GB2437264A

GB2437264A - Polishing a substrate surface

Info

Publication number: GB2437264A
Application number: GB0608800A
Authority: GB
Inventors: Eoin O'dea
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-04-18
Filing date: 2006-05-04
Publication date: 2007-10-24
Also published as: IES20060298A2; GB0608800D0

Abstract

An apparatus 10 for polishing a substrate surface, such as a semiconductor wafer or the like, by Chemical Mechanical Planarization (CMP) comprises a rotatable platen 11 which is held against a conical body 13 having a polishing pad 12 which contacts the wafer along a tangential length of the curved surface of the conical body 13. The polishing pad is optionally a belt 12 tensioned over the conical body 13 or a conical pad (42, Fig. 4a) securely mounted to the conical body. The apparatus may include a housing or process vessel to encapsulate substantially the process interface region, particulary where a chemical slurry is used in the polishing media. A method of polishing a substrate, such as a semiconductor wafer, is also disclosed. The method optionally includes immersion of the process interface in polishing media.

Description

AN APPARATUS FOR AND METHOD OF POLISHING A

SEMICONDUCTOR WAFER USING CHEMICAL MECHANICAL

PLANARIZATION

Field of the Invention

The present invention relates to an apparatus for and method of polishing a substrate, usually in the form of a preprepared semiconductor wafer. More particularly, the invention relates to an improved apparatus for and method of chemical mechanical planarization (CMP) of the working surface of a wafer.

It will be appreciated by the skilled reader that, although the present invention is directed to the polishing of semiconductor wafers, the invention may be adapted for other polishing purposes. most particularly for polishing surfaces of optical devices and interface connections.

Backzround to the Invention It is well appreciated by those skilled in the art that it is essential to form clean.

highly polished semiconductor wafers prior to applying the relevant fabrication techniques, for example those normally associated with the formation of microprocessor integrated circuits, such as VSLI. Given that masking, etching.

doping and other steps are now conducted at nanometer scales, it is imperative that contaminants, impurities and polishing debris are removed from the substrate surface.

Before polishing, a high-grade semiconductor substrate. most notably silicon in disc wafer form, is cleaned of any bulk defects such as dust, grease or the like.

The substrate surface is polished using a polishing pad which moves relative to the substrate surface, normally in a circular motion. A polishing compound, generally referred to as a "chemical slurry". is provided to improve the polishing process by increasing the rate at which material may be removed from the substrate surface.

In the description that follows the term "pad" or "polishing pad" is intended to relate to any surface used to achieve the relevant polishing effect. Similarly, the term "substrate" and "wafer" are used interchangeably, although the term "substrate" is intended to indicate a more general application of the invention to materials other than semiconductor wafers.

The primary existing methods of removing material from a substrate surface are generally referred to as orbital and linear belt techniques. These and others will be reviewed briefly below but are generally well known in the art. In each case.

complex manipulation of applied force (pressure) is required in multiple isolated regions across the substrate surface to ensure uniform removal of substrate material.

It will be appreciated by the skilled reader that any improvement in any of the cleaning and polishing stages could have a profound effect on the devices formed on the subject substrate.

It will further be appreciated that the polishing surface of the pad will lose efficiency during the polishing process as slurry and particles of the polished substrate will accumulate thereon. If the spent slurry and waste substrate material is not efficiently removed from the interface of the pad and wafer, a barrier layer will!brm. Normally, due to the relative movement of the pad and wafer, the majority of this material is pushed away from the interface, however, if the polishing pad is relatively small with respect to the total surface area of the wafer.

this waste material will accumulate on the wafer.

To increase the working life of the polishing pad, it is known to either increase the working area of the pad or provide a means of conditioning the polishing pad or pads in use. In an alternative known arrangement, a circular planar pad has a series of groove patterns cut into the polishing surface to direct waste substrate and used slurry material radially outwardly as the pad rotates. A known disadvantage of this arrangement is that the volume of slurry required is increased and, as it is essential to avoid "dry spots" towards the centre of the pad, slurry is often fed through a feed pipe centrally disposed within the pad. These pads are relatively expensive and, although hard wearing, require conditioning between use.

A disadvantage of the known art is that the apparatus are cumbersome and are only suited to specialised workspaces which are ventilated by vacuum extraction methods. There are also significant health and safety risks associated with the slurries and other materials traditionally used in CMP.

Process limitations of existing methods of CMP have been well documented throughout the semiconductor industry. Publications such as "Semiconductor International" and "Semiconductor Manufacturing" tend to quote the current CMP production limitation geometry as being at the 45tm node. The die-yield and uniformity issues on product geometry below 45tm tend to be poor.

The semiconductor industry is currently moving from aluminium (Al) to copper (Cu) based conductor lines, primarily due to its lower electrical resistance.

However, the CMP process step has proven to be a constraint in regard to this transition also. Copper CMP issues such as wafer contamination, corrosion.

scratching, layer delamination and dishing of large copper structures are additional to the existing issues of uniformity and geometry limitation.

One of the major disadvantages of prior CMP apparatus and methodologies is the inherent variation in rotational speeds or. more particularly, surface point velocities encountered at the process interface between the substrate surface and the polishing pad.

In general, the available apparatus used to implement current methods of CMP deliver variable velocity levels. Hence, these CMP apparatus require complicated variable regionalised downforce pressure systems to counteract this velocity variance. The following outlines the fundamentals of such other CMP methodologies.

Orbital CMP is the most popular methodology currently used. To implement this a flat substrate or wafer surface is rotated with downward pressure against a larger rotating circular abrasive pad onto which a physically and chemically abrasive/corrosive fluid, the "slurry". is applied. Variable polishing pad or platen speed and direction of rotation is used to ensure material removal uniformity is good. Additionally,complicated control of force (pressure) actuators is required to create variable and/or concentric pressure zones across the wafer surface.

With Linear Belt CMP a flat substrate surface is rotated, again with downward pressure, against a rotating linear belt onto which the polishing media or slurry is applied. To ensure material removal uniformity is good, significant effort is required to control concentric pressure zones across the wafer surface.

By way of historical reference, Roller CMP uses the rotation of a wafer against one or more rotating rollers onto which the polishing slurry is applied. As with the previously mentioned methodologies, concentric pressure zones are sought.

using complex control algorithms, across the wafer surface to ensure material removal uniformity.

There are known solutions to above problems. however, many of these solutions have disadvantages in themselves.

Japanese Patent Publication No. JP 10-0158 10 (1998) to Canon KK and Japanese Patent Publication No. JP 2003-173992 to Hitachi Ltd disclose proposed solutions

to the prior art.

In JP 10-015810. a CMP method is disclosed in which the slurry is fed from a supply nozzle onto a substrate surface presented in an upwardly facing orientation on a rotating horizontal platen. A conical polishing pad is brought to bear on a portion of the large diameter substrate wafer and the slurry supply to the process interface is said to be efficient, resulting in homogeneous grinding of the substrate.

The size of the polishing pad relative to the wafer is also relevant and varies in the disclosures of the established art. In some instances, the polishing pad has a significantly smaller surface area than the surface to be polished and the amount of movement required of the pad during polishing is relatively large. Where the pad and wafer are of more equal sizes, the range of relative movement required is significantly less.

Another problem associated with a relatively smaller polishing pad is that the polishing efficiency diminishes with time as the profile of the pad changes. One of the causes of this is the build-up of slurry on the pad.

In JP 2003-173992, a CMP apparatus for polishing semiconductor wafers during VLSI fabrication is disclosed, the apparatus having a conical head which is rotated about a vertical axis and a substrate jig which is brought into contact with the angled polishing surface of the significantly larger polishing head. The jig is reciprocated in a direction normal to the contact line of the substrate with the polishing surface. Polishing slurry is supplied to the apex of the conical polishing head.

Usually, the polishing media or chemical slurry is applied to the wafer via a supply pipe or via an aperture provided in the polishing pad.

There are known disadvantages associated with slurry flow through a relatively small bore pipe or channel. A particular problem is associated with the uneven distribution of the slurry and build-up of slurry on the process surface. This may result in an uneven polishing effect where it is of critical importance to yield repeatable polishing so that the whole surface of the substrate is polished evenly at the same time. It is also important that spent slurry and substrate debris are removed from the process interface otherwise scratching of the substrate surface will result.

One known solution or approach is to provide grooves in the polishing pad spirally outwards from its central axis to carry slurry to the outer periphery. An associated problem with this arrangement is that it has a high maintenance cost and failure rate.

One of the major operational issues of CMP is the maintenance of the polishing pad surface which tends to wear significantly more quickly where process pressures are applied to compensate for uneven polishing of the subject substrate.

A common problem involves the build-up of slurry on the pad surface and various devices have been introduced to solve this issue.

A method and apparatus for conditioning a polishing pad is disclosed in US Patent No. 5,775,983 to SHENDON et al and aims to improve the polishing characteristics of the pad by providing an embedded pattern that facilitates polishing and reduces glazing. The invention further discloses means and method for conditioning a pad without significantly abrading the polishing surface.

thereby prolonging the pads useful life. A series of independently rotatable rollers having a knurled outer surface is used to embed a pattern or score marks in the surface of the polishing pad. Alternatively, a knurled conical roller engages a radius of the pad. The apparatus is adaptable to either manual or automated processes The closest acknowledged prior art is. disclosed in US Patent No. 5,688,360 to JAIRATH which describes a semiconductor wafer polishing apparatus which includes a housing and a turntable mounted in the housing. The turntable has an axis of rotation and a surface for affixing the working surface of a semiconductor wafer in an upwardly facing horizontal position. The polishing apparatus also includes a motor mounted to the housing and connected to the turntable or platen to supply a torque for rotating the turntable about the axis of rotation. A polishing assembly is connected to the housing and extends adjacent to the turntable surface. A polishing pad is affixed to the polishing assembly and is positionable to contact the semiconductor wafer. Some polishing pads are cylindrical in form and others have a conical form. The document also discloses a housing for encapsulating the apparatus.

It is appreciated in this document that an established problem of the prior art systems is that, just as the dynamic complexity of the conventional system makes uniform polishing of the wafer difficult, uniform degradation and restoration of the polishing pad are similarly rendered onerous.

In the disclosure of US 5,688,360, the issue of uniformity of removal of substrate surface is not fully addressed in that there are inherent disadvantages associated with the accuracy with which the positioning of the polishing pads with respect to the substrate surface must be achieved.

It is generally appreciated that high wear and tear on the or each polishing pad diminishes fabrication productivity due to down time of a polishing apparatus and increases manufacturing costs due both to the reduced operational time and increased maintenance costs, including the cost of replacing polishing pads, for

example.

It is also well appreciated that it is difficult to enclose the apparatus as it requires a significant amount of space to house the apparatus, implement the method and it is also necessary to contain and ventilate the toxic chemical slurry used in the process.

It is an object of the present invention to provide an apparatus for and method of polishing a substrate, to provide an even polished surface and to attenuate the incidence of substrate surface defects.

It is a particular object of the present invention to provide a chemical mechanical planarization system that seeks to alleviate the disadvantages associated with the prior art and seeks to minimise the risk of damage to a wafer or the introduction of other surface defects.

It is also object of the present invention to provide a polishing apparatus and method to remove substrate material uniformly across the surface thereof achieving high polishing tolerances.

It is further an object of the invention to enclose the apparatus of the invention so that a controlled amount of chemical slurry is used and facilitate enhanced ventilation and easier maintenance.

By eliminating a potentially toxic atmosphere maintenance access to components of the apparatus is enhanced. This and further objects of the invention will become evident to the reader as the advantages of the invention are set out below.

Summary of the Invention

Accordingly, the present invention provides an apparatus for polishing a substrate surface comprising: a rotatable platen adapted to secure the substrate surface for presentation to a polishing pad; a substantially conical body having a curved surface and being adapted to retain the polishing pad against the substrate surface along a locus defining a region of contact; means of rotating the conical body and the polishing pad in a predetermined ratio to the rotation of the substrate surface.

wherein, the region of contact comprises a length of the curved surface of the conical body tangential to the substrate surface and the ratio of rotation is selected to remove material uniformly from the substrate.

The term rotation" as used herein is taken to include parameters of both speed and direction.

Advantageously, the region of contact extends across the entire width of the substrate surface.

In a preferred construction, the polishing pad has a diameter or region of contact length substantially equal to the diameter of the subject substrate surface.

The phrase "region of contact length" is directed to the locus of contact points between the polishing pad and the substrate surface at the process interface when in use.

By defining the region of contact along a line, it is easier to control the process parameters and calculate the optimum operating conditions. Crucially, the pad material is passed at uniform speed across the full diameter of the substrate surface thereby enhancing uniform removal of substrate.

Conveniently, the ratio of rotation of the platen to the conical body is selected so that, at a process interface between the substrate surface and the polishing pad.

there is a uniform velocity at each point along the region of contact.

The uniform or fixed velocity along the locus defining the region of contact ensures uniform rates of substrate removal at the process interface.

Advantageously, the rotatable platen is adapted to include controlled lateral movement along the locus. Ideally, where lateral movement of the platen is involved, a polishing pad having a diameter or region of contact length greater than the diameter of the subject substrate surface is used.

Preferably, the profile of the substantially conical body is determined by the apex angle of the body and the ratio of rotational speeds of the substrate surface and the conical body.

The ratio is given by the formula: sin a = where a is the angle between the central longitudinal axis of the conical body and the curved surface thereof Preferably, the rotatable platen includes adjustable biasing means to apply a desired frictional pressure at the substrate surface against the polishing pad.

This arrangement allows control of the frictional pressure at the process interface during polishing and facilitates correction of defects or uneven polishing.

Advantageously, the desired frictional pressure is realised by applying pressure along the tangential region of contact and is optionally simplified to an arrangement where one pressure actuator is provided on each side of the central rotational axis of the platen along said locus.

The present arrangement obviates much of the control requirements for downforce pressure variables used for the implementation of linear belt and orbital planarization techniques. The apparatus of the invention facilitates use of only two load cells or similar actuator/feedback loops.

In alternative arrangements, further load cell configurations are used, for example.

edge cell configurations for pad compression devices and the like.

Conveniently, the polishing pad is selected from a polishing belt or a conical pad securely mounted on the conical body. In several arrangements of the invention.

the polishing pad comprises a belt of the type known in the art but modified to ensure it is retained in position. The belt pad includes a series of retaining holes adjacent the edges thereof for receiving securing tabs or teeth mounted on or adjacent the conical body. Ideally, the belt comprises an endless belt.

In one arrangement, an endless belt is tensioned between two rotatable conical bodies one of which is positioned to present the region of contact to the substrate surface.

In a first realisation of the above arrangement, two identical conical bodies are disposed in spaced apart relationship with parallel central longitudinal axes. the apexes of the conical bodies directed in opposite senses. In a second realisation of the above arrangement, the apexes are directed in the same sense and a polishing belt having one side longer than the other is required.

In another arrangement, the belt is tensioned over the conical body by tensionin means which ensure the polishing belt is in the correct position at the process interface. Advantageously, the tensioning means includes spring biasing means.

Preferably, the conical body is frusto-conical and is mounted for rotation on a central longitudinal axial spindle, the spindle being connected to means for altering the angle of the body so that a length of the curved surface thereof is disposed to present the polishing pad to the substrate surface along a tangential length which is equal to or greater than the diameter of the substrate being polished.

Advantageously, the spindle is disposed at an operational angle of between 5 and 600 to the vertical. Conveniently, the operational angle is between 8 and 453* Ideally, the angle is selected according to the apex angle of the conical body so that the region of contact defines a horizontally disposed tangential length.

In a preferred arrangement of the invention, a truncated cone or frusto-conical body is provided with a polishing pad secured to the active curved surface thereof.

Ideally, the polishing pad is an abrasive polishing pad. The cone is rotated to present a tangential length of the curved surface of the polishing pad to the rotating cylindrical end surface of the substrate. such as a semiconductor wafer. at the process interface, whereby material is uniformly removed from the substrate in a highly uniform manner.

Conveniently, a polishing media which includes corrosive fluids and is generally referred to as a "chemical slurry", optionally containing small abrasive solids and/or high molecular weight polymer suspended therein, is applied to the polishing pad to aid removal of substrate material.

Ideally, the polishing media or slurry is introduced via a plurality of fluid jets as the polishing pad approaches the process surface. In a preferred construction. the fluid jets are variably controllable so as to ensure an even distribution of slurry to the pad surface area.

Preferably, the platen is adapted to retain the substrate surface, comprising a substantially flat circular semiconductor disc, in a horizontal position using a vacuum applied to the non-process side of the semiconductor disc or wafer.

It will be appreciated by the skilled reader that the term "non-process side" refers only to the side opposite that actively undergoing CMP and that both sides of a substrate surface may be processed.

Ideally, the substrate surface is disposed in an inverted position in a substantially horizontal plane to abut the substantially horizontally disposed tangential region of the polishing pad. One advantage provided by the above arrangement is that swarf and other waste material do not tend to accumulate at the process interface.

Advantageously, the conical body and the platen are rotated by a drive motor.

Ideally, the conical body and the platen are rotated by separate drive motors.

Optionally, the conical body and the platen are driven by a common drive motor and rotated at a ratio predetermined by gearing, which may be variable.

Conveniently, platen and pad motion is controlled by electronic automation control means.

Advantageously, the apparatus includes a housing or process vessel, effectively encapsulating the platen, conical body and polishing pad within. Preferably, the housing or process vessel is so sized and shaped to form a container for the process fluid or slurry. In one preferred arrangement, the housing or process vessel is shaped to conform substantially to the shape of the conical body and its

rotatable axis.

Preferably, a positioning means is coupled between the housing and the platen for positioning the substrate surface for rotation at the process interface and for pressing the substrate surface against the rotating polishing pad along the tangential region of contact. Ideally, the positioning means includes actuators along said region of contact to selectively alter the contact pressure.

Advantageously, further positioning means is provided between the housing and the or each conical body for positioning the polishing pad at the process interface.

Ideally, the positioning means presents a tangential length of the curved surface thereof in a horizontal orientation at the process interface. 1-I

-i _,-Conveniently, there is provided a fluid circuit for the provision, monitoring and recycling of the process fluid or slurry. Ideally, a plurality of slurry supply lines/or inlet jets are provided at or adjacent the process interface. Used slurry is collected via outlet drains within the housing. In a number of the arrangements described, the slurry is carried to the substrate interface by the movement of the polishing pad towards the process interface. In a preferred arrangement of the invention, the process vessel is filled with slurry up to a level where the process interface and substrate surface is submerged. The fluid circuit in this arrangement includes means for monitoring the quality of the slurry, to determine its polishing efficiency, and means for draining spent slurry and replenishing the slurry to maintain the required level.

Another advantage of the above arrangement is that the amount of chemical slurry required is reduced. The reduction in the processing quantity of slurry has the effect of lowering operating costs, increasing intervals between maintenance service, reducing apparatus wear and reducing the environmental impact of CMP processing.

Advantageously, dynamic seals are provided to isolate critical moving parts of the apparatus from corrosive components of the slurry. By providing excellent isolation of certain components, such as bearings and sensor elements, from the highly corrosive slurry chemistries, apparatus downtime is minimised.

Conveniently, the housing is sealed to provide a substantially gas secure enclosure to confine the spread of potentially harmful and/or corrosive fumes generated by working the slurry or other polishing media.

In this arrangement, the prior art disadvantages of harmful fumes emanating from the apparatus are confined or eliminated. A vacuum extractor unit may optionally be utilised.

Owing to the simplicity ol the design, the apparatus of the invention is more robust than existing apparatus. The advantages associated with this include higher productivity due to reduced downtime, easier maintenance, less consumable parts required and improved process quality. As a result, the mean time between service (M.T.B.S.) is extended and the mean time between fail (M.T.B.F.) is also extended. It is a further advantage of the invention that the planarization results achieved are highly repeatable.

By utilising the features of the invention as set out herein, a CMP apparatus which is self-contained and portable may be realised.

Conveniently, the apparatus includes means for cleaning the polishing pad in situ.

In one arrangement, a series of brushes or wipers is used to remove spent slurry from the rotating pad.

1 0 Optionally or additionally, the apparatus includes means for reconditioning the polishing pad in situ, ideally using a diamond abrasive pad. In one arrangement. a rotating reconditioning pad is passed along a tangential length of the polishing pad as the pad rotates. In an alternative arrangement, a reconditioning pad, shaped to conform to a sector of the curved surface of the polishing pad, is brought into contact with the rotating polishing pad.

Advantageously, the apparatus includes pad support means adapted to abut the polishing pad adjacent the region of contact and maintain a pressure thereon corresponding to the pressure exerted by the substrate surface at the process interface.

Pad support and/or pad compression means may be provided to attenuate or eliminate pad edge defects known to affect the uniformity of polishing.

Conveniently, pad support andor pad compression means may be selected from a group of pressure applicators including: point actuators; pad actuators; pad edge shoulder supports; annular ring actuators; rotatable roller actuators; and conical or frusto-conical roller actuators.

In a particular embodiment of the invention, there is provided an apparatus for polishing a semiconductor wafer by chemical mechanical planarization comprising: a platen mounted for rotation on a spindle adapted to secure a semiconductor wafer for presentation to a polishing belt; first and second conical bodies mounted for rotation on respectivespindles and adapted to tension the polishing belt therebetween and define a region of contact with a process interface surface of the wafer; drive and controller means for rotating the polishing belt in a predetermined ratio to the rotation of the wafer surface.

wherein the region of contact comprises a tangential length of the polishing belt positioned at the process interface and the ratio of rotation is selected to remove material uniformly from the wafer surface.

In another embodiment of the invention, there is provided an apparatus for polishing a semiconductor wafer by chemical mechanical planarization.

comprising: a platen mounted for rotation on a spindle adapted to secure a iS semiconductor wafer for presentation to a polishing belt; a roller arrangement adapted to tension the polishing belt over a rotatable conical body to define a region of contact with a process interface surface of the wafer; drive and controller means for rotating the polishing belt in a predetermined ratio to the rotation of the wafer surface, wherein the region of contact comprises a tangential length of the polishing belt positioned at the process interface and the ratio of rotation is selected to remove material uniformly from the wafer surface.

Advantageously, the wafer is presented to the polishing pad by moving the platen carrying the wafer into contact with the polishing pad.

In the above arrangements, the polishing belt can be reconditioned in situ and is easily removable when expended.

In a preferred embodiment of the invention, there is provided an apparatus for polishing a semiconductor wafer by chemical mechanical planarization.

comprising: a platen mounted for rotation on a spindle adapted to secure a semiconductor wafer for presentation to a polishing pad; a frusto-conical body having a curved surface to which the polishing pad is secured, the body being movable to present a curved surface of the polishing pad at a region of contact with a process interface surface of the wafer; drive and controller means for rotating the polishing pad in a predetermined ratio to the rotation of the wafer surface, wherein the region of contact comprises a tangential length of the curved surface of the polishing pad positioned at the process interface and the ratio of rotation is selected to remove material uniformly from the wafer surface.

It will be appreciated that the polishing pad can be reconditioned in situ to prolong operational life and is easily removable when expended.

The invention further provides a method of polishing a substrate surface, the method including: securing a substrate to a rotatable platen for presenting a surface of the substrate to a polishing pad; urging the substrate surface into contact with the polishing pad. via a curved surface region of a substantially conical body, to define a region of contact between the pad and the substrate surthce; and rotating the conical body and the polishing pad in a predetermined ratio to the rotation of the substrate surface, wherein the region of contact comprises a length of the curved surface of the conical body tangential to the substrate surface and the ratio of rotation uniformly removes material from the substrate surface.

Conveniently, the method includes selecting the ratio of rotation of the platen to the conical body so that, at a process interface between the substrate surface and the polishing pad, there is a uniform velocity at each point along the region of contact.

Preferably, the method includes applying a desired frictional pressure at the substrate surface against the polishing pad via an adjustable biasing means of the

rotatable platen.

Advantageously, the method includes encapsulating the platen, conical body and polishing pad within a housing or process vessel. Preferably, the housing or process vessel is so sized and shaped to form a container for the process fluid or slurry. In one preferred arrangement, the housing or process vessel is shaped to conform substantially to the shape of the conical body and its rotatable axis.

Conveniently, the housing or process vessel is sealed to provide a substantially gas secure enclosure to confine the spread of potentially harmful andlor corrosive fumes generated by working the slurry or other polishing media.

The term "substantially gas secure enclosure" is intended to cover gas tight enclosures and enclosures where sufficient negative pressure within the enclosure ensures the surrounding environment is not contaminated, for example, as with a fume cupboard.

Preferably, the method includes cleaning and/or reconditioning the polishing pad in situ.

The process vessel may include ultrasonic or megasonic actuators therein so as to aid cleaning the vessel and/or conditioning of the polishing pad.

In a preferred method of polishing a substrate surface, the method includes: mounting a semiconductor wafer on a rotatable platen for presenting a process interface surface thereof to a polishing pad; urging the interface surface into contact with the polishing pad, via a curved surface region of a substantially conical body, to define a region of contact between the pad and the wafer surface; enclosing the platen, conical body and polishing pad within a housing to define a process vessel; charging the vessel with a polishing media or chemical slurry; and polishing the wafer by rotating the conical body and the polishing pad in a predetermined ratio to the rotation of the substrate surface.

wherein the region of contact comprises a length of the curved surface of the conical body tangential to the wafer surface and the ratio of rotation uniformly removes material from the wafer surface.

Advantageously, the method includes moving the rotatable platen in a lateral direction along the locus so as to prevent edge wear steps on the pad.

Furthermore, the apparatus and method allows for the movement of the rotatable platen in a lateral direction along the locus so as to facilitate sequential polishing steps as the platen moves laterally along the locus encountering different pad grades or types so that different process steps may be conducted within the same process vessel on the one conical polishing body.

As already outlined, the most essential feature is the ability to ensure that a fixed velocity occur at all process surface loci. thereby ensuring removal rate uniformity. Such fixed velocity can be uniquely achieved by the Conical Frustrum method.

It obviates the disadvantages associated with the existing methods of orbital belt and linear belt removal techniques. These methods require complicated procedures of "multiple regionalised" areas of different pressure application and variable speed processing to a wafer to give uniform removal of material. It will be seen that the invention provides a significant reduction in the process variables, associated automation and assemblies normally associated with CMP. The Conical Frustrum apparatus and method reduce the amount of process variables due to the uniform velocities found at the process interface.

Ideally, the or each conical body, platen and housing or process vessel is made from or lined with a corrosive resistant material so that the normally corrosive polishing media does not adversely affect the integrity of the polishing apparatus.

Brief Description of the Drawings

The present invention will now be described more particularly with reference to the accompanying drawings, which show, by way of example only, a number of separate embodiments of polishing apparatus in accordance with the invention. In the drawings: Figure 1 is a schematic perspective view of a first embodiment of polishing apparatus using a first drive arrangement of polishing belt; Figure 2 is a schematic perspective view of a second embodiment of polishing apparatus using a second drive arrangement of polishing belt; Figure 3 is a schematic perspective view of a third embodiment of polishing apparatus using a third drive arrangement of polishing belt; Figure 4a is a schematic sectional side elevation of a fourth embodiment of polishing apparatus using a frusto-conical polishing pad; Figure 4b is an exploded perspective view of the components of the embodiment illustrated in Figure 4a; Figure 4c is simplified schematic sectional side elevation of the embodiment illustrated in Figure 4a, illustrating the angular displacement, rotational aspects and sealing of the frusto-conical body; Figure 4d is a detailed schematic sectional side elevation of the fourth embodiment of CMP apparatus indicating method steps in accordance with the invention; Figure 5a is a schematic sectional side elevation of a first pad conditioning arrangement for the fourth embodiment of CMP apparatus in accordance with the invention; Figure 5b is a schematic sectional side elevation of a second pad conditioning arrangement for the fourth embodiment of CMP apparatus in accordance with the invention; Figure 6a is a schematic sectional side elevation, similar to the views of Figures 5a and Sb, of a uniformity pad compression ring arrangement for the substrate platen of the apparatus of Figure 4a; Figure 6b is a schematic sectional side elevation of a bilateral uniformity pad boundary support shoulder arrangement for the substrate platen of the apparatus of Figure 4a; Figure 6c is a schematic sectional side elevation of a bilateral uniformity pad compression roller arrangement for the substrate platen of the apparatus of Figure 4a; Figure 6d is a schematic sectional side elevation of a bilateral uniformity pad compression frustrii arrangement for the substrate platen of the apparatus of Figure 4a; Figures 7a and 7b are a perspective view from below and a sectional side elevation of a vacuum platen; and Figure 8 is a schematic perspective view of a modified apparatus of Figure 4a which includes means for automating the polishing method of the invention using an optical sensor arrangement.

Detailed Description of the Drawings

As discussed in the preamble of the specification, the traditional techniques used to achieve optimum polishing of semiconductor wafers and the like utilised chemical mechanical planarization (CMP) with orbital pattern and linear belt polishing pads. These techniques and the apparatus used to implement them presented one overriding inherent characteristic which either present the known problems and irregularities or require complex compensation. The characteristic referred to involves the variable velocities encountered across the process surface of the substrate. As a result, such prior art processes and apparatus need to utilie one of more of a multitude of complex additional pressure control variables to counteract the variable velocities in attempt to achieve a uniform removal rate.

All CMP methods are subject to Preston's Law, which states: RR = K1 J U where the removal rate (RR) depends linearly on the speed (v) between the polishing pad and the wafer and also depends linearly on the pressure (p) which the substrate is pressed against the pad. Properties of the slurry and the pad used for the process are summarised in the Preston coefficient (ic,).

Consequently, it is understood that to achieve a uniform removal rate, a constant speed and a constant pressure needs to be applied to all points on a substrate process surface, the Preston coefficient (Kr) being determined by the pad and the chemical and material properties of the slurry, together with their respective characteristics of integrity and distribution.

The present invention presents a method and apparatus to achieve substantially uniform velocities across the contact loci of polishing pad and substrate process surface. The following mathematics reveals the reasoning behind what is referred to hereinafter as Conical Frustrum CMP.

The curved surface area of a cone is known by definition to be Curved surface areacone = 7t q 1 where q is the radius of the base of the cone and / is the length of the curved surface from base to apex.

Furthermore, taking the angle a between the central longitudinal axis and the curved surface at any radius d, yields: sina=d/l or lsina=d If we now consider the substrate process surface, presented as a disc or platen having a radius r and utilise a portion of the curved surface of the cone to overlie a region of the platen, extending radially from the centre of the platen, then at any radius r along the platen, the length p of the curved surface of the cone from apex to the platen radius r will be p = (1 -r).

Therefore, sin a = d/ (1 -r,,) Where c/is the radius of the cone corresponding to the point of contact between the curved surface of the cone and the platen at any radius r.

Thus. (7-rsina=d and the angular speed of the cone at d will be given by (2 r d (Ocone.

Given that the angular speed of the plates at any radius r is given by (2 r r) (Odr.

then the total angular speed of the cone at its maximum radius D will be given by (2 D) Ocone However, (2 r D) is equivalent to (2 ir tO (Ocie + (2 ir r) (Ocir -Li-Yielding (D -d) (Ocone = r (Ucir [1 sin a -1 sin a + r Sifl (2] (-0cone = r (Ocir r sin a (Ocone = r (Ocir Thus, by utilising the ratio (Ocjr!(Oconc = Sfl (2 the angle a (1/2 the angle of the cone apex) can be set and an appropriate angular rotational speed of the platen or wafer (cylinder) (Ocir is selected. The rotation of the cone is then determined from: (Ocir/sin a = O)cone To choose a cone of an appropriate size and shape and, thus an acceptable range of rotational speeds, the extremes of the range are first acquired: If the angle a is large (-* 90) sin a -I and (Ucir (Ocone With the above result, the surface contact area becomes too large and this is likely to cause an imbalance in the uniform removal of material.

If the angle a is small (-0 ) sin a -0 and With the above result, it will be appreciated that a conical body having an apex angle approaching 0 will require an angular speed of the conical body which is too large and this is likely to cause an imbalance in the uniform removal of material.

From the graph below it will be seen that a range of suitable values of a may be found between 5 and 600, for example, without encountering practical problems or the limitations of material science. In a prototype arrangement, an angle of 8 was found optimum. It will be appreciated that the invention is in no way limited to the above values.

I __ H. __

H

I H N

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C r-(Si Lii -(i (N -= (.ujeewo) suonjo,ie w JOjC4/JpuqkJ jo poodS Referring now to the drawings and initially to Figure 1, the first embodiment of Conical Frustrum CMP apparatus 10 comprises a rotating platen 11 adapted to hold a substrate surface against a polishing pad comprising an endless belt 12.

The endless belt 12 is tensioned between two frusto-conical bodies 13, 14 end of which is rotated around driven axial spindles 15. The endless belt 12 includes a series of engagement holes 16 for securing the belt on corresponding teeth (not-shown) on the frusto-conical bodies 13, 14.

It will be appreciated from Figure 1 and the drawings which follow that the substrate surface is rotated while being held against the moving polishing belt 12 and that the region of contact between the belt and the substrate surface is a tangential length of the curved surface of the upper conical body 13.

In the illustrated arrangement, the axial spindles 15 may be arranged in a parallel configuration so that the belt has an even length along each side, and having an even number of engagement holes. The spindles iS are driven via separate electronically controlled drive motors, however, the spindles are optionally driven via a single drive motor directly or via a gear mechanism.

Adjacent the platen 11 and to maintain the polishing pad in an optimum position during polishing of the substrate process surface, there is provided at least one mechanism to facilitate pad edge compression or similar (which will be described in further detail hereinbelow with reference to Figures 6a to 6d). Also provided is a pad cleaner and/or reconditioner which comprises either a rotary disc or a trough-shaped section adapted to conform with the outer profile of the lower conical body 14. Pad cleaning and conditioning will be addressed more comprehensively below.

Figure 2 illustrates a second embodiment of Conical Frustrum CMP apparatus 20 comprising a rotating platen 21 adapted to hold a substrate surface, as before. The polishing pad comprises an endless belt 22 tensioned between a pair of frusto-conical bodies 23, 24, again mounted on driven axial spindles 25. As the conical bodies 23, 24 are arranged in a side by side configuration with their respective apexes to one side, the arrangement of engagement holes 26 along each edge of the belt 22 and the retention of the belt 22 to the corresponding teeth on the conical bodies 23, 24 is of particular importance.

In a similar manner to that briefly described with respect to the first embodiment of apparatus 10 shown in Figure 1, the second embodiment of apparatus 20 may include pad edge compression and a pad cleaning and/or conditioning mechanism.

In the third embodiment of Conical Frustrum CMP apparatus 30, there is provided a rotating platen 31, as before, adapted to hold the substrate surface against its polishing belt 32. In this arrangement a single frusto-conical body 33 is provided on a driven axial spindle 35 and at least a pair of rollers 37 are used to tension the belt 32 over the conical body 33. The belt is again provided with engagement holes 36 disposed along the edges thereof to aid driving of the belt and securing it to the body 33 via the corresponding drive teeth thereon. In an unillustrated variant of the third embodiment, at least one pair and optionally two pairs of conical tensioning rollers are provided. It will be seen from Figure 3 that the belt is of an irregular shape with one edge being substantially longer than the other to compensate for the difference in circumferences of the conical body near it apex and at its base.

As will be appreciated by the skilled reader, pad conditioning is advantageously conducted on sections of the polishing pad or belt that are under tension. In this embodiment, conditioning may be realised by combining the action of the rollers 37 with a conditioning mechanism. Alternatively, a conditioning mechanism may be used to act on the untensioned section of the belt 32, for example, by feeding belt through a set of tensioning rollers.

It will be apparent to the skilled addressee that each of the three embodiments of CMP apparatus 10,20,30 as described may be modified in a number of convenient ways without altering the fundamental principles underlying the characterising features of the present invention. One such modification includes adding to the rotational motion of the platen, a controlled lateral movement along the locus of the process interface. This additional component may be included where the diameter of the substrate surface is less than the tangential length of the polishing pad.

As referred to above, the apparatus includes means for moving the rotatable platen in a lateral direction along the locus so as to facilitate sequential polishing steps of the substrate surface as the platen moves laterally along the locus encountering different pad grades or types so that different process steps may be conducted within the same process vessel on one conical polishing body.

In the illustrated embodiments, endless belts are provided in various forms to conform with the arrangement of the frusto-conical bodies. It will be appreciated however that ended or non-continuous belts may be utilised with insignificant modification to the embodiments shown. In each case, whether the ended belts are fed from a reel or another conical body. it is imperative that the appropriate tension is maintained on the belt at the process interface. Tensioning mechanisms as simple as springs may be attached to the spindles of the frusto-conical bodies.

rollers or belt material supply reels. Optionally, a tensioning roller may be provided adjacent the frusto-conical body carrying the polishing pad to the process interface. In each case, tensioning of the belt is enhanced by use of the teeth and corresponding engagement holes on the belt.Furthermore, in each of the three embodiments of CMP apparatus 10. 20, 30 described above, it will he appreciated that the polishing material or slurry may be provided at or adjacent the contact region between the substrate surface and the polishing belt 12, 22. 32 and that a belt conditioning or cleaiuing means is optionally provided remote from the contact region, for example, against the lower conical body 14, 24 or rollers 37. Optionally, the belt 12. 22, 32 or a section of the outer surface thereof passes through a bath of polishing slurry which is then carried to the contact interface.Referring now to Figures 4a to 4d which illustrate aspects of a fourth embodiment of Conical Frustrurn CMP apparatus 40, comprising a rotating platen 41 adapted to hold a substrate surface against a polishing pad 42 which is secured for rotation on a irusto-conical body 43 driven via an axial spindle 45. The polishing pad 42 is shaped to conform with and be adhered to the curved surface area of the conical body 43. The conical body 43 and platen 41 are constrained within a housing 50 which acts also as a containment vessel for the polishing fluid or chemical slurry.

The housing 50 is adapted to conform substantially with the shape of the spindle-mounted frusto-conical body 43 and is retained at an angle so that an upper tangential length 52 of the curved surface of the conical body 43 is presented in a horizontal orientation. This tangential region or length 52 corresponds to the contact interface between the conical polishing pad 42 and the substrate process surface. The horizontal orientation and the corresponding tangential region are presented in this arrangement so that upper fluid level 54 of the polishing slurry constrained with the housing is coincident with or slightly above the substrate process surface.

A plurality of high quality seals 55 are required the upper and lower ends of the spindle 45 to allow the conical body to be rotated with respect thereto on bearings which are isolated from the caustic slurry.An additional dynamic seal is required to seal a rotational spindle 56 of the platen. These seals must be sufficiently 1 5 resilient to withstand an abrasive and caustic environment and, in the case of the lower seal, the constant presence of the chemical slurry and debris removed from the substrate surface which collects adjacent said lower seal. A seal failure sensor is provided to observe for degradation of the seal.

A chuck drive bearing for the rotational spindle 56 of the platen uses one of the known advanced bearing types to achieve the required performance parameters.

Conventional mechanical bearings may be substituted with electromagnetic levitation bearings andlor drive systems.

Conventional mechanical bearings, angular contact bearings or electromagnetic levitation bearings may be added for the upper and lower bearings 59 provided on the spindle, adjacent the conical body to support the assembly within the housing or process vessel 50. At least one of the angular contact bearings 59 is provided with an adjustment mechanism 60 to attenuate or substantially remove axial movement which would translate to lateral movement at the process interface.

Looking more particularly at the exploded perspective view of the components of the apparatus, as illustrated in Figure 4b, the lower angular contact bearing 59 is mounted on the spindle 45 to sit on an annular land 61 provided on the spindle which is then mounted into the lower end of the conical body. The upper angular contact bearing is placed onto the spindle at a corresponding upper land 62 and held in position by an adjuster nut and nut locking cage combination 60 or alternative mechanism to eliminate wobble or other unwanted movement of the body on the spindle. The conical body 43 which is located within the housing or process vessel 50 is operationally immersed in the chemical slurry used as the polishing media at the substrate process surface. To retain the slurry within the housing, two flexible rubber boots 65 are provided to overlie the end of the spindle 46, the end portion of the conical body 43 and the housing 50. The boots are held in position by clips 67. At the upper end of the conical body 43 a gas sealing end cap 71 is secured thereto via an 0-ring 72. The sealing cap is provided with a drive engagement coupling so that the conical body may be rotated with respect to the static housing 50 and axial spindle 45. The conical body 43 has upper and lower pad edge supports 73, 74 to retain the conical polishing pad 42 in position during use. An adjustable bearing block 75 is also provided to fasten the apparatus securely and to provide power input centering. A pair of circlips 76 retains the block 75 to the apparatus.

In an alternative unillustrated embodiment. the block and pivot arrangement may be substituted by a fixed two-point anchorage. It will be appreciated that the term "two-point anchorage" should include multipoint anchorages and the term as includes the pivot arrangement already described. In the two-point anchorage system, at least one anchor point is provided on the spindle axis on either side of the frusto-conical body but remote from rotating elements thereof. To provide CMP process stability, it is essential that the anchorage points are vertically supported from the machine base and directly opposed to the sense of the platenlchuck actuator downforce. The skilled addressee will appreciate that any significant flexing or vibration in the support anchors will result in poor CMP performance. Similarly, the selection of anchor support materials lacking the requisite characteristics of compression. stress and temperature-expansion resistance will also adversely affect CMP process results.

P33'. GB The housing 50 has an open-mouthed portion defining a lip 80 onto which a platen cap 82 is sealingly placed. The platen includes a vacuum circuit to retain the subject substrate in place during polishing. The platen is also provided with a pair of pressure adjustment mechanisms, usually comprising a feedback sensor arrangement to alter the position of a leadscrew 84 against a compression spring 85. The leadscrew 84 is connected to a stepper motor 86 and the compression spring acts on one side of the platen 41 through a load cell 87 which feeds a pressure signal back through a controller circuit to enable the motor to drive the leadscrew 84. It will be appreciated that other forms or locations of force actuators and/or sensors may be used.

The apparatus 40 also includes a fluid circuit comprising a plurality of chemical slurry delivery lines (leading to variably controllable directional jets 90) which direct the polishing media or slurry onto the polishing pad adjacent the substrate process surface 52 or onto the pad 42 at another position to be carried to the process interface 52. The control of the fluid jets provides for even distribution of slurry onto the pad surface. The slurry may be allowed to accumulate in the housing 50 until an upper level 54 is reached if a submersion process is desired or specified. This upper level 54 should correspond to the process interface 52 to at least ensure polishing media circulates at the substrate surface. An upper overflow outlet 92 is provided with an overflow sensor 93 to regulate the delivery of additional slurry. The outflow ports 95, 96disposed towards the lower ends of the housing, where used media and substrate waste tends to accumulate, are provided with valves 97, 98 which may be controlled for further regulation of slurry flow and throughput. A further sensor is provided within the fluid circuit and this is the seal failure sensor 57 referred to above.

The skilled addressee will appreciate from Figure 4c and others that it is advantageous to use a dynamic seal to prevent excessive contact of the spindle and other bearing mechanisms with the polishing media. In the particular arrangement shown, the dynamic seal traps air to exclude substantially the polishing media or slurry from the inner region of the seal in a manner similar to that used with diving bells. It will further be appreciated that as the "bell portionS' of the seal is disposed at an angle and as the seal spins, the polishing media will have a tendency to advance up the inner wall of the seal bell portion. However, the gyroscopic effect on the media will tend to spread the material across the inner wall and hence higher within the inner confines of the seal. The level to which the media reaches will depend on the rotational speed, the angle the seal is disposed with respect to the vertical and the density of the polishing media. The level or "waterline" may be reduced by providing an annular partition or shoulder within the seal to attenuate movement of the media along the inner wall thereof.

This bell type seal arrangement may be supplemented by a conventional seal or lip seal adjacent the bearing on the liquid side to act as a splash guard as it will not be fully immersed in the polishing media or slurry.

As part of the fluid circuit, a controller regulates the quality of the slurry before and, optionally, during the CMP process. The slurry pressure and flow is controllable and the vessel fluid level is also monitored. The controller (not shown, although many of its functions are indicated schematically in Figure 4d) is utilised in connection with the platen lateral pressure adjustment as described above and controls the spindle or chuck axis angular position with respect to gravity. Chuck vibration, lateral position, rotational speed and platen rotational speed are all measured and controlled via sensors providing signal to the controller. An optional feedback circuit takes substrate surface sensor 100 readings to the controller and pad pressure is adjusted accordingly and corresponding signals are taken via pad pressure sensors 101. The readings provided by the substrate surface sensor 100 are also used to determine the end points of successive process steps, including the end of the CMP process for the process surface of the wafer. Both surfaces of the wafer may be planarized. It will also be appreciated that the controller provides for the regulation and control of the rotation of the conical body 43 and allows for monitoring of cone motor load current, rotational speed, vibration and the axis angle relative to the substrate process surface to account for uneven wear and to compensate accordingly.

The housing or process vessel 50 is proved with ultrasonic or megasonic actuators for aiding cleaning of the apparatus within vessel and/or conditioning of the polishing pad.

Figure 5a and Sb are arrangements of pad conditioning devices adapted to recondition the pad in situ to extend operational life and to attenuate the incidence of irregularities in the polished surface of the substrate. In Figure 5a, one or more conditioning pads 120 are rotated and moved laterally along a tangential length of the polishing pad 42. In an alternative arrangement as illustrated in Figure Sb, a profiled conditioning pad 125 engages a sector of the curved surface of the pad 42. It will be understood that the arrangements of Figures 5a and 5b may be adapted for use with all embodiments of polishing apparatus in accordance with the invention.

Figure 6a to 6d illustrate a number of modifications to the fourth embodiment of CMP apparatus 40 particularly concerning the pad edge supports referred to above. The modifications illustrated are adaptations to counteract or attenuate wafer edge material removal uniformity issues which arise due to the non-uniform deformation of the polishing pad at the wafer edge and surrounding regions. The mechanisms shown compress the pad at the wafer edge region to prevent such non-uniform deformation of the polishing pad.In Figure 6a, a CMP apparatus is shown having a platen 41 which utilises an annular compression ring to transfer the occurrence of non-uniform pad deformation safely away from the edge region of the wafer to the corresponding edge region of the compression ring.

Figure 6b illustrates a CMP apparatus where non-uniform pad deformation is eliminated or attenuated by the provision of pad edge supports or shoulders which are placed in close proximity to the wafer edge on the platen.

Figure 6c shows a CMP apparatus utilising bilateral compression cylindrical rollers adjacent the platen edge to transfer the occurrence of pad deformation from the wafer edge region to the outer region of the bilateral compression rollers.

In an arrangement substantially similar to Figure 6c, Figure 6d illustrates a CMP apparatus having bilateral compression rollers of a conical or frusto-conical shape to eliminate or attenuate non-uniform pad deformation by transferring it from the edge region of the wafer towards the outer region of the conical rollers. -ji-

lt will be understood that the arrangements of Figures 6a to 6d may be adapted for use with all embodiments of polishing apparatus in accordance with the invention.

Referring now to Figures 7a and 7b, a substrate platen 150, similar to those illustrated with respect to the platens 11,21.3 1.41 of the earlier embodiments, is shown having a spiral groove 152 formed therein. Centrally disposed within the platen there is provided a bore 154 which connects the platen surface to an outlet port 155 at a shoulder region 156 of the platen spindle 157.

As the substrate is retained to the platen by a vacuum, the outlet port 155 of the bore 1 54 is connected to a vacuum circuit which, together with the narrow spiral groove 152, ensures uniform adhesion of the substrate wafer to the platen which the vacuum is enabled. The bore ordinarily has a diameter equal to or less than the width of the groove so as not to adversely affect process uniformity. The spiral pattern of the groove is preferred as it evenly disperses vacuum pressure without causing oversized crossover points which are more likely to occur with radial and br matrix distribution of vacuum paths. It will be appreciated that other patterns may be chosen to achieve the desired result.

A dynamic seal is provided to the outlet port 155 of the bore 154 to ensure sealing integrity during platen rotation so that the vacuum pressure at the platenlsubstrate interface does not vary.

Finally, with reference to Figure 8. a Conical Frustrum CMP device 200 of the type shown in Figures 4a to 4c having an optical feedback ioop (including substrate surface sensor 100) optimised for the present invention.

Substantially as before, there is provided a rotatable platen 211 having a vacuum circuit to retain a substrate wafer surface against a rotating conical polishing belt or pad 212 mounted on a frusto-conical body 213. The chemical slurry is introduced adjacent the substrate process interface which is defined as a tangential length 252 of the curved surface of the conical body. A combined optical source and sensor array is provided adjacent the substrate surface to provide continuous real-time process feedback to the controller so that process control algorithms may alter one or more of the parameters controlled and determine the correct endpoint(s) for the process(es).It will be appreciated by the skilled reader that any one of a number of configurations may be utilised to effect optical feedback. Of particular concern is the environment adjacent the process surface is the efficiency of the optical illumination and reflection. The simplest configuration involves a transparent vIewport, however, self-cleaning viewports are preferred and may be realised by providing a water jet onto the viewport, optionally adding a wiper arrangement, or using a rotating transparent tube or disc against a wiper or seal with or without a water jet.

Although the preferred sensor arrangement uses optical circuitry, it will be appreciated that other sensor arrangements can be used.

The method of the invention will now be described with reference to the drawings and particularly with reference to Figure 4c. It will be appreciated that there are variations and modifications to the method that may be performed without altering the general scope of the protection sought or conferred.

A wafer is selected to undergo CMP by conveying the wafer from a cassette of process wafers by a transport arm which applies a vacuum to the exposed surface of the wafer. Optionally, a pre-CMP cleaning process may be used. The surface to be processed is cleaned to remove contamination at a cleaning station where cleaning solutions are applied, usually via spray jets or submersion in a cleansing fluid with optional ultrasonic or megasonic cleaning. The surface is dried usually by spinning and blowing an inert gas such a Nitrogen (N2) towards the centre of the wafer and applying heat via a light source. Although both sides of the wafer are often processed, in which case both sides are cleansed and dried, the following description relates to the planarization of a single side. The surface requiring CMP is oriented downwards and the wafer is aligned at an alignment station where it is positioned in the platen so that spinning edge occurance" is unbiased.

Where an alignment notch is provided in the wafer, incremental notch positioning steps are taken to ensure the accumulated effect of degradation of the platen is avoided. The platen vacuum is enabled so that the wafer is held securely thereto and the transport arm vacuum is disabled and removed from the process location.

The platen with wafer is then lowered into position adjacent the conical polishing pad.

During the first polishing phase, often referred to as the "bulk polish step", a relatively large thickness of material is removed. The polishing slurry is introduced and the platen and polishing body and pad are rotated. Once the appropriate ratio of speeds is achieved and stabilised, the platen is lowered further until the wafer surface just touches the pad. Using the load cells and pressure sensor control circuitry, the platen is lowered to achieve the desired mean process compression pressure at the process interface. Additionally, the angular position of the conical body may be adjusted until the load cells and pressure sensors indicate an equilibrium of pressure. During this step, variables such as time.

platen motor drive current. polishing body/pad motor drive current, reflected optical feedback, mean pressure feedback. harmonic vibration of the polishing body/frustrum and/or platen and used slurry removed material content, may be measured to determine the endpoint of the bulk polish step.

The next process step is referred to as "clear/touchdownloverpolish step" and is used to remove selectively any remaining material of a first type without excessive removal of a second type material underlying the first. A different polishing media, being significantly less abrasive than the first step polishing slurry, is used and a less abrasive polishing pad may also be utilised. As before.

platen and polishing pad rotation is initialised and stabilised at the appropriate ratio. The wafer is brought into contact with the polishing pad and the process variables are monitored to determine the process step endpoint.

Similar steps are taken to finally remove the second type material and to uniformly planarize a third type material during a "barrier removal step". Again.

the process variables are monitored to determine the process step endpoint.

A final polishing step is used to buff and passivate" the wafer surface to prevent corrosion. This step requires the least aggressive abrasion of the process surface.

When the step is completed. the wafer is removed from the platen via a transport arm for optional post-CMP cleaning and drying before being conveyed for storage or further processing. As will be appreciated from the forgoing, movement of the platen optionally includes a lateral component along the contact locus at the process interface.

Optionally, the second and subsequent steps may be conducted on a separate planarizing apparatus/process module having different abrasive characteristics (although utilising the identical components as the apparatus of the present invention).

The apparatus and method of the invention is designed to deliver a fixed uniform material removal rate across a full substrate process surface. This is achieved by geometrically applying a constant velocity rate to all substrate process contact loci while also maintaining a constant downforce pressure to all loci via only 2 pressure control points, both of which should ideally apply an equal amount of pressure).

It will of course be understood that the invention is not limited to the specific details described herein, which are given by way of example only, and that various modifications and alterations are possible within the scope of the appended claims.

Claims

CLAIMS: 1. An apparatus for polishing a substrate surface comprising: a

rotatable platen adapted to secure the substrate surface for presentation to a polishing pad; a substantially conical body having a curved surface and being adapted to retain the polishing pad against the substrate surface along a locus defining a region of contact; means of rotating the conical body and the polishing pad in a predetermined ratio to the rotation of the substrate surface.

wherein, the region of contact comprises a length of the curved surface of the conical body tangential to the substrate surface and the ratio of rotation is selected to remove material uniformly from the substrate.

2. An apparatus for polishing a substrate surface as claimed in Claim 1. in which the region of contact extends across the entire width of the substrate surface 3. An apparatus for polishing a substrate surface as claimed in Claim I or Claim 2, in which the polishing pad has a diameter or region of contact length substantially equal to the diameter of the subject substrate surface.

4. An apparatus for polishing a substrate surface as claimed in any one of Claims I to 3, in which the ratio of rotation of the platen to the conical body is selected so that, at a process interface between the substrate surface and the polishing pad, there is a uniform velocity at each point along the region of contact.

5. An apparatus for polishing a substrate as claimed in any one of Claims 1. 2 and 4, in which the rotatable platen is adapted to include controlled lateral movement along the locus.

6. An apparatus for polishing a substrate as claimed in Claim 5, in which, where lateral movement of the platen is involved, a polishing pad having a diameter or region of contact length greater than the diameter of the subject substrate surface is used.

7. An apparatus for polishing a substrate as claimed in Claim 5 or Claim 6, in which the apparatus includes means for moving the rotatable platen in a lateral direction along the locus so that the substrate surface encounters different pad grades or types in sequential polishing steps so that different process steps may be conducted within one housing or process vessel on one conical polishing body.

8. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which the profile of the substantially conical body is determined by the apex angle of the body and the ratio of rotational speeds of the substrate surface and the conical body.

9. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which the rotatable platen includes adjustable biasing means to apply a desired frictional pressure at the substrate surface against the polishing pad.

10. An apparatus for polishing a substrate surface as claimed in Claim 9. in which the desired frictional pressure is realised by applying pressure along the tangential region of contact and is optionally simplified to an arrangement where one pressure actuator is provided on each side of the central rotational axis of the platen along said locus.

11. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which the polishing pad is selected from an endless polishing belt or a conical pad securely mounted on the conical body.

12. An apparatus for polishing a substrate surface as claimed in Claim 11. in which the belt comprises an endless belt. -3 -

13. An apparatus for polishing a substrate surface as claimed in Claim 11 or Claim 12, in which the belt is tensioned between two rotatable conical bodies one of which is positioned to present the region of contact to the substrate surface.

14. An apparatus for polishing a substrate surface as claimed in Claim 11 or Claim 12, in which the belt is tensioned over the conical body by tensioning means which ensure the polishing belt is in the correct position at the process interface.

15. An apparatus for polishing a substrate surface as claimed in Claim 14. in which the tensioning means includes spring baising means.

16. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which the conical body is frusto-conical and is mounted for rotation on a central longitudinal axial spindle, the spindle being connected to means for altering the angle of the body so that a length of the curved surface thereof is disposed to present the polishing pad to the substrate surface along a tangential length which is equal to or greater than the diameter of the substrate being polished.

17. An apparatus for polishing a substrate surface as claimed in Claim 16. in which the spindle is disposed at an operational angle of between 5 and 60 to the vertical.

18. An apparatus for polishing a substrate surface as claimed in Claim 17. in which the operational angle is between 8 and 45 19. An apparatus for polishing a substrate surface as claimed in Claim 16 or Claim 17, in which the angle is selected according to the apex angle of the conical body so that the region of contact defines a horizontally disposed tangential length.

20. An apparatus for polishing a substrate surface as claimed in any one of Claims 16 to 19, in which a truncated cone or frusto- conical body is provided with an abrasive polishing pad secured to the active curved surface thereof.

21. An apparatus for polishing a substrate surface as claimed in any one of Claims 16 to 19 in which a truncated cone or frusto-conical body is provided with a non-abrasive polishing pad secured to the active curved surface thereof.

22. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which a polishing media or chemical slurry which includes corrosive fluids, optionally containing small abrasive solids andlor high molecular weight polymers suspended therein, is applied to the polishing pad to aid removal of substrate material.

23. An apparatus for polishing a substrate as claimed in Claim 22 in which.

the polishing media or slurry is introduced via a plurality of fluid jets as the polishing pad approaches the process surface.

24. An apparatus for polishing a substrate as claimed in Claim 23 in which.

the fluid jets are variably controllable so as to ensure an even distribution of slurry to the pad surface area.

25. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which the platen is adapted to retain the substrate surface.

comprising a substantially flat circular semiconductor disc, in a horizontal position using a vacuum applied to the "non-process side" of the semiconductor disc or wafer.

26. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which the substrate surface is disposed in an inverted position in a substantially horizontal plane to abut the substantially horizontally disposed tangential region of the polishing pad.

27. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which the conical body and the platen are rotated by separate drive motors.

28. An apparatus for polishing a substrate surface as claimed in any one of Claims I to 26, in which the conical body and the platen are driven by a common drive motor and rotated at a ratio predetermined by variable gearing.

29. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which platen and pad motion is controlled by electronic automation control means.

30. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which the apparatus includes a housing or process vessel.

effectively encapsulating the platen, conical body and polishing pad within.

31. An apparatus for polishing a substrate surface as claimed in Claim 30, in which the housing or process vessel is so sized and shaped to form a container for the process fluid or slurry.

32. An apparatus for polishing a substrate surface as claimed in Claim 30 or Claim 31, in which the housing or process vessel is shaped to conform substantially to the shape of the conical body and its rotatable axis.

33. An apparatus for polishing a substrate surface as claimed in any one of Claims 30 to 32, in which a positioning means is coupled between the housing or process vessel and the platen for positioning the substrate surface for rotation at the process interface and for pressing the substrate surface against the rotating polishing pad along the tangential region of contact.

34. An apparatus for polishing a substrate surface as claimed in Claim 33. in which the positioning means includes actuators along said region of contact to selectively alter the contact pressure.

35. An apparatus for polishing a substrate surface as claimed in Claim 33 or Claim 34, in which further positioning means is provided between the housing or process vessel and the or each conical body for positioning the polishing pad at the process interface.

36. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which there is provided a fluid circuit for the supply, monitoring and recycling of a polishing media or slurry.

37. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which dynamic seals are provided to isolate critical moving parts of the apparatus from corrosive components of a polishing media or slurry.

38. An apparatus for polishing a substrate surface as claimed in any one of Claims 30 to 37, in which the housing or process vessel is sealed to provide a gas tight enclosure to confine the spread of potentially harmful and/or corrosive fumes generated by working a polishing media or slurry.

39. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which the apparatus includes means for cleaning the polishing pad in situ.

40. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which the apparatus includes means for reconditioning the 1 5 polishing pad in situ.

41. An apparatus for polishing a substrate surface as claimed in any one of Claims 30 to 40. in which the process vessel includes ultrasonic or megasonic actuators therein so as to aid cleaning the vessel and/or conditioning of the polishing pad.

42. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which the apparatus includes pad support and/or pad compression means adapted to abut the polishing pad adjacent the region of contact and maintain a pressure thereon corresponding to the pressure exerted by the substrate surface at the process interface.

43. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which the pad support and/or pad compression means is selected from a group of pressure applicators including: point actuators: pad actuators; pad edge shoulder supports; annular ring actuators; rotatable roller actuators; and conical or frusto-conical actuators.

44. An apparatus for polishing a semiconductor wafer by chemical mechanical planarization comprising: a platen mounted for rotation on a spindle adapted to secure a semiconductor wafer for presentation to a polishing belt; first and second conical bodies mounted for rotation on respective spindles and adapted to tension the polishing belt therebetween and define a region of contact with a process interface surface of the wafer; drive and controller means for rotating the polishing belt in a predetermined ratio to the rotation of the wafer surface, wherein the region of contact comprises a tangential length of the polishing belt positioned at the process interface and the ratio of rotation is selected to remove material uniformly from the wafer surface.

45. An apparatus for polishing a semiconductor wafer by chemical mechanical planarization comprising: a platen mounted for rotation on a spindle adapted to secure a semiconductor wafer for presentation to a polishing belt; a roller arrangement adapted to tension the polishing belt over a rotatable conical body to define a region of contact with a process interface surface of the wafer; drive and controller means for rotating the polishing belt in a predetermined ratio to the rotation of the wafer surface.

wherein the region of contact comprises a tangential length of the polishing belt positioned at the process interface and the ratio of rotation is selected to remove material uniformly from the wafer surface.

46. An apparatus for polishing a semiconductor wafer by chemical mechanical planarization, comprising: a platen mounted for rotation on a spindle adapted to secure a semiconductor wafer for presentation to a polishing pad; a frusto-conical body having a curved surface to which the polishing pad is secured, the body being movable to present a curved surface of the polishing pad at a region of contact with a process interface surface of the wafer; drive and controller means for rotating the polishing pad in a predetermined ratio to the rotation of the wafer surface, wherein the region of contact comprises a tangential length of the curved surface of the polishing pad positioned at the process interface and the ratio of rotation is selected to remove material uniformly from the wafer surface.

47. A method of polishing a substrate surface, the method including: securing a substrate to a rotatable platen for presenting a surface of the substrate to a polishing pad: urging the substrate surface into contact with the polishing pad. via a curved surface region of a substantially conical body, to define a region of contact between the pad and the substrate surface; and rotating the conical body and the polishing pad in a predetermined ratio to the rotation of the substrate surface, wherein the region of contact comprises a length ol the curved surface of the conical body tangential to the substrate surface and the ratio of rotation uniformly removes material from the substrate surface.

48. A method of polishing a substrate surface as claimed in Claim 47, in which the method includes selecting the ratio of rotation of the platen to the conical body so that, at a process interface between the substrate surface and the polishing pad, there is a uniform velocity at each point along the region of contact.

49. A method of polishing a substrate surface as claimed in Claim 47 or Claim 48, in which the method includes applying a desired frictional pressure at the substrate surface against the polishing pad via an adjustable biasing means of the

rotatable platen.

50 A method of polishing a substrate surface as claimed in any one of Claims 47 to 49, in which the method includes encapsulating the platen, conical body and polishing pad within a housing or process vessel.

51. A method of polishing a substrate surface as claimed in Claim 50. in which, the housing or process vessel is so sized and shaped to form a vessel for the process fluid or slurry.

52. A method of polishing a substrate surface as claimed in Claim 50 or Claim 51, in which the housing or process vessel is shaped to conform substantially to the shape of the conical body and its rotatable axis.

53. A method of polishing a substrate surface as claimed in any one of Claims 50 or Claim 5 1, in which the housing or process vessel is sealed to provide a substantially gas secure enclosure to confine the spread of potentially harmful and/or corrosive fumes generated by working a polishing media or slurry.

54. A method of polishing a substrate surface as claimed in any one of Claims 47 to 53, in which the method includes cleaning and/or reconditioning the polishing pad in situ.

55. A method of polishing a substrate surface as claimed in any one of Claims 47 to 54, in which the method includes cleaning the vessel and/or conditioning the polishing pad using ultrasonic or megasonic actuators mounted therein.

56. A method of polishing a substrate surface, the method including: mounting a semiconductor wafer on a rotatable platen for presenting a process interface surface thereof to a polishing pad; urging the interface surface into contact with the polishing pad, via a curved surface region of a substantially conical body, to define a region of contact between the pad and the wafer surface; enclosing the platen, conical body and polishing pad within a housing to define a process vessel; charging the vessel with a polishing media or chemical slurry; and polishing the wafer by rotating the conical body and the polishing pad in a predetermined ratio to the rotation of the substrate surface, wherein the region of contact comprises a length of the curved surface of the conical body tangential to the wafer surface and the ratio of rotation uniformly removes material from the wafer surface.

57. A method of polishing a substrate surface as claimed in any one of Claims 47 to 56 in which, the method includes moving the rotatable platen in a lateral direction along the locus.

58. A method of polishing a substrate surface as claimed in any one of Claims 47 to 57 in which, the method includes sequential polishing steps as the platen moves laterally along the locus encountering different pad grades or types so that different process steps are conducted within the same process vessel on one conical polishing body.

59. A method of polishing a substrate surface as claimed in any one of Claims 47 to 58, in which at least a substantial portion of the conical body is immersed in a volume of polishing media which is constrained by a housing or process vessel encapsulating at least said substantial portion of the conical body.

60. A method of polishing a substrate surface as claimed in Claim 59, in which the region of contact between the pad and the substrate surface is also immersed.

61. A semiconductor wafer polishing apparatus substantially as herein described, with reference to and as shown in the accompanying drawings.

62. A method of polishing a semiconductor wafer substantially as herein described with reference to the accompanying drawings.

63. A semiconductor wafer where polished in accordance with the method of Claim 47 or Claim 56.

64. A semiconductor wafer where polished in accordance with the method substantially as herein described with reference to the accompanying drawings.

Amendments to the claims have been filed as follows CLAIMS: 1. An apparatus for polishing a substrate surface comprising: a rotatable platen adapted to secure the substrate surface for presentation to a polishing pad; a substantially conical body having a curved surface and being adapted to retain the polishing pad against the substrate surface along a locus defining a region of contact; means of rotating the conical body and the polishing pad in a predetermined ratio to the rotation of the substrate surface, :* S. * wherein the region of contact comprises a length of the curved surface of the conical body tangential to the substrate surface and the ratio of rotation of the platen to the conical body is selected so that, at a process interface between the:. . substrate surface and the polishing pad, there is a uniforni velocity at each point *5** along the region of contact to remove material uniformly from the substrate, and ** . wherein the rotatable platen is adapted to include controlled lateral movement along the locus.

2. An apparatus for polishing a substrate surface as claimed in Claim 1, in which the region of contact extends across the entire width of the substrate surface.

3. An apparatus for polishing a substrate surface as claimed in Claim I or Claim 2, in which the polishing pad has a diameter or region of contact length substantially equal to the diameter of the subject substrate surface.

4. An apparatus for polishing a substrate as claimed in any of the preceding claims, in which, where lateral movement of the platen is involved, a polishing pad having a diameter or region of contactjength greater than the diameter of the subject substrate surface is used.

5. An apparatus for polishing a substrate as claimed in any one of the preceding claims, in which the apparatus includes means for moving the rotatable platen in a lateral direction along the locus so that the substrate surface encounters different pad grades or types in sequential polishing steps so that different process steps may be conducted within one housing or process vessel on one conical polishing body.

6. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which the profile of the substantially conical body is determined by the apex angle of the body and the ratio of rotational speeds of the substrate surface and the conical body. . : : : 7. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which the rotatable platen includes adjustable biasing means to apply a desired frictional pressure at the substrate surface against the polishing: pad.

8. An apparatus for polishing a substrate surface as claimed in Claim 7, in. * which the desired frictional pressure is realised by applying pressure along the tangential region of contact.

9. An apparatus for polishing a substrate as claimed in Claim 7 or Claim 8, in which the desired frictional pressure is provided by an arrangement where one pressure actuator is provided on each side of the central rotational axis of the platen along said locus.

10. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which the polishing pad is selected from a polishing belt or a conical pad securely mounted on the conical body.

11. An apparatus for polishing a substrate surface as claimed in Claim 1 0, in which the belt comprises an endless belt.

12. An apparatus for polishing a substrate surface as claimed in Claim 10 or Claim 11, in which the belt is tensioned between two rotatable conical bodies one of which is positioned to present the region of contact to the substrate surface.

13. An apparatus for polishing a substrate surface as claimed in Claim 10 or Claim 11, in which the belt is tensioned over the conical body by tensioning means which ensure the polishing belt is in the correct position at the process interface.

14. An apparatus for polishing a substrate surface as claimed in Claim 13, in which the tensioning means includes spring baising means.

15. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which the conical body is fmsto-conical and is mounted for: ..

rotation on a central longitudinal axial spindle, the spindle being connected to * means for altering the angle of the body so that a length of the curved surface * thereof is disposed to present the polishing pad to the substrate surface along a *: . . tangential length which is equal to or greater than the diameter of the substrate being polished. a.. S * S

16. An apparatus for polishing a substrate surface as claimed in Claim 15, in which the spindle is disposed at an operational angle of between 5 and 60 to the vertical.

17. An apparatus for polishing a substrate surface as claimed in Claim 1 6, in which the operational angle is between 8 and 45 18. An apparatus for polishing a substrate surface as claimed in Claim 15 or Claim 16, in which the angle is selected according to the apex angle of the conical body so that the region of contact defines a horizontally disposed tangential length.

19. An apparatus for polishing a substrate surface as claimed in any one of Claims 15 to 1 8, in which a truncated cone or frusto-conical body is provided with an abrasive po1ishingDad secured to the active curved surface thereof.

20. An apparatus for polishing a substrate surface as claimed in any one of Claims 15 to 18 in which a truncated cone or frusto-conical body is provided with a non-abrasive polishing pad secured to the active curved surface thereof.

21. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which a polishing media or chemical slurry which includes corrosive fluids, is applied to the polishing pad to aid removal of substrate material.

22. An apparatus for polishing a substrate surface as claimed in Claim 21 in which the polishing media or chemical slurry contains small abrasive solids and/or high molecular weight polymers suspended therein.

23. An apparatus for polishing a substrate as claimed in Claim 21 or Claim 22: in which, the polishing media or slurry is introduced via a plurality of fluid jets as: : the polishing pad approaches the process surface.

24. An apparatus for polishing a substrate as claimed in Claim 23 in which, S the fluid jets are variably controllable so as to ensure an even distribution of slurry *.

to the pad surface area. . 25. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which the platen is adapted to retain the substrate surface, comprising a substantially flat circular semiconductor disc, in a horizontal position using a vacuum applied to the "non-process side" of the semiconductor disc or wafer.

26. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which the substrate surface is disposed in an inverted position in a substantially horizontal plane to abut the substantially horizontally disposed tangential region of the polishing pad.

27. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which the conical body and the platen are rotated by separate drive motors. 5-i

28. An apparatus for polishing a substrate surface as claimed in any one of Claims 1 to 26, in which the conical body and the platen are driven by a common drive motor and rotated at a ratio predetermined by variable gearing.

29. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which platen and pad motion is controlled by electronic automation control means.

30. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which the apparatus includes a housing or process vessel, effectively encapsulating the platen, conical body and polishing pad within.

31. An apparatus for polishing a substrate surface as claimed in Claim 30, in which the housing or process vessel is so sized and shaped to form a container for: the process fluid or slurry. *1** S..

32. An apparatus for polishing a substrate surface as claimed in Claim 30 or Claim 31, in which the housing or process vessel is shaped to conform substantially to the shape of the conical body and its rotatable axis. * : ::*

SSS S

33. An apparatus for polishing a substrate surface as claimed in any one of Claims 30 to 32, in which a positioning means is coupled between the housing or process vessel and the platen for positioning the substrate surface for rotation at the process interface and for pressing the substrate surface against the rotating polishing pad along the tangential region of contact.

34. An apparatus for polishing a substrate surface as claimed in Claim33, in which the positioning means includes actuators along said region of contact to selectively alter the contact pressure.

35. An apparatus for polishing a substrate surface as claimed in Claim 33 or Claim 34, in which further positioning means is provided between the housing or process vessel and the or each conical body for positioning the polishing pad at the process interface. 52%

36. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which there is provided a fluid circuit for the supply, monitoring and recycling of a polishing media or slurry.

37. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which dynamic seals are provided to isolate critical moving parts of the apparatus from corrosive components of a polishing media or slurry.

38. An apparatus for polishing a substrate surface as claimed in any one of Claims 30 to 37, in which the housing or process vessel is sealed to provide a gas tight enclosure to confine the spread of potentially harmful and/or corrosive fumes generated by working a polishing media or slurry.

39. An apparatus for polishing a substrate surface as claimed in any one of the: : preceding claims, in which the apparatus includes means for cleaning the polishing pad in situ. * ** *

40. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which the apparatus includes means for reconditioning the.

polishing pad in situ.

41. An apparatus for polishing a substrate surface as claimed in any one of Claims 30 to 40, in which the process vessel includes ultrasonic or megasonic actuators therein so as to aid cleaning the vessel and/or conditioning of the polishing pad.

42. An apparatus for polishing a substrate surface as claimed in any one of the preceding claims, in which the apparatus includes pad support and/or pad compression means adapted to abut the polishing pad adjacent the region of contact and maintain a pressure thereon corresponding to the pressure exerted by the substrate surface at the process interface.

43. An apparatus for polishing a substrate surface as claimed in Claim 42, in which the pad support and/or pad compression means is selected from a group of pressure applicators including: point actuators; pad actuators; pad edge shoUlder supports; annular ring actuators; rotatable roller actuators; and conical or frusto-conical actuators.

44. An apparatus for polishing a semiconductor wafer by chemical mechanical planarization comprising: a platen mounted for rotation on a spindle adapted to secure a semiconductor wafer for presentation to a polishing belt; first and second conical bodies mounted for rotation on respective spindles and adapted to tension the polishing belt therebetween and define a region of contact with a process interface surface of the wafer; drive and controller means for rotating the polishing belt in a predetermined ratio to the rotation of the wafer surface, .....

wherein the region of contact comprises a tangential length of the polishing belt positioned at the process interface and the ratio of rotation of the platen to the conical body is selected so that, at a process interface between the substrate *: : ::* surface and the polishing pad, there is a uniform velocity at each point along the * region of contact to remove material uniformly from the wafer surface, and wherein the rotatable platen is adapted to include controlled lateral movement along the locus.

45. An apparatus for polishing a semiconductor wafer by chemical mechanical planarization, comprising: a platen mounted for rotation on a spindle adapted to secure a semiconductor wafer for presentation to a polishing belt; a roller arrangement adapted to tension the polishing belt over a rotatable conical body to define a region of contact with a process interface surface of the wafer; 5.".

drive and controller means for rotating the polishing belt in a predetermined ratio to the rotation of the wafer surface, wherein the region of contact comprises a tangential length of the polishing belt positioned at the process interface and the ratio of rotation of the platen to the conical body is selected so that, at a process interface between the substrate surface and the polishing pad, there is a uniform velocity at each point along the region of contact to remove material uniformly from the wafer surface, and wherein the rotatable platen is adapted to include controlled lateral movement along the locus. S. S

46. An apparatus for polishing a semiconductor wafer by chemical mechanical plariarization, comprising: a platen mounted for rotation on a spindle adapted to secure a semiconductor wafer for presentation to a polishing pad; S S * *. S S...

a frusto-conical body having a curved surface to which the polishing pad is secured, the body being movable to present a curved surface of the polishing pad at a region of contact with a process interface surface of the wafer; drive and controller means for rotating the polishing pad in a predetermined ratio to the rotation of the wafer surface, wherein the region of contact comprises a tangential length of the curved surface of the polishing pad positioned at the process interface and the ratio of rotation of the platen to the conical body is selected so that, at a process interface between the substrate surface and the polishing pad, there is a uniform velocity at each point along the region of contact to remove material uniformly from the wafer surface, and wherein the rotatable platen is adapted to include controlled lateral movement along the locus.

47. A method of polishing a substrate surface, the method including: securing a substrate to a rotatable platen for presenting a surface of the substrate to a polishing pad; urging the substrate surface into contact with the polishing pad, via a curved surface region of a substantially conical body, to define a region of contact between the pad and the substrate surface; and rotating the conical body and the polishing pad in a predetermined ratio to the rotation of the substrate surface, wherein the region of contact comprises a length of the curved surface of the conical body tangential to the substrate surface and the ratio of rotation of the: platen to the conical body is selected so that, at a process interface between the substrate and the polishing pad, there is a uniform velocity at each point along the region of contact to remove material uniformly from the substrate surface, and wherein the rotatable platen is adapted to include controlled lateral movement along the locus.

48. A method of polishing a substrate surface as claimed in Claim 47, in which the method includes selecting the ratio of rotation of the platen to the conical body so that, at a process interface between the substrate surface and the polishing pad, there is a uniform velocity at each point along the region of contact.

49. A method of polishing a substrate surface as claimed in Claim 47 or Claim 48, in which the method includes applying a desired frictional pressure at the substrate surface against the polishing pad via an adjustable biasing means of the

rotatable platen.

A method of polishing a substrate surface as claimed in any one of Claims 47 to 49, in which the method includes encapsulating the platen, conical body and polishing padwithin a housing or process vessel. S.'

51. A method of polishing a substrate surface as claimed in Claim 50, in which, the housing or process vessel is so sized and shaped to form a vessel for the process fluid or slurry.

52. A method of polishing a substrate surface as claimed in Claim 50 or Claim 51, in which the housing or process vessel is shaped to conform substantially to the shape of the conical body and its rotatable axis.

53. A method of polishing a substrate surface as claimed in any one of Claims or Claim 51, in which the housing or process vessel is sealed to provide a substantially gas secure enclosure to confine the spread of potentially harmful and/or corrosive fumes generated by working a polishing media or slurry. *.

54. A method of polishing a substrate surface as claimed in any one of Claims: e.' 47 to 53, in which the method includes cleaning and/or reconditioning the:: polishing pad in situ. I *

55. A method of polishing a substrate surface as claimed in any one of Claims 47 to 54, in which the method includes cleaning the vessel and/or conditioning the * : : polishing pad using ultrasonic or megasonic actuators mounted therein. * * 56. A method of polishing a substrate surface, the method including: mounting a semiconductor wafer on a rotatable platen for presenting a process interface surface thereof to a polishing pad; urging the interface surface into contact with the polishing pad, via a curved surface region of a substantially conical body, to define a region of contact between the pad and the wafer surface; enclosing the platen, conical body and polishing pad within a housing to define a process vessel; charging the vessel with a polishing media or chemical slurry; and polishing the wafer by rotating the conical body and the polishing pad in a predetermined ratio to the rotation of the substrate surface, wherein the region of contact comprises a length of the curved surface of the conical body tangential to the wafer surface and the ratio of rotation of the platen to the conical body is selected so that, at a process interface between the substrate and the polishing pad, there is a uniform velocity at each point along the region of contact to remove material uniformly from the wafer surface, and where in the rotatable platen is adapted to include controlled lateral movement along the locus.

57. A method of polishing a substrate surface as claimed in any one of Claims 47 to 56 in which, the method includes moving the rotatable platen in a lateral: * direction along the locus. S..

58. A method of polishing a substrate surface as claimed in Claim 57 in which, the method includes sequential polishing steps as the platen moves S...

laterally along the locus encountering different pad grades or types so that different process steps are conducted within the same process vessel on one * conical polishing body.

59. A method of polishing a substrate surface as claimed in any one of Claims 47 to 58, in which at least a substantial portion of the conical body is immersed in a volume of polishing media which is constrained by a housing or process vessel encapsulating at least said substantial portion of the conical body.

60. A method of polishing a substrate surface as claimed in Claim 59, in which the region of contact between the pad and the substrate surface is also immersed.

61. A semiconductor wafer polishing apparatus substantially as herein described, with reference to and as shown in the accompanying drawings. 5-s

62. A method of polishing a semiconductor wafer substantially as herein described with reference to the accompanying drawings.

63. A semiconductor wafer where polished in accordance with the method of Claim 47 or Claim 56.

64. A semiconductor wafer where polished in accordance with the method substantially as herein described with reference to the accompanying drawings. I. I * S S * **

SS S * S S S. S

S S..

I * S * S. S. 55 S... * S * S.. *SS S * S S.