Method for eliminating thin film stress

A thin-film stress and thin-film technology, applied in the field of conformal optical components, can solve problems such as film cracking, affecting laser system performance, plastic deformation, etc., and achieve the effect of increasing types

Pending Publication Date: 2021-06-18

DALIAN INST OF CHEM PHYSICS CHINESE ACAD OF SCI

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AI-Extracted Technical Summary

Problems solved by technology

Such high stress will cause elastic deformation of thin film optical components, and even plastic deformation in severe cases, resulting in cracking and peeling of ...

Method used

Prepared thin film adopts Zygo Fizeau interferometer test, test result curve as shown in F...

Abstract

The invention relates to a method for eliminating a thin film stress. A double-ion-beam sputter coating technology is adopted, and after thin film plating is completed on an optical substrate, a series of annealing heat treatment are carried out, thermodynamic characteristics of a coating material are combined, and annealing heat treatment parameters such as process conditions of an annealing temperature, annealing time, annealing times, a heating/cooling rate and the like are controlled so as to implement stress control. According to the obtained experimental phenomenon, a set of complete thin film stress elimination process flow and theoretical system is established by combining theoretical guidance. By using the method, the thin film stress can be macroscopically regulated and controlled on the premise of ensuring good optical characteristics of a thin film. The method can provide theoretical guidance for an optical element shape preserving technology, and can provide samples for production of complex optical thin films, high-light optical elements and the like.

Application Domain

Vacuum evaporation coatingSputtering coating +1

Technology Topic

PhysicsThin membrane +11

Image

Examples

Experimental program(3)

Example Embodiment

[0023] Example 1: Ta 2 O 5 Film stress characteristics

[0024] 1. Characterizing the size of the JGS1 substrate having a size of φ25.4 × 5 mm, and placed in a ion beam sputtering coating machine after cleaning, set the single layer film thickness of 500 nm, and the coating material is Ta 2 O 5. The film deposition conditions are: the substrate temperature is 80 ° C, the method of reaction sputtering, TA target purity is 99.99%, vacuum pumping to 8 × 10 -7 Torr.

[0025] 2. TA 2 O 5 The film is characterized by a size of 0.018λ, and brought into the Stoney formula (5) to get Ta 2 O 5 Film stress.

[0026] The relationship between the substrate diameter, the height, and the radius of curvature can be expressed as:

[0027]

[0028] Where R is the radius of curvature, D s For the substrate diameter, H is rising.

[0029] The relationship between the Height and Power is:

[0030] H = 2 × 632.8 × power (2)

[0031] Usually, the substrate caused by the film stress is small, so the relationship between Power and the radius R R is approximately:

[0032]

[0033] Where DS is the diameter of the circular substrate.

[0034] Can be further obtained:

[0035]

[0036] This definition ΔPower is before and after the coating (Power 2 , Power 1 ) The difference between the surface precision Power, R 0 R 1 The radius of curvature of the substrate before and after the coating is respectively. λ is the main detection light wavelength, and this example corresponds to 632.8 nm.

[0037]

[0038] Where σ is a thin film stress, T s T f The thickness of the substrate and film, e s And V s Elastic modulus and Poisson ratio of the substrate (reference [1]: S.W.deg, F.Wang, S.LIU, Residual Stress Prediction andControl of Ta 2 O 5 / Sio 2 Multilayer based on layer structure designing, chin.opt.let.11 (2013) 10701. When the stress is negative, the pressure stress is indicated, and the tension stress is indicated when the stress is positive.

[0039] 3. For TA2 O 5 The film is retired and heat treatment, the constant temperature temperature is set at 80 to 600 ° C, from room temperature to an annealing temperature temperature rate of 100 ° C / h, at a constant temperature time of 16 h, and finally naturally cooling, complete 1 time annealing heat treatment. A total of 5 annealing heat treatment was carried out, and the annealing temperature was 300 ° C, 350 ° C, 400 ° C, 450 ° C, 500 ° C.

[0040] 4. After being retired and heat treatment, TA after characterizing the annealing heat treatment 2 O 5 The stress characteristics of the film are obtained by TA 2 O 5 The correspondence between film stress and annealing temperature, respectively, with a cross-sectional stress and annealing temperature, such as image 3 (a) shows that the specific relationship is:

[0041] σ T = -698.14 + 1.17T (6)

Example Embodiment

[0042] Example 2: SiO 2 Film stress characteristics

[0043] 1. Characterization of the JGS1 substrate surface of φ25.4 × 5 mm is characterized, and then add ion beam sputter coating machine after drying, set the single layer film thickness of 500 nm, and the coating material is SiO. 2. The film deposition conditions are: the substrate temperature is 80 ° C, the method of reaction sputtering, Si target purity is 99.99%, vacuum pumping to 8 × 10- 7 Torr.

[0044] 2. For SIO 2 The film surface accuracy is characterized, and the size is 0.032λ and brought into the Stoney formula (5), and the specific derivation process refers to the first step (2) to obtain SiO 2 Film stress.

[0045] 3. For SIO 2 The film is retired and heat treatment, and the annealing constant temperature temperature is set at 80 to 600 ° C, from room temperature to an annealing temperature temperature rise rate of 100 ° C / h, the constant temperature time is 6 h, and finally naturally cooling, complete 1 time annealing heat treatment. A total of 5 annealing heat treatment was carried out, and the annealing temperature was 300 ° C, 350 ° C, 400 ° C, 450 ° C, 500 ° C.

[0046] 4. After being retired and heat treatment is completed, the SIO is characterized after the annealing heat treatment. 2 The stress characteristics of the film, the correspondence relationship of the film stress and the annealing temperature, respectively, with the thin film stress and the annealing temperature, such as image 3 (b), the specific relationship is:

[0047] σ T = -657.37 + 2T (7)

Example Embodiment

[0048] Example 3:

[0049] 1. The relationship formula (6) and (7) according to Examples 1 and 2 are designed for SUB / HL ^16 / AIR, high, low refractive index coating material is TA 2 O 5 SiO 2 The thickness is from 197 nm and 115 nm, respectively.

[0050] Then, the size of the JGS1 substrate having a size of φ25.4 × 5 mm is characterized. After cleaning, the ion beam sputtering coating machine is placed, the film deposition conditions are: the substrate temperature is 80 ° C, and the method of reaction sputtering is used. TA target purity 99.99%, vacuum pumping to 8 × 10 -7 Torr.

[0051] 2. Based on the formula (5), (6) and (7), the selected annealing temperature is 450 ° C, for TA 2 O 5 / Sio 2 The multilayer film is annealing heat treatment.

[0052] σ H (T H , T) t H + σ L (T L , T) t L = 0 (4)

[0053] Where T H , T L High, low refractive index material film thickness, T is annealing temperature;

[0054] The heating rate is 100 ° C / h, and TA is at this time. 2 O 5 SiO 2 The stress sizes of the film were 197 MPa and -115 MPa, and the constant temperature time was 6 h, and finally naturally cooled.

[0055] According to the spectral requirements of the desired transmittance, the thickness of the high and low refractive index is divided into 16 cycles, respectively;

[0056] 3. After the cooling is completed, the stress characteristics of the multilayer film after the annealing heat treatment are measured.

[0057] The prepared film is tested with Zygo Fiso interferometer, and the test results are Figure 4 The curve shown, which can be seen from the figure that the film stress has been effectively controlled.

[0058] The present invention has been prepared on the optical substrate by a method of ion beam sputtering. 2 O 5 SiO 2 Single-layer film, the change in single layer film stress characteristics is carried out by annealing heat treatment, and then, on the basis of the change of the stress characteristics of the single layer film, the compression stress and the stress film layer are used to alternately deposit the compensation stress. The optical film obtained and prepared to obtain a good optical performance and a low stress state, which can be applied to the light light optics. The obtained optical element has a small surface precision variation, effectively improves the laser beam quality. The present invention can provide samples for experimental research or industrial production of optical components.

PUM

Property	Measurement	Unit
Thickness	1.0 ~ 5.0	nm

Description & Claims & Application Information

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Classification and recommendation of technical efficacy words

increase variety

Method for eliminating thin film stress

A thin-film stress and thin-film technology, applied in the field of conformal optical components, can solve problems such as film cracking, affecting laser system performance, plastic deformation, etc., and achieve the effect of increasing types

AI-Extracted Technical Summary

Problems solved by technology

Method used

Abstract

Image

Examples

Example Embodiment

Example Embodiment

Example Embodiment

PUM

Description & Claims & Application Information

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