JP2008270341A - Polishing agent for flattening semiconductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing agent for flattening a semiconductor, capable of assuring high-speed polishing of the front surface of the semiconductor in a wiring forming process, excellent surface flatness and scratch reduction. <P>SOLUTION: The polishing agent for flattening the semiconductor includes cerium oxide particle having a half-value width in a range of 0.28 to 0.32 degrees of the main peak of the powder X-ray diffraction pattern and water. In this polishing agent, the center value of the diameter of cerium oxide particle is within the range of 100 to 2,000 nm. It is also possible to use the polishing agent for flattening the semiconductor which can be obtained by adding a dispersion agent to the above polishing agent for flattening the semiconductor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an abrasive, and more particularly to an abrasive for planarizing a semiconductor.

  Examples of applications that require precise polishing of the surface of the material: crystals such as optical disks, magnetic disks, glass substrates for flat panel displays, watch plates, camera lenses, and various lenses used for optical components. There are materials, substrates such as semiconductor silicon wafers, insulating films, metal layers, barrier layers and the like formed in each process of semiconductor device manufacturing.

  The surface of these materials is required to be polished with high accuracy. For this purpose, for example, an abrasive that uses silica, zirconium oxide, alumina or the like alone or in combination of two or more as abrasive particles is generally used.

  As the form of the abrasive, for example, abrasive particles are dispersed in a liquid to form a slurry, abrasive particles are solidified with a resin or other binder, and the abrasive particles are based on a fiber, resin, metal, or the like. In general, the surface of the material, which is adhered and / or fixed together with a binder only with fine particles, is used as an abrasive.

  In particular, silica abrasives using silica fine particles as abrasive particles are widely used as precision polishing abrasives for wiring formation in the manufacture of semiconductor integrated circuits (hereinafter referred to as semiconductors) because they produce less scratches on the surface to be polished. However, since the polishing rate is low, in recent years, a cerium oxide abrasive containing cerium oxide having a high polishing rate has attracted attention (see, for example, Patent Document 1 and Patent Document 2).

  However, the cerium oxide abrasive has a problem that it has more scratches than the silica abrasive.

A cerium oxide abrasive has been used for glass polishing for a long time, but is applied to planarization of an inorganic insulating film such as a SiO ₂ insulating film formed by a method such as a TEOS-CVD method, which is performed in semiconductor manufacturing. Therefore, it was necessary to avoid contamination with impurities as much as possible. Therefore, the rare earth material is once purified to obtain high-purity cerium oxide via a cerium salt.

Examples of cerium salts include cerium carbonate, cerium oxalate, and cerium nitrate.
A cerium oxide obtained by firing and pulverizing these cerium salts is dispersed to produce an abrasive for planarizing a semiconductor.

The cerium oxide abrasive used for polishing SiO ₂ insulating film, etc., is capable of high-speed polishing as the primary particle diameter of the abrasive particles is large and the crystal distortion is small, that is, the better the crystallinity, but there is a tendency that scratches are likely to occur. is there. However, the relationship between the polishing rate and the crystallinity with respect to scratch has been conceptually understood, and the optimum value has not been sufficiently studied.

  On the other hand, higher integration of semiconductors has progressed, and the processing dimensions of wiring and the like have been reduced to 100 nm. As processing becomes finer, the demand for reducing defects such as scratches is increasing, and an abrasive that satisfies all of the polishing speed, flattening, and scratch reduction is required.

JP 2000-026840 A Japanese Patent Laid-Open No. 02-371267

  An object of the present invention is to provide a semiconductor planarization polishing agent capable of polishing a semiconductor surface at a high speed in a wiring formation step, having good flatness and reducing scratches. .

  As a result of intensive investigations on the speeding up of polishing and the reduction of scratches by the polishing agent for semiconductor flattening, the present inventors have used a cerium oxide prepared in a suitable range of crystallinity as a polishing agent. The present inventors have found that scratches can be reduced while maintaining the present invention and have completed the present invention.

The present invention includes a semiconductor flat having a cerium oxide particle having a half-value width of 0.28 to 0.32 ° of a main peak of a powder X-ray diffraction pattern and water, and having a median cerium oxide particle diameter of 100 to 2000 nm. The present invention relates to a polishing abrasive.
The present invention also relates to the above-described polishing agent for planarizing a semiconductor, wherein the content of cerium oxide particles having a particle diameter of 3 μm or more is 500 ppm or less in the solid by weight.

The present invention also relates to a semiconductor flattening polishing slurry further containing a dispersing agent in the semiconductor flattening polishing slurry.
Furthermore, the present invention relates to the above-described polishing agent for planarizing a semiconductor, wherein 99% by volume of the entire cerium oxide particles have a particle diameter of 1 μm or less.

  According to the present invention, the semiconductor surface in the wiring forming process can be polished at high speed, and the flatness is good, and scratches can be reduced.

Hereinafter, the best mode for carrying out the invention will be described in detail.
The semiconductor planarization abrasive (hereinafter also referred to as abrasive) according to the present invention is characterized by containing cerium oxide particles and water.

In general, cerium oxide is obtained by firing cerium compounds such as carbonates, oxalates, and nitrates.
The cerium oxide abrasive used for polishing the SiO ₂ insulating film formed by TEOS-CVD method, etc. can be polished at a higher speed as the primary particle diameter of the abrasive particles is larger and the crystal distortion is smaller, that is, the crystallinity is better. However, there is a tendency for scratches to easily enter.

Therefore, the cerium oxide particles used in the present invention are produced without increasing crystallinity.
Moreover, since it uses for semiconductor element grinding | polishing, it is preferable to suppress the content rate of an alkali metal and halogens to 10 ppm or less in a cerium oxide particle.

  In the present invention, a firing method can be used as a method for producing cerium oxide particles. However, low temperature firing that does not increase crystallinity as much as possible is preferable in order to produce particles that do not contain scratches.

  Since the oxidation temperature of the cerium compound is 300 ° C, the firing temperature is preferably 600 ° C or higher and 900 ° C or lower. It is preferable to burn cerium carbonate in an oxidizing atmosphere such as oxygen gas at 600 ° C. or higher and 900 ° C. or lower for 5 to 300 minutes.

  The cerium oxide particles produced by the above method can be pulverized by dry pulverization using a jet mill or the like, or wet pulverization using a planetary bead mill or the like.

The abrasive according to the present invention preferably has a composition containing the cerium oxide particles, a dispersant and water. For example, it can be obtained by dispersing a composition containing cerium oxide particles and a dispersant prepared by the above method in water.
Although there is no restriction | limiting in the density | concentration of a cerium oxide particle, From the ease of handling of a dispersion | distribution liquid abrasive | polishing agent, the range of 0.1 to 20 weight% is preferable.

  As the dispersant, since it is preferably used for polishing semiconductor elements, it is preferable to suppress the content of alkali metals such as sodium ions and potassium ions and halogens to 10 ppm or less. For example, polymer dispersants such as ammonium polyacrylate Is preferred.

  The added amount of the dispersant is 0.01 parts by weight or more and 5.0 parts by weight with respect to 100 parts by weight of the cerium oxide particles due to the dispersibility of the particles in the abrasive and the prevention of settling, and the relationship between the scratch and the added amount of the dispersant. A range of parts or less is preferred.

The weight average molecular weight of the dispersant is preferably from 100 to 50,000, and more preferably from 1,000 to 10,000. When the molecular weight of the dispersant is less than 100, it is difficult to obtain a sufficient polishing rate when polishing the SiO ₂ film or the silicon nitride film, and when the molecular weight of the dispersant exceeds 50,000, the viscosity is high. This is because the storage stability of the abrasive tends to decrease.
In the present invention, the weight average molecular weight is a value measured by gel permeation chromatography and converted to standard polystyrene.

  As a method for dispersing these cerium oxide particles in water, a homogenizer, an ultrasonic disperser, a wet ball mill or the like can be used in addition to a dispersion treatment using a normal stirrer.

In the cerium oxide particles dispersed in the abrasive according to the present invention, the half width of the main peak of the powder X-ray diffraction pattern is 0.28 to 0.32 °. When the full width at half maximum exceeds 0.32 °, the SiO ₂ film or the silicon nitride film cannot be polished at high speed. When the full width at half maximum is less than 0.28 °, scratches are generated on the surface of the film to be polished. This is because it tends to occur.

  The content of coarse particles having a particle diameter of 3 μm or more in the entire solid in the abrasive according to the present invention is preferably small. In the present invention, the coarse particles of 3 μm or more mean particles captured by filtering with a filter having a pore diameter of 3 μm.

  In the present invention, the content of particles having a particle diameter of 3 μm or more in the entire solid in the abrasive is preferably 500 ppm or less by weight, and the scratch reducing effect is clear. When the content of particles of 3 μm or more in the entire solid is 200 ppm or less, the effect of reducing scratches is large, which is more preferable. When the content of particles of 3 μm or more occupying the whole solid is 100 ppm or less, the effect of reducing scratches is the largest and more preferable.

  The coarse particle content of 3 μm or more can be obtained by gravimetric measurement of particles captured by filtering with a filter having a pore diameter of 3 μm. The content of the entire solid in the abrasive is measured by drying the abrasive separately. For example, 10 g of an abrasive is dried at 150 ° C. for 1 hour, and the remainder is weighed to obtain a solid concentration.

And the content of the whole solid is obtained by multiplying the mass of the abrasive used for filtration with a filter having a pore diameter of 3 μm by the solid concentration.
As means for reducing the coarse particle content, filtration and classification are possible, but not limited thereto.

  Since the secondary particle diameter of the cerium oxide particles in the abrasive according to the present invention has a distribution, the median value of the cerium oxide secondary particle diameter is preferably 100 to 2000 nm (0.1 to 2.0 μm). 0.1 to 0.5 μm is more preferable, and 0.1 to 0.3 μm is particularly preferable. This is because if the median value of the secondary particle diameter is less than 0.1 μm, the polishing rate tends to be low, and if it exceeds 2.0 μm, scratches are likely to occur on the surface of the film to be polished.

  It is preferable that 99% by volume (hereinafter referred to as D99) of the cerium oxide particles has a particle diameter of 1 μm or less. When D99 exceeds 1 μm, the generation of scratches increases. When D99 is 0.7 μm or less, scratches can be reduced, which is more preferable.

  The median secondary particle diameter of the cerium oxide particles in the abrasive and the D99 can be measured by a light scattering method, for example, a particle size distribution meter (for example, Mastersizer Micro Plus manufactured by Malvern Instruments Inc.). it can.

In addition, a polymer additive that further improves the flatness and dispersibility can be added to the abrasive. Although not limited to the following additives, for example, polymers such as acrylic acid ester derivatives, acrylic acid, and acrylates can be added.
The addition amount of the polymer additive is not particularly limited, but is preferably 5 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the cerium oxide particles.

The weight average molecular weight of the polymer additive is preferably 100 to 50,000, more preferably 1,000 to 10,000. When the molecular weight is less than 100, it is difficult to obtain a sufficient polishing rate when polishing the SiO ₂ film or the silicon nitride film. When the molecular weight exceeds 50,000, the viscosity becomes high and the abrasive is stored. This is because the stability tends to decrease.

  The pH of the abrasive is preferably 3 or more and 9 or less, and more preferably 5 or more and 8 or less. If the pH is less than 3, the chemical action force tends to be small, and the polishing rate tends to decrease. If the pH is higher than 9, the chemical action is too strong and the surface to be polished may be dished (dishing).

  The pH is a value measured with a pH meter (for example, Model pH81 manufactured by Yokogawa Electric Corporation). After calibrating two points using a standard buffer solution (phthalate pH buffer solution pH: 4.21 (25 ° C.), neutral phosphate pH buffer solution pH 6.86 (25 ° C.)), the electrode was polished. The value can be measured after 2 minutes or more have elapsed and stabilized.

  The abrasive according to the present invention can be prepared, for example, as a one-part abrasive composed of cerium oxide particles, a dispersant, a polymer additive, and water, and also consists of cerium oxide particles, a dispersant, and water. It can also be prepared as a two-component abrasive that separates a cerium oxide slurry and an additive solution composed of a polymer additive and water. In either case, stable characteristics can be obtained.

  When storing as a two-component abrasive in which the cerium oxide slurry and the additive solution are separated, the blending of these two components can be arbitrarily changed to adjust the planarization characteristics and polishing rate. In the case of the two-component system, the additive solution and the cerium oxide slurry are sent at different flow rates through separate pipes, and these pipes are merged, that is, both are mixed just before the supply pipe outlet, and the polishing surface plate Either a method of supplying the sample at the top (immediate mixing method) or a method of supplying the two after mixing them in a container in advance (pre-mixing method) is used.

  The polishing agent according to the present invention presses and presses the substrate against the polishing pad while supplying a polishing liquid between the polishing film formed on the substrate and the polishing pad. It can be used for polishing to move the film relatively and polish the film to be polished flat.

As the substrate, for example, an inorganic insulating layer is formed on a substrate related to a semiconductor device formation process, specifically, a semiconductor substrate at a stage where a circuit element and a wiring pattern are formed, a semiconductor substrate at a stage where a circuit element is formed, or the like. Examples include a formed substrate. Examples of the film to be polished include an inorganic insulating layer such as a SiO ₂ film layer or a silicon nitride film layer.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.
Example 1
6 kg of commercially available cerium carbonate was put in an alumina container, held at 850 ° C. for 2 hours in an air atmosphere, and then heated at 500 ° C. for 2 hours to obtain 3 kg of yellowish white powder.

When this powder was phase-identified by X-ray diffraction, it was confirmed to be cerium oxide. The fired powder particle size was 30 to 100 μm.
Further, 3 kg of the obtained cerium oxide powder was dry-ground using a jet mill to obtain cerium oxide particles.

  1000 g of the produced cerium oxide particles, 80 g of an aqueous polyacrylic acid ammonium salt solution (40% by weight) and 3920 g of deionized water were mixed and subjected to ultrasonic dispersion for 10 minutes while stirring.

  The obtained dispersion was allowed to settle at room temperature (25 ° C.) for 100 hours, and the supernatant was collected. This supernatant is filtered through a 0.7 μm filter, then filtered through a 0.7 μm filter again, and deionized water is added to adjust the solids concentration to 5% by weight. Produced.

  As a result of measuring the powder X-ray diffraction pattern after drying the obtained polishing agent for semiconductor flattening, the full width at half maximum of its main peak was 0.284 °. X-ray diffraction was measured using RAD-2C manufactured by Rigaku Electric Co., Ltd.

  Using a laser diffraction particle size distribution meter (manufactured by Malvern Instruments, Mastersizer Micro Plus), the particle size of the obtained semiconductor flattening abrasive was measured using a refractive index of 1.9285, a light source: a He—Ne laser, and an absorption. As a result of measuring the polishing slurry stock solution for semiconductor flattening under the condition of 0, the median value of the secondary particle diameter was 160 nm and D99 was 0.5 μm.

  In order to examine the content of coarse particles, the obtained semiconductor flattening polishing slurry was diluted 15-fold, and 30 g was filtered through a 3 μm filter (a cyclopore track etch membrane filter manufactured by Whatman).

After filtration, the filter was dried at room temperature, the weight of the filter was measured, and the amount of coarse particles of 3 μm or more was determined from the weight increase before and after filtration.
Separately, 10 g of this abrasive was dried at 150 ° C. for 1 hour, and the solid concentration in the abrasive was calculated. As a result, the amount of coarse particles (weight ratio) of 3 μm or more was 50 ppm in the solid.

  Moreover, the polishing agent for semiconductor flattening obtained above was diluted 5 times with deionized water, and was polished by the following method. When the polishing speed was 350 nm / min and the wafer surface was observed with an optical microscope, 20 scratches were observed on the entire surface of the 200 mm wafer.

(Polishing test method)
・ Polishing load: 30 kPa
Polishing pad: Rodel foam polyurethane resin (IC-1000)
・ Rotation speed: surface plate 75 min ⁻¹ , pad 75 min ⁻¹
・ Abrasive supply rate: 200 mL / min
・ Polishing object: Si wafer with P-TEOS film (200mm)

(Example 2)
6 kg of commercially available cerium carbonate was put in an alumina container, held at 750 ° C. for 2 hours in an air atmosphere, and then heated at 500 ° C. for 2 hours to obtain 3 kg of yellowish white powder.
When this powder was phase-identified by X-ray diffraction, it was confirmed to be cerium oxide. The fired powder particle size was 30 to 100 μm.

Further, 3 kg of the obtained cerium oxide powder was dry-ground using a jet mill to obtain cerium oxide particles.
Using this cerium oxide, a semiconductor planarizing abrasive was produced in the same manner as in Example 1.

  After drying the obtained semiconductor planarizing abrasive, the powder X-ray diffraction pattern was measured in the same manner as in Example 1. As a result, the half width of the main peak was 0.317 °.

Moreover, as a result of measuring the particle diameter of the above-mentioned polishing agent for semiconductor flattening in the same manner as in Example 1, the median value of the secondary particle diameter was 160 nm and D99 was 0.5 μm.
In order to examine the content of coarse particles, the amount of coarse particles of 3 μm or more was determined from the weight increase before and after filtration of the obtained polishing slurry for semiconductor planarization in the same manner as in Example 1. As a result, the amount of coarse particles of 3 μm or more was 50 ppm in the solid.

  Further, the above-mentioned polishing agent for planarizing the semiconductor was diluted 5 times with deionized water, and was polished by the same polishing test method as in Example 1. When the polishing speed was 320 nm / min and the wafer surface was observed with an optical microscope, ten scratches were observed on the entire surface of the 200 mm wafer.

(Comparative Example 1)
6 kg of commercially available cerium carbonate was put in an alumina container, held at 950 ° C. for 1 hour in an air atmosphere, and then heated at 500 ° C. for 2 hours to obtain 3 kg of yellowish white powder.
When this powder was phase-identified by X-ray diffraction, it was confirmed to be cerium oxide. The fired powder particle size was 30 to 100 μm.

Further, 3 kg of the obtained cerium oxide powder was dry-ground using a jet mill to obtain cerium oxide particles.
Using this cerium oxide, a semiconductor planarizing abrasive was produced in the same manner as in Example 1.

  After drying the obtained semiconductor planarization abrasive, the powder X-ray diffraction pattern was measured in the same manner as in Example 1. As a result, the half width of the main peak was 0.242 °.

Moreover, as a result of measuring the particle diameter of the above-mentioned polishing agent for semiconductor flattening in the same manner as in Example 1, the median value of the secondary particle diameter was 160 nm and D99 was 0.5 μm.
In order to examine the content of coarse particles, the amount of coarse particles of 3 μm or more was determined from the weight increase before and after filtration of the obtained polishing slurry for semiconductor planarization in the same manner as in Example 1. As a result, the amount of coarse particles of 3 μm or more was 50 ppm in the solid.

  Further, the above-mentioned polishing agent for planarizing the semiconductor was diluted 5 times with deionized water, and was polished by the same polishing test method as in Example 1. When the polishing speed was 380 nm / min and the wafer surface was observed with an optical microscope, 70 scratches were observed on the entire surface of the 200 mm wafer.

(Comparative Example 2)
6 kg of commercially available cerium carbonate was put in an alumina container, held at 550 ° C. for 4 hours in an air atmosphere, and then heated at 500 ° C. for 2 hours to obtain 3 kg of yellowish white powder.
When this powder was phase-identified by X-ray diffraction, it was confirmed to be cerium oxide. The fired powder particle size was 30 to 100 μm.

Further, 3 kg of the obtained cerium oxide powder was dry-ground using a jet mill to obtain cerium oxide particles.
Using this cerium oxide, a semiconductor planarizing abrasive was produced in the same manner as in Example 1.

  After drying the obtained semiconductor planarization abrasive, the powder X-ray diffraction pattern was measured in the same manner as in Example 1. As a result, the half width of the main peak was 0.363 °.

Moreover, as a result of measuring the particle diameter of the above-mentioned polishing agent for semiconductor flattening in the same manner as in Example 1, the median value of the secondary particle diameter was 160 nm and D99 was 0.5 μm.
In order to examine the content of coarse particles, the amount of coarse particles of 3 μm or more was determined from the weight increase before and after filtration of the obtained polishing slurry for semiconductor planarization in the same manner as in Example 1. As a result, the amount of coarse particles of 3 μm or more was 50 ppm in the solid.

  Further, the above-mentioned polishing agent for planarizing the semiconductor was diluted 5 times with deionized water, and was polished by the same polishing test method as in Example 1. When the polishing speed was 250 nm / min and the wafer surface was observed with an optical microscope, 45 scratches were observed on the entire surface of the 200 mm wafer.

(Comparative Example 3)
1000 g of cerium oxide particles produced by the same method as in Comparative Example 1, 80 g of an aqueous solution of ammonium polyacrylate (40% by weight) and 3920 g of deionized water were mixed and subjected to ultrasonic dispersion for 10 minutes while stirring.

  The obtained dispersion was allowed to settle at room temperature for 4 hours, and the supernatant was collected. The supernatant was filtered with a filter having a pore size of 10 μm, and then deionized water was added to adjust the solid content concentration to 5% by weight to prepare a semiconductor planarization abrasive.

After drying the obtained semiconductor planarization abrasive, the powder X-ray diffraction pattern was measured in the same manner as in Example 1. As a result, the half width of the main peak was 0.238 °.
Moreover, as a result of measuring the particle diameter of the polishing agent for semiconductor flattening in the same manner as in Example 1, the median value of the secondary particle diameter was 240 nm, and D99 was 2.5 μm.

  In order to examine the content of coarse particles, the amount of coarse particles of 3 μm or more was determined from the weight increase before and after filtration of the obtained polishing slurry for semiconductor planarization in the same manner as in Example 1. As a result, the amount of coarse particles of 3 μm or more was 1200 ppm in the solid.

  Further, the above-mentioned polishing agent for planarizing the semiconductor was diluted 5 times with deionized water, and was polished by the same polishing test method as in Example 1. When the polishing speed was 650 nm / min and the wafer surface was observed with an optical microscope, 100 scratches were observed on the entire surface of the 200 mm wafer.

Claims (4)

  A polishing agent for planarizing a semiconductor, comprising cerium oxide particles and a water having a half-value width of 0.28 to 0.32 ° of a main peak of a powder X-ray diffraction pattern, and having a median cerium oxide particle diameter of 100 to 2000 nm .   The polishing slurry for semiconductor planarization according to claim 1, wherein the content of cerium oxide particles having a particle diameter of 3 µm or more is 500 ppm or less in the solid by weight.   A polishing agent for semiconductor flattening, further comprising a dispersing agent in the polishing agent for flattening semiconductor according to claim 1 or 2.   The polishing slurry for semiconductor planarization according to any one of claims 1 to 3, wherein 99% by volume of the entire cerium oxide particles has a particle diameter of 1 µm or less.