JPH0521333B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to fine pattern formation in which a reduced image of a mask pattern is exposed to light on a resist.

[Conventional technology]

As a conventional technique for forming extremely fine patterns on a resist, there is a method called shadowing, as shown in FIG. 8, for example. In this method, a line 2 having a rectangular cross section is formed on a substrate 1, and a vapor deposited film 3 is formed by vapor depositing gold, for example, on the surface of the line 2. Next, as shown in FIG. 8a, when the vapor deposited film 3 is etched by irradiating with an ion shower from an oblique direction, only the shadow of line 2 remains as shown in FIG. By removing this, it is possible to form a pattern in which lines much finer than the line 2 are repeated, as shown in FIG. The above pattern forming method is well known as a method capable of forming extremely fine patterns of 0.1 μm or less.

Other methods for forming ultra-fine patterns include:
A method of exposure using an electron beam or an ion beam is known.

[Problem that the invention seeks to solve]

The ultra-fine pattern according to the former method is determined by the pattern of the lines 2 shown in FIG. 8a, and has the disadvantage that there is no degree of freedom in changing the spacing between lines. Furthermore, in the latter method of forming ultra-fine patterns, it is difficult to form ultra-fine patterns over a large area.

[Means for solving problems]

The present invention uses X-rays with good beam directionality as an exposure light source, and after one exposure, shifts the relative position of the resist surface and the mask and performs multiple exposure, thereby changing the pattern on the original mask. A reduced pattern is formed on the resist.

[Effect]

In the fine pattern forming method according to the present invention, a mask on which a predetermined pattern is formed is stacked on a substrate coated with a resist at a predetermined interval, and light is irradiated through the mask to transfer the pattern on the mask onto the resist surface. In a method and apparatus for forming a fine pattern for transferring onto a resist surface, an X-ray source with a wavelength shorter than 100 Å and a variation in the directivity of the light flux of 10 milliradian or less is used as an exposure light source to transfer the pattern of the mask onto a resist surface. After exposure, the mask or the substrate is moved a predetermined distance relative to each other within their respective planes by a moving device, and the pattern of the mask is exposed onto the resist surface again, thereby multiple exposing the mask pattern onto the resist surface. As a result, a reduced pattern of the mask pattern is formed on the resist.

The present invention is a method of exposure using light having a wavelength in the X-ray region where the influence of Fresnel diffraction is small, and is particularly suitable for exposure using a laser plasma X-ray source or synchrotron radiation, which has good directivity of the light flux. In other words, by focusing on the ability to adjust the extremely small amount of movement (approximately 10 Å) of piezoelectric elements and the directivity of laser plasma The X-ray light source mentioned above has a wavelength shorter than 100 Å, and there is no variation in the directivity of the light beam.
Use one that is 10 milliradian or less.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a micro pattern forming apparatus according to the present invention, FIG. 2 is a diagram showing the intensity distribution of light exposed by a slit pattern, and FIG.
The figure shows the gap dependence of pattern blur.
5 are diagrams showing pattern formation according to the present invention, in which a is a mask, b is a light intensity distribution of first exposure, c is a light intensity distribution of second exposure, d is a formed resist pattern, and FIG. The figures are diagrams showing another pattern formation according to the present invention, in which a is a mask pattern, b is a resist pattern, and FIG. 7 is a diagram showing still another example of the above pattern formation.

In FIG. 1, a substrate support 6 is attached to the tip of the piezoelectric element 5, and a substrate 7 coated with a photosensitive resin 8 is placed on the substrate support 6. An X-ray mask is mounted on a support base 9 facing the substrate 7 and spaced apart from it at a predetermined distance. The X-ray mask has a thin pattern support film 11 with good X-ray transmittance on a mask substrate 10, and a predetermined pattern 12 is formed on the pattern support film 11 using a material that easily absorbs X-rays, such as gold or tantalum. It is formed by etc.

The piezoelectric element 5 has the property of changing its length by applying a voltage, and although the amount of change varies depending on the material, for example, a change in length of about 100 Å to 10 Å can be easily realized at 1 V. can. Therefore, the first
In the configuration shown in the figure, after exposure is performed once, the pattern 12 on the mask is transferred to the photosensitive resin 8 by applying a voltage to the piezoelectric element 5, moving the substrate support 6 by a predetermined distance to the right in the figure, and exposing again. A double exposure can be performed on the surface in which the first exposure and the second exposure are shifted by a predetermined length. In particular, in order to form ultra-fine patterns on the order of 100 Å, it is essentially important to eliminate the effects of changes due to thermal expansion of the materials constituting the device. Therefore, the substrate support stand 6 and the X-ray mask support stand 9 are
In addition to being made of a material with a coefficient of thermal expansion smaller than 1×10 ^-6 , such as quartz or superinvar, it is also desirable that the piezoelectric element 5 itself be made of crystal with a small coefficient of thermal expansion. It is also effective to house the entire device in a vacuum to remove the effects of room temperature fluctuations and acoustic vibrations. Therefore, there is good consistency in using the above light source.

Next, examples of fine patterns formed by the fine pattern forming apparatus having the above configuration and factors that limit miniaturization will be explained. FIG. 2 shows the intensity distribution of light when a pattern having a space of width l is exposed on a photosensitive resin surface placed a gap g apart. The intensity of the light of the pattern to be transferred has a blurred edge portion due to Fresnel diffraction, and the width d of this blur is called a blur due to diffraction. When a fine pattern is formed using the above apparatus, the first factor that limits the miniaturization of the pattern is the blur caused by the diffraction, and the smaller the gap g and the shorter the wavelength of the exposure light, the smaller the blur. The second factor that further limits miniaturization is what is called penumbral blur, which is caused by the fact that the directivity of the light flux of the exposing light is not uniform. The above-mentioned penumbra blur is zero when the directivity of the light flux is completely aligned. Furthermore, if the directivity of the light beams is not uniform, the difference will increase in proportion to the gap g. Figure 3 shows the dependence A of the blur d due to diffraction on the gap g when X-rays with a wavelength of 10 Å are used, and the gap dependence of the penumbra blur in the case of X-rays using a normal electron beam irradiation method. B shows a typical numerical example of the gap dependence C of penumbra blur when electron synchrotron radiation is used as an X-ray source. As is clear from the figure, when a normal X-ray source is used, the blur of a fine pattern becomes a form in which both diffraction blur and penumbra blur are added, whereas when synchrotron radiation is used, a penumbra blur is added. The effect of blur can be almost completely ignored, and the limit of pattern refinement is determined only by the blur caused by diffraction. In other words, if the wavelength of the light source for exposure is 100 Å or more, blurring will occur due to diffraction, and if the dispersion in the directivity of the light flux exceeds 10 milliradians, penumbra blur will occur. If the above-mentioned gap can be controlled to be sufficiently small, it is possible to form a fine pattern of 100 to 150 Å.

The first fine pattern formed by the method of the present invention
In FIG. 4 showing an example, a indicates an X-ray mask, and a pattern support film 1 with good X-ray transmittance on a substrate 10 is shown.
Pattern 1 is made of a substance that easily absorbs X-rays on the surface of 1.
2 is formed. The above pattern is line and space in this embodiment. The intensity distribution of the transfer pattern exposed by the pattern 12 is b
It becomes as shown in . After transferring the pattern b above, move the X-ray mask relatively to the right by a predetermined distance S and transfer the pattern of intensity distribution shown in c. This will require heavy exposure. If a positive resist is used as the photosensitive resin 8, the pattern finally formed will be a resist pattern as shown in d, and therefore has a fine width L' which is a reduction of the line width L of the pattern on the X-ray mask. lines can be formed.
According to the apparatus of the present invention, as is clear from the description of FIGS. 2 and 3 above, it is possible to form a line pattern with a width of 100 to 500 Å from a relatively wide line pattern.

FIG. 5 is a diagram showing a second example of a fine pattern formed by the method of the present invention, in which a shows a pattern 12 in which spaces are repeated at regular intervals using an X-ray mask. It is difficult with conventional technology to repeatedly form space patterns with a width of 100 Å or less over a wide area with intervals of the same width, but it is possible to create these with wide intervals using, for example, the shadowing method. It is. It is also possible by the method shown in FIG. 4 according to the present invention. Therefore, by slightly shifting the space pattern shown in FIG.
It is possible to form a pattern that looks like it is doubled.
That is, according to the present invention, first a space pattern with a fine width is created by the pattern forming method shown in FIG. 4, and then the space pattern is formed into a pattern shown in FIG. Can form lines and spaces.
It is also possible to increase the repetition period three times, four times or more.

FIG. 6 is a diagram showing a third example of a fine pattern that can be formed according to the present invention. In a large-area pattern arrangement as shown in a, the relative positions of the X-ray mask and the resist surface are adjusted above and below the pattern. By moving the pattern by a predetermined distance in the direction and exposing it again, and then moving the pattern by a predetermined distance in the left-right direction and performing multiple exposure, it is possible to form a fine pattern array as shown in b.

Although the above explanation does not mention the method of forming the original mask pattern, for example, FIGS.
If a periodic pattern in which lines and spaces are repeated as shown in the figure is created by laser two-beam interferometry, the periodic pattern will have extremely high precision, with the period determined by the stability of the laser frequency. Therefore, the fourth
In the first and second examples shown in FIG. 5 and FIG. 5, if the mask prepared by the above method is used, it is possible to form an extremely fine periodic resist pattern with extremely high periodic precision. It is possible.

Examples of applications of the patterns formed according to the present invention include the formation of transmission diffraction gratings used in the X-ray region, the formation of crystals having a lateral superlattice structure, and the formation of superlattice structures with a modulated period ( Formation of chirp grating super lattice), point contact diode for optical frequency mixing,
In addition to single devices such as the formation of DFB semiconductor lasers, the present invention can also be applied to the formation of LSI patterns, an example of which is shown in FIG. Figure 7 shows the gate pattern of a MOS FET. The above pattern consists of an elongated linear gate part and a wide area electrode lead-out part, and in an LSI pattern, there are many unit patterns in one chip. However, the method of arranging the unit patterns is usually such that the elongated gate portions are aligned in one direction or are arranged orthogonal to each other as shown in FIG. In addition, for high-speed operation of the device, the width of the gate line is made extremely thin (about 0.1 μm).
It also needs to be manufactured with high dimensional accuracy. In order to form the gate pattern shown in FIG. 7 by the fine pattern forming method according to the present invention, a gate pattern having a relatively wide line width (about 1 μm) is formed, and the gate pattern described in the above embodiment is used. A desired pattern can be obtained by reducing the line width of the gate portion of the gate pattern using this method. When the gate portions are arranged in two mutually orthogonal directions as shown in FIG. 7, the substrate support 6 is shifted by the piezoelectric element 5 in the two directions shown by arrows a and b in FIG. Multiple exposure may be performed twice, for a total of three times.

In the present invention, the narrower the distance between the mask and the resist surface, the smaller the effects of Fresnel diffraction and penumbra blur, and the more fine the pattern can be formed. However, when moving the mask or resist substrate, it is desirable that the interval be wide to avoid damage to the mask. Therefore, the distance between the resist surface and the mask is configured to be changeable by intermittent application of current to the electromagnet or intermittent application of hydraulic pressure, etc., and exposure is performed at a predetermined narrow interval, and when moving, the interval is changed to a predetermined wide interval. This results in the desired solution.

Furthermore, other methods for changing the distance between the resist surface and the mask during movement and during exposure include the following methods. That is, in the micro pattern forming apparatus shown in FIG. 1, the entire apparatus is placed in a container filled with a predetermined gas pressure (for example, helium, nitrogen, etc.), and the pattern support film 11 of the mask is made of an elastic material (for example, a polyimide film). ,
pressure on the side of the substrate 7 coated with the photosensitive resin 8 in the pattern support film 11;
Regarding P ₁ and the pressure P ₂ on the opposite side, at the time of exposure
P ₁ is made smaller than P ₂ so that the pattern support film 11 has a convex shape on the substrate 7 side and comes into close contact with the substrate 7, and when moving, P ₁ is made larger than P ₂ so that the pattern support film 11 is in contact with the substrate 7. By forming a convex shape on the side opposite to the substrate 7 and moving it away from the substrate 7, the desired solution can be obtained. The above method also has the advantage that contact exposure can be performed without damaging the pattern support film 11.

〔Effect of the invention〕

As described above, the method and apparatus for forming a fine pattern according to the present invention includes stacking a mask on which a predetermined pattern is formed on a substrate coated with a resist at a predetermined interval, and irradiating light through the mask.
In the fine pattern forming method and apparatus for transferring the pattern on the mask onto the resist surface, the support base that supports the mask and the substrate support base attached to the tip of the piezoelectric element are made of a material with a small coefficient of thermal expansion, and the exposure As a light source for use, the wavelength is shorter than 100Å,
Using an X-ray source with a directivity variation of 10 milliradian or less, the pattern of the mask is exposed on the resist surface, and then the mask and the substrate are moved relative to each other in a predetermined position within their respective planes using a moving device. By moving a distance and exposing the mask pattern to the resist surface again, the mask pattern can be multiple-exposed to the resist surface, and an extremely fine micro pattern can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a micro pattern forming apparatus according to the present invention, FIG. 2 is a diagram showing the intensity distribution of light exposed by a slit pattern, and FIG. 3 is a diagram showing the gap dependence of pattern blur. Figure shown, 4th
5 are diagrams showing pattern formation according to the present invention, in which a is a mask, b is a light intensity distribution of first exposure, c is a light intensity distribution of second exposure, d is a formed resist pattern, and FIG. The figures are diagrams showing another pattern formation according to the present invention, in which a is a mask pattern, b is a resist pattern, and FIG. 7 is a diagram showing still another example of the above pattern formation. FIG. 8 shows a conventional fine pattern forming method, and figures a, b, and c show each step. 5... Piezoelectric element (moving device), 6... Substrate support stand, 7... Substrate, 8... Resist, 9... Support stand, 12... Mask pattern.

Claims (1)

[Claims] 1. A mask on which a predetermined pattern is formed is stacked on a substrate coated with a resist at a predetermined interval, and light is irradiated through the mask to transfer the pattern on the mask onto the resist surface. In the fine pattern forming method, an X-ray source with a wavelength shorter than 100 Å and a variation in the directivity of the light flux of 10 milliradians or less is used as an exposure light source to expose the pattern of the mask on the resist surface, and then move the mask. The method is characterized in that the mask panter is multiple-exposed to the resist surface by moving the mask or the substrate a predetermined distance relatively within their respective planes using a device and exposing the pattern of the mask to the resist surface again. Fine pattern formation method. 2. The fine pattern forming method according to claim 1, wherein the exposure light source is electron synchrotron radiation light. 3. The distance between the substrate and the mask is a predetermined narrow interval during exposure, and a predetermined wide interval is maintained when the mask or substrate is moved. The described fine pattern forming method. 4. In a fine pattern forming apparatus that overlaps a mask with a predetermined pattern at a predetermined interval on a substrate coated with resist, irradiates light through the mask, and transfers the pattern on the mask onto the resist surface. , a fine pattern forming apparatus comprising: a support base made of a material with a small coefficient of thermal expansion that supports the mask; and a substrate support base made of a material with a low coefficient of thermal expansion attached to the tip of the piezoelectric element. .