JP2003297778A - Composition for polishing and method for modifying the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition for polishing and a method for modifying the composition for polishing to polish the surface or the edge face of a silicon wafer or a semiconductor device substrate or the surface or edge face of a silicon wafer or a semiconductor device substrate whose surface is coated with an oxide film or a nitride film or the like. <P>SOLUTION: Mono-dispersed oxide silicon particles whose mean primary particle diameters range from 30 to 200 nm are made of colloidal solutions whose concentration ranges from 1 to 25 wt.%, and the colloidal solution is modified as a buffer solution having buffer action in the range of pH 8.7 to 10.5, and a fluorine ion or anion coordinated with fluorine is contained in one of components for composing a composition for polishing. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polishing composition for polishing a surface or an end surface of a silicon wafer or a semiconductor device substrate, or a surface or an end surface whose surface is coated with an oxide film or a nitride film, and the polishing composition. It relates to a method for preparing a composition.

[0002]

2. Description of the Related Art Conventionally, as a polishing composition for polishing a silicon wafer or a semiconductor device substrate (hereinafter abbreviated as a wafer or the like), a suspension of colloidal dispersion of silicon oxide or its hydrate, Many compositions containing so-called colloidal silica have been proposed. For example, in US Pat. No. 3,170,273, silica sol and silica gel are proposed as abrasives. Also,
U.S. Pat. No. 4,910,155 discloses the use of an aqueous dispersion slurry of fumed silica as an abrasive for the insulating layer of semiconductor wafers. JP-A-7-22105
No. 9, it is described that colloidal silica composed of elongated and distorted spherical silica particles exhibits a high polishing rate. Japanese Unexamined Patent Publication No. 2001-11433 describes that colloidal silica composed of silica particles in the form of beads connected in a bead shape exhibits a high silicon polishing rate. On the other hand, a great number of proposals have been made regarding the liquid composition. U.S. Pat. No. 3,328,141 discloses that the polishing rate is increased by adjusting the pH of the suspension within the range of 10.5 to 12.5. US Pat. No. 4,169,337 discloses adding amines to a polishing composition. JP-A-2-1586
Japanese Patent Publication No. 84 discloses a polishing composition comprising water, colloidal silica, a water-soluble polymer having a molecular weight of 100,000 or more, and water-soluble salts. Further, JP-A-5-154760 discloses a polishing method using a polishing composition containing piperazine, which is one of water-soluble amines, in an amount of 10 to 80% by weight based on the silica sol or silica gel. These disclosed methods increase the dispersibility of the abrasive and stabilize the processing force by adding various additives to the slurry in which fine silica particles are dispersed in an alkaline mother liquor or colloidal silica. Or increase the processing speed, and cannot sufficiently meet the presently required polishing performance, that is, high speed and stable polishing speed, good cleaning property after processing, flatness of polishing surface, etc. It was

JP-A-11-315273, JP-A-11-302635, and JP-A-11-302634.
In Japanese Patent Laid-Open No. 2000-158329 and Japanese Patent Laid-Open No. 2000-158329,
Using a weak acid and / or a weak base having a logarithmic value of the reciprocal of the acid dissociation constant of 8.0 to 12.0, a combination of a weak acid and a strong base, a strong acid and a weak base, or a weak acid and a weak base is used. There is disclosed a colloidal silica composition which is a buffer solution having a pH buffering action when added. The use of a buffer solution provides a stable polishing composition with little change in pH due to changes in external conditions and little change even after repeated use, but the lower the pH, the lower the polishing rate, Further improvements were desired. Particularly, in recent years, as the integration of electronic circuits has increased and the size of the wafer itself has increased, it has become essential to highly planarize the surfaces of silicon wafers and semiconductor device substrates. Furthermore, in order to improve production efficiency, a polishing composition having a high processing speed is desired.

[0004]

SUMMARY OF THE INVENTION The inventors of the present invention have
In view of the problems of the conventional polishing composition, earnestly researched, as a polishing composition solution, a colloid containing particles of silicon oxide having a specific particle size, that is, an alkaline aqueous solution of colloidal silica, pH of It has been found that stable high-speed processing can be achieved by constructing a specific ionic composition having a buffering effect, and has completed the present invention. To provide a polishing composition having a small polishing rate, a high polishing rate, stable polishing with little change even after repeated use, and improved cleaning properties after polishing, and adjusting the polishing composition. To provide a method.

[0005]

The above-mentioned object is to provide a substantially monodisperse silicon oxide particle having an average primary particle diameter of 30 to 200 nm which is a colloidal solution having a concentration of 1 to 25% by weight. The colloidal solution has a pH of 8.7 to 10.5
It was prepared as a buffer solution having a buffering action between 1 to 100 millimol / fluorine ion or anion having fluorine coordinated as one of the components.
This is achieved by a polishing composition containing Kg. This polishing composition can be prepared, for example, by diluting a concentrated stock solution of 15 to 65% by weight with water, an organic solvent, a solution containing salts or a mixture thereof each time it is used.

DETAILED DESCRIPTION OF THE INVENTION

The fine particles of silicon oxide are divided into gas phase method silicon oxide and liquid phase method silicon oxide according to the manufacturing method. As the vapor-phase method silicon oxide, a slurry in which fumed silica is dispersed in an aqueous medium has been frequently used for semiconductor polishing, but these fine particles have a wide particle size distribution and further aggregate to form secondary particles. It is a polydisperse system. Liquid phase silicon oxide includes general colloidal silica made from water glass and high-purity colloidal silica obtained by a hydrolysis method of an organic silicon compound. The colloidal solution of silicon oxide fine particles used in the present invention is
These are general colloidal silica and high-purity colloidal silica. In particular, general colloidal silica made from water glass is inexpensive, has a high polishing rate, and is preferably used.

The fine particles of silicon oxide contained in the colloidal solution used in the present invention are substantially monodisperse silicon oxide particles having an average primary particle diameter of 30 to 200 nm, preferably 40 to 100 nm. The average primary particle diameter mentioned here is a value obtained by converting the specific surface area measured by the nitrogen adsorption BET method into the diameter of spherical particles. For the BET particle size (specific surface area) of colloidal silica, see THE CHEMISTRY OF SILICA Solubility, Polymeriza
toin, Colloid and Surface Properties ， and Biochemis
try (P344-354, RALPH K. ILER, A Wiley-Interscienc
e Publication JOHN WILEY & SONS P). The calculation formula is particle diameter (nm) = 2720 / specific surface area (m ² / g).

The use of particles having an average primary particle diameter smaller than 30 nm causes the colloidal solution to easily aggregate when the electrolyte concentration of the buffer solution component is increased, which lowers the stability as a polishing composition, and further after polishing. The cleaning property of particles adhering to the wafer surface decreases. The average primary particle size is 200
The use of particles of nm or larger is not preferable in device polishing because it is close to the wiring width. In particular, it is necessary to remove polishing scraps and pad scraps by filtration when they are repeatedly used for polishing a plurality of sheets.
Particles with a size of 00 nm or more cannot be separated from dust.
Further, also in other applications, coarse particles settle, it is difficult to secure the stability of the product over time, and it is also disadvantageous in terms of price.

From this point of view, it is necessary to use monodisperse particles having substantially a single particle size that does not contain fine particles or coarse particles. The term “substantially monodisperse” as used in the present invention means a number average diameter (Dn) and a volume average diameter (Dn) measured by a general colloidal particle diameter measuring method such as an electron microscope method, a centrifugal sedimentation method and a laser light scattering method. It is defined that the ratio (Dv / Dn) or (Dw / Dn) of Dv) or the weight average diameter (Dw) is in the range of 1.00 to 1.50. Monodisperse colloidal silica includes "Silica Doll" manufactured by Nippon Kagaku Kogyo Co., Ltd. and "TCSOL" manufactured by Tama Chemical Co., Ltd.
703 ”and“ Ultra-high-purity colloidal silica PL-7 ”manufactured by Fuso Chemical Industry Co., Ltd. A dispersion system that is not substantially monodisperse is described as polydisperse. As the polydisperse colloidal silica, DuPontAirProducts Nano is used.
Materials L.M. L. C. "Syto
n ”,“ Mazin ”,“ Ascend ”, etc.

It is essential that the concentration of silicon oxide is 1 to 25% by weight in the actual polishing process, and a more preferable range is 3 to 15% by weight in the surface polishing of a silicon wafer or a semiconductor device substrate. , 10 for edge polishing
~ 25 wt% is good. If the concentration of silicon oxide during polishing is less than 3% by weight, the polishing rate will be low, which is not practical. If the concentration of silicon oxide during polishing increases, the polishing rate itself increases, but if it exceeds about 25% by weight, contamination of the wafer increases and cleaning performance deteriorates.

The present invention will be further described below. In the present invention, it is important that the pH of the polishing composition is in the range of 8.6 to 10.5. More preferably, the pH is 9.5.
It is preferably in the range of 10.5. If the pH is 8.6 or less, the polishing rate will be remarkably reduced and will be out of the practical range. Further, when the pH is 10.6 or higher, the contamination of the wafer increases and the cleaning property deteriorates. And again, this p
H must not be easily changed by conceivable changes in external conditions such as friction, heat, contact with outside air or mixing with other components, but in the present invention, a polishing composition solution is used. The necessary condition is that the liquid itself has a small change in pH with respect to changes in external conditions and has a so-called strong buffering action.

As an ion forming the buffer solution of the present invention, an anion is, for example, hydrochloric acid, nitric acid, hydrofluoric acid,
Examples thereof include strong acids such as sulfuric acid and weak acids such as boric acid, carbonic acid, phosphoric acid and water-soluble organic acids, and a mixture thereof may be used. Particularly preferred is carbonate ion or hydrogen carbonate ion. As the cations, alkali metal ions such as sodium and potassium, ammonium ions such as ammonium, choline, and tetramethylammonium, and amines ions such as ethylenediamine and piperazine that show alkalinity by pairing with hydroxide ions, such as It may be a mixture of. Particularly, potassium ion, tetramethylammonium ion and a mixture thereof are preferable. The buffer solution described in the present invention refers to a solution formed by a combination of the above-mentioned ions, added as an acid, an alkali, or a salt, dissociated as ions, and a non-dissociated state coexisting, and a small amount. The feature is that there is little change in pH even if the acid or base is mixed.

One of the components is a fluorine ion or an anion in which fluorine is coordinated as fluorine, and the amount is 1 to 100 mm.
It is necessary to contain 1 / Kg. In particular, when polishing is performed at a relatively low pH using a pH buffer solution as in the present invention, it is necessary to use such a component having a large erosion effect. Fluoride ions may be added as hydrofluoric acid, or may be added as a fluoride of each of the above bases. Tetrafluoroborate ion and hexafluorosilicate ion are preferable as the anion coordinated with fluorine. These may be added to a concentrated stock solution containing 15 to 65% by weight of silicon oxide, or may be added when the stock solution is diluted and adjusted each time it is used. Fluorine ions or anions coordinated with fluorine improve the polishing rate of the surface or end face of a silicon wafer or semiconductor device substrate, or the surface or end face whose surface is covered with an oxide film or nitride film, and at the same time after polishing. Has the effect of improving the cleaning property. If the amount of fluorine ion or anion coordinated with fluorine is 1 millimol / Kg or less, a sufficient polishing rate cannot be obtained. If it is added in an amount of 100 millimol / Kg or more, the erosion is too strong to obtain a flat mirror surface and the cleaning property is deteriorated. Preferably 3 to 60 millimol / Kg
Is.

Further, generally, the silicon oxide concentration is 25 to 65.
%, It is convenient to prepare a high-concentration composition and dilute it with water or a mixture of water and an organic solvent before use. It is also possible to omit any of the above-mentioned essential components other than silicon oxide in the high-concentration composition and add them at the time of dilution.

In order to improve the physical properties of the polishing composition of the present invention, a surfactant, a dispersant, an antisettling agent and the like can be used in combination. Examples of the surfactant, dispersant and anti-settling agent include water-soluble organic substances and inorganic layered compounds. The polishing composition of the present invention is basically an aqueous solution, but an organic solvent may be added.

[0016]

EXAMPLES Next, the polishing composition of the present invention and the polishing method using the same will be specifically described with reference to Examples and Comparative Examples, but the invention is not particularly limited thereto. The monodisperse colloidal silica used in the examples has an average particle diameter of 15 nm of “silica dol 30” and an average particle diameter of 40 nm.
nm is "Silicadol 30G", average particle diameter 80nm is "Silicadol 40G-80", average particle diameter 120nm
"Silica Doll 40G-120" was used, and colloidal silica having other average particle diameters was produced using water glass as a raw material. Number average diameter (Dn) and volume average diameter (Dv)
Was measured using Microtrac UPA manufactured by Nikkiso Co., Ltd., and it was confirmed that the ratio (Dv / Dn) was in the range of 1.00 to 1.50. The polydisperse colloidal silica was prepared as follows. "Silica Doll 30" having an average particle diameter of 15 nm, "Silica Doll 30G" having an average particle diameter of 40 nm, "Silica Doll 40" having an average particle diameter of 80 nm
G-80 "," Silica Doll 4 "having an average particle diameter of 120 nm
0G-120 "in an arbitrary ratio to obtain an average particle size of 40
nm and (Dv / Dn) were set to 2.0.

A commercially available aqueous solution was used as tetramethymelammonium hydroxide (hereinafter abbreviated as TMAH). Further, the above TMAH aqueous solution was neutralized with carbon dioxide gas to prepare tetramethyl methylammonium hydrogen carbonate (hereinafter abbreviated as TMAHC). The creation method was as follows. 20
% TMAH aqueous solution was put into a 500 ml gas washing bottle, carbon dioxide gas was made into fine bubbles and blown for 12 hours, and absorbed in the TMAH aqueous solution to obtain a TMAHC solution. The amount of carbonation was determined by performing neutralization titration with dilute hydrochloric acid and calculating from the inflection point of the titration curve, and the degree of neutralization was 97%.

As the fluorine, an aqueous solution of hydrofluoric acid, an aqueous solution of borofluoric acid and an aqueous solution of hydrofluoric silicic acid were used as the reagents, and similarly, sodium fluoride, sodium silicofluoride and potassium fluoride were used as the reagents. As the carbonate, reagents such as sodium hydrogen carbonate and potassium hydrogen carbonate were used. In addition, sodium hydroxide was used by diluting an industrial 50% aqueous solution.

Examples of surface polishing of silicon wafers of Examples 1 to 5 and Comparative Examples 1 to 3 will be shown. Using the polishing composition adjusted to have the composition shown in Table 1, mirror polishing was carried out under the following polishing conditions. Polishing device: manufactured by Speedfam Co., Ltd., SH-24 type single-sided processing machine, surface plate rotation speed: 70 RPM Pressure plate rotation speed: 50 RPM Polishing cloth: SUBA400 (manufactured by Rodel Nitta Co.) Surface pressure: 200 g / cm2 Polishing composition flow rate: 80 ml / Min Polishing time: 2 minutes Workpiece: 4 inches, silicon wafer with oxide film 1200 nm. The pH of the polishing composition was measured using a pH meter. The polished surface was evaluated by observing the state of haze and pits with the naked eye under a concentrating lamp. The polishing rate was calculated from the weight difference between the silicon wafers before and after polishing and converted to μm / min. The results are shown in Table 1. Examples 1 to 5 are comparative examples 1 to 3.
The polishing rate is higher than that of, and the surface condition is good.

The methods for preparing the polishing compositions in Examples 1-5 and Comparative Examples 1-3 are as follows. Comparative Examples 1-2 and Examples 1-2: A predetermined amount of hydrofluoric acid aqueous solution was added and mixed to the diluted TMAH aqueous solution, and then potassium hydrogen carbonate was added and dissolved under stirring. Add this additive solution to colloidal silica of each particle size with stirring,
Finally, it was diluted with pure water to obtain the composition shown in Table 1. Comparative Example 1 uses colloidal silica having an average particle diameter of 15 nm, and Comparative Example 2 uses the polydisperse colloidal silica prepared by the above method. Example 3: A predetermined amount of diluted TMAH aqueous solution and a predetermined amount of TMAHC aqueous solution were mixed, and predetermined amounts of sodium fluoride and potassium fluoride were added thereto and dissolved under stirring. Then
Add this additive solution to colloidal silica with stirring,
Finally, it was diluted with pure water to obtain the composition shown in Table 1. Example 4: A predetermined amount of diluted TMAH aqueous solution and a predetermined amount of TMAHC aqueous solution were mixed, and a predetermined amount of hydrofluoric acid aqueous solution was added and mixed, and then potassium hydrogen carbonate was added and dissolved under stirring. Next, this additive solution was added to colloidal silica with stirring, and finally diluted with pure water to obtain the composition shown in Table 1. Comparative Example 3: The composition of Table 1 was prepared in the same manner as in Example 4 except that the hydrofluoric acid aqueous solution was not added. Example 5: A predetermined amount of diluted TMAH aqueous solution and TMAHC aqueous solution were mixed, a predetermined amount of borohydrofluoric acid aqueous solution was added and mixed, and this additive solution was added to colloidal silica with stirring, and finally with pure water. The composition of Table 1 was diluted.

[Table 1]

An example of polishing the surface of a silicon wafer using the polishing composition liquids of Example 6 and Comparative Example 4 in circulation will be described. Using the polishing composition adjusted to have the composition shown in Table 2, the polishing conditions were the same as in Example 1, the polishing composition solution was circulated 10 times, and 10 wafer polishing experiments were performed. The pH and polishing rate of each polishing composition were measured.
The results are shown in Table 2. The pH of Example 6 is smaller than that of Comparative Example 4 up to 9 times of circulation, and the polishing rate is high.

The method for preparing the polishing composition in Example 6 and Comparative Example 4 is as follows. Example 6: A predetermined amount of diluted TMAH aqueous solution and TMAHC aqueous solution were mixed, a predetermined amount of hydrofluoric acid aqueous solution was added and mixed, and this additive solution was added to colloidal silica with stirring, and finally with pure water. It diluted and it was set as the composition of Table 2. Comparative Example 4: TMAH aqueous solution and TMAHC aqueous solution were not added, only sodium fluoride and sodium hydroxide were added to colloidal silica with stirring, and finally diluted with pure water to obtain the composition of Table 2.

[Table 2]

Examples of polishing the end faces of the silicon wafers of Examples 7 to 11 and Comparative Examples 5 to 7 will be shown. Using the polishing composition adjusted to have the composition shown in Table 3, mirror polishing was performed under the following polishing condition method. Polishing device: manufactured by Speedfam Co., EP-IV type end surface processing machine Drum rotation speed: 800 RPM Wafer rotation speed: 70 seconds / REV Wafer rotation speed: 4 times / sheet Polishing cloth: DRP-II (manufactured by Speedfam) Load Polishing composition flow rate: 250 ml / min Workpiece: 8 inches, oxide film 800 nm + polysilicon film 2000 nm with silicon wafer The polishing composition pH was measured using a pH meter. The polished surface was evaluated by observing the state of haze and pits with the naked eye under a concentrating lamp. The polishing rate was calculated from the weight difference between the silicon wafers before and after polishing and converted into mg / min. The results are shown in Table 3. Examples 7 to 11 are comparative examples 5 to 5.
The polishing rate is higher than that of No. 7, and the surface condition is good.

The methods for preparing the polishing compositions in Examples 7 to 11 and Comparative Examples 5 to 7 are as follows. Example 7: A predetermined amount of a hydrofluoric acid aqueous solution was added to and mixed with a diluted TMAH aqueous solution, and then potassium hydrogen carbonate and sodium hydrogen carbonate were added and dissolved under stirring. Next, this additive solution was added to colloidal silica with stirring, and finally diluted with pure water to obtain the composition shown in Table 3. Examples 8 to 9: A predetermined amount of diluted TMAH aqueous solution and a predetermined amount of TMAHC aqueous solution were mixed, and a predetermined amount of an aqueous solution of borofluoric acid was added to and mixed with this, and this additive solution was added to colloidal silica with stirring, and finally pure water was added. It was diluted with water to obtain the composition shown in Table 3. Example 10: A predetermined amount of a hydrofluoric acid aqueous solution was added to and mixed with a diluted TMAH aqueous solution, and then sodium hydrogencarbonate was added and dissolved under stirring. Next, this additive solution was added to colloidal silica with stirring, and finally diluted with pure water to obtain the composition shown in Table 3. Example 11: A predetermined amount of diluted TMAH aqueous solution and a predetermined amount of TMAHC aqueous solution were mixed, and a predetermined amount of hydrofluoric silicofluoric acid solution was added and mixed, and then sodium silicofluoride was added and dissolved under stirring. Next, this additive solution was added to colloidal silica with stirring, and finally diluted with pure water to obtain the composition shown in Table 3. Comparative Example 5: The composition of Table 3 was obtained in the same manner as in Example 10 except that the polydisperse colloidal silica prepared by the above method was used in place of the monodisperse colloidal silica. Comparative Example 6: A predetermined amount of hydrofluoric acid aqueous solution was added to and mixed with the diluted TMAH aqueous solution, and then sodium hydrogen carbonate was added and dissolved under stirring. Next, this additive solution was added to colloidal silica with stirring, and finally diluted with pure water to obtain the composition shown in Table 3. The composition had a pH of 8.2. Comparative Example 7: A predetermined amount of a hydrofluoric acid aqueous solution was added to and mixed with the diluted TMAH aqueous solution, then sodium hydrogen carbonate was added and dissolved under stirring, and a sodium hydroxide aqueous solution was further added and mixed. Next, this additive solution was added to colloidal silica with stirring, and finally diluted with pure water to obtain the composition shown in Table 3. The composition had a pH of 11.0.

[Table 3]

[0025]

As described above, the polishing composition of the present invention has a concentration of 1 to 25% by weight of substantially monodisperse silicon oxide particles having an average primary particle diameter of 30 to 200 nm. Consisting of a colloidal solution, the colloidal solution comprising:
It is prepared as a buffer solution having a buffering action between pH 8.7 and 10.5, and one of the components is a fluorine ion or an anion in which fluorine is coordinated as fluorine.
It was found that the polishing composition characterized by containing ˜100 millimol / Kg has a small pH change, a high polishing rate, and a good cleaning property. Using the polishing composition of the present invention, a silicon wafer or a semiconductor device substrate can be stably and rapidly polished without degrading the quality of the polished surface.

Claims (5)

[Claims] 1. A substantially monodisperse silicon oxide particle having an average primary particle diameter of 30 to 200 nm is composed of a colloidal solution having a concentration of 1 to 25% by weight, and the colloidal solution is
It is prepared as a buffer solution having a buffering action between pH 8.7 and 10.5, and one of the components is a fluorine ion or an anion in which fluorine is coordinated as fluorine.
A polishing composition containing 100 to 100 millimoles / Kg. 2. The cation forming the buffer solution is potassium ion and / or sodium ion and / or
The polishing composition according to claim 1, which is a tetramethylammonium ion. 3. The polishing composition according to claim 1 or 2, wherein the anion forming the buffer solution contains carbonate ion and / or hydrogen carbonate ion. 4. The content of sodium is 2 millimol / Kg
The polishing composition according to claim 1, claim 2 or claim 3, wherein: 5. A substantially monodisperse silicon oxide particle having an average primary particle diameter of 30 to 200 nm has a concentration of 25 to 65.
It is composed of a colloidal solution having a weight percentage of 5 to 500, and the colloidal solution is prepared as a buffer solution having a pH buffering action. Millimol
A method for adjusting the polishing composition according to any one of claims 1 to 4, wherein the polishing composition is diluted with a solution containing Kg / Kg, water, an organic solvent, a salt or a mixture thereof.