This Non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 2004-173518 filed in Japan on Jun. 11, 2004, and Patent Application No. 2005-015180 filed in Japan on Jan. 24, 2005, the entire contents of which are hereby incorporated by reference.
The present invention relates to a thin film coating apparatus and an immersion exposure apparatus which are used for forming a resist pattern on a wafer in manufacturing a semiconductor wafer.
Conventional photolithography processes for manufacturing a semiconductor wafer include the steps of: 1) a resist application step of forming a resist film having uniform thickness by applying a photoresist on the surface of a wafer; 2) a pre-baking step of hardening the resist film by evaporating a solvent mixed in the photoresist to increase adhesiveness to an underlying substance and to enhance photochemical reactivity; 3) an exposure step of irradiating ultraviolet rays on the wafer through a photomask to print a device pattern on the resist; 4) a development step of dissolving an unexposed part of the photoresist by developer to form a pattern of the photoresist; and 5) a post-baking step of hardening the photoresist, which is swelled by the development, to increase the adhesiveness to the underlying substance. In recent years, in association with pattern miniaturization, an additional step is carried out for forming an anti-reflection coating on the photoresist as 6) an application step. In general, in application of chemical solution to be photoresist films, anti-reflection coatings and the like, a method of dropping the chemical solution while rotating the wafer is employed (see Japanese Patent Application Laid Open Publication No. 7-320999A, for example).
When the operation of the thin film coating apparatus starts, the chemical solution bottle 108 retaining the chemical solution 103 is placed at a predetermined position and the pipe 109 and a N2 gas pressure pipe 115 are connected to the chemical solution bottle 108 under a sealed state. Then, N2 gas pressure is applied through the N2 gas pressure pipe 115 and a valve of a buffer tank drain 116 is opened so that the chemical solution 103 is filled up to the buffer tank 110. Thereafter, the valve of the buffer tank drain 116 is closed and a valve of a drain 117 of the particle filtering unit 112 is opened so that the chemical solution 103 is filled up to the pump 111 and the particle filtering unit 112. Driving the pump 111 under this state causes the chemical solution 103 to reach the discharge nozzle 107 via the chemical solution level adjustment unit 114. The chemical solution 103, which reaches the discharge nozzle 107, is dropped on the rotating wafer 101, thereby being applied thereon uniformly by centrifugal force. During the series of this processes, an amount of particulate matters (hereinafter referred to as particles) such as bubble, minute dust (particulates) included in the chemical solution 103 is measured by a particle measurement unit 119. The particles diffuse or scatter ultraviolet rays used for irradiation in the exposure step of printing the device pattern on the resist by irradiating the ultraviolet rays to the waver 101 through the photomask. The diffusion and the confusion may cause defects of the device pattern on the wafer 101, resulting in lowered yield. For preventing this disadvantage, the state of the thin film coating apparatus is checked from the a measured result of the particle measurement unit 119 and whether or not the thin film coating apparatus is operated or stopped is judged based on the measured result, so that the thin film coating apparatus is controlled in accordance with the judged result. The aforementioned technique enables to send a signal such as an alarm signal to an operator and to stop the coating operation automatically in the case where particles enter by disturbance such as equipment trouble. As a result, significant damage by lowered yield can be avoided (see Japanese Patent Application Laid Open Publication No. 10-240897A, for example).
However, the thin film coating apparatus as described above involves the following two problems.
In general, for processing one wafer 101, the rotation of the wafer is continued during the time when a given amount of chemical solution is discharged and dropped one time and until the chemical solution 103 comes to have uniform thickness even after discharge of the chemical solution 103 stops. For this reason, the discharge of the chemical solution 103 is actually discontinuous in the aforementioned series of the processes. On the other hand, the particle measurement unit 119 that performs all time measurement uses, as a measured value, an integrated value of the number of particles included in the chemical solution 103 passing through the particle measurement unit 119 per a given time period (per second, for example), regardless of whether or not the chemical solution 103 is being discharged. In this connection, the total number of the particles in the chemical solution 103 to be discharged and dropped on one wafer 101 is an integrated value of the number measured by the particle measurement unit 119 which is measured during the discharge of the chemical solution 103 on the wafer 101. Without exact time of discharge and of stop of the chemical solution 103, the integrated value cannot be obtained and the exact total number of particles in the chemical solution 103 to be discharged and dropped on one wafer 101 cannot be obtained.
Further, with apparatuses having some constitutions or mechanisms, the particle measurement unit 119 is difficult to be arranged at the discharge nozzle 107 and must be arranged in a midway point of the line. For this reason, particles in the chemical solution 103 immediately before drop on the wafer 101 cannot be measured. Specifically, as shown in
The present invention has its object of forming a no-defect, high-quality resist pattern by providing means for more exactly grasping the number of particles included in a chemical solution or liquid and means for surely removing bubbles.
A thin film coating apparatus of the present invention is an apparatus for forming a thin film in such a manner that a chemical solution supplied from a delivery source of the chemical solution through a particle filtering unit is discharged from a discharge nozzle so as to be applied on a surface of a wafer, and includes: a pipe that connects the particle filtering unit and the discharge nozzle; a solenoid control valve that opens/closes the pipe; a particle measurement unit that measures a number of particulate matters included in the chemical solution in the pipe; a data collecting unit that collects a control voltage value of the solenoid control valve and a measured value of the particle measurement unit; and an arithmetic circuit that calculates a number of the particulate matters included in the chemical solution to be applied on the wafer as a unit from the control voltage value and the measured value which are collected in the data collecting unit.
It is noted that in the thin film coating apparatus of the present invention, information on a time-varying voltage value that indicates the flow state of the chemical solution to be measured is used as the control voltage value of the solenoid control valve. Also, the arithmetic circuit has a function of judging the flow state of the chemical solution from the control voltage value of the solenoid control valve and calculating the total number of particles in the chemical solution to be discharged in one time from a time period and the measured value of the particle measurement unit during when the chemical solution flows.
In the thin film coating apparatus of the present invention, the number of particulate matters included in the chemical solution to be applied on one wafer as a unit is calculated, so that whether to stop the thin film coating apparatus can be judged based on the calculated value. Specifically, in the case where many particles and bubbles are included in the chemical solution accidentally by disturbance such as equipment trouble and such chemical solution flows in a chemical solution line, the thin film coating apparatus can be stopped automatically. Hence, a defective pattern of a resist can be prevented from being formed.
Further, the particulate matters in the chemical solution can be measured in real time during the product processing, thereby enabling automatic judgment of normal/abnormal states of the apparatus in all time. In comparison with the conventional cases where after forming a thin film on a monitor wafer, particulate matters in the film is measured by a surface defect inspection system or the like, the aforementioned apparatus reduces operation time of an operator and improves the yield. Further, the particulate matters in the chemical solution can be measured without interruption of the operation of the apparatus, resulting in increase in availability ratio of the apparatus.
It is preferable that the arithmetic circuit compares the number of the particulate matters included in the chemical solution to be applied on the wafer as a unit with a standard value determined in advance.
A thin film coating method of the present invention uses a thin film coating apparatus for forming a thin film in such a manner that a chemical solution supplied from a delivery source of the chemical solution through a particle filtering unit is discharged from a discharge nozzle so as to be applied on a surface of a wafer, and includes: a step (a) of collecting a control voltage value of a solenoid control valve provided in a pipe that connects the particle filtering unit and the discharge nozzle and judging whether or not the chemical solution is being applied on the surface of the wafer; a step (b) of measuring a number of particulate matters included in the chemical solution flowing in the pipe; a step (c) of calculating a number of the particulate matters included in the chemical solution to be applied on the wafer as a unit based on results of the step (a) and of the step (b); and a step (d) of judging based on a result of the step (c) whether or not the thin film coating apparatus is to be stopped.
In the thin film coating method of the present invention, in the case where many particulate matters are included in the chemical solution accidentally by disturbance such as equipment trouble and such chemical solution flows in a chemical solution line, the thin film coating apparatus can be stopped automatically. Hence, a defective pattern of the resist can be prevented from being formed.
Moreover, the particulate matters in the chemical solution can be measured in real time during the product processing, thereby enabling automatic judgment of normal/abnormal states of the apparatus in all time. Hence, the above method reduces operation time of an operator and improves the yield, in comparison with the conventional methods in which after forming a thin film on a monitor wafer, particulate matters in the film is measured by a surface defect inspection system or the like. Further, the particulate matters in the chemical solution can be measured without interruption of the operation of the apparatus, resulting in increase in availability ratio of the apparatus.
It should be noted that for calculating the number of particulate matters in the chemical solution to be applied on the wafer as a unit, it is preferable to grasp an interval until the chemical solution measured by the particle measurement unit is released from the discharge nozzle actually. More specifically, on what number wafer the chemical solution measured by the particle measurement unit is applied after a wafer being processed at that time is grasped.
In the thin film coating method of the present invention, it is preferable that in the step (d), the judgment is performed by comparing the number of particulate matters included in the chemical solution to be applied on the wafer as a unit with a standard value predetermined in advance, and the comparison of the number of particulate matters included in the chemical solution to be applied on the wafer as a unit with the standard value is continued even after it is judged that the thin film coating apparatus is to be stopped, and the thin film coating apparatus is stopped until it is judged that the number of the particulate matters falls within a normal range. By this method, chemical solution discharge to another region can be continued automatically until the abnormal state returns to the normal state with less number of the particulate matters, resulting in mitigation of the burden on an operator. In comparison with the conventional methods in which a constant amount of a solution is discharged by an operator, a more appropriate amount of the chemical solution is discharged in the present method. Hence, required time for solution discharge can be minimized and the availability ratio is increased.
An immersion exposure apparatus of the present invention is an apparatus for printing a mask pattern on a wafer from a tip end portion of an optical element of a projection optical system with a state that liquid is filled between the tip end portion of the optical element and a surface of the wafer, and includes: a liquid discharge nozzle that supplies the liquid to the surface of the wafer; a pipe that connects a delivery source of the liquid and the liquid discharge nozzle; a solenoid control valve that opens/closes the pipe; a particle filtering unit intervening in the middle of the pipe; and a bubble removal unit which intervenes between the particle filtering unit and the liquid discharge nozzle in the pipe and removes bubbles in the liquid.
In general, particulate matters such as bubbles in liquid on a wafer scatter exposure light, so that a pattern not accorded with a reticle pattern is formed, resulting in pattern defects that may invite yield lowering. In contrast, in the present invention, the bubble removal unit removes bubbles, thereby preventing a pattern defect more surely. Note that the bubble removal unit selectively removes gaseous molecules only, without variation in composition and in flow rate of the liquid invited.
The immersion exposure apparatus of the present invention may further includes: a particle measurement unit which intervenes between the bubble removal unit and the liquid discharge nozzle in the pipe and measures a number of particulate matters included in the liquid; a data collecting unit that collects a control voltage value of the solenoid control valve and a measured value of the particle measurement unit; and an arithmetic circuit that calculates the number of particulate matters included in the liquid to be supplied on the wafer as a unit from the control voltage value and the measured value which are collected in the data collecting unit. With this arrangement, if bubbles enter in the solution accidentally by disturbance such as equipment trouble, the immersion exposure apparatus can be stopped automatically. Further, the particulate matters in the liquid can be measured in real time during the product processing, thereby enabling automatic judgment of normal/abnormal states of the apparatus in all time. The above apparatus reduces operation time of an operator and improves the yield, in comparison with the conventional cases where which a pattern defect is detected by a surface defect inspection system or the like after performing a series of processing of resist coating on a monitor wafer, exposure, and development. Moreover, the particulate matters in the liquid can be measured without interruption of the operation of the apparatus, with a result of increase in availability ratio of the apparatus.
A specific immersion exposure method using an immersion exposure apparatus in the present invention includes: a step (a) of collecting the control voltage value of the solenoid control valve and judging whether or not the liquid is being supplied to the surface of the wafer; a step (b) of measuring the number of particulate matters included in the liquid flowing in the pipe; a step (c) of calculating the number of the particulate matters included in the liquid to be supplied to the wafer as a unit based on results of the step (a) and of the step (b); and a step (d) of judging based on a result of the step (c) whether or not the immersion exposure apparatus is to be stopped.
In the immersion exposure method of the present invention, it is preferable that in the step (d), the judgment is performed by comparing the number of particulate matters included in the liquid to be supplied to the wafer as a unit with a standard value predetermined in advance, and the comparison of the number of particulate matters included in the liquid to be supplied to the wafer as a unit with the standard value is continued even after it is judged that the immersion exposure apparatus is to be stopped, and the immersion exposure apparatus is stopped until it is judged that the number of the particulate matters falls within a normal range. With this arrangement, liquid discharge to the other region can be continued automatically until the abnormal state returns to the normal state with less number of particulate matters, resulting in mitigation of the burden on an operator. In comparison with the conventional cases where a constant amount of liquid is discharged by an operator, a more appropriate amount of the liquid is discharged in the present method. Hence, required time for solution discharge can be minimized and the availability ratio is increased.
A first embodiment of the present invention will be described below in detail with reference to the drawings.
Difference of this thin film coating apparatus from the conventional one lies in that the apparatus additionally includes: a data collecting unit 15 which collects all time a control voltage value of the solenoid control valve 10 that opens/closes the pipe 7 and a measured value of the particle measurement unit 13; a voltage converter circuit 14 that voltage converts the control voltage of the solenoid control valve 10; and an arithmetic unit 16 that performs calculation of the measured value.
A method of measuring particles in the chemical solution 3 in the present embodiment will be described next.
It is noted that the data shown in
In view of the above knowledge, the correlation shown in
Based on the correlation shown in
Control with the use of this standard value will be described with reference to
Subsequently, in a step S4, judgment for comparing with the standard value the measured value integrated by the arithmetic unit 16, that is, the particle count included in the chemical solution 3 to be applied on a wafer as a unit (one-time discharge) is performed in the arithmetic unit 16. When the particle count is less than the standard value, a normal operation instruction is output in a step S5 so that the thin film coating apparatus is driven in a normal operation. While, when it is judged that the particle count exceeds the standard value, an abnormal operation stop instruction is output from the arithmetic unit 16 to the control unit 12 in a step S6 so that the thin film coating apparatus is stopped due to presence of abnormality and the chemical solution 3 is discharged through the discharge nozzle 6 to another region. At this time, the particles are discharged together with the chemical solution 3. In a step S7, the judgment for comparing the chemical solution 3 to be discharged with the standard value is performed in all time, likewise in the normal operation of the coating apparatus so that the thin film coating apparatus is driven normally when the particle count becomes less than the standard value and otherwise the solution discharge to the other region is continued when it exceeds the standard value.
In the present embodiment, when the chemical solution 3 includes many particles or bubbles accidentally by disturbance such as equipment trouble and flows into the chemical solution line, the thin film coating apparatus can be stopped automatically. In association, pattern defects of a resist can be prevented from being caused.
Further, the particles in the chemical solution 3 can be measured in real time while processing the wafer 1, and therefore, the normal/abnormal operations of the apparatus can be judged all time automatically. Hence, the operation time of an operator is reduced and the yield is improved in comparison with the conventional cases where the particles in a thin film is measured by the surface defect inspection system or the like after the thin film is formed on a monitor wafer. Moreover, the particles in the chemical solution 3 can be measured without interruption of the operation of the apparatus, with a result of increase in the availability ratio of the apparatus.
The chemical solution 3 is discharged to the other region automatically during the abnormal operation until the particle count becomes less than the standard value. Therefore, a more appropriate amount of the chemical solution 3 is discharged in comparison with the case where a given amount of solution is discharged by an operator. Moreover, check of the particle count in the chemical solution 3 while discharging the chemical solution 3 attains time reduction.
A second embodiment of the present invention will be described below with reference to drawings.
The reticle 33 is held by a reticle stage 34, and the pattern of the reticle 33 is reduction-projected, through a mirror cylinder 35 and a projection optical lens 36, on a wafer 38 on which a photoresist is applied.
The wafer 38 is placed on a wafer stage 39, and liquid 37 such as pure water is filled between the wafer 38 and the projection optical lens 36. The liquid 37 filled therebetween substantially shortens the wavelength of the exposure light 32, thereby increasing the resolution and substantially widening the depth of focus. The liquid 37 is supplied from a delivery source (not shown) of the liquid 37 through a pipe 35. In the pipe 53, there intervenes a pump 47, a particle filtering unit 46, a bubble removal unit 44 that removes bubbles in the liquid 37 selectively, a particle measurement unit 45 that measures particles such as bubbles in the liquid 37, a solenoid valve 43, and a liquid discharge nozzle 40 in this order when viewed from the supply source of liquid 37.
The bubble removal unit 44 not shown in detail has a structure of which inside is partitioned into two rooms by a special film permeable to gas with high selectivity. One of the two rooms is connected to the pipe 53 directly while the other room is connected to a vacuum pump 52. In the bubble removal unit 44, air in the other rooms is discharged by the vacuum pump 52 while the liquid 37 is allowed to pass through the room connected to the pipe 53. This causes the bubble included in the liquid 37 to pass through the film permeable to gas with high selectively, to move into the other room, and then, to be discharged outside by the vacuum pump 52.
The liquid 37 filled on the wafer 38 is returned through a liquid flow nozzle 41 to be regenerated by a liquid recovery unit 42 after exposure. Further, the present immersion exposure apparatus includes: a data collecting unit 49 that collects all time a control voltage value of the solenoid control valve 43 that opens/closes the pipe 53 and a measured value of the particle measurement unit 45; a voltage converter circuit 48 that voltage converts the control voltage of the solenoid control valve 43; an arithmetic unit 50 that performs calculation of the measured value of the particle measurement unit 45; and a control unit 51 that controls discharge/stop of the liquid 37.
In general immersion exposure apparatuses, particles such as bubbles in the liquid 37 on the wafer 38 scatter the exposure light 32, resulting in formation of a pattern not accorded with a reticle pattern. This causes pattern defects which may invite yield lowering. In the present embodiment, almost all particles and bubbles are filtered by the particle filtering unit 44 and bubbles still remaining after passing through the particle filtering unit 44 are removed by the bubble removal unit 44. Thus, pattern defects are prevented from causing further surely. It is noted that the bubble removal unit 44 selectively removes gaseous molecules only, as described above, so that the liquid 37 is not changed in its composition and flow rate.
Moreover, even if many bubbles enter into the liquid 37 accidentally by disturbance such as equipment trouble, the apparatus can be stopped while discharging the liquid 37 to another region automatically if the same particle measuring and control methods as described in the first embodiment are employed. The specific methods thereof will be described below. First, whether or not the liquid 37 is being supplied is judged in the data collecting unit 49 from the control voltage value of the solenoid control valve 10. When it is judged that the liquid 37 is being supplied, the measured result of the particle measurement unit 45 obtained during the time period when the liquid 37 is supplied is taken into the data collecting unit 49, and then, the measured result and the time period are integrated in the arithmetic unit 50.
Next, judgment for comparing with a standard value the measured value integrated in the arithmetic unit 50, that is, the particle count included in the liquid 37 to be supplied to a wafer as a unit (one-time discharge) is performed in the arithmetic unit 50. When the particle count is less than the standard value, a normal operation instruction is output so that the immersion exposure apparatus is driven in a normal operation. While, when it is judged that the particle count exceeds the standard value, an abnormal operation stop instruction is output from the arithmetic unit 50 to the control unit 51 so that the immersion exposure apparatus is stopped due to presence of abnormality and the liquid 37 is discharged through the discharge nozzle 6 to the other region. At this time, the particles are discharged together with the liquid 37. Herein, the judgment for comparing the liquid 37 to be discharged with the standard value is always performed, likewise in the normal operation of the immersion exposure apparatus so that the immersion exposure apparatus is driven normally when the particle count is less than the standard value and otherwise the liquid discharge to the other region is continued as long as it exceeds the standard value.
Number | Date | Country | Kind |
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2004-173518 | Jun 2004 | JP | national |