JP3172008B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device such as an VLSI, and more particularly to a polishing method in a process of manufacturing a semiconductor device.

[0002]

2. Description of the Related Art In recent years, various microfabrication techniques have been developed with the increasing integration of LSIs. The minimum processing size of a pattern is getting smaller year by year, and is now on the order of submicron.

One of the technologies that have been developed to satisfy such strict requirements for miniaturization is a CMP (Chemical Mechanical Polishing) technology. This technology is used in the manufacturing process of a semiconductor device, for example, for flattening an interlayer insulating film,
This technique is indispensable when forming a plug, forming a buried metal wiring, and separating a buried element.

FIGS. 7A to 7D show an example of formation of a buried metal wiring using the CMP technique. First, FIG.
As shown in (1), an insulating film 2 is formed on a semiconductor substrate 1, and the surface of the insulating film 2 is flattened. Next, as shown in FIG. 7B, a groove for wiring or an opening 3 for connection wiring is formed in the insulating film 2 by ordinary photolithography and etching. Next, as shown in FIG. 7C, a wiring metal film 4 is formed on the insulating film 2. In this case, a barrier metal film may be formed between the insulating film 2 and the wiring metal film 4 in order to prevent mutual diffusion or reaction between them.

Next, in order to leave the wiring metal film 4 only in the grooves or openings, the wiring metal film 4 is subjected to CMP using alumina particles or the like as abrasive particles. In this case, a film made of a material having a high polishing rate selection ratio with respect to the wiring metal film 4 may be formed as a polishing-resistant film under the wiring metal film 4. The applicant has filed a Japanese Patent Application No. 5-6 / 1993.
As described in Japanese Patent No. 7410, an Al film 5 is used as a metal film for wiring, and an Al film 4 is deposited by sputtering as shown in FIG. As shown in FIG. 7D, Al is monocrystallized in the concave portions,
The film 4 may be separated and left on the convex portion of the insulating film 2 and then the remaining Al film may be removed by CMP. Thus, as shown in FIG. 7E, the surface of the insulating film 2 and the surface of the wiring metal film 5 are coplanar.

However, in the actual CMP process,
Due to the mechanical action between the polished surface of the wiring metal film 4 and the abrasive particles or between the polished surface and the platen holding the abrasive, the surface of the wiring metal film is scratched and roughened. Then, the abrasive particles are buried or remain in the wiring metal film 4.

Further, as shown in FIG. 7F, a phenomenon called dishing occurs in which the thickness of the central portion of the wiring metal film 4 buried in the trenches and openings, particularly in a wide region, becomes thin. When this dishing phenomenon occurs, abrasive particles tend to remain there. For example, when a metal having low hardness and ductility, such as Al or Cu, is used as the material of the wiring metal film 4, those tendencies appear remarkably. Occurrence of scratches or dishing on the surface of the wiring metal film, residual abrasive particles, and the like increase the resistance of the obtained wiring or cause disconnection, resulting in lower reliability and lower product yield.

[0008]

In the process of manufacturing a semiconductor device, there is a great problem that abrasive particles remain after CMP. That is, the remaining abrasive particles cause a failure of the semiconductor device. Therefore, it is necessary to completely remove the abrasive particles after the CMP.

Conventionally, removal of abrasive particles after CMP includes washing with pure water, scrubbing with a sponge scrubber or brush scrubber, ultrasonic washing, or chemical washing with a mixed solution of sulfuric acid and hydrogen peroxide. Done. However, these cleanings cannot sufficiently remove abrasive particles. Here, cerium oxide particles were used as abrasive particles, and an SiO ₂ film formed on a 6-inch Si wafer was subjected to CM using an abrasive dispersed in pure water.
Number of residual particles by particle size when scrub cleaning using brush scrubber (cleaning 1) or combined cleaning of scrub cleaning and chemical cleaning with a mixed solution of sulfuric acid and hydrogen peroxide (cleaning 2) after P Are shown in Table 1 below.

[0010]

[Table 1]

As is clear from Table 1, it can be seen that the amount of residual abrasive particles is large in any of the residual particles of any particle size as compared with the number of residual particles before CMP. L
Considering that the minimum processing size of SI is already in the sub-half micron generation and the level of required dust count is becoming increasingly severe, even small residual particles of 0.3 μm or less can be used in products. It is clear that this greatly affects the yield. Therefore, the conventional polishing method using the conventional polishing particles cannot cope with the next-generation LSI manufacturing.

The present invention has been made in view of the above points, and the polishing particles can be polished without causing dishing or the like by minimizing the residual amount of the polishing particles after polishing. An object of the present invention is to provide a method for manufacturing a semiconductor device capable of forming a metal wiring or the like.

[0013]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, it has been found that particles or at least organic polymer compounds which have not been used in the conventional semiconductor device manufacturing process. The present inventors have found that the use of particles containing carbon as a main component as polishing particles minimizes the residual amount of the polishing particles after polishing and enables polishing without causing dishing or the like, and has led to the present invention.

That is, the present invention provides a method of manufacturing a semiconductor device, comprising a step of polishing a film to be processed by using particles made of an organic polymer compound or particles containing at least carbon as a main component as abrasive particles. Provide a way.

In the present invention, it is preferable that the method further comprises the step of removing the abrasive particles by burning them after polishing. Here, as the organic polymer compound,
A methacrylic resin such as PMMA, a phenolic resin, a urea resin, a melamine resin, a polystyrene resin, a polyacetal resin, a polycarbonate resin, or the like having the same hardness can be used. In addition, as a material containing at least carbon as a main component, it is possible to use amorphous carbon, gold sand, carbon black in which one or more layers of a graphite structure are united and randomly bonded.

It is preferable that the abrasive particles have a spherical shape. The spherical shape is meant to include a substantially spherical shape without an acute angle portion. This is to suppress the mechanical action during polishing and prevent the surface of the film to be processed from being scratched or roughened.

The average particle size of the abrasive particles is 0.01 to 0.1.
μm is preferred. If the average particle size of the abrasive particles is less than 0.01 μm, the particles tend to aggregate, so that the surface roughness increases, and the polishing rate becomes unstable.
If the thickness exceeds 1 μm, the surface roughness increases, and the dishing amount also increases in proportion to the particle size.

As a method of burning the abrasive particles after polishing, ashing treatment by plasma, such as exposure to oxygen plasma or supply of oxygen radicals in a downflow manner, a high temperature treatment in an oxygen atmosphere, or the like is used. Can be. These methods make it possible to easily remove the abrasive particles.

As a film to be processed, a pure Al film, AlSi
Examples include a film made of an alloy containing Al as a main component such as a Cu alloy and an AlCu alloy, a silicon oxide film, a silicon nitride film, an amorphous silicon film, a polycrystalline silicon film, and a single crystal silicon film.

The film to be processed, the abrasive particles, and the solution in which the abrasive particles are dispersed need to be appropriately selected in consideration of hardness, chemical etching action, and the like. For example, when the solution in which the abrasive particles are dispersed is preferably alkaline, pure Al, Al-Si-Cu alloy, Al
Using a film made of a Cu alloy or the like, using organic polymer compound particles or carbon black particles as the abrasive particles, and preferably using a film containing Cu as a main component in the film to be processed when it is preferably acidic. And organic polymer compound particles and the like are used as abrasive particles.

[0021]

The method of manufacturing a semiconductor device according to the present invention comprises a step of polishing a film to be processed using spherical particles made of an organic polymer compound or particles containing at least carbon as a main component as abrasive particles. I have.

Since the above-mentioned abrasive particles are spherical, they have a small mechanical action, and do not damage the surface of the film to be processed or cause dishing during CMP. In addition, since these abrasive particles can be completely removed from the film to be processed by burning, they may cause a failure of the semiconductor device such as a decrease in reliability and a decrease in product yield due to residual abrasive particles. Absent.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings. Example 1 First, as shown in FIG. 1, an SiO ₂ film 12 was formed on a Si substrate 11, and the width was 0.4 to 10 μm and the depth was 0.4 μm by ordinary photolithography and etching.
m of wiring grooves 13 were formed. Then, a pressure of 10 ^-4 Torr
An Al film 14 having a thickness of 4500 angstroms was formed on the entire surface in a non-heated state by a DC magnetron sputtering method in an Ar atmosphere. Thus, a sample 20 was produced. At this time, the number of abrasive particles remaining on the surface of the sample 20 was measured using a dust counter. The results are shown in Table 2 below.

Next, the sample 20 was subjected to CMP using the apparatus shown in FIG. This apparatus is arranged above a rotatable polishing plate 21, a polishing pad 22 stuck on the polishing plate 21, and a polishing plate 21, and is connected to a rotatable sample holder 23 and a polishing liquid tank. And a polishing liquid supply pipe 24 whose discharge section extends to the vicinity of the polishing pad 22.
The sample 20 is vacuum-chucked to the sample holder 23 such that the surface to be processed faces the polishing pad 22. In addition, the polishing liquid supply pipe 24 includes means for controlling the supply amount of the polishing liquid. As the polishing pad 22, a polishing pad made of foamed polyurethane was used.

In the CMP, a slurry in which PMMA (polymethyl methacrylate) particles having an average particle diameter of 1000 angstroms were dispersed in an alkaline aqueous solution having a pH of about 10 at a ratio of 10.0% by weight was used as an abrasive. As a dispersant, ammonium polycarboxylate was used. The polishing conditions were a polishing pressure of 300 gf / cm ² ,
The rotation speed of the platen and the sample holder was 100 rpm. As a result, Al was almost completely left in the wiring groove 13 in FIG. Almost no scratch was seen on the surface of the Al wiring. The polishing rate of Al with this polishing agent was VAl = 150 Å / min. Further, the number of abrasive particles remaining on the sample surface after the CMP was measured in the same manner as described above. The results are shown in Table 2 below.

Next, the sample after CMP was washed with pure water using a sponge and dried. At this time, the number of abrasive particles remaining on the sample surface was measured in the same manner as described above. The results are shown in Table 2 below. In addition,
Ashing treatment with oxygen plasma was performed under the conditions of a plasma output of 500 W and an O ₂ partial pressure of 0.9 Torr to remove remaining abrasive particles. At this time, the number of abrasive particles remaining on the sample surface was measured in the same manner as described above. The results are shown in Table 2 below. All the values in Table 2 are average values per wafer.

[0027]

[Table 2]

As is evident from Table 2, the abrasive particles remaining on the surface of the sample subjected to the incineration treatment were almost completely removed. In addition, it is considered that most of the components counted on the surface of the sample after the incineration treatment detected dust other than the abrasive particles, and irregularities on the sample surface.

Here, when CMP was performed using a slurry in which PMMA particles were dispersed in pure water having a pH of 7,
1 was not polished at all. That is, PMMA is added to pure water.
The polishing rate of Al of the abrasive in which the particles are dispersed is a polishing pressure of 1
At 0 to 1000 gf / cm ² , V Al = 0 A / min. From these results, it was found that when the PMMA particles were used for polishing Al, it was necessary to make the polishing agent solution acidic or alkaline so that the chemical etching action proceeded. A practical polishing rate can be obtained by adding a chemical etching action. In particular, it is desirable that the solution to be dispersed is alkaline from the viewpoint of increasing the polishing rate by adding a chemical etching effect and at the same time not damaging the Al surface.

In the present embodiment, the sample having the structure shown in FIG. 1 is used, but as shown in FIG.
An SiO ₂ film 12 is formed on an i-substrate 1 and a pressure 1
A carbon film 15 which is a polishing-resistant film having a thickness of 500 Å is formed by a DC magnetron sputtering method in an Ar atmosphere of 0 ^-4 Torr, and a wiring having the same size as that of FIG. 1 is formed by a usual photolithography method and etching method. After forming the groove 13, the sample was heated to 500 ° C. and a 4000 Å-thick Al film was formed by DC magnetron sputtering in an Ar atmosphere at a pressure of 10 ⁻⁴ Torr.
It was found that the same effect can be obtained in a sample having a structure in which the film 14 is formed. That is, according to the method of the present invention, it was found that the abrasive particles could be almost completely removed regardless of the presence or absence of the polishing-resistant film and regardless of the surface shape of the film to be processed. When the abrasive particles are removed by the ashing treatment using oxygen plasma as in the first embodiment, the carbon film 15 can be removed at the same time, and the number of steps can be reduced. Example 2 As shown in FIG. 4, an SiO ₂ film 12 was formed on a Si substrate 11, and a wiring groove 13 having the same size as that of FIG. 1 was formed by ordinary photolithography and etching. Next, an Nb film 16 having a thickness of 500 Å is formed on the entire surface by a DC magnetron sputtering method in an Ar atmosphere at a pressure of 10 ⁻⁴ Torr, and a pressure of 1 Å is formed on the entire surface.
A CuOx (x = 0 to 0.5) film 17 having a thickness of about 4000 Å was formed by a reactive sputtering method in a mixed gas atmosphere of Ar and O ₂ at 0 ^-4 Torr.
Thus, a sample was prepared.

This sample was treated with C under the same polishing conditions as in Example 1.
MP was performed. However, the abrasive has an average particle size of 10
A dispersion in which 00 Å PMMA particles were dispersed in an acidic aqueous solution having a pH of about 3 at a ratio of 10.0% by weight was used. As a result, the number of rotations of the platen and the sample holder was 10
CuOx film 1 at 0 rpm and polishing pressure of 300 gf / cm ²
The polishing rate of No. 7 was 200 to 250 Å / min, which was slightly faster than that of Al.

After the sample was subjected to a sponge cleaning treatment after the CMP, an ashing treatment was performed by oxygen plasma under the same conditions as in Example 1. As a result, abrasive particles remaining on the sample surface were completely removed.

According to the present embodiment, when a CuOx film is polished using PMMA particles as an abrasive, from the viewpoint of increasing the polishing rate by adding a chemical etching effect, the solution to be dispersed contains an ammonium salt. An acidic aqueous solution having a pH of about 3 or a solution containing ions that form a complex ion or a chelate compound with copper is preferable. Example 3 As shown in FIG. 5, an SiO ₂ film 12 was formed on a Si substrate 11 to a thickness of 5000 Å, and an Al film was formed thereon.
Forming a film 14 with a thickness of 4000 angstrom and a carbon film 15 with a thickness of 500 angstrom;
After forming the Al wiring leaving the carbon film 15 only on the upper surface by the usual photolithography and etching, the SiO ₂ film 12 is formed to a thickness of 45 by plasma CVD.
It was formed at 00 Å. Thus, Al
A sample having a structure in which the wiring was embedded in the SiO ₂ film 12 was manufactured.

This sample was subjected to polishing under the same polishing conditions as in Example 1.
MP was performed. However, the abrasive has an average particle size of 0.1.
A dispersion obtained by dispersing amorphous carbon particles of 5 μm in pure water at a ratio of 1.0% by weight was used. At this time, as the dispersant,
Ammonium polycarboxylate was used.

As a result, the SiO ₂ film 12 remained between the Al wirings, and the entire SiO ₂ film 12 on the carbon film 15 could be removed. The number of rotations of the platen and the sample holder was 1
The polishing rate of the SiO ₂ film 12 at 00 rpm and a polishing pressure of 300 gf / cm ² was approximately 2000 Å / min.

After the sample was subjected to a sponge cleaning treatment after the CMP, an ashing treatment with oxygen plasma was performed. As a result, abrasive particles remaining on the sample surface were completely removed. The plasma output was 500 W and the O ₂ partial pressure was 0.9 Torr.
In this ashing process using oxygen plasma, the Al wiring 1
4 can be removed at the same time, and the number of steps can be reduced.

From this example, it was found that the abrasive had an average particle size of 0.1.
When polishing an SiO ₂ film using amorphous carbon particles of 5 μm, from the viewpoint of increasing the polishing rate by adding a chemical etching action, an aqueous alkali hydroxide solution is preferable as the solution to be dispersed. Embodiment 4 In this embodiment, the method of the present invention is applied to the step of separating buried elements. First, as shown in FIG.
A groove 18 for burying element isolation having a depth of 0.8 μm and a width of 0.35 μm is formed in the Si substrate 11 by ordinary photolithography and etching, and TEOS gas and O
_An SiO ₂ film 12 was formed to a thickness of 0.8 μm by a CVD method using _two gases to fill the groove 18. Thus, a sample was prepared.

Next, as shown in FIG.
The sample was subjected to CMP in the same manner as described above. Then, FIG.
As shown in (C), the sample was placed in an oxygen atmosphere under atmospheric pressure for 1 hour.
The abrasive particles 19 were completely removed by performing a heat treatment at 000 ° C. for 30 minutes. Example 5 In this example, organic polymer compound particles and other abrasive particles were used in combination as abrasive particles. Fig. 3
The following was used. This sample was subjected to CMP. As the polishing agent, silica particles having an average particle size of 350 Å dispersed in an alkaline aqueous solution having a pH of 11 were used. At this time, the polishing rate of the Al in the polishing agent was 100 rpm at the rotation speed of the platen and sample holder, and the polishing pressure was
Under the conditions of gf / cm ² , VA = 900 angstroms / min.

Next, at the same time as polishing the sample, the PMMA particles having an average particle diameter of 1000 Å were transferred to an alkaline aqueous solution having a pH of 3 using a platen different from the polished platen in order to remove silica particles remaining on the sample surface. Polishing was performed using the dispersed abrasive at a polishing pressure of 100 gf / cm ² , a rotation speed of the platen and the sample holder of 100 rpm, and a polishing time of 1 minute.

Thereafter, the sample was ashed by oxygen plasma under the same conditions as in Example 1 to form an Al wiring in which silica particles and PMMA particles did not remain. Note that the carbon film 15 can be removed at the same time during the incineration process using oxygen plasma. As described above, by using a normal abrasive in combination, a practical polishing rate can be obtained, and the remaining abrasive particles can be easily removed. Comparative Example When CMP was performed in the same manner as in Example 3 except that diamond particles having an average particle size of 0.5 μm were used as abrasive particles, the abrasive particles were removed by washing with a sponge after the CMP and heat treatment in an oxygen atmosphere. Was formed, but countless scratches were made on the surface of the sample SiO ₂ film, and the surface roughness Ra
Was about 2600 angstroms and the surface was very rough. It is considered that this is because the modified Mohs hardness of the diamond particles is 15, which is higher than the modified Mohs hardness 8 of the SiO ₂ film, and the particle shape is not uniform and not spherical. Thus, diamond particles are found to be unsuitable in terms of surface roughness and generation of surface flaws.

[0041]

As described above, in the method of manufacturing a semiconductor device according to the present invention, a film to be processed is polished using spherical particles made of an organic polymer compound or particles containing at least carbon as a main component. The remaining amount of the abrasive particles after the polishing is minimized, the polishing can be performed without causing dishing or the like, and the flattening of the film, the formation of the buried metal wiring, and the like can be performed with high reliability and high yield.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of a sample used in Example 1.

FIG. 2 is a schematic diagram showing an apparatus used for a polishing process.

FIG. 3 is a sectional view showing another example of the sample used in the first embodiment.

FIG. 4 is a cross-sectional view showing a sample used in Example 2.

FIG. 5 is a cross-sectional view showing a sample used in Example 3.

FIGS. 6A to 6C are cross-sectional views illustrating a fourth embodiment.

7A to 7F are cross-sectional views illustrating a conventional polishing method.

[Explanation of symbols]

11 ... Si substrate, 12 ... SiO ₂ film, 13 ... wiring trench,
14 ... Al film, 15 ... Carbon film, 16 ... Nb film, 17 ... C
uOx film, 18 groove, 19 abrasive particles, 20 sample, 2
1 Polishing plate, 22 Polishing pad, 23
Sample holder, 24 ... Piping for supply of polishing liquid.

Continuation of the front page (72) Inventor Nobuo Hayasaka 1 Toshiba-cho, Komukai, Koyuki-ku, Kawasaki City, Kanagawa Prefecture (56) References JP-A-5-154761 (JP, A) JP-A-63 JP-A-160338 (JP, A) JP-A-63-160341 (JP, A) JP-A-5-102112 (JP, A) JP-A-6-140393 (JP, A) JP-A-7-86215 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/304 B24B 1/00 B24B 37/00

Claims (3)

(57) [Claims] 1. A method for manufacturing a semiconductor device, comprising a step of polishing a film to be processed using particles made of an organic polymer compound as abrasive particles. 2. The semiconductor device according to claim 1, further comprising a step of polishing a film to be processed by using, as abrasive particles, particles mainly containing carbon selected from the group consisting of amorphous carbon and carbon black. Production method. 3. The method of manufacturing a semiconductor device according to claim 1, further comprising a step of burning and removing the abrasive particles after polishing.