JP2005033072A - Foreign substance removal method and device on transfer mask for charged particle beam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a foreign substance removal method and device, which facilitates the removal of a foreign substance that is unlikely to be removed by chemical means such as cleaning and that adheres to the surface of a transfer mask for a charged particle beam, and which does not damage the mask at other portions. <P>SOLUTION: The foreign substance removal device on a transfer mask for a charged particle beam is to attract for removal or repel for removal a foreign substance with electrostatic force by making a prober having a pointed tip end to which electric charges are applied approach the foreign substance. The device comprises a movable stage for placing the transfer mask serving to remove a foreign substance; a loader/unloader for discharging the transfer mask from which the foreign substance is removed; an imaging apparatus movable in X and Y axis directions with a Z axis of the stage taken as an optical axis thereof; the prober having its tip end located on the optical axis, being movable in the Z axis direction and movable in the X and Y directions in synchronism with the imaging apparatus, and imparting enough electric charges to the foreign substance contained therein; a releasing device for releasing the foreign substance from the prober; a control device for controlling the stage, loader/unloader, imaging device, and prober; and a monitor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to foreign matter removal from a transfer mask used in semiconductor manufacturing, and more particularly, to a foreign matter removal method and a foreign matter removal apparatus for a charged particle beam transfer mask.

In recent years, along with miniaturization of semiconductor integrated circuits, research and development of lithography techniques using charged particle beams such as electron beam lithography and ion beam lithography have been actively conducted as manufacturing techniques thereof. Specifically, among such lithography techniques, as a method corresponding to the miniaturization of a semiconductor, a method called a cell projection exposure method or a block exposure method using an electron beam, and an EPL (Electron Projection) capable of further increasing the throughput.
An electron beam projection exposure method called a Lithography method and a LEEPL (Low Energy E-beam Proximity Projection Lithography) method has been developed.

  On the transfer mask for the electron beam exposure apparatus, various minute patterns and holes of several μm or 1 μm or less are formed on the basis of design data so that the electron beam can pass and electron beam drawing can be performed. In semiconductor manufacturing, an electron beam passes therethrough and is projected and exposed on a wafer.

  Therefore, in charged particle beam transfer masks typified by electron beams, the minute foreign matter adhering during the production is the cause of transfer defects such as pattern chipping during charged particle beam exposure. Even if the foreign matter does not become attached, if it adheres to the transfer mask, it will fall into the exposure machine or on the wafer, and therefore it is necessary to strictly manage the manufacturing process so that there is no foreign matter attached.

  Among semiconductor masks, conventional light-transmissive photomasks are designed to prevent foreign matter from entering the pellicle by covering the surface of the photomask with a thin film called a pellicle after the final stage of the manufacturing process. Is given. According to this method, even if foreign matter adheres to the pellicle, the exposure pattern is hardly affected because it is not on the direct surface of the photomask.

  However, in a transfer mask for charged particle beam exposure, a thin film such as a pellicle blocks the passage of an electron beam and cannot be used, so there is always a risk of foreign matter adhering to the mask surface.

  The adhered foreign matter may be kept clean by performing chemical treatment such as washing, but may not be removed by chemical treatment such as washing.

  In such a case, there is a method of removing while destroying the foreign matter using FIB (Focused Ion Beam) or laser. However, in the former case, it is necessary to work in a vacuum and it takes a very long time. It was practically impossible to use inside.

  In the latter case, there is a problem that the laser beam cannot be condensed to about 1 μm or less due to the optical principle, and there are various conditions that can be broken depending on the type of foreign matter, and the damage to other places is large. It was.

Under such circumstances, there is a problem of foreign matter removal even in the manufacturing process of the light transmission type phase shift type photomask, and the transparent protrusion-like defect existing on the phase shift layer or the glass substrate A method has also been devised in which a defective portion is scratched and physically removed by a fine probe with sharp edges (see, for example, Patent Document 1).
JP-A-6-148870

  As described above, in a charged particle beam transfer mask that cannot take measures against foreign matter such as pellicle, a chemical method such as cleaning or the removal of foreign matter by condensing a laser is used. Depending on the composition, there is a limit to chemical means, and the laser method has problems such as scattering to the periphery and damage to the mask surface due to beam irradiation even if a foreign object hits the beam.

  In view of the above problems, the present invention provides a charged particle beam transfer mask capable of easily removing foreign substances adhering to the surface of the charged particle beam transfer mask and damaging other places. It is an object of the present invention to provide a foreign matter removing method and a foreign matter removing device.

  The present invention relates to a method for removing foreign matter adhering to a transfer mask for charged particle beam, by bringing a prober having a sharp tip to which a charge having a different sign or potential difference with respect to the charge of the foreign matter is applied to the foreign matter. A foreign matter removing method for a charged particle beam transfer mask, wherein foreign matter is removed by suction or repulsion by force.

  The present invention is also the foreign particle removal method for a charged particle beam transfer mask according to the above invention, wherein the prober material is a conductive material.

Further, the present invention provides a foreign matter removing apparatus for a charged particle beam transfer mask,
1) A stage that can be moved in the X, Y, Z axis directions, and θ directions by placing a transfer mask that removes foreign matters,
2) A loader / unloader for carrying a transfer mask for removing foreign matter into the stage and discharging the transfer mask for removing foreign matter;
3) An imaging device that is positioned above the stage with the Z-axis of the stage as its optical axis and that is movable in the X- and Y-axis directions, including an objective lens that can move in the Z-axis direction, a focusing mechanism, and a camera. 4) The tip is always on the optical axis, can move between the stage on the optical axis and the objective lens in the Z-axis direction, and is synchronized with the movement of the imaging device in the X and Y-axis directions. , A prober having a pointed tip that is movable in the Y-axis direction and is given a charge of a different sign or a potential difference of the same sign with respect to the charge of the foreign matter,
5) A detaching device for detaching foreign matter adsorbed by the prober from the prober.
6) Control device and monitor for controlling the stage, loader / unloader, imaging device, and prober,
A foreign matter removing apparatus for a charged particle beam transfer mask. It is.

  The present invention is a foreign matter removal method and a foreign matter removal apparatus in which a prober with a sharp tip is brought close to a foreign matter, and the foreign matter is adsorbed and removed or repelled by electrostatic force, so that the probe sticks to the surface of the charged particle beam transfer mask. A foreign particle removing method and a foreign particle removing apparatus for a charged particle beam transfer mask that can easily remove foreign particles without damaging other places.

  As a result, the foreign matter removal rate of the transfer mask is greatly improved, which contributes to improving the quality of the charged particle beam transfer mask.

  Hereinafter, the present invention will be described based on embodiments.

  If the foreign matter adhered on the transfer mask has a certain charge, if a charge with a sufficient potential difference with the opposite sign from that charge is given to the prober with a sharp tip and the sharp tip is brought very close to the foreign matter, At this point, an electrostatic force is generated between the foreign object and the sharp tip of the prober, and the foreign object is adsorbed and removed.

  In addition, when the foreign matter attached on the transfer mask has a certain charge, if a probe with a sufficient potential difference of the same sign as that charge is given to a prober with a sharp tip, the sharp tip is brought close to the foreign matter. At that time, an electrostatic force is generated between the foreign object and the sharp tip of the prober, and the foreign object is repelled and removed.

  The prober material is preferably a conductive material in order to give a charge having a different potential or a sufficient potential difference of the same sign to the prober having a sharp tip with respect to the charge charged by the foreign matter.

  FIG. 1 is an explanatory view showing an embodiment of a foreign matter removing apparatus for a charged particle beam transfer mask according to the present invention. As shown in FIG. 1, this embodiment includes a stage 6, a loader / unloader 7, an imaging device 10, a prober 3 with a sharp tip, a separation device 11, a control device 8, and a monitor 9. . The imaging device 10 includes an objective lens 2 that can move in the Z-axis direction, a focusing mechanism 4, and a camera 5.

  The stage 6 is movable in the X, Y, Z axis directions and the θ direction, and places a transfer mask 1 for removing foreign matter. The loader / unloader 7 carries the transfer mask 1 for removing foreign matter to the stage 6 and removes the transfer mask 1 after removing the foreign matter. The imaging device 10 is movable in the X and Y axis directions, and is positioned above the stage 6 with the Z axis of the stage 6 as its optical axis.

  The prober 3 having a sharp tip is given a charge having a sufficient potential difference with a different sign or the same sign as the charge of the foreign matter. The tip portion is always on the optical axis of the imaging device 10 and can move in the Z-axis direction between the stage on the optical axis and the objective lens. In addition, the imaging apparatus 10 can move in the X and Y axis directions in synchronization with the movement in the X and Y axis directions.

The detachment device 11 is located on the left part on the stage 6 in FIG. The control device 8 controls a stage, a loader / unloader, an imaging device, and a prober.
1) Positioning As an initial state of the foreign matter removing apparatus for the charged particle beam transfer mask, the prober is moved sufficiently upward from the transfer mask surface. Alignment marks P and Q are engraved in advance on the transfer mask surface. The position of the foreign matter on the transfer mask surface is detected in advance using a defect inspection apparatus, and the coordinates are output and stored in a floppy (registered trademark) or a storage medium.

  First, a transfer mask on which foreign matter to be removed is attached is set on a loader. The transfer mask is transported to a specified position on the stage on which the transfer mask is placed.

  As shown in FIG. 2, Q is detected with reference to the alignment mark P, and the angle (θ) is corrected. Next, the position (X1, Y1) where the foreign matter to be removed is attached is moved to the center of the visual field.

In addition, the external shape of the transfer mask is processed accurately, and when the transfer mask is placed, it is correlated with the defect inspection device that outputs the coordinates of foreign matter with pins etc. provided on the stage, and reproduced. If it is well positioned, it is not always necessary to correct the angle (θ).
2) Focusing Next, focusing is performed at the first foreign matter removal position (X1, Y1). 3 and 4, the objective lens 2 is moved up and down in the Z-axis direction, and the stage 6 is moved up and down in the Z-axis direction as shown in FIGS. 5 and 6. There is. At this time, in order to avoid contact with the transfer mask surface, focusing is performed in a state (D) where the prober is sufficiently separated from the transfer mask. Further, the prober may be moved or stored in a completely different place during the focusing operation.
3) Fine adjustment of the position As shown in FIG. 7, the target foreign matter becomes clear in the field of view by focusing. Further, by slightly moving the transfer mask in the X and Y axis directions, the target foreign matter is accurately moved to the center of the field of view of the objective lens as shown in FIG.
4) Adsorption removal of foreign matter After that, as shown in FIG. 9, the transfer mask is once moved away from the objective lens 2, and the prober is moved to the focal position of the objective lens as shown in FIG.

Next, as shown in FIG. 11, if the transfer mask is moved in a direction approaching the objective lens 2, the foreign matter on the transfer mask surface and the tip of the prober are in close proximity. When approaching a reasonable distance, foreign matter is attracted to the tip of the prober by electrostatic force.
5) Removal of foreign matter from prober When it is confirmed that the foreign matter 9 is adsorbed by the prober, the transfer mask is moved away from the objective lens as shown in FIG.

  Next, as shown in FIG. 13, the imaging device 10 and the prober 3 are synchronized and moved to the left (arrow) in FIG. 13 up to the foreign substance detaching device 11 provided outside the transfer mask on the stage 6. The stage 6 is moved to the right in FIG. 13, the tip of the prober is brought into contact with the foreign material adsorbing tape attached to the detaching device 11, and the foreign material is detached from the prober to complete the removal.

  In addition to the foreign matter adsorbing tape, a liquid substance may be used for detachment of the foreign matter, and the surface tension may be used for detachment. According to this method, it becomes easy to keep the tip portion clean.

  Subsequently, the transfer mask is moved to the second foreign matter removal position (X2, Y2), and the same operation is repeated. When the removal of the nth foreign matter is completed, the transfer mask is conveyed to the unloader.

  Note that the above operations may be performed automatically or manually while monitoring the monitor 9.

It is explanatory drawing which shows one Example of the foreign material removal apparatus of the transfer mask for charged particle beams by this invention. It is explanatory drawing of the alignment method. It is explanatory drawing of focusing (an objective lens approaches). It is explanatory drawing of focusing (an objective lens leaves | separates). It is explanatory drawing of focusing (a transfer mask approaches). It is explanatory drawing of focusing (a transfer mask leaves | separates). It is explanatory drawing of the foreign material in a visual field. It is explanatory drawing of the foreign material of the center in a visual field. It is explanatory drawing when an objective lens is separated from a foreign material. It is explanatory drawing which set the prober to the focus position. It is explanatory drawing when a prober approaches very close to a foreign material. It is explanatory drawing when a prober removes the transfer mask. It is explanatory drawing when removing a foreign material from a prober.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Transfer mask for charged particle beam 2 ... Objective lens 3 ... Prober 4 ... Focusing mechanism 5 ... Camera 6 ... Stage 7 ... Loader / Unloader 8 ... Control Device 9 ... Foreign object 10 ... Imaging device 11 ... Detachment device 12 ... Objective lens field of view D ... Prober sufficiently separated from the transfer mask

Claims (3)

  In the method for removing foreign matter adhering to the charged particle beam transfer mask, a prober with a pointed tip that is given a charge of a different sign or the same potential as the charge of the foreign matter is brought close to the foreign matter, and the foreign matter is removed by electrostatic force. A method for removing foreign matter from a transfer mask for charged particle beam, characterized by performing adsorption removal or repulsion removal.   2. A method for removing foreign matter from a charged particle beam transfer mask according to claim 1, wherein the prober is made of a conductive material. In the particle removal device for charged particle beam transfer mask,
1) A stage that can be moved in the X, Y, Z axis directions, and θ directions by placing a transfer mask that removes foreign matters,
2) A loader / unloader for carrying a transfer mask for removing foreign matter into the stage and discharging the transfer mask for removing foreign matter;
3) An imaging device that is positioned above the stage with the Z-axis of the stage as its optical axis and that is movable in the X- and Y-axis directions, including an objective lens that can move in the Z-axis direction, a focusing mechanism, and a camera. 4) The tip is always on the optical axis, can move between the stage on the optical axis and the objective lens in the Z-axis direction, and is synchronized with the movement of the imaging device in the X and Y-axis directions. , A prober having a pointed tip that is movable in the Y-axis direction and is given a charge of a different sign or a potential difference of the same sign with respect to the charge of the foreign matter,
5) A detaching device for detaching foreign matter adsorbed by the prober from the prober.
6) Control device and monitor for controlling the stage, loader / unloader, imaging device, and prober,
A foreign matter removing apparatus for a charged particle beam transfer mask.