JPS60125840A - Resist solution - Google Patents

Abstract

PURPOSE:To prevent dissolution of an underneath resist and formation of a mixed layer and to simplify a lithographic process by using a satd. hydrocarbon for the solvent of a polysiloxane type resist used for a resist to senstitive to electron beam, X-rays, or UV rays. CONSTITUTION:A satd. hydrocarbon is used for the solvent of a polysiloxane (PSL) type resist to be used as the resist sensitive to electron beams, X-rays, or UV rays. Such a solvent is chain or cyclic satd. hydrocarbon having a boiling point of 120-170 deg.C, such as n-octane, various kinds of nonanes, various kinds of decanes, undecanes, and their mixtures. Even when the PSL type resist layer 8 is formed on a novolak resin resist layer 3 by using the PSL type resist soln. contg. such a solvent, the layer 3 is prevented from being dissolved and forming a mixed layer, thus not necessitating an operation, such as prebaking of the layer 3, and permitting simplification and speeding up of the lithographic process. Striation phenomenon does not occur and a thin uniform film can be formed.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a resist used in beam lithography technology,
In particular, the present invention relates to a resist using a solvent that can suitably perform resist coating and other handling.

[Background technology]

For example, lithography technology is used in the field of manufacturing technology for semiconductor devices, and resist is used for this technology.

This resist includes electron beam resist, ultraviolet resist, and others depending on the pattern baking method. Conventionally, polysiloxane has been applied to these electron beam and ultraviolet ray resists.

Incidentally, since such a resist is used by coating it in a thin film on the surface of a workpiece, it is necessary to liquefy the resist using an appropriate solvent. This solvent also needs to evaporate after coating to form a resist into a film. Conventionally, isoamyl acetate, methyl ethyl ketone, xylene, etc. have been used as this type of solvent. Namely, Journal Electrochemical Society Volume 116 (1969) 9
An example of using isoamyl acetate as a solvent for polysiloxane used in an electron beam resist is reported on page 4. Further, in the same magazine, Vol. 120 (1973), p. 1716, an example is reported in which methyl isobutyl ketone is used as the same solvent.

However, according to the inventor's study, this type of solvent does not cause any problems when the resist is applied directly onto the workpiece, but it is a unique lithographic technique that uses novolac resin-based solvents applied to the workpiece. A problem arises when the polysiloxane resist is applied over a photoresist. That is, the solvent of the polysiloxane resist coated on the upper side serves as a solvent for the lower resist, forming a mixed layer at the boundary between the two resist films. This mixed layer is insoluble in a developer when the polysiloxane film is developed after exposure, and becomes a hindrance such as not being etched when the lower novolak resist film is etched with oxygen plasma.

For this reason, it is conceivable to bake the novolac resin-based 7-otoresist at a high temperature (approximately 250° C.) after coating to make it insoluble in the solvent, thereby preventing the formation of a mixed layer. However, with this measure, it becomes difficult to remove the fumetresist that has been baked at a high temperature after the completion of the required processing steps, and there is a problem that the number of processing steps increases in combination with the above-mentioned baking, resulting in a complicated processing.

[Purpose of the invention]

It is an object of the present invention to provide a resist with a suitable solvent that prevents the dissolution of the lower photoresist and prevents the formation of mixed layers, thereby making it extremely easy to carry out the lithography process using two-layer resist technology. It is in.

The above and other objects and novel features of the present invention include:
It will become clear from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

That is, by using a saturated hydrocarbon as a solvent for the polysiloxane resist, it is possible to obtain a polysiloxane resist solution in which the novolac resin photoresist is insoluble. A lithography process using a layered structure can be performed extremely easily.

For this purpose, a solvent may be used that dissolves only the polysiloxane and does not dissolve the resist containing novolak or other polymers at all.

Such solvents include saturated hydrocarbons, such as normal nonane C, H,. etc. are used as a solvent. However, even with this type of solvent, if a solvent such as isooctane, which has a boiling point of about 100°C, is used, the solvent evaporates too quickly during spin coating of this resist, resulting in a film thickness distribution called striation. .

As shown in FIG. 1, this is a phenomenon in which the film thickness is distributed in the radial direction on the surface of the wafer 1, and color differences appear in the radial direction due to interference colors. If such a phenomenon occurs, it becomes impossible to carry out suitable lithography, and therefore it becomes practically difficult to use the above-mentioned solvents. For this reason, preferably a chain or cyclic saturated hydrocarbon having a boiling point in the range of 120 to 170°C is preferable. Specifically, normal octane (C1Hu), various nonanes (C, H
,. ) and various decanes (C1°H3,) are used.

〔Example〕

FIG. 2 shows an example of a process using the resist of the present invention.

First, as shown in the same figure (A), a novolac resin-based positive resist 3 is applied to a thickness of 1 μm on an oxide film (S iOt MA ) 2 of a silicon wafer 1 made of semiconductor (silicon).
Pre-bake for 30 minutes at a low temperature of 120°C. A common method for applying this resist is spin coating.

As shown in FIG. 3, the coating machine has a motor 4 that rotates at a variable speed and a vacuum chuck 6 fixed to a rotating shaft 5 of the motor 4. The wafer 1 is fixed to this chuck 6, the resist solution 7 is poured onto the wafer 1, and the wafer is rotated at an appropriate rotation speed between 1000 and 4000 rpm to form a thin resist solution layer with a uniform thickness on the wafer. Excess resist liquid is blown away from the wafer periphery. Then, the solvent in the resist solution immediately evaporates, leaving behind a resist thin film. Here, by adjusting the viscosity of the resist solution and the rotation speed of the wafer, the
It can be applied to a film thickness of m to several μm.

Next, as shown in FIG. 3(B), a polysiloxane film 8 is coated on the novolac resin photoresist film 3 to a thickness of 0.3 μm, and similarly prebaked at 120° C. for 15 minutes. The polysiloxane resist has a molecular weight (Mw - 350,000, Mn
-170,000) polydimethylsiloxane boiling point 1'50
．． It is dissolved in n-nonane (C++Hzo) at 8° C. at a concentration of 6% and filtered through a Teflon filter with a diameter of 0.2 μm to obtain a resist solution. Then, this is set in an electron beam lithography device and the required pattern is exposed.

Next, polysiloxane resist group 8 is developed using decane as a developer. Since the polysiloxane resist film 8 becomes a negative resist, the resist 8 remains in the exposed area 9 as shown in FIG. 3(C). Thereafter, heat treatment is performed at 120° C. for 30 minutes to remove the developer.

Next, oxygen gas is introduced into the plasma etching device,
The pressure inside the reaction tank is maintained at ITorr while being evacuated, and high frequency discharge is generated to create oxygen plasma. A wafer is placed here, and the novolac resist 3 is oxidized and removed using the remaining polysiloxane resist film 8 as a mask as shown in FIG. 3(D). At this point, the polysiloxane resist is not oxidized by the active oxygen plasma and acts as a mask.

Next, the gas introduced into the plasma etching equipment was changed to CF4.
+Oz (5%) and perform plasma etching of silicon oxide 2. At this time, the silicon oxide film 2 and the polysiloxane resist film 8 are etched by the Freon plasma, but since the Novo-based resist 3 underneath is resistant to the Freon plasma, this resist 3 is used as a mask as shown in the same figure. Etching of the silicon oxide film 2 as shown in E) is completed.

Finally, if you soak the wet cloth in a stripping solution containing phenol and benzene dichloride heated to 110°C,
), the novolak resist swells and peels off. A silicon oxide film 2 having a desired pattern can be obtained by washing with methanol, washing with water, and drying.

〔effect〕

(1) Since a saturated hydrocarbon is used as the solvent for the polysiloxane resist, even if a two-layer structure is constructed in which the polysiloxane resist is coated on a novolac resin resist film, the lower film will not be dissolved. A suitable sogerafye process can be carried out without forming a mixed layer.

(2) Since a mixed layer is not formed, a process such as high-temperature baking of the lower film is not necessary, and the lithography process can be simplified and speeded up.

(3) Since chain and cyclic saturated hydrocarbons with boiling points in the range of 120 to 170° C. are used, a uniform thin film can be formed by preventing non-uniformity in film thickness in the radial direction called striation.

Although the invention made by the present inventor has been specifically explained above based on examples, it should be noted that the present invention is not limited to the above-mentioned examples, and can be modified without departing from the gist thereof. Not even. For example, the saturated hydrocarbon does not need to be a single compound, and may be a mixture of the exemplified hydrocarbons (So [Field of Application] In the above explanation, the invention made by the present inventor will be mainly described in terms of the field of application that is its background. The present invention will be described with reference to a case where it is applied to a two-layer lithography technique for manufacturing a certain semiconductor device, but the present invention is not limited thereto and can be applied to all general lithography techniques.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a wafer to explain striations, Fig. 2 (A) to (F) are partial cross-sectional views of a wafer in an example process, and Fig. 3 is a conceptual configuration diagram of a resist coating machine. It is. 1... Wafer, 2... Silicon oxide film, 3...
Novolac resin photoresist film, 4... motor,
6... Chuck, 7 - Resist solution, 8... Polysiloxane resist film. Figure 1 Figure 3

Claims (1)

[Scope of Claims] 1. A resist liquid which is a polysiloxane resist configured as a photoresist for electron beams, X-rays or ultraviolet rays, characterized in that it is made using a saturated hydrocarbon as a solvent. 2. The resist liquid according to claim 1, wherein the solvent is a chain or cyclic saturated hydrocarbon having a boiling point in the range of 120 to 170°C. 3, all are normal octane, various nonanes, each m-
The resist liquid according to claim 2, which is a decane, a saturated hydrocarbon having 11 carbon atoms, or a mixture thereof.