JP2000026841A - Method for abrasion of semiconductor substrate and preparation of semiconductor equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease a defect arising on semiconductor substrate, retain an abrasion speed level so that productibity is not harmed and enable stable abrasion treatment by using an abrasive in which an alumina content of corundum structure crystal contained in an abrasive particle thereof is controlled in a specific range. SOLUTION: An abrasive in which an alumina content of corundum structure crystal is controlled in a range of 4-16% is used. An abrasion area is arranged on an abrasion stationary board, a substance to be abraded having an area to be abraded is holding in a holding section at a site oppsite to the abrasion area, the abrasive contained a controlled abrasive particle is supplied on the abrasion area, pressure is applied to between the holding section and the abrasion stationary board, and the abrasion area and the area to be abraded is slided therebetween to abrade the substance to be abraded. The abrasive is a liquid abrasive comprising a mixture of the abrasive particle, an oxidizing agent and pure water. The alumina is used as the abrasive particle. As the oxidizing agent, e.g. ferric nitrate is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for polishing a semiconductor device and a method for manufacturing the same, and more particularly to a method for polishing a semiconductor device by chemical mechanical polishing (C
The present invention relates to a method for polishing a semiconductor wafer using the MP) technique and a method for manufacturing a semiconductor device using the same.

[0002]

2. Description of the Related Art Today's ultra-large-scale integrated circuits (ULSI)
Then, there is a tendency to increase the packing density by reducing the size of transistors and other semiconductor elements. For this reason, various microfabrication techniques have been researched and developed, and the design rules are already on the order of submicron.

[0003] CMP is one of the technologies that have been developed to satisfy such strict requirements for miniaturization. This C
MP is a technology that is indispensable in the process of manufacturing a semiconductor device, for example, when forming a buried metal wiring, flattening an interlayer insulating film, forming a plug, separating a buried element, forming a buried capacitor, and the like.

In this CMP technique, an abrasive (polishing liquid) containing abrasive particles is supplied onto a polishing surface, and a substrate having a surface to be polished is slid while being pressed against the polishing surface, whereby the substrate is polished. A polishing film is chemically and mechanically polished. Various materials are used for the abrasive particles at this time, but those mainly composed of alumina are often used for forming metal wiring and plugs.

FIGS. 7A to 7C are cross-sectional views showing a step of forming a buried metal wiring using the CMP technique. First, as shown in FIG. 7A, an insulating film 1 is formed on a semiconductor substrate.
1 is formed thereon, and a wiring groove is formed thereon by using ordinary photolithography and etching. Then
After the metal film 12 is formed by a PVD (physical deposition) method or a CVD (chemical vapor deposition) method, a polishing process is performed to form a buried metal wiring.

FIG. 7B shows a cross-sectional shape when the polishing process is performed on the insulating film, and FIG. 7C shows an example of the surface state after polishing. The polishing amount of the film to be polished and the surface state of the surface to be polished are the pressing force during polishing, the sliding speed between the substrate and the polished surface, the type and supply amount of the abrasive,
Although it depends on the polishing time, the state of the polishing surface, and the like, many of the variables are controlled by the polishing apparatus.

In order to keep the content of abrasive particles and chemicals in the polishing agent constant, it is controlled by accurate weighing and quantitative analysis of chemical components. Scratch (defect) as shown in 7 (c)
13 are generated on the substrate.

[0008] The defect 13 caused here causes damage to the inside of the substrate and causes a product defect as shown in FIGS. 8A and 8B, for example, in combination with a semiconductor manufacturing process following the polishing process. Cause.

That is, as shown in FIG. 8A, an interlayer insulating film 14 is formed after the formation of the metal wiring 12, and a lower metal wiring film is formed thereon by using ordinary photolithography and etching. Is formed.

Next, after a metal film for forming a plug is formed by a PVD method or a CVD method, a polishing process is performed to form a plug 15. At this time, a portion 15a of the metal film for forming the plug, which corresponds to the portion above the scratch generated in the step of forming the metal wiring, remains without being removed by the polishing process.

Therefore, as shown in FIG. 8B, when the upper metal wiring 17 is formed after the formation of the plug 15,
Short circuit between wirings occurs. Incidentally, the relationship between the lot of the abrasive used in the conventional polishing method and the product defect (the number of defects) is, for example, as shown in FIG. 9, and the number of defects varies depending on the lot of the abrasive. You can see that it is causing a lot.

[0012]

As described above, the conventional method for polishing and manufacturing a semiconductor device cannot perform a stable polishing process, and the number of defects varies depending on the lot of the polishing agent.
There was a problem that many product defects were caused.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is intended to reduce defects occurring on a semiconductor substrate, maintain a polishing rate that does not impair productivity, and perform a stable polishing process. It is an object of the present invention to provide a method for polishing a semiconductor device, which enables the polishing. Another object of the present invention is to provide a method of manufacturing a semiconductor device capable of suppressing the occurrence of defects while maintaining a polishing rate to such an extent that productivity is not impaired.

[0014]

According to the method for polishing a semiconductor substrate of the present invention, as a polishing agent containing abrasive particles used in a polishing step of a semiconductor substrate, alumina which is a corundum type crystal contained in the polishing particles is used. It is characterized in that a material managed so as to be 4% or more and 16% or less is used.

The method for polishing a semiconductor substrate according to the present invention comprises the steps of: providing a polished surface on a polishing platen; and holding an object to be polished having a surface to be polished on a holding portion provided at a position facing the polished surface. A polishing agent containing abrasive particles is supplied onto the polishing surface, and pressure is applied between the holding portion and the polishing platen to slide the polishing surface and the surface to be polished. Polishing the polished material, and using, as the abrasive, one controlled so that alumina, which is a corundum type crystal contained in the abrasive particles, is at least 4% and at most 16%. I do.

According to the method of manufacturing a semiconductor device of the present invention, a step of forming a film to be polished on a semiconductor substrate, and at least a part of the film to be polished is made of alumina, which is a corundum type crystal contained in polishing particles, of 4%. % By using an abrasive controlled to be at least 16%.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention have proposed alumina (α-alumina) which is a corundum type crystal contained in abrasive particles.
From the relationship between the defect rate on the substrate and the polishing rate of the film to be polished with respect to the content of, the occurrence of defects is suppressed while maintaining the polishing rate so as not to impair productivity, and it was found that stable polishing can be performed. The present invention has been made based on this finding.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. <First Embodiment of Polishing Method for Semiconductor Device> First Embodiment of Polishing Method
In the example, a polishing liquid in which abrasive particles, an oxidizing agent, and pure water were mixed was used as the polishing agent. Ferric nitrate was used as an oxidizing agent and alumina was used as abrasive particles, and several types of abrasives were prepared by changing the content of alumina, which is a corundum crystal contained in the alumina particles.

Two types of films to be polished were prepared.
FIG. 1A shows a first film to be polished, in which a silicon oxide film 32 is formed on a silicon substrate 31 by a CVD method.

FIG. 1B shows a second film to be polished, and a silicon oxide film 4 is formed on a silicon substrate 41 by a CVD method.
2, a barrier metal (Barrier Metal) 43 is further formed by a PVD method, and a tungsten film 44 is formed thereon by a CVD method.

As the polishing apparatus, for example, an ordinary polishing apparatus as shown in FIG. 2 was used. The polishing apparatus shown in FIG. 2 includes a rotatable polishing table 51, a polishing cloth 52 stuck on the polishing table 51, and a rotatable vacuum chuck holder 53 disposed above the polishing table 51. , Polishing table 5
1 is connected to a rotatable plate 54 on which diamond particles are electrodeposited and a polishing tank (not shown) having a polishing agent stirring function, and a polishing agent discharge portion is brought to the vicinity of the polishing cloth 52. And an extended abrasive supply pipe 55.

The abrasive supply pipe 55 has a means for controlling the supply amount of the abrasive. The film to be polished 50 is vacuum-chucked to the vacuum chuck holder 53 so that the surface to be polished faces the polishing cloth 52. The pressure at which the film-to-be-polished 50 contacts the polishing pad 52 can be arbitrarily controlled by compressed air.

The polishing of the silicon oxide film 32 and the polishing of the tungsten film 44 were performed using the respective polishing agents. In this case, a commonly used polishing cloth (for example, polyurethane) was used as the polishing cloth 52 of the polishing apparatus. Regeneration of the polishing cloth 52 was performed after polishing, and was performed using a plate 54 on which diamond was electrodeposited.

The pressing force during polishing, the supply amount of the abrasive, and the relative rotation speed between the substrate 50 and the polishing platen 51 are determined under normal conditions (for example, a polishing pressure of 200 gf / cm.
^2. The rotation speed of the polishing platen 51 and the vacuum chuck holder 53 was 50 rpm, and the abrasive supply amount was 200 ml / min.

The average particle size of the abrasive particles is from 0.01 to
Desirably, it is 5.0 μm. The reason is that if the average particle size of the abrasive particles is less than 0.01 μm, the polishing rate becomes too low, and if the average particle size exceeds 5.0 μm, it causes defects of the film to be polished.

After polishing for a certain period of time under the above-described polishing conditions, the silicon oxide film 32 and the tungsten film 44 are polished.
Number of defects, silicon oxide film 32 and tungsten film 44
Of the silicon oxide film 3 was determined from the difference in film thickness before and after polishing.
2 and the polishing rate of the tungsten film 44 were calculated.

In this case, an image processing type measuring device is used for measuring the number of defects, and a light interference type film thickness measuring device is used for measuring the film thickness of the silicon oxide film 32, and the film thickness of the tungsten film 44 is calculated. , A sheet resistance measuring instrument was used.

FIG. 3 (a) shows the relationship between the number of defects on the substrate and the content of alumina (α-alumina), which is a corundum type crystal, contained in abrasive particles according to the first embodiment of the polishing method. .

FIG. 3 (b) shows the relationship between the polishing rate of the film to be polished and the content of alumina (α-alumina) which is a corundum type crystal contained in the polishing particles according to the first embodiment of the polishing method. Was.

As shown in FIG. 3A, as the content of α-alumina increases, the number of defects tends to increase.
It can be seen that a small number is stable at 16%. As shown in FIG. 3B, the polishing rate of the silicon oxide film 32 and the tungsten film 44 tends to be higher as the content of α-alumina is higher. It can be understood that the polishing rate ratio of the tungsten film 44 to the polishing rate is sufficiently large and stable.

From these facts, by controlling the content of α-alumina in the abrasive particles to 4% to 16%, it is possible to maintain the polishing rate of the tungsten film W to the extent that productivity is not impaired while maintaining the polishing rate of defects. It can be seen that generation can be suppressed.

<First Embodiment of Manufacturing Method of Semiconductor Device> Next, FIG. 4A shows the result of applying the first embodiment of the polishing method to the polishing step when actually forming the buried metal wiring. , (B) and FIG. 5 will be described in detail.

FIG. 4 (a) shows a film to be polished. A silicon oxide film 72 is formed on a silicon substrate 71, and a wiring groove is formed thereon by using a usual photolithography method and an etching method. Thereafter, a barrier metal 73 is formed by a PVD method, and a tungsten film 7 is formed by a CVD method.
4 is formed.

The film to be polished was polished up to the silicon oxide film 72 as shown in FIG. 4B using the polishing apparatus shown in FIG. The polishing process at this time used the same polishing conditions as in the first embodiment of the polishing method. The measurement of defects after polishing was performed using an image processing type measuring instrument.

FIG. 5 shows the relationship between the abrasive lot and the number of product defects before (conventional) and after (this embodiment) the first embodiment of the polishing method is applied in the manufacture of a semiconductor device. .

FIG. 5 shows that the occurrence of defects can be suppressed by controlling the content of α-alumina contained in the abrasive particles. That is, according to the first embodiment of the method for manufacturing a semiconductor device, when polishing a film formed on a semiconductor substrate using an abrasive containing alumina particles, the alumina which is a corundum type crystal contained in the abrasive particles is used. The use of an abrasive whose content is controlled to 4% or more and 16% or less can suppress (reduce) the number of defects on the substrate and reduce the polishing rate of the film to be polished to such an extent that productivity is not impaired. Can be maintained.

In addition, in the polishing step of polishing the metal film such as the formation of the metal wiring and the plug and stopping the polishing at the insulating film, the polishing rate ratio of the metal film to the insulating film must be sufficiently large and stable. Although desired, according to the present invention, stable polishing with a sufficiently large speed ratio can be performed.

FIG. 6 shows the crystal structure of α-alumina (α-Al ₂ O ₃ ) (corundum type) used in each of the above embodiments. In the figure, open circles are oxygen atoms, and black circles are aluminum atoms.

Since α-alumina is the hardest of the aluminas, reducing the amount of α-alumina can reduce scratches generated on the substrate surface. Also, γ
-As alumina grows and becomes α-alumina, α
-Alumina has a large particle size, and by reducing the amount of α-alumina, large scratches are unlikely to be formed on the substrate surface. As a result, the occurrence of defects can be suppressed by reducing the amount of α-alumina.

The present invention is not limited to the embodiment described above. For example, as the material of the substrate may be a silicon, quartz, sapphire, Al ₂ O _3, the III~V compound like.

The oxidizing agent in the polishing agent is not limited to the ferric nitrate of the above embodiment, but can be applied to polishing using another oxidizing agent. In the above embodiment, the case where a silicon oxide film and a tungsten film are used as the film to be polished has been described. However, SiO ₂ , α-Si, poly Si, SiON, S
iOF, BPSG (Boron-Phospho-Silicata Glass),
PSG (Phospho-Silicata Glass), SiN, Si ₃ N
₄ , Si, Al, W, Ag, Cu, Ti, TiN, A
A film mainly containing u, Pt, Ru, AlCu, AlSiCu, or the like can be used. Further, the polishing apparatus is not limited to the embodiment described above.

[0042]

As described above, according to the present invention, defects generated on a semiconductor substrate can be reduced by using an abrasive whose alumina content, which is a corundum type crystal contained in abrasive particles, is controlled. In addition, a polishing method for a semiconductor device capable of maintaining a polishing rate that does not impair productivity and performing a stable polishing process, and suppressing occurrence of defects while maintaining the polishing rate so as not to impair productivity. It is possible to provide a method for manufacturing a semiconductor device to be obtained.

That is, in the polishing method according to the first aspect, the abrasive containing the abrasive particles used in the polishing step of the semiconductor substrate contains 4% to 16% of alumina, which is a corundum type crystal, contained in the abrasive particles. Is used.

By using the abrasive whose content of alumina, which is a corundum type crystal contained in the abrasive particles, is controlled in this manner, a stable polishing treatment can be performed. In the polishing method according to claim 2, a polishing surface is provided on a polishing platen,
A step of holding an object to be polished having a surface to be polished on a holding portion provided at a position facing the polishing surface, and supplying an abrasive containing abrasive particles onto the polishing surface, Polishing the object to be polished by applying pressure between the platen and sliding the surface to be polished and the surface to be polished, the corundum crystal contained in the abrasive particles. It is characterized by using the above-mentioned abrasive whose alumina is 4% or more and 16% or less.

By using an abrasive whose content of alumina, which is a corundum type crystal contained in the abrasive particles, is controlled in this manner, a stable polishing treatment can be performed. In the manufacturing method according to the fourth aspect, a step of forming a film to be polished on the semiconductor substrate, and at least a part of the film to be polished is made of a corundum type crystal alumina contained in abrasive particles of 4%.
% By polishing with an abrasive of not less than 16% and not more than 16%.

As described above, by using the abrasive whose alumina content, which is a corundum type crystal contained in the abrasive particles, is controlled, the generation of defects can be suppressed while maintaining the polishing rate to such an extent that productivity is not impaired. The resulting semiconductor device can be manufactured.

In the manufacturing method according to the fifth aspect, the step of forming a film to be polished on the semiconductor substrate having irregularities on the surface, and the step of forming the film to be polished by using at least 4% of alumina, which is a corundum type crystal contained in the polishing particles. Polishing with an abrasive that is 16% or less for flattening.

As described above, the use of the abrasive whose alumina content, which is a corundum type crystal contained in the abrasive particles, is controlled allows the generation of defects to be suppressed while maintaining the polishing rate to such an extent that productivity is not impaired. The resulting semiconductor device can be manufactured.

[Brief description of the drawings]

FIG. 1 is a sectional view showing two types of films to be polished used in a first embodiment of a method for polishing a semiconductor device according to the present invention.

FIG. 2 is a configuration explanatory view schematically showing a polishing apparatus used in a first embodiment of a method of polishing a semiconductor device according to the present invention.

FIG. 3 shows the number of defects on a substrate with respect to the content of alumina (α-alumina), which is a corundum type crystal, contained in polishing particles according to the first embodiment of the method for polishing a semiconductor device of the present invention, The figure which shows the relationship with a polishing rate.

FIG. 4 is a sectional view showing a film to be polished used in the first embodiment of the method of manufacturing a semiconductor device according to the present invention.

FIG. 5 is a diagram showing a comparison between the relationship between the abrasive lot and the number of product defects in the first embodiment of the semiconductor device manufacturing method of the present invention and the conventional manufacturing method.

FIG. 6 is a view showing a crystal structure of α-alumina used in each example of the present invention.

7A and 7B are a cross-sectional view and a perspective view showing a buried metal wiring forming step using the CMP technique.

FIG. 8 is a cross-sectional view illustrating an example of a product defect in a manufacturing method using a conventional semiconductor device polishing method.

FIG. 9 is a diagram showing a relationship between a lot of abrasive used in a conventional method of polishing a semiconductor device and a product defect (the number of defects).

[Explanation of symbols]

 50: film to be polished, 51: polishing platen, 52: polishing cloth, 53: vacuum chuck holder, 54: plate, 55: piping for supplying abrasive.

Continued on the front page (72) Inventor Nobuhiro Kato 800 Yamano Isshiki-cho, Yokkaichi-shi, Mie Prefecture Inside the Toshiba Yokkaichi Plant Co., Ltd.

Claims (7)

[Claims] 1. A polishing agent containing abrasive particles used in a polishing step of a semiconductor substrate, which is controlled so that alumina which is a corundum type crystal contained in the abrasive particles is 4% or more and 16% or less. A method for polishing a semiconductor substrate, characterized by using: 2. A step of providing a polishing surface on a polishing platen, and holding an object to be polished having a surface to be polished on a holding portion provided at a position facing the polishing surface; Supplying an abrasive containing particles, and polishing the workpiece by applying pressure between the holding portion and the polishing platen to slide the polishing surface and the surface to be polished. A method for polishing a semiconductor substrate, comprising using, as the polishing agent, one controlled so that alumina, which is a corundum crystal contained in the polishing particles, is at least 4% and at most 16%. 3. The method for polishing a semiconductor substrate according to claim 1, wherein the polishing particles in the polishing slurry contain alumina as a main component. 4. A step of forming a film to be polished on a semiconductor substrate, wherein at least a part of the film to be polished contains 4% to 16% of alumina which is a corundum type crystal contained in abrasive particles. Polishing with a polishing agent controlled in accordance with the above method. 5. A step of forming a film to be polished on a semiconductor substrate having irregularities on the surface, wherein the film to be polished is such that alumina, which is a corundum type crystal contained in abrasive particles, is 4% or more and 16% or less. Polishing by a polishing agent controlled in step (1) and flattening. 6. The method of manufacturing a semiconductor device according to claim 5, wherein the film to be polished is a metal laminated film and a silicon-containing film. 7. The method of manufacturing a semiconductor device according to claim 4, wherein said abrasive particles in said abrasive mainly comprise alumina. .