CN1685081A

CN1685081A - Electroless plating method

Info

Publication number: CN1685081A
Application number: CNA03822688XA
Authority: CN
Inventors: 丸茂吉典; 佐藤浩; 定免美保
Original assignee: Tokyo Electron Ltd
Current assignee: Tokyo Electron Ltd
Priority date: 2002-09-27
Filing date: 2003-05-23
Publication date: 2005-10-19
Also published as: JP2004115885A; WO2004029328A1; KR20050059178A; AU2003241757A1

Abstract

A method of elctroless plating, which comprises forming catalytically active nuclei comprising a catalytically active material having a catalytic activity toward a reducing agent contained in an electroless plating solution on a diffusion inhibiting layer (such as a barrier layer), and then carrying out an electroleless plating using the electroless plating solution. The method allows the formation of an electrolessly plated coating on a barrier layer through the acceleration of the reaction of a reducing agent contained in an electroless plating solution by catalytically active nuclei.

Description

Electroless plating method

Technical Field

The present invention relatesto an electroless plating method for forming an electroless plating film.

Background

When a semiconductor device is formed, wiring is formed on a semiconductor substrate.

With the increase in the degree of integration of semiconductor devices, miniaturization of wirings has been progressing, and in response to this, a manufacturing technology of wirings has been developed. For example, as a method for forming a copper wiring, a dual damascene method in which a seed layer of copper is formed by a sputtering method, a groove is buried by plating, and wiring and interlayer connection are formed has been put into practical use. It is difficult to plate the surface to be plated on which the seed layer is not formed by this method.

On the other hand, electroless plating is known as a plating method that does not require a seed layer. Electroless plating is a method of forming a plating film by chemical reduction, and the formed plating film has a function as a spontaneous catalyst and can continuously form a plating film made of a wiring material. Electroless plating does not require a seed layer to be formed in advance, and there is little concern about unevenness of a plating film due to unevenness of the seed layer (particularly, step coverage in concave portions and convex portions).

In some cases, a barrier layer is formed on a substrate and a plating layer is formed thereon in order to prevent diffusion of a wiring material. Since metal nitrides such as TiN and TaN are used for the barrier layer, they are inactive to electroless plating, and it is difficult to perform electroless plating on the barrier layer.

Here, in the case of using a barrier layer, a technique has been disclosed in which copper is formed on the barrier layer by sputtering or the like, and then an electroless plating film of copper can be formed on the barrier layer (see japanese patent laid-open No. 2001-85434).

Disclosure of Invention

In the technique disclosed in the above document, the same material as the plating film is formed on the barrier layer, which limits the processing contents.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an electroless plating method which can realize electroless plating onto a barrier layer by various treatments.

A. In order to achieve the above object, an electroless plating method according to the present invention includes: a diffusion-limiting layer forming step of forming a diffusion-limiting layer that limits diffusion of a predetermined material on a substrate, a catalytic activity nucleus forming step of forming a catalytic activity nucleus made of a catalytic activity material that has catalytic activity for an oxidation reaction of a reducing agent in an electroless plating reaction and is different from the predetermined material, on at least a part of the diffusion-limiting layer formed on the substrate in the diffusion-limiting layer forming step, and a plating film forming step of forming a plating film made of the predetermined material with an electroless plating solution containing the reducing agent on the substrate on which the catalytic activity nucleus is formed in the catalytic activity nucleus forming step.

After forming catalytically active nuclei composed of a catalytically active material having catalytic activity with respect to a reducing agent contained in an electroless plating film on a diffusion-limiting layer (for example, a barrier layer), electroless plating is performed with an electroless platingsolution. The reaction of the reducing agent contained in the electroless plating film is promoted by the catalytically active nuclei, and the electroless plating film can be formed.

Here, the catalytically active nuclei may be formed discontinuously on the diffusion-limiting layer. That is, the catalyst active nuclei formed on the diffusion-limiting layer can be formed into an electroless plating film either continuously (for example, a layered continuous film) or discontinuously (for example, an island-like dispersed discontinuous film).

B. The electroless plating method according to the present invention includes: a diffusion-limiting layer forming step of forming a diffusion-limiting layer on a substrate, the diffusion-limiting layer including a catalytically active material having catalytic activity for an oxidation reaction of a predetermined reducing agent and being different from the predetermined material, and limiting diffusion of the predetermined material, and a plating film forming step of forming a plating film made of the predetermined material on the substrate on which the diffusion-limiting layer is formed in the diffusion-limiting layer forming step, with an electroless plating solution containing the predetermined reducing agent.

After the diffusion-limiting layer (e.g., barrier layer) containing the catalytically active material is formed, electroless plating is performed with an electroless plating solution. The reaction of the reducing agent contained in the electroless plating film is promoted by the catalytically active material in the diffusion-limiting layer, whereby the electroless plating film can be formed.

C. The electroless plating method according to the present invention includes: a diffusion-limiting layer forming step of forming a diffusion-limiting layer on a substrate, the diffusion-limiting layer being made of a catalytically active material that has catalytic activity for an oxidation reaction of a predetermined reducing agent and is different from the predetermined material and limiting diffusion of the predetermined material, and a plating film forming step of forming a plating film made of the predetermined material on the substrate on which the diffusion-limiting layer is formed in the diffusion-limiting layer forming step, with an electroless plating solution containing the predetermined reducing agent.

After forming a diffusion limiting layer (e.g., a barrier layer) from a material having both catalytic activity and diffusion limitation, electroless plating is performed with an electroless plating solution. The reaction of the reducing agent contained in the electroless plating film is promoted by the catalytically active material constituting the diffusion-limiting layer, and the electroless plating film can be formed.

Drawings

Fig. 1 is a flowchart showing the sequence of the electroless plating method according to the first embodiment.

Fig. 2A to 2D are cross-sectional views showing cross-sections of the wafer W in the sequence of fig. 1.

Fig. 3 is a partial sectional view showing an electroless plating apparatus used for the electroless plating in fig. 1.

Fig. 4 is a partial sectional view showing a state in which a wafer W or the like provided in the electroless plating apparatus shown in fig. 3 is tilted.

Fig. 5 is a flowchart showing an example of a procedure for performing electroless plating by the electroless plating apparatus according to the first embodiment.

Fig. 6 is a partial sectional view showing a state of the electroless plating apparatus when electroless plating is performed in the order shown in fig. 5.

Fig. 7 is a partial sectional view showing a state of the electroless plating apparatus when electroless plating is performed in the order shown in fig. 5.

Fig. 8 is a partial sectional view showing a state of the electroless plating apparatus when electroless plating is performed in the order shown in fig. 5.

Fig. 9 is a partial sectional view showing a state of the electroless plating apparatus when electroless plating is performed in the order shown in fig. 5.

Fig. 10 is a partial sectional view showing a state of the electroless plating apparatus when electroless plating is performed in the order shown in fig. 5.

Fig. 11 is a partial sectional view showing a state of the electroless plating apparatus when electroless plating is performed in the order shown in fig. 5.

Fig. 12 is a partial sectional view showing a state of the electroless plating apparatus when electroless plating is performed in the order shown in fig. 5.

Fig. 13 is a flowchart showing a procedure of the electroless plating method according to the second embodiment.

Fig. 14A and 14B are sectional views showing the cross section of the wafer W in the sequence of fig. 13.

Fig. 15 is a flowchart showing the sequence of the electroless plating method according to the third embodiment.

Fig. 16A and 16B are sectional views showing the cross section of the wafer W in the sequence of fig. 15.

Detailed Description

Next, an electroless plating method according to an embodiment of thepresent invention will be described in detail with reference to the drawings.

(first embodiment)

Fig. 1 is a flowchart showing the sequence of the electroless plating method according to the first embodiment. Fig. 2A to 2D are cross-sectional views showing cross-sections of the wafer W in the sequence of fig. 1.

As shown in fig. 1, in the electroless plating method according to the first embodiment of the present invention, the wafer W is processed in the order of steps S11 to S13. Next, details of this processing procedure will be described.

(1) Barrier layer formation for wafer W (step S11, FIG. 2A)

A barrier layer is formed on the wafer W. The barrier layer functions as a diffusion limiting layer and is a barrier for preventing diffusion of a wiring material (e.g., copper) or the like. Due to the barrier layer, contamination of the wafer W caused by diffusion (e.g., electromigration) of the wiring material or the like can be prevented. As the material of the barrier layer, for example, Ta, TaN, W, WN, Ti, TiN can be used.

The wafer W is appropriately provided with irregularities for embedding wiring materials such as grooves and vias, and the barrier layer is formed in accordance with the irregularities. Fig. 2A shows a state in which the barrier layer 2 is formed corresponding to the recess 1. The barrier layer 2 can be formed by a physical film formation method (sputtering, vacuum deposition, or the like) or a chemical film formation method (CVD, or the like).

(2) Catalyst active nuclei formed on the barrier layer (step S12, FIG. 2B)

A catalyst active core 3 is formed on the barrier layer 2. The catalytically active nuclei 3 are formed from the electroless plating solution used in step S13, and in particular, from a catalytically active material having catalytic activity for promoting the oxidation reaction of the reducing agent of the component, and function as nuclei (starting points) for forming an electroless plating film. The catalyst active core 3 may be a continuous film having a layered structure or a discontinuous film having island-like (island) distribution.

Here, an example of the catalyst active material constituting the catalyst active core 3 is shown. The catalytically active material can be selected in accordance with a reducing agent used as a component of an electroless plating solution to be described later.

1) When the reducing agent is formaldehyde: ir, Pd, Ag, Ru, Rh, Au, Pt

Reaction in electroless plating:

2) when the reducing agent is a hypophosphite: au, Ni, Pd, Co, Pt (arranged in such a manner that the catalyst activity becomes higher on the left side (Au>Pt))

Reaction in electroless plating:

3) when the reducing agent is glyoxylic acid: ir, Pd, Ag, Ru, Rh, Au, Pd, Pt

Reaction in electroless plating:

4) when the reducing agent is a metal salt (cobalt nitrate, etc.): ag. Pt, Rh, Ir, Pd, Au

5) When the reducing agent is Dimethylamine Borane (diamine Borane): ni, Pd, Ag, Au, Pt

Reaction in electroless plating:

(3) electroless plating of wafer W (step S13, FIGS. 2C and 2D)

The wafer W is subjected to electroless plating to form an electroless plating film. As described later, the electroless plating can be performed in the order of fig. 5 using the apparatus shown in fig. 3.

In the initial stage of electroless plating, an electroless plating film is formed on the catalytically active nuclei 3 (fig. 2C). That is, when the catalytically active core 3 is a discontinuous film at this stage, the electroless plating film is also a discontinuous film.

Thereafter, the electroless plating film 4 is grown, and the electroless plating film 4 on the catalyst active nuclei 3 spreads over the surface of the wafer W. That is, even when the catalytically active cores 3 are discontinuous films, the electroless plated films 4 on the catalytically active cores 3 are connected to each other to form a continuous film.

When the catalytically active nuclei 3 are continuous films, the electroless plating films 4 are formed continuously without going through the step of forming the electroless plating films 4 as discontinuous films as shown in fig. 2C and 2D.

(details of electroless plating apparatus for electroless plating)

Fig. 3 is a partial sectional view showing the structure of the electroless plating apparatus 10 used for the electroless plating in step S13.

The electroless plating apparatus 10 can perform an electroless plating process on a wafer W as a substrate, a pretreatment thereof, a cleaning process after plating, and a drying process using a treatment liquid.

That is, the treatment liquid may include various liquids such as a chemical liquid for pretreatment and post-treatment of plating, and pure water, in addition to a chemical liquid for electroless plating.

As the chemical solution for electroless plating (electroless plating solution), a chemical solution prepared by mixing the following materials dissolved in pure water can be used.

1) Metal salt: it is a material that supplies metal ions constituting the plating film. When the plating film is copper, the metal salt is, for example, copper sulfate, copper nitrate, copper chloride.

2) Complexing agent: it is a material for complexing metal to improve the stability in a liquid medicine in a manner that metal ions are not precipitated as hydroxides under strong alkalinity. The complexing agent may be, for example, HEDTA, EDTA or ED which are amine-based materials, or citric acid, tartaric acid or gluconic acid which are organic materials.

3) Reducing agent: it is a material used for catalytic reduction to extract metal ions. As the reducing agent, for example, formaldehyde, hypophosphite, glyoxylic acid, a metal salt (such as cobalt nitrate), dimethylamine borane, tin chloride, and a borohydride compound can be used.

4) A stabilizer: it is a material that prevents the natural decomposition of the plating solution caused by the unevenness of the oxide (copper oxide when the plating film is copper). As the stabilizer, for example, dipyridine (dipyridyl), cyanide, thiourea, phenanthroline, and neocuprine (neocuprine) which preferentially form a complex with 1-valent copper can be used as the nitrogen-based material.

5) pH buffer: it is a material for suppressing a change in pH at the time of the reaction of the plating solution. As the pH buffer, for example, boric acid, carbonic acid, and hydroxy acid can be used.

6) Additive: it is a material for promoting and suppressing deposition of a plating film and a material for modifying the surface or plating solution.

The material for suppressing the deposition rate of the plating film and improving the stability of the plating solution and the characteristics of the plating film can be a sulfur-based material, for example, thiosulfuric acid or 2-MBT.

A nonionic material, such as polyalkylene glycol or polyethylene glycol, which can be used as a surfactant, is used as a material for reducing the surface tension of the plating solution and uniformly disposing the plating solution on the surface of the wafer W.

As shown in fig. 3, the electroless plating apparatus 10 includes a base 11, a hollow motor 12, a wafer chuck 20 as a substrate holding portion, an upper plate 30, a lower plate 40, a cup 50,

nozzle arms

61, 62, a substrate tilting mechanism 70 as a tilting adjustment portion, and a liquid supply mechanism 80. Here, the hollow motor 12, the wafer chuck 20, the upper plate 30, the lower plate 40, the cup 50, and the

nozzle arms

61 and 62 are directly or indirectly connected to the susceptor 11, move together with the susceptor 11, and are tilted by the substrate tilting mechanism 70.

The wafer chuck 20 holds and fixes the wafer W, and is composed of wafer holding claws 21, a wafer chuck base plate 23, and a wafer chuck support 24.

A plurality of wafer holding claws 21 are arranged on the outer periphery of the wafer chuck base plate 23 to hold and fix the wafer W.

The wafer chuck base plate 23 is a substantially circular flat plate connected to the upper surface of the wafer chuck support 24, and is disposed on the bottom surface of the cup 50.

The wafer chuck support portion 24 has a substantially cylindrical shape, is connected to a circular opening portion provided in the wafer chuck base plate 23, and constitutes a rotation shaft of the hollow motor 12. As a result, the wafer chuck 20 can be rotated by driving the hollow motor 12 to hold the wafer as it is. As will be described later, since the cup 50is movable up and down, the wafer chuck 20 disposed at the bottom of the cup 50 also moves up and down along with the cup 50.

The upper plate 30 has a substantially circular flat plate shape, has a heater H (not shown), a treatment liquid ejection port 31, a treatment liquid inflow portion 32, and a temperature measurement mechanism 33, and is connected to an elevation mechanism 34.

The heater H is a heating member such as a heating wire for heating the upper plate 30. The heater H controls the amount of heat generated by a control means (not shown) so as to maintain the upper plate 30 and thus the wafer W at a desired temperature (for example, in a range of about room temperature to about 60 ℃) in accordance with the temperature measurement result obtained by the temperature measuring means 33.

A single or a plurality of treatment liquid discharge ports 31 are formed in the lower surface of the upper plate 30 to discharge the treatment liquid flowing in from the treatment liquid inflow portion 32.

The treatment liquid inflow unit 32 is located on the upper surface side of the upper plate 30, and allows the treatment liquid to flow therein and distribute the treatment liquid to the treatment liquid ejection port 31. The treatment liquid flowing into the treatment liquid inflow unit 32 can be switched between pure water (RT: room temperature) and heated chemical solutions 1 and 2 (for example, in a range from room temperature to about 60 ℃). The chemical solutions 1 and 2 mixed in the mixing box 85 (which will be described later) (in some cases, a plurality of chemical solutions including other chemical solutions may be mixed) may be allowed to flow into the treatment solution inflow portion 32.

The temperature measuring means 33 is a temperature measuring means such as a thermocouple embedded in the upper plate 30, and measures the temperature of the upper plate 30.

The elevating mechanism 34 is connected to the upper plate 30, and can elevate and lower the wafer W in a state where the upper plate 30 faces the wafer W, for example, the distance between the wafer W and the elevating mechanism can be controlled to be 0.1 to 500 mm. In the electroless plating, the wafer W and the upper plate 30 are brought close to each other (for example, the gap between the wafer W and the upper plate 30 is 2mm or less), and the space between these gaps is limited, so that the processing liquid supplied to the surface of the wafer W can be made uniform and the amount of the processing liquid used can be reduced.

The lower plate 40 has a substantially circular flat plate shape disposed to face the lower surface of the wafer W, and can appropriately heat the wafer W by supplying heated pure water to the lower surface thereof in a state of being close to the wafer W.

In order to efficiently heat the wafer W, the size of the lower plate 40 is preferably made to be similar to the size of the wafer W. Specifically, the size of the lower plate 40 is preferably 80% or more, or 90% or more of the area of the wafer W.

The lower plate 40 has a treatment liquid discharge port 41 formed at the center of the upper surface thereof and is supported by a support portion 42.

The treatment liquid discharge port 41 discharges the treatment liquid passing through the support portion 42. The treatment liquid can be switched between pure water (RT: room temperature) and heated pure water (for example, ranging from room temperature to about 60 ℃).

The support portion 42 penetrates the hollow motor 12 and is connected to a lifting mechanism (not shown) as a space adjusting portion. By operating the lifting mechanism, the support portion 42 and thus the lower plate 40 can be lifted up and down.

The cup 50 is a member for holding the wafer chuck 20 therein and receiving and discharging a processing liquid for processing the wafer W, and includes a cup side 51, a cup bottom 52, and a waste liquid pipe 53.

The cup side 51 has a substantially cylindrical shape along the outer periphery of the wafer chuck 20 at its inner periphery and has its upper end located in the vicinity above the holding surface of the wafer chuck 20.

The cup bottom plate 52 is connected to the lower end of the cup side portion 51, has an opening at a position corresponding to the hollow motor 12, and the wafer chuck 20 is disposed at a position corresponding to the opening.

The waste liquid pipe 53 is a pipe connected to the cup bottom plate 52 for discharging waste liquid (treatment liquid after the wafer W is treated) from the cup 50 to a waste liquid pipe or the like in a factory where the electroless plating apparatus 10 is installed.

The cup 50 is connected to a not-shown elevating mechanism and can move up and down with respect to the susceptor 11 and the wafer W.

The

nozzle arms

61 and 62 are disposed near the upper surface of the wafer W, and eject a fluid such as a processing liquid or air from an opening at the tip thereof. As the fluid to be discharged, pure water, chemical solution, and nitrogen gas can be appropriately selected. A moving mechanism (not shown) for moving the

nozzle arms

61 and 62 in a direction toward the center of the wafer W is connected to the

nozzle arms

61 and 62, respectively. In the case of ejecting the fluid onto the wafer W, the

nozzle arms

61, 62 are moved above the wafer W, and when the ejection is completed, the

nozzle arms

61, 62 are moved outside the outer periphery of the wafer W. The number of nozzle arms may be 1 or 3 or more depending on the amount and type of the chemical solution.

The substrate tilting mechanism 70 is connected to the base 11, and can tilt the base 11, the wafer chuck 20, the wafer W, the upper plate 30, the lower plate 40, and the cup 50 connected thereto, for example, within a range of 0 to 10 ° or 0 to 5 ° by moving one end of the base 11 up and down.

Fig. 4 is a partial sectional view showing a state in which the wafer W or the like is tilted by the substrate tilting mechanism 70. The susceptor 11 is tilted by the substrate tilting mechanism 70, and the tilt angle θ of the wafer W or the like directly or indirectly connected to the susceptor 11 is determined.

The liquid supply mechanism 80 supplies the heated processing liquid to the upper plate 30 and the lower plate 40, and is composed of a temperature adjustment mechanism 81, processing liquid containers 82, 83, 84, pumps P1 to P5, valves V1 to V5, and a mixing box 85. Fig. 3 shows the chemical solutions 1 and 2 and the case of using 2 chemical solutions, but the number of processing containers, pumps, and valves can be set appropriately according to the number of chemical solutions to be mixed in the mixing box 85.

The temperature adjusting mechanism 81 has warm water and treatment liquid containers 82 to 84 inside thereof, and heats the treatment liquids (pure water, chemical solutions 1 and 2) in the treatment liquid containers 82 to 84 with the warm water, and appropriately heats the treatment liquids, for example, within a range from room temperature to about 60 ℃. For adjusting the temperature, for example, a water bath, a drop heater, and an external heater can be appropriately used.

The treatment liquid containers 82, 83, and 84 are containers for holding pure water and chemical solutions 1 and 2, respectively.

The pumps P1-P3 suck the processing liquid from the processing liquid containers 82-84. Further, the liquid may be sent out from the treatment liquid containers 82 to 84 by pressurizing the treatment liquid containers 82 to 84, respectively.

The valves V1 to V3 open and close the pipes to supply or stop the supply of the processing liquid. The valves V4 and V5 are used to supply room-temperature (unheated) hot water to the upper plate 30 and the lower plate 40, respectively.

The mixing box 85 is a container for mixing the chemical solutions 1 and 2 sent from the processing solution containers 83 and 84.

The chemical solutions 1 and 2 can be mixed appropriately in the mixing box 85, temperature-adjusted, and transferred to the upper plate 30. Further, the temperature-adjusted pure water can be appropriately transferred to the lower plate 40.

(details of electroless plating Process)

Fig. 5 is a flowchart showing an example of the procedure of performing electroless plating on the wafer W having undergone the steps of S11 and S12 by the electroless plating apparatus 10. Fig. 6 to 12 are partial sectional views showing states of the electroless plating apparatus 10 in the respective steps when the electroless plating is performed in the order shown in fig. 5. Next, we explain this sequence in detail with reference to FIGS. 5 to 12.

(1) Holding of wafer W (step S1 and FIG. 6)

The wafer W having undergone the steps S11 and S12 is held by the wafer chuck 20. For example, a suction arm (substrate transfer mechanism), not shown, which sucks the wafer W to the upper surface thereof places the wafer W on the wafer chuck 20. The wafer W is held and fixed by the wafer holding claws 21 of the wafer chuck 20. Further, by lowering the cup 50, the suction arm can be moved in the horizontal direction below the upper surface of the wafer W.

(2) Pretreatment of wafer W (step S2 and FIG. 7)

The wafer W is rotated, and the treatment liquid is supplied from the nozzle arm 61 or the nozzle arm 62 onto the upper surface of the wafer W, to thereby perform the pretreatment of the wafer W.

The rotation of the wafer W is performed by rotating the wafer chuck 20 by the hollow motor 12, and the rotation speed at this time can be 100 to 200rpm as an example.

One or both of the

nozzle arms

61 and 62 move above the wafer W to discharge the processing liquid. The treatment liquid supplied from the

nozzle arms

61 and 62 is, for example, pure water for cleaning the wafer W or a chemical liquid for activating the catalyst of the wafer W, which is supplied sequentially in accordance with the purpose of the pretreatment. The discharge amount at this time is an amount necessary to form a puddle (layer) of the processing liquid on the wafer W, and is, for example, about 100 mL. However, if necessary, the ejection amount is increased. The discharged treatment liquid may be appropriately heated (for example, in a range of about room temperature to 60 ℃).

(3) Heating of wafer W (step S3 and FIG. 8)

In order to maintain the wafer W at a temperature suitable for the bath reaction, the wafer W is heated.

The lower plate 40 is heated so as to be close to the lower surface of the wafer W (for example, the distance between the lower surface of the wafer W and the upper surface of the lower plate 40: about 0.1 to 2mm), and the heated pure water is supplied from the treatment liquid ejection port 41 by the liquid supply mechanism 80. The heated pure water fills the gap between the lower surface of the wafer W and the upper surface of the lower plate 40, thereby heating the wafer W.

In addition, by rotating the wafer W during the heating of the wafer W, the heating uniformity of the wafer W can be improved.

By heating the wafer W with a liquid such as pure water, the wafer W and the lower plate 40 can be easily rotated or not rotated individually, and contamination of the lower surface of the wafer W can be prevented.

The heating of the wafer W may be performed by other methods. For example, the wafer W may be heated by radiant heat of a heater and a lamp. In some cases, the wafer W may be heated by bringing the heated lower plate 40 into contact with the wafer W.

(4) Supply of plating solution (step S4 and FIG. 9)

The upper plate 30 is heated to be close to the upper surface of the wafer W (for example, the distance between the upper surface of the wafer W and the lower surface of the upper plate 30: about 0.1 to 2mm), and a chemical solution for plating (plating solution) (for example, 30 to 100mL/min) is supplied from the treatment solution outlet 31. The plating solution supplied is filled between the upper surface of the wafer W and the lower surface of the upper plate 30, and flows out to the cup 50. At this time, the temperature of the plating solution is adjusted by the upper plate 30 (for example, in a range from room temperature to about 60 ℃). Further, it is preferable that the chemical liquid supply mechanism 80 adjusts the temperature of the plating liquid to be supplied.

Here, by rotating the wafer W by the wafer chuck 20, the uniformity of the plating film formed on the wafer W can be improved. For example, the wafer W is rotated at a rotation speed of 10 to 50 rpm.

In any of the preceding steps S1 to S3, the upper plate 30 may be heated. The processing time of the wafer W can be reduced by heating the upper plate 30 in parallel with other processes.

As described above, the plating solution heated to the desired temperature is supplied onto the upper surface of the wafer W to form a plated film on the wafer W. By rotating the wafer W during the supply of the plating solution, the uniformity of formation of the plated film on the wafer W can be improved.

When the above plating solution is supplied, the following operations may be performed.

1) Before the plating liquid is supplied, the wafer chuck 20 and the upper plate 30 can be tilted by the substrate tilting mechanism 70.

By tilting the wafer W, the gas between the wafer W and the upper plate 30 can be rapidly removed to replace the plating solution. If the gas between the wafer W and the upper plate 30 is not completely removed, bubbles remain between the wafer W and the upper plate 30, which may hinder the uniformity of the formed plating film.

Further, as the plating film is formed by the plating solution, gas (e.g., hydrogen) is generated, and bubbles are formed from the generated gas, which may inhibit the uniformity of the plating film.

By tilting the wafer W by the substrate tilting mechanism 70, the generation of bubbles is reduced and the escape of generated bubbles is promoted, thereby improving the uniformity of the plating film.

2) The temperature of the plating solution can be changed with time.

By so doing, it is possible to change its configuration and composition in the layer direction of the formed plating film.

3) The plating solution may be supplied not continuously but intermittently during the process of forming the plating film. By consuming the plating solution supplied to the wafer W efficiently, the amount of the plating solution used can be reduced.

(5) The wafer W is cleaned (step S5 and fig. 10).

The wafer W is cleaned with pure water. The cleaning can be performed by switching the treatment liquid discharged from the treatment liquid discharge port 31 of the upper plate 30 from the plating liquid to pure water. In this case, pure water can be supplied from the treatment liquid ejection port 41 of the lower plate 40.

The

nozzle arms

61 and 62 may be used for cleaning the wafer W. At this time, the supply of the plating liquid from the treatment liquid outlet 31 of the upper plate 30 is stopped, and the upper plate 30 is separated from the wafer W. Thereafter, the

nozzle arms

61 and 62 are moved to above the wafer W to supply pure water. In this case, it is also preferable to supply pure water from the treatment liquid ejection port 41 of the lower plate 40.

By rotating the wafer W during the above cleaning of the wafer W, the uniformity of cleaning of the wafer W can be improved.

(6) Drying of the wafer W (step S6 and fig. 11).

The supply of pure water to the wafer W is stopped, and the wafer W is rotated at a high speed to remove the pure water from the wafer W. In this case, the nitrogen gas may be ejected from the

nozzle arms

61 and 62 to accelerate the drying of the wafer W.

(7) And taking out the wafer W (step S7 and fig. 12).

After the drying of the wafer W is completed, the holding of the wafer W by the wafer chuck 20 is stopped. Thereafter, the wafer W is taken out from the wafer chuck 20 by a suction arm (substrate transfer mechanism) not shown in the drawing.

(second embodiment)

Fig. 13 is a flowchart showing steps of an electroless plating method according to a second embodiment of the present invention. Fig. 14A and 14B are cross-sectional views showing a cross-section of the wafer W in the step of fig. 13.

As shown in fig. 13, in the electroless plating method according to the second embodiment of the present invention, the wafer W is processed in the order of steps S21 to S22. In the following, we explain the details of this processing sequence.

(1) Barrier layer formation on wafer W (step S21, FIG. 14A)

A barrier layer 2a is formed on a wafer W. On the barrier layer 2a, a catalytically active material having catalytic activity with respect to the reducing agent of the electroless plating solution is mixed (doped) with a non-catalytically active material having no catalytic activity with respect to the reducing agent of the electroless plating solution, and used.

As the non-catalyst active material, any of Ta, TaN, W, WN, Ti, and TiN can be used. By doping the catalytically active material in the non-catalytically active material, the catalytic activity can be imparted to the barrier layer 2 a.

As the catalytically active material, the catalytically active material described in the first embodiment can be selected in accordance with the reducing agent of the electroless plating solution.

The barrier layer 2a can be formed by a physical film formation method, for example. Specifically, the barrier layer 2a can be formed by a sputtering method using a target in which a non-catalytically active material and a catalytically active material are mixed (or using respective targets of a non-catalytically active material and a catalytically active material at the same time). The barrier layer 2a can also be formed by vacuum evaporation (co-evaporation) that simultaneously evaporates a non-catalytically active material and a catalyticallyactive material.

(2) Electroless plating of wafer W (step S22, FIG. 14B)

The wafer W is subjected to electroless plating to form an electroless plating film 4 a. At this time, since the catalytic activity is imparted by the catalytically active material doped into the barrier layer 2a, the electroless plating film 4a is formed on the barrier layer 2 a.

(third embodiment)

Fig. 15 is a flowchart showing steps of an electroless plating method according to a third embodiment of the present invention. Fig. 16A and 16B are cross-sectional views showing a cross-section of the wafer W in the step of fig. 15.

As shown in fig. 15, in the electroless plating method according to the third embodiment of the present invention, the wafer W is processed in the order of steps S31 to S32. In the following, we explain the details of this processing sequence.

(1) Formation of Barrier layer on wafer W (step S31, FIG. 16A)

The barrier layer 2b is formed on the wafer W. The barrier layer 2b is made of a catalytically active material having catalytic activity with respect to a reducing agent of the electroless plating solution.

The barrier layer 2b can be formed by, for example, a physical film formation method (e.g., sputtering method, vacuum evaporation method) or a chemical film formation method (e.g., CVD method).

(2) Electroless plating of wafer W (step S32, FIG. 16B)

The wafer W is subjected to electroless plating to form an electroless plating film. At this time, since the catalytically active material constituting the barrier layer 2b has catalytic activity, the electroless plating film 4b is formed on the barrier layer 2 b.

(example 1)

As for the metal salt and the reducing agent constituting the electroless plating solution, copper salt and glyoxylic acid are used to form an electroless plating film of copper in the order corresponding to the third embodiment (barrier layer made of the catalytically active material).

Specifically, electroless plating of copper is performed on the substrate (barrier layer) for each of Ru, Ag, Pt, V, In, Ir, Co, and Rh. In addition, as comparative examples, electroless plating of copper was performed for the cases where the substrates were Cu, TaN, TiN, W, WN, and Ta, respectively.

In the case of Ru, Ag, Pt or Ir as the substrate, the adhesion and the deposition rate were good as compared with those in the case of Cu as the substrate. In particular, the case where the substrate was Ru or Ag showed good adhesion as compared with the case where the substrate was Cu.

On the other hand, WN and Ta do not precipitate Cu itself. In the case of TaN, TiN, or W as the substrate, Cu is formed, but it is difficult to say that the adhesion of the formed Cu to the substrate is good.

(example 2)

As for each metal salt and reducing agent constituting the electroless plating solution, copper salts and metal salts (cobalt nitrate) were used to form an electroless plating film of copper in the order corresponding to the third embodiment (barrier layer made of a catalytically active material).

Specifically, electroless plating of copper is performed on a base (barrier layer) of Ag, Ir, Rh, respectively. In addition, as comparative examples, electroless plating of copper was also performed for substrates of Cu, TaN, TiN, W, WN, V, Co, In, Ru, and Pt.

In any case, Ag, Ir or Rh as the base showed good adhesion and deposition rate as compared with the case where Cu was the base. In particular, the case where the substrate is Ag shows good adhesion as compared with the case where the substrate is Cu.

In contrast, In the case where the substrate is Ta, TaN, TiN, W, WN, V, In, or Ru, Cu itself is not precipitated In any case. In the case where the substrate is Pt, Cu is formed, but this is not sufficient. In the case where the base is Co or Rh, Cu is formed, but it is difficult to say that the adhesion of the formed Cu to the base is good.

(other embodiments)

The embodiments of the present invention are not limited to the embodiments described above, and can be extended and modified. The embodiments that have been expanded and modified are also included in the technical scope of the present invention.

For example, a glass plate or the like other than the wafer W can be used as the substrate.

Industrial applicability

The electroless plating method according to the present invention can realize electroless plating on the barrier layer by various treatments, and can be industrially used.

Claims

1. An electroless plating method, comprising:

a diffusion limiting layer forming step of forming a diffusion limiting layer for limiting diffusion of a predetermined material on a substrate;

a catalyst active nucleus forming step of forming a catalyst active nucleus made of a catalyst active material having a catalytic activity for an oxidation reaction of a reducing agent in an electroless plating reaction and different from the predetermined material, on at least a part of the diffusion limiting layer formed on the substrate in the diffusion limiting layer forming step; and

and a plating film forming step of forming a plating film made of the predetermined material on the substrate on which the catalytically active nuclei have been formed in the catalytically active nucleus forming step, with an electroless plating solution containing the reducing agent.

2. The electroless plating method according to claim 1, characterized in that:

the catalyst active core is discontinuously formed on the diffusion limiting layer.

3. The electroless plating method according to claim 1, characterized in that:

the predetermined reducing agent is any one of formaldehyde and glyoxylic acid, and the catalyst active material contains at least any one of Ir, Pd, Ag, Ru, Rh, Au, Pt and Ti.

4. The electroless plating method according to claim 1, characterized in that:

the predetermined reducing agent is a hypophosphite, and the catalyst active material contains at least any one of Au, Ni, Pd, Ag, Co, and Pt.

5. The electroless plating method according to claim 1, characterized in that:

the predetermined reducing agent is a metal salt, and the catalyst active material contains at least one of Ag, Rh, Ir, Pd, Au, and Pt.

6. The electroless plating method according to claim 1, characterized in that:

the predetermined reducing agent is dimethylamine borane, and the catalyst active material contains at least one of Ni, Pd, Ag, Au, and Pt.

7. An electroless plating method, comprising:

a diffusion limiting layer forming step of forming a diffusion limiting layer on a substrate, the diffusion limiting layer containing a catalytically active material having catalytic activity for an oxidation reaction of a predetermined reducing agent and being different from the predetermined material, and limiting diffusion of the predetermined material; and

and a plating film forming step of forming a plating film made of the predetermined material on the substrate on which the diffusion limiting layer is formed in the diffusion limiting layer forming step, by using an electroless plating solution containing the predetermined reducing agent.

8. The electroless plating method according to claim 7, characterized in that:

9. The electroless plating method according to claim 7, characterized in that:

10. The electroless plating method according to claim 7, characterized in that:

11. The electroless plating method according to claim 7, characterized in that:

12. An electroless plating method, comprising:

a diffusion limiting layer forming step of forming a diffusion limiting layer on the substrate, the diffusion limiting layer being made of a catalytically active material having catalytic activity for an oxidation reaction of a predetermined reducing agent and being different from the predetermined material, and limiting diffusion of the predetermined material; and

13. The electroless plating method according to claim 12, characterized in that:

14. The electroless plating method according to claim 12, characterized in that:

15. The electroless plating method according to claim 12, characterized in that:

16. The electroless plating method according to claim 12, characterized in that: