JP2013046017A - Manufacturing method of semiconductor device - Google Patents

Abstract

The manufacturing yield of a semiconductor device is improved by suppressing a problem that foreign matters are generated when a mask for EUV lithography is transported or when it is attached to or detached from a mask stage.
When a mask is held by a handler and conveyed to a mask stage of an exposure apparatus, permanent magnets are attached to the side surfaces of the mask in advance. Further, electromagnets 34 and 35 arranged so that repulsive force acts between the permanent magnets 20 and 21 of the mask 10 are attached to the arm portions 32 and 33 of the handler 30. Accordingly, when the mask 10 is transported, the mask 10 sandwiched between the arm portions 32 and 33 of the handler 30 is brought into a non-contact state with the arm portions 32 and 33 and is held by the handler 30 in a floating state.
[Selection] Figure 4

Description

  The present invention relates to a semiconductor device manufacturing technique, and more particularly to a technique that is effective when applied to the manufacture of a semiconductor device having an optical lithography process using extreme ultraviolet (Extreme Ultra-Violet: hereinafter referred to as EUV) as an exposure light source. is there.

  A semiconductor device such as a semiconductor integrated circuit device irradiates a mask, which is an original on which a circuit pattern is drawn, with exposure light, and the circuit pattern is placed on a semiconductor substrate (hereinafter referred to as “wafer”) via a reduction optical system. It is mass-produced by repeatedly using a photolithographic process for transferring to the substrate.

  In recent years, the miniaturization of semiconductor devices has progressed, and methods for increasing the resolution by shortening the exposure wavelength of photolithography have been studied. That is, until now, ArF lithography using an argon fluoride (ArF) excimer laser beam having a wavelength of 193 nm as a light source has been developed, but recently, EUV light having a much shorter wavelength (wavelength = 13.5 nm). Development of lithography using) is underway.

  In the wavelength range of the EUV light, a conventional transmission mask for optical lithography cannot be used due to the light absorption of the substance. Therefore, as a mask blank for EUV lithography, for example, a multilayer film reflective substrate using reflection by a multilayer film in which Mo (molybdenum) films and Si (silicon) films are alternately stacked is used. The reflection by the multilayer film is a reflection using a kind of interference.

  Recently, some studies on EUV pellicles using Si membranes and the like have also been made. However, since there is almost no film that can transmit EUV light sufficiently with a thickness suitable for a pellicle film, the mask is basically operated in a pellicle-less state in the EUV lithography process.

  For this reason, the EUV lithography mask is extremely sensitive to foreign matters such as particles generated during transport or mounting / desorption of the exposure apparatus on the mask stage, and the probability that the foreign matter is directly connected to a transfer defect is extremely high.

  Further, since EUV light is significantly attenuated even under a gas such as air, exposure is performed in a vacuum or a reduced pressure state close thereto. For this reason, when the EUV lithography mask is set and fixed on the mask stage of the exposure apparatus, an electrostatic chuck suction method is used.

  Japanese Patent Application Laid-Open No. 11-95414 discloses a technique for transferring a mask between a mask transport system and a mask table of an exposure apparatus using the attractive force of a magnet. In the mask described in this document, a magnetic member is provided outside a predetermined region where a pattern is formed. Further, the mask table of the exposure apparatus is provided with a suction pad having an electromagnet at a position corresponding to the magnetic member of the mask. Therefore, the mask can be fixed to the mask table by attracting the magnetic member of the mask with the electromagnet of the suction pad.

JP-A-11-95414

  As described above, the EUV lithography mask is used in a pellicle-less state in which a pellicle that prevents foreign matter from adhering to the mask surface is not mounted. For this reason, a transfer defect caused by the adhesion of foreign matter generated on the mask surface at the time of transportation or mounting / detaching to / from the mask stage is a major problem that directly affects the manufacturing yield.

  Further, when the EUV lithography mask is mounted on the mask stage of the exposure apparatus, an electrostatic chuck suction method is used. However, when the mask is attracted to the electrostatic chuck and a certain time or more has elapsed, there arises a problem that the mask cannot be easily removed from the electrostatic chuck even if the electrostatic state is released.

  In that case, even if the back surface of the mask is forcibly peeled off by mechanically pressing it with a pin, it cannot be peeled off unless a force is applied to the extent that the mask is damaged and foreign matter is generated. For this reason, foreign matter is generated in the mask detachment process and adheres to the mask surface, thereby causing the above-described transfer defect and thus a decrease in manufacturing yield.

  An object of the present invention is to provide a technique for improving the manufacturing yield of a semiconductor device by suppressing a problem that foreign matter is generated when an EUV lithography mask is transported or attached to / detached from a mask stage.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in the present application, one aspect of a typical one will be briefly described as follows.

This aspect includes (a) a step of transporting the mask to the exposure apparatus while being held by the handler, (b) a step of mounting the mask held by the handler on the mask stage of the exposure apparatus, and (c) ) Irradiating the mask mounted on the mask stage with exposure light to transfer a pattern formed on the mask to a semiconductor wafer;
(D) after the step (c), by holding the mask with the handler and detaching the mask from the mask stage,
A first magnet is provided on a side surface of the mask,
A second magnet arranged to exert a repulsive force on the first magnet is provided in a region facing the side surface of the mask of the handler,
When the mask is held by the handler, the mask is held in a non-contact state with respect to the handler by a repulsive force acting between the first magnet and the second magnet.

  Among the inventions disclosed in the present application, effects obtained by one embodiment of a representative one will be briefly described as follows.

  When the mask is held by the handler, the mask and the handler can be kept in a non-contact state by utilizing the repulsive force of the magnet. As a result, foreign matter can be prevented from adhering to the surface of the mask when the mask is transported or attached to / detached from the mask stage, thereby suppressing transfer defects caused by the foreign matter and improving the manufacturing yield of the semiconductor device. Can do.

It is a top view of the mask for EUV lithography used in embodiment of this invention. It is the sectional view on the AA line of FIG. It is the BB sectional view taken on the line of FIG. (A) is a top view which shows the principal part of the handler provided in the exposure apparatus for EUV lithography, (b) is CC sectional view taken on the line of (a). It is a flowchart of the exposure process which is embodiment of this invention. (A) is sectional drawing which shows the method of adsorb | sucking the mask hold | maintained at the handler to a mask stage, (b) is sectional drawing which shows the method of detach | desorbing a mask from a mask stage.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted. In the embodiments, the description of the same or similar parts will not be repeated in principle unless particularly necessary. Furthermore, in the drawings for describing the embodiments, hatching may be applied even in a plan view or hatching may be omitted even in a cross-sectional view for easy understanding of the configuration.

  First, the configuration of the EUV lithography mask used in this embodiment will be described. 1 is a top view of a mask for EUV lithography, FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, and FIG. 3 is a cross-sectional view taken along line BB in FIG.

  As shown in FIG. 1, a device pattern area 11 is arranged at the center of the upper surface (pattern surface) of an EUV lithography mask (hereinafter simply referred to as a mask) 10. Although not shown, a semiconductor integrated circuit pattern to be transferred to the semiconductor wafer is formed in the device pattern area 11. Outside the device pattern area 11, alignment mark areas 12a, 12b, 12c, and 12d in which marks for aligning the mask 10 and wafer alignment marks are formed are arranged.

  As shown in FIG. 2, the mask blank of the mask 10 is formed on the main surface of the substrate 13 made of quartz glass or low thermal expansion glass and having a thickness of about 6 to 8 mm, and alternately Mo films and Si films. A multilayer film 14 having a thickness of about 300 nm, a capping layer 15 formed on the multilayer film 14, and a back surface of the substrate 13 are formed. And the metal film 16 to be adsorbed on the metal.

  Further, an absorber pattern 18 having a thickness of about 50 to 70 nm is formed on the uppermost layer (capping layer 15) of the mask blank with a buffer layer 17 interposed therebetween. The integrated circuit pattern in the device pattern area 11 and the various marks in the alignment mark areas 12a, 12b, 12c, and 12d are configured by the absorber pattern 18.

  The buffer layer 17 is a barrier that prevents damage to the underlying multilayer film 14 and adhesion of contamination when the absorber pattern 18 is corrected using FIB (Focus Ion Beam). The buffer layer 17 on the reflecting surface that is a layer and on which the absorber pattern 18 is not formed is removed at the final stage of the mask manufacturing process. However, when EB (Electron Beam) correction or the like is used, the buffer layer 17 (barrier layer) can be omitted.

  Although not shown in the drawing, a film with a reduced reflectivity for defect inspection light having a wavelength of about 250 nm or about 193 nm is formed on the surface of the absorber pattern 18 so that semiconductor defect inspection can be made highly sensitive by oxidation treatment or the like. ing.

  As shown in FIGS. 1 and 3, permanent magnets 20 and 21 are attached to two opposing side surfaces of the mask 10.

  In the two permanent magnets 20 and 21, the arrangement of the N pole and the S pole is opposite to each other. That is, in the permanent magnet 20 attached to one side surface of the mask 10, the N pole is disposed on the upper surface side of the mask 10 and the S pole is disposed on the back surface side of the mask 10. On the other hand, in the permanent magnet 21 attached to the other side surface of the mask 10, the S pole is disposed on the upper surface side of the mask 10 and the N pole is disposed on the back surface side of the mask 10. On the contrary, the N pole of the permanent magnet 20 may be arranged on the back side of the mask 10, and the N pole of the permanent magnet 21 may be arranged on the upper surface side of the mask 10.

  As shown in FIG. 3, the respective surfaces of the permanent magnets 20, 21 attached to the side surface of the mask 10 are arranged in an inclined state with respect to the upper surface and the back surface of the mask 10.

  4A is a top view showing the main part of the handler provided in the exposure apparatus for EUV lithography, and FIG. 4B is a cross-sectional view taken along the line CC in FIG. 4A.

  As shown in FIG. 4A, the handler 30 has a U-shaped planar shape, and is moved in the vertical (Z) direction, the horizontal (X) direction, and the longitudinal (Y) direction by the drive device 31. Movement, X-axis (θ) rotation, and Y-axis (φ) rotation are possible.

  Electromagnets 34 and 35 are attached to each of the pair of arm portions 32 and 33 of the handler 30. When the EUV lithography mask 10 shown in FIGS. 1 to 3 is transported, the N pole of the permanent magnet 20 attached to one side of the mask 10 and the N pole of the electromagnet 34 of the arm portion 32 And the south pole of the permanent magnet 20 and the south pole of the electromagnet 34 face each other. Further, the N pole of the permanent magnet 21 attached to the other side surface of the mask 10 and the N pole of the electromagnet 35 of the arm portion 33 face each other, and the S pole of the permanent magnet 21 and the S pole of the electromagnet 35 face each other. .

  That is, when the mask 10 is transported, the permanent magnet 20 of the mask 10 and the electromagnet 34 of the arm portion 32 are arranged to exert a repulsive force, and the permanent magnet 21 of the mask 10 and the electromagnet 35 of the arm portion 33 are also repulsive to each other. It will be an influence arrangement. In addition, the surfaces of the permanent magnets 20 and 21 attached to the side surface of the mask 10 are disposed in an inclined state with respect to the upper surface and the back surface of the mask 10 (see FIG. 3). 4 and the repulsive force between the permanent magnet 21 and the electromagnet 35 act not only in the left and right (X) direction of FIG. 4A but also in the up and down (Z) direction.

  Therefore, when the mask 10 is transported, the mask 10 sandwiched between the arm portions 32 and 33 of the handler 30 is in a non-contact state with the arm portions 32 and 33 and is held by the handler 30 in a floating state.

  As shown in FIG. 4A, a stress detector 36 is attached to the handler 30. The stress detector 36 has a repulsive force acting between the permanent magnets 20 and 21 of the mask 10 and the electromagnets 34 and 35 of the arm portions 32 and 33, and the rotation ( The balance in the [theta], [phi] direction is detected. The repulsive force acting between the permanent magnets 20 and 21 and the electromagnets 34 and 35 is optimized by adjusting the magnetic force of the electromagnets 34 and 35 and the driving device 31 so that the mask 10 can be stably held by the handler 30. To do.

  The balance detection by the stress detector 36 is particularly useful when the mask 10 is detached from the mask stage or the mask case. For example, when removing the mask 10 electrostatically attracted to the mask stage, if the electrostatic attraction is released in a state where the balance of repulsive force is lost, the mask 10 slips on the mask stage or causes lateral shift. Foreign matter is likely to occur. Therefore, if the electrostatic attraction is canceled after the balance detection and adjustment by the stress detector 36 are performed, the occurrence of such a problem can be avoided.

  Next, an exposure process when manufacturing a semiconductor device will be described with reference to the flowchart of FIG.

  Lithography techniques used for manufacturing semiconductor devices are classified into fine, middle, and rough according to required dimensional fineness and dimensional accuracy, and exposure is performed according to each.

  In the case of a semiconductor device manufactured using EUV lithography, EUV lithography is usually applied to the formation of a fine layer, but not only one layer, for example, a gate layer, a contact layer, a first layer metal wiring, EUV lithography is performed using a plurality of layers, that is, a plurality of masks. Therefore, it is common to repeatedly perform exposure using one exposure apparatus while changing the mask.

  Therefore, in an actual exposure process, a plurality of masks are stored in a mask stocker, and necessary masks are taken out from the masks and mounted on a mask stage of an exposure apparatus for exposure. After the exposure, the mask is removed from the mask stage and stored in the mask stocker. Then, a new mask is taken out from the mask stocker and mounted on the mask stage of the exposure apparatus, and the next exposure is performed.

  The series of steps will be described in more detail. First, the EUV lithography mask 10 accommodated in the mask case is stored in the mask stocker together with the mask case (step S1). Next, the mask 10 to be exposed first is taken out and conveyed together with the mask case (step S2), and the mask case lid is opened at the place where the handler 30 shown in FIG. 4 is waiting (step S3).

  Next, the handler 30 is moved to the vicinity of the mask 10 (step S4), and the electromagnets 34 and 35 attached to the arm portions 32 and 33 are energized and activated (step S5). Then, the mask 10 is moved to the electrostatic chuck portion of the mask stage while being held by the handler 30 (step S6). At this time, since the arm portions 32 and 33 of the handler 30 and the mask 10 are not in contact with each other, the mask 10 is transferred to the mask stage in a floating state.

  At this time, it is preferable to cover the upper surface (pattern surface) of the mask 10 with a cover in order to minimize the amount of foreign matter adhering to the mask 10. That is, it is preferable that the mask case for storing the mask 10 has a double structure of the outer case and the inner case, and the mask 10 is taken out from the outer case together with the inner case and transported in the above-described step S2.

  Next, electricity is supplied to the electrostatic chuck portion of the mask stage to electrostatically attract the mask 10 (step S7). FIG. 6A shows a state in which the mask 10 held by the handler 30 in a floating state is attracted to the mask stage.

  The back surface (lower surface in FIG. 6) of the mask stage 40 of the exposure apparatus is an electrostatic chuck portion, and the mask 10 is electrostatically charged by the metal film 16 formed on the back surface (upper surface in FIG. 6). It is electrostatically attracted to the chuck part.

  This will be partly repeated, but in more detail, when the mask 10 is attracted and held on the mask stage 40, first, current is supplied to the electromagnets 34 and 35 attached to the arm portions 32 and 33 of the handler 30. The mask 10 is held so as to be sandwiched between the vertical (Z) direction and the horizontal (X) direction. At this time, since a repulsive force acts between the permanent magnets 20 and 21 of the mask 10 and the electromagnets 34 and 35 of the handler 30, the mask 10 is held in the handler 30 in a floating state without contacting the arm portions 32 and 33. Is done. In this state, the mask 10 is transported to the mask stage 40, the back surface (metal film 16) of the mask 10 is brought into contact with the back surface (electrostatic chuck portion) of the mask stage 40, and then the electrostatic chuck portion is energized. Thus, the mask 10 is attracted to the mask stage 40.

  Next, the energization of the electromagnets 34 and 35 of the handler 30 is shut off (step S8), and the handler 30 is moved to the original standby position (step S9), using the above-described double structure mask case. In this case, the inner case is removed from the mask 10 until the mask 10 is attracted to the mask stage 40 and before the next exposure process.

  Next, exposure is performed in this state (step S10), and after the exposure is completed, the handler 30 is moved from the standby position to the vicinity of the mask 10 ((step S11), and the electromagnets 34 and 35 attached to the arm portions 32 and 33 are moved. Is activated (step S12).

  Next, the balance of forces applied to the handler 30 in the vertical (Z) direction and the horizontal (X) direction is monitored using the stress detector 36 shown in FIG. (Step S14). When the balance of the force applied to the handler 30 is equal to or greater than a predetermined value, that is, when the balance of the force is lost, the position of the handler 30 is finely adjusted or further attached to the arm portions 32 and 33. The current supplied to the electromagnets 34 and 35 is also finely adjusted (step S15), and the balance of the force applied to the handler 30 is monitored again (step S13). When the balance of the force applied to the handler 30 falls below a predetermined value, that is, when the balance of the force is achieved, the energization to the electrostatic chuck portion of the mask stage 40 is shut off (step S16).

  Here, the monitoring of the balance of the force applied to the handler 30 (step S13), the comparison between the monitored value and a predetermined value (step S14), and the fine adjustment step (step S15) are performed by removing the mask 10 from the mask stage 40. When removing, it is possible to prevent a problem that the mask 10 slips on the mask stage 40 or causes a lateral shift, so it is a preferable work for avoiding the generation of foreign matter, but it is not an essential process but an optional process. Good.

  Next, the handler 30 is lowered (step S17). At this time, since a downward force is applied to the mask 10 held in the handler 30 in a floating state, the mask 10 can be detached from the mask stage 40 as shown in FIG. . Here, when the mask 10 is difficult to peel off from the mask stage 40, torsional rotation is applied to the arm portions 32 and 33 of the handler 30. In this way, the lever principle works and the mask 10 can be easily detached from the mask stage 40.

  Next, the mask 10 held by the handler 30 is moved to the mask case and grounded (step S18). Subsequently, the current supplied to the electromagnets 34 and 35 of the handler 30 is shut off (step S19), the handler 30 is moved to the original standby place (step S20), and the mask case lid is closed (step S21). When the above-described double-structure mask case is used, the mask 10 is stored in the inner case after the exposure step (step S10) is finished and before the mask case lid is closed (step S21). deep.

  Thereafter, the mask 10 is transported together with the mask case (step S2) and stored in a mask stocker (step S1).

  Next, another mask is taken out from the mask stocker, exposed according to the flow described above, and then stored in the mask stocker.

  Thus, according to the present embodiment, when the mask 10 is held by the handler 30, the mask 10 and the handler 30 can be kept in a non-contact state by utilizing the repulsive force of the magnet. As a result, foreign matters can be prevented from adhering to the surface of the mask 10 when the mask 10 is transported or attached to or detached from the mask stage 40, so that transfer defects caused by the foreign matters can be suppressed and the manufacturing yield of the semiconductor device can be reduced. Can be improved.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  In the above-described embodiment, an example in which the present invention is applied to a mask for EUV lithography used for manufacturing a semiconductor device has been described. However, the present invention can also be applied to a mask that uses exposure light other than EUV.

  Further, the present invention can be generally applied to a case where a workpiece is conveyed while being held by a handler. That is, if the first magnet is provided on the work and the second magnet arranged so as to exert a repulsive force on the first magnet is provided in a region facing the work of the handler, the first magnet is provided. The repulsive force acting between the magnet and the second magnet makes it possible to hold the workpiece in a non-contact state with respect to the handler. Thereby, the malfunction which a foreign material adheres to a workpiece | work by the contact with a handler, or the surface of a workpiece | work can be prevented reliably.

  The present invention can be applied to a lithography technique using EUV as an exposure light source.

DESCRIPTION OF SYMBOLS 10 EUV lithography mask 11 Device pattern area 12a, 12b, 12c, 12d Alignment mark area 13 Substrate 14 Multilayer film 15 Capping layer 16 Metal film 17 Buffer layer 18 Absorber pattern 20, 21 Permanent magnet 30 Handler 31 Driving device 32, 33 Arm part 34, 35 Electromagnet 36 Stress detector 40 Mask stage

Claims (7)

(A) a step of transporting the mask to the exposure apparatus while being held by the handler;
(B) mounting the mask held by the handler on a mask stage of the exposure apparatus;
(C) transferring a pattern formed on the mask to a semiconductor wafer by irradiating the mask mounted on the mask stage with exposure light; and
(D) after the step (c), holding the mask with the handler to detach the mask from the mask stage;
A method of manufacturing a semiconductor device including:
A first magnet is provided on a side surface of the mask,
A second magnet arranged to exert a repulsive force on the first magnet is provided in a region facing the side surface of the mask of the handler,
When the mask is held by the handler, the mask is held in a non-contact state with respect to the handler by a repulsive force acting between the first magnet and the second magnet. A method for manufacturing a semiconductor device.   2. The method for manufacturing a semiconductor device according to claim 1, wherein the mask is a mask for EUV lithography having at least a substrate, a multilayer film, and an absorber pattern.   2. The method of manufacturing a semiconductor device according to claim 1, wherein the mask is mounted on the mask stage by an electrostatic chuck adsorption method.   2. The semiconductor device manufacturing method according to claim 1, wherein when the mask is held by the handler, the electromagnetic force of the second magnet is controlled by monitoring the magnitude of the repulsive force exerted on the handler. Method.   5. The method of manufacturing a semiconductor device according to claim 4, wherein the electromagnetic force of the second magnet is controlled by controlling the position of the handler with respect to the mask.   The method of manufacturing a semiconductor device according to claim 1, wherein when the mask is held by the handler, the handler is torsionally rotated when the mask is detached from the mask stage.   When the work is held by the handler and transported, a first magnet is provided on the work, and a first magnet is disposed in a region of the handler facing the work so as to exert a repulsive force on the first magnet. A conveying method comprising: providing two magnets, and holding the workpiece in a non-contact state with respect to the handler by a repulsive force acting between the first magnet and the second magnet.

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