JPS62226047A - Multi-layered film reflecting mirror and its production - Google Patents

Abstract

PURPOSE:To increase the reflectivity of a multi-layered reflecting mirror formed by alternately laminating thin heavy element films and thin light element films on a substrate and to permit the control of the spectral band width thereof by using B or Be as the material for the thin light element films. CONSTITUTION:This multi-layered reflecting mirror is formed by laminating M-pieces of the periodic unit multi-layered films 6 superposed with the two- layered films of a pitch dn consisting of the thin heavy element films 4 of a thickness An which are reflective layers and the thin light element films 5 of a thickness Bn which are spacer layers in Nn layers on the substrate 1, successively from the substrate 1 side. The B or Be is used for the material to constitute the thin light element films. The coefft. of absorption of the B or Be in the soft X-ray region which is important for exposure of X-rays exhibits the lower value than the coefft. of absorption of C which is heretofore used and the refractive index of the B or Be in the soft X-ray region exhibits the value lower than the value of the C with respect to the refractive index as well. Since the absorption of the soft X-rays by the spacer layer material is decreased, the extremely high reflectivity is obtd.

Description

Detailed Description of the Invention (Industrial Application Field) The invention relates to an X-ray reflective boundary having a multilayer structure and a method for manufacturing the same.0 (Prior art and problems to be solved by the invention) Conventional As a multilayer film reflector, a multilayer film reflector is generally known, as shown in FIG. 8(a), in which light element thin films 2 and heavy element thin films 3 are alternately formed on a substrate 1 at a constant pitch. . In this case, since there is a certain relationship between the reflectance and the wavelength bandwidth of the reflectance spectrum (increasing the number of layers VC, increasing the reflectance narrows the growth bandwidth), so
It is not possible to obtain an arbitrary wavelength bandwidth while maintaining high reflectance, and the integrated reflectance is low. Furthermore, when X-rays of a predetermined wavelength are used as incident light, the angle of incidence at which black reflection occurs is within a very limited range. The incident angles of X-rays with respect to each point are different, and the area of the reflecting surface that contributes to Bragg reflection of a predetermined wavelength becomes extremely small. Therefore, it is not possible to obtain a high reflectance at the wavelength of the light source. As another example, L shown in FIG. 8 (1))
There is a multilayer reflector whose beak pitch gradually changes upward from the substrate, but it is difficult to accurately form a multilayer beak while maintaining a constant change in pitch, and the cylindrical beak reflection The disadvantage is that the ratio is not obtained. In addition, as for the constituent materials of the above-mentioned conventional multilayer film reflecting mirror, heavy elements such as W + Re + Pt t Au were used as the material for the reflective layer, and light elements such as Al and St + C were used as the material for the spacer layer. However, in this case, the absorption coefficient of the light element thin film is large, especially in the soft X-ray region, and the drawback is that the reflectance cannot be increased. In addition, in the ion beam sputtering method, which is the conventional method for manufacturing multilayer monomer reflective mirrors, one drawback is that the scattered ions damage the deposited film, making it impossible to form an extremely thin film entirely.

(Means for solving the problems) The invention solves the above-mentioned problems of the prior art, and has a high reflectance, the bandwidth of the reflectance spectrum can be arbitrarily set, and a curved structure. It is an object of the present invention to provide a multilayer film reflector that can obtain a high reflectance even in various cases, and a method for manufacturing the same.

In order to achieve the above object, the present invention uses B or Bek as a constituent material of the light element thin film of the multilayer reflective mirror, thereby increasing the reflectance of the reflective mirror. Furthermore, the structure of the multilayer film reflecting mirror according to the present invention is such that a plurality of unit multilayer films with different pitches are laminated, so that an appropriate wavelength bandwidth for X-ray exposure can be freely selected. In order to obtain a high reflectance over a wide wavelength range, the absorption of X-rays on the long wavelength side by the elements constituting the multilayer film should be minimized to obtain a high reflectance over a wide wavelength range. The main feature of the invention is that the pitch of /lltl1M increases sequentially from the substrate side upwards, resulting in nine structures.

Furthermore, using atomic beam sputtering method to form a thin filmTI
/C Process 9 There is no damage to the thin film as in the ion beam sputtering method.Next, it is possible to manufacture a multilayer film reflector with a smooth multilayer film interface, and the scattering of X-rays at the interface can be reduced. can. It is possible to manufacture a multilayer reflector having an extremely fine pitch with high manufacturing precision.

Next, the present invention will be explained in detail.

It should be noted that the embodiments are merely illustrative, and it goes without saying that all modifications and improvements may be made without departing from the spirit of the present invention.

First (8) shows an embodiment of the multi-JWIm reflection boundary according to the present invention. A periodic level multilayer @ 6 in which 2M films with a pitch dn consisting of a heavy element thin film 4 with a thickness An which is non-reflective and a light element thin film 5 with a thickness Bn which is a single spacer layer are stacked on a substrate 1. The principle of the optical characteristics of a 0 to 1-simulating mirror, which is formed by laminating M pieces of 1 to 1 in order from the substrate 1 side, will be explained using the case of M=2 as an example. A multilayer film of a given pitch reflects X-rays of a certain peak wavelength and bandwidth with a high reflectance. In other words, when two unit multilayer films with different pitches are layered, the multilayer film reflecting mirror has a different center wavelength λ1.corresponding to each unit multilayer film. By synthesizing a spectrum of 7°8 having a peak at λ2, it is possible to achieve a higher reflectance than VtC over a wide wavelength range (see line in Figure 2). The features of this intricately structured multilayer reflector are that it can achieve a high reflectance over a wide wavelength range, that is, it can achieve spectral characteristics with a high integrated reflectance, and the thickness of the heavy element thin film with a pitch of dn1 and an l By changing the thickness Nn of the light element thin film and the stacking number M, it is possible to set the entire desired wavelength bandwidth, and because the wavelength bandwidth is wide, the allowable range of the incident angle is widened, as will be explained later. A wide range of reflectance can be obtained even in the case of a curved surface structure.

A more detailed explanation of the structure, constituent materials, and optical characteristics of the multilayer mirror in this example will be provided.

Since the long wavelength component of the light source is more easily absorbed by the constituent material of the multilayer 1 than the short wavelength component, since the unit multilayer a7+ has the peak wavelength of the reflectance spectrum on the single wavelength side, that is, the pitch d
The pitch dn is increased in ascending order from the unit multilayer film with small n.
The effect of absorption can be minimized by stacking layers on the substrate so that the long wavelength components are reflected by the upper unit multilayer film and the short wavelength components are mainly reflected by the lower unit multilayer film. ,
High reflectance can be achieved.

Furthermore, the multilayer reflective mirror of the present invention is characterized in that B or Bet is used as the material for the light element thin film.

The effect will be explained below. When the complex refractive index of the multilayer film constituent material is 1-δ-1β, the complex amplitude reflectance at the multilayer film interface is (△δ
10iΔβ). However, Δδ and Δβ are the differences in refractive index and absorption coefficient between the heavy element thin film and the light element thin film.

Furthermore, in order to obtain a higher peak reflectance, it is desirable that the absorption of soft X-rays in the material of the spacer layer be smaller. FIG. 3 shows the absorption coefficient μ of each heavy element in the wavelength range of 1 to 100 OA. In the soft X-ray region important for X-ray exposure, the absorption coefficient of B or Be is lower than that of C, which has been widely used as a single-layer spacer material. The absorption coefficient of Be is sometimes significantly different from the absorption coefficient of C. Regarding the refractive index, the refractive index of B or Be in the soft X-ray region is lower than that of C (Reference, B. L.).

Atomic Data and Nucl
ear Data Tables (1982)” No. 27
roll). Therefore, by using B or Be′It in place of C, which is generally used for conventional spacer single-layer materials, Δδ and Δβ are maximized in the soft xm region, and the soft X-rays due to the spacer single-layer material are Very high reflectance can be obtained since absorption is reduced. For example, according to calculations by the inventor, s W/Be multilayer film multilayer film reflection wavelength λp”11
At ^, a peak reflectance nearly twice as high as that of a W/C multilayer mirror can be obtained.

Furthermore, as a feature of the multilayer film reflecting mirror according to the present invention, the multilayer film reflection #! Optimum AVdn so that the maximum peak reflectance can be obtained for each of the M types of unit multilayer films that make up the entire structure.
One example is that it has a ratio. Therefore, the maximum peak reflectance can be obtained for soft X-rays in a predetermined wavelength bandwidth. When calculating the reflectance spectrum of the W/Be multilayer reflective film Tfl (M=2) proposed as an embodiment of the present invention and having the structure shown in FIG. 1, the L-shaped spectrum shown by the solid line 9 in FIG. Obtained. For comparison, the reflectance spectrum of a conventional W/C multilayer film reflector is shown by broken line 1.
(Table 1, design parameters of both multilayer J-film reflectors and peak reflectance R1, wavelength bandwidth Δλ/λ, integral reflectance IR) In 2), an integrated reflectance that is approximately three times higher than that of the conventional multilayer film reflection m (M=1) with a periodic structure can be obtained.

Table 1 N! A study using a light element such as B or Be, which has a smaller absorption coefficient than C in the spacer layer material of a multilayer reflector, takes the number of thin films on the upper layer relative to the substrate, and the wavelength λ = 124A There was an elaborate thing that was once done (Literature, Tee, Double, Barbie, Junior.

X, Ray, Micro, Scobee,' X-Ray
MicroscoP)'+ edited by
G, Schmahl and D, Rudolph
, (Springer-Verlag+ 198
4) "p144-162) In the soft X region on the rainbow short wavelength side, which is particularly important when performing X-ray exposure while

There has been no study including the structure of the multilayer film reflecting mirror and the AnZdn ratio, and no proposal has been made regarding a laminated structure of multilayer films with different pitches as in the present invention.

In the above description, the multilayer mirror is a plane mirror, but by making it a curved surface, rainbow X-rays can be focused, and the total intensity of the reflected X-rays can be increased. The multilayer reflector with the laminated structure according to the invention provides a wide reflectance spectral bandwidth, which means that it provides a very high reflectance over a wide range of Bragg angles α. Therefore, it is suitable for the structure of a curved multilayer film reflecting mirror with a constant spread 9 of the incident angle and the output angle. This point will be explained in detail below.

FIG. 5 shows a second embodiment of the multilayer film reflector according to the present invention, and is a mf plane view of a curved multilayer film reflector in which a multilayer film 12 is formed on a 7-lindrical surface substrate 11 with a radius of curvature R. It is. Here, the structure of the multilayer film 12 is one in which a plurality of unit multilayers are laminated as shown in the embodiment of FIG.
X-rays 13 parallel to this reflecting mirror strike a point 14 on the mirror surface at a glancing angle θ
Incident at .

In this case, the reflected light has a peak wavelength as shown in FIG. 6, and the wavelength bandwidth is λ/λ.
However, if the position of the reflection point shifts from 14, the peak wavelength of the reflectance spectrum also changes, and the reflectance at wavelength λp also decreases. 6 In the structure shown in FIG. 18, the reflectance of λp1 is 0. Let the reflection point at this position be 15, and let the distance between 14 and 15 be 'kL.

That is, as the viewing angle in FIG. 5 changes from θ to θ-Δθ, the reflectance spectrum of the reflected light changes from 17 to 18 in FIG. 6. However, the distance from Fig. 5 14 by L is fc1.
There is also a wavelength λp at the position opposite to 5.

There is a point where the reflectance at is O. Therefore, 14
The sum of reflected light from reflection points within a range of 2L with λp as the center is the reflection intensity of λp at the focal point 16. In this case, the wider Δλ/λ of the reflectance spectrum, the longer it becomes, and the intensity of wavelength λp at 16 increases. In the multilayer reflector according to the present invention, Δλ/λ is different from that of the conventional periodic structure (M=
It is larger than the reflector in 1) and has a high reflectance, so the focal point 1
The intensity of the reflected light of wavelength λp at 6 is large.

This is also true for wavelengths other than λp, so
As a result, reflected light with high intensity is obtained at the focal point 16. This is an example of a multilayer film reflecting mirror according to the present invention (W/Be multi-layered 1 m
ff1 reflector (M = 2) and (ll) conventional structure W/
For C multilayer mirror (M=1), the length of L is λp,
=11^) Save tJllIIS. (*), (io respectively at λp, = 11A, if the reflectance spectrum has a peak reflectance on the order of a chime, Δλ/λ is 2 in (1)
4%, and (11) about 6%. However, (1) is d
, = 37^, dt = 43 large, (1θ is d = 39.
It is 5^.

In this case, if the difference between the glancing angles at points 14 and 15 is 80, then L is expressed as R-muθjiπ/18o, and (I) is (
11). Therefore, the intensity of λp,=1oA at the focal point 16 is about 4 times greater in (1) than in (11).

This tendency is soft X&! The same is true for other wavelengths in the region.

Up to now, examples of the multilayer film reflecting mirror according to the present invention have been described, and next, an example of a method for manufacturing the multilayer film reflecting mirror will be described. FIG. 7 shows an embodiment of the method for manufacturing a multilayer mirror according to the present invention. First, the principle of atomic beam generation will be explained using FIG. Ar gas f 10-” to 10-’ tor is introduced into the atomic beam source from the gas inlet 19.
When a high voltage of about 3 to 9 kV is applied to the anode electrode 20, the anode electrode is applied and the cathode electrode 21
．． Glow discharge starts between 22 and 22 seconds. cathode 1 [i2
The electrons emitted from the surface of 1°4 are transferred to the central anode electrode 2.
High frequency vibrations occur at the 0 center. Inside the atomic beam source, a large amount of ions are generated due to collisions between vibrating electrons and Ar atoms. The ions are accelerated towards the cathode 21.22. Since there are electrons with a large collision cross section near the cathode, they are accelerated at several kilovolts and easily combine with friend ions, making them atoms that have the same energy as the ions! 2
3, and the beam emitting port 24L is taken out.

The method for manufacturing a multilayer film reflecting mirror according to the present invention includes using the M atom #23 obtained using the atomic beam source as a target multilayer film constituent material 25, and depositing sputtered particles 26 on a substrate n. This is done by forming a film. Note that the formation of the heavy element thin film and the light element thin film is carried out while alternately exchanging targets. The feature of the method for manufacturing a multilayer film reflector according to the present invention is that a smooth multilayer film with few irregularities at the interface can be formed. According to the evaluation results of the multilayer film interface using X-ray diffraction (α rays for Cu-) by the present inventors, the unevenness is about 1^9. Therefore, it was found that an extremely smooth multilayer film was formed. A further feature of this method is that an extremely thin continuous film can be formed. Based on the observation results of the multilayer film and the single J-film using a transmission electron microscope, the manufacturing method is approved.

It was found that a thin film of about IOA was formed for each Be. Taking W as an example, since the minimum thickness of a conventionally formed t-continuous thin film is 3 degrees, it can be seen that an extremely thin film can be formed using this manufacturing method. Furthermore, since the sputtering rate is very stable (measured by the present inventors, the fluctuation is less than 1 hour per hour), it can be said that this method has very good film thickness controllability. Furthermore, when used as a material constituting a spacer layer of a Brt multilayer film, the sputtering rate is high (according to measurements by the present inventors, the sputtering rate of Be is 1.74^/min, and the sputtering rate of C: 0.38 ^/min), a multilayer film reflecting mirror can be created in a short time. From the above examples, it is clear that the method for manufacturing a multilayer reflector according to the present invention is a multilayer reflector in which the interface of the multilayer film is extremely smooth, that is, the scattering of X-rays at the multilayer film interface is extremely small, and the reflection is close to the theoretical value. It is possible to manufacture a multilayer reflector having a high ratio. It is possible to manufacture a multilayer reflector having a fine pitch with good manufacturing precision.

(Effects of the Invention) The multilayer film reflecting mirror according to the present invention has a high reflectance and can control the spectral bandwidth, so it is useful as various spectroscopic elements and bandpass filters.

The W/Be multilayer reflector according to the present invention has a large reflectance over a wide viewing angle, especially in the soft X@ region that is important for X-ray lithography. It is possible to obtain reflected light intensity several times higher than that of a film reflector. Therefore, when applied to X-ray lithography, the exposure time can be significantly shortened.
Useful as a condensing reflector.

In addition, the method for manufacturing a multilayer film reflecting mirror according to the present invention has a multilayer film reflecting mirror with an extremely smooth multilayer film interface, that is, a multilayer film with very little scattering of X-rays at the multilayer film interface and a reflectance close to the theoretical value. A reflective fa can be manufactured. It is possible to manufacture a multilayer reflector having a fine pitch with high manufacturing accuracy.

[Brief explanation of drawings]

FIG. 1 is a three-dimensional diagram showing the structure of an embodiment of the multilayer reflector according to the present invention, FIG. 2 is a diagram explaining the principle of the optical characteristics of the multilayer reflector according to the present invention, and FIG. FIG. 4 is a diagram showing the wavelength dependence of the absorption coefficient, FIG. 4 is a diagram showing the reflectance spectrum of the multilayer reflective mirror according to the present invention, and FIG. 5 is a diagram showing another embodiment of the multilayer reflective mirror according to the present invention. Diagram showing a cylindrical multilayer film reflector and the state of condensation of X-rays by it,
FIG. 6 is a diagram explaining the reflectance spectrum characteristics of a cylindrical multilayer reflector, FIG. 7 is an example of a method for manufacturing a multilayer reflector according to the present invention, and FIG. Show the structure. 1...Substrate 2...One layer of spacer 3...Reflection layer 4...Reflection layer 5...One layer of spacer 6...・Unit multilayer film 7...Reflectance spectrum 8...Reflectance spectrum 9...Reflectance spectrum 10 of W/Be multilayer conversion multilayer mirror reflecting mirror = 2)... ...Reflectance spectrum 11 of W/C multilayer film reflection ti8 (M=1)...Cylindrical surface substrate ν...
Multilayer film reflecting mirror 13 according to the present invention...Incoming X-rays 14...Reflection point 15...Reflection point 16...Focus 17... Reflectance spectrum 18... Reflectance spectrum 19... Gas inlet addition... Anode electrode 21... Cando electrode 22... Cathode electrode 23...Atomic beam 24...Beam emission port 25...Multilayer film constituent material 26...Sputtered particle I...Substrate patent applicant Nippon Telegraph and Telephone Corporation FA2 Figure 3 Figure 10' 10 102
103 Shikinagairi (A) Fig. 4 Fig. 5 Fig. 6 Fig. No. 7 Fig. 8

Claims (4)

[Claims] (1) In a multilayer film reflecting mirror obtained by alternately stacking heavy element thin films and light element thin films on a substrate, the light element thin film is formed from a multilayer film using B or Be as the material. A multilayer reflective mirror characterized by: (2) A patent claim characterized in that, as a multilayer film structure, a multilayer film having a predetermined pitch and number of layers is used as a unit multilayer film, and a plurality of unit multilayer films of different types with different pitches and numbers of layers are laminated. The multilayer film reflecting mirror according to item 1. (3) The multilayer film reflecting mirror according to claim 1, wherein the substrate has a curved surface. (4) In the production of a multilayer reflector obtained by alternately stacking a heavy element thin film of a predetermined thickness and a B or Be thin film of a predetermined thickness on a substrate, atomic beam sputtering is used to A method for manufacturing a multilayer reflective mirror, comprising forming the thin film on top.