JP2000100760A - Polishing method and manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove shavings or the like of polishing cloth which are clogged in the cavity of the surface of a polished film after polishing or a water by exposing a semiconductor substrate to organic amine solution or organic amine atmosphere, after chemically and mechanically polishing the film to be polished being made on the semiconductor substrate. SOLUTION: An interlayer insulating film 14 is made on a base board 10, and a contact hole 16 which reaches a wiring layer 12 is made in the interlayer insulating film 14, subsequently a tungsten film 20 is stacked over the entire surface. Then, the tungsten film 20 is polished until the interlayer insulating film 14 is exposed by a chemical or mechanical polishing method, using for example, silicon polishing liquid, and the tungsten film 20 is left within the contact hole 16, thus an electrode plug 24 embedded in the contact hole 16 is made. After this, the washing treatment using organic amine solution is performed. For organic amine solution, for example the aqueous solution of, for example, monomethanol amine or monoethanol amine can be cited.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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]

2. Description of the Related Art In recent years, CMP (Chemical Mechanical Polishing) technology has attracted attention due to demands for multilayer wiring and improvement of global flatness of semiconductor devices. The CMP technique is a technique of flattening the wafer surface by chemically and mechanically polishing a film to be polished on the wafer.

In order to planarize a wafer using the CMP method, a film to be polished on a wafer attached to a spindle head is supplied onto a surface plate while a polishing liquid (slurry) is supplied to a polishing cloth attached to the surface plate. The polishing is performed by rotating the platen and the spindle head in this state, and polishing 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 have been actively studied.

For example, the polishing liquid sometimes contains contaminants such as sodium and potassium which affect the characteristics of the semiconductor device. After polishing, a treatment 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]

When a wafer or a film to be polished having a deep dent or groove is polished by the conventional polishing method using the CMP technique, it is the first time by the present inventor that foreign matter is clogged in the dent or groove. Was found. Such foreign substances cannot be removed by the above-described conventional process for removing contaminants, and it has been desired to investigate the cause of the foreign substances and to provide an effective method for removing them.

If 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 makes it impossible to perform alignment and misalignment measurement. There was something. Also, even if it is not a dent or the like used for such a purpose, shavings will peel off during subsequent processing,
This may cause the generation of foreign matter.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a polishing method and a method for manufacturing a semiconductor device, which can remove a film to be polished after polishing and shavings of a polishing cloth clogged in a depression on a wafer surface.

[0008]

The object of the present invention is to chemically and mechanically polish a film to be polished formed on a semiconductor substrate while supplying a polishing liquid to the surface of the semiconductor substrate. Exposing the semiconductor substrate to foreign matter by exposing the semiconductor substrate to an amine-based solution or an organic amine-based atmosphere. After polishing the substrate, if the substrate is exposed to an organic amine-based solution or an organic amine-based atmosphere, even if shavings such as an abrasive cloth are clogged in the dents and grooves of the substrate, this shaving removes the shavings. Can be removed. Therefore, it is possible to prevent a problem caused by the shavings in a subsequent process, for example, an insufficient detection of an alignment mark and a generation of foreign matter due to shavings.

In the above polishing method, in the step of removing the foreign matter, the semiconductor substrate may be immersed in the organic amine solution. Further, in the above polishing method, in the step of polishing the semiconductor substrate,
In 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 organic amine-based solution is placed on a second platen in the polishing apparatus. The semiconductor substrate may be scrub-cleaned while dropping.

In the above polishing method, in the step of removing the foreign matter, the foreign matter on the semiconductor substrate is placed in an organic amine solution or an organic amine atmosphere containing a compound having a dissolution inhibiting effect on metal. May be removed. When a compound having a dissolution inhibiting effect on a metal is mixed into an organic amine solution or an organic amine atmosphere, the metal film can be prevented from being damaged by the organic amine substance. Therefore, when polishing a substrate such that the metal film is exposed after polishing,
It is extremely effective to mix a compound having a dissolution inhibiting effect on the metal.

In the above-mentioned polishing method, the 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] Further, the above object is to provide 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; Exposing the semiconductor substrate to foreign matter by exposing the semiconductor substrate to an organic amine-based atmosphere.

[0013]

[First Embodiment] A polishing method and a method for manufacturing a semiconductor device according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a process diagram showing a polishing method according to the present embodiment, FIGS. 2 and 3 are process sectional views showing a method for manufacturing a semiconductor device according to the present embodiment, and FIG. It is a top view showing the state of the alignment mark after performing washing.

As shown in FIG. 1, the polishing method according to the present embodiment includes a step of flattening the wafer surface by polishing (step S11) and a cleaning step of mainly removing contaminants of a polishing liquid attached on the wafer. (Step S1
The feature is that the surface of the wafer is flattened by 2) and a cleaning step (step S13) for removing foreign substances clogged in the film to be polished and the depressions on the wafer surface.

Here, step S11 and step S1
2 is a polishing step and a cleaning step similar to 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.

The cleaning step in step S13 is a main feature of the polishing method according to the present embodiment. The wafer is exposed to an organic amine-based solution or an organic amine-based atmosphere to be polished after polishing. This is a step of removing foreign substances clogged in the dents on the film or wafer surface. As a result of the inventor's intensive studies, the 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 the continuous use of the polishing cloth and the polishing cloth compared with the polishing target film. It is the first time that the amount of such foreign matter varies depending on the type of polishing liquid or polishing cloth. Also,
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 when 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.

The organic amine-based solution applicable to the polishing method according to the present embodiment is not particularly limited.
For example, aqueous solutions of monomethylamine, dimethylamine, trimethylamine, monomethanolamine, monoethanolamine, choline, tetramethylhydroxide and the like can be mentioned. 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, a metal film (for example, a tungsten film) is formed on the substrate surface.
If metal is exposed, the metal film may be damaged by the organic amine-based aqueous solution. 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.

The compound which can obtain a dissolution inhibiting effect on metals by being mixed with an aqueous solution of an organic amine or the like is not particularly limited, but phenol compounds such as phenol, catechol and pyrogallol are applied. be able to. 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.

2 and 3 are sectional views showing the steps of the method for fabricating the semiconductor device according to the present embodiment. The left side of each figure shows the alignment mark forming 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. 2).
(A)). 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. In FIG. 2A, the wiring layer 12
Is assumed to be formed on the base substrate 10.

Next, using the usual lithography technique and etching technique, the interlayer insulating film 14 has an opening diameter of about 0.1 mm.
A contact hole 16 reaching the 5 μm wiring layer 12 is formed. At this time, in the alignment mark forming region, the opening 1 forming an alignment mark for aligning the contact hole 16 with the wiring layer formed thereon is formed.
8 is formed (FIG. 2B).

Subsequently, the entire surface is formed by, for example, a CVD method.
A tungsten film 20 having a thickness of about 0.5 μm is deposited. As a result, the tungsten film 2 is formed in the contact hole 16.
Completely padded with zeros. 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).

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,
Electrode plug 24 embedded in contact hole 16
Is formed (FIG. 2D). At this time, for example, if the polishing cloth surface is roughened due to continuous use of the polishing cloth or the hardness of the polishing cloth is reduced as compared with the film to be polished, as shown in FIG. The shavings 26 of the polishing cloth remain.

Next, the wafer after CMP is
In a quartz water tank, immersed in 5% ammonia water for 60 seconds, then in a Teflon water tank, immersed in 2% hydrofluoric acid for 60 seconds,
The polishing liquid contaminants attached to the wafer are removed. The wafer after the cleaning process is, for example, washed with ultrapure water,
Spin dry. In this cleaning step, contaminants such as sodium and potassium contained in the polishing liquid are removed, but the shavings 26 in the recess 22 cannot be removed.

In the case where these contaminants can be removed by a later-described cleaning treatment using an organic amine-based solution or the like or a subsequent post-treatment, the cleaning step 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 depression 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.

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 formed by a usual lithography technique and an etching technique using an alignment mark formed by the opening 18. By patterning, a 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.

A semiconductor device was manufactured by the above-described process, and the alignment marks were observed with a scanning electron microscope. As a result, it was found that the sample not washed with a 50% aqueous solution of monomethanolamine had a tungsten width of about 2 μm. Depression 22 in opening 18 covered by membrane 20
It is confirmed that the foreign matter 32 is clogged in FIG.
(A)), such a foreign substance was not confirmed in the sample subjected to the washing treatment with the 50% aqueous solution of monomethanolamine (FIG. 4 (b)). Similarly, when a 5% aqueous solution of tetramethylammonium hydroxide was used instead of the 50% aqueous solution of monomethanolamine, no foreign matter was observed. Similarly, no foreign matter was found when an aqueous solution in which 20 mg of phenol was dissolved in 500 ml of a 50% aqueous solution of monomethanolamine was used.

As described above, according to the present embodiment, since the cleaning treatment using the organic amine-based solution is performed after the polishing step, for example, the polishing cloth surface is roughened due to continuous use of the polishing cloth and the film to be polished is compared. Even when the hardness of the polishing pad is reduced and shavings remain in the depressions, the shavings can be effectively removed. In addition, it is possible to prevent the shaving foreign matter in the dent from peeling off in a later process and causing foreign matter to be generated.

In the above embodiment, after the cleaning step (step S12) for removing the contaminants of the polishing liquid adhering to the wafer, the polishing process is performed after the polishing process is completed. Although the cleaning step (Step S13) for removing shavings and the like of the cloth is performed, any of these cleaning steps may be performed first. [Second Embodiment] The polishing method and the method for fabricating a semiconductor device according to a second embodiment of the present invention will be explained with reference to FIGS.

FIG. 5 is a process diagram showing a polishing method according to the present embodiment, and FIG. 6 is a schematic diagram showing a 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 in 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 contaminants of a polishing liquid attached to the wafer, comprising a step S21 and a step S22. Are performed in the same polishing apparatus.

Normally, 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 thereafter, another surface plate is used. Polishing with pure water (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 a wafer is mounted, and at this time, an organic amine-based aqueous solution is used instead of pure water. 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.

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 in a normal CMP method. Then, the wafer is transferred to the second platen, and then an organic amine-based aqueous solution is dropped. Then, a scrub treatment similar to the normal buff polishing is performed, and thereafter, the organic amine aqueous solution is switched to pure water and the normal buff polishing is performed while the wafer is mounted on the second platen.

Hereinafter, the method for fabricating the semiconductor device according to the present embodiment will be described with reference to specific examples. First, the interlayer insulating film 14, the contact hole 16, and the opening 1 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 shown in FIGS. 2A to 2C, for example.
8. A tungsten film 20 is formed.

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. Surface plate 42
Polishing cloths 44a and 44b are provided on a 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.

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 while dropping a silica-based or alumina-based polishing liquid from the supply device 50a until the interlayer insulating film 14 is exposed, 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).

At this time, for example, if the polishing cloth surface is roughened due to continuous use of the polishing cloth or if the hardness of the polishing cloth is lower than that of the film to be polished, as shown in FIG.
2, 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, a 50%
The substrate is polished for 60 seconds while dripping from 0b.
After stopping the dropping of the 0% monomethanolamine aqueous solution, the substrate is polished for 20 seconds while the pure water is dropped from the supply device 50c, and the substrate is washed. By this cleaning, the depression 22 of the substrate is formed.
The shavings 26 of the polishing cloth remaining in the inside can be removed (see FIGS. 6 and 3A).

Next, the substrate is taken out of the polishing apparatus,
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.

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 the alignment mark with a scanning electron microscope, no foreign matter was found in the depression 22 covered by the tungsten film 20 having a width of about 2 μm.

As described above, according to the present embodiment, the cleaning for removing the foreign matter remaining in the depression of the substrate or the film to be polished is performed.
Subsequent to the polishing step, the polishing can be performed in one polishing apparatus. [Modified Embodiments] The present invention is not limited to the above embodiment, and various modifications are possible. For example, in the above embodiment, the example in which the present invention is applied to the manufacturing process of the electrode plug has been described.
The present invention is not limited to the manufacturing process of the electrode plug, but can be widely applied to cleaning after the polishing step. In addition, 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.

In the above embodiment, the cleaning process after polishing by the CMP method has been described. However, the present invention is similarly applied to a case where a substrate is polished only by physical polishing without chemical polishing. be able to.

[0040]

As described above, according to the present invention, a step of chemically and mechanically polishing a film to be polished formed on a semiconductor substrate while supplying a polishing liquid to the surface of the semiconductor substrate; Polishing is performed by exposing the semiconductor substrate to foreign substances by exposing it to an organic amine-based solution or an organic amine-based atmosphere. Even if there is, the shavings can be removed by washing in the foreign matter removing step. Therefore, it is possible to prevent a problem caused by the shavings in a subsequent process, for example, an insufficient detection of an alignment mark and a generation of foreign matter due to shavings. Therefore, according to the present invention, VLSI,
It is possible to flatten a substrate and to clean it afterwards, which is effective for manufacturing a semiconductor device such as 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 sectional view (part 2) illustrating the method for manufacturing 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 cleaning is performed by the 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 in a polishing method according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Base board 12 ... Wiring layer 14 ... Interlayer insulating film 16 ... Contact hole 18 ... Opening 20 ... Tungsten film 22 ... Depression 24 ... Electrode plug 26 ... Shavings 28 ... Aluminum film 30 ... Wiring layer 32 ... Foreign material 40 ... Polishing Apparatus 42: Surface plate 44: Polishing cloth 46: Substrate 48: Spindle head 50: Feeder

Claims (7)

[Claims] 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 step of polishing the semiconductor substrate with an organic amine solution or an organic amine atmosphere. Removing the foreign matter on the semiconductor substrate by exposing to a semiconductor substrate. 2. The polishing method according to claim 1, wherein, in the step of removing the foreign matter, the semiconductor substrate is immersed in the organic amine-based solution. 3. The polishing method according to claim 1, wherein, in the step of polishing the semiconductor substrate, the first step in a polishing apparatus is performed.
In the step of polishing the semiconductor substrate while dropping the polishing liquid on the surface plate of the above, and removing the foreign matter, in the step of polishing the semiconductor while dropping the organic amine solution onto a second surface plate in the polishing apparatus A polishing method comprising scrub cleaning a substrate. 4. The polishing method according to claim 1, wherein, in the step of removing the foreign matter, an organic amine-based solution or an organic amine containing a compound having a dissolution inhibiting effect on metal. A polishing method, wherein the foreign matter on the semiconductor substrate is removed in a system atmosphere. 5. The polishing method according to claim 1, further comprising a step of removing contaminants of the polishing liquid remaining on the semiconductor substrate after polishing. Polishing method. 6. The polishing method according to claim 1, wherein in the step of polishing the semiconductor substrate, the semiconductor substrate is polished using the alumina-based or silica-based polishing liquid. A polishing method characterized by the above-mentioned. 7. 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 solution or an organic amine atmosphere of the semiconductor substrate. Removing the foreign matter on the semiconductor substrate by exposing the semiconductor device to a semiconductor device.