Patent Application
20050178672
The present document is based on Japanese Priority Application JP2002-121333 filed to the Japanese Patent Office on Apr. 23, 2002, the content of which being incorporated herein by reference to the extent permitted by law.
The present invention relates to a polishing method and a polishing apparatus for electropolishing a metallic film formed on a substrate by passing an electric current to the metallic film, and particularly to the layout of a current passing electrode for passing the electric current to the metallic film. The present invention relates also to a method of manufacturing a semiconductor device in which the polishing method is carried out during the manufacturing process.
For such demands as smaller size, higher performance and a higher degree of multi-functions in electronic apparatuses such as TV sets, personal computers and cellular phones, a further enhancement of operating speed and a further reduction of power consumption have been requested in LSIs (Large Scale Integrations) used for these electronic apparatuses. To meet the demand for higher operating speed and lower power consumption in LSIs, miniaturization and conversion to multi-layer structure have been conducted in the manufacture of semiconductor devices and, in addition, optimization of materials has also been practiced.
In the field of semiconductor devices in which miniaturization has been progressing, a shift from the 0.1 μm generation, so-called in design rule, to the latter generations has been under way. In such circumstances, in the manufacturing process of semiconductor devices, planarization of surface is required in view of the limit in the depth of focus (DOF) on the exposure side attendant on the miniaturization, and, for achieving the surface planarization, chemical mechanical polishing (hereinafter referred to as CMP) process has been introduced and already widely generalized. The CMP is carried out for planarizing the wafer surface by removing surplus portions of a metallic film when the metallic film has been formed over the entire surface of a semiconductor wafer for filling up trenches, which are to be wiring trenches or contact holes or the like, with a metallic material to be metallic wirings, in the wiring forming methods represented by the dual Damascene process, for example.
From the viewpoint of wiring material, on the other hand, for the purpose of reducing the wiring delay whose contribution to operational delay has come to a non-negligible level due to the miniaturization of devices, a shift of the conductive metallic material for forming the wirings from the conventionally used aluminum to copper having a lower electric resistance has been under way after the 0.1 μm generation.
In addition, in the 0.07 μm generation, the combination of the above-mentioned copper wiring and a silicone oxide film based insulation film results in that device transistor delay is higher than wiring delay in the percentage of contribution to operational delay, and, therefore, improvements in wiring structure, particularly a further reduction in the dielectric constant of the insulation film is indispensable. For this reason, in the manufacture of semiconductor devices, the adoption of super-low dielectric constant materials such as porous silica with a dielectric constant of 2 or below has been investigated. However, the super-low dielectric constant materials such as porous silica are all low in mechanical strength, and the insulation films formed of the super-low dielectric constant materials would undergo collapse, cracking, exfoliation or the like under the process pressure of 4 to 6 PSI (i.e., 280 to 420 g/cm2, because 1 PSI is equivalent to about 70 g/cm2) exerted in carrying out the conventional CMP, making it impossible to carry out favorable wiring formation. Besides, in the case where the pressure in the CMP is lowered to or below the pressure of 1.5 PSI (105 g/cm2) which the insulation films formed of the above-mentioned materials can endure, for preventing the collapse or the like from occurring, it is impossible to obtain a polishing rate required for the ordinary production rate. Thus, where a super-low dielectric constant material is used for the insulation film, many problems are involved in carrying out the CMP for planarizing the semiconductor wafer surface.
In view of the above, there has been proposed a polishing method by which the polishing rate required for the ordinary production rate can be obtained while using a low pressure by simultaneously carrying out electropolishing and wiping with a pad, instead of the above-mentioned CMP. In this method, an electric current is passed to a metallic film (for example, a copper film) on the semiconductor wafer surface which is the object of polishing, in the mode of using the metallic film as anode, and an electric current through an electrolyte is passed by supplying an electrolytic voltage between the metallic film and a opposite electrode which is a cathode disposed oppositely to the semiconductor wafer through an electrolytic solution, so as to electropolish the metallic film. By the electropolishing, the surface of the metallic film subjected to an electrolytic action as anode is anodically oxidized, with the result of formation of an oxide coating at the surface layer thereof. Furthermore, the oxide and a complex forming agent contained in the electrolytic solution react with each other, to form a denatured layer such as a high electric resistance layer, an insoluble complex coating and a passivated coating on the surface of the metallic film. Simultaneously with the electropolishing, the denatured layer is wiped with a pad, whereby the denatured layer is removed. In this case, only the denatured layer at the projected surface layer of the metallic film having unevenness is removed, to expose the metal therebeneath, while the denatured layer at the recessed surface layer is left as it is. Therefore, only the projected portions where the base (underlying) metal is exposed are re-electrolyzed and, further, are wiped, whereby the polishing of the projected portions proceeds. Such a cycle is repeated, whereby the semiconductor wafer surface is planarized.
In the above-mentioned polishing method, it is necessary to pass an electric current with the metallic film on the semiconductor wafer surface (which is the object of polishing) as anode, for carrying out the electropolishing. However, since the wiping is conducted by sliding the pad on the semiconductor wafer surface simultaneously with the electropolishing, a current passing electrode (anode) projecting on the wafer surface in such a manner as to impede the sliding motion of the pad cannot be disposed in a fixed state. In view of this, there may be contemplated a method in which a metallic film is formed up to the back side of the semiconductor wafer, and an electric current is passed via a wafer chuck coming into contact with the back side. Such a method, however, exerts great influences on the manufacturing process flow for the semiconductor device, such as contamination between itself and other apparatus at the time of handling, modifications in the method of forming the metallic film, etc.
Besides, in the electropolishing, such a current passing method as to provide a uniform current density distribution stably on the semiconductor wafer surface is required, since the polishing conditions and the polishing rate depend greatly on the current density. When electropolishing is conducted with an instable current density distribution in the case where the ratio of the area of the metallic film on the semiconductor wafer surface is reduced from the 100% state in which the metallic film is formed over the entire surface in the beginning of polishing to the state in which only the wiring patterns are left upon completion of the removal of surplus portions, there will occur such problems as corrosion or roughening of the surface of the metallic film upon the end point of polishing, generation of pits due to concentration of the electric current, etc. In addition, the difference in removal rate between the left large metal remaining portions or wide wiring portions and the independent narrow wiring portions would be increased due to concentration of dissolution rate on the narrow wirings, whereby the dissolution rate of the narrow wirings would be increased acceleratedly, leading to disappearance of the wirings. Thus, with the electropolishing under an instable current density distribution, it is difficult to form a favorable end point surface.
The above-mentioned problems may similarly occur also in the case where an electropolishing medium based on a CMP slurry containing abrasive grains and rendered electrically conductive is substituted for the electrolytic solution in carrying out the electropolishing.
Furthermore, since the metallic film to which the electric current is to be passed is itself the object of polishing in the above-mentioned polishing method, when the metallic film in the area where the electric current is passed by the current passing electrode is dissolved in advance, it becomes impossible to pass the electric current to the other areas where the metallic film still remains. Particularly, where a current passing electrode for passing an electric current by being slid in the vicinity of the peripheral edge of the semiconductor wafer is provided, electrolysis would be concentrated due to mechanical causes such as scratches, flaws, cuts, etc. and electrochemical causes such as sparks, electro-corrosion, etc. generated at the contact point between the current passing electrode and the metallic film, so that the contact point portion between the current passing electrode and the metallic film which should be left until the end point of polishing so as to perform the electropolishing over the entire surface might be dissolved precedingly. As a result, serious defects such as remaining of metal due to insufficient polishing, over-polishing, etc. would be generated, with the result of shortcircuit or opening of the wirings, or the formation of a surface which has a coarse surface roughness and an instable wiring electric resistance.
Accordingly, it is an object of the present invention to provide a polishing method and a polishing apparatus by which an electric current can be passed to the object of polishing with a stable current density distribution up to the end point of polishing, and further to provide a method of manufacturing a semiconductor device in which the polishing method is introduced into the manufacturing process and which makes it possible to use the same plating apparatus, cleaning apparatus and other apparatuses as those in the related art and to carry out the conventional manufacturing process flow.
In order to attain the above object, according to the present invention, there is provided a polishing method including the steps of: disposing a substrate provided thereon with a metallic film and a opposite electrode oppositely to each other with a predetermined interval therebetween in an electrolytic solution; and passing an electric current to the metallic film through the electrolytic solution by a current passing electrode set out of contact with the metallic film so as to electropolish the metallic film.
In addition, according to the present invention, there is provided a polishing apparatus including, in an electrolytic solution: a substrate provided thereon with a metallic film; a opposite electrode disposed oppositely to the substrate with a predetermined interval therebetween; and a current passing electrode set out of contact with the metallic film, wherein an electric current is passed to the metallic film through the electrolytic solution by the current passing electrode so as to electropolish the metallic film.
In the polishing method and the polishing apparatus according to the present invention as mentioned above, an electric current is passed to the metallic film through the electrolytic solution by the current passing electrode set in the state of being out of contact with the metallic film, to thereby perform electropolishing. Therefore, in the present invention, the current passage portion of the metallic film opposite to the current passing electrode acts as a cathode, on which electrons are concentrated and the cations in the electrolytic solution are deposited. In addition, since the current passing electrode is out of contact with the metallic film, there would not occur the problem that flaws or the like might be generated due to contact or sliding between the current passing electrode and the metallic film, the electrolysis might be concentrated on the flawed portions, and the current passage portions might be dissolved precedingly. Therefore, according to the present invention, it is ensured that the electropolishing proceeds favorably up to the end point of polishing, and such problems as remaining of the metallic film, over-polishing, etc. are prevented from being generated.
In addition, in the present invention, wiping is conducted simultaneously with the above-mentioned electropolishing. A pad to be used at the time of the wiping is smaller in diameter than the metallic film, and the current passing electrode is disposed at a peripheral edge portion of the metallic film protruding outwards from the area of the pad. Therefore, even through the current passing electrode is disposed on the side of the surface to the polished, it does not hinder the wiping, and the electropolishing and the wiping are conducted simultaneously and favorably.
Besides, according to the present invention, there is provided a method of manufacturing a semiconductor device, including the steps of: disposing a wafer substrate and a opposite electrode oppositely to each other with a predetermined interval therebetween in an electrolytic solution, the wafer substrate being provided thereon with a metallic film formed of a metallic wiring material so as to fill up connection holes or wiring trenches formed in an inter-layer insulation film or both of the connection holes and the wiring trenches; and passing an electric current to the metallic film through the electrolytic solution by a current passing electrode set out of contact with the metallic film so as to electropolish the metallic film.
In the method of manufacturing a semiconductor device according to the present invention, like in the above-mentioned polishing method, the electropolishing proceeds favorably up to the end point of polishing, such problems as remaining of the metallic film and over-polishing are prevented from being generated, and the electropolishing and the wiping are performed simultaneously and favorably. As a result, according to the present invention, such defects as shortcircuit and opening of the metallic wirings are restrained from being generated, and a surface which is smooth and has a stable wiring electric resistance is formed. In addition, unlike in the case of, for example, forming a metallic film also on the back side of the wafer substrate and passing an electric current from the back side, it is unnecessary to take into account contamination between the metallic film and other apparatuses, modifications in the method of forming the metallic film or the like, and it is possible to manufacture a semiconductor device by using the same film forming apparatus and post-polishing cleaning apparatus as those conventionally used and following the conventional semiconductor device manufacturing process flow.
Furthermore, in the present invention, the current passing electrode is set out of contact with the metallic film, and the inter-layer insulation film is not pressed at the time of passing an electric current. Therefore, according to the present invention, breakage of the inter-layer insulation film such as exfoliation and cracking is prevented from occurring and a favorable wiring formation is realized, even in the case where a low-strength low dielectric constant film formed of a low dielectric constant material such as porous silica is used as the inter-layer insulation film.
Now, an information transmission system and an information transmission method pertaining to the present invention will be described in detail below, taking into consideration the drawings which illustrate embodiments thereof.
Specific embodiments of the polishing method, the polishing apparatus and the method of manufacturing a semiconductor device according to the present invention will be described in detail below referring to the drawings.
The polishing method according to the present invention includes, in planarizing a metallic film, for example, a copper (Cu) film formed on a substrate and having unevenness, the steps of performing electropolishing with the metallic film on the substrate as the object of polishing, and simultaneously wiping the surface of the metallic film by sliding a pad on the metallic film surface. Incidentally, the following description will be made by taking as an example the case where the metallic film is a Cu film.
As shown in
In the case where the non-contact type anode 4 is thus used, when the anode 4 is so disposed that the distance d between the Cu film 2 and the anode 4 is overwhelmingly smaller than the distance D between the Cu film 2 and the opposite electrode 3, a portion (region A in
Where electropolishing is conducted by passing the electric current through an electrolyte by use of the non-contact type anode 4, electrons are concentrated into the region B of the Cu film 2 opposed to the anode 4 and serving as cathode to receive the electrolytic action, and cations in the electrolytic solution will be deposited on the region B of the Cu film 2; for example, where copper ions are present in the electrolytic solution, copper will be deposited on the region B of the Cu film 2. For this reason, the electropolishing proceeds while the region B of the Cu film 2 remains due to the deposition of the cations. Therefore, in the above-mentioned polishing method, the electropolishing can be made to proceed to the end point without the problem that the Cu film 2 in the region B for passing the electric current to the anode 4 might be precedingly dissolved during the electropolishing to make it impossible to pass the electric current in the course of polishing. Incidentally, contrary to the above-mentioned region B of the Cu film 2, the region A of the Cu film 2 opposed to the opposite electrode 3 and serving as anode to receive the electrolytic action is deprived of electrons by the Cu film 2 in the region B, so that the surface thereof is anodically oxidized to form the above-mentioned denatured layer.
In addition, by conducting the electropolishing by use of the non-contact type anode 4, concentration of electrolysis due to mechanical causes such as scratches, flaws, cuts, etc. due to contact or sliding between the Cu film 2 and the anode 4 or electrochemical causes such as sparks, electro-corrosion, etc. is prevented from occurring, and it is possible to pass the electric current with a uniform current density distribution.
In the polishing method according to the present invention, wiping of the surface of the Cu film 2 with a pad is conducted simultaneously with the above-mentioned electropolishing. The wiping consists in sliding the pad on the surface of the Cu film 2 having been anodically oxidized, thereby to remove the denatured layer coating present at the surface layer of projected portions of the Cu film 2 having an unevenness, to expose the Cu therebeneath, and to cause re-electrolysis of the exposed Cu portions. This cycle of electropolishing and wiping is repeatedly conducted, whereby planarization of the Cu film 2 formed on the substrate 1 is made to proceed.
In the wiping, there is used such a pad that the area of contact between the pad and the Cu film 2 is smaller than the area of the Cu film 2 on the substrate 1 serving as the object of polishing. Therefore, the wiping is conducted in the condition where a part of the Cu film 2 is always protruding outwards from the area of the pad. Incidentally, the wiping is conducted under the condition where the above-mentioned anode 4 is disposed over the portion protruding outwards from the pad, for example, over a peripheral edge portion of the Cu film 2, and the pad is slid on the Cu film 2 in other area than the area where the anode 4 is disposed, i.e., while avoiding the layout position of the anode 4. Therefore, in the above-described polishing method, the anode 4 for passing the electric current can be disposed over the surface to be polished of the Cu film 2 serving as the object of polishing, and the wiping is not inhibited by the anode 4 disposed over the surface to be polished.
In addition, the wiping is conducted while driving, for example rotating, the pad itself. Besides, at the time of wiping, the substrate 1 is also driven to rotate, in the direction opposite to the driving direction of the pad.
In the above-mentioned wiping, with the substrate 1 rotated, uniform polishing is conducted over the whole surface of the Cu film 2 formed on the substrate 1. Namely, while the wiping is conducted by sliding the pad on the Cu film 2 in other area than the area where the anode 4 is disposed, the rotation of the substrate 1 enables sequential changeover between the peripheral edge portion where the anode 4 is disposed and the sliding range of the pad is not located and the peripheral edge portion where the sliding range of the pad is located, so that uniform polishing can be conducted over the whole surface of the Cu film 2. In addition, even where the substrate 1 is rotated, the anode 4 for passing the electric current to the Cu film 2 is out of contact with the Cu film 2 as above-described, so that concentration of electrolysis due to mechanical causes such as scratches, flaws, cuts, etc. at the contact point between the Cu film 2 and the anode 4 or electrochemical causes such as sparks, electro-corrosion, etc. is obviated, and the passage of the electric current is prevented from becoming impossible due to, for example, complete losing of the Cu film 2 at the current passage portion precedent to the end point of polishing. Therefore, according to the present polishing method, the passage of the electric current can be conducted up to the completion of polishing, the electropolishing proceeds favorably, and remaining of Cu on the inner circumferential side and the like trouble can be prevented from occurring.
In the polishing method in which electropolishing and wiping are conducted simultaneously as above-described, it suffices that the Cu film 2 and the anode 4 are out of contact with each other at least only at the time of passing the electric current. Therefore, the electric current may be passed to the Cu film 2 by an anode 4 which is always out of contact with the Cu film 2, specifically, which is out of contact with the Cu film 2 before, during, and after the polishing, or the electric current may be passed to the Cu film 2 by an anode 4 which is out of contact with the Cu film 2 only during the polishing when the current must be passed to the Cu film 2. In order to pass the electric current in the non-contact condition only during the polishing, for example, there is utilized a dynamic pressure of the electrolytic solution flowing into the gap between the anode 4 and the substrate 1 attendant on the rotation of the substrate 1. The dynamic pressure effect of the electrolytic solution levitates the anode 4 from the Cu film 2 by a tiny distance, whereby it is possible to set the Cu film 2 and the anode 4 out of contact with each other at the start of polishing. Incidentally, the levitation amount of the anode 4 can be regulated by the flow rate of the electrolytic solution, which is determined by the viscosity of the electrolytic solution and the rotating speed of the substrate 1, and the shape of the anode 4. By stably maintaining the levitation amount of the anode 4, the electric current through an electrolyte can be passed to the Cu film 2 with a stable electric resistance.
By polishing the Cu film 2 by the above-described polishing method, the electric current is passed stably and with a uniform current density distribution, whereby the electropolishing can be performed under favorable polishing rate and polishing conditions. In addition, the current passage portion between the Cu film 2 and the anode 4 would not be precedingly dissolved before completion of polishing, and the electropolishing can be made to proceed favorably up to the end point of polishing. Therefore, in the above-described polishing method, such problems remaining of Cu and over-polishing can be prevented from being generated.
In addition, in the polishing method as above, the anode 4 is disposed on the side of the surface to be polished of the Cu film 2, and the wiping is conducted by sliding the pad on the Cu film 2 in other area than the area where the anode 4 is disposed, so that the anode 4 does not hinder the wiping, and the electropolishing and the wiping can be conducted simultaneously and favorably. Therefore, the anode 4 can be disposed on the surface to be polished of the Cu film 2, and it is unnecessary to take into account contamination between itself and other apparatuses, modifications in the method of forming the Cu film 2 on the substrate 1 or the like, unlike in the case where, for example, the Cu film 2 is formed also on the back side of the substrate 1 and the current is passed from the back side.
Incidentally, the polishing method as above is also applicable to the case where an electropolishing medium based on a CMP slurry containing abrasive grains and rendered electrically conductive is substituted for the electrolytic solution, for enhancing the planarizing capability.
Besides, while the above polishing method has been described referring to the case where the electrolytic solution E containing a complex forming agent is used to form the denatured layer on the surface of the Cu film 2 through electropolishing and the denatured layer is wiped away to thereby polish the Cu film 2, there may be adopted a system in which Cu is dissolved out of the Cu film 2 by electropolishing to thereby polish the Cu film 2.
The polishing method as above can be applied to a polishing step in which the unevenness of a metallic film formed for filling up wiring trenches is planarized by polishing so as to form metallic wirings, in the manufacture of a semiconductor device. Now, the method of manufacturing a semiconductor device in which the above-described polishing method is carried out in the manufacturing process will be described below. The method of manufacturing a semiconductor device resides in forming metallic wirings composed of Cu by use of the so-called Damascene process. Incidentally, while the following description will be made referring to the formation of Cu wirings in a dual Damascene structure in which wiring trenches and contact holes are processed simultaneously, it is natural that the method of manufacturing a semiconductor device be also applicable to the formation of Cu wirings in a single Damascene structure in which only wiring trenches or connection holes are formed.
First, as shown in
Next, as shown in
Subsequently, as shown in
After the formation of the barrier metal film 13 as above-mentioned, the wiring trenches M and the contact holes CH are filled up with Cu. The filling with Cu can be carried out by any of various kinds of known techniques conventionally used, for example, an electroplating method, a CVD method, a sputtering-and-flow method, a high-pressure reflow method, an electroless plating method or the like. Incidentally, from the viewpoints of film formation rate, film formation cost, the purity of the metallic material formed, adhesion performance and the like, it is preferably to carry out the filling with Cu by the electroplating method. Where the filling with Cu is conducted by the electroplating method, as shown in
The filling of the wiring trenches M and the contact holes CH with Cu is carried out by forming a Cu film 15 over the whole area on the inter-layer insulation film 12 inclusive of the inside of the wiring trenches M and the contact holes CH by any of the above-mentioned various methods, as shown in
Subsequently, a polishing step is applied to the wafer substrate 11 provided thereon with the Cu film 15 as above-described. In the polishing step, the above-described polishing method in which electropolishing and wiping with a pad are simultaneously conducted is carried out. Specifically, as shown in
In the manufacture of a semiconductor device, after the above-described polishing step, polishing of the barrier metal film 13 and cleaning are conducted, and a cap film is formed on the wafer substrate 11 provided with the Cu wirings. Then, the steps ranging from the formation of the inter-layer insulation film 12 (illustrated by
As has been described above, by carrying out the polishing method of performing the electropolishing and the wiping during the semiconductor device manufacturing process, an electric current is passed stably and with a uniform current density distribution, and planarization of the Cu film 15 is contrived by the electropolishing which proceeds under the favorable polishing rate and polishing conditions up to the end point of polishing; therefore, such problems as remaining of Cu and over-polishing are prevented from occurring. Accordingly, such defects as shortcircuit and opening of the Cu wirings can be restrained from being generated, and it is possible to form a surface which is smooth and has a stable wiring electric resistance.
In addition, since the electropolishing and the wiping are conducted simultaneously and favorably while the anode is disposed on the side of the surface to be polished of the Cu film 15, it is unnecessary to take into account contamination between itself and other apparatuses or modifications in the method of forming the Cu film 15 on the wafer substrate 11, and the semiconductor device can be manufactured by using the same Cu film forming apparatus and post-polishing cleaning apparatus as those conventionally used and by using the conventional semiconductor device manufacturing process flow, unlike in the case where, for example, the Cu film 15 is formed also on the back side of the wafer substrate 11 and the electric current is passed from the back side.
Furthermore, since the wiping of the denatured layer is conducted with a pressing pressure lower than that in CMP, specifically, with a pressing pressure lower than the breaking pressure of the inter-layer insulation film 12 formed from a low dielectric constant material such as porous silica and having a low strength, breakage of the inter-layer insulation film 12 such as exfoliation and cracking is prevented from occurring. In addition, since the anode for passing the electric current to the Cu film 15 is in a non-contact state, no pressure is exerted on the inter-layer insulation film 12, so that the inter-layer insulation film 12 is prevented from undergoing exfoliation, cracking or the like. Therefore, favorable wiring formation can be achieved even where a low dielectric constant film with low strength is used as the inter-layer insulation film 12.
Incidentally, the above-described method of manufacturing a semiconductor device can be applied also to the case where an electropolishing medium based on a CMP slurry containing abrasive grains and rendered electrically conductive is substituted for the electrolytic solution in the above-described polishing step for the purpose of enhancing the planarizing capability.
Besides, the above-described polishing method in which electropolishing is conducted by passing an electric current through the electrolytic solution by the anode serving as the current passing electrode set in a non-contact state can naturally be carried out not only in the polishing step in manufacture of a semiconductor device but also in all kinds of other manufacturing processes including a step of polishing a metallic film.
The polishing apparatus for use in the above-described polishing method and in the polishing step in the method of manufacturing a semiconductor device will be described.
As shown in
On the Cu film 15 of the semiconductor wafer W held under suction by the wafer chuck 23, a pair of anode portions 24 are disposed in the vicinity of the peripheral edge thereof, as shown in
The anode portion 24 is supported by a first arm 25 for moving the anode portion 24 in the direction perpendicular to the surface to be polished of the Cu film 15 and a second arm 26 for moving the anode portion 24 in the direction horizontal to the surface to be polished, and is disposed at the tip end of the second arm 26 through an elastic member which will be described later. In the polishing apparatus 21, the pressing pressure of the anode portion 24 is regulated by the first arm 25 so that the anode portion 24 is levitated into a non-contact state over and in proximity to the Cu film 15 when the semiconductor wafer W is rotated. In addition, in the polishing apparatus 21, at the times of loading and unloading the semiconductor wafer W onto and from the wafer chuck 23, the anode portion 24 is moved by the second arm 26 to a retracted position for letting free the upper side of the wafer chuck 23. Therefore, the wafer W can be loaded and unloaded via the upper side of the wafer chuck 23.
As shown in
The anode portion 24 is disposed on the current passage area in the vicinity of the peripheral edge of the Cu film 15 as above-mentioned, in such a manner that it is supported on the second arm 26 through an elastic member, for example, a spring 27 and that the cutout portion is located on the upstream side with respect to the rotating direction of the semiconductor wafer W, as shown in
In addition, as shown in
In the polishing apparatus 21 as above, the Cu film 15 on the semiconductor wafer W is electropolished by passing an electric current to the Cu film 15 serving as anode by the anode portions 24, and, simultaneously with the electropolishing, wiping is conducted with the pad 28 sliding on the Cu film 15 through moving in the direction of arrows G while rotating. The wiping with the pad 28 is carried out with a pressing pressure of not less than 140 g/cm2 which is the breaking pressure of the inter-layer insulation film formed of a low dielectric constant material such as porous silica.
By thus passing the electric current to the Cu film 15 by use of the anode portions 24 set out of contact with the Cu film 15, the electric current can be passed stably and with a uniform current density distribution, whereby electropolishing is conducted under favorable polishing rate and polishing conditions. In addition, precedent dissolution of the current passage portions between the Cu film 2 and the anodes 4 before completion of polishing is obviated, and the electropolishing proceeds favorably up to the end point of polishing. Therefore, in the polishing apparatus 31 as above-described, such problems as remaining of Cu and over-polishing are prevented from occurring, such defects as shortcircuit and opening of the Cu wirings can be restrained from being generated, and it is possible to form a surface which is smooth and has a stable wiring electric resistance.
In addition, in the polishing apparatus 21, since the electropolishing and the wiping are conducted simultaneously and favorably while the anodes 4 are disposed on the side of the surface to be polished of the Cu film 15, it is unnecessary to take into account contamination between itself and other apparatuses, and a semiconductor device can be manufactured by using the same Cu film forming apparatus and post-polishing cleaning apparatus as those conventionally used and using the conventional semiconductor device manufacturing process flow, unlike in the case where, for example, the Cu film 15 is formed also on the back side of the wafer substrate 11 and the electric current is passed from the back side.
Furthermore, the wiping of the denatured layer is carried out with a pressing pressure of not more than the breaking pressure of the inter-layer insulation film formed of a low dielectric constant material and having a low strength. Therefore, in the polishing apparatus 21, unlike in the case of polishing by CMP, breakage of the inter-layer insulation film such as exfoliation and cracking would not occur, and, as a result, a favorable wiring formation can be achieved. Besides, since the anodes for passing an electric current to the Cu film 15 is out of contact with the Cu film 15, the passage of the electric current to the Cu film 15 does not involve application of a pressure to the inter-layer insulation film, so that the inter-layer insulation film does not undergo exfoliation, cracking or the like.
The polishing apparatus according to the present invention is not limited to the above-described configuration but may have other configuration. Now, polishing apparatuses of other configurations will be described. Incidentally, in the following description, the same members as those in the above-described polishing apparatus 21 will be denoted by the same symbols as used above, and detailed description thereof will be omitted.
As shown in
In the polishing apparatus 31, wiping is conducted while the semiconductor wafer W held face-down under suction is pressed against the pad 32 which is moved while being rotated in the direction of arrow I. Electropolishing is conducted by passing an electric current by anode portions 24 disposed, in the state of being supported by arms 34, at peripheral edge portions of the semiconductor wafer W protruding outwards from the pad 32. In this case, the anode portions 24 are levitated attendant on the rotation of the semiconductor wafer W, so that the passage of the electric current is conducted in the condition where the anode portions 24 are out of contact with the Cu film on the semiconductor wafer W.
Besides, the above-described polishing apparatus 31 may be have the configuration shown in
Next, a polishing apparatus 41 having still another configuration will be described. As shown in
In the polishing apparatus 41, the semiconductor wafer W held face-down under suction, while rotating in the direction of arrow K, is pressed against the pad 42 rotated in the direction of arrow J, whereby wiping is conducted. Electropolishing is conducted by passing an electric current by anode portions 24 supported by an arm 43 at a peripheral edge portion of the semiconductor wafer W protruding outwards from the pad 42. In this case, the anode portions 24 are levitated attendant on the rotation of the semiconductor wafer W as shown in
Next, a polishing apparatus 51 having a still further configuration will be described. As shown in
In this polishing apparatus 51, wiping is conducted in the condition where the semiconductor wafer W held face-down under suction is, while rotating in the direction of arrow M, pressed against the pad 52 rotated in the direction of arrow L and performing the planetary motion. Electropolishing is conducted by passing an electric current by anode portions 24 supported by arms 53 at peripheral edge portions of the semiconductor wafer W protruding outwards from the pad 52. In this case, the anode portions 24 are levitated attendant on the rotation of the semiconductor wafer W, so that the electric current is passed to a Cu film on the semiconductor wafer W in the condition where the anode portions 24 are out of contact with the Cu film.
In the polishing apparatuses 31, 41, and 51 configured as above-described, like in the case of the above-described polishing apparatus 21, such problems as remaining of Cu and over-polishing are prevented from occurring, such defects as shortcircuit and opening of Cu wirings can be restrained from being generated, and it is possible to form a surface which is smooth and has a stable wiring electric resistance. In addition, a semiconductor device can be manufactured by using the same Cu film forming apparatus and post-polishing cleaning apparatus as those conventionally used and following the conventional semiconductor device manufacturing process flow.
As has been described in detailed above, according to the polishing method and the polishing apparatus provided by the present invention, the electric current is passed to the metallic film by use of the current passing electrode set out of contact with the metallic film and the electropolishing is thereby conducted, whereby the metallic film at the current passing portion(s) can be left until the end point of polishing, the electropolishing of the metallic film can be made to proceed favorably, and such problems as remaining of the metallic film and over-polishing can be prevented from occurring.
In addition, according to the present invention, the pad smaller in diameter than the metallic film is used, and the current passing electrode is disposed at a peripheral edge portion of the metallic film protruding outwards from the area of the pad, whereby the current passing electrode disposed on the side of the surface to be polished does not inhibit the wiping, and the electropolishing and the wiping can be conducted simultaneously and favorably.
Furthermore, by the method of manufacturing a semiconductor device according to the present invention, like in the case of the above-described polishing method, electropolishing can be made to proceed favorably up to the end point of polishing, such problems as remaining of the metallic film and over-polishing can be prevented from occurring, and the electropolishing and the wiping can be conducted simultaneously and favorably. Therefore, according to the present invention, such defects as shortcircuit and opening of the metallic wirings can be restrained from being generated, and it is possible to form a surface which is smooth and has a stable wiring electric resistance. Besides, it is unnecessary to take into account contamination between the metallic film and other apparatuses, modifications in the method of forming the metallic film, or the like, and a semiconductor device can be manufactured by using the same film forming apparatus and post-polishing cleaning apparatus as those conventionally used and following the conventional semiconductor device manufacturing process flow.
Furthermore, according to the present invention, since the current passing electrode is used in a non-contact state and no pressure is exerted on the inter-layer insulation film at the time of passing the electric current, breakage of the inter-layer insulation film such as exfoliation and cracking can be prevented from occurring and a favorable wiring formation can be achieved, even where a low dielectric constant film formed of a low dielectric constant material such as porous silica and having a low strength is used as the inter-layer insulation film.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2002-121333 | Apr 2002 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP03/05108 | 4/22/2003 | WO |
