JP2001035818A - Abrasive powder for semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent in the CMP process of the manufacture of a semiconductor device its erosion and the abrasive unevenness of the contacting portion of its different materials with each other and make uniform the flatness of the whole of its wafer, by using in its chemical mechanical polishing the abrasive powder containing a specific quantity of abrasive grains whose aspect ratios are specified. SOLUTION: As an abrasive powder used in the chemical mechanical polishing of the manufacturing process of a semiconductor device, there is used the one wherein the quantity of the abrasive grains contained in it is not larger than 10 wt.% of the weight of its whole solid portion, and the aspect ratios of the abrasive grains range from 1.5 to 10. The aspect ratio of the abrasive grain is represented by the ratio of its major axis diametric length to its minor axis diametric length which is observed through a scanning type electron microscope. As the shapes of the grain, there are used preferably such conical-surface bodies as tetragonal and trigonal conical-surface bodies. To obtain such abrasive powder of a high aspect ratio, the cerium carbonate obtained by the double decomposition of a commercial cerium carbonate or cerium nitride and a commercial ammonium bicarbonate is heated and aged at 60-100 deg.C to bake it thereafter, preferably after its drying.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abrasive for chemical mechanical polishing for polishing a thin film such as an oxide film or a metal film in the manufacture of semiconductor devices. The present invention also relates to a method for planarizing a semiconductor substrate using the polishing agent.

[0002]

2. Description of the Related Art In semiconductor devices, especially semiconductor integrated circuits,
A multilayer wiring structure is generally used in which a wiring structure in which a wiring pattern is embedded on an insulating layer formed on a semiconductor substrate is multilayered. In general, when forming a multi-layer wiring, after depositing an interlayer insulating film or a metal film on a silicon wafer, the resulting irregularities are flattened by a polishing technique by chemical mechanical polishing (hereinafter sometimes abbreviated as CMP). Conversion process,
A step of stacking new wiring on the flattened surface is essential. However, in the case of a wiring portion near the end point of polishing in such CMP, an insulating film, a metal film, a barrier metal, and the like are mixed as polishing targets. Since these materials have different polishing rates, uneven polishing occurs in the mixed portions. In particular, in a portion where wiring is dense, unevenness tends to be formed during polishing due to a difference in polishing rate. Since stress is likely to be applied to the uneven portion, a phenomenon called erosion occurs in which both the insulating film and the metal portion are depressed in a portion where the wiring is dense.

[0003]

Therefore, there has been a demand for a high flattening means capable of suppressing such a phenomenon and polishing the entire wafer to a uniform flatness.

An object of the present invention is to provide a polishing agent which prevents erosion and uneven polishing of a contact portion between different materials in a CMP process for manufacturing a semiconductor device as described above and makes the entire wafer uniform in flatness. That is.

[0005]

Means for Solving the Problems (1) According to the present invention,
An abrasive used in chemical mechanical polishing in a semiconductor device manufacturing process, wherein the abrasive has an aspect ratio of 1.5 to 10.
(Hereinafter, also referred to as "abrasive grains of the present invention") characterized by containing 10% by weight or more of the total solid content weight.
Also referred to as "the abrasive of the present invention". ), Are provided.

(2) Further, according to the present invention, there is provided a method for planarizing a semiconductor substrate by polishing an insulating film and / or a metal film formed on the semiconductor substrate using the polishing slurry of the present invention.

[0007]

DETAILED DESCRIPTION OF THE INVENTION The abrasive grains of the present invention have an aspect ratio of 1.5 to 10, preferably 2 to 8, and more preferably 2.5 to 6. If it is less than 1.5, the desired effect of preventing erosion cannot be obtained sufficiently. Also,
The upper limit of the aspect ratio is preferably less than 10 from the viewpoint of easy preparation. However, anything beyond this can be used basically. The aspect ratio can be appropriately designed according to the object to be polished and the polishing conditions.

In the present invention, the aspect ratio is represented by (ratio of length of major axis / length of minor axis) of abrasive grains as observed by a scanning electron microscope (SEM).

If the aspect ratio is within the above range, the particle shape is not particularly limited. For example, the particle shape is arbitrary such as needle shape, plate shape, column shape, cigar shape, weight shape, etc. It is also preferable that the shape is a pyramidal shape such as a shape or a trigonal pyramidal shape.

The means for obtaining such high aspect ratio abrasive grains is not particularly limited, and can be appropriately selected depending on the type of the abrasive grains.

For example, with respect to abrasive grains composed of cerium oxide, cerium carbonate is used as a raw material and
It can be prepared according to the method disclosed in No. 1932. That is, cerium carbonate obtained by double-decomposing commercially available cerium carbonate or cerium nitrate and ammonium bicarbonate is heated and aged at 60 to 100 ° C., preferably dried, and then fired. Cerium carbonate becomes cerium monooxycarbonate during the heating and aging process, and it is considered that sintering of the cerium carbonate results in cerium oxide having a high aspect ratio.

Since the abrasive grains of the present invention are intended for polishing a semiconductor substrate, which is not the subject of the above publication,
It must be much smaller than the cerium oxide particles described in the above publication. Therefore, it is preferable that the raw material cerium carbonate is pulverized by wet pulverization or the like to have a desired particle size before the heat aging, or that the cerium oxide obtained after the heat aging is further pulverized.

In the above process, the wet pulverization is carried out in an aqueous medium such as water or a non-aqueous medium such as alcohol by means of a wet medium stirring mill or the like.
It is desirable to carry out at 800 ° C, preferably at 650 to 750 ° C.

The abrasive of the present invention most preferably comprises abrasive grains having an aspect ratio of 1.5 to 10. In some cases, abrasive grains having an aspect ratio of less than 1.5 are used. May be included. The content of the abrasive grains of the present invention based on the total solid content in the abrasive of the present invention is at least 10%
At least 20% by weight, more preferably at least 50% by weight, even more preferably at least 80% by weight.

The abrasive grains of the present invention have a weight average particle diameter of 0.01 to 2.0 in consideration of the polishing rate and the amount of scratches generated.
μm, and more preferably 0.1 μm.
０．５0.5 μm. Particles having a weight average particle diameter in this range can be obtained by preferably classifying the particles after firing.

As the classification operation, dry classification can be used, but wet classification is preferable because more accurate classification can be performed. Among them, examples of the wet classifier that can be preferably applied to the classification of particles having a particle size targeted by the present invention include centrifugal classifiers such as liquid cyclones, centrifugal sedimenters, and centrifugal decanters (decanters); hydroseparators, bowl decils And mechanical classifiers such as a water classifier, bowl classifier, spiral classifier, and drag classifier; hydraulic classifiers such as dolcosizers and supersorters; and sedimentation classifiers such as Spitzkasten and side cones.

In the present invention, the weight average particle diameter is a particle diameter at a point where the cumulative curve is 50% in a cumulative curve in which the particle weight distribution is determined on a mass basis and the total mass is 100%. This is also referred to as a 50% diameter based on mass (for example, Chemical Engineering Handbook “Revised 5th Edition” (edited by the Society of Chemical Engineers), pp. 220-2).
21).

The measurement of these particle diameters was carried out using a device such as Microtrac HRAX-100 manufactured by Nikkiso Co., Ltd., at the time when the dispersed state of the abrasive grains was stabilized by ultrasonically treating the abrasive grains with a medium such as water. This is performed by measuring the particle size distribution.

In order to obtain abrasive grains having a desired particle size range, it is preferable to combine a classification operation with a pulverization operation.

[0020] The abrasive grains of the present invention may be oxidized from the grinding power.
Cerium (Ceria, CeO_Two ), Aluminum oxide (A
Lumina, Al_Two O_Three ), Silicon dioxide (silica, SiO
_Two ), Zirconium oxide (zirconia_,ZrO_Two ), Acid
Titanium (Titania_,TiO _Two ), Silicon nitride (Si_Three 
N_Four ), Manganese oxide (MnO)_Two , Mn_Two O_Three , Mn _Three 
O_Four Etc.), germanium oxide (germania, GeO.G)
eO_Two ) Is preferred.
A, alumina and silica are particularly preferred, and
And ceria are most preferred. These are used alone
However, it is also possible to use a mixture.

The abrasive of the present invention is obtained by mixing a high aspect ratio abrasive grain as described above with water or an aqueous medium (in the present specification, these are collectively referred to as "aqueous medium"), a stirring mixer, a homogenizer, and a ball mill. Etc., and the abrasive particles are 0.1
It is preferably used as a slurry (hereinafter also referred to as an abrasive slurry) in which the slurry is dispersed in an amount of up to 30% by weight, preferably 0.1 to 20% by weight, and more preferably 1 to 15% by weight. Here, the aqueous medium is a mixed solvent containing water as a main component and containing a water-soluble or water-miscible organic solvent such as methanol, ethanol, or isopropanol in an amount of about 30% by weight or less, preferably about 20% by weight or less. In addition, a dispersant, a thickener, a fungicide, an oxidizing agent, a pH adjuster, or the like may be appropriately added to the abrasive slurry according to the intended use.

As the dispersant, a surfactant is usually used, and anionic surfactants such as ammonium oleate, ammonium lauryl sulfate and triethanolamine lauryl sulfate, polyoxyethylene lauryl ether and polyoxyethylene sorbitan monolau are used. Non-ionic surfactants such as polyethylene glycol and polyethylene glycol distearate are preferably used.

The polishing agent of the present invention is used in a method of polishing a semiconductor substrate for polishing an insulating film and / or a metal film formed on the semiconductor substrate.

More specifically, the polishing slurry of the present invention is carried on a polishing cloth of a chemical mechanical polishing apparatus to polish an insulating film and / or a metal film formed on a semiconductor substrate. Can be performed according to a conventional method. For example, a polishing head provided with a drive device for rotating while holding a material to be polished such as a semiconductor substrate on an upper portion, and a lower polishing pad (a polishing cloth) opposed thereto.
) Is attached to a rotating platen (platen) using a CMP apparatus, the abrasive cloth of the present invention is carried on the abrasive cloth, specifically, the abrasive of the present invention is an abrasive slurry While supplying this on a polishing cloth,
The substrate is brought into contact with a rotating semiconductor substrate at about 300 rpm and a polishing pressure of about 50 to 250 g / cm ² to polish and planarize an insulating film and / or a metal film formed on the substrate. is there. In the thin film, several tens nm to several thousands nm are removed.

[0025]

Since the abrasive grains of the present invention have a high aspect ratio, they are likely to be caught at the edges of the projections and depressions in the thin film, which is liable to be subjected to stress during polishing, and are likely to lie sideways. For this reason, the particles are caught in a wider area than the spherical particles, and the stress per unit area applied to the concave and convex portions is weaker than that of the spherical particles. This means that the polishing force of the uneven portion becomes weaker than that of the spherical particles. Therefore, in the abrasive grain of the present invention, it is considered that by utilizing this property, it is possible to prevent uneven polishing of the wiring portion and erosion in which the portion where the wiring is dense is excessively shaved.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, but the technical scope of the present invention is not limited thereto.

(I) Production of abrasive [Example 1] Commercially available cerium carbonate was wet-pulverized,
The mixture was heated and aged at ℃ until the generation of carbon dioxide gas was completed, and then dried. This was fired at 700 ° C. in an electric furnace to obtain CeO ₂ . This was subjected to wet classification to obtain CeO ₂ particles having a weight average particle size of 0.25 μm.

Ion-exchanged water was added thereto to prepare an abrasive slurry containing 2% by weight of CeO ₂ particles. In addition, CeO
_{As a result} of visual observation by SEM of the _two particles, 95% by weight or more of the particles had an aspect ratio in the range of 2.5 to 4.0. The shape of the particles was a weight surface shape.

Comparative Example 1 Commercially available cerium carbonate was wet-pulverized and then dried. This was fired at 700 ° C. using an electric furnace, and then wet-classified so as to have a weight average particle size of 0.25 μm.

Ion-exchanged water was added thereto to prepare an abrasive slurry containing 2% by weight of CeO ₂ particles. In addition, CeO
_{As a result} of visual observation by SEM of the _two particles, 95% or more by weight of the particles had an aspect ratio in the range of 1.0 to 1.3.

With respect to the abrasives obtained in Example 1 and Comparative Example 1, a polishing test was performed by the following method, and a polishing rate was measured.

(II) Polishing test [Polishing conditions] Polishing pressure: 200 g / cm ² Polishing pad: IC1000 / Suba400 (manufactured by Rodale) Number of rotations: upper plate 25 rpm, lower plate 60 rpm Slurry supply speed: 20 ml / min

[Measurement of Polishing Rate] Under the above polishing conditions, each of the wafer with an oxide film and the wafer with an oxide film and wiring was polished for 3 minutes, and the weight difference between SiO ₂ before and after polishing was measured. .

The results were evaluated by relative values with the weight difference when polishing the silicon wafer with an oxide film using the polishing agent of Comparative Example 2 under the same conditions as 100.

[Observation of Particle Shape] Observation was performed using an SEM (Hitachi, S-3500H) at an acceleration voltage of 20 kV and a magnification of 50,000 times. The results are shown in Table 1.

[0036]

[Table 1]

[0037]

When the polishing agent of the present invention is used for polishing,
There is an effect that the polishing rate hardly changes even on a flat surface or a fine uneven surface. From this, it can be used effectively for the purpose of realizing excellent global planarization (complete flattening) by coping with uneven surfaces generated by various actual wiring patterns. Further, a semiconductor integrated circuit manufactured using the abrasive of the present invention can be expected to have excellent performance.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) // C01F 17/00 H01L 21/306 MF term (reference) 3C058 AA07 AC04 CB10 DA02 DA17 4G076 AA02 AB09 AC01 AC04 BA39 BA46 BC08 CA15 CA26 DA30 5F043 AA22 AA29 BB30 DD16 DD30 FF07 GG10

Claims (5)

[Claims] An abrasive used in chemical mechanical polishing in a semiconductor device manufacturing process, which has an aspect ratio of 1.
An abrasive containing 5 to 10 abrasive grains in an amount of 10% by weight or more based on the total solid weight. 2. The weight average particle size of the abrasive grains is 0.01 to
The abrasive according to claim 1, which has a thickness of 2.0 µm. 3. The abrasive according to claim 1, wherein the abrasive grains are cerium oxide particles. 4. The abrasive according to claim 1, wherein the abrasive is suspended in an aqueous medium and used in a slurry state. 5. An insulating film formed on a semiconductor substrate and / or
A method for planarizing a semiconductor substrate, comprising polishing a metal film using the polishing agent according to claim 1.