JP2001164375A - Electroless plating bath and method for depositing electrically conductive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an electroless plating bath capable of depositing a film to form into a barrier metal layer uniformly and also at a film deposition rate higher than the conventional case even in wiring and connecting holes fined or whose aspect ratio is made high and to provide a method for depositing an electrically conductive film using the same. SOLUTION: In a process in which an electrically conductive film to form into a barrier metal layer 31 is deposited on the inner walls of fined grooves (G1, G2) for wiring and of a conduct hole C2, the surface to be plated is subjected to activating treatment, and after that, using an electroless plating bath at least containing a first metallic material feeding the essential components in the electrically conductive film, a second metallic material feeding components imparting barrier metal function to the electrically conductive film, a first complex of an amphoteric ionic type, a second complex promoting plating reaction, a reducer and a pH conditioner, and whose pH is controlled to the range from neutrality to alkalinity, the electrically conductive film is deposited.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroless plating bath and a method for forming a conductive layer using the same, and more particularly, to an electroless plating bath for forming a conductive layer having a barrier metal function and a barrier metal function. The present invention relates to a method for forming a conductive layer.

[0002]

2. Description of the Related Art Conventionally, aluminum or an alloy thereof has been widely used as a material for fine wiring of a semiconductor device obtained by forming an integrated circuit on a semiconductor wafer at a high density. However, in order to further increase the operation speed of the semiconductor device, it is necessary to use a material having a lower specific resistance, such as copper or silver, as the material of the wiring. In particular, copper has a low specific resistance of 1.8 μΩcm, which is advantageous in increasing the speed of semiconductor devices, and has an electromigration resistance that is about an order of magnitude higher than that of aluminum-based alloys. I have.

[0003] However, copper is characterized in that it is easily diffused into an insulating material such as silicon oxide and the diffusion speed is high. Therefore, when copper is used as a wiring material, a barrier metal layer for preventing diffusion of copper is usually formed at the boundary between copper and an insulating material. As a material used as the barrier metal layer, for example, tantalum, tantalum nitride, titanium, titanium nitride, tungsten, tungsten nitride, or the like is used.

[0004] Conventionally, the above barrier metal layer is formed by PVD (Physical Vapor Deposit) such as sputtering.
ion) method or CVD (Chemical Vapor Deposit)
ion) method or the like. However, as the semiconductor device is miniaturized and highly integrated, the wiring rule is similarly miniaturized to 0.13 μm or less, and further, as the height of the semiconductor element is increased, an interlayer insulating film such as silicon oxide covering the element is formed. Has a tendency to be thicker, but the opening area of the connection hole (contact hole or via hole for electrically connecting between elements or multilayer wiring) is rather narrowed, so that the aspect ratio of the connection hole is 1: 5 or more. In such a situation, the PV ratio has been increasing.
When the barrier metal layer is formed by the D method or the CVD method, the coverage is deteriorated, and it is very difficult to uniformly form a film on the wall surface of the connection hole.

To solve the above problem, US Pat.
Japanese Patent Application Laid-Open No. 695810 discloses CoW as a barrier metal layer.
A technique for forming a P layer by an electroless plating method is disclosed. Also, Japanese Patent Application Laid-Open No. 8-83796 discloses a technique of forming a film such as cobalt or nickel by an electroless plating method.

[0006]

However, in the method described in the above-mentioned US Pat. No. 5,695,810, a sodium salt is used as a chelating agent (complexing agent) or a reducing agent as a composition of an electroless plating bath solution. Therefore, it is not suitable for semiconductor applications due to the problem of sodium contamination. Further, the film formation rate is as low as 35 nm / min, which makes practical use difficult.

In the method described in JP-A-8-83796, the electroless plating bath does not contain alkali metals such as sodium, but the wiring rules are becoming finer and the connection holes are also smaller. While increasing the aspect ratio, a method of uniformly forming a barrier metal layer even in this situation is desired.

The present invention has been made in view of the above-mentioned problems, and the present invention provides a barrier metal layer having a uniform deposition rate and a higher deposition rate than conventional ones even in a wiring or a connection hole having a finer or higher aspect ratio. An object of the present invention is to provide an electroless plating bath capable of forming a film to be formed and a method for forming a conductive layer using the same.

[0009]

In order to achieve the above object, an electroless plating bath of the present invention is an electroless plating bath for forming a conductive film by electroless plating. A first metal material that supplies a main component, a second metal material that supplies a component that imparts a barrier metal function to the conductive film, a first complexing agent of an amphoteric ion type, and a second complex that promotes a plating reaction It contains at least an agent, a reducing agent, and a pH adjuster, and the pH is adjusted to a range from neutral to alkaline.

The above electroless plating bath of the present invention preferably contains a compound containing at least nickel or cobalt as the first metal material. More preferably, the first metal material contains nickel chloride or cobalt chloride.

The above electroless plating bath of the present invention preferably contains a compound containing at least tungsten or molybdenum as the second metal material. More preferably, the second metal material contains an ammonium salt of tungstic acid or molybdic acid. Also,
More preferably, the tungsten or molybdenum is contained at a concentration of 0.2 to 2 atomic weight%.

The above electroless plating bath of the present invention preferably contains an amino acid as the first complexing agent and an organic acid as the second complexing agent. Also, preferably,
None of the first complexing agent, the second complexing agent, the reducing agent, and the pH adjuster substantially contain a metal in the formula. Preferably, the pH is adjusted to 7 to 12, and the temperature is adjusted to 20 to 95C.

The above-described electroless plating bath of the present invention does not contain sodium or other alkali metals, so there is no problem of sodium contamination, and uniformity is achieved even in finer and higher aspect ratio wirings and connection holes. In addition, a film to be a barrier metal layer can be formed at a higher film formation rate than before.

In order to achieve the above object, a method for forming a conductive film according to the present invention is a method for forming a conductive film on a substrate, comprising: a first metal material for supplying a main component of the conductive film; A second metal material that supplies a component that imparts a barrier metal function to the conductive film, a first complexing agent of an amphoteric ion type, a second complexing agent that promotes a plating reaction, a reducing agent,
The substrate is immersed in an electroless plating bath containing at least an H adjuster and having a pH adjusted from neutral to alkaline, and a conductive film is formed on the substrate by electroless plating.

In the above-described method for forming a conductive film according to the present invention, an electroless plating bath containing a compound containing at least nickel or cobalt is preferably used as the first metal material. More preferably, as the first metal material,
An electroless plating bath containing nickel chloride or cobalt chloride is used.

In the method of forming a conductive film according to the present invention, an electroless plating bath containing at least a compound containing tungsten or molybdenum is preferably used as the second metal material. More preferably, an electroless plating bath containing an ammonium salt of tungstic acid or molybdic acid is used as the second metal material. More preferably, an electroless plating bath containing the tungsten or molybdenum at a concentration of 0.2 to 2 atomic weight% is used.

In the method for forming a conductive film according to the present invention, preferably, an electroless plating bath containing an amino acid as the first complexing agent and an organic acid as the second complexing agent is used. Used. Preferably, an electroless plating bath is used in which the first complexing agent, the second complexing agent, the reducing agent and the pH adjuster do not substantially contain any metal in the formula.
Also, preferably, the pH is adjusted to 7 to 12, and the temperature is 2
An electroless plating bath adjusted to 0 to 95 ° C is used.

In the method for forming a conductive film according to the present invention, the first metal material for supplying a main component of the conductive film such as nickel or cobalt and the component for imparting a barrier metal function to the conductive film such as tungsten or molybdenum are used. The second metal material to be supplied and the first zwitterion type such as amino acids
A complexing agent, a second complexing agent such as an organic acid that promotes a plating reaction, a reducing agent, and a pH adjuster.
The substrate is immersed in an electroless plating bath in which H is adjusted to a neutral to alkaline range (for example, 7 to 12) and the temperature is adjusted to 20 to 95 ° C., and a conductive film is formed on the substrate by electroless plating. Form a film. Here, tungsten or molybdenum is contained in the electroless plating bath at a concentration of 0.2 to 2 atomic weight%.

According to the above-described method for forming a conductive film of the present invention, there is no problem of sodium contamination due to the electroless plating process, and the wiring and the connection hole having a finer and higher aspect ratio are uniformly and conventionally obtained. An alloy film (a film that becomes a barrier metal layer) containing a component that imparts a barrier metal function to a conductive film such as tungsten or molybdenum can be formed in a conductive film such as nickel or cobalt at a higher film formation rate. .

In order to achieve the above object, a method for forming a conductive film according to the present invention is a method for forming a conductive film on a substrate, wherein the method exists at least on the surface of the substrate in the conductive film forming region. Removing an organic material, hydrophilizing at least the surface of the substrate in the conductive film forming region, bonding a coupling agent to the hydrophilized surface, A step of bonding a catalyst metal to a ring agent; a step of exposing and activating the catalyst metal; a first metal material supplying a main component of the conductive film; and providing a barrier metal function to the conductive film. An electroless device containing at least a second metal material for supplying components, a first complexing agent of an amphoteric ion type, a second complexing agent for promoting a plating reaction, a reducing agent, and a pH adjuster. In Tsu key bath, and immersing the substrate, and a step of forming a conductive film on the metal catalyst by electroless plating.

In the method for forming a conductive film according to the present invention, the pH of the electroless plating bath is preferably adjusted to a range from neutral to alkaline.

In the method for forming a conductive film according to the present invention, preferably, in the step of removing the organic substance, the surface of the substrate is oxidized to remove the organic substance. Preferably, in the step of hydrophilizing the surface of the substrate, a hydroxyl group is introduced into the surface of the substrate.

In the method of forming a conductive film according to the present invention, preferably, at least a silane coupling agent or a titanium coupling agent is used in the step of bonding a coupling agent to the surface. Further, preferably, in the step of binding a catalytic metal to the coupling agent, using a palladium colloid protected with tin chloride as the catalytic metal, and coordinate the tin atom of the tin chloride to the coupling agent, More preferably, in the step of exposing and activating the catalyst metal, tin chloride is peeled off from the palladium colloid protected with tin chloride to expose palladium.

In the method of forming a conductive film according to the present invention, preferably, in the step of forming a conductive film on the metal catalyst by the electroless plating, the first metal material is
An electroless plating bath containing at least nickel or cobalt, more preferably a compound containing nickel chloride or cobalt chloride is used.

Preferably, in the method of forming a conductive film according to the present invention, in the step of forming a conductive film on the metal catalyst by the electroless plating,
An electroless plating bath containing at least tungsten or molybdenum, more preferably a compound containing an ammonium salt of tungstic acid or molybdic acid is used. Preferably, in the step of forming a conductive film on the metal catalyst by the electroless plating, an electroless plating bath containing the tungsten or molybdenum at a concentration of 0.2 to 2 atomic% by weight is used. .

In the method for forming a conductive film according to the present invention, preferably, in the step of forming a conductive film on the metal catalyst by the electroless plating, an amino acid is contained as the first complexing agent. Then, an electroless plating bath containing an organic acid is used as the second complexing agent. Preferably, in the step of forming a conductive film on the metal catalyst by the electroless plating, any one of the first complexing agent, the second complexing agent, the reducing agent, and the pH adjusting agent is used. Also, an electroless plating bath containing substantially no metal in the formula is used. Preferably, in the step of forming a conductive film on the metal catalyst by the electroless plating, the pH is adjusted to 7 to 12, and the temperature is adjusted to 20 to 95 ° C. Is used.

In the method for forming a conductive film according to the present invention, preferably, after the step of forming the conductive film on the metal catalyst by the electroless plating, the conductive film containing copper is formed on the conductive film. The method further includes a step of forming a film.

In the method for forming a conductive film according to the present invention, the surface of the substrate is oxidized to remove at least the organic substance present on the surface of the substrate in the conductive film forming region. A hydroxyl group is introduced into the surface of the substrate in step 2 to perform a hydrophilic treatment. Next, a coupling agent such as a silane coupling agent or a titanium coupling agent is bonded to the surface subjected to the hydrophilic treatment, and a catalyst metal such as a palladium colloid protected with tin chloride is bonded to the coupling agent on the surface. Then, the tin chloride is peeled off to expose a catalytic metal such as palladium, followed by an activation treatment. Next, a first metal material that supplies a main component of a conductive film such as nickel or cobalt, a second metal material that supplies a component that imparts a barrier metal function to a conductive film such as tungsten or molybdenum, and an amphoteric such as an amino acid It contains at least an ion-type first complexing agent, a second complexing agent such as an organic acid that promotes a plating reaction, a reducing agent, and a pH adjuster, and has a pH in a neutral to alkaline range (for example, 7 ~ 1
The substrate is immersed in an electroless plating bath adjusted to 2) and the temperature is adjusted to 20 to 95 ° C., and a conductive film is formed on the substrate by electroless plating. Here, in the electroless plating bath, tungsten or molybdenum is 0.2 to 0.2%.
It is contained at a concentration of 2 atomic weight%.

According to the above-described method for forming a conductive film of the present invention, the surface of the plating surface is activated before the electroless plating treatment, and the electroless plating treatment eliminates the problem of sodium contamination, thereby reducing fineness. A barrier metal function is imparted to a conductive film such as tungsten or molybdenum in a conductive film such as nickel or cobalt at a uniform and faster film forming rate even in a wiring or a connection hole having an increased aspect ratio and a higher aspect ratio. An alloy film (a film to be a barrier metal layer) containing the component can be formed.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the method for forming an electroless plating bath and a conductive film according to the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a semiconductor device in which a conductive film is formed by the method for forming a conductive film according to the present embodiment.
A first insulating film 20 made of, for example, silicon oxide is formed on a semiconductor substrate 10 on which MOS transistors and other semiconductor elements are formed, an opening reaching the semiconductor substrate 10 is formed, and copper, polysilicon or A first wiring 30 made of a conductive material such as tungsten is formed. Above the first insulating film 20 and the first wiring 30, a second insulating film 21 made of, for example, silicon oxide, a first etching stopper 22 made of silicon nitride, a third insulating film 23 made of silicon oxide, and a Two etching stoppers 24 are formed by lamination.

Wiring grooves (G1, G2) are formed in the third insulating film 23 and the second etching stopper 24, and further penetrate the second insulating film 21 and the first etching stopper 22. A contact hole C2 exposing the upper surface of the first wiring 30 is formed so as to communicate with the wiring groove G1. In the communicating contact hole C2, the wiring groove G1, and the wiring groove G2, a wall surface is covered with a barrier metal layer 31a made of, for example, CoWP (a cobalt-tungsten alloy containing phosphorus) or the like. For example, a conductive layer 32a made of copper is buried and formed, and a contact plug P and a second wiring W2 are formed in the contact hole C2 and the wiring groove G1.
However, the third wiring W3 is formed in the wiring groove G2. In the above structure, the second wiring W2 is connected to the first wiring 30 as the lower wiring via the contact plug P.

A method for forming the above conductive film will be described with reference to the drawings. First, as shown in FIG.
On a semiconductor substrate 10 on which OS transistors and other semiconductor elements (not shown) are formed, for example, CVD (Chemical V)
The first insulating film 20 is formed by depositing silicon oxide by an apor deposition method or the like. Next, the first insulating film 20
Then, an opening reaching the semiconductor substrate 10 is formed, and a first wiring 30 is formed by embedding a conductive material such as copper, polysilicon or tungsten.

Next, as shown in FIG.
Silicon oxide is deposited on the first insulating film 20 and the first wiring 30 by a VD method to form a second insulating film 21;
Further, silicon nitride is deposited thereon by, for example, a CVD method to form a first etching stopper 22.

Next, as shown in FIG. 2C, the first etching stopper 22 is formed by a photolithography process.
A resist film R1 opening in a contact hole pattern is formed in a pattern on the upper layer, and etching such as RIE (reactive ion etching) is performed using the resist film R1 as a mask. Pattern opening C1 for exposing the upper surface of C21
To form

Next, as shown in FIG.
Silicon oxide is deposited in the pattern opening C1 and over the first etching stopper 22 by the VD method,
An insulating film 23 is formed, and further thereon, for example, CVD
A second etching stopper 24 is formed by depositing silicon nitride by a method.

Next, as shown in FIG. 3B, a resist film R2 having an opening in a wiring groove pattern is formed on the second etching stopper 24 by patterning, for example, by a photolithography process. Next, the resist film R2
Etching such as RIE using
The etching stopper 24 is patterned, and furthermore, the first etching stopper 22 is subjected to etching such as RIE under such a condition that the second insulating film 23 can be selectively removed by etching. 2 Form wiring grooves (G1, G2) in the etching stopper 24. At this time, by arranging the pattern opening C1 formed in the first etching stopper 22 in a region to be the wiring groove (G1, G2), the first etching stopper 22 is used as a mask to form the pattern opening C1 region. The first insulating film 21 is also etched away, and a contact hole C2 exposing the upper surface of the first wiring 30 is formed so as to communicate with the wiring groove G1.

Next, as shown in FIG. 4A, the contact hole C2 and the inner wall surfaces of the wiring grooves (G1, G2) are covered and the entire surface is formed as a conductive film by electroless plating according to the present invention. For example, a barrier metal layer 31 made of CoWP (a cobalt-tungsten alloy containing phosphorus) is formed. Here, in forming the barrier metal layer 31, as a pretreatment for electroless plating, palladium or the like is formed on the surface to be plated (the surface of an insulating film such as silicon oxide and the surface of a conductive film such as copper, polysilicon, or tungsten). It is necessary to perform the activation (catalysis) treatment using a metal having a high catalytic property. For example, the activation (catalysis) treatment can be performed by the following steps.

(1) Removal of organic substances First, organic contaminants on the surface to be plated are removed by ultraviolet / ozone treatment, plasma ashing treatment or ozone water treatment. (2) Hydrophilizing treatment Next, the surface to be plated is hydrophilized by oxidizing the surface to be plated in water to introduce a hydroxyl group (-OH group) into the surface. (3) Silane (titanium) coupling treatment Next, using a coupling agent such as a silane coupling agent or a titanium coupling agent, the above hydroxyl group and the above coupling agent are reacted and bonded. (4) Catalytic Treatment Next, using a catalytic metal such as a palladium colloid protected by tin chloride, the tin atom of tin chloride is coordinated to a coupling agent to bind the catalytic metal to the surface to be plated. (5) Activation treatment Next, for example, tin chloride is peeled off from the palladium colloid protected with tin chloride to expose palladium (catalyst metal) for activation treatment.

After the surface to be plated is activated as described above, the semiconductor substrate 10 is immersed in an electroless plating bath described below to form a barrier metal layer 31 having a uniform thickness on the entire surface to be plated. . The electroless plating bath includes, for example, a first metal material that supplies a main component of a conductive film serving as a barrier metal layer, a second metal material that supplies a component that imparts a barrier metal capability to the conductive film, and an amphoteric ion. A first complexing agent of the type (a first chelating agent) and a second complexing agent to promote the plating reaction
It contains at least a complexing agent (second chelating agent), a reducing agent, and a pH adjuster.

As the first metal material, for example, a compound containing nickel or cobalt such as nickel chloride or cobalt chloride can be used.
濃度 100 g / liter. Further, as the second metal material, for example, a compound containing tungsten or molybdenum, such as an ammonium salt of tungstic acid or molybdic acid, can be used.
/ Liter concentration.

The first zwitterionic complexing agent includes, for example, glycine, alanine, valine, leucine, isoleucine, methionine, phenylalanine, proline, tryptophan, serine, threonine, and the like.
Amino acids such as tyrosine, asparagine, glutamine, cysteine, glutamic acid, aspartic acid, lysine, histidine and arginine can be used.
濃度 50 g / liter.

As the second complexing agent for accelerating the plating reaction, an organic acid compound (ammonium salt) such as ammonium succinate, ammonium malate, ammonium citrate, ammonium malonate, and ammonium formate is used. For example, the concentration is 2 to 50 g / liter.

As the reducing agent, for example, ammonium hypophosphite, formalin, glyoxylic acid, hydrazine, ammonium borohydride and the like can be used, for example, at a concentration of 2 to 200 g / liter.

As the pH adjuster, ammonia water can be preferably used. As an electroless plating bath, for example, a neutral to alkaline range (pH of 7 to 1) is used.
The addition amount is appropriately adjusted in the range of, for example, 5 to 200 ml / liter so as to satisfy 2).

It is preferable that all of the first complexing agent, the second complexing agent, the reducing agent and the pH adjusting agent constituting the above electroless plating bath contain substantially no metal in the formula. When a metal such as a sodium salt is contained, the metal is contaminated by such a metal such as sodium, so that it is not suitable for semiconductor use.

The above electroless plating bath has a temperature of 20-9.
The temperature is preferably adjusted to 5 ° C. When a compound containing nickel is used as the first metal material,
A film can be formed preferably in the range of 0 to 95 ° C, and when a compound containing cobalt is used, a film can be formed particularly preferably in the range of 50 to 95 ° C.

By immersing the semiconductor substrate in the above electroless plating bath, the barrier metal layer 31 can be formed more uniformly at a speed of, for example, 100 nm / min. In the preferred temperature range and pH range of the electroless plating bath, the higher the temperature,
The higher the H, the higher the above film forming rate tends to be.

As the conductive film serving as the barrier metal layer formed above, an alloy of a metal supplied from the first metal material and the second metal material is formed. When a compound containing cobalt or nickel is used as the first metal material that supplies the main component of the conductive film as described above, and a compound containing tungsten or molybdenum is used as the second metal material that imparts a barrier metal function to the conductive film. Has C
oW (cobalt-tungsten alloy), NiW (nickel-tungsten alloy), CoMo (cobalt-molybdenum alloy) or NiMo (nickel-molybdenum alloy) can be formed. When ammonium hypophosphite is used as a reducing agent in the electroless plating bath, phosphorus is taken into the alloy film and, for example, the above-mentioned CoW
To be precise, CoWP (a cobalt-tungsten alloy containing phosphorus) is formed, and phosphorus is similarly taken in when another alloy film is formed.

The above electroless plating bath preferably contains tungsten or molybdenum at a concentration of 0.2 to 2 atomic weight%. Tungsten or molybdenum is contained as a component for imparting a barrier metal function to a conductive film formed by electroless plating. However, in order for the conductive film to function as a barrier metal, one atom of tungsten or molybdenum is contained in the conductive film. % Is required. FIG. 5 shows the content (atomic weight%) of tungsten in the plating film to be formed with respect to the amount of ammonium tungstate (concentration: g / liter) in the electroless plating bath.
It is the figure which measured and plotted. As shown in FIG. 5, when the concentration of ammonium tungstate is 3 g / liter or more in the electroless plating bath, that is, when tungsten is contained at a concentration of 0.2 atomic weight% or more, it is formed by the above-described electroless plating. Atomic% of tungsten in conductive film
The above concentration can be realized. On the other hand, in a concentration region where the content of ammonium tungstate is 30 g / liter or more, that is, in a concentration region where the tungsten concentration is 2 atomic weight% or more, a precipitate of tungstic acid is formed in the electroless plating bath. Since plating becomes difficult to deposit, it cannot be used as a stable electroless plating bath. Therefore, as described above, it is preferable that the electroless plating bath contains ammonium tungstate in an amount of 3 to 30 g / liter, that is, tungsten in a concentration of 0.2 to 2 atomic weight%. Similar results are obtained when tungsten is replaced with molybdenum.

After forming the barrier metal layer 31 on the surface to be plated of the semiconductor substrate 10 as described above, as shown in FIG. 4B, a barrier metal layer 31 such as a cobalt tungsten alloy film is By electroplating as a negative electrode coating layer in the plating, the contact hole C2 and the wiring grooves (G1, G2) are buried in the entire upper surface of the barrier metal layer 31, for example, copper is deposited, and the conductive layer 32 is formed. Form. As the electrolytic plating treatment for depositing copper, a general copper sulfate acidic plating bath or a copper pyrophosphate neutral plating bath can be used. Examples of the composition of the copper sulfate acidic plating bath and plating conditions are shown below.

Copper sulfate acid plating bath composition and plating conditions Copper sulfate: 200 to 250 g / l Sulfuric acid: 10 to 50 g / l Chloride ion: 20 to 80 mg / l Brightener: appropriate amount Temperature: 25 to 30 ° C. Cathode current density: 2 ~5A / dm ²

Alternatively, a contact hole C2 and a contact hole C2 are formed on the barrier metal layer 31 by electroless plating using the barrier metal layer 31 such as a cobalt tungsten alloy film as a catalyst layer (a surface coating layer in electroless plating). The conductive layer 32 can also be formed by burying copper, for example, by filling the entire surface of the wiring groove (G1, G2). Since cobalt and nickel have a higher catalytic activity than copper, there is no need to further activate the surface to be plated, and copper can be deposited by electroless plating. Examples of the composition of the plating bath and the plating conditions for the electroless plating for depositing the above copper are shown below.

Electroless copper plating bath composition and plating conditions Copper salt (copper chloride, copper sulfate, copper sulfamate, etc.): 5 to 50 g / liter Chelating agent (ethylene diamine, EDTA (ethylene diamine tetraacetic acid), etc.): 20 to 40 g / Liter Reducing agent (such as cobalt sulfate): 25-250g / liter

In the above-described copper plating, in any of the above-described electrolytic plating and electroless plating, it is not necessary to perform a pre-treatment on the surface of the barrier metal layer 31 such as a cobalt tungsten alloy film. Copper and the barrier metal layer can be formed continuously, whereby copper and the barrier metal layer are bonded to each other, and strong adhesion can be obtained. The above-mentioned copper plating treatment is not limited to the above-described composition in both the electrolytic plating treatment and the electroless plating treatment, and any composition may be used as long as copper is deposited.

As described above, the contact hole C2 and the wiring groove (G1, G
2) The inside is buried in the entire surface, for example, copper is deposited to form the conductive layer 32, and then, for example, CMP (Chemical Mechanical)
The conductive layer 32 and the barrier metal layer 31 deposited outside the contact hole C2 and the wiring trenches (G1, G2) are removed by a polishing process by a cal polishing method and an etch-back process by RIE or the like. As described above, the barrier metal layer 31a made of, for example, CoWP or the like covers the wall surfaces in the contact hole C2, the wiring groove G1, and the wiring groove G2 which communicate with each other, as shown in FIG. For example, a conductive layer 32a made of copper is buried and formed, and a contact plug P and a second wiring W2 are formed in the contact hole C2 and the wiring groove G1.
However, the third wiring W3 may be formed in the wiring groove G2, and the second wiring W2 may be connected to the first wiring 30 as a lower wiring via the contact plug P.

The electroless plating bath for forming a conductive film to be a barrier metal layer such as CoWP according to the present embodiment contains an amphoteric amino acid such as glycine as a first complexing agent, This can produce a stable chelation state. Further, as a second complexing agent, an organic acid compound (ammonium salt) such as succinic acid, formic acid, citric acid, malic acid or malonic acid is contained, which has a promoting effect such that the chelate is easily reduced. By using two kinds of complexing agents having different functions as described above, stable and high-speed plating film formation processing can be realized. Further, since the conductive film serving as the barrier metal layer can conformally rotate, it has an advantage that coverage in a fine contact hole or a wiring groove in a semiconductor substrate is extremely good. A conductive film serving as a barrier metal layer can be uniformly formed on inner walls of five or more contact holes.

According to the electroless plating bath according to the present embodiment and the method for forming a conductive film using the same, there is no problem of contamination by an alkali metal such as sodium, and the fineness and the aspect ratio are further improved. An alloy film containing a component that imparts a barrier metal function to a conductive film such as tungsten or molybdenum in a conductive film such as nickel or cobalt at a film forming rate that is uniform and faster than before in a wiring or a connection hole. (A film that becomes a barrier metal layer).

Example 1 An electroless plating bath having the following composition and condition A was formed, and the deposition rate of CoWP on a semiconductor substrate by the electroless plating treatment was measured. As a result, a deposition rate of 100 nm / min was realized. .

Electroless plating bath composition and plating conditions A Cobalt chloride: 50 g / l Glycine: 25 g / l Ammonium succinate: 10 g / l Ammonium hypophosphite: 50 g / l Ammonium tungstate: 10 g / l Temperature: 75 ° C pH (adjusted with aqueous ammonia): 8

Example 2 An electroless plating bath having the following composition and condition B was formed, and the deposition rate of NiWP on a semiconductor substrate by electroless plating was measured. As a result, a deposition rate of 100 nm / min was realized. .

Electroless plating bath composition and plating conditions B Nickel chloride: 50 g / l Glycine: 25 g / l Ammonium succinate: 10 g / l Ammonium hypophosphite: 30 g / l Ammonium tungstate: 10 g / l Temperature: 50 ° C pH (adjusted with aqueous ammonia): 7

As a semiconductor device for forming a conductive film according to the present invention, a MOS transistor semiconductor device, a bipolar semiconductor device, a BiCMOS semiconductor device, a semiconductor device on which logic and a memory are mounted, and a connection hole such as a contact hole or a via hole. Any semiconductor device having a trench wiring can be applied.

The method for forming the electroless plating bath and the conductive film of the present invention is not limited to the above embodiment. For example, the method for forming a conductive film to be a barrier metal layer such as a cobalt tungsten alloy according to the present invention is applicable to both a damascene process (a trench wiring forming process) and a dual damascene process (a process for simultaneously forming a trench wiring and a contact). It is also possible to apply to a process of forming only a contact. Further, as a conductive material for filling the wiring groove, the contact hole, and the like on the barrier metal layer, a material other than copper can be used.
In addition, various changes can be made without departing from the gist of the present invention.

[0065]

As described above, according to the electroless plating bath of the present invention, since there is no alkali metal such as sodium contained therein, there is no problem of sodium contamination, and the wiring is further miniaturized and has a high aspect ratio. A film that becomes a barrier metal layer can be formed uniformly at a contact hole and at a film formation rate higher than before.

According to the conductive film forming method of the present invention, there is no problem of sodium contamination due to the electroless plating treatment, and the wirings and connection holes with finer and higher aspect ratios are uniformly and conventionally formed. An alloy film (a film that becomes a barrier metal layer) containing a component that imparts a barrier metal function to a conductive film such as tungsten or molybdenum can be formed in a conductive film such as nickel or cobalt at a higher film formation rate. .

[Brief description of the drawings]

FIG. 1 is a sectional view of a semiconductor device according to the present invention and a conventional example.

FIGS. 2A and 2B are cross-sectional views illustrating a process of forming a conductive film in a semiconductor device according to the present invention; FIG. (C) shows up to the step of forming a pattern opening in the first etching stopper film.

FIG. 3 shows a step that follows the step of FIG. 2;
(B) shows the process up to the step of forming the etching stopper film and the process up to the step of opening the wiring groove and the contact hole.

FIG. 4 shows a step subsequent to that of FIG. 3, in which (a) shows up to a step of forming a barrier metal layer, and (b) shows up to a step of depositing a conductive film (copper).

FIG. 5 is a diagram in which the content of tungsten in a plated film to be formed is plotted against the amount of ammonium tungstate in an electroless plating bath of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Semiconductor substrate, 20 ... 1st insulating film, 21 ... 2nd insulating film, 22 ... 1st etching stopper film, 23 ... 3rd insulating film, 24 ... 2nd etching stopper film, 30 ... 1st wiring, 31, 31a: barrier metal layer, 32, 32a: conductive layer, R1, R2: resist film, C1: pattern opening, C2: contact hole, G1, G2: wiring groove,
P: plug, W2: second wiring, W3: third wiring.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G048 AA01 AB02 AC04 AD02 AE05 AE06 AE07 4K022 AA02 AA37 AA41 BA06 BA12 BA14 BA16 BA24 DA01 DB01 DB02 DB04 DB07 DB08 DB24 4M104 BB04 BB05 DD52 DD53 FF17 HH13 HF07H01H20H JJ15 JJ20 JJ22 KK04 KK11 KK19 MM02 MM12 MM13 NN06 NN07 PP27 PP28 QQ09 QQ10 QQ13 QQ21 QQ25 QQ28 QQ37 QQ48 QQ96 RR04 RR06 SS11 WW00 WW03 WW04 XX02 XX04

Claims (40)

[Claims] An electroless plating bath for forming a conductive film by electroless plating, wherein the first metal material supplies a main component of the conductive film, and a barrier metal function is provided to the conductive film. A second metal material that supplies the component, a first complexing agent of an amphoteric ion type, a second complexing agent that promotes a plating reaction, a reducing agent, and a pH adjuster, wherein the pH is neutral. Electroless plating bath adjusted to the alkaline range. 2. The method according to claim 1, wherein the first metal material contains a compound containing at least nickel or cobalt.
Electroless plating bath as described. 3. The electroless plating bath according to claim 2, wherein the first metal material contains nickel chloride or cobalt chloride. 4. The electroless plating bath according to claim 1, wherein the second metal material contains a compound containing at least tungsten or molybdenum. 5. The electroless plating bath according to claim 4, wherein said second metal material contains an ammonium salt of tungstic acid or molybdic acid. 6. The electroless plating bath according to claim 4, wherein said tungsten or molybdenum is contained at a concentration of 0.2 to 2 atomic weight%. 7. The electroless plating bath according to claim 1, wherein the first complexing agent contains an amino acid. 8. The electroless plating bath according to claim 1, wherein the second complexing agent contains an organic acid. 9. The electroless plating bath according to claim 1, wherein all of the first complexing agent, the second complexing agent, the reducing agent and the pH adjuster do not substantially contain a metal in the formula. 10. The electroless plating bath according to claim 1, wherein the pH is adjusted to 7 to 12. 11. The electroless plating bath according to claim 1, wherein the temperature is adjusted to 20 to 95 ° C. 12. A method for forming a conductive film on a substrate, comprising: a first metal material that supplies a main component of the conductive film; and a second metal that supplies a component that imparts a barrier metal function to the conductive film. It contains at least a material, a first complexing agent of a zwitterion type, a second complexing agent for accelerating a plating reaction, a reducing agent, and a pH adjuster, and the pH is adjusted from neutral to alkaline. Immersing the substrate in an electroless plating bath,
A method for forming a conductive film, wherein the conductive film is formed on the substrate by electroless plating. 13. The method for forming a conductive film according to claim 12, wherein an electroless plating bath containing a compound containing at least nickel or cobalt is used as said first metal material. 14. The method according to claim 13, wherein an electroless plating bath containing nickel chloride or cobalt chloride is used as the first metal material. 15. The method according to claim 12, wherein an electroless plating bath containing a compound containing at least tungsten or molybdenum is used as the second metal material. 16. The method for forming a conductive film according to claim 15, wherein an electroless plating bath containing an ammonium salt of tungstic acid or molybdic acid is used as said second metal material. 17. The method for forming a conductive film according to claim 15, wherein an electroless plating bath containing said tungsten or molybdenum at a concentration of 0.2 to 2 atomic weight% is used. 18. The method according to claim 12, wherein an electroless plating bath containing an amino acid is used as the first complexing agent. 19. The method according to claim 12, wherein an electroless plating bath containing an organic acid is used as the second complexing agent. 20. An electroless plating bath in which the first complexing agent, the second complexing agent, the reducing agent and the pH adjuster do not substantially contain any metal in the formula. The method for forming a conductive film described above. 21. The method according to claim 12, wherein an electroless plating bath whose pH is adjusted to 7 to 12 is used. 22. The method for forming a conductive film according to claim 12, wherein an electroless plating bath whose temperature is adjusted to 20 to 95 ° C. is used. 23. A method for forming a conductive film on a substrate, the method comprising: removing at least an organic substance present on a surface of the substrate in the conductive film forming region; A step of hydrophilizing the surface, a step of bonding a coupling agent to the surface subjected to the hydrophilization processing, a step of bonding a catalyst metal to the coupling agent on the surface, exposing the catalyst metal An activation process; a first metal material that supplies a main component of the conductive film; a second metal material that supplies a component that imparts a barrier metal function to the conductive film; The substrate is immersed in an electroless plating bath containing at least an agent, a second complexing agent for accelerating a plating reaction, a reducing agent, and a pH adjuster. Forming method of the conductive film and a step of forming a conductive film on the catalyst. 24. The method according to claim 23, wherein the pH of the electroless plating bath is adjusted to a range from neutral to alkaline. 25. The method according to claim 23, wherein, in the step of removing the organic substance, the surface of the substrate is oxidized to remove the organic substance. 26. A method according to claim 2, wherein in the step of hydrophilizing the surface of the substrate, a hydroxyl group is introduced into the surface of the substrate.
4. The method for forming a conductive film according to 3. 27. The method according to claim 23, wherein in the step of bonding a coupling agent to the surface, at least a silane coupling agent or a titanium coupling agent is used. 28. In the step of bonding a catalyst metal to the coupling agent, a palladium colloid protected with tin chloride is used as the catalyst metal, and the tin atom of the tin chloride is coordinated to the coupling agent. 24. A method for forming a conductive film according to claim 23. 29. The method for forming a conductive film according to claim 28, wherein, in the step of exposing and activating the catalytic metal, tin chloride is peeled off from the palladium colloid protected with tin chloride to expose palladium. 30. An electroless plating bath containing a compound containing at least nickel or cobalt as the first metal material in the step of forming a conductive film on the metal catalyst by the electroless plating. 24. A method for forming a conductive film according to claim 23. 31. An electroless plating bath containing nickel chloride or cobalt chloride as the first metal material in the step of forming a conductive film on the metal catalyst by the electroless plating. The method for forming a conductive film described above. 32. An electroless plating bath containing a compound containing at least tungsten or molybdenum as the second metal material in the step of forming a conductive film on the metal catalyst by the electroless plating. 2
4. The method for forming a conductive film according to 3. 33. In the step of forming a conductive film on the metal catalyst by the electroless plating, an electroless plating bath containing a tungstic acid or an ammonium salt of molybdic acid is used as the second metal material. Item 32
The method for forming a conductive film according to the above. 34. An electroless plating bath containing said tungsten or molybdenum at a concentration of 0.2 to 2 atomic weight% in said step of forming a conductive film on said metal catalyst by said electroless plating. Item 34. The method for forming a conductive film according to Item 32. 35. The conductive film according to claim 23, wherein in the step of forming a conductive film on the metal catalyst by the electroless plating, an electroless plating bath containing an amino acid is used as the first complexing agent. Formation method. 36. The electroconductive plating method according to claim 23, wherein in the step of forming a conductive film on the metal catalyst by the electroless plating, an electroless plating bath containing an organic acid is used as the second complexing agent. Method of forming a film. 37. In the step of forming a conductive film on the metal catalyst by the electroless plating, the first complexing agent comprises:
24. The method for forming a conductive film according to claim 23, wherein the second complexing agent, the reducing agent, and the pH adjuster all use an electroless plating bath containing substantially no metal in the formula. 38. The formation of a conductive film according to claim 23, wherein in the step of forming the conductive film on the metal catalyst by the electroless plating, an electroless plating bath whose pH is adjusted to 7 to 12 is used. Method. 39. In the step of forming a conductive film on the metal catalyst by the electroless plating, a temperature of 20 to 95 is used.
24. Use of an electroless plating bath adjusted to a temperature of ° C.
The method for forming a conductive film according to the above. 40. The conductive film according to claim 23, further comprising, after the step of forming the conductive film on the metal catalyst by the electroless plating, forming a conductive film containing copper as an upper layer of the conductive film. Method of forming a film.