JPH0547649A - Pattern forming method by charged particle beam exposure and charged particle beam exposure apparatus - Google Patents

Abstract

(57) [Abstract] [Purpose] It is an object of the present invention to further improve alignment accuracy in a pattern forming method for performing exposure using a charged particle beam. A position of an alignment mark formed of a step formed on a substrate is optically detected, the substrate is aligned, and a charged particle beam photosensitive resin on the substrate is irradiated with at least one of them. Draw a preliminary mark, then
The position of the latent image of the preliminary mark is optically detected, the positional deviation of the substrate is obtained, and then the main pattern is drawn by the charged particle beam in the state of being realigned so as to correct the positional deviation. To configure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern forming method in which a plurality of patterns are sequentially superposed and printed by using a charged particle beam, and particularly with high precision as in the case of manufacturing a highly integrated and fine semiconductor device. The present invention relates to a pattern forming method that requires drawing.

In recent years, semiconductor integrated circuits have been required to achieve rapid scale-up and rapid detailing at the same time, and there has been a further demand for a technique for drawing a pattern with extremely high accuracy. For this reason, EB (electron beam)
The development of fine processing technology by charged particle beam lithography represented by exposure has been continuously conducted.

In order to perform the fine processing by the charged particle beam lithography with high accuracy, it is used for alignment accuracy, that is, how to adjust the pattern to a predetermined position on the substrate surface, and aberration accuracy, that is, for drawing the pattern. It is well known that the accuracy with respect to the image distortion that inevitably occurs in the lens to be used is a very important parameter. In the development of microfabrication technology by charged particle beam lithography, the emergence of technologies for improving these two types of precision has long been awaited in recent years.

[0004]

2. Description of the Related Art In conventional pattern formation by EB (electron beam) exposure, a substrate is aligned using several substrate alignment marks formed on the substrate, and then several chip alignment marks are formed for each chip. It was used for final alignment and aberration correction. Each alignment mark is formed by, for example, digging a groove in the substrate, and the position of the alignment mark is detected by an EB (electron beam) drawing system, that is, an electron beam generated by an electron beam source and taken out through a lens A system configured to project at a desired position was used to scan the mark with an electron beam to detect reflected electrons or scattered electrons due to unevenness of the mark.

[0005]

In EB (electron beam) exposure, since the etching resistance of the EB (electron beam) resist is not so good, a multi-layer resist method represented by a three-layer resist method is widely used. However, the multi-layer resist method has a problem that since the resist is flattened by the lower layer resist, the unevenness of the resist surface on the alignment mark becomes small and the S / N ratio at the time of detecting the position of the alignment mark deteriorates. The details are as follows.

[0006] For example, in the conventional three-layer resist patterning technique, a resist made of a nopolak resin is spin-coated on the surface of a substrate, and an SOG serving as an intermediate layer is formed on this surface.
(Silicon On Glass) is applied and formed, and then E
A B (electron beam) photosensitive resist is formed by coating. this house,
Since the novolak resin in the lowermost layer is opaque to EB (electron beam) and these multilayer resists are sufficiently thick in total, what is actually observed in alignment is to observe the EB (electron beam) in the uppermost layer. Electron beam) It is only a slight dent formed on the surface of the photosensitive resist. As the precision of flattening increases, even this recess becomes unclear, and it becomes more difficult to perform alignment based on this recess.

Further, in order to precisely form the shape of the fine pattern, in the example of the three-layer resist method, the upper layer resist (EB
It is desirable that the resist) and the intermediate layer have a constant film thickness. This requires the unevenness of the resist surface to be small, but this is contrary to the improvement of S / N at the time of detecting the alignment mark position. If the groove forming the alignment mark is deepened, the unevenness of the resist surface increases and the S / N at the time of detecting the alignment mark position is improved, but the film thickness of the resist and the intermediate layer becomes uneven, and the accuracy of the pattern shape deteriorates. That is, there is a problem that the accuracy of the pattern shape and the alignment accuracy cannot be compatible with each other.

Further, in photolinography, in the case of layers that usually require high alignment accuracy, the previously formed layers are patterned to form alignment marks.
This mark is used to establish a so-called direct alignment relationship in which a layer to be formed later is aligned. However, E
In the conventional method of detecting reflected electrons or scattered electrons due to the unevenness of the mark in B (electron beam) exposure, the mark cannot be accurately detected unless the mark is sufficiently deep. However, there is a problem in that the marks cannot be formed as a matter of course, and a so-called indirect alignment relationship occurs, which limits the improvement of alignment accuracy.

Many techniques for reading the alignment mark with high accuracy have been proposed so far. Proposals for such improved techniques are disclosed, for example, in Japanese Patent Laid-Open Nos. 55-102228, 57-95627, and 5-6.
No. 8-21326. Individually, in the invention described in Japanese Patent Laid-Open No. 55-102228, when attempting to correct the vertical displacement of the sample by the alignment mark measurement, if the accuracy is improved, the number of alignment marks becomes extremely large. It is possible to solve the problem that a large increase is inevitable by means of measuring and storing the displacement in the vertical direction prior to drawing and using it for correction. On the other hand, JP-A-57-956
In the invention described in Japanese Patent Publication No. 27, the problem that the mark cannot be read due to damage to the mark due to etching or vapor deposition is solved by means of separately forming an alignment mark to be used instead when the damage occurs. In the description of Japanese Patent Laid-Open No. 58-21326,
The problem of misalignment between the sample cassette and the drive system is solved by providing an alignment mark on the sample cassette.

Further, the resist of the alignment mark portion is set to E
A method of removing the B (electron beam) exposure prior to the alignment operation has been proposed, but this method has a problem that the removed resist becomes dust or the number of steps is increased when trying to remove it cleanly. .

However, by any technique,
In order to scan the mark with an electron beam and detect reflected or scattered electrons due to the unevenness of the mark, the mark must be formed sufficiently deep, and therefore, a layer formed of a thin film must be formed. Since it is not possible to form marks in that layer during patterning, the patterning of the layer above this is so-called indirect alignment, and there is a limit to the improvement of alignment accuracy.

It is an object of the present invention to provide a charged particle beam exposure pattern forming method and a charged particle beam exposure apparatus which solve the problems of the prior art described above.

[0013]

The object of the present invention is to form a charged particle beam photosensitive resin layer on a substrate having an alignment mark composed of steps, and to determine the position of the alignment mark on the substrate by the light irradiated on the substrate. Detecting the change in the reflected light of the substrate, aligning the substrate with the first position, and then irradiating the charged particle beam photosensitive resin layer on the substrate with the charged particle beam to form at least one preliminary mark. The step of drawing and the position of the latent image of the preliminary mark formed on the charged particle beam photosensitive resin layer in the step are detected from the change in the reflected light of the light applied to the substrate, and the position of the latent image is detected. Measuring the positional deviation from the position where the preliminary mark is to be formed, and then aligning the substrate so as to correct the positional deviation, after which the charged particle beam photosensitive resin layer is charged onto the charged particle beam. Irradiate the main pattern Pattern forming method by charged particle beam exposure having a step of drawing a pattern, optical measuring means for optically measuring the position of an alignment mark previously formed on the substrate, substrate moving means for moving the substrate, and charged particles A drawing means for drawing a pattern on the charged particle beam photosensitive resin on the substrate by a line, and a control means for controlling the optical measuring means, the substrate moving means and the drawing means. The charged particle beam exposure apparatus is configured to detect a latent image of the pattern formed on the charged particle beam photosensitive resin layer.

[0014]

In the present invention, since the alignment mark is optically detected and the position is measured, the unevenness of the alignment mark inside can be measured with good S / N even if the resist is flattened.

Conventionally, since the position is measured using the EB (electron beam) drawing (exposure) system itself, it is not possible to detect and correct the deviation of the EB (electron beam) drawing system itself due to drift or aberration. Although not possible, the present invention utilizes the fact that the latent image in the resist caused by EB (electron beam) exposure is accompanied by a change in the optical constant, and once the preliminary mark is drawn by the EB (electron beam) exposure system. And EB it
The drift and aberration can be corrected by detecting with an optical system separate from the (electron beam) drawing system.

[0016]

An embodiment of the present invention will be described below with reference to the drawings. See FIG. FIG. 1 shows a charged particle beam exposure apparatus according to an embodiment of the present invention, which has a structure in which a semiconductor wafer 1 to be exposed is placed in a processing chamber in a chamber 12 of the apparatus,
On the other hand, an EB (electron beam) drawing system 6 for irradiating an electron beam is arranged at a position facing the main surface of the semiconductor wafer 1. The diffracted light detector 3, the EB (electron beam) drawing system 6 and the stage rotation / movement mechanism 5 can detect a predetermined position of an alignment mark or can accurately draw on a predetermined position of a semiconductor wafer. A signal is transmitted from the computer 7 to control each of the above. Stage rotation
The semiconductor wafer 1 is placed on the stage 4 on the moving mechanism 5, and the diffracted light detector 3 is configured to receive the light emitted from the light source 2 and reflected on the wafer surface.

An exposure method using the charged particle beam exposure apparatus shown in FIG. 1 will be described step by step. Prior to exposure, an alignment mark having a step is formed at a predetermined position on the semiconductor wafer 1 by a known technique, and then an electron beam resist layer (not shown) is formed by coating on the semiconductor wafer by a known technique.

Then, the semiconductor wafer 1 is mounted on the stage 4 by performing a known mechanical alignment (the mechanism is not shown) on the semiconductor wafer 1. After this,
The position of the alignment mark formed on the semiconductor wafer 1 is optically measured. At this time, the surface of the semiconductor wafer 1 is irradiated with the light generated by the light source 2, and the stage 4 is appropriately moved or rotated in the X and Y directions so that the irradiation light can scan the surface of the semiconductor wafer 1. The light reflected from the surface of the semiconductor wafer 1 is incident on the diffracted light detector 3, converted into an electric signal, and transmitted to the calculator 7.

The light generated by the light source 2 is preferably a coherent laser light, and if it is a sheet beam, it has a feature that mechanical operation during scanning can be reduced. When scattering is detected as a result of scanning in the X direction and the Y direction, it is possible to rotate the semiconductor wafer 1 around it and search for the alignment mark position.

The following steps are repeated for each chip. The chip alignment marks 22X and 22Y are measured by the optical systems 2 and 3, and accordingly the semiconductor wafer 1 is rotated and moved to align the chip positions. The stage is moved so as to be near the EB (electron beam) exposure position, and a preliminary mark is drawn on the electron beam resist layer by EB (electron beam) exposure. For example, as shown in FIG. 2, spare marks 21A, 21B,
21C and 21D are drawn. Each of the spare marks
It is preferable to include a diffraction grating in each of the X and Y directions. The positions of the latent images of the diffraction gratings are measured by the optical systems 2 and 3. The light beam to be used at this time is preferably light that does not expose the electron beam resist layer to light even when irradiated, but light that can be easily detected by the diffracted light from the latent image.
For example, a sheet beam of He-Ne (helium neon) laser light can be preferably used. The difference between the measured position of the preliminary mark and the reference position where the preliminary mark should be formed when the EB (electron beam) drawing system is in an ideal state is calculated, and the position shift of the EB (electron beam) drawing system is calculated. The aberration is measured, and then the substrate is adjusted so as to correct the positional deviation and the aberration, and the alignment is performed again. Thereafter, the main pattern is drawn by EB (electron beam).

In the above-described embodiment of the present invention, the chip alignment mark is used to perform the alignment for each chip. Instead, the mark position selected from the entire wafer is measured and statistical processing is performed. You may do so.

The number of spare marks is not limited to four, and their positions are not limited to four corners. In addition, drawing of the preliminary mark 4 and its measurement do not necessarily have to be performed for each chip. Also,
The alignment mark measurement position is not always E due to the optical system.
It does not have to be the center of the B (electron beam) drawing area.

In the above embodiment of the present invention, an electron movie was used as the charged particle beam, but the same action and effect can be obtained by using a focused ion beam instead of the electron beam. can get.

[0024]

According to the pattern forming method and the charged particle beam exposure apparatus by the charged particle beam exposure of the present invention, the S / when reading the alignment mark even if the resist is flattened.
Since the decrease in N can be avoided, it becomes possible to form a fine pattern with high accuracy.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a preliminary marker in an exposure method according to an embodiment of the present invention.
FIG.

[Explanation of symbols]

 1 Wafer (Substrate) 2 Light Source (Optical System) 3 Diffracted Light Detector 4 Stage 5 Stage Rotation / Movement Mechanism (Substrate Moving Means) 6 EB (Electron Beam) Drawing System (Drawing System) 7 Computer (Control Means) 8-11 Signal transmission path 20 Chip to main pattern 21A to 21D Spare mark 22X, 22Y Chip alignment mark

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location G03F 7/20 521 7818-2H 9/00 H 7818-2H

Claims (4)

[Claims] 1. A step of forming a charged particle beam photosensitive resin layer on a substrate having an alignment mark composed of steps, and the position of the alignment mark on the substrate is detected from a change in reflected light of the light irradiated on the substrate. Aligning the substrate at a first position, then irradiating the charged particle beam photosensitive resin layer on the substrate with a charged particle beam to draw at least one preliminary mark; and The position of the latent image of the preliminary mark formed on the charged particle beam photosensitive resin layer should be detected from the change in the reflected light of the light irradiated on the substrate to form the preliminary mark at the position of the latent image. A step of measuring the positional deviation from the position, and then aligning the substrate so as to correct the positional deviation, and then irradiating the charged particle beam photosensitive resin layer with a charged particle beam to draw a main pattern. With the process The pattern forming method according to a charged particle beam exposure that. 2. By drawing a plurality of the preliminary marks and detecting the position of each latent image of the plurality of preliminary marks,
The pattern forming method by charged particle beam exposure according to claim 1, further comprising a step of measuring an aberration of the charged particle beam drawing mechanism. 3. The pattern forming method by charged particle beam exposure according to claim 1, wherein the preliminary mark forms a diffraction pattern with respect to the light. 4. An optical measuring means for optically measuring the position of an alignment mark previously formed on a substrate, a substrate moving means for moving the substrate, and a pattern on a charged particle beam photosensitive resin on the substrate by a charged particle beam. And a control means for controlling the optical measuring means, the substrate moving means and the drawing means, the optical measuring means of the pattern formed on the charged particle beam photosensitive resin layer. A charged particle beam exposure apparatus, which is configured to detect a latent image.