on the workstation (automatic measurement).

8.5. Conversion coefficients a0 to a3, b obtained in
Processing position (S (u0) + X, T (v0) + Y) in the focused ion beam (coordinates) by using 0 to b3 and Equations 1 and 2
Is calculated and the corresponding processing location is displayed on the focused ion beam image.

9. Set machining parameters and perform machining.

Further, the above method can be similarly applied to a compound device in which a laser microscope is mounted on an electron beam device. As an example, when moving the stage based on the foreign substance information measured by the dust inspection device and performing observation measurement with an electron beam, for a foreign substance for which information cannot be obtained (cannot be observed) with the electron beam, close to the observation position. Irradiate an electron beam to make a mark with carbon contamination in a vacuum or electron beam induced deposition, and use it as a mark to observe with a laser microscope, identify the observation position with a laser microscope, or reverse the above sequence. The position can be identified by operation.

[0054]

EFFECTS OF THE INVENTION Obtained by scanning a focused ion beam,
It can be observed by using a confocal optical microscope in which the lowermost layer wiring of the semiconductor device, which cannot be observed in the secondary particle image, is mounted in parallel with the focused ion optical system. According to the correction method of the present invention using this confocal optical microscope, even if it is the lowermost layer wiring of the planarization device that is covered with passivation, the observation and processing position can be easily adjusted with submicron accuracy. You can make an accurate decision.

[Brief description of drawings]

FIG. 1 is an explanatory view of a conventional device.

FIG. 2 is an explanatory diagram of a device structure.

FIG. 3 is an explanatory diagram of an apparatus for implementing the present invention.

FIG. 4 is an explanatory diagram of mark positional relationships.

[Explanation of symbols]

1 ... Machining power supply controller, 2 ... Ion source, 3 ... Ion source controller, 4 ... Ion beam, 5 ... Lens controller, 6 ... Electrostatic lens, 7 ... Deflector controller, 8 ... Deflector, 9 ... Sample, 14 ... Detector Controller, 16 ... Device control computer, 18 ... Interlayer insulating film, 20
... Second layer Al wiring.

Claims (5)

[Claims] 1. An ion beam irradiation mechanism for focusing and irradiating ions extracted from an ion source onto a sample placed on a moving mechanism capable of moving in a multidimensional manner, and scanning the irradiation position two-dimensionally. And a secondary particle detection mechanism that performs mark processing at a plurality of points on the sample by irradiation of the ion beam, detects secondary particles generated from the mark, and forms a secondary particle image by the detection signal. In the ion beam irradiating device, the ion beam irradiating device includes a device in which a heterogeneous image observation system including information insufficient in the secondary particle image is mounted in parallel with the ion beam irradiating mechanism.
As a polymerization mechanism for adjusting and superimposing the heterogeneous image containing the position information of the processed portion under the surface which cannot be observed by the secondary particle image, the coordinate conversion between the heterogeneous optical systems is performed as a focusing ion. An ion beam irradiation apparatus capable of performing observation and processing with high precision of submicron simply and quickly, which is characterized by performing marks processed by a beam as reference coordinates. 2. The ion beam irradiation method according to claim 1, wherein the coordinate conversion is performed by the following procedure. 1. A desired processing position is searched for using a heterogeneous optical system mounted in parallel with the focused ion beam device. 2. The processing position determined by the different optical system is moved to the focused ion beam. Process marks with focused ion beam (Xi, Y
i) i = 0 to 4 (for example, the four corners and the center of the quadrangle). This processing position (Xi, Yi) is processed by the coordinate system of the deflector of the focused ion beam device, and since the cross-section processing is also performed by the focused ion beam device, the coordinate system of the focused ion beam device is used as the reference coordinate. . Therefore, the signals (si, ti) i = 0 to 4 given to the deflector and the deflection amount (Xi, Y
i) Consider that i = 0 to 4 are equal. That is, si = X
i, ti = Yi; i = 0-4. 3. Move the mark to the different optical system. A mark processed by a focused ion beam is displayed on an observation workstation by using a heterogeneous optical system. 4. From the image on this workstation, each mark position is measured as 5 points (xi, yi) i = 0-4. Next, (Sj = sj−s0, Tj
= Tj-t0) j = 1-4, the actual deflection distance (coordinates) is (uj = xj-x0, vj = yj
-Y0) Convert so that j = 1 to 4. 5. Therefore, the coordinates ((ui, vi) i =
0-3: measurement position) is adjusted to the coordinates ((Si, ti) i = 0-3: processing position) of the focused ion beam optical system using the conversion formula of the following formula. That is, when i = 0 to 3, ui = Si + a1Si + a2Ti + a3SiTi + a0 (Equation 1) vi = Ti + b1Si + b2Ti + b3SiTi + b0 (Equation 2) Mathematical formula 1 and mathematical formula 2 are solved by a control computer, and conversion coefficients a0 to
Calculate a3, b0 to b3. Next, the arbitrary points (ui, vi) surrounded by the marks and the above a0 to a3 and b0 to b3 are substituted into equations 1 and 2 to solve for Si and Ti. 6. The processing area (u0, v0) is searched for on the different optical image displayed on the workstation, and the processing area (Δu, Δ
v) is set. 7. Move the mark towards the focused ion beam. The focused ion beam image is taken into the workstation and the center mark position (X, Y) is measured. 8.6. Processing location (u0, v0) and 5. Positions (S (u0), T (v) in the focused ion beam (coordinates) using the conversion coefficients a0 to a3, b0 to b3 and
0)) is calculated and the machining position (S (u0) + X, T (v0) +
Y) is displayed on the focused ion beam image. 9. Set machining parameters and perform machining. 3. When a heterogeneous image is captured in a control computer and the machining position is controlled from the workstation by using the image, the stage is moved to the machining position based on the data of the foreign substance inspection device to obtain an image of the heterogeneous optical system. The ion beam irradiation device according to claim 1, wherein the position of dust or processing is confirmed by using the ion beam irradiation device. 4. A laser microscope is used as the heterogeneous optical microscope, the alignment mark position of the wafer is detected by using the laser light, and a memory function for accumulating images obtained by changing the focus of the objective lens of the laser microscope is provided. Item 1. The ion beam irradiation device according to item 1. 5. The ion beam irradiation apparatus according to claim 1, wherein the mark processing is performed by ion induced deposition.