JP2007027166A - Method of manufacturing semiconductor device and apparatus for manufacturing semiconductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To extend the exchange life of a retainer ring by changing the shape of the retainer ring in a chemical and mechanical polishing process in the manufacture of a semiconductor device. <P>SOLUTION: The retainer ring 24, on which a taper is provided such that plate thickness is progressively increased from an outer diameter side 26 to an inner diameter side 27, is mounted from the beginning of the polishing on a base mounting part 23 of a polishing head 20. The foregoing taper is provided making an allowance for a fact that the inner diameter side 27 is worn unevenly to become thinner than the outer diameter side 26 as the chemical and mechanical polishing advances. Hereby, the exchange life of the retainer ring 24 is prolonged. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is a technique related to the manufacture of a semiconductor device, and particularly an effective technique for extending the replacement life of retainer rings in a polishing process in chemical mechanical polishing (CMP).

  The technology described below has been studied by the present inventors in completing the present invention, and the outline thereof is as follows.

  In manufacturing a semiconductor device, a process for polishing a semiconductor wafer flatly and accurately is required. In particular, in the recent demand for higher integration of semiconductor devices, it is indispensable to realize more advanced planarization. As the planarization technique, a chemical mechanical polishing technique is used.

  In such chemical mechanical polishing, the uniformity of the polishing amount within the wafer surface is important. In particular, ensuring uniformity on the edge side of the semiconductor wafer is a problem. The uniformity of the polishing amount on the edge portion side is greatly influenced by the surface shape of the retainer ring (also called retainer). Since the retainer ring surface is polished together with the polishing of the semiconductor wafer, the unevenness of the retainer ring related to the holding of the semiconductor wafer has a delicate influence.

  That is, undulations opposite to the undulations on the lower surface of the retainer ring appear at the edge of the semiconductor wafer. Therefore, flatness management is required for the retainer ring, and periodic replacement is required.

Patent Document 1 discloses a configuration for providing an appropriate gradient to the retainer ring by providing an inclination adjusting means. The inclination adjusting means includes a screw hole provided in the retainer ring holder, an adjustment bolt that is screwed into the screw hole, a contact plate that abuts the tip of the adjustment bolt so as to be flush with the upper surface of the retainer ring, and the like. ing. By adjusting the inclination difference between the inner peripheral side edge and the outer peripheral side edge of the lower surface of the retainer ring to 0.1 mm, for example, by this inclination adjusting means, uneven wear of the edge portion can be effectively prevented. It is stated.
Japanese Patent Laid-Open No. 2005-11999

  However, the present inventor has found that the technique provided with the tilt adjusting means has the following problems.

  That is, as described above, the tilt adjusting means is a mechanism that is adjusted by adjusting screws that are screwed into a plurality of screw holes provided in the retainer ring holder. However, since it is actually a fine mechanism, the adjustment can be sufficiently performed. Often not. Further, there is no description as to how much and how much the tilt adjustment provided on the retainer ring should be performed, and the retainer ring adjustment based on the difference in tilt of the lower surface of the retainer ring may be 0.1 mm. It is only described.

  In the above configuration, the replacement life of the retainer ring to be used is not particularly mentioned, but it is expected that the replacement life is extended by preventing uneven wear of the retainer ring. However, in order to prevent uneven wear of the retainer ring, adjusting each time with the tilt adjusting means is complicated and difficult to employ on site.

  Therefore, the present inventor considered that the replacement life of the retainer ring could be extended with a simpler configuration.

  It has been found that the retainer ring wears and deforms with the number of polished semiconductor wafers. For this reason, the polishing rate of the edge portion changes, and a difference occurs in the polishing amount distribution in the surface of the semiconductor wafer. That is, due to uneven wear of the retainer ring surface, the surface pressure of the pad near the retainer ring applied to the semiconductor wafer changes, and as a result, the polishing rate of the edge portion of the semiconductor wafer varies.

  At present, the replacement life of the retainer ring of the chemical mechanical polishing apparatus is exchanged based on the fact that the uniformity of the polishing amount on the semiconductor wafer deteriorates. The uniformity of the polishing amount changes with an increase in the number of polished sheets, but the polishing rate of the edge portion is low when it is new, and the polishing rate is high when it is replaced. Therefore, the retainer ring is replaced when the polishing rate at the time of replacement is higher than a certain value and the uniformity of the polishing amount is out of specification.

  The reason why the polishing rate of the edge portion increases with the increase in the number of polishings depends on the thickness of the retainer ring and the shape of the pad contact surface. In particular, the shape of the pad contact surface of the retainer ring is worn more on the inner side than on the outer side due to the characteristics of the polishing head. That is, the inner surface is deformed into a substantially square shape that is worn more than the outer side, so that the pad surface pressure at the edge portion is increased, resulting in a higher polishing rate at the edge portion and edge first.

  Therefore, it was considered that the replacement life could be extended by changing the shape of the retainer ring from the beginning within the range permitted by the polishing amount distribution standard.

  An object of the present invention is to extend a retainer ring replacement cycle in a polishing process by chemical mechanical polishing when manufacturing a semiconductor device from the viewpoint of the shape of the retainer ring.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  That is, assuming the shape of the retainer ring from the beginning that the inner diameter side wears out more quickly than the outer diameter side, in advance, forming a taper so as to become thicker from the outer diameter side toward the inner diameter side from the beginning of polishing, The replacement life was extended.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  In the present invention, since the retainer ring is provided with a taper that gradually increases from the outer diameter side toward the inner diameter side from the beginning, it takes time to wear the inner diameter side, which is the replacement time of the retainer ring, from the outer diameter side. . As a result, the replacement life of the retainer ring can be extended.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof may be omitted.

  The present invention relates to a polishing technique by chemical mechanical polishing of a semiconductor wafer, and in particular, can extend the replacement life of a retainer ring of a chemical mechanical polishing apparatus.

(Embodiment 1)
First, a chemical mechanical polishing apparatus as a semiconductor manufacturing apparatus according to the present invention will be described.

  FIG. 1 is an explanatory cross-sectional view schematically showing an outline of a chemical mechanical polishing apparatus. FIG. 2A is a cross-sectional view schematically showing a polishing head of a chemical mechanical polishing apparatus, FIG. 2B is a plan view seen from the pad side of the retainer ring shown in FIG. (A) is the enlarged view of the retainer ring part enclosed with the circle of (a).

  As shown in FIG. 1, the chemical mechanical polishing apparatus (CMP apparatus) 10 is provided with a polishing pad 13 on a surface plate 12 rotated by a motor 11. The polishing surface of the semiconductor wafer W is disposed facing the polishing head 20 rotated by the motor 14 with respect to the surface of the polishing pad 13.

  In addition, a nozzle 15 is provided above the polishing pad 13 so that the slurry S is supplied to the surface of the polishing pad 13. Using the slurry S supplied to the surface of the polishing pad 13 in this way, the polishing surface of the semiconductor wafer W is planarized while rotating the polishing surface of the semiconductor wafer W facing the polishing surface of the polishing pad 13 with each other. I do.

  As shown in FIG. 2A, the polishing head 20 includes a housing hub 21, a housing plate 22, a base mounting portion 23, a retainer ring 24, a flexible film 25 such as a rubber film, and the like. The housing hub 21 or the like is provided with an attachment hole 16 that can be attached to a rotating shaft that is rotated by the motor 14. In such a configuration, the semiconductor wafer W is vacuum-sucked on the mount surface 25a formed of the flexible film 25 and is held by the retainer ring 24 so as not to be removed during polishing.

  In this state, the polishing surface of the semiconductor wafer W is pressed against the polishing pad 13. The state of the retainer ring 24 viewed from the surface of the polishing pad 13 is shown in FIG.

  The retainer ring 24 is formed so that the plate pressure gradually increases from the outer diameter side 26 toward the inner diameter side 27 as shown in a partially enlarged view in FIG. That is, the retainer ring 24 is different from the conventional flat flat shape so that the surface of the retainer ring 24 that contacts the pad 13 surface increases from the outer diameter side 26 toward the inner diameter side 27 of the retainer ring 24. Is tapered. Thus, the retainer ring 24 described in the present embodiment is formed so that the outer diameter side 26 and the inner diameter side 27 have different thicknesses from the beginning.

  In the case shown in FIG. 2 (c), from the beginning, the portion with the smallest plate thickness on the outer diameter side 26 and the portion with the thickest plate thickness on the inner diameter side are, for example, heights of 50 μm or more and 100 μm or less. A difference gradient is provided. The retainer ring 24 in which the side facing the pad 13 is formed thicker on the inner diameter side 27 than on the outer diameter side 26 is attached to the base mounting portion 23.

  On the other hand, the retainer ring attachment surface 23a of the base attachment portion 23 is formed in a horizontal plane that is not provided with a taper. Therefore, since the base mounting surface 24a of the retainer ring 24 is also formed in a horizontal plane, when the retainer ring 24 is mounted on the base mounting portion 23, the outer surface 26 faces the inner surface 27 with respect to the pad 13 surface. Thus, the taper is provided so that the plate thickness gradually increases.

  As a means for attaching the retainer ring 24 to the base attaching portion 23, any means can be adopted as long as it is securely attached to the base attaching portion 23 and the attaching portion does not come out on the surface 24b of the retainer ring 24. For example, it does not matter whether it is attached via an adhesive or using mechanical means such as screwing. Incidentally, in the case shown in FIG. 2 (c), an example in which it is attached via an adhesive is shown.

  For the retainer ring 24 having such a configuration, for example, a resin such as PPS, PEEK, PET, polyethylene, polypropylene, PFA, or PTFE can be used.

  The taper slope provided from the outer diameter side 26 toward the inner diameter side 27 may be set to, for example, 50 μm or more and 100 μm or less as described above. According to the study of the present inventor, when the difference in height is less than 50 μm, the taper effect cannot be surely grasped and may fall within the error range. In addition, when the height difference exceeds 100 μm, it may be assumed that it is out of specification from the viewpoint of uniformity of the polishing amount. Therefore, it was confirmed that it was preferable to set the thickness to 50 μm or more and 100 μm or less, and it was confirmed that stable polishing was possible.

  By adopting such a configuration, the replacement life of the retainer ring 24 can be reliably extended. That is, as shown in FIG. 3A, initially, a taper of 50 μm to 100 μm, for example, is provided so that the plate thickness gradually increases from the outer diameter side 26 toward the inner diameter side 27. Chemical mechanical polishing is started.

  When chemical mechanical polishing is started in the state shown in FIG. 3 (a) and a certain amount of time has elapsed after the start of polishing, the inner diameter side 27, which tends to be chemical mechanical polishing, is shown in FIG. 3 (b). The moment comes when the wearer wears unevenly from the outer diameter side 26 and the surface of the retainer ring 24 becomes flat. That is, the thickness of the inner diameter side 27 that was initially attached is gradually eliminated as the polishing progresses, and finally becomes flat.

  This state is the same as the state in which the flat flat retainer ring is mounted so far, and the replacement life of the retainer ring 24 is extended from the time shown in FIGS. 3A to 3B.

  When the retainer ring 24 in the state of FIG. 3B is further polished, the inner diameter side 27 starts to be worn away from the outer diameter side 26 as shown in FIG. 3C. For example, if the state of uneven wear is 30 μm or more and less than 50 μm than the inner diameter side 27 on the outer diameter side 26, the uniformity of the polishing amount is still ensured within the standard and can be used sufficiently. This is a state in a so-called stable region.

  Thereafter, when the polishing is further continued, as shown in FIG. 3D, uneven wear becomes severe, and the outer diameter side 26 becomes thicker than the inner diameter side 27 by 50 μm or more. When the plate thickness is reached, the uniformity of the polishing amount deviates from the standard. At this point, the retainer ring 24 is replaced. That is, when the edge portion polishing rate increases and the edge first state is reached, the replacement life of the retainer ring 24 is reached.

  4A to 4C show the state of the retainer ring 30 of the conventional chemical mechanical polishing apparatus. That is, as shown in FIG. 4A, when the retainer ring 30 is mounted, the surface of the retainer ring 30 is flat. From this state, chemical mechanical polishing is started, and as shown in FIG. 4B, the inner diameter side 27 wears unevenly from the outer diameter side 26 side. Thereafter, as shown in FIG. 4 (c), the retainer ring 30 is replaced in a state where the inner diameter side 27 is worn by 50 μm or more.

  3A to 3D and 4A to 3C, the surface pressure received from the pad 13 surface on the edge portion side of the semiconductor wafer W is gradually increased as the polishing progresses. This is indicated by an arrow a. The thicker the arrow a, the higher the surface pressure.

  Thus, the replacement time of the retainer ring 30 so far was the start from the state in which the initial mounting state is flat, but in the present invention, from the state in which the amount was added in consideration of partial wear in advance. Since it is a start, the replacement life can be extended accordingly. By the way, the judgment of the replacement time is the same as before.

  The effect of extending the exchange life is apparent from, for example, the profile of the polishing rate in the radial direction from the wafer center in FIG. It can be seen that the arrow indicating the replacement life of the retainer ring 24 (proposed product) is longer than the arrow indicating the replacement life of the retainer ring 30 so far.

  Next, a case where a semiconductor device is manufactured using the chemical mechanical polishing apparatus 10 having the configuration of the retainer ring 24 will be described.

  The chemical mechanical polishing step using the chemical mechanical polishing apparatus 10 having the above-described structure is performed by forming a buried insulating film of a process trench isolation (STI), planarizing an interlayer insulating film, forming a W plug, and Cu damascene. It is used in metal CMP such as forming. As described above, in the semiconductor device manufacturing process, chemical mechanical polishing is used in various situations. In particular, the present invention is a process that requires a long polishing time such as polishing in an oxide film process and a high polishing rate. The effect of extending the replacement life is noticeable.

Therefore, in the following description, the SiO ₂ polishing process used in the configuration of the STI inter-element isolation insulating film will be described as an example. First, as shown in the flowchart showing the method of manufacturing the semiconductor device of FIG. 6, a STI groove forming step of the semiconductor wafer is performed in step S100. That is, after cleaning a silicon wafer, it is exposed to high temperature steam in an oxidation furnace to form SiO ₂ having a required film thickness. Thereafter, a silicon nitride film is formed by chemical vapor deposition (CVD) using silane gas and ammonia gas.

  Thereafter, a photoresist film is formed on the silicon nitride film, and a resist pattern is formed by a photolithography process using a reticle onto which an IC circuit pattern is baked. Using the resist pattern as a mask, the silicon nitride film and the silicon oxide film are sequentially removed by dry etching to form STI grooves on the silicon substrate surface.

Thereafter, the process proceeds to the step of forming a buried insulating oxide film in step S200. First, the remaining resist with oxygen plasma is ashed, washed and removed, and further thermally oxidized with high-temperature steam to form SiO ₂ on the surface of the inner wall of the STI. Thereafter, a thick insulating oxide film for STI filling is formed by chemical vapor deposition using silane gas and oxidizing gas.

  In step S300, the insulating oxide film for embedding STI is polished by chemical mechanical polishing and planarized. In the chemical mechanical polishing apparatus 10 used for polishing, the retainer ring 24 that prevents the semiconductor wafer W vacuum-adsorbed on the mount surface 25a from being detached during polishing is provided from the outer diameter side 26 to the inner diameter side 27 from the beginning of polishing. A plate having a gradually increased thickness and a taper is used.

  In such a state, as shown in FIG. 3A, chemical mechanical polishing is started. As shown in FIG. 3 (b), the retainer ring 24 wears unevenly within the required number of polished sheets, and the inner diameter side 27 becomes thinner than the outer diameter side 26, so that the surface of the pad 13 of the retainer ring 24 becomes smaller. The contact surface becomes flat. Furthermore, if polishing is continued, as shown in FIG. 3D, the inner diameter side 27 becomes 50 μm thinner than the outer diameter side 26, and the retainer ring 24 is replaced at that time. By replacing the retainer ring 24 with a taper so that the plate thickness gradually increases from the outer diameter side 26 toward the inner diameter side 27, the planarization of the STI buried insulating oxide film is continued.

  When the planarization of the required number of STI buried insulating oxide films is completed in this manner, as shown in step S400, the semiconductor wafer W is subjected to further required processes to manufacture the semiconductor device. It will be.

(Embodiment 2)
In the present embodiment, unlike the first embodiment, as shown in FIG. 7A, the retainer ring mounting surface 23a of the base mounting portion 23 is provided with a taper. A taper is provided so that the thickness gradually increases from the outer diameter side 28 toward the inner diameter side 29. For example, a gradient of 50 μm or more and 100 μm or less may be provided.

  On the other hand, the structure of the retainer ring 31 is the same as that of the conventional one, and is formed in a flat plane. When the retainer ring 31 having such a configuration is bonded to the retainer ring mounting surface 23a via an adhesive, a taper that gradually increases from the outer diameter side 26 to the inner diameter side 27 of the retainer ring 31 is provided. For example, a taper of 50 μm or more and 100 μm or less can be easily attached.

  The attachment means of the retainer ring 31 to the retainer ring attachment surface 23a may be attached by mechanical means such as screwing, without using the adhesive.

  By adopting such a configuration, the configuration of the retainer ring 31 as a consumable can be kept flat and flat as before, and the retainer ring 31 is not required to take measures such as a new mold raising. Become.

  The taper provided on the retainer ring mounting surface 23a of the base mounting portion 23 can be configured such that the inner diameter side 29 is gradually thinner than the outer diameter side 28. In this case, the structure of the retainer ring 32 may be formed in a substantially convex shape from the inner diameter side 27 toward the outer diameter side 26 as shown in FIG.

(Embodiment 3)
In the present embodiment, the retainer ring 33 is attached to the base attachment portion 23 via an inclusion such as an O-ring. As shown in FIG. 8, the retainer ring mounting surface 23a of the base mounting portion 23 is provided with O-ring mounting grooves for O-rings 41 and 42 on the outer diameter side 28 and the inner diameter side 29, respectively. The O-ring mounting groove is formed so that the inner diameter side 29 is thicker and the outer diameter side 28 is narrower.

  On the other hand, the retainer ring 33 attached to the base attachment portion 23 is formed in a flat plane, and the same O-ring attachment groove as that provided in the base attachment portion 23 is provided on the base attachment surface 33a side.

  In the O-ring mounting groove having such a configuration, when the O-rings 41 and 42 are interposed, the inner diameter side 27 has a larger gap between the base mounting portion 23 and the retainer ring 33 than the outer diameter side 26. It is configured.

  When the thick O-ring 41 is interposed on the inner diameter side 27 and the thin O-ring 42 is interposed on the outer diameter side 26 and joined to the base mounting portion 23 and the retainer ring 33, the outer diameter side 26 is directed toward the inner diameter side 27. The retainer ring 33 is attached obliquely so as to be gradually lowered. The attachment taper of the retainer ring 33 can be adjusted by adjusting the thickness of the O-rings 41 and 42, and can be set to, for example, 50 μm or more and 100 μm or less.

  In addition, when the base attachment part 23 and the retainer ring 33 were attached via the O-rings 41 and 42 as described above, it was found that the effect of preventing slurry from entering the attachment surface was also obtained.

  In the above configuration, the O-rings 41 and 42 are employed as inclusions. However, the inclusions other than the O-rings are interposed, and the flat flat retainer ring gradually decreases from the outer diameter side 26 toward the inner diameter side 27. You may attach it diagonally.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  For example, when the retainer ring is attached to the base attachment portion, in the above-described embodiment, both the retainer ring attachment surface and the base attachment surface have a planar configuration. You may make it possible to fix both more reliably.

  The present invention can be used in the field of chemical mechanical polishing used in semiconductor manufacturing technology.

It is explanatory drawing which shows typically the structure of one Example of the chemical mechanical polishing apparatus of one embodiment of this invention. (A) is sectional drawing which shows typically the polishing head of a chemical mechanical polishing apparatus, (b) is the top view seen from the pad side of the retainer ring shown to (a), (c) is ( It is an enlarged view of the retainer ring part enclosed with the circle | round | yen of a). (A)-(d) is explanatory drawing which shows typically the process from the time of mounting | wearing of a retainer ring to the time of replacement | exchange. (A)-(c) is explanatory drawing which shows typically the background from the time of the mounting | wearing of a conventional retainer ring to the time of replacement | exchange. It is explanatory drawing which shows the profile of the polishing rate of a radial direction from a wafer center. It is a flowchart which shows one Example of the manufacturing method of the semiconductor device of one embodiment of this invention. (A), (b) is a fragmentary sectional view which shows the modification of a retainer ring part. It is a fragmentary sectional view which shows the modification of a retainer ring part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Chemical mechanical polishing apparatus 11 Motor 12 Surface plate 13 Polishing pad 14 Motor 15 Nozzle 16 Mounting hole 20 Polishing head 21 Housing hub 22 Housing plate 23 Base mounting part 23a Retainer ring mounting surface 24 Retainer ring 24a Base mounting surface 24b Surface 25 Flexible membrane 25a Mount surface 26 Outer diameter side 27 Inner diameter side 28 Outer diameter side 29 Outer diameter side 30 Retainer ring 31 Retainer ring 32 Retainer ring 33 Retainer ring 33a Base mounting surface 41 O ring 42 O ring a Arrow S Slurry S100 Step S200 Step S300 step S400 step

Claims (5)

A method of manufacturing a semiconductor device having a polishing step by chemical mechanical polishing of a semiconductor wafer,
In the polishing step, the retainer ring provided on the periphery of the semiconductor wafer is formed thicker from the outer diameter side to the inner diameter side with respect to the pad surface at the time of the new retainer ring attachment, and the height of the lower surface on the outer diameter side is increased. Is set higher than the height of the lower surface on the inner diameter side. A method of manufacturing a semiconductor device having a polishing step by chemical mechanical polishing of a semiconductor wafer,
In the polishing step, the retainer ring provided on the peripheral edge of the semiconductor wafer is tapered so as to become thicker in the range of 50 μm to 100 μm from the outer diameter side to the inner diameter side with respect to the pad surface from the beginning of polishing. A method for manufacturing a semiconductor device, wherein: A method of manufacturing a semiconductor device having a polishing step by chemical mechanical polishing of a semiconductor wafer,
In the polishing step, the retainer ring mounting surface of the base portion to which the retainer ring provided on the periphery of the semiconductor wafer is attached has a taper that gradually increases from the outer diameter side toward the inner diameter side from the beginning of polishing. A method of manufacturing a semiconductor device. A method of manufacturing a semiconductor device having a polishing step by chemical mechanical polishing of a semiconductor wafer,
In the polishing step, the retainer ring is attached to the base portion to which the retainer ring provided on the peripheral edge of the semiconductor wafer is attached via an inclusion whose inner diameter side is thicker than the outer diameter side. Manufacturing method. A semiconductor manufacturing apparatus for polishing a semiconductor wafer by chemical mechanical polishing,
In the semiconductor manufacturing apparatus, the retainer ring provided on the periphery of the semiconductor wafer is provided with a taper that gradually increases from the outer diameter side toward the inner diameter side with respect to the pad surface from the beginning of polishing. Manufacturing equipment.

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