BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described, by way of example, with reference to the accompanying drawings, in which:
FIGS. 1 and 2 are perspective views of a substrate with a layer to be etched deposited thereon, illustrating a conventional photolithography method for transmitting a circuit pattern from a photomask onto a photoresist layer by UV light exposure, followed by development of the photoresist;
FIG. 3 is a schematic diagram illustrating a direct printing lithography system according to the present invention;
FIG. 4 is a bottom perspective view of a jet printing head element of the system of FIG. 3;
FIG. 5 is a cross-section of a nozzle opening of the jet printing head, illustrating multiple drops of liquid photoresist being dispensed from the nozzle opening;
FIG. 6 is a perspective view of a substrate having a layer to be etched deposited thereon, illustrating jet-printing of a liquid photoresist layer in the form of a circuit pattern onto the layer to be etched according to the method of the present invention;
FIG. 7 is a perspective view of the photoresist layer deposited in the form of a circuit pattern according to the step shown in FIG. 6, illustrating jet-printing of an etchant onto the regions of the layer to be etched which are not covered by the photoresist layer;
FIGS. 8A-8D are schematic views illustrating sequential jet-printing of a pre-wetting solution, a liquid photoresist, an etchant and a photoresist chemical, respectively, onto a circuit exposure field on a substrate to form a circuit pattern in a layer on the substrate;
FIG. 9 is a flow diagram illustrating sequential process steps carried out according to a first embodiment of the method according to the present invention;
FIG. 10 is a flow diagram illustrating sequential process steps carried out according to a second embodiment of the method according to the present invention; and
FIG. 11 is a flow diagram illustrating sequential process steps carried out according to a third embodiment of the method according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring initially to FIGS. 3-5, an illustrative embodiment of the direct printing lithography system, hereinafter system, of the present invention is generally indicated by reference numeral 30 in FIG. 3. The system 30 includes a computer system 36 and a jet printing head 40 connected to the computer system 36. The computer system 36 is provided with supporting software which facilitates the storage of a circuit layout file containing various circuit layout pattern configurations to be etched in a material layer or layers on a substrate 88 by operation of the jet printing head 40, as hereinafter further described. The software enables the computer system 36 to generate and transmit printing signals 38, which correspond to a circuit pattern programmed into the computer system 36 and selected for etching into the material layer on the substrate 88, to the jet printing head 40. The printing signals 38 correspond to the circuit pattern image transmitted from the computer system 36 via the printing signals 38 and cause the jet printing head 40 to jet-print a liquid photoresist 81 (FIG. 5) onto a layer to be etched provided on the substrate 88, in the configuration of the circuit pattern. This eliminates the need to blanket-deposit a photoresist layer on the layer to be etched, expose the photoresist to UV light through a photomask or reticle, and develop the photoresist to remove the non-cross-linked regions of photoresist from the layer, since the photoresist is deposited on the layer in the configuration of the circuit pattern.
As shown in FIG. 4, the jet printing head 40 typically includes an elongated printing head body 42 which is a corrosion-resistant and etch-resistant material such as quartz, for example. The printing head body 42 may be divided into a pre-wetting section 44, provided with an array of pre-wetting nozzle openings 46; a photoresist-printing section 48, provided with an array of photoresist-printing nozzle openings 50; an etchant-printing section 52, provided with an array of etchant printing nozzle openings 54; and a photoresist strip section 56, provided with an array of photoresist strip nozzle openings 58. Heating elements 60 typically separate the adjacent pre-wetting section 44, photoresist-printing section 48, etchant-printing section 52 and photoresist strip section 56 from each other in the printing head body 42.
As shown in FIG. 3, a reservoir 76 provided on or separate from the jet printing head 40 may include a pre-wetting solution compartment 78 for containing a pre-wetting solution 79; a photoresist compartment 80 for containing a liquid photoresist 81; an etchant compartment 82 for containing a liquid or gas etchant 83; and a photoresist strip chemical compartment 84 for containing a photoresist strip chemical 85.
As shown in FIG. 5, each photoresist-printing nozzle opening 50 is typically provided at the bottom of a corresponding tapered chamber 50a having an inlet 50b that is provided in fluid communication with the photoresist compartment 80 of the reservoir 76. A flexible or deformable membrane 62 is provided in the top of each chamber 50a. A deformable piezo crystal 64 engages each membrane 62. The computer system 36 (FIG. 3) is electrically connected to the deformable piezo crystal 64 of each photoresist-printing nozzle opening 50. Accordingly, in operation of the system 30 as hereinafter further described, the computer system 36, into which is programmed the circuit pattern image to be etched in a layer on the substrate 88, generates and transmits printing signals 38, which correspond to the circuit pattern image, to the printing head 40. The printing signals 38 activate and expand the piezo crystals 64 of certain ones of the photoresist-printing nozzle openings 50. Each activated piezo crystal 64, in turn, deforms the membrane 62, causing a pressure impulse within the chamber 50a. The resulting pressure impulse expels a single droplet of photoresist 81 from the photoresist printing nozzle opening 50 onto a substrate 88. The chamber 50a is refilled with the photoresist 81 by capillary action at the nozzle opening 50. In the foregoing manner, liquid photoresist 81 is expelled from certain ones of the multiple photoresist-printing nozzle openings 50 in the photoresist-printing section 48 of the jet printing head 40 to jet-print the photoresist 81 on the substrate 88 in the form of the desired circuit pattern.
As heretofore described in FIG. 5 with respect to each photoresist-printing nozzle opening 50, each pre-wetting nozzle opening 46 in the pre-wetting section 44; each etchant-printing nozzle opening 54 in the etchant-printing section 52; and each photoresist strip nozzle opening 58 in the photoresist strip section 56 is typically also provided at the bottom of a corresponding tapered chamber 50a having an inlet 50b, a deformable membrane 62 in the top of the chamber 50a, and a deformable piezo crystal 64 engaging the membrane 62 for receiving printing signals 38 from the computer system 36. This facilitates jet-printing of the corresponding liquid from the pre-wetting solution compartment 78, etchant compartment 82 and photoresist strip chemical compartment 84, respectively, depending on the circuit pattern to be etched into the layer on the substrate 88.
Referring next to FIGS. 3, 6, 7 and 8A-8D, typical operation of the system 30 is as follows. A material layer 90, which may be an oxide or metal layer, for example, to be etched in the form of a selected circuit pattern, is deposited on a semiconductor substrate 88. A spin-on BARC (bottom anti-reflective coating) layer 92 may be blanket-deposited on the material layer 90. The portion of the material layer 90 that is to be etched in the form of a circuit pattern defines a circuit exposure field 96 on the substrate 88. Multiple exposure fields 96 are typically provided on the substrate 88, in adjacent relationship to each other, for sequential formation of the circuit pattern in each of the exposure fields 96.
The circuit pattern to be etched into the material layer 90 is initially programmed into the computer system 36. The heating elements 60 in the jet printing head 40 generate heat which prevents solidification of the photoresist 81 as it is dispensed from the jet printing head 40, as hereinafter described. As shown in FIG. 8A, the jet printing head 40 of the system 30 is positioned over the substrate 88, with the pre-wetting section 44 positioned directly over the first exposure field 96 to be processed. Depending on the circuit pattern to be etched in the material layer 90, the computer system 36 generates and transmits printing signals 38 that activate certain ones of the pre-wetting nozzle openings 46 in the pre-wetting section 44, through the piezo crystal 64 and membrane 62 (FIG. 5) of each pre-wetting nozzle opening 46, to cause the jet-printing of pre-wetting solution 79 onto the BARC layer 92, in the form of the programmed circuit pattern. In typical application, the pre-wetting solution is hexamethlydisilazane, although alternative pre-wetting solutions known by those skilled in the art may be used instead.
As shown in FIG. 8B, after pre-wetting of the exposure field 96, the jet printing head 40 is shifted to position the photoresist-printing section 48 of the jet printing head 40 over the pre-wetted exposure field 96. The computer system 36 generates and transmits printing signals 38, which correspond to a pattern forming the portions of the material layer 90 which are to be shielded and not etched to define the programmed circuit pattern, to the printing head 40. Depending on the circuit pattern programmed into the computer system 36, the printing signals 38 activate certain ones of the photoresist-printing nozzle openings 50 in the photoresist-printing section 48, through the piezo crystal 64 and membrane 62 (FIG. 5) of each. This causes the jet-printing of liquid photoresist 81 onto the BARC layer 92 in the form of the programmed circuit pattern, as shown in FIG. 6. Accordingly, photoresist 81 is not dispensed from those nozzle openings 50 which are located above the regions of the material layer 90 that are to be etched, thus forming windows 94 in those areas on the BARC layer 92.
After it is dispensed onto the exposure field 96, the photoresist 81 is hard-baked to solidify the photoresist 81 in the form of the circuit pattern. As shown in FIG. 8C, the jet printing head 40 is next shifted to position the etchant-printing section 52 of the jet printing head 40 over the exposure field 96. The computer system 36 transmits printing signals 38, which correspond to those regions of the material layer 90 that are to be etched, to the printing head 40. Via the printing signals 38, the computer system 36 activates certain ones of the etchant-printing nozzle openings 54 in the etchant-printing section 52, through the piezo crystal 64 and membrane 62 (FIG. 5) of each. This causes the jet-printing of the liquid or gas etchant 83 onto the BARC layer 92 in the form of the regions of the material layer 90 which are to be etched to define the circuit pattern, as shown in FIG. 7. Accordingly, etchant 83 is not dispensed from those etchant-printing nozzle openings 54 which are located above the hardened photoresist layer 81a, thus etching those regions of the BARC layer 92 and the underlying material layer 90 that correspond to the windows 94.
As shown in FIG. 8D, after jet-printing of the etchant 83 onto the exposure field 96, the jet printing head 40 is shifted to position the photoresist strip section 56 of the jet printing head 40 over the etched exposure field 96. The computer system 36 transmits printing signals 38, which correspond to the portions of the material layer 90 covered by the photoresist layer 81a to define the programmed circuit pattern, to the jet printing head 40. The computer system 36, via the printing signals 38, activates certain ones of the photoresist strip nozzle openings 58 in the photoresist strip section 56, through the piezo crystal 64 and membrane 62 (FIG. 5) of each. This causes the jet-printing of photoresist strip chemical 85 onto the photoresist layer 81a in the form of the programmed circuit pattern. Accordingly, the photoresist layer 81a is stripped from the underlying portions of the material layer 90 which were not etched during the etching step of FIG. 8B, thus leaving the material layer 90 in the form of the desired circuit pattern.
A flow diagram which illustrates sequential process steps carried out according to one embodiment of the present invention is shown in FIG. 9. In step 1, a substrate having a metal or other layer to be etched is provided. In step 2, an anti-reflection layer, such as SiON, SiN or SiC, for example, is provided on the layer to be etched. In step 3, a pre-clean or pre-wetting solution is applied to the anti-reflection layer. In step 4, a bottom anti-reflective coating (BARC) layer is spin-coated on the anti-reflection layer. In step 5, a photoresist layer is net-printed on the BARC layer, which overlies the layer to be etched. The photoresist layer is jet-printed on the BARC layer in the circuit pattern which is to be etched in the layer. The photoresist is then baked in-situ, and an etchant is applied to the BARC layer along the regions not exposed to photoresist. This etches the BARC layer and the underlying material layer in the circuit pattern. In step 6, the photoresist is stripped from the BARC layer.
A flow diagram which illustrates sequential process steps carried out according to another embodiment of the present invention is shown in FIG. 10. In step 1a, a substrate having a metal or other layer to be etched is provided. In step 2a, an anti-reflection layer, such as SiON, SiN or SiC, for example, is provided on the layer to be etched. In step 3a, a pre-clean or pre-wetting solution is applied to the anti-reflection layer. In step 4a, a bottom anti-reflective coating (BARC) layer is spin-coated on the anti-reflection layer. In step 5a, a photoresist layer is jet-printed on the BARC layer overlying the layer to be etched according to the circuit pattern which is to be etched in the layer. This step does not require the use of a mask. In step 6a, the photoresist is then baked in-situ. In step 7a, the photoresist is exposed without the use of a photomask. In step 8a, an etchant is applied to the BARC layer along the regions not exposed to photoresist to etch the BARC layer and the underlying material layer according to the desired circuit pattern. In step 9a, the photoresist is stripped from the BARC layer.
FIG. 11 illustrates sequential process steps carried out according to yet another embodiment of the present invention. In FIG. 1b, a substrate having a metal or other layer to be etched is provided. In step 2b, various process steps are sequentially carried out on each of multiple exposure fields on the substrate. These sequential process steps include pre-wetting or pre-cleaning the layer to be etched; jet-printing a photoresist layer on the layer to be etched, according to a desired circuit pattern; baking of the photoresist; etching the layer according to the desired circuit pattern by jet-printing an etchant on the layer to be etched along the regions of the layer not covered by the photoresist; and stripping the photoresist from the layer, respectively.
While the preferred embodiments of the invention have been described above, it will be recognized and understood that various modifications can be made in the invention and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the invention.
Patent Application
20070289467
