JP2000230169A - Slurry for polishing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a novel slurry for chemically and mechanically flattening dielectric materials capable of improving a polishing speed without essentially containing a volatile base such as ammonia, and the like, and metal ions. SOLUTION: This slurry for polishing comprises (a) 100 pts.wt. of an aqueous medium, (b) 1-50 pts.wt. of SiO2 particles, (c) 0.1-10 pts.wt. of a pH buffer and (d) 0.1-10 pts.wt. of a polishing-accelerating agent selected from the group consisting of a water soluble alcohol, a water soluble amine, a water soluble aminoalcohol and a mixture of two or more of them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing slurry for chemically polishing a dielectric layer in the manufacture of integrated circuits.
anionic planarizing dielectric layers, especially those that do not substantially contain metal ions.
nical planarization).

[0002]

2. Description of the Related Art At present, the only way in which global planarization can be practiced in the manufacture of integrated circuits is chemical mechanical planarization (CMP). That is,
The elastomer pad is pressed against the semiconductor substrate and rotated, and at the same time, the semiconductor substrate is washed or rinsed with a polishing slurry, so that the slurry particles are pressed against the substrate under a load. As a result of the lateral movement of the elastomer pad, the slurry particles move on the substrate surface, so that the substrate surface can be chemically and mechanically removed.

[0003] The slurries used to polish dielectric materials such as SiO ₂ (the most commonly used dielectric material) are characterized by consisting of colloidal silica suspended in a basic solution. In general, a sufficient removal rate (removal ra
In order to realize te), the pH value of the slurry needs to be higher than 9, and the removal rate increases as the pH value increases. For this reason, commercial production of slurry for chemical mechanical planarization (CMP) of insulating layers (commerci)
When al production) which is, by using a base such as KOH or NH ₄ OH, is achieved the pH value of 10-11.

[0004] Slurries used to remove dielectric materials include:
The use of potassium and ammonium hydroxide raises several problems. Alkali metal ions, especially sodium and potassium ions, diffuse into the dielectric oxide layer and contaminate it. As a result, a complicated cleaning process must be performed following CMP in order to remove metal ions from the wafer surface. Therefore, it is common practice to avoid using alkali metal ions in semiconductor device slurries. On the other hand, since ammonium hydroxide is easily decomposed, a slurry using this compound emits an odor due to liberated ammonia. This ammonia vapor
It also harms other semiconductor manufacturing processes, especially the negative effect on the photoresist material. Therefore, if it is possible to obtain a slurry that does not substantially contain volatile bases such as ammonia and metal ions,
It will certainly be a major advance in the field.

[0005] US Patent No. 5,769,689 discloses Si
A composition for polishing O ₂ , silicate, and silicon nitride has been disclosed. Here, the polishing rate was improved by utilizing the salt effect of the soluble inorganic salt, and at the same time, the solidification of the slurry was prevented.

[0006] US Patent No. 5,480,476 disclosed a composition for polishing glass, semiconductors, and integrated circuits. Here, the polishing rate was improved by including a cation such as Ce ⁴⁺ and activating a polishing base.

[0007] US Patent No. 5,391,258 describes an anion which contains an anion which can control the rate of silica removal.
A polishing composition has been disclosed. As used herein, the anion is a derivative of a comparable compound and contains at least two acid radicals, such as tartaric acid.

[0008] US Patent No. 5,264,010 disclosed a polishing composition containing various abrasives, such as cerium oxide, fumed silica, and precipitated silica.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a dielectric material which can improve the polishing rate and is substantially free from volatile bases such as ammonia and metal ions. Another object of the present invention is to provide a novel slurry for mechanically planarizing.

[0010]

In order to achieve the above-mentioned object, in the present invention, the pH of the slurry is controlled by using another strong base instead of metal hydroxide or ammonium hydroxide. More specifically, in the present invention,
By using a base that does not contain metal and can improve the polishing rate, such as an alcohol-type base, an amine-type base, and an amino-alcohol-type base, the desired polishing rate can be achieved without causing a problem of metal contamination. To improve Therefore, in the slurry disclosed in the present invention, the content of metal ions is suppressed to as low as 10 ppm or less.

The slurry according to the present invention comprises (a) 100 parts by weight of an aqueous medium, (b) 1 to 50 parts by weight of SiO ₂ particles, and (c) 0.1 to 10 parts by weight of a pH buffer. And (d) 0.1 to 10 parts by weight of a polishing accelerator selected from the group consisting of a water-soluble alcohol, a water-soluble amine, a water-soluble amino alcohol, and a mixture of two or more thereof.

[0012]

DETAILED DESCRIPTION OF THE INVENTION In order to further clarify the above and other objects, features and advantages of the present invention, preferred embodiments will be described below in more detail.

[0013] The slurry according to the present invention contains an aqueous solvent. This aqueous solvent is preferably deionized or distilled water.

The slurry according to the present invention further contains 1 to 50 parts by weight, preferably 1 to 20 parts by weight, of SiO ₂ particles as an abrasive based on 100 parts by weight of the aqueous medium.
When the content of the SiO ₂ particles is small, the polishing speed tends to be slow, and when it is large, the polishing tends to be difficult. The SiO ₂ particles used in the slurry according to the present invention preferably have a particle size of about 10 nm to 1 μm.
One or more types of S having a particle size within this range.
iO ₂ particles can be used as a polishing component. In the case of SiO ₂ particles having a small particle size, the polishing effect is poor,
Moreover, aggregation (agglomerate) tends to occur, and large SiO ₂ particles have poor suspension properties and
The object to be polished tends to be easily damaged.

The slurry according to the present invention further contains 0.1 to 10 parts by weight, preferably 0.1 to 3 parts by weight, of a polishing accelerator based on 100 parts by weight of the aqueous medium. If the content of the polishing accelerator is small, the effect of accelerating the polishing speed tends to be lost, and if the content is large, the phenomenon of suppressing the polishing speed tends to occur.

[0016] In order to promote the erosion of silica material, SiO
Strong bases that can chelate with ₂ are suitable for the polishing accelerator used in the present invention. Accordingly, the slurry according to the present invention contains a polishing accelerator selected from the group consisting of a water-soluble alcohol, a water-soluble amine, a water-soluble amino alcohol, and a mixture of two or more thereof. The polishing accelerator used in the present invention preferably contains at least two functional groups selected from the group consisting of a hydroxyl group and an amino group. If the number of functional groups selected from the group consisting of a hydroxyl group and an amino group is small, there is a tendency that chelate cannot be caused, and if the number is large, water solubility tends to be poor.

The polishing accelerator used in the present invention has a strong basicity and can maintain a good polishing speed by chelating with SiO ₂ . More preferably, the polishing accelerator also contains from 2 to 5 carbon atoms. If the number of carbon atoms is small, the chelate (chel
ate), and when the amount is large, the water solubility tends to deteriorate.

Such polishing accelerators suitable for use in the present invention include, for example, ethylenediamine, ethanolamine, ethylene glycol, 1,2-propylene glycol and the like.

The polishing accelerator used in the present invention includes, for example, amines having at least two amino groups such as ethylenediamine, amino alcohols such as ethanolamine, ethylene glycol, and at least such as 1,2-propylene glycol. Alcohols containing two hydroxyl groups are preferred, with ethylene glycol being particularly preferred. When ethylene glycol is mixed as a polishing accelerator, the polishing rate by SiO ₂ can exceed 1700 ° / min.

The slurry according to the invention also contains 0.1 to 10 parts by weight, preferably 1 to 5 parts by weight, of a pH buffer, based on 100 parts by weight of the aqueous medium. When the content of the pH buffer is small, there is a tendency that stable pH action cannot be performed, and when the content is large, the viscosity of the solution tends to increase.

The pH buffer used in the present invention is preferably an organic salt (for example, an ammonium salt).
As such a pH buffering agent, carbonates can be used, and examples thereof include ammonium carbonate, ammonium bicarbonate, sodium carbonate, lithium carbonate, and sodium bicarbonate. The most preferred is ammonium carbonate. And ammonium bicarbonate.

The slurry according to the present invention can be prepared by adding one or more kinds of SiO ₂ particles to an aqueous solvent, and then adding the above-mentioned pH buffering agent and polishing accelerator and mixing them well.

The slurry according to the invention can maintain a pH value generally above 9, and can preferably achieve a pH value of about 10 to about 12. In a slurry having a low pH value, the solubility of the oxide (SiO ₂ ) film tends to decrease, and in a slurry having a high pH value, the corrosiveness tends to increase.

The slurry according to the invention is particularly suitable for polishing dielectric materials. However, it is also possible to apply the same to polishing of glass, ceramics and the like.

[0025]

Next, the slurries prepared in each of the following Examples and Comparative Examples were mixed with at least two thermal oxide wafers using a Westech 372 Polishing Machine.
Weffers). The resulting polishing rates and non-uniformities are shown in Table 1. The polishing rate is obtained by measuring the thickness before and after polishing using Nanospec, and dividing by the polishing time. The non-uniformity was obtained by measuring the polishing rate at nine different positions on the wafer surface using the 1σ method. As used herein, "parts by weight" shall refer to the weight of each component indicated relative to 100 parts by weight of aqueous medium, i.e., deionized water.

Example 1 A slurry was prepared according to the following procedure. First, 15 layers
Amount of SiO_TwoAdd particles to 100 parts by weight deionized water
Stir until completely dispersed. This SiO _Twoparticle
Has a particle size of about 10 nm to about 1 μm and a specific surface area (specific
 area) is 100m ^Two/ G. In addition, polishing
0.7 parts by weight of ethylenediamine as a promoter
Add 2 parts by weight of ammonium carbonate
Stir to obtain a final pH 10.2 slurry
Was.

With respect to the polishing slurry obtained in this example,
Its ion content was analyzed by ICP-AES and found to contain Na, K, Fe, Al, Ca, Mg, M
None of the ion contents of n, Ti, Cu, and Zn could be measured (less than 1 ppm).

Example 2 A slurry containing two types of SiO ₂ particles was prepared in the following procedure. First, the specific surface area is 100 m ² / g
With less than ₂ SiO ₂ particles and a specific surface area of 100 to 20
0 m ² / g of SiO ₂ particles were added in 15 parts by weight and 1 part by weight respectively to 100 parts by weight of deionized water and stirred until completely dispersed. Further, 1 part by weight of ethylenediamine as a polishing accelerator and 2 parts by weight of ammonium carbonate as a pH buffer were added and sufficiently mixed to obtain a slurry having a final pH value of 11.3.

Example 3 A slurry was prepared according to the following procedure. First, 10 layers
Amount of SiO_TwoAdd particles to 100 parts by weight deionized water
Stir until completely dispersed. This SiO _Twoparticle
Has a particle size of about 10 nm to about 1 μm and a specific surface area of 100 m
^Two/ G. In addition, as a polishing accelerator
1 part by weight of lenglycol, carbonated carbonate as a pH buffer
Add 2 parts by weight of ammonium and mix thoroughly,
A slurry with a pH value of 11.5 was obtained.

Example 4 A slurry was prepared according to the following procedure. First, 15 layers
Amount of SiO_TwoAdd particles to 100 parts by weight deionized water
Stir until completely dispersed. This SiO _Twoparticle
Has a particle size of about 10 nm to about 1 μm and a specific surface area of 100 m
^Two/ G. Further, 1, as a polishing accelerator,
1 part by weight of 2-propylene glycol as a pH buffer
Add 2 parts by weight of ammonium carbonate and mix thoroughly.
As a result, a slurry having a final pH value of 11.5 was obtained.

Example 5 A slurry was prepared according to the following procedure. First, 13 layers
Amount of SiO_TwoAdd particles to 100 parts by weight deionized water
Stir until completely dispersed. This SiO _Twoparticle
Has a particle size of about 10 nm to about 1 μm and a specific surface area of 100 m
^Two/ G. Furthermore, eta as a polishing accelerator
0.7 parts by weight of nolamine, carbonic acid as a pH buffer
Add 2 parts by weight of ammonium and stir well
A slurry having a pH value of 10.8 was obtained.

Comparative Example A KOH-based slurry was prepared for comparative purposes by the following procedure. First, 10 parts by weight of SiO ₂ particles were added to 100 parts by weight of deionized water and stirred until completely dispersed. These SiO ₂ particles have a particle size of about 10 nm.
約 1 μm, and the specific surface area was less than 100 m ² / g.
Further, add KOH and mix thoroughly to obtain the final pH.
A slurry with a value of 11.0 was obtained.

[0033]

[Table 1]

As can be seen from the data in Table 1, the slurries prepared in the above Examples achieve the desired polishing rate without adding KOH by using the polishing accelerator disclosed in the present invention. can do. In particular, when ethylenediamine is used as a polishing accelerator, a polishing rate exceeding 1700 ° / min can be achieved.

While the preferred embodiments have been disclosed above, they are not intended to limit the scope of the invention in any way, and anyone skilled in the art will be able to do so without departing from the spirit and scope of the invention. Various variations and additions should be made, and accordingly, the protection scope of the present invention is based on the contents specified in the claims.

[0036]

From the above, it can be seen that the slurry according to the present invention has the following various advantages over the conventional slurry. 1. The content of metal ions in the slurry can be significantly reduced. 2. The cleaning step following chemical mechanical planarization (CMP) can be simplified. 3. By using a strong base compound that can promote the erosion of silica, the polishing rate by SiO ₂ can be increased. 4. Odors caused by liberated ammonia can be prevented.

Claims (17)

[Claims] (A) 100 parts by weight of an aqueous medium, (b)
1-50 parts by weight of SiO ₂ particles, (c) 0.1 to 10 parts by weight of pH buffering agent, and (d) 0.1 to 10 parts by weight, water-soluble alcohol, water-soluble amines, water-soluble A slurry for chemically and mechanically planarizing a dielectric layer containing a polishing accelerator selected from the group consisting of amino alcohols and mixtures of two or more thereof. 2. A slurry according to claim 1, wherein said aqueous medium is deionized water. 3. The slurry according to claim 1, wherein said aqueous medium is distilled water. 4. The method according to claim 1, wherein the SiO ₂ particles have a particle size of 10 nm or more.
_2. The slurry according to claim 1, comprising one or more kinds of SiO2 particles of 1 [mu] m. 5. The slurry according to claim 1, wherein the content of the SiO ₂ particles is 1 to 20 parts by weight. 6. The method of claim 1, wherein the pH buffer is an organic salt.
The described slurry. 7. The slurry of claim 6, wherein said organic salt is selected from the group consisting of ammonium carbonate, ammonium bicarbonate, and a mixture of two or more thereof. 8. The slurry according to claim 1, wherein the content of the pH buffer is 1 to 5 parts by weight. 9. The slurry according to claim 1, wherein the polishing accelerator contains at least two functional groups selected from the group consisting of a hydroxyl group and an amino group. 10. The slurry according to claim 9, wherein said polishing accelerator contains 2 to 5 carbon atoms. 11. The polishing accelerator according to claim 11, wherein the polishing accelerator is ethylenediamine, ethanolamine, ethylene glycol, 1,2-.
The slurry of claim 10, wherein the slurry is selected from the group consisting of propylene glycol and a mixture of two or more thereof. 12. The slurry according to claim 11, wherein said polishing accelerator is ethylenediamine. 13. The content of the polishing accelerator is 0.1-3.
The slurry according to claim 1, which is in parts by weight. 14. The slurry according to claim 1, wherein the pH value is greater than 9. 15. The slurry according to claim 14, wherein the pH value is in the range of 10-12. 16. The slurry according to claim 2, wherein the content of metal ions is 10 ppm or less. 17. The slurry according to claim 3, wherein the content of metal ions is 10 ppm or less.