JP2003209076A - Cmp abrasive and abrading method for substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an abrasive and an abrading method for a substrate in which a surface to be abraded such as an SiO<SB>2</SB>insulating film can be abraded at a high speed without causing flaws. <P>SOLUTION: The CMP abrasive contains an oxide film weakening agent, oxide cerium grains and water. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CMP polishing agent used in a step of flattening a substrate surface, which is a semiconductor manufacturing technique, and particularly a step of forming a shallow trench isolation, and a substrate polishing using the CMP polishing agent. Regarding the method.

[0002]

2. Description of the Related Art In the present ultra-large-scale integrated circuits, various microfabrication techniques have been researched and developed because the packaging density tends to be increased. The design rule is already on the order of sub-harf micron. CM is one of the technologies that have been developed to satisfy such strict requirements for miniaturization.
There is P (Chemical Mechanical Polishing) technology. This technique can completely flatten the layer to be exposed in the manufacturing process of the semiconductor device, reduce the burden of the exposure technique, and stabilize the yield. Therefore, for example, an interlayer insulating film or BP.
This is an indispensable technique for flattening the SG film, shallow trench isolation, and the like.

In the process of manufacturing a semiconductor device, plasma-CVD (Chemical Vapor Deposi) is used.
(chemical vapor deposition method), low pressure-CVD, etc., the application of a cerium oxide-based polishing agent has been studied as a CMP polishing agent for planarizing an inorganic insulating film layer such as a silicon oxide insulating film. There is. Cerium oxide particles have a lower hardness than silica particles and alumina particles, and therefore scratches are less likely to occur on the polishing surface, and are therefore useful for finish mirror polishing.
Further, cerium oxide has a chemically active property as known as a strong oxidant. Taking advantage of this advantage, it is useful to be applied to a chemical mechanical polishing agent for insulating films, which enables high-speed polishing. However, although the cerium oxide-based abrasives currently used can perform high-speed polishing, many polishing scratches are formed on the surface of the insulating film.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a polishing agent and a substrate polishing method capable of polishing a surface to be polished such as a SiO ₂ insulating film at high speed without scratches.

[0005]

The present invention relates to the following. (1) CMP abrasive containing oxide film weakening agent, cerium oxide particles and water (2) (1) CMP abrasive whose oxide film weakening agent is a strong alkali (3) (1) oxide film weakening (4) CMP abrasive for semiconductor insulating film containing oxide film weakening agent, cerium oxide particles and water by pressing the substrate on which the polishing film is formed against the polishing cloth of the polishing platen A method of polishing a substrate in which the substrate and the polishing platen are relatively moved while being supplied between the polishing film and the polishing cloth to weaken the polishing film. When the interlayer insulating film is flattened and shallow trench isolation is performed using the above-mentioned semiconductor CMP polishing agent, the oxide film weakening agent chemically acts on the surface to be polished and weakens during CMP polishing, It is possible to reduce polishing scratches by performing CMP polishing having a larger chemical action.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION As a method for preparing cerium oxide particles in the present invention, it is obtained by calcining a cerium compound of carbonate, nitrate, sulfate or oxalate. The firing temperature is preferably 400 ° C. or higher and 900 ° C. or lower,
To reduce the particle size of cerium oxide, 700 ℃ or higher 9
More preferably, it is not higher than 00 ° C. Since the cerium oxide particles obtained by oxidation are usually agglomerated, it is preferable to mechanically grind them. As the pulverization method, dry pulverization such as jet mill and ball mill, or wet pulverization such as bead mill and ball mill can be employed. The jet mill is described, for example, in Chemical Industry Papers Vol. 6, No. 5 (1980), pages 527-532. The cerium oxide slurry in the present invention is obtained by dispersing an aqueous solution containing cerium oxide produced by the above method, or cerium oxide particles recovered from this aqueous solution, and water. If necessary, the cerium oxide particles can be classified by a filter or the like. Here, although the concentration of the cerium oxide particles is not limited,
From the viewpoint of easy handling of the suspension (polishing agent), a range of 0.5 to 20% by weight is preferable, a range of 1% by weight to 10% by weight is more preferable, and a range of 1.5% to 5% by weight. Is particularly preferable. As a method for dispersing the cerium oxide particles in water, a homogenizer, an ultrasonic disperser, a ball mill, or the like can be used in addition to the usual dispersion treatment using a stirrer. In order to disperse cerium oxide particles of sub-μm order,
It is preferable to use a wet disperser such as a ball mill, a vibrating ball mill, a planetary ball mill, or a medium stirring type mill.

The average particle size of the cerium oxide particles in the CMP abrasive is preferably 0.01 to 1.0 μm.
If the average particle size of cerium oxide is less than 0.01 μm, the polishing rate tends to be too low, and if it exceeds 1.0 μm, the film to be polished tends to be scratched.

The CMP abrasive of the present invention can be obtained by dispersing a composition containing an oxide film weakening agent, cerium oxide particles, and water.

Examples of the oxide film weakening agent include strong alkalis such as sodium hydroxide, potassium hydroxide, calcium hydroxide, tetramethylammonium hydroxide, barium hydroxide and lithium hydroxide. These may be used alone or in combination of two or more.

When it contains a strong alkali, the pH of the abrasive is 9
-14 are preferable and 11-12 are more preferable. pH 9
If it is less than 14, the polishing rate is remarkably reduced, and if it is more than 14, the surface roughness of the oxide film is remarkably exhibited.

Further, examples of the oxide film weakening agent include fluorine-containing acid. As the fluorinated acid, one selected from the following is suitable. Trifluoroacetic acid, trifluoropropionic acid, F-butyric acid, F-hexanoic acid, F-octanoic acid, F-decanoic acid, F-dodecanoic acid, trifluoroacrylic acid, pentafluorobenzoic acid, pentafluorophenol, tri Sodium fluoroacetate, potassium trifluoroacetate, ammonium trifluoroacetate, sodium trifluoropropionate, potassium trifluoropropionate, ammonium trifluoropropionate,
F-sodium butyrate, potassium F-butyrate, ammonium F-butyrate, sodium F-hexanoate, potassium F-hexanoate, ammonium F-hexanoate, sodium F-octanoate, potassium F-octanoate, ammonium F-octanoate , F-sodium decanoate, potassium F-decanoate, ammonium F-decanoate, sodium F-dodecanoate, potassium F-dodecanoate, ammonium F-dodecanoate, sodium trifluoroacrylate,
Potassium trifluoroacrylate, potassium trifluoroacrylate, ammonium trifluoroacrylate,
Organic fluorine compounds such as sodium pentafluorobenzoate, potassium pentafluorobenzoate, ammonium pentafluorobenzoate, sodium pentafluorophenol, potassium pentafluorophenol, and ammonium pentafluorophenol, and ammonium salts thereof, fluorine salts, and the like. Hydrofluoric acid, fluorophosphoric acid, hexafluorosilicic acid, tetrafluoroboric acid, hexafluorotitanic acid, sodium fluoride, potassium fluoride, ammonium fluoride, ammonium hydrogen difluoride, potassium hydrogen difluoride, sodium fluorophosphate, potassium fluorophosphate, Ammonium fluorophosphate, sodium hexafluorosilicate, potassium hexafluorosilicate, ammonium hexafluorosilicate, sodium tetrafluoroborate,
Inorganic fluorine compounds such as potassium tetrafluoroborate, ammonium tetrafluoroborate, sodium hexafluorotitanate, potassium hexafluorotitanate and ammonium hexafluorotitanate, and ammonium salts thereof can be mentioned.

When it contains a fluorine-containing acid, the pH of the abrasive is 1
-5 are preferable, 1.5-4 are more preferable, 2-3 are still more preferable. When the pH is less than 1, the surface roughness of the oxide film is remarkably exhibited, and when the pH is more than 5, the polishing rate is remarkably reduced.

The compounding amount of the oxide film brittleness agent is preferably 0 to 0.05 mol, and 0.00005 mol to 0.005 mo with respect to 100 g of the total weight of the CMP abrasive.
More preferably, it is 1. This blend amount is 0.025
When it exceeds mol, it becomes difficult to adjust the pH of the above-mentioned CMP abrasive within a preferable range.

As a method for producing an inorganic insulating film which can be polished by the CMP polishing agent of the present invention, a low pressure CVD method and a plasma C method are used.
VD method etc. are mentioned. For forming a silicon oxide film by the low pressure CVD method, monosilane: SiH _{4 is} used as a Si source and oxygen: O ₂ is used as an oxygen source. It is obtained by carrying out this SiH ₄ —O ₂ system oxidation reaction at a low temperature of 400 ° C. or lower.
In some cases, heat treatment is performed at a temperature of 1000 ° C. or lower after CVD. When phosphorus: P is doped to achieve surface flattening by high temperature reflow, SiH ₄ -O
It is preferable to use a _2- PH ₃ -based reaction gas. The plasma CVD method has an advantage that a chemical reaction that requires a high temperature under normal thermal equilibrium can be performed at a low temperature. There are two plasma generation methods, a capacitive coupling type and an inductive coupling type. SiH ₄ as a Si source and N as an oxygen source are used as a reaction gas.
SiH ₄ -N ₂ O based gas using ₂ O and TEOS-O ₂ based gas using tetraethoxysilane (TEOS) as Si source
(TEOS-plasma CVD method). The substrate temperature is preferably 250 ° C. to 400 ° C., and the reaction pressure is preferably 67 to 400 Pa. Thus, the silicon oxide film of the present invention may be doped with elements such as phosphorus and boron. Similarly, for forming a silicon nitride film by the low pressure CVD method, dichlorosilane: SiH ₂ Cl ₂ is used as a Si source, and ammonia: NH ₃ is used as a nitrogen source. The _SiH 2 _Cl 2 -NH ₃
It is obtained by carrying out the system oxidation reaction at a high temperature of 900 ° C. In the plasma CVD method, SiH ₄ using SiH ₄ as a Si source and NH ₃ as a nitrogen source as a reaction gas is used.
-NH ₃ based gas. Substrate temperature is 300 ℃ -4
00 ° C is preferred.

CMP of the present invention for shallow trench isolation
When using an abrasive, it is preferable that the ratio of the polishing rate of the silicon oxide film to the polishing rate of silicon nitride and the polishing rate of silicon oxide / polishing rate of silicon nitride are 10 or more from the viewpoint of easy control of polishing stop. When this ratio is less than 10, the difference between the polishing rate of silicon oxide and the polishing rate of silicon nitride is small, and it tends to be difficult to stop polishing at a predetermined position when performing shallow-trench separation.

The polishing device holds a semiconductor substrate.
A holder and a polishing cloth (pad) were attached (rotation speed changed
(Available motors, etc.)
Any polishing device can be used. As a polishing cloth,
Woven cloth, polyurethane foam, porous fluororesin, etc. are used
Yes, there are no particular restrictions. Also, the polishing cloth is CMP abrasive
It is preferable to perform a groove processing that accumulates. Polishing condition
Although there is no limit to the
Do not do 200 min^-1Following low rotation is preferred
The pressure applied to the semiconductor substrate does not cause scratches after polishing.
Like 9.8 × 10 ^FourPa or less is preferable. Polishing
While polishing, the slurry is continuously supplied to the polishing cloth with a pump, etc.
It There is no limit to the amount of this supply, but the surface of the polishing cloth is always smooth.
It is preferably covered with a slurry. Half after polishing
After cleaning the conductor board thoroughly in running water, use a spin dryer, etc.
After removing the water droplets that have adhered to the semiconductor substrate using
It is preferably dried.

The CMP polishing compound of the present invention is applicable not only to a silicon oxide film formed on a substrate such as a semiconductor substrate, but also to a silicon oxide film formed on a substrate such as a wiring board having predetermined wiring, glass, or silicon nitride. Inorganic insulation film such as polysilicon, Al, C
Film mainly containing u, Ti, TiN, W, Ta, TaN, etc., optical glass such as photomask, lens, prism, etc., inorganic conductive film such as ITO, optical integrated circuit / light composed of glass and crystalline material Switching element / optical waveguide,
Optical fiber end face, optical single crystal such as scintillator,
It is possible to polish a solid laser single crystal, a blue laser LED sapphire substrate, a semiconductor single crystal such as SiC, GaP, or GaAs, a magnetic disk glass substrate, and a magnetic head.

[0018]

EXAMPLES The present invention will be described below with reference to examples. Example 1 (Preparation of cerium oxide particles) 4 kg of cerium carbonate hydrate
Was put in a platinum container and baked in air at 800 ° C. for 2 hours to obtain about 2 kg of yellowish white powder. X of this powder
When the phase was identified by the line diffraction method, it was confirmed to be cerium oxide. The particle size of the calcined powder was 30 to 100 μm. When the surface of the calcined powder particles was observed with a scanning electron microscope, grain boundaries of cerium oxide were observed. When the cerium oxide primary particle diameter surrounded by the grain boundaries was measured, the median volume distribution was 190 nm and the maximum value was 500 nm. 2 kg of cerium oxide powder was dry ground using a jet mill. Observation of the crushed particles with a scanning electron microscope revealed that, in addition to small particles having a size equivalent to the primary particle size, large crushed residual particles of 1 to 3 μm and 0.5 to 1
The uncrushed particles of μm were mixed. (Production of Cerium Oxide Slurry) 1 kg of the cerium oxide particles produced above and 1 kg of deionized water were mixed and ultrasonically dispersed for 10 minutes while stirring. 1 of the obtained slurry
A 5% by weight slurry was obtained by filtering with a micron filter and further adding deionized water. In order to measure the slurry particles with a laser diffraction type particle size distribution meter, the slurry particles were diluted to an appropriate concentration and the result was measured, and the median particle diameter was 190 nm.
Met. 600 g of the above-mentioned cerium oxide slurry (solid content: 5% by weight), 600 g of 2.5% by weight hydrofluoric acid as an oxide film weakening agent, and 1800 g of deionized water were mixed to obtain a cerium oxide polishing agent (solid content: 1% by weight) was prepared.

(Polishing of Interlayer Insulating Film) A silicon oxide film (thickness: 1000 n
m) was polished with a polishing load of 30 kPa, a platen and a carrier rotation speed of 50 rpm, an abrasive supply rate of 200 ml / min, and a polishing time of 1 minute. The polished silicon oxide film was measured in an in-plane X-Y direction with an interference film thickness meter (Lambda Å: manufactured by Dainippon Screen).
When measured at 0 points, the residual film thickness was 450 nm (polishing rate 550 nm / min), and the in-plane film thickness uniformity was 3%. In addition, the polished silicon oxide film is subjected to a defect inspection device (S
When the number of defects was measured with FS-6220: manufactured by KLA-Tencor, the number of defects of 0.2 μm or more was 30 / wafer. After that, a wafer appearance microscope (AL200
0: made by Olympus Co., Ltd.), the defects were observed, and there were no polishing scratches and all were foreign substances.

Comparative Example 1 (Preparation of Cerium Oxide Slurry) A cerium oxide abrasive was prepared in the same manner as in Example 1 except that 600 g of 2.5 wt% hydrofluoric acid was replaced with 600 g of deionized water. (Solid content: 1% by weight) was prepared.

(Polishing of Interlayer Insulating Film) Polishing was performed in the same manner as in Example 1 using the produced polishing agent. The silicon oxide film after polishing was measured at 10 points in the in-plane X-Y direction with an interference film thickness meter (Lambda Å: manufactured by Dainippon Screen), and the residual film thickness was 46.
It was 0 nm (polishing rate 540 nm / min), and the in-plane uniformity was 3.3%. In addition, the polished silicon oxide film is subjected to a defect inspection device (SFS-6220: KLA-Tenco).
When the number of defects was measured by R), the number of defects of 0.2 μm or more was 50 / wafer. After that, when the defect portion was observed with a wafer appearance microscope (AL2000: made by Olympus), it was confirmed that 20 pieces were foreign matters and 30 pieces were polishing scratches.

Comparative Example 2 (Preparation of Cerium Oxide Slurry) Cerium Oxide Slurry
(Solid content: 5 wt%) 600 g, 2.5 wt% hydrofluoric acid as an oxide film weakening agent 600 g, and deionized water 180
A cerium oxide abrasive (solid content: 1% by weight) was used in the same manner as in Example 1 except that 30 g of polyvinylpyrrolidone (weight average molecular weight: 15,000) was further added when 0 g was mixed. It was made.

(Polishing of Interlayer Insulating Film) Polishing was performed in the same manner as in Example 1 using the produced polishing agent. The silicon oxide film after polishing was measured with an interference film thickness meter (Lambda Å: manufactured by Dainippon Screen) at 10 points in the in-plane X-Y direction, and the residual film thickness was 68.
It was 0 nm (polishing rate 320 nm / min), and the in-plane uniformity was 3%. In addition, the polished silicon oxide film has a defect inspection apparatus (SFS-6220: manufactured by KLA-Tencor).
When the number of defects was measured with, the number of defects of 0.2 μm or more was 34 / wafer. After that, the wafer appearance microscope (A
L2000: manufactured by Olympus Co., Ltd.), and the defective portion was observed.

[0024]

According to the present invention, it is possible to provide a CMP abrasive containing an oxide film weakening agent, cerium oxide particles and water. Further, by using this CMP polishing agent and polishing the surface of the film to be polished during CMP while weakening the surface, a method of polishing a substrate capable of high-speed polishing and high planarization without causing polishing scratches Can be applied.

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) C09K 3/14 C09K 3/14 550Z

Claims (4)

[Claims] 1. A CMP abrasive containing an oxide film weakening agent, cerium oxide particles and water. 2. The CMP abrasive according to claim 1, wherein the oxide film weakening agent is a strong alkali. 3. The CMP abrasive according to claim 1, wherein the oxide film weakening agent is a fluorinated acid. 4. A substrate on which a film to be polished is formed is pressed against a polishing cloth of a polishing platen, and a CMP polishing agent containing an oxide film weakening agent, cerium oxide and water is supplied between the polishing film and the polishing cloth. While polishing the substrate while moving the substrate and the polishing platen relatively while weakening the polishing film.