JP2006013210A - Exposure system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To safely maintain an exposure system whose inner side is purged with inert gas. <P>SOLUTION: The exposure device is provided with a tank for air supply as a means for replacing inert gas in an inert gas purging space with air, and a means capable of automatically supplying the air in the tank to the inert gas purging space in whatever state the device is when the maintenance door of the inert-gas purging space is opened. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In the semiconductor exposure apparatus, when the sealed space replaced with the inert gas (for example, nitrogen) in the apparatus is opened for maintenance, inspection, and repair of the apparatus, the inert gas inside the sealed space is automatically removed. The present invention relates to an exposure apparatus provided with an inert gas purge space automatic ventilation device that dynamically replaces air.

  2. Description of the Related Art Conventionally, in a semiconductor exposure apparatus that projects and transfers (retries) a reticle pattern onto a wafer, as the semiconductor element becomes finer, the accuracy of the apparatus becomes higher (for example, wafer and reticle alignment accuracy and reticle pattern transfer accuracy to the wafer). Is required. In order to improve the transfer accuracy, there are a method of shortening the exposure wavelength and a method of increasing the numerical aperture of the projection optical system. For this reason, with the increase in accuracy of the exposure apparatus, the exposure wavelength has been shortened to i-line (365 nm), KrF laser (248 nm), and ArF laser (193 nm).

  However, with the shortening of the exposure light wavelength, impurities adhere to the optical element in the exposure optical path, and the problem of deterioration of optical characteristics (deterioration of transfer accuracy) has started to occur. Impurities are mainly silicon dioxide SiO2 and ammonium sulfate (NH4) 2SO2 produced by a chemical reaction between ammonia NH3, sulfurous acid SO2 and Si compound in the air and ultraviolet light (exposure light).

  Conventionally, an optical element in the exposure optical path is sealed (a purge space is formed) and an inert gas such as nitrogen is allowed to flow through the space.

  Furthermore, when an F2 laser (157.6 nm) having a shorter wavelength was used, the existence of a little unpurged space that could be ignored until now could not be ignored.

  The main cause is that the oxygen present in the unpurged space decreases the transmittance of exposure light, and sufficient illuminance cannot be obtained on the wafer.

  For example, the transmittance of F2 laser light in air is only 1% / mm. Therefore, when the distance between the lower surface of the projection lens that is not purged and the wafer surface is about 20 mm, sufficient illuminance cannot be obtained on the wafer surface.

  Against this background, the inert gas purge space in the exposure apparatus has been expanded over the entire exposure optical path. As a result, many units constituting the exposure apparatus are configured inside the inert gas purge space, and the walls (maintenance doors) constituting the inert gas purge space are opened in order to maintain and inspect the units inside the inert gas purge space. However, the number of accesses to the inside of the inert gas purge space has increased.

When the inside of the inert gas purge space is accessed, there is a risk of lack of oxygen due to the remaining inert gas, so the following safety measures have been conventionally taken.
(1) A label was put on and the worker was obliged to wear an oxygen mask.
(2) The interlock mechanism is provided in the maintenance door of the oxygen concentration meter and the inert gas purge space inside the inert gas purge space. Normally, the maintenance door interlock works, and the maintenance door is designed not to open carelessly. In order to open the maintenance door during maintenance, the inside of the inert gas purge space is ventilated, and the oxygen concentration inside the inert gas purge space is sufficiently secured with an oximeter (for example, the oxygen concentration must be 18% or more). After confirming that there is no danger of oxygen deficiency, the maintenance door was unlocked.
JP 2001-326162 A

However, the above conventional example has the following problems.
An oxygen concentration meter for the inert gas purge space and an interlock mechanism for the maintenance door of the inert gas purge space are configured, and the inside of the inert gas purge space is sufficiently ventilated by the oxygen concentration meter so that there is no risk of suffocation. If it is not confirmed, there is the following problem even in the conventional system in which the interlock mechanism works and the maintenance door cannot be opened.
(1) Although the interlock mechanism is normally operated, it often has a mechanism called a defeet switch for releasing the interlock mechanism for service personnel. In this case, the service person may release the interlock and inadvertently open the inert gas purge space.
(2) Since the interlock mechanism is released after confirming that the oximeter has a safe oxygen concentration, the maintenance door of the apparatus cannot be opened if the oximeter fails.
(3) In order to solve the problem in (2) and to maintain the inside of the inert gas purge space when the device is stopped, a system that releases the interlock when the device is stopped (nitrogen is turned off before the device is stopped). It is replaced with air to ensure safety). In that case, there is no problem if the device stops normally, but the power supply of the device is stopped at the time of emergency stop by EMO, the function of replacing the inert gas with air does not work, and the inside of the inert gas purge space Insufficient ventilation allowed access to the inert gas purge space, leaving the danger of suffocation.

  In order to solve the above-described problems, the present invention can be realized by opening an air supply tank, which is a means for replacing the inert gas in the inert gas purge space with air, and a maintenance door in the inert gas purge space. In any state, means (for example, mechanical means that does not use electricity) that can automatically supply tank air to the inert gas purge space without electrical control is provided.

  According to the present invention, when the maintenance door of the inert gas purge space is opened, the inert gas replacement air can be automatically supplied into the inert gas purge space regardless of the state of the apparatus. Therefore, the inert gas inside the inert gas purge space can be replaced with air having a level of oxygen concentration that allows the operator to work safely, and suffocation accidents can be reliably prevented when maintaining the unit inside the inert gas purge space. it can.

(First embodiment)
A first embodiment of the present invention will be described. FIG. 1 shows a first embodiment of the present invention. 1 is a reticle as an original, 2 is a wafer on which a reticle pattern is projected and exposed, 3 is a laser oscillator as an exposure light source, 4 is an illumination optical system for illuminating the reticle 2, and 5 is a reticle pattern projected onto the wafer 2 A projection optical system for exposure, 6 is a wafer stage for moving the wafer 2 to a predetermined position, 7 is a reticle stage for positioning the reticle 1 at a predetermined position, 8 is a wafer transfer system for placing the wafer 2 on the wafer stage 6 and lowering, 9 Reticle transfer system for loading and unloading reticle 1 on reticle stage 7, 10 is a wafer chuck for holding wafer 2 on wafer stage 6, 12 is an alignment unit A for measuring the tilt of wafer 2, and 13 is for measuring the position of wafer 2. The alignment units B and 14 that perform the alignment are used to measure the position of the reticle 1. Reference numerals C and 15 denote a wafer purge chamber that forms a space between the lower surface of the projection optical system 5 and the upper surface of the wafer 2, and reference numeral 16 denotes a reticle purge chamber that seals a space between the lower surface of the illumination optical system 4 and the upper surface of the projection optical system 5. , 17 is a load lock A for loading / unloading the wafer 2 into / from the wafer chamber 15, 18 is a load lock B for loading / unloading the reticle 1 from / to the reticle chamber 16, and 19 is a nitrogen purge apparatus for supplying nitrogen to the wafer purge chamber 15 and the reticle purge chamber 18. , 20 is a maintenance door that is opened when the inside of the wafer purge chamber 15 is maintained, 21 is an air tank that stores air supplied to the interior of the wafer purge chamber 15 when the maintenance door 20 is opened, and 22 is a maintenance door 20. When it is opened, the air in the air tank 21 is automatically removed from the wafer. It is an automatic air supply mechanism for supplying the interior of the purge chamber 15.

  The feature of the present invention is that an air tank 21 and an automatic air supply mechanism 22 which are not in the conventional example shown in FIG. 2 are configured. First, based on the conventional example in FIG. The maintenance procedure will be described.

  As an example of maintaining the inside of the wafer purge chamber 15, repair of the wafer stage 6, alignment unit B 13, wafer transfer system 8, etc. can be considered. In order to repair the wafer stage 6, it is necessary to remove (or open) the maintenance door 20 from the wafer purge chamber 15 and access the wafer stage 6 inside the wafer purge chamber 15. At this time, the problem is that the inside of the wafer purge chamber 15 is normally purged with nitrogen supplied from a nitrogen purge device 19. The purpose is omitted because it has been described in the conventional example, but since the inside of the nitrogen purge space is purged with nitrogen with high purity, there is a danger of suffocation when a person works inside. Usually, the safe oxygen concentration is said to be 18% or more, but the oxygen concentration in the nitrogen purge space during the nitrogen purge operation is a level of 1-1000 ppm (100 ppm = 0.01%), and it is certain if a human enters it. Suffocate.

  Therefore, conventionally, safety measures as shown in FIG. 2 have been taken. 2 differs from FIG. 1 in that the air tank 21 and the automatic air supply mechanism 22 are not configured, but the measured values of the oxygen concentration meter 23 and the oxygen concentration meter 23 for measuring the oxygen concentration in the wafer purge chamber 15. An interlock control mechanism 25 that determines whether the maintenance door can be removed based on the above, and a maintenance door interlock mechanism 24 that prohibits the opening operation of the maintenance door 20 (removal from the wafer purge chamber 15) are configured.

  When the exposure apparatus is in operation, the inside of the wafer purge chamber 15 is purged with nitrogen to a concentration of about 1 to 1000 ppm with nitrogen supplied from the nitrogen purge apparatus 19. At that time, the maintenance door 20 cannot be removed from the wafer purge chamber 15 by the interlock control mechanism 24, so that a suffocation accident does not occur due to an operation mistake such as accidentally removing the maintenance door 20.

  When maintaining the wafer stage 6, the nitrogen purge device 19 is stopped and the supply of nitrogen to the wafer purge chamber 15 is stopped. Thereafter, a ventilation device (not shown) is operated to replace the inside of the wafer purge chamber 15 with air. At the same time (or after a certain time), the oxygen concentration inside the wafer purge chamber 15 is measured by the oxygen concentration meter 23. If the oxygen concentration does not reach a specified value (for example, 18% or more), the interlock control mechanism 25 determines that it is dangerous to remove the maintenance door 20, and continues to operate the ventilator while maintaining the maintenance door interlock. At 24, prohibition of the opening operation of the maintenance door 20 is continued. If the oxygen concentration in the wafer purge chamber 15 is increased by continuing the ventilation operation thereafter and the oxygen concentration meter 23 measures an oxygen concentration of 18% or more, it is safe even if the interlock control mechanism 25 removes the maintenance door 20. The maintenance door interlock mechanism 24 is operated to cancel the prohibition of the opening operation of the maintenance door 20. The maintenance door interlock mechanism may be, for example, a mechanism in which a general shaft enters and exits and the protruding shaft enters a hole in the maintenance door 20 and prohibits the opening operation of the maintenance door 20.

  However, in the conventional example, when the function of disabling the interlock control mechanism called the defeet switch is operated, or when the apparatus is stopped, the power supply is cut off and the maintenance door interlock mechanism 24 does not operate, so that the maintenance door 20 can be removed freely. Was made. In particular, when an emergency stop device called EMO works, the function of ventilating the inside of the wafer purge chamber 15 does not work, and there is a danger of suffocation if the maintenance door 20 is removed.

  The maintenance door interlock mechanism 24 may be configured with a system that does not work when the power supply is stopped (the maintenance door 20 can be freely removed) in consideration of maintainability when the power supply is stopped (and workability in a place where power cannot be supplied). In many cases, there is a mechanism that always releases the system even if the system works with interlock even when the power is turned off. If the system is mishandled, the risk of suffocation could not be ignored.

  Therefore, according to the present invention, in any state of the apparatus, when the maintenance door 20 is removed, there is no risk of suffocation even if the maintenance door 20 is removed. ) A mechanism for supplying air into the wafer purge chamber 15 was provided.

  Specifically, as shown in FIG. 1, when the air tank 21 for storing the air supplied to the wafer purge chamber 15 and the maintenance door 20 are removed, the air in the air tank 21 is supplied to the inside of the wafer purge chamber 15. A supply mechanism 22 is configured.

  In FIG. 1, the oximeter 23, the maintenance door interlock mechanism 24, and the interlock control mechanism 25 shown in FIG. 2 are not configured, but adding the function of the present invention to the conventional example of FIG. It becomes a double safety measure to prevent suffocation accidents and becomes more effective.

  Next, operations of the air tank 21 and the automatic air supply mechanism 22 will be described with reference to FIG. The main components are a door knob 31 that fixes the maintenance door 20 to the wafer purge chamber 15, an air supply valve 37 that controls the inflow of air from the air tank 21 into the wafer purge chamber 15, and a rotary lever that drives the air supply valve 37. 33 etc.

  In a normal exposure apparatus movable state, the air supplied from the air supply line 41 passes through the back support valve 40 and is stored in the air tank 21. The stored air is not supplied to the wafer purge chamber 15 because it is closed by the air supply valve 37 at the tip of the air supply line B42. Even if the facility air supplied to the exposure apparatus stops, the reverse support valve 40 works and air is continuously stored in the air tank 21 even if the pressure of the air supply line 41 decreases.

  Next, the case where the inside of the wafer purge chamber 15 is maintained will be described. When removing the maintenance door 20, first, the door knob 31 that fixes the maintenance door 20 to the wafer purge chamber 15 is removed (loosened), but when the door knob 31 is loosened, the tip position of the knob (position of contact with the rotary lever 33). Moves to the right. On the other hand, the rotary lever 33 has a structure that can rotate around the fulcrum 34, and receives the force in the clockwise direction by the spring A32. However, the door knob 31 directly applies the force in the counterclockwise direction to the rotary lever 33. When the door knob 31 is fixed, the door knob 31 is held at a position rotated counterclockwise. At this position, the abutting portion 36 attached to the tip of the rotation lever 33 is not in contact with the air supply valve 37 and no force is generated to move the air supply valve 37.

  When the door knob 31 is loosened, the contact position with the rotary lever 33 moves to the right. Then, the rotation lever 33 rotates clockwise around the fulcrum 34 by the clockwise force of the spring A32. Then, the abutting portion 36 at the tip of the rotating lever 33 comes into contact with the air supply valve 37. On the other hand, the air supply valve 37 receives a force in the left direction by the spring B38, moves to the left position, and contacts the wafer purge chamber 15 with the O-ring 39 interposed therebetween. The air supply line B42 of the air tank 21 is connected to the air supply valve 37. When the air supply valve 37 is at the left position, the air in the air tank 21 is supplied into the wafer purge chamber 15 by the O-ring 39. It is never done.

  However, when the rotating lever 33 rotates in the clockwise direction, the abutting portion 36 at the tip of the rotating lever 33 contacts the air supply valve 37, and further continues to move in the rotating direction, the abutting portion 36 moves to the air supply valve 37. Will be moved to the right. When the air supply valve 37 moves to the right, the O-ring 39 cannot be crushed and the air in the air tank 21 is supplied into the wafer purge chamber 15.

  When the rotating lever 33 further rotates in the clockwise direction, the abutting portion 36 is not in contact with the air supply valve 37, and the air supply valve 37 is returned to the left by the spring B38. Then, the supply of air from the air tank 21 to the wafer purge chamber 15 is stopped, and the accumulation of air in the air tank 21 is resumed. Therefore, wasteful air supply can be prevented.

  In this way, when the maintenance door 20 is opened, air can be automatically supplied into the wafer purge chamber 15 by the mechanical mechanism, and the oxygen concentration inside the wafer purge chamber 15 which has been lowered by the nitrogen purge is reduced to a safe oxygen without danger of suffocation. The concentration can be adjusted.

  When the maintenance door 20 is squeezed, the rotation lever rotates counterclockwise by the force of the door knob 31 from the position rotated in the clockwise direction, and returns to the initial position. The abutting portion 36 contacts the air supply valve 37 in the middle of rotation, but the air supply valve 37 cannot move to the left from the position where it contacts the wafer purge chamber 15 (the position where the air supply of the air tank 21 is shut off). Therefore, when the spring C35 formed at the base of the abutting portion 36 contracts, the rotating lever 33 moves counterclockwise to a position where the abutting portion 36 does not contact the rotating lever 33 (returns to the initial position).

  Although the example of maintenance of the wafer stage 6 inside the wafer purge chamber 15 has been described, the present invention can be applied to all cases in which the inside of the inert gas purge space in the exposure apparatus is accessed.

  Further, the air in the air tank 21 may be blown into the purge space from the vicinity of the door so as not to be suffocated by nitrogen coming out of the gap when the maintenance door 20 is opened.

  Further, the volume V1 of the air tank 21 is V1 = 9V2 assuming that the volume V2 of the wafer purge chamber 15 is mixed with air V1 with an oxygen concentration of 20% and the oxygen concentration of the volume V1 + V2 is 18%. . This assumption assumes that V1 and V2 are the same pressure, but assuming that the pressure of the air tank is 0.3 Mpa and the pressure of the wafer purge chamber 15 is 1000 Pa (= 0.001 Mpa), V1 = 9/3 / 100V2 = 0.03V2. The volume of the air tank and the air pressure may be determined in consideration of the leakage amount and the safety factor.

  Further, in the present embodiment, the case where one air tank 21 and one maintenance door 20 are provided has been described. In that case, the air tank 21 may be used as a plurality of maintenance doors 20, or a small air tank 20 may be provided for each of the plurality of maintenance doors 20.

(Second embodiment)
In general, resumption of nitrogen purge to the wafer purge space 15 after removing the maintenance door 20 is started when a maintenance door 20 attachment confirmation sensor (not shown) confirms that the maintenance door 20 is attached. Therefore, if air is not supplied to the air tank 21 after the maintenance door 20 is removed, the first embodiment will not function. Therefore, the second embodiment adds to the first embodiment a function in which the maintenance door 20 cannot be attached unless air is stored in the air tank 21 after the maintenance door 20 is removed. A second embodiment will be described with reference to FIGS. 4 and 5 show only functions added to the first embodiment. The functions of the maintenance door 20, the wafer purge chamber 15, and the door knob 31 are the same as in the first embodiment, but an air cylinder 43, a spring D44, and a knob stopper 45 are newly configured. The knob stopper 45 can move up and down, and the door knob 31 cannot move to a position where the maintenance door 20 is fixed to the wafer purge chamber 15 when it is in the lower position as shown in FIG. (The maintenance door 20 cannot be attached). The air cylinder 43 uses the spring D44 and the air pressure of the air tank 21 to move up and down the knob stopper 45. That is, as shown in FIG. 4, when air pressure is present in the air tank 21 (when air is stored), the air pressure in the air tank 21 is supplied to the air cylinder 43, and the air cylinder 43 has the force of the spring D44. The knob stopper 45 is pushed up to the upper position. When the knob stopper 45 is in the upper position, the door knob 31 can fix the maintenance door 20 to the wafer purge chamber 15. That is, the maintenance door 20 can be attached. On the other hand, as shown in FIG. 5, when there is no air in the air tank 21, no air pressure is supplied to the air cylinder 43, and the air cylinder 43 does not generate a force that pushes the knob stopper 45 upward. Accordingly, the knob stopper 45 is moved to the lower position by the spring D44. As a result, the door knob 31 cannot move to a position where the maintenance door 20 is fixed to the wafer purge chamber 15. In other words, the maintenance door 20 cannot be attached.

(Third embodiment)
7 and 8 show a third embodiment. The purpose is opposite to that of the second embodiment, and is to prevent the maintenance door 20 from being opened when air is not stored in the air tank 21. The configuration and function are the same as in the second embodiment, and the difference is that the knob stopper a48 prevents the door knob 31 from coming off.

  As shown in FIG. 7, when air is not stored in the air tank 21, the knob stopper a 48 is lowered to the position where the door knob 31 cannot be removed. On the other hand, as shown in FIG. 8, when air is stored in the air tank 21, the knob stopper a48 is raised to the upper position, and the door knob 31 comes out, that is, the maintenance door 20 can be removed.

(Fourth embodiment)
In the first embodiment, air supplied into the wafer purge chamber may be used to drive a fan (not shown) to forcibly supply air into the wafer purge chamber.

  In this case, air may be supplied only to the fan drive source, or may be supplied into the wafer purge chamber after the fan is driven.

(Fifth embodiment)
In the first embodiment, an example of one maintenance door has been described. However, when a plurality of maintenance doors are provided, an air tank may be provided in each maintenance door. By doing so, air in the air tank can be supplied only to the vicinity of the maintenance door that is opened (the space necessary for maintenance work), and thus the air tank can be made smaller.

(Sixth embodiment)
FIG. 6 shows a fourth embodiment. In the first and second embodiments, the oxygen concentration inside the wafer purge chamber 15 is increased by supplying air. However, in the third embodiment, nitrogen inside the wafer purge chamber 15 is sucked out and the maintenance door 20 and the wafer are discharged. The oxygen concentration in the wafer purge chamber 15 is increased by sucking air from the gap between the purge chambers 15. The functions of the maintenance door 20, the wafer purge chamber 15, and the door knob 31 are the same as in the first embodiment, but the packing 46 and the exhaust line 47 are configured, and the air tank 21 is eliminated. In the exposure apparatus movable state, the packing 46 fixed to the maintenance door 20 fills the gap between the wafer purge chamber 15 and the exhaust line 47. Therefore, nitrogen in the wafer purge chamber is not sucked out by the exhaust line 47.

  On the other hand, when the maintenance door 20 is removed, the packing 46 is also removed, and the interior of the wafer purge chamber 15 and the exhaust line 47 are connected. Therefore, nitrogen inside the wafer purge chamber 15 is exhausted to the outside by the exhaust line 47. At the same time, air enters the wafer purge chamber through the gap between the maintenance door 20 and the wafer purge chamber 15, and the oxygen concentration inside the wafer purge chamber 15 can be increased.

  Therefore, as in the first and second embodiments, when the maintenance door 20 is removed, the oxygen concentration in the wafer purge chamber 15 can be automatically raised to a safe height without the danger of suffocation by the mechanical means.

It is a figure which shows the 1st Example of this invention. It is a figure which shows a prior art example. It is a figure explaining a 1st Example in detail. It is a figure which shows the 2nd Example which shows that a maintenance door can be closed when there exists air in an air tank. It is a figure which shows the 2nd Example which shows that a maintenance door cannot be closed when there is no air in an air tank. It is a figure which shows the 3rd Example which shows increasing oxygen concentration using an exhaust line. It is a figure which shows the 3rd Example which shows that a maintenance door cannot be removed when there is no air in an air tank. It is a figure which shows the 3rd Example which shows that a maintenance door can be removed when there exists air in an air tank.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reticle 2 Wafer 3 Laser is an oscillator 4 Illumination optical system 5 Projection optical system 6 Wafer stage 7 Reticle stage 8 Wafer conveyance system 9 Reticle conveyance system 10 Wafer chuck 12 Alignment unit A
13 Alignment unit B
14 Alignment unit C
15 Wafer purge chamber 16 Reticle purge chamber 17 Load lock A
17a Outer door 17b Inner door 18 Load lock B
19 Nitrogen purge device 20 Maintenance door 21 Air tank 22 Automatic air supply mechanism 23 Oxygen concentration meter 24 Maintenance door interlock mechanism 25 Interlock control mechanism 31 Door knob 32 Spring A
33 Rotating lever 34 Support point 35 Spring C
36 Abutting part 37 Air supply valve 38 Spring B
39 O-ring 40 Reverse valve 41 Air supply line 42 Air supply line B
43 Air cylinder 44 Spring D
45 Knob stopper 46 Packing 47 Exhaust line 48 Knob stopper a

Claims (7)

  In the semiconductor exposure apparatus, the semiconductor exposure apparatus includes means for supplying an inert gas, a sealed space to which the inert gas is supplied, a means for supplying oxygen to the sealed space, and a means for opening the sealed space. 2. A semiconductor exposure apparatus according to claim 1, wherein the oxygen supply means automatically operates as the space is opened regardless of the state of the apparatus.   2. The semiconductor exposure apparatus according to claim 1, further comprising means for preventing the closed space from being opened when the oxygen supply means is not in an operable state.   2. The semiconductor exposure apparatus according to claim 1, further comprising means for preventing the sealed space from being opened when the oxygen supply means is not operable.   4. The semiconductor exposure apparatus according to claim 1, wherein the means for opening the sealed space operates the means for supplying oxygen.   The exposure apparatus according to claim 1, wherein the oxygen supply means has means for constantly storing oxygen inside the supply means.   6. The semiconductor exposure apparatus according to claim 1, wherein the oxygen supply means includes means for supplying a certain amount of oxygen as the sealed space is opened.   3. The exposure apparatus according to claim 1, wherein the oxygen supply means supplies the oxygen in the outside air to the opened sealed space by sucking out the inert gas inside the opened sealed space. .

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