JP2000233375A - Flattening polishing segment type resin grinding wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin grinding wheel which has a polishing surface hardly causing a scratch, and has a satisfactory polishing speed, and is excellent in flattening performance by arranging small segment-like grinding wheels at spaces on a base plate and fixing the same. SOLUTION: Since the space between drain grooves of a grinding wheel depends on the size of a small segment grinding wheel, the size is important. Though the optimum size depends on the polishing speed, the pressure load and the quantity of supplied polishing liquid, the practical range is from 5 mm to 50 mm. The shape of the segment is preferably a small-segment magnet without an acute angle under 60 deg.. A magnet to be used is a structure having continuous pores with the porosity of 35-70%, preferably 45-55%, in which the bending elasticity of binding resin for binding abrasive grains is 35,000 kgf/cm2 or less, the maximum abrasive grain of the grinding wheel is 2 μm, and the compounding ratio of abrasive grain to resin preferably ranges from 40:60 to 60:40 by volume ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a silicon wafer,
A grindstone that polishes the surface of a thin plate-like object to be polished such as a magnetic disk or a glass substrate flat and smooth, particularly a wiring material formed on a semiconductor wafer, a resin useful for polishing an interlayer insulating film formed when performing multilayer wiring. The present invention relates to a resin whetstone which is less related to a whetstone and has less flattening performance with less occurrence of scratches.

[0002]

2. Description of the Related Art In recent years, with the increase in density of electronic devices, formation of devices on flat substrates has become important in the fields of semiconductors, magnetic disks, flat displays, and the like. For example, as semiconductor devices become more highly integrated, device miniaturization and multilayer wiring structure have progressed. Wiring layers formed on silicon wafers must have a flat surface for miniaturization and higher reliability. Has become indispensable. As flattening technology,
Conventionally, a method of forming an inorganic film by a method such as CVD after applying a thin liquid insulating film such as SOG (Spin On Glass), a method of forming a heat resistant organic film such as polyimide, or an ion etching of the formed inorganic film. Etch-back method has been adopted. However, planarization by such a method has almost reached its limit.

Instead of these methods, CMP (Mh) polishing with a slurry of silica or cerium oxide on a polishing pad is performed.
A polishing method called emical and Mechanical Polishing) has been put to practical use. When polishing by this polishing method,
Since a soft resin sheet is used for the polishing pad, the projections and depressions on the surface of the object to be polished are also polished, making it difficult to finish the entire surface of the object to be polished to a completely flat surface. Has a problem that many scratches occur. In addition, since the life of the polishing pad is short, the polishing pad has to be replaced frequently, and it is necessary to adjust the polishing conditions each time, and there is a further problem in the cost of consumables and maintenance. In addition, it is necessary to dispose of an expensive chiller as an abrasive and to treat the waste liquid, which is a factor that raises the cost.

[0004] In order to further improve the flatness of the polished surface, there is a flattening method using grinding stone polishing. As a method of manufacturing a grinding stone, for example, a method of dry-blending abrasive grains and a phenol-melamine-based thermosetting powder binder and molding the mixture under a pressure controlled so as to obtain a desired porosity (Japanese Patent Laid-Open No. 9-13945)
No. 4) and a method of kneading with polyvinyl alcohol, liquid phenol resol and formalin, and then curing the mixture in a mold. Further, since the polishing liquid enters between the grindstone and the body to be polished and floats the body to be polished, the grindstone requires a drain groove. However, depending on the shape of the groove processing, there is a problem that scratches are caused on the surface of the polished object due to a chip that is easily chipped, and a problem that scratches occur due to the adhesion of hard foreign substances that have fallen off from the groove processing tool during formation. Furthermore, it is necessary to change the shape of the grindstone in accordance with the size of the apparatus or the silicon wafer to be polished, and there is a problem that a molding die is required accordingly.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and provides a polished surface free of scratches without using a large amount of expensive slurry as an abrasive. It is an object of the present invention to provide a resin grindstone having a sufficient polishing rate and excellent in flattening performance, and particularly useful for polishing a semiconductor wafer.

[0006]

According to the present invention, this object is attained by a polishing whetstone in which small-segment whetstones are fixedly arranged on a hard substrate such as metal or FRP with a gap therebetween. That is, by forming a small-segment grindstone in advance and arranging it with a gap on a flat substrate, there is no phenomenon that the polishing liquid between the grindstone and the semiconductor wafer makes it impossible to polish, and the polishing liquid is discharged. Since there is no processing for forming the grooves, defects due to dropping of hard foreign matter from the processing tool, and problems of generation of scratches due to chipping of a grindstone during polishing are eliminated by eliminating an acute angle shape. In addition, by changing the number of small-segment grindstones, ideally, a single die can be used to manufacture a grindstone having a small diameter to a large diameter. Further, the grindstone in which the small segments according to the present invention are arranged has an advantage that even if a part is damaged during use, it can be regenerated by replacing only the damaged part. Further, in order to eliminate polishing unevenness, the grooves may be arranged so as not to be concentric.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the distance between the drain grooves of the grindstone depends on the size of the small segment grindstone. The optimum dimensions vary depending on the polishing rate, the pressing load, and the amount of the polishing liquid to be supplied.
mm to 50 mm (the diameter of a circle, the diameter of the largest inscribed circle touching three sides in the case of a parallelogram, and the diameter of the inscribed circle in the case of a regular polygon). In addition, the shape of the segment is preferably a small segment grindstone having no sharp angle of less than 60 degrees so as not to cause chipping due to stress during polishing and cause scratches. For example, a circle, a parallelogram, a regular polygon, and the like can be considered. The gap between the grooves also needs to be appropriately changed depending on the shape and size of the segment grindstone and the polishing conditions. The grindstone used in the present invention is a structure having continuous pores having a porosity of 35 to 70%, preferably 45 to 55%, and a bending elastic modulus of a binder resin for binding abrasive grains is 35,000. kgf / cm ² or less, the maximum grain size of the abrasive grains is 2 μm, and the mixing ratio of the abrasive grains to the resin is preferably in the range of 40:60 to 60:40 by volume ratio.

The binder resin of the abrasive used in the present invention includes:
Polyvinyl acetal, phenolic resin, melamine resin, urea resin, unsaturated polyester resin, epoxy resin, or at least one resin material selected from diallyl phthalate resin is suitable, practically,
Thermosetting resins such as unsaturated polyester resin, diallyl phthalate resin or epoxy resin are easy to use. Examples of the abrasive grains that are the main components of the grindstone used in the present invention include cerium oxide, silica, alumina, zirconia, and silicon carbide. The segment whetstones are arranged and fixed on the substrate by a known adhesive. The substrate is not particularly limited, but a disc-shaped aluminum plate, glass plate, plastic molded plate, or the like can be used. In the present invention, when polishing a semiconductor wafer, it is preferable to devise a method such that there is no portion where the local time always hits the groove and another portion does not. For example, as shown in Example 1 below, so that the grooves are not aligned on concentric circles,
It is preferable to arrange the small-segment whetstones off-center because uniform polishing can be performed. Hereinafter, the present invention will be further described with reference to examples.

[0009]

EXAMPLES Example 1 A solid unsaturated polyester resin having a flexural modulus of elasticity of 35,000 kgf / cm ² after curing (8523 manufactured by Iupika Co., Ltd.)
20 parts (the same applies to parts by weight hereinafter), 2 parts of a curing accelerator dicumyl peroxide (DCP-F manufactured by Mitsui Toatsu Co., Ltd.), and 80 parts of cerium oxide having a maximum particle diameter of 2 μm,
After mixing with a Henschel mixer, the mixture was further pulverized and mixed with a jet mill. This mixed powder was put in a mold and molded at a mold temperature of 160 ° C. for 40 minutes. In order to completely cure the resin after demolding, the molded body was post-cured with a dryer at 160 ° C. for 2 hours to obtain a segment resin grindstone. The shape of the mold is
It is a regular hexagon having a side of 1 cm, a thickness of 1 cm, and a shape capable of forming 25 pieces at a time. The amount of the mixed powder filled in the mold was measured and filled so that a porosity of 50% by volume based on the volume of the cavity of the mold remained. Next, a 5 mm thick aluminum plate was adhered to the aluminum plate with a thickness of 5 mm using an epoxy adhesive so that the segment interval became 2 mm, and dressed with a diamond grindstone so that the surface became flat. Thus, a resin grindstone having a diameter of about 320 mmφ was obtained.

Next, the interlayer insulating film (SiO 2 film formed by the plasma CVD method) formed on the silicon wafer was polished using the resin grindstone. In the polishing test, the pressure was 200 g / cm ² and the sliding speed was 19 while flowing pure water through the resin grindstone.
cm / sec and a processing time of 3 minutes. The scratch on the wafer surface after polishing was measured by an optical microscope to find that large scratches (scratches thought to affect the lower wiring layer) were 6
The scratches (other fine scratches) on the entire surface of the inch wafer were observed on a part of the wafer, and were converted into the total amount of the 6 inch wafer. The flattening performance was measured by measuring the residual step in the polishing of the convex portion 500 nm with respect to the initial step 500 nm in the wafer having the 7 mm pattern wiring. As a result of the polishing evaluation, according to the grindstone according to the present invention, there was no occurrence of chipping of the grindstone during polishing, no scratches / wafer, and a polishing speed of 10
It was found that the polishing performance was as excellent as 5 nm / min and the flatness was 18 nm.

Example 2 A solid epoxy resin (EP-1004 manufactured by Shell Co.) 100 having a flexural modulus after curing of 35,000 kgf / cm ^2.
Part and phenol novolak resin (HP8 manufactured by Hitachi Chemical Co., Ltd.)
50) Melt mixture with 12 parts) 20 parts, curing accelerator tetraphenylphosphine tetraphenylborate 2.5
And cerium oxide having a maximum particle diameter of 2 μm in a ratio of 80 parts with a Henschel mixer, and then finely pulverized and mixed with a jet mill. This mixed powder was placed in a mold and molded at a mold temperature of 160 ° C. for 60 minutes. After demolding, the molded article was post-cured at 160 ° C. for 2 hours with a drier in order to completely cure the resin to obtain a segment resin grindstone. The shape of the mold is a square having a side of 2 cm, a thickness of 1 cm, and a shape capable of forming 25 pieces at a time. The amount of the mixed powder filled in the mold was weighed and filled so that a porosity of 50% by volume based on the volume of the cavity of the mold remained. Next, using a epoxy adhesive to adhere to the shape as shown in FIG. 2 on an aluminum plate with a thickness of 5 mm so that the segment interval becomes 2 mm, and further dressing with a diamond grindstone so that the surface becomes flat. Thus, a resin grindstone having a diameter of about 360 mmφ was obtained. Next, a polishing experiment was performed in the same manner as in Example 1 using this resin grindstone. As a result of the polishing evaluation, there was no chipping of the grindstone during the polishing, no scratches / wafer, the polishing rate was 125 nm / min, and the flatness was 25 n.
m and very excellent polishing performance.

Example 3 The segment-type resin grindstone of Example 2 was used, and the diameter was about 700.
A resin whetstone of mmφ was obtained. Next, polishing of the SiO2 interlayer insulating film formed on the silicon wafer using this resin grindstone was performed in the same manner as in Examples 1 and 2. In the polishing test, the pressure was 250 g / cm ² and the sliding speed was 5 while pure water was flowing through the resin grindstone.
The test was performed under the conditions of 3 cm / sec and a processing time of 1 minute. As a result of the polishing evaluation, there was no chipping of the grindstone during the polishing, no scratches / wafer, and the polishing rate was 650 nm.
/ Min, and the flatness was 25 nm, which was very excellent polishing performance.

Example 4 The segment-type resin grindstone of Example 2 was used and the diameter was about 100.
A resin whetstone of mmφ was obtained. Next, using this resin grindstone, polishing of the SiO2 interlayer insulating film formed on the silicon wafer was performed in the same manner as in Examples 1 and 2. The polishing test was performed under the conditions of a pressure of 200 g / cm ² , a sliding speed of 9 cm / sec, and a processing time of 3 minutes while flowing pure water through the resin grindstone. However, in this case, the silicon wafer was fixed in a lower rotating disk shape, the silicon wafer was attached to the grindstone holder, and the polishing was performed so that only the central portion of the wafer was constantly polished. As a result of the polishing evaluation, it was found that there was no occurrence of chipping of the grindstone during the polishing, the scratch was 0 pieces / wafer, the polishing speed was 65 nm / min, and the flatness was 20 nm, which was a very excellent polishing performance. The polishing speed largely depends on the polishing pressure and the sliding speed.

Comparative Example 1 A CMP polishing experiment was performed using a commercially available urethane polishing pad which is usually used for polishing a semiconductor wiring layer. The pad is made of polyurethane and has a compression modulus of 10,000 kgf / cm.
^The polishing slurry used was prepared by dispersing cerium oxide using polyammonium polyacrylate as a dispersing agent in pure water to a concentration of 3% by weight. Polishing pressure is 250 g / cm ² , sliding speed 53 cm /
sec. As a result, 0 scratches / wafer,
The polishing rate was 265 nm / min, and the flatness was 200 nm. In the CMP method using a urethane pad, the scratch and the polishing rate are good, but the flatness is poor.

Comparative Example 2 A resin grindstone having the same composition as that of Example 2 and having a diameter of 380 mmφ was divided into eight fan-shaped parts to form a grindstone, bonded to an aluminum plate, and pitched with a diamond cutter at a pitch of 20 mm and a width of 20 mm.
mm grooves were formed in a grid pattern. When the inside of the groove was observed, a residue which was considered to be a locally black metal foreign matter was formed. This was removed by polishing to such an extent that it could not be visually observed, but the operation was extremely difficult. Next, a polishing experiment was performed using this resin grindstone under the same conditions as in Example 2. As a result, the number of large scratches was 0 / wafer, but the number of micro scratches was about 100 / wafer. Polishing rate: 90 nm / min, flatness: 20 nm
Met. Although the flatness and polishing rate were good, scratches occurred due to impurities that seemed to be mixed during processing.

Comparative Example 3 A resin grindstone having the same composition as that of Example 2 and having a diameter of 380 mmφ was divided into eight fan-shaped sections to form a grindstone, which was adhered to an aluminum plate to obtain a resin grindstone. As a result of conducting a polishing experiment without forming a groove, the number of scratches was 0 / wafer, but the polishing rate was extremely low at 12 nm / min. Although the polishing conditions are the same as in Example 2, the reason why the polishing rate is very low is considered to be that the polishing could not be performed because the polishing liquid entered between the wafer and the grindstone.

[0017]

As described above, the segment type resin grindstone according to the present invention can obtain a polished surface free of scratches without using an expensive slurry, has a sufficient polishing rate, and has a flattening performance. Excellent in forming grooves with no foreign matter, making it easy to manufacture large and small whetstones with different dimensions, no chipping of whetstones during polishing, wiring material formed on semiconductor wafers, multi-layer wiring It is useful for polishing an interlayer insulating film to be formed.

[Brief description of the drawings]

FIG. 1 is a plan view of a regular hexagonal segment type resin grindstone.

FIG. 2 is a plan view of a square segment type resin grindstone.

[Explanation of symbols]

 1 segment type resin whetstone 2 groove

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor K. Tomita 1500 Oji Ogawa, Shimodate City, Ibaraki Prefecture Inside the Shimodate Plant of Hitachi Chemical Co., Ltd. Inside the Shimodate Plant of the Company (72) Inventor Shunichi Numata 48 Wadai, Tsukuba, Ibaraki Prefecture Hitachi Chemical Co., Ltd.

Claims (7)

[Claims] 1. A flattening-polishing segment-type resin grindstone comprising small-segment grindstones made of abrasive grains and a binder resin fixedly arranged on a substrate with a gap therebetween. 2. The shape of a segment-type resin grindstone is a circle, a parallelogram, or a regular polygon, and the unit segment shape of the segment-type resin grindstone is a circle; The segmented resin grindstone for flattening and polishing according to claim 1, wherein the diameter of the largest inscribed circle in contact with the surface, or in the case of a regular polygon, the diameter of the inscribed circle is in the range of 5 mm to 50 mm. 3. The segment type resin grindstone for flattening and polishing according to claim 1, wherein the small segment grindstone does not have an acute angle of less than 60 degrees. 4. The segment type resin grindstone for flattening and polishing according to claim 1, wherein the main components of the grindstone are abrasive grains, a binder resin, and voids. 5. A structure having continuous pores of a grindstone having a porosity of 35 to 70%, wherein a bending elastic modulus of a binder resin for binding the abrasive grains is 35,000 kgf / cm ² or less. Has a maximum particle size of 2 μm, and the compounding ratio of the abrasive and the resin is 4 by volume.
The segmented resin grindstone for flattening and polishing according to any one of claims 1 to 4, which is in a range of 0:60 to 60:40. 6. The segment type resin for flattening and polishing according to claim 1, wherein the abrasive grains as a main component of the grindstone are at least one selected from cerium oxide, silica, alumina, and zirconia. Whetstone. 7. The resin according to claim 1, wherein the binder resin for binding the abrasive grains is at least one selected from polyvinyl acetal, phenol resin, melamine resin, urea resin, unsaturated polyester resin, epoxy resin, and diallyl phthalate resin. 7. The segment type resin grindstone for planarization polishing according to any one of 6.