1. Field of the Invention
The present invention relates to a programmable mask for fabricating a biomolecule array or polymer array, an apparatus for fabricating biomolecule array or polymer array including the programmable mask, and a method of fabricating biomolecule array or polymer array using the programmable mask.
2. Description of the Related Art
Research has been conducted on performing various kinds of experiments into one combined experiment using a biomolecule array or polymer array. Examples of a biomolecule array or polymer array include polypeptide, carbohydrate, or an array of nucleic acid (DNA, RNA). In order to conduct such an experiment, array having high density needs to be formed on a substrate with a reasonable price.
A conventional method of fabricating a biomolecule array or polymer array may be divided into spotting, electronic addressing and photolithography. Spotting is performed by having a micro robot selectively drop a biochemical substance on a desired spot while the micro robot three-dimensionally moves. Electronic addressing is performed by fixing a biomolecule to a specific electrode of a microelectrode array after controlling the electrode voltage. Photolithography is performed by selectively exposing a desired spot on a surface to light to change the surface, which then causes a reaction at a specific location due to bonding between the surface and a biomolecule at the specific location.
In more detail, the spotting method is divided into contact printing and non-contact printing in which a solution is stamped on a paper and a solution is dropped on a paper, respectively. In contact printing, loading, printing, and washing are sequentially performed by an XYZ robot. Non-contact printing can be divided into dispensing and ink-jet printing. Dispensing involves applying a solution in a dropwise fashion, like when a micropipette is used. Ink jet printing involves applying minute pressure to a reservoir which causes a solution to be ejected.
Electronic addressing involves fixing a biomolecule to a plate using a voltage control function of the microelectrode array. Electronic addressing can be divided into a method of generating a physicochemical bond by moving a biomolecule having an electric charge to the surface of an electrode and a method of fixing a biomolecule in a thin film when the thin film is formed by electrochemical deposition.
Photolithography used in a semiconductor production process can be used to manufacture an array having high density and enables parallel synthesis. However, a number of photo masks is required, thereby increasing cost and consuming time. Therefore, a programmable mask which can control light paths through a plurality of pixels without using a photo mask is being developed and is disclosed in U.S. Pat. No. 6,271,957. The programmable mask includes a method of regulating reflection of light and a method of regulating penetration of light. For example, a micromirror array or a liquid crystal display (LCD) can be used.
The method of fabricating a biomolecule array has two problems: fabrication of a high density pattern is difficult due to diffraction of incident light, and more time is needed for forming a biomolecule such as DNA synthesis, since light intensity is decreased due to an insufficient amount of light penetration on a polarizing plate disposed at both ends of a panel in a LCD. The reasons of raising such problems are described below.
FIG. 1 is a side cross-sectional view of an apparatus for fabricating a biomolecule array including a programmable mask, in which a conventional LCD is used. Referring to FIG. 1, the apparatus includes UV polarizing plates 110 and 120, a LCD panel 130 having a color filter excluded, a DNA synthesis chamber 140, and a DNA chip board 150. Oligomers 160 and 160′ are synthesized at the bottom of the DNA chip board 150. UV light that has passed through the UV polarizing plates 110 and 120 passes through a chip having a thickness (t) and is diffracted, and thus, adjacent spots of UV light are overlapped (d). In other words, the diffraction of UV light is increased compared to the diffraction of UV in the width of a black matrix that isolates each pixel in an LCD. Therefore, when considering each pixel of a backlit LCD as an independent optical system, UV beams that have passed through a light pixel reach to the lower part of a glass substrate of a DNA chip and mix with each other. When this DNA chip is analyzed using a DNA scanner, not every DNA spot pattern is separated, and instead, it can be seen that the whole substrate of the chip is coated with oligomer. When an oligomer spot is observed on a plane surface, the overlapped oligomer 160′ can be seen. Consequently, isolation of spots is not possible and thus, the chip cannot be embodied in the form of a spot array. In order to embody a spot array of an oligomer, not all pixels can be used, and instead, unused pixels should be arranged between pixels. Therefore, since not all of the LCD pixels can be used, an array having high density cannot be embodied.
FIG. 2 is a plane view of a programmable mask and a driving circuit unit using a conventional LCD. Pattern isolation between adjacent pixels is not impossible as in FIG. 1, and pixels of the LCD should be driven in a mosaic pattern, as illustrated in FIG. 2. Each pixel in FIG. 2 is divided into domain pixels 210 (O) where an oligomer is attached and pixel areas 220 (X) where an oligomer is not attached. Since pixels X which are in complete blocking mode permanently intercepting UV light are maintained between operating pixels O, pattern mixing due to diffraction can be prevented. This also decreases the density of a DNA pattern on the oligomer chip.
Although a mosaic patterned oligomer array can be manufactured with an increase in the density of a DNA pattern, the amount of polarized light transmitted through a UV polarizing plate is small, and thus, UV exposure time which is 10 times greater is required compared to the case where photo masks for manufacturing the semiconductor are used.