JPS62210624A - Ion beam processing and apparatus therefor - Google Patents

Abstract

PURPOSE:To prevent the movement of a processing position due to the charging of a target by detecting secondary particles discharged from an object being processed and moving an ion beam irradiating region in a direction wherein the irradiating region coincides with a prescribed region in synchronism with the deflection of an ion beam. CONSTITUTION:When the present scanning region 2 deviates from a processed region 1 that is the prescribed region of an object being processed, the edge portion 3 of the processed region 1 appears in a secondary particle image due to the present scanning region 2. Secondary particles 5 are produced from a target by the irradiation of an ion beam 4. Far more secondary particles are produced in the stage portion of the edge due to the edge effect of an internal scattering as compared with the flat portion of the bottom of a processed portion. In result, the edge portion 3 of the processed region 1 is observed as a very bright portion in the secondary particle image due to the present scanning region 2. From the direction wherein the highly bright edge effect region 3 appears and its magnitude, the direction and the quantity of the movement of a processing region are obtained and, by applying a feedback to the beam scanning region, the processed region and the beam scanning region coincide with each other.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an ion beam processing method and apparatus, and in particular to an ion beam processing method and apparatus suitable for performing micromachining on a workpiece such as a VLSI. Regarding equipment.

[Conventional technology]

In a focused ion beam device, when the target is an insulator, charge-up, in which the charge of primary ions accumulates on the surface of the target, poses a problem in analysis, processing, and the like.

For example, semiconductor devices such as VLSI have a multilayer wiring structure in the vertical direction to increase the degree of integration, but when cutting the lower layer wiring by ion beam processing for purposes such as depacking, the above-mentioned charno assembly is required. The problem arises. In a multilayer wiring structure, when cutting the lower wiring through a thick insulating layer such as StO, which has two or three overlapping layers, charges accumulate on the surface, as shown in Figure 9, for example. The trajectory of the primary ion is bent due to the influence of Therefore, without taking any measures against the bending of the trajectory of the primary ions, for example, as shown in FIG.
Even if an attempt is made to cut a 4 μm x 4 μm rectangular hole through the insulating layer 6 with an ion beam, the processed area 10 will move while wobbling due to the influence of charge-up, resulting in a hole size of up to 5 μm.
A positional shift of m degrees occurs, and the processing often does not reach the wiring 8.

Further, when a photomask is created by turning a Cr film deposited on a positive substrate, the above-mentioned charge-up problem also occurs when an isolated Crz lean is processed. Furthermore, when modifying the X-ray mask used to print 1,000 turns on a wafer using X-rays, PIQ (
A charge-up problem also occurs when processing Au/# turns through a protective film.

In order to solve this charge-up problem, conventionally,
Ionics 45.7 (1979) No. 33, page 33
Page (l0NIC845, 7 (1979) P 28-P
33) using an electron shower, or using negative ions as primary ions.

[Problem that the invention seeks to solve]

In the method using an electron shower, it is difficult to finely adjust conditions such as the amount and energy of electrons irradiated from the electron gun to the target. Therefore, there is a problem in that the temperature of the target increases due to the irradiated electron beam. When the target is a semiconductor device such as a VLSI, a rise in temperature has a negative effect on the device, so it must be avoided as much as possible. With methods that neutralize positive charges with negative charges, such as the method using an electron shower, it is basically difficult to avoid the heating of the target as described above, and it is difficult to avoid the heating of the target as described above. Since it is provided in the primary ion optical system or the secondary electron detection system, the structure becomes complicated and design problems occur with the primary ion optical system or the secondary electron detection system.

Further, the method of using negative ions as primary ions has a problem in that it is difficult to obtain a device that stably generates negative ions.

An object of the present invention is to provide an ion beam processing method and apparatus that can prevent movement of the processing position due to charge-up of the target without affecting the primary ion optical system or the secondary electron detection system.

[Means for solving problems]

The above purpose is to focus and deflect the ion beam onto a predetermined area of the workpiece and to emit 2 ion beams from the workpiece.
Detect secondary particles, synchronize the detection signal with the deflection of the ion beam to obtain a secondary particle image of the actual processing area, and when the processing area deviates from the predetermined area, move the processing area to the predetermined area. This is achieved by moving the ion beam irradiation area in a direction that matches the ion beam. In addition, an ion beam processing device that performs such an ion beam processing method is
In an ion beam processing apparatus that includes an ion source and an ion optical system that focuses and deflects an ion beam extracted from the ion source, and processes a predetermined region of a workpiece, secondary particles emitted from the workpiece are an image memory for synchronizing the output of the means with the deflection of the ion beam and capturing it as a secondary particle image; and a secondary particle image in the image memory that indicates that the ion beam irradiation area has moved from the predetermined area. a processing means for determining the movement direction and the movement amount and outputting a control signal according to the movement direction and movement amount; This can be achieved by providing a means for feedback controlling the direction.

[Effect]

If target charno aggregation occurs and the current scanning area 2 deviates from the processed area 1, which is a predetermined area of the workpiece, as shown in FIG. The edge portion 3 of the processing area 1 is exposed. Secondary particles 5 are generated from the target by the irradiation of the ion beam 4, but compared to the flat area at the bottom of the processing section, a much larger amount of secondary particles are generated at the stepped part of the etso due to the etso effect due to internal scattering. do. As a result, in the secondary particle image obtained by the current scanning area 2, the edge part 3 of the processed area 1 is observed as a very bright part.

The present invention calculates the movement direction and amount of movement of the processing area from the direction and size of the edge effect area 3 with high brightness, and applies feedback to the beam scanning area, thereby scanning the already processed area and the beam scanning. Match areas. At this time, the amount of charge on the Charshaft in the processing area initially increases, but the increase in charge stops when it reaches equilibrium with the amount of leakage from the processing area to the substrate of the workpiece. As a result, the processing area is only slightly larger than the actual beam scanning area, and movement of the processing area due to charge-up is almost eliminated. Figure 2 shows that while observing the processing area 10 with a secondary particle image, when a high-brightness part of the edge part of the processed area appears, the workpiece mounting stake is sequentially operated in a direction to cancel it. 10 is a cross-sectional view of a workpiece that was machined, and is compared with FIG. 10 of the conventional example described above. As described above, when the method of the present invention is applied to perform ion beam processing, the fluctuation of processing can be reduced to ±0.3 μm or less, and the reliability of cutting is 90 inches or more.

The apparatus of the present invention has a configuration in which a secondary particle image is captured into an image memory, a deviation in the processing area is automatically detected by a processing means such as a microprocessor, and the ion beam irradiation area is feedback-controlled in a direction to eliminate the deviation. Therefore, charge-up can be dealt with without affecting the primary ion optical system or the secondary particle detection system.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 3 to 8.

FIG. 3 is an explanatory diagram of the principle of the first embodiment of the present invention. In this embodiment, S I M (Scan-n
Based on the brightness distribution (secondary electron signal intensity distribution) on the central vertical and horizontal lines A and B in the scanning ion microscope (scanning ion microscope) image, the direction and amount of movement of the processing area are detected, and the beam Feed into the scan area
This is what you put the pack on. When the edge region 3 of the processed portion appears in the current beam scanning region 2, a beak P corresponding to the edge region appears in the brightness distribution on the A and B lines. The direction and amount of movement of the processing area are determined from the position and width of this beak P, and the beam scanning area 2 is moved to the position of the processed area 1. As a result, when the processed area 1 and the beam scanning area 2 coincide, the peaks corresponding to the two horns disappear from the brightness distribution on the A and B lines. By sequentially performing the above operations during processing, movement of the processing area is prevented and accurate processing is performed.

Next, an example of the device configuration of this embodiment is shown in FIG.

A full voltage is applied between the ion source 11 and the extraction electrode 12 to extract the ion beer 4, and the ion beam that has passed through the beam-defining aperture 14 is focused onto the tar duct 16 by the electrostatic lens 13. Further, a deflection voltage is applied from the deflector controller 24 to the deflector electric wire 15 to deflect the ion beam and scan the target 9 soto 16 for processing. Secondary electrons 21 emitted from the tarded 16 during ion beam irradiation
is detected by the secondary electron detector 22, and the detection signal is amplified by the head amplifier f23. The same voltage as the deflection voltage applied to the deflector electrode 15 from the Urogumi deflector controller 24 is also applied to the deflection electrode of the CRT 25, and the CRT 25 is subjected to brightness modulation using the secondary electron amplified signal output from the amplifier 23, thereby processing. A secondary electron image or SIM image of region 2 (FIG. 3) is obtained. At the same time, the secondary electron amplified signal is digitalized by the A/D converter 26 and synchronized with the deflector controller 24 to capture the SIM image into the image memory in the main controller 27. On the other hand, the position of the stage 17 on which the tar duct 16 is placed is controlled by the stage controller 20 using the X drive unit 18. This is done via the Y drive section 19.

In this embodiment, two line memories corresponding to vertical and horizontal lines /A and B (FIG. 3) at the center of the SIM image are used as the image memories. And on the main controller,
The distribution of secondary electron signals taken into the line memory at the same time as processing is sequentially determined, and when a peak corresponding to the edge area of the processed part appears, the direction and width of the peak are determined as the moving direction of the processed area. The amount of movement is determined by a computer (not shown) in the main controller, and the current beam scanning area 2 is moved to a point f where it overlaps the processed area 1. This movement of the beam scanning area is performed by applying feedback to one or both of the deflector controller 24 and the station controller 20.

Note that if it is necessary to directly move the stage with an accuracy of about 0.1 μm, a fine movement mechanism such as a piezo element may be used in the stage drive section.

FIG. 5 is an explanatory diagram of the principle of the second embodiment of the present invention. In this embodiment, the direction and amount of movement of the processing area are detected based on the projection signal distribution obtained by adding the luminance distribution in the SIM image of the beam scanning area 2 in the vertical and horizontal directions, and the information is fed back to the beam scanning area. It is something that multiplies. The detection principle is the same as in the first embodiment. Current beam scanning area 2
When the edge region 3 of the processed portion l appears within the area, a peak P corresponding to the edge region appears in each of the vertical and horizontal projection signal distributions. The direction and amount of movement of the processing area are calculated from the direction and width of this peak P. At this time, noise components in the projected signal distribution are canceled by signal addition, and the S/N ratio is improved, so the accuracy of detecting the amount of movement of the processing area is also improved. The device configuration of this embodiment is similar to the device configuration shown in FIG. 4, but the image memory in the main controller 27 uses an image memory that corresponds to the entire SIM image, and has a projection calculation function in the vertical and horizontal directions. It is necessary to use one that has

FIG. 6 is an explanatory diagram of the principle of the third embodiment of the present invention. In this embodiment, a SIM image of the beam scanning area 2 has a plurality of vertical and horizontal lines, and in this embodiment, three lines A each.
Based on the brightness distribution on I*At+AS and B, , B, , B, the moving directions and moving angles of X, Y, θ of the processing area and the respective moving amounts are detected, and the beam scanning area 2 is detected. This is to provide feedback.

In this embodiment, as in the first embodiment described above, the edge region of the processed portion 1 is detected as a signal peak in the luminance distribution on each line. Here, when the current beam scanning area 2 and the processed area 1 are shifted in the θ direction, each peak P1 + Pt +P of the above signal corresponds to each line AI + At r A3 or BI, B,.

B, with different widths on top. Therefore, positioning in the θ direction is performed by moving in the θ direction so that the peak widths on each line are equal. For example, when performing rectangular processing of 4 μm x 4 μm, the detection accuracy of the peak width is 0.15 μm, which is half of the focused beam diameter, so the alignment accuracy in the θ direction is txa-'(-v) tool 2', Accuracy sufficient for practical use can be obtained. After alignment in the θ direction, alignment in the x and y force directions is performed in the same manner as in the first embodiment, thereby aligning the beam scanning area with the processed area.

FIG. 7 shows an apparatus configuration according to this embodiment. The configuration of this device is basically the same as the device configuration shown in FIG. , SIM as an image memory in the main controller 27
The point is that line memories corresponding to a plurality of lines in the vertical and horizontal directions of the image are used. Feedback control of the processing area in the θ direction is performed by using the θ drive unit 31, and also by applying a deflection voltage to the deflector electrode 15 using the deflector controller 24 so as to move the ion beam itself in the θ direction.
You may also adjust it with .

FIG. 8 is an explanatory diagram of the principle of the fourth embodiment of the present invention. In this example, in addition to determining the movement direction and amount in the x and y directions from the vertical and horizontal projected signal distributions of the luminance distribution in the SIM image, as in the second example, the movement direction and amount in the θ direction are also calculated. is calculated and the machining area is feedback-controlled. As shown in FIG. 8, when the current beam scanning area 2 and the processed area 1 are shifted in the θ direction, the esso area 3 of the processed area appears obliquely in the SIM image. As a result, the signal intensity also tilts diagonally in each of the vertical and horizontal projected signal distributions.

Therefore, positioning in the θ direction is performed by moving in the θ direction so that the signal intensity becomes horizontal in each projected signal distribution. After alignment in the θ direction, alignment in the X and Y directions is performed in the same manner as in the second embodiment, and the beam scanning area is made to coincide with the processed area.

The device configuration of this embodiment is similar to that shown in FIG. 7, but it is necessary to use an image memory having a projection calculation function as in the second embodiment.

In each of the above-mentioned embodiments, the SIM image is obtained from secondary electrons, but in the step part of the esso part of the processed area, the yield of secondary ions that are scattered from the targut is also very low. Exactly the same effect can be obtained using a secondary ion image. In this case, a secondary ion image is obtained using a mass spectrometer instead of a secondary electron detector.

〔Effect of the invention〕

According to the present invention, it is possible to prevent movement of the processing area due to the charno ablation and perform accurate processing without affecting the primary ion optical system or the secondary electron detection system. Processing accuracy depends on the distance that the processing area moves during one scan and the resolution of the secondary particle image, but the present invention makes it possible to suppress the processing accuracy to ±0.3 μm or less.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the principle of the present invention, Fig. 2 is a cross-sectional view of a workpiece subjected to ion beam processing of the present invention, Fig. 3 is an explanatory diagram of the principle of the first embodiment of the invention, Fig. 4 is a configuration diagram of the ion beam processing apparatus according to the first embodiment, and FIG.
FIG. 6 is a diagram explaining the principle of the third embodiment of the present invention, FIG. 7 is a configuration diagram of the ion beam processing apparatus according to the third embodiment, and FIG. 8 is a diagram explaining the principle of the third embodiment of the present invention. A diagram explaining the principle of the embodiment, Figure 9 is a schematic diagram showing the influence of the Charno knob, Figure 1
Figure 0 is a cross-sectional view of a workpiece that has been subjected to ion beam processing without taking any measures against charge-up. 1... Already processed area, 2... Current beam scanning area, 3
...A region of high brightness in the SIM image due to the Enono effect (
4. Ion beam, 5.
...Secondary electron, 6...Sin, layer (insulating layer), 7...
・St, N. layer (insulating layer), 8... At wiring, 9... positive charge, 1
0...Processing area, 11...Ion source, 12...Extraction electrode, 13...Electrostatic lens, 14...Beam defining aperture, Process 5...Deflector electrode, 16...Targut , 17...stage, 18
...X drive unit, 19...Y drive unit, 20...Station controller, 21...Secondary electron, 22...2
Next electronic detector, 23... Head amplifier, 24...
・Deflector controller, %...CRT126...
・A/D converter, 27...main controller,
31...θ drive unit. Agent Patent Attorney Tadashi Akimoto Fig. 1 Fig. 2 Fig. 3 Fig. B Win Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 8 Rikiki Projection Figure 9 (〉

Claims (1)

[Claims] 1. When a predetermined region of a workpiece is irradiated with a focused and deflected ion beam, secondary particles emitted from the workpiece are detected, and the detection signal is applied to the deflection of the ion beam. A secondary particle image of the actual processing area is obtained in synchronization, and when the processing area deviates from the predetermined area, the ion beam irradiation area is moved in a direction to match the processing area with the predetermined area. Ion beam processing method. 2. The ion beam processing method according to claim 1, wherein the movement of the ion beam irradiation area is performed by controlling a deflection voltage of the ion beam. 3. The ion beam processing method according to claim 1, wherein the ion beam irradiation area is moved by moving a stage on which the workpiece is placed. 4. The ion beam processing method according to any one of claims 1 to 3, wherein the secondary particles are secondary electrons. 5. The ion beam processing method according to any one of claims 1 to 3, wherein the secondary particles are secondary ions. 6. An ion beam processing apparatus for processing a predetermined region of a workpiece, comprising an ion source and an ion optical system that focuses and deflects the ion beam extracted from the ion source,
a secondary particle detection means for detecting secondary particles emitted from the workpiece; an image memory for synchronizing the output of the secondary particle detection means with the deflection of the ion beam and capturing it as a secondary particle image; processing means that determines from the secondary particle image that the ion beam irradiation area has moved from the predetermined area and outputs a control signal according to the direction and amount of movement, and upon receiving the control signal, sets the amount of movement to zero. 1. An ion beam processing apparatus comprising means for feedback controlling a moving direction of a stage on which a workpiece is placed or a deflection direction of an ion beam. 7. The ion beam processing apparatus according to claim 6, wherein the secondary particle detection means is a secondary electron detector. 8. The ion beam processing apparatus according to claim 6, wherein the secondary particle detection means is a mass spectrometer.