JP5047192B2 - Electron beam exposure system - Google Patents

Description

  The present invention relates to an electron beam exposure apparatus, and more particularly to an electron beam exposure apparatus that can reduce the charging of a wafer.

  In recent years, an electron beam exposure apparatus has been used to form a fine pattern in a lithography process in manufacturing a semiconductor device or the like.

  In the formation of a fine pattern using an electron beam exposure apparatus, a phenomenon occurs in which the electron beam is bent by charge-up that accumulates charges on the wafer, and the drawing position accuracy deteriorates.

  In order to prevent this phenomenon, a conductive antistatic film is generally formed. By forming the antistatic film, for example, the potential of the antistatic film is set to the ground potential so that electrons are not charged to the resist.

  Various techniques for directly connecting a ground to the wafer have been studied in order to prevent electric charges from accumulating on the wafer.

  As a technique related to this, Patent Document 1 discloses a mechanism that can reduce the deflection of a wafer caused by a force that connects a ground to the wafer.

  As described above, when the wafer is exposed using an electron beam, an antistatic film is formed on the wafer and the potential of the antistatic film is set to the ground potential in order to ensure straightness of the electron beam. I have to.

However, even in this case, a phenomenon may occur in which the wafer is charged and exposure cannot be performed accurately. As the cause, it is conceivable that the terminal connected to the wafer is displaced from the portion where the antistatic film is formed. Normally, such a connection portion is provided at the peripheral portion of the wafer. However, since the antistatic film is peeled off by applying edge rinse to the peripheral portion, the wafer is charged even if a conductor is connected to this portion. Charges cannot be removed sufficiently.
JP-A-9-306808

  The present invention has been made in view of the problems of the prior art, and even when the antistatic film is not formed on the entire surface of the wafer, the charge on the wafer can be reduced and the pattern can be accurately exposed. An object is to provide a possible electron beam exposure apparatus.

An object of the present invention is to provide an electron beam exposure apparatus having a wafer stage on which a wafer is placed and charge discharge means for discharging charges charged on the wafer, the charge discharge means being an upper surface in contact with an upper portion of the wafer A first connection means having a contact portion; a second connection means having a lower surface contact portion in contact with the lower portion of the wafer; a shaft for rotatably connecting the first connection means and the second connection means; An electron beam exposure apparatus comprising: a plate spring connected to a second connection means and a wafer stage, and fixing the first connection means and the second connection means on the wafer stage. .

  In the electron beam exposure apparatus according to this aspect, the portion of the second connecting means that contacts the wafer may have a needle shape, and the needle portion may reach the inside of the wafer. The surface of the first connecting means and the second connecting means may be coated with a conductive material.

  In the present invention, a part of the peripheral edge (edge) of the wafer is sandwiched from both the upper and lower sides by the charge discharging means. The upper part of the wafer is in contact with the wafer surface, and the lower part of the wafer uses needle-like terminals that pierce. The charge discharging means is made of ceramic and has a surface coated with a conductive material. As a result, the charge charged on the wafer can be captured and discharged not only from the surface of the wafer but also from the inside of the wafer, and the wafer can be effectively prevented from being charged.

  In the present invention, the wafer upper surface contact portion that contacts the upper side of the wafer and the wafer lower surface contact portion that contacts the lower portion are connected via a shaft (axis), and the one that contacts the lower portion of the wafer via a leaf spring. Is fixed to the wafer stage. In this way, the charge discharging means is in a floating state due to the spring property, and follows the surface of the wafer while sandwiching the wafer, so that no additional load is applied and the wafer is bent. Can be prevented.

FIG. 1 is a block diagram of an electron beam exposure apparatus used in an embodiment of the present invention. FIGS. 2A and 2B are diagrams for explaining a method of discharging the charge charged on the wafer. FIGS. 3A and 3B are diagrams illustrating the configuration of the charge discharge mechanism. FIGS. 4A and 4B are diagrams illustrating an initial state of the charge discharge mechanism. 5A to 5C are diagrams for explaining the operation of the charge discharging mechanism in time series.

  Embodiments of the present invention will be described below with reference to the drawings.

First, the configuration of the electron beam exposure apparatus will be described. Next, an outline of a charge discharge mechanism that efficiently discharges the charge charged on the wafer will be described. Next, a specific configuration and installation method of the charge discharge mechanism will be described.
(Configuration of electron beam exposure system)
FIG. 1 is a block diagram of an electron beam exposure apparatus according to the present embodiment.

  The electron beam exposure apparatus is broadly divided into an exposure unit 100 and a control unit 200 that controls each unit of the exposure unit 100. Among these, the exposure unit 100 includes an electron beam generation unit 130, a mask deflection unit 140, and a substrate deflection unit 150, and the inside thereof is decompressed.

  In the electron beam generator 130, the electron beam EB generated from the electron gun 101 is converged by the first electromagnetic lens 102, then passes through the rectangular aperture 103 a of the beam shaping mask 103, and the cross section of the electron beam EB is rectangular. To be shaped.

  Thereafter, the electron beam EB is imaged on the exposure mask 110 by the second electromagnetic lens 105 of the mask deflection unit 140. The electron beam EB is deflected to a specific pattern S formed on the exposure mask 110 by the first and second electrostatic deflectors 104 and 106, and the cross-sectional shape thereof is shaped into the pattern S.

  Although the exposure mask 110 is fixed to the mask stage 123, the mask stage 123 is movable in a horizontal plane, and the deflection range (beam deflection region) of the first and second electrostatic deflectors 104 and 106 is set. In the case of using the pattern S in the portion exceeding, the pattern S is moved into the beam deflection region by moving the mask stage 123.

  The third and fourth electromagnetic lenses 108 and 111 arranged above and below the exposure mask 110 play a role of forming an image of the electron beam EB on the wafer W by adjusting their current amounts.

  The size of the electron beam EB that has passed through the exposure mask 110 is reduced by the fifth electromagnetic lens 114 after being returned to the optical axis C by the deflection action of the third and fourth electrostatic deflectors 112 and 113.

  The mask deflection unit 140 is provided with first and second correction coils 107 and 109, which correct beam deflection aberrations generated by the first to fourth electrostatic deflectors 104, 106, 112, and 113. Is done.

  Thereafter, the electron beam EB passes through the aperture 115 a of the shielding plate 115 constituting the substrate deflecting unit 150 and is projected onto the wafer W by the first and second projection electromagnetic lenses 116 and 121. As a result, the pattern image of the exposure mask 110 is transferred onto the wafer W at a predetermined reduction ratio, for example, a reduction ratio of 1/10.

  The substrate deflecting unit 150 is provided with a fifth electrostatic deflector 119 and an electromagnetic deflector 120, and the electron beam EB is deflected by these deflectors 119 and 120, and an exposure mask is formed at a predetermined position on the wafer W. The pattern image is projected.

  Further, the substrate deflection unit 150 is provided with third and fourth correction coils 117 and 118 for correcting the deflection aberration of the electron beam EB on the wafer W.

The wafer W is fixed by an electrostatic chuck to a wafer stage 124 that can be moved in the horizontal direction by a driving unit 125 such as a motor. By moving the wafer stage 124, the entire surface of the wafer W can be exposed. It becomes. In addition, charges are accumulated on the wafer W by being irradiated with an electron beam, and a charge discharge mechanism that allows the charges to be discharged is attached to prevent the accumulation of the charges.
(Description of control unit)
On the other hand, the control unit 200 includes an electron gun control unit 202, an electron optical system control unit 203, a mask deflection control unit 204, a mask stage control unit 205, a blanking control unit 206, a substrate deflection control unit 207, and a wafer stage control unit 208. Have. Among these, the electron gun control unit 202 controls the electron gun 101 to control the acceleration voltage of the electron beam EB, beam emission conditions, and the like. Further, the electron optical system control unit 203 controls the amount of current to the electromagnetic lenses 102, 105, 108, 111, 114, 116 and 121, and the magnification and focus of the electron optical system in which these electromagnetic lenses are configured. Adjust the position. The blanking control unit 206 controls the voltage applied to the blanking electrode 127 to deflect the electron beam EB generated before the start of exposure onto the shielding plate 115, and onto the wafer W before the exposure. Prevents EB from being irradiated.

  The substrate deflection control unit 207 controls the voltage applied to the fifth electrostatic deflector 119 and the amount of current to the electromagnetic deflector 120 so that the electron beam EB is deflected to a predetermined position on the wafer W. To.

  The wafer stage control unit 208 adjusts the driving amount of the driving unit 125 to move the wafer W in the horizontal direction so that a desired position on the wafer W is irradiated with the electron beam EB. Further, control for fixing the wafer W to the wafer stage and attaching a charge discharge mechanism to the wafer W is performed.

The above-described units 202 to 208 are controlled in an integrated manner by an integrated control system 201 such as a workstation.
(Outline of charge discharge mechanism)
Next, a charge discharge mechanism (charge discharge means) for efficiently discharging the charge charged on the wafer will be described.

  FIG. 2 is a diagram for explaining the principle of discharging the charge charged on the wafer. As shown in FIG. 2A, the wafer 21 is placed on the wafer stage via the electrostatic chuck portion 22. The wafer 21 is fixed on the wafer stage by the following electrostatic chuck. For example, a voltage 25 is applied to the electrodes (32a, 32b) embedded in the main body formed of alumina ceramics, and negative charges 26a and positive charges 26b are electrostatically induced near the surface of the main body. A charge opposite to that of the electrostatic chuck unit 22 is electrostatically induced on the surface of the wafer 21 that contacts the electrostatic chuck unit 22, and the wafer 21 is attracted to the electrostatic chuck unit 22.

  In this way, the electron beam 23 is irradiated with the wafer 21 fixed on the wafer stage. When the electron beam 23 is irradiated, a negative charge is charged on the surface of the wafer 21, and the orbit of the electron beam 23 becomes unstable due to this charging. In order to avoid this phenomenon, the conductor 24 is connected to the wafer 21 so as to prevent the electric charge from being charged on the wafer 21, and the electric charge is discharged.

  FIG. 2B is a diagram for explaining a method for discharging charges more efficiently than the antistatic means for the wafer shown in FIG.

  As shown in FIG. 2B, a conductive antistatic film 28 is formed on the surface of the wafer 21. A charge is efficiently discharged by connecting a conductor to the antistatic film 28 and setting it to the ground potential.

  However, if a conductor is connected to the portion 29 where the antistatic film 28 does not exist, or if the antistatic film 28 peels off for some reason even if a conductor is connected to the portion where the antistatic film 28 exists, the wafer Even if it was attempted to remove the charge from the top surface, the effect was almost the same as in FIG. 2A, and a case where a sufficient effect could not be obtained was observed.

Therefore, in this embodiment, attention is paid to connecting the conductor 31 not only to the upper surface of the wafer 21 but also to the lower surface of the wafer 21 to discharge electric charges from both upper and lower sides of the wafer 21.
(Configuration and installation method of charge discharge mechanism)
Next, the structure of the charge discharge mechanism for discharging the charge charged on the wafer and the method for installing the charge discharge mechanism on the wafer will be described with reference to the drawings.

  FIGS. 3A and 3B are diagrams for explaining the charge discharge mechanism (charge discharge means). The charge discharge mechanism includes a wafer upper surface contact portion (first connection means) 41 and a wafer lower surface contact portion (second connection means) 42.

  The wafer upper surface contact portion 41 includes an upper surface contact portion 41a and an upper surface contact main body portion 41b. The upper surface contact portion 41 a has a flat portion in contact with the upper surface of the wafer 48. The upper surface contact portion 41a is configured, for example, by ion plating titanium nitride (TiN) on nonmagnetic conductive ceramics. It is not preferable to make this portion needle-like because the needle-like portion pierces the wafer 48 and particles are generated, contaminating the surface of the wafer 48, leading to a decrease in yield and reliability.

  The wafer lower surface contact portion 42 includes a lower surface contact portion 42a and a lower surface contact main body portion 42b. A portion of the lower surface contact portion 42 a that contacts the lower surface of the wafer 48 has a needle shape. The needle-like portion is formed of, for example, non-magnetic super steel and pierces the back surface of the wafer 48. The lower surface contact portion 42a and the lower surface contact main body portion 42b are bonded using a conductive adhesive.

  The upper surface contact main body portion 41b and the lower surface contact main body portion 42b are formed using a conductive material. The whole may be a conductive material, but the use of a conductive material is preferably minimal. This is because an eddy current is generated when the magnetic flux generated by the deflection coil of the electromagnetic deflector 120 disposed above the wafer stage passes through the upper surface contact body 41b or the lower surface contact body 42b formed of a conductive material. This is to prevent unnecessary phenomena such as heat generation. Therefore, the upper surface contact main body portion 41b and the lower surface contact main body portion 42b are formed of, for example, ceramic, and a conductive material such as titanium nitride (TiN) is plated (coated) by a method such as ion plating. Therefore, the minimum necessary conductive material is used.

  A leaf spring 43 is attached to the lower surface contact main body portion 42 b, and the leaf spring 43 is connected and fixed via a wafer stage 47 and a stage connection portion 45.

  The upper surface contact main body portion 41 b and the lower surface contact main body portion 42 b are connected by a shaft 44. Further, the wafer upper surface contact portion 41 and the wafer lower surface contact portion 42 can rotate around the central axis of the shaft 44 as shown in FIG.

  The upper surface contact main body 41b and the lower surface contact main body 42b are arranged with an elliptical cam 53 interposed therebetween. As the cam 53 rotates, the upper surface contact main body portion 41 b that contacts the upper surface of the cam 53 rotates upward in accordance with the shape of the cam 53, and the upper surface contact portion 41 a opens to contact the lower surface of the cam 53. The part 42b rotates downward in accordance with the shape of the cam 53, and the lower surface contact part 42a is opened.

  The upper surface contact main body portion 41b and the lower surface contact main body portion 42b are connected via a spring 46 so that the upper surface contact portion 41 and the lower surface contact portion 42 are kept closed.

  By sandwiching a part of the periphery of the wafer 48 between the upper surface contact portion 41a of the wafer upper surface contact portion 41 and the lower surface contact portion 42a of the wafer lower surface contact portion 42, for example, 1 to 2 mm from the edge of the wafer, It constitutes a charge discharge mechanism.

  If the upper and lower edges of the wafer 48 are sandwiched, the wafer 48 may be bent depending on the force applied to that portion. That is, if the force applied to the wafer from above or from below is not balanced, the wafer is bent. In this embodiment, in order to avoid this phenomenon, the charge discharge mechanism is configured as follows.

  As described above, the lower surface contact main body 42 b is fixed to the wafer stage 47 by the leaf spring 43. As described above, the wafer upper surface contact portion 41 and the wafer lower surface contact portion 42 are fixed only by the leaf spring 43 and are in a floating state due to the spring property. For this reason, since it follows the surface of the wafer while the wafer is sandwiched, it is possible to prevent the wafer from being bent without applying an extra load.

  Next, a method for installing the charge discharge mechanism on the wafer will be described with reference to FIGS.

  The charge discharge mechanism is as shown in FIG. 4 in an initial state where no wafer is sandwiched. As shown in FIG. 4, the wafer upper surface contact portion 41 is in a state of riding on the flat portion of the cam 53 having a shape having a flat surface portion and a curved surface portion (hereinafter also referred to as an elliptical shape). The cam 53 is connected to a bearing 56 by a shaft 57, and the bearing 56 is interlocked with the bearing 52 via a bearing 55. These bearings 52, 55, 56 and the cam 53 are rotatable about the central axis of the cam 53. On the other hand, the bearing 54 is fixed.

  The cam 53 is made of phosphor bronze, for example, and is subjected to DLC coating (diamond-like coating) in order to reduce the friction coefficient of the surface thereof.

  In this embodiment, a push-up mechanism is used to increase the distance between the upper surface contact portion 41a and the lower surface contact portion 42a (hereinafter also referred to as a wafer contact portion) from the initial state. The push-up mechanism is an independent mechanism different from the charge discharge mechanism, and uses a push-up portion 61 whose tip is tapered as shown in FIG.

  FIGS. 5A to 5C are diagrams for explaining processing for opening the wafer contact portion in time series.

  FIG. 5A shows an initial state before the wafer contact portion has a constant interval and sandwiches the wafer. The push-up portion 61 is disposed below the bearings 52 and 53. From this state, the wafer stage controller 208 raises the push-up unit 61 simultaneously with the wafer positioning mechanism, and inserts the push-up unit 61 between the bearing 52 and the bearing 54.

  In FIG. 5B, the push-up portion 61 is inserted between the bearing 52 and the bearing 54, and the cam 53 rotates and moves along the tapered inclined surface in conjunction with the bearing 52 and the bearing 52 by the taper portion of the push-up portion 61. Shows the state.

  As the elliptical cam 53 rotates and moves in conjunction with the movement of the bearing 52, the entire wafer upper surface contact portion 41 on the horizontal plane of the cam is moved to the center of the shaft 44 as shown in FIG. Is rotated upward in accordance with the shape of the cam 53 around the center of rotation. Further, the entire wafer lower surface contact portion 42 that is in contact with the lower surface of the cam 53 rotates downward along the shape of the cam 53 with the center of the shaft 44 as the center of rotation. Thereby, the space | interval of a wafer contact part spreads and it will be in an open state. In this state, the wafer 48 is transferred.

  Next, the wafer is lightly fixed with a guide (not shown) so that the wafer is placed at a correct position, and the position of the wafer is adjusted by observing the position of the wafer with a camera from above. With the wafer placed at a correct position, the wafer is fixed to the wafer stage by the electrostatic chuck 62.

  Thereafter, as shown in FIG. 5C, the push-up portion 61 is lowered, and the spring 46 moves so that the positional relationship between the wafer upper surface contact portion 41 and the wafer lower surface contact portion 42 is in an initial state, and the wafer is moved. A part of the peripheral edge of 48 is sandwiched.

  The distance between the lower surface contact portion 42 a and the upper surface contact portion 41 a is adjusted in advance according to the known thickness of the wafer 48.

  In this way, the wafer 48 is sandwiched from both the upper and lower sides. In particular, since the lower surface contact portion 42a has a needle shape, it is possible to pierce a single point on the lower surface of the wafer, capture the charge accumulated in the wafer 48, and discharge the charge.

  As described above, in this embodiment, a part of the peripheral portion of the wafer is sandwiched from both the upper and lower sides by the charge discharge mechanism. The upper part of the wafer is in contact with the wafer surface, and the lower part of the wafer uses needle-like terminals that pierce. The charge discharge mechanism is made of ceramic and the surface thereof is plated with a conductive material. As a result, the charge charged on the wafer can be captured and discharged not only from the surface of the wafer but also from the inside of the wafer, and the wafer can be effectively prevented from being charged.

  In this embodiment, the wafer upper surface contact portion that contacts the upper side of the wafer and the wafer lower surface contact portion that contacts the lower portion are connected via a shaft, and the one that contacts the lower portion of the wafer via a leaf spring. It is fixed on the stage. In this way, the charge discharge mechanism is in a floating state due to its spring property, and it follows the surface of the wafer with the wafer sandwiched therebetween, so that no additional load is applied and the wafer is bent. Can be prevented.

  As in the present embodiment, by discharging the charge with the charge discharge mechanism sandwiching the upper and lower sides of the wafer 21, the electron beam can be more accurately exposed on the wafer than when the conventional antistatic means is applied. It has been confirmed.

  In this embodiment, the case where the charge discharge mechanism is installed at one location of the wafer has been described as an example. However, the present invention is not limited to this, and the charge discharge mechanism may be installed at a plurality of locations on the wafer. By installing a plurality of charge discharge mechanisms, the distance between the generated charges and the charge discharge mechanism can be shortened, and the wafer can be more efficiently prevented from being charged.

In the present embodiment, the case where both the wafer upper surface contact portion and the wafer lower surface contact portion constituting the charge discharge mechanism are movable has been described. However, the present invention is not limited to this. For example, only the wafer upper surface contact portion is movable. Also good.

Claims (7)

A wafer stage on which the wafer is placed;
An electron beam exposure apparatus having charge discharge means for discharging the charge charged on the wafer,
The charge discharging means includes
First connection means having an upper surface contact portion in contact with the upper portion of the wafer;
Second connection means having a lower surface contact portion in contact with the lower portion of the wafer;
A shaft that rotatably connects the first connecting means and the second connecting means;
A leaf spring connected to the second connection means and the wafer stage, and fixing the first connection means and the second connection means on the wafer stage;
An electron beam exposure apparatus comprising: 2. The electron beam exposure apparatus according to claim 1 , wherein a portion of the second connecting means that contacts the wafer is needle-shaped, and the needle-shaped portion reaches the inside of the wafer. 3. The electron beam exposure apparatus according to claim 1, wherein surfaces of the first connection means and the second connection means are coated with a conductive material. The wafer is loaded onto the wafer stage in a state where at least one of the first connection means or the second connection means rotates and the upper surface contact portion and the lower surface contact portion are open. The electron beam exposure apparatus according to any one of claims 1 to 3 . The wafer is sandwiched between the upper surface contact portion and the lower surface contact portion by rotating at least one of the first connection means or the second connection means in a state where the wafer is fixed to the wafer stage. The electron beam exposure apparatus according to any one of claims 1 to 4 . The charge discharging means, an electron beam exposure apparatus according to any one of claims 1 to 5, characterized in that sandwich the wafer at a position 2mm from 1 from the edge of the wafer. The charge discharging means, an electron beam exposure apparatus according to any one of claims 1 to 6, characterized in that sandwich the wafer at least one position of the edge of the wafer.

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