JP3306598B2 - Semiconductor device manufacturing method and cleaning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device having a copper-based wiring and a cleaning apparatus used in the manufacturing process.

[0002]

2. Description of the Related Art Conventionally, aluminum alloys have been used for circuit wiring and electrode materials of semiconductor devices. In recent years, as semiconductor devices have become more highly integrated, wiring patterns have become finer, and wiring widths of 0.5 μm or less have been required. However, with the decrease in the wiring cross-sectional area, there are concerns about problems such as a reduction in circuit response speed due to wiring delay, and a reduction in wiring life due to an increase in heat generation and an increase in current density resulting in progress of electromigration. In order to avoid this problem, as described in JP-A-61-294838 or JP-A-63-248538, the electrical conductivity, heat resistance, and electromigration resistance are higher than those of aluminum-based wiring materials. Wiring materials using excellent copper or copper alloys have been developed.

[0003]

However, copper has problems in corrosion resistance and oxidation resistance. That is, copper is less susceptible to oxidation at a high temperature and more susceptible to corrosion in an aqueous solution because copper has a lower protective property of an oxide film formed on its surface than aluminum. Since the wiring material includes many water washing steps in the manufacturing process, the wiring material is required to have high corrosion resistance in a cleaning liquid.

It is known that benzotriazole (BTA) is used as a copper corrosion inhibiting method (JP-A-52-12636 and JP-A-56-847).
No. 9) has not been studied in the field of semiconductor manufacturing. Japanese Patent Application Laid-Open No. Hei 2-285696 discloses that, in the production of a printed wiring board, copper wiring is immersed in an aqueous solution containing a salt of a 2-aminothiazole derivative and a copper salt of an inorganic acid to contain copper ions on the copper surface. -A technique for forming a protective film comprising an aminothiazole derivative has been disclosed,
The protective film is an etching resist film in a subsequent etching step. No mention is made of measures against corrosion of the ultrafine copper wiring pattern by pure water in a cleaning step with pure water unrelated to etching. This is because the wiring of the printed circuit board has a cross-sectional extension of about 210 μm, which is thicker than a semiconductor copper wiring pattern. Here, the cross-sectional extension refers to the total length of the cross-section of the exposed portion where the copper wiring formed on the substrate comes into contact with the cleaning water.

An object of the present invention is to provide a method of manufacturing a semiconductor device in which corrosion of ultrafine copper wiring during water washing is suppressed and a cleaning apparatus used in the manufacturing process.

[0006]

To achieve the above object, the present invention provides a method for forming a copper wiring pattern on a substrate, comprising the steps of:
A method of manufacturing a semiconductor device, comprising a step of cleaning the copper wiring pattern with an aqueous solution containing copper ions. Here, the copper ion concentration in the aqueous solution is 5 × 1
It is preferably from 0 to ^{8 to} 5 × 10 to ⁶ mol · dm to ² . Alternatively, the electrical conductivity of the aqueous solution due to copper ions is 0.07-1.
It is preferably 0 μS / cm.

The present invention also includes a step of forming a copper wiring pattern on a substrate and then cleaning the copper wiring pattern with an aqueous solution containing benzotriazole.
Benzotriazole concentration of 2 × 10 ⁶ to 10 ¹
a method of manufacturing a semiconductor device which is a ^mol · ^dm ¯2.

The present invention is also a semiconductor device cleaning apparatus used in a cleaning step of forming a wiring pattern containing copper on a substrate and then cleaning the copper wiring pattern with an aqueous solution. It is characterized by comprising a concentration detecting means containing ions and detecting the concentration of copper ions, and a supply means for supplying copper ions into the aqueous solution based on a signal from the detecting means.

The present invention is also an apparatus for cleaning a semiconductor device used in a cleaning step of forming a wiring pattern containing copper on a substrate and then cleaning the copper wiring pattern with an aqueous solution. A concentration detecting means for detecting the concentration of benzotriazole containing triazole, and a concentration of benzotriazole in the aqueous solution of 2 × 10 ⁶ to 10 ¹ mol · d based on a signal from the detecting means.
It is characterized in that a supply means for supplying a benzotriazole such that ^m ¯2.

[0010]

In an aqueous solution, copper is in a chemical equilibrium state between Cu and a +2 ion of Cu as shown in (Chemical Formula 1).

[0011]

Embedded image

According to Le Chatelier's law,
When the concentration of +2 valence ions of Cu decreases in the system in the chemical equilibrium state, Cu is newly oxidized to generate +2 valence ions of Cu. In the water washing step, when the copper ions on the copper wiring are washed away by the cleaning liquid, the copper wiring is newly oxidized. That is, the corrosion of the copper wiring proceeds by washing with water. Therefore, in order to prevent corrosion of the copper wiring in the water washing step, copper ions may be added to the cleaning solution in advance and the copper wiring may be cleaned without changing the chemical equilibrium state. However, if the addition concentration of copper ions is too high,
Corrosion products are deposited on the copper wiring by the precipitation reaction of (Chemical formula 2) or (Chemical formula 3).

[0013]

Embedded image

[0014]

Embedded image

Therefore, by controlling the concentration of copper ions in the cleaning solution and keeping the concentration of copper ions on the copper wiring within a specific range, corrosion of the copper wiring can be suppressed to a minimum.
Further, since pure water is usually used for cleaning the semiconductor device, the electric conductivity of the cleaning liquid can be represented by a function of the copper ion concentration. Therefore, by keeping the electrical conductivity of the cleaning liquid within a specific range, the copper ion concentration in the cleaning liquid can be controlled, and the corrosion of the copper wiring can be suppressed to a minimum.

As described above, the extension of the cross section of the wiring means the sum of the lengths of three exposed sides of the wiring cross section when the wiring is formed. Since the cross-sectional area of the wiring in the LSI chip is smaller than that of the wiring on the printed board, oxidation or corrosion at a level that has no problem in reliability on the printed board leads to a fatal increase in resistance in the wiring in the LSI chip. The rate of increase in the wiring resistance increases as the length of the cross section of a wiring having a constant cross section increases. Assuming a wiring with an aspect ratio of 1, the resistance increase rate when the surface is oxidized at 0.1 μm is
0.3 when the wiring cross section is 300 μm (100 μm square)
%, It is estimated to be 0.9% (about 33 μm square) at 100 μm. If the rate of increase in resistance exceeds 1%, the reliability of the wiring is remarkably reduced. Therefore, in the present invention, it is effective that the upper limit of the wiring cross-sectional extension is 100 μm. Incidentally, the wiring currently used on the printed circuit board is the finest and has a cross-sectional extension of about 210 μm as described above.

Next, the action of BTA for suppressing corrosion of copper wiring will be described. When a cleaning solution containing BTA is brought into contact with the copper wiring, the copper and BTA react, and the insoluble Cu-BTA
A compound is formed. Since the Cu-BTA compound serves as a barrier between the copper wiring and the cleaning liquid, corrosion of the copper wiring can be suppressed.
However, excess BTA becomes a source of contamination for semiconductor devices. Therefore, by keeping the BTA concentration within a specific range, it is possible to suppress the corrosion of the copper wiring and minimize the contamination of the semiconductor device.

Incidentally, in the formation of the wiring pattern, in the wet etching, the corrosion of the wiring pattern can be suppressed by adding an inhibitor to the etching solution. Therefore, in the present invention, a dry process is preferred as a method of forming the wiring pattern. This dry etching is achieved by a SiCl ₄ -based gas. The present invention relates to a means for suppressing corrosion caused by rinsing water in a rinsing step for removing a residue or a residual adsorbed gas or the like attached to wiring after etching. Corrosion caused by adhered residue, residual adsorbed gas and the like can also be suppressed.

[0019]

FIG. 1 shows a procedure of an embodiment of a method of manufacturing a semiconductor device according to the present invention. According to a normal semiconductor manufacturing process, an insulating film is formed on a silicon wafer on which a semiconductor has been formed, and a contact hole is formed thereon to form a wiring film. When copper is used as the wiring material, corrosion is likely to occur in the cleaning step after forming the wiring pattern, unlike the case where a conventional aluminum alloy is used. Therefore, when copper was used, first, it was washed with an aqueous solution containing copper ions, and the deposits on the silicon wafer on which the semiconductor was formed were sufficiently washed away. Since the cleaning solution contains copper ions, corrosion of the copper wiring is minimized.

Next, in order to remove copper ions remaining on the silicon wafer, the silicon wafer was washed with pure water and dried. If copper ions remain, corrosion will occur from that starting point. Further, if the cleaning time with pure water is long, the corrosion of the copper wiring in pure water easily proceeds. Therefore, the cleaning time with pure water is desirably a minimum time sufficient to remove the remaining copper ions.

FIG. 2 shows the relationship between the concentration of copper ions added to the cleaning solution and the corrosion rate of copper wiring in the embodiment of the present invention. When copper ions were added to pure water, the concentration reached a minimum value when the concentration was approximately 10 to ⁷ mol · dm- ² , and the corrosion rate increased even if the concentration was higher or conversely lower. This value was at least one digit smaller than the corrosion rate in pure water. From this, the concentration of copper ions contained in the cleaning solution is 5 × 10 to ^{8 to} 5 × 10 to ⁶ mol · dm.
~ ² is desirable. According to the present embodiment, as compared with the case where pure water is used alone as the cleaning liquid, the corrosion rate of the copper wiring can be reduced by one digit or more, and a means for forming a copper wiring excellent in corrosion resistance can be provided. The pure water has a Cu ion concentration of 1 × 10 to ⁸ mol.
-It is dm ~ ² or less.

Although the copper ion concentration is specified in the above embodiment, it is difficult to continuously monitor the copper ion concentration during the actual semiconductor manufacturing process. Therefore, an embodiment of a method for controlling the concentration of the cleaning liquid will be described below. FIG. 3 is a diagram showing the relationship between the copper ion concentration in pure water and the electrical conductivity. When pure water and copper ions coexist in the cleaning solution, the electrical conductivity of the cleaning solution was uniquely determined by the copper ion concentration as shown in FIG. Therefore, the copper ion concentration can be monitored and controlled by continuously monitoring the electric conductivity in the cleaning liquid. 2 and 3, the electric conductivity of the cleaning liquid is 0.07 to
1.0 μS / cm is desirable. According to the present embodiment, it is possible to provide a means for easily controlling copper ions in the cleaning liquid and forming a copper wiring excellent in corrosion resistance. The electric conductivity of pure water is 0.05 μS / cm or less.

Next, FIG. 4 shows a procedure of an embodiment of a method of manufacturing a semiconductor device using a cleaning solution in which BTA is added to a cleaning solution in order to suppress corrosion of copper wiring during cleaning. According to a normal semiconductor manufacturing process, an insulating film was formed on a silicon wafer on which a semiconductor was formed, a contact hole was formed thereon, and a wiring film was formed. Next, the substrate was washed with an aqueous solution containing BTA, and the deposits on the silicon wafer on which the semiconductor was formed were sufficiently washed away. Since BTA is contained in the cleaning solution, corrosion of the copper wiring is minimized. Next, in order to remove BTA remaining on the silicon wafer, it was washed with pure water and dried. If the BTA remains, the BTA becomes a new attachment during drying, which causes a reduction in the reliability of the semiconductor device. The copper wiring surface is Cu-BTA
Does not corrode because it is covered with a compound. Therefore, the cleaning time with pure water is desirably long enough to remove the remaining BTA.

Next, FIG. 5 shows the relationship between the concentration of BTA added to the cleaning solution and the corrosion rate of copper wiring in the embodiment of the present invention. When BTA was added to pure water and the concentration was higher than about 10 to ⁵ mol · dm- ² , the corrosion rate of the copper wiring was reduced by one digit compared to the corrosion rate in pure water.
From this, the BTA concentration contained in the cleaning solution was 2 × 1
It is preferably from 0 to ⁶ to 10 to ¹ mol · dm- ² . 10 ~ ¹ mol
· Dm ~ to exceed the solubility is ² or more is not preferable because BTA is deposited. According to the present embodiment, the corrosion rate of the copper wiring is 1 compared with the case where pure water is used alone as the cleaning liquid.
It is possible to provide a means for forming a copper wiring which can be reduced by an order of magnitude or more and has excellent corrosion resistance.

Next, an embodiment showing a structure of a semiconductor device cleaning apparatus according to the present invention used in a cleaning step of forming a wiring pattern containing copper on a substrate and then cleaning the copper wiring pattern with an aqueous solution. As shown in FIG. A part of the primary purified water 1 obtained from raw water through processes such as coagulation, filtration, and ion exchange is stored in a solution tank 2, and copper ions are injected from an injector 3 into the solution tank 2. And this copper ion-containing aqueous solution and secondary pure water 4
Are mixed to a predetermined concentration by the mixer 5. The concentration of copper ions is monitored by a concentration detector 6 such as a copper ion concentration monitor or an electric conductivity meter installed in the mixer 5, and the injection amount of copper ions is controlled to a predetermined concentration. The aqueous solution thus adjusted is used to clean the silicon wafer on which the copper wiring is formed, a part of the washed aqueous solution is drained, and the rest is returned to the primary pure water system and reused. BTA instead of copper ion
May be injected.

[0026]

According to the present invention, copper ions or BT
Due to the anti-corrosion effect of A, corrosion of pure copper wiring formed on the semiconductor device due to pure water can be suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a method of manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a copper ion concentration and a corrosion rate when the present invention is applied.

FIG. 3 is a diagram showing a relationship between copper ions and electric conductivity in pure water.

FIG. 4 is a view illustrating a method of manufacturing a semiconductor device according to another embodiment of the present invention.

FIG. 5 is a diagram showing a relationship between a BTA concentration and a corrosion rate when the present invention is applied.

FIG. 6 is a diagram illustrating a configuration of a cleaning liquid manufacturing apparatus used in an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Primary pure water 2 Solution tank 3 Cu ion implanter 4 Secondary pure water tank 5 Mixer 6 Concentration detection means

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-12547 (JP, A) JP-A-5-36690 (JP, A) JP-A-4-64233 (JP, A) JP-A-4-254 42529 (JP, A) JP-A-3-167829 (JP, A) JP-A-2-83930 (JP, A) JP-A-56-84479 (JP, A) JP-B-58-36061 (JP, B1) (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/3205 H01L 21/28 301 H01L 21/304 647 H05K 3/26

Claims (4)

(57) [Claims] After forming a copper wiring pattern on a substrate,
A method for manufacturing a semiconductor device, comprising a step of cleaning the copper wiring pattern with an aqueous solution containing copper ions. 2. After forming a copper wiring pattern on a substrate,
As the copper wiring pattern - it comprises the step of cleaning the emissions with an aqueous solution containing benzotriazole, Benzotori in aqueous solution
The azole concentration is 2 × 10 ⁶ to 10 ¹ mol · dm
The method of manufacturing a semiconductor device which is a ^2. 3. A semiconductor device cleaning apparatus used in a cleaning step of cleaning a wiring pattern turn containing copper on a substrate with an aqueous solution, wherein the aqueous solution contains copper ions, and the concentration of the copper ions is detected. An apparatus for cleaning a semiconductor device, comprising: a concentration detecting means; and a supplying means for supplying copper ions to the aqueous solution based on a signal from the detecting means. 4. A cleaning device for a semiconductor device used in a cleaning step of forming a wiring pattern containing copper on a substrate and then cleaning the copper wiring pattern with an aqueous solution, wherein the aqueous solution contains benzotriazole. Concentration detecting means for detecting the benzotriazole concentration, and the concentration of benzotriazole in the aqueous solution based on a signal from the detecting means.
Degree becomes the ^{2 × 10 ¯6 ~10 ¯1 mol ·} dm ¯2
And a supply means for supplying benzotriazole as described above .