JP2008013783A - Method and device for displacement plating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for displacement plating capable of reducing the dissolved oxygen concentration in a displacement plating liquid as much as possible, and using the displacement plating liquid for the displacement plating treatment while reducing the dissolved oxygen concentration in the displacement plating liquid. <P>SOLUTION: The device for displacement plating comprises a substrate holder 100 for holding a substrate with its surface downwardly, a sealed holding tank 104 for holding a displacement plating liquid 102, a treatment tank 106 in which the displacement plating liquid 102 held by the holding tank 104 is introduced inside, and the surface of the substrate held by the substrate holder 100 is brought into contact with the displacement plating liquid 102, and a liquid circulation passage 120 for circulating the displacement plating liquid 102 via the holding tank 104 and the treatment tank 106. The substrate holder 100 and the treatment tank 106 are arranged in a sealed casing 144 capable of controlling the internal atmosphere, and a diffuser tube 126 for reducing the dissolved oxygen concentration in the displacement plating liquid 102 by bubbling an inert gas in the displacement plating liquid 102 in the treatment tank 106 is arranged in the treatment tank 106. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a displacement plating method and apparatus, and more particularly to electroless plating prior to selectively forming a protective film by electroless plating on an exposed surface of an embedded wiring provided on the surface of a substrate such as a semiconductor wafer. The present invention relates to a displacement plating method and apparatus used for forming a catalytic metal film serving as a catalyst nucleus at the time of substitution reaction.

  In the back-end field of semiconductor device manufacturing, in order to ensure the reliability of semiconductor devices, for example, a protective film made of a CoWP alloy or the like is selectively formed on the exposed surface of a damascene copper wiring to protect the wiring. Has been.

FIG. 1 shows an example of forming a copper wiring in a semiconductor device in the order of steps. First, as shown in FIG. 1A, an insulating film (interlayer insulating film) such as an oxide film made of SiO ₂ or a Low-K material film is formed on a conductive layer 201a on a semiconductor substrate 201 on which a semiconductor element is formed. ) 202 is deposited, and a via hole 203 and a wiring groove 204 are formed as fine recesses for wiring inside the insulating film 202 by, for example, lithography / etching technique, and a barrier layer 205 made of TaN or the like is further formed thereon. A seed layer 206 as a power feeding layer for electrolytic plating is formed thereon by sputtering or the like.

  Then, as shown in FIG. 1B, copper is plated on the surface of the substrate W to fill the via holes 203 and the wiring grooves 204 of the substrate W with copper, and a copper film 207 is formed on the insulating film 202. Deposit. Thereafter, the barrier layer 205, the seed layer 206, and the copper film 207 on the insulating film 202 are removed by chemical mechanical polishing (CMP) or the like, and the surface of the copper film 207 filled in the via hole 203 and the wiring groove 204 is formed. The surface of the insulating film 202 is almost flush with the surface. Thereby, as shown in FIG. 1C, a wiring (copper wiring) 208 composed of the seed layer 206 and the copper film 207 is formed inside the insulating film 202.

Next, as shown in FIG. 1D, electroless plating is applied to the surface of the substrate W, and a protective film 209 made of a Co alloy, Ni alloy, or the like is selectively formed on the exposed surface of the wiring 208. Thus, the surface of the wiring 208 is covered with the protective film 209 to be protected.
Here, in order to selectively form the protective film 209 made of a CoWP alloy or the like on the surface of the wiring 208 made of copper or the like by electroless plating, the surface of the wiring 208 is replaced by plating on the surface before the electroless plating. It is common to provide a palladium (Pd) catalyst.

A step of applying a Pd catalyst to the surface of the wiring 208 by a substitution reaction using an acidic catalyst solution containing Pd, that is, a Pd metal film is formed on the surface of the wiring 208 by substitution plating using an acidic substitution plating solution. In the forming step, since dissolved oxygen is present in the catalyst solution (substitution plating solution), a substitution reaction between Pd and Cu occurs, and at the same time, dissolution of copper is promoted by a reduction reaction of oxygen. In particular, at the interface between the wiring 208 and the barrier layer 205, there is a tendency that local dissolution of copper is accelerated. Therefore, the flatness of the surface of the wiring 208 is not impaired, and the resistance of the wiring 208 increases. In order to avoid this, the applicant has proposed to reduce the dissolved oxygen concentration in the catalyst solution (substitution plating solution) as much as possible (see Patent Document 1).
JP 2005-29810 A

  However, merely reducing the dissolved oxygen concentration in the catalyst solution (displacement plating solution) prevents copper dissolution as much as possible, and suppresses the resistance increase rate of the copper wiring to 3% or less, preferably 2% or less, for example. It was found that it was difficult to perform the Pd catalyst application (substitution plating) treatment.

  On the other hand, in the front end of semiconductor device manufacturing, a process of reducing the contact resistance of the electrode part by forming an alloy film such as cobalt or nickel on the gate electrode part or drain / source silicon by electroless plating is considered. . Thus, in order to form an alloy film on silicon by electroless plating, it is necessary to form a metal film serving as a catalyst nucleus on silicon by displacement plating before that. In general, if the oxygen-dissolved concentration in the displacement plating solution is high, the displacement efficiency between the catalytic metal and the silicon base during displacement plating decreases, and excess silicon is eluted in the displacement plating solution.

  As a device for forming a metal film serving as a catalyst on the surface of a copper wiring or the like by displacement plating, a device in which a catalyst solution (displacement plating solution) is sprayed from a spray nozzle toward the surface of a substrate is widely known. Yes. In this case, however, the catalyst solution (substitution plating solution) sprayed from the spray nozzle reaches the substrate even if the catalyst solution (substitution plating solution) is one in which the dissolved oxygen concentration in the solution is reduced as much as possible. In the meantime, oxygen is again taken into the catalyst solution (substitution plating solution), and it becomes difficult to reduce the dissolved oxygen concentration in the catalyst solution (substitution plating solution) during the substitution plating treatment.

  The present invention has been made in view of the above circumstances. For example, it is possible to perform a Pd catalyst application (substitution plating) treatment in which the rate of increase in resistance of copper wiring is suppressed to 3% or less, preferably 2% or less. Displacement plating method, and the dissolved oxygen concentration in the displacement plating solution can be reduced as much as possible, and the displacement plating solution can be used for displacement plating treatment while the dissolved oxygen concentration in the solution is reduced. An object of the present invention is to provide a displacement plating apparatus.

  The invention according to claim 1 pre-cleans the metal base surface in contact with a cleaning liquid containing an organic acid, and the pre-cleaned metal base surface has a dissolved oxygen concentration in the liquid lower than the saturated oxygen solubility at the operating temperature, Preferably, the displacement plating method is characterized in that it is brought into contact with a displacement plating solution reduced to 70% or less and a metal film is formed on the surface of the metal base by a substitution reaction.

  In this way, by combining the pre-cleaning treatment in which the metal base surface such as copper wiring is brought into contact with the cleaning solution containing the organic acid, and the replacement plating processing using the replacement plating solution in which the dissolved oxygen concentration in the solution is reduced. In other words, before performing displacement plating, the oxide and anticorrosive material remaining on the surface of the metal base is cleaned and removed with a cleaning liquid containing an organic acid while suppressing the etching of the metal base, for example, copper. It is possible to perform the Pd catalyst application (substitution plating) treatment that prevents the dissolution as much as possible and suppresses the resistance increase rate of the copper wiring to, for example, 3% or less, preferably 2% or less.

  The invention according to claim 2 is a displacement plating method characterized in that the dissolved oxygen concentration in the displacement plating solution is 40% or less of the saturated oxygen solubility at the operating temperature.

  According to a third aspect of the present invention, the metal base is an embedded wiring embedded in a wiring recess formed on the surface of the substrate, and the metal film is formed when a protective film is formed on the surface by electroless plating. 3. The displacement plating method according to claim 1, wherein the displacement plating method is a catalytic metal film serving as a catalyst nucleus.

The invention according to claim 4 is characterized in that the displacement plating solution contains an organic acid contained in the cleaning solution and / or a compound having an N atom which is chemically adsorbed on a metal substrate. The displacement plating method according to claim 1.
Thus, by including the organic acid contained in the cleaning solution in the displacement plating solution, one part of the metal ions in the displacement plating solution is complexed with the organic acid, and the etching effect of the metal base is relaxed, The influence of the mixing of the cleaning solution into the replacement plating solution can be ignored. Further, the substitution plating solution contains a compound having N atoms that are chemically adsorbed on the metal substrate, so that the compound having N atoms can be selectively adsorbed on the crystal grain boundary of the metal substrate during the substitution plating. Can be protected.

  The invention according to claim 5 introduces a substrate holder for holding a substrate with the surface facing downward, a sealed holding tank for holding a replacement plating solution, and a replacement plating solution held in the holding tank. And a treatment tank for bringing the surface of the substrate held by the substrate holder into contact with a replacement plating solution, and a liquid circulation system for circulating the replacement plating solution through the holding tank and the treatment tank, The holder and the processing tank are arranged in a sealed casing capable of controlling the internal atmosphere, and in the processing tank, an inert gas is bubbled into the replacement plating solution of the processing tank to replace the inside of the replacement plating solution. The displacement plating apparatus is characterized in that an air diffuser for reducing the dissolved oxygen concentration is disposed.

  As a result, the dissolved oxygen concentration in the replacement plating solution is reduced in the holding tank away from the treatment tank, and the replacement plating solution with the reduced dissolved oxygen concentration is prevented from coming into contact with the air as much as possible. By carrying out the displacement plating treatment by contacting, the displacement plating solution can be used for the displacement plating treatment while the dissolved oxygen concentration in the solution is reduced.

The invention according to claim 6 allows the replacement plating solution to circulate through the liquid circulation system at a flow rate of 0.3 to 3 L / min while passing through the diffuser tube in the replacement plating solution of the holding tank. The displacement plating apparatus according to claim 5, wherein an inert gas of 1 to 10 L / min is introduced.
Thereby, it is possible to reduce the dissolved oxygen concentration in the substitution plating solution to 1/3 or less of the saturation solubility while preventing an increase in the amount of oxygen taken into the substitution plating solution from the gas-liquid free surface.

  The invention described in claim 7 introduces a substrate holder for holding the substrate with the surface facing downward, a sealed holding tank for holding the replacement plating solution, and a replacement plating solution held in the holding tank. And a processing tank for bringing the surface of the substrate held by the substrate holder into contact with the plating solution, and a liquid circulation system for circulating the replacement plating solution through the holding tank and the processing tank, and the substrate holder And the said processing tank is arrange | positioned in the sealed housing which can control internal atmosphere, The deaeration module is interposed in the said liquid circulation system path | route, It is a displacement plating apparatus characterized by the above-mentioned.

  As a result, the dissolved oxygen concentration in the displacement plating solution flowing along the liquid circulation system is reduced, and the displacement plating solution with the reduced dissolved oxygen concentration is kept in contact with the substrate while preventing contact with air as much as possible. By performing the displacement plating treatment, the displacement plating solution can be used for the displacement plating treatment while the dissolved oxygen concentration in the solution is reduced.

The invention according to claim 8 is the displacement plating apparatus according to claim 7, wherein the displacement plating solution is circulated at a flow rate of 1 to 4 L / min through the liquid circulation system.
It has been confirmed that the degassing efficiency of the replacement plating solution is the highest in the flow rate range of the replacement plating solution.

According to a ninth aspect of the present invention, in the upper portion of the holding tank, there is a constricted portion that minimizes the cross-sectional area at the free liquid level position of the replacement plating solution. It is a displacement plating apparatus of description.
Thereby, it can prevent as much as possible that the dissolved oxygen concentration of the displacement plating solution located in a holding tank raises.

The invention according to claim 10 is characterized in that a plurality of rectifying plates for arranging the flow of the displacement plating solution flowing inside the treatment tank are arranged in the treatment tank. It is a displacement plating apparatus of description.
Thereby, a metal film having a uniform film thickness can be formed on the surface of the substrate by displacement plating.

  The invention according to claim 11 is characterized in that the displacement plating solution contains an organic acid contained in the cleaning solution and / or a compound having N atoms which are chemically adsorbed on a metal substrate. A displacement plating apparatus according to claim 1.

  According to the displacement plating method of the present invention, a pre-cleaning treatment in which a metal base surface such as copper is brought into contact with a cleaning solution containing an organic acid, and a displacement plating treatment using a displacement plating solution in which the dissolved oxygen concentration in the solution is reduced, For example, a Pd catalyst application (substitution plating) treatment that prevents the dissolution of copper as much as possible and suppresses the rate of increase in resistance of the copper wiring to, for example, 3% or less, preferably 2% or less is performed. It becomes possible. Further, according to the displacement plating apparatus of the present invention, the displacement plating solution can be used for the displacement plating treatment while the dissolved oxygen concentration in the solution is reduced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the following example, a catalyst applying device using a catalyst solution as a replacement plating solution is used as the replacement plating device, and the surface of the wiring 208 made of copper as a metal base shown in FIG. A palladium metal film is formed as a catalyst nucleus by plating, and then, as shown in FIG. 1D, the surface of the wiring 208 on which the palladium metal film is formed as a catalyst nucleus is made of a CoWP alloy by electroless plating. An example in which the protective film 209 is formed is shown.

  In addition to copper, the metal substrate may be a copper alloy, Al, Ag, or an alloy thereof, W, Ta, Ti, Ru, an alloy thereof, or the like. Further, Si, Ge or a compound thereof may be used. The displacement plating may contain at least one metal selected from Ag, Co, Ni, Au, and Pt in addition to Pd.

  FIG. 2 includes a replacement plating apparatus according to an embodiment of the present invention, and a protective film used to selectively form a protective film 209 made of a CoWP alloy or the like on the exposed surface of the embedded wiring 208 by electroless plating. An overall configuration of the forming apparatus 50 is shown. As shown in FIG. 2, the protective film forming apparatus 50 includes a load / unload unit 1, a transfer robot 2, a rinse / drying apparatus 3, a transfer robot 4, a pre-cleaning apparatus 5, and a catalyst applying apparatus (substitution plating apparatus) 7. , An electroless plating apparatus 9 and a substrate delivery apparatus 17 are provided. Further, the protective film forming apparatus 50 is a low oxygenated gas supply device 11 capable of controlling the temperature and humidity in the device, a low oxygenated gas supply port 12, and a gas provided in each device is circulated or discharged. An exhaust port 13 for discharging to the device, a gas circulation device 14 for circulating gas from the exhaust port 13, and a circulation gas supply port 15 are provided.

  In this protective film forming apparatus 50, low oxygen gas whose temperature and humidity are controlled is sent from the low oxygen gas supply device 11 through the low oxygen gas supply port 12, and the rinse / drying device 3 is transported. The environment of the robot 4, the pre-cleaning device 5, the catalyst applying device 7, the electroless plating device 9, and the substrate delivery device 17 as a whole is set to a low oxygen condition. The rinse / drying device 3, the pre-cleaning device 5, the catalyst applying device 7, and the electroless plating device 9 are respectively supplied with means for supplying and discharging pure water, cleaning solution and electroless plating solution, and the respective solutions. A device for reducing the dissolved oxygen concentration therein is provided.

  FIG. 3 shows an outline of the displacement plating apparatus 7 according to the embodiment of the present invention applied to the catalyst applying apparatus. The catalyst applying device (displacement plating device) 7 uses an acidic catalyst solution containing catalytic metal ions such as palladium ions as a replacement plating solution, and copper (Cu) constituting the wiring 208 and Pd in the catalyst solution. Is used to form a Pd metal film made of Pd serving as catalyst nuclei on the surface of the wiring 208.

  As shown in FIG. 3, the catalyst applying device (displacement plating device) 7 includes a substrate holder 100 that holds the substrate W with the surface facing downward, and a vertically movable and rotatable substrate holder 100, and a catalyst solution (displacement plating solution) 102. A holding tank 104 to be held, and a catalyst tank 102 held in the holding tank 104 are introduced into the inside, and the surface of the substrate W held by the substrate holder 100 is brought into contact with the catalyst solution 102. have. The processing tank 106 is disposed above the holding tank 104. The holding tank 104 and the bottom wall of the processing tank 106 are connected by a liquid supply pipe 114 in which a circulation pump 108, a filter 110, and a degassing module 112 are installed. The liquid recovery groove 116 and the holding tank 104 are connected by a liquid recovery pipe 118. Thus, the catalyst solution 102 in the holding tank 104 is introduced into the processing tank 106 as the circulation pump 108 is driven, and the catalyst solution 102 overflowed into the liquid recovery groove 116 of the processing tank 106 is held by its own weight. A liquid circulation system path 120 is configured to return to the tank 104 and circulate.

  A filter having a mesh size of 0.2 μm or less, preferably 0.05 μm or less is used as the filter 110. The volume of the processing tank 106 is, for example, 20 L or less and preferably about 7 L. The volume of the holding tank 104 is, for example, 1.5 to 10 times that of the solution in the processing tank 106, and is preferably about 4 times. The amount of the catalyst solution 102 is, for example, 5 to 100 L, and preferably 15 to 40 L.

The holding tank 104 is sealed with a lid body 122 that can be opened and closed by automatic control. An inert gas introduction for introducing an inert gas such as N ₂ gas into the space above the catalyst solution 102 in the holding tank 104 is introduced into this peripheral wall. A tube 124 is connected. The flow rate of the inert gas introduced into the holding tank 104 from the inert gas introduction pipe 124 is adjusted at, for example, 0 to 10 L / min. Further, a diffuser pipe 126 having a large number of diffuser holes is arranged in the vicinity of the bottom portion immersed in the catalyst solution 102 in the holding tank 104. The air diffuser 126 is used for bubbling an inert gas such as N ₂ gas into the catalyst solution 102 in the holding tank 104 to reduce the dissolved oxygen concentration in the catalyst solution 102. Connected to tube 128. The flow rate of the inert gas introduced into the holding tank 104 through the air diffuser 126 is adjusted, for example, at 1 to 20 L / min.

The treatment tank 106 is configured to introduce the catalyst solution 102 into the inside from the bottom, create a flow upward of the catalyst solution 102, and overflow the peripheral wall. The treatment tank 106 has a catalyst flowing therethrough. Two rectifying plates 130a and 130b that arrange the flow of the solution 102 are arranged. Further, an air diffusion tube 132 having a large number of air diffusion holes is disposed around the bottom of the processing tank 106. The diffuser tube 132 is used for bubbling an inert gas such as N ₂ gas into the catalyst solution 102 in the treatment tank 106 to reduce the dissolved oxygen concentration in the catalyst solution 102. Connected to tube 134. The flow rate of the inert gas introduced into the processing tank 106 through the air diffuser 132 is adjusted at, for example, 0 to 10 L / min.

  A processing tank lid 136 is disposed in the vicinity of the processing tank 106 so as to automatically open and close the upper end opening of the processing tank 106. A pure water spray nozzle 138 for injecting pure water for rinsing upward is attached to the upper surface of the treatment tank lid 136, and the pure water spray nozzle 138 is connected to a pure water supply pipe 140 extending from the outside. ing. Thus, the substrate W held by the substrate holder 100 is lowered in a state where the processing tank lid 136 is retracted from the position covering the upper end opening of the processing tank 106, and the surface (lower surface) of the substrate W is placed in the processing tank 106. The catalyst solution 102 is contacted. Then, after the substrate W held by the substrate holder 100 is raised, the processing tank lid 136 is positioned so as to cover the upper end opening of the processing tank 106, and pure water (rinsing liquid) is directed from the pure water spray nozzle 138 toward the substrate W. ) And the surface of the substrate W is rinsed with pure water. At this time, the pure water is prevented from flowing into the treatment tank 106.

Further, when the upper end opening of the processing tank 106 is covered with the processing tank lid 136, an inert gas such as N ₂ gas is formed in the space between the free surface of the catalyst solution 102 in the processing tank 106 and the processing tank lid 136. An inert gas introduction pipe 141 is provided. The flow rate of the inert gas introduced from the inert gas introduction pipe 141 into the space between the free surface of the catalyst solution 102 in the treatment tank 106 and the treatment tank lid 136 is adjusted, for example, at 0 to 10 L / min. .

The substrate holder 100, the processing tank 106, and the processing tank lid 136 are disposed inside a housing 144 that can control the internal atmosphere via the atmosphere control unit 142. The housing 144 has a window for taking in and out the substrate, and adjusts the atmosphere in the housing 144 according to the flow rate and discharge flow rate of an inert gas such as N ₂ gas to be introduced.

Next, a processing procedure of the substrate W by the catalyst applying device 7 will be described.
First, the substrate W is introduced into the housing 144 from a window (not shown) provided in the housing 144, and the substrate W is held with the substrate holder 100 installed above the processing bath 106 facing down. To do. Then, after closing the window of the casing 144 and adjusting the inside of the casing 144 to a predetermined inert gas atmosphere, the processing tank lid 136 covering the upper end opening of the processing tank 106 is moved to the retracted position, and the substrate W is set to a predetermined position. The catalyst metal 102 is brought into contact with the catalyst solution 102 in the treatment tank 106 while rotating at a rotation speed of, for example, 0 to 100 rpm, whereby the catalyst metal is formed on the surface of the substrate by displacement plating, that is, in this example, the wiring 208 (FIG. 1). A Pd metal film is formed as a catalyst nucleus on the surface of (c).

As the catalyst solution 102, for example, a solution in which a concentration of PdSO ₄ of about 0.1 g / L or less is dissolved in an aqueous solution of H ₂ SO ₄ of a concentration of 100 g / L or less and the pH is adjusted to 2 or less is used. . In the catalyst solution 102, an organic acid such as carboxylic acid or alkanesulfonic acid, or a compound having an N atom such as benzotriazole, pyrazole, imidazole, or benzimidazole, contained in the following pretreatment liquid, is included as necessary. Added. The processing time is, for example, about 30 seconds.

At this time, an inert gas such as N ₂ gas is introduced into the catalyst solution 102 in the holding tank 104 through the air diffusion pipe 126 while circulating the catalyst solution 102 via the liquid circulation system 120. Further, if necessary, introducing an inert gas such as _{N 2} gas in the holding tank 104 from the inert gas inlet tube 124, at the same time, through the diffusion pipe 132, in the catalyst solution 102 in the treating tank 106 _{N 2} An inert gas such as a gas is introduced.

  Thereby, while reducing the dissolved oxygen concentration in the catalyst solution 102 in the holding tank 104 away from the treatment tank 106, and while preventing the catalyst solution 102 having the reduced dissolved oxygen concentration from coming into contact with air as much as possible, By performing the displacement plating process in contact with the substrate, the catalyst solution (replacement plating solution) 102 can be used for the displacement plating process while the dissolved oxygen concentration in the liquid is reduced.

  In particular, when the deaeration module 112 in this example is omitted, the catalyst solution 102 in the holding tank 104 is circulated through the liquid circulation system 120 at a flow rate of 0.3 to 3 L / min. In addition, by introducing an inert gas of 1 to 10 L / min through the diffuser tube 126, the amount of oxygen taken into the catalyst solution 102 from the gas-liquid free surface is prevented, and dissolved in the catalyst solution 102 The oxygen concentration can be reduced to 1/3 or less of the solubility.

  Here, in this example, by providing the degassing module 112 in the liquid circulation path 120, the dissolved oxygen concentration in the catalyst solution 102 flowing along the liquid circulation path 120 can be reduced. In this case, the degassing efficiency of the catalyst solution 102 can be maximized by circulating the catalyst solution 102 at a flow rate of 1 to 4 L / min via the liquid circulation path 120.

As a result, the surface of the metal substrate such as the wiring 208 of the substrate after the pre-cleaning is reduced to a dissolved oxygen concentration in the liquid lower than the saturated oxygen solubility at the operating temperature, preferably 70% or less, more preferably 40% or less. A metal film such as a Pd metal film is formed on the surface of the metal base by a substitution reaction in contact with the displacement plating solution.
Further, for the purpose of increasing the reducibility of the catalyst solution, elution of the metal substrate such as the wiring 208 can be suppressed by dissolving hydrogen having a relatively low standard unipolar potential in the catalyst solution.

Then, after pulling up the substrate W from the catalyst solution 102, the upper end opening of the processing tank 106 is covered with a processing tank lid 136. In this state, if necessary, an inert gas such as N ₂ gas is introduced from the inert gas introduction pipe 141 into the region covered with the treatment tank lid 136 so that the catalyst solution 102 comes into contact with the air and dissolves. While preventing the oxygen concentration from increasing, pure water is sprayed from the pure water spray nozzle 138 installed on the upper surface of the treatment tank lid 136 to rinse the substrate W. After rinsing, by rotating the substrate W, the catalyst solution 102 remaining on the surface of the substrate W is shaken out to some extent, and the substrate W is pulled out from the housing 144.

  As described above, by supplying the catalyst solution 102 to the inside of the processing tank 106 from below, the liquid level of the catalyst solution 102 supplied and held in the processing tank 106 is bubbled, and the catalyst solution 102 is in the atmosphere. It is possible to prevent an increase in the amount of dissolved oxygen in the catalyst solution 102 due to the air being entrained. Further, the catalyst solution 102 overflowing the processing tank 106 is returned to the holding tank 104 through the liquid recovery pipe 118, and the lower end of the liquid recovery pipe 118 reaches below the liquid level of the catalyst solution 102 in the holding tank 104. By doing so, it is possible to prevent ripples due to the return liquid of the catalyst solution 102 in the holding tank 104.

  Further, the surface (lower surface) of the substrate W held horizontally by the substrate holder 100 is simultaneously brought into contact with the catalyst solution 102 in the processing tank 106, thereby making the flow of the catalyst solution 102 near the surface of the substrate W uniform. Variations in plating growth on the surface of W can be prevented. Moreover, the flow of the catalyst solution in the treatment tank 106 can be made more uniform through the rectifying plates 130a and 130b.

  In this example, a rectangular box-shaped container is used as the holding tank 104. However, as shown in FIG. 4, a narrowed portion that minimizes the cross-sectional area at the free liquid surface position of the catalyst solution 102 is provided at the top. Providing 104a may prevent the dissolved oxygen concentration of the catalyst solution 102 located in the holding tank 104 from increasing as much as possible.

Next, processing of the substrate W by the electroless plating system shown in FIG. 2 will be described.
First, the substrate W formed with the wiring 208 shown in FIG. 1C is transferred from the load / unload unit 1 to the transfer device 17 by the transfer robot 2.

  Subsequently, the substrate in the delivery device 17 is introduced into the pre-cleaning device 5 by the transfer robot 4, and the surface of the substrate is pre-cleaned by contacting with a cleaning liquid containing an organic acid such as carboxylic acid or alkanesulfonic acid, thereby The surface of the wiring 208 is activated by removing the oxide and anticorrosive remaining on the surface of the substrate while suppressing the etching of the wiring 208 as a metal base. As this cleaning solution, a solution obtained by adding a compound having an N atom that is chemically adsorbed to the wiring (metal base) 208 such as benzotriazole, pyrazole, imidazole, or benzimidazole may be used. Thereby, a compound having N atoms is preferentially attached to the gaps between the crystal grain boundaries of the wiring 208, and the intrusion of the catalyst solution into the crystal grain boundaries can be prevented, thereby suppressing an increase in wiring resistance.

  As the pre-cleaning liquid, citric acid having a pH of 2 or more, preferably 2 to 5 or an organic acid mainly composed of citric acid may be used. As a method for bringing the pre-cleaning liquid into contact with the substrate W, an arbitrary method such as an immersion method, a spray method or a roll cleaning method is adopted. The pre-cleaning time is, for example, 10 seconds or more at room temperature, and the substrate may be rotated at that time.

  In this pre-cleaning device 5, there is a possibility that an unexpected gas or the like may be generated. Therefore, the gas discharged from the exhaust port 13 is not circulated as it is, and preferably is not directly discharged outside the device. To send to. The treatment liquid used in the pre-cleaning device 5 preferably has a reduced dissolved oxygen concentration, and the pre-cleaning device 5 and the entire apparatus are in a low oxygen condition. There is no possibility that the dissolved oxygen concentration will increase in the subsequent transport process.

  After supplying pure water to the surface of the substrate after pre-cleaning by the pre-cleaning device 5 and rinsing, the substrate is transferred to a catalyst applying device (substitution plating device) 7 where the surface of the substrate W is as described above. Is subjected to displacement plating by contacting the catalyst solution 102, thereby forming a Pd metal film as a catalyst nucleus on the surface of the wiring 208. Then, pure water is supplied to the surface of the substrate in the catalyst applying device 7 and rinsed.

  The catalyst solution 102 may contain an organic acid such as carboxylic acid contained in the cleaning liquid and / or a compound such as benzotriazole having an N atom that is chemically adsorbed on the metal substrate. Thus, by including the organic acid contained in the cleaning solution in the catalyst solution 102, a part of the metal ions (Pd ions) in the catalyst solution 102 is complexed with the organic acid, and the etching effect of the wiring 208 is reduced. In addition, the influence of the mixing of the cleaning liquid into the catalyst solution 102 can be ignored. In addition, the catalyst solution 102 includes a compound having an N atom that is chemically adsorbed on the wiring 208, whereby the compound having an N atom is selectively adsorbed on the crystal grain boundary of the wiring 208 in the catalyst solution 102. 208 can be protected.

  In this catalyst applying device 7, there is a risk that an unexpected gas or the like may be generated. Therefore, the gas discharged from the exhaust port 13 is not circulated as it is, and preferably is not directly discharged outside the device. To send to.

  Under such conditions, the substrate on which the Pd metal film serving as the catalyst core is formed is transferred by the transfer robot 4 to the electroless plating apparatus 9 that forms a protective film by electroless plating. In the electroless plating apparatus 9, a protective film 209 made of, for example, a CoWP alloy (see FIG. 1D) is formed on the surface of the wiring 208 on which a Pd metal film is formed as a catalyst nucleus. Regarding the plating solution used in the electroless plating apparatus 9, the dissolved oxygen concentration can be reduced as necessary. The apparatus is kept in a low oxygen condition. Further, since the plating solution may generate gas or the like, the gas discharged from the exhaust port 13 is not circulated as it is, and preferably is not directly discharged outside the apparatus but sent to the exhaust gas treatment apparatus. To do.

The composition and conditions of this CoWP electroless plating solution are as follows, for example.
CoWP electroless plating solution Composition:
Sodium hypophosphite 10g / L
Cobalt sulfate 4g / L
Sodium citrate 40g / L
Boric acid 30g / L
Sodium tungstate 6g / L
Conditions:
Liquid temperature 75 ℃
pH 9 (sodium hydroxide was used for pH adjustment)

Then, the substrate W on which the protective film 209 is formed is transferred to the rinsing / drying apparatus 3 by the transfer robot 4. At this stage, since the wiring 208 is not exposed to the atmosphere, it is not necessary to reduce dissolved oxygen. However, for the convenience of taking in and out the substrate W, the inside of the apparatus is kept under a low oxygen condition. Although depending on the cleaning process, the gas discharged from the exhaust port 13 is not circulated as it is, and preferably is not discharged as it is to the outside but is sent to the exhaust gas treatment device.
Then, after the substrate W is introduced into the atmospheric gas replacement chamber 3 by the transfer robot 4, the substrate W is transferred to the load / unload unit 1 by the transfer robot 2 and transferred to the next process.

  According to this example, a pre-cleaning treatment in which the surface of the wiring 208 is brought into contact with a cleaning solution containing an organic acid, and a catalyst application (substitution) using a catalyst solution (replacement plating solution) 102 in which the dissolved oxygen concentration in the solution is reduced. In combination with the plating process, that is, before applying the catalyst, the oxide and the anticorrosive remaining on the surface of the wiring 208 are suppressed from being etched with a cleaning solution containing an organic acid. However, it is possible to prevent the dissolution of copper as much as possible by reliably cleaning and removing the Pd, and the resistance increase rate of the wiring 208 made of copper can be suppressed to, for example, 3% or less, preferably 2% or less. It is possible to perform catalyst application (substitution plating) treatment.

  In the apparatus of the present invention, the oxygen-reducing gas supply device 11 can use a method of removing oxygen in the circulated gas in addition to using an inert gas. The gas flow rate of the low oxygenation gas supply device 11 is preferably adjusted according to the oxygen concentration in the device.

  A planarization apparatus used in a planarization process such as CMP is also reduced in oxygen as shown in FIG. FIG. 5 shows an example of the overall configuration of a substrate processing apparatus in which this planarization apparatus is connected to the protective film forming apparatus of FIG. FIG. 5 is a drawing showing the overall configuration of the substrate processing apparatus from the planarization process to the protective film formation.

  In addition to the protective film forming apparatus 50 shown in FIG. 2, the substrate processing apparatus includes a cassette 21, a transfer robot 22, an atmospheric gas replacement chamber 23, a transfer robot 24, a flattening apparatus 25, a cleaning / drying apparatus 26, Low oxygenated gas supply device 27 capable of controlling temperature and humidity, low oxygenated gas supply port 28, circulating gas supply port 29, and exhaust for exhausting gas provided in each device to the circulating or exhaust gas processing device A flattening device 52 having a gas circulation device 31 that circulates gas from the port 30 and the exhaust port 30 is provided. The protective film forming apparatus 50 and the planarizing apparatus 52 are connected by a substrate transport unit 32 that can transport the substrate W under low oxygen conditions.

  In this substrate processing apparatus, each apparatus can individually create a hypoxic state, but the substrate transport unit 32 can transport the substrate while maintaining the hypoxic state between the apparatuses. . The substrate transport by the substrate transport unit 32 is not limited to a dry state, but can be performed in a wet state.

  By using the substrate transfer unit 32, the processing time is shortened and the inert gas is saved. Further, by carrying the substrate by the substrate carrying unit 32 in a wet state, there is no fear of adhesion of particles due to drying of the substrate, and further, the protective film is maintained while suppressing the oxidation of the wiring 208 and maintaining the wet state as it is. Since 209 can be formed, an ideal protective film 209 is formed.

  However, when a process that modifies the substrate surface in a dry state is necessary as the finishing of the planarization step, the substrate transport by the substrate transport unit 32 may be in a dry state in a low oxygen atmosphere as it is.

  As shown in FIG. 5, it is also preferable not to use the connection method but to configure all the apparatuses related to the wet process from the planarization process to the protective film formation process as one apparatus to create a low oxygen state. However, considering the case where a new process is added from the planarization process to the protective film formation process in the future, the connection type as shown in FIG. It is done.

  Next, the protective film forming apparatus 50 shown in FIG. 2 provided with the catalyst applying apparatus (displacement plating apparatus) 7 in which the deaeration module 112 shown in FIG. 3 is omitted is used, and the conditions are changed, and FIG. As shown, the results when a protective film 209 made of a CoWP alloy is formed on the surface of the wiring 208 will be described below. Here, a 300 mm semiconductor wafer was used as the substrate. The catalyst solution is used at room temperature, and the dissolved oxygen concentration that reaches the saturated oxygen solubility at room temperature of the catalyst solution is about 8.4 ppm. And the electrical resistance with respect to the specific wiring after protective film formation was measured, and the change value (resistance increase rate) was computed compared with the value before a process. Moreover, the dissolved oxygen concentration in the catalyst solution (substitution plating solution) at the time of the catalyst provision (substitution plating) process of a board | substrate was measured. Table 1 shows the processing conditions of each substrate and the average value of the rate of increase in resistance of each wiring.

Substrate No. 1, the catalyst application treatment was performed on the surface of the substrate without bubbling N ₂ gas through the air diffuser 126 into the catalyst solution 102 in the treatment tank 106. The dissolved oxygen concentration at this time is 8.4 ppm near the saturated oxygen solubility, and the resistance increase rate is 6.3%. Thereby, in this case, it can be seen that the rate of increase in resistance cannot be suppressed to about 3% or less.

  Next, when the pre-cleaning of the substrate is performed using a cleaning liquid containing an organic acid that has an effect of suppressing the etching of the wiring (No. 2 to No. 18), and when the pre-cleaning of the substrate is not performed ( No. 19 to No. 21), when the pre-cleaning is performed (No. 2 to No. 18), the resistance increase rate is suppressed to about 3% or less, preferably 2% or less. When pre-cleaning is not performed (No. 19 to No. 21), the rate of increase in resistance exceeds 4%. In this way, by combining the pre-cleaning treatment in contact with the cleaning liquid containing the organic acid and the catalyst application (substitution plating) process using the catalyst solution (displacement plating liquid) in which the dissolved oxygen concentration in the liquid is reduced, It can be seen that the rate of increase in resistance of the wiring can be suppressed to, for example, 3% or less, preferably 2% or less.

However, for example, the substrate No. As shown in FIG. 4, when the circulating flow rate is as high as 5 L / min, the resistance increase rate exceeds 3%. Therefore, in order to keep the resistance increase rate within 3%, the circulating flow rate is set to 3 L / min or less. In order to keep the resistance increase rate within 2%, the circulation flow rate is preferably 1 L / min or less.
As a result, the dissolved oxygen concentration in the catalyst solution can be reduced to about 3.3 ppm or less, which is about 40% of the saturated oxygen solubility, and the resistance increase rate can be suppressed to about 3% or less.

Substrate No. 5, no. 6 shows a case where the catalyst application treatment was performed under the condition that the flow rate of the N ₂ gas bubbled into the catalyst solution 102 in the holding tank 104 was changed. 2, when the flow rate of N ₂ gas bubbling into the catalyst solution 102 in the holding tank 104 decreases, the dissolved oxygen concentration increases and the resistance increase rate also increases. Thereby, in order to suppress the resistance increase rate to 2% or less, it is desirable to maintain the flow rate of N ₂ gas to be bubbled into the catalyst solution 102 in the holding tank 104 at 10 L / min or more.

Substrate No. 7-No. Reference numeral 9 denotes a case in which N ₂ gas is bubbled through the diffusion tubes 106 and 132 into the catalyst solution 102 in both the holding tank 104 and the processing tank 106. In this case, since the total flow rate of the N ₂ gas introduced into the catalyst solution 102 increases, the effect of reducing the dissolved oxygen concentration is promoted. For this reason, even if the circulation flow rate is 3 L / min, the wiring resistance increase rate can be suppressed to 2% or less.

Substrate No. 10-No. No. 12 is a case where the flow rate of N ₂ gas introduced into the catalyst solution 102 is 10 L / min, but N ₂ gas is put into the catalyst solution 102 in both the holding tank 104 and the treatment tank 106 by 5 L / min. is there. In this case, the substrate No. 2-No. It can be seen that almost the same effect was obtained as compared to 4.
Substrate No. 13-No. Reference numeral 18 denotes a case in which N ₂ gas is sealed in the upper atmosphere of at least one of the holding tank 104 and the processing tank 106. Under either condition, the effect of reducing the increase in wiring resistance is recognized, although slightly less than the same condition in which N ₂ gas is not sealed.

Next, the results obtained when a protective film 209 made of a CoWP alloy was formed on the surface of the wiring 208 in the same manner as described above except that a catalyst solution to which a compound containing an organic acid and an N atom was added were used. It is shown in 2.

  Substrate No. shown in Table 1 2-No. 4 and Table 2 shown in Table 2. 22-No. 24, by using a catalyst solution (displacement plating solution) to which a compound containing an organic acid and an N atom is added, a catalyst application (displacement plating) treatment is performed, thereby further reducing the increase in wiring resistance. You can see it.

  Next, the protective film forming apparatus 50 shown in FIG. 2 provided with the catalyst applying apparatus (displacement plating apparatus) 7 having the deaeration module 112 shown in FIG. 3 is used, and the CoWP is formed on the surface of the wiring 208 in the same manner as described above. Table 3 shows the results when the protective film 209 made of an alloy is formed. No organic acid and a compound containing an N atom are added to the catalyst solution.

表１の基板Ｎｏ．１に比較すると、表３に示す基板Ｎｏ．２５〜Ｎｏ．２８には、配線の抵抗上昇率の低減効果が見られる。特に、流量が３Ｌ／ｍｉｎの条件では、脱気効果および配線抵抗上昇の抑制効果が最も顕著であることが判る。
基板Ｎｏ．２８は、脱気モジュール１１２による脱気処理と、保持槽１０４内の触媒溶液１０２中へのＮ_２ガスのバブリング処理を併用のケースであり、単一条件に比べて、脱気効果及び配線抵抗上昇の抑制効果がより顕著であることが判る。

Substrate No. in Table 1 As compared with the substrate No. 1, the substrate No. 25-No. 28 shows the effect of reducing the rate of increase in resistance of the wiring. In particular, it can be seen that the deaeration effect and the effect of suppressing the increase in wiring resistance are most remarkable under the condition of a flow rate of 3 L / min.
Substrate No. 28 is a case in which the deaeration process by the deaeration module 112 and the bubbling process of N ₂ gas into the catalyst solution 102 in the holding tank 104 are used in combination, and the deaeration effect and the wiring resistance are compared with a single condition. It can be seen that the effect of suppressing the rise is more remarkable.

It is a figure which shows the copper wiring formation example in a semiconductor device in order of a process. It is a figure which shows the whole structure of the protective film formation apparatus provided with the displacement plating apparatus (catalyst provision apparatus) of embodiment of this invention. It is a schematic diagram of the displacement plating apparatus (catalyst provision apparatus) of FIG. It is a figure which shows the modification of the processing tank of the displacement plating apparatus (catalyst provision apparatus) of FIG. It is a figure which shows the whole structure of the substrate processing apparatus provided with the displacement plating apparatus (catalyst provision apparatus) of embodiment of this invention.

Explanation of symbols

5 Pre-cleaning device 7 Catalyst application device (displacement plating device)
9 Electroless plating apparatus 25 Flattening apparatus 32 Substrate transport unit 50 Protective film forming apparatus 52 Flattening apparatus 100 Substrate holder 102 Catalyst solution (displacement plating solution)
104 Holding tank 104a Narrow part 106 Processing tank 110 Filter 112 Deaeration module 114 Liquid supply pipe 118 Liquid recovery pipe 120 Liquid circulation system 122 Lid 124, 128, 134, 140 Inert gas introduction pipe 126, 132 Aeration pipe 130a, 130b Current plate 136 Processing tank lid 138 Pure water spray nozzle 142 Atmosphere control unit 144 Housing 208 Wiring (metal base)
209 Protective film

Claims (11)

Pre-cleaning the metal base surface by bringing it into contact with a cleaning solution containing an organic acid,
The surface of the metal substrate after pre-cleaning is brought into contact with a displacement plating solution in which the dissolved oxygen concentration in the solution is reduced below the saturation oxygen solubility at the operating temperature, and a metal film is formed on the surface of the metal substrate by a substitution reaction. Substitution plating method to do.   A displacement plating method, wherein the dissolved oxygen concentration in the displacement plating solution is adjusted to 40% or less of the saturated oxygen solubility at the use temperature.   The metal base is a buried wiring embedded in a wiring recess formed on the surface of the substrate, and the metal film is a catalytic metal film that becomes a catalyst nucleus when a protective film is formed on the surface by electroless plating. The displacement plating method according to claim 1 or 2, wherein:   The displacement plating method according to any one of claims 1 to 3, wherein the displacement plating solution includes an organic acid contained in the cleaning solution and / or a compound having an N atom that is chemically adsorbed on a metal base. A substrate holder for holding the substrate with the surface facing down;
A sealed holding tank for holding a displacement plating solution;
A treatment tank for introducing the replacement plating solution held in the holding tank into the interior and bringing the surface of the substrate held by the substrate holder into contact with the replacement plating solution;
A liquid circulation system for circulating the replacement plating solution through the holding tank and the treatment tank;
The substrate holder and the processing tank are arranged in a sealed casing capable of controlling an internal atmosphere,
A displacement plating apparatus is provided in the treatment tank, wherein an aeration tube for bubbling an inert gas in the replacement plating solution of the treatment tank to reduce the dissolved oxygen concentration in the replacement plating solution is disposed.   While circulating the replacement plating solution at a flow rate of 0.3 to 3 L / min through the liquid circulation system, the replacement plating solution in the holding tank is inactivated at 1 to 10 L / min through the air diffuser. The displacement plating apparatus according to claim 5, wherein a gas is introduced. A substrate holder for holding the substrate with the surface facing down;
A sealed holding tank for holding a displacement plating solution;
A treatment tank for introducing a replacement plating solution held in the holding tank into the interior and bringing the surface of the substrate held by the substrate holder into contact with the plating solution;
A liquid circulation system for circulating the replacement plating solution through the holding tank and the treatment tank;
The substrate holder and the processing tank are arranged in a sealed casing capable of controlling an internal atmosphere,
A displacement plating apparatus, wherein a degassing module is interposed in the liquid circulation path.   The displacement plating apparatus according to claim 7, wherein the displacement plating solution is circulated at a flow rate of 1 to 4 L / min through the liquid circulation system.   The displacement plating apparatus according to any one of claims 5 to 8, wherein a narrowing portion that minimizes a cross-sectional area at a free liquid surface position of the displacement plating solution is provided in an upper portion of the holding tank.   The displacement plating apparatus according to any one of claims 5 to 9, wherein a plurality of rectifying plates for arranging a flow of a displacement plating solution flowing inside the treatment tank are arranged in the treatment tank.   11. The displacement plating apparatus according to claim 5, wherein the displacement plating solution includes an organic acid contained in the cleaning solution and / or a compound having N atoms that are chemically adsorbed on a metal base.

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