JPH05281365A - Soft x-ray detector - Google Patents

Abstract

PURPOSE:To obtain a soft X-ray detector which can detect SOR light having the same wavelength distribution as that of the SOR light absorbed in a resist for SOR lithography. CONSTITUTION:The title detector is provided with a slit 3 through which SOR light is made incident on the detector, inclined incident mirror 2, and silicon photodiode 4 and the aperture of the slit 3 and incident angle of the mirror 2 are set so that only reflected light from the mirror 2 can be received by the detectctor. The mirror 2 is formed of silicon and the incident angle of the mirror 2 is set at about 1.0 deg. so that a short-wavelength component can be eliminated from the incident light.

Description

Detailed Description of the Invention

[0001]

The present invention relates to SOR (Synchrotron Orb).
The present invention relates to a soft X-ray detector used for detecting an exposure amount in lithography having high precision resolution and high throughput using ital radiation light.

[0002]

2. Description of the Related Art In recent years, SOR lithography has attracted attention as a technology for the next generation of optical lithography and laser lithography. However, the former pattern formation technology has made remarkable progress, and due to the introduction of a phase shift method that shifts the phase of the exposure light that passes through the reticle by increasing the NA, narrowing the wavelength band, etc., SOR lithography pattern formation is less than 0.1 μm. Aiming for high resolution performance of the line width rule. The required transfer pattern dimension controllability must be suppressed to ± 10% or less. For this purpose, the fluctuation range of the exposure dose must be controlled sufficiently accurately.

Next, the controllability of exposure variation in conventional lithography will be described.

In the case of photolithography, in the i-line (bright line spectrum of a mercury lamp) exposure using a lens of NA 0.42, the permissible range of exposure amount variation is about 20% with a 0.5 μm pattern. Further, in SOR exposure, the allowable range of exposure amount variation is 20% even for 0.2 μm patterns, and it is a dogma that this method is effective for finer patterns. Even so, in the case of the 0.1 μm pattern, the exposure amount variation allowable range is 5 to 8%, which is extremely small.

At the practical level of SOR lithography, the allowable range of exposure amount fluctuation must be several percent or less. That is,
It is important to accurately measure the amount of SOR light absorbed inside the resist for forming the transfer pattern on the wafer surface.

As shown in FIG. 4, the SOR lithography system includes an SOR ring 11, an oblique incidence mirror 12 for reflecting the SOR light 17 emitted from the SOR ring 11 at an incident angle of about 1 degree, and the oblique incidence mirror 12. Means for vertically sweeping the SOR light 17 by swinging the entrance mirror 12,
It is equipped with a device 10 called a beamline, which is composed of a Be window 13 for extracting SOR light, which is made of a beryllium film having a thickness of about 30 μm, and the inside atmosphere maintains a high vacuum degree of 10 ⁻⁸ Torr or less. Therefore, the intensity of SOR light is not attenuated by the atmosphere.

The SOR light 17 is emitted from the Be window 13 into the stepper atmosphere. However, the atmosphere inside the stepper is filled with helium gas or the like in order to reduce the attenuation of air or SOR light as much as possible. Since the SOR light is attenuated in this internal atmosphere, it is necessary to configure the stepper mechanism so as to make this path as short as possible.

On the mask stage installed in this, made of SiN and having a thickness of 2 μm for transmitting SOR light.
Membrane and thickness 1 formed in a pattern on it
An X-ray mask 14 consisting of a heavy metal absorber layer of a little less than μm is arranged.

On the other hand, the resist 15 is placed on the wafer stage.
The wafer 16 coated with is highly parallel to the X-ray mask 14 and is arranged with a gap of 10 to 50 .mu.m. S
The OR light is projected onto the X-ray mask 14 and the SOR light beam having the pattern is transmitted therethrough, so that the resist 15 on the wafer 16 is exposed.
Transfer the pattern to.

Due to the structure of such SOR lithography,
It is impossible to install the detector 20 for measuring the intensity of the SOR light absorbed by the resist 15 after the X-ray mask 14,
As shown in FIG. 1, after the Be window 13, the X-ray mask 14 is installed as much as possible and at an end position where the expanded SOR light beam is not blocked. For this reason, it is desirable for the detector 20 to have a small light receiving portion, and a cylindrical silicon photodiode having an outer diameter of about 7 mm is used.

The current operating specifications of the SOR light source during exposure are, for example, an accelerating voltage of 1 GeV, an electron current of 200 mA,
The intensity of the SOR irradiation under the condition of the deflection magnet magnetic field of 1.2 T is high, and the output of the silicon photodiode of the detection element is saturated. The linearity between the intensity and the output of the detection element is obtained.

[0012]

However, according to such a conventional structure, the wavelength component of the SOR light detected by the detector 20 does not match the wavelength component of the SOR light absorbed by the resist 15. .. That is, as shown in the characteristic curve diagram of FIG. 5, the wavelength distribution of SOR light reaching the resist surface exhibits the characteristic indicated by the solid line a, and the wavelength distribution of SOR light reaching the detection surface of the detector is , Has the characteristics shown by the broken line b. Further, the SOR light absorbed inside the resist 15 has wavelength dependence, and the wavelength dependence of SOR light that actually contributes as an exposure pattern is the wavelength distribution shown by the solid line c in FIG.

Therefore, the deviation from the wavelength component of the SOR light reaching the detection surface of the detector shown by the broken line b in FIGS. 5 and 6 is caused not only by the mismatch of the wavelength ranges but also by the maximum value. There is. There is a problem that the relationship between the irradiation intensity of SOR light for exposing the resist 15 and the output of the detector does not maintain substantially linearity.

The present invention has been conceived in order to solve such a conventional problem, and is absorbed inside the resist 15 so as to achieve a fluctuation range of the exposure amount of several percent or less. It is an object of the present invention to provide a soft X-ray detector capable of detecting SOR light having the same wavelength distribution as that of the SOR light used.

[0015]

To achieve this object, the soft X-ray detector of the present invention comprises an oblique incidence mirror and a silicon photodiode, and can receive only the light reflected by the oblique incidence mirror. The silicon photodiode is arranged as described above.

Further, the material of the grazing incidence mirror is selected from silicon, and its incident angle is set to about 1.0 degree so as to remove the short wavelength component of the incident light.

[0017]

With this structure, it is possible to make the wavelength distribution of the SOR light that reaches the detection surface of the soft X-ray detector and is detected correspond to the wavelength distribution of the SOR light that is absorbed by the exposed resist. Become.

[0018]

【Example】

(Embodiment 1) As shown in FIG. 1, a soft X-ray detector of the present invention comprises a base 1, an oblique incidence mirror 2 made of a silicon wafer fixed on an inclined surface of the base 1, and an incident mirror. It has a slit 3 serving as a mouth and a silicon photodiode 4.

The bottom surface and the top surface of the base 1 have a fixed angle of about 1 degree from the parallel surface in the front-back direction, that is, the oblique incidence mirror 2
The grazing incidence mirror made of a silicon wafer having a thickness of 0.5 to 2 mm, which is formed at an angle corresponding to the incident angle of ∫ and is mirror finished on the upper surface of the base 1 with a surface roughness of several Å. Fix 2 It is also possible to integrally process the base 1 itself by using silicon crystals as a material and mirror-finishing only the surface corresponding to the upper surface of the silicon wafer.

In order to form the irradiation surface of the silicon photodiode 4 substantially perpendicular to the bottom surface of the base 1, a cylindrical diode mounting portion 5 is fixed to the base 1 and further shields stray light. For this reason, the entire periphery and front surface are covered with a cover case 6. A slit 3 having a width of 3 to 7 mm and a height of 0.5 mm is provided on the front surface of the cover case 6 so as to be in contact with the mirror surface of the oblique incidence mirror 2 so as to function as a SOR light receiving window.

When the optical axis of the incident SOR light and the bottom surface of the base 1 are parallel, all the SOR light incident through the slit 3 hits the mirror surface of the oblique incidence mirror 2 and directly enters the silicon photodiode 4. The angle of inclination of the opening of the slit 3 and the mirror surface of the mirror is set so that the light does not enter.

The silicon photodiode 4 is inserted and fixed in the cylinder of the cylindrical diode mounting portion 5, and is installed at the position 20 shown in FIG. 1 as a soft X-ray detector. An oblique incidence mirror is generally a very large structure, but in this case, the height of the slit 3 on which SOR light is incident is made as small as possible, and the mirror mirror 2 made of a silicon wafer is used.
Has a length of 20 mm, and the total length of the soft X-ray detector is 40 ~
It can be made as small as 50 mm.

It is desirable to make the distance between the Be window 13 and the X-ray mask 14 in FIG. 4 as short as possible. However, since it is about 300 mm at present, the miniaturization is suitable for installation in such a limited space. Is possible.

By selecting the material of the grazing incidence mirror 2 and adjusting the reflection angle, it is possible to set the cutoff wavelength acting as a low-pass cutoff filter. For example, when silicon is selected as the material of the oblique incidence mirror 2 and the reflection angle is adjusted to 1.02 degrees, the wavelength distribution characteristic shown by the broken line d in FIG. 2 can be obtained, and this characteristic is the resist shown by the solid line c. The wavelength distribution characteristics of the SOR light absorbed by 15 are almost the same. Further, when the incident angle of the grazing incidence mirror 2 is adjusted to 0.85 degrees, it becomes as shown by the broken line e in FIG. 3, and the wavelength of the maximum value is slightly shifted to the short wavelength side, but it is almost the same as the solid line c. I am doing it.

[0025]

As is clear from the description based on the above embodiments, according to the soft X-ray detector of the present invention, an extremely small silicon grazing incidence mirror is provided immediately before the silicon photodiode and the incidence angle of this mirror is set. It is possible to detect the soft X-ray having the same wavelength distribution as the SOR light that is adjusted and exposed the resist in the SOR lithography.

In SOR lithography, the wavelength distribution of SOR light that exposes the resist and the wavelength distribution of the detector that controls the exposure amount match, and the amount of SOR light absorbed inside the resist on the wafer surface that forms the transfer pattern is determined. It becomes possible to control accurately, and the transfer pattern dimension control of SOR lithography can be performed accurately.

[Brief description of drawings]

FIG. 1 is a front view (A) and a longitudinal sectional view (B) showing an embodiment of a soft X-ray detector of the present invention,

FIG. 2 is a mirror incident angle of 1.02 in the embodiment of the present invention.
Characteristic curve diagram showing the detected wavelength distribution in the case of degrees,

FIG. 3 is a mirror incident angle of 0.85 according to an embodiment of the present invention.
Characteristic curve diagram showing the detected wavelength distribution in the case of degrees,

FIG. 4 is a schematic view of conventional SOR lithography,

FIG. 5 is a characteristic curve diagram showing a wavelength distribution detected by a conventional detector and a wavelength distribution of SOR light on the exposed resist surface,

FIG. 6 is a characteristic curve diagram showing a comparison between a wavelength distribution detected by a conventional detector and a wavelength distribution of SOR light absorbed inside a resist during exposure.

[Explanation of symbols]

1 base 2 oblique incidence mirror 3 slit 4 silicon photodiode 5 diode mounting part 6 cover case 11 SOR ring 12 oblique incidence mirror 13 Be window 14 X-ray mask 15 resist 16 wafer 17 SOR light a SOR light reaching the resist surface B. Wavelength distribution characteristic of SOR light on the detection surface of a conventional detector c Wavelength distribution characteristic of SOR light absorbed inside the resist d Wavelength distribution characteristic of a detector with a mirror incident angle of 1.02 degrees in the embodiment e Wavelength distribution characteristic of the detector of Example with mirror incidence angle of 0.85 degrees

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location // H01L 31/10 H05H 13/04 R 9014-2G

Claims (3)

[Claims] 1. A soft X-ray detector comprising a grazing incidence mirror and a silicon photodiode, wherein the silicon photodiode is arranged so as to receive only light reflected by the grazing incidence mirror. 2. A SOR comprising a SOR source, a grazing incidence mirror, a Be window, an X-ray mask and a resist-coated wafer.
In lithography, the angle of incidence of the oblique incidence mirror is adjusted so as to detect the same wavelength component as the radiated light absorbed by the resist, and it is installed between the Be window and the X-ray mask. The soft X-ray detector according to claim 1. 3. The soft X-ray detector according to claim 1, further comprising a silicon grazing incidence mirror having an incident angle of about 1.0 degree to remove a short wavelength component of incident light.