JP5997973B2 - Metal film polishing pad and polishing method using the same - Google Patents

Description

  The present invention relates to a metal film polishing pad and a polishing method using the same.

  In order to improve the performance of semiconductor circuits, it is required to increase the density by miniaturizing elements and wiring circuits having functions such as transistors and resistors, and by stacking wirings.

  The increase in the density of semiconductor circuit elements and wiring is due to the accuracy of the photolithography process at the time of circuit pattern formation. A fine circuit pattern is formed by accurately transferring a fine circuit pattern onto a semiconductor wafer by exposure through a resist mask in a photolithography process.

  In order to meet the demand for higher performance of semiconductor circuits, the depth of focus of a projection lens used for photolithography becomes shallower as the circuit pattern becomes finer. In this case, it is required that the irregularities on the surface of the semiconductor wafer be within the focal depth of the projection lens. For this reason, with the miniaturization of circuit patterns, the demand for flatness required on the surface of a semiconductor wafer increases.

Chemical mechanical polishing (CMP) is widely used as a technique for imparting high flatness to the surface of a semiconductor wafer. The chemical mechanical polishing is a method of polishing by bringing a rotating object to be in contact with the surface of the rotating polishing pad (polishing layer) while dripping the polishing slurry. By chemical mechanical polishing, a flat surface with irregularities controlled to the nanometer order can be obtained. Chemical mechanical polishing is performed by doping an interlayer insulating film, a PTEOS film (a SiO ₂ film formed by plasma CVD using tetraethyl orthosilicate as a target and an oxidizing agent such as ozone), a BPSG film (boron, phosphorus, etc.). (Silicon oxide film), shallow trench isolation, plug and formation of buried metal wiring, etc. are widely used for polishing.

  In particular, due to the increase in processes accompanying the lamination of metal wiring, metal wiring polishing is required to improve throughput and yield, and high polishing speed and good polishing uniformity during chemical mechanical polishing are required. .

  Conventionally, as a polishing pad used for chemical mechanical polishing, a relatively soft polishing pad in which a nonwoven fabric is impregnated with a polyurethane resin, a polishing pad made of foamed polyurethane, or the like has been used.

  For example, in the manufacture of semiconductor devices, a relatively hard polishing pad made of foamed polyurethane as in Patent Document 1 is generally employed for the purpose of achieving both a high polishing rate and polishing uniformity.

  Also, the polishing performance varies greatly depending on the groove and hole processing formed on the polishing pad surface. By supplying the polishing slurry uniformly and sufficiently to the wafer surface polished by the processing, high polishing speed and uniform polishing can be achieved. A method for improving the property is known (see, for example, Patent Documents 1 to 5).

However, depending on the types of grooves and holes on the surface of the polishing pad, it is difficult to satisfy all of the high polishing rate and the polishing uniformity. For example, in a configuration in which grooves are formed on the surface of the polishing pad, single grooves in a lattice pattern or single grooves in a radial pattern, the polishing slurry has a high fluidity on the surface of the polishing pad, but also has a high discharge capacity. It becomes difficult to supply the polishing slurry, and the polishing rate and the polishing uniformity are likely to decrease. On the other hand, when the number of revolutions of the polishing pad is increased to improve the polishing rate, the polishing slurry discharge property is also increased, and thus the polishing rate may be lowered.
In addition, when holes are formed on the surface of the polishing pad, the flowability of the polishing slurry on the polishing pad is inferior, so the supply of the polishing slurry to the wafer surface is reduced, and the polishing rate and polishing uniformity are likely to decrease. . In addition, scratching is likely to occur on the wafer surface because of low polishing dust discharge.

JP 2004-314215 A Japanese Patent Laid-Open No. 11-156699 JP 2000-286218 A JP 2006-005339 A JP 2007-201449 A

  The present invention has been made in view of the above circumstances, and provides a metal film polishing pad having a polishing performance with a high polishing rate and excellent polishing uniformity, and a polishing method using the polishing pad. To do.

That is, the present invention
[1] The land width (x) is 5.0 to 7.0 (mm) and the groove width (y) is only a concentric circular groove having a groove width (y) of 0.25 to 0.75 (mm). A metal film polishing pad;
[2] The metal film according to claim 1, wherein the land width (x) is 5.1 to 6.8 (mm) and the groove width (y) is 0.29 to 0.71 (mm). Polishing pad;
[3] The metal film polishing pad according to [1] or [2], comprising a thermoplastic polyurethane ;
[4] In the method for polishing a metal film using the metal film polishing pad according to any one of [1] to [3], the rotation speed of the surface plate to which the metal film polishing pad is attached is 50 to 120 (rpm And a polishing method of the metal film .

  According to the present invention, a metal film polishing pad having a polishing performance with a high polishing rate obtained by having concentric grooves of a specific width and excellent polishing uniformity, and a polishing method using the polishing pad are provided. Can be provided.

[Metal polishing pad]
The metal polishing pad of the present invention has concentric grooves having a land width (x) of 5.0 to 7.0 (mm) and a groove width (y) of 0.25 to 0.75 (mm). Have.

  Here, the land width in this specification refers to the width of the convex portion between the concentric circular grooves in the metal film polishing pad, and the groove width refers to the width of the concave portion between the concentric circular grooves in the metal film polishing pad.

When the land width is larger than 7.0 mm, the slurry cannot be held on the land, and when the land width is smaller than 5.0 mm, the balance between the slurry holding and the replacement is deteriorated.
Also, when the groove width is larger than 0.75 (mm), the amount of slurry retained after polishing in the groove portion is increased, so that the replacement with fresh slurry becomes insufficient, while the smaller than 0.25 (mm). Since the balance between slurry holding and substitution is deteriorated and conditioning waste is easily clogged into the grooves, scratches are easily generated.
From the viewpoint of slurry retention and substitution balance, the land width (x) in the metal film polishing pad is 5.1 to 6.8 (mm), and the groove width (y) is 0.29 to 0.00. 71 (mm) is preferable, the land width (x) is 5.2 to 6.5, and the groove width (y) is more preferably 0.32 to 0.67.

  The depth of the concentric grooves provided in the metal film polishing pad of the present invention is preferably 0.2 to 2.5 mm from the viewpoint of achieving both appropriate retention and discharge of the polishing slurry, and 0.3 to 2. 0 mm is more preferable, and 0.4 to 1.5 mm is more preferable.

  The cross-sectional shape of the concentric groove provided in the metal film polishing pad of the present invention (the cross-sectional shape when cut perpendicular to the longitudinal direction of the groove) may be any of a rectangle, a trapezoid, a triangle, a semicircle, and the like. From the viewpoint that the groove width does not change even when the metal film polishing pad is worn and the polishing performance hardly changes, the rectangular shape is preferable.

  The D hardness of the metal film polishing pad of the present invention is preferably in the range of 50 to 80, preferably in the range of 53 to 77, from the viewpoint of improving polishing uniformity and suppressing the occurrence of scratches on the wafer surface. More preferably, it is more preferably in the range of 56 to 74. The D hardness can be measured according to JIS K6253.

  As a material constituting the metal film polishing pad of the present invention, a known polymer can be used, for example, polyethylene, polypropylene, polybutadiene, ethylene-vinyl acetate copolymer, polyvinyl acetal resin such as butyral resin, polystyrene, Polyvinyl chloride, acrylic resin, epoxy resin, polyurethane, polyester, polyamide and the like can be mentioned. These may be used alone or in combination of two or more. Among them, polyurethane is preferable from the viewpoint of excellent polishing performance such as excellent polishing uniformity and resistance to scratches on the wafer surface. Thermoplastic obtained by reacting a high molecular diol, an organic diisocyanate and a chain extender. Polyurethane is more preferred.

  Examples of the polymer diol include polyether diols such as polyethylene glycol and polytetramethylene glycol; poly (nonamethylene adipate) diol, poly (2-methyl-1,8-octamethylene adipate) diol, and poly (2-methyl- Polyester diols such as 1,8-octamethylene-co-nonamethylene adipate) diol, poly (methylpentamethylene adipate) diol; poly (hexamethylene carbonate) diol, poly (hexamethylene-co-2,2-dimethyl-1, And polycarbonate diols such as 3-propylene carbonate) diol. These may be used alone or in combination of two or more.

  As the organic diisocyanate, any of the organic diisocyanates used in the production of ordinary polyurethanes may be used. For example, aliphatic or alicyclic such as hexamethylene diisocyanate, isophorone diisocyanate, 4,4′-dicyclohexylmethane diisocyanate. Diisocyanates; aromatic diisocyanates such as 4,4′-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,5-naphthylene diisocyanate and the like. These may be used alone or in combination of two or more. Among these, 4,4'-diphenylmethane diisocyanate is preferable from the viewpoint of wear resistance of the resulting polishing pad.

  As the chain extender, any chain extender used in the production of ordinary polyurethane may be used. As the chain extender, it is preferable to use a low molecular weight compound having a molecular weight of 350 or less having two or more active hydrogen atoms capable of reacting with an isocyanate group, for example, ethylene glycol, diethylene glycol, 1,2-propanediol. 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6 -Hexanediol, 3-methyl-1,5-pentanediol, 1,4-bis (β-hydroxyethoxy) benzene, 1,4-cyclohexanediol, cyclohexanedimethanol (1,4-cyclohexanedimethanol, etc.), bis (Β-hydroxyethyl) terephthalate, 1,9-nonanediol, Diols such as pyroglycol; ethylenediamine, trimethylenediamine, tetramethylenediamine, hexamethylenediamine, octamethylenediamine, nonamethylenediamine, hydrazine, xylylenediamine, isophoronediamine, piperazine, o-phenylenediamine, m-phenylenediamine, Examples thereof include diamines such as p-phenylenediamine, adipic acid dihydrazide, isophthalic acid dihydrazide, 4,4′-diaminodiphenylmethane, and 4,4′-diaminodiphenyl ether. These may be used alone or in combination of two or more. Among these, 1,4-butanediol and / or 1,4-cyclohexanedimethanol is preferable.

  The thermoplastic polyurethane can be produced by a known method such as a prepolymer method or a one-shot method using a polymer diol, an organic diisocyanate and a chain extender as raw materials, but in the substantial absence of a solvent. The polymer diol, the organic diisocyanate and the chain extender are preferably produced by melt-kneading at a predetermined ratio, and more preferably produced by a continuous melt polymerization method using a multi-screw extruder. .

The use ratio of the polymer diol, organic diisocyanate, and chain extender is appropriately determined in consideration of physical properties that should be imparted to the polishing layer made of thermoplastic polyurethane, such as abrasion resistance. It is preferable to use each component at a ratio of 0.95 to 1.3 mol of the isocyanate group contained in the organic diisocyanate with respect to 1 mol of the active hydrogen atom contained in.
If the ratio is less than 0.95 mol, the mechanical strength and abrasion resistance of the resulting metal film polishing pad made of thermoplastic polyurethane tend to be reduced, and if it exceeds 1.3 mol, the thermoplastic polyurethane Productivity and storage stability tend to decrease. From the viewpoint of the mechanical strength and abrasion resistance of the resulting metal film polishing pad and the productivity and storage stability of thermoplastic polyurethane, the organic diol and the organic hydrogen can be added to 1 mol of active hydrogen atoms contained in the chain extender. It is more preferable to use each component at a ratio of 0.96 to 1.1 mol of the isocyanate group contained in the diisocyanate, and it is even more preferable to use each component at a ratio of 0.97 to 1.05 mol. .

The polymer used as the material constituting the metal film polishing pad of the present invention may contain other components as long as the effects of the present invention are not impaired. Other components include, for example, crosslinking agents, fillers, crosslinking accelerators, crosslinking aids, softeners, tackifiers, anti-aging agents, foaming agents, processing aids, adhesion promoters, crystal nucleating agents, heat resistance Stabilizers, weathering stabilizers, antistatic agents, colorants, lubricants, flame retardants, flame retardant aids (such as antimony oxide), blooming inhibitors, mold release agents, thickeners, antioxidants, conductive agents, etc. It is done.
The content of other components in the metal film polishing pad of the present invention is preferably 50% by mass or less, more preferably 20% by mass or less, and further preferably 5% by mass or less.

  The metal film polishing pad of the present invention is excellent in polishing uniformity, and since there are no pores exposed on the side surfaces of the grooves or holes, the abrasive grains in the polishing slurry are aggregated and adhered in the pores. From the standpoint that there is no risk of generating scratches, a substantially non-foamed structure is preferable.

The polishing pad for polishing a metal film of the present invention may have a single layer structure consisting of only a polishing layer, but from the viewpoint of further improving the polishing uniformity within the wafer surface, the back surface of the polishing layer (the polishing side surface and A cushion layer may be laminated on the opposite surface.
For the lamination of the polishing layer and the cushion layer, a known pressure-sensitive adhesive or adhesive can be used. The A hardness of the cushion layer is preferably 30 to 90. The material of the cushion layer is not particularly limited, and examples thereof include non-foamed or foamed elastomers and non-woven fabrics impregnated with resin.

  From the viewpoint of polishing performance and workability, the thickness of the polishing layer is preferably 0.6 to 3.0 mm, more preferably 0.7 to 2.5 mm, and 0.8 to 2.0 mm. More preferably. If the thickness of the polishing layer is less than 0.6 mm, the polishing performance is not stable due to the wear of the polishing layer due to the influence of the hardness of the surface plate of the polishing apparatus and the hardness of the cushion layer itself. Tend. On the other hand, if the thickness of the polishing layer is larger than 3.0 mm, the bending rigidity of the entire metal film polishing pad is increased, so that the polishing layer becomes difficult to be deformed.

  The polishing pad for polishing a metal film of the present invention has a polishing uniformity when a cushion layer is laminated on the lower layer when the depth of the groove opened on the polishing side surface is 30 to 90% of the thickness of the polishing layer. It is preferable because it can be improved. The depth of the groove is more preferably 35 to 85% of the thickness of the polishing layer, and further preferably 40 to 80%.

[Method of manufacturing metal polishing pad]
The method for producing the metal film polishing pad of the present invention is not particularly limited, but a sheet comprising one or two or more kinds of polymers or polymer compositions described above is produced, and the metal film is produced from the sheet. A polishing pad can be manufactured.
The sheet can be produced by extruding the polymer or polymer composition with an extruder. For example, the sheet is melt-extruded with the polymer or polymer composition using an extruder equipped with a T-die. The method of doing is mentioned.
As an extruder, a single screw extruder, a twin screw extruder, etc. can be used. The sheet can also be produced by previously producing a block made of the polymer or polymer composition described above and slicing it.
If necessary, the obtained sheet can be processed into a desired size and shape by cutting, punching, cutting, or the like, or processed to a desired thickness by grinding or the like to form a polishing layer.

The method for forming concentric grooves provided in the metal film polishing pad of the present invention is not particularly limited.
(1) A method of forming a groove by cutting a resin sheet;
(2) A method of forming a groove by bringing a heated mold or metal wire into contact with a resin sheet or irradiating a light beam such as a laser beam to dissolve or decompose and volatilize the portion;
(3) A method in which a melt of a raw material for a resin sheet is poured into a mold having convex portions and then solidified;
Etc.
Of the methods (1) to (3), the method (1) is preferable from the viewpoint of excellent machining accuracy.

[Polishing method using metal polishing pad]
The polishing method of the present invention polishes the wiring material formed on the semiconductor substrate using the above-described metal film polishing polishing pad of the present invention.
Here, at the time of polishing, chemical mechanical polishing can be performed using a known polishing slurry. Examples of the polishing slurry that can be used in the polishing method of the present invention include liquid media such as water and oil; polishing agents such as silica, alumina, cerium oxide, zirconium oxide, and silicon carbide; bases, acids, oxidizing agents, and interfaces. What contains components, such as an activator and a chelating agent, is mentioned. Moreover, when performing chemical mechanical polishing, you may use lubricating oil, a coolant, etc. together with polishing slurry as needed.

  In the polishing method of the present invention, a known chemical mechanical polishing apparatus is used to perform polishing by bringing a surface to be polished and a polishing pad into contact with each other at a predetermined speed under a pressure for a predetermined time via a polishing slurry. Can do. In addition, before or during polishing, it is preferable to condition the polishing pad by using a dresser such as a diamond dresser to condition the surface of the polishing pad.

  Examples of articles to be polished include wiring materials such as copper, aluminum, and tungsten.

When polishing is performed while flowing a polishing slurry using the polishing pad for polishing a metal film of the present invention, the number of rotations of the surface plate (the number of rotations of the polishing pad) with the polishing pad attached to the surface is the slurry inflow property. -50-120 (rpm) is desirable from the relationship between discharge property and groove shape.
When the rotation speed of the platen is lower than 50 rpm, the polishing is difficult to proceed, and when it is higher than 120 rpm, the slurry is excessively discharged and the polishing rate is lowered. 58-110 (rpm) is more preferable, and 66-100 (rpm) is still more preferable.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.

[Evaluation of polishing performance for copper film]
The polishing pads produced in each of the examples and comparative examples were installed in a polishing apparatus “nHance 6EG” manufactured by Strasbaugh, and ultrapure water was added at 200 mL / min using a diamond dresser (diamond count # 100) manufactured by Asahi Diamond Industrial Co., Ltd. The polishing pad surface was polished for 60 minutes at a dresser rotation speed of 100 rpm, a polishing pad rotation speed of 50 rpm, and a dresser load of 40 N while flowing at a speed of 5 mm (hereinafter, the unevenness and shavings on the polishing surface were removed from the polishing surface. The process of rotating the dresser to remove the surface on the polishing side to remove it is called “conditioning”). After conditioning the polishing pad by the above-described method, polishing slurry (polishing slurry “PL-7101” manufactured by Fujimi Incorporated Co., Ltd., ultrapure water and 31% concentration hydrogen peroxide water mixed at a ratio of 1: 2: 0.09) at a rate of 300 mL / min. The silicon wafer with inch copper film was polished for 60 seconds.
Thereafter, conditioning was performed for 60 seconds at a dresser rotation speed of 100 rpm, a polishing pad rotation speed of 40 rpm, and a dresser load of 40 N while flowing ultrapure water at a rate of 200 mL / min.
Thereafter, the wafers were replaced, and polishing and conditioning were repeated alternately, and a total of 10 wafers were polished.

For the tenth wafer polished above, the film thickness of the copper film before polishing and after polishing was measured 81 points within the wafer surface, and the polishing rate at each point was determined.
The average value of the 81 polishing rates was defined as the polishing rate (R), and the polishing uniformity was evaluated by the non-uniformity determined by the formula [non-uniformity (%) = (σ / R) × 100].
The smaller the non-uniformity value, the more uniformly the copper film is polished within the wafer surface, indicating better polishing uniformity.

[Example 1]
(1) Production of thermoplastic polyurethane Polytetramethylene glycol having a number average molecular weight of 2000 [abbreviation: PTMG], poly (2-methyl-1,8-octamethylene-co-nonamethylene adipate) diol having a number average molecular weight of 2000 [abbreviation: PNOA: molar ratio of nonamethylene unit to 2-methyl-1,8-octamethylene unit = 7 to 3], 1,4-cyclohexanedimethanol [abbreviation: CHDM], 1,4-butanediol [abbreviation: BD] And 4,4′-diphenylmethane diisocyanate [abbreviation: MDI] with a mass ratio of PTMG: PNOA: CHDM: BD: MDI of 24.5: 10.5: 5.0: 12.5: 47.5 Using such a ratio, it is continuously fed to a twin-screw extruder that rotates coaxially by a metering pump to perform continuous melt polymerization. It was prepared a thermoplastic polyurethane.
The resulting thermoplastic polyurethane melt was continuously extruded into water in a strand form, and then chopped with a pelletizer to obtain pellets. The pellets were dehumidified and dried at 70 ° C. for 20 hours to produce a thermoplastic polyurethane.

(2) Formation of polishing layer The thermoplastic polyurethane obtained above was charged into a single screw extruder, extruded from a T-die, a 2.0 mm thick sheet was formed, and then the surface of the obtained sheet was ground. Thus, a uniform sheet having a thickness of 1.3 mm was obtained. In accordance with JIS K 7311, the D hardness measured at a measurement temperature of 25 ° C. was 63.
Next, this sheet is cut into a circular shape having a diameter of 81 cm, and concentric grooves (cross-sectional shape is rectangular) having a groove width of 0.6 mm, a groove depth of 0.8 mm, and a land width of 5.5 mm on one surface thereof, It was formed by cutting.
Next, a foamed polyurethane sheet (A hardness 46) having a thickness of 1.2 mm is bonded to the surface opposite to the surface on which concentric grooves are formed (the surface on the polishing side) with an adhesive tape to produce a laminated structure polishing pad. did.

  The results of evaluating the polishing performance are shown in Table 1. In addition, Tables 1 and 2 also show the results of evaluating the values of the respective parts and the polishing performance in Examples 2 to 7 and Comparative Examples 1 to 4 shown below.

[Example 2]
A polishing pad having a laminated structure was prepared in the same manner as in Example 1 except that the land width of the concentric grooves was 6.3 mm, and the polishing performance was evaluated.

Example 3
A polishing pad having a laminated structure was prepared in the same manner as in Example 1 except that the groove width of the concentric grooves was 0.4 mm and the land width was 5.2 mm, and the polishing performance was evaluated.

Example 4
A laminated polishing pad was prepared in the same manner as in Example 1 except that the groove width of the concentric grooves was 0.4 mm, the groove depth was 0.8 mm, and the land width was 6.4 mm, and the polishing performance was evaluated. did.

Example 5
A polishing pad having a laminated structure was prepared in the same manner as in Example 1 except that the groove width of the concentric grooves was 0.35 mm and the land width was 5.4 mm, and the polishing performance was evaluated.

Example 6
A polishing pad having a laminated structure was prepared in the same manner as in Example 1 except that the groove width of the concentric grooves was 0.3 mm, and the polishing performance was evaluated.

Example 7
A polishing pad having a laminated structure was prepared in the same manner as in Example 1 except that the groove width of the concentric grooves was 0.5 mm and the land width was 6.0 mm, and the polishing performance was evaluated.

[Comparative Example 1]
A polishing pad having a laminated structure was prepared in the same manner as in Example 1 except that the groove width of the concentric grooves was 0.1 mm, and the polishing performance was evaluated.

[Comparative Example 2]
A polishing pad having a laminated structure was prepared in the same manner as in Example 1 except that the groove width of the concentric grooves was 1.0 mm, and the polishing performance was evaluated.

[Comparative Example 3]
A polishing pad having a laminated structure was prepared in the same manner as in Example 1 except that the groove width of the concentric grooves was 0.5 mm and the land width was 7.5 mm, and the polishing performance was evaluated.

[Comparative Example 4]
A polishing pad having a laminated structure was prepared in the same manner as in Example 1 except that the groove width of the concentric grooves was 0.5 mm and the land width was 1.5 mm, and the polishing performance was evaluated.

  From the results of Table 1 above, the polishing pads for metal polishing obtained in Examples 1 to 7 satisfying the conditions of the present invention showed a specific increase in polishing rate and good polishing uniformity. On the other hand, in the polishing pad for metal polishing of Comparative Example 1, since the groove width was too narrow, the polishing rate was low and the polishing uniformity was also deteriorated. Further, the polishing pad for metal polishing of Comparative Example 2 also had a low polishing rate and deteriorated polishing uniformity. In the polishing pad for metal polishing of Comparative Example 3, since the land width was too wide, the polishing rate was low and the polishing uniformity was also deteriorated. Further, the polishing pad for metal polishing of Comparative Example 4 also had a low polishing rate and deteriorated polishing uniformity.

Claims (4)

The land width (x) is 5.0 to 7.0 (mm) and the groove width (y) is only a concentric groove having a width of 0.25 to 0.75 (mm), and has a non-foamed structure . Metal film polishing pad. The metal film polishing pad according to claim 1, wherein the land width (x) is 5.1 to 6.8 (mm), and the groove width (y) is 0.29 to 0.71 (mm). . The metal film polishing pad according to claim 1 , comprising a thermoplastic polyurethane. In the metal film polishing method using the metal film polishing pad according to any one of claims 1 to 3 , the rotational speed of the surface plate to which the metal film polishing pad is attached is 50 to 120 (rpm). Metal film polishing method.