JP2005342837A - Grinding device and grinding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple grinding device and a grinding method capable of grinding a surface of a grounded element with waviness along the waviness without computer controlling. <P>SOLUTION: The grinding device includes (1) a rotating spindle, (2) a disc holder provided on a lower surface of the rotating spindle, and (3) an elastic pad attached to the disc holder and having (i) a curved end portion, (ii) a disc-shaped flexible plastic sheet attached to the elastic pad and having a diameter slightly larger than that of an elastomer elastic plate, and (iii) a multilayer element stuck to a lower surface of the plastic sheet and made from a sheet grinding wheel including a grinding abrasive layer having a diameter smaller than that of the plastic sheet. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for grinding a surface of a semiconductor and a grinding apparatus used for the machining method. The present invention relates to a grinding apparatus and a grinding method particularly suitable for planarizing a surface of a semiconductor multilayer wiring circuit board in a semiconductor device manufacturing process.

  During the process of forming a high-density semiconductor integrated circuit element (LSI), the surface of the LSI wafer has complex irregularities due to pattern formation of an insulating film or a metal film. As LSI is highly integrated, the unevenness on the surface of the LSI wafer having the unevenness is made finer. To achieve this high integration, the wavelength of the exposure light source has been shortened. As a result, the planarization of the semiconductor circuit board surface has become more and more important due to the shallow depth of focus in the lithography process and the sophistication of the manufacturing process. It is coming.

  As a method for smoothing the surface of the LSI wafer, there has been conventionally a CMP method in which a polishing liquid is slid while pressing a polishing elastic pad against a polishing surface plate while supplying a polishing liquid containing an abrasive, and unevenness is flattened by polishing. It has been adopted.

Since the semiconductor wafer itself is wavy with a unit pitch of several mm to 20 mm at a portion where an integrated circuit is formed and a portion where it is not, for example, a cut portion, and a circuit is formed only on the surface side of the wafer, film stress In many cases, the wafer was warped due to non-uniformity.

When flattening and polishing the unevenness of the warped wafer surface with the CMP, the polishing pressure is high because the CMP pressure is high in the portion along the surface side and the pressure in the valley shape is low. When flattening progresses quickly, and flattening to a low pressure part, the required residual film thickness becomes too thin or disappears in the high pressure part flattened first. To do.

  In order to solve the above problem, a hard and soft two-layer pad is used for CMP in the first problem. That is, a hard layer is in contact with the surface to be processed, and a soft layer is disposed on the back of the hard layer. Thus, the polishing pressure difference between the portion along the surface side and the portion along the valley shape is reduced. However, this method has a problem that the pressure difference cannot be sufficiently relaxed and the entire surface of the large wafer cannot be uniformly flattened.

Further, in the circuit pattern, a region where fine patterns of about 1 μm are integrated and a region where a large pattern of several tens to several hundreds μm is often mixed. If these mixed surfaces are planarized at the same time, the fine pattern region is planarized before the large pattern region, and eventually the large pattern region is not flattened. In fact, no effective solution has been found to alleviate this problem, the difference in flattening speed in the size of patterns and in dense regions.

  An object of the present invention is to provide a grinding apparatus and a grinding method capable of uniformly smoothing the surface of an object to be ground having waviness along the waviness. Another object of the present invention is to provide a simple apparatus and a grinding method capable of grinding the surface of a ground object with waviness along the waviness without computer control. Another object of the present invention is to provide a grinding apparatus and a grinding method in which scratches such as scratches are unlikely to occur on a material to be ground.

  That is, the present invention includes (1) a rotating spindle, (2) a disc holder provided on the lower surface of the rotating spindle, (3) an elastic pad attached to the disc holder and (i) an end formed in a curved shape. (Ii) a disc-like flexible plastic sheet attached to the elastic pad and having a diameter slightly larger than the diameter of the elastomeric elastic plate; (iii) adhered to the lower surface of the plastic sheet and smaller than the diameter of the plastic sheet It is a grinding device including a multilayer body composed of a sheet grindstone including a grinding abrasive layer having a diameter.

The sheet grindstone is preferably embedded in the central portion of the plastic sheet so as to have a thickness substantially equal to that of the sheet.

  Viewed from another aspect, the present invention is (1) a rotating spindle, (2) a disk holder provided on the lower surface of the rotating spindle, (3) attached to the disk holder, and (i) an end is formed in a curved surface shape. (Ii) a disc-shaped plastic sheet attached to the elastic pad and having a diameter slightly larger than the diameter of the elastomeric elastic plate; (iii) pasted on the lower surface of the plastic sheet; A grinding fluid having an oxidizing agent and a metal complexing agent is interposed between the surface of the multilayer grinding body and the surface of the object to be ground by rotating the multilayer grinding body of the grinding machine comprising a multilayer grinding body including a sheet grindstone layer having a small diameter at high speed. And grinding only the extreme surface layer of the object to be ground by scanning the object to be ground.

  The grinding fluid preferably has an oxidizing agent and a metal complexing agent.

  The object to be ground is preferably a semiconductor wafer that requires planarization of the insulating film or metal wiring film during the multilayer wiring formation process.

    With the grinding apparatus and grinding method of the present invention, the surface of an object to be ground with undulation that has not been performed so far can be uniformly smoothed and ground along the undulation. Further, it is possible to provide a simple apparatus and a grinding method that can grind the surface of a ground object with waviness along the waviness without computer control. According to the method of the present invention, it is possible to efficiently grind a semiconductor wafer provided with a metal wiring such as copper. In addition, if the grinding method according to the present invention is used, the integrated circuit in which fine patterns and large patterns are mixed can be speeded up in comparison with the case where the large pattern portion is not ground in the CMP work that is a subsequent finishing process. There is an advantage that the entire surface of the multilayer wiring wafer can be uniformly flattened. In the grinding apparatus and the grinding method of the present invention, since the edge of the sheet grindstone does not contact the wafer surface, there is an advantage that scratches such as scratches are hardly generated on the material to be ground.

  Hereinafter, an embodiment of the apparatus of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic view showing an example of a main part of a grinding apparatus of the present invention. In FIG. 1, 1 is a wheel spindle, 2 is a spindle shaft, 3 is a disk holder, 4 is an elastic pad, 5 is a plastic sheet, and 6 is a sheet grindstone.

  The spindle is driven and rotated by a motor or the like. It is preferable that the tilt angle of the spindle, the rotation speed, and the pressure applied to the wafer fixing plate can be adjusted.

  The disk holder 3 is a disk-shaped component that plays a role of holding a multilayered grinding body, is attached to the spindle 1, and rotates together with the spindle shaft 2. The diameter of the disc holder is preferably equal to that of the elastic pad 4.

The elastic pad 4 is made of a material having a high elasticity, and has a role of arranging the multilayer ground body in parallel with the body to be ground. As a material used for the elastic pad, an elastomer or an elastomer foam can be used. Specific examples of the elastomer include urethane resin, ethylene / propylene rubber, polybutadiene rubber, styrene-butadiene rubber, neoprene rubber, chloroprene rubber, polyester elastomer, and silicone rubber. Among these, polyurethane, particularly polyurethane foam, is preferable because of its excellent elasticity and durability.

The polyurethane foam can be produced by a known casting method, continuous foam molding method or the like. The foam molded product obtained as necessary is sliced into an elastic pad.

As shown in FIG. 1, the elastic pad 4 preferably has a convex shape with a curved end. In the grinding apparatus of the present invention, the size of the pad is desirably in the range of usually 10 to 100 mm, preferably 20 to 50 mm in diameter. The thickness is usually in the range of 1 to 50 mm, preferably 5 to 20 mm.

The elastic pad 4 is fixed to the disc holder 3 with an adhesive. The adhesive is preferably a heat-sensitive or pressure-sensitive adhesive mainly composed of an elastomeric polymer and a tackifier so that the elastic pad can be replaced when it becomes old.

  A plastic sheet 5 is fixed to the lower surface of the elastic pad 4. The material of the plastic sheet is excellent in abrasion resistance and heat resistance, and can be film-molded, such as polyvinyl chloride, polyvinylidene fluoride, polyethersulfone, polystyrene, polyethylene, polytetrafluoroethylene, acrylic resin , Polycarbonate, polyamide, polyester, polyimide or the like can be used alone or in combination. Among these, a polyimide film is preferable because it is excellent in wear resistance and heat resistance and can easily be bonded to a binder of a sheet grindstone.

  The thickness of the plastic sheet needs to be flexible so that it can bend following the unevenness of the material to be ground, and is, for example, in the range of 10 to 1000 μm, particularly 50 to 500 μm. It is preferable.

  The plastic sheet preferably has a disk shape, and its diameter needs to be larger than the diameter of the elastic pad. Further, only the central part of the plastic sheet and the elastic pad is fixed, and the end parts are separated from each other. By adopting such a shape, the plastic sheet can be automatically positioned on the semiconductor wafer at equal intervals with respect to the wafer surface by the hydrodynamic effect of the grinding liquid during the grinding operation.

  In the grinding apparatus of the present invention, a sheet grindstone layer 6 composed of grinding abrasive grains and a binder is fixed to the lower surface of the plastic sheet. The binder and the grinding abrasive grains can form a sheet grindstone layer by, for example, applying a material dissolved in an appropriate solvent to the sheet surface.

Examples of the abrasive grains that can be used in the present invention include diamond, silicon nitride, boron nitride, CBN, silicon carbide, titanium carbide, aluminum oxide, iron oxide, zirconia, garnet, emery, and the like.

The sheet grindstone layer 6 composed of abrasive grains and a binder needs to have a diameter smaller than that of the plastic sheet 5, and by using such a shape, the edge of the sheet grindstone suddenly contacts and cuts the wafer surface. Can be prevented.

  The sheet grindstone layer 6 may be provided as a layer on the lower surface of the plastic sheet 5 as shown in FIG. 1, but as shown in FIG. It is preferable to embed a sheet grindstone as a layer and to make the outer periphery of the plastic sheet and the thickness of the sheet grindstone embedment portion substantially equal. By making such a shape, the contact surface with respect to the wafer surface acts as a surface in which the plastic sheet and the sheet grindstone surface are continuous, and the risk that the edge of the grindstone contacts the wafer surface can be reduced.

  FIG. 2 shows an example of an overall view of the apparatus of the present invention. FIG. 2 is a schematic view showing an example of an overall view of the apparatus of the present invention. As shown in FIG. 2, the grinding apparatus according to the present invention fixes the wafer spindle 12, the grinding wheel 11, the multilayer grinding body, the biaxial stage 14 for moving the wheel spindle / grinding wheel, and the wafer. A wafer holder, a rotary table 15 for rotating the wafer holder, a drive motor for rotating the spindle and wear holder, and the like are provided.

Next, the grinding method of the present invention will be described. FIG. 3 is a schematic view for explaining the grinding method of the present invention. In FIG. 3, 22 is a rotary spindle, 23 is a disk holder, 24 is an elastic pad, 25 is a plastic sheet, 26 is a sheet grindstone, 27 is a grinding fluid, 28 is a wafer, and 29 is a wafer fixing platen.

  The procedure for grinding a semiconductor wafer will be described in sequence. First, the wafer 28 is fixed to the wafer fixing plate 29. On the other hand, a multilayered grinding body comprising the elastic pad 24 / plastic sheet 25 / sheet grindstone 26 is fixed to the disc holder 23 with an adhesive or by vacuum suction. The rotation spindle axis is inclined several degrees from the vertical direction with respect to the wafer surface, and several millimeters from the outer periphery of the plastic sheet are set to face and contact the wafer surface, and the outer peripheral edge of the sheet grindstone is set to contact the wafer surface.

The wafer is rotated by rotating the wafer fixing platen 29. On the other hand, the grinding body is rotated by rotating the spindle. Only the extreme surface of the wafer is ground by scanning and sliding on the wafer while pressing the multilayer grinding body against the wafer.

  In the grinding method of the present invention, the grinding liquid is supplied between the semiconductor wafer and the multilayer grinding body. By supplying the grinding liquid in this grinding process, the plastic sheet of the multilayer grinding body is subjected to hydroplaning phenomenon by the grinding liquid, the viscosity of the grinding liquid from the semiconductor wafer surface to be polished, the relative speed between the plastic sheet and the wafer, A certain gap is automatically formed according to the facing area. Therefore, the semiconductor wafer is deformed along the waviness of the wafer surface, and the grinding liquid is interposed between the semiconductor wafer and the multi-layered grinding body. The distance from the plastic sheet is kept equal. As a result, the abrasive layer of the sheet grindstone comes into contact with the semiconductor wafer surface at equal intervals and with equal pressure, and as a result, the semiconductor wafer is uniformly ground along the surface waviness.

When the edge of the sheet grindstone touches the wafer surface, there is a high possibility of scratching, which would damage the wafer surface deeply due to local grinding stress, but according to the grinding method of the present invention, the edge of the sheet grindstone is on the wafer surface. Since the sheet grindstone is slightly convex toward the wafer surface side in accordance with the deformation of the plastic sheet without contact, it can be ground only at the convex portion having a gentle curvature of the sheet grindstone. The structure of the multilayer grinding body of the present invention is such that this is automatically realized by the hydrodynamic effect.

  When the film to be ground is a Cu film or a metal film on the wafer, the grinding liquid used in the grinding method of the present invention is preferably an aqueous liquid containing an oxidizing agent and a metal complexing agent. Of these, the oxidizing agent instantaneously oxidizes the surface of the metal wiring disposed on the semiconductor wafer to form a metal oxide, embrittles it, and is easily removed by grinding with abrasive grains. On the other hand, the metal complexing agent serves to protect the metal surface so that the ground interface is not further oxidized.

  Examples of the oxidizing agent that can be used as one component of the grinding fluid in the grinding method of the present invention include hydrogen peroxide, potassium permanganate, dimanganese trioxide, chromium oxide, and cerium oxide. Of these, water peroxide is most preferred because it has a high oxidizing capacity and is readily decomposed into water, leaving no residue and not adversely affecting the ground material. The blending amount of the oxidizing agent in the grinding fluid is preferably 0.1 to 20% by weight, particularly 1 to 5% by weight.

  The grinding fluid used in the grinding method of the present invention preferably contains a metal deactivator. Examples of such metal deactivators include benzotriazole, zinc dialkylthiophosphates, and dialkyl selenium. Of these, benzotriazole is most preferable from the viewpoints of cost and environmental impact. The compounding amount of the metal deactivator in the grinding fluid is preferably 0.1 to 10% by weight, particularly 0.5 to 2% by weight.

  The grinding fluid used in the present invention may contain an abrasive. Examples of such an abrasive include colloidal silica, alumina-silica grinding fluid, alumina grinding fluid, cerium grinding fluid, and quinaldic acid grinding fluid. The abrasive can be contained at a concentration of up to 10% by weight.

  According to a preferred aspect of the grinding method of the present invention, by supplying a grinding liquid containing an oxidizing agent, particularly hydrogen peroxide, to a metal surface such as a wafer, the metal surface is oxidized to form a metal oxide. By the grinding operation by the grinding device, the semiconductor part is ground uniformly and equally.

  The semiconductor wafer ground and roughened by the grinding method of the present invention is then polished by a normal CMP technique, that is, chemical mechanical polishing, and finally flattened to a surface having a roughness of submicron order.

EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not restrict | limited to these Examples at all. The surface roughness and level difference of the wafer are measured with a precision step gauge (Alpha-Step manufactured by KLA Tencor).
500) The 3D topograph was measured with an optical interference surface shape measuring instrument (WYKO NT-3300 manufactured by Veeco).

(Example 1)
(apparatus)
The apparatus shown in FIG. 7 was used.
Disc holder diameter: 30mm
Pad material: Polyurethane foam
Diameter: 30mm
Thickness: 5mm
Plastic sheet material: Polyimide
Diameter: 45mm
Thickness: 0.1mm
Abrasive layer material: Diamond + Polyimide resin Average particle diameter of diamond: 5 μm
Diameter: 30mm
Thickness: 0.1mm
Spindle rotation speed: 1000rpm
Angle: 2 degree tilt with respect to the direction of travel
Pressing pressure: 100 grf / cm ²

(To-be-ground)
Wafer material: silicon Surface: 2 μm thick silicon oxide film and copper wiring are formed Groove depth: 1 μm
Diameter: 150mm
Rotation speed: 20rpm
Movement speed: 75mm / min

(Grinding fluid)
Hydrogen peroxide: 30ml / L
Benzotriazole: 10 g / L
Supply amount: 100ml / min

  The grinding result is shown in FIG. 4, and the 3D topograph of the ground sample surface is shown in FIG. It is clear that the order of roughness is around ± 80 nm with respect to a film thickness of 2000 nm, and only the pole surface can be ground uniformly. As can be seen from FIG. 5, the concave portion is not ground and only the flat portion of the convex portion is ground uniformly.

  FIG. 6 shows the flattening characteristics after CMP with and without grinding. Since the projections are roughened by grinding traces, the rough projections have a large surface area and polishing strain remains, so that the polishing selectivity is higher than the depressions during CMP and the planarization efficiency is promoted. I understand.

  The grinding apparatus and grinding method of the present invention are used for ultra-LSI wafers such as silicon, GaAs, GaP, and InP formed with multilayer wiring, precision molds, lenses, liquid crystal panels, photomasks, magnetic disks, and other mechanical grinding. It can be preferably used for grinding a workpiece to be ground.

FIG. 1 is a schematic view showing an example of a grinding apparatus of the present invention. FIG. 2 is a schematic view showing an example of an overall view of the apparatus of the present invention. FIG. 3 is a schematic view for explaining the grinding method of the present invention. FIG. 4 is a graph showing the grinding result in the example of the present invention. FIG. 5 is a 3D topograph showing the grinding result in the example of the present invention. FIG. 6 is a graph showing the flattening characteristics after CMP according to the presence or absence of grinding in the example of the present invention. FIG. 7 is a schematic view showing another example of the grinding apparatus of the present invention.

Explanation of symbols

1: Wheel spindle
2: Spindle shaft 3: Disc holder 4: Elastic pad 5: Plastic sheet 6: Sheet grindstone 11: Polishing wheel 12: Wheel spindle 13: Wafer 14: Biaxial stage 15: Rotary table 22: Rotary spindle 23: Disc holder 24: Elastic pad 25: Plastic sheet 26: Sheet grindstone 27: Grinding liquid 28: Wafer 29: Wafer fixing plate

Claims (5)

  (1) a rotating spindle, (2) a disk holder provided on the lower surface of the rotating spindle, (3) an elastic pad attached to the disk holder (i) an end having a curved surface, and (ii) an elastic pad A disk-shaped flexible plastic sheet having a diameter slightly larger than the diameter of the elastomeric elastic plate, and (iii) a ground abrasive layer having a diameter smaller than the diameter of the plastic sheet, which is adhered to the lower surface of the plastic sheet Grinding device including a multilayer body made of a sheet grindstone including   The grinding apparatus according to claim 1, wherein the sheet grindstone is embedded in the central portion of the plastic sheet so as to have a thickness substantially equal to that of the sheet.   (1) a rotating spindle, (2) a disk holder provided on the lower surface of the rotating spindle, (3) an elastic pad attached to the disk holder (i) an end having a curved surface, and (ii) an elastic pad A disc-shaped plastic sheet with a diameter slightly larger than the diameter of the elastomeric elastic plate, and (iii) multi-layer grinding including a grinding grain layer adhered to the lower surface of the plastic sheet and having a diameter smaller than that of the plastic sheet Grinding only the extreme surface layer of the object to be ground by scanning the surface of the object to be ground with the grinding fluid interposed between the surface of the object to be ground and the surface of the object to be ground. A grinding method characterized by:   The grinding method according to claim 3, wherein the grinding liquid has an oxidizing agent and a metal complexing agent.   The grinding method according to claim 3, wherein the object to be ground is a semiconductor wafer that requires planarization of an insulating film or metal wiring film in the middle of a multilayer wiring formation process.