JPS60254036A - Formation of pattern - Google Patents

Abstract

PURPOSE:To remarkably enhance sensitivity by using a combination of of specified polysilsesquioxane and an aromatic bisazido cross-linking agent as the upper layer resist of the two-layer resist film. CONSTITUTION:A negative type resist pattern is formed by using two-layer resist film consisting of upper and loser layers by using radiation rays. The upper layer is composed of a mixture system of polysilsequioxane represented by formula (I) in which (R1-R4 are independent of each other and each is optionally an substd. methyl or vinyl group), and an aromatic bisazido compd., such as 2,6-bis(4'-azidobenzal)acetone or 2,6-(4-azidobenzylidene)(methyl)cyclohexane. Said bisazido comp. is used in an amt. of 1-30wt% of polysilsequioxane, and if it is out of this range, sufficient cross-linking effect, that is, a sensitization function can not be exhibited. Phenol, polyimide, and polystyrene resin, etc., are used for the lower layer.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to the use of electron beams and soft , ionizing radiation such as an ion beam, far ultraviolet rays, etc. (hereinafter collectively referred to simply as 6 radiations).The present invention relates to
More specifically, the present invention relates to a method of irradiating a dual-structured resist material with radiation as described above to form a high aspect ratio negative type resist pattern as a result of exposure and development. Here, as is well known, "1 high aspect ratio" refers to a large ratio between the resist film thickness and the width, and means that microfabrication can be performed with extremely high dimensional accuracy. .

2. Description of the Related Art Conventionally, various devices using semiconductors, ferroelectric materials, and ferromagnetic crystals, such as LSIs, bubble memories, and surface acoustic wave filters, have extremely fine circuit configurations. It is well known that this requires a fine processing technology of less than μm for /IP turn width 1 width. Microfabrication technology can be broadly divided into ringography technology and etching technology, and both technologies have been greatly improved compared to conventional ones. For example, lithography technology uses electron beams with shorter wavelengths, taking into account the reduction in resolution due to light diffraction and interference effects.

Technologies using soft X-rays and the like as radiation sources have been put into practical use. Regarding etching technology, conventional wet etching involves short side etching, making it impossible to obtain highly accurate patterns, but active ion etching has recently been introduced.

Dry etching techniques such as sputter etching have come into use, making it possible to etch fine patterns. By the way, negative resist materials using radiation such as electron beams generally have a drawback of poor dry etching resistance.

In other words, when dry etching is performed, the resist film disappears during the dry etching process, and even if erasing is not achieved in 1, the edges of the wiring pattern are removed and the edges of the resulting wiring pattern become moth-eaten. An inconvenience will occur.

Etching speed is also an issue in dry etching processes. For example, silicon dioxide on a silicon wafer (
If you want to etch the Si02) insulating film through a normal photoresist mask, the etching speed of 5IO2 is about 1/3 to 1 times that of photoresist, so
In order to etch the 5IO2 film to a depth of 1 .mu.m, a photoresist film with a thickness of 3 to 4 .mu.m or more is required.

With such a thick resist film, it is very difficult to form a pattern with a width of 1 to 2 μm, and even if it were possible, the resolution would inevitably deteriorate significantly.

Recently, a two-layer resist film has been developed in which the lower layer is thickly coated with a resin having excellent dry etching resistance, and the upper layer is thinly coated with a radiation-sensitive negative resist. In this two-layer structure resist film, a fine pattern is formed on the upper layer, and this pattern is directly transferred to the lower layer, which has excellent plasma etching resistance. By configuring the resist film in this way, it is possible not only to suppress problems with dry etching resistance and resolution, but also to eliminate the problem of reduced pattern accuracy caused by the presence of underlying steps. can.

Problems to be Solved by the Invention In view of the current state of the prior art as described above, it has been found that a particularly high Sensitive negative resist materials are now desired.

The present invention seeks to solve this problem of providing negative resist materials.

Means to Solve the Problems In order to solve the above-mentioned problem, the inventors of the present invention have made the following research results:
Sensitive to radiation 7]? Focusing on the existence and properties of lysylsesquioxane, it was discovered that when a specific lysylsesquioxane is used in combination with an aromatic bisazide compound as a crosslinking agent, the molecular weight can be increased and sensitivity can be significantly increased. Ta. That is, the aromatic bisazide compound used in the present invention functions as a sensitizer.

The method for forming a pattern according to the present invention is a method of forming a patterned resist glossy turn by radiation irradiation using a two-layer resist film consisting of a lower layer and an upper layer, wherein the upper layer is a polysilyl resin represented by the following formula. Sesquioxane: Space below (in the above formula, R+ * R2r R3 and R4 may be the same or different from each other and each represents a substituted or unsubstituted methyl group or a substituted or unsubstituted vinyl group)
and an aromatic bisazide compound.

In the practice of the invention, it is advantageous to use the bisacide compound in an amount of 1 to 30% by weight of the polysilsesquioxane. If the amount of the bisazide compound is out of the above-mentioned range, it is not preferable because a sufficient crosslinking effect, that is, the function as a sensitizer cannot be achieved.

Examples of aromatic bisat compounds that can be advantageously used as crosslinking agents include 2,6-bis(4'-azidobenzal)acetone, 2,6-bis(4'-azidopendel)
Cyclohexane, 2,6-bis(,i/-azidopendel)-4-methylcyclohexane, 2,6-bis(47
-azidostyl)acetone, 2,6-bis(4-azidobenzylidene)(methyl)cyclohexane, and the like. Here, aromatic bisazide means that the azide group (-N,) is directly or radically azide. Refers to a compound indirectly bonded to an aromatic ring via a nyl group or an aromatic azide that does not contain a water-soluble group (e.g., a carboxylic acid group, a sulfonic acid group, and their salts), such as an azide.・Groups such as cytophenyl, azidostyl, azidobenzal, azidobenzoyl, azidocinnamoyl, etc.
Refers to a compound having more than one.

Examples of the polysilsesquioxane of formula (1) that can be advantageously used as the base polymer include polymethylflusesquioxane, polyvinylsilsesquioxane, and the like. Polyvinylsilsesquioxane is
In the form of a copolymer, for example Idyl? ')C methylsilsesquioxane-vinylsilsesquioxane).

The upper layer made of a mixed system of polysilsesquioxane and an aromatic bisat compound according to the present invention not only has significantly increased sensitivity but also has excellent resolution due to its composition and film thickness. Furthermore, since the pattern is resistant to oxygen plasma etching, the pattern can be easily and precisely transferred to the underlying layer by oxygen plasma etching.

In the practice of the present invention, any resinous material can be used as the bottom layer of the two-layer resist film, as long as it has high drying resistance and high corrosion resistance.

However, since oxygen plasma etching is used to transfer the holes and turns of the upper resist layer to the lower layer, the material forming the lower layer must be capable of being etched by oxygen plasma. Commonly useful underlayer-forming materials include AZ series photorenost, phenolic resin, polyimide resin, and 7f!
It is made of listyrene resin.

In the practice of the invention, it is advantageous to construct the top layer of the bil-resist film to be thinner and the bottom layer to be thicker.

As a result of making the upper layer thinner, combined with the use of a mixed system of polysilsesquioxane of formula (1) and an aromatic bisazide compound as the upper resist layer, excellent sensitivity and resolution can be achieved. Furthermore, by transferring this excellent upper layer resist pattern to a thick lower layer having excellent dry etching resistance, good dry etching resistance can also be achieved.

Furthermore, since the lower layer is a thick film, it is also possible to flatten steps such as unevenness in the degree of processing. Preferably, the thickness of the upper layer is about 0.2-0.5 μm, and that of the lower layer is about 1 μm.
, 5 to 3.0 μm.

The pattern forming method according to the present invention can be carried out by the following procedure: For example, a lower layer forming material is thickly applied onto a work piece such as a silicon wafer and cured. A mixed resist is further thinly applied on the formed lower V cyst film, and this is heated to evaporate the solvent, thereby forming a two-layer resist film. The resulting two-layer resist film is irradiated with radiation as defined above in a desired image pattern, and the unexposed areas of the upper layer that have not been cine-solubilized by cross-linking are dissolved and removed by development. Next, using the obtained upper layer resist pattern as a mask, the lower resist film below it is etched with oxygen plasma, and the i4 turn, which is the same as the upper resist pattern, is transferred to this -F layer resist film. do. A high aspect ratio negative mold like this)
A turn can be obtained, and by dry etching using this as a mask, a fine turn can be easily processed on the layer to be processed.

EXAMPLES The following examples further illustrate the patterning method according to the invention.

Example 1: In this example, a resist film having a two-layer structure shown in cross section in Figure 2g1 was prepared.

A silicon wafer 1 was thermally oxidized to grow a 5I02 thermal oxide film (film thickness: 0.5 μm) 2. This S which is the layer to be processed
First, on the iO2 film 2, a positive photoresist (trade name) AZ-1350J (trade name) manufactured by Siladeley Co., Ltd. in the United States was applied to a film thickness of 3.
μm and baked at 200° C. for 60 minutes. On the obtained lower layer 3, a mixed resist of polymethylsilsesquioxane (MW = 400,000 at 1 microcoulomb) and bisazide compound: 2,6-bis-(4-azidobenzylidene)(methyl)cyclohexane (
A methyl ingthyl ketone (MIBK) solution with a mixing ratio of 90/I 0% by weight was applied to a film thickness of 0.5 μm, and
Bake for 10 minutes at °C. Upper layer 4 was obtained. Layer 3 plus layer 4 in FIG. 1 is a two-layer resist film.

Example 2: The silicon wafer with the two-layer resist film prepared in Example 1 (see FIG. 1) was filled into an electron beam exposure device 17.
A pattern was drawn by irradiating an electron beam at an acceleration voltage of 20 kV and an exposure dose of 50 μ. As shown in FIG. 2, as a result of exposure, the exposed area 4' of the upper resist film 4 is
Cross-linking was performed at the step to insolubilize this portion. Next, the exposed wafer was developed with xylene, and an upper layer negative turn (0.5 μm lines and spaces) as shown in FIG. 3 was obtained. Then,
This wafer was packed into a parallel plate type dry etching apparatus, and using the remaining upper layer pattern 4' as a mask, an oxygen plasma IJ' was applied at a pressure of 30 mTorr and an applied power of 0.3.
3 Wlrrn'' for 20 minutes. As shown in FIG. 4, the upper layer 4' could be accurately transferred to the lower layer 3. The aspect ratio of these 4 turns was 3. 5 / 0.5 = 7,
This was significantly larger than that of the prior art. Next, using the /IP turn of this two-layer resist film as a mask, the 5i02 film 2 below it is treated with C3F8 plasma (gas pressure 40
Etching was performed for 30 minutes at mTorr + applied power 0.30 W/cm2 (FIG. 5). During this etching, along with selective removal of the SiO2 film 2,
The upper resist pattern 4' was also removed. Then,
When the remaining lower resist pattern 3 was removed, 5
A 0.5 μm line and space pattern was obtained which was transferred to the 102 film 2 (FIG. 6).

Effects of the Invention According to the present invention, a resist material having significantly increased sensitivity to radiation such as electron beams and soft X-rays is provided, and this can be applied to a two-layer resist film to form a negative pattern. As a result, finer patterns than ever before can be easily formed in a dry process in the manufacture of semiconductor integrated circuits and the like.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, and FIG. 6 are cross-sectional views sequentially showing the pattern forming method according to the present invention. In the figure, 1 is a silicon wafer, 2 is a 5i02 thermal oxide film,
3 is a lower resist film, and 4 is an upper Renost film. Patent applicant Fujitsu Limited Patent agent Akira Aoki Patent attorney Kazuyuki Nishidate Patent attorney 1) Yukio Patent attorney Akira Yamaguchi

Claims (1)

[Scope of Claims] 1. A method of forming a negative mold (by radiation irradiation) using a two-layer resist film consisting of a lower layer and an upper layer to form a diston 9 turn, wherein the upper layer is a polysilyl resin represented by the following formula. Sesquioxane: (In the above formula, R11 R2+ Rs and R4 may be the same or different from each other and each represents a substituted or unsubstituted methyl group or a substituted or unsubstituted vinyl group), an aromatic bisazide compound, A pattern forming method according to claim 1, characterized in that the pattern forming method consists of a mixed system of Formation method.