US20060081461A1

US20060081461A1 - Electroless plating apparatus and method

Info

Publication number: US20060081461A1
Application number: US11/248,223
Authority: US
Inventors: Miho Jomen; Kenichi Hara
Original assignee: Tokyo Electron Ltd
Current assignee: Tokyo Electron Ltd
Priority date: 2004-10-15
Filing date: 2005-10-13
Publication date: 2006-04-20
Also published as: CN1769520A; JP2006111938A; KR100751102B1; KR20060052152A

Abstract

An electroless plating solution includes a first liquid chemical containing a metal salt and a second liquid chemical containing a reducing agent. In respective liquid chemical supply lines, liquid chemical opening/closing units are installed in the vicinity of a junction therebetween, and at the same time, a plating solution opening/closing unit is provided in the vicinity of an discharge opening in supply line of an electroless plating solution after the first and the second liquid chemical are joined together. A plating solution in the supply line disposed between these opening/closing units corresponds to a discharge amount needed for a plating processing of about one time. Further, both of the liquid chemicals are mixed together only during the time period between the time when a plating processing on one substrate has been started and the time when a plaiting processing is to start on a following substrate.

Description

FIELD OF THE INVENTION

The present invention relates to an electroless plating apparatus and method for plating a surface of a substrate, e.g., a surface of a wiring metal of a semiconductor substrate by supplying an electroless plating solution thereonto.

BACKGROUND OF THE INVENTION

A multilayered structure of a semiconductor device is formed by stacking interlayer insulating films, into which wirings are embedded, at multiple levels. As a typical wiring material that is resistant to electromigration, a copper has been preferably used. Further, as a method for forming the wiring, there has been employed a damascene process: wherein a recess portion having a groove is formed in an interlayer insulating film to be filled with a copper; and a residual copper is polished by a so-called CMP (chemical mechanical polishing).
Recently, as a technology for carrying out such a copper wiring, a possibility of introducing an electroless plating method has been studied. An electroless plating is a method for forming a metal film by using electrons supplied from a reducing agent added in a plating solution without using an electrolysis from the outside; and the method is applied in a technology for forming a copper seed layer in a recess portion before it is filled with the copper, or in a technology for forming a coating made of CoWP (cobalt tungsten phosphide) as an adhesion layer between a barrier film and the copper before forming the barrier film on a copper wiring (e.g., a film such as silicon nitride, silicon carbide, silicon carbon nitride or the like).
As for the electroless plating, reference 1 discloses that, e.g., both upper and lower sides of a semiconductor wafer (hereinafter, referred to as a wafer), a periphery of which is supported by a chuck, are heated by temperature control plates, and at the same time an electroless plating solution heated to a predetermined temperature, e.g., a set temperature within a range between room temperature and 60° C., is supplied onto a surface of the wafer through an upper plate.
However, since the reducing agent as an electron supply source is included in the electroless plating solution, so-called precipitation in solution, i.e., precipitation of a metal in solution, is likely to be produced in case when the reducing agent is used, particularly when it is heated. If precipitation in solution is produced, the condition of the electroless plating solution becomes changed, and therefore, the electroless plating processing of inter-wafer is changed accordingly. For example, a film thickness of a coating becomes non-uniform, and precipitated particles may cause a particle contamination and bring about clogging of pipe in the electroless plating apparatus. Reference 1 hasn't paid any attention on such an unstability of the electroless plating solution.
Reference 1: Japanese Patent Laid-open Application No. 2004-107747 (FIG. 1 and paragraph 0026)

SUMMARY OF THE INVENTION

The present invention has been made under such a background, and it is, therefore, an object of the present invention to provide an electroless plating apparatus and method capable of stabilizing a status of an electroless plating solution and stably performing a plating processing on a surface of a substrate, since a reducing agent as an electron supply source is included in an electroless plating solution and a metal is precipitated in solution to thereby be in an unstable state, particularly when it is heated, in an electroless plating processing of, e.g., a semiconductor device fabrication processing.
In accordance with one aspect of the present invention, there is provided an electroless plating apparatus, including: a substrate supporting unit for supporting a substrate at a substantially horizontal position; a first liquid chemical supply line for supplying a first liquid chemical therethrough; a first liquid chemical supply source communicating with an upstream end of the first liquid chemical supply line; a first liquid chemical opening/closing unit, installed in the vicinity of a downstream end of the first liquid chemical supply line, for controlling a flow of the first liquid chemical; a second liquid chemical supply line for supplying a second liquid chemical therethrough; a second liquid chemical supply source communicating with an upstream end of the second liquid chemical supply line; a second liquid chemical opening/closing unit, installed in the vicinity of a downstream end of the second liquid chemical supply line, for controlling a flow of the second liquid chemical; an electroless plating solution supply line, communicating with the downstream ends of the first and the second liquid chemical supply line, for supplying an electroless plating solution therethrough, which is formed by mixing the first and the second liquid chemical together, to supply it to a top surface of the substrate; a supply line temperature control unit for adjusting a temperature of a plating solution in the electroless plating solution supply line; a plating solution opening/closing unit, installed in the vicinity of a downstream end of the electroless plating solution supply line as a discharge opening thereof, for controlling a flow of the electroless plating solution; and a control unit for controlling the first liquid chemical opening/closing unit, the second liquid chemical opening/closing unit and the plating solution opening/closing unit to supply the electroless plating solution to the top surface of the substrate, wherein a volume in the electroless plating solution supply line surrounded by the first liquid chemical opening/closing unit, the second liquid chemical opening/closing unit and the plating solution opening/closing unit corresponds to a discharge amount required for performing an electroless plating processing on one substrate. Here, the first and the second liquid chemical opening/closing unit may be also used as one liquid chemical opening/closing unit. This electroless plating apparatus may have, e.g., flow rate adjusting units for adjusting flow rates of the first and the second liquid chemical, respectively.
It is an object of the present invention to mix the first and the second liquid chemical right before the electroless plating processing if possible, and to reduce the amount of the liquid chemicals to be used as much as possible. Further, the present invention is based on an idea that both of the liquid chemicals are mixed together while a processing is carried out on one substrate until a processing on a subsequent substrate is started, and then, a mixed solution (an electroless plating solution) is used up in the processing on the subsequent substrate. Thus, the liquid chemical opening/closing units are provided in the vicinity of the junction between the first and the second liquid chemical supply line, i.e., they may be disposed as close as possible to the junction in a permissible range of a component layout. If a distance between the junction and the respective liquid chemical opening/closing units is large, both of the solutions are mixed together by diffusion to become a solution filling therebetween. However, since such a mixing operation is carried out at a stationary state after the liquid chemical opening/closing units are closed, both of the liquid chemicals may be supplied onto the substrate while they are not fully mixed, and thus, lowering uniformity in plating. In other words, “the vicinity of the junction” may include a range where non-uniformity in plating due to insufficient mixing does not occur, even though the respective liquid chemical opening/closing units are slightly away from the junction due to a configuration of component, a limitation on layout or the like.
Further, the phrase “a volume V1 in the electroless plating solution supply line between the liquid chemical opening/closing units and the plating solution opening/closing unit corresponds to a discharge amount V2 required for performing the electroless plating processing on one wafer” used herein means that V1 and V2 become uniform. Further, V2 means a total amount obtained by summing an amount of solution to be deposited on a corresponding surface so as to electrolessly plate, e.g., a surface of a substrate and a volume (a volume of solution) from the plating solution opening/closing unit to the discharge opening. As to a relationship between V1 and V2, in case where V1 is greater than V2, if V2 is given as a discharge amount for one time, the plating solution remains in the plating solution supply line; and, if V1 is given as a discharge amount for one time, too much solution will be discharged, thereby wasting the liquid chemicals. Contrary to this, in case where V1 is smaller than V2, given that V2 is a discharge amount for one time, the first and the second liquid chemical in the liquid chemical supply lines, respectively, are discharged without remaining in the plating solution supply line, and thus, lowering uniformity in the plating solution on the substrate. For the same reason, it is an ideal that V1 and V2 are equal to each other, but a difference therebetween may be generated somewhat on design. In this case also, uniformity in plating processing is secured, and V1 and V2 become uniform if such a design idea is adopted that waste of liquid chemicals is prevented as much as possible.
In a preferred embodiment of the present invention, there may be included an upper temperature controller facing the top surface of the substrate supported by the substrate supporting unit, and at the same time, being made to be larger than an effective area of the substrate, the upper temperature controller having in a bottom surface thereof a discharge opening of the electroless plating solution supply line; and a moving mechanism for relatively moving the upper temperature controller between a processing position for filling a space between the upper temperature controller and the top surface of the substrate with an electroless plating solution and a waiting position far away from the processing position. Here, the upper temperature controller may have therein a circulation chamber of a temperature control fluid, and the entire electroless plating solution supply line may be disposed in the circulation chamber of the upper temperature controller such that the supply line temperature control unit adjusts a temperature of an electroless plating solution by a heat exchange between the temperature control fluid and the electroless plating solution. Further, in the first and the second liquid chemical supply line, parts thereof filled with liquid chemicals that will subsequently fill the electroless plating solution supply line may be disposed in the circulation chamber of the upper temperature controller. In this case, since a part or an entire part of the electroless plating solution supply line can be disposed in the upper temperature controller, a part or an entire part of the supply line temperature control unit comes to be also used by the upper temperature controller.
Further, it can be configured such that the upper temperature controller has therein a circulation chamber of a temperature control fluid; and the entire part of the electroless plating solution supply line is disposed in the circulation chamber to be also used as the supply line temperature control unit such that a heat exchange is made between the electroless plating solution and the temperature control fluid.
Still further, in the present invention, the first and the second liquid chemical supply line may have temperature control units for controlling temperatures of parts thereof filled with liquid chemicals that will subsequently fill the electroless plating solution supply line. In case where an inside of the upper temperature controller is formed as the circulation chamber of the temperature control fluid, the circulation chamber may be used as a means for temperature controlling the parts filled with the liquid chemicals.
Still further, the electroless plating apparatus of the present invention may include a lower temperature controller, disposed to face the bottom surface of the substrate, having a substrate temperature control unit for adjusting a temperature of the substrate. Here, it is preferable that the substrate temperature control unit adjusts a temperature of the substrate by filling a space between the lower temperature controller and the substrate with a fluid, a temperature of which is adjusted in the lower temperature controller.
In accordance with another aspect of the present invention, there is provided an electroless plating method using the electroless plating apparatus of the present invention, wherein the first liquid chemical is a solution containing a metal salt of a plating metal, and the second liquid chemical is a solution containing a reducing agent as an electron supply source.
In accordance with still another aspect of the present invention, there is provided an electroless plating method using the electroless plating apparatus of the present invention, wherein opening and closing operations of the first liquid chemical opening/closing unit, the second liquid chemical opening/closing unit and the plating solution opening/closing unit are simultaneously carried out.
In accordance with still another aspect of the present invention, there is provided an electroless plating method using the electroless plating apparatus of the present invention, wherein the supply line temperature control unit and the upper temperature controller are adjusted at a plating process temperature.
In accordance with still another aspect of the present invention, there is provided an electroless plating method using the electroless plating apparatus of the present invention, wherein the supply line temperature control unit and the temperature control units installed in the first and the second liquid chemical supply line are adjusted at a plating process temperature.
In accordance with still another aspect of the present invention, there is provided an electroless plating method using the electroless plating apparatus of the present invention, wherein the supply line temperature control unit and the substrate temperature control unit are adjusted at a plating process temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:
FIG. 1 provides a longitudinal side view showing an overall configuration of an electroless plating apparatus in accordance with a preferred embodiment of the present invention;
FIG. 2 sets forth a schematic configuration view showing a main part of the electroless plating apparatus;
FIGS. 3A to 3C are explanatory diagrams, each showing a surface configuration of a wafer used for an electroless plating processing;
FIGS. 4A and 4B present explanatory diagrams, each showing in stages states of a processing carried out on the wafer by using the electroless plating apparatus;
FIGS. 5A and 5B describe explanatory diagrams, each showing in stages states of a processing carried out on the wafer by using the electroless plating apparatus;
FIGS. 6A and 6B offer explanatory diagrams, each showing in stages states of a processing carried out on the wafer by using the electroless plating apparatus;
FIGS. 7A and 7B are schematic side views respectively showing modified examples of a configuration in the vicinity of a junction between a first and a second liquid chemical supply line;
FIG. 8 provides a perspective view schematically showing a main part in accordance with another embodiment of the present invention; and
FIG. 9 illustrates a longitudinal side view schematically showing an inside of an upper temperature controller shown in FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a view for showing an overall configuration of an electroless plating apparatus in accordance with a preferred embodiment of the present invention. Reference numeral 11 in FIG. 1 indicates a wafer chuck forming a cylindrical flat substrate supporting unit, an upper portion of which is opened; and a step portion 12 for supporting a peripheral portion of a wafer W as a substrate is formed at a peripheral portion of a top portion of the wafer chuck 11 over an entire periphery thereof. A barrel shaped rotation axis 13, provided in a central portion of the wafer chuck 11, is coupled to a rotation driving unit, e.g., a hollow motor 14. The wafer chuck 11 is configured to be rotated by the hollow motor 14 around a vertical axis while the wafer W is supported thereon. The hollow motor 14 is fixed to a base 15, which is attached to an incline mechanism 16 to be inclined.
Outside the wafer chuck 11, a cup 21 for receiving a solution is provided to surround the corresponding wafer chuck 11, the cup 21 being configured to be lifted up and down from the base 15 by an elevation mechanism (not shown). An upper portion of a side peripheral surface of the cup 21 is inwardly bent to prevent a solution shaken out during the rotation of the wafer W from spilling over by bouncing it back. Further, an opening 22 is formed in a bottom central portion of the cup 21 such that the rotation axis 13 penetrates therethrough; and at the same time, at a part close to a periphery of the bottom, there is provided a drain discharge opening 23 for discharging as a drain a solution, which is overflown from the wafer W. Still further, a hole (not shown) is formed in a bottom surface at a distance away from the center of the wafer chuck 11 such that an overflown solution into the wafer chuck 11 flows down to the cup 21.
Above the wafer chuck 11, an upper temperature controller 3 is provided to face the surface of the wafer W supported by the wafer chuck 11. The upper temperature controller 3, having a flat columnar shaped outward appearance, is made to be slightly larger than the wafer W; and at the same time, it is configured to be lifted up and down by an elevation mechanism 30 as a moving mechanism between a processing position where an electroless plating solution is supplied to the wafer W and a waiting position placed thereabove. It is preferable that the upper temperature controller 3 is larger than an effective area of the wafer W (an integrated circuit formation area). However, recently, since an integrated circuit has been formed in a region substantially close to the periphery of the wafer W, the upper temperature controller 3 may have the same size with the wafer W or greater. Further, a lower temperature controller 24, disposed in the wafer chuck 11, is configured to be lifted up and down against a back side surface of the wafer W kept on the wafer chuck 11 by an elevation mechanism (not shown) through a supporting shaft 25 penetrating through the rotation axis 13. The upper temperature controller 3 and the lower temperature controller 24 are formed of plates made of, e.g., ceramic, having a heater formed of, e.g., a resistance heating material; and they may be formed of plates through which a heat transfer medium flows.
One end side of a pure water supply pipe 26 as a supply line of a temperature control water, e.g., a pure water, is inserted in a central portion of a bottom surface of the lower temperature controller 24, wherein the pure water supply pipe 26 is arranged in a supporting shaft 25; and the other end side thereof is coupled to a pure water tank 29 through a valve 27 and a pump 28. Further, the pure water also serves as a rear surface side rinse solution.
The elevation mechanism 30 of the upper temperature controller 3 and the elevation mechanism (not shown) of the lower temperature controller 24 are fixed to the base 15 such that the upper temperature controller 3, the wafer W and the lower temperature controller 24 are inclined as a unit by an incline mechanism 16. This is to move upwardly and hence get rid of bubbles that are mixed in a processing solution, e.g. an electroless plating solution or the like, while a space between the upper temperature controller 3 and the wafer W is being filled therewith as described hereinafter. However, in the configuration of the present embodiment, bubbles are difficult to be mixed, so that the incline mechanism 16 may not be provided.
In the following, a supply system of the electroless plating solution will be discussed with reference to FIG. 2. One end side of an electroless plating solution supply line 41 formed of, e.g., a pipe, is disposed in the central portion of the upper temperature controller 3; and, in a lower end thereof, there is formed a discharge opening 42 of an electroless plating solution whose bottom surface coincides with the bottom surface of the upper temperature controller 3. At an upper portion side of the upper temperature controller 3 in the electroless plating solution supply line 41, there is provided a valve 43 corresponding to a plating solution opening/closing valve for stopping a supply of the solution into the corresponding supply line 41; and at the same time, an upstream side of the electroless plating solution supply line 41 is ramified into a first liquid chemical supply line 5 and a second liquid chemical supply line 6. Namely, the first and the second liquid chemical supply line 5 and 6 are joined together in an upstream end of the electroless plating solution supply line 41. It is configured such that the electroless plating solution supply line 41 is surrounded by a supply line temperature control unit 44 and the electroless plating solution in the corresponding supply line 41 is set at a predetermined temperature, e.g., in the range from room temperature to 60° C. In the present embodiment, the supply line temperature control unit 44 is configured such that a heat transfer medium, e.g., a pure water is supplied through a heat transfer medium supply line 46 to flow through in a barrel shaped case body 45 and then to be discharged through a heat transfer medium discharge line 47. A heater 48 forming a part of the supply line temperature control unit 44 is provided around the valve 43 such that a temperature control of the electroless plating solution in the valve 43 is carried out.
The first and the second liquid chemical supply line 5 and 6 are supply lines for supplying a first and a second liquid chemical to flow therethrough, respectively, which will be mixed together to form an electroless plating solution; and respective valves 51 and 61 as liquid chemical opening/closing units are provided in the vicinity of a junction (in a top portion of the electroless plating solution supply line 41). The valves 51 and 61 are disposed as close as possible to the junction in a permissible range of a component layout. It is intended to allow the liquid chemicals to be uniformly diffused and mixed together as much as possible, during a stationary state where the liquid chemicals stand by for a subsequent processing on the wafer W.
In the first liquid chemical supply line 5, there are sequentially provided a liquid chemical supply source 52, a pump 53 and a flow rate adjusting unit 54, from the upstream side thereof; and, in the second liquid chemical supply line 6, there are sequentially provided a liquid chemical supply source 62, a pump 63 and a flow rate adjusting unit 64, from the upstream side thereof. The first liquid chemical includes a metal salt containing a component for forming an electroless coating; a complexing agent for complexing a metal such that metal ions are not precipitated as hydroxide in a strong alkaline condition; and a pH adjuster for adjusting pH of the solution.
The metal salt is formed of a first and a second metal salt containing an alloy component in case where a film is an alloy. Specifically, as the component of the first liquid chemical, the first metal salt may be selected from, e.g., cobalt sulfate, cobalt chloride, nickel sulfate or nickel chloride; the second metal salt may be selected from, e.g., tungstate or ammonium tungstate; the complexing agent may be, e.g., citric acid or sodium citrate; and the pH adjuster may be, e.g., sodium hydroxide or TMAH (tetramethylammoniumhydroxide).
The second liquid chemical includes a reducing agent for catalytically reducing and precipitating metal ions; and a pH adjuster for adjusting pH of the solution. As the reducing agent, e.g., DMAB (dimethylamineborane) or the like may be enumerated. The first and the second liquid chemical are stored, e.g., at a room temperature and pH 10. Further, the components as enumerated above are a mere example, and it may not be used necessarily.
Flow rates of the first and the second liquid chemical are adjusted by the flow rate adjusting units 54 and 64, respectively, to have a predetermined mixing ratio, e.g., the first liquid chemical:the second liquid chemical=9:1, and to have a discharge amount, e.g., 50 cc, of the electroless plating solution for processing one wafer W.
Herein, a volume V1 in the electroless plating solution supply line 41 between the valves 51 and 61 as the liquid chemical opening/closing units and the valve 43 as the plating solution opening/closing unit is designed to correspond to a discharge amount V2 (50 cc in this embodiment) required for performing the electroless plating processing on one wafer W. As to a relationship between V1 and V2, as specifically described in Summary, the discharge amount V2 may correspond to an amount of solution passing the valve 43 while a space between the wafer W and the upper temperature controller 3 is being filled with the electroless plating solution starting from the state where the solution is not present in a downstream side of the valve 43 (the amount of solution needed for a processing of one wafer W). In other words, it corresponds to a total volume obtained by summing a volume between the wafer W and the upper temperature controller 3 and a volume from the valve 43 to the discharge opening 42. In this case, it is preferable that the valve 43 is disposed as close as possible to the discharge opening 42 since the electroless plating solution between the valve 43 and the discharge opening 42 becomes useless; and there may be provided in the upper temperature controller 3 a valve for opening or closing a flow path by using a piezoelectric sensor.
In the vicinity of the electroless plating solution supply line 41 of the upper temperature controller 3, there is disposed a supply line 71 of a pure water as a cleaning solution: wherein a downstream end thereof is formed as a discharge opening 72 opened in the bottom surface of the upper temperature controller 3; and at the same time, in an upstream end thereof, a pure water tank 73 is provided. The downstream end of the pure water supply line 71 may be opened between the valve 43 and the discharge opening 42 in the electroless plating solution supply line 41. Reference numeral 74 is a pump, and 75 is a valve for stopping a supply of the pure water through the pure water supply line 71. Further, the electroless plating apparatus has a control unit 100 having, e.g., a computer, which includes a sequence program for controlling operations of the pumps 53, 63 and 74, and the respective valves 43, 51, 61 and 75.
Now, back to FIG. 1, the electroless plating apparatus has a plurality of nozzles, which are freely movable between a supply position of fluid and a waiting position thereof above the wafer W supported by the wafer chuck 11. FIG. 1 shows two nozzles 17 and 18 for convenience. For example, the nozzle 17 for supplying a substitute plating solution onto the surface of the wafer W before supplying the electroless plating solution is coupled to a substitute plating solution supply source through a piping (not shown). Further, the nozzle 18 for supplying a drying gas, e.g., a nonreactive gas, is coupled to a drying gas supply source through a piping (not shown). These nozzles 17 and 18, each having, e.g., a slit shaped discharge opening whose length is longer than a radius of the wafer W, are configured to be freely elevatable and horizontally movable, e.g., to be revolvable by a driving mechanism (not shown).
In the following, an operation of the aforementioned embodiment will be discussed. First, the upper temperature controller 3 stands by at the waiting position, and at the same time, the wafer chuck 11 is lowered; the wafer W is transferred to an upper side of the wafer chuck 11 by a transfer unit (not shown) to which the surface of the wafer W is adsorbed; and the wafer chuck 11 is elevated to receive the wafer W from the transfer unit (state shown in FIG. 1). Further, as shown in FIG. 3A, in the surface of the wafer W, a copper wiring 302 is buried, e.g., in a recess portion of an interlayer insulating film 301. Reference numeral 303 is a barrier film for preventing the copper in the recess portion from diffusing into the insulating film 301.
Subsequently, as shown in FIG. 4A, e.g., the nozzle 17 is moved onto the wafer W to supply a pre-processing solution thereon while the wafer W is being rotated by the wafer chuck 11, thereby forming a puddle of the pre-processing solution. The pre-processing solution is a substitute plating solution for performing, e.g., a palladium substitute plating, wherein the substitute solution to be used may be obtained by dissolving palladium salt made of palladium sulfate or palladium chloride in an acid solution such as sulfuric acid or hydrocholoric acid. The substitute plating solution is supplied onto the surface of the wafer W at a controlled temperature, e.g., in the range from room temperature to 60° C. Hence, at an interface between the copper wiring 302 and the substitute plating solution, copper of an oxidation-reduction potential lower than that of palladium gives up electrons to palladium to be dissolved therein, and a catalyzer layer 304 made of palladium receiving the electrons is selectively precipitated on a surface of the copper wiring 302, as shown in FIG. 3B. The catalyzer layer 304 serves as a catalyzer of the electroless plating processing in a subsequent processing, but the catalyzer may not be required depending on the electroless plating solution. In that case, a pre-processing may be carried out by supplying an organic acid solution to the wafer W through the nozzle 17. Thereafter, as shown in FIG. 4B, a cleaning solution, e.g., a pure water, is supplied onto the wafer W through the nozzle 18 while the wafer W is being rotated, to thereby remove the pre-processing solution.
After that, the nozzle 18 is retreated from the position above the wafer W, and the upper temperature controller 3 is lowered to be set at a position where a distance between the bottom surface thereof and the surface of the wafer W becomes, e.g., 0.1 mm˜2 mm. At this time, the lower temperature controller 24 is elevated to be set at a position where a distance from the rear surface of the wafer W becomes, e.g., 0.1 mm˜2 mm. Further, if the pure water as a temperature adjusting solution is supplied by the pump 28 to the lower temperature controller 24 through the pure water supply line 26, the pure water is heated to a preset temperature while it passes through the lower temperature controller 24.
A heated pure water fills a gap between the lower temperature controller 24 and the rear surface of the wafer W to flow down into the wafer chuck 11, and hence, flowing down into the cup 21 through a hole (not shown). Further, since the top surface of the lower temperature controller 24 is to be maintained at a set temperature, the wafer W is heated from the rear surface thereof to be maintained at a plating process temperature. After the wafer W is heated for a predetermined time, e.g., 10 seconds, as described above, the pumps 53 and 63 shown in FIG. 2 are operated, and at the same time, the valves 43, 51 and 61 are opened simultaneously. After a set time, the pumps 53 and 63 are stopped and the valves 43, 51 and 61 are simultaneously closed. As described above, by simultaneously performing opening and closing operations of the valves, it is possible to prevent backflows of the liquid chemicals. Further, the set time is a time needed for the solution between the valves 43, 51 and 61 in the electroless plating solution supply line 41 to be totally discharged; and therefore, as shown in FIG. 5A, the electroless plating solution in the electroless plating solution supply line 41 is supplied into the space between the wafer W and the upper temperature controller 3 at a flow rate of, e.g., 30˜100 ml/minute to thereby fill the space.
While the electroless plating solution is supplied to a wafer W loaded prior to a present corresponding wafer W, the first and the second liquid chemical from the first and the second liquid chemical supply line 5 and 6 through the valves 51 and 61, respectively, are provided together into the electroless plating solution supply line 41; and mixed together by diffusion to form an electroless plating solution and temperature-controlled by the temperature control unit 44 to become an active state until the mixture is supplied to the corresponding wafer W. Further, since the upper temperature controller 3 has been also heated to, e.g., the same temperature as the set temperature of the electroless plating solution, the electroless plating processing is performed while temperatures of the front and the rear surface of the wafer W are being adjusted. Namely, palladium, which has been precipitated on the surface of the wafer W during the pre-processing, serves as a catalyzer to induce a reaction between the electroless plating solution and copper; and, as shown in FIG. 3C, there is formed on a surface of the copper wiring 302 an electroless coating 305 made of an alloy selectively containing phosphorous P, e.g., NiP, CoWP, NiP, CoP or the like, as an adhesion layer of a film thickness in the range of, e.g., 100˜200 Å.
Further, the electroless plating solution kept in a region between the valves 51, 61 and 43 in the electroless plating solution supply line 41 is discharged as an electroless plating solution for the present corresponding wafer W; but, simultaneously, new first and second liquid chemicals are provided into the corresponding region through the valves 51 and 61 by an amount of solution (V1) capable of filling the region, while a flow rate thereof is being adjusted at 9:1 by the flow rate adjusting units 54, 64, respectively, as described above.
At this time, the pure water also serving as a cleaning water has been supplied to the rear surface side of the wafer W, so that a so-called back rinse is carried out by the pure water to prevent the electroless plating solution from being introduced to the rear surface of the wafer W. Further, the wafer W may be rotated through the wafer chuck 11 during the processing to enhance in-surface temperature uniformity in the wafer W. In this processing, the wafer W, the upper temperature controller 3 and the lower temperature controller 24 may be inclined by using the incline mechanism 16 such that bubbles introduced in the gap are removed from the electroless plating solution. Such a processing is effective, e.g., in case where a gas is generated by the reaction between the electroless plating solution and copper.
In the following, the valve 75 of the pure water supply line 71 shown in FIG. 2 is opened to supply a pure water to a space between the wafer W and the upper temperature controller 3 through the discharge opening 72, as shown in FIG. 5B, to thereby substitute the electroless plating solution on the surface of the wafer W with the pure water. Thereafter, the upper temperature controller 3 is elevated; and, as described in FIG. 6A, a post-cleaning solution is supplied onto the wafer W that is being rotated, to perform a post-cleaning on the surface thereof by using a nozzle (for convenience, given by 18) selected from a nozzle group indicated by the nozzles 17 and 18. At this time also, the pure water is supplied as a back rinse to the rear surface side of the wafer W. The post-cleaning is performed to reduce an inter-line leakage current; and, e.g., an organic acid and a fluorine based aqueous solution are employed as a post-cleaning solution. Further, the pure water may be supplied after the electroless plating processing by using the nozzle 18 after the upper temperature controller 3 is lifted up.
Continuously, the pure water as a cleaning solution is supplied onto the surface of the wafer W that is being rotated through the nozzle (for convenience, given by 18) of the aforementioned nozzle group; and, subsequently, the discharge of the cleaning solution is stopped and then the wafer W is rotated at a high speed to dry it, as described in FIG. 6B. At this time, a drying gas such as a nonreactive gas may be sprayed out on the surface of the wafer W through the nozzle of the aforementioned nozzle group to facilitate drying. After a series of processing is completed as described above, the surface of the wafer W is adsorbed by a transfer unit (not shown) to be unloaded from the wafer chuck 11.
In accordance with the aforementioned embodiment, the valves 51 and 61 as the liquid chemical opening/closing units are provided in the vicinity of the junction between the first and the second liquid chemical supply line 5 and 6; and at the same time, the valve 43 as the electroless plating solution opening/closing unit is provided in the vicinity of the discharge opening 42 in the electroless plating solution supply line 41, wherein a volume of the supply line 41 disposed between the valves 43, 51 and 61 corresponds to a discharge amount required for a plating processing of one wafer W. Therefore, both of the liquid chemicals are being mixed with each other only during the time period between the time when the plating processing on the present corresponding wafer W has been started and the time when the electroless plaiting processing is to start on a following wafer, so that a period while both of the liquid chemicals have been mixed is short, i.e., both of the liquid chemicals come to be mixed right before an electroless plating processing being started. Thus, the electroless plating solution can be prevented from being in an unstable state as much as possible, thereby suppressing precipitation in solution. As a result, it is possible to perform the electroless plating processing on the surface of the wafer W in a state where the electroless plating solution is stable, and thus, improving uniformities in the film thickness and the film quality of the wafer W. Further, since precipitations of particles are not likely to be generated, particle contamination or clogging of wiring does not occur.
Still further, since almost all electroless plating solution in standby status is used for the electroless plating processing on the wafer W, the amount of electroless plating solution to be used can be reduced, thereby contributing to a processing cost reduction since the cost therefor is substantially high. Still further, if the valve is positioned at a place far away from the junction between the first and the second liquid chemical supply line 5 and 6, the liquid chemicals may not be sufficiently mixed. However, in the present embodiment, the valves 51 and 61 are provided in the vicinity of the junction, so that two liquid chemicals are sufficiently mixed together, and concentration of the electroless plating solution becomes uniform to thereby perform a processing with high in-surface of inter-substrate uniformity. Further, if the first and the second liquid chemical supply line 5 and 6 are configured to be joined together in V-shape in the longitudinal direction, the solution will not be stagnated and bubbles are not likely to be introduced.
Herein, as to the liquid chemical supply lines 5 and 6, it can be configured such that, as illustrated in FIG. 7A, the second liquid chemical supply line 6 is thinner than the first liquid chemical supply line 5; and the second liquid chemical supply line 6 is slantingly joined to the uprightly standing first liquid chemical supply line 5. Otherwise, as illustrated in FIG. 7B, it can be configured such that both liquid chemical supply lines 5 and 6 are joined together in V-shape; and a three-way valve 40 is provided at a junction thereof, which is configured to select one of states where both of the liquid chemical supply lines 5 and 6 are either simultaneously communicated or simultaneously closed.
Further, a flow rate adjusting unit may not be provided as a unit for adjusting flow rates of the first and the second liquid chemical; and a mixing ratio therebetween may be set by adjusting discharge amounts of respective liquid chemicals by using a pump, e.g., a bellows pump, capable of controlling the discharge amounts.
Still further, FIGS. 8 and 9 are views for showing main parts of the upper temperature controller 3 in accordance with another embodiment of the present invention. In this embodiment, an upper temperature controller 3 has a columnar shaped outward appearance and is made to be slightly larger than a wafer W, wherein an inside thereof is formed as a circulation chamber 31 through which a heat transfer medium such as a temperature control fluid, e.g., pure water or the like, passes. A heat transfer medium supply line 32 is coupled to a top surface of the upper temperature controller 3 in the vicinity of an outer periphery thereof; and, further, a heat transfer medium discharge pipe 33 is coupled to, e.g., a symmetrically located position of the heat transfer medium supply line 32 with respect to a central portion of the upper temperature controller 3.
In the circulation chamber 31, the pipe-shaped first and second liquid chemical supply lines 5 and 6 are arranged from a top surface side thereof, wherein the liquid chemical supply lines 5 and 6, formed, e.g., in spiral shapes, are joined together in the line; and a lower end of an electroless plating solution supply line 41 as a joined pipe thereof is formed as a discharge opening 42 in a bottom surface of the upper temperature controller 3. The present embodiment is the same as the aforementioned embodiment except that the respective liquid chemical supply lines 5 and 6 and the electroless plating solution supply line 41 are disposed in the circulation chamber 31 of the heat transfer medium of the upper temperature controller 3; and the valves 51 and 61 are provided in the vicinity of a junction between the first and the second liquid chemical supply line 5 and 6, and at the same time, a valve 43 is provided in the vicinity of the discharge opening 42 in the electroless plating solution supply line 41. Further, a volume of the supply line 41 disposed between the valves 43, 51 and 61 corresponds to a discharge amount required for a plating processing of one wafer W. In such a configuration, since a temperature change in the electroless plating solution is moderate, there is a merit that the electroless plating solution is not over-heated in case of setting the temperature thereof at a high temperature.
Further, in the first and the second liquid chemical supply line 5 and 6, parts filled with liquid chemicals to be used next time for one substrate by passing the valves 51 and 61 as liquid chemical opening/closing units, i.e., parts filled with liquid chemicals required for a processing of one wafer W from the respective valves 51 and 61, are disposed in the circulation chamber 31. By doing this, it is possible to reduce a period while an electroless plating is started after the first and the second liquid chemical are mixed together, since the liquid chemicals have already been heated to a processing temperature of the electroless plating solution.
This is related to the temperature of the electroless plating processing; and, in case of setting the temperature of the electroless plating solution high, e.g., at 60° C., if the time to prepare an electroless plating processing on a surface of a next wafer W after the electroless plating solution is supplied on the surface of the present one wafer W, a waiting time may be required since the electroless plating solution is heated to the processing temperature in the electroless plating solution supply line 41, in the embodiment shown in FIG. 1. Contrary to this, if the first and the second liquid chemical are heated in advance (pre-heated) like in the present embodiment, the time for heating a mixed liquid chemical to the processing temperature becomes reduced, and thus, enhancing the product yield. Further, in the embodiment shown in FIG. 1, it can be also configured such that the first and the second liquid chemical are pre-heated, e.g., temperature control units may be provided in the first and the second liquid supply line 5 and 6, respectively.
The first and the second liquid chemical of the present invention are not limited to the aforementioned examples; and the present invention may be applied to a liquid chemical, which is precipitated in solution or causes other failures after a predetermined time passes since they are mixed.

EFFECT OF THE INVENTION

In accordance with the present invention, liquid chemical opening/closing units are provided in a first and a second liquid chemical supply line, respectively, in the vicinity of a junction therebetween; and at the same time, a plating solution opening/closing unit is provided in the vicinity of a discharge opening in an electroless plating solution supply line, wherein a volume of a supply line disposed between these valves substantially matches to a discharge amount required for a plating processing for one time. Thus, since both of the liquid chemicals are mixed together while the plating processing on the substrate is carried out until the plating processing on a subsequent substrate is started, i.e., since the liquid chemicals are mixed together right before the electroless plating processing is started, the electroless plating solution can be prevented from being kept in the unstable state as much as possible, and, e.g., precipitation in solution can be prevented. As a result, the electroless plating solution can be supplied onto the surface of the substrate in the identical state at all time so that a stable electroless plating processing can be carried out, and uniformities in the film thickness of inter-substrate and the film quality are improved.
While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined in the following claims.

Claims

1. An electroless plating apparatus, comprising:

a substrate supporting unit for supporting a substrate at a substantially horizontal position;

a first liquid chemical supply line for supplying a first liquid chemical therethrough;

a first liquid chemical supply source communicating with an upstream end of the first liquid chemical supply line;

a first liquid chemical opening/closing unit, installed in the vicinity of a downstream end of the first liquid chemical supply line, for controlling a flow of the first liquid chemical;

a second liquid chemical supply line for supplying a second liquid chemical therethrough;

a second liquid chemical supply source communicating with an upstream end of the second liquid chemical supply line;

a second liquid chemical opening/closing unit, installed in the vicinity of a downstream end of the second liquid chemical supply line, for controlling a flow of the second liquid chemical;

an electroless plating solution supply line, communicating with the downstream ends of the first and the second liquid chemical supply line, for supplying an electroless plating solution therethrough, which is formed by mixing the first and the second liquid chemical together, to supply same to a top surface of the substrate;

a supply line temperature control unit for adjusting a temperature of a plating solution in the electroless plating solution supply line;

a plating solution opening/closing unit, installed in the vicinity of a downstream end of the electroless plating solution supply line as a discharge opening thereof, for controlling a flow of the electroless plating solution; and

a control unit for controlling the first liquid chemical opening/closing unit, the second liquid chemical opening/closing unit and the plating solution opening/closing unit to supply the electroless plating solution to the top surface of the substrate,

wherein a volume in the electroless plating solution supply line surrounded by the first liquid chemical opening/closing unit, the second liquid chemical opening/closing unit and the plating solution opening/closing unit corresponds to a discharge amount required for performing an electroless plating processing on one substrate.

2. The electroless plating apparatus of claim 1, further comprising:

an upper temperature controller facing the top surface of the substrate supported by the substrate supporting unit, and at the same time, being made to be larger than an effective area of the substrate, the upper temperature controller having in a bottom surface thereof a discharge opening of the electroless plating solution supply line; and

a moving mechanism for relatively moving the upper temperature controller between a processing position for filling a space between the upper temperature controller and the top surface of the substrate with an electroless plating solution and a waiting position far away from the processing position.

3. The electroless plating apparatus of claim 2, wherein the upper temperature controller has therein a circulation chamber of a temperature control fluid, and

wherein the entire electroless plating solution supply line is disposed in the circulation chamber of the upper temperature controller such that the supply line temperature control unit adjusts a temperature of an electroless plating solution by a heat exchange between the temperature control fluid and the electroless plating solution.

4. The electroless plating apparatus of claim 2, wherein the upper temperature controller has therein a circulation chamber of a temperature control fluid, and

wherein, in the first and the second liquid chemical supply line, parts thereof filled with liquid chemicals that will subsequently fill the electroless plating solution supply line are disposed in the circulation chamber of the upper temperature controller.

5. The electroless plating apparatus of claim 1, wherein the first and the second liquid chemical supply line have temperature control units for controlling temperatures of parts thereof filled with liquid chemicals that will subsequently fill the electroless plating solution supply line.

6. The electroless plating apparatus of claim 1, wherein the first and the second liquid chemical opening/closing unit are also used as one liquid chemical opening/closing unit.

7. The electroless plating apparatus of claim 1, further comprising flow rate adjusting units for adjusting flow rates of the first and the second liquid chemical, respectively.

8. The electroless plating apparatus of claim 1, further comprising a lower temperature controller, disposed to face the bottom surface of the substrate, having a substrate temperature control unit for adjusting a temperature of the substrate.

9. The electroless plating apparatus of claim 8, wherein the substrate temperature control unit adjusts a temperature of the substrate by filling a space between the lower temperature controller and the substrate with a fluid, a temperature of which is adjusted in the lower temperature controller.

10. An electroless plating method using the electroless plating apparatus of claim 1, wherein the first liquid chemical is a solution containing a metal salt of a plating metal, and the second liquid chemical is a solution containing a reducing agent as an electron supply source.

11. An electroless plating method using the electroless plating apparatus of claim 1, wherein opening and closing operations of the first liquid chemical opening/closing unit, the second liquid chemical opening/closing unit and the plating solution opening/closing unit are simultaneously carried out.

12. An electroless plating method using the electroless plating apparatus of claim 2, wherein the supply line temperature control unit and the upper temperature controller are adjusted at a plating process temperature.

13. An electroless plating method using the electroless plating apparatus of claim 5, wherein the supply line temperature control unit and the temperature control units installed in the first and the second liquid chemical supply line are adjusted at a plating process temperature.

14. An electroless plating method using the electroless plating apparatus of claim 8, wherein the supply line temperature control unit and the substrate temperature control unit are adjusted at a plating process temperature.