JPH0535865B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a resist material made of a silicon atom-containing α-methylstyrene polymer, which is particularly suitable for forming fine patterns in semiconductor integrated circuits, magnetic bubble memories, etc. It is.

[Prior Art] When forming fine patterns using optical lithography or electron beam lithography in the manufacture of integrated circuits, bubble memory devices, etc., optical lithography involves the influence of reflected waves from substrates, It is known that in beam lithography, resolution decreases when the resist is thick due to electron scattering. Dry etching is used to accurately transfer the resist pattern obtained by development onto the substrate. However, if a thin resist layer is used to obtain a high-resolution resist pattern, the resist will also be etched by dry etching and the substrate will be etched. It has the disadvantage that it does not exhibit sufficient resistance for processing. Furthermore, in order to flatten the step portion, it is necessary to apply a thick resist layer, and it can be said that it is extremely difficult to form a fine pattern on such a resist layer.

In order to solve these inconveniences, a three-layer resist was developed by J.M. Moran et al. in the Journal of Vacuum Science and Technology.
Science and Technology) Volume 16, Page 1620 (1979). In a three-layer structure, a thick organic layer is applied as the first layer (bottom layer), and then an inorganic layer, such as a silicon oxide film, a silicon nitride film, or a silicon film, which is difficult to be etched by dry etching using O ₂ is used as an intermediate layer. form a substance material; Thereafter, a resist is spin-coated onto the intermediate layer, and the resist is exposed and developed using an electron beam or light. Using the resulting resist pattern as a mask, dry-etch the intermediate layer, and then
Using this intermediate layer as a mask, the first thick organic layer is exposed to O ₂
Etching is performed using a reactive sputter etching method. This method allows converting thin high-resolution resist patterns into thick organic layer patterns. However, in such a method, after forming the first layer, the intermediate layer is formed by vapor deposition,
Since it is formed by a sputtering method or a plasma CVD method and a patterning resist is further applied, it has the disadvantage that the process is complicated and long.

If the patterning resist is resistant to dry etching, a thick organic layer can be etched onto the mask using the patterning resist, so that a two-layer structure can be obtained and the process can be simplified.

[Problems to be solved by the invention] Polydimethylsiloxane has excellent resistance to oxygen reactive ion etching (O ₂ RIE);
It is known that the etching rate is almost zero (G.N. Taylor, T.M. Wolf and G.M. Moran, Journal of Vacuum Science and Technology, 19(4), 872, 1981) (GNToylor,
TM Wolf and JMMoran, J. Vacuum Sci,
and Tech., 19(4), 872, 1981), but since this polymer is liquid at room temperature, dust easily adheres to it. It has drawbacks such as difficulty in obtaining high resolution and is not suitable as a resist material.

We have already proposed homopolymers and copolymers of triarykylsilylstyrene as the above-mentioned patterning resists [Japanese Patent Application No. 57-123866 (Japanese Unexamined Patent Publication No. 59-15419), Japanese Patent Application No. 57-123865 ( However, these polymers have excellent sensitivity to far ultraviolet or electron beam exposure and are suitable as resists for far ultraviolet or electron beam exposure, but they are not suitable for near ultraviolet or visible light. It did not crosslink when exposed to light, and could not be used as a photoresist.

Furthermore, we have already provided silane polymers as resists for optical exposure for the above-mentioned patterning (Japanese Patent Application No. 60-001636 and Japanese Patent Application No. 60-001637). However, the resist provided here has a silicon atom concentration of approximately 10 to 13% (W/W) relative to the polymer, so if the lower layer is thick, for example, if the thickness of the lower layer is 1.5 μm or more, it may be dry etched as the upper layer for patterning. Resistance was insufficient.

The purpose of the present invention is to form fine patterns with extremely high sensitivity to electron beams, X-rays, far ultraviolet rays, ion beams, or near ultraviolet rays in addition to these.
Moreover, it is an object of the present invention to provide a resist composition comprising a polymer having stronger resistance to dry etching.

[Means for Solving the Problems] In view of the above situation, the present inventors continued their research and found that a polymer having three or more silicon atoms and an allyl group in the monomer unit of the polymer It is extremely resistant to reactive sputter etching caused by oxygen, serves as a mask when etching thick organic films, and is extremely sensitive to electron beams, X-rays, deep ultraviolet rays, and ion beams. In addition, we discovered that adding a bisazide compound resulted in extremely high sensitivity to near ultraviolet rays.
The present invention has been accomplished.

That is, the present invention provides a silicon atom-containing α-methylstyrene polymer with a molecular weight of 3,000 to 1,000,000, whose main chain is composed of the following structural units, (in the formula, n represents a positive integer of 3 or more) A resist composition comprising the silicon atom-containing α-methylstyrene polymer and bisazide, and a resist layer having an organic film and a predetermined resist pattern are sequentially formed on the substrate. In a pattern forming method using a two-layer resist method using a dry etching mask for forming this resist pattern on an organic film, the resist layer has a composition consisting of the silicon atom-containing α-methylstyrene polymer or this polymer and bisazide. This is a pattern forming method characterized in that the pattern is formed of a material.

In the structural unit represented by the general formula () of the present invention, n is 3 or more, particularly preferably in the range of 3 to 6. The terminal group is usually an alkyl group such as n-butyl group or a hydrogen atom.

Furthermore, when a polymer is used as a negative resist, if the molecular weight is high, the sensitivity is generally high, but resolution is impaired due to swelling during development. Generally, if the molecular weight exceeds 1 million, high resolution cannot be expected. on the other hand,
Decreasing the molecular weight improves resolution, but not only does the sensitivity drop in proportion to the molecular weight, making it impractical, but it also becomes difficult to form a uniform and firm swelling when the molecular weight is less than 3,000. There is. Therefore, the molecular weight of α-methylstyrene polymer is
A range of 3,000 to 1,000,000 is suitable.

The α-methylstyrene polymer of the present invention can be produced, for example, as follows. .

(In the formula, n and x represent positive integers of 3 or more.) As shown in the above formula, the polymer of the present invention is n-
By using BuLi, that is, by an anionic polymerization method, it is possible to produce a polymer having a low polydispersity and having any molecular weight from low to high molecular weight.

This polymer is soluble in common organic solvents such as benzene, toluene, xylene, chlorobenzene, methyl ethyl ketone, chloroform, etc., and insoluble in methanol, ethanol, etc.

Further, the α-methylstyrene derivative which is the raw material for the α-methylstyrene polymer of the present invention can be produced as follows.

(In the formula, n represents a positive integer of 3 or more.) As shown in the formula, twice the molar amount of acetyl chloride is added dropwise to the alkylsilane and twice the molar amount of anhydrous aluminum chloride at room temperature, and the reaction is completed. rear,
1,n-dichloroalkylsilane is produced by distillation. Furthermore, after methoxylating the silyl chloride, it is reacted with an equimolar amount of allyl bromide as a Grignard reagent to produce 1-allyl-n-methoxyalkylsilane. Then 4-chloroα
- Methystyrene can be reacted with a Grignard reagent to produce the monomers shown above.

The resist material in the present invention is extremely sensitive to electron beams, X-rays, and deep ultraviolet rays as it is, but when bisazide, which is known as a photocrosslinking agent, is added, the resist becomes highly sensitive to ultraviolet rays. The bisazide used in the present invention includes:
4,4'-Diazidochalcone, 2,6-di-(4'-
azidobenzal)cyclohexanone, 2,6-di-(4'-azidobenzal)-4-methylcyclohexanone, 2,6'-di-(4'-azidobenzal)-4
- Hydroxycyclohexanone and the like. If the amount of photocrosslinking agent added is too little or too much, the sensitivity to ultraviolet rays will decrease, and if too much is added, the composition will have poor resistance to O ₂ dry etching, so it should be 0.1 to 30% by weight based on the polymer. It is desirable to add %.

It is known that the uniformity of molecular weight distribution also affects resolution, and the smaller the polydispersity, the better the resolution. In this regard, when produced by anionic polymerization, a polymer with a low polydispersity, for example, 1.2 or more, can be directly obtained without molecular weight fractionation, so the resist material has excellent resolution.

[Example] Next, the present invention will be explained with reference to examples.

Raw material production example 1 Production of 1,3-dichlorohexamethyltrisilane 60.1 g of powdered AlCl ₃ in a 300 ml flask
(0.45 mol), octamethyltrisilane 40.8g (0.2
35.0 g (0.45 mol) of acetyl chloride was added dropwise over a period of 2 hours. After the dropwise addition was completed, the reaction was continued for another hour at room temperature and distilled to obtain the target compound. The yield was 36.7g (75%).

Raw material production example 2 Production of 1,3-dimethoxyhexamethyltrisilane 25.6 g of methanol in the three-neck flask from 1
(0.8 mol), pyridine 63.2g (0.8 mol), benzene
300ml was charged and stirred with a mechanical stirrer. The mixture was cooled in an ice bath, 85.7 g (0.35 mol) of 1,3-dichlorohexamethyltrisilane was added, the reaction was continued for 2 hours, and the mixture was filtered. After distilling off the solvent under reduced pressure, the residue was distilled to obtain the target compound. The yield was 54.2g (66%).

Raw material production example 3 Production of 1-allyl-3-methoxyhexamethyltrisilane 4.3 g atoms of magnesium and 10 ml of ether were placed in a 300 ml flask. After adding a small amount of ethyl bromide and heating to activate the magnesium, 200 ml of ether was added. 25.5 g (0.14 mol) of allyl bromide was added dropwise over a period of 2 hours. Stirring was continued for an additional 2 hours to complete the reaction. In another 500 ml flask, 33.0 g (0.14 mol) of 1,3-dimethoxyhexamethyltrisilane and 50 ml of ether were charged, and Grignard reagent of allyl bromide was slowly added dropwise over a period of about 4 hours. After filtration, the solvent was removed under reduced pressure and distilled to obtain the target compound. The yield was 15.4g (55%).

Raw material production example 4 Production of 4-allyldimethylsilyldimethylsilyldimethylsilyl-α-methylstyrene 2.4 g of magnesium in a 300 ml three-necked flask
(0.1 gram atom), 10 ml of THF was charged, and after heating a little, a small amount of ethylmagnesium was added to activate the magnesium. After adding 100ml of THF, 13.7g of 4-chloro-α-methylstyrene
(0.09 mol) was added dropwise over a period of 3 hours. After continuing the reaction for an additional 2 hours, 17.7 g (0.072 mol) of 1-allyl-3-methoxyhexamethyltrisilane was added.
was added dropwise over a period of 1 hour. heated to reflux;
The reaction was allowed to proceed for 2 hours. After the reaction was completed, the mixture was poured into a dilute aqueous HCl solution, and extracted with ether. After drying the ether layer with MgSO ₄ , the ether was distilled off and the residue was distilled to obtain the monomer. 9.5g (40%)
The yield was .

Example 1 Production The monomer synthesized in Raw Material Production Example 4 and THF were pre-dried with calcium hydride. All polymerization reactions described below were conducted under high vacuum. 11 g of the monomer produced in Raw Material Production Example 4 was charged into a 100 ml flask with a branch, the branch was sealed with a rubber septum, and the flask was connected to a high vacuum line. It was frozen in a liquid nitrogen bath and then returned to a liquid state by applying vacuum. After repeating this operation four times to remove air contained in the monomer, 0.5 ml of n-butyllithium (1.6 M in hexane) was added to completely dehydrate the monomer.
It was then distilled into a similar side flask.
50 ml of THF was similarly degassed and dehydrated and distilled into a polymerization flask. 80μ of n-butyllithium (1.6M in hexane) was added through a rubber septum at room temperature using a microsyringe, and the mixture was immediately cooled in an acetone-dry ice bath to carry out polymerization. After 2 hours, 1 ml of methanol was added using a syringe to stop the polymerization, the pressure was returned to normal, and the polymer solution was poured into 500 ml of methanol. The polymer precipitated out as a white solid and was separated by filtration. Further dissolve in 100ml of benzene and 500ml of methanol.
I invested in it. After repeating this operation three times, it was dried at 50° C. under reduced pressure.

Weight average molecular weight (Mw) = 45000 Number average molecular weight (Mn) = 41600 Polydispersity (Mw/Mn) = 1.06 This polymer has 3 silicon atoms in one unit, so the silicon content is The amount is 25.5% (W/W) of the entire polymer.

Example 2 0.42 g of the polymer produced in Example 1 and 0.021 g of 2,6-di-(4'-azidobenzal)-4-methylcyclohexanone were dissolved in 6.0 ml of xylene, thoroughly stirred, and filtered through a 0.2 μm filter. It was filtered and used as a sample solution. This solution was spin-coated (3000 rpm) onto a silicon substrate and dried at 80°C for 30 minutes. Exposure was performed through a chrome mask using an ultraviolet exposure device (4800DSW (manufactured by GCA)).

After developing by immersing in methyl isobutyl ketone (MIBK) for 1 minute, it was developed with isopropanol for 1 minute.
I rinsed it for a minute. After drying, the film thickness of the irradiated area was measured using a stylus method. Initial film thickness is 0.25μ
It was m. Whether fine patterns have been resolved can be determined by drawing line-and-space patterns of various dimensions and observing the resist images obtained through development using an optical microscope or scanning electron microscope. Examined.

From the sensitivity curve, it was found that the gel point (D ⁱ _g ) was approximately 0.7 seconds. Shipley MP-1300, a photoresist widely used for ultraviolet exposure
(1 μm thickness), the appropriate exposure amount was 0.32 seconds.

Example 3 Resist material mainly composed of novolac resin (MP-1300 (manufactured by Shippray)) on a silicon substrate
was applied to a thickness of 1.5 μm and baked at 250°C for 1 hour. After that, the solution prepared in Example 2 was applied by spin coating and dried at 80°C for 30 minutes.
A uniform coating film with a thickness of 0.25 μm was obtained. This substrate was exposed for 10.0 seconds through a chrome mask using an ultraviolet exposure device (4800DSW (manufactured by GCA)). MIBK/n-
After development was performed by immersing in BuOH (50/100V/V) for 1 minute, rinsing was performed for 1 minute with isopropanol. This substrate was etched for 7 minutes using a parallel plate reactive sputter etching device (DEM-451 manufactured by Anelva) under the conditions of 2 sccm of O ₂ , 3.0 Pa and 0.16 W/cm ² . Observation with a scanning electron microscope revealed that the submicron pattern of the upper layer was accurately transferred to the lower resist material, forming a more vertical pattern.

[Effects of the Invention] As explained above, the polymer of the present invention has three or more silicon atoms per structural unit;
In the case of a high silicon concentration, for example 3 silicon atoms, it is 25.5% (W/W). Therefore, the resist composition is extremely resistant to dry etching.
A film thickness of about 2000 Å can be used as a mask for etching an organic layer as thick as 1.5 μm.
Therefore, the resist film for pattern formation may be thin. Additionally, if there is a thick organic layer underneath, the proximity effect will be reduced in electron beam exposure, so
In optical exposure, since the adverse effects of reflected waves are reduced, high-resolution patterns can be easily obtained.
Also, high-resolution patterns can be easily obtained using other exposure methods.

Furthermore, since the polymer used in the present invention is synthesized by an anionic polymerization method, a polydispersity of molecular weight distribution is obtained. Therefore, when a composition of the above polymer and bisazide is used as a resist,
The resulting pattern has better resolution.

Claims (1)

[Claims] 1. General formula (In the formula, n is a positive integer in the range of 3 to 10,
X depends on the value of n and has a molecular weight of 3000 to 1000000
A resist material characterized by using a silicon atom-containing α-methylstyrene-based polymer consisting of a structural unit represented by a positive integer in the range of 4 to 3500, such that 2 General formula (In the formula, n is a positive integer in the range of 3 to 10,
X depends on the value of n and has a molecular weight of 3000 to 1000000
0.1 to 30% by weight of the polymer is added to an α-methylstyrene polymer containing a silicon atom consisting of a constituent unit represented by a positive integer in the range of 4 to 3500, such that A resist material characterized by using a composition to which bisazide is added.