JPH0374803B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a method for producing fine patterns with a large aspect ratio.

In recent years, transmission gratings have been attracting attention as spectroscopic elements in the soft X-ray region, and Fresnel zone plates have been attracting attention as image forming elements. These elements have an arrangement structure in which absorption bands and transmission bands for soft X-rays (1 Å to several 100 Å) are alternately adjacent to each other, and gold is most often used as the material for the absorption bands. When this gold is used, the thickness of the gold must be 1 μm or more in order to achieve a transmittance of 1% or less at a wavelength of 4 Å. Also, since the pitch of the array structure is around 1 μm, the width of the absorption band is
It is about 0.5μm. To create a fine gold pattern with such thickness and width, the necessary pattern is generally made of polyimide as a mold for gold plating on gold foil spread on a substrate, and then electroplated using the gold foil on the substrate as an electrode. The method used is to remove the polyimide later to create a thick gold pattern. The present invention relates to a method for creating a fine pattern with a large aspect ratio corresponding to the gold pattern electroplating type of a transmission grating for soft X-rays and a Fresnel zone plate. Further, effects can be expected even if the above-mentioned fine pattern with a large aspect ratio is used for other purposes.

B. Prior Art When creating soft X-ray transmission gratings or Fresnel zone plates, there is a method of repeating optical reduction projection using an enlarged image of the required pattern as a mask to create a fine pattern on photoresist. This limits the line width to about 1 μm. Furthermore, when drawing a pattern by electron beam direct writing, especially in the case of a transmission grating, it takes a very long time. In contrast, when a pattern is formed by holographic exposure using interference between two beams of light, not only does it take only a few seconds to create a resist pattern, but the periodic accuracy of the pattern itself is also improved. However, in the holographic exposure method, the cross-sectional shape is sinusoidal and the aspect ratio is small, so it is necessary to transfer the resist pattern created by the holographic exposure method to a gold plating mold with the required large aspect ratio as described above. was strongly desired.

C. Problems to be Solved by the Invention The present invention involves transferring a resist pattern with a fine structure created by an exposure method to an underlying insulating layer that will serve as a mold for gold plating. It is an attempt to create a pattern.

D. Means for Solving Problems The present invention attempts to create an openwork-like fine structure with a large cross-sectional aspect ratio by digging grooves in the insulator layer deeper than the width according to the photoresist pattern. In this method, one or more intervening layers are provided between the target layer in which a fine structure with a large aspect ratio is to be formed and the photoresist layer, and the intervening layers and the etching ratio are sequentially increased from the photoresist layer toward the target layer. The material of the target layer and the etching method are selected.

E. Effects Specifically, ion beam etching is suitable as the etching method, and various etching ratios can be set by selecting the combination of materials to be etched and the type of gas. Considering a target layer and an intervening layer thereon, it is assumed that a desired pattern is formed on the intervening layer and that the target layer is exposed in the portion of the target layer to be engraved. When etching is performed here, both the intervening layer and the target layer are etched, but since the target layer has a higher etching ratio, the target layer is etched more than the intervening layer. The target layer is etched to a depth equal to or greater than the thickness of the intervening layer until the intervening layer is completely removed.
The same relationship holds between the photoresist layer and the intervening layer below it; the intervening layer is engraved deeper than the thickness of the photoresist layer, and in this way progressively deeper incisions are formed until the final target layer is reached. In this case, a fine structure with a very large aspect ratio is formed.

F. Example This example is intended to manufacture a gold (Au) grating for soft X-rays as shown in Fig. 1, where g is the absorption band portion of the grating, t is the transmission band portion, and 6 is a reinforcing support beam, which is formed integrally with g by electroforming. The method of manufacturing this grating will be explained below with reference to FIG.

First, Ni1 is deposited on Si wafer B, and then Au2 is deposited on Si wafer B.
Deposit. Ni is a coating to improve adhesion between the Si wafer and Au, and is not necessarily necessary. After applying polyimide 3 on the Au thin film using a spinner, a SiO ₂ layer 4 is applied using a sputtering method. Finally, layer 5 of photoresist AZ1350J is applied with a spinner to prepare the sample (FIG. 2A). In this example, for example, Ni=200Å, Au500Å,
Polyimide=2μmSiO ₂ =2000Å, AZ1350J=1μm
It is. Also, in this example, if we take the case of creating a transmission grating with 1000 lines/mm as an example,
Since the optimal thickness of Au is about 0.5 μm, the polyimide used as the gold plating mold needs to be 0.5 μm or more, but here it was set to 2 μm. Also, the thickness of SiO ₂ is
The etching ratio by CHF ₃ ion beam etching is resist:SiO ₂ = approximately 1:10, and the etching ratio by O ₂ ion beam is SiO ₂ :polyimide =
Considering the ratio of about 1:20, it was set to 2000 Å.

Next, a resist pattern is created on the photoresist layer 5 by a niholographic exposure method (FIG. 2B).
Using this resist pattern as a mask, the resist pattern was etched by CHF ₃ ion beam etching.
After transferring to the pattern of the SiO ₂ layer 4, the resist 5 is removed by acetone or plasma ashing.
At this stage, the remaining part of the SiO ₂ layer is resist and SiO ₂
The resist layer 5 is etched by the etching rate of
Since it remains covered, the angle of inclination of the shoulder of the SiO ₂ pattern increases. (FIG. 2C) Next, using the SiO ₂ pattern created in FIG. 2B as a mask, the polyimide layer 3 is etched by O ₂ ion beam etching, and the pattern is transferred to the polyimide layer 3. Here, due to the etching ratio of SiO ₂ and polyimide, the polyimide pattern stands vertically without having its corners cut (FIG. 2D).

Next, use this polyimide pattern as a mold for electroplating, and use the Au plating layer 2 as a plating electrode to fill in the engraved areas of the polyimide pattern.
Perform Au electroplating (Fig. 2 E).

Next, remove SiO ₂ with hydrofluoric acid or CF ₄ plasma, and then remove polyimide with O ₂ plasma (second step).
Figure F).

Next, a supporting pattern is formed by photolithography or electron beam exposure. Then, similar to Figure 2 E, use this pattern as a metal mold,
After performing Au electroplating using the Au pattern as an electrode, the resist is removed with acetone or O ₂ plasma to form the supporting beam 6 (FIG. 2G).

This is because there is no suitable material with high transmittance over the entire soft Then, add a supporting pattern.

Next, the gold layer 2 of the metal electrode was removed using an Ar ion beam.
Finally, back-quenching the Si wafer B with a mixed acid of nitric acid and nitric acid, or
Use KOH etc. (Figure 2 H).

By leaving Si around the pattern created at this time, it becomes a holding frame for the grating and increases the tension.

Of course, resists and etching gases are not limited to those listed above as long as they can be expected to have the same effect, and back-etching, etc.
Of course, the present invention is not limited to this method as long as the same result can be expected using a method other than Au electroplating. The point is that it is important to create fine patterns with a large aspect ratio of polyimide, etc., using holographic exposure and reactive ion beam etching, and that this method of manufacturing fine patterns can be applied to a variety of other products. Of course, you can also expect it.

Effects According to the present invention, since a holographic exposure method is used, a large area and highly accurate resist pattern can be created in a short time, and then by using ion beam etching, a large area and highly accurate resist pattern can be created for Au electroplating. You can create a pattern and use it as a type.
By performing Au electroplating, it is possible to create a transmission grating for soft X-rays with large area and high precision. In addition, gold Fresnel zone plates with the necessary thickness and precision can also be manufactured using this method.

[Brief explanation of drawings]

Figure 1 shows a partial perspective view of an Au transmission type grating using the present invention, and Figure 2 shows semi-finished products and finished products at each stage of the manufacturing method of an embodiment of the present invention, which progresses in that order from A to H. It is a diagram schematically showing a cross section.

Claims (1)

[Claims] 1. A resist pattern formed on a photoresist by a holographic exposure method and having a sinusoidal cross-sectional shape (generally the positive part of a sine wave) is transferred to a target layer so that the target layer has a large aspect ratio. When forming a pattern with a rectangular cross-sectional shape, at least one uniform layer is formed between the target layer and the photoresist layer, and the first layer, second layer, etc. are sequentially formed from the target layer side, Etching ratio is always 1st layer > 2nd layer
Layer＞...＞Choose an appropriate material for each layer and etching gas between adjacent layers so that it becomes photoresist, and sequentially change the mask pattern to layers with smaller numbers, forming the desired pattern on the final first layer. A method for manufacturing fine patterns with a large aspect ratio. 2 Polyimide as first layer, second layer
SiO ₂ , a photoresist according to claim 1 is used as the third layer, and CHF ₃ reactive ion etching or reactive ion beam etching is used to convert the resist pattern on the photoresist into the second layer SiO ₂ pattern. was carried out and converted
A fine polyimide pattern with a large aspect ratio as claimed in claim 1, wherein the SiO ₂ pattern is converted into the first layer polyimide pattern by O ₂ reactive ion etching or reactive ion beam etching. production method.