JP2006294753A - Method of using photomask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of using a photomask which prevents sticking of electrically-charged particle on a photomask front surface, and which performs a pattern transfer with a high contrast and pattern imprint without pattern defect. <P>SOLUTION: The photomask 20 has a mask pattern 22 which consists of a lightproof material on a quartz substrate 21, is covered with a conductive film 23 of thickness which can assure the sufficient amount of transmitting lights, and is configured so that a slope does not arise in a potential on the above front surface of the photomask. The potential of the photomask front surface is controlled from an outside by a potential control circuit 24. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method of using a photomask used in a photolithography process in manufacturing a semiconductor device or the like.

  Conventionally, as this type of photomask, as shown in FIG. 1, a mask pattern 12 made of a light shielding material is formed on a quartz substrate 11 which is a light transmissive material. The mask pattern 12 is generally formed by forming a single layer of a chromium-based light-shielding material such as chromium (Cr) or chromium oxide, or by laminating it. The quartz substrate 11 is covered with a conductive polymer 13 that can secure a sufficient amount of transmitted light while covering the mask pattern 12. The conductive polymer 13 allows the isolated mask pattern 12 to have the same potential without being electrically isolated, thereby preventing electrostatic breakdown.

  In general, ultraviolet light is used for a transfer operation using a photomask. This ultraviolet light ionizes floating particles such as molecules, and the floating particles become charged particles having a positive or negative charge. Furthermore, charged particles may adhere to the photomask surface due to electrostatic attraction. In particular, the charged particles may adhere to the light-transmitting area of the photomask surface, thereby reducing the amount of transmitted light and reducing the contrast of the mask pattern, or causing a transfer pattern defect. As a result, inconvenience occurs in the transfer of the mask pattern.

  Therefore, in order to cope with this problem, as shown in Patent Document 1, for example, the following measures have been conventionally taken. First, a photomask handling worker performs antistatic such as wearing an earth band or antistatic shoes. Second, an ionizer is disposed in the photomask handling environment to prevent the photomask from being charged. Third, a cover called a pellicle is used to prevent airborne particles from approaching the photomask. This pellicle creates a space in which the photomask surface is closed to the outside air. Fourth, by covering the entire surface of the mask pattern with a conductive film, the mask pattern is not electrically isolated and electrostatic breakdown is prevented.

JP 2004-61884 A (FIG. 1)

  However, although the above measures are performed as a minimum, it is still impossible to eliminate problems such as a decrease in the amount of transmitted light in the light transmitting region and a defect in the transfer pattern due to the adhesion of charged particles on the pattern surface of the photomask. is the current situation.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent charged floating particles, that is, charged particles, from adhering to the photomask surface, and to transfer a pattern with high contrast and pattern transfer without pattern defects. It is an object of the present invention to provide a method of using a photomask that can be

  The present invention adopts the following means in order to solve the above problems. The reference numerals used in the description of the best mode for carrying out the invention and the drawings to be described later are appended in parentheses for reference, but the constituent elements of the present invention are not limited to the appended description.

  First, the invention according to claim 1 has a mask pattern (22) made of a light-shielding material on a photomask substrate (quartz substrate 21), and a film thickness at which the photomask surface on the mask pattern side can secure a sufficient amount of transmitted light. In the photomask (20), which is covered with the conductive film (23) and configured so as not to cause a gradient in the potential on the surface of the photomask, the potential of the conductive film is controlled from the outside. How to use.

  In the photomask (30) having a mask pattern (32) made of a light shielding material on a photomask substrate (quartz substrate 31), an electrode (33) is provided near the photomask on the mask pattern side. , 34) and the potential of the electrode is controlled from the outside.

  First, according to the method of using a photomask according to claim 1, the charged particles can be prevented from adhering to the surface of the photomask by controlling the potential of the conductive film from the outside. Pattern transfer with high contrast is possible without reducing the amount of light, and pattern transfer without pattern defects is possible.

  Further, according to the method of using the photomask according to claim 2, the electric potential of the electrode arranged in the vicinity of the photomask is controlled from the outside, and charged particles floating in the vicinity of the photomask are electrostatically adsorbed to the electrode, thereby Since it is possible to prevent the particles from adhering to the photomask surface, it is possible to transfer a pattern with a high contrast without reducing the amount of light transmitted through the light transmitting region, and it is possible to transfer a pattern without pattern defects.

  Therefore, according to the method of using these photomasks, when suspended particles become charged particles due to ultraviolet light used for pattern transfer, it is possible to effectively prevent the charged particles from adhering to the photomask surface. Therefore, deterioration of the quality of the photomask can be prevented. As a result, transmitted light with high contrast can be used without lowering the amount of transmitted light in the light transmitting region, and a good transfer pattern can be obtained. As a result, process controllability and process stability in the subsequent process can be improved. Furthermore, it is possible to prevent the occurrence of defects in the pattern transferred to the silicon wafer, and to obtain a good transfer pattern. As a result, the yield in semiconductor manufacturing can be improved.

  The method for using the photomask according to the present invention will be described below.

  2 and 3 are views showing a first embodiment of a method of using the photomask 20 according to the present invention. This photomask 20 is obtained by forming a mask pattern 22 made of a light shielding material on a quartz substrate 21 which is a photomask substrate. The mask pattern 22 is formed of a light shielding material such as chrome.

  The photomask surface on the side of the mask pattern 22 on the quartz substrate 21 is covered with a conductive film 23 made of a metal having a film thickness that can secure a sufficient amount of transmitted light while covering the mask pattern 22. The conductive film 23 is formed of, for example, an element such as gold or platinum or an alloy containing these elements in order to avoid a change in the amount of transmitted light over time due to film quality modification such as natural oxidation. The conductive film 23 may be formed of a conductive material such as a conductive polymer that can secure a sufficient amount of transmitted light.

  The conductive film 23 is formed so as to cover all the mask patterns 22 and substantially cover the effective area on the quartz substrate 21, that is, the area irradiated with ultraviolet light at the time of transfer. The surface of the photomask surface on the mask pattern 22 side is set to the same potential surface so as not to cause a gradient. Note that the conductive film 23 may be formed not only on the surface of the photomask on the mask pattern 22 side of the quartz substrate 21 but also on the back surface of the quartz substrate 21 as shown in FIG.

  For example, when performing pattern transfer onto a silicon wafer using such a photomask 20, the potential of the conductive film 23 is externally controlled by the potential control circuit 24. The action of the potential control circuit 24 can prevent floating charged particles from adhering to the conductive film 23 on the photomask 20. For example, when the suspended particles are charged particles having a positive charge due to ultraviolet light, the potential of the conductive film 23 is also made positive by the potential control circuit 24, so that the photo of the charged particles having a positive charge can be obtained. Adhesion to the mask surface can be prevented. Further, since the conductive film 23 has a sufficient amount of transmitted light, transmitted light with high contrast can be used, and the mask pattern 22 is correctly transferred to the silicon wafer.

  Next, FIG. 4 is a figure which shows 2nd Embodiment of the usage method of the photomask 30 based on this invention. The photomask 30 also has a mask pattern 32 made of a light shielding material formed on a quartz substrate 31 that is a photomask substrate. The mask pattern 32 is formed of a light shielding material such as chrome.

  An electrode 33 and an electrode 34 are disposed in the vicinity of the photomask 30 on the mask pattern 32 side. When such a photomask 30 is used, for example, when pattern transfer to a silicon wafer is performed, the potentials of the electrodes 33 and 34 are controlled from the outside by the potential control circuit 35. Due to the action of the potential control circuit 35, the floating charged particles can be electrostatically adsorbed to the electrodes 33 and 34. For example, charged particles having a positive charge can be electrostatically adsorbed on the negative electrode, and charged particles having a negative charge can be electrostatically adsorbed on the positive electrode. This action can prevent floating charged particles from adhering to the mask pattern surface on the photomask 30, and the mask pattern 32 is correctly transferred to the silicon wafer.

  According to the photomask 20 and the photomask 30 described above, adhesion of floating particles can be prevented and a defect can be prevented from occurring in the pattern transferred to the silicon wafer. Therefore, the quality and productivity of the photomask 20 and the photomask 30 can be improved, and the costs related to this can be greatly reduced.

  Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. For example, in the first embodiment, the conductive film 23 may be formed in a minimum size and shape in which all the mask patterns 22 are electrically connected through the conductive film 23. In the second embodiment, the shape, the arrangement position, and the number of arrangement of the electrodes may be changed. In the above embodiment, a quartz substrate is used as the photomask substrate. However, for example, a glass substrate can also be used.

FIG. 1 is a view showing a form of a conventional photomask. FIG. 2 is a diagram showing a first embodiment of a method for using a photomask according to the present invention. FIG. 3 is a view showing a modification of the first embodiment of the method of using the photomask according to the present invention. FIG. 4 is a diagram showing a second embodiment of a photomask usage method according to the present invention.

Explanation of symbols

10 ... Photomask 11 ... Quartz substrate (Photomask substrate)
DESCRIPTION OF SYMBOLS 12 ... Mask pattern 13 ... Conductive polymer 20 ... Photomask 21 ... Quartz substrate (photomask substrate)
DESCRIPTION OF SYMBOLS 22 ... Mask pattern 23 ... Conductive film 24 ... Potential control circuit 30 ... Photomask 31 ... Quartz substrate (photomask substrate)
32 ... Mask pattern 33 ... Electrode 34 ... Electrode 35 ... Potential control circuit

Claims (2)

A photomask substrate has a mask pattern made of a light-shielding material, and the photomask surface on the mask pattern side is covered with a conductive film having a film thickness that can secure a sufficient amount of transmitted light, and a gradient occurs in the potential of the photomask surface. In the photomask configured so that there is no
A method of using a photomask, wherein the potential of the conductive film is controlled from the outside. In a photomask having a mask pattern made of a light shielding material on a photomask substrate,
A method of using a photomask, comprising: arranging an electrode near the photomask on the mask pattern side, and controlling the potential of the electrode from the outside.

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