Enhanced illuminator for use in photolithographic systems

Methods and apparatus for enabling both isolated and dense patterns to be accurately patterned onto a wafer are disclosed. According to one aspect of the present invention, an illumination system that is suitable for use as a part of a projection tool includes an illumination source and an illuminator aperture. The illuminator aperture has a center point and an outer edge, and also includes a first pole and a second pole. The first pole is defined substantially about the center point, and the second pole is defined substantially between the first pole and the outer edge of the first pole. The illumination source is arranged to provide a beam to the illuminator aperture.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates generally to semiconductor processing equipment. More particularly, the present invention relates to an illuminator layout of a projection tool which enables both dense and isolated patterns on reticles to be precisely projected onto a wafer surface during a lithographic process.

2. Description of the Related Art

For precision instruments such as photolithography machines which are used in semiconductor processing, factors which affect the performance, e.g., accuracy, of the precision instrument generally must be dealt with and, insofar as possible, eliminated. When the performance of a precision instrument is adversely affected, products formed using the precision instrument may be improperly formed and, hence, function improperly. For instance, a photolithography machine with an illuminator which does not allow circuit patterns or features associated with a reticle to be precisely projected onto a semiconductor wafer surface may result in the formation of integrated circuits or semiconductor chips which do function as expected.

FIG. 1is a diagrammatic representation of a photolithography or exposure apparatus. An exposure apparatus100includes a reticle104which effectively serves as a mask or a negative for a wafer108. Patterns, e.g., patterns formed using a thin metal layer or layers, which are resident on reticle104are projected as images onto wafer108when reticle104is positioned over wafer108in a desired position. An illuminator112is used to provide a broad beam of light to reticle104. In other words, illuminator112distributes light. Portions of a light beam, for example, may be absorbed by reticle104while other portions pass through reticle104and are focused onto wafer108through lens assembly116.

Wafer scanning stages (not shown) are generally used hold and to position wafer108such that portions of wafer108may be exposed as appropriate during masking process or an etching process. Reticle scanning stages (not shown) are generally used to hold reticle104, and to position reticle104for exposure over wafer108.

Illuminator112includes an illumination source120which provides a beam of light or a relatively broad beam of electrons. The beam provided by illumination source120illuminates illuminator aperture124which provides poles or areas through which the beam may pass. As will be discussed below, the pattern of poles provided by illuminator aperture124is typically dependent upon an anticipated type of patterning on reticle104. Once a beam, or portions of the beam, passes through illuminator aperture124, the beam is condensed by a condenser lens128. Condenser lens128delivers the beams passing through illuminator aperture124to reticle104at a desired angle of incidence.

Reticle104may be patterned with an isolated geometry, a dense geometry, or a varied geometry. The type of patterning on reticle104is typically dependent upon a desired integrated circuit design to be patterned on wafer108. When reticle104has a varied geometry, reticle104may include areas which are sparsely populated and areas which are densely populated.FIG. 2ais a diagrammatic representation of a reticle with an isolated pattern geometry, i.e., a reticle which is relatively sparsely populated. A reticle200includes patterned features or contacts204which may have at least one dimension ‘d1’208that is a critical dimension. As will be appreciated by those skilled in the art, contacts204are generally open segments or print holes in reticle200.

Typically, dimension ‘d1’208is in the range of approximately one micron or less. More generally, the critical dimensions including dimension ‘d1’208are in a range from approximately a fraction of an illumination wavelength to approximately a relatively low multiple of the illumination wavelength. When reticle200is considered to have an isolated geometry, then adjacent contacts204are typically spaced at distances of approximately a few times dimension ‘d1’208, or a relatively low multiple of dimension ‘d1’208. As shown, contact204ais spaced apart from contact204bby a distance ‘d2’212which is generally substantially more than the distance associated with dimension ‘d1’208.

FIG. 2bis a diagrammatic representation of a reticle with a dense pattern geometry. A reticle220includes features or contacts224which have at least one dimension ‘d1’228that is defined as a critical dimension. When reticle220is densely patterned, contacts224are typically spaced apart such that a distance ‘d2’232between adjacent contacts224a,224bis less than or approximately equal to the critical dimension, e.g., dimension ‘d1’228.

The configuration of an illuminator aperture that is used in an illuminator which provides a beam, e.g., a beam of light, to a reticle is generally dependent upon the pattern of features or contacts on the reticle. In other words, an illuminator aperture is typically chosen based upon the requirements of a reticle which is to be used with the illuminator aperture. The layout of an illuminator aperture effectively defines the directions at which features on a reticle are illuminated. In addition, the layout or configuration of an illuminator aperture also defines the direction or directions in which light scatters from a reticle.

Typically, the configuration of an illuminator aperture that is to be used with a reticle which has an isolated or sparse pattern geometry varies from the configuration of an illuminator aperture that is to be used with a reticle which has a dense pattern geometry. Since the illuminator aperture serves as an attenuated phase shift mask, different illumination requirements are associated with the patterning of isolated and dense geometries. When a reticle has an isolated pattern geometry, a small sigma, on-axis illuminator aperture is used to meet illumination requirements for patterning isolated pattern images onto a wafer. Alternatively, an off-axis illuminator aperture is used to meet illumination requirements for patterning dense pattern images onto a wafer.

With reference toFIG. 3, a small sigma, on-axis illuminator aperture will be described. An illuminator aperture300includes a pole304, e.g., an opening, that is positioned substantially in the center to illuminator aperture300. Pole304is arranged to allow a beam such as a beam of light to pass therethrough to a reticle (not shown). Illuminator aperture300is configured to substantially optimize the patterning of isolated features onto a wafer (not shown). While the configuration of illuminator aperture300is effective for use in accurately patterning isolated features, the configuration of illuminator aperture300is generally relatively poor with respect to the accurate patterning of dense features.

As previously mentioned, when dense features are to be patterned, an off-axis illuminator aperture is typically used.FIGS. 4aand4bare diagrammatic representations of off-axis illuminator apertures with substantially circular poles. A first off-axis illuminator aperture400with substantially circular poles404is arranged with four poles404in a square pattern, as shown inFIG. 4a. The arrangement of poles404generally enables precise patterning of dense features. However, the arrangement of poles404does not allow for the precise patterning of isolated features. Poles414of illuminator aperture410, as shown inFIG. 4b, are positioned in a diamond pattern. Like poles404of illuminator aperture400, the positioning of poles414of illuminator aperture410is substantially optimized for the patterning of dense features. When the positioning of poles414is substantially optimized for the patterning of dense features, illuminator aperture410does not allow for the accurate patterning of isolated features.

In lieu of having substantially circular poles, an off-axis illuminator aperture may have poles of other shapes. By way of example, poles may have substantially triangular shaped poles.FIGS. 5aand5bare diagrammatic representations of off-axis illuminator apertures which have substantially triangular shaped poles. An illuminator aperture500includes substantially triangular poles504which are arranged in a square pattern, as shown inFIG. 5a. Substantially triangular poles514which are included on an illuminator aperture510ofFIG. 5bare arranged in a diamond pattern. While both the square pattern and the diamond pattern of poles504and poles514, respectively, are effective for optimizing the patterning of isolated features, neither pattern allows for the precise patterning of dense features.

When an illuminator aperture allows isolated features to be accurately patterned, the illuminator aperture patterns dense features relatively poorly. That is, when an illuminator aperture provides relatively good dimensional control of isolated feature images on a wafer, the illuminator aperture generally does not provide good dimensional control for dense feature images on a wafer. Similarly, when an illuminator aperture allows dense features to be accurately patterned, the illuminator aperture patterns isolated features relatively poorly.

Often, semiconductor wafers require areas which require isolated patterning and areas which require dense patterning. In other words, many wafers have areas which will have isolated feature images and areas which have dense feature images. Reticles that are used to pattern both isolated feature images and dense feature images on a wafer will also portions which have isolated features and portions which have dense features. When reticles include both isolated features and dense features, then the use of an illuminator aperture which is good for patterning the isolated features is not as good for patterning the dense features. Alternatively, the use of an illuminator aperture which is good for patterning the dense features is not as good for patterning the isolated features. As such, it is generally necessary to sacrifice the precise dimensional control of some feature images for the precise dimensional control of other feature images.

Sacrificing the dimensional control or the accuracy with which feature images, i.e., either isolated feature images or dense feature images, are patterned onto a wafer may cause the quality of semiconductor chips formed from the wafer to suffer. As such, when a wafer has both an isolated pattern geometry and a dense pattern geometry, the choice of either a small sigma, on-axis illuminator aperture or an off-axis illuminator aperture to use in patterning the wafer will result in the sacrifice of the accuracy with which either dense feature images or isolated feature images, respectively, are patterned onto the wafer. When some features on a wafer are inaccurately formed, the functionality, e.g., the performance, of semiconductor chips included on the wafer may be unacceptable.

Therefore, what is needed is a system and a method which enables both isolated pattern geometries and dense pattern geometries to be relatively accurately formed on a wafer. More specifically, what is desired is an illuminator aperture which enables good dimensional control of both isolated pattern images and dense pattern images formed on a wafer.

SUMMARY OF THE INVENTION

The present invention relates to a method and an apparatus for enabling both isolated and dense patterns to be accurately patterned onto a wafer. According to one aspect of the present invention, an illumination system that is suitable for use as a part of a projection tool includes an illumination source and an illuminator aperture. The illuminator aperture has a center point and an outer edge, and also includes a first pole and a second pole. The first pole is defined substantially about the center point, and the second pole is defined substantially between the first pole and the outer edge of the first pole. The illumination source is arranged to provide a beam to the illuminator aperture. In one embodiment, the second pole has an edge that is substantially coincident with the outer edge of the illuminator aperture.

An illuminator or, more specifically, an illuminator aperture, which includes a center pole and at least one outer pole allows the different requirements associated with patterning isolated features and dense features of an integrated circuit design using an attenuated phase shift mask to be substantially addressed using a single illuminator aperture. That is, features of both a small sigma, on-axis illuminator aperture and an off-axis illuminator aperture may be incorporated into a single illuminator aperture such that neither the patterning of isolated features nor the patterning of dense features is significantly sacrificed for the other.

According to another aspect of the present invention, an illuminator aperture that is suitable for use as a component of an illumination system that is a part of a projection tool includes a center pole and a plurality of outer poles. The center pole is located about a center point of the illuminator aperture, and each outer pole is located between the center pole and an outer edge of the illuminator aperture. In one embodiment, the center pole has a first area and each outer pole has a second area that is effectively the same as the second area. In another embodiment, the center pole has an area that is approximately equal to the sum of the areas of all outer poles.

In accordance with still another aspect of the present invention, a photolithography apparatus includes an object, a reticle, and an illuminator. The reticle has a plurality of patterns that is to be patterned onto the object, and the illuminator has an illumination source and an illuminator aperture. The illumination source projects a beam through the illuminator aperture to the reticle. The illuminator aperture has a layout that includes an on-axis element and at least one off-axis element. In one embodiment, the plurality of patterns includes isolated patterns and dense patterns, and the layout of the illuminator aperture allows both the isolated patterns and the dense patterns to be patterned onto the object.

These and other advantages of the present invention will become apparent upon reading the following detailed descriptions and studying the various figures of the drawings.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The accuracy with which feature images, i.e., either isolated feature images or dense feature images, are patterned onto a wafer is typically crucial, since inaccurately formed images may adversely affect the performance of semiconductor chips formed from the wafer. When a small sigma, on-axis illuminator aperture is used to optimize the patterning of isolated features on a wafer which is to be patterned with both isolated features and dense features, the accuracy with which dense features may be formed is effectively sacrificed. Conversely, when an off-axis illuminator aperture is used to optimize the patterning of dense features on such a wafer, the accuracy with which isolated features may be formed is effectively sacrificed.

An illuminator aperture which has a layout that is conducive to both the patterning of isolated feature geometries and the patterning of dense feature geometries allows each of the geometries to be patterned substantially without sacrificing the other geometries. Creating an overall illuminator aperture which effectively combines a small sigma, on-axis illuminator aperture with an off-axis illuminator aperture effectively enables both isolated features and dense features to be relatively accurately patterned. Hence, the dimensional control of patterns including both isolated features and dense features may be enhanced. By controlling the sizes of poles as well as the location of poles in an illuminator aperture, the precision with which features may be formed on a wafer may be substantially optimized such that both isolated features and dense features are relatively accurately patterned.

With reference toFIG. 6, the use of an overall illuminator aperture which effectively combines components of a small sigma, on-axis illuminator aperture with components of an off-axis illuminator aperture will be described in accordance with an embodiment of the present invention. An illumination source604, e.g., a source of light or a source of electrons, provides a beam to an illuminator aperture608. It should be appreciated that the beam provided by illumination source604may generally be a beam of light. Illuminator aperture608includes poles610that are arranged in a layout which encompasses both a layout for a small sigma, on-axis illuminator aperture and a layout for an off-axis illuminator aperture. As such, the use of illuminator aperture608allows for good patterning of dense features substantially without significantly adversely affecting the patterning of isolated features, and vice versa.

Once the beam passes through illuminator aperture608, the beam is provided to a reticle612which is patterned with both isolated features614and dense features616. It should be appreciated that although the beam may be provided to reticle612through a condenser lens, a condenser lens has not been shown for ease of illustration. Poles610are arranged such that the illumination provided to reticle612is relatively good for both isolated features614and dense features616. As a result, when features614,616are projected onto a wafer618, the dimensions associated with features614,616as patterned onto wafer618are substantially as expected. In other words, since illuminator aperture608includes poles610which are positioned as appropriate for both a small sigma, on-axis layout and an off-axis layout, the dimensional control of feature images (not shown) on wafer618is relatively precise for both isolated features614and dense features616.

Illuminator aperture608may take on a variety of different configurations in that the number of poles610, as well as the shape of poles610may vary. The location of poles610may also vary. Generally, however, since illuminator aperture608is substantially a combination of a small sigma, on-axis illuminator aperture and an off-axis illuminator aperture, illuminator aperture608includes a pole610that is approximately in the center of illuminator aperture608, as well as at least one pole610that is located between the approximate center and the outer edge of illuminator aperture608. In one embodiment, the number of poles610may be three, e.g., for a 3-pole illuminator aperture, or five, e.g., for a 1-4-pole illuminator aperture or a 5-pole illuminator aperture.

Referring next toFIG. 7a, one configuration of a 5-pole illuminator aperture will be described in accordance with an embodiment of the present invention. A 5-pole illuminator aperture700includes outer poles710a-dand a center pole712. As shown, poles710a-dand center pole712have approximately the same sigma (σ) and approximately the same area. Pole712, which is arranged to facilitate the patterning of isolated features, is located substantially at or about a center point714of illuminator aperture700and is a small sigma, on-axis pole. Poles710a-d, which are arranged to facilitate the patterning of dense features are located along axes716,720which meet at center point714. In other words, poles710a-dare each in line with an appropriate axis716,720. In the described embodiment, poles710a-deach have an area that is substantially equal to the area of pole712. Additionally, poles710a-dare such that each pole710a-dhas an outer edge that substantially coincides with the outer edge of illuminator aperture700. By either or both substantially optimizing sigma (σ) for poles710a-dand substantially optimizing the distance between center point714and poles710a-d, the exposure latitude associated with illuminator aperture700may be improved.

Illuminator aperture700may be considered to be a “straight” off-axis 5-pole illuminator aperture in that poles710a-dare each in line with an appropriate axis716,720. The location of poles710a-drelative to pole712and the outer edge of illuminator aperture700may be chosen, e.g., substantially optimized, to provide good patterning of both isolated features and dense features imaged using illuminator aperture700during a process such as an integrated circuit manufacturing process.

While poles710a-dare in a straight off-axis alignment, poles710a-dmay instead be in a “diagonal” off-axis alignment.FIG. 7bis a diagrammatic representation of a diagonal 5-pole off-axis illuminator aperture in accordance with an embodiment of the present invention. A 5-pole illuminator aperture740includes outer poles760a-dand a center pole712. Poles760a-dare in a substantially diagonal layout with respect to axes766,770in that none of poles760a-dare aligned along axes766,770. The location of poles760a-dis such that poles760a-dare located between a center756of illuminator aperture740and an outer periphery of illuminator aperture740. Pole752is located substantially at or about center756of illuminator aperture740. As shown, each of poles760a-dand pole752have substantially the same area.

When the layout of an illuminator aperture used as a part of an overall illuminator is optimized to provide the best possible patterning of both isolated and dense pattern geometries, in addition to changing the locations of poles of the illuminator aperture, the sizes of the poles may also be changed. For instance, the area of a center pole, e.g., center pole712ofFIG. 7a, may be changed to allow the patterning of isolated features to be improved substantially without significantly affecting the patterning of dense features. Typically, by changing the ratio of the area of a center pole relative to the area of an outer pole, the patterning quality of both isolated and dense pattern geometries may be altered.

An illuminator aperture in which a center pole has a greater area than outer poles may be considered to be a 1-4-pole illuminator aperture when there are four outer poles on the illuminator aperture.FIG. 8ais a diagrammatic representation of a straight, 1-4-pole illuminator aperture in accordance with an embodiment of the present invention. A 1-4-pole illuminator aperture800includes a center pole812and four outer poles810a-d. Center pole812is positioned at or about a center814of illuminator aperture800, while outer poles810a-dare positioned between center pole812and an outer edge of illuminator aperture800. As shown, edges of outer poles810a-dsubstantially coincide with the outer edge of illuminator aperture800.

In one embodiment, when design considerations are such that substantially equal illumination power is to be provided to both isolated and dense geometries, the area of center pole812may be approximately equal to the combined areas of poles810a-d. That is, in order to spread power relatively evenly with respect to different pattern geometries, the area of center pole812may be approximately equal to four times the area of one of poles810a-d. When the proportions between the area of center pole812is increased relative to the area of off-axis poles810a-d, i.e., when the area of center pole812is larger than the area of each pole810a-d, then isolated contact hole image formation may be enhanced. On the other hand, when the proportions between the area of center pole812is decreased relative to the area of poles810a-d, dense feature image formation may be enhanced substantially at the expense of the isolated feature images.

Poles810a-dare in a straight, off-axis alignment that poles810a-dare aligned along axes816,820. It should be appreciated that outer poles in a 1-4-pole illuminator aperture may also be in a diagonal, off-axis alignment. With reference toFIG. 8b, a 1-4-pole illuminator aperture in which outer poles are configured in a diagonal orientation will be described in accordance with an embodiment of the present invention. An illuminator aperture840includes a center pole852which is substantially centered about a center point856, and outer poles860a-d. Center pole852has a larger sigma (σ) than each of outer poles860a-d, and may be sized, in one embodiment, such that the area of center pole852is substantially equal to the sum of the areas of outer poles860a-d.

Outer poles860a-dare positioned such that an outer edge of each pole860a-deffectively coincides with an outer edge of illuminator aperture840. The orientation of poles860a-dis such that poles860a-dare offset from axes866,870. As shown, poles860a-deffectively diagonally offset from axes866,870such that poles860a-dform a square pattern on illuminator aperture866,870.

Generally, the use of either a 5-pole illuminator aperture or a 1-4-pole illuminator aperture is particularly suitable for a two-dimensional erase of contact geometries which may include either or both dense feature patterns and isolated feature patterns. It should be appreciated that a two-dimensional pattern layout typically occurs when features have two critical dimensions and are placed in two directions. The two critical dimensions as well as the separation between the features in two directions may vary. As such, to reflect such a variance, the location and the shape of poles in an illuminator aperture may be adjusted as needed. While a 5-pole illuminator aperture or a 1-4-pole illuminator aperture are also suitable for use for other types of overall geometries which include either or both dens feature patterns and isolated feature patterns, some geometries may be better suited for use with a 3-pole illuminator aperture or a 1-2 pole illuminator aperture. By way of example, for one dimensional line space geometries, the use of an illuminator aperture which includes one center pole and two outer poles may result in better performance than an illuminator aperture which includes one center pole and four outer poles.

FIG. 9ais a diagrammatic representation of an illuminator aperture which includes a center pole and two outer poles in accordance with an embodiment of the present invention. An illuminator aperture900includes a center pole912that is substantially centered about a center point914of illuminator aperture900, and outer poles910a,910bwhich are positioned between center point914and an outer edge of illuminator aperture900. Outer poles910a,910b, which are positioned such that an outer edge of each pole910a,910bcoincides with an outer edge of illuminator aperture900.

Poles910a,910bare aligned along axes916,920. Specifically, in the described embodiment, poles910a,910bare aligned along axis920. As such, illuminator aperture900is a straight illuminator aperture. It should be appreciated that the location of poles910a,910bmay vary. By way of example, poles910a,910bmay be oriented in a diagonal configuration.

As shown, center pole912has an area that is approximately equal to the sum of the areas of poles910a,910b. Hence, illuminator aperture900may be considered to be a 1-2-pole illuminator aperture. When center pole912has an area that is approximately equal to the area of one pole910a,910b, illuminator aperture900may generally be considered to be a 3-pole illuminator aperture.FIG. 9bis a diagrammatic representation of an illuminator aperture which includes a center pole and two outer poles which are in a substantially diagonal orientation in accordance with an embodiment of the present invention. An illuminator aperture930includes a center pole952positioned about a center point944of illuminator aperture930and outer poles940a,940bwhich are offset from axes946,950. Since outer poles940a,940bare substantially diagonally displaced relative to axes946,960, illuminator aperture930is a diagonal, off-axis illuminator aperture.

Poles on an illuminator aperture may vary in size and location, as previously mentioned. Poles may also vary in shape, i.e., poles are not necessarily circular in shape. The shapes of poles, for example, may vary depending upon the requirements of a particular system. In some instances, substantially triangular or rectangular shaped outer or center poles may be preferred over circular shaped outer or center poles. Referring next toFIG. 10, an illuminator aperture which includes outer poles that are substantially triangular shaped will be described in accordance with an embodiment of the present invention. A 1-4 pole illuminator aperture970includes a center pole982that is positioned about a center point974. Illuminator aperture970also includes outer poles980a-dwhich are positioned between center point974and an outer edge of illuminator aperture970such that edges of outer poles980a-dare substantially coincident with the outer edge. In the described embodiment, poles980a-dare substantially triangular shaped, and are offset from axes986,990. Additionally, the area of center pole982is approximately equal to the combined areas of poles980a-d. Hence, illuminator aperture970is a diagonal, off-axis 1-4 pole illuminator aperture.

With reference toFIG. 11, a photolithography apparatus which may include an enhanced illuminator, i.e., an illuminator which uses an illuminator aperture which combines features of a small sigma illuminator aperture with features of an off-axis illuminator aperture, will be described in accordance with an embodiment of the present invention. A photolithography or exposure apparatus40includes a wafer positioning stage52that may be driven by a planar motor (not shown), as well as a wafer table51that is magnetically coupled to wafer positioning stage52by utilizing an actuator such as an EI-core actuator, e.g., an EI-core actuator with a top coil and a bottom coil which are substantially independently controlled. The planar motor which drives wafer positioning stage52generally uses an electromagnetic force generated by magnets and corresponding armature coils arranged in two dimensions. A wafer64is held in place on a wafer holder or chuck74which is coupled to wafer table51. Wafer positioning stage52is arranged to move in multiple degrees of freedom, e.g., between three to six degrees of freedom, under the control of a control unit60and a system controller62. The movement of wafer positioning stage52allows wafer64to be positioned at a desired position and orientation relative to a projection optical system46.

Wafer table51may be levitated in a z-direction10bby any number of voice coil motors (not shown), e.g., three voice coil motors, which are effectively an array of motors. The motor array of wafer positioning stage52is typically supported by a base70. Base70is generally supported to a ground via isolators54. Reaction forces generated by motion of wafer stage52may be mechanically released to a ground surface through a frame66.

An illumination system42, which includes an enhanced illuminator aperture80, is supported by a frame72. Frame72is supported to the ground via isolators54. Illumination system42includes an illumination source (not shown), and is arranged to project a radiant energy, e.g., light, through illuminator aperture80to a mask pattern on a reticle68that is supported by and scanned using a reticle stage assembly44which may include a coarse stage and a fine stage. At least some of the radiant energy passes through reticle68, and is focused through projection optical system46, which is supported on a projection optics frame50and may be supported the ground through isolators54. Isolators54may be part of an overall active vibration isolation system (AVIS).

A first interferometer56is supported on projection optics frame50, and functions to detect the position of wafer table51. Interferometer56outputs information on the position of wafer table51to system controller62. A second interferometer58is supported on projection optical system46, and detects the position of at least a part of reticle stage assembly44which supports a reticle68. Interferometer58also outputs position information to system controller62.

It should be appreciated that there are a number of different types of photolithographic apparatuses or devices. For example, photolithography apparatus40may be used as a scanning type photolithography system which exposes the pattern from reticle68onto wafer64with reticle68and wafer64moving substantially synchronously. In a scanning type lithographic device, reticle68is moved perpendicularly with respect to an optical axis of a lens assembly associated with projection optical system46or illumination system42by reticle stage assembly44. Wafer64is moved perpendicularly to the optical axis of projection optical system46by a wafer stage52. Scanning of reticle68and wafer64generally occurs while reticle68and wafer64are moving substantially synchronously.

Alternatively, photolithography apparatus or exposure apparatus40may be a stepping type, or a step-and-repeat type, photolithography system that exposes reticle68while reticle68and wafer64are stationary, i.e., at a substantially constant velocity of approximately zero meters per second. In one step and repeat process, wafer64is in a substantially constant position relative to reticle68and projection optical system46during the exposure of an individual field. Subsequently, between consecutive exposure steps, wafer64is consecutively moved by wafer positioning stage52perpendicularly to the optical axis of projection optical system46and reticle68for exposure. Following this process, the images on reticle68may be sequentially exposed onto the fields of wafer64so that the next field of wafer64is brought into position relative to illumination system42, reticle68, and projection optical system46.

It should be understood that the use of photolithography apparatus or exposure apparatus40, as described above, is not limited to being used in a photolithography system for semiconductor manufacturing. For example, photolithography apparatus40may be used as a part of a liquid crystal display (LCD) photolithography system that exposes an LCD device pattern onto a rectangular glass plate or a photolithography system for manufacturing a thin film magnetic head.

The illumination source of illumination system42may be g-line (436 nanometers (nm)), i-line (365 nm), a KrF excimer laser (248 nm), an ArF excimer laser (193 nm), and an F2-type laser (157 nm). Alternatively, illumination system42may also use charged particle beams such as x-ray and electron beams. For instance, in the case where an electron beam is used, thermionic emission type lanthanum hexaboride (LaB6) or tantalum (Ta) may be used as an electron gun. Furthermore, in the case where an electron beam is used, the structure may be such that either a mask is used or a pattern may be directly formed on a substrate without the use of a mask.

With respect to projection optical system46, when far ultra-violet rays such as an excimer laser is used, glass materials such as quartz and fluorite that transmit far ultra-violet rays is preferably used. When either an F2-type laser or an x-ray is used, projection optical system46may be either catadioptric or refractive (a reticle may be of a corresponding reflective type), and when an electron beam is used, electron optics may comprise electron lenses and deflectors. As will be appreciated by those skilled in the art, the optical path for the electron beams is generally in a vacuum. In addition, with an exposure device that employs vacuum ultra-violet (VUV) radiation of a wavelength that is approximately 200 nm or lower, use of a catadioptric type optical system may be considered. Examples of a catadioptric type of optical system include, but are not limited to, systems which include a reflecting optical device and incorporates a concave mirror, or a concave mirror in addition to a beam splitter.

Further, in photolithography systems or projection tools, when linear motors are used in a wafer stage or a reticle stage, the linear motors may be either an air levitation type that employs air bearings or a magnetic levitation type that uses Lorentz forces or reactance forces. Additionally, the stage may also move along a guide, or may be a guideless type stage which uses no guide.

Alternatively, a wafer stage or a reticle stage may be driven by a planar motor which drives a stage through the use of electromagnetic forces generated by a magnet unit that has magnets arranged in two dimensions and an armature coil unit that has coil in facing positions in two dimensions. With this type of drive system, one of the magnet unit or the armature coil unit is connected to the stage, while the other is mounted on the moving plane side of the stage.

Movement of the stages as described above generates reaction forces which may affect performance of an overall photolithography system. Reaction forces generated by the wafer (substrate) stage motion may be mechanically released to the floor or ground by use of a frame member as described above. Additionally, reaction forces generated by the reticle (mask) stage motion may be mechanically released to the floor (ground) by use of a frame member.

A photolithography system according to the above-described embodiments, e.g., a photolithography apparatus which may include one or more dual force actuators, may be built by assembling various subsystems in such a manner that prescribed mechanical accuracy, electrical accuracy, and optical accuracy are maintained. In order to maintain the various accuracies, prior to and following assembly, substantially every optical system may be adjusted to achieve its optical accuracy. Similarly, substantially every mechanical system and substantially every electrical system may be adjusted to achieve their respective desired mechanical and electrical accuracies. The process of assembling each subsystem into a photolithography system includes, but is not limited to, developing mechanical interfaces, electrical circuit wiring connections, and air pressure plumbing connections between each subsystem. There is also a process where each subsystem is assembled prior to assembling a photolithography system from the various subsystems. Once a photolithography system is assembled using the various subsystems, an overall adjustment is generally performed to ensure that substantially every desired accuracy is maintained within the overall photolithography system. Additionally, it may be desirable to manufacture an exposure system in a clean room where the temperature and humidity are controlled.

Although only a few embodiments of the present invention have been described, it should be understood that the present invention may be embodied in many other specific forms without departing from the spirit or the scope of the present invention. By way of example, an illuminator aperture which is effectively a combination of a small sigma, on-axis illuminator aperture and an off-axis illuminator aperture has been described as having either three poles or five poles. The number of poles, however, may vary widely. That is, the number of poles in an illuminator aperture is not limited to being either three or five.

The configuration of poles in an illuminator aperture may be widely varied. The areas of each pole relative to other poles may vary and the location of poles may vary. In addition, the shape of each pole may vary. For example, while a 3-pole illuminator aperture has been described as having an on-axis pole that has a greater area than each off-axis pole, each of the poles may have substantially the same area. The off-axis poles may also be substantially triangular or rectangular in shape, i.e., the off-axis poles are not necessarily circular in shape.

The outer poles of an illuminator aperture may be arranged such that an outer edge of each pole substantially coincides with the outer edge of the illuminator aperture, as discussed above. In some embodiments, however, the outer edge of each outer pole is not necessarily coincident with the outer edge of the illuminator aperture.

The size of outer poles of an illuminator aperture have generally been described as each either having approximately the same area as a center pole, or having a smaller area than the than the center pole. The size of the outer poles, in one embodiment, may be such that each outer pole has a larger area than the center pole.

While the outer poles of an illuminator aperture have been described as having substantially the same size and shape, as well as the same sigma (σ), it should be appreciated that the outer poles are not necessarily uniform. That is, each outer pole of an illuminator aperture may have a different area or shape. The choice of an appropriate are or shape for each outer pole may be based upon the requirements of a particular system without departing from the spirit or the scope of the present invention. Therefore, the present examples are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope of the appended claims.