JP3545220B2 - Polishing method and semiconductor device manufacturing method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a polishing method and a method for manufacturing a semiconductor device, and more particularly to a polishing method for flattening a substrate surface by chemical mechanical polishing and a method for manufacturing a semiconductor device having a polishing step.
[0002]
[Prior art]
2. Description of the Related Art In recent years, CMP (Chemical Mechanical Polishing) technology has been attracting attention due to demands for multilayer wiring and improvement in global flatness of semiconductor devices. The CMP technique is a technique for planarizing a wafer surface by chemically and mechanically polishing a film to be polished on the wafer.
[0003]
The planarization of a wafer using the CMP method is performed by supplying a polishing liquid (slurry) to a polishing cloth attached to a surface plate, and polishing a film to be polished on a wafer mounted on a spindle head to a polishing cloth on the surface plate. In this state, the platen and the spindle head are rotated to polish the film to be polished on the wafer.
In such a CMP technique, since the wafer and the film to be polished are mechanically and physically contacted with the polishing cloth, the wafer or the film to be polished is easily scratched. May adhere to the wafer, and techniques for reducing these are being actively studied.
[0004]
For example, a polishing liquid sometimes contains contaminants such as sodium and potassium that affect the characteristics of a semiconductor device, and after polishing, a process for removing these contaminants has been performed. Conventional treatments for removing contaminants include re-polishing with pure water, scrubbing with a brush, high-pressure pure water treatment, ultrasonic cleaning, HF treatment, ammonia water treatment, or a combination of these treatments. Was.
[0005]
[Problems to be solved by the invention]
When a wafer or a film to be polished having a deep dent or groove is polished by a conventional polishing method using the CMP technique, it has been found for the first time by the present inventor that the dent or groove is clogged with foreign matter. Such foreign matter cannot be removed by the above-described conventional treatment for removing contaminants, and it has been desired to investigate the cause of the foreign matter and to provide an effective method for removing the foreign matter.
[0006]
In addition, when the dents and grooves are alignment marks used in the photolithography process or marks for measuring the amount of misalignment, clogging of the dents and grooves may make it impossible to perform alignment or misalignment measurement. Was.
In addition, even if it is not a dent or the like used for such a purpose, shavings may come off during subsequent processing, which may cause generation of foreign matter.
[0007]
SUMMARY OF THE INVENTION An object of the present invention is to provide a polishing method and a method for manufacturing a semiconductor device capable of removing shavings and the like of a polishing cloth clogged in a film to be polished and a depression in a wafer surface after polishing.
[0008]
[Means for Solving the Problems]
The above object, the while supplying a polishing liquid to the semiconductor base plate and the insulating film and a metal film are laminated to the insulating film is exposed by polishing the metal film chemically mechanically, formed in the insulating film a step of Ru is left the metal film in the opening, by exposing the semiconductor substrate to the organic amine solution or an organic amine atmosphere, the step of removing the foreign matter remaining on the metal film in the opening after polishing And a polishing method characterized by having the following. After the substrate is polished, if the substrate is exposed to an organic amine-based solution or an organic amine-based atmosphere, even if shavings such as a polishing cloth are clogged in the dents and grooves of the substrate, the washing removes the shavings. Can be removed. Therefore, it is possible to prevent a problem due to the shavings, for example, insufficient detection of the alignment mark and a generation of foreign matter due to shavings in a subsequent process.
[0009]
In the above polishing method, in the step of removing the foreign matter, the semiconductor substrate may be immersed in the organic amine-based solution.
In the above polishing method, in the step of polishing the semiconductor substrate, the step of polishing the semiconductor substrate while dropping the polishing liquid on a first platen in a polishing apparatus, and removing the foreign matter, The semiconductor substrate may be scrubbed while dropping the organic amine-based solution on a second platen in the polishing apparatus.
[0010]
In the above polishing method, in the step of removing the foreign matter, the foreign matter on the semiconductor substrate is removed in an organic amine solution or an organic amine atmosphere containing a compound having a dissolution inhibiting effect on metal. You may do so. If a compound having a dissolution inhibiting effect on a metal is mixed into an organic amine-based solution or an organic amine-based atmosphere, it is possible to prevent the metal film from being damaged by the organic amine-based substance. Therefore, when polishing a substrate such that a metal film is exposed after polishing, it is extremely effective to mix a compound having a dissolution inhibiting effect on the metal.
[0011]
The polishing method may further include a step of removing contaminants of the polishing liquid remaining on the semiconductor substrate after polishing.
In the above polishing method, in the step of polishing the semiconductor substrate, the semiconductor substrate may be polished using the alumina-based or silica-based polishing liquid.
[0012]
The above-described object, the while supplying a polishing liquid to the semiconductor base plate and the insulating film and a metal film are laminated to the insulating film is exposed by polishing the metal film chemically mechanically, formed in the insulating film a step of the metal film in the opening Ru is left that is, removing the by the semiconductor substrate is exposed to an organic amine solution or an organic amine atmosphere, the foreign matter remaining on the metal film in the opening after polishing And a method of manufacturing a semiconductor device.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
[First Embodiment]
The polishing method and the method for manufacturing a semiconductor device according to the first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a process diagram showing the polishing method according to the present embodiment, FIGS. 2 and 3 are process sectional views showing the method for manufacturing the semiconductor device according to the present embodiment, and FIG. It is a top view showing the state of the alignment mark after performing washing.
[0014]
As shown in FIG. 1, the polishing method according to the present embodiment includes a step of flattening a wafer surface by polishing (step S11) and a cleaning step (step S12) for mainly removing contaminants of a polishing liquid adhered on the wafer. ) And a cleaning process (step S13) for removing foreign substances clogged in the film to be polished and the depressions on the wafer surface mainly after polishing.
[0015]
Here, step S11 and step S12 are the same polishing step and cleaning step as the conventional polishing method. In the polishing step of step S11, for example, the surface of the wafer is flattened by a CMP (Chemical Mechanical Polishing) method using a silica-based or alumina-based polishing liquid. In addition, in the cleaning step of step S12, for example, re-polishing with pure water, scrubbing with a brush, high-pressure pure water treatment, ultrasonic cleaning, HF treatment, ammonia water treatment, or a combination of these treatments, A contaminant, such as sodium or potassium, in a polishing liquid attached to a surface and adversely affecting characteristics of a semiconductor device is removed.
[0016]
The cleaning process in step S13 is a process that is a main feature of the polishing method according to the present embodiment, and by exposing the wafer to an organic amine solution or an organic amine atmosphere, the polished film or wafer after polishing is exposed. This is a step of removing foreign substances clogged in the depressions on the surface.
As a result of the inventor's intensive studies, foreign matter clogged in the polished film or the recesses on the wafer surface after polishing is mainly due to the roughness of the polishing cloth surface due to continuous use of the polishing cloth and the polishing cloth compared with the polished film. It is the first time that the amount of such foreign matter varies depending on the type of polishing liquid or polishing cloth. It has also been found for the first time that such a foreign substance can be removed by a treatment using an organic amine-based solution. Therefore, even if foreign matter is generated by polishing a wafer having a deep depression or groove or a film to be polished, such foreign matter can be removed by performing the main cleaning step.
[0017]
The organic amine-based solution that can be applied to the polishing method according to the present embodiment is not particularly limited, but includes, for example, monomethylamine, dimethylamine, trimethylamine, monomethanolamine, monoethanolamine, choline, and tetramethylhydroxide. And the like.
When an organic amine-based aqueous solution is used for cleaning to remove foreign matter remaining in the depressions of the substrate or the film to be polished, if a metal film (for example, a tungsten film) is exposed on the substrate surface, the organic amine-based aqueous solution is used. The metal film may be damaged. Therefore, in such a case, it is desirable to use an organic amine-based solution or an organic amine-based atmosphere containing a compound having a dissolution inhibiting effect on the metal.
[0018]
The compound capable of obtaining a dissolution inhibiting effect on metals by mixing with an organic amine-based aqueous solution or the like is not particularly limited, but phenol-based compounds such as phenol, catechol, and pyrogallol can be applied. . Hereinafter, the method for fabricating the semiconductor device according to the present embodiment will be described with specific examples. The following example is an example in which the polishing method according to the present embodiment is applied to an electrode plug embedding process.
[0019]
2 and 3 are sectional views of the semiconductor device according to the present embodiment in the steps of the method for fabricating the semiconductor device, in which the left side of each figure shows the alignment mark formation region and the right side shows the device region.
First, a silicon oxide film having a thickness of about 1 μm is deposited on the base substrate 10 by, for example, a CVD method, and an interlayer insulating film 14 made of a silicon oxide film is formed (FIG. 2A). The base substrate 10 may be a semiconductor substrate, or may be a case in which one or two or more wiring layers have already been formed. FIG. 2A assumes a base substrate 10 on which a wiring layer 12 is formed.
[0020]
Next, a contact hole 16 reaching the wiring layer 12 having an opening diameter of about 0.5 μm is formed in the interlayer insulating film 14 by using a usual lithography technique and an etching technique. At this time, an opening 18 which forms an alignment mark for performing alignment between the contact hole 16 and an upper wiring layer is formed in the alignment mark forming region (FIG. 2B).
[0021]
Subsequently, a tungsten film 20 having a thickness of about 0.5 μm is deposited on the entire surface by, eg, CVD. Thereby, the inside of the contact hole 16 is completely filled with the tungsten film 20. On the other hand, since the opening 18 has a large opening width, the opening 18 is not completely buried by the tungsten film 20, and a depression 22 is formed on the surface (FIG. 2C).
[0022]
Thereafter, the tungsten film 20 is polished by, for example, a CMP method using a silica-based or alumina-based polishing liquid until the interlayer insulating film 14 is exposed, and the tungsten film 20 is left in the contact hole 16. Thus, the electrode plug 24 embedded in the contact hole 16 is formed (FIG. 2D).
At this time, for example, if the surface of the polishing pad is roughened due to continuous use of the polishing pad or the hardness of the polishing pad is reduced as compared with the film to be polished, as shown in FIG. The shavings 26 of the polishing cloth remain.
[0023]
Next, the wafer after CMP is immersed in, for example, 5% ammonia water for 60 seconds in a quartz water tank, and then immersed in 2% hydrofluoric acid for 60 seconds in a Teflon water tank to contaminate the polishing liquid attached to the wafer. Remove material. The wafer after the cleaning process is, for example, rinsed with ultrapure water and then spin-dried. In this cleaning step, contaminants such as sodium and potassium contained in the polishing liquid are removed, but the shavings 26 in the depression 22 cannot be removed.
[0024]
In the case where these contaminants can also be removed by a later-described cleaning process using an organic amine-based solution or a subsequent post-process, the cleaning process in step S12 is not necessarily required.
Subsequently, for example, the wafer is immersed in a 50% aqueous solution of monomethanolamine for 10 minutes. Thereby, the shavings 26 in the recess 22 are removed (FIG. 3A). Instead of being immersed in the organic amine-based solution, an organic amine-based aqueous solution may be spouted from a nozzle to clean the organic amine-based solution. Any method other than the above may be used as long as the substrate after polishing can be washed by exposing it to an organic amine-based atmosphere.
[0025]
Thereafter, an aluminum film 28 is deposited on the entire surface by, for example, a sputtering method (FIG. 3B), and the aluminum film 28 is patterned by a normal lithography technique and an etching technique using an alignment mark formed by the opening 18. The wiring layer 30 is formed (FIG. 3C). At this time, since no shavings 26 remain in the recess 22, the alignment signal obtained from the alignment mark is not weakened. Thereby, the aluminum film 28 can be accurately aligned with the pattern of the contact hole 16.
[0026]
As a result of manufacturing a semiconductor device by the above process and observing the alignment mark with a scanning electron microscope, the sample which was not washed with a 50% aqueous solution of monomethanolamine had a tungsten film 20 having a width of about 2 μm. It was confirmed that the foreign matter 32 was clogged in the dent 22 in the covered opening 18 (FIG. 4A). However, such a foreign matter was not found in the sample subjected to the cleaning treatment with the 50% aqueous solution of monomethanolamine. It was not confirmed (FIG. 4 (b)). Similarly, when a 5% aqueous solution of tetramethylammonium hydroxide was used in place of the 50% aqueous solution of monomethanolamine, no foreign matter was similarly observed. Similarly, when an aqueous solution in which 20 mg of phenol was dissolved in 500 ml of a 50% aqueous solution of monomethanolamine was used, no foreign matter was similarly observed.
[0027]
As described above, according to the present embodiment, since the cleaning treatment using the organic amine solution is performed after the polishing process, for example, the polishing cloth surface is roughened due to continuous use of the polishing cloth and the polishing cloth is compared with the film to be polished. Even when the hardness decreases and the shavings remain in the depressions, the shavings can be effectively removed. Further, it is possible to prevent the shaving foreign matter in the recess from peeling off in a later step and causing the generation of foreign matter.
[0028]
In the above embodiment, after the cleaning step (Step S12) for removing the contaminant of the polishing liquid adhering to the wafer, the polished film to be polished and the polishing cloth clogged in the depressions on the wafer surface are removed. Although the cleaning step (Step S13) for removing dust and the like was performed, any of these cleaning steps may be performed first.
[Second embodiment]
A polishing method and a method for manufacturing a semiconductor device according to a second embodiment of the present invention will be described with reference to FIGS.
[0029]
FIG. 5 is a process diagram illustrating the polishing method according to the present embodiment, and FIG. 6 is a schematic diagram illustrating the structure of a polishing apparatus used in the polishing method according to the present embodiment.
As shown in FIG. 5, the polishing method according to the present embodiment includes a step of flattening the wafer surface by polishing (step S21) and a step of mainly removing a film to be polished after polishing and foreign matter clogged in a depression on the wafer surface. A polishing method for flattening the surface of a wafer by a cleaning step (step S22) and a cleaning step (step S23) for mainly removing a contaminant of a polishing liquid attached to the wafer, comprising: a step S21; Are performed in the same polishing apparatus.
[0030]
Usually, two or more surface plates are provided in the polishing apparatus. For example, main polishing (polishing using a polishing liquid) is performed using one surface plate, and then, using another surface plate. Pure water polishing (cleaning with pure water) is performed.
In pure water polishing, scrubbing is performed by scrubbing the wafer surface with a polishing cloth while dropping pure water on a surface plate on which the wafer is placed, and at this time, instead of pure water, an organic amine-based aqueous solution is used. If the scrubbing process is performed while dropping, the same cleaning as in step S13 in the polishing method according to the first embodiment can be performed.
[0031]
Therefore, in the polishing method according to the present embodiment, the wafer is placed on the first platen in the polishing apparatus, and the wafer is polished in the same manner as the normal CMP method, and then the wafer is transferred to the second platen. Then, a scrub treatment similar to the usual buff polishing is performed while the organic amine-based aqueous solution is dropped, and thereafter, the organic amine-based aqueous solution is switched to pure water while the wafer is placed on the second platen. Buffing is performed.
[0032]
Hereinafter, the method for fabricating the semiconductor device according to the present embodiment will be described with specific examples.
First, the interlayer insulating film 14, the contact hole 16, the opening 18, and the like are formed on the base substrate 10 in the same manner as in the method of manufacturing the semiconductor device according to the first embodiment, for example, as shown in FIGS. 2A to 2C. A tungsten film 20 is formed.
[0033]
Next, this substrate is loaded into a polishing apparatus as shown in FIG. The polishing apparatus 40 shown in FIG. 6 has a plurality of surface plates 42a and 42b in the apparatus. Polishes 44a and 44b are provided on the surface plates 42a and 42b, respectively. Spindle heads 48a and 48b for holding the substrate 46 and bringing the polishing cloths 44a and 44b into close contact with the substrate are provided on the surface plates 42a and 42b, respectively. A supply device 50a for dropping a polishing liquid is provided on the surface plate 42a, and a supply device 50b for dropping an organic amine-based aqueous solution and a supply device 50c for dropping pure water are provided on the surface plate 42b. Have been.
[0034]
Subsequently, the substrate loaded in the polishing apparatus 40 is gripped by the spindle head 48a and polished on the surface plate 42a. For example, the tungsten film 20 is polished until the interlayer insulating film 14 is exposed while a silica-based or alumina-based polishing liquid is dropped from the supply device 50a, and the tungsten film 20 is left in the contact hole 16. Thus, the electrode plug 20 buried in the contact hole 16 is formed (see FIGS. 6 and 2D).
[0035]
At this time, for example, if the surface of the polishing pad is roughened due to continuous use of the polishing pad or the hardness of the polishing pad is reduced as compared with the film to be polished, as shown in FIG. The shavings 26 of the polishing cloth remain.
Thereafter, the substrate is transferred from the spindle head 48a to the spindle head 48b, and is washed on the surface plate 42b. For example, the substrate is polished for 60 seconds while a 50% aqueous solution of monomethanolamine is dropped from the supply device 50b. Then, after the dropping of the 50% aqueous solution of monomethanolamine is stopped, pure water is dropped from the supply device 50c while the substrate is polished. Polish for 2 seconds and wash the substrate. By this cleaning, shavings 26 and the like of the polishing cloth remaining in the depression 22 of the substrate can be removed (see FIGS. 6 and 3A).
[0036]
Next, the substrate is taken out of the polishing apparatus, and the substrate is cleaned in the same manner as in step S12 in the method for manufacturing a semiconductor device according to the first embodiment. For example, the wafer is immersed in 5% ammonia water for 60 seconds in a quartz water tank, and then immersed in 2% hydrofluoric acid for 60 seconds in a Teflon water tank to remove contaminants of the polishing liquid attached to the wafer. The wafer after the cleaning process is, for example, rinsed with ultrapure water and then spin-dried.
[0037]
Thereafter, an aluminum film or the like is formed in the same manner as in the method of manufacturing the semiconductor device according to the first embodiment shown in FIGS. 3B and 3C.
As a result of manufacturing a semiconductor device by the above process and observing an alignment mark with a scanning electron microscope, no foreign matter was found in the depression 22 covered with the tungsten film 20 having a width of about 2 μm.
[0038]
As described above, according to the present embodiment, cleaning for removing foreign matter remaining in the depressions of the substrate or the film to be polished can be performed in one polishing apparatus following the polishing step.
[Modified embodiment]
The present invention is not limited to the above embodiment, and various modifications are possible.
For example, in the above-described embodiment, the example in which the present invention is applied to the manufacturing process of the electrode plug is described. However, the present invention is not limited to the manufacturing process of the electrode plug, and can be widely applied to cleaning after the polishing step. Further, the present invention can be applied not only to polishing of a substrate in a semiconductor device manufacturing process but also to polishing of another substrate.
[0039]
Further, in the above-described embodiment, the cleaning process after the polishing is performed by the CMP method is described. However, the present invention can be similarly applied to a case where the substrate is polished only by the physical polishing without the chemical polishing. .
[0040]
【The invention's effect】
As described above, according to the present invention, a step of chemically and mechanically polishing a film to be polished formed on the semiconductor substrate while supplying a polishing liquid to the surface of the semiconductor substrate, and an organic amine-based solution or Polishing is performed by exposing the semiconductor substrate to foreign matter by exposing it to an organic amine-based atmosphere. Therefore, even if shavings such as polishing cloth are clogged in the dents and grooves of the substrate in the polishing process, foreign matter is removed. The shavings can be removed by washing in the removing step. Therefore, it is possible to prevent a problem due to the shavings, for example, insufficient detection of the alignment mark and a generation of foreign matter due to shavings in a subsequent process. Therefore, according to the present invention, it is possible to flatten a substrate and to perform subsequent cleaning, which is effective for manufacturing a semiconductor device such as a VLSI and a ULSI.
[Brief description of the drawings]
FIG. 1 is a process chart showing a polishing method according to a first embodiment of the present invention.
FIG. 2 is a process sectional view (part 1) illustrating the method for fabricating the semiconductor device according to the first embodiment of the present invention;
FIG. 3 is a process sectional view (part 2) illustrating the method for fabricating the semiconductor device according to the first embodiment of the present invention;
FIG. 4 is a plan view showing a state of an alignment mark after being cleaned by a conventional method of manufacturing a semiconductor device according to the first embodiment of the present invention;
FIG. 5 is a process chart showing a polishing method according to a second embodiment of the present invention.
FIG. 6 is a schematic view showing a structure of a polishing apparatus used for a polishing method according to a second embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Underground substrate 12 ... Wiring layer 14 ... Interlayer insulating film 16 ... Contact hole 18 ... Opening 20 ... Tungsten film 22 ... Dent 24 ... Electrode plug 26 ... Shavings 28 ... Aluminum film 30 ... Wiring layer 32 ... Foreign matter 40 ... Polishing Device 42 Surface plate 44 Polishing cloth 46 Substrate 48 Spindle head 50 Feeder

Claims (7)

Until said insulation layer is exposed by polishing the metal film chemically mechanically, the the opening formed in the insulating film while supplying a polishing liquid to the semiconductor base plate and the insulating film and a metal film are laminated a step of Ru is left metal film,
Exposing the semiconductor substrate to an organic amine solution or an organic amine atmosphere to remove foreign matter remaining on the metal film in the opening after polishing. The polishing method according to claim 1,
The polishing method, characterized in that in the step of removing the foreign matter, the semiconductor substrate is immersed in the organic amine solution. The polishing method according to claim 1,
In the step of polishing the semiconductor substrate, the semiconductor substrate is polished while dropping the polishing liquid on a first platen in a polishing apparatus,
The polishing method, wherein in the step of removing the foreign matter, the semiconductor substrate is scrub-washed while dropping the organic amine-based solution on a second platen in the polishing apparatus. In the polishing method according to any one of claims 1 to 3,
The polishing method, wherein in the step of removing the foreign matter, the foreign matter on the semiconductor substrate is removed in an organic amine solution or an organic amine atmosphere containing a compound having a dissolution inhibiting effect on metal. In the polishing method according to any one of claims 1 to 4,
A polishing method, further comprising the step of removing contaminants of the polishing liquid remaining on the semiconductor substrate after polishing. In the polishing method according to any one of claims 1 to 5,
The polishing method, characterized in that in the step of polishing the semiconductor substrate, the semiconductor substrate is polished using the alumina-based or silica-based polishing liquid. Until said insulation layer is exposed by polishing the metal film chemically mechanically, the the opening formed in the insulating film while supplying a polishing liquid to the semiconductor base plate and the insulating film and a metal film are laminated a step of Ru is left metal film,
Exposing the semiconductor substrate to an organic amine-based solution or an organic amine-based atmosphere to remove foreign matter remaining on the metal film in the opening after polishing. .

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