JP2002264099A - Fine machining device and fine machining method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fine machining device and a fine machining method allowing easy machining even to the interior of a closed region surrounded by a pattern of an insulator and free machining of a more complicated fine pattern in machining a machining pattern transformed into an insulator, on a conductive workpiece. SOLUTION: In this fine machining device or method, wherein voltage is applied between a conductive probe and the conductive workpiece to form the machining pattern transformed into the insulator, on the workpiece, has a machining condition computing means for computing a machining condition on the basis of data from a machining data input means and a machined data storage means, and the workpiece is machined on the basis of the machining condition computed by the machining condition computing means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine processing apparatus and a fine processing method, and more particularly to an SPM (scanning probe microscope) for relatively scanning a measurement sample with a probe to obtain information on the measurement sample, and in particular, a non-contact atomic force microscope. Atomic force microscope (NC-AFM)
The present invention relates to a microfabrication apparatus and a microfabrication method for processing the sample using the principle described above.

[0002]

2. Description of the Related Art In recent years, a scanning tunneling microscope (hereinafter abbreviated as STM) capable of directly observing the electronic structure of a conductor has been developed [G. Binning et al. Phys. R
ev. Lett, 49, 57 (1982)]
M (atomic force microscope), SCM (scanning capacity microscope),
Microscope devices, such as NSOM (near field microscope), which obtain various information and its distribution by scanning a probe with a sharp tip, have been developed one after another. At present, these microscope groups are collectively referred to as scanning probe microscopes (SPM), and have been widely used as means for observing microstructures having resolution at the atomic and molecular levels. Above all, a scanning atomic force microscope (AFM) has attracted attention because it can measure the surface shape regardless of the electrical characteristics of the object to be measured. The atomic force microscope has two measurement modes, a contact (contact) mode and a non-contact (non-contact) mode.
M is useful because it hardly deteriorates the probe or the sample.

[0005] On the other hand, a method of performing processing on the order of nanometers using the principle and apparatus configuration of SPM has also been proposed and actually reported as an apparatus. The most obvious method is to relatively move the probe and the sample surface while the probe supported by the elastic body is in contact with the sample surface, as described in JP-A-10-340700. Accordingly, a cutting method for processing a sample surface has been proposed. According to this method, a wiring pattern can be formed or an element itself can be formed by forming an electrically insulating layer by digging a groove in a conductive thin film. However, in practice, due to changes in the tip of the probe due to friction and the effects of cutting chips, it is necessary to set conditions (selecting the probe and the material to be processed, selecting the shape of the tip , Pressing conditions for the target material, etc.)
Need to be considered.

[0004] Next, a relatively simple method that has recently attracted attention is a local metamorphic effect on a conductive workpiece using a scanning tunneling microscope as disclosed in JP-A-9-172213. It is. As an example actually reported, a voltage is applied between a conductive probe and a conductive thin film to be processed (such as a semiconductor thin film or a metal thin film on an insulating substrate), and thereby the processing target is processed. Is locally oxidized to form an electrically insulating pattern, thereby making a wiring or an element. For example, Appl. P
hys. 86, 1898-1903 (1999), in a non-contact mode scanning atomic force microscope (NC-AFM: non-contact AF).
M), the insulating pattern is processed by applying a specified bias to the Si substrate electrode to be processed. Devices using a nanometer-order structure manufactured by using such a method are also being devised.

[0005]

By the way, an appropriate bias between a probe (probe) and a sample (object to be processed) is applied in the processing method using the technique of the scanning probe microscope as described above. In the method of transforming the object to be processed and electrically insulating the object, generally, it is necessary that both the probe and the sample have good conductivity. For example, in the aforementioned J.I. Appl. Phys. 86, 1898-
In the case of anodic oxidation as shown in 1903 (1999), an Si substrate electrode is used as a processing target, a silicon cantilever coated with a Ti thin film by sputtering as a probe, and a specified bias is applied between the probe and the sample. The Si substrate is used in a state where it is electrically connected to a power supply. By doing so, the voltage between the probe and the sample is controlled to the voltage set by the power supply. Where S
The i-substrate is doped with p-type and has a resistance of 14Ω /
cm.

However, when this mechanism is applied to actual device processing, it is not always possible to connect the potential of the processing point by a conductive path. When a certain part of a device is processed by a probe, it is difficult to process the same using the above method as it is. For example, when patterning is performed by oxidizing a conductive thin film, the situation shown in FIG. 2 falls. That is, the conductive region is surrounded by the insulating pattern, and even if an attempt is made to form a pattern further inside, the pattern cannot be formed because there is no current path. In this situation, there is a problem that processing is no longer possible.

Accordingly, the present invention has been made to solve the above-described problems, and when processing a conductive workpiece into a processing pattern transformed into an insulator, the inside of a closed region surrounded by the pattern of the insulator is processed. It is another object of the present invention to provide a fine processing apparatus and a fine processing method that can easily process even more complicated patterns finely.

[0008]

SUMMARY OF THE INVENTION The present invention provides a fine processing apparatus and a fine processing method configured as described in the following (1) to (8) in order to solve the above-mentioned problems. (1) a conductive probe is provided, the conductive probe is relatively scanned with respect to a conductive workpiece, and a voltage is applied between the conductive probe and the conductive workpiece; In a micromachining device for forming a processed pattern transformed into an insulator on the workpiece, processed data input means for inputting processed pattern data to be processed, and processed data storage means for storing processed pattern data A processing condition calculating means for calculating a processing condition based on the data from the processed data input means and the processed data storage means, and processing the workpiece based on the processing condition by the processing condition calculating means. A fine processing apparatus characterized by performing. (2) The processing condition calculation means includes a closed region search unit that searches for a closed region in which a region including the processing pattern to be processed is surrounded by the processing pattern transformed into the insulator. The microfabrication device according to (1). (3) The fine processing method according to (2), wherein the processing condition calculation means has a configuration of calculating an area of the closed region from the searched closed region and calculating a processing condition from the area. Processing equipment. (4) The fine processing apparatus according to (3), wherein the processing condition is a processing voltage condition applied between the conductive probe and the conductive workpiece. (5) The conductive probe is relatively scanned with respect to the conductive workpiece, and a voltage is applied between the conductive probe and the conductive workpiece so that an insulator is applied to the workpiece. In the micromachining method for forming a modified machining pattern, a step of inputting machining pattern data to be machined, a step of storing machined pattern data, and a step of calculating machining conditions from each data in each of the steps , Including
A micromachining method, wherein the workpiece is machined based on the machining conditions calculated in the step of calculating the machining conditions. (6) The step of calculating the processing condition includes a step of searching for a closed area in which a region including the processing pattern to be processed is surrounded by the processing pattern transformed into the insulator. The fine processing method according to 5). (7) The step of calculating the processing condition includes a step of calculating an area of the closed region from the searched closed region and calculating a processing condition from the area. Fine processing method. (8) The processing method according to (7), wherein the processing condition is a processing voltage condition applied between the conductive probe and the conductive workpiece.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In an embodiment of the present invention,
By applying the above configuration, when processing a processing pattern transformed into an insulator on a conductive workpiece, it is also easy to process the inside of a closed region surrounded by the pattern of the insulator. It is possible to realize a fine processing apparatus and a fine processing method that can freely process a more complicated and fine pattern.

Next, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of a microfabrication apparatus according to the present embodiment. The central structure is a non-contact type AFM. The probe 101 has a cantilever structure, and has a unique mechanical resonance point depending on its shape and the like. The laser beam from the semiconductor laser unit 105 is reflected at the tip of the probe, and the reflected light is received by the four-division photodiode 106, whereby the deflection of the probe can be detected. This is the so-called “light lever” method. A vibration actuator 104 is attached to the support portion of the probe, so that the probe can be vibrated. The excitation signal is generated through a displacement detector 107, a variable gain amplifier 108, and a phase shifter 109 based on the output of the four-division photodiode 106.
This system is designed to vibrate the probe at the resonance point of the probe with a constant intensity, and is configured to maintain this operation even when the resonance point fluctuates.
Next, the displacement detected by the displacement detector 107 has a waveform that oscillates at the resonance frequency of the probe. From this signal, the FM detector 110 picks up a frequency fluctuation and sends it to the subsequent stage as a detection signal (arrow in the figure). ). Although the latter stage is not shown, a general signal measuring device such as a monitor or an analyzer is connected here.

When the tip of the probe 101 resonating at the resonance point approaches the substrate 102 to be processed and the interatomic force starts to act as a restraining force between the two, the resonance point of the probe fluctuates. That is, a change in the distance between the tip of the probe and the substrate is observed as a change in the resonance frequency. Therefore, the frequency fluctuation of the FM detector, that is, the above-described detection signal has as its component the unevenness information of the substrate surface. This is the AFM signal. AFM detected by detector 110
The signal is also sent to the Z-direction feedback controller 111. The controller 111 calculates a control amount by comparing with a preset set value, generates a drive signal based on the control amount, and applies the drive signal to the Z drive element unit of the stage scanner 103. That is, this enables feedback control with a constant distance between the probe tip and the substrate. The controller 111 also sends the calculated control amount to a subsequent stage (arrow in the figure) as a signal of the surface unevenness. This signal is the actual distance control between the probe and the sample.

Next, details of a machining control portion which is a characteristic configuration of the present embodiment will be described. The processing data input from the processing data input unit 115 is transmitted to the processing control unit 1
14 and is subjected to data processing based on a predetermined procedure described later. Thereafter, the processing control unit 114 outputs a processing signal to the processing voltage application unit 113, and the processing voltage application unit 113 applies a processing voltage based on the processing signal to the processing target substrate (sample) 102 installed in a stage shape, Execute the processing.

FIG. 5 is a block diagram showing an example of the signal processing of the processing control unit 114. When the data is input, the processed area and the closed area search unit 501 searches for the processed and closed area to determine whether the input data is in the processed closed area. If the processing point is in the processed closed region, the closed region area calculation unit 503 calculates the area of the closed region. Then, a processing condition (processing voltage condition) is calculated based on the area in the processing condition calculation unit 504 of the next stage, and the scanning signal and the processing signal are respectively combined with the processing position data input by the input data. Output. The input new processing data is stored in the processed storage area 502.

The calculation method of the processing condition calculation unit 504 will be described. As an example, as shown in FIG.
A case is shown in which processing is performed at a probe position as shown in the figure, using a conductive thin film formed on a thin insulating layer on a conductive substrate like I. In this case, the conductive probe 201 is controlled at a fixed distance from the surface of the processed substrate (conductive region 202) by the non-contact AFM system. There is a processing point in the conductive region 202 which is a region surrounded by the processed insulating pattern 203 and electrically insulated from the conductive substrate 205 below by the insulating layer 204. However, in the case of processing, the conductive region 2 is located between the conductive region 202 and the conductive probe 201.
It is necessary to apply a predetermined voltage corresponding to the area No. 02, and in this case, it is considered that an electrical equivalent circuit is as shown in FIG. 3, and the voltage between the substrate and the probe is the capacitor C of FIG.
It corresponds to the voltage applied to both ends of t. Here, Ct is the capacitance between the conductive probe 201 and the conductive region 202, Rt is the resistance between the conductive probe 201 and the conductive region 202, Ci
Denotes a conductive region 202 sandwiching the insulating layer 204 and the conductive substrate 2
The capacitance between 05 and E is the applied voltage. That is,
The voltage between the conductive probe 201 and the conductive region 202 can be obtained by dividing the applied voltage E.

Here, however, Ci is not constant but varies depending on the area of the conductive region 202, that is, the pattern shape. Therefore, when the above-mentioned predetermined voltage is applied between the conductive probe 201 and the conductive region 202, the voltage E which must be applied by the processing power source takes into account the partial voltage between the capacitors Ct and Ci. You need to decide. Therefore, the processing condition calculation unit 504 shown in FIG. 5 performs processing using the following relationship to determine the voltage.

Rt is a very large value obtained by combining the tunnel resistance, the field emission current at the time of processing, and the like.
It is considered to be a value from 00 MΩ to several tens GΩ. Vth is a voltage required for processing. As described above, Ct is the area S obtained from the shape of the conductive region and the thickness d (constant) of the insulating layer.
Required by Ci can be estimated from the effective area and distance. The distance is several nm to several tens of nm, and the effective area is about several hundred nm ² .

The above-described capacitance Ci is relatively strictly determined by calculation based on the area, material, and thickness of the insulating layer. However, the capacitance, resistance value, and the like between the conductive probe 201 and the conductive region 202 may deviate from values estimated by calculation depending on the material, surface state, atmosphere state, and the like of the probe and the processing substrate. General. Therefore, at the time of actual machining, it is necessary to determine the voltage E that can be machined in the first machining, and then determine the value of Ct.

Further, in the electric circuit as shown in FIG. 3, since a steady current does not flow, the electric charge accumulated in the conductive region does not come out. Therefore, it is actually necessary to apply the voltage as shown in FIG. That is, after processing is performed at a certain voltage, a voltage having an opposite polarity is applied to discharge electric charges. By doing so, the system is refreshed every cycle and processed stably. The frequency at this time is the above-mentioned ω
It is.

[0019]

Embodiments of the present invention will be described below. This embodiment is an example of actual processing using the above apparatus.
Using an SOI substrate having an insulating layer thickness of 300 nm and an n-type doped upper conductive film thickness of 10 nm as a processing target substrate, a pattern having a shape as shown in FIG. 4 was processed. As the probe, a silicon cantilever having a resonance frequency of 355 kHz on which Au was deposited was used. The tip radius of curvature was about 100 nm. The reference frequency at the time of feedback, that is, the center position of the feedback is -100 Hz from the free resonance frequency.
The control was performed by setting the position. First, a closed curve pattern having a known area is formed on a substrate on which nothing has been processed, and a test process is performed inside the closed curve pattern to measure an actual capacitance between the probe and the processed substrate, a resistance value, and a workable voltage threshold. As long as processing is performed in the same probe, the same processing substrate, and the same atmosphere, this measured value does not greatly change. Actually, processing was performed on a basic pattern having a size of 200 nm × 200 nm (4 × 10 ⁻¹⁴ m ² ), and a partial pressure ratio was calculated from a bias capable of performing good processing to obtain Zt and Zi. In the case of this embodiment, the applied voltage was 15.0 V with respect to the processing voltage threshold value of 3.0 V, and the voltage division ratio was 4: 1.
Since the buried SiO ₂ layer of the SOI is 300 nm, the capacitance is calculated assuming that the relative permittivity of SiO ₂ is 3.9.
Assuming that the applied frequency is 3 kHz, Zi is 7.27 × 10 ¹³
Ω. Therefore, Zt is estimated to be 1.82 × 10 ¹³ Ω.

The pattern shown in FIG. 4 was actually processed.
The pattern (a) was processed by inputting the data of A and then processing and inputting the data of B. After inputting A, the system stored the shape in the storage area and processed it. Next, when B is input, the system searches for a closed area including the processing position of B in the processed data. When we discovered that it was inside A, we calculated the area of A. The area is calculated by counting the minimum number of units inside by image processing. The minimum unit number is a square of 1 nm ² , which is arranged side by side in the interior, and counts how many blocks are formed after all the blocks are arranged. Basically, the pattern used straight lines. According to this method, the inside of A is 2.80 × 10 ^−13.
m ² , from which Zi is calculated to be 1.04 × 10 ¹³ Ω. From this, the applied voltage E is It was decided. The processing machine calculates the applied waveform as Va = V in FIG.
d = 4.72V, Ta = Td = 0.5ms, B
Was processed.

The probe sweep speed during this processing is 1
It was set to 00 nm / sec. As a result, the processing was performed well, and according to the AFM observation, a pattern B having the same height and width as the pattern A was formed in the portion indicated by the dotted line in FIG. Next, the pattern shown in FIG. 4B was processed by the processing machine of the present invention. After processing C, first process D,
Finally, E indicated by a dotted line was processed. Observation of the AFM revealed that all the processing lines had the same width and height, indicating that good processing was performed. In forming the pattern E, the area of two areas (the area inside C and outside D and the area inside D) is obtained (the area obtained by subtracting the area of D from C and the area of D). Thus, a voltage corresponding to each area is applied while passing through each area.

[0022]

As described above, according to the present invention, when a processing pattern transformed into an insulator is formed on a conductive workpiece, a closed region surrounded by the pattern of the insulator is formed. The inside can be easily processed, and a fine processing apparatus and a fine processing method capable of freely processing a more complicated and fine pattern can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a microfabrication device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a relationship between a probe and a processing substrate.

FIG. 3 is an equivalent circuit for explaining an operation by voltage application in the embodiment of the present invention.

FIG. 4 is a diagram showing an example of a processing pattern according to the embodiment of the present invention.

FIG. 5 is a block diagram illustrating a data processing part according to the embodiment of the present invention.

FIG. 6 is an example of a machining voltage waveform for describing an embodiment of the present invention.

[Explanation of symbols]

 101: Probe 102: Processing target substrate 103: Stage scanner 104: Vibration actuator 105: Semiconductor laser 106: Quadrant photodiode 107: Displacement detector 108: Variable gain amplifier 109: Phase shifter 110: FM detector 111: z Direction feedback controller 112: Scanner controller 113: Processing voltage application unit 114: Processing control unit 115: Processing data input unit 201: Conductive probe 202: Conductive area 203: Insulating pattern 204: Insulating layer 205: Conductive substrate

Claims (8)

[Claims] A conductive probe for scanning a conductive workpiece relative to the conductive workpiece; applying a voltage between the conductive probe and the conductive workpiece; A processing data input means for inputting processing pattern data to be processed, and a processed data storage for storing processed pattern data in a micro-processing apparatus for forming a processed pattern transformed into an insulator on the workpiece; Means, a processing condition calculating means for calculating a processing condition based on the data from the processed data input means and the processed data storage means, and a processing condition of the workpiece based on the processing condition by the processing condition calculating means. A micromachining device characterized by performing machining. 2. A processing apparatus according to claim 1, wherein said processing condition calculating means includes a closed area search section for searching for a closed area in which an area including the processing pattern to be processed is surrounded by the processing pattern transformed into the insulator. The microfabrication device according to claim 1. 3. The processing condition calculating means calculates an area of the closed region from the searched closed region, and calculates a processing condition from the area.
3. The microfabrication apparatus according to item 1. 4. The fine processing apparatus according to claim 3, wherein the processing condition is a processing voltage condition applied between the conductive probe and the conductive workpiece. 5. A conductive probe is scanned relative to a conductive workpiece, a voltage is applied between the conductive probe and the conductive workpiece, and a voltage is applied to the workpiece. In a micromachining method for forming a machining pattern transformed into an insulator, a step of inputting machining pattern data to be machined, a step of storing machined pattern data, and calculating machining conditions from each data in each of the steps And a step of processing the workpiece based on the processing conditions calculated in the step of calculating the processing conditions. 6. The step of calculating the processing condition includes a step of searching for a closed region in which a region including the processing pattern to be processed is surrounded by the processing pattern transformed into the insulator. The microfabrication method according to claim 5. 7. The method according to claim 6, wherein the step of calculating the processing condition includes a step of calculating an area of the closed region from the searched closed region and calculating a processing condition from the area. The microfabrication method described. 8. The fine processing method according to claim 7, wherein the processing condition is a processing voltage condition applied between the conductive probe and the conductive workpiece.