JP2001035812A - Method for filling copper into trench or via hole of wafer by electrolytic-copper plating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To fill the inside of a trench or via hole using copper without generating any void, etc., by performing an electrolysis under the presence of a wafer in the electrolytic-copper plating bath of a specific pH which includes copper ions and the complex compounds of copper ions. SOLUTION: A wafer is the one wherein a trench or via hole is formed. The trench is a groove formed in the wafer, and the via hole is a hole formed in the wafer and may be allowably a blind via hole of which one-end is closed. Still, a barrier layer can be formed previously in the trench or via hole. An electrolytic-copper plating bath includes copper ions and a complexing agent for copper ions. As the complexing agent for copper ions, there are exemplified polyamine and the salts thereof; aminocarboxylic acid and the salts thereof; amine alkanol compound; hydroxycarboxylic acid and the salts thereof; and the like. The electrolytic-copper plating bath is adjusted to have its pH of 6-8, preferably its pH of 6.8-7.2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming copper wiring by filling copper in a trench or a via hole of a wafer by electrolytic copper plating without causing defects such as voids, and a method of filling with such copper. Forming a wafer having a trench or via hole formed.

[0002]

2. Description of the Related Art In recent years, in order to cope with high performance and downsizing of recent electronic devices such as personal computers, copper wiring is formed by a copper film having extremely high electric conductivity in trenches or via holes in a wafer. ,
Methods to improve performance are being adopted.
In the case of forming a copper wiring in a trench or a via hole in a wafer with an electrically conductive film, a film has been conventionally formed by a dry method such as sputtering, PVD or CVD. However, in the case of dry film formation, work efficiency is reduced, and a film formed by sputtering or the like is made of aluminum or the like, so that high electrical resistance has been a problem.
Therefore, recently, an electrically conductive film in a trench or a via hole in a wafer is formed by copper sulfate plating. Since this method is a wet method, the working efficiency can be improved, and the wiring density can be improved by copper wiring. However, since the copper sulfate plating solution used is strongly acidic, sputtering,
The seed layer in the trench or via hole formed by PVD or CVD dissolves, making it impossible to perform electro-copper plating well and causing a problem such as generation of voids. In addition, the barrier layer formed on the trench or the via hole as needed is attacked, which also causes a defect such as a void. on the other hand,
When using electroless copper plating, it is necessary to increase the alkalinity.In this case, the conductive layer or the barrier layer used as needed is attacked, and this attacks defects such as voids. And cause problems. In addition, in electroless copper plating, bath management is difficult and toxicity has been a problem, such as the use of formaldehyde.

[0003]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for filling a trench or a via hole with copper without causing defects such as voids in the trench or the via hole in the wafer. .

[0004]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventor has found that a conductive copper plating bath having a pH of 6 to 8 containing copper ions and a complexing agent of the copper ions has been used. By electrolyzing the wafer on which the trenches or via holes are formed, without causing defects such as voids between the walls of the trenches or via holes and the filling copper, the trenches or via holes formed on the wafer can be filled with copper, The inventors have found that copper wiring can be formed, and have reached the present invention. That is, the present invention relates to a method of filling copper in the trench or via hole of a wafer having a conductive trench or via hole formed therein, the method comprising: an electrode having a pH of 6 to 8 containing copper ions and a complexing agent for copper ions. The present invention relates to a method for performing electrolysis in the presence of the wafer in a copper plating bath.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The wafer used in the present invention is a wafer having a trench or a via hole formed therein. The trench is a groove formed in the wafer, and the cross-sectional shape of the groove is not particularly limited. Examples of the cross-sectional shape of the groove include a rectangle, a square, and a trapezoid. The trench can be expressed by an aspect ratio indicating a value obtained by dividing the depth by the width. For example, a trench having an aspect ratio of 0.1 to 30, preferably 0.5 to 10 is appropriate. The via hole is
It is a hole formed in the wafer and may be a closed brand via hole. The cross-sectional shape of the via hole is not particularly limited. Usually, the cross section is rectangular or trapezoidal in shape, and the size is usually 0.05-1.
Those having a thickness of 0 μm, preferably 0.1 to 0.5 μm are suitable. The trench or the via hole can be formed in the wafer by, for example, dry etching, plasma etching, or the like.

Incidentally, a barrier layer may be formed in advance in the trench or the via hole. This barrier layer is for preventing the copper metal to be filled from diffusing into the wafer and causing a short circuit or the like. The barrier layer is formed, for example, in a trench or a via hole by PVD or CVD.
Can be formed by evaporating TaN or TiN. The conductive trench or via hole is formed in a trench or via hole formed in the wafer.
A conductive film (for example, a copper seed layer or the like) may be formed by sputtering, PVD, CVD, or the like, or may be formed by a catalizing process (for example, Pd catalyst application or the like) as a pretreatment for electroless copper plating. it can. However, the material for imparting conductivity is not limited to copper metal, and is not particularly limited as long as it is a metal capable of imparting conductivity.

The electrolytic copper plating bath used in the present invention contains copper ions and a complexing agent for copper ions. Copper ions may be added to the electrolytic copper plating bath as a salt thereof. Copper salts
There is no particular limitation as long as it is a source of copper ions in the electrolytic copper plating bath. As such a copper salt, various copper salts can be used as long as the anion is not harmful to the electrolytic copper plating bath. Suitable copper salts include, for example, copper sulfate, copper chloride, copper nitrate, copper hydroxide, copper sulfamate, copper carbonate, copper oxide and the like. Particularly, copper sulfate and copper chloride are preferable. The copper ion concentration in the electrolytic copper plating bath is, for example, 0.5 to 5 g / L, preferably 1 to 2 g / L. In addition,
When the concentration of the complexing agent described in detail below is high, it can be used even if the copper concentration is 2 g / L or more. Up to 60g / L
Applicable up to. Furthermore, as a source of copper ions,
An anode may also be used. As the anode, a soluble anode such as a phosphorous copper anode or an insoluble anode such as platinum, SUS, or titanium may be used.

The complexing agent used in the electrolytic copper plating bath of the present invention is used for complexing copper ions.
As long as it has such an effect, various complexing agents can be used from among known complexing agents. Such complexing agents include, for example, polyamines and salts thereof,
Examples include aminocarboxylic acids and salts thereof, amine alkanol compounds, oxycarboxylic acids and salts thereof, and the like. Examples of the polyamine include ethylene diamine, diethylene triamine, diethylene tetramine, triethylene tetramine and the like. As these salts, for example, sulfates, hydrochlorides, nitrates, acetates and the like can be used. Such a complexing agent is, for example, 1 to 100 g / L,
Preferably, the concentration is 5 to 50 g / L.

Examples of the aminocarboxylic acid include iminodiacetic acid, nitrilotriacetic acid, hydroxyethylethylenediaminetriacetic acid, tetrahydroxyethylenediamine, dihydroxymethylethylenediaminediacetic acid, ethylenediaminetetratetraacetic acid, cyclohexane-1,2-
Examples thereof include diaminetetraacetic acid, ethylene glycol diethyletherdiaminetetraacetic acid, ethylenediaminetetrapolopionic acid, N, N, N ′, N′-tetrakis-2- (2-hydroxypropyl) ethylenediamine, and the like. Examples of these salts include alkali metal salts such as sodium and potassium. Such a complexing agent is used in an amount of 1 to 100 g / L, preferably 5 to 50 g / L.
The concentration is preferably As the amine alkanol compound, for example, mono-, di-, tri-ethanolamine and the like are preferable. Such complexing agents are 5-2
It is suitable that the concentration is 00 mL / L, preferably 50-100 mL / L.

Examples of the oxycarboxylic acid include tartaric acid, citric acid and gluconic acid. Examples of the oxycarboxylic acid salt include sodium tartrate, potassium tartrate, sodium potassium tartrate, sodium citrate, and the like.
Examples thereof include potassium citrate, ammonium citrate, sodium gluconate, potassium gluconate and the like. Such a complexing agent is used in an amount of 1 to 100 g / L, preferably 5 to 100 g / L.
Preferably, the concentration is 50 g / L. The above-mentioned complexing agents can be used alone, but by appropriately mixing and using them, the stability of the plating bath can be improved and the properties of the deposited film can be improved.

In the electrolytic copper plating bath used in the present invention, a reducing agent can be used, if necessary, in order to promote the reduction of copper ions to metallic copper. The reducing agent is not particularly limited as long as it promotes the reduction of copper ions to metallic copper, and various reducing agents can be used. In the present invention, when the reducing agent is present in the electrolytic copper plating solution, copper can be effectively deposited in the trench or the via hole in the wafer by electrolysis. Examples of the reducing agent include dimethylamine borane, hydrazine hydrate, hydrazine hydrochloride, hydrazine salts such as hydrazine acetate, hypophosphorous acid, sodium hypophosphite, sodium borohydride and the like. Particularly preferred reducing agents include dimethylamine borane and the like. The concentration of the reducing agent is usually 0.5 to 20 g / L, preferably 1 to 20 g / L.
If the concentration of the reducing agent exceeds 20 g / L, the electrolytic copper plating bath is likely to be unstable, and the consumption of the reducing agent is undesirably increased.

The electrolytic copper plating bath used in the present invention includes:
If necessary, for example, in order to improve the characteristics of the electrolytic copper plating bath and the film characteristics of the precipitate, various sulfur compounds such as cyanide, cyanate, sulfide, and thio compound having solubility in the plating bath solution. A compound, a dipyridyl compound, an ethylene oxide type surfactant and the like can be added.
The pH of the electrolytic copper plating bath used in the present invention is adjusted to pH 6 to 8, preferably 6.8 to 7.2. PH in this range
Can be adjusted by adding an acid or an alkali, if necessary. In the present invention, this pH value is important when filling the trench or the via hole of the wafer with the electrolytic copper plating. By adjusting the pH value in this range, the attack on the seed layer in the trench or via hole of the wafer can be minimized.

In the present invention, the wafer having the conductive trenches or via holes formed thereon is preferably subjected to the above-mentioned electrolytic copper plating bath, preferably, to a wafer having a barrier layer and a seed layer formed thereon, or after the barrier layer is formed, to be subjected to catalystizing. The immersed wafer is immersed for electrolysis. The barrier layer is formed by forming known TiN, TaN, Ti, Ta, or the like into a film by sputtering, CVD, or the like. The seed layer is formed by forming a known conductive metal such as Cu by sputtering or CVD. The catalyzing, that is, the activation step until the catalyst is applied, is performed, for example, by immersing the appropriately pretreated wafer in a solution containing a known palladium or tin compound, washing with water, and then drying as necessary.

In the present invention, the electrolysis is suitably performed by setting the temperature of the electrolytic copper plating bath to preferably 15 to 50 ° C., more preferably 20 to 30 ° C. Under the above pH and temperature conditions, when electroless plating is performed using a bath solution having the same composition, precipitation by a copper reduction reaction does not occur, and a copper deposition reaction can be caused only by performing electrolysis. Moreover, copper can be efficiently deposited by electrolysis by using the above reducing agent. The area of the anode used in the electrolytic copper plating bath using the reducing agent used in the present invention is preferably 1/5 or more of the cathode. If the anode area is too small, the voltage rises, so that organic substances in the electrolytic copper plating bath, for example, a complexing agent and additives are decomposed, which is not preferable.

In the present invention, the electrolysis is carried out at a cathode current density of usually 0.1 to 1.0 A / dm ² , preferably
It is appropriate to carry out at 0.3 to 0.5 A / dm ² . The plating time is usually 5 minutes to 20 minutes, preferably 7 to 1 minutes.
Five minutes is preferred. The power supply used in the present invention may be a general-purpose DC power supply, but a pulse power supply, a PR power supply, and the like are also very effective for improving uniform electrodeposition. In addition, conventional PR
Current reversal electrolysis in which the polarity is changed at a higher speed than electrolysis is also effective. In the present invention, unlike the strongly acidic copper sulfate plating bath, a neutral electrolytic copper plating bath is used, so that it is possible to minimize the attack on the seed layer on the wafer that is vulnerable to a strong acid, and to reduce voids and the like. The copper metal can be filled in the trench or the via hole without causing a defect or the like, and as a result, a copper wiring having no defective portion in the trench or the via hole can be formed.

The outline of a typical process of the present invention is as follows. Step 1: (1) formation of trench or via hole (2) formation of barrier layer (3) formation of seed layer (4) copper electroplating

Step 2: (1) Formation of trench or via hole (2) Formation of barrier layer (3) Catalizing (4) Copper plating

[0018]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the scope of the present invention is not limited by these Examples and Comparative Examples.

Example 1 (1) Formation of trench or via hole (2) Formation of barrier layer of TiN by sputtering (3) Formation of Cu seed layer by CVD (4) Electrocopper plating treatment Plating solution: copper sulfate 5 g / L Tetrasodium ethylenediaminetetraacetate 5 g / L Dimethylamine borane 1 g / L pH 7.0 Temperature 25 ° C Current density 0.5 A / dm ² hours 10 minutes

Comparative Example 1 (1) Formation of trench or via hole (2) Formation of barrier layer of TiN by sputtering (3) Formation of seed layer of Cu by CVD (4) Electrocopper plating treatment Plating solution: 190 g / L sulfuric acid Copper sulfate 75 g / L Chloride ion 60 mg / L Additive (Note) 5 mL / L Current density 0.5 A / dm ² pH 1 or less Plating time 10 minutes (Note: Copper sulfate plating additive Copper Glyme 125 manufactured by Nippon Leelonal Co., Ltd .: Glossy Agent)

An 8-inch wafer was formed with a 0.18 μm trench (accept ratio: 2) by copper plasma etching. TiN was sputtered as a barrier layer, and then SiO ₂ was formed as a seed layer by CVD.
Using this as a sample, copper was filled by the method of Example 1 and Comparative Example 1 to form a copper wiring, and filling of the trench was confirmed by FIB (focused ion beam). Example 1
Then, when 100 trenches of 0.18 μm were observed by FIB, all trenches were completely filled by copper plating (see FIG. 1). In Comparative Example 1, when a 0.18 μm trench was observed by FIB for 100 grooves, voids were confirmed in 52 grooves (see FIG. 2). As can be seen from FIG. 2, voids are formed in some places in the walls of the trench (white portion).

Example 2 (1) Formation of trench or via hole (2) Formation of TiN barrier layer by sputtering (3) Application of Pd catalyst (4) Electrocopper plating treatment Plating solution: copper sulfate 5 g / L ethylenediaminetetraacetic acid Tetrasodium 5 g / L Dimethylamine borane 1 g / L Temperature 25 ° C Current density 0.5 A / dm ² hours 10 minutes

Comparative Example 2 (1) Formation of trench or via hole (2) Formation of TiN barrier layer by sputtering (3) Application of Pd catalyst (4) Electrocopper plating treatment Plating solution: sulfuric acid 190 g / L copper sulfate 75 g / L chloride ion 60 mg / L additive (Note) 5 mL / L current density 0.5A / ^dm 2 pH 1 or less plating time 10 minutes (Note: Nippon Rironaru Ltd. copper sulfate plating additive copper Gleam 125)

An 8-inch wafer was formed with a 0.18 μm trench (accept ratio: 2) by copper plasma etching, and after sputtering TiN as a barrier layer, SiO ₂ was formed as a seed layer by CVD.
Using this as a sample, copper wiring was formed by the method of Example 2 and Comparative Example 2, and filling of the trench was confirmed by FIB. In Example 2, 100 trenches of 0.18 μm were observed by FIB and found to be completely filled with copper plating. In Comparative Example 2, when 100 trenches of 0.18 μm trench were observed by FIB, it was confirmed that copper wiring could not be formed in 100 trenches.

[0025]

According to the method of the present invention, a copper wiring can be formed by filling a copper metal without causing defects such as voids in trenches or via holes in a wafer. In addition, the electrolytic copper plating process of the present invention can minimize the attack on the seed layer in the trench or via hole in the wafer. Further, after the lightning copper plating treatment, the wafer is precisely physically or chemically polished, and the above-described steps are repeated, whereby a high multilayer structure can be easily achieved.

[Brief description of the drawings]

FIG. 1 is an ion beam image photograph showing a fine structure of a trench of a wafer manufactured according to Example 1.

FIG. 2 is an ion beam image photograph showing a fine structure of a trench of a wafer manufactured according to Comparative Example 1.

Continued on the front page F term (reference) 4K024 AA09 AB01 AB02 AB15 BA11 BB12 BC10 CA02 CA03 GA16 4M104 BB04 BB14 BB17 BB30 BB32 DD06 DD37 DD43 DD52 HH20

Claims (2)

[Claims] 1. A method of filling copper in a trench or via hole of a wafer having a conductive trench or via hole formed therein, the electrolytic copper having a pH of 6 to 8 containing copper ions and a complexing agent for the copper ions. A method comprising electrolyzing in a plating bath in the presence of the wafer. 2. A method for forming a wafer having copper-filled trenches or via holes, comprising the steps of: forming a conductive trench or a conductive trench in a pH 6-8 electrolytic copper plating bath containing copper ions and a complexing agent for copper ions; A method comprising electrolyzing in the presence of a wafer having a via hole.