JPH0354817A - Pattern formation - Google Patents

Abstract

PURPOSE:To enable a pattern to be formed rapidly with high precision by a method wherein the pattern is formed by exposing a contour part thereof to one exposing means while the inner part thereof is exposed to the other exposing means. CONSTITUTION:In order to form a pattern using two kinds of beams or radiation, firstly, an electron beam exposed part 6 is formed by electron beam exposure (A). Next, an ultraviolet ray exposed part 7 as well as an electron beam and ultraviolet ray exposed part 8 are formed by ultraviolet ray exposure (B). Then, a contact hole 9 can be formed with high precision by developing (C) these parts 7, 8. In order to form such a pattern, a negative type and a positive type metals are required respectively for the electron beam and the ultraviolet rays. At this time, the material meeting the whole requirements is a resist containing alkali soluble polymer and azinaphthoquinone base sensitizer while this resist can exercise the maximum effect to form the pattern with high precision.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming fine patterns using light or radiation.

[Conventional technology]

Pattern formation using ultraviolet rays has been used for a long time in fields that require fine patterning, such as semiconductor integrated circuits and optical components. To form fine patterns in current semiconductor integrated circuits, a reduction projection exposure apparatus that uses ultraviolet light having a wavelength of 436 nm (g-line) as a light source is mainly used. This reduction projection exposure apparatus is called a stepper, and the resolution of the pattern is 0.
Although it is about 5 μm, the pattern forming speed is extremely fast6
As many as 40 to 50 inch wafers can be exposed per hour.

BACKGROUND ART Semiconductor integrated circuits are rapidly becoming denser and larger, and demands for miniaturization of processing technology are also increasing. In general, when forming fine patterns, techniques using electron beams or ion beams have much better resolution than techniques using ultraviolet light. For example, in writing using an electron beam, it is not so difficult to form a pattern by several hundred people. For this reason, various electron beam lithography apparatuses have been developed since early on, but the speed of lithography on a wafer is extremely slow, at less than a tenth of a tenth of that of a stepper.

In order to overcome the current state of these fine pattern technologies, pattern forming technologies using a combination of ultraviolet rays and electron beams have been proposed in recent years [for example, The Society of Photo-Optical Instrumentation Engineers (SP
IE),! Volume 773, pages 54-60 (1987
)reference].

In this method, as shown in Fig. 2, the relatively large integrated circuit pattern 1 is exposed with a stepper, and the fine pattern 2 is drawn with an electron beam lithography system. The aim is to reduce the overall drawing time by significantly reducing the amount of time required. That is, FIG. 2 is an explanatory diagram of an example of the conventional method, in which reference numeral 1 means a large pattern and 2 means a small pattern.

[Problem to be solved by the invention]

Although the method described above is extremely effective in improving the pattern formation speed, it has many drawbacks as described below, which pose obstacles to practical use. The first drawback is that the pattern formation accuracy is poor.

That is, since the large pattern 1 and the small pattern 2 are drawn using different devices, it is necessary to ensure sufficient overlay accuracy between these devices.

However, steppers have pattern position errors due to lens distortion inherent to the device, and electron beam lithography devices have deflection distortion when deflecting the beam, so it is difficult to superimpose patterns formed by these devices with high precision. It was difficult.

Also, regarding the dimensional accuracy of the pattern, pattern 2 drawn with an electron beam reflects the good resolution of the electron beam, so the dimensional accuracy is good, but pattern 1 exposed with a stepper is not so good, so the circuit Another drawback is that a large margin for alignment must be taken in pattern design.

The second drawback is that it takes too much time to divide the designed circuit pattern into a pattern drawn by an electron beam drawing device and a pattern drawn by a stepper, that is, to classify the patterns. In other words, when relatively large patterns are adjacent to each other as shown in Fig. 3, if the adjacent pattern width 3 is below the resolution limit of the stepper, pattern formation will not be possible. It becomes necessary to classify the circuit patterns by taking into account not only the size of the circuit patterns but also the arrangement of each pattern. This process has the disadvantage that it takes several hours or more even if a large computer is used when the number of patterns is enormous, such as in an LSI. In addition, FIG. 3 is an explanatory diagram of an example of the conventional method, and the reference numeral 1 means the pattern and 3 means the adjacent width of the pattern.

An object of the present invention is to provide a pattern forming method that can eliminate these drawbacks and form fine patterns at high speed and with high precision.

[Means to solve the problem]

To summarize the present invention, the present invention relates to a pattern forming method, and in a pattern forming method using two types of light or radiation as exposure means, one exposure means is used to define the outline of the pattern, The method is characterized in that an exposure means exposes the inside of the pattern.

The present invention will be explained with reference to FIG. That is, FIG. 1 is a diagram showing one embodiment of the present invention, in which reference numeral 1 indicates a large pattern;
2 means a small pattern, 4 means contour data, and 5 means internal data. W+H+W2 and H2 indicate the dimensions of the large pattern 1 and the small pattern 2 when the designed one circuit pattern is divided into rectangles. When classifying patterns, first,
The designed circuit pattern data is divided into pattern data with a division size a or more and pattern data with a division size a or less. Next, the pattern data having the division size a or more is divided into outline data 4 and internal data 5 by the outline width b.

For example, if WI Hl > a > Wz, H2, large pattern 1 is divided into an outline part and an internal pattern, and small pattern 2
will not be divided. Then, a pattern having a division size a or less and the outline of the divided pattern are drawn using an electron beam drawing device, and the inside of the divided pattern is exposed using a stepper.

Here, the division dimension a is determined by the resolution limit T of the stepper and the overlay error (±σ) between the electron beam drawing device and the stepper.
It is a constant given by a≧r+2σ. In addition, the contour width b of the contour part is b≧2σ, and the internal data is (W2−2b+2σ
．． H. −2b+2σ). When b=2σ, it becomes (W2 2σ, H, −2σ). As a result, the large pattern 1 is exposed using the electron beam lithography device and the stepper so that its outline and interior overlap by σ. In other words, the overlay error between the electron beam drawing device and the stepper does not affect pattern accuracy. Furthermore, it is clear that if the overlay error σ and the resolution limit T of the stepper are reduced, the contour width b and the division dimension a can be reduced, which is a preferable situation.

In the present invention, a circuit pattern is formed using an electron beam lithography system and a stepper using the method described above, so that: 1) the overlay error between the electron beam lithography system and the stepper can be ignored; and 2) the pattern dimensions can be calculated for all patterns. The dimensional accuracy is improved because it is determined by an electron beam lithography system with excellent image quality.The classification of patterns in (■) can be processed by focusing on the pattern dimensions (C), which has the advantage of significantly shortening computer processing time. Motsu.

In the above explanation, an electron beam lithography device and a stepper have been described, but the present invention is not limited to this. Instead of an electron beam, an ion beam or a laser beam, and instead of an ultraviolet stepper, an X-ray or laser beam can be used. It is possible to use

The resist material used in the pattern forming method of the present invention is required to have characteristics of high sensitivity to light and radiation and high resolution at the same time. In general, a well-known material that is highly sensitive to light and electron beams is a material prepared by adding a bisazide compound to a cyclized rubber, but this material has the disadvantage of having a post-polymerization effect when exposed to electron beams. As a material that does not undergo post-polymerization, there is a material made of polyvinylphenol and a bisazide compound (Hitachi Chemical: RD2000N), but this material is negative to both light and electron beams, for example, as shown in Figure 4. It cannot be used to form fine contact hole patterns. In order to form the pattern shown in FIG. 4, a material that is negative type when exposed to electron beams and positive type when exposed to light is required. A material that can satisfy all of these requirements is a resist containing an alkali-soluble polymer and a diazonaphthoquinone photosensitizer, which can maximize the effects of the present invention. This resist can be used in both positive and negative types depending on the patterning process. That is, a positive type pattern can be formed using the standard process of developing after exposure, and a negative type pattern can be formed using a post-exposure heat treatment, chemical treatment, or an image reversal process in which the entire surface is irradiated with ultraviolet rays. The materials include AZ type non-resist in which the alkali-soluble polymer is novolak resin or polyvinylphenol, and the alkali-soluble polymer is a silicon-containing polymer2.
There are two types of layered photoresists, but the latter is more advantageous in forming fine patterns because it can reduce the proximity effect during electron beam exposure.

FIG. 4 is a process diagram of one example of the method of the present invention for forming fine contact holes, in which reference numeral 6 is an electron beam exposure section, 7 is an ultraviolet exposure section, and 8 is an electron beam and ultraviolet exposure section. 9 is the exposed portion and 9 is the contact hole.

〔Example〕

Examples of the present invention will be shown below. The embodiments are merely illustrative, and it goes without saying that various changes and improvements may be made without departing from the spirit of the invention.

Example 1 Example 1 shows formation of a positive pattern.

Electron beam drawing device (30kV) and stepper (λ: 4
36 nm, NA: 0.35) was used. Divided dimension a = 1.5 μm (γ = 1 μm, σ - 0.25 μm
) was used to determine the division of pattern data.

Also, the contour width is -0. It was set to 5 μm. The values of a and b should be appropriately optimized depending on the performance of the equipment used and the resist used, and are not necessarily limited to the values used here. Photoresist FPR800 (manufactured by Tokyo Ohka) was coated on the wafer to a thickness of 0.5 μm, and prebaked at 100° C. for 2 minutes (hot plate). The wafer was exposed continuously using a stepper and an electron beam lithography system. Each dose is 8
It was carried out at 0 mJ/cm2 and 200 μc/cm'.

It was developed with a commercially available developer, and the designed pattern from 0.1 μm to 100 μm was formed with high precision. The pattern could be formed in about 1/10 of the time required when all patterns were formed using an electron beam lithography system, and the positional accuracy of the pattern was within ±0.05 μm, which is equivalent to the accuracy of the electron beam lithography system. Regarding pattern dimensional accuracy, a remarkable improvement effect was observed, especially in the dimensional accuracy of small patterns sandwiched between large patterns.

This is because the proximity effect is drastically reduced due to the reduction in the area to be drawn with the electron beam, and is a major feature of the present invention. Furthermore, the processing time for pattern data has been reduced to less than 1/10 of the conventional method.

In this example, OFPR resist was used as the resist material to form a normal positive pattern, but the present invention is not limited thereto. Examples of other resist materials and pattern forming methods will be shown below.

Example 2 In Example 1, a method of forming a positive pattern using an electron beam lithography apparatus and a stepper was explained. Here, we will explain the pattern-type power method, in which both methods are negative-type. AZ type photoresist (
OFPR (manufactured by Tokyo Ohka Chemical Co., Ltd.) was applied to a thickness of 0.5 μm, and prebaked on a hot plate at 100° C. for 1 minute. The wafer was exposed to light using a stepper and then continuously exposed to light using an electron beam lithography system. Each exposure amount is 120mJ/cm250
It was performed in μc/cm'. Electron beam sensitivity is improved if electron beam exposure precedes stepper exposure. After exposure, post-exposure beta (FEB) was performed at 100° C. for 5 minutes in an amine atmosphere to change the exposed area to Alka IJ ffil solubility. Next, the entire surface was irradiated with an exposure amount of 500 mJ/cm2 using an ultra-high pressure mercury lamp (35 onm filter), and the areas other than the exposed areas were exposed. Changed to alkaline soluble. Developed with a commercially available developer diluted twice with water to obtain a 0. Design patterns from 1 μm to 100 μm could be formed using a negative mold.

Example 3 15 g of anhydrous aluminum chloride and 50 g of acetyl chloride were added to a 300 flask equipped with a stirrer, a thermometer, and a dropping funnel.
- and stir. Next, polyphenylsilsesquioxane with a molecular weight of 820 (glass resin GR950,
(manufactured by Owens Illinois) 5g acetyl chloride 50m
A solution dissolved in 1 ml was gradually added dropwise. The reaction is allowed to proceed while maintaining the temperature at 19°C. Hydrogen chloride is generated as the reaction progresses. After reacting for 3 hours, it is cooled and the contents are poured into ice water containing hydrochloric acid. Stir well to decompose the aluminum chloride, and after confirming that the ice water is monoacidic, filter out the precipitated polymer. Wash thoroughly with dilute hydrochloric acid water and finally dry in a vacuum dryer. The molecular weight of the obtained polymer was 980.

A resist was prepared by adding 20% by weight of novolac resin diazonaphthoquinone sulfonic acid ester to the alkali-soluble silicone polymer thus obtained.

This resist is coated with a lower layer resist (1.5 μm thick) with a thickness of about 0.5 μm.
It was applied onto a silicon substrate that had been previously coated with a film (μm thick) and prebaked at 80° C. for 20 minutes. Exposure was carried out in the same manner as in Example 2 using a stepper and an electron beam drawing device. The respective exposure doses were 100 mJ/cm2 and 20 μ
It was C/cm2. After exposure, heat treatment was performed on a 120° C. hot plate for 5 minutes. In this case, the silicone polymer has a silanol group, which undergoes dehydration condensation only by heating using indene carboxylic acid produced by exposure as a catalyst, and becomes poorly soluble in alkali. Therefore, there is no need to perform the amine treatment as in Example 2.

After heat treatment, use an ultra-high pressure mercury lamp to irradiate the entire surface with ultraviolet rays.
Irradiation was performed at 00 mJ/cm2. Then 1.2% by weight of tetramethylammonium hydroxide (TMA
H) By developing with an aqueous solution, a negative pattern could be formed with high precision.

Next, the upper resist pattern was transferred to the lower resist using a parallel plate type oxygen plasma etching apparatus. By this method, a 0.2 μm pattern with an aspect ratio of 5 could be formed with high precision and high throughput.

Example 4 In place of the AZ type photoresist in Example 1, a resist in which 20% by weight of diazonaphthoquinone sulfonic acid ester of novolac resin was added to the silicone polymer used in Example 3 was used to form a positive pattern.

A lower layer resist with a thickness of about 0.5 μm (1.5 μm) was coated on a silicon substrate and heated at 80°C for 20 minutes.
Briebaked for a minute. After exposure using an electron beam lithography system and a stepper in the same manner as in Example 1, 2.3% T was applied.
Developed with MAH aqueous solution. The exposure amount is 15 for the stepper.
0 mJ/cm', and the electron beam was 200 μC/cm2.

Example 5 Using the silicon-containing resist used in Example 3, a positive pattern was formed using a stepper and a negative pattern was formed using an electron beam. This pattern forming method is advantageous in forming fine contact holes as explained in FIG. After applying a resist in the same manner as in Example 3, the pattern shown in FIG. 4(A) was exposed using an electron beam lithography system. Next, the pattern shown in FIG. 4(B) was exposed using a stepper. After that, 1
．． Developed with 4% TMAH aqueous solution to 0. A contact hole of 2 μm square was formed [Fig. 4(C):]. The exposure amount was 20μC/cm' with the electron beam drawing device and 3 with the stepper.
It was 60 mJ/cm2.

Example 6 20% by weight of diazonaphthoquinone sulfonic acid ester of novolac resin was added to the silicone polymer used in Example 3.
The added resist was applied to a thickness of about 0.5 μm on a silicon substrate on which a lower layer resist had been applied in advance, and prebaked at 80° C. for 20 minutes. An excimer laser stepper (λ: 248 nm,
NA=0. 35), a minimum 0.4 μm pattern was exposed at 20 mJ/cm”. Next, a 0.2 μm pattern was exposed at 2 μm by direct writing using an electron beam.
Exposure was made at C/cm2. After exposure, the entire surface is exposed to ultraviolet rays at 500 m using an ultra-high pressure mercury lamp without heat treatment.
Irradiated at J/cm'. Next item, 1.2 wt% TM
By developing with an AH aqueous solution, a negative pattern could be formed with high precision.

Example 7 A negative pattern was formed in the same manner as in Example 6 except that an XIS optical device (λ: 0.7 nm) was used instead of the excimer laser stepper in Example 6.

The X-ray exposure amount was 160 rnJ/cm'.

Example 8 A negative pattern was formed in the same manner as in Example 3, using an ion beam lithography system instead of the electron beam lithography system in Example 3. Ion beam exposure dose is 100μC/c
It was m2.

〔Effect of the invention〕

As explained above, when forming a pattern using two types of light or radiation, the present invention is capable of exposing the outline of the pattern using one exposure means and the inside of the pattern using another exposure means. Since the pattern is formed using the above method, it is possible to form a pattern at high speed and with high accuracy.

[Brief explanation of drawings]

Figure I is a diagram showing an embodiment of the present invention, Figures 2 and 3 are explanatory diagrams of the conventional method, and Figure 4 is an example of the steps of the method of the present invention for forming fine contact holes. It is a diagram. 1... Large pattern, 2... Small pattern, 3... Adjacent width of pattern, 4... Contour data, 5... Internal data, 6... Electron beam exposure area, 7...・Ultraviolet exposure section, 8・
... Part exposed to electron beam and ultraviolet rays, 9... Contact hole

Claims (1)

[Claims] 1. In a pattern forming method using two types of light or radiation as exposure means, one exposure means exposes the outline of the pattern and another exposure means exposes the inside of the pattern. Characteristic pattern formation method. 2. The pattern forming method according to claim 1, wherein the resist used is a resist containing an alkali-soluble silicon-containing polymer and a diazonaphthoquinone photosensitizer.