JP2006152421A - Electroplating device and electroplating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably form a plating film of fixed film quality at all times even if a polarization curve is changed owing to an initial surface state, the progression of plating or the like. <P>SOLUTION: The electroplating device comprises: an anode 134; a reference electrode 140 formed on the surface of a substrate and composing a three electrode system with an electrically conductive layer to form into a cathode in the case of electroplating; and a potentiostat 144 of controlling the cathode potential of the electrically conductive layer with the potential of the reference electrode 140 as a reference. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrolytic plating apparatus and an electrolytic plating method, and more particularly, to form a buried wiring by embedding a conductor (wiring material) such as copper or silver in a wiring recess provided on the surface of a substrate such as a semiconductor wafer. The present invention relates to an electroplating apparatus and an electroplating method used in the above.

  In recent years, as a metal material for forming a wiring circuit on a semiconductor substrate, a movement of using copper (Cu) having a low electrical resistivity and a high electromigration resistance instead of aluminum or an aluminum alloy has become prominent. This type of copper wiring is generally formed by embedding copper in a fine wiring recess provided on the surface of the substrate. As a method of forming this copper wiring, there are methods such as CVD, sputtering, and plating. In any case, copper is formed on almost the entire surface of the substrate, and unnecessary copper is formed by chemical mechanical polishing (CMP). To be removed.

FIG. 1 shows a manufacturing example of this type of copper wiring board W in the order of steps. First, as shown in FIG. 1A, an insulating film 2 such as an oxide film made of SiO ₂ or a low-k material film is deposited on a conductive layer 1a on a semiconductor substrate 1 on which a semiconductor element is formed. In the insulating film 2, via holes 3 and trenches 4 are formed as wiring recesses by lithography and etching techniques. A barrier layer 5 made of Ta, TaN, TiN, WN, SiTiN, CoWP, CoWB or the like is formed thereon, and a seed layer (conductive layer) 7 is formed thereon as a power feeding layer for electrolytic plating.

  Then, as shown in FIG. 1B, the surface of the seed layer 7 of the substrate W is plated with copper so that the via hole 3 and the trench 4 are filled with copper, and the copper film 6 is formed on the insulating film 2. accumulate. Thereafter, the surface of the copper film 6 filled in the via hole 3 and the trench 4 and the insulating film are removed by chemical mechanical polishing (CMP) to remove the copper film 6, the seed layer 7 and the barrier layer 5 on the insulating film 2. The two surfaces are almost flush with each other. Thereby, as shown in FIG.1 (c), the wiring which consists of the copper film 6 is formed.

  As integration of semiconductor devices progresses, it is required to reliably embed copper and other wiring materials into wiring recesses such as fine trenches and via holes formed on the surface of the substrate. Therefore, precise plating technology is required. Therefore, using the plating solution to which additives such as an inhibitor that controls the deposition of plating metal on the substrate surface and an accelerator that promotes the deposition of plating metal on the bottom of the trench is used. In general, the embeddability is improved by selectively depositing a plated metal from the above.

  FIG. 2 shows an outline of a conventional general electroplating apparatus employing a so-called face-up method. The electroplating apparatus includes, for example, a substrate holding unit 130 that holds a substrate W having a conductive layer such as a seed layer 7 shown in FIG. 1A on its surface, and conductivity of the surface of the substrate W held by the substrate holding unit 130. It has an electrical contact 132 for supplying power so that the conductive layer becomes a cathode in contact with the layer (seed layer), and an anode 134 disposed above the substrate W held by the substrate holder 130. Then, the plating solution 136 is filled between the substrate W held by the substrate holding unit 130 and the anode 134, the anode 134 is used as the anode of the power source 138, and the conductive layer on the surface of the substrate W is connected to the power source 138 via the electrical contact 132. A plating film is formed on the surface of the conductive layer (cathode) by connecting a current to the cathode 134 and applying a predetermined voltage between the anode 134 and the conductive layer (cathode) on the surface of the substrate W. .

  In this type of electroplating apparatus, the conductive layer (cathode) on the surface of the anode 134 and the substrate W is constant so that the current flowing between the anode 134 and the conductive layer (cathode) on the surface of the substrate W is constant. The plating reaction is controlled by changing the voltage applied between and. In addition, as described above, when an additive is added to the plating solution, the remaining amount of the additive is analyzed, and the plating solution is repeatedly used while replenishing the amount of additive corresponding to the reduced additive. This is also widely done.

  For example, when copper plating is applied to the surface of a substrate having a wiring recess such as a trench, and a wiring material such as copper is embedded in the wiring recess, the plating area depends on the density (data rate) of the wiring recess. Is different. For example, an insulating film (oxide film) having a diameter of 200 mm and a surface of 300 nm is formed, and trenches having a width of 0.2 μm are provided in the insulating film at intervals of 0.2 μm. (Area) has a diameter of 200 mm and does not have a recess for wiring on the surface, that is, 1.5 times the surface area of a substrate with a data rate of 0%.

  For this reason, when plating is performed on the substrate surface by electrolytic plating, the polarization curve (potential-current curve) at the time of plating varies due to a substantial difference in plating area. For example, as shown in FIG. 3, the polarization curve A when the above-described substrate surface with a data rate of 20% is plated using a Cu—Cl aqueous plating solution is the polarization curve A on the substrate surface with a data rate of 0%. Compared with the polarization curve B when plating is performed using a Cu—Cl aqueous solution plating solution, the whole moves to the right. For this reason, when the electroplating apparatus shown in FIG. 2 is used and plating is performed while controlling the current to be constant (for example, 0.07 V), the potential of the substrate surface serving as the cathode (cathode potential) has a data rate of 0%. This is about 0.18 V (vs. NHE) for a substrate of approximately 0.12 V (vs. NHE) for a substrate with a data rate of 20%.

  As described above, when the plating is performed while the current is kept constant even though the polarization curves are different, the governing electrochemical reaction (plating reaction) changes, and the film quality of the plating film (for example, the crystal grain size) Or crystal orientation), and it becomes difficult to ensure the reliability of the wiring obtained by plating. In other words, the equation governing the electrochemical reaction in the Cu—Cl (chlorine) aqueous solution is as shown in Table 1 below, and the substrate surface potential (cathode potential) is about 0.18 V (vs. NHE). At this time, reaction formulas (4) to (6) in Table 1 proceed as →, and reaction formulas (1) to (3) do not proceed as →. For this reason, as for the electrochemical reaction concerning plating precipitation, Formula (4)-(6) becomes dominant. However, when the substrate surface potential (cathode potential) is about 0.12 V (vs. NHE), the reaction formulas (4) to (6) in Table 1 proceed as follows: 3) Also proceed as →. For this reason, as for the electrochemical reaction concerning plating precipitation, Formula (2)-(6) becomes dominant. Thus, the quality of the plating film changes due to the difference in the electrochemical reaction that is dominant in plating deposition.

  For this reason, for example, when plating is performed on the surface of a substrate with a data rate of 20% under the plating conditions set to an optimum current for a substrate with a data rate of 0%, the potential of the substrate surface (cathode potential) due to the difference in polarization curves. As a result, the dominant electrochemical reaction is different, an unexpected reaction occurs, and a plating film (wiring) having a film quality different from the desired film quality is formed.

  The same applies to the case where the remaining amount of the additive in the plating solution is analyzed and the plating solution is repeatedly used while supplying the plating solution with an amount corresponding to the reduced additive. That is, the polarization curve (potential-current curve) fluctuates due to a change in the amount of the additive contained in the plating solution, a temporal variation in the amount of by-products generated, and the like. For this reason, when plating is performed with a constant current, an unexpected reaction may occur, and a plating film (wiring) having a film quality different from the desired film quality may be formed.

  In addition, the substantial difference in the plating area is not only the difference in the initial state of the substrate surface, but also the wiring material such as copper is gradually embedded in the wiring recess such as the trench as the plating progresses. It also occurs on the way and before and after being completely buried. For this reason, the polarization curve (potential-current curve) fluctuates even during the progress of plating, and it becomes increasingly difficult to form a plating film having a uniform film quality over the whole.

  As described above, the characteristics of the plating solution have greatly depended on the additive, and an additive composed of a large amount of an organic / inorganic compound is mixed in the plating solution. In addition, with the miniaturization of wiring, the seed layer necessary for electroplating is gradually thinned, and the seed layer is prevented from dissolving when the seed layer is brought into contact with the plating solution. It is important.

  By the way, for example, in the field of electrochemical, it is widely known that a reference electrode (reference electrode) is used and an electrochemical reaction is controlled by a potential based on the reference electrode. On the other hand, electrolytic plating is a technique for forming a film on the surface of an object to be plated by an electrochemical reaction, and this is also well known as an industrially important technique for a long time.

  Here, the plating solution is generally a strong acid and contains a large amount of high-concentration metal ions and electrolytes. For this reason, if the reference electrode is immersed in the plating solution for a long time, not only the reference electrode is severely deteriorated, but also the component of the plating solution diffuses into the electrolytic solution in the reference electrode and the reference potential changes. Resulting in. If an attempt is made to cause a reaction using the reference electrode whose reference potential has changed, the standard of the electrochemical reaction changes, and therefore a reaction other than the expected reaction occurs. Thus, the reference electrode has not been generally used in the conventional electrolytic plating apparatus from the viewpoint of stability and life.

  The present invention has been made in view of the above circumstances, and even when the polarization curve changes due to the initial surface state or the progress of plating, etc. An object is to provide a plating apparatus and an electrolytic plating method.

  According to the first aspect of the present invention, there is provided a reference electrode constituting a three-electrode system between an anode and a conductive layer formed on the surface of a substrate and serving as a cathode during plating, and the cathode potential of the conductive layer is referred to It is an electroplating apparatus characterized by having a potentiostat controlled based on the electric potential of an electrode.

  In this way, plating is performed by passing a current between both electrodes of the anode and the conductive layer (cathode) while controlling the electrode potential (cathode potential) of a conductive layer such as a seed layer, which becomes a cathode during plating, at a constant level. By doing this, the same electrochemical reaction is always caused without causing a reaction that is not desired to proceed, and the film quality (crystal grain size and crystal orientation) is controlled, while the film quality is constant on the surface of the conductive layer. A plating film can be formed. In addition, when a plating solution containing an additive such as an inhibitor or an accelerator is used, the electrode potential (cathode potential) of the conductive layer is controlled in consideration of the characteristics of the plating solution, for example, trench or By selectively depositing a plating film only on the bottom of the via hole, plating with no voids or seams and excellent embedding can be performed.

The invention according to claim 2 is the electrolytic plating apparatus according to claim 1, further comprising an electrolytic solution tank for holding an electrolytic solution in which the reference electrode is immersed during non-plating.
Thus, the deterioration of the reference electrode can be suppressed by bringing the reference electrode into contact with the electrolytic solution during non-plating so as not to touch the plating solution.

The invention according to claim 3 includes a movable electrode head including the anode and the reference electrode, a plating solution tray for holding a plating solution for immersing the anode during non-plating, and the electrolytic solution tank. Is provided in or near the plating solution tray, and the anode is immersed in the plating solution in the plating solution tray and the reference electrode is simultaneously immersed in the electrolytic solution in the electrolytic solution tank. Item 2. The electrolytic plating apparatus according to Item 2.
Thereby, it is not necessary to separately provide a moving mechanism for moving the reference electrode, and the structure can be simplified.

The invention according to claim 4 is the electrolytic plating apparatus according to claim 3, wherein the electrolytic bath holds the same electrolytic solution as the internal electrolytic solution of the reference electrode.
Thereby, even if the component of the electrolytic solution in which the reference electrode is immersed in the electrolytic solution in the reference electrode diffuses, the reference potential of the reference electrode can be prevented from changing.

The invention according to claim 5 is characterized in that the electrolyte bath has a potential measuring electrode for measuring a deviation of the natural electrode potential of the reference electrode from the initial potential. An electroplating apparatus according to any one of the above.
As a result, a deviation (difference) between the natural electrode potential of the reference electrode and the initial potential is obtained during non-plating, and the potential (cathode potential) of the seed layer to be controlled becomes a reference by correcting this deviation difference. It can be prevented that the reference electrode shifts with time due to the shift of the reference electrode. The electrode measuring electrode is composed of, for example, another reference electrode.

The invention according to claim 6 has an alarm for generating an alarm when the deviation of the natural electrode potential of the reference electrode from the initial potential becomes a certain value or more. Device.
Accordingly, it is possible to promptly detect that the reference electrode has reached the end of its life and prompt the user to replace the reference electrode.

The invention according to claim 7 has a plating solution exchange section for replacing the plating solution for immersing the conductive layer, the anode and the reference electrode on the surface of the substrate every time the substrate is changed. The electroplating apparatus according to any one of 1 to 6.
Thus, by applying to a so-called single-wafer type electroplating apparatus in which the plating solution is replaced for each substrate, it is possible to prevent an electrochemical change due to deterioration of the additive solution.

The invention according to claim 8 has an electroplating apparatus according to any one of claims 1 to 7, further comprising a high-resistance structure disposed between the anode and the substrate during plating. It is.
By placing a high-resistance structure between the anode and the substrate and plating with the resistance on the plating solution side increased to such an extent that the electrical resistance of the conductive layer such as the seed layer can be ignored, The in-plane difference of the current density due to the electric resistance of the conductive layer (seed layer) can be reduced, and the in-plane uniformity of the plating film can be improved.

  According to the ninth aspect of the present invention, a current is passed between the conductive layer and the anode while the cathode potential of the conductive layer formed on the surface of the substrate and serving as the cathode during plating is controlled based on the reference electrode. An electrolytic plating method is characterized in that a plating metal is deposited on the surface of the conductive layer.

The invention according to claim 10 is characterized in that the cathode potential of the conductive layer is controlled so that the gradient of the potential-current curve obtained by monitoring the current flowing during plating is minimized. Electrolytic plating method.
By monitoring the current flowing during plating, a potential-current curve is obtained, which is unique to the plating solution. For example, when the cathode potential of the conductive layer is set to the negative side for plating, the current value increases. This potential-current curve changes depending on the solution conditions such as the flow state of the plating solution and the type / mixing amount of the additive. By performing plating at a potential in a region where the gradient of the potential-current curve is minimized, the uniformity of the plating film thickness within the substrate surface can be improved.

The invention according to claim 11 is the electrolytic plating method according to claim 10, wherein the reference electrode is immersed in an electrolyte solution other than the plating solution during non-plating.
The invention according to claim 12 is characterized in that a deviation of the natural electrode potential of the reference electrode from an initial potential is measured, and the cathode potential of the conductive layer is controlled in consideration of the deviation. The electrolytic plating method according to any one of 9 to 11.

A thirteenth aspect of the present invention is the electrolytic plating method according to the twelfth aspect, wherein the deviation of the natural electrode potential of the reference electrode from the initial potential is measured during non-plating.
The invention according to claim 14 is the electrolytic plating method according to claim 12 or 13, wherein an alarm is issued when the deviation of the natural electrode potential of the reference electrode from the initial potential becomes a certain value or more. .

  According to the present invention, for example, by performing plating while controlling the potential (cathode potential) of a conductive layer such as a seed layer, the electrochemical reaction can be controlled so as not to cause a reaction that is not desired to proceed. Accordingly, it is possible to control the plating film formed by plating so that the film quality such as crystal grain size and crystal orientation is constant, or to control the internal stress of the plating film.

In particular, in plating solutions containing additives such as inhibitors (suppressors) and accelerators (accelerators), for example, plating at the cathode potential due to the difference in adsorbed state of the trench or via bottom and the substrate surface. Although the deposition rate is different, by controlling the cathode potential in consideration of this characteristic, the plating metal is effectively deposited only on the bottom of the trench and via, and there is no void or seam, and it has excellent embeddability. Plating can be performed.
Furthermore, by controlling the cathode potential of the conductive layer so that the gradient of the potential-current curve obtained by monitoring the current flowing during plating can be minimized, the uniformity of the plating film thickness within the substrate surface can be improved. it can.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following example, as shown in FIG. 1A, by preparing a substrate W having a seed layer 7 as a conductive layer on the surface and performing copper plating using the seed layer (conductive layer) 7 as a cathode, An example of forming a copper film 6 on the surface of the seed layer 7 as shown in FIG.

  FIG. 4 shows an outline of the electroplating apparatus according to the embodiment of the present invention. This electrolytic plating apparatus is in contact with the substrate holding unit 130 that holds the substrate W having the seed layer (conductive layer) 7 on the surface upward, and the seed layer 7 on the surface of the substrate W held by the substrate holding unit 130. It has an electrical contact 132 that feeds power so that the seed layer 7 serves as a cathode, and an anode 134 disposed above the substrate W held by the substrate holder 130. Furthermore, a reference electrode 140 constituting a three-electrode system is provided between the seed layer (cathode) 7 on the surface of the substrate W and the anode 134 at the time of plating, and these three electrodes 7, 134, 140 are used as electrode cells. Is configured. The seed layer (cathode) 7 and the anode 134 on the surface of the substrate W are connected to the current measuring circuit 144 of the potentiostat 142, and the seed layer (cathode) 7 and the reference electrode 140 on the surface of the substrate W are connected to the potentiostat 142. Are connected to the potential control circuit 146.

  As a result, the potentiostat 142 performs plating using the seed layer 7 as a cathode while controlling the potential (cathode potential) of the seed layer 7 on the surface of the substrate constant with the reference electrode 140 as a reference. A plating film is formed on the surface. That is, the current generated by the plating reaction flows between the seed layer (cathode) 7 and the anode 134 while controlling the potential difference between the reference electrode 140 and the seed layer 7 to be a predetermined constant value. And plating.

  As the reference electrode 140, it is preferable to use an electrolytic solution similar to the plating solution or an electrolytic solution composed of a component that does not affect the plating reaction as an internal electrolytic solution. Specific examples of the reference electrode 140 include a mercury / mercury sulfate electrode, a silver / silver chloride electrode, and a saturated calomel electrode. A copper sulfate-sulfuric acid aqueous solution system is generally used as the copper plating solution. At that time, it is preferable to use a mercury / mercury sulfate electrode as the reference electrode 140.

  In this electrolytic plating apparatus, the plating solution 136 is filled between the substrate W held by the substrate holding unit 130 and the anode 134, and the reference electrode 140 is immersed in the plating solution 136. In this state, the anode 134 is connected to the anode of the power source, and the seed layer 7 on the surface of the substrate W is connected to the cathode of the power source via the electrical contact 132. As shown in FIG. ) A copper film 6 is formed on the surface of 7. At this time, the potentiostat 142 is controlled so that the potential (cathode potential) of the seed layer 7 is constant with the reference electrode 140 as a reference, and a plating reaction is performed between the seed layer (cathode) 7 and the anode 134. Allow the resulting current to flow.

  In this way, a current is passed between the anode and cathode (conductive layer) electrodes while the electrode potential (cathode potential) of a conductive layer such as the seed layer 7 that becomes the cathode during plating is controlled to be constant. By plating, the same electrochemical reaction is always caused without causing a reaction that is not desired to proceed, and the film quality (crystal grain size and crystal orientation) is controlled, while the surface of the cathode (conductive layer) is controlled. A plating film having a constant film quality can be formed.

In this example, a mercury / mercury sulfate electrode is used as the reference electrode 140, a Cu—Cl aqueous solution is used as the plating solution, and the reference electrode (mercury / mercury sulfate electrode) 136 is used as a reference. The potential (cathode potential) of the seed layer (conductive layer) 7 on the surface is constantly controlled to −0.45 V (vs. Hg / HgSO ₄ ) by the potentiostat 142. Since the Hg / HgSO ₄ electrode is 0.61 V (vs. NHE) based on the standard hydrogen electrode (NHE), −0.45 V (vs. Hg / HgSO ₄ ) is 0.16 V (vs. NHE). ).

  As described above, when plating is performed with the potential (cathode potential) of the seed layer 7 on the substrate surface kept constant at 0.16 V (vs. NHE), the reaction formulas (4) to (6) in Table 1 described above are performed. ) Proceeds as →, and reaction formulas (1) to (3) do not proceed as →. For this reason, only the formulas (4) to (6) are dominant in the electrochemical reaction related to plating deposition. This is the same even when the substantial plating area changes and the polarization curve changes, and the reaction formulas (2) to (3) in Table 1 do not become dominant. As a result, the film quality is always constant.

  That is, as shown in FIG. 3, the polarization curve A when electrolytic plating is performed on the above-described substrate surface with a data rate of 20% using a Cu—Cl aqueous plating solution is the substrate surface with a data rate of 0%. Furthermore, as compared with the polarization curve B when plating is performed using a Cu—Cl aqueous solution type plating solution, the whole moves to the right side. However, by using the electrolytic plating apparatus shown in FIG. 4 and performing plating while controlling the potential of the seed layer 7 serving as the cathode (cathode potential) to be constant (0.16 V (vs. NHE)), the anode 134 and Although the current flowing between the seed layer (cathode) 7 is different, the same electrochemical reaction (plating reaction) is always dominant so that the film quality of the plating film formed on the surface of the seed layer 7 is changed. Can always be constant.

  This means that when the additive in the plating solution is added, the remaining amount of the additive is analyzed, and the plating solution is repeatedly used while replenishing the plating solution with an amount corresponding to the reduced additive. The same applies to the case where it is performed. In other words, even if the polarization curve (potential-current curve) fluctuates due to changes in the amount of additive contained in the plating solution or temporal variations in the amount of by-products generated, the conductivity that becomes the cathode By performing plating while controlling the layer potential (cathode potential) to be constant, it is possible to prevent an unexpected reaction from occurring and formation of a plating film (wiring) having a film quality different from the desired film quality. .

  In addition, as the plating progresses, the wiring material such as copper is gradually embedded in the wiring recesses such as the trench, and before and after being completely embedded. Even if the actual plating area changes and the polarization curve (potential-current curve) fluctuates, plating is performed while the potential of the conductive layer serving as the cathode (cathode potential) is controlled to be constant. A plating film having a uniform film quality can be formed.

  When the surface of a substrate having a wiring recess such as a trench is subjected to electrolytic plating using a plating solution containing an additive to embed copper or the like, the upper surface of the wiring recess such as a trench is caused by the action of the additive. And the bottom have different polarization curves. For example, as shown in FIG. 5, an insulating film (oxide film) 200 having a diameter of 200 mm and a surface of 300 nm is formed on the surface as described above, and a trench 202 having a width of 0.2 μm is formed on the insulating film 200 with a thickness of 0.2 μm. A substrate W in which a barrier layer 204 made of Ta / TaN and a seed layer 206 are sequentially provided on the surface of the substrate W having a data rate of 20% provided at intervals is prepared. Then, a plating solution comprising a Cu—Cl aqueous solution, to which an inhibitor (suppressor) and an accelerator (accelerator) are added as additives, plating using the seed layer 206 as a cathode is performed. Consider a case where a plating film is formed on the surface.

  As the inhibitor 210 that is added to the plating solution 208 and suppresses the precipitation of ions, generally, a polymer compound having a molecular volume that does not enter the inside of the trench 202, specifically, polyethylene glycol or the like is used. For this reason, the inhibitor 210 is adsorbed only on the surface of the seed layer 206 located on the upper surface U of the trench 202 and suppresses the deposition of the plating film on the surface. However, the inhibitor 210 does not enter the inside of the trench 202, and therefore, the effect of suppressing the plating film formation on the surface of the seed layer 206 located inside the trench 202 does not act. On the other hand, the accelerator 212 added to the plating solution 208 easily enters the trench 202 and accumulates at the bottom of the trench 202. For this reason, the accelerator 212 mainly promotes the formation of a plating film at the bottom of the trench 202.

  Therefore, the polarization curve at the upper surface U of the trench 202 is as shown in FIG. 6A, and the polarization curve at the bottom D of the trench 202 is as shown in FIG. That is, the polarization curve at the bottom D of the trench 202 is shifted to the left as a whole with respect to the polarization curve at the upper surface U of the trench 202.

  Since the plating rate is proportional to the current flowing between the electrodes, the plating rate at the bottom D of the trench 202 is faster than the plating rate at the upper surface U of the trench 202 due to the difference in the polarization curve during plating. For this reason, as shown in FIG. 6, the potential (cathode potential) of the seed layer 206 is set to 0, for example, so that the plating rate of the upper surface U of the trench 202 becomes almost zero and the plating proceeds only to the bottom D of the trench 202. The plating film is deposited only at the bottom of the trench 202 by flowing a current between the seed layer (cathode) 206 and the anode while controlling the voltage to .3 V (vs. NHE) constant. Plating without seam and excellent embedding can be performed. Even in this case, the electrochemical reaction is controlled, and the film quality of the plating film becomes constant. Also, the internal stress of the plating film can be controlled.

  Further, in the potential-current curve of the plating solution to be used, plating is performed while controlling the potential of the seed layer 7 serving as the cathode (cathode potential) so that the current gradient is minimized, so that the surface of the seed layer 7 is formed. In-plane uniformity of the film thickness of the plated film to be formed can be improved. FIG. 6C shows a graph in which a part of the potential-current curve of the actual plating solution is enlarged. As described above, the potential-current curve generally has a potential at which the current gradient is the smallest in a part thereof. When the copper film was deposited to a thickness of 500 nm at a potential A having a small current gradient and the film thickness was measured at 361 points within the substrate surface, the deviation rate was 1.38%. On the other hand, when plating was performed by a conventional method, the deviation rate, which is the degree of film thickness variation, was 1.98%. From this, it was found that the film thickness uniformity when plating at the potential A was greatly improved as compared with the conventional method. From this, after completing the filling in the trench or via hole, plating is performed while controlling the potential of the seed layer 7 serving as the cathode (cathode potential) so that the current gradient becomes the smallest, and plating within the substrate surface is performed. By making the film thickness uniform, more favorable results can be obtained with respect to the embedding property and the CMP efficiency of the subsequent process.

Next, control of the film quality of the plating film will be described.
For example, a copper film formed by plating can be crystallized simply by leaving it at room temperature. This phenomenon is called self-annealing. Although the cause of this is not specified, there are various theories whether it occurs when the gas taken into the plating film escapes or due to internal stress of the plating film. As the self-annealing of the plating film proceeds, the plating film becomes denser, and there is a concern that the internal stress of the plating film is generated accordingly. The internal stress of the plating film is considered to be related to the occurrence of stress migration and is not preferable.

  When depositing copper by plating, various electrochemical reactions are involved. As an example, in the electrode reaction examples shown in Table 1 above, copper was deposited by controlling the cathode potential to −0.015 V (vs. NHE) so as to proceed from left to right until reaction (1). The change in the electrical resistance of the plating film (copper) when the deposition of copper was performed by controlling the cathode potential to 0.275 V (vs. NHE) so as to proceed from left to right until reaction (4). Examined. Here, the change in the electrical resistance of the plating film represents a change in the degree of connection of crystal grains in the plating film. When the plating was performed while controlling the cathode potential to -0.015V (vs. NHE), the rate of change in electrical resistance in the plated film (copper) was 4.1%, but the cathode potential was 0.275V. The rate of change in electrical resistance in the plating film (copper) when plating was carried out under the control of (vs. NHE) was 2.8%. Thereby, the rate of change in electrical resistance can be suppressed by controlling the cathode potential. A plating film having a small change rate of electrical resistance has a high possibility of avoiding stress migration because the crystal grains are originally densely formed.

  When plating is performed while controlling the current as in the conventional example, a specific cathode potential cannot be maintained. Therefore, it is difficult to selectively deposit a plating film from the bottom of the trench or the like. Therefore, it was highly dependent on the performance of the additive. According to the present invention, the electrochemical reaction can be controlled by controlling the cathode potential, and a plating layer having a constant film quality can be formed regardless of the surface state. In particular, when an additive such as an inhibitor is added to the plating solution and plating is performed while controlling the cathode potential, selective plating film deposition may occur due to the difference in the precipitation reaction between the bottom and the surface of the trench and the like. It becomes possible.

  FIG. 7 shows a main part of an electroplating apparatus according to another embodiment of the present invention. This electroplating apparatus is provided with an electrode head 152 attached to a free end of a movable arm 150 that can move up and down and move in the horizontal direction, and is disposed below the electrode head 152 and holds a plating solution 154 inside to perform plating. And a plating tank 156 for holding the electrolytic solution 158 therein. The plating tank 156 is configured to be disposed at a position where the electrode head 152 on the side of the plating tank 156 can be reached.

  The electrode head 152 has a housing 164 that opens downward and houses an anode 162 therein. A reference electrode 166 is attached to a side portion of the housing 164 so as to protrude downward. As a result, the reference electrode 166 moves together with the anode 162, and is immersed together with the anode 162 in the plating solution 154 in the plating bath 156 and in the electrolyte solution 158 in the electrolyte bath 160. In this way, by making the reference electrode 166 move integrally with the anode 162, it is not necessary to separately provide a moving mechanism for moving only the reference electrode 166, and the structure can be simplified.

  The plating tank 156 is provided with a plating solution injection unit 168 for injecting the plating solution 154 into the plating tank 156 and a plating solution discharge unit 170 for discharging the plating solution 154 in the plating tank 156. It is configured. A through hole 156a is provided in the central portion of the lower surface. The through hole 156a holds the substrate W with the surface facing upward, and a seed layer as a conductive layer on the surface of the substrate W via the electrical contact 172. The substrate is energized (see FIG. 1A) and is sealed in a watertight manner by the substrate holding part 174 using the seed layer as a cathode.

  The electrolytic bath 160 is for immersing the reference electrode 166 in the internal electrolytic solution 158 together with the anode 162 at the time of non-plating, and for measuring a deviation (difference) from the initial potential of the natural electrode potential of the reference electrode 166. An electrode for electric potential measurement 176 is provided by being immersed in an electrolytic solution 158. In this example, another reference electrode is used as the potential measurement electrode 176. As described above, the reference electrode 166 is immersed in the electrolyte solution 158 in the electrolyte bath 160 during non-plating so that the reference electrode 166 does not touch the plating solution 154 in the plating bath 156, thereby deteriorating the reference electrode 166. Can be suppressed. In addition, by providing a potential measuring electrode 176 for measuring the deviation of the natural electrode potential of the reference electrode 166 from the initial potential in the electrolyte bath 160, the initial potential of the natural electrode potential of the reference electrode 166 can be reduced during non-plating. The deviation can be measured.

  The anode 162, the reference electrode 166, the electrical contact 172 of the substrate holding unit 174, and the potential measurement electrode (other reference electrode) 176 are connected to a potentiostat 178 via wires, respectively, and the potentiostat 178 is controlled. Connected to the unit 180. Further, the signal from the control unit 180 is input to the alarm device 182.

  According to this example, first, the substrate holding part 174 holding the substrate W is raised with the surface facing upward, and the through hole 156a of the plating tank 156 is sealed in a watertight manner by the substrate holding part 174. In this state, the plating solution 154 is injected from the plating solution injection unit 168 into the plating tank 156, and the plating tank 156 is filled with the plating solution 154. At this time, the anode 162 and the reference electrode 166 of the electrode head 152 are immersed in the electrolytic solution 158 in the electrolytic solution tank 160.

  Next, the electrode head 152 is once raised and moved to a position directly above the plating tank 156 and then lowered to immerse the anode 162 and the reference electrode 166 of the electrode head 152 in the plating solution 154 in the plating tank 156.

  In this state, the anode 162 is connected to the anode of the power source, and the seed layer 7 on the surface of the substrate W is connected to the cathode of the power source via the electrical contact 172, and as shown in FIG. ) A copper film 6 is formed on the surface of 7. At this time, the potentiostat 178 is controlled so that the potential of the seed layer 7 (cathode potential) is constant at 0.16 V (vs. NHE), for example, as described above, with the reference electrode 166 as a reference. A current generated by the plating reaction flows between the seed layer (cathode) 7 and the anode 162.

  After the completion of plating, the anode 162 and the electrical contact 172 are disconnected from the power source. Then, the electrode head 152 is once lifted, moved directly above the electrolytic solution tank 160, and then lowered, so that the anode 162 and the reference electrode 166 of the electrode head 152 are immersed in the electrolytic solution 158 in the electrolytic solution tank 160. . Thus, by pulling out the reference electrode 166 from the plating solution 154 during non-plating, it is possible to prevent the reference electrode 166 from deteriorating or the components of the plating solution from diffusing into the electrolyte in the reference electrode 166. it can.

  While the reference electrode 166 is immersed in the electrolyte solution 158 in the electrolyte bath 160, the potential measurement electrode 176 is used to measure the difference between the natural electrode potential of the reference electrode 166 and the initial potential. Find the difference (difference) and correct this difference. For example, when another reference electrode is used as the potential measurement electrode 176, if the reference electrode 166 used for plating is normal, the potential measurement electrode (separate reference) installed in the reference electrode 166 and the electrolyte bath 160 The potential difference of the electrode 176 is always constant. However, for example, when the reference electrode 166 deteriorates due to the use of the reference electrode 166 for a long period of time, the potential difference between the reference electrode 166 and the potential measurement electrode (another reference electrode) 176 is shifted. Therefore, the potential of the seed layer (cathode potential) is controlled so that the potential required for electrolytic plating is obtained while feedback is applied to the power supply so that this deviation can be corrected. This prevents the potential of the seed layer (cathode potential) from shifting with time as the reference electrode 166 serving as a reference shifts. When the difference between the measured natural electrode potential of the reference electrode 166 and the initial potential exceeds a certain value, the reference electrode 166 becomes unusable by sending a signal to the alarm device 182 to issue an alarm. Let them know.

  As a result of performing plating for a long time using this electrolytic plating apparatus, the plating film formation speed and the film quality of the plating film were always constant. When the potential of the reference electrode itself used in the electroplating apparatus was measured using a new reference electrode, the reference potential was not different from the initial value. From this, it was found that the degradation of the reference electrode can be suppressed in this electrolytic plating apparatus.

In addition, the potential (cathode potential) is set to −0.45 V (vs. Hg / HgSO ₄ ) for the formation of the plating film, and the reference electrode is continuously used while being immersed in the plating solution. It was. Then, after 3 days, when the film was formed again, the film formation rate and film quality were different from the initial state. When compared with a new reference electrode, it was shifted by -0.005 V from the original potential. Therefore, it is considered that the deposition rate and the film quality have changed.

  As shown in FIG. 8, there may be a plating solution tray 184 that holds the plating solution 154 therein and immerses the anode 162 in the plating solution 154 during non-plating to idle the anode 162. In such a case, an electrolyte bath 186 is provided in or around the plating solution tray 184, and the anode 162 is immersed in the plating solution 154 in the plating solution tray 184, and at the same time, the reference electrode 166 is placed in the electrolyte bath 186. It is preferable to be immersed in the electrolytic solution 188 held inside.

In this case, it is preferable to use the same electrolytic solution as the internal electrolytic solution of the reference electrode 166 as the electrolytic solution 188 held in the electrolytic solution tank 186, so that the electrolytic solution tank 186 is used as the electrolytic solution in the reference electrode 166. The reference potential of the reference electrode 166 can be prevented from changing even if the components of the electrolyte solution 188 in the inside diffuse.
Although not shown, a potential measuring electrode 176 (see FIG. 7) is installed at a position in contact with the electrolytic solution 188 in the electrolytic solution tank 186, and the reference is made during non-plating similarly to the example shown in FIG. It is preferable to measure the difference from the initial potential of the natural electrode potential of the electrode 166 to obtain a deviation from the initial potential and correct the deviation.

  FIG. 9 shows an overall layout of a substrate processing apparatus provided with an electroplating apparatus according to still another embodiment of the present invention. As shown in FIG. 9, this substrate processing apparatus includes two load / unload units 10 which are located in the same facility and accommodate a plurality of substrates W therein, and an electroplating process and an incidental process thereof. Two electroplating apparatuses 12 to be performed, a transfer robot 14 for delivering the substrate W between the load / unload unit 10 and the electroplating apparatus 12, and a plating solution supply facility 18 having a plating solution tank 16 are provided. ing.

  As shown in FIG. 10, the electroplating apparatus 12 includes a substrate processing unit 20 that performs a plating process and an incidental process thereof, and a plating solution tray 22 that stores a plating solution is disposed adjacent to the substrate processing unit 20. Has been. Further, an electrode arm unit 30 having an electrode head 28 that is held at the tip of a movable arm 26 that swings about the rotation shaft 24 and that swings between the substrate processing unit 20 and the plating solution tray 22 is provided. . Further, a precoat / recovery arm 32 and a fixed nozzle 34 for injecting a chemical solution such as pure water or ionic water, gas, or the like toward the substrate are disposed on the side of the substrate processing unit 20. In this embodiment, three fixed nozzles 34 are provided, and one of them is used for supplying pure water.

  As shown in FIG. 11, the substrate processing unit 20 includes a substrate holding unit 36 that holds the substrate W with the surface (surface to be plated) facing upward, and a peripheral edge of the substrate holding unit 36 above the substrate holding unit 36. The electrode part 38 arrange | positioned so that a part may be enclosed is provided. Further, a bottomed substantially cylindrical scattering prevention cup 40 that surrounds the periphery of the substrate holding part 36 and prevents the scattering of various chemicals used during processing is arranged to be movable up and down via an air cylinder (not shown). Has been.

  Here, the substrate holding unit 36 is moved up and down between a lower substrate delivery position A, an upper plating position B, and an intermediate pretreatment / cleaning position C by an air cylinder 44, and a rotary motor (not shown). And it is comprised so that it may rotate integrally with the electrode part 38 with arbitrary acceleration and speed | velocity | rate via a belt. Opposite to the substrate delivery position A, a substrate carry-in / out port (not shown) is provided on the side of the transfer robot 14 on the side of the frame of the electroplating apparatus 12, and when the substrate holding part 36 is raised to the plating position B. The sealing member 90 and the electrical contact 88 of the electrode unit 38 described below come into contact with the peripheral edge of the substrate W held by the substrate holding unit 36. On the other hand, the anti-scattering cup 40 has an upper end positioned below the substrate carry-in / out entrance, and as shown by a phantom line in FIG. .

  The plating solution tray 22 is for performing idling to wet the following high resistance structure 110 and the anode 98 of the electrode arm portion 30 with the plating solution when the plating treatment is not performed (when not plating). The high resistance structure 110 is set to a size that can be accommodated, and has a plating solution supply port and a plating solution drain port (not shown). In addition, a photo sensor is attached to the plating solution tray 22 so that the plating solution in the plating solution tray 22 is fully filled, that is, overflow and drainage can be detected.

  The electrode arm unit 30 moves up and down through a vertical movement motor and a ball screw, which are not shown, and rotates (swings) between the plating solution tray 22 and the substrate processing unit 20 through a turning motor. It is like that.

  Further, as shown in FIG. 12, the precoat / collection arm 32 is connected to the upper end of a support shaft 58 extending in the vertical direction, and pivots (swings) via a rotary actuator 60, and an air cylinder (not shown). It is comprised so that it may move up and down via. The precoat / collection arm 32 holds a precoat nozzle 64 for discharging a precoat liquid on the free end side, and a plating solution recovery nozzle 66 for collecting a plating liquid on the base end side. The precoat nozzle 64 is connected to a syringe driven by an air cylinder, for example, and the precoat liquid is intermittently discharged from the precoat nozzle 64, and the plating solution recovery nozzle 66 is connected to, for example, a cylinder pump or an aspirator. The plating solution on the substrate is sucked from the plating solution recovery nozzle 66.

  As shown in FIGS. 13 to 15, the substrate holding unit 36 includes a disk-shaped substrate stage 68, and the substrate W is horizontally placed on the upper surface at six locations along the circumferential direction of the peripheral portion of the substrate stage 68. A support arm 70 is erected to be placed and held on the head. A positioning plate 72 is fixed to one upper end of the support arm 70 to be positioned in contact with the end surface of the substrate W, and a substrate is fixed to the upper end of the support arm 70 facing the support arm 70 to which the positioning plate 72 is fixed. A pressing piece 74 is pivotally supported so as to be rotated in contact with the end face of W and press the substrate W against the positioning plate 72 side. In addition, chuck claws 76 that pivot and press the substrate W downward from above are rotatably supported at the upper ends of the other four support arms 70.

  Here, the lower end of the pressing piece 74 and the chuck claw 76 is connected to the upper end of the pressing bar 80 biased downward via the coil spring 78, and the pressing piece 74 and the chuck are moved along with the downward movement of the pressing bar 80. A claw 76 is pivoted inwardly and closed, and a support plate 82 is disposed below the substrate stage 68 so as to abut the lower surface of the pressing rod 80 and push it upward.

  Thus, when the substrate holding portion 36 is positioned at the substrate delivery position A shown in FIG. 11, the pressing rod 80 abuts on the support plate 82 and is pushed upward, so that the pressing piece 74 and the chuck claw 76 rotate outward. When the substrate stage 68 is raised by moving, the pressing rod 80 is lowered by the elastic force of the coil spring 78, and the pressing piece 74 and the chuck claw 76 are rotated inward to close.

  As shown in FIGS. 16 and 17, the electrode portion 38 includes an annular frame 86 fixed to the upper end of a column 84 erected on the peripheral edge of a support plate 82 (see FIG. 15 and the like), and the frame 86. In this example, an electrical contact 88 divided into six parts and an annular sealing material 90 attached to the upper surface of the frame 86 so as to cover the upper side of the electrical contact 88 are provided. is doing. The electrical contact 88 contacts the seed layer (conductive layer) 7 (see FIG. 1A) on the surface of the substrate W held by the substrate holding portion 36 during plating, and makes the seed layer 7 a cathode. . The seal member 90 is configured such that an inner peripheral edge thereof is inclined downward inward and gradually becomes thin, and an inner peripheral end portion hangs downward.

Accordingly, as shown in FIG. 19, when the substrate holding portion 36 is raised to the plating position B, the electrical contact 88 is pressed against the peripheral portion of the substrate W held by the substrate holding portion 36 and energized, and at the same time, the sealing material The inner peripheral end of 90 is in pressure contact with the upper surface of the peripheral edge of the substrate W, and this is sealed in a watertight manner, so that the plating solution supplied to the upper surface (surface to be plated) of the substrate W oozes out from the end of the substrate W. In addition, the plating solution is prevented from contaminating the electrical contacts 88.
In this embodiment, the electrode unit 38 cannot move up and down and rotates integrally with the substrate holding unit 36. However, the electrode unit 38 can move up and down, and the seal member 90 is plated on the substrate W when it is lowered. You may comprise so that it may press-contact to a surface.

  As shown in FIGS. 18 and 19, the electrode head 28 of the electrode arm portion 30 includes an electrode holder 94 connected to the free end of the movable arm 26 via a ball bearing 92, and a lower end opening of the electrode holder 94. And a high resistance structure 110 arranged so as to be closed. That is, the electrode holder 94 is formed in a bottomed cup shape that opens downward, and a concave portion 94a is fitted on the inner peripheral surface of the lower portion, and a concave portion 94a is fitted on the upper portion of the high resistance structure 110. Each of the flange portions 110a is provided, and the high resistance structure 110 is held by the electrode holder 94 by fitting the flange portions 110a into the concave portions 94a. Thus, a hollow plating solution chamber 100 is defined in the electrode holder 94.

  The high resistance structure 110 is made of, for example, a porous ceramic such as alumina, SiC, mullite, zirconia, titania, cordierite, or a hard porous body such as a sintered body of polypropylene or polyethylene, a composite thereof, or a woven material. Consists of cloth and non-woven fabric. For example, in the case of alumina-based ceramics, the pore diameter is 30 to 200 μm, and in the case of SiC, the pore diameter is 30 μm or less, the porosity is 20 to 95%, the thickness is 1 to 20 mm, preferably 5 to 20 mm, and more preferably 8 to About 15 mm is used. In this example, for example, the porous ceramic plate is made of alumina with a porosity of 30% and an average pore diameter of 100 μm. And, by containing the plating solution inside this, that is, the porous ceramic plate itself is an insulator, by allowing the plating solution to enter inside intricately and by following a fairly long path in the thickness direction, It is comprised so that it may have an electrical conductivity smaller than the electrical conductivity of a plating solution.

  Thus, by disposing the high resistance structure 110 in the plating solution chamber 100 and generating a large resistance by the high resistance structure 110, the influence of the resistance of the seed layer 7 (see FIG. 1A) is ignored. As much as possible, the in-plane difference of the current density due to the electric resistance of the surface of the substrate W can be reduced, and the in-plane uniformity of the plating film can be improved.

  In the plating solution chamber 100, an anode 98 having a large number of through holes 98 a penetrating vertically is disposed above the high resistance structure 110. The electrode holder 94 is provided with a plating solution discharge unit 103 that sucks and discharges the plating solution in the plating solution chamber 100. The plating solution discharge unit 103 is provided with the plating solution supply equipment 18 (see FIG. 1). Is connected to a plating solution discharge pipe 106 extending from. Further, a plating solution injection portion 104 is provided inside the peripheral wall of the electrode holder 94 and is located on the side of the anode 98 and the high resistance structure 110 and penetrates vertically. In this example, the plating solution injection unit 104 is configured by a tube having a nozzle shape at the lower end, and is connected to a plating solution supply pipe 102 extending from the plating solution supply facility 18 (see FIG. 9). The plating solution injection unit 104 and the plating solution discharge unit 103 constitute a plating solution exchange unit.

  In the plating solution injection unit 104, when the substrate holding unit 36 is at the plating position B (see FIG. 11), the gap between the substrate W held by the substrate holding unit 36 and the high resistance structure 110 is, for example, 0.5 to 3 mm. The electrode head 28 is lowered to a certain extent, and in this state, a plating solution is injected into the region between the substrate W and the high resistance structure 110 from the side of the anode 98 and the high resistance structure 110. Thus, the lower end nozzle portion opens in a region sandwiched between the sealing material 90 and the high resistance structure 110. A rubber shield ring 112 that electrically shields the high resistance structure 110 is attached to the outer periphery of the high resistance structure 110.

  Thereby, the plating solution injected from the plating solution injection unit 104 at the time of injecting the plating solution flows in one direction along the surface of the substrate W, and the flow of the plating solution causes a gap between the substrate W and the high resistance structure 110. The air in this area is pushed outward and discharged to the outside, and this area is filled with a fresh and adjusted plating solution injected from the plating solution injection section 104, and is partitioned by the substrate W and the sealing material 90. Stored in the area.

  As described above, when the plating solution is injected into the region between the substrate W and the high-resistance structure 110, the electrode holder 94 is immersed in the plating solution, and the electrical contacts 88 A reference electrode 114 constituting a triode electrode system is attached between the seed layer (conductive layer) 7 on the surface of the substrate that comes into contact with the cathode and the anode 98. The electrical contact 88, the anode 98, and the reference electrode 114 are connected to the potentiostat 116 via wiring, and the potentiostat 116 is connected to the control unit 118. Thus, the potentiostat 116 controls the potential (cathode potential) of the seed layer (conductive layer) 7 on the substrate surface, which becomes the cathode during plating, with the reference electrode 114 as a reference.

  As shown in FIG. 10, the same electrolyte 120 as the internal electrolyte of the reference electrode 114 is held inside the plating solution tray 22, and the anode 98 and the high resistance structure 110 are placed in the plating solution tray 22 during non-plating. An electrolyte bath 122 is provided in which the reference electrode 114 is immersed in the electrolyte 120 simultaneously with being wetted with the plating solution. This prevents the reference electrode 114 from coming into contact with the plating solution during non-plating, thereby suppressing the deterioration of the reference electrode 114, and the electrolyte solution in the electrolyte bath 122 is added to the electrolyte solution in the reference electrode 114. Even if the component diffuses, the reference potential of the reference electrode 114 does not change.

  Furthermore, a potential measuring electrode 124 made of, for example, another reference electrode is installed at a position immersed in the electrolytic solution 120 in the electrolytic solution tank 122, and the potential measuring electrode 124 is connected to the potentiostat 116. . Thereby, at the time of non-plating, using the potential measurement electrode 124, the difference between the natural electrode potential of the reference electrode 114 and the initial potential is measured to obtain a deviation from the initial potential, and by correcting this deviation, The potential of the seed layer (cathode potential) is prevented from shifting with time as the reference electrode 114 serving as a reference shifts. Then, when the measured difference between the natural electrode potential of the reference electrode 114 and the initial potential becomes equal to or greater than a certain value, the alarm is sent to the alarm device 126 connected to the control unit 118 and an alarm is generated, so that the reference electrode 114 is informed that it has become unusable.

  Here, in order to suppress the production of slime, the anode 98 is composed of copper containing 0.03 to 0.05% phosphorus (phosphorus-containing copper), but an insoluble insoluble anode is used. You may make it do.

Next, the operation of the substrate processing apparatus provided with the electrolytic plating apparatus 12 of this embodiment will be described.
First, the substrate W before plating processing is taken out from the loading / unloading unit 10 by the transfer robot 14, and one surface is electroplated from the substrate loading / unloading port provided on the side surface of the frame with the surface (surface to be plated) facing upward. It is conveyed inside the device 12. At this time, the substrate holding unit 36 is at the lower substrate delivery position A, and the transport robot 14 lowers the hand after the hand reaches just above the substrate stage 68, thereby supporting the substrate W on the support arm 70. Place on top. Then, the hand of the transfer robot 14 is retreated through the substrate carry-in / out entrance.

  After the removal of the hand of the transfer robot 14 is completed, the anti-scattering cup 40 is raised, and at the same time, the substrate holding part 36 that was in the substrate delivery position A is raised to the pretreatment / cleaning position C. At this time, with this rise, the substrate placed on the support arm 70 is positioned by the positioning plate 72 and the pressing piece 74 and is securely gripped by the chuck claws 76.

  On the other hand, the electrode head 28 of the electrode arm unit 30 is at a normal position on the plating solution tray 22 at this time, and the high resistance structure 110 or the anode 98 is located in the plating solution tray 22. Simultaneously with the rising of the anti-scattering cup 40, supply of the plating solution to the plating solution tray 22 and the electrode head 28 is started. Then, until the substrate plating process is started, a new plating solution is supplied, and suction through the plating solution discharge pipe 106 is performed to replace the plating solution contained in the high resistance structure 110 and remove bubbles. At this time, the reference electrode 114 is immersed in the electrolytic solution 120 in the electrolytic solution tank 122 and is not immersed in the plating solution. When the raising of the scattering prevention cup 40 is completed, the substrate carry-in / out entrance on the side of the frame is closed and closed by the scattering prevention cup 40, and the atmosphere inside and outside the frame is cut off.

  When the anti-scattering cup 40 rises, the precoat process is started. That is, the substrate holding part 36 that has received the substrate W is rotated, and the precoat / collection arm 32 that has been in the retracted position is moved to a position facing the substrate. When the rotational speed of the substrate holding unit 36 reaches a set value, a precoat liquid made of, for example, a surfactant is applied to the surface of the substrate (surface to be plated) from a precoat nozzle 64 provided at the tip of the precoat / collection arm 32. Discharge intermittently. At this time, since the substrate holding part 36 is rotating, the precoat liquid spreads over the entire surface of the substrate W. Next, the precoat / collection arm 32 is returned to the retracted position, the rotational speed of the substrate holding part 36 is increased, and the precoat liquid on the surface to be plated of the substrate W is shaken off and dried by centrifugal force.

  After pre-coating is completed, the process proceeds to plating. First, the substrate holding unit 36 is raised to the plating position B where plating is performed in a state where the rotation is stopped or the rotation speed is reduced to the plating speed. Then, the peripheral portion of the substrate W comes into contact with the electrical contact 88 and can be energized. At the same time, the sealing material 90 is pressed against the upper surface of the peripheral portion of the substrate W, and the peripheral portion of the substrate W is sealed watertight. .

  On the other hand, based on the signal that the precoat process of the loaded substrate W has been completed, the electrode arm unit 30 is swung horizontally from above the plating solution tray 22 so that the electrode head 28 is positioned above the position where the plating process is performed. After that, the electrode head 28 is lowered toward the electrode portion 38. At this time, the high-resistance structure 110 is brought into a position close to about 0.5 mm to 3 mm without contacting the surface of the substrate W. When the lowering of the electrode head 28 is completed, the plating solution is injected into the region between the substrate W and the high resistance structure 110 from the plating solution injection unit 104 to fill the region with the plating solution.

  In this state, the anode 98 is connected to the anode of the power source, and the seed layer 7 on the surface of the substrate W is connected to the cathode of the power source via the electrical contact 132, and as shown in FIG. ) A copper film 6 is formed on the surface of 7. At this time, the potentiostat 116 is controlled so that the potential (cathode potential) of the seed layer 7 is constant at 0.16 V (vs. NHE), for example, as described above, with the reference electrode 114 as a reference. A current generated by a plating reaction flows between the seed layer (cathode) 7 and the anode 98.

  When the plating process is completed, the electrode arm part 30 is raised and turned to return to the upper part of the plating solution tray 22 and lowered to the normal position. Thereby, the reference electrode 114 is immersed in the electrolytic solution 120 in the electrolytic solution tank 122 to prevent the reference electrode 114 from being immersed in the plating solution, and at the same time, via the potential measuring electrode 124, The difference between the natural electrode potential of the reference electrode 114 and the initial potential is measured to obtain a deviation from the initial potential, and the deviation is corrected by feeding back to the power source.

  Next, the precoat / recovery arm 32 is moved from the retracted position to a position facing the substrate W and lowered, and the plating solution remaining solution on the substrate W is recovered from the plating solution recovery nozzle 66. After the collection of the residual liquid is completed, the precoat / collection arm 32 is returned to the retracted position, and pure water is discharged from the fixed nozzle 34 for pure water to the central portion of the substrate W in order to rinse the substrate plating surface. At the same time, the substrate holder 36 is rotated at an increased speed to replace the plating solution on the surface of the substrate W with pure water. Thus, by rinsing the substrate W, when the substrate holding part 36 is lowered from the plating position B, the plating solution is prevented from splashing and the electrical contacts 88 of the electrode part 38 are prevented from being contaminated.

  After rinsing, the water washing process is started. That is, the substrate holding part 36 is lowered from the plating position B to the pretreatment / cleaning position C, and the substrate holding part 36 and the electrode part 38 are rotated while supplying pure water from the fixed nozzle 34 for pure water, and water washing is performed. To do. At this time, the sealing material 90 and the electrical contacts 88 can be cleaned simultaneously with the substrate by pure water directly supplied to the electrode unit 38 or pure water scattered from the surface of the substrate W.

  After the water washing is completed, the drying process is started. That is, the supply of pure water from the fixed nozzle 34 is stopped, the rotation speed of the substrate holding part 36 and the electrode part 38 is increased, and the pure water on the substrate surface is shaken off and dried by centrifugal force. At the same time, the sealing material 90 and the electrical contacts 88 are also dried. When the drying process is completed, the rotation of the substrate holding unit 36 and the electrode unit 38 is stopped, and the substrate holding unit 36 is lowered to the substrate delivery position A. Then, the grip of the substrate W by the chuck claws 76 is released, and the substrate W is placed on the upper surface of the support arm 70. At the same time, the splash prevention cup 40 is also lowered.

  Thus, the plating process and all the pre-processing and cleaning / drying processes incidental thereto are completed, and the transfer robot 14 inserts the hand into the lower part of the substrate W from the substrate loading / unloading port and lifts the substrate as it is, thereby holding the substrate. The processed substrate W is received from the unit 36. Then, the transfer robot 14 returns the processed substrate W received from the substrate holding unit 36 to the load / unload unit 10.

It is a figure which shows one manufacture example of the copper wiring board W in order of a process. It is a figure which shows the outline | summary of the conventional electrolytic plating apparatus. It is a graph which shows the polarization curve (potential-current curve) at the time of plating in the case where plating areas differ substantially. It is a figure which shows the outline | summary of the electroplating apparatus of embodiment of this invention. It is a figure attached | subjected to description of an effect | action of the additive added in a plating solution. (A) is a graph which shows the polarization curve in the upper surface of the recessed part (trench) for wiring when an additive is added in plating solution, (b) shows the polarization curve in the bottom part of the recessed part (trench) for wiring. In the graph, (c) is an enlarged graph showing a part of the polarization curve of the plating solution. It is a figure which shows the outline | summary of the electroplating apparatus of other embodiment of this invention. It is a figure which shows the plating solution tray and electrode head of the electroplating apparatus of other embodiment of this invention. It is a top view which shows the whole substrate processing apparatus provided with the electroplating apparatus of further another embodiment of this invention. It is a top view of the electroplating apparatus shown in FIG. It is an expanded sectional view of the board | substrate holding | maintenance part and electrode part of the electroplating apparatus shown in FIG. It is a front view which shows the precoat and collection | recovery arm of the electroplating apparatus shown in FIG. It is a top view of the board | substrate holding part of the electroplating apparatus shown in FIG. It is the BB sectional view taken on the line of FIG. It is CC sectional view taken on the line of FIG. It is a top view of the electrode part of the electroplating apparatus shown in FIG. It is the DD sectional view taken on the line of FIG. It is a top view of the electrode arm part of the electroplating apparatus shown in FIG. It is sectional drawing at the time of the electroplating which shows schematically the electrode head and board | substrate holding | maintenance part of the electroplating apparatus shown in FIG.

Explanation of symbols

3 Via hole (recess for wiring)
4,202 trench (recess for wiring)
5,204 Barrier layer 6 Copper film 7,206 Seed layer 10 Load / unload unit 12 Electrolytic plating apparatus 18 Plating solution supply equipment 20 Substrate processing unit 22,184 Plating solution tray 26,150 Movable arm 28,152 Electrode head 30 Electrode arm part 32 Precoat / collection arm 34 Fixed nozzle 36, 130, 174 Substrate holding part 38 Electrode part 68 Substrate stage 70 Support arm 76 Chuck claw 88, 132, 172 Electrical contact 90 Sealing material 92 Ball bearing 94 Electrode holder 98, 134 , 162 Anode 103, 170 Plating solution discharge unit 104, 168 Plating solution injection unit 110 High resistance structure 112 Shield ring 114, 140, 166 Reference electrode 116, 142, 178 Potentiostat 118, 180 Control unit 120, 158, 188 Electrolysis Liquid 12 2,160,186 Electrolyte bath 124,176 Potential measuring electrode 126,182 Alarm 130 Substrate holder 136,154,208 Plating solution 144 Current measuring circuit 146 Potential control circuit 156 Plating bath 210 Inhibitor 212 Accelerator

Claims (14)

A reference electrode forming a three-electrode system between the anode and a conductive layer formed on the surface of the substrate and serving as a cathode during plating;
An electroplating apparatus comprising a potentiostat for controlling the cathode potential of the conductive layer based on the potential of the reference electrode.   The electrolytic plating apparatus according to claim 1, further comprising an electrolytic solution tank that holds an electrolytic solution in which the reference electrode is immersed during non-plating.   A movable electrode head having the anode and the reference electrode; and a plating solution tray for holding a plating solution for immersing the anode during non-plating; 3. The electroplating apparatus according to claim 2, wherein the electroplating apparatus is provided in the vicinity, and the anode is immersed in a plating solution in the plating solution tray and the reference electrode is simultaneously immersed in an electrolytic solution in the electrolytic solution tank.   4. The electrolytic plating apparatus according to claim 3, wherein the electrolytic bath holds the same electrolytic solution as the internal electrolytic solution of the reference electrode.   5. The electroplating apparatus according to claim 2, wherein the electrolytic bath has a potential measuring electrode for measuring a deviation of a natural electrode potential of the reference electrode from an initial potential. 6.   The electroplating apparatus according to claim 5, further comprising an alarm device that generates an alarm when a difference between a natural electrode potential of the reference electrode and an initial potential becomes a predetermined value or more.   7. The plating solution replacement unit according to claim 1, further comprising a plating solution replacement unit that replaces the plating solution for immersing the conductive layer, the anode, and the reference electrode on the surface of the substrate each time the substrate is changed. Electroplating equipment.   The electroplating apparatus according to claim 1, further comprising a high-resistance structure disposed between the anode and the substrate during plating.   While controlling the cathode potential of the conductive layer, which is formed on the surface of the substrate and becomes the cathode during plating, using the reference electrode as a reference, a current is passed between the conductive layer and the anode to apply the plating metal to the surface of the conductive layer. Electrolytic plating method characterized by depositing.   10. The electrolytic plating method according to claim 9, wherein the cathode potential of the conductive layer is controlled so that the gradient of the potential-current curve obtained by monitoring the current flowing during plating is minimized.   The electrolytic plating method according to claim 9 or 10, wherein the reference electrode is immersed in an electrolytic solution other than a plating solution during non-plating.   12. The deviation of the natural electrode potential of the reference electrode from the initial potential is measured, and the cathode potential of the conductive layer is controlled in consideration of this deviation. Electroplating method.   The electrolytic plating method according to claim 12, wherein the deviation of the natural electrode potential of the reference electrode from the initial potential is measured during non-plating.   The electroplating method according to claim 12 or 13, wherein an alarm is issued when a difference between a natural electrode potential of the reference electrode and an initial potential becomes a predetermined value or more.

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