Method and system for enhanced lithographic alignment

#The invention relates to a system and method of enhancing alignment in lithographic systems. The invention also relates to use of a hard mask system for improving alignment processes.

#The invention is directed to the field of lithography and lithographic projection apparatus that encompass a radiation system for supplying a projection beam of radiation, a support structure for supporting a patterning device, which serves to pattern the projection beam according to a desired pattern, a substrate table for holding a substrate; and, a projection system for projecting the patterned beam onto a target portion of the substrate.

#The term “patterning device” as employed here should be broadly interpreted as referring to devices that can be used to endow an incoming radiation beam with a patterned cross-section, corresponding to a pattern that is to be created in a target portion of the substrate. The term “light valve” can also be used in this context. Generally, the pattern will correspond to a particular functional layer in a device being created in the target portion, such as an integrated circuit or other device. Examples of such patterning devices include: A mask. The concept of a mask is well known in lithography and it includes mask types such as binary, alternating phase-shift, and attenuated phase-shift, as well as various hybrid mask types. Placement of such a mask in the radiation beam causes selective transmission (in the case of a transmission mask) or reflection (in the case of a reflective mask) of the radiation impinging on the mask, according to the pattern on the mask. In the case of a mask, the support structure will generally be a mask table, which ensures that the mask can be held at a desired position in the incoming radiation beam, and that it can be moved relative to the beam if so desired; A programmable mirror array. One example of such a device is a matrix-addressable surface having a visco-elastic control layer and a reflective surface. The basic principle behind such an apparatus is that addressed areas of the reflective surface reflect incident light as diffracted light, for example, whereas unaddressed areas reflect incident light as non-diffracted light. Using an appropriate filter, the non-diffracted light can be filtered out of the reflected beam leaving only the diffracted light behind. In this manner, the beam becomes patterned according to the addressing pattern of the matrix-addressable surface. An alternative embodiment of a programmable mirror array employs a matrix arrangement of tiny mirrors, each of which can be individually tilted about an axis by applying a suitable localized electric field or by employing piezoelectric actuators. Once again, the mirrors are matrix-addressable, such that addressed mirrors will reflect an incoming radiation beam in a different direction to unaddressed mirrors. In this manner, the reflected beam is patterned according to the addressing pattern of the matrix-addressable mirrors. The required matrix addressing can be performed using suitable electronic circuitry.

#Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, as set forth below.

#FIG. 1 illustrates a lithographic projection apparatus that includes at least one marker structure.

#FIG. 2 schematically illustrates a computer arrangement according to one embodiment of the invention;

#FIG. 1 schematically depicts lithographic projection apparatus that includes at least one marker structure in accordance with an embodiment of the invention. The apparatus includes: an illumination system IL for providing a projection beam PB of radiation (e.g. UV or EUV radiation). In this particular case, the radiation system also includes a radiation source SO; a first support structure MT (e.g. a mask table) for supporting a patterning device, MA (e.g. a mask) and connected to a first positioner (not shown) for accurately positioning the patterning device with respect to item PL; a second support structure WT (e.g. a wafer table) for holding a substrate, W (e.g. a resist-coated silicon wafer) and connected to a second positioner PW for accurately positioning the substrate with respect to item PL; and a projection system PL (e.g. a reflective projection lens) for imaging a pattern imported to the projection beam PB by patterning device MA onto a target portion C (e.g. comprising one or more dies) of the substrate W.

#The projection system PL is provided with an actuating device AD for adjusting settings of the system. The operation of adjusting settings will be explained hereinafter in more detail.

#As depicted here, the apparatus is of a transmissive type (i.e. has a transmissive mask). However the apparatus may alternatively be of a reflective type (with a reflective mask). Alternatively the apparatus may employ another kind of patterning device, such as a programmable mirror array of a type as referred to above.