JP2791932B2 - 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 an X-ray exposure apparatus for exposing and transferring a circuit pattern of a semiconductor integrated circuit onto a wafer by using X-rays.

[0002]

2. Description of the Related Art A conventional X-ray exposure apparatus uses an X-ray using SR light or the like as a light source 31 and an LSI or the like on a wafer 32 as shown in the principle explanatory diagram of the X-ray exposure system in FIG. Is exposed. The light source 31 is 1
X-rays of about 0 ^-9 Torr are generated in a high vacuum. The generated X-rays are reflected by the oscillating mirror 33 from the light source 31 and are stepped through a beam port 36 through a vacuum blocking film (blocking window) 35 of beryllium (Be) or the like.
From the mask 34 to the wafer 32.

On the other hand, a mask 3 onto which a circuit pattern is transferred
2 is placed in a body pressure or a reduced pressure He gas (helium gas) atmosphere.

In order to suppress the attenuation of X-rays, it is desirable that the space from the vacuum blocking film 35 to the wafer 32 be in a vacuum state. However, in order to install a stepper in a vacuum, it is necessary to take measures against the heat generated by the vacuum seal and each driving unit, or to generate heat due to X-rays in the mask 34 serving as a transfer original image pattern, and to generate the distortion of the mask 34 due to the heat. Need to be resolved. For this reason, the stepper is moved to the reduced pressure He chamber 3.
An X-ray exposure apparatus has been proposed in which an X-ray exposure apparatus is hermetically accommodated in a vacuum chamber 7 and transferred to a mask 32 in a reduced-pressure He gas atmosphere. (See, for example, JP-A-3-135010 and JP-A-3-108311.) In particular, the mask 34 is required to have a circuit patterning accuracy of the order of 0.01 μm in X-ray equal-size exposure for VLSI manufacturing. ing. For this reason, the temperature rise is 0. It must be kept below a few degrees. For this reason, it is necessary to use He gas, which can exchange heat several times as much as the atmosphere, as the atmospheric gas.

Therefore, X transferred to the wafer 32 through the mask 34 in such a reduced pressure He gas atmosphere.
In a line exposure apparatus, the entire stepper is housed in an airtightly sealed reduced-pressure He chamber. In this X-ray exposure apparatus, wiring, pipes, a wafer exchange port, a mask exchange port, and the like with internal equipment have a strict seal structure similar to a vacuum seal.

[0006] It is known that the He gas concentration and pressure are involved in the attenuation of X-rays. The attenuation at a certain wavelength of X-rays is as shown in the following Equation 1. In Equation 1, I is the X-ray intensity after the distance t, I _{o is the} original X-ray intensity, and μ is the line absorption coefficient.

[0007]

(Equation 1)

At this time, since the linear absorption coefficient μ is determined by the composition of the substance, the gas changes depending on the pressure and the composition (concentration), and the element having the lower pressure and the element constituting the gas have lighter molecules. An object (for example, He gas) has smaller attenuation. In the following, the effect of the He gas concentration on the dose is calculated on the assumption that the distance from the beryllium film as the vacuum blocking film 35 to the mask 34 is 30 cm.

Dose amount EA / Sec Dose change value ± dE% Distance from beryllium film to mask t cm (H
e gas atmosphere distance) He line attenuation coefficient μ _o = 0.48 m ^-1 = 0.004
8 cm ^-1 8A 20 ° 1 atm air line attenuation coefficient μ ₁ = 1.22 cm ^-1 8A
Assuming that the pressure is 20 degrees and 1 atm He x%, it is shown in the following Expression 2 and Table 1.

[0010]

(Equation 2)

[0011]

[Table 1]

From Table 1 above, in order to suppress the dose amount to a variation of about 1%, an oxygen concentration meter of 200 ± 100 pp
m.

Further, Table 2 shows the influence of the change in the reduced pressure He gas pressure on the exposure amount together with the X-ray intensity.
The results are shown in Table 3 together with the line intensity.

[0014]

[Table 2]

[0015]

[Table 3]

[0016]

In the above X-ray exposure apparatus using He gas, from the viewpoint of throughput,
It is desirable that the attenuation be low, but since a strict sealing structure similar to a vacuum seal is employed, the number of design and production steps is increased, and the degree of freedom of the structure is limited.

From the viewpoint of the manufacturing process, the uniformity and stability of the exposure amount (the integrated amount of X-rays) are reduced by several percent (±
2-3%). For this reason, various measures have been proposed. However, since the flow of air from the outside into the reduced-pressure He chamber 37 is low, the pressure of the He gas is controlled while controlling the pressure of the He gas in the reduced-pressure He gas atmosphere.
There is a problem that it is difficult to control the e gas concentration.

Further, even if an X-ray exposure apparatus is manufactured, it is extremely difficult to design and manufacture the apparatus in consideration of the dimensions, shape, and design of the seal portion assuming cooling of each part, exposure accuracy, and stable exposure. .

It is therefore an object of the present invention to provide an X-ray exposure apparatus for improving the throughput, making the exposure amount uniform, and improving the transfer accuracy.

Another object of the present invention is to provide an X-ray exposure apparatus that can be easily designed and manufactured.

[0021]

According to the present invention, a mask and a stepper body for holding a wafer to be exposed to X-rays through the mask, and a stepper body for attenuating the X-rays and heat of the mask. A reduced-pressure He chamber housed in a sealed state in a reduced-pressure He gas for suppressing distortion;
An X-ray exposure apparatus including a shielding window for introducing the X-rays from an X-ray source into a chamber, comprising an atmospheric pressure He chamber that covers the outside of the reduced-pressure He chamber with a He gas. X-ray exposure apparatus is obtained.

[0022]

First, the atmosphere in the atmospheric pressure He chamber is replaced with air from He gas. This replacement is performed by expelling air with He gas. After the replacement, the pressure is controlled to reduce the supply amount of He gas. After that, the leaking H
By supplying e gas, this atmosphere is maintained.

After replacing the atmospheric pressure He chamber, the replacement of the reduced pressure He chamber is started. After reducing the pressure in the reduced-pressure He chamber, He gas is supplied, and replacement is performed until a predetermined He gas concentration is reached. Thereafter, the internal pressure is controlled to a predetermined reduced pressure atmosphere while supplying He gas.

If a problem arises in the sealing performance of the reduced pressure He chamber, leakage from the outside may occur, but the outside of the reduced pressure He chamber is filled with high purity He gas. Therefore, the He gas concentration in the reduced pressure He chamber is kept at a predetermined value. Further, even if the sealing of the atmospheric pressure He chamber is insufficient, the He gas pressure is higher than the external atmospheric pressure, so that the air does not enter.

[0025]

1 to 3 show an embodiment of the X-ray exposure apparatus according to the present invention. The principle of transfer to a wafer by X-rays in the X-ray exposure apparatus is the same as that shown in FIG.

Referring first to FIGS. 1 and 2, an X-ray exposure apparatus includes a reduced-pressure He chamber 1 containing a reduced-pressure He gas (a reduced-pressure helium gas) for suppressing X-ray attenuation and thermal distortion of a mask. And an atmospheric pressure He chamber 2 that covers the outside of the reduced pressure He chamber 1. Inside the reduced pressure He chamber 1, a stepper main body 3 is housed in an airtight manner.

The stepper body 3 includes a mask stage 5 provided on a stepper base 4 and a wafer stage 6 provided opposite the mask stage 5.
And A mask 7 is held on the mask stage 5. The wafer 8 is held on the wafer stage 6. The mask 7 and the wafer 8 are opposed to each other, and the wafer stage 6 is moved in parallel on the stepper base 4 so as to advance and retreat with respect to the mask stage 5. To change the distance between them. This stepper body 3 is １ ／
It is placed in a reduced pressure He gas atmosphere of about atmospheric pressure.

The reduced pressure He chamber 1 is made of a metal plate such as stainless steel or aluminum.
It is designed and manufactured to have sufficient strength to withstand a reduced pressure He gas (1/2 atm) atmosphere.

Further, a shielding window 25 such as a beryllium film is attached to a partition constituting the reduced-pressure He chamber 1. The atmospheric pressure He chamber 2 is provided with a beam port 26 that penetrates a partition wall that is configured to cover the outside of the partition wall that constitutes the reduced pressure He chamber 1, and whose tip extends so as to contact the blocking window 25. I have. The X-ray is guided by the beam port 26 to the mask 7 and the wafer 8 of the stepper body 3 through the blocking window 25 as shown by the arrow SR in FIGS. 1 and 2.

Further, as shown in FIG. 3, a power supply line to a drive unit (motor, pzt) for driving the mask stage 5 and the wafer stage 6 of the stepper body 3 and a signal to be connected to a detector device of each unit. The line is the stepper body 3
Is drawn out by a relay connector (not shown) provided on the partition wall of the reduced pressure He chamber 1. These relay connectors do not necessarily have to be strictly vacuum-compatible, and may be those provided with a simple seal. The vacuum chamber 1 is connected to a vacuum pump B for reducing the internal pressure to about 1/2 atmosphere and a supply line for supplying high purity He gas (about 99.9999%). An oxygen concentration meter c for monitoring the internal He gas concentration, a pressure gauge D for monitoring the pressure, and the like are provided at predetermined locations.

The atmospheric pressure He chamber 2 is connected to a vacuum pump B for sucking air and a supply line for supplying high purity He gas (about 99.9999%). As in the case of the decompression chamber 1, an oximeter c for monitoring the inside He gas concentration is provided at a predetermined position.

As shown in FIG. 3, a cylinder 22 containing high-purity He gas is connected to the He gas supply line.
It is led to a plurality of pressure regulators A via the temperature regulators 23, and from each pressure regulator A, the reduced pressure He chamber 1, the atmospheric pressure He chamber 2, the mask cassette exchange chamber 1 described later.
2 and the wafer cassette exchange chamber 18, respectively. Further, a differential pressure gauge E is provided between a supply line between one pressure regulator A and the atmospheric pressure He chamber 2,
The pressure is controlled to atmospheric pressure + a few millimeters of H ₂ O by a pressure controller A. The mask exchange chamber 12 and the wafer exchange chamber 18 are provided at predetermined locations with an oxygen concentration meter c for monitoring the inside He gas concentration and a pressure sensor D for monitoring the pressure and adjusting the pressure. I have.

The outside of the aforementioned reduced pressure He chamber 1 is as follows:
It is covered with an atmospheric pressure He chamber 2 whose pressure is controlled to atmospheric pressure + a few millimeters of H ₂ O. Since the atmospheric pressure He chamber 2 only needs to withstand atmospheric pressure + several tens mH ₂ O,
It is made of a thin plate such as aluminum or stainless steel. Further, the seal of each part may be formed by a sealing method which is extremely simple as compared with the vacuum container, for example, a seal using a silicone rubber sealant or the like. Various power lines derived from the decompressed He chamber 1 are
The connection is made to the outside by a relay connector provided with a simple seal in the same manner as described above.

Returning to FIG. 1, the stepper body 3 is provided with a mask handling device for supplying the mask 7. A robot hand unit 10 for attaching the mask 7 to the mask chuck is provided in the reduced pressure He chamber 1.
Is provided. The robot hand unit 10 uses the reduced pressure He
The mask cassette 11, which is placed in the chamber 1 but contains a plurality of masks 7, is placed in a mask cassette exchange chamber 12 for exchanging with the outside. The mask cassette exchange chamber 12 is attached to the reduced-pressure He chamber 1 via an airtight shutter 13. Further, the outside air can be shut off by the outside airtight shutter 14.

Further, the stepper body 3 is provided with a wafer handling device for supplying the wafer 8.
The robot hand unit 15 for attaching the wafer 8 to the wafer chuck is placed in the reduced-pressure He chamber 1, and a wafer cassette 16 containing a plurality of wafers 8 is provided.
Is placed in a wafer cassette exchange chamber 18 for exchanging with the outside. The wafer cassette exchange chamber 18 is provided with a reduced pressure He.
The airtight shutter 19 is attached to the chamber 1. The outside can be shut off by the outside airtight shutter 20. Further, the wafer cassette exchange chamber 18 is firmly designed and manufactured so as to withstand a reduced pressure of about 1/2 atm.

Next, H in the X-ray exposure apparatus of the above embodiment is used.
The e gas replacement operation will be described. As the He gas to be supplied, a He gas having a high concentration of 99.9999 or more is prepared. First, the atmosphere in the atmospheric pressure He chamber 2 is replaced with air from He gas. At this time, the pressure and flow controller A connected to the atmospheric pressure He chamber 2 is operated. This replacement is performed by setting the atmospheric pressure + several tens mH ₂ O to H.
This is performed by expelling air with e-gas. After the replacement (He gas 99.95% or more), the pressure control is set to the atmospheric pressure + a few millimeters of H ₂ O, and at the same time, the vacuum pump B is stopped to reduce the supply amount of the He gas. Thereafter, the He gas atmosphere is maintained by replenishing the leaked He gas at atmospheric pressure + a few millimeters of H ₂ O.

After replacing the atmospheric pressure He chamber 2 with a He gas atmosphere, the He gas replacement of the mask cassette replacement chamber 12 and the wafer cassette replacement chamber 18 is started. First, after reducing the pressure to about 1/2 atm by the vacuum pump B, He gas is supplied while performing vacuum, and when the He gas concentration reaches a predetermined He gas concentration (99.95% or more), the vacuum pump B is stopped. After that, the He gas atmosphere is maintained by replenishing the leaked He gas at atmospheric pressure + a few millimeters of H ₂ O pressure.

Further, after replacing the mask cassette replacement chamber 12 and the wafer cassette replacement chamber 18 with a He gas atmosphere, the replacement of the reduced pressure He chamber 1 is started. First, after reducing the pressure to about 1/2 atm by the vacuum pump B, He gas is supplied while performing vacuum, and replacement is performed until a predetermined He gas concentration (99.95% or more) is reached. Thereafter, while the high-purity He gas is being supplied, the internal pressure is controlled to a predetermined reduced pressure (1/2 atm ± 10 Torr or less) by the vacuum pump B and the pressure and flow rate controller A.

When exchanging the mask 7 and the wafer 8, the mask cassette 1 is opened by opening the outer airtight shutters 14 and 20.
After exchanging the wafer cassette 1 and the wafer cassette 16, He gas replacement is performed according to the above-described procedure, and the mask 7 and the wafer 8 are supplied to the stepper body 3.

In the event that a problem occurs in the sealing performance of the chamber 1 under reduced pressure He, leakage from the outside may occur, but the atmospheric pressure He covering the outside of the chamber 1 under reduced pressure He is assumed. Since the chamber 2 is filled with high-purity He gas (99.95% or more), the He gas concentration in the chamber 1 under reduced pressure He is maintained at a predetermined concentration.
Further, even if the sealing of the atmospheric pressure He chamber 2 is insufficient, the He gas pressure is slightly higher than the external atmospheric pressure, so that the atmosphere does not enter.

[0041]

As described above, as described in the embodiments,
According to the X-ray exposure apparatus of the present invention, the outside of the reduced pressure He atmosphere for suppressing the attenuation of X-rays and the thermal distortion of the mask is adjusted to the atmospheric pressure H.
Since the e-chamber is configured to be covered with the He atmosphere, the design and production of the seal portion are easier than in a normal reduced-pressure He chamber, and mixing of air can be inhibited, so that X-ray attenuation is reduced.

Further, by supplying the supplied He gas at a controlled temperature, the dimensions and shape stability of the device, the improvement of the temperature characteristics of the detector, the detection accuracy, the exposure accuracy, etc. are improved, and the mask size is stabilized. Is possible.

Further, since He gas has a heat transfer characteristic four to five times that of air, the effect of cooling He, such as masks, motors, and various detectors, by using He gas is improved as compared with air.

Therefore, an X-ray exposure apparatus capable of supplying a stable exposure amount and exposure atmosphere by a simple sealing structure and pressure control can be realized.

[Brief description of the drawings]

FIG. 1 is a simplified cross-sectional view of an embodiment of an X-ray exposure apparatus according to the present invention as viewed from above a plane.

FIG. 2 is a simplified cross-sectional view of the X-ray exposure apparatus of FIG. 1 viewed from a side.

FIG. 3 is a schematic explanatory view illustrating each instrument and a He gas supply line used in the X-ray exposure apparatus in FIG.

FIG. 4 is a schematic explanatory view illustrating the principle of the conventional and the X-ray exposure apparatuses of the present invention.

[Explanation of symbols]

 1,37 Decompression He chamber 2 Atmospheric pressure He chamber 3 Stepper body 7,34 Mask 8,32 Wafer 10 Robot hand unit 11 Mask cassette 12 Mask cassette exchange chamber 13,19 Inner airtight shutter 14,20 Outer airtight shutter 16 Wafer cassette 18 Wafer exchange chamber 22 Cylinder 23 Temperature controller 25, 35 Shut-off window 26, 36 Beam port 31 Light source A Pressure controller B Vacuum pump C Oxygen concentration meter D Pressure sensor

Claims (1)

(57) [Claims] 1. A stepper body for holding a mask and a wafer exposed to X-rays through the mask, and the stepper body is sealed in a reduced pressure He gas for suppressing the attenuation of the X-rays and the thermal distortion of the mask. A reduced-pressure He chamber housed in a state, and an X-ray source in the reduced-pressure He chamber.
What is claimed is: 1. An X-ray exposure apparatus comprising: a shielding window for introducing a line; and an atmospheric pressure He chamber covering the outside of said reduced-pressure He chamber with He gas.