Anticorrosive agent

Details Anticorrosive agent Anticorrosive agent

2001-01-25

2003-02-25

Green, Anthony J. (Department: 1755)

Compositions: coating or plastic

Coating or plastic compositions

Corrosion inhibiting coating composition

C106S014410, C106S014430, C106S014440, C252S079100, C252S394000, C438S692000

Reexamination Certificate

active

06524376

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an anticorrosive agent capable of preventing a corrodible metal such as copper or the like from being corroded.
2. Description of the Related Art
In the process for producing a semiconductor device, a metal film of particular pattern is formed on a semiconductor wafer to form wirings and contact plugs. In such a step for formation of wirings and contact plugs, a corrosion inhibition technique is important in order to prevent the metal film from being corroded, for prevention of, for example, an increase in resistance. In recent years, copper, in particular, has come to be used widely as a material constituting the wirings and contact plugs, in order to make semiconductor devices operable at a high speed; therefore, the corrosion inhibitability requirement for the metal film has become stronger. It is because copper easily undergoes oxidation, etc. and tends to corrode although copper has such advantages as excellent electromigration resistance and low resistance.
As an example of the process in which corrosion inhibition for metal film is important, there can be mentioned a peeling step using a resist-stripper solution. When through holes are formed on metal wirings, a step is necessary which comprises forming holes by dry etching and then peeling and removing the residue of resist and the residue of etching. In this case, it is important to prevent the metal wirings from being corroded by the stripper solution used. Hence, it is widely conducted to allow the resist-stripper solution to contain an anticorrosive agent and thereby prevent the metal wirings from being corroded. As such an anticorrosive agent, there have heretofore been used aromatic hydroxy compounds such as catechol, pyrogallol, hydroxybenzoic acid and the like; carboxyl group-containing organic compounds such as acetic acid, citric acid, succinic acid and the like; and benztriazole (BTA) (e.g. JP-A-8-334905).
In the chemical mechanical polishing (CMP) conducted when the metal wirings are copper wirings, corrosion inhibition for copper is important not only for the prevention of quality deterioration of wiring copper due to corrosion but also for an operational reason. In the case of copper wirings, since fine processing by dry etching is difficult, patterning of wirings is ordinarily conducted by a so-called damascene process (FIG.
3
). In the damascene process, first, wiring grooves are formed in an insulating film
3
[FIG.
3
(
a
)], after which a barrier metal film
4
is formed on the whole surface of the resulting material. Then, thereon is formed a copper film
5
so as to fill the wiring grooves. Thereafter, chemical mechanical polishing (hereinafter referred to as CMP) is conducted to remove the copper film
5
at the areas other than the wiring grooves. Thus, copper wirings filled in the wiring grooves are formed. In CMP, since a corrosive slurry is used, copper corrosion easily proceeds; therefore, corrosion inhibition for copper becomes important. In CMP, there also arise other problems unique in CMP, such as (i) generation of dishing and erosion, (ii) generation of slit between copper film and barrier metal film and (iii) sticking of copper (polished by CMP) to polishing pad and wafer. To prevent these problems, corrosion inhibition for copper becomes important also. Description is made below on these problems.
Dishing refers to a phenomenon as shown in
FIG. 4
that the surface of a copper film
5
is dented at the center. This is caused by a fact that the polishing rate of the copper film
5
is far larger than the polishing rate of a barrier metal film
4
. Generation of dishing gives rise to various problems, for example, reduction in sectional area of wiring and resultant local increase in resistance.
Erosion refers to a phenomenon as shown in FIG.
3
(
c
) that CMP proceeds excessively at a region of densely arranged wirings and the surface of the region is dented. Generation of erosion gives rise to an increase in wiring resistance and deteriorates the flatness of substrate surface, causing, for example, short-circuiting of wirings.
Slit between copper film and barrier metal film refers to a slit as shown in
FIG. 4
, generated by a kind of battery action during CMP. Generation of slit gives rise to an increase in wiring resistance and makes later film formation insufficient.
Sticking of copper (polished by CMP) to wafer, etc. refers to a phenomenon that copper ions generated during CMP accumulate on a polishing pad, then restick onto the wafer, whereby the flatness of wafer surface is deteriorated and short-circuiting is incurred. This problem is described in, for example, JP-A-10-116804.
Thus, corrosion inhibition for metal is necessary in CMP for prevention of the quality deterioration of wiring metal caused by corrosion and also for the operational reason. In conventional CMP, an anticorrosive agent has been used for the main reasons of prevention of dishing and prevention of sticking of copper to polishing pad, and benztriazole or a derivative thereof has been used (JP-A-8-83780 and JP-A-11-238709).
In the above, corrosion inhibition in production of semiconductor device has been stated. In other technical fields as well, various studies have been made on anticorrosive agents capable of appropriately preventing corrodible metals from being corroded. For example, JP-A-10-265979 discloses a technique of using BTA, etc. as an anticorrosive agent for preventing a copper material (e.g. copper wire or twisted copper wire) from being corroded.
SUMMARY OF THE INVENTION
As mentioned above, BTA and derivatives thereof all having relatively high corrosion inhibitability are in general use as an anticorrosive agent for corrodible metals (e.g. copper). BTA and derivatives thereof, however, have had a problem in that they are difficult to decompose by using biological organisms and the disposal of the waste liquid generated is difficult.
In recent years, the requirement for low environmental load has become increasingly strong and the safety requirement for waste liquid from plant has become higher. Waste liquids from plants are ordinarily decomposed by biological treatment (hereinafter referred to as “biodegradation treatment”). The above-mentioned BTA and derivatives thereof are difficult to subject to biodegradation treatment.
Therefore, in using an anticorrosive agent containing BTA or a derivative thereof, the waste liquid generated therefrom has inevitably been disposed by a method other than the biodegradation treatment, requiring a higher cost and more labor.
Meanwhile, in the field of resist-stripper solution, aromatic hydroxy compounds, carboxyl group-containing organic compounds, etc. have been used as an anticorrosive agent in some cases, as mentioned previously. These anticorrosive agents are generally superior in biodegradability to BTA and derivatives thereof; however, since they are intended for corrosion inhibition for mainly a wiring material made of an aluminum-copper alloy, they have no sufficient corrosion inhibitability for highly corrodible metals (e.g. copper) and have been difficult to use as an anticorrosive agent functioning under severe conditions such as CMP.
In view of the above situation, the present invention aims at providing an anticorrosive agent which has high corrosion inhibitability capable of effectively preventing a corrodible metal such as copper or the like from being corroded and also has good decomposability by biological organisms.
In developing an anticorrosive agent, how to allow the anticorrosive agent to have high corrosion inhibitability for metals has been an important technical task. In order to allow an anticorrosive agent to have biodegradability in addition to the corrosion inhibitability for metals, a study must be made from a standpoint different from conventional standpoints. The present inventors made a study from such a standpoint and found out that both high corrosion inhibitability and excellent biodegradability can be achieved by using an an

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