JPH0364861B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resist material and pattern forming method suitable for forming fine patterns applied to the manufacture of semiconductor integrated circuits, magnetic bubble memories, and the like.

BACKGROUND OF THE INVENTION Optical linkage or electron beam linkage is used as a main method in the manufacture of integrated circuits, bubble memory devices, and the like.

In recent years, with the miniaturization of patterns, in order to accurately transfer the resist pattern obtained by development onto the substrate, we have replaced the conventional wet etching.
Dry etching using gas plasma, reactive sputtering, ion milling, etc. has come into use. For this reason, there has been a need for a resist material that has high sensitivity, high resolution, and strong resistance to dry etching. Various resist materials have been developed to meet this requirement, but there are few that meet these requirements. For example, chloromethylated polystyrene is a resist material with excellent dry etching resistance, but it is difficult to achieve both high sensitivity and high resolution.

Furthermore, in an actual manufacturing process, the compound may have a step difference. In order to flatten this level difference, it is necessary to apply a thick resist layer.
However, in negative resists, pattern accuracy deteriorates due to swelling, especially during development, so that as the film thickness increases, resolution is impaired, and it is extremely difficult to form a thick resist layer with high resolution. Furthermore, even with positive resists, it is known that it is difficult to form a thick resist layer with high resolution due to the adverse effects of backscattering from the substrate in electron beam exposure and reflected waves from the substrate in optical exposure. There is. Particularly in stepped portions, there is a disadvantage that the pattern width differs significantly even with the same exposure amount due to the abnormal proximity effect. In order to solve this inconvenience, a three-layer structure was developed by Moran (JM
Moran et al. in the Journal of Baquium Science and Technology (J.
Vacuum Sci-ncs and Technology, Volume 16, No.
1620 (1979)).

In the three-layer structure, a thick organic layer is applied as the first layer, and then an inorganic material, such as a silicon oxide film, a nitride film, a silicon film, etc., which is difficult to be etched by dry etching using oxygen is formed as an intermediate layer. Thereafter, a resist is spin-coated onto the intermediate layer, and the resist is exposed and developed using an electron beam or light. The intermediate layer is dry-etched using the resulting resist pattern as a mask, and then the first thick organic layer is etched with O ₂ using this intermediate layer as a mask.
Etching is performed using a reactive sputter etching method. When a three-layer structure is used in this way, the resist for pattern formation can be thin, and a high-resolution pattern can be formed because the backscattering of electrons from the substrate and the adverse effects of reflected waves from the substrate can be avoided. After patterning, high resolution patterns can be transferred to the thick organic layer by etching.

However, this method has the disadvantage that after forming the first layer, the intermediate layer is formed by vapor deposition, sputtering, or plasma CVD, and then a patterning resist is applied, making the process complicated and long. .

If the patterning resist is resistant to dry etching using oxygen, a thick organic layer can be etched using the patterning resist as a mask, resulting in a two-layer structure and simplifying the process.

Polydimethylsiloxane is known to have an almost zero etching rate with O ₂ plasma, but since it remains liquid at room temperature even after the coating film is formed, it tends to attract dust, scratches, and has poor fluidity. The disadvantage is that it is difficult to handle. In addition, although polydimethylsiloxane is a negative resist, it does not have sufficient sensitivity;
It has the disadvantage that it is not easy to introduce functional groups to increase sensitivity.

As a result of addressing these points and proceeding with the study, the present inventors determined that the general formula (However, R is a hydrogen atom or a lower alkyl group,
The polymer compound containing the monomer unit represented by (R' represents a lower alkyl group) is extremely resistant to reactive sputter etching caused by oxygen, forms a hard and uniform film after coating, is easy to handle, and has a high The present inventors have discovered that it has excellent properties such as easy introduction of sensitive functional groups and can be used as a positive resist, leading to the completion of the present invention.

That is, the present invention aims to provide a resist material that has high sensitivity and can easily form fine and highly accurate patterns, and a pattern forming method using the resist material.

That is, the present invention is based on the general formula (R represents a hydrogen atom or a lower alkyl group, and R' represents a lower alkyl group) is a resist material characterized by having as a main component a polymer compound containing at least one monomer unit represented by: , a step of applying an organic polymer film on the material to be etched; (However, R is a hydrogen atom or a lower alkyl group,
R' represents a lower alkyl group. ) A step of applying a resist material whose main component is a polymer compound containing at least one monomer unit represented by It is characterized by comprising the steps of dry etching the organic polymer film using the resist film on which the pattern is formed as a mask, and etching the material to be etched using the organic polymer film that remains unetched as a mask. This is a pattern forming method.

Hereinafter, the present invention will be described in detail. The present invention comprises spin coating a thick organic layer on the first layer, evaporating it to dryness, and then applying the general formula (R represents a hydrogen atom or a lower alkyl group, and R' represents a lower alkyl group) A resist material whose main component is a polymer compound containing at least one monomer unit represented by is spun on a thick organic layer. Apply. After heating and drying, a desired pattern is drawn using radiation or light such as electron beams, X-rays, and deep ultraviolet rays, and development is performed using an appropriate developer. Using the obtained pattern as a mask, the first thick organic layer is etched by reactive sputter etching using O ₂ . Thereafter, the workpiece is etched using the thick organic layer with the fine pattern formed thereon as a mask.

Since the resist material in the present invention is extremely resistant to reactive sputter etching caused by oxygen,
A film thickness of about 1000 Å to 2500 Å can be used as a mask for etching an organic film as thick as about 1.5 μm. Therefore, since the resist needs to be thin for pattern formation, a high-resolution pattern can be easily obtained. Furthermore, since the first layer has a thick organic layer, it is possible to eliminate adverse effects such as backscattering of electrons from the substrate, reflected waves from the substrate, and abnormal proximity effects at stepped portions. Furthermore, the process is simpler than that of the three-layer structure, making it more practical.

Furthermore, since the resist material of the present invention is solid at room temperature, it can solve various drawbacks that have been seen due to dimethylsiloxane being liquid at room temperature. That is, the resist material in the present invention forms a hard and uniform film after drying, and is therefore easy to handle. Furthermore, since a copolymer is created with a monomer having a highly sensitive functional group, a highly sensitive functional group can be easily introduced.

Furthermore, it has many advantages such as being able to be used as a positive resist.

The present invention will be explained in more detail below using Examples.

Example 1 A copolymer with a weight average molecular weight Mw of 60,000 and a copolymerization ratio of 3-trimethoxysilyl-propyl methacrylate (abbreviated as SiMA) and glycidyl methacrylate (abbreviated as GMA) _{of 1} :4. (abbreviated as P( _GMA80 - ^SiMA20 )) 0.8g was dissolved in 15ml _of methyl cellosolve acetate to make a 5wt% solution, thoroughly stirred, and then filtered through a 0.2μm filter to prepare a sample solution. This solution was spin-coated onto a silicon substrate, heat-treated at 80° C. for 30 minutes in a N ₂ stream, and then subjected to electron beam irradiation using an electron beam lithography system.

After developing for 1 minute using a mixed solvent of trichlene and acetone in a volume ratio of 3:1, rinsing was performed for 30 seconds with ethanol. After drying, the film thickness of the irradiated area was measured using a stylus method. Whether fine patterns are resolved or not is determined by electron beam drawing of line and space patterns of various dimensions.
The resist image obtained by the development process was examined by observing it with an optical microscope and a scanning electron microscope.

The sensitivity curve (electron-sensitive beam characteristics) obtained as a result is shown in curve 1 in FIG. The vertical axis of the figure shows the relative value when the film thickness before development (hereinafter referred to as initial film thickness) is set to 1, and the horizontal axis shows the common logarithm of the electron beam irradiation amount (microcoulomb/cm ² ). be. The sensitivity of a negative resist is often expressed as the irradiation dose at the point where the film thickness becomes half of the initial film thickness. From the sensitivity curve in Figure 1, the sensitivity in this example is 0.7 μc/cm ²
It can be seen that it is. The resolution also reflected the thin initial film thickness (0.250 μm), and was able to sufficiently resolve submicrons. Curve 3 in FIG. 1 is a sensitivity curve of polydimethylsiloxane shown for comparison.
It can be seen that in the case of this example, the sensitivity is about 8 times higher than that of polydimethylsiloxane in terms of the irradiation dose at the point where gelation starts.

Furthermore, the obtained resist film was hard and could be handled in the same manner as ordinary photoresists and electron beam resists, and had no defects that were noticeable with polydimethylsiloxane.

Curve 1 in Figure 2 shows the O ₂ of P(GMA ₈₀ −SiMA ₂₀ ).
This shows how the film decreases due to reactive sputter etching. The vertical axis of the figure shows the film thickness (μm), and the horizontal axis shows the etching time (minutes). The first layer of organic polymer film is a novolac resin (product name: AZ-
1350J) was used. The patterning resist must be more resistant to O ₂ dry etching than this resin. 3 in FIG. 2 shows the film thinning of novolac resin (product name AZ-1350J) shown for comparison. For P(GMA ₈₀ - SiMA ₂₀ ), the amount of film loss decreases with time, and the etching rate _approaches zero. −SiMA ₂₀ ) was shown to be etched by only 0.22 μm, while P(GMA ₈₀ −
It can be seen that SiMA ₂₀ ) can be used as a mask when etching the resin.

Example 2 Novolak resin (product name: AZ) was deposited on a silicon substrate.
-1350J) was spin-coated to a thickness of 1.5 μm and heated at 200° C. for 1 hour. Example 1 after the substrate reaches room temperature
The sample solution prepared above was spin coated onto the resin. Thereafter, heat treatment was performed at 80° C. for 30 minutes in a N ₂ stream. The film thickness of P(GMA ₈₀ −SiMA ₂₀ ) is
0.4μ due to the relationship between rotation speed and film thickness during spin coating
It was estimated that m.

Electron beam exposure was performed using an electron beam lithography system at a dose of 0.8 μc/cm ² . Using a mixed solvent of trichlene and acetone in a volume ratio of 3:1,
After developing for a minute, rinsing was performed with ethanol for 30 seconds. After that, with oxygen gas
Reactive sputter etching was performed for 20 minutes under the conditions of 4sccm, 8mTorr, and 120W. This allows P
(GMA ₈₀ -SiMA ₂₀ ) The submicron pattern drawn on the resin AZ-
Transcribed to 1350J.

Example 3 A _copolymer ( _P
(abbreviated as GMA ₅₀ -SiMA ₅₀ )) was dissolved in 19 ml of methyl cellosolve acetate to form a 5 wt % solution, thoroughly stirred, and then filtered through a 0.2 μm filter to obtain a sample solution. Spin-coat 1.5 μm of novolak resin (product name AZ-1350J) on a silicon substrate,
Heated for 1 hour at <0>C. After the substrate reached room temperature, the above sample solution was spin coated onto the resin AZ-1350J.

Thereafter, heat treatment was performed at 80° C. for 30 minutes in a N ₂ stream. The film thickness of P (GMA ₅₀ −SiMA ₅₀ ) is 0.22 μm based on the relationship between the rotation speed and film thickness during spin coating.
It was estimated that

Electron beam exposure was performed using an electron beam lithography system at a dose of 0.4 μc/cm ² . 1 using a mixed solvent of trichlene and acetone in a volume ratio of 3:1.
After developing for a minute, rinsing was performed with ethanol for 30 seconds. Thereafter, as in Example 2, reactive sputter etching was performed using oxygen gas at 4 sccm, 8 mTorr, and 120 W for 20 minutes. As a result, the submicron pattern drawn on P (GMA ₅₀ -SiMA ₅₀ ) was accurately transferred onto a 1.5 μm thick novolac resin (product name: AZ-1350J).

Curve 2 in Figure 2 shows the O ₂ of P(GMA ₅₀ −SiMA ₅₀ ).
(This shows the thinning of the film due to reactive sputter etching.) The etching rate approaches zero faster than P(GMA ₈₀ - SiMA ₂₀ ). While the resin is etched by 1.5 μm, P(GMA ₅₀ - SiMA ₅₀ ) is 620
It can be seen that only Å is etched.

Moreover, the obtained membrane was hard and easy to handle.

Example 4 Weight average molecular weight Mw = 75,000, number average molecular weight 3.1
10,000, Dispersion (Mw/Mn) 2.4 Copolymerization ratio of trimethoxysilylpropyl methacrylate (abbreviated as SiMA) and chloromethylated styrene (abbreviated as CMS)
_Copolymer (P(CMS _{70 −}
Dissolve 0.9 g of SiMA ₈₀ ) in 9.5 ml of xylene to make a 10 wt% solution and stir thoroughly.
The sample solution was filtered through a 0.2 μm filter.

This solution was spin-coated onto a silicon substrate and 65
After vacuum drying at ℃ for 40 minutes, electron irradiation was performed using an electron beam lithography device. After developing with benzyl acetate for 1 minute, rinsing was performed with isopropyl alcohol for 30 seconds.
Sensitivity and resolution were examined in the same manner as in Example 1.
The resulting sensitivity curve is shown in curve 2 in FIG. From Figure 1, in the case of this example, the sensitivity is 2.3μc/
It turns out that cm ² . In addition, the resolution was sufficient to resolve sub-microns.

Further, the obtained film was hard and uniform, and no defects that were noticeable with polydimethylsiloxane were observed.

Example 5 Novolak resin (product name: AZ) was deposited on a silicon substrate.
-1350J) was spin-coated to a thickness of 1.5 μm and heated at 200° C. for 1 hour. After the substrate reached room temperature, the sample solution prepared in Example 4 was spin coated onto the resin. Thereafter, vacuum drying was performed at 65°C for 40 minutes. The film thickness of P (CMS ₇₀ -SiMA ₃₀ ) was estimated to be 0.250 μm from the relationship between the rotation speed and film thickness in spin coating. Electron beam exposure was performed using an electron beam lithography system at a dose of 2.5 μc/cm ² . Development was performed for 1 minute using a mixed solvent of methyl ethyl ketone and isopropyl alcohol in a volume ratio of 1:1, followed by rinsing for 30 seconds with isopropyl alcohol. After that, with oxygen gas,
Reactive sputter etching was performed for 20 minutes under the conditions of 4sccm, 8mTorr, and 120W. This allows P
The submicron pattern drawn on (CMS ₇₀ - SiMA ₈₀ ) was accurately transferred onto the 1.5 μm thick resin.

Example 6 Weight average molecular weight Mw is 200,000, copolymerization ratio m ₁ of SiMA and methyl methacrylate (abbreviated as MMA):
_Copolymer (P(MMA ₈₀ −
0.8 g of SiMA ₂₀ ) was dissolved in 15 ml of methyl cellosolve acetate to make a 5 wt % solution, thoroughly stirred, and then filtered through a 0.2 μm filter to obtain a sample solution. Novolac resin (product name) on silicon substrate
AZ-1350J) was spin-coated to a thickness of 1.5 μm and heated at 200° C. for 1 hour. After the substrate reached room temperature, the sample solution was spin coated onto the resin. Thereafter, heat treatment was performed at 80° C. for 30 minutes in a N ₂ stream.

The film thickness of P(MMA ₈₀ −SiMA ₂₀ ) could be estimated to be 0.32 μm from the relationship between the rotation speed and film thickness during spin coating. Electron beam exposure was performed using an electron beam lithography system at a dose of 180 μc/cm ² . After developing for 1 minute using a mixed solvent of methyl isobutyl ketone and isopropyl alcohol in a volume ratio of 1:3, rinsing was performed for 30 seconds with isopropyl alcohol. Thereafter, as in Example 2, reactive sputter etching was performed using oxygen gas at 4 sccm, 8 mTorr, and 120 W for 20 minutes.
As a result, a positive submicron pattern drawn with P (MMA ₈₀ -SiMA ₂₀ ) was accurately transferred onto the resin having a thickness of 1.5 μm.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the electron beam characteristics of Examples 1 and 4 and polydimethylsiloxane. Curves 1 and 2: Sensitivity curves of the resist materials produced in Examples 1 and 4, respectively. Curve 3: Sensitivity curve of polydimethylsiloxane. FIG. 2 is a diagram showing how the films of Examples 1 and 3 and the novolak resin (trade name AZ-1350J) were reduced by reactive sputter etching with oxygen. Curves 1 and 2: Characteristic curves of the resist materials produced in Examples 1 and 3, respectively. Curve 3: Characteristic curve of novolac resin (product name AZ-1350J).

Claims (1)

[Claims] 1. General formula (However, R is a hydrogen atom or a lower alkyl group,
A resist material characterized in that its main component is a polymer compound containing at least one monomer unit represented by R' represents a lower alkyl group. 2 Process of coating an organic polymer film on the material to be etched, general formula (However, R is a hydrogen atom or a lower alkyl group,
R′ represents a lower alkyl group) A step of applying a resist material mainly composed of a polymer compound containing at least one monomer unit represented by a lower alkyl group on the organic polymer film; forming a desired pattern on the film, dry etching the organic polymer film using the resist film on which the pattern is formed as a mask; and dry etching the organic polymer film remaining without being etched as a mask. A pattern forming method comprising the step of etching a material.