JP2006128206A - Exposure method and exposure apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure method and an exposure apparatus for preventing pattern distortion of wafer resulting from temperature change during evacuation with higher accuracy. <P>SOLUTION: A wafer cassette 20 for accommodating a plurality of wafers, a prealigner 21, and a robot arm 23 are allocated under the atmospheric condition. At the area near the robot arm 23, a temperature rising means (lamp) 24 is also allocated. In the upper direction of the lamp 24, a temperature measuring means (temperature sensor) 26 is mounted. The wafer W can be extracted with the robot arm 23 from the wafer cassette 20 and is then carried to a load rock chamber 27 after the prealignment for the purpose of evacuation. The temperature sensor 26 measures actual temperature of the wafer W to obtain the measured temperature and then sends this temperature value to a controller 25. The controller 25 operates the lamp 24 on the basis of the measured temperature value sent from the temperature sensor 26 in order to control irradiation time and an output or the like of the lamp 24. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exposure method and an exposure apparatus used for lithography such as a semiconductor integrated circuit. In particular, the present invention relates to an exposure method and an exposure apparatus using a charged particle beam such as an electron beam or an ion beam, or X-rays, which are exposed in a vacuum environment.

  In an apparatus that performs exposure in a vacuum atmosphere such as an electron beam exposure apparatus, a wafer (sensitive substrate) is taken out of a cassette and pre-aligned by a pre-aligner apparatus or the like, and then placed in a chamber called a load lock chamber or a load chamber. Be transported. A vacuum pump is attached to the load lock chamber, and the chamber can be evacuated. In the load lock chamber, a wafer is received from the pre-aligner under normal pressure, and after the chamber is evacuated, these are moved into the exposure apparatus.

  FIG. 4 is a plan view schematically showing a conventional example of a wafer transfer mechanism. Arrows in the figure indicate wafer transfer paths. A wafer cassette 60 for storing a plurality of wafers, a wafer pre-aligner 71, and a robot arm 73 are arranged in the atmosphere. A temperature raising means (lamp) 74 is disposed in the vicinity of the robot arm 73. Further, the vacuum load chamber 83, the pre-aligner chamber 91, and the exposure apparatus 100 are kept in a vacuum.

  A gate valve 79 is provided at the entrance of the load lock chamber 77. The load lock chamber 77 is connected to the wafer vacuum load chamber 83 via a gate valve 81. A vacuum robot arm 85 is disposed in the chamber 83.

  Wafer vacuum load chamber 83 is connected to pre-aligner chamber 91 via gate valve 89. A pre-aligner 93 is provided in the chamber 91. Wafer vacuum load chamber 83 is connected to wafer chamber 106 of exposure apparatus 100 via gate valve 95. A wafer stage 131 is provided in the chamber 106, and a wafer holder 130 is provided on the stage 131.

  Hereinafter, a procedure for transporting a wafer from the cassette 60 to the exposure apparatus 100 will be described. First, in the atmosphere, one wafer is taken out from the cassette 60 by the robot arm 73 and placed on the pre-aligner 71 to perform wafer pre-alignment. After the pre-alignment is completed, the wafer is taken out from the pre-aligner 71 by the robot arm 73. Then, the wafer is moved above the temperature raising means (lamp) 74 and irradiated with the lamp 74 to heat the wafer.

  Thereafter, the gate valve 79 is opened and the wafer is transferred to the load lock chamber 77. Then, the gate valve 79 is closed and the load lock chamber 77 is evacuated. When the load lock chamber 77 reaches the target degree of vacuum, the gate valve 81 on the vacuum load chamber 83 side is opened, the wafer is taken out from the load lock chamber 77 by the vacuum robot arm 85, and the prealigner 93 in the prealigner chamber 91 is removed. Place on top. Then, the prealigner 93 performs pre-alignment with higher accuracy.

After the alignment is completed, the vacuum robot arm 85 takes out the wafer from the pre-aligner chamber 91, opens the gate valve 95, and conveys it to the exposure apparatus 100. Then, the wafer is placed on the wafer holder 130 on the wafer stage 131 in the wafer chamber 106.
JP 2003-031470 A

  Normally, when the load lock chamber 77 is evacuated, the temperature of the wafer placed in the chamber is reduced by about 2 to 4 ° C. due to the adiabatic expansion of the gas. When the temperature decreases in this way, the wafer may be distorted by the temperature change. In one example, in a Si wafer having a diameter of 200 mm, a dimensional change of about 0.5 μm occurs with a temperature change of 1 ° C. Such a dimensional change makes it impossible to obtain a highly accurate pattern. Therefore, it is necessary to wait for several tens of minutes until the temperature rises to the original temperature, or to perform alignment again and again before exposure.

  Therefore, in the above-described technique, the wafer is preheated by the temperature raising unit after the pre-alignment in the atmosphere is completed. As a result, when evacuating in the load lock chamber, even if the temperature of the wafer placed in the chamber decreases due to adiabatic expansion of the gas, the wafer temperature returns to the original standard temperature. There is no change.

  However, even if a certain amount of heat is applied to the wafer, the temperature does not always return to the standard temperature. This is due to various causes. For example, due to the influence of the residual heat accompanying the heat capacity of the temperature raising means, the first wafer and the last wafer in one lot of the exposure sequence after the temperature of the substrate is raised. The temperature is not exactly the same, and the first sheet after the exposure is interrupted may not have sufficient heat applied to the wafer due to the influence of the heat capacity of the temperature raising means. Further, since the temperature of the wafer substrate before raising the temperature of the wafer is minute for each wafer, it does not return to the standard temperature strictly even if a certain amount of heat is applied to the wafer. Furthermore, since the thermal efficiency of the temperature raising means also changes over time, there is a case where the predetermined amount of heat is not actually applied even if it is considered that the predetermined amount of heat is added.

  In view of the above points, the present invention controls the substrate temperature with high accuracy without being affected by the temperature of the substrate and the exposure apparatus, the ambient atmosphere, etc., and prevents substrate pattern distortion caused by temperature changes during evacuation. An object of the present invention is to provide an exposure method and an exposure apparatus that can perform the above.

  The first aspect of the present invention is "an exposure method for selectively irradiating a sensitive substrate with an energy beam under vacuum to form a pattern, wherein the measurement result of a temperature measuring means for measuring the temperature of the substrate is used as described above. An exposure method characterized in that a temperature raising means for raising the temperature of a substrate is controlled. Thus, an exposure method capable of controlling the substrate temperature with high accuracy without being affected by the temperature of the substrate and the exposure apparatus, the ambient atmosphere, and the like, and preventing the pattern distortion of the substrate due to the temperature change during evacuation. Can be provided.

  Secondly, the present invention provides an exposure apparatus for selectively irradiating a sensitive substrate with an energy beam under vacuum to form a pattern, a temperature raising means for raising the temperature of the substrate, and measuring the temperature of the substrate. There is provided an exposure apparatus comprising: a temperature measuring means for performing control; and a control means for controlling the temperature raising means based on a measurement result of the temperature measuring means. Thereby, without being affected by the temperature of the substrate and the exposure apparatus, the ambient atmosphere, etc., the exposure apparatus can control the substrate temperature with high accuracy and prevent the pattern distortion of the substrate caused by the temperature change during evacuation. Can be provided.

  Thirdly, the present invention provides "the exposure apparatus according to claim 2, wherein the temperature measuring means is a non-contact type temperature measuring sensor" (claim 3). Accordingly, since the temperature of the substrate can be measured in a non-contact manner, there is no need for dust on the substrate, no large measuring device is required, and an exposure apparatus that can cope with various shapes of the substrate is provided. it can.

  Fourthly, the present invention provides "the exposure apparatus according to claims 2 and 3, wherein the temperature measuring means is a lamp" (claim 4). As a result, the temperature of the substrate can be raised in a non-contact manner, so that there is no dust on the substrate, no large measuring device is required, and an exposure apparatus that can handle various shapes of the substrate is provided. can do.

  According to a fifth aspect of the present invention, "the exposure apparatus according to any one of claims 2 to 4, wherein the temperature raising means and the temperature measuring means are both in the air or in a vacuum" (Claim 5). provide. Accordingly, it is possible to provide an exposure apparatus capable of highly accurate substrate temperature control in the air or in a vacuum regardless of the measurement atmosphere.

  The present invention is effective for temperature control of a substrate when the substrate is transported from the atmosphere to a vacuum environment. According to the present invention, the temperature control of the substrate can be performed with high accuracy and the substrate pattern distortion can be prevented when canceling the temperature decrease of the substrate due to the temperature change during evacuation.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, the configuration of the entire exposure apparatus will be described with reference to FIG. FIG. 3 is a view showing an outline of the imaging relationship and the control system in the entire optical system of the exposure apparatus according to an embodiment of the present invention. An optical barrel 101 is disposed on the electron beam exposure apparatus 100. A vacuum pump (not shown) is connected to the optical barrel 101, and the inside of the optical barrel 101 is evacuated.

  An electron gun 103 is disposed above the optical lens barrel (including the mask chamber) 101 and emits an electron beam downward. Under the electron gun 103, a condenser lens 104, an electron beam deflector 105, and a mask M are arranged in this order.

  The electron beam emitted from the electron gun 103 is converged by the condenser lens 104, and then sequentially scanned by the electron beam deflector 105 in the horizontal direction in the figure, and each small region (in the mask M within the field of view of the optical system) Subfield lighting is performed. The illumination optical system also has a beam shaping aperture, a blanking aperture, and the like (not shown).

  The mask M is fixed to the chuck 110 provided on the mask stage 111 by electrostatic adsorption or the like. The mask stage 111 is placed on the mount body 116. A driving device 112 shown on the left side of the drawing is connected to the mask stage 111. The driving device 112 is connected to the control device 115 via the driver 114. The mask stage 111 is provided with a laser interferometer 113 shown on the right side of the drawing. The laser interferometer 113 is connected to the control device 115. Accurate position information of the mask stage 111 measured by the laser interferometer 113 is input to the control device 115. Based on this, a command is sent from the control device 115 to the driver 114, and the drive device 112 is driven. In this way, the position of the mask stage 111 can be accurately feedback controlled in real time.

  Below the mount body 116, a wafer chamber 106 (vacuum chamber) is shown. A vacuum pump (not shown) is connected to the wafer chamber 106 to evacuate the chamber. A wafer transfer mechanism 10 including a vacuum load chamber 33 and a load lock chamber 27 is connected to the wafer chamber 106. The wafer transfer mechanism 10 will be described later with reference to FIGS. In addition, each code | symbol in the wafer conveyance mechanism 10 shown in FIG. 3 is equivalent to the code | symbol in FIG.1 and FIG.2.

  A projection optical system barrel (not shown) in the wafer chamber 106 is provided with a projection lens 124, a deflector 125, and the like. Further, a wafer stage (precision device) 131 is placed on the bottom surface of the wafer chamber 106 below. A chuck 130 is provided above the wafer stage 131, and the wafer W is fixed by electrostatic adsorption or the like.

  The electron beam that has passed through the mask M is converged by the projection lens 124. The electron beam that has passed through the projection lens 124 is deflected by the deflector 125, and an image of the mask M is formed at a predetermined position on the wafer W. The projection optical system also has various aberration correction lenses, a contrast aperture (not shown), and the like.

  A driving device 132 shown on the left side of the drawing is connected to the wafer stage 131. The driving device 132 is connected to the control device 115 via the driver 134. The wafer stage 131 is provided with a laser interferometer 133 shown on the right side of the drawing. The laser interferometer 133 is connected to the control device 115. Accurate position information of the wafer stage 131 measured by the laser interferometer 133 is input to the control device 115. Based on this, a command is sent from the control device 115 to the driver 134, and the drive device 132 is driven. In this way, the position of the wafer stage 131 can be accurately feedback controlled in real time.

  Next, the wafer transfer mechanism 10 of the above-described exposure apparatus will be described with reference to FIGS. FIG. 1 is a plan view showing a wafer transfer mechanism according to an embodiment of the present invention. FIG. 2 is an enlarged view showing a state where the robot arm holds the wafer. FIG. 2A is a plan view, and FIG. 2B is a side view.

  A wafer cassette (container) 20 for storing a plurality of wafers, a pre-aligner 21 and a robot arm 23 are arranged in the atmosphere. A temperature raising means (lamp) 24 is disposed in the vicinity of the robot arm 23. The lamp 24 is preferably a halogen lamp. Further, the vacuum load chamber 33, the pre-aligner chamber 41, and the exposure apparatus 100 are kept in a vacuum.

  A gate valve 29 is provided at the inlet of the load lock chamber 27. The load lock chamber 27 is connected to the wafer vacuum load chamber 33 via the gate valve 31. A vacuum robot arm 35 is disposed in the chamber 33.

Wafer vacuum load chamber 33 is connected to pre-aligner chamber 41 via gate valve 39. A pre-aligner 43 is provided in the chamber 41.
Wafer vacuum load chamber 33 is connected to wafer chamber 106 of exposure apparatus 100 through gate valve 45. A wafer stage 131 is provided in the chamber 106, and a wafer holder 130 is provided on the stage 131.

  As shown in FIG. 2B, a temperature measuring means (temperature sensor) 26 is disposed above the lamp 24. The temperature sensor 26 measures the actual temperature of the surface of the wafer W and obtains a temperature measurement value. The temperature sensor 26 is connected to the control device 25 and sends a temperature measurement value to the control device 25. The control device 25 operates the lamp 24 based on the temperature measurement value sent from the temperature sensor 26 to control the irradiation time of the lamp 24 and the like.

  Note that the control device 25 and the temperature sensor 26 are omitted in FIGS. 1 and 2A. Hereinafter, a procedure for transporting the wafer W from the cassette 20 into the exposure apparatus 100 will be described with reference to FIGS.

  First, as shown in FIG. 2A, one wafer W is taken out from the cassette 20 by the robot arm 23 and placed on the pre-aligner 21 in the atmosphere. Then, pre-alignment of the wafer W is performed in the pre-aligner 21.

  After the pre-alignment is completed, the wafer W is taken out from the pre-aligner 21 by the robot arm 23. Then, as shown in FIG. 2B, the wafer W is moved above the temperature raising means (lamp) 24 and irradiated with the lamp 24 to heat the wafer W. Here, the time for irradiating the lamp 24 is 5 to 8 seconds as an example.

  As described above, when the wafer W is heated using the lamp 24 to cancel the temperature decrease of the wafer W due to the temperature change during evacuation, the temperature of the substrate and the exposure apparatus, the ambient atmosphere, and the like are affected. The wafer W may not be heated to a desired temperature. Therefore, in this embodiment, the wafer W is heated to a desired temperature by the lamp 24 by adjusting the lamp irradiation time.

  Here, a method for controlling the irradiation time of the lamp 24 will be described. First, the temperature of the wafer W immediately before the wafer W is loaded into the load lock chamber 27 is obtained in advance from the change in the set temperature of the wafer W due to the adiabatic expansion of the gas during evacuation. Further, the relationship between the irradiation time of the lamp 24 and the temperature rise of the wafer W is measured in advance, and the measurement data is stored in the control device 25. Further, the relationship between the irradiation time after the irradiation of the lamp 24 is stopped and the temperature rise of the wafer W is measured in advance, and measurement data is stored in the control device 25.

  Next, the irradiation time (normal value) of the lamp 24 is set in advance from the temperature to be raised, the output of the lamp 24, and the like. And the temperature measurement value sent from the temperature sensor 26 and said measurement data are compared, and the irradiation time of the lamp | ramp 24 is adjusted. Specifically, when the temperature measurement value is maintained to be the same as the output of the lamp 24 when the normal value is set, the lamp 24 is irradiated with the irradiation time kept at the normal value. If the temperature measurement value is lower than the output of the lamp 24 when the normal value is set, the irradiation time of the lamp 24 is extended so that the wafer has a predetermined temperature based on the measurement data. To do.

  Thereafter, the gate valve 29 is opened, and the wafer W is transferred to the load lock chamber 27. Then, the gate valve 29 is closed and the load lock chamber 27 is evacuated. When the load lock chamber 27 reaches the desired degree of vacuum, the gate valve 31 on the vacuum load chamber 33 side is opened, the wafer W is taken out from the load lock chamber 27 by the vacuum robot arm 35, and the prealigner in the prealigner chamber 41 is removed. 43. Then, the prealigner 43 performs higher-precision prealignment.

  After the alignment is completed, the vacuum robot arm 35 takes out the wafer W from the pre-aligner chamber 41, opens the gate valve 45, and carries it to the exposure apparatus 100. Then, the wafer is placed on the wafer holder 130 on the wafer stage 131 in the wafer chamber 106.

  In this embodiment, the irradiation time of the lamp 24 is adjusted, but the present invention is not limited to this. For example, the power supply voltage to the lamp 24 may be increased to increase the output of the lamp 24. Further, the voltage supplied to the lamp 24 and the time may be controlled simultaneously.

  Further, in this embodiment, an embodiment using a wafer as a substrate has been shown, but the substrate may be a mask (reticle) used in an electron beam exposure apparatus, an X-ray exposure apparatus, or the like. Although the time required to raise the temperature of the substrate and the output of the lamp may be different from those of the wafer, the same apparatus and procedure can be used and the same effect can be obtained.

  In the present embodiment, the temperature raising means and the temperature measuring means are disposed in the atmosphere, but may be disposed in a vacuum. Further, although the temperature raising means and the temperature measuring means are disposed between the pre-aligner and the load lock chamber, it may be located in other places in the atmosphere.

In this embodiment, the lamp is used as the temperature raising means, but other temperature raising means such as a hot plate may be used.
Further, in this embodiment, an example in which one temperature raising means and one temperature measuring means are used is shown, but a plurality of temperature raising means and temperature measuring means may be provided. By measuring with a plurality of temperature measuring means, a measurement value with high measurement accuracy can be obtained, and by raising the temperature of the substrate with the plurality of temperature raising means, it is possible to raise the temperature without unevenness of the substrate. Further, the temperature raising means and the temperature measuring means may be arranged at substantially the same place, or may be arranged so as to be separated from each other. One may be in the atmosphere and the other in a vacuum.

It is a top view which shows the wafer conveyance mechanism which concerns on one Example of this invention. It is a figure which expands and shows the state in which the robot arm which concerns on one Example of this invention is holding the wafer. It is a figure which shows the outline of the imaging relationship in the whole optical system of the exposure apparatus which concerns on one Example of this invention, and a control system. It is a top view which shows typically the prior art example of the conveyance mechanism of a wafer.

Explanation of symbols

10 Wafer transfer mechanism 20 Wafer cassette (container)
21 Pre-aligner 23 Robot arm 24 Lamp 25 Controller 26 Temperature sensor 27 Load lock chamber 29 Gate valve 33 Vacuum load chamber 35 Vacuum robot arm 39 Gate valve 41 Pre-aligner chamber 43 Pre-aligner 45 Gate valve W Wafer M Mask 100 Electron beam exposure device 101 Optical barrel 103 Electron gun 104 Condenser lens 105 Electron beam deflector 106 Wafer chamber 110 Chuck 111 Mask stage 112 Drive device 113 Laser interferometer 114 Driver 115 Control device 116 Mount body 124 Projection lens 125 Deflector 130 Chuck 131 Wafer stage 132 Drive Equipment 133 Laser interferometer 134 Driver

Claims (5)

An exposure method for forming a pattern by selectively irradiating an energy beam onto a sensitive substrate under vacuum,
An exposure method comprising: controlling a temperature raising means for raising the temperature of the substrate based on a measurement result of a temperature measuring means for measuring the temperature of the substrate. An exposure apparatus that selectively irradiates energy rays onto a sensitive substrate under vacuum to form a pattern,
An exposure apparatus comprising: a temperature raising means for raising the temperature of the substrate; a temperature measuring means for measuring the temperature of the substrate; and a control means for controlling the temperature raising means based on a measurement result of the temperature measuring means. The exposure apparatus according to claim 2, wherein the temperature measuring unit is a non-contact type temperature measuring sensor. 4. An exposure apparatus according to claim 2, wherein the temperature measuring means is a lamp. 5. An exposure apparatus according to claim 2, wherein both the temperature raising means and the temperature measuring means are in the atmosphere or in a vacuum.