JPS63236320A - X-ray exposure apparatus - Google Patents

Abstract

PURPOSE:To protect a beryllium window and to stabilize an exposure, by controlling operation of a switching means such as a shutter or the like in accordance with information on gaseous concentration as detected. CONSTITUTION:An X-ray 10 from a target 2 is applied into a hellium chamber 7 through a window 6 provided by a thin film of beryllium or the like. A mechanical shutter 5 is arranged between the window 6 and an X-ray source such that it is opened by a drive section 20. A concentration of oxygen in the chamber 7 is detected by a concentration sensor 8. A control circuit 24 receives information on the oxygen concentration detected by the sensor 3 and determines whether exposure can be performed without breaking the window 6 at such oxygen concentration. If determined impossible, the control circuit inhibits the drive section 20 from opening the shutter even if the operator gives it a command to start exposure. If exposure is possible at the detected oxygen concentration without damaging the window, the control circuit corrects a duration of time for opening the shutter 5 in accordance with that concentration, and outputs a command to the drive section 20 so that a constant and appropriate exposure is given to a wafer 11.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an X-ray exposure device used in the glue processing process when manufacturing semiconductor devices, etc., and in particular to X-ray irradiation control on sensitive substrates (wafers). technology, and technology to ensure the safety of equipment.

(Prior art) Conventionally, as this type of X-ray exposure apparatus, for example, Japanese Patent Laid-Open No. 58
As disclosed in Publication No. 73116, a mask is irradiated with X-rays through a chamber filled with a gas that has low attenuation for X-rays (especially soft X-rays), such as helium,
An apparatus is known in which a wafer (having an X-ray resist layer) arranged with a proximity gap is irradiated with X-rays transmitted through the mask to transfer a circuit pattern of the mask onto the wafer. In this conventional device, the X-ray source is installed in a high-vacuum chamber, and a beryllium window (extraction window) with high transmittance for X-rays is installed at the connection with the helium chamber, and this window allows the pressure to be approximately equal to atmospheric pressure. The inside of the helium chamber and the high vacuum chamber are isolated. A mask is attached to the lower end of the helium chamber, and the mask itself is used to isolate the inside of the helium chamber from the outside air.

In this conventional device, when replacing the mask, a special cover is attached to the helium chamber so as to cover the mask from below, and the inside of this cover is also replaced with helium to prevent the mask from deforming.

(Problems to be Solved by the Invention) In the conventional device described above, the helium chamber and the area around the mask are evacuated once when replacing the mask or when starting up the device, and then the helium chamber and the area around the mask are replaced with He, so the device is large-scale. Become something. Furthermore, when the mask is replaced without creating a vacuum chamber as in the conventional apparatus described above, the inside of the He chamber is filled with atmosphere (air). Therefore, after a new mask is attached to the chamber, it is necessary to replace the air in the chamber with helium. If the side of the mask facing the wafer is open to the atmosphere, this replacement must be performed while supplying helium into the chamber and exhausting air from the chamber under controlled pressure to prevent the mask from deforming. It takes time because of that. Of course, if a special cover is provided as in the conventional method, deformation of the mask can be prevented, but there is a problem that the cover is difficult to handle. In addition, after replacing the mask, the original exposure operation will be performed after the inside of the chamber is replaced with helium, but this replacement is not completed completely, that is, the oxygen (0□) component in the air is present in the chamber. If some residual oxygen is present, if Xta is generated from an X-ray source in this state, serious problems such as pinholes etc. will occur in the beryllium window due to the influence of residual oxygen when the X-rays pass through the beryllium (thin film) window. An accident occurs. Alternatively, exposure may be started by predicting that the replacement with helium will be almost completed after a certain period of time, but this requires waiting time as described above.

Furthermore, if the replacement is not completed, the attenuation rate of X-rays within the chamber will increase, making it impossible to obtain the appropriate exposure amount (X-ray energy amount or x'4!A dose amount) for the wafer. This will cause inconvenience.

The present invention has been made in view of these problems, and an object of the present invention is to provide an X-ray exposure apparatus that protects the beryllium window, stabilizes the amount of exposure, and so on.

(Means for Solving the Problems) The present invention provides concentration detection means, such as an oxygen concentration detection sensor, for detecting information regarding the concentration of a gas with low attenuation, such as helium, contained in a chamber. and,
A means such as a shutter is provided to switch between a state in which the sensitive substrate is irradiated with X-rays and a state in which it is not irradiated, and the operation of the switching means such as a shank is controlled based on the detected concentration information.

(Function) In the present invention, until the inside of the helium chamber reaches a predetermined helium concentration, in other words, until the oxygen concentration etc. become below a predetermined concentration, X-ray irradiation is performed by the switching means, especially through the beryllium window (extraction window). X-rays are prohibited from passing through. This provides protection for the beryllium window.

After the helium concentration has increased to a level that does not damage the beryllium window (after the oxygen concentration has sufficiently decreased), the switching means is controlled so that the exposure amount is corrected according to the helium concentration. This allows stable exposure control even if the helium concentration (oxygen concentration) changes.

(Embodiment) FIG. 1 is a diagram showing the configuration of an X-ray exposure apparatus according to an embodiment of the present invention.

In FIG. 1, a high vacuum chamber 1 includes a rotating target 2,
X*a consisting of an electron gun 3 and the like is arranged, and characteristic X-rays (soft X-rays) 10 are generated by irradiating the rotating target 2 with an electron beam 4 from the electron gun 3. The X-rays 10 are emitted from the target 2 into the helium chamber 7 through an extraction window 6 made of a film of beryllium or the like. Window 6 and X-ray source (irradiation point of electron beam 4 on target 2)
A mechanical shutter 5 for passing and blocking the generated X-rays 10 is arranged between the two and the mechanical shutter 5 is opened and closed by a drive section 20.

Now, the X-ray 10 that passed through the chamber 7
A mask 9 attached to the lower end surface of the is irradiated. This mask 9 is vacuum-adsorbed around the lower end surface of the chamber 7 and has the function of sealing the inside of the chamber 7. A pipe 21a for supplying helium gas and a bi 121b for exhausting helium gas or air are provided on the side wall of the chamber 7, and these pipes 21a, 21b
is connected to a gas replacement device (not shown). Further, a wafer 11 is placed below the mask 9 and is positioned with a proximity gap during exposure or alignment. Alignment between the mask 9 and the wafer 11 is performed using an alignment optical system 22 provided in the chamber 7 so as to be movable forward and backward. The alignment optical system 22 penetrates the side wall of the chamber 7 and is moved in the horizontal direction by a drive unit 23.

The objective lens 22a of the alignment optical system 22 is a mask 9.
observes the alignment marks formed on each of the wafers 11. Since a part of the alignment optical system 22 moves back and forth within the chamber 7 in this way, a bellows 2 [stock] is provided between the side wall of the chamber 7 and the outer wall of the alignment optical system 22 to maintain a seal with the outside air. .

Now, the oxygen (0□) concentration in the chamber 7 is detected by the concentration sensor 8. Ideally, this concentration sensor 8 would be one that directly detects the proportion of helium contained in the gas in the chamber 7, but among the currently commercialized sensors, those that detect helium are extremely expensive. Therefore, in this embodiment, it was decided to indirectly estimate the helium concentration using a small and inexpensive oxygen concentration sensor 8.

However, in this embodiment, the purpose is not to determine the concentration of helium itself, but only to know how much helium has been substituted, so predetermined calculations and control are performed only based on information on the oxygen concentration.

The control circuit 24 inputs the oxygen concentration information detected by the concentration sensor 8, and judges whether or not it is possible to expose the take-out window 6 without damaging it under that concentration. , commands to the drive unit 20 are prohibited so that the shutter 5 does not open even if an operator commands to start exposure.

If exposure is possible without causing damage under the detected concentration, the control circuit corrects the opening time of the shutter 5 according to the concentration to maintain a constant exposure amount (appropriate exposure it).
A command is output to the drive unit 20 so that the wafer 11 is given a command.

FIG. 2 is a circuit block diagram showing a specific example of the main circuit configuration within the control circuit 24. As shown in FIG. This configuration blocks the functions of the control circuit 24, and in addition to the hardware configuration, it may also be replaced with a software configuration using a microcomputer, etc. Although not shown in FIG. The X-ray intensity sensor 240 receives the X-rays 10 that have passed through the shutter 5 and outputs a signal corresponding to the intensity to the integrating section 241. Integration section 241
is the shutter 5 close command signal (
The amount of X-rays reaching the wafer 11 is measured in response to the pulse signal (CO). The integrated X-ray dose is calculated by the comparison unit 242
and is compared with the reference value S2. The comparison unit 242 closes the shutter 5 when the measured X-ray dose reaches the reference value S2.
A close command signal (pulse signal) is output to the drive unit 20 of the controller.

The reference value S2 is created by a setting section 243 in which a value corresponding to the appropriate exposure amount is set. The concentration determination correction section 244 outputs a prohibition signal S1 and a correction signal S2 based on the concentration (%) of oxygen detected by the concentration sensor 8. The prohibition signal SI is applied as a switching control signal to a switch 245 that switches whether or not to send the open command signal CO to the drive unit 20.

On the other hand, the correction signal St is output as correction magnification information to the setting section 243, and the setting section 243 outputs as a reference value S a value corresponding to the appropriate exposure amount multiplied by the correction magnification. This correction magnification is obtained by determining the corrected exposure amount for the oxygen concentration in the chamber 7 in advance through experiments or the like, and is stored in the determination correction section 244 as, for example, a table.

Next, the operation of this embodiment will be explained with reference to FIG. Third
The figure is a graph showing the change characteristics of the oxygen concentration in the chamber 7 when the mask 9 is changed.The horizontal axis represents time and the vertical axis represents the concentration (%), up to time t in Figure 3. Since the chamber 7 is sealed by a mask, when mask replacement is started at time 0, when the oxygen concentration is sufficiently lower than the predetermined value P+, the attached mask disappears and the chamber 7 is sealed. The inside of 7 is suddenly released to the outside air, and the oxygen concentration rises rapidly. The concentration value P7 when the concentration rises to the maximum at this time is when the inside of the chamber 7 is completely filled with air, and is usually 21 to 22% (that is, the oxygen concentration in natural air). Now, at time L2, the mask exchange is finished, replacement with helium is started, and the oxygen concentration in the chamber 7 decreases over time, and at time t.
1 reaches the predetermined value P2. This concentration value P! is set to a value of oxygen content that will not cause damage such as pinholes to the extraction window 6 even if the extraction window 6 is irradiated with X-rays. The density value P2 is stored in advance in the determination correction section 244, and if the detected density is larger than the value P2, the prohibition signal S1 is output and the switch 245 remains open. Therefore, even if an operator or the like commands the start of exposure, the opening command signal C○ is not sent to the drive unit 20, and the take-out window 6 is protected.

Now, at the time, the concentration is P! If it is determined that it is below, the determination correction unit 244 stops outputting the prohibition signal S1, and the switch 245 is closed.

Therefore, from now on, the shutter 5 receives the open command signal C○.
can be released in response to That is, the exposure operation becomes possible when the oxygen concentration in the chamber 7 becomes smaller than the value pg (%). On the other hand, the gas replacement device continues to replace the inside of the chamber 7 with helium gas, and the oxygen concentration continues to decrease over time. Since the helium concentration is changing, accurate exposure control cannot be guaranteed as it is.
calculates a correction magnification according to the density change characteristic V after time t8, and outputs a correction signal S8 according to the magnification to the setting section 243. The set value 243 calculates a reference value S based on the input correction signal S. This reference value S becomes larger than the value corresponding to the appropriate exposure amount as the oxygen concentration approaches the value P2, and becomes smaller as the concentration decreases from the value P2 and approaches the value P1. The concentration value P1 is determined to be an oxygen content value that does not substantially affect the accuracy of exposure control, and this value P is also stored in advance in the determination correction unit 244. Therefore, when the detected density value is equal to or less than P, the correction magnification becomes 1, and the reference value S becomes the value corresponding to the appropriate exposure amount.

Now, when the exposure operation starts immediately after time t, under the same exposure conditions, when the oxygen concentration is high (however, 22 or less), the shutter 5 remains open for a long time, and the concentration reaches the value P. As it gets closer, the exposure time becomes shorter.Thus, from time t4 to time t4, the release time of the shutter 5 is adjusted to be longer than the original exposure time, and the exposure amount is corrected.For this reason, after time t3 Even if exposure is performed immediately, the exposure amount is always controlled to be appropriate.

As described above, in this embodiment, the shutter 5 provided above the extraction window 6 protects the X-rays from passing through the window 6 when the oxygen concentration is higher than the value P2, but when the oxygen concentration is higher than the value P2, the electron gun A similar effect can be obtained by prohibiting the generation of the electron beam 4 from. Furthermore, a plasma excitation method, an SOR (synchrotron orbital emission) method, etc. can be similarly used as the X-ray source. Further, the oxygen concentration detection sensor 8 may be replaced with a sensor that detects the concentration of nitrogen (N2) in the atmosphere. Further, as the gas with a small X-ray attenuation rate to be filled in the chamber 7, hydrogen (Hl) gas may be used, although it is difficult to handle.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a sectional view showing only the vicinity of the helium chamber, and differs from FIG. 1 in that the mask 9 is not used to seal the lower end surface of the chamber 7. For this reason, the second
In this embodiment, the lower end surface of the chamber 7 is sealed with a thin film 30 made of polyimide or polypropylene that is transparent to X-rays or alignment illumination light. Since the inside of the mask 7 is not exposed to the atmosphere, no waiting time is required until the exposure operation starts after mask intercourse.

However, since the alignment optical system 22 moves out during alignment between the mask 9 and the wafer 11 and retreats during exposure, the pressure inside the chamber 7 momentarily increases (
It can change. This pressure change causes a pressure difference between the thin film 30 and the atmospheric pressure to act on the thin film 30, causing the thin film 30 to bend. For this reason, even in this type of always-sealed chamber structure, helium gas is allowed to flow in minute amounts to prevent the thin film 30 from being bent. However, outside air leaks from the joint between chamber 7 and 1111130, the joint between bellows 23, the joint between chamber 7 and the X-ray source, etc. due to changes in the internal pressure of chamber 7 (especially instantaneous decompression). Sometimes it happens.

Therefore, when moving the wafer W in a step-and-repeat manner and sequentially transferring the pattern of the mask 9 to different areas on the wafer 11, it is necessary to perform alignment for each step. The number of advances of the alignment optical system 22 increases until the entire surface is exposed, and the helium concentration in the chamber 7 may gradually decrease (oxygen concentration increases) due to leakage of outside air. In this case, as shown in Fig. 3. As shown in FIG. 2, even if the density value does not exceed P3, the control accuracy of the exposure amount becomes unstable.

FIG. 5(A) shows the change characteristic V of the oxygen concentration in such a state. In FIG. 5(A), the oxygen concentration is below the value P+ until time T,
Due to the leakage of outside air due to the evacuation in step 2, the time T
Until 1, the concentration becomes P or more. Similarly, from time Tc to T4
The oxygen concentration is above P even during the period. Fifth
Figure (B) shows a change in the correction magnification (correction signal S
t). The range of correction magnification values shown on the vertical axis in FIG. 5(B) is merely a guideline and is not necessarily accurate. As shown in FIG. 5(B), between time T and T5, time T
c""'T The magnification is 1 depending on the concentration value between aO
Takes a value greater than or equal to This makes it possible to always accurately control the exposure amount even if the exposure operation is performed immediately after time T1 or Te.

Of course, the change in the helium concentration in the chamber due to this leak occurs similarly in the embodiment shown in FIG. 1, and is controlled in the same manner as the correction magnification characteristic shown in FIG. 5(B).

As described above, in each of the embodiments of the present invention, the circuit block shown in FIG. Since Sl is output, if the shutter 5 is in the open state at this time, a configuration can be added that immediately outputs a close command signal to the drive unit 20.

(Effects of the Invention) As described above, according to the present invention, when the concentration of gaseous components such as helium in the chamber is low and the concentration of oxygen is high, the extraction window that isolates the X-ray source and the chamber is irradiated with X-rays. Therefore, serious accidents to the equipment can be prevented.

Furthermore, since unevenness in exposure amount due to changes in gas concentration within the chamber can be corrected, waiting time can be minimized or eliminated, and throughput and device operating rate can be significantly improved.

In addition, even if air enters the chamber due to an unexpected accident during exposure, the exposure operation can be stopped immediately when the oxygen concentration starts to rise (helium concentration decreases) using the concentration detection sensor, so the X-ray source There is no impact on

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an X-ray exposure apparatus according to the first embodiment of the present invention, FIG. 2 is a circuit block diagram showing the specific configuration of the control circuit, and FIG. 3 is a diagram showing the configuration of the oxygen concentration in the chamber. A graph showing an example of the change characteristics. FIG. 4 is a diagram showing the configuration of the X-ray exposure apparatus according to the second embodiment. FIGS. 5 (A) and (B) are the change characteristics of oxygen concentration and the corresponding exposure amount. 3 is a graph showing the corrected magnification characteristics of FIG. (Explanation of symbols of main parts) 1...xvAfl high vacuum chamber

Claims (3)

[Claims] (1) In an apparatus that exposes a substrate sensitive to X-rays through a chamber filled with a gas containing a specific component that has low attenuation to X-rays from a radiation source, the a concentration detection means for detecting information related to the concentration of a specific component gas; a switching means for switching between a state in which the sensitive substrate is irradiated with X-rays from the radiation source and a state in which the sensitive substrate is not irradiated; An X-ray exposure apparatus comprising: a control means for controlling the operation of the switching means based on information detected by the X-ray exposure apparatus. (2) The concentration detection means has an oxygen detection sensor that detects the concentration of oxygen contained in the gas in the chamber, and the control means is configured such that the concentration detected by the oxygen detection sensor is within a predetermined first range. When the concentration is higher than the first concentration, the switching means is controlled so that the X-rays are prohibited from reaching the sensitive substrate, and when the detected concentration is lower than the first concentration, the switching means is controlled so that the X-rays are prohibited from reaching the sensitive substrate. X given to the substrate
2. The apparatus according to claim 1, wherein the switching means is controlled so that the dose is corrected. (3) The switching means is disposed between the radiation source and an X-ray extraction window provided between the radiation source and the chamber, and blocks and allows X-rays from the radiation source to pass through. 3. The device according to claim 1 or 2, characterized in that the device includes a shutter.