JP2004115885A - Electroless plating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electroless plating method for performing electroless plating on a barrier layer through various treatments. <P>SOLUTION: Electroless plating is performed by using electroless plating solution after catalytically active cores formed of a catalytically active material with catalytical activity to a reducing agent contained in an electroless plating film is formed on a diffusion restrictive layer (for example, a barrier layer). The reaction of the reducing agent contained in the electroless plating film is promoted by the catalytically active cores, and the electroless plating film is formed thereby. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electroless plating method for forming an electroless plating film.
[0002]
[Prior art]
When manufacturing a semiconductor device, wiring is formed on a semiconductor substrate.
With the increase in the degree of integration of semiconductor devices, the miniaturization of wiring has been promoted, and in response to this, the technology for creating wiring has been developed. For example, as a method of forming a copper wiring, a dual damascene method of forming a wiring and interlayer connection by forming a copper seed layer by sputtering and filling a groove or the like by electroplating has been put to practical use. With this method, it is difficult to form electroplating on the surface to be plated on which the seed layer is not formed.
On the other hand, there is an electroless plating method as a plating method that does not require a seed layer. In electroless plating, a plating film is formed by chemical reduction, and a plating film formed of a wiring material can be continuously formed by the formed plating film acting as an autocatalyst. In electroless plating, it is not necessary to form a seed layer in advance, and there is no possibility that the plating film becomes non-uniform due to non-uniformity of the seed layer (particularly, step coverage in concave portions and convex portions).
In order to prevent the diffusion of the wiring material, a barrier layer may be formed on a substrate, and a plating film may be formed thereon. The barrier layer is made of a metal nitride such as TiN or TaN or the like, and is inert to electroless plating. Therefore, 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 that enables formation of an electroless plating film of copper on the barrier layer by previously forming copper on the barrier layer by sputtering or the like. (See Patent Document 1).
[0003]
[Patent Document 1]
JP 2001-85434 A (page 4, FIG. 1)
[0004]
[Problems to be solved by the invention]
However, in the technique disclosed in Patent Document 1, the same material as the plating film is formed on the barrier layer, and the processing content is limited.
In view of the above, an object of the present invention is to provide an electroless plating method that can realize electroless plating on a barrier layer by various processes.
[0005]
[Means for Solving the Problems]
A. In order to achieve the above object, an electroless plating method according to the present invention comprises: a diffusion limiting layer forming step of forming a diffusion limiting layer for limiting diffusion of a predetermined material on a substrate; On at least a part of the diffusion limiting layer formed above, a catalytically active nucleus having a catalytic activity for an oxidation reaction of a reducing agent in the electroless plating reaction, and comprising a catalytically active material different from the predetermined material. Forming a catalytically active nucleus forming step, and forming a plating film made of the predetermined material on the substrate on which the catalytically active nucleus is formed in the catalytically active nucleus forming step, using an electroless plating solution containing the reducing agent. And forming a plating film.
After forming a catalytically active nucleus made of a catalytically active material having a catalytic activity on a reducing agent contained in an electroless plating film on a diffusion limiting layer (for example, a barrier layer), electroless plating is performed using an electroless plating solution. Perform plating. The reaction of the reducing agent contained in the electroless plating film is promoted by the catalytically active nuclei, whereby the electroless plating film can be formed.
[0006]
Here, the catalytically active nuclei may be discontinuously formed on the diffusion limiting layer. That is, the electroless plating film can be formed irrespective of whether the catalytically active nuclei formed on the diffusion limiting layer are continuous (for example, a layered continuous film) or discontinuous (for example, a discontinuous film scattered like islands). .
[0007]
B. The electroless plating method according to the present invention has a diffusion limiting layer that has catalytic activity for an oxidation reaction of a predetermined reducing agent, and includes a catalytically active material different from the predetermined material, and restricts diffusion of the predetermined material. Forming a diffusion limiting layer on a substrate, and forming the predetermined material on the substrate on which the diffusion limiting layer has been formed in the diffusion limiting layer forming step, using an electroless plating solution containing the predetermined reducing agent. And a plating film forming step of forming a plating film comprising:
After forming a diffusion limiting layer (for example, a barrier layer) containing a catalytically active material, electroless plating is performed using 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, and the electroless plating film can be formed.
[0008]
C. The electroless plating method according to the present invention is characterized in that the substrate has a catalytic activity for an oxidation reaction of a predetermined reducing agent, is made of a catalytically active material different from the predetermined material, and includes a diffusion limiting layer for restricting diffusion of the predetermined material. A diffusion limiting layer forming step to be formed thereon; and a substrate formed with the diffusion limiting layer in the diffusion limiting layer forming step, comprising the predetermined material using an electroless plating solution containing the predetermined reducing agent. A plating film forming step of forming a plating film.
After forming a diffusion limiting layer (for example, a barrier layer) using a material having both catalytic activity and diffusion limiting property, electroless plating is performed using 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.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an electroless plating method according to an embodiment of the present invention will be described in detail with reference to the drawings.
(1st Embodiment)
FIG. 1 is a flowchart showing a procedure of the electroless plating method according to the first embodiment of the present invention. FIG. 2 is a sectional view showing a section of the wafer W in the procedure of FIG.
As shown in FIG. 1, in the electroless plating method according to the first embodiment of the present invention, a wafer W is processed in the order of steps S11 to S13. Hereinafter, the details of this processing procedure will be described.
[0010]
(1) Formation of barrier layer on 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 (for example, copper) or the like. The barrier layer prevents contamination of the wafer W due to diffusion (for example, electromigration) of a wiring material or the like. For example, Ta, TaN, W, WN, Ti, and TiN can be used as the material of the barrier layer.
Irregularities for burying wiring materials such as trenches and vias are appropriately formed on the wafer W, and a barrier layer is formed corresponding to the irregularities. FIG. 2A shows a state in which the barrier layer 2 is formed corresponding to the concave portion 1. The barrier layer 2 can be formed by, for example, a physical film forming method (such as a sputtering method or a vacuum deposition) or a chemical film forming method (such as a CVD method).
[0011]
(2) Formation of catalytically active nuclei on barrier layer (step S12, FIG. 2 (B))
A catalytically active nucleus 3 is formed on the barrier layer 2. The catalytically active nucleus 3 is composed of the electroless plating solution used in step S13, particularly a catalytically active material having an activity as a catalyst for accelerating an oxidation reaction of a reducing agent as a component thereof, and is used for forming an electroless plating film. Functions as a nucleus (origin). This catalytically active nucleus 3 may be a layered continuous film or a discontinuous film scattered in an island shape (island shape).
[0012]
Here, examples of the catalytically active material constituting the catalytically active core 3 will be described. This catalytically active material can be selected according to the reducing agent used as a component of the electroless plating solution described later.
{Circle around (1)} When the reducing agent is formaldehyde: Ir, Pd, Ag, Ru, Rh, Au, Pd, Pt
Reaction during electroless plating: 2HC (OH) O ⁻ + 2OH ^{−
_{→ 2HCOO + + 2H 2 O +}} H 2 ↑ + 2e -
{Circle around (2)} When the reducing agent is hypophosphite: Au, Ni, Pd, Co, Pt (arranged so that the catalytic activity becomes higher toward the left (Au> Pt))
Reaction during electroless plating: H ₂ PO ₂ ⁻ + 2OH ⁻
→ 2H ₂ PO ₃ ⁻ + H ₂ ↑ + 2e ⁻
{Circle around (3)} When the reducing agent is gluquioxylic acid: Ir, Pd, Ag, Ru, Rh, Au, Pd, Pt
Reaction during electroless plating: 2HC (OH) O ⁻ + 2OH ^{−
_{→ 2HCOO + + 2H 2 O +}} H 2 ↑ + 2e -
{Circle around (4)} When the reducing agent is a metal salt (such as cobalt nitrate): Ag, Pt, Rh, Ir, Pd, Au
(5) When the reducing agent is dimethylamine borane: Ni, Pd, Ag, Au, Pt
Reaction during electroless plating: (CH ₃ ) ₂ HN · BH ₃ + 3H ₂ O
_{→ H 3 BO 3 + (CH} 3) 2H 2 N + + 5H + + 6e -
[0013]
(3) Electroless plating of wafer W (Step S13, FIGS. 2C and 2D)
Electroless plating is performed on the wafer W to form an electroless plating film. In addition, this electroless plating can be performed by the procedure shown in FIG. 5 using the apparatus shown in FIG. 3 as described later.
In an initial stage of the electroless plating, an electroless plating film is formed on the catalytically active nuclei 3 (FIG. 2C). That is, at this stage, if the catalytically active core 3 is a discontinuous film, the electroless plating film also becomes a discontinuous film.
Thereafter, the electroless plating film 4 grows, and the electroless plating film 4 on the catalytically active nuclei 3 spreads on the surface of the wafer W. That is, even when the catalytically active nuclei 3 are discontinuous films, the electroless plating films 4 on the catalytically active nuclei 3 are connected to each other to form a continuous film.
In the case where the catalytically active nucleus 3 is a continuous film, a continuous non-continuous electroless plating film 4 as shown in FIGS. 2C and 2D is not necessarily required. An electrolytic plating film 4 is formed.
[0014]
(Details of electroless plating equipment used for electroless plating)
FIG. 3 is a partial cross-sectional view illustrating the configuration 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 using a processing solution, a pretreatment thereof, a cleaning process after plating, and a drying process.
That is, as the treatment liquid, various liquids such as a plating pre-treatment liquid, a post-treatment liquid liquid, and pure water can be included in addition to the electroless plating liquid chemical.
[0015]
As a chemical solution (electroless plating solution) used for electroless plating, a solution obtained by mixing the following materials and dissolving the same in pure water can be used.
{Circle around (1)} Metal salt: A material for supplying metal ions constituting the plating film. When the plating film is copper, for example, copper sulfate, copper nitrate, copper chloride.
{Circle around (2)} Complexing agent: a material for complexing a metal to improve stability in a liquid so that a metal ion does not precipitate as a hydroxide under strong alkalinity. HEDTA, EDTA, ED, and citric acid, tartaric acid, and gluconic acid can be used as organic materials.
{Circle around (3)} Reducing agent: a material for catalytically reducing and depositing metal ions, for example, formaldehyde, hypophosphite, glyoxylic acid, metal salts (such as cobalt nitrate), dimethylamine borane, and secondary chloride Tin and borohydride compounds can be used.
{Circle around (4)} Stabilizer: a material for preventing spontaneous decomposition of a plating solution due to non-uniformity of an oxide (copper oxide when a plating film is copper). Bivirdyl, a cyanide, a thiourea, 0-phenanthroline, and neobroin, which form a complex preferentially with copper having a valency, can be used.
(5) pH buffer: a material for suppressing a change in pH when the reaction of the plating solution proceeds, for example, boric acid, carbonic acid, and oxycarboxylic acid can be used.
{Circle around (6)} Additives: Additives include materials for accelerating and suppressing the deposition of the plating film, and materials for modifying the surface or the plating film.
As a material for suppressing the deposition rate of the plating film, stabilizing the plating solution and improving the characteristics of the plating film, for example, thiosulfuric acid or 2-MBT can be used as a sulfur-based material.
As a material for lowering the surface tension of the plating solution so that the plating solution is uniformly disposed on the surface of the wafer W, for example, polyalkylene glycol or polyethylene glycol is used as a nonionic surfactant material. be able to.
[0016]
As shown in FIG. 3, the electroless plating apparatus 10 includes a base 11, a hollow motor 12, a wafer chuck 20 serving as a substrate holding unit, an upper plate 30, a lower plate 40, a cup 50, nozzle arms 61 and 62, and a substrate serving as a tilt adjusting unit. It has a tilt mechanism 70 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 base 11, move together with the base 11, and move the substrate tilt mechanism 70. Is performed.
[0017]
The wafer chuck 20 holds and fixes the wafer W, and includes a wafer holding claw 21, a wafer chuck bottom 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 bottom plate 23 to hold and fix the wafer W.
The wafer chuck bottom 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 24 has a substantially cylindrical shape, is connected to a circular opening provided in the wafer chuck bottom plate 23, and forms a rotation shaft of the hollow motor 12. As a result, by driving the hollow motor 12, the wafer chuck 20 can be rotated while holding the wafer W. Further, since the cup 50 can be moved up and down as described later, the wafer chuck 20 disposed at the bottom of the cup 50 also moves up and down with the cup 50.
[0018]
The upper plate 30 has a substantially circular flat plate shape, includes a heater H (not shown), a processing liquid discharge port 31, a processing liquid inflow section 32, a temperature measuring mechanism 33, and is connected to an elevating mechanism 34. .
The heater H is a heating unit such as a heating wire for heating the upper plate 30. The heater H controls the upper plate 30 and thus the wafer W at a desired temperature (for example, in the range from room temperature to about 60 ° C.) according to the temperature measurement result by the temperature measurement mechanism 33. Controls the calorific value.
One or more processing liquid discharge ports 31 are formed on the lower surface of the upper plate 30, and discharge the processing liquid flowing from the processing liquid inflow portion 32.
The processing liquid inflow section 32 is on the upper surface side of the upper plate 30, into which the processing liquid flows, and the flowing processing liquid is distributed to the processing liquid discharge port 31. The processing liquid flowing into the processing liquid inflow section 32 can be switched between pure water (RT: room temperature) and heated chemicals 1 and 2 (for example, a range from room temperature to about 60 ° C.). Further, the chemicals 1 and 2 (in some cases, a plurality of chemicals including other chemicals are mixed) mixed in a mixing box 85 described later can flow into the processing liquid inflow section 32.
The temperature measuring mechanism 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 moves up and down in a state where the upper plate 30 faces the wafer W. For example, the distance between the elevating mechanism 34 and the wafer W can be controlled between 0.1 and 500 mm. During the electroless plating, the wafer W and the upper plate 30 are brought close to each other (for example, the distance between the wafer W and the upper plate 30 is 2 mm or less), and the size of the space of these gaps is limited. It is possible to make the supplied processing liquid uniform and to reduce the amount used.
[0019]
The lower plate 40 has a substantially circular flat plate shape disposed to face the lower surface of the wafer W, and supplies heated pure water to the lower surface in a state close to the wafer W, thereby appropriately changing the wafer W. Can be heated.
In order to efficiently heat the wafer W, it is preferable that the size of the lower plate 40 be close to the size of the wafer W. Specifically, it is preferable that the size of the lower plate 40 be 80% or more of the area of the wafer W, or 90% or more.
The lower plate 40 has a processing liquid discharge port 41 formed at the center of the upper surface thereof, and is supported by a support portion 42.
The processing liquid discharge port 41 discharges the processing liquid that has passed through the support portion 42. As the treatment liquid, pure water (RT: room temperature) or heated pure water (for example, a range from room temperature to about 60 ° C.) can be used by switching.
The support portion 42 penetrates through the hollow motor 12 and is connected to an elevating mechanism (not shown) serving as an interval adjusting portion. By operating the elevating mechanism, the support part 42 and thus the lower plate 40 can be moved up and down.
[0020]
The cup 50 holds the wafer chuck 20 therein, receives and discharges a processing liquid used for processing the wafer W, and has a cup side portion 51, a cup bottom plate 52, and a waste liquid pipe 53.
The cup side portion 51 has a substantially cylindrical shape with its inner periphery along the outer periphery of the wafer chuck 20, and its upper end is located near the upper side of 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 arranged at a position corresponding to the opening.
The waste liquid pipe 53 is connected to the cup bottom plate 52 and is a pipe for discharging a waste liquid (a processing liquid obtained by processing the wafer W) from the cup 50 to a waste liquid line of a factory where the electroless plating apparatus 10 is installed.
The cup 50 is connected to a lifting mechanism (not shown), and can move up and down with respect to the base 11 and the wafer W.
[0021]
The nozzle arms 61 and 62 are disposed near the upper surface of the wafer W, and discharge a processing liquid, a fluid such as air, etc. from an opening at the tip thereof. As the fluid to be discharged, pure water, a 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. When discharging the fluid onto the wafer W, the nozzle arms 61 and 62 are moved above the wafer W, and when the discharge is completed, the nozzle arms 61 and 62 are moved out of the outer periphery of the wafer W. The number of nozzle arms may be singular or three or more depending on the amount and type of the chemical solution to be discharged.
[0022]
The substrate inclining mechanism 70 is connected to the base 11 and raises and lowers one end of the base 11 to move the base 11 and the wafer chuck 20, the wafer W, the upper plate 30, the lower plate 40, and the cup 50 connected thereto, for example. , 0 to 10 °, or 0 to 5 °.
FIG. 4 is a partial cross-sectional view illustrating a state where the wafer W and the like are tilted by the substrate tilting mechanism 70. It can be seen that the base 11 is tilted by the substrate tilting mechanism 70, and the wafer W or the like directly or indirectly connected to the base 11 is tilted by the angle θ.
[0023]
The liquid supply mechanism 80 supplies the heated processing liquid to the upper plate 30 and the lower plate 40, and includes a temperature control mechanism 81, processing liquid tanks 82, 83, 84, pumps P1 to P5, valves V1 to V5, It is composed of a mixing box 85. Although FIG. 3 shows a case where two types of chemicals are used as the chemicals 1 and 2, the number of processing tanks, pumps, and valves can be appropriately set according to the number of chemicals mixed in the mixing box 85.
The temperature control mechanism 81 has warm water and processing liquid tanks 82 to 84 therein, and is a device for heating the processing liquids (pure water, chemical liquids 1 and 2) in the processing liquid tanks 82 to 84 with hot water. The liquid is appropriately heated, for example, in a range from room temperature to about 60 ° C. For this temperature adjustment, for example, a water bath, a throw-in heater, and an external heater can be appropriately used.
The processing liquid tanks 82, 83 and 84 are tanks for holding pure water and chemicals 1 and 2, respectively.
The pumps P1 to P3 suck out the processing liquid from the processing liquid tanks 82 to 84. The liquid may be sent from the processing liquid tanks 82 to 84 by pressurizing the processing liquid tanks 82 to 84, respectively.
The valves V1 to V3 open and close the pipes, and supply and stop the supply of the processing liquid. The valves V4 and V5 are for supplying pure water at room temperature (not heated) to the upper plate 30 and the lower plate 40, respectively.
The mixing box 85 is a container for mixing the chemicals 1 and 2 sent from the processing liquid tanks 83 and 84.
The chemicals 1 and 2 can be appropriately mixed and temperature-controlled in the mixing box 85 and sent to the upper plate 30. Further, temperature-controlled pure water can be appropriately sent to the lower plate 40.
[0024]
(Details of electroless plating process)
FIG. 5 is a flowchart illustrating an example of a procedure for performing electroless plating on the wafer W that has undergone the above-described steps S11 and S12 using the electroless plating apparatus 10. 6 to 12 are partial cross-sectional views showing the state of the electroless plating apparatus 10 in each step when electroless plating is performed according to the procedure shown in FIG. Hereinafter, this procedure will be described in detail with reference to FIGS.
[0025]
(1) Holding of wafer W (step S1 and FIG. 6)
The wafer W that has undergone the steps S11 and S12 is held on the wafer chuck 20. For example, a suction arm (substrate transfer mechanism) (not shown) that sucks the wafer W on its upper surface places the wafer W on the wafer chuck 20. Then, the wafer W is held and fixed by the wafer holding claws 21 of the wafer chuck 20. By lowering the cup 50, the suction arm can be moved horizontally below the upper surface of the wafer W.
[0026]
(2) Pre-processing of wafer W (Step S2 and FIG. 7)
By rotating the wafer W and supplying the processing liquid to the upper surface of the wafer W from the nozzle arm 61 or the nozzle arm 62, the pre-processing of the wafer W is performed.
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, for example, 100 to 200 rpm.
Either or both of the nozzle arms 61 and 62 move above the wafer W to discharge the processing liquid. As the processing liquid supplied from the nozzle arms 61 and 62, for example, pure water for cleaning the wafer W or a chemical liquid for catalyst activation processing of the wafer W is sequentially supplied according to the purpose of the preprocessing. The discharge amount at this time is sufficient to form a paddle (layer) of the processing liquid on the wafer W, for example, about 100 ml. However, if necessary, the discharge amount may be increased. The discharged processing liquid may be appropriately heated (for example, in a range from room temperature to about 60 ° C.).
[0027]
(3) Heating of wafer W (step S3 and FIG. 8)
The wafer W is heated to maintain the temperature of the wafer W at a temperature suitable for the reaction of the plating solution.
The lower plate 40 is heated so as to approach 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 2 mm), and is heated by the liquid supply mechanism 80 from the processing liquid discharge port 41. Supply purified water. The heated pure water is filled between the lower surface of the wafer W and the upper surface of the lower plate 40, and heats the wafer W.
By rotating the wafer W during the heating of the wafer W, the uniformity of the heating 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 non-rotated separately, and contamination of the lower surface of the wafer W is prevented.
The heating of the wafer W described above may be performed by other means. For example, the wafer W may be heated by radiation heat of a heater or a lamp. In some cases, the wafer W may be heated by bringing the heated lower plate 40 into contact with the wafer W.
[0028]
(4) Supply of plating solution (step S4 and FIG. 9).
The upper plate 30 is heated so as to approach 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 2 mm). (For example, 30 to 100 ml / min). The supplied plating solution 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 ° C.). It is preferable that the temperature of the supplied plating liquid is adjusted by the liquid supply mechanism 80.
Here, the uniformity of the plating film formed on the wafer W can be improved by rotating the wafer W by the wafer chuck 20. As an example, the wafer W is rotated at 10 to 50 rpm.
In addition, the heating of the upper plate 30 can be performed in advance in any of the steps S1 to S3. By heating the upper plate 30 in parallel with other steps, the processing time of the wafer W can be reduced.
As described above, the plating film is formed on the wafer W by supplying the plating solution heated to the desired temperature to the upper surface of the wafer W. By rotating the wafer W during the supply of the plating solution, the uniformity of the formation of the plating film on the wafer W can be improved.
[0029]
In supplying the above plating solution, the following can be performed.
(1) The wafer chuck 20 and the upper plate 30 can be tilted by the substrate tilting mechanism 70 before the supply of the plating solution.
By tilting the wafer W, gas between the wafer W and the upper plate 30 can be quickly removed and replaced with a plating solution. If the gas between the wafer W and the upper plate 30 is not completely removed, air bubbles remain between the wafer W and the upper plate 30 and the uniformity of the formed plating film is hindered.
Further, gas (for example, hydrogen) is generated with the formation of the plating film by the plating solution, and bubbles are formed by the generated gas, which may hinder the uniformity of the plating film.
By inclining the wafer W by the substrate inclining mechanism 70, it is possible to reduce the generation of bubbles and to promote the escape of the generated bubbles, thereby improving the uniformity of the plating film.
(2) The temperature of the plating solution can be changed over time.
By doing so, the structure and composition of the formed plating film can be changed in the layer direction.
{Circle around (3)} The plating solution can be supplied intermittently instead of continuously during the formation of the plating film. The plating solution supplied on the wafer W can be efficiently consumed, and the amount of the plating solution used can be reduced.
[0030]
(5) Cleaning of the wafer W (Step S5 and FIG. 10).
The wafer W is washed with pure water. This cleaning can be performed by switching the processing liquid discharged from the processing liquid discharge port 31 of the upper plate 30 from the plating liquid to pure water. At this time, pure water can be supplied from the processing liquid discharge 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 solution from the processing solution discharge port 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 above the wafer W to supply pure water. Also at this time, it is preferable to supply pure water from the processing liquid discharge port 41 of the lower plate 40.
By rotating the wafer W during the cleaning of the wafer W, the uniformity of the cleaning of the wafer W can be improved.
[0031]
(6) Dry the wafer W (Step S6 and FIG. 11).
The supply of pure water to the wafer W is stopped, and the pure water on the wafer W is removed by rotating the wafer W at a high speed. In some cases, drying of the wafer W may be promoted by ejecting nitrogen gas from the nozzle arms 61 and 62.
(7) Removal of 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 removed from above the wafer chuck 20 by a suction arm (substrate transfer mechanism) not shown.
[0032]
(2nd Embodiment)
FIG. 13 is a flowchart showing the steps of the electroless plating method according to the second embodiment of the present invention. FIG. 14 is a sectional view showing a section of the wafer W in the step of FIG.
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. Hereinafter, the details of this processing procedure will be described.
[0033]
(1) Formation of barrier layer on wafer W (step S21, FIG. 14A)
The barrier layer 2a is formed on the wafer W. In the barrier layer 2a, a non-catalytic active material having no catalytic activity with respect to the reducing agent of the electroless plating solution is mixed (doped) with a catalytically active material having catalytic activity with respect to the reducing agent of the electroless plating solution. Used.
For example, any of Ta, TaN, W, WN, Ti, and TiN is used as the non-catalytic active material. By doping the non-catalytically active material with the catalytically active material, catalytic activity can be imparted to the barrier layer 2a.
As the catalytically active material, the catalytically active material described in the first embodiment can be selected according to the reducing agent of the electroless plating solution.
The formation of the barrier layer 2a can be performed by, for example, a physical film formation method. 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 simultaneously using a target of each of the non-catalytically active material and the catalytically active material). . This can also be performed by vacuum evaporation (co-evaporation) in which the non-catalytically active material and the catalytically active material are simultaneously evaporated.
(2) Electroless plating of wafer W (step S22, FIG. 14B)
Electroless plating is performed on the wafer W to form an electroless plating film 4a. In this case, since the barrier layer 2a is provided with catalytic activity based on the doped catalytically active material, the electroless plating film 4a is formed on the barrier layer 2a.
[0034]
(Third embodiment)
FIG. 15 is a flowchart illustrating steps of an electroless plating method according to the third embodiment of the present invention. FIG. 16 is a sectional view showing a section of the wafer W in the step of FIG.
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. Hereinafter, the details of this processing procedure will be described.
(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 for a reducing agent of the electroless plating solution.
As the catalytically active material, the catalytically active material described in the first embodiment can be selected according to the reducing agent of the electroless plating solution.
The formation of the barrier layer 2b can be performed by, for example, a physical film forming method (for example, a sputtering method or a vacuum deposition method) or a chemical film forming method (for example, a CVD method).
(2) Electroless plating of wafer W (step S32, FIG. 16B)
Electroless plating is performed on the wafer W to form an electroless plating film. In this case, since the catalytically active material constituting the barrier layer 2b has catalytic activity, the electroless plating film 4b is formed on the barrier layer 2b.
[0035]
(Example 1)
Using a copper salt and a glyoxylic acid as a metal salt and a reducing agent, respectively, of the electroless plating solution, a copper electroless plating film according to a procedure corresponding to the third embodiment (a barrier layer is formed of a catalytically active material). Was formed.
Specifically, electroless plating of copper was performed for each of Ru (Ag), Pt, V, In, Ir, Co, and Rh as the base (barrier layer). In addition, as a comparative example, electroless plating of copper was also performed when the base was Cu, TaN, TiN, W, WN, and Ta.
When the underlayer was made of Ru, Ag, Pt, and Ir, all showed better adhesion and deposition rate than the case where the underlayer was made of Cu. In particular, when the underlayer was Ru or Ag, better adhesion was exhibited than when the underlayer was Cu.
On the other hand, in WN and Ta, Cu deposition itself was not performed. When the underlayer was TaN, TiN, or W, although Cu was formed, it was difficult to say that the formed Cu had good adhesion to the underlayer.
[0036]
(Example 2)
The copper salt and the metal salt (cobalt nitrate) are used as the metal salt and the reducing agent constituting the electroless plating solution, respectively, and the copper salt and the metal salt (cobalt nitrate) are used. An electroless plating film was formed.
Specifically, electroless plating of copper was performed for each of the underlying layers (barrier layers) of Ag, Ir, and Rh. Further, as a comparative example, electroless plating of copper was performed even when the underlayer was made of Cu, TaN, TiN, W, WN, V, Co, In, Ru, and Pt. When the underlayer was made of Ag, Ir, and Rh, all exhibited better adhesion and deposition rate than the case where the underlayer was made of Cu. In particular, when the underlayer was Ag, better adhesion was exhibited than when the underlayer was Cu.
On the other hand, in the case where the underlayer was Ta, TaN, TiN, W, WN, V, In, or Ru, Cu deposition itself was not performed. When the base was Pt, Cu was formed, but not enough. Further, when the base was Co or Rh, Cu was formed, but it was hard to say that the formed Cu had good adhesion to the base.
[0037]
(Other embodiments)
The embodiment of the present invention is not limited to the above-described embodiment, and can be extended and changed. Extended and modified embodiments are also included in the technical scope of the present invention.
For example, a glass plate other than the wafer W, for example, can be used as the substrate.
[0038]
【The invention's effect】
As described above, according to the present invention, it is possible to provide an electroless plating method that can realize electroless plating on a barrier layer by various processes.
[Brief description of the drawings]
FIG. 1 is a flowchart showing a procedure of an electroless plating method according to a first embodiment.
FIG. 2 is a cross-sectional view illustrating a cross section of a wafer W in the procedure of FIG.
FIG. 3 is a partial cross-sectional view illustrating an electroless plating apparatus used for the electroless plating in FIG.
4 is a partial cross-sectional view showing a state where a wafer W and the like installed in the electroless plating apparatus shown in FIG. 3 are inclined.
FIG. 5 is a flowchart illustrating an example of a procedure when performing electroless plating using the electroless plating apparatus according to the first embodiment.
FIG. 6 is a partial cross-sectional view illustrating a state of an electroless plating apparatus when electroless plating is performed according to the procedure illustrated in FIG.
FIG. 7 is a partial cross-sectional view illustrating a state of an electroless plating apparatus when electroless plating is performed according to the procedure illustrated in FIG.
8 is a partial cross-sectional view illustrating a state of an electroless plating apparatus when electroless plating is performed according to the procedure illustrated in FIG.
9 is a partial cross-sectional view illustrating a state of an electroless plating apparatus when electroless plating is performed according to the procedure illustrated in FIG.
FIG. 10 is a partial cross-sectional view illustrating a state of an electroless plating apparatus when electroless plating is performed according to the procedure illustrated in FIG.
FIG. 11 is a partial cross-sectional view illustrating a state of an electroless plating apparatus when electroless plating is performed according to the procedure illustrated in FIG.
12 is a partial cross-sectional view illustrating a state of an electroless plating apparatus when electroless plating is performed according to the procedure illustrated in FIG.
FIG. 13 is a flowchart illustrating a procedure of an electroless plating method according to a second embodiment.
FIG. 14 is a sectional view illustrating a section of the wafer W in the procedure of FIG.
FIG. 15 is a flowchart showing a procedure of an electroless plating method according to a third embodiment.
16 is a cross-sectional view illustrating a cross section of the wafer W in the procedure of FIG.
[Explanation of symbols]
W wafer 2, 2 a, 2 b barrier layer 3 catalytically active nucleus 4, 4 a, 4 b electroless plating film

Claims (8)

A diffusion limiting layer forming step of forming a diffusion limiting layer for limiting diffusion of a predetermined material on the substrate,
At least a portion of the diffusion limiting layer formed on the substrate in the diffusion limiting layer forming step has a catalytic activity on an oxidation reaction of a reducing agent in an electroless plating reaction, and a catalyst different from the predetermined material. Forming a catalytically active nucleus comprising an active material;
A plating film forming step of forming a plating film made of the predetermined material using an electroless plating solution containing the reducing agent on the substrate on which the catalytically active nucleus is formed in the catalytically active nucleus forming step;
An electroless plating method characterized by comprising: The catalytically active nuclei are formed discontinuously on the diffusion limiting layer,
The electroless plating method according to claim 1, wherein: Forming a diffusion limiting layer having catalytic activity on an oxidation reaction of a predetermined reducing agent and containing a catalytically active material different from the predetermined material, and forming a diffusion limiting layer on the substrate to limit diffusion of the predetermined material. Steps and
On the substrate on which the diffusion limiting layer is formed in the diffusion limiting layer forming step, a plating film forming step of forming a plating film made of the predetermined material using an electroless plating solution containing the predetermined reducing agent,
An electroless plating method characterized by comprising: A diffusion-restricting layer forming step of forming a diffusion-restricting layer having a catalytic activity on an oxidation reaction of a predetermined reducing agent, comprising a catalytically active material different from the predetermined material, and restricting diffusion of the predetermined material on the substrate ,
On the substrate on which the diffusion limiting layer is formed in the diffusion limiting layer forming step, a plating film forming step of forming a plating film made of the predetermined material using an electroless plating solution containing the predetermined reducing agent,
An electroless plating method characterized by comprising: The predetermined reducing agent is one of formaldehyde and glyoxylic acid, and the catalytically active material includes at least one of Ir, Pd, Ag, Ru, Rh, Au, Pd, Pt, and Ti. Item 5. The electroless plating method according to any one of Items 1 to 4. The method according to claim 1, wherein the predetermined reducing agent is hypophosphite, and the catalytically active material includes at least one of Au, Ni, Pd, Ag, Co, and Pt. 2. The electroless plating method according to 1. The said predetermined reducing agent is a metal salt, The said catalytically active material contains at least any one of Ag, Rh, Ir, Pd, Au, Pt, The Claims 1 to 4 characterized by the above-mentioned. Electroless plating method. 5. The method according to claim 1, wherein the predetermined reducing agent is dimethylamine borane, and the catalytically active material includes at least one of Ni, Pd, Ag, Au, and Pt. 6. Electroless plating method.

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