The present invention relates to a method for manufacturing a device, a mask for use in the method and a device manufactured by the method.
A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. comprising part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.
In the manufacture of CCD and CMOS image sensors color filters are applied to the surface of the image sensors such that each detection pixel is covered by a color filter. Most applications use red, green and blue filters and some applications also use cyan, magenta, green and yellow color filters. Thus, one of the last phases of manufacture of a CCD or CMOS image sensor comprises applying to the substrate a layer of a colored radiation sensitive material (resist) and irradiating that radiation sensitive material (the color resist is typically a negative resist) so that during subsequent development of the resist the required filters of that particular color remain in place over the desired pixels. Generally a green or red resist is used first, followed by the other of the green or red resist and finally a blue resist to build up a grid of pixels such as that shown in
It is desirable to provide a method in which the accuracy of alignment of the substrate relative to the mask can be improved during the final manufacturing steps of creating colored filters on CCD and CMOS image sensors.
According to an aspect of the invention, there is provided a device manufacturing method comprising:
projecting a patterned beam of radiation onto a substrate covered in a first layer of colored radiation sensitive material, the pattern of said patterned beam including a pattern for use in forming device features in areas of product die and a pattern for use in forming features of an alignment mark in other areas.
According to an aspect of the invention, there is provided a mask for use in the method comprising patterning structures for endowing a projection beam of radiation with a pattern useful in forming color filters on a die or dies on a substrate and patterning structures for endowing said projection beam of radiation with a pattern useful in forming an alignment mark in areas outside said dies.
According to an aspect of the invention, there is provided a device manufactured according to the method comprising features of said alignment mark.
Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:
a illustrates the substrate of
b illustrates the substrate of
The illumination system may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, for directing, shaping, or controlling radiation.
The support structure supports, i.e. bears the weight of, the patterning device. It holds the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions, such as for example whether or not the patterning device is held in a vacuum environment. The support structure can use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The support structure may be a frame or a table, for example, which may be fixed or movable as required. The support structure may ensure that the patterning device is at a desired position, for example with respect to the projection system. Any use of the terms “reticle” or “mask” herein may be considered synonymous with the more general term “patterning device.”
The term “patterning device” used herein should be broadly interpreted as referring to any device that can be used to impart a radiation beam with a pattern in its cross-section such as to create a pattern in a target portion of the substrate. It should be noted that the pattern imparted to the radiation beam may not exactly correspond to the desired pattern in the target portion of the substrate, for example if the pattern includes phase-shifting features or so called assist features. Generally, the pattern imparted to the radiation beam will correspond to a particular functional layer in a device being created in the target portion, such as an integrated circuit.
The patterning device may be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography, and include mask types such as binary, alternating phase-shift, and attenuated phase-shift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted so as to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in a radiation beam which is reflected by the mirror matrix.
The term “projection system” used herein should be broadly interpreted as encompassing any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, or for other factors such as the use of an immersion liquid or the use of a vacuum. Any use of the term “projection lens” herein may be considered as synonymous with the more general term “projection system”.
As here depicted, the apparatus is of a transmissive type (e.g. employing a transmissive mask). Alternatively, the apparatus may be of a reflective type (e.g. employing a programmable mirror array of a type as referred to above, or employing a reflective mask).
The lithographic apparatus may be of a type having two (dual stage) or more substrate tables (and/or two or more mask tables). In such “multiple stage” machines the additional tables may be used in parallel, or preparatory steps may be carried out on one or more tables while one or more other tables are being used for exposure.
The lithographic apparatus may also be of a type wherein at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, e.g. water, so as to fill a space between the projection system and the substrate. An immersion liquid may also be applied to other spaces in the lithographic apparatus, for example, between the mask and the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of projection systems. The term “immersion” as used herein does not mean that a structure, such as a substrate, must be submerged in liquid, but rather only means that liquid is located between the projection system and the substrate during exposure.
Referring to
The illuminator IL may comprise an adjuster AD for adjusting the angular intensity distribution of the radiation beam. Generally, at least the outer and/or inner radial extent (commonly referred to as σ-outer and σ-inner, respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. In addition, the illuminator IL may comprise various other components, such as an integrator IN and a condenser CO. The illuminator may be used to condition the radiation beam, to have a desired uniformity and intensity distribution in its cross-section.
The radiation beam B is incident on the patterning device (e.g., mask MA), which is held on the support structure (e.g., mask table MT), and is patterned by the patterning device. Having traversed the mask MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of the second positioner PW and position sensor IF (e.g. an interferometric device, linear encoder or capacitive sensor), the substrate table WT can be moved accurately, e.g. so as to position different target portions C in the path of the radiation beam B. Similarly, the first positioner PM and another position sensor (which is not explicitly depicted in
The depicted apparatus could be used in at least one of the following modes:
Combinations and/or variations on the above described modes of use or entirely different modes of use may also be employed.
A colored radiation sensitive material 10 is then applied in a first layer. Typically this first layer of color radiation sensitive material is chosen to be red or green and the substrate W can be aligned on an original alignment mark because alignment sensors can penetrate through the green or red colored first radiation sensitive material 10.
However, with the current alignment sensors used in lithographic apparatus, it can be difficult to accurately align the substrate through a blue (or cyan) color resist because the state of the art alignment sensors use a red laser based alignment system. Alternatives like broadband applications increase the chance that, over the wavelength range, some signal can be detected but this can lead to alignment failure.
In order to alleviate the above mentioned difficulty during imaging of the first layer of colored radiation sensitive material 10 or during imaging of subsequent layer or layers of colored radiation sensitive material, a patterned beam of radiation PB, which is patterned to illuminate only certain areas of the colored radiation sensitive material 10, is patterned to illuminate both areas of a die 40 and areas of a scribe line 50 which are located between dies. Thus, the patterned beam of radiation PB has areas 80 which are patterned for use in forming device features (i.e. filters) in areas of product die 40 as well as areas 90 which are patterned for use in forming features of an alignment mark, particularly in the scribe lines 50.
In
As will be appreciated, if a pattern according to that illustrated in
a shows a first embodiment in which a second radiation sensitive material 20 is applied to the substrate W following development of the first colored radiation sensitive material 110. The second radiation sensitive material 20 is of a different color to the first radiation sensitive material 10. In the embodiment of
A second embodiment is illustrated in
In this way, the substrate may be aligned once through a colored resist (for aligning before exposure of the first colored resist). By carefully choosing the first colored resist to be used (i.e. the one through which conventional alignment marks can most easily be imaged), any difficulties with aligning through colored resist can be minimized. Subsequent alignment will occur on the alignment mark 101 in the resist 10.
The alignment mark 101 will remain during the processing involving all subsequent colored radiation sensitive materials and it is not necessary to add further alignment features during imaging of subsequent colored radiation sensitive materials, though this may be done if desired. Furthermore, the method has been described above in relation to making features in the colored radiation sensitive material 10 which is the first to be applied on the substrate W. However, this is not necessarily the case and the features can be made in other colored radiation sensitive materials further down the processing route. For example, the red radiation sensitive material could be processed in the normal way and the alignment marks only formed in the scribe line areas 50 during imaging of the green colored radiation sensitive material. This is possible because both red and green colored resists do not pose a particular problem for current alignment systems and at the moment it is the blue and cyan colored resists which pose difficulties for the alignment system to image through. However, with future alignment systems, different colored resists may pose problems and the order of laying down of the resist and when the alignment marks are first produced in the resist can be chosen accordingly.
The alignment marks in the scribe line area 50 exist after the processing of the substrate has been completed and may exist at the edge of devices once they have been cut from the substrate W. Therefore, it may be possible to tell whether or not a device has been manufactured using the above described method from the device alone.
As will be appreciated, the mask used to pattern both the device 40 and the alignment mark in the scribe line area 50 will be different to previous masks in that previous masks would not have had a patterning structure for endowing the projection beam of radiation with a pattern used for forming an alignment mark in areas outside the dies. Patterning structures for forming alignment marks would previously have been used at lower levels and such masks would not have been suitable for imaging color resists to form color filters of an image sensor.
Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, liquid-crystal displays (LCDs), thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein may be considered as synonymous with the more general terms “substrate” or “target portion”, respectively. The substrate referred to herein may be processed, before or after exposure, in for example a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology tool and/or an inspection tool. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.
Although specific reference may have been made above to the use of embodiments of the invention in the context of optical lithography, it will be appreciated that the invention may be used in other applications, for example imprint lithography, and where the context allows, is not limited to optical lithography. In imprint lithography a topography in a patterning device defines the pattern created on a substrate. The topography of the patterning device may be pressed into a layer of resist supplied to the substrate whereupon the resist is cured by applying electromagnetic radiation, heat, pressure or a combination thereof. The patterning device is moved out of the resist leaving a pattern in it after the resist is cured.
The terms “radiation” and “beam” used herein encompass all types of electromagnetic radiation, including ultraviolet (LV) radiation (e.g. having a wavelength of or about 365, 355, 248, 193, 157 or 126 nm) and extreme ultra-violet (EUV) radiation (e.g. having a wavelength in the range of 5-20 nm), as well as particle beams, such as ion beams or electron beams.
The term “lens”, where the context allows, may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic and electrostatic optical components.
While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. For example, the invention may take the form of a computer program containing one or more sequences of machine-readable instructions describing a method as disclosed above, or a data storage medium (e.g. semiconductor memory, magnetic or optical disk) having such a computer program stored therein.
The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.