Abrading – Machine – Rotary tool
Reexamination Certificate
2002-05-28
2004-02-24
Rose, Robert A. (Department: 3723)
Abrading
Machine
Rotary tool
C451S388000, C451S289000
Reexamination Certificate
active
06695687
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates in general to an apparatus for chemical-mechanical polishing (CMP) of semiconductor substrates for polishing and flattening a surface of the semiconductor substrate. More particularly, the invention relates to a semiconductor substrate holder for holding the semiconductor substrate to be polished whereby the substrate is held and pressed against a polishing pad. The holder contains a main body for holding the semiconductor substrate in a predetermined position relative to the main body. The main body has a base plate and a ring-shaped elevation provided thereon. A pressurizing device is provided for pressurizing the semiconductor substrate from inside the ring-shaped elevation towards the underlying polishing pad.
In the processing of integrated semiconductor wafers and integrated circuits many process steps require a subsequent flattening or planarizing of the semiconductor topographical structure. Therefore it is highly important to provide a method and an apparatus for polishing and flattening the surface of the semiconductor substrate to a high flatness degree.
In order to achieve the extent of planarity and thickness homogeneity necessary to produce ultra high-density integrated circuits, chemical-mechanical planarization processes are employed. The chemical-mechanical planarization or polishing (CMP) processes involve in general pressing a semiconductor wafer against a moving polishing surface that contains an abrasive material or is wetted with a chemically reactive, abrasive slurry. The slurries are either basic or acidic and may contain alumina, silica or other abrasive particles. Typically, the polishing surface is a planar pad made of a soft, porous material, such as polyurethane foam or non-woven fabric, and the pad is generally mounted on a planar platen.
A major obstacle for the achievement of a high planarity and a high thickness homogeneity of the surface of a layer to be polished lies in the fact that either the semiconductor substrate below the layer to be polished or the polishing pad may contain thickness or surface variations due to warping or waviness of the wafer or the polishing pad. These variations would normally lead to corresponding local variations in the pressure applied to the semiconductor substrate during polishing and thus to local variations of polishing rates. The construction of a semiconductor substrate holder should therefore provide facilities that would allow to compensate for the inhomogeneities.
A simple configuration of the substrate holder includes a rigid metal plate for pressing the semiconductor substrate against the polishing pad. The standard construction, however, does not allow for any compensation measures for inhomogeneities of substrate thickness or polishing pad thickness.
In U.S. Pat. No. 6,012,964 a semiconductor substrate holder (carrier) is described which is constituted by a housing, a carrier base, a retainer ring, a sheet supporter, a hard sheet and a soft backing sheet. The sheet supporter is formed by a supporter body portion having an air opening communicating with an air outlet/inlet of the carrier base, a flexible diaphragm and an outer ring. A wafer is uniformly pressed by the air pressure in the pressure chamber and fluctuation in the force pressing against the outer peripheral rim of the wafer caused by the wear of the retainer ring is countered by the diaphragm. Also presented in this document are embodiments in which holes are formed in the hard sheet and the soft backing sheet in the area of the wafer center by which it becomes possible to apply an additional back pressure for locally enhancing the polishing rate. These embodiments are, however, applicable only in case of specific known thickness variations of the semiconductor substrate and/or the polishing pad.
In U.S. Pat. No. 5,791,973 and U.S. Pat. No. 6,074,289 a substrate holding apparatus is described which contains a rotary shaft, a substrate holding head in the form of a disc which is provided integrally with the lower edge of the rotary shaft, a sealing member in the form of a ring which is made of an elastic material and fastened to the peripheral portion of the lower face of the substrate holding head, and a guiding member in the form of a ring which is fastened to the back face of the substrate holding head to be located outside the sealing member. A fluid under pressure, preferably air, is introduced into a fluid flow path formed in the rotary shaft from one end thereof and supplied to a space from the other end of the fluid flow path so as to form an air cushion on one side of the substrate and to press the substrate against the polishing pad. Due to the fact that the semiconductor substrate can be deformed in accordance with the surface of the polishing pad and/or the semiconductor substrate the semiconductor substrate can be pressed onto the polishing pad with a locally constant contact pressing force so that also the polishing rate is locally constant over the entire wafer. However, with this configuration it is not possible to introduce a specific local polishing profile by a local variation of the pressing force and hence the polishing rate.
The only way to achieve this would be the incorporation of a plurality of chambers to be supplied with fluids of varying pressure that appears too complicated.
In the introductory portion of U.S. Pat. No. 5,791,973 there is further described with respect to FIG. 16 another configuration of a semiconductor substrate holder wherein an elastic polishing pad is adhered to the top surface of a table. The bottom portion of a substrate holding head is formed with a recessed portion. The substrate is solidly supported by a plate-shaped elastic member that can be elastically deformed in the recessed portion of the substrate. The substrate holding head, elastic member and the substrate define a hermetically sealed space into which a gas under controlled pressure is introduced through a gas supply path. The gas under pressure introduced into the hermetically sealed space presses the substrate solidly supported by the elastic member against the polishing pad, so that the pressure on the upper face of the substrate achieves equal polishing. A disadvantage of the embodiment is the rather complicated mechanism of mounting and dismounting the substrate to the elastic member.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a semiconductor substrate holder for chemical-mechanical polishing containing a movable plate which overcomes the above-mentioned disadvantages of the prior art devices of this general type, which allows polishing of a semiconductor surface with excellent uniformity over the entire surface area and which also allows the introduction of a specific wanted polishing profile.
With the foregoing and other objects in view there is provided, in accordance with the invention, a semiconductor substrate holder for holding a semiconductor substrate to be polished by chemical-mechanical polishing (CMP). The semiconductor substrate holder contains a main body for holding the semiconductor substrate in a predetermined position relative to the main body. The main body has a base plate and a ring-shaped elevation with an inner wall extending from the base plate. A pressurizing device is provided for pressurizing the semiconductor substrate from inside the ring-shaped elevation towards an underlying polishing pad. The pressurizing device has a movable plate disposed inside the ring-shaped elevation. The movable plate is mounted to the main body such that the movable plate is movable in a direction toward and away from the semiconductor substrate. A support member is disposed on a portion of the inner wall of the ring-shaped elevation. The support member has a support surface for supporting the semiconductor substrate.
With the semiconductor substrate holder according to the present invention the polishing operation can be performed in two basic operation modes corresponding to two different vertica
Hollatz Mark
Lahnor Peter
Greenberg Laurence A.
Infineon - Technologies AG
Locher Ralph E.
Rose Robert A.
Stemer Werner H.
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