JPS6290949A - Method for forming pattern - Google Patents

Abstract

PURPOSE:To prevent the resolution from decreasing due to the step of a primary substrate in a photolithography and the accuracy of a pattern from decreasing by disposing a semiconductor substrate in aqueous silver nitrate solution containing reducing agent, and emitting an excimer laser to precipitate silver on the substrate. CONSTITUTION:A semiconductor substrate 1 having a stepwise pattern 2a is put in a water tank 3 in which 1l of aqueous silver nitrate solution (10wt%) and 100cc of pyrogallol are put, and secured at the prescribed position. An excimer laser light 4 is emitted perpendicularly to the substrate 1 from above the tank 3, and a desired wiring is drawn. A silver wiring pattern 5 is momentarily formed on the substrate. The silver wirings are not affected by the primary step, but formed as desired in size.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a pattern forming method used in the manufacture of semiconductor integrated circuits, and more particularly to a method of forming a wiring pattern using phosphorography.

BACKGROUND OF THE INVENTION High integration and high density of integrated circuits have been improved with advances in conventional phosphorography technology. That is, so far, reduction projection exposure method and electron beam exposure method have been used.

1.0μ due to the development of X-ray proximity exposure method etc.
It is now possible to form a resist pattern with a diameter of m or less.

However, unevenness inevitably occurs on an actual integrated circuit, and after coating a radiation-sensitive resin (hereinafter referred to as resist), differences in resist film thickness occur at the uneven parts, making it difficult to maintain a good line width. Control becomes impossible. (For example, IEEE TRANSACTIONS on Electron Devices)
ON ELECTRON DEVICE), VOL,
22. P, 467-470) This will be explained using FIG. FIG. 2 shows a state in which a single-layer resist film is applied to a stepped portion by a conventional method and patterned to cross over the stepped portion. FIG. 2(8) is a sectional view of a state in which a step pattern 2a such as an S102 film 2 is formed on a substrate 1 such as a semiconductor substrate, and a resist 6 is applied thereon. In this case, when the resist 3 is coated to a thickness tRl (flat portion), the thickness of the resist 3 on the step pattern 2a is determined to be tR2 depending on the viscosity of the resist itself and the number of revolutions during coating. At this time tR1=tR
2, that is, it is physically impossible to completely eliminate the difference in the thickness of the resist film at the uneven portions. Like this t
A plan view of a resist pattern formed with a film thickness of R14tR2 is shown in FIG. 2(B).

Problems to be Solved by the Invention In such conventional methods, the step
If the turn width is determined to be 21 at the position of the film thickness tR1 of the resist pattern 6 formed perpendicularly to a, then at the position of the film thickness "R2" there is a relationship of tHl>tR2. The pattern width is 22 and 21>2°, which causes a difference in dimension conversion at the stepped portion.In other words, when the pattern is extremely fine, good line width control cannot be obtained, and furthermore, the edge portion 2b of the stepped object 2a Substantially, the resist film becomes thicker than the film thickness tR1 of the flat portion, and thus the resolution decreases.Generally, the resolution improves as the resist film thickness becomes thinner.

This is because the incident energy is attenuated due to interference and diffraction development when fine gaps are formed due to the wavelength of the radiation itself. In other words, in order to reduce the difference in the resist film thickness on the stepped object, simply applying a thick layer of resist to reduce the apparent difference in the resist film thickness on the stepped object lowers the resolution, which is not preferable in terms of forming a turn.

The present invention particularly aims to prevent a decrease in resolution and a decrease in pattern accuracy caused by a step difference in a base substrate in photo IJ lithography.

Means for Solving the Problems The present invention provides a pattern forming method in which a semiconductor substrate is placed in a silver nitrate aqueous solution containing a reducing agent, and silver is deposited on the semiconductor substrate by irradiating it with an excimer laser. It is. Here, as the reducing agent, for example,
Thiosulfuric acid, resorcinol, nitrous acid, etc. may also be mentioned.

Function The present invention is capable of forming a fine pattern regardless of the level difference of the base substrate by the method described above.Example: The pattern forming method of the present invention involves applying a conventional resist wiring pattern and then etching the base A2. This is completely different from the method of forming the A2 wiring. That is,
By irradiating a solution containing silver nitrate and a reducing agent with a high-energy excimer laser, silver will precipitate only in the irradiated areas, allowing silver wiring to be formed directly on the substrate. The reaction mechanism is as shown in the following formula.

■ AqN03μ Aq(NH3)2 and top Go Acr + 2NH3 Here, as the excimer laser, XeF (350n
m), XeC1 (308 nm), XeBr (282 nm)
).

KrF (249nm), KrCλ (222nm)
nm), ArF (193 nm), ArC4 (175 nm)
), F2 (157 nm), etc. can produce oscillation lines (the oscillation lines shown in parentheses for each gas). ■ The oscillation of Lera's excimer laser is Aq (NH3) 2
Since the beam diameter of the excimer laser, which has enough energy to break the Ag-N bond and precipitate the Aq solid, can be freely varied in the submicron range, it can be adjusted to any submicron range. A+2 A pattern can be formed on the substrate 0 Of course, since the pattern is formed directly on the substrate, there is no effect of the difference in base level or reflection at all. Hereinafter, detailed examples will be described with reference to FIG. 1.

A water tank 3 was charged with 12 cc of silver nitrate aqueous solution (10% by weight) and 1 oo CC of pyrogallol. The semiconductor substrate 1 was placed in this water tank 3 and fixed at a predetermined position.

(FIG. 1(A)) Note that the semiconductor substrate 1 has a step pattern 2a.
have. Excimer laser light 4 (KrF; 249 nm) is irradiated from the top of this water tank 3 perpendicularly to the substrate 1.
The desired wiring was drawn (Fig. 1(B)). A silver pattern was instantly formed on the substrate (Fig. 1 (Q) 0. Note that this silver wiring could be formed to the desired dimensions without any influence from the underlying step. This can be seen in Fig. 1 (P). ). That is, FIG. 1 ρ is a plan view when the silver wiring pattern 6 is formed at right angles on the step pattern 2a. The silver pattern width λ'1 on the concave part of the step pattern and the pattern width L' on the convex part are λ'1 = 2'2, and it is confirmed that there is no dimension variation of the pattern even on the step pattern. Recognize.

Note that the width of the silver wiring pattern formed in this example was at least 0.
．． It was 2 μm.

Effects of the Invention As described above, according to the present invention, a wiring pattern can be formed with high precision without being affected by a step difference in the base, leading to an improvement in the yield of semiconductor devices as a whole, and having high industrial value.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing a pattern forming method according to an embodiment of the present invention, and FIG. 2 is a process diagram showing a conventional pattern forming method. 1... Semiconductor substrate, 3... Water tank, 4.
...Excimer laser light, 5... Silver wiring pattern. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
figure

Claims (2)

[Claims] (1) A pattern forming method in which a semiconductor substrate is placed in a silver nitrate aqueous solution containing a reducing agent, and silver is deposited on the semiconductor substrate by irradiating the semiconductor substrate with an excimer laser. (2) The reducing agent is pyrogallol, thiosulfate, resorcinol,
The pattern forming method according to claim 1, wherein nitrous acid is used.