JPS6364771B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to resist materials for lithography using ionizing radiation such as electron beams, X-rays, and ion _beams . The present invention relates to a positive pattern forming method that facilitates processing by dry etching.

Polymethyl methacrylate (PMMA) and polyn are used as resists for electron beams, X-rays, and ion beams.
- Methacrylic acid ester-based resists such as butyl methacrylate, poly-1-butenesulfone (PBS), polymethacrylamide, polymethacrylonitrile, and the like have been proposed. However, Al,
The resistance is insufficient for dry etching semiconductor wiring materials such as Al alloys and SiO ₂ , and insulating layers.
Before the layer to be processed is completely etched, the resist may run out, or the pattern may become thin or blurry. Therefore, resist materials with higher resistance are required. It is known that dry etching resistance can be improved by creating a molecular structure that contains a large amount of aromatic rings, but there is a reciprocity law in which this significantly reduces sensitivity. There is no resist that will satisfy you at the same time.

The present invention has been made in view of the above points, and when silicone resin is placed in oxygen plasma, its surface changes.
It changes to SiO ₂ and is not completely etched. Taking advantage of this phenomenon, it was mixed into a general positive resist to give it oxygen plasma resistance. This positive resist containing silicone resin has a two-layer structure in which the upper layer and the lower layer are coated with a material with high dry etching resistance that can be etched with O ₂ plasma, and the resist pattern on the upper layer is coated with O ₂ plasma etching on the lower layer. The object of the present invention is to provide a method for processing a layer to be processed using the plasma-resistant properties of the lower layer. The amount of silicone resin added is 1 to 10wt%, and 1wt%
If it is less than 10wt%, the effect will be small, and if it is more than 10wt%, the original resolution of the positive resist will be impaired. Furthermore, the sensitivity of the silicone resin must be lower than that of the resist used, and the developing method must be such that it will not be extracted by the developer.

The present invention will be described in detail below with reference to Examples.

FIG. 1 is a process sectional view showing the pattern forming method of the present invention. As shown in FIG. 1a, Al, Al alloy,
A layer made of _polystyrene , polyvinylcarbazole, phenolic resin, polyimide, cyclized polyisoprene, etc., which is highly resistant to other etchants that can be etched with oxygen plasma, is placed on the substrate 1 on which the layer 2 to be processed, such as SiO 2 , is formed. A resist layer 3 of No. 1 is applied. Next, a second resist layer 4 made of a mixture of a positive resist and polysilsesquioxane is applied thereon to a film thickness of 0.3 to 0.7 μm after drying.
Coating is performed by spin coating so that the thickness becomes m.
Then, as shown in FIG. 1b, only the second resist layer 4 is exposed and developed. Next, by etching in oxygen plasma, a pattern as shown in FIG. 1c is formed in which the exposed portions of the first resist layer that are not covered with the second resist layer 4 are etched away by the oxygen plasma. Next, as shown in FIG. 1d, the layer 2 to be processed is etched away using an etchant.
It is used for patterning.

Next, the resist used in the pattern forming method of the present invention will be explained.

(1) Upper second layer resist and polysilsesquioxane Polysilsesquioxane represented by the following general formula () is: [However, n: degree of polymerization R ₁ : H or one or more groups selected from phenyl group or alkyl group (C = 1 to 4) or CN group R ₂ : phenyl group or alkyl group (C = 1 to 4) or represents one or more groups selected from CN groups. ] Since it is a material that crosslinks when exposed to energy rays such as electron beams, when adding it, it is necessary to select a material whose sensitivity is lower than that of the basic positive resist. For this purpose, the following general formula () with phenyl groups attached to R ₁ and R ₂ ,
Alternatively, it is necessary to lower the sensitivity by lowering the molecular weight.

Figure 2 is a graph showing the relationship between exposure amount and residual film thickness for positive resist materials and polysilsesquioxane (silicon resin), with the normalized residual film thickness on the system minor axis and the exposure amount as a function of the horizontal axis. It was plotted.

In the present invention, it is basically necessary that the characteristic curves of each material do not mix.

(2) Development conditions for the second upper layer and the first lower layer The material that can be used for the first lower layer is a substance that can be etched by oxygen plasma.
Use a material with excellent dry etching resistance. For example, photoresists made of phenolic resin, polystyrene, polyvinylcarbazole, polyimide resin, and cyclized polyisoprene are preferred. However, in order to develop the upper second layer with a developer, it is necessary to select development conditions that do not dissolve the first resin layer, or to use a developer for the second resist as the first layer resin. It is necessary to select a material that does not dissolve in the water, or to cure the first layer resin to make it insolubilized. Furthermore, when developing the second layer resist, it is necessary to select components that have low resist swelling properties so that the silicone resin mixed therein is not extracted.

(3) Features of this silicone resin Because it is rich in SiO (more than other linear types), it has excellent O ₂ plasma resistance.

It has excellent solubility and is compatible with commonly used resist solvent developers. It also has good compatibility with resins.

Example 1 A layer of Al to be processed was applied to a silicon wafer to a thickness of 1 μm,
On top of this, polystyrene was coated to a thickness of 1.2 μm as a lower first resist layer. After heating at 120℃ for 60 minutes, methyl methacrylate and 2.2.3.4.4.4-
Copolymer with hexafluorobutyl methacrylate (copolymerization ratio 1:1 mol%, = 6×10 ⁵ ,
Mw/=2.5) is a silicone resin represented by the general formula () (R ₁ :H/C ₂ H ₅ =2/1, R ₂ :CH ₃ /
C ₆ H ₅ =2/1, =2×10 ³ , /=2.7)
A 0.5 μm thick mixture of 5 wt% was applied. and
After heating at 80° C. for 20 minutes, a 1 μm line and space pattern was drawn using an electron beam exposure device (exposure amount: 7×10 ⁻⁶ C/cm ² , 20 kV). This was developed for 60 seconds with a developer consisting of ethyl cellosolve (30 vol%) and isopropyl alcohol (70 vol%) to obtain a resist pattern. Next, using a parallel plate type dry etching device, the oxygen pressure was
0.4Torr, applied power 0.25W/cm ² , applied frequency
The styrene layer was etched under plasma conditions of 13.56 MHz for 12 minutes. As a result, the second resist layer is hardly etched,
The resist pattern was transferred to the first resist layer, the styrene layer. Next, add
By changing to CCl ₄ and etching for 10 minutes under the conditions of 0.04 Torr and 0.25 W/cm ² , the Al layer to be processed was completely etched to the same size as the upper first layer.

Example 2 The same process as Example 1 is used. However, as the second upper layer resist, a ternary copolymer of methyl methacrylate (94 mol%), methacrylic acid (5.5 mol%), and methacrylic acid chloride (0.5 mol%) is used, and R ₁ in the general formula () is H. /C ₂ H ₅ = 2/1, R ₂
is C ₆ H ₅ (=1.5×10 ³ ,
A positive resist with a composition containing Mw/=1.8) 5wt is used. The heating temperature is 140°C for 30 minutes, and the developing method is methyl isobutyl ketone for 3 minutes.
The exposure amount of the electron beam was 1×10 ⁵ C/cm ² and 20 kV.
Resolves 0.5μm lines and spaces. Furthermore, a phenol resin is used as the first resist layer which is the lower layer. Heat treatment at 160℃ for 60 minutes. The film thickness and etching were performed under the same conditions as in Example 1, and the same results as in Example 1 were obtained.

According to the present invention, by using a resist in which polysilsesquioxane is mixed into a normal positive resist material as the second upper layer, a resist pattern can be formed on the first layer resin with high dry etching resistance. It became possible to transfer the
Dry etching of the processed layer can be easily performed using the layer resin as a mask.

[Brief explanation of drawings]

FIG. 1 is a process sectional view of the pattern forming method of the present invention, and FIG. 2 is a graph showing the relationship between the exposure amount and the remaining film thickness of a positive resist and silicone resin. 1: Substrate, 2: Layer to be processed, 3: Lower first resist layer, 4: Upper second resist layer.

Claims (1)

[Claims] 1. A resist material prepared by mixing a positive resist for electron beams, X-rays, ion beams, and polysilsesquioxane represented by the following general formula (1) with electron beams, X-rays, ion beams, etc. A method for forming a positive pattern, comprising irradiating with any one of energy rays, exposing and developing the pattern to form a positive pattern. [However, n: degree of polymerization R ₁ : H or one or more groups selected from phenyl group or alkyl group (C = 1 to 4) or CN group R ₂ : phenyl group or alkyl group (C
=1 to 4) or one or more groups selected from CN groups. 2. Forming a first resist layer that can be etched with oxygen plasma on the substrate to be processed, and then forming a second resist layer on top of which polysilsesquioxane is mixed with a positive resist for electron beams, X-rays, and ion beams. a step of forming a second resist layer, a step of exposing the second resist layer by irradiating it with an energy beam such as an electron beam, an X-ray, an ion beam, and a step of developing and removing the exposed portion;
a step of etching and patterning the first resist layer using the second resist layer as a mask on the substrate in oxygen plasma; and a step of patterning the substrate to be processed using the resist layer as a mask. A positive pattern forming method characterized by the following.