JPS58217901A - Laminate vapor-deposited on both sides - Google Patents

Abstract

PURPOSE:To easily obtain both side vapor deposition laminates free from strain without requiring any pretreatment or the like, by correcting strain produced in a base due to the first vapor deposited film formed on one side through formation of the second vapor deposited film on the other side. CONSTITUTION:For example, in forming a thin high-reflectance mirror material, a layer H of high refractive index material, such as TiO2, and a layer L of low index material, such as SiO2 are alternately laminated on the first free 31a of the base glass 31 to form a high-reflectance mirror 32, and MgF2 is vapor deposited onto the second face 31b of the glass 31 so as to form an MgF2 vapor deposited film 22, 23 as the second vapor deposited film also used as prevention of reflection having a thickenss thick enough to erase the strain of the glass 31 due to the formation of the mirror 32. Said example is the case of the base strained by the tensile stress of the first film, but when the first film generates compressive stress, a vapor deposition film exhibiting compressive stress, such as SiO2, may be used as the second vapor deposition film.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a double-sided vapor deposited laminate in which distortion of the substrate surface due to internal stress of the vapor deposited film is corrected.

Conventionally, substrates have been manufactured using vacuum evaporation or sputtering methods.
It is known that in some cases, a large internal stress exists in a vapor-deposited thin film formed on a substrate (e.g., Trans, 8th Natl,
Vacuum Symp.

Published in 1961, P943~).

Due to the internal stress in the deposited film, the substrate 11 (FIG. 11(a)), whose both surfaces have been polished into a planar shape, is deformed to the extent that it can be detected from the outside if it is very thin. For deformation, as shown in FIG. 1(b) or (c), the vapor deposited film 12
Depending on the case, there are cases where the stress is caused by tensile stress (FIG. 1(b)) and cases where the stress is caused by compressive stress (FIG. 1(C)).

Strictly speaking, even if the deposited films are made of the same substance, the deposition method (e.g., vacuum evaporation, sputtering, CVD) and the various conditions during the deposition (e.g., substrate temperature, deposition rate, degree of vacuum, If the positional relationship between the evaporation source and the substrate differs, the internal stress generated inside the deposited film 12 and, by extension, the strain gauge of the substrate 11 will also change.

The relationship between the internal stress in the deposited film and the strain ld on the substrate surface has already been analyzed, and the relationship expressed by the following equation is known (A, E, C, TechnicalRepo
rt'A 15, I 96]. When the substrate has a rectangular cross section, l, 4Eb2 where σ: internal stress in the deposited film (dyn/cr/l
) E Young's modulus of the substrate (dyn lcr!) ν, Poisson's ratio of the substrate, thickness of the substrate (crn) L Length of the substrate ctn) Δ: Amount of strain on the substrate (m) What is the amount of strain on the substrate 11? , is the height h of a perpendicular line drawn from a straight line connecting both ends of the board to the center of the board in a state where both ends are not restrained.

- As is clear from both of them, when the internal stress σ generated in the deposited film 12 is constant, if the length of the substrate is very long or the thickness is very thin, the substrate surface will be distorted due to the internal stress of the film. The amount Δ increases.

The distortion of the substrate 11 is actually a problem when a particularly high level of surface precision (distortion amount λ/100 to λ/200, where λ is wavelength) is required, that is, for example, in an etalon plate. . As is well known, the etalon plate is used in a spectrometer that utilizes multiple interference. Since the surface of the etalon plate is required to have high reflectance, a multilayer film of an inorganic dielectric is often deposited. However, due to the internal stress of this multilayer film, the substrate (glass) was
Even if polished to a high surface accuracy of 00 or less, λ1 after vapor deposition
It may be distorted up to 50 to λ.

In addition, dichroic mirrors used in laser rangefinders, etc., use thin substrates due to the requirements of their optical systems, and are coated with a multilayer dielectric film to selectively reflect only the laser wavelength. be done. Interference fringes at laser wavelengths are used for distance measurement, but this requirement requires dichroic mirrors to have extremely high surface accuracy. In this case, the material selection and thickness are usually made with priority given to satisfying the spectral characteristics of the multilayer deposited film V'5. And the resulting distortion of the film surface must be solved by other means.

A possible solution to this problem is to measure the internal stress and substrate distortion caused by the film deposited on the substrate in advance, and then polish the substrate surface in advance to give it a curvature in the opposite direction.

This situation is shown in FIG. FIGS. 2(b) and 2(d) show the case where the deposited film 22 exhibits tensile stress, and the substrate 21 is previously processed to have a convex surface (curved downward) on this platform.

On the other hand, FIGS. 2C and 2E show cases in which the deposited film 23 exhibits compressive stress, and in this case, the substrate 21 is preliminarily processed to have a concave surface (curved in one direction).

However, this method has the following drawbacks.

(1) Each time different membrane materials and multilayer configurations are used,
It is necessary to measure the distortion [i] of each substrate through preliminary experiments.(2) Considerable precision is required in the curvature processing and polishing of the substrate surface, which is the previous process.The present invention solves these drawbacks. However, it is an object of the present invention to provide a vapor-deposited laminate that does not require any preliminary experiments or pre-processing, and therefore can shorten the manufacturing time and improve the yield rate by -4.

The present inventors came up with the idea of obtaining a high degree of surface accuracy by later correcting the distortion of the substrate surface due to the internal stress of the deposited film.
After depositing a multilayer film or a single layer film having desired properties on one side of the substrate, another deposited film is deposited on the other side of the substrate, thereby reducing the internal stress of both deposited films. We have invented a double-sided vapor-deposited laminate that eliminates the problem of distortion on the substrate surface by offsetting the above.

In carrying out the present invention, if the target vapor-deposited laminate is a reflective optical system, the film deposited on the back side of the substrate for stress correction can be arbitrarily selected in quality and thickness. On the other hand, in the case of transmissive optical systems, this cannot be done arbitrarily as it affects the spectral transmittance.For example, an antireflection layer is often deposited on the back side of the substrate to prevent stray light.In this case The material should be selected to produce a stress that balances the film stress of the surface deposited layer.Furthermore, if the distortion of the substrate cannot be corrected by keeping the film thickness constant,
By later changing the film thickness as necessary within a range that does not impair the antireflection effect, it is possible to form an antireflection film having stress balanced with the film stress of the surface deposited layer.

In other words, even if there are variations in the film stress of the first blood-related deposition layer or variations in the polished finish (surface accuracy) of the substrate surface before vapor deposition, they can be corrected in the subsequent second deposition, making the manufacturing process relatively easy. , and high substrate surface accuracy can be obtained.

Examples of the present invention are shown below.

Here, the substrate glass 31 has a thickness of 0.6 nrtn
As shown in Figure 3, the structure of the double-sided vapor-deposited laminate is a high-reflection layer in which H layers made of a high refractive index material and L layers made of a low refractive index material are alternately combined on the first surface 31a. To form the mirror 32 (the high refractive index and low refractive index referred to herein refer to the refractive index of the substrate glass), a single-layer antireflection layer film 33 is formed on the second surface 31b on the opposite side. It will be done.

The configuration of the high reflection mirror 32 includes TiO2 as the H layer, L
Using SiO2 as the layers, six sets of 11 layers and L layers are alternately formed on a glass substrate 31, and finally, another H layer is formed (see FIG. 4).

Each layer is formed by a general vacuum evaporation method using an electron beam, and its thickness is 580 layers for TL O2 layer and 580 layers for SL 02 layer.
There are 900 people in the group. As a result, the membrane stress generated was a tensile stress of 4.5×10′ dyn/crl.

Next, in order to correct the distortion of the substrate 31 caused by the tensile stress caused by the high reflection mirror 32, the opposite surface 3 of the substrate
1b, the same tensile force, oh L, fl-'l) □ 1 piece 4
1°67. A M9 F2 single layer film with a refractive index of
/cJ. Therefore, it was predicted that in order to balance the tensile stress caused by the high reflection mirror 32, it would be sufficient to form approximately 2,500 M and F 2 films.

Based on this prediction, 2,500 MgF2 films were formed, and 32 4.5X 10' dynA high-reflection mirror layers were formed.
The tensile stress of i is 0.5 x 10' dyn 1crl
As a result, the strain on the surface of the substrate 31 is drastically reduced to λ<a or less, and a high reflection mirror material (one of the double-sided vapor deposited laminates in the present invention) that achieves the desired surface precision Embodiment] was obtained.

As described above, in the present invention, even if a completely flat surface cannot be obtained, there is no problem as long as an acceptable surface precision can be obtained.

However, if the high-reflection mirror layer 32 is made of a different film material and the generated stress exhibits compressive stress, t,1, the anti-reflection layer 33 for stress correction on the opposite side has the same compressive stress. A deposited film must be used that exhibits the following properties. According to experiments conducted by the present inventors on a vaporized 1NlSt02 film that exhibits compressive stress, the compressive stress value at a film thickness of 1000 mm is approximately 2.6 x 10
' dyn/ca.

Further, as described above, in the present invention, when the laminate is an optical member (reflection mirror, lens, filter, etc.), either a reflection type or a transmission type may be used. It goes without saying that the laminate does not have to be an optical member.

As described above, according to the present invention, the distortion of the substrate due to the internal stress of the first deposited film is corrected by the second deposited film, and this second deposited material can be additionally deposited later as necessary. Therefore, the optimum thickness and type can be determined in consideration of the distortion of the substrate due to the internal stress of the first deposited film.

Moreover, since this can be done without requiring troublesome preliminary experiments or precise polishing, it is possible to mass-produce excellent laminates at low cost and with high yield.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(c) are cross-sectional views illustrating distortion of a substrate due to conventional vapor deposition. FIGS. 2(a) to 2(e) are cross-sectional views illustrating one method for eliminating distortion of a substrate caused by vapor deposition. FIG. 3 is a sectional view of a double-sided vapor deposited laminate showing an embodiment of the present invention. FIG. 4 is a partially enlarged view of FIG. 3. [Explanation of symbols of main parts] 21.31 ... Yamakawa substrate 22.32.33 ... Deposited film Applicant: Nippon Kogaku Kogyo Co., Ltd. Yuki Yasui -g! , ¥, ,i oldness -+>
- ;+-j figure (12) Spear figure 3

Claims (1)

[Claims] a first deposited film having internal stress deposited on one side of the substrate;
A double-sided structure characterized by comprising a substrate which causes distortion due to the internal stress, and a second vapor deposited film deposited on the opposite side of the first vapor deposited film and having an internal stress balanced with the internal stress of the first vapor deposited film. Vapor-deposited laminate.