JPH11277380A - Surface polishing system for semiconductor product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable stably preferable polishing while maintaining high polishing efficiency by using a polishing solution of an alkaline silica gel composition for the polishing of a semiconductor product surface in a first process, regenerating the polishing solution in a second process, and replacing the regenerated polishing solution with the polishing solution in the first process in a third process. SOLUTION: An alkaline silica gel composition containing low metal is used for surface polishing of the semiconductor product as an alkaline silica gel composition used in the first process. Silica concentration, pH, and a metal content of the used polishing solution generated in the first process is adjusted as a regenerated polishing solution in the second process. Next, a part of the polishing solution in the first process or all thereof is replaced with the regenerated polishing solution obtained in the second process in the third process. Accordingly, the polishing solution is regenerated in the second process according to a batch method, thereby enabling the necessary polishing solution to be repeatedly used in accordance with the desire. The used polishing solution is regenerated without stopping the operation of the system according to a continuous method, thereby enabling efficient polishing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for polishing a surface of a semiconductor product, and more particularly, to a system for polishing a surface of a semiconductor product such as an LSI, for example, a surface of an insulating oxide film or the like, for flattening. The present invention relates to a surface polishing system for semiconductor products. In the process of flattening, for example, an insulating oxide film on the surface of a semiconductor product such as an LSI, a source having excellent leveling property is selected by a CVD (chemical vapor deposition) method to obtain an insulating oxide film having high flatness. There is a method of once obtaining an insulating oxide film without considering the flatness so much, and then flattening the insulating oxide film by chemical mechanical polishing. The present invention belongs to the latter method.

[0002]

2. Description of the Related Art Conventional chemical mechanical polishing methods include:
Polishing is performed by dropping an abrasive slurry (polishing liquid) onto a polishing cloth surface attached to a polishing board and pressing it against a silicon wafer surface with an insulating oxide film while applying a constant load. At this time, in the polishing of the silicon-based insulating film, a process of polishing using a slurry containing silica-based abrasive grains as a component is usually employed. As a specific process, a silicon wafer with an insulating oxide film is attached to a polishing block, and the polishing block is pressed with a suitable pressure onto a polishing cloth (polisher) adhered on a rotary polishing plate to mainly adjust pH 9 to 1.
By dropping a polishing slurry liquid of ultra-fine silica dispersed in about two waters, the polishing liquid and the insulating silicon oxide film have a mechanochemical action, and the polishing proceeds.

[0003] However, the polishing liquid used in this manner is so-called dripping, and the polishing liquid once used is discarded, so that the running cost increases and a waste liquid treatment facility is required. It was not highly suitable for industrialization.

[0004]

SUMMARY OF THE INVENTION Under such circumstances,
In recent years, it has been demanded that the polishing liquid be recycled without being discarded. However, since the conventional polishing liquid is mainly an ultrafine silica-based slurry liquid, secondary aggregation is likely to occur over time, and the circulation method However, it is not suitable for a polishing system or the like, and the polishing ability is significantly deteriorated.

On the other hand, as a method for improving the dispersion stability, JP-A-63-285112 and JP-A-2-27.
No. 8822, Japanese Patent Laid-Open No. 4-2606, etc.
An abrasive containing a silica sol (colloidal silica) -based polishing liquid as a component is disclosed. However, the silica sol-based polishing agent also deteriorates in polishing ability over time, and the used polishing liquid is dripped and discarded in the same manner as described above, which is not highly industrially suitable.

Accordingly, an object of the present invention is to regenerate a used polishing liquid in a surface polishing system for semiconductor products using a silica sol-based polishing liquid and circulate the used polishing liquid to maintain a high polishing efficiency and stably. It is an object of the present invention to provide a semiconductor product surface polishing system capable of performing good polishing by using the method.

[0007]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have made intensive studies and arrived at the present invention. That is, a first step of the present invention is a first step of polishing a semiconductor product surface using a polishing liquid comprising an alkaline silica sol composition, and a regeneration by adjusting the silica concentration, pH and / or metal content of the used polishing liquid. A semiconductor product surface polishing system, comprising: a second step of using a polishing liquid; and a third step of replacing the regenerated polishing liquid obtained in the second step with a part or all of the polishing liquid of the first step. is there.

A second aspect of the present invention is to store a used polishing liquid generated in the first step, and perform a second step of regenerating the used polishing liquid when necessary, and obtain a regenerated polishing liquid obtained. Is a batch polishing method for replacing a part or all of the polishing liquid of the first step with the polishing liquid of the first step.

A third aspect of the present invention is the above-mentioned semiconductor product surface polishing system employing a continuous method in which the first step, the second step and the third step are simultaneously operated.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The alkaline silica sol composition used in the first step of the present invention may be a conventionally known low metal content alkaline silica sol composition which can be used for surface polishing of semiconductor products. For example, it can be obtained by removing a metal component from a general-purpose silica sol (also referred to as colloidal silica) and adjusting the pH as needed.

The term "low metal content" as used herein refers to a material having a low content of metal ions (also referred to as a semiconductor grade in commercial transactions). Since a large amount of metal ions has a chemical adverse effect on a material constituting a semiconductor product, it is preferable to minimize the content of metal ions, but it is particularly preferable to make Na ions less than 15 ppm. In order to remove the metal component of the general-purpose silica sol (also referred to as colloidal silica), it may be treated with a cation exchange resin. As the cation exchange resin, for example, Amberlite IR-116, I
Polystyrenesulfonic acid type such as R-120B (manufactured by Rohm and Haas), Duolite C-20 and C-26 (manufactured by Sumitomo Chemical Co., Ltd.) can be used as typical examples.
Further, the degree of purification can be further increased by using in combination with an anion exchange resin such as IRA-400, IRA-410 (manufactured by Rohm and Haas).

When a water-insoluble or hardly water-soluble metal compound or the like (including a simple substance) is contained, it has little chemical adverse effect as in the case of the above-mentioned metal ions. If the particle size is larger than the silica particles in the silica sol, physical adverse effects may occur. Therefore, it is better to filter those having a particle size of about 150% or more of the silica particle size. The silica particle diameter in the alkaline silica sol composition has an average particle diameter of 15 to 100 n.
m is preferable in terms of polishing efficiency and polishing accuracy.

To adjust the pH, ammonia and / or an organic water-soluble amine may be added, but it is preferable to use one having a low metal content as described above, and the pH is preferably adjusted to pH = 9.6. Adjustment within the range of 11.5 is preferable in terms of polishing efficiency and polishing accuracy. Organic water-soluble amines
A linear, branched or cyclic amine having 1 to 6 carbon atoms, for example, N, N-diethylethanolamine, aminoethylethanolamine, monoethanolamine, monoethylamine, hydrazine, ethylenediamine, diethylenetriamine, benzylamine , 1-aminoethylpiperazine and the like can be exemplified as preferable ones. From the viewpoint of solution stability, more preferable organic water-soluble amines are alkanolamines and alkylamines, and particularly preferable are aminoethylethanol. Amines, monoethanolamine, monomethylamine, hydrazine, ethylenediamine, diethylenetriamine, and tetramethylammonium hydroxide.

The silica solid content in the alkaline silica sol composition is preferably from 10 to 50% by weight, and more preferably from 20 to 50% by weight in terms of good polishing efficiency and stability.

In the first step of the present invention, the surface of a semiconductor product is usually polished by using the above alkaline silica sol composition as a polishing liquid.

The second step of the present invention is to adjust the silica concentration, pH and metal content of the used polishing liquid generated in the first step to obtain a regenerated polishing liquid.

The silica concentration of the used polishing liquid decreases over time due to the mixing of water during polishing. If the silica concentration decreases, good polishing efficiency cannot be obtained. To adjust the silica concentration, for example, in the case of a batch method, a polishing solution is sampled, the silica concentration is detected, and concentrated silica sol is added so as to have a desired concentration, or in the case of a continuous method, an ultrafiltration membrane is used. And concentrate.

The pH of the used polishing liquid decreases over time due to the mixing of the water and the influence of substances removed from the constituent materials of the semiconductor product by polishing. If the pH is lowered, good polishing efficiency cannot be obtained. For example, in the case of the batch method, the pH is adjusted by extracting a sample of the polishing liquid and detecting the pH. The content of ammonia and / or organic water-soluble amine may be added.

The metal content of the used polishing liquid increases due to the incorporation of substances removed from the constituent materials of semiconductor products by polishing. An increase in the metal content has a bad chemical effect on the materials constituting the semiconductor product. To reduce the metal content, the used polishing liquid may be treated with a cation exchange resin in the same manner as described above, regardless of whether it is a batch method or a continuous method.

In the present invention, the adjustment of the used polishing liquid means that the silica concentration, the pH and the metal content are all maintained within desired tolerances depending on the polishing purpose. In some cases, it may not be necessary to perform active control, for example, when the allowable range is not reached.

In addition, water-insoluble or hardly water-soluble metal compounds and the like increase in the used polishing liquid due to the incorporation of a substance scraped off from a semiconductor product constituent material by polishing. The particles having the above particle diameters are preferably separated by filtration.

The third step of the present invention is a step of replacing part or all of the polishing liquid of the first step with the regenerated polishing liquid obtained in the second step.

Incidentally, in order to increase the washing property after polishing, the content of metal may be reduced, and a surfactant or the like may be added in any of the above steps.

According to a second aspect of the invention, the used polishing liquid generated in the first step is stored, and a second step of regenerating the used polishing liquid when necessary is performed. It replaces a part or all of the polishing liquid in the process. This system is a batch method, and preferable conditions of the system in the batch method are as described above.

The third invention comprises a first step, a second step and a third step.
The process is operated simultaneously. This system is a continuous process, and suitable conditions for the system in the continuous process are as described above. In the continuous method, after the used polishing liquid generated in the first step is used, the regenerated polishing liquid is used in the first step without stopping the operation of the entire system after the silica concentration, pH and / or metal content are adjusted in the second step. It replaces a part or all of the polishing liquid used in the process. In this continuous method, it is not impossible to replace the entire polishing liquid with the regenerated polishing liquid, but it is preferable to partially replace the polishing liquid. Specifically, a continuously generated regenerated polishing liquid is continuously used. What is necessary is just to mix with the polishing liquid of the 1st process introduce | transduced specifically.

In the batch method, the polishing liquid is regenerated in the second step, so that the polishing liquid can be regenerated and used as needed as needed. Further, in the continuous method, since the used polishing liquid is regenerated without stopping the operation of the system, efficient polishing can be performed.

[0027]

EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited to these examples. (Example 1) An alkaline silica sol solution having an average particle diameter of 25 nm and a silica solid content of 30% by weight [Adeleite EX-3]
0N: manufactured by Asahi Denka Kogyo Co., Ltd.] and a cation exchange resin (manufactured by Rohm and Haas, trade name: Amberlite IR-11)
6), pH 1 with low metal content ammonia
0.5 (the metal component in the liquid is Fe0.3
ppm, Al 25 ppm, Ca 0.1 ppm, Mg
(0.2 ppm, Na 10 ppm) was used as a polishing liquid to polish a silicon wafer with an insulating oxide film under the following conditions.

Polishing machine: LPH-15 manufactured by Lappmaster
Improved polishing machine diameter: 15 inches Polishing machine rotation speed: 90 rpm Polishing sample: 6-inch wafer with thermal oxide film (thickness: 1 μm) Pressure: 150 g / cm ² Polishing liquid temperature: 30 ° C. Abrasive supply amount: 100 ml / min Polishing Time: 3 minutes (per sheet)

Under the above conditions, 30 wafers with an oxide film were polished. The polishing removal amount of the oxide film on the wafer surface after polishing was measured by a polarization analyzer (manufactured by Mizojiri Optical Industrial Co., Ltd.) to determine the polishing efficiency, and the surface state was observed with a microscope. The average polishing efficiency at this time was 2380 ° / min, and the surface to be polished had no scratches and was good.

The used polishing liquid generated here was diluted with water during the process, and had a pH of 10.0 and a silica solid content of 27% by weight. The metal content in the liquid is Fe3 ppm,
Al80ppm, Ca2ppm, Mg2ppm, Na2
It was 5 ppm.

Next, this used polishing liquid is passed through a cation exchange resin (trade name: IR-120B, manufactured by Rohm and Haas) having been subjected to a regeneration treatment at an S / V value of 3 to 4,
After removing metal components, add 1 with semiconductor grade ammonia.
The pH was adjusted to 0.5, and a silica sol having a low metal content and a high concentration was added to adjust the silica solid content to 30% by weight to obtain a reclaimed polishing liquid. The metal content of the obtained reclaimed polishing liquid is Fe0.2pp
m, Al 23 ppm, Ca 0.1 ppm, Mg 0.2
ppm and Na 10 ppm.

The reclaimed polishing liquid obtained here was used as a polishing liquid and polished again under the same conditions as above, and the polishing properties were measured. As a result, the polishing efficiency was 2350 ° / min, the surface condition was not scratched, and the polishing liquid was centrifuged (3500 rpm × 30
As a result, no precipitate was found and good stability was shown.

In the present example, the entire apparatus was covered with a vinyl tent to form a substantially closed system in order to suppress a change in composition due to volatilization of ammonia.

Example 2 A polishing and regenerating treatment was performed in the same manner as in Example 1, except that aminoethylethanolamine having a low metal content was used as the initial polishing liquid and the alkali for adjusting the pH at the time of regenerating the polishing liquid. The metal content in the reclaimed polishing liquid is F
e0.7ppm, Al 26ppm, Ca0.1pp
m, Mg 0.3 ppm and Na 12 ppm. As a result of polishing using this regenerated polishing liquid as a polishing liquid, polishing efficiency 2
300 ° / min, the surface to be polished has no scratches,
The stability of the polishing liquid was good without any precipitate. Also,
Regeneration of polishing liquid and polishing using the regenerated polishing liquid as polishing liquid
Although the polishing was repeated several times, the decrease in polishing efficiency was within an error range, and both the state of the surface to be polished and the stability of the polishing solution were good.

Example 3 Polishing and second step corresponding to the first step under the same conditions as in Example 1 except that a cation exchange resin (Duolite C-20; manufactured by Sumitomo Chemical) was used as the ion exchange resin. The polishing liquid generated was immediately and continuously supplied to the regeneration step. The metal content in the reclaimed polishing liquid is Fe 0.1 ppm, Al 19 pp
m, Ca 0.1 ppm, Mg 0.1 ppm, Na 9p
pm. Polishing was continued by immediately supplying a continuously regenerated polishing liquid as a polishing liquid. As a result of continuing polishing for 2 hours, the final polishing efficiency was 2350 ° /
As a result, the surface to be polished was free of scratches, and the stability of the polishing liquid was good with no precipitate. Similarly,
However, the same result was obtained when the regenerated polishing liquid was mixed with the initial polishing liquid and supplied as the polishing liquid.

(Comparative Example 1) A used polishing liquid produced by polishing using the same polishing liquid as in Example 1 was reused as a polishing liquid 10 times without regenerating.
As a result, the decrease in silica concentration was only 25% by weight, but p
H dropped to 9.1, the polishing efficiency became 1950 ° / min,
Although there was no scratch on the surface, metal and particle contamination on the wafer surface was remarkable due to the high metal content.

(Comparative Example 2) A slurry of ultrafine silica (manufactured by Nippon Aerosil Co., Ltd.) of semiconductor grade ammonia alkali having an average particle diameter of 25 nm and a silica solid content of 12% by weight was used under the same conditions as in Example 1. A silicon wafer with an insulating oxide film was polished, and 30 wafers were polished. The used polishing slurry liquid generated here is diluted with water in the process, and the pH is 10.1 and the silica solid content is 1
It was 1.8% by weight. The metal component in the liquid is Fe2.
7 ppm, Al 55 ppm, Ca 1.9 ppm, Mg
It was 1.8 ppm and Na19 ppm. Next, this used polishing slurry liquid is passed through an ion exchange resin (IR-120B) which has been regenerated in advance at an S / V value of 3 to 4 to remove a metal component, and then is treated with semiconductor grade ammonia. The pH was adjusted to 10.5 to obtain a regenerated polishing slurry liquid. The silica solid content of the obtained adjusted slurry liquid was 11.7% by weight.
However, the concentration was not adjusted because it was within the allowable range.
In this reclaimed polishing slurry liquid, the metal component in the liquid is Fe0.2
ppm, Al 0.3 ppm, Ca 0.3 ppm, Mg
Although it was 0.2 ppm and Na was 0.2 ppm, secondary agglomeration was promoted during the passage of the ion-exchange resin due to the use of the ultrafine silica slurry, and a precipitate was generated. This regenerated polishing slurry liquid was used as a polishing liquid and polished again under the same conditions as above, and the polishing property was measured. The result is a polishing efficiency of 1810 °
As a result of observing the surface state with a microscope for semiconductor inspection (manufactured by Olympus Optical Industrial Co., Ltd.), four scratches were confirmed.

[0038]

According to the present invention, in a semiconductor product surface polishing system using a silica sol-based polishing liquid, a used polishing liquid is regenerated and circulated to maintain high polishing efficiency while maintaining a stable polishing rate. The present invention provides a semiconductor product surface polishing system capable of performing good polishing.

Claims (3)

[Claims] A first step of polishing a semiconductor product surface using a polishing liquid comprising an alkaline silica sol composition;
A second step of adjusting the silica concentration, pH, and / or metal content of the used polishing liquid to be a regenerated polishing liquid, and using the regenerated polishing liquid obtained in the second step as part of the polishing liquid of the first step or And a third step of completely replacing the surface. 2. A second polishing apparatus for storing used polishing liquid generated in the first step and regenerating the used polishing liquid when necessary.
2. The semiconductor product surface polishing system according to claim 1, wherein a batch method of performing a step and replacing the obtained reclaimed polishing liquid with a part or all of the polishing liquid of the first step is adopted. 3. The semiconductor product surface polishing system according to claim 1, wherein a continuous method for simultaneously operating the first, second, and third steps is employed.