JP2002313768A - Cleaning method for semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning method by which re-sticking of particles is reduced after forming a metal film and a metal wiring pattern. SOLUTION: In the cleaning method of a semiconductor device, a semiconductor wafer after metal film formation is cleaned by using cleaning liquid for which the mixing mass ratio of aqueous ammonia (NH4 OH) of density 24 to 34 mass%: aqueous hydrogen peroxide (H2 O2 ) of density 26 to 36 mass%: pure water (H2 O) is 1:1:50 to 1:1:150.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for cleaning a semiconductor device, and more particularly to a method for cleaning a semiconductor wafer after forming a metal film.

[0002]

2. Description of the Related Art There are many cleaning steps in a semiconductor device manufacturing process. For example, cleaning with pure water using ultrapure water or pure water, cleaning using various chemicals, and the like.

Conventionally, pure water cleaning has been used for cleaning after forming a metal film in order to prevent the metal film from being corroded by chemicals.

[0004]

However, the pure water cleaning has a drawback that particles are easily re-attached after cleaning, although the purpose is to remove particles.

[0005] This is a phenomenon caused by the relationship between the potential of the particles and the wafer (zeta potential). As shown in FIG. 6, the re-attachment of particles near the wafer center is a feature of rotating and cleaning the wafer, such as spin scrubber cleaning. In this case, since there is no place for the electric charge to escape, static electricity is generated in the brush, which causes the adhesion of particles.

On the other hand, a cleaning method using a chemical, particularly RC
As is well known, a cleaning method called "A cleaning" is one of the cleaning methods which is very effective for removing foreign substances such as particles and metal contaminants on the surface. However, this cleaning method is based on, for example, RCA cleaning standard 1 solution (SC
In the case of using 1), NH ₄ OH (29% by mass): H ₂
O ₂ (30 _{wt%): H 2 O = 1} : 1: 5~1: 2: 7 concentration, for use temperature of the washing solution at 50-70 ° C.,
After the formation of the metal film, the metal is eluted and cannot be used.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for cleaning a semiconductor device, which can reduce reattachment of particles, as a cleaning method after forming a metal film or a metal wiring pattern.

[0008]

The present invention is achieved by the following means.

(1) A mixture mass ratio of aqueous ammonia (NH ₄ OH) having a concentration of 24-34% by mass: aqueous hydrogen peroxide (H ₂ O ₂ ) having a concentration of 26-36% by mass: pure water (H ₂ O). Is 1: 1:
A method for cleaning a semiconductor device, comprising cleaning a semiconductor wafer after forming a metal film using a cleaning liquid of 50 to 1: 1: 150.

[0010]

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIGS. 1 to 3 are views showing an example of a metal wiring step, which is one of the steps for forming a joint between metal wirings.

In the illustrated metal wiring step, first, as shown in FIG. 1, a contact is made in an interlayer insulating film 2 formed on a first metal wiring film 3 to form a tungsten film 1. Next, as shown in FIG. 2, the tungsten plugs 1a and 1b are formed by performing etch back of the entire surface of tungsten without using a photomask. At this time, foreign matter 4 such as a tungsten residue and particles is generated by the etching. Thereafter, conventionally, spin scrubber cleaning using pure water is performed. After the cleaning, as shown in FIG.
A metal wiring film 5 is formed by a sputtering method.
As shown in (1), etching is performed using a photomask to form predetermined wiring patterns 5a and 5b.

At this time, if there are many foreign substances 4 such as tungsten residues and particles, a wiring short 6 is induced as shown in FIGS. 4A and 4B.

In this embodiment, after the formation of the tungsten plugs 1a and 1b shown in FIG. 2, cleaning using low-concentration SC1 is performed.

FIG. 5 is a schematic diagram for explaining a spin scrubber cleaning method.

In the spin scrubber cleaning, first, the wafer 7 is placed on the wafer suction stage 8 and sucked. Then, the wafer 7 is rotated at about 3000 rpm, and the cleaning liquid is supplied onto the wafer 7 from the discharge lines 9 and 10 at the same time.

At this time, in this embodiment, a low-concentration SC1 cleaning solution is used as the cleaning solution. Specifically, SC
The temperature of one washing liquid was set to normal temperature (25 ° C. ± 5 ° C.), and the mixing mass ratio was set to 1: 1: 150 (NH ₄ OH: H ₂ O ₂ : H ₂ O). However, the concentration of the used ammonia water is 29% by mass, and the concentration of the hydrogen peroxide solution is 31% by mass.

Thereafter, the brush head 12 is moved onto the wafer 7 while supplying the low-concentration SC1 cleaning solution, and the sponge brush 11 is brought into contact with the wafer 7 at an arbitrary pressing pressure. Scan in the direction.

The scrubbing is performed for an arbitrary time, and after completion, the brush head 12 is moved to the standby position, the supply of the low-concentration SC1 cleaning liquid from both the discharge lines 9 and 10 is changed to pure water, and the rinse cleaning is performed for an arbitrary time. I do. After the rinsing is completed, the rotation speed is increased to about 5000 rpm, spin drying is performed, the wafer 7 is transferred to a predetermined position, and the cleaning process is completed.

As a result, in the present embodiment, as shown in FIG. 4C, a short circuit of the wiring pattern due to particles could be suppressed.

As described above, in the present embodiment,
In the cleaning process after the formation of the metal film, very low concentration SC
(1) By performing scrubbing using a cleaning solution, the potentials of the particles and the wafer can be reversed, so that reattachment of the particles is prevented, and furthermore, the lift-off property by slight etching of the base insulating film is utilized. Efficient particle removal can be performed.

It should be noted that the present invention is not limited to the embodiment using such a tungsten plug, but can be used in a cleaning process after forming various metal films. For example, it is effective in a cleaning step after forming a metal film of aluminum, titanium, molybdenum or the like or a silicide film of these metals, or after forming a wiring pattern of these metals or silicide.

The mixing mass ratio of SC1 was also 1: 1: 15.
It is not limited to 0 (NH ₄ OH: H ₂ O ₂ : H ₂ O), but may be basically determined by the process margin of the metal film or wiring. However, in order to sufficiently achieve the effect of the present invention, the mixing mass ratio of the cleaning liquid is, for example, from 1: 1: 50 to 1: 1: 150 (NH ₄ OH: H ₂ O).
₂ : H ₂ O) is preferred. This is because, when pure water (H ₂ O) is less than 1: 1: 50 (the concentration of ammonia water and hydrogen peroxide solution is high), most kinds of metal films used in semiconductor production such as aluminum and tungsten are eluted. On the other hand, if the amount of pure water (H ₂ O) is more than about 1: 1: 150 (the concentration of aqueous ammonia and hydrogen peroxide is low), the effect is not changed as in pure water. The concentrations of the aqueous ammonia and the aqueous hydrogen peroxide used may be those generally available on the market. For example, the concentration of the aqueous ammonia is 24-34% by mass, and the concentration of the aqueous hydrogen peroxide is 26-36% by mass. . Of course, ammonia water or hydrogen peroxide water other than these concentration ranges may be used, but the mass mixing ratio of the entire cleaning liquid should be the mixing mass ratio when the above concentration range is used. It is.

[Brief description of the drawings]

FIG. 1 is a drawing for explaining a metal wiring step.

FIG. 2 is a drawing for explaining a metal wiring step following FIG. 1, in which FIG. 2A is a cross-sectional view and FIG. 2B is a plan view.

FIG. 3 is a view for explaining a metal wiring step following FIG. 2;

4A and 4B are views showing a state after metal wiring is formed, FIG. 4A is a sectional view in the case of cleaning with pure water, FIG. 4B is a plan view in the case of cleaning with pure water, and FIG. Shows when applied.

FIG. 5 is a view for explaining spin scrubber cleaning.

FIG. 6 is a view for explaining reattachment of particles by a conventional cleaning method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Tungsten film 1a, 1b ... Tungsten plug 2 ... Interlayer insulating film 3 ... 1st metal wiring film 4 ... Foreign material 5 ... 2nd metal wiring film 5a, 5b ... Wiring pattern 6 ... Wiring short circuit 7 ... Wafer 8 ... Wafer suction stage 9, 10: Discharge line 11: Sponge brush 12: Brush head

Claims (1)

[Claims] A mixed mass ratio of aqueous ammonia (NH ₄ OH) having a concentration of 24-34% by mass: aqueous hydrogen peroxide (H ₂ O ₂ ) having a concentration of 26-36% by mass: pure water (H ₂ O). 1: 1: 5
A method of cleaning a semiconductor device, comprising cleaning a semiconductor wafer after forming a metal film using a cleaning liquid of 0 to 1: 1: 150.