JP2579921B2 - Substrate manufacturing method - Google Patents

Description

The present invention relates to a method of manufacturing a substrate, and more particularly, to a method of manufacturing a substrate for forming an organic thin film.

(Prior Art) In recent years, as the development of electrical and optical elements using an organic thin film has been activated, a method of manufacturing an organic thin film by a Langmuir-Blodgett method (LB method) has attracted attention. Thin film (LB film) made by LB method is 20 ~ per layer
Due to its extremely small thickness of 50 mm, it is being applied as an insulating layer or an electrical or optical functional layer for devices having a structure such as MIS or MIM.

In particular, when a thin film formed by the LB method is applied to an element having a fine pattern represented by an LSI, a fine processing technique for the thin film is required. As the microfabrication technology of the organic thin film, the idea of photodimerization using photodimerization or photopolymerizable LB film molecules has been proposed. However, this method greatly limits the molecular materials that can be used. Therefore, a technique capable of forming a fine pattern on all LB molecular materials is desired.

(Problems to be Solved by the Invention) The present invention has been made in view of such a problem, and an object of the present invention is to provide a method of manufacturing a substrate in which an organic thin film pattern can be easily formed.

[Configuration of the invention]

(Means and Actions for Solving the Problems) The present invention is a method for producing a substrate for forming an organic thin film by the Langmuir-Blodgett method, comprising at least one hydrophobic group as a silicon substituent. A silane coupling agent containing a group is used as a surface treating agent for a substrate having a hydroxyl group on its surface, and the contact angle θ of the substrate surface with pure water becomes a contact angle θ3 at which a monomolecular film can be accumulated when the substrate descends. A step of defining a first region with the surface treatment agent and a step of defining a second region with the surface treatment agent such that the contact angle θ2 at which the accumulation of the monomolecular film is impossible during both lowering and rising of the substrate. And a method of manufacturing a substrate.

The present inventors have conducted intensive studies on the properties of the substrate surface and the cumulative nature of the monomolecular film, and as a result, have come to discover a completely novel fact as described below. That is, a molecule (LB film molecule) capable of forming a thin film (especially a monomolecular film) on the water surface is a surfactant having a structure in which one end has a hydrophobic group and the other end has a hydrophilic group. A substrate composed of surfaces exhibiting various contact angles θ is moved in the gas-liquid or liquid-gas direction on a monolayer on the water surface made from this LB film molecule, and the cumulative film area and substrate area ratio is expressed. When the ratio is examined, the results are as shown in FIGS. 8 and 9 for all the LB film molecules.

Here, the contact angle θ is the angle between the tangent to the water surface passing through the contact point between the meniscus water surface and the substrate formed when the substrate is immersed perpendicularly to the pure water surface and the water side formed by the substrate (Nos. 5 and 6).
Figure). The contact angle θ and its measurement method are described in detail in New Experimental Chemistry Course, Vol. 18, “Interface and Colloid”, pp. 93 to 106. Rather than measuring, measuring the height of the meniscus and obtaining θ from the theoretical formula, measuring the tilt angle of the substrate when the meniscus is inclined to the same horizontal plane as the water surface, tilting the substrate, placing horizontally The contact angle θ obtained by any method of dropping a water droplet on the substrate and measuring the angle between the surface of the water droplet and the substrate has the same value as θ defined above.

Here, the contact angle of a fine region is a problem, but it is impossible to actually measure such a contact angle experimentally. Therefore, the same processing method is performed for a large area region, The contact angle is measured and applied to the contact angle of a fine area.

If it increases the substrate according to the eighth and ninth FIG performing accumulation of monomolecular film, during the critical contact angle of the upper range of possible cumulative theta have a from theta = 0 ° (hereinafter referred to as theta _a) Limited. This theta _a varies depending on the kind of the hydrophilic groups of the LB membrane molecules,
Never exceed 90 ゜. Sometimes down the substrate limited from the critical contact angle is the range of possible cumulative theta limit (hereinafter referred to as θ _b) θ <between 180 °. θ _b is approximately 90 ° value. The critical contact angle is a contact angle at which the cumulative ratio changes from 1 to 0 or from 0 to 1 before and after the contact angle. theta _a is not exceed theta _b, thus increasing always the substrate in LB membrane molecules, regions of contact angle be moved in any direction of the downward at a cumulative ratio 0 is present.

Therefore, the contact angle theta ₃ of the present invention is between 180 ° from such theta _b as described above. The contact angle θ ₂ of the present invention is θ _a
It is between θ _b. Note that θ _a and θ _b are values determined by the types of molecules to be accumulated.

Next, production of an organic thin film using the substrate of the present invention will be described.

First, accumulation of the first layer is performed by lowering the substrate (FIGS. 2 to 4). When the accumulation of the first layer in the region having the contact angle that can be accumulated is completed, the moving direction of the substrate in the second layer is reversed. When the accumulation is performed by descending the first layer, the hydrophilic group is exposed, and the surface of this region is in a range of the contact angle where accumulation is possible by completely ascending the substrate, and Accumulation can be performed. Thereafter, the same relationship holds when the n-th layer accumulates the (n + 1) -th layer. Therefore, if the contact angle of the first substrate surface is set to be accumulable, the first layer can form an n-th accumulated film only in that region.

A first method for obtaining the substrate of the present invention is to treat a substrate (FIG. 1a) having a contact angle with pure water smaller than the critical contact angle in the accumulation when the substrate is raised with a surface treatment agent to obtain a new contact angle. The contact angle is set to be larger than the critical contact angle in the accumulation when the substrate is lowered (FIG. 1B). A resist is applied thereto, a resist pattern is formed to a minimum dimension of 0.1 μm by lithography using light or an electron beam (FIG. 1c), and the surface treatment agent at the resist-removed portion is removed (FIG. 1d). The surface treatment agent treatment is again performed so that the contact angle of the resist removing portion is larger than the critical contact angle in the accumulation when the substrate is raised and smaller than the critical contact angle in the accumulation when the substrate is lowered (FIG. 1e). The residual resist is obtained by completely removing the resist so as not to affect each contact angle of the substrate (FIG. 1f).

In the second method, a resist is applied to a substrate (FIG. 1a) in which the contact angle with pure water is smaller than the critical contact angle when the substrate is raised, and a minimum dimension of 0.1 μm is formed by a lithography technique using light or an electron beam. (FIG. 1g), and a surface treatment agent treatment (FIG. 1h) is performed so that the contact angle of the resist-removed portion becomes larger than the critical contact angle in the accumulation when the substrate is lowered (FIG. 1h). After removing the resist (FIG. 1i), the contact angle of the surface that was the resist remaining portion was made larger than the critical contact angle in the accumulation when the substrate was raised, and was smaller than the critical contact angle in the accumulation when the substrate was lowered. (FIG. 1f).

As the surface treatment agent of the present invention, a silane coupling agent can be used as long as the substrate has a hydroxyl group on the surface.

As the silane coupling agent, one containing at least one hydrophobic group as a substituent of silicon is used. Further, when the substrate is used for an electric element, a treatment agent which does not affect the electric characteristics is preferable. It is desirable that the compound reacts with a surface hydroxyl group as represented by bis (trimethylsilyl) amine or trimethylchlorosilane to form a monomolecular film and has a hydrophobic group as small as possible, such as a methyl group.

 For example, the following are mentioned.

Is one of

When using bis (trimethylsilyl) amine, the contact angle θ of the substrate can be controlled by the reaction time of the substrate in the saturated vapor phase at normal temperature of bis (trimethylsilyl) amine (FIG. 7).

In the present invention, CH ₃ OCH ₂ SiCl ₃ or the like can be used as a surface treatment agent. The substrate used in the present invention is made of any one of a semiconductor, a metal, an inorganic material, an organic material, and a composite material thereof, and can control a contact angle of the substrate surface with pure water by surface treatment. If so, any can be applied. In addition, an element which has already been subjected to fine processing for forming an element on a substrate is also applicable.

(Example) (Example 1) A thermally oxidized Si substrate is subjected to SH treatment with sulfuric acid / hydrogen peroxide solution (3: 1), dried, and then put into a bis (trimethylsilyl) amine saturated vapor phase and reacted for 24 hours. Bake for 5 minutes and apply chloromethylated polystyrene resist with a coater
Various patterns of 1 μm to 100 μm are exposed by DeepUV (1: 1) contact exposure, developed, treated with a 50% H ₂ SO ₄ aqueous solution for 1 minute, washed with water, dried, and washed with an organic solvent to remove the remaining resist. After reacting again for 2 hours with bis (trimethylsilyl) amine and baking at 100 ° C. for 5 minutes, a predetermined substrate is obtained.

(Example 2) After thermal processing of a thermally oxidized silicon substrate, the substrate was washed with water, dried, coated with a positive photoresist (trade name: AZ1450) by a coater, exposed to various patterns of 1 μm to 100 μm by a reduction projection exposure apparatus, and subjected to alkali development. Place in bis (trimethylsilyl) amine saturated vapor phase. After 24 hours, baking is performed at 100 ° C. for 5 minutes, the remaining resist is removed by washing with an organic solvent, bis (trimethylsilyl) amine is again applied for 2 hours, and baking is performed at 100 ° C. for 5 minutes to obtain a predetermined substrate.

(Example 3) Stearic acid is spread on the water surface of a 0.5 mM cadmium chloride aqueous solution, and compressed to a surface pressure of 25 dyne / cm. The substrates obtained in Examples 1 and 2 are lowered and raised in the gas-liquid direction. This was repeated to perform accumulation from 2 layers to 100 layers. According to the differential interference microscope, SEM, and TEM, it was found that cadmium stearate was accumulated uniformly only in all the substrate regions having a contact angle larger than the critical contact angle when the substrate was lowered,
A finely patterned organic thin film was obtained.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, the board | substrate with which the pattern formation of an organic thin film is easy can be provided.

[Brief description of the drawings]

FIG. 1 is a view showing a process for producing a substrate of the present invention, and FIG.
FIGS. 4 to 5 show the preparation of an organic thin film using the substrate of the present invention, FIGS. 5 and 6 show the contact angles, and FIG. 7 shows the relationship between the processing time and the contact angle. 8 and 9
The figure shows the relationship between the contact angle and the cumulative ratio. DESCRIPTION OF SYMBOLS 1 ... board | substrate 2, ... board | substrate surface 3 ... area | region whose contact angle is between 0 degree and (theta) _a 4 ... 2nd area, 5 ... LB film molecule 6 ... hydrophilic group, 7 ... hydrophobic Base 8 ... Aqueous solution, 9 ... Water surface 10 ... First area, 11 ... Pure water 12 ... Tangential line, 15 ... [theta] _a16 ... [theta] _b , 17 ... Resist

Claims (1)

(57) [Claims] 1. A method for producing a substrate for forming an organic thin film by a Langmuir-Blodgett method, wherein a silane coupling agent containing at least one hydrophobic group as a silicon substituent is added to the surface. A first region is defined by the surface treatment agent so that the contact angle θ of the substrate surface with pure water becomes a contact angle θ3 at which the monomolecular film can be accumulated when the substrate is lowered, when used as a surface treatment agent for a substrate having a hydroxyl group. And a step of defining a second region with the surface treatment agent so as to have a contact angle θ2 that makes it impossible to accumulate a monomolecular film both when the substrate is lowered and when the substrate is raised. Production method.