JP3612708B2 - Grooved polishing cloth, workpiece polishing method and polishing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polishing process for a workpiece, particularly a semiconductor wafer (hereinafter, sometimes simply referred to as a wafer), and more specifically, a grooved polishing cloth used for workpiece polishing and a workpiece polishing using the grooved polishing cloth. The present invention relates to a method and a polishing apparatus.
[0002]
[Related technologies]
Recently, CMP (Chemical Mechanical Polishing) technology is used in the manufacturing process of the most advanced devices. This technique is used to remove an extra film forming portion generated in element isolation formation, capacitor formation, etc. in a semiconductor element manufacturing process.
[0003]
In the silicon wafer manufacturing process, this CMP technique is sometimes used for the purpose of removing unevenness (generally called nanotopology or nanotopography) having a wavelength of several mm to several hundred μm existing on the wafer surface. is there. In such polishing (copy polishing), it is important to make the polishing allowance uniform within the wafer surface.
[0004]
The CMP that is usually performed is as follows. A workpiece such as a semiconductor wafer as a material to be polished is held by a polishing head to which a soft sheet (generally called a backing pad) formed of foamed urethane or the like is attached. The wafer is surrounded by a ring-shaped member (generally called a retainer ring) formed of a resin such as glass epoxy, and the ring-shaped member prevents the workpiece from popping out during polishing.
[0005]
A polishing surface plate is installed facing the polishing head, and a polishing cloth is attached to the surface of the polishing surface plate. At the time of polishing, the wafer held by the polishing head is brought into contact with the polishing cloth, and at the same time, an abrasive is supplied onto the polishing cloth, and the wafer is applied by applying a load to the wafer while rotating the polishing surface plate and the polishing head. To polish.
[0006]
In this CMP, a hard polishing cloth having a Shore D hardness of 50 or more is generally used in order to increase the efficiency of removing excess film forming portions and improving the efficiency of nanotopology. The Shore D hardness is a hardness measured by a Shore hardness tester D type, which is a type of repulsive Katasa tester, and conforms to JIS Z2246.
[0007]
In the hard polishing cloth as described above, the polishing agent generally has poor wraparound. This is because foaming is smaller than that of a soft abrasive cloth (for example, a nonwoven cloth type abrasive cloth). In particular, when the workpiece is increased in size, the influence of poor wraparound of the abrasive becomes noticeable, leading to deterioration of the flatness of the workpiece. Therefore, in order to improve the wraparound of the abrasive, it has been proposed to form grooves such as lattices, spirals, radials, etc. on the surface of the hard polishing cloth (for example, Japanese Patent Application Laid-Open No. 2001-1255, No. 2000-42901, JP-A-10-277721, JP-A-8-11051, etc.). That is, as shown in FIG. 13, the conventional polishing cloth has a groove-free polishing cloth 29 having a flat surface without forming grooves on the surface of the polishing cloth main body P, and a groove G on the surface of the polishing cloth main body P. It is roughly classified into the formed grooved polishing cloth 30. In FIG. 13B, M is the groove pitch.
[0008]
[Problems to be solved by the invention]
When a workpiece is polished with such a grooved hard polishing cloth, in the wafer manufacturing process, a shape abnormality such as a surface sag occurs at the outer periphery of the workpiece, and when the step is corrected in the device manufacturing process, the outer periphery of the workpiece is sag. Will be caused. This is because the polishing allowance varies within the workpiece surface during polishing, but the polishing allowance particularly at the outer periphery of the wafer is different. For this reason, when the workpiece is a semiconductor wafer, there is a problem that the quality required for the most advanced product, that is, the quality that satisfies both the nanotopology and the flatness cannot be obtained.
[0009]
In addition, in the above proposal, measures mainly aiming at uniform wrapping of the polishing agent are disclosed, but it is impossible to completely prevent the abnormal shape of the outer periphery of the wafer only by these measures. It was.
[0010]
The present invention has been made in view of the above-described problems. When polishing a workpiece, particularly a semiconductor wafer, the wafer manufacturing process improves the peripheral sag of the workpiece and performs polishing with improved nanotopology level. Furthermore, there are provided a grooved polishing cloth capable of correcting a step without causing a peripheral sag of the work even in a device manufacturing process, and a work polishing method and a polishing apparatus using the grooved polishing cloth. For the purpose.
[0011]
[Means for Solving the Problems]
According to a first aspect of the grooved polishing cloth of the present invention, a groove formed on the surface of the polishing cloth main body is a grooved polishing cloth used for polishing a workpiece, and the surface of the polishing cloth main body, the side surface of the groove, The angle formed by is such that it is greater than the chamfering angle of the workpiece.
[0012]
According to a second aspect of the grooved polishing cloth of the present invention, in the grooved polishing cloth used for polishing a groove formed on the surface of the polishing cloth main body, at least a depth of 0. 0 from the surface of the polishing cloth main body. The cross-sectional shape of the side surface of the groove at a location shallower than 2 mm is linear, and the angle formed by the surface of the polishing cloth body and the side surface of the groove is equal to or greater than the chamfering angle of the workpiece.
[0013]
When the polishing cloth is pressed by the workpiece, the thickness of the portion with and without the workpiece varies due to the compression of the polishing cloth. As shown in FIG. 14, the cross-sectional shape of the groove G formed in the polishing pad body P is, for example, U-shaped (FIG. 14A) or V-shaped with a deep groove depth (FIG. 14B). In this case, when the workpiece hits the side surface G1 of the groove G, a large local pressure is applied to the outermost peripheral portion of the workpiece, resulting in surface sagging at the outermost peripheral portion of the workpiece. That is, the polishing allowance becomes large at the outermost periphery of the workpiece.
[0014]
Further, when the workpiece is held on the backing pad, a phenomenon that the workpiece escapes to the backing pad side occurs, and therefore a portion with less polishing allowance is generated on the inner side than the above-described surface sag generation portion. That is, a shape abnormality such as undulation occurs on the outer periphery of the workpiece.
[0015]
In FIG. 14, P1 is the surface of the polishing pad body, D is the groove depth, E is the groove width, and θp is the angle formed by the polishing pad body surface P1 and the side surface G1 of the groove. FIG. 14A shows the case where θp = about 90 ° and FIG. 14B shows the case where θp = about 135 °.
[0016]
On the other hand, when the polishing cloth of the present invention is used, the contact resistance between the outermost peripheral part of the workpiece and the side surface of the groove is reduced, and abnormal shapes such as surface sag in the outer peripheral part of the work can be suppressed. In particular, as shown in FIG. 1, the angle θp formed by the surface of the polishing cloth body and the side surface of the groove is the chamfering angle θw of the workpiece (in this specification, as shown in FIG. 12, the surface F1 of the workpiece W When the angle formed by the chamfered surface F2 is referred to as a chamfer angle or more), the shape abnormality at the outer periphery of the workpiece is improved in a singular point.
[0017]
In the first and second aspects of the grooved polishing cloth of the present invention, the groove is particularly preferably a V-shaped groove having a linear cross-sectional shape and satisfying the above conditions. This is because the groove can be easily formed if it is V-shaped.
[0018]
According to a third aspect of the grooved abrasive cloth of the present invention, in the grooved abrasive cloth used for polishing a groove formed on the surface of the abrasive cloth body, at least a depth of 0. 0 from the surface of the abrasive cloth body. The cross-sectional shape of the side surface of the groove in a place shallower than 2 mm is curved, and the angle formed by the surface of the polishing cloth body and the tangent line of the side surface of the groove is equal to or greater than the chamfering angle of the workpiece. To do.
[0019]
In this way, the angle θt (FIG. 3B) formed by the tangent to all points on the side surface of the groove and the surface of the polishing cloth body at a location shallower than the depth of 0.2 mm from the polishing cloth body surface is equal to or greater than the chamfering angle θw. That is, that is, if the minimum value of the angle θt formed by the tangent to the groove side surface and the surface of the polishing cloth body in the portion shallower than the depth of 0.2 mm is equal to or greater than the chamfering angle θw, The contact resistance with the side surface of the groove is reduced, and shape abnormality such as sag in the outer periphery of the workpiece can be suppressed. In the third aspect of the grooved abrasive cloth of the present invention, the cross-sectional shape of the groove can be U-shaped, and a shape satisfying the above conditions can be adopted.
[0020]
The angle θp formed by the surface of the polishing cloth main body and the side surface of the groove or the angle θt formed by the tangent to the side surface of the groove and the surface of the polishing cloth main body is preferably 160 ° or more. Most wafers have a chamfering of about 20 ° (the angle between the chamfered surface and the wafer surface, ie, the chamfering angle θw of about 160 °). If the angle is set to 160 ° or more, most wafers are polished without problems. Because it can. The upper limits of the angles θp and θt are not particularly limited, but are preferably within 175 °. Specifically, these angles θp and θt are determined as appropriate by setting the necessary groove depth in consideration of the wraparound of the abrasive.
[0021]
The groove width on the surface of the polishing cloth body is not particularly limited, but is preferably 3 mm or less. If the groove width exceeds 3 mm, the outer peripheral part of the workpiece may fall into the groove due to elastic deformation of the workpiece, and there is a possibility that a shape abnormality such as outer peripheral sag may be caused by a factor other than the above-described factors.
[0022]
The effect of the cross-sectional shape of the groove can be obtained with any polishing cloth, but a particularly remarkable effect is exhibited with a polishing cloth having a Shore D hardness of 50 or more. This is because when the polishing cloth is soft (for example, in the case of a non-woven fabric), the impact caused by the contact between the outer periphery of the workpiece and the groove of the polishing cloth can be absorbed to some extent on the polishing cloth side. This is because the impact that can be absorbed is small.
[0023]
The workpiece polishing method of the present invention is a workpiece polishing method in which a workpiece held on a workpiece holding plate is pressed against a polishing cloth affixed to a polishing surface plate with a predetermined polishing load, thereby polishing one surface of the workpiece. The grooved polishing cloth of the present invention described above is used as the polishing cloth. By polishing the workpiece with the polishing method of the present invention, it is possible to prevent abnormal shapes on the outer periphery of the workpiece. This is particularly effective in copying polishing that makes the polishing allowance uniform. In addition, the use of a hard abrasive cloth also improves the nanotopology. Therefore, when the workpiece is a semiconductor wafer, a wafer required for a state-of-the-art device that requires both flatness and nanotopology can be manufactured by the polishing method of the present invention.
[0024]
The workpiece polishing apparatus of the present invention polishes one side of the workpiece by pressing the workpiece held by the workpiece holding plate constituting the polishing head against a polishing cloth affixed to the polishing surface plate with a predetermined polishing load. A polishing apparatus for a workpiece to be processed, wherein the above-described grooved polishing cloth of the present invention is used as the polishing cloth. By polishing the workpiece with the polishing apparatus of the present invention, for example, when the workpiece is a semiconductor wafer, a wafer that can be used in the most advanced device can be obtained.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below in more detail with reference to FIGS. 1 to 7 in the accompanying drawings. However, the illustrated examples are illustrative only, and various embodiments are possible without departing from the technical idea of the present invention. Needless to say, it is possible to modify this.
[0026]
FIG. 1 is a cross-sectional explanatory view of an essential part showing an example of a grooved polishing cloth having a V-shaped groove of the present invention. FIG. 2 is an explanatory cross-sectional view of a principal part showing various modifications of the V-shaped groove of FIG. 1, wherein (a) is a first modification, (b) is a second modification, and (c) is a third modification. Respectively. FIGS. 3A and 3B are cross-sectional explanatory views showing an example of a grooved polishing cloth having a U-shaped groove according to the present invention. FIG. 3A is an overall view, and FIG. 3B is an enlarged view of a circle A portion in FIG. It is. FIG. 4 is an explanatory cross-sectional view of a main part showing various modifications of the U-shaped groove of FIG. 3, wherein (a) is a first modification and (b) is a second modification. FIG. 5 is a cross-sectional explanatory view of a main part showing various modified examples of the groove shape in the grooved polishing cloth having a groove formed by combining the V-shape and the U-shape of the present invention, and (a) is a first modification. An example, (b) shows a second modification, and (c) shows a third modification. FIG. 6 is an overall plan view of the grooved polishing cloth of the present invention, wherein (a) shows a first groove pattern, (b) shows a second groove pattern, and (c) shows a third groove pattern. 7A and 7B are cross-sectional explanatory views showing an example of the polishing apparatus of the present invention. FIG. 7A is an overall view and FIG. 7B is an enlarged view of the polishing head.
[0027]
In FIG. 1, reference numeral 30A denotes a grooved polishing cloth according to the present invention, and a groove VG is formed on the surface P1 of the polishing cloth main body P. The groove VG is cut in the vertical direction so as to be orthogonal to the groove VG (as shown in FIG. 6A, when the groove pattern is a straight line, the direction orthogonal to the groove G and FIGS. 6B and 6C). As shown in FIG. 1, when the groove pattern is a curve, the cross-sectional shape when the groove pattern is cut so as to form a cut surface B in a direction perpendicular to the tangent LS of the curve is V-shaped as shown in FIG. It is formed to be a mold. In this case, the cross-sectional shape of the side surface VG1 of the groove VG is linear. It is essential that the angle θp formed by the surface P1 of the polishing pad main body P and the side surface VG1 of the groove VG is equal to or greater than the chamfering angle θw (FIG. 12) of the workpiece W. In the present specification, as described above, an angle θw formed by the surface F1 and the chamfered surface F2 of the workpiece W is defined as a chamfer angle (FIG. 12).
[0028]
That is, if the chamfering angle θw of the workpiece W is, for example, 160 °, the angle θp formed by the polishing pad body surface P1 and the side surface VG1 of the groove VG is also set to 160 ° or more. For example, in the case of the V-shaped groove VG described above, the groove depth d is set to about 0.5 mm with respect to the groove width E of 3 mm. In the present specification, as described above, an angle θw formed by the surface F1 and the chamfered surface F2 of the workpiece W is defined as a chamfer angle (FIG. 12).
[0029]
Various shapes can be adopted as the shape of the V-shaped groove VG described above. FIG. 2 shows a modification of the V-shaped groove VG. The polishing pad 30B shown in FIG. 2A is an example in which θp = about 160 ° and the groove width E is 2 mm. The polishing pad 30C shown in FIG. 2B is an example in which θp = about 160 ° and the groove width E is 3 mm. In the case of FIG. 2B, the groove depth d can be formed deeper than 2 mm. The polishing pad 30D shown in FIG. 2C is an example in which θp> 160 °. In the case of FIG. 2C, the groove depth d is shallow.
[0030]
The groove shape of the grooved polishing cloth of the present invention can adopt various shapes in addition to the V-shape described above, and will be described next. FIG. 3 shows a U-shaped grooved polishing cloth 30E. In the figure, a groove UG having a U-shaped cross-section is formed on the surface P1 of the polishing pad body P. In this case, the cross-sectional shape of the side surface UG1 of the groove UG in contact with the polishing pad main body P is a curved shape, and the polishing pad main body P in a place shallower than the surface P1 of the polishing pad main body P is at least a depth d = 0.2 mm. The angle θt formed by the surface P1 of the groove tangent to the tangent L of the side surface UG1 of the groove UG needs to be equal to or greater than the chamfering angle θw (FIG. 12) of the workpiece W. That is, if the chamfering angle θw of the workpiece W is, for example, 160 °, the angle θt is set to 160 ° or more.
[0031]
Various shapes can be adopted as the shape of the U-shaped groove UG. FIG. 4 shows a modification of the U-shaped groove UG. The polishing pad 30F shown in FIG. 4A is an example in which θt> about 160 ° and the lateral width is 2 mm. The angle θt formed by the tangent L at the position of the groove depth d = 0.2 mm and the surface P1 of the polishing pad main body P is approximately 160 °. The polishing pad 30G shown in FIG. 4B is an example in which θp> 160 ° and the lateral width is 3 mm. In this example, the angle θt> approximately 160 ° up to a position deeper than the groove depth d = 0.2 mm.
[0032]
The groove shape of the grooved polishing cloth of the present invention adopts various groove shapes in addition to the V-shape and U-shape described above. For example, as shown in FIG. The shape can also be a combination of molds. In the groove VUG of the polishing pad 30H shown in FIG. 5A, from the surface P1 of the polishing pad main body P to the groove depth d = 0.2 mm, it is linear (similar to the groove side surface of the V-shaped groove). A concave portion UG2 (similar to the central portion of the U-shaped groove) is formed in a portion deeper than the groove depth d = 0.2 mm, that is, in the central portion of the groove VUG. FIG. 5A shows an example in which θp = about 160 ° and the groove width E is 2 mm.
[0033]
In the groove VUG of the polishing pad 30I shown in FIG. 5B, the groove VUG is linearly formed from the surface P1 of the polishing pad main body P to the position where the groove depth d exceeds 0.2 mm, and the central portion of the groove VUG. A recess UG2 is formed in the upper surface. FIG. 5B shows an example in which θp> 160 ° and the groove width E is 2 mm.
[0034]
The groove shape where the groove depth d is deeper than 0.2 mm does not have a special effect on the polishing effect of the grooved polishing cloth of the present invention, so as shown in FIGS. 5 (a) and 5 (b). , May be U-shaped, or other shapes. For example, as in the groove VUG of the polishing pad 30J shown in FIG. 5 (c), the shape of the recess UG2 at the center of the groove VUG can be a semicircular shape. In FIG. 5C, other groove shapes are the same as those in FIG. The recess UG2 shown in FIGS. 5 (a), (b), (c), FIGS. 4 (a), (b), and FIG. 3 (a) has an action of retaining the abrasive, so by devising its shape The amount of retention of the abrasive can be adjusted.
[0035]
The groove pattern on the surface P1 of the polishing cloth body P of the grooved polishing cloth of the present invention is not particularly limited, and a lattice pattern is formed on the surface P1 of the polishing cloth body P as in the grooved polishing cloth 30K shown in FIG. It is also possible to form a concentric groove G on the surface P1 of the polishing pad main body P as in the grooved polishing cloth 30L shown in FIG. Furthermore, a spiral groove G may be formed on the surface P1 of the polishing pad main body P as in the grooved polishing cloth 30M shown in FIG. 6C, or grooves of other shapes may be formed. Needless to say.
[0036]
The method of forming the groove shape of the grooved polishing cloth 30A to 30M of the present invention is not particularly limited. For example, the surface P1 of the polishing cloth main body P with a processing machine having a blade having the same shape as the groove shape. It can be formed by shaving.
[0037]
The material of the abrasive cloth body is not particularly limited, and for example, urethane foam abrasive cloth, nonwoven cloth type abrasive cloth, or the like can be used. Further, a laminated abrasive cloth, for example, an abrasive cloth in which foamed urethane and a nonwoven fabric are laminated in two layers, or an abrasive cloth in which an intermediate layer is added to form three layers can be used. In particular, when the polishing surface has a Shore D hardness of 50 or more, the effect of forming grooves in the grooved polishing cloth of the present invention is significant.
[0038]
The grooved polishing cloth 30A to 30M of the present invention can be used as a polishing cloth of a conventionally used polishing apparatus, but the grooved polishing cloth of the present invention is used as the polishing cloth in FIGS. 7 (a) and 7 (b). An example of the polishing apparatus of the present invention used was shown.
[0039]
The basic configuration of the polishing apparatus 10 of the present invention shown in FIG. 7A is the same as that of a conventionally known polishing apparatus, and there is no particular limitation. However, the grooved polishing cloths 30A to 30M of the present invention (in the illustrated example) 30A) is used as an abrasive cloth.
[0040]
The polishing apparatus 10 of the present invention is configured as an apparatus for polishing one surface of a workpiece, for example, a wafer W. The polishing apparatus 10 includes a rotating polishing platen 12, a work holding plate 16 mounted on the lower surface of the polishing head 14, and an abrasive supply pipe 18. A grooved polishing cloth 30A of the present invention is attached to the upper surface of the surface plate 12. The surface plate 12 is rotated at a predetermined rotation speed by a rotating shaft 22. The polishing head 14 is rotated by a rotation shaft 15 at a predetermined rotation speed.
[0041]
A backing pad 19 is affixed to the surface of the workpiece holding plate 16, and the workpiece W is held on the workpiece holding plate 16 via the backing pad 19. A retainer ring 17 is provided around the work holding plate 16 to prevent the work W held on the work holding plate 16 from jumping out. The workpiece holding plate 16 is mounted on the lower surface of the polishing head 14 and is rotated by the polishing head 14 and simultaneously presses the workpiece W against the polishing cloth 30A with a predetermined polishing load. The abrasive is supplied onto the grooved abrasive cloth 30A from the abrasive supply pipe 18 at a predetermined flow rate, and the abrasive is supplied between the workpiece W and the abrasive cloth 30A, whereby the work W is polished.
[0042]
More specifically, the work holding plate 16 has a structure as shown in FIG. In FIG. 7B, reference numeral 21 denotes an air supply path, and an air bag rubber sheet is provided by supplying air to an air bag pressurizing region 23 provided inside the work holding plate 16 and above the work holding plate main body 16a. 27, the work holding plate main body 16a supported by the work holding plate 16 in a swingable manner is pressed downward, and the work W can be pressed against the grooved polishing cloth 30A of the surface plate 12 in a pressurized state.
[0043]
The surface of the workpiece W is polished by making sliding contact with the polishing apparatus 10 as described above while supplying the abrasive. By polishing the workpiece W using the polishing apparatus using the grooved polishing cloth of the present invention having the groove shape as described above, the workpiece W with high flatness can be manufactured.
[0044]
【Example】
The present invention will be described more specifically with reference to the following examples. However, it is needless to say that these examples are shown by way of illustration and should not be construed in a limited manner.
[0045]
As a wafer to be used as a workpiece to be polished, a silicon mirror polished wafer having a diameter of 200 mm (8 inches) (wafer after primary polishing) was used. The angle formed between the chamfered surface of the sample wafer and the wafer surface was 160 °. The sample wafer was polished using a polishing apparatus similar to the apparatus shown in FIG. As basic polishing conditions, polishing pressure: 40 kPa (400 g / cm ² ), Relative speed: 50 m / min, polishing margin: 1 μm, polishing agent: colloidal silica-based polishing agent (pH adjusted to 10.5 by addition of inorganic alkali), backing pad: BP104 (manufactured by Fuji Boseki Co., Ltd.), polishing cloth : Implemented with urethane foam hard polishing cloth (Shore D hardness: 55 °). Unless otherwise specified, the following examples and comparative examples were all polished under the above conditions.
[0046]
In the polishing process using the grooved polishing cloth of the present invention, it is preferable that the polishing allowance distribution is uniform within the wafer surface. Therefore, in the method for evaluating the effect of polishing using the grooved polishing cloth of the present invention, the wafer shape before and after polishing is measured with a capacitance-type flatness measuring instrument (ULTRAGAGE 9700 manufactured by ADE), and the wafer surface is measured. The polishing allowance distribution (excluding the outer periphery of 2 mm) was compared.
[0047]
FIG. 8 shows a method for judging the peripheral sag of the polished wafer. 8A is an explanatory diagram showing measurement points on the polished wafer W, and FIG. 8B is a schematic explanatory diagram showing a polishing margin distribution observed along the wafer diameter line DL in FIG. 8A. Polishing allowance [value of wafer shape before and after polishing (thickness, etc., measured difference in shape before and after polishing at the same point) and setting the wafer diameter direction on the horizontal axis, This shows the distribution of polishing allowance in the thickness direction). As shown in FIG. 8 (a), a large number (35 points) of measurement points of the polishing allowance in the wafer diameter direction are taken at the outer peripheral edge, and an average polishing allowance distribution is obtained to obtain an outer periphery of 10 mm (from the outer periphery toward the center). The difference between the polishing allowances at a point of 10 mm) and an outer periphery of 2 mm (a point of 2 mm from the outer periphery toward the center) was determined and used as a sagging amount. That is, the wafer cross-sectional shape [FIG. 8B] of the polishing allowance distribution was analyzed, and the sagging amount in the range of 2 to 10 mm on the outer periphery was evaluated.
[0048]
The nanotopography on the wafer surface was also evaluated. Nanotopography is unevenness having a wavelength of about 0.1 mm to 20 mm and an amplitude of about several nm to 100 nm. As an evaluation method thereof, a square having a side of about 0.1 mm to 10 mm, or a diameter of 0.1 mm. In a region of a circular block range of about 1 mm to 10 mm (this range is called WINDOW SIZE etc.), the height difference (PV: Peak to Valley) of the unevenness on the wafer surface is evaluated.
[0049]
This PV value is also called Nanotopography Height or the like. As nanotopography, it is desired that the maximum value of the unevenness existing in the evaluated wafer surface is small. Here, a plurality of block ranges were evaluated with a 2 mm square, and the maximum PV value was obtained. If this value was 20 nm or less, it was judged as a good product. In this example, nanotopography was measured with Nanomapper (2 mm × 2 mm square area) manufactured by ADE.
[0050]
(Distribution of polishing allowance depending on the presence of grooves and the cross-sectional shape of grooves)
(Examples 1 and 2 and Comparative Examples 1 and 2)
The distribution of the polishing allowance due to the difference in the cross-sectional shape of the groove and the grooved abrasive cloth was confirmed. The groove pattern of the grooved polishing cloth was a lattice pattern as shown in FIG. 6A, and the pitch from groove to groove was 20 mm.
[0051]
As a polishing cloth, a grooved polishing cloth having a V-shaped groove having a groove width of 3 mm and a depth of 0.5 mm (the angle θp formed by the surface of the polishing cloth main body and the groove side surface is 160 °) [FIG. 2B; Example 1 ] U-shaped groove having a groove width of 2 mm and a depth of 0.5 mm (however, the angle θt formed between the tangent to the groove side surface and the surface of the polishing cloth body at a location shallower than the depth of 0.2 mm from the polishing cloth body surface is 160 ° or more) [FIG. 4 (a); Example 2], groove-free polishing cloth (Comparative Example 1), grooved polishing cloth of U-shaped groove having a groove width of 2 mm and a depth of 0.5 mm [FIG. ); Comparative Example 2] was used.
[0052]
As a result of comparing the polishing allowance distribution in the wafer surface (excluding the outer periphery of 2 mm), in Example 1, the distribution of the polishing allowance was substantially uniform in the wafer surface as shown in FIG. The maximum PV value of nanotopography was about 9 nm. As a result, the wafer is polished without sagging and the nanotopography is improved. Also in Example 2, as in Example 1, the polishing allowance was uniform within the wafer surface.
[0053]
In Comparative Example 1, since the abrasive wraparound is poor, it can be seen that the distribution of the polishing allowance has a concave shape that decreases at the center of the wafer as shown in FIG. 10, and as a result, the wafer shape becomes convex. It became a trend. The maximum PV value of nanotopography was about 12 nm.
[0054]
In Comparative Example 2, as shown in FIG. 11, the distribution of the polishing allowance was uniform as a whole, but there was variation in the allowance at the outermost peripheral portion. That is, although it was the tendency to maintain the front shape, the polishing amount increased at the outermost periphery (so-called outer periphery sag), and a decrease in the polishing amount (outer periphery splash) was observed on the inner side. The maximum PV value of nanotopography was about 13 nm.
[0055]
As described above, by polishing the wafer with the polishing apparatus provided with the grooved polishing cloth of the present invention, it was possible to suppress sagging of the outer peripheral portion of the wafer.
[0056]
(About the effect of groove angle)
(Examples 3 and 4 and Comparative Examples 3 to 5)
The shape of the surface of the polishing cloth body was a lattice pattern, and grooves were formed at a pitch of 20 mm. Polishing was performed by changing the angles of the U-shape and V-shape. The groove depth is 0.5 mm. The groove shapes are a V-shaped groove with θp = 160 ° (Example 3), a V-shaped groove with θp = 170 ° (Example 4), and a U-shaped groove with θp = 90 ° (FIG. 14A). Comparative Example 3), V-shaped groove with θp = 120 ° (Comparative Example 4), and V-shaped groove with θp = 140 ° (Comparative Example 5).
[0057]
As a result of confirming the sagging amount at the outer peripheral portion of the wafer, no sagging was found in Example 3 (angle θp = 160 °) (the outer sagging amount was 0.02 μm or less). In Example 4 (angle θp = 170 °), the amount of outer peripheral sag was 0.05 μm. The maximum PV value of nanotopography was about 10 ± 2 nm.
[0058]
In Comparative Example 3 (so-called U-shaped groove), an outer sagging amount of 0.20 μm was generated. In Comparative Example 4 (angle θp = 120 °), an outer sagging amount of 0.13 μm was generated. In Comparative Example 5 (angle θp = 140 °), an outer peripheral sag amount of 0.10 μm was generated. The maximum PV value of nanotopography was about 12 ± 2 nm.
[0059]
As described above, when the angle θp is smaller than the chamfering angle θw, the contact between the groove side surface and the wafer outer periphery becomes strong, and the effect of suppressing the outer peripheral sag becomes insufficient. In addition, when the angle θp = 170 °, the groove width becomes as wide as about 5 mm when the groove depth is set to 0.5 mm. Therefore, a phenomenon that the outer peripheral portion of the wafer falls into the groove occurs. There is a tendency that the sagging of the outer periphery of a good one is somewhat worse.
[0060]
(Examples 5 and 6 and Comparative Examples 6 and 7)
Next, an example of chamfering the U-shaped groove will be shown. The edge portion of the U-shaped groove is chamfered, and the angle θt formed by the tangent to the side surface of the groove and the surface of the polishing cloth body is 160 ° (Example 5) and 170 ° (implemented) at a depth shallower than 0.2 mm. Example 6), polishing cloths of 120 ° (Comparative Example 6) and 140 ° (Comparative Example 7) were prepared. The shape of the surface of the polishing cloth body was a lattice pattern, and grooves were formed at a pitch of 20 mm.
[0061]
As a result of checking the sagging of the outer periphery of the wafer, there was no sagging in Example 5 (the sagging amount was 0.02 μm or less), and there was no sagging in Example 6 (the sagging amount was 0.02 μm or less). In the case of 0.15 μm and Comparative Example 7, the sagging amount was 0.10 μm. The maximum PV value of nanotopography was about 11 ± 2 nm.
[0062]
If the angle θt formed between the tangent to the groove side surface and the surface of the polishing pad body is smaller than the chamfering angle θw, the effect of reducing the contact between the wafer outer periphery and the groove side surface becomes insufficient. It is desirable that the angle θt formed between the tangent to the groove side surface and the surface of the polishing pad main body is not less than the chamfering angle θw.
[0063]
In the above-described embodiment, only the example in which the edge portion of the V-shaped groove and the U-shaped groove is chamfered is shown, but if the cross-sectional shape of the groove adopts the technical idea of the grooved polishing cloth of the present invention, It is not limited to the groove shape of each of the embodiments described above. For example, a groove shape combining a V shape and a U shape as shown in FIG. 5 has the same effect.
[0064]
As described above, the groove shape is particularly important for the sagging shape of the wafer (uniformity of polishing allowance distribution), but nanotopography is also important for the grooved polishing cloth of the present invention. When the maximum PV value of nanotopography is 20 nm or less, the surface state is good. However, in both the above examples and comparative examples, the nanotopography is good at 15 nm or less, particularly in the examples, around 10 nm. This is because a hard polishing cloth is used. Nanotopography is also affected by the hardness of the polishing cloth, and the higher the hardness, the greater the improvement effect, but the effect of the groove shape of the grooved polishing cloth of the present invention on a relatively soft polishing cloth is confirmed. The results are shown below.
[0065]
(Effect of polishing cloth hardness)
(Examples 7 and 8)
Among the above polishing conditions, polishing was performed by changing the hardness of the polishing cloth. Specifically, a non-woven polishing cloth (Suba600 manufactured by Rodel Nitta, Asker C hardness: about 70) was used as the polishing cloth. The Asker C hardness is a value measured by an Asker rubber hardness meter C type which is a kind of spring hardness tester. In addition, when measuring with a Shore hardness tester D type in the nonwoven fabric-based abrasive cloth, the measurement terminal (contactor) may be stuck in the gap of the nonwoven fabric, so that the accurate hardness may not be measured. Therefore, it was indicated by Asker C hardness. Moreover, when the polishing cloth of Shore D hardness 55 is measured by Asker C hardness, Asker C hardness is about 95-100 grade. Therefore, the Asker C hardness 70 is approximately 30-50 in terms of Shore D hardness.
[0066]
As the groove shape, a V-shaped groove having a width of 3 mm and a depth of 0.5 mm (FIG. 2B, Example 7), a chamfered U-shaped groove having a width of 2 mm and a depth of 0.5 mm [FIG. The sample wafer was polished using a grooved polishing cloth having a) and Example 8].
[0067]
As a result of confirming the sagging of the outer peripheral portion of the polished wafer, the sagging amount in Example 7 (V-shaped groove) is 0.02 μm or less, and the sagging amount in Example 8 (U-shaped groove) is 0.03 μm. Met. The maximum PV value of nanotopography was about 20 nm.
[0068]
Even with a relatively soft nonwoven fabric-based polishing cloth, the effect of improving the sagging due to the cross-sectional shape of the groove can be seen. It can be seen that the groove shape of the grooved polishing cloth of the present invention is effective in improving sagging. However, the soft abrasive cloth is not as effective as used when using the hard abrasive cloth, and the PV value of the nanotopogee is also increased overall, so in the grooved abrasive cloth of the present invention, the hard abrasive cloth, It is particularly suitable when applied to a polishing cloth having a Shore D hardness of 50 or more.
[0069]
【The invention's effect】
As described above, the polishing apparatus using the grooved polishing cloth of the present invention is used to polish a workpiece, particularly a semiconductor wafer, thereby improving the sagging of the workpiece and improving the nanotopology level in the wafer manufacturing process. Polishing can be performed, and further, step correction can be performed without causing sagging of the outer periphery of the workpiece even in the device manufacturing process. In particular, when the wafer is polished using the grooved polishing cloth of the present invention to which a hard polishing cloth is applied, there is almost no sagging and a polished wafer with a very small maximum PV value of nanotopography can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional explanatory view of an essential part showing an example of a grooved polishing cloth having a V-shaped groove of the present invention.
FIGS. 2A and 2B are cross-sectional explanatory views of main parts showing various modifications of the V-shaped groove of FIG. 1, wherein FIG. 2A is a first modification, FIG. 2B is a second modification, and FIG. Each example is shown.
3A and 3B are cross-sectional explanatory views showing an example of a grooved polishing cloth having a U-shaped groove according to the present invention, in which FIG. 3A is an overall view and FIG. FIG.
FIGS. 4A and 4B are cross-sectional explanatory views of main parts showing various modifications of the U-shaped groove of FIG. 3, wherein FIG. 4A is a first modification, and FIG. 4B is a second modification.
FIGS. 5A and 5B are cross-sectional explanatory views of main parts showing various modifications of groove shapes in a grooved polishing cloth having grooves formed by combining a V shape and a U shape according to the present invention. FIG. A modification, (b) shows a second modification, and (c) shows a third modification.
6A and 6B are overall plan views of a grooved polishing cloth according to the present invention, in which FIG. 6A shows a first groove pattern, FIG. 6B shows a second groove pattern, and FIG. 6C shows a third groove pattern.
FIGS. 7A and 7B are cross-sectional explanatory views showing an example of the polishing apparatus of the present invention. FIG. 7A is an overall view and FIG. 7B is an enlarged view of the polishing head.
FIGS. 8A and 8B are explanatory views showing a method for determining the peripheral sag of a polished wafer in Examples and Comparative Examples, wherein FIG. 8A is a top view of the wafer showing measurement points, and FIG. 8B is along the diameter line of FIG. It is a schematic explanatory drawing showing the observed polishing allowance distribution, where the vertical axis indicates the polishing allowance and the horizontal axis indicates the wafer diameter direction, and shows the polishing allowance distribution in the wafer cross-sectional direction.
9 is a graph showing a polishing allowance distribution in a wafer surface in Example 1. FIG.
10 is a graph showing a polishing allowance distribution in a wafer surface in Comparative Example 1. FIG.
11 is a graph showing a polishing margin distribution in a wafer surface in Comparative Example 2. FIG.
FIG. 12 is an explanatory diagram showing a chamfer angle of a workpiece.
FIGS. 13A and 13B are cross-sectional explanatory views showing a main part of a conventional polishing cloth, in which FIG. 13A shows a grooveless polishing cloth and FIG. 13B shows a grooved polishing cloth.
FIGS. 14A and 14B are cross-sectional explanatory views of the main part showing the groove shape of a conventional grooved polishing cloth, wherein FIG. 14A shows a U-shaped groove and FIG. 14B shows a V-shaped groove.
[Explanation of symbols]
10: Polishing device, 12: Polishing platen, 14: Polishing head, 15: Rotating shaft, 16: Work holding plate, 16a: Work holding plate body, 17: Retainer ring, 18: Abrasive supply pipe, 19: Backing pad 21: Air supply path, 22: Rotating shaft, 23: Air bag pressurizing area, 27: Air bag rubber sheet, 29: Non-grooved polishing cloth, 30, 31A, 31B: Conventional grooved polishing cloth, 30A to 30M : Grooved polishing cloth of the present invention, D, d: groove depth, E: groove width, G, UG, VG, VUG: groove, G1, UG1, VG1: groove side surface, L, LS: tangent, P: polishing Cloth body, P1: surface of polishing cloth body, UG2: recess, W: work (wafer).

Claims (11)

In a grooved polishing cloth having a groove formed on the surface of the polishing cloth body and used for polishing the workpiece, an angle formed between the surface of the polishing cloth body and the side surface of the groove is equal to or greater than a chamfering angle of the workpiece. A grooved polishing cloth characterized by being provided. In a grooved polishing cloth having grooves formed on the surface of the polishing cloth body and used for polishing a workpiece, the cross-sectional shape of the side surface of the groove at a location shallower than the depth of 0.2 mm from the surface of the polishing cloth body A grooved polishing cloth, wherein the angle between the surface of the polishing cloth body and the side surface of the groove is equal to or greater than the chamfering angle of the workpiece. The grooved abrasive cloth according to claim 1 or 2, wherein a cross-sectional shape of the groove is V-shaped. The grooved abrasive cloth according to any one of claims 1 to 3, wherein an angle formed between a surface of the abrasive cloth body and a side surface of the groove is 160 ° or more. In a grooved polishing cloth having grooves formed on the surface of the polishing cloth body and used for polishing a workpiece, the cross-sectional shape of the side surface of the groove at a location shallower than the depth of 0.2 mm from the surface of the polishing cloth body A grooved polishing cloth, wherein the angle between the surface of the polishing cloth body and the tangent to the side surface of the groove is equal to or greater than the chamfering angle of the workpiece. 6. The grooved polishing cloth according to claim 5, wherein the groove has a U-shaped cross section. The grooved polishing cloth according to claim 5 or 6, wherein an angle formed by a surface of the polishing cloth main body and a tangent to a side surface of the groove is 160 ° or more. The grooved polishing cloth according to any one of claims 1 to 7, wherein a concave portion for adjusting an abrasive stagnation is provided at a central portion of the groove. The grooved abrasive cloth according to any one of claims 1 to 8, wherein the hardness of the abrasive cloth body is 50 or more in Shore D hardness. A work polishing method for polishing a surface of a work by pressing a work held on a work holding plate against a polishing cloth affixed to a polishing surface plate with a predetermined polishing load. Item 10. A method for polishing a workpiece, wherein the grooved polishing cloth according to any one of Items 1 to 9 is used. This is a workpiece polishing apparatus that applies a polishing process to one surface of a workpiece by pressing the workpiece held on a workpiece holding plate constituting the polishing head against a polishing cloth affixed to a polishing surface plate with a predetermined polishing load. A polishing apparatus for a workpiece, wherein the polishing cloth according to any one of claims 1 to 9 is used as the polishing cloth.

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