JP3167382B2 - X-ray exposure equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchrotron (SO
The present invention relates to an X-ray exposure apparatus that performs exposure using X-rays generated by emission light of R), electron beam excitation, plasma, or the like.

[0002]

2. Description of the Related Art As semiconductors become more highly integrated in recent years, the minimum line width of ultra LSI patterns is also approaching the submicron region. An exposure apparatus used for manufacturing such an VLSI performs exposure using a synchrotron (SOR) emitted light from a current optical stepper, an electron beam excitation, or an X-ray generated from plasma or the like. An X-ray exposure apparatus to be performed has attracted attention.

In such an X-ray exposure apparatus, generally, an X-ray is taken out of an X-ray source placed in a vacuum into a chamber filled with helium gas through a window made of a beryllium thin film, and an X-ray exposure mask is used. Is configured to transfer the mask pattern to a wafer disposed in the atmosphere through the mask.

In such an X-ray exposure apparatus, since the attenuation of X-rays is very large, it is necessary to maintain a low-attenuation atmosphere (helium atmosphere) of X-rays with high purity. In addition, since the beryllium thin film window and the X-ray exposure mask are very thin films, the difference between the pressure in the chamber and the atmospheric pressure must be controlled with high precision in order to prevent their deformation and breakage. No.

As a conventional technique for controlling the pressure in the chamber, for example, a helium chamber for an X-ray exposure apparatus as disclosed in Japanese Patent Application Laid-Open Nos. 1-181518 and 1-181521 has been proposed. I have.

In the technique described in Japanese Patent Application Laid-Open No. 1-181521 shown in FIG. 8, a flow rate controller 100 for controlling the flow rate of helium gas and a chamber 101 for controlling the flow rate of helium gas passing through the flow rate controller 100 are provided. A variable flow valve 102 for introducing helium gas into the inside, and a pressure transmitter 10 for converting a differential pressure between the inside of the chamber 101 and the atmospheric pressure into an electric signal.
3, a pressure controller 104 for controlling the variable flow rate valve 102 by a signal from the pressure transmitter 103, and an exhaust port 105 for opening the gas in the chamber 101 to the atmosphere.

[0007] Further, Japanese Patent Laid-Open No. 1-181518 shown in FIG.
In the above-mentioned technology, an oxygen monitor 106 for measuring the oxygen concentration in a chamber 101 instead of the flow controller 100 for controlling the flow rate of helium gas is used in the above-mentioned technology.
And a tank 10 having an exhaust port 107 connected to the exhaust port of the chamber 101 and opening the gas in the chamber to the atmosphere.
8.

[0008] In these techniques, the differential pressure between the chamber and the atmosphere + 3mmH ₂ O (0.2mmHg which H ₂ O
And the specific gravity difference between Hg and Hg is 1: 13.6). However, according to various experiments or simulations of the present inventors, when the pressure difference between the inside of the chamber and the atmospheric pressure is 0.2 mmHg, a standard X-ray mask (membrane thickness 1 μm, about 25 mm square) is used.
And the amount of deformation (deflection, distortion) is about 15 μm. In the X-ray exposure apparatus, it is considered that the proximity exposure is performed by setting the gap between the mask and the wafer to about 30 μm.
With a mask deformation amount of 15 μm, accurate exposure is impossible.

In the above conventional example, as shown in the embodiment, the differential pressure between the chamber internal pressure and the atmospheric pressure is equal to 0.1.
At about 2 mmHg, the amount of deformation of the mask is too large to perform accurate exposure, and there is a concern that the window of the thin film may be deformed.

Further, when monitoring the oxygen concentration, measuring the oxygen concentration in the chamber with an oxygen monitor equipped with a suction pump for sucking a sample gas changes the pressure in the chamber. Is extremely disadvantageous to

[0011]

In the above-mentioned conventional helium chamber for an X-ray exposure apparatus, the pressure difference between the chamber pressure and the atmospheric pressure is too large, the amount of deformation of the mask becomes large, and accurate exposure cannot be performed. Alternatively, there is a concern that the thin film window may be deformed, and it is required to control the pressure to a smaller value.

Further, measuring the oxygen concentration in the chamber with an oxygen monitor equipped with a sample gas suction pump is disadvantageous to the above-mentioned requirement because the pressure in the chamber changes slightly when the monitor is stopped. . The present invention has been made in consideration of the above circumstances, and has as its object to provide an X-ray exposure apparatus capable of controlling the pressure in a chamber with high accuracy.

[0013]

An X-ray exposure apparatus according to the present invention guides X-rays generated from an X-ray source from an X-ray extraction window to a mask through a chamber in an X-ray low-attenuating atmosphere. In an X-ray exposure apparatus for exposing a pattern on a wafer, a supply line for supplying the gas in the X-ray low attenuation atmosphere into the chamber, a discharge line for discharging the gas from the chamber, and a supply line for supplying the gas to the supply line Flow rate control means for controlling the pressure in the chamber by controlling the gas flow rate, comprising a small diameter portion provided in the supply line between the flow rate control means and the chamber, the diameter of the small diameter portion is Setting the diameter of the minimum diameter portion of the flow path cross section of the discharge line smaller than the minimum diameter, and controlling the pressure in the chamber to a pressure substantially equal to the atmospheric pressure. It is an butterfly.

[0014]

According to the present invention, if the pressure of the gas supply line of the chamber is controlled by the same pressure control method as in the prior art, the pressure of the downstream chamber is reduced by the small diameter portion (orifice or throttle) of the supply line and the discharge line. Is uniquely determined by the ratio of the sizes (flow path areas) of the two.

Here, the diameter of the small diameter portion of the supply line is a,
If the diameter of the small diameter portion of the discharge line is b and the pressure in the supply line is controlled to P ₀ (gauge pressure, that is, the difference between the supply line pressure and the atmospheric pressure), the pressure in the chamber becomes P
₁ (gauge pressure, that is, the difference between the pressure in the chamber and the atmospheric pressure) can be approximated as P ₁ = P ₀ (a / b) ⁴ . Assuming that the flow rate of the gas flowing through the supply line and the discharge line is Q, Q ² = a ⁴ (P ₀ −P ₁ ) = b ⁴ × P ₁ P ₁ / (P ₀ −P ₁ ) = (a / b) ⁴ Here, since P ₁ / P ₀ is sufficiently smaller than 1, the approximation of the above equation holds.

As is apparent from the above equation, the pressure in the chamber can be controlled to a smaller value than the pressure difference controlled in the preceding supply line. It can be controlled with extremely high precision.

Further, since the present invention always discharges helium gas from the discharge part of the chamber, if an oxygen concentration meter is provided in the discharge path, the oxygen concentration can be monitored at all times. Does not require a pump for sucking sample gas.

[0018]

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

(First Embodiment) FIG. 1 is a schematic diagram showing a main part of an X-ray exposure apparatus according to a first embodiment of the present invention. As shown in FIG. 1, an X-ray 1 radiated from an X-ray source (not shown) is guided in a vacuum, and is taken out of an X-ray extraction window (a beryllium thin film) 2 through a high-purity helium atmosphere (X-ray low-energy). After being guided into the chamber 3 in a decaying atmosphere, X
A pattern such as an LSI drawn on the line mask 4 is transferred to a wafer 5 placed in the atmosphere. The chamber 3 is provided with an inlet 6 for supplying helium gas into the chamber 3 and an outlet 7 for discharging helium gas from inside the chamber 3. Hereinafter, the introduction section 6 and the discharge section 7 related to the main part of the present invention will be described in detail.

The introduction portion 6 has a relatively large pressure control chamber 8 connected to the chamber 3 and a diameter a formed at a connection portion between the pressure control chamber 8 and the chamber 3. An orifice 6a (a portion having a small helium gas passage cross-sectional area), a differential pressure gauge 9 for measuring a differential pressure between the pressure control chamber 8 and the atmosphere, and a helium gas supplied from the helium tank 14 into the pressure control chamber 8; Flow control valve 10 for controlling flow
And a pressure controller 11 that controls the opening of the flow control valve based on an output signal from the differential pressure gauge 9,
The pressure between the orifice 6a and the flow control valve 10 (substantially in the pressure control chamber 8) can be controlled to a predetermined pressure.

On the other hand, the discharge portion 7 is connected to the chamber 3 and has a throttle portion 7a having a diameter b (a portion having a larger helium gas flow path cross-sectional area than the orifice 6a, ie, diameter a <diameter b). A shielding valve 13 and an oxygen concentration meter 12 provided on the upstream side of the throttle portion 7a;
And an outlet 7b that is open to the atmosphere.

First embodiment of the present invention configured as described above
According to the example, a helium tank in the pressure control chamber 8
Helium at a flow rate Q from 14 through the flow control valve 10
Gas is injected, and the pressure in the pressure control chamber 8 becomes P0.
If controlled, the pressure P in the chamber 3₁Is P₁= P₀(A / b)^Four  Can be approximated by Where a is the diameter of the orifice 6a, b
Is the diameter of the throttle 7a

Therefore, for example, P ₀ = 1 mmHg,
a = 1 mm, when set to b = 10mm, P ₁ As apparent from the above equation 1/10000 against the atmospheric pressure 1mmH
g (10 ⁻⁴ mmHg).

Standard X-ray mask (1 μm membrane thickness)
m, about 25 mm square), the pressure P ₁ in the chamber 3 is 1/1000 mmHg (10 ⁻³ mmHg) with respect to the atmospheric pressure.
When the pressure is set to a value about large, the deformation amount is set to 0.1.
It can be suppressed to about 5 μm. Further, even in the case of an X-ray mask which is easily deformed, in the case of the above pressure difference, the deformation amount is 1 to 2 μ
m.

Therefore, as in the above embodiment of the present invention, the pressure P ₁ in the chamber 3 is set to be 1/10000 m with respect to the atmospheric pressure.
When set to a value slightly higher than mHg, the amount of deformation of the X-ray mask is suppressed to a very small value, and a sufficiently high-precision exposure is achieved even when the mask and the wafer are close to each other with a gap set to about 30 μm. it can. Further, the deformation of the X-ray extraction window is suppressed to a very small value, and the prevention of breakage is achieved.

Further, in the X-ray exposure apparatus, the place where the oxygen concentration is to be measured is in the chamber 3 where the helium purity is a problem, but even if the oxygen concentration in the chamber 3 is not directly measured, as in the above embodiment. If the oxygen concentration meter 12 is provided in the helium gas discharge unit 7, the oxygen concentration can be constantly monitored, and a pump for sucking the sample gas is not required. That is, since there is no part of the chamber 3 that is open to the atmosphere other than the discharge part 7, if the oxygen concentration is measured at the outlet, the oxygen concentration in the chamber 3 located upstream thereof is the oxygen concentration of the discharge part 7. It can be guaranteed equal to or less than.

The most conceivable cause of the increase in the oxygen concentration in the chamber 3 is diffusion from the discharge unit 7. As a countermeasure against this, in the first embodiment, in the discharge unit 7, the throttle unit 7a and the open port 7b are provided. And a lead-out pipe 7c is provided to prevent diffusion of oxygen in the atmosphere. In addition, when helium gas is not supplied when the apparatus is started or shut down, the inside of the chamber 3 can be sealed by the shielding valve 13.

(Second Embodiment) FIG. 2 is a schematic diagram showing a main part of an X-ray exposure apparatus according to a second embodiment of the present invention. In FIG. 2, portions that technically overlap with FIG. 1 are given the same reference numerals and description thereof is omitted.

As in the present invention, the pressure P1 in the chamber 3 is 1/1000 mmHg (10 ⁻³ mmHg) with respect to the atmospheric pressure.
In the case where the pressure can be controlled to an extremely small differential pressure, an influence due to a difference in specific weight between helium and the atmosphere (air) occurs. Second
Is an example considering the influence of the specific weight.

That is, in FIG. 2, the discharge unit 7 is connected to the bottom of the chamber 3 and the position of the opening 7b is set to a height position substantially equal to the height of the mask 4 (indicated by h in the figure). The piping route is set so that Assuming that the atmospheric pressure P ₀ (absolute pressure) at the center of the mask, the chamber pressure P ₁ (absolute pressure) at the center of the mask, and the height difference between the mask 4 and the opening 7b are Δh [cm], the height difference is assumed. Is the differential pressure generated by the following _equation : P ₀ −P ₁ = (γ _air −γ _He ) · Δh where γ _air is the specific weight of air, and γ _He is the specific weight of helium. Assuming that the pressure of helium at the opening 7b of the discharge unit 7 is P _D , P ₀ = P _D + γ _air · Δh P ₁ = P _D + γ _He · Δh + ΔP where ΔP is the pressure loss of the discharge unit. If is sufficiently small, the above equation is derived. Here, when the height difference Δh = 10 cm, γ _air = 1.293 × 10 ⁻⁶ [Kg / cm ³ ] γ _He = 0.179 × 10 ⁻⁶ [Kg / cm ³ ], P A differential pressure of ₁₋ P ₀ = 1.12 × 10 ⁻⁵ [Kg / cm ³ ] = 8.5 × 10 ⁻³ [mmHg] is generated. Is preferably set at a height position (h) substantially equal to the height (h) of the center position of the mask 4. The allowable range of the height difference Δh is appropriately set according to the type of the mask or the like based on the above equation.

In this embodiment, the diameter of the pipe itself used for the discharge portion 7 is set to b without separately forming the throttle portion 7a, and is equivalent to the case where the throttle portion 7a having the diameter b is provided. Has gained action.

(Third Embodiment) FIG. 3 is a schematic structural view showing a main part of an X-ray exposure apparatus according to a third embodiment of the present invention. In FIG. 3, portions that technically overlap with FIGS. 1 and 2 are denoted by the same reference numerals and description thereof is omitted.

In the third embodiment, a helium reservoir 7d is provided around the open port 7b in order to more reliably prevent the diffusion and intrusion of the atmosphere from the outlet port 7. The helium reservoir 7d is specifically a tube arranged around the outlet tube 7c, and a helium reservoir 7d is formed around the outlet tube 7c in a double tube structure. The helium reservoir 7d extends further below the outlet pipe 7c, and rises because the helium gas discharged from the opening 7b has a lower specific gravity than air, so that the helium reservoir 7d rises.
It is something that accumulates inside. Thus, the opening 7b
By holding helium gas around the
It is possible to prevent air (oxygen) from entering the chamber 3 by diffusion from b.

Further, in view of the fact that the density of the helium gas is lower than that of the air, a configuration is employed in which the middle of the pipe is bent upward so that the pipe path of the discharge port 7 has a portion higher than the open port 7b at least in the middle of the pipe path. And With this configuration, even if the air is slightly mixed in from the open port 7b by diffusion, the specific weight is larger than that of the helium gas, and the air collects below the middle of the pipe and can be more reliably prevented from being mixed into the chamber 3.

If the heights of the X-ray mask 4 and the opening 7b for which the pressure difference between the helium and the air is to be controlled are different due to the difference in the density between the helium and the air, as described above, the difference in the height is 1 cm. Since a differential pressure of about 1 / 1,000 mmHg is generated, it is desirable that the X-ray mask section 4 and the opening 7b are made substantially coincident as described above.

(Fourth Embodiment) FIG. 4 is a schematic structural view showing a main part of an X-ray exposure apparatus according to a fourth embodiment of the present invention. In FIG. 4, portions that technically overlap with FIGS. 1 to 3 are denoted by the same reference numerals and description thereof is omitted.

In order to more reliably prevent the diffusion and intrusion of air from the outlet 7, a helium reservoir 7d is provided around the opening 7b, and a helium gas supply line 15 is provided in the helium reservoir 7d. It is a thing.
This line 15 is connected to the helium tank 14. With such a configuration, by holding a large amount of helium gas around the opening 7b at all times, the effect of purging around the opening 7b with helium gas is obtained, and air (oxygen) is diffused. Can be more reliably prevented from entering the chamber 3.

(Fifth Embodiment) FIG. 5 is a schematic structural view showing a main part of an X-ray exposure apparatus according to a fifth embodiment of the present invention. In FIG. 5, portions that technically overlap with FIGS. 1 to 4 are denoted by the same reference numerals and description thereof is omitted.

This embodiment is an embodiment in which the pressure control chamber 8 of the introduction section 6 in the first embodiment is replaced by a pipe 16. The pressure control chamber 8 needs a certain volume in order to make the pressure uniform, but a simple pipe 16 is also applicable. When the diameter of the pipe 16 is larger than the diameter a of the orifice 6a, it is necessary to form a throttle portion corresponding to the orifice 6a as shown in FIG. If the diameters of the pipes 1 are equal, the same action as the orifice 6a shown in the first embodiment can be obtained by the pipe 16 itself.
It is not necessary to separately form the orifice 6a in 6, and the entire configuration can be simplified.

(Sixth Embodiment) FIG. 6 is a schematic structural view showing a main part of an X-ray exposure apparatus according to a sixth embodiment of the present invention. In FIG. 6, portions that technically overlap with FIGS. 1 to 5 are denoted by the same reference numerals and description thereof is omitted.

This embodiment is an example in which a bypass path 18 having a shutoff valve 17 is provided in the introduction section 6. With this configuration, when replacing the helium gas in the chamber 3 at the time of starting up the apparatus, the shut-off valve 17 is opened and a large amount of the helium gas from the helium tank 14 is passed through the bypass passage 18 to the chamber 3. Helium gas replacement can be realized in a short time.

(Seventh Embodiment) FIG. 7 is a schematic structural view showing a main part of an X-ray exposure apparatus according to a seventh embodiment of the present invention. In FIG. 7, parts that are technically the same as those in FIGS. 1 to 6 are given the same reference numerals, and descriptions thereof are omitted.

In this embodiment, the position where the differential pressure gauge 9 is provided is different from each of the above embodiments. That is, the differential pressure gauge 9
Is configured to directly measure the pressure in the chamber 3. The differential pressure gauge 9 has a relatively high accuracy and detects a pressure difference of a predetermined pressure difference between the inside of the chamber 3 and the atmospheric pressure on the order of 10 @ -3 mmHg. As described above, the pressure difference in the pressure control chamber 8 may be relatively roughly controlled to the order of about 1 mmHg.
Even if the pressure controller 11 has the same level of accuracy as the conventional one, the pressure inside the chamber 3 can be controlled several tens times higher than the conventional one.

In each of the above embodiments, the introduction section 6 and the discharge section 7 are described as one line, but in the present invention, at least one of the introduction section 6 and the discharge section 7 is divided into a plurality of lines. It can also be configured. Even in the case where the gas flow path is divided into a plurality of parts, the sum of the cross-sectional areas of the divided gas flow paths may be set to be larger in the discharge part 7 than in the introduction part 6 as described above. Also, the cross-sectional shape of the gas flow path of the introduction part 6 and the discharge part 7 is not limited to a circle, but can be implemented in various shapes such as a square and an ellipse.

Although the oxygen concentration meter 12 is provided in the discharge section 7, the oxygen concentration meter 12 may be arranged in the chamber 3 so as to directly measure the inside of the chamber 3 to be measured. good.

Although the various embodiments have been described above, it is possible to apply each embodiment repeatedly, and the present invention is not limited to the contents disclosed in the above embodiments. Various modifications can be made without departing from the scope of the invention.

[0047]

As described above, according to the present invention, the differential pressure between the inside of the chamber and the atmospheric pressure can be controlled to a minimum by a simple method.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a main part of an X-ray exposure apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a main part of an X-ray exposure apparatus according to a first embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a main part of the X-ray exposure apparatus according to the first embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a main part of the X-ray exposure apparatus according to the first embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of a main part of the X-ray exposure apparatus according to the first embodiment of the present invention.

FIG. 6 is a schematic configuration diagram of a main part of the X-ray exposure apparatus according to the first embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of a main part of an X-ray exposure apparatus according to a first embodiment of the present invention.

FIG. 8 is a configuration diagram of a conventional X-ray exposure apparatus.

FIG. 9 is a configuration diagram of a conventional X-ray exposure apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 X-ray 2 Extraction window 3 Chamber 6 Introducing part 6a Orifice 7 Discharge part 7a Restriction part 7b Opening port 7c Outlet pipe 7d Helium reservoir 8 Pressure control room 9 Differential pressure gauge 10 Flow control valve 11 Pressure controller 12 Oxygen concentration meter 14 Helium supply line

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/027

Claims (4)

(57) [Claims] An X-ray exposure apparatus for guiding an X-ray generated from an X-ray source from an X-ray extraction window to a mask through a chamber in an X-ray low attenuation atmosphere and exposing a pattern of the mask to a wafer, A supply line for supplying the gas of the X-ray low attenuation atmosphere into the chamber; a discharge line for discharging the gas from the chamber; and a gas flow rate supplied to the supply line to control the pressure in the chamber. A flow control means for controlling, and a small-diameter portion provided in the supply line between the flow control means and the chamber; An X-ray exposure apparatus, wherein the X-ray exposure apparatus is set smaller than the diameter of the small-diameter portion, and controls the pressure in the chamber to be substantially equal to the atmospheric pressure. 2. A pressure measuring means for measuring a pressure in the supply line upstream of the small diameter portion in a gas flow direction,
2. An X-ray exposure apparatus according to claim 1, wherein said flow rate control means is controlled such that the pressure measured by said pressure measurement means is substantially equal to or equal to the atmospheric pressure. 3. The X-ray exposure apparatus according to claim 1, wherein the height of the end of the discharge line open to the atmosphere is set to be substantially equal to the height of the center of the mask. 4. The apparatus according to claim 1, wherein a bypass line having a diameter larger than the diameter of the small-diameter portion is provided to introduce the gas into the chamber avoiding the small-diameter portion. X-ray exposure equipment.