JPH0689886A - Ultra-fine processing method - Google Patents

Abstract

(57) [Summary] [Purpose] The purpose of the STM processing method is to enable correction of positional deviation due to drift of the sample temperature. [Structure] 1) A probe is made to face the surface to be processed, and while scanning the probe, electron flow or electric field emitted or absorbed from the tip of the probe causes holes or holes to be formed at a plurality of positions on the surface to be processed. A protrusion is formed as a marker, the position of the marker is measured at a plurality of scanning speeds, and the amount of drift in the relative position between the tip of the needle and the surface to be processed is obtained from the obtained positional deviation data, Drawing the drift amount into the drawing data and controlling the scanning speed of the probe, applied voltage, and current to perform drawing, 2)
In the surface to be processed having a known surface structure, the shape of the surface to be processed is used instead of the marker.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a processing method for forming an ultrafine structure such as a semiconductor device. The trend of semiconductor device technology is to increase the degree of integration and improve the function. For the former, development of fine processing technology is indispensable. For the latter, devices using the quantum effect are being developed, but since quantum functions are likely to occur in microstructures of 100 nm or less, development of microfabrication technology is indispensable.

Photolithography is mainly used for fine processing of semiconductor devices, and its limit is several 100 nm.
In order to perform finer processing, processing technology using ion beam or electron beam has been developed, and its limit is considered to be several tens nm. New technology is required for smaller microfabrication.

A promising next-generation ultrafine processing technology is a processing technology using a scanning tunneling microscope (STM).
STM is originally for observing the arrangement of atoms three-dimensionally, but because the STM measuring needle is sharp, it is possible to emit or absorb an electron beam from its tip with a small voltage. Utilizing this, as shown in FIG. 4, the probe 1 brought close to the substrate 2 makes a minute hole in the substrate 2 (a positive voltage is applied to the probe) or a minute protrusion is formed (the probe). Negative voltage can be applied). Using this processing technology, the world's smallest letters can be drawn, and atoms scattered on the substrate can be moved one by one with a needle to rearrange them into letter shapes.

However, such a technique is in the stage of exploring the possibility of a processing technique using STM, and many problems must be overcome for practical use.

[0005]

2. Description of the Related Art There are two types of conventional STM drawing, similar to electron beam drawing, that is, raster scanning, which is the same as television scanning, and vector scanning, which is the same as one-stroke writing.

In raster scanning, a voltage is applied to the probe when the probe reaches a position to be drawn. On the other hand, in vector scanning, since the probe is moved while voltage is applied, it is not possible to draw a complicated pattern that is not a single stroke, so raster scanning is usually adopted.

However, in raster scanning, even if the sample temperature slightly fluctuates, the sample position fluctuates, so that the drawn image is distorted. There is a misalignment of about 1Å with a temperature fluctuation of 10 ^-4 ° C. This effect cannot be ignored if the drawing area becomes large.

Since the change of the sample temperature varies depending on the drawing conditions, it is impossible to previously store the correction data in the drawing control device.

[0009]

In the conventional example, the drift of the sample temperature could not be corrected, and accurate drawing could not be performed.

An object of the present invention is to provide an STM processing method capable of correcting a positional deviation with respect to a sample temperature drift.

[0011]

[Means for Solving the Problems] 1)
The first step of setting a marker at arbitrary plural positions on the surface to be machined, measuring the position of the marker plural times at plural scanning speeds, and searching from the data of positional deviation in the plural times measurement of the specific marker. Ultra-fine having a second step of obtaining a drift amount of a relative position between the tip of the needle and the surface to be processed, and a third step of controlling the probe based on the drift amount and performing drawing Processing method, or 2) In the first step, the probe is opposed to the surface to be processed, and while scanning the probe, the probe is scanned by an electron flow or an electric field radiated or absorbed from the tip of the probe. This is achieved by the ultrafine processing method described in 1) above, which includes the step of forming markers composed of holes or protrusions at a plurality of positions on the processing surface.

Further, in the work surface having a known surface structure, the shape of the work surface can be used instead of the marker.

[0013]

FIG. 1 is a diagram for explaining the principle of the present invention. Two or more markers 3 serving as a reference for measuring the temperature drift are formed on the substrate 2 to be processed inside or outside the drawing area.

In the figure, the white circle indicates the position to be marked, the black circle indicates the actual marking position, and at the position of the last marker 34 in the scanning order, the temperature with the passage of time from the first marker 31 to the last marker 34. Due to the change, drift (positional deviation) occurs in the X and Y directions as indicated by the arrow.

Before drawing, a plurality of markers are formed in advance by applying a voltage to the probe while raster-scanning the probe. Next, immediately before drawing, the marker position is detected multiple times at different scanning speeds. Since the drift velocity is obtained from this result (see FIG. 3) and the drift velocity is corrected in the image data input in advance to the control device before the drawing, it is possible to perform the drawing in which the distortion due to the drift is corrected.

[0016]

Embodiments FIGS. 2A to 2D are plan views illustrating an embodiment of the present invention. The substrate to be processed is a silicon (Si) wafer on which a Ge-Se film and an Ag-Se film are deposited by sputtering and plating, respectively. An Ag electrode is provided on the surface of the Ag-Se film, and a voltage is applied between this and the probe.

As the probe, a Pt needle having a sharpened tip by mechanical polishing is used. Using this needle, the atomic image on the surface of highly oriented sintered graphite is observed in advance, and it is confirmed that the tip is sufficiently sharp. The shape is measured by applying a voltage of +1 V to the probe and applying a current of 0.1 nA.

For marking and drawing, when the probe reaches a predetermined position on the way of raster scanning, the voltage and current of the probe are +
This is done by making holes in the Ag-Se film at 3 V and 0.1 nA. At this time, the number of scanning lines in one screen is 256, and the number of moving steps in the horizontal direction is 256.

Specific steps for drawing "F" using the STM drawing apparatus will be described below in order. (1) A scanning area 4 having a scanning area of 75 nm × 75 nm is set on the substrate [FIG. 2 (A)]. (2) Set the scanning time to 30 seconds, set the controller so that marking is performed at the four corners of the 50 nm square region, and perform marking under these conditions. At this time, the markers 32 to 34 are attached at positions deviated from the four corners of the square due to drift. [FIG. 2 (B)] The marker 31 is attached at an accurate position because it is the initial scanning position, but the markers 32 to 34 are attached in the latter stage of scanning, so that the position shift due to temperature change occurs. (3) Next, the surface condition of the substrate is observed for five scanning times of 15 seconds, 30 seconds, 60 seconds, 90 seconds, and 120 seconds, and the marker position is measured. The drift velocity is calculated from FIG. 3 from the displacement of the marker position measured at each scanning time.

FIG. 3 is a diagram for obtaining the drift velocity, and shows the relationship of the positional deviation (nm) of the marker in the X-axis and Y-axis directions with respect to the scanning time (second). The longer the scanning time, the larger the change in the substrate temperature, and the larger the amount of displacement of the marker. The slope of the straight line represents the drift velocity (nm / s).

Based on the obtained drift velocity, the drawing data registered in advance in the control device is corrected. (4) Draw "F" [Fig. 2 (C)]. When the image is drawn without correction, the image is distorted as shown by the dotted line in FIG.

Although a hole is used as the marker in this embodiment, a protrusion formed by applying a negative voltage to the probe may be used. If the surface shape of the substrate to be drawn is known and this shape is stable, the shape can be observed instead of the marker and the drift velocity can be obtained from the amount of strain. For example, the 7 × 7 structure of the Si (111) substrate surface or the shape of the graphite surface can be used instead of the marker. In this case, the image is complicated and a large-scale image processing device is required.

The method of detecting the position of the shape of the marker or the known structure at different scanning speeds by the above method and measuring the drift speed due to temperature is effective not only for drawing but also for correction of the image at the time of observation.

Next, the process of correcting the drawing data registered in advance in the controller based on the obtained drift velocity will be described in order. (1) Registration of drawing data Register the plot position (P _x , P _y ) as the coordinate (0, 0) at the upper left of the screen as the coordinate (X, Y) at the lower right of the screen. (Fig. 2
Reference) Next _{, the} drawing speed is registered. (2) Drift Velocity Measurement From FIG. 3, the drift velocities D _x and D _y in the x direction and the y direction are obtained using the method of least squares. (3) Drawing data correction Lot position (P _x , from the coordinates (0, 0) on the upper left of the screen)
The P _y) the time required to t _x, and t _y, rewrite the _{P x → P x -D x ·} t x P y → P y -D y · t y and data.

Here, t _x and t _y are expressed as a function including the drawing speed and the speed of returning from the left end to the right end during raster scanning. (4) Start drawing

[0026]

According to the present invention, it becomes possible to correct the positional deviation due to the drift of the sample temperature, and the accurate STM processing can be performed.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of the present invention.

FIG. 2 is a plan view illustrating an embodiment of the present invention.

[Fig. 3] Diagram for obtaining drift velocity

[Figure 4] Explanatory drawing of an example of processing by STM

[Explanation of symbols]

 1 probe 2 substrate to be processed 3, 31, 32, 33, 34 marker 4 scanning area

Claims (2)

[Claims] 1. A first step of setting a marker at arbitrary plural positions on a surface to be processed, a position of the marker is measured plural times at plural scanning speeds, and a specific position of the marker in plural measurements. A second step of obtaining a drift amount of a relative position between the tip of the probe and the surface to be processed from the deviation data, and a third step of controlling the probe based on the drift amount and performing drawing. An ultrafine processing method comprising: 2. In the first step, the probe is opposed to the surface to be processed, and the surface to be processed is caused by an electron flow or an electric field emitted or absorbed from the tip of the probe while scanning the probe. 2. The ultrafine processing method according to claim 1, further comprising the step of forming markers composed of holes or protrusions at a plurality of upper positions.