JP2003059870A - Cmp pad and wafer-polishing method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a CMP pad by which a polished surface can be planarized efficiently and the uniformity of a wafer surface can be improved in CMP technology, by which an insulation film made of silicon oxide, etc., such as an interlayer insulating film, a BPSG film, a shallow trench isolating insulation film, a capacitor ferrodielectric film, a wiring metal layer, a metal alloy layer, etc., can be planarized and an embedded layer can be formed. SOLUTION: This CMP pad is used for chemically-mechanically polishing a polished film formed on a board and has a support layer and a thin film layer, whose hardness varies in the layer direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing method used in a semiconductor device manufacturing technique, and more particularly to a polishing process of a substrate surface, particularly a shallow trench device isolation process, a process of forming a buried layer in a groove such as a capacitor or metal wiring , A method of polishing a substrate used in a step of flattening an interlayer insulating film and the like.

[0002]

2. Description of the Related Art In the current ultra-large scale integrated circuits, there is a tendency to increase the packaging density, and various fine processing techniques have been researched and developed. Already, the design rules are on the order of sub-half micron. CMP (Chemical Mechanical Polishing) technology is one of the technologies that have been developed to satisfy such strict requirements for miniaturization. This technology completely flattens the layer to be exposed in the semiconductor device manufacturing process, reducing the burden of exposure technology,
This is a technology that can stabilize the yield. The CMP technique in the manufacturing process of a semiconductor device includes a recess CMP technique for removing an excessive film formation portion of a film formation layer embedded in a groove in element isolation formation, memory capacitor formation, plug and embedded metal wiring formation, and the like. There is also a flattening CMP technique after forming an interlayer insulating film. LOCOS (Silicon Local Oxidation) has been used in the generation of design rule 0.5 μm or more in the element isolation formation technology in integrated circuits. Trench isolation technology is being adopted. In shallow trench isolation, CMP is an indispensable technique for removing the excess silicon oxide film embedded on the substrate. Also in the metal wiring forming technology, W and the like were used for the Al wiring and the plug on the interlayer insulating film in the generation with the design rule of 0.25 μm or more. Cu or Cu to fill
Al alloys are being adopted. In the Cu or CuAl alloy wiring technology, embedded wiring technology such as damascene or dial damascene has been studied, and CMP is an essential technology for removing an extra metal film embedded on a substrate. In order to realize a trench structure or a complicated stack type structure also in forming a capacitor of a memory device, a recess CM of silicon oxynitride, a tantalum oxide film or other ferroelectric substance is used.
P technology becomes an essential technology.

Conventionally, in a manufacturing process of a semiconductor device, an insulating film such as silicon oxide formed by a method such as plasma-CVD, low-pressure-CVD, sputtering, electrolytic plating, a ferroelectric film of a capacitor, a wiring metal or a metal alloy, etc. As a polishing method for flattening and forming a buried layer, a substrate on which a film to be polished is formed is pressed against a CMP pad, and an abrasive is supplied between the polishing film and the CMP pad while the substrate or I am moving the CMP pad. At this time, C
A urethane foam type is generally used as the MP pad.

[0004]

When polishing with the above-mentioned urethane foam type polishing cloth, it is necessary to periodically perform a pretreatment called dressing. This is an operation for keeping the surface condition of the pad constant by shaving the surface of the pad with a diamond grindstone or the like. However, the unevenness formed on the pad surface by this dressing treatment is uneven in shape and size, resulting in instability of polishing characteristics. The present invention is for forming an insulating film such as an interlayer insulating film, a BPSG film, an insulating film for shallow trench isolation, etc., a capacitor ferroelectric film, and a planarizing and burying layer for a wiring metal or a metal alloy. In the CMP technique, it is possible to efficiently flatten the surface to be polished and improve the uniformity within the wafer surface.
An MP pad and a polishing method are provided.

[0005]

SUMMARY OF THE INVENTION The present invention provides a pad for chemically and mechanically polishing a polishing film formed on a substrate, comprising a support layer and a thin film layer whose hardness changes in the layer direction. The present invention provides a pad for CMP. Further, according to the present invention, a predetermined substrate is pressed against a CMP pad comprising a support layer and a thin film layer whose hardness changes in the layer direction, and an abrasive is supplied between the polishing film and the CMP pad. Provided is a method for polishing a substrate, characterized in that the surface to be polished of a substrate, which is a semiconductor chip, and a polishing pad are moved relative to each other while being in contact with each other, and the surface of the substrate is polished while dispersing a load bias applied to the polishing surface. It is a thing.

Generally, as a method of changing the hardness in the layer direction of the thin film layer for the purpose of efficiently flattening the surface to be polished and improving the uniformity within the wafer surface,
For example, a method of using a photocurable resin for the thin film layer can be mentioned. By adjusting the irradiation amount of ultraviolet rays or electron beams and changing the light transmission amount in the layer direction, for example, it is possible to form a thin film layer in which the surface is hard and the depth becomes deeper from the surface. From this, it is presumed that the function of the pad is similar to that of the multi-layer pad even though the pad has only one functional portion.

[0007]

DETAILED DESCRIPTION OF THE INVENTION A CMP pad comprises a support layer and a thin film layer having a hardness varying in the layer direction. Also,
Minute protrusions can be formed on the surface of the thin film layer. CM
As a method of manufacturing the P pad, a method of transferring from a mold while photocuring using a photocurable resin can be mentioned. An example of a manufacturing method using this method will be shown below. First, a photocurable resin thin film layer is formed on the support layer. This thin film layer is the surface on which the minute protrusions are to be formed. A transfer pattern processed to have a large number of microscopic depressions of the same shape is pressed against the thin film layer, and the surface of the transfer pattern is transferred to the thin film layer while exposing and curing the thin film layer. Through these steps, a desired CMP pad having the same shape of micro-projections arranged on the surface can be obtained.

As the support layer, one that is chemically and thermally stable and can be formed into a sheet or plate can be used. Examples thereof include polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose acetate, polyamide, polystyrene, polycarbonate, polyimide and polyester. Of these, biaxially stretched polyethylene terephthalate, which has excellent dimensional stability, is particularly preferable. It is also possible to adjust the polishing characteristics by controlling the elastic modulus by selecting the material and thickness of the support layer suitable for the object to be polished depending on the purpose. For example, in order to improve the uniformity of the object to be polished, it is effective to use a support having a low elastic modulus (polyethylene, polypropylene, polyamide, etc.). The preferable thickness of the support layer is 5 to 2000 μm. The material used for the thin film layer is not particularly limited, but a photocurable resin is more preferable.

The photocurable resin includes, for example, a photopolymerizable monomer, a base resin and a photoinitiator, and if necessary, an ultraviolet ray transmission inhibitor and the like can be added. As the photo-polymerizable monomer, monofunctional or polyfunctional ethylenically unsaturated monomers such as various acrylates, various acrylamides, and vinyl compounds can be used. As the base resin, polyester, epoxy, polyurethane acrylates or the like can be used. Examples of the photoinitiator include benzophenone, N,
N'-tetraethyl-4,4'-diaminobenzophenone, 4-methoxy-4'-dimethylaminobenzophenone, benzyl, 2,2-diethoxyacetophenone, benzoin, benzoin methyl ether, benzoin isobutyl ether, benzyl dimethyl ketal, α- Hydroxyisobutylphenone, thioxanthone, 2-chlorothioxanthone, 1-hydroxyisobutylphenone, 2-methyl-1- [4- (methylthio) phenyl]
-2-morpholino-1-propane, t-butylanthraquinone, 1-chloroanthraquinone, 2-ethylanthraquinone, 1,4-naphthoquinone, 9,10-phenanthraquinone, 1,2-benzanthraquinone, 1,
4-dimethylanthraquinone, 2-phenylanthraquinone, 2-benzyl-2-N, N-dimethylamino-1
-(4-morpholinophenyl) -1-butanone, 2-
(O-Chlorophenyl) -4,5-diphenylimidazole dimer or the like can be used. These photoinitiators are used alone or in combination of two or more.

Examples of the UV transmission inhibitors include aureoline (K ₃ [Co (NO ₂ ) ₆ ]), cobalt green (CoO-ZnO), and cerulean blue 2 (Co,
Mg) O.SnO ₂ , cobalt blue (Co, Mg) O
Inorganic pigments such as cobalt violet 3CoO.P ₂ O ₅ , iron oxide (K [Fe ^II Fe ^III (CN) ₆ ]), chromium oxide, lead chromate and barium chromate; organic pigments such as phthalocyanine, dioxazine and anthraquinone , Etc. can be used.

The amount of the photocurable resin used is preferably 0.01 to 25% by weight, and more preferably 1 to 20% by weight, based on the total solid content of the photosensitive composition. Further, if necessary, additives such as a sensitizer and an adhesion improver may be added.

The coating method of the photo-curable resin layer on the support layer includes roll coater coating, spin coater coating, spray coating, dip coater coating, curtain flow coater coating, wire bar coater coating, gravure coater coating and air knife coater. Coating, die coater coating, etc. The thickness of the photocurable resin layer is preferably 1 to 300 μm.

Examples of the exposure device include a carbon arc lamp, an ultra-high pressure mercury lamp, a high pressure mercury lamp, a xenon lamp, a metal halide lamp, a fluorescent lamp and a tungsten lamp. The material of the transfer master is not limited to metal, resin, etc., but preferably an iron alloy such as stainless steel, which is excellent in dimensional stability and conductivity, and a laminate of copper, which has a processing margin, are used. The surface is made uniform by mechanical polishing, etching, cleaning, etc. The shape of the transfer master is not limited to a plate shape, a sheet shape, a roll shape, or the like, but a roll shape is more preferable because it enables processing while rotating.

As a method for producing a micro recess of a transfer pattern,
There are an etching method, an electroforming method, a method of pressing an engraver, and the like. Further, the surface hardness may be increased or protective plating may be applied for the purpose of preventing oxidation. Further, it is preferable to plate chromium, nickel or the like in order to enhance the releasability from the photocurable resin. It is necessary to design the degree of micro-indentation of the transfer master in consideration of the fact that it is usually deformed by curing the thin film layer.

The area of the upper surface of the convex portion of the microprojection after photocuring is 1
It is desired that the thickness is 00 μm ² or more and 0.25 mm ² or less. If it is larger than 0.25 mm ² , the polishing rate is lowered, and if it is smaller than 100 μm ² , it is difficult to form fine irregularities.

It is desired that the height of the micro-projections after photo-curing has little variation. If the variation in height (1σ / average height) exceeds 10%, minute projections that do not come into contact with the substrate are generated during polishing, and the stability of polishing characteristics is poor.

The average height of the fine protrusions is 1 μm or more and 200.
It is preferably μm or less. If it is larger than 200 μm, the polishing liquid will flow too much and the polishing rate will decrease. On the other hand, 1μ
The polishing surface smaller than m and the upper surface of the minute protrusion are attracted to each other, which hinders smooth polishing. The shape of the minute protrusion may be a pyramid, a cone, a prism, or the like, but is not particularly limited. The average pitch of the fine protrusions is preferably 30 μm or more and 1000 μm or less. If it is less than 30 μm, the intervals between the protrusions are too narrow, and clogging occurs due to polishing dust and the like.
On the other hand, if it is larger than 1000 μm, the number of minute projections in contact with the polishing surface is small and the polishing rate is lowered.

The polishing liquid used with the polishing pad is not particularly limited. An insulating film polishing liquid such as silicon oxide for an interlayer insulating film, a BPSG film, a shallow trench isolation insulating film, etc. can be obtained by dispersing a composition comprising solid abrasive grains, a dispersant and water. The abrasive grains used may be any of cerium oxide, silicon oxide, aluminum oxide, titanium oxide, inorganic particles such as silicon carbide, polystyrene, polyacryl, organic abrasive particles such as polyvinyl chloride, but especially cerium oxide particles. Is preferred. Further, examples of the abrasive containing no abrasive grains include those disclosed in JP-A-11-135466. Since the dispersant is used for semiconductor polishing, the content of alkali metals such as sodium ions and potassium ions, halogens, and sulfur is 1
It is preferably suppressed to 0 ppm or less, and for example, a polymer dispersant containing an ammonium acrylate salt as a copolymerization component is preferable.

The film to be polished is a silicon oxide film or a silicon nitride film formed on a semiconductor substrate, a metal film such as Cu or CuAl alloy,
And a ferroelectric film. Further, a silicon oxide film formed on a wiring board having a predetermined wiring, an inorganic insulating film such as glass or silicon nitride, a metal film, an optical glass such as a photomask / lens / prism, an inorganic conductive film such as ITO, a glass or the like. Optical integrated circuit composed of crystalline material, optical switching element,
Optical waveguides, end faces of optical fibers, optical single crystals such as scintillators, solid-state laser single crystals, LED sapphire substrates for blue lasers, semiconductor single crystals such as SiC, GaP, and GaAs, glass for magnetic disks It is also applied to substrates, magnetic heads, etc.

There is no limitation on the polishing device, and it can be used in a disk-type polishing device and a linear-type polishing device. As an example, there is a general polishing apparatus having a holder for holding a semiconductor substrate and a surface plate on which a pad is attached (a motor or the like whose rotation speed is changeable is attached). Although the polishing conditions are not limited, the rotation speed of the surface plate is preferably a low rotation of 200 rpm or less so that the semiconductor substrate does not jump out, and the pressure applied to the semiconductor substrate is 100 k so that scratches do not occur after polishing.
Pa (1 kg / cm 2) or less is preferable. During polishing, slurry is continuously supplied to the CMP pad by a pump or the like. Although the supply amount is not limited, it is preferable that the surface of the polishing pad is always covered with the slurry. It is preferable that the semiconductor substrate after the polishing is thoroughly washed in running water, and then water droplets adhering to the semiconductor substrate are removed by using a spin dryer or the like and then dried.

[0021]

EXAMPLES Examples of the present invention will be described below. Examples 1 and 2 and Comparative Examples 1 and 2 (Preparation of Transfer Master) A photosensitive film was laminated on a copper foil film having a thickness of 25 μm. The photosensitive film was exposed and developed using a negative mask in which circles having a radius of 100 μm were two-dimensionally arranged at a pitch of 250 μm. Further, after the copper is etched, the exposed photosensitive film is peeled off to form a cylinder having a depth of 20 μm and a radius of 100 μm at a pitch of 25.
A copper foil film two-dimensionally arranged at 0 μm was obtained. This copper foil film was wrapped around a cylindrical iron base material having a diameter of 130 mm, and then Cr plating was performed to produce a transfer pattern. (Material of pad) A polyethylene phthalate film having a thickness of 125 μm was used as a support layer, and a photocurable resin was applied onto this film by a coater so as to have a film thickness of 100 μm. The photocurable resin includes acrylic acid-butyl acrylate-vinyl acetate copolymer 5 parts by weight, butyl acetate (monomer) 8 parts by weight, vinyl acetate (monomer) 8 parts by weight, acrylic acid (monomer) 0.3 parts by weight,
Hexanediol acrylate (monomer) 0.2 parts by weight, hexanediol acrylate (monomer) 0.2
Parts by weight, benzoin isobutyl ether (initiator)
2.5 parts by weight. Material 1 is obtained by adding 3.0 parts by weight of a pigment (melamine) as an ultraviolet ray transmission inhibiting factor, and material 2 is not added.

(Preparation of Pad 1) The transfer pattern is pressed against the film coated with the material 1 and an ultraviolet ray of 300 mJ / c is applied.
After irradiation with m2 to cure the photocurable resin, it was separated to obtain a film-like film. This film was irradiated with ultraviolet rays at 500 mJ / cm 2 and further post-cured. This film CMP
The surface of the pad was observed with an optical microscope and SEM, and it was found to be a truncated cone close to a cylinder with a pitch of 250 μm, a height of protrusions of 20 μm, and a radius of the upper surface of 90 μm, that is, an area of 0.025 mm ² . (Preparation of Pad 2) The transfer mold was pressed against the film coated with the material 2 and the photocurable resin was cured by irradiation with ultraviolet rays at 300 mJ / cm 2 and then separated to obtain a film-like film. The film is not post-cured. This film CM
When the surface of the P pad was observed with an optical microscope and SEM, it had the same shape as the pad 1. (Preparation of Pad 3) The transfer mold was pressed against the film coated with the material 2 and the photocurable resin was cured by irradiation with ultraviolet rays at 1000 mJ / cm 2 and then separated to obtain a film-like film. This film was irradiated with ultraviolet rays at 1000 mJ / cm 2 and further post-cured. When the surface of the film-like CMP pad was observed with an optical microscope and SEM, it had the same shape as the pad 1. (Production of Pad 4) A commercially available foamed polyurethane pad was prepared as Comparative Example 2. Table 2 shows the hardness of the front surface side and the hardness of the back surface side of each CMP pad. For the measurement of hardness, the Swade method used for measuring rubber hardness was used. When measuring the back surface side, the polyethylene phthalate support film was peeled off, and then the measurement was performed.

[0023]

[Table 1]

(Preparation of polishing liquid) (Preparation of cerium oxide slurry) Cerium carbonate hydrate 2
About 1 kg of a yellowish white powder was obtained by putting kg in a platinum container and baking in air at 800 ° C. for 2 hours. When this powder was subjected to phase identification by X-ray diffraction, it was confirmed to be cerium oxide. 1 kg of cerium oxide powder was dry-ground using a jet mill to obtain cerium oxide particles. 1 kg of the above-prepared cerium oxide particles, 23 g of an aqueous solution of polyacrylic acid ammonium salt (40% by weight) and 8977 g of deionized water were mixed, and ultrasonic dispersion was carried out while stirring.
It was applied for 0 minutes. The resulting slurry is filtered through a 1 micron filter and further deionized water is added to add 5
A wt% slurry was obtained. The slurry pH was 8.3.

(Polishing of Substrate) Pads 1-2 prepared above
(Examples 1 and 2) and Pad 3 (Comparative Example 1) are 1.2
φ380mm with a polyurethane foam of mm thickness sandwiched between
I stuck it on the surface plate of. Also, the prepared polyurethane foam pad (Comparative Example 2) was attached in the same manner.
Before the experiment, polishing was performed with a dressing grindstone made of 100-diameter diamond particles to give unevenness of Ra of about 5 μm on the surface.

Polishing Experiment 1 A blanket wafer was prepared by forming a 2000 nm thick silicon oxide film on a φ127 mm Si substrate by the TEOS-plasma CVD method. The above wafer is set in a holder to which a suction pad for substrate mounting is attached, and the above CM
The holder was placed on the P pad with the film surface down, and the processing load was set to 30 kPa (300 gf / cm ² ). 200 cc / mi of the above polishing liquid on the CMP pad
While dropping at a speed of n, the platen and the wafer are rotated at 38 rpm.
It was rotated for 2 minutes to polish the film on the substrate. The polished wafer was thoroughly washed with pure water and then dried. For the silicon oxide film, a film thickness difference before and after polishing was measured at 49 points using an optical interference type film thickness measuring device, and uniformity (3σ / average value × 100) was calculated in%.

Polishing Experiment 2 Al wiring having a height of 1000 nm was formed on a φ127 mm Si substrate at a wiring / space of 100 μm / 100 μm pitch, and a silicon oxide film was formed to a thickness of 1000 nm by TEOS-plasma CVD method to form an unevenness of 1000 nm. A sample (to be polished) was prepared. Under the same conditions as polishing experiment 1 (excluding polishing time), a step difference of 1000 nm between the convex portion and the concave portion of the TEG wafer is polished, and the final step difference before the aluminum of the convex portion is exposed is Dektak3030.
Measurement was performed using a stylus type step meter (manufactured by SLOAN), and the flatness was calculated by subtracting the minimum value from the maximum value of the measured values. Table 2 shows the evaluation results of the polishing characteristics of Examples and Comparative Examples according to Polishing Experiments 1 and 2.

[0028]

[Table 2]

[0029]

As described above, the CMP pad of the present invention is
Maintaining a high polishing rate and accurately planarizing the polishing of the insulating film and removal of the extra layer of the buried film such as metal in the semiconductor substrate manufacturing process, and at the same time, expressing the uniformity of the entire wafer. Is possible.

Claims (7)

[Claims] 1. A pad for chemically mechanically polishing a polishing film formed on a substrate, which comprises a support layer and a thin film layer whose hardness changes in the layer direction. 2. The thin film layer is a photocurable resin.
The described CMP pad. 3. The CMP pad according to claim 1, wherein the thin film layer further contains an ultraviolet ray transmission inhibitor. 4. The CMP pad according to claim 1, wherein minute projections are formed on the surface of the thin film layer. 5. The CMP pad according to claim 4, wherein the minute protrusions are formed by transferring a photocurable resin from a mold. 6. The pad according to claim 1, which has a web shape.
The CMP pad according to 5. 7. A predetermined substrate is pressed against a CMP pad comprising a support layer and a thin film layer whose hardness changes in the layer direction, and an abrasive is supplied between the polishing film and the CMP pad. A method of polishing a substrate, characterized in that the surface to be polished of a substrate, which is a semiconductor chip, and a polishing pad are brought into relative motion while being brought into contact with each other, and the surface of the substrate is polished while a load bias applied to the polishing surface is dispersed.