Source: http://www.google.com/patents/US7121938?dq=6437692
Timestamp: 2016-10-23 16:24:19
Document Index: 671531942

Matched Legal Cases: ['arts 80', 'arts 80', 'arts 80', 'arts 80', 'arts 80', 'arts 80', 'art 80', 'art 80']

Patent US7121938 - Polishing pad and method of fabricating semiconductor substrate using the pad - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsIt is provided a polishing pad of novel construction capable of controlling actively and efficiently a slurry flow during polishing a surface of a semiconductor substrate, such as a wafer, thus making it possible to precisely and stably performing a desired polishing process. Onto a surface of a pad...http://www.google.com/patents/US7121938?utm_source=gb-gplus-sharePatent US7121938 - Polishing pad and method of fabricating semiconductor substrate using the padAdvanced Patent SearchTry the new Google Patents, with machine-classified Google Scholar results, and Japanese and South Korean patents.Publication numberUS7121938 B2Publication typeGrantApplication numberUS 10/482,740PCT numberPCT/JP2003/004189Publication dateOct 17, 2006Filing dateApr 1, 2003Priority dateApr 3, 2002Fee statusLapsedAlso published asCN1647255A, CN100356515C, US20040198056, US20070032182, WO2003083918A1Publication number10482740, 482740, PCT/2003/4189, PCT/JP/2003/004189, PCT/JP/2003/04189, PCT/JP/3/004189, PCT/JP/3/04189, PCT/JP2003/004189, PCT/JP2003/04189, PCT/JP2003004189, PCT/JP200304189, PCT/JP3/004189, PCT/JP3/04189, PCT/JP3004189, PCT/JP304189, US 7121938 B2, US 7121938B2, US-B2-7121938, US7121938 B2, US7121938B2InventorsTatsutoshi SuzukiOriginal AssigneeToho Engineering Kabushiki KaishaExport CitationBiBTeX, EndNote, RefManPatent Citations (11), Referenced by (24), Classifications (21), Legal Events (5) External Links: USPTO, USPTO Assignment, EspacenetPolishing pad and method of fabricating semiconductor substrate using the pad
3. A polishing pad according to claim 1, wherein said slant groove measures 0.005–2.0 mm in a width dimension.
In the process of fabricating semiconductor devices such as LSI devices, conventionally, a lamination of various kinds of thin layers including metallic layers and insulative layers are formed on a silicon wafer, for example, through various processing steps. As one major for polishing or planarizing an outer or upper most surface of the wafer to obtain a substrate surface having a high degree of planarity, chemical mechanical polishing (hereinafter referred to as “CMP”) is known, wherein a thin disk-shaped polishing pad of synthetic resin material or expanded material thereof may be employed, and the polishing pad and the wafer (semiconductor substrate) are made to undergo relative rotation while supplying between the wafer and the pad a slurry consisting of fine abrasive particles and a suitable kind of liquid, for effect polishing.
In order to meet a great demand for a highly integrated, high-precision semiconductor device, it is required to produce multiple layers of intricate patterns of extremely fine lines. To meet this end, the CMP process is required to ensure (a) “polishing precision”, i.e. the ability to polish an entire wafer surface with highly precise planarization, and (b) “polishing efficiency”, i.e. the ability to polish a wafer with high process efficiency. Higher circuit densities seen in semiconductor devices in recent years have raised the bar still further as regards these two capabilities.
However, notwithstanding the use of these polishing pads of conventional design, it is still exceedingly difficult to achieve both “polishing precision” and “polishing efficiency” at levels adequate to meet requirements. In the field of super LSI in particular, metallic interconnect or metallization width of lines formed on the wafer (line patterns with metal line) is extremely narrow, i.e., 0.18 μm or smaller, and accordingly the surface must be polished to a very low degree of surface roughness (Rz), i.e. 0.25 μm or smaller. Also, the use of recently soft metal such as cooper and gold for metallization has entered the stage of research directed to practical application. In view of the above, still further improvements are required to polishing pads in order to achieve satisfactory levels of polishing precision and polishing efficiency.
The present invention has been developed in order to solve the above-described problems, and it is therefore one object of this invention to provide a polishing pad of novel construction whereby the surface of a semiconductor substrate or similar material can be processed with consistently high levels of “polishing precision” and “polishing efficiency” using a CMP or similar process.
It is another object of the present invention to provide a novel semiconductor substrate fabrication method employing a polishing pad, whereby in a semiconductor fabrication process employing a suitable method such as CMP for polishing the substrate surface, the object semiconductor substrate may be fabricated with consistently high levels of “precision” and “efficiency”.
An eighth mode of the invention relating to a polishing pad provides a polishing pad according to any one of first to seventh modes, wherein said slant groove measures 0.005–2.0 mm in width dimension. In this mode, the slant groove width dimension is made sufficiently small, making it possible to achieve a high degree of polishing precision. In this regard, since the side walls of the slant groove incline, problems tending to occur as a result of the small-width slant groove, such as retaining of slurry within the groove or clogging of the groove by polishing residues, can be effectively avoided, thereby effectively and consistently providing the desired degree of polishing precision.
Groove depth dimension and diametric pitch are not particularly limited, and may be selected appropriately with reference to the material of the polishing pad, the material being polished, properties of the slurry being used, the required degree of polishing precision, and other parameters. The groove depth dimension is typically 0.1–2.0 mm, and particularly in the case of substantially circular grooves extending in the circumferential direction, the slant grooves will be formed substantially parallel at intervals of 0.1–3.0 mm apart. In the case of linear grooves, even if grooves are spaced widely away from one another, localized action on an article being polished due to rotation of the polishing pad is less intense than with circular grooves extending in the circumferential direction. Therefore, it is a simple matter to achieve good polishing characteristics even with larger groove spacing, which preferably may be appropriately set within a wide range of 0.1 to 60.0 mm, for example.
A ninth mode of the first aspect of the invention provides a polishing pad according to any one of first to eighth modes, wherein the slant groove is provided with a groove dimensional error of 5% or smaller. According to this mode, the slant groove is formed with a dimensional accuracy enhanced to a predetermined value, permitting the polishing pad to polish a semiconductor substrate with minimized variation in polishing pressure exerted through the polishing pad on the semiconductor substrate. For instance, the polishing pad according to this mode is capable of minimizing variation in polishing pressure to a theoretical target value, e.g., in an order of 2% or smaller. By the term “groove dimensional error”, meant is not only a groove width, but also a groove pitch and a groove depth.
A third mode of the invention relating to a cutting tool provides a cutting tool characterized by that the cutting tool includes a groove cutting tool for turning a groove extending substantially circumferentially into said surface of said pad substrate, while rotating said pad substrate about a center axis thereof, said groove cutting tool having at least one cutting part having a tooth width of 0.005–3.0 mm, a wedge angle of 15–35 degrees, and a front clearance angle of 65–45 degreee.
The use of the cutting tool of construction according to the present mode makes it possible to produce more advantageously a groove (including a slant groove) into the polishing pad, and to improve the precision and shape consistency of the inside surfaces of the groove. Particularly, since the front clearance angle measures 65–45 degrees, when cutting a groove with a small radius of curvature sufficiently close to the inner diameter of the pad substrate, catching of the sides of the cutting part can be reduced or avoided, so that the outer diameter side of the groove can be produced with high dimensional precision or accuracy, making it possible to produce substantially uniform grooves extending substantially in the circumferential direction over a wide surface area on the polishing pad with high precision.
Preferably, the groove-machining cutting tool is arranged to have a tooth width of 0.005–2.0 mm. Such a narrow tool is employed. In the groove machining tool according to the present invention, it is advantageous to employ a multi-edged tool having a plurality of cutting parts arrayed in the tooth width direction, whereby a plurality of concentric grooves can be turned efficiently. In the case of a multi-edged tool having a plurality of cutting parts arranged in the tooth width direction, the cutting parts may be arranged at the same pitch as the desired groove pitch (spacing), or alternatively may be arranged with a wide gap in between by making the cutting part pitch some suitable multiple (two times or greater) of the desired groove pitch. The latter multi edged tool may be used for cutting a plurality of grooves all at once, while being offset in small increments depending on the groove pitch.
As a specific example, shown in enlarged longitudinal cross section in FIG. 3, the groove 16 has an inner diameter side wall (hereinafter referred to as “inside wall”) 20 and an outer diameter side wall (hereinafter referred to as “outside wall”) 22, both of which are slant faces slant by a predetermined angle α(α=intersect angle with a straight line parallel to the center axis 18) with respect to the center axis 18 around the entire circumference. That is, in the groove 16 shown in FIG. 3, the inside wall 20 and the outside wall 22 are mutually parallel faces, with the groove 16 having a substantially constant width dimension B over the entirety of groove 16, not only in the circumferential direction but also the depthwise direction thereof. The groove 16 going towards the opening thereof moves gradually further away toward the outer diameter side from the center axis 18 to open diagonally outward in the diametric direction of pad substrate 12.
The polishing pad 10 having the groove 16 is used for polishing a wafer or the like in the conventional manner. More specifically, as shown in FIG. 4, for example, the polishing pad 10 is arranged on the support face of a rotating plate (support plate) of a polishing apparatus (not shown), and clamped against the rotating plate by air-induced negative pressure suction or other means. Next, while rotating the polishing pad 10 about its center axis 18, a wafer 24 is juxtaposed against the surface 14 for polishing. Generally, during this polishing process, an abrasive liquid (hereinafter referred to as “slurry”) 28 is supplied to opposing the faces, i.e. the surface 14 of the polishing pad 10 and the process face 26 of the wafer 24, like the conventional manner, while also rotating the wafer 24 itself about its center axis. The slurry 28 is supplied, for example, to the surface of the polishing pad 10 from the vicinity of the central portion of the polishing pad 10 so as to be spread out over the surface of the polishing pad 10 due to the action of centrifugal force created by rotation of polishing pad 10 about the center axis 12.
As shown in FIG. 6, this simulation was carried out on a specimen of the polishing pad 10 having grooves 16 1.0 mm deep formed extending parallel to each other at 1.0 mm intervals. With the bottom end face of the polishing pad 10 fixed and a pressing load of 5.0 gf/mm2 applied to a wafer 24 placed on the surface 14 of the polishing pad 10, a polishing process was simulated according to a finite element method, by slightly moving the wafer 24 at a relative speed of 583.3 mm/s towards the horizontal direction (rightward in FIG. 6) with respect to the polishing pad 10. This simulation was conducted with five different values for groove 16 slant angle α: α=0� (opening parallel to pad center axis); α=−5� (opening slant towards pad center axis); α=−10�; α=+5� (opening slant towards pad outer diameter), and α=+10�. Results of the simulation are shown in graphs of FIGS. 7–11, respectively.
As is apparent from the results presented in FIGS. 7–11, by varying the slant angle of the grooves 16, it is possible to significantly and efficiently adjust contact pressure of the polishing pad 10 against the wafer 24 during polishing. Experiments conducted by the inventors has revealed that the greater the maximum value for contact pressure, i.e., the more positive the value of groove 16 slant angle α within a predetermined range and the greater the slant towards pad outer diameter, the greater the improvement in polishing efficiency. This may be attributed to an edge effect or a bite like function of the polishing pad. Thus, by adjusting the slant angle of the grooves 16 of the polishing pad 10 in consideration of the polishing pad and wafer material, required precision, and the like, it is possible to achieve both suitable polishing precision and polishing efficiency. Also, this achieved excellent polishing precision and polishing efficiency can be maintained at consistent level, without being largely diminished by wear of the polishing pad or by dressing.
Referring next to FIGS. 12–18, there will be described grooves 16 formed in polishing pads according to another specific embodiments of the invention. In the interest of brevity and simplification, the same reference numerals as used in the first embodiment will be used in the following embodiments to identify the corresponding components, and redundant description of these components will not be provided.
With the polishing pad 50 provided with such grooves 52, differences in the level of centrifugal force exerted on the slurry 28 in the grooves 52, the grooves 52—due to difference in peripheral speed at points different distances away from the center axis of rotation 18—can be reduced or eliminated through adjustment of the slant angle of the grooves 52, so that uniform effect on the part of slant grooves 52 can be achieved over the entire surface 14 of the polishing pad 50.
Where a groove pattern composed of a plurality of grooves extending linearly as exemplified above, the pattern, pitch, number of lines etc. produced on the polishing pad 10 substrate 12 can be selected arbitrarily. Specifically, it would be possible as well to employ first, second, and third groove groupings each composed of a plurality of grooves 62 a, 62 b, 62 c extending in mutually different directions, as shown in FIG. 17 and FIG. 18, and the density of the mesh pattern formed by this plurality of groove groupings can be selected arbitrarily as will be apparent from FIGS. 17–18. While not shown in the drawings, a plurality of linear grooves 62 composed of a single or a plurality of groupings may be produced on the surface of polishing pad 10 in combination with grooves 16 extending in the circumferential direction as shown in FIG. 1 or 2.
As specifically illustrated in FIGS. 20–21, the desired grooves 16, 42, 52, 56, or 62 can be produced using a cutting tool having a multi-edged tool tip 82 with cutting parts 80 corresponding in shape to the desired grooves arranged at suitable pitch at the distal edge, for example. This multi-edged tool tip 82 is exchangeably fixed to a suitable tool holder 84, to cut the surface 14 of the pad substrate 12.
As shown in FIG. 21( a), the tool holder 84 has an ion blowing passage 90 straightly extending through an interior part thereof, while to the front side of the tool holder 84 toward which the cutting parts 80 protrude, a vacuum suction apparatus 92 may be attached. Described in detail, The upper end of the ion blowing passage 90 is connectable to an external air blower for neutralizing static charge, while the lower end of the ion blowing passage 90 is open on the back side of the cutting parts 80 in a direction in which the cutting parts 80 protrude. Ions provided together with compression air from the external air blower (hereinafter referred to as “ion blow”) are discharged downwardly with a slant angle substantially equal to that of the cutting parts 80. According to this arrangement, the ion blow is directly discharged to the pad substrate 12 cut by the cutting parts 80 and resultant cut-parts (chips), effectively preventing these members being statically charged, thus advantageously preventing the chips being adhered to the pad substrate, especially to the walls of the grooves, due to the static charge. Preferably, the direction of discharge of the ion blow is slant toward the front in a cutting direction. Namely, the chips can be transmitted to the front of the multi edged tool tip 82 through the gaps between blades of the multi edged tool tip 82, at the same time when the groove is cut onto the pad substrate. This arrangement permits a further effective prevention of adhere of the chips to the inside of the groove. In this regards, a variety of known air blower for neutralizing static charge may be adoptable as the external air blower connectable to the ion blowing passage 90.
A specific exemplary preferred configuration for a cutting part 80 for use in a cutting process is shown in FIG. 25, wherein a tooth width is held within the range of 0.005–3.0 mm, corresponding to the width B of the groove to be produced, a blade angle β is held within a range of 15–35 degrees, and a front clearance angle γ is held within a range of 65–45 degrees. Hence, as the pad substrate 12 is somewhat more elastic than metal or similar materials, if the front clearance angle γ is less than 45�, the back portion of the blade 80 will tend to interfere with the pad substrate 12 during cutting. This making it difficult to obtain well-machined groove faces. Particularly when cutting a circumferential groove as shown in FIG. 1, the back portion of the blade 80 tends to interfere with the pad substrate 12 during cutting of the inside diameter portion having a small radius of curvature, and it will therefore be important to set cutting part 80 the front clearance angle γ to within the range of 65–45 degrees. Where the front clearance angle γ exceeds 65 degrees or the blade angle β is outside the range of 15–35 degrees, it becomes difficult to assure an adequate rake angle θ of the blade front surface, making it difficult to achieve good cutting performance, or to ensure adequate durability and strength.
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