CVD PREPARATION METHOD FOR MINIMIZING CAMERA MODULE DOT DEFECTS AND PRODUCT THEREOF

Abstract

A CVD preparation method for minimizing camera module dot defects includes: performing ultrasonic cleaning and drying on a base substrate to obtain a pre-treated base substrate; placing the pre-treated base substrate into a reaction chamber, evacuating, and introducing nitrogen or inert gas to slightly positive pressure; simultaneously introducing precursor I and precursor II at a temperature of 500-700° C. to deposit a low-refractive-index L layer on the base substrate; halting introduction of the precursor I and the precursor II, and purging the reaction chamber with nitrogen or the inert gas; introducing raw gas precursor III and precursor IV at a temperature of 600-800° C. to deposit a high-refractive-index H layer on the low-refractive-index L layer; and halting introduction of the precursor III and precursor IV, and purging the reaction chamber with nitrogen or inert gas; and cooling to room temperature to obtain an optical element with coating films having different refractive indices.

Claims

1. A CVD preparation method for minimizing camera module dot defects, comprising the following steps: S1: performing ultrasonic cleaning and drying on a base substrate to obtain a pre-treated base substrate; S2: placing the pre-treated base substrate into a reaction chamber, evacuating the reaction chamber, and introducing first nitrogen or a first inert gas into the reaction chamber to a slightly positive pressure; S3: simultaneously introducing a first raw gas precursor and a second raw gas precursor at a temperature of 500-700° C. to deposit and form a low-refractive-index layer on the base substrate, wherein a flow rate of the first raw gas precursor is 10-80 sccm, and a flow rate of the second raw gas precursor is 20-80 sccm; S4: halting introduction of the first raw gas precursor and the second raw gas precursor, and purging the reaction chamber with second nitrogen or a second inert gas; S5: introducing a third raw gas precursor and a fourth raw gas precursor at a temperature of 600-800° C. to deposit a high-refractive-index layer on the low-refractive-index layer, wherein a flow rate of the third raw gas precursor is 20-90 sccm, and a flow rate of the fourth raw gas precursor IV is 20-60 sccm; and S6: halting introduction of the third raw gas precursor and the fourth raw gas precursor, and purging the reaction chamber with third nitrogen or a third inert gas; S7: cooling the reaction chamber to room temperature to obtain an optical element with coating films having different refractive indices; wherein a refractive index of the high-refractive-index layer is greater than a refractive index of the low-refractive-index layer.

2. The CVD preparation method for minimizing the camera module dot defects of claim 1, wherein, steps S3-S4 and/or steps S5-S6 are periodically repeating.

3. The CVD preparation method for minimizing the camera module dot defects of claim 2, wherein, the coating films of the optical element comprise: a combination of a SiO.sub.2 low-refractive-index layer and a TiO.sub.2 high-refractive-index layer; a combination of the SiO.sub.2 low-refractive-index layer and a Nb.sub.2O.sub.5 high-refractive-index layer; a combination of the SiO.sub.2 low-refractive-index layer and a Ta.sub.2O.sub.5 high-refractive-index layer; a combination of a MgF.sub.2 low-refractive-index layer and the TiO.sub.2 high-refractive-index layer; a combination of the MgF.sub.2 low-refractive-index layer and the Nb.sub.2O.sub.5 high-refractive-index layer; a combination of a Nb.sub.2O.sub.5 low-refractive-index layer and the Ta.sub.2O.sub.5 high-refractive-index layer; a combination of the MgF.sub.2 low-refractive-index layer, an Al.sub.2O.sub.3 high-refractive-index layer and the SiO.sub.2 low-refractive-index layer; a combination of an Al.sub.2O.sub.3 low-refractive-index layer, a lanthanum titanium oxide high-refractive-index layer and the MgF.sub.2 low-refractive-index layer; and a combination of the Al.sub.2O.sub.3 low-refractive-index layer, a ZrO.sub.2 high-refractive-index layer and the MgF.sub.2 low-refractive-index layer.

4. The CVD preparation method for minimizing the camera module dot defects of claim 3, wherein, a difference between a refractive index of the TiO.sub.2 high-refractive-index layer and a refractive index of the SiO.sub.2 low-refractive-index layer is greater than or equal to 0.5; a difference between a refractive index of the Nb.sub.2O.sub.5 high-refractive-index layer and the refractive index of the SiO.sub.2 low-refractive-index layer is greater than or equal to 0.5; a difference between a refractive index of the Ta.sub.2O.sub.5 high-refractive-index layer and the refractive index of the SiO.sub.2 low-refractive-index layer is greater than or equal to 0.5; a difference between the refractive index of the TiO.sub.2 high-refractive-index layer and a refractive index of the MgF.sub.2 low-refractive-index layer is greater than or equal to 0.5; a difference between the refractive index of the Nb.sub.2O.sub.5 high-refractive-index layer and the refractive index of the MgF.sub.2 low-refractive-index layer is greater than or equal to 0.5; and a difference between the refractive index of the Ta.sub.2O.sub.5 high-refractive-index layer and a refractive index of the Nb.sub.2O.sub.5 low-refractive-index layer is greater than or equal to 0.5.

5. The CVD preparation method for minimizing the camera module dot defects of claim 1, wherein, the base substrate is one selected from the group consisting of a glass substrate, a crystal substrate and a sapphire substrate.

6. The CVD preparation method for minimizing the camera module dot defects of claim 3, wherein, the first raw gas precursor is one selected from the group consisting of SiH.sub.4, SiHCl.sub.3, SiCl.sub.2H.sub.2, SiCl.sub.4, Al(CH.sub.3).sub.3 and Cp.sub.2Mg; the second raw gas precursor is at least one selected from the group consisting of O.sub.2, O.sub.3, CO.sub.2, CO, NO.sub.2, NO, H.sub.2O and F.sub.2; the third raw gas precursor is one selected from the group consisting of TiH.sub.4, TiCl.sub.4, NbCl.sub.5, TaCl.sub.5 and ZrCl.sub.4; and the fourth raw gas precursor is at least one selected from the group consisting of O.sub.2, O.sub.3, CO.sub.2, CO, NO.sub.2, NO, H.sub.2O and F.sub.2.

7. A multilayer film structure, wherein, the multilayer film structure is prepared by the CVD preparation method of claim 1.

8. The multilayer film structure of claim 7, wherein, in the multilayer film structure, a number of dots with a size greater than or equal to 1 μm is 0.

9. The multilayer film structure of claim 7, wherein, a surface roughness of the multilayer film structure ranges from 0.01 nm to 20 nm.

10. A CLCC package cover plate, comprising: a cover plate substrate, and a functional film; wherein the functional film covers the cover plate substrate; the functional film comprises a multilayer film structure; and the multilayer film structure is deposited by the CVD preparation method of claim 1.

11. A CLCC package, comprising a substrate; wherein a CMOS is attached in a middle of the substrate; a capacitor resistor and a driving motor are attached on an edge of the substrate; a separation wall base is provided on the substrate; a CMOS sensor vacancy is provided at a first position on the separation wall base, wherein the first position on the separation wall base corresponds to the CMOS on the substrate, a capacitor resistor vacancy is provided at a second position on the separation wall base, wherein the second position on the separation wall base corresponds to the capacitor resistor on the substrate, and a driving motor vacancy is provided at a third position on the separation wall base, wherein the third position on the separation wall base corresponds to the driving motor on the substrate; and the CLCC package cover plate of claim 10 is mounted on an upper surface of the CMOS sensor vacancy.

12. A camera module, comprising the CLCC package of claim 11.

13. The multilayer film structure of claim 7, wherein, steps S3-S4 and/or steps S5-S6 are periodically repeating.

14. The multilayer film structure of claim 13, wherein, the coating films of the optical element comprise: a combination of a SiO.sub.2 low-refractive-index layer and a TiO.sub.2 high-refractive-index layer; a combination of the SiO.sub.2 low-refractive-index layer and a Nb.sub.2O.sub.5 high-refractive-index layer; a combination of the SiO.sub.2 low-refractive-index layer and a Ta.sub.2O.sub.5 high-refractive-index layer; a combination of a MgF.sub.2 low-refractive-index layer and the TiO.sub.2 high-refractive-index layer; a combination of the MgF.sub.2 low-refractive-index layer and the Nb.sub.2O.sub.5 high-refractive-index layer; a combination of a Nb.sub.2O.sub.5 low-refractive-index layer and the Ta.sub.2O.sub.5 high-refractive-index layer; a combination of the MgF.sub.2 low-refractive-index layer, an Al.sub.2O.sub.3 high-refractive-index layer and the SiO.sub.2 low-refractive-index layer; a combination of an Al.sub.2O.sub.3 low-refractive-index layer, a lanthanum titanium oxide high-refractive-index layer and the MgF.sub.2 low-refractive-index layer; and a combination of the Al.sub.2O.sub.3 low-refractive-index layer, a ZrO.sub.2 high-refractive-index layer and the MgF.sub.2 low-refractive-index layer.

15. The multilayer film structure of claim 14, wherein, a difference between a refractive index of the TiO.sub.2 high-refractive-index layer and a refractive index of the SiO.sub.2 low-refractive-index layer is greater than or equal to 0.5; a difference between a refractive index of the Nb.sub.2O.sub.5 high-refractive-index layer and the refractive index of the SiO.sub.2 low-refractive-index layer is greater than or equal to 0.5; a difference between a refractive index of the Ta.sub.2O.sub.5 high-refractive-index layer and the refractive index of the SiO.sub.2 low-refractive-index layer is greater than or equal to 0.5; a difference between the refractive index of the TiO.sub.2 high-refractive-index layer and a refractive index of the MgF.sub.2 low-refractive-index layer is greater than or equal to 0.5; a difference between the refractive index of the Nb.sub.2O.sub.5 high-refractive-index layer and the refractive index of the MgF.sub.2 low-refractive-index layer is greater than or equal to 0.5; and a difference between the refractive index of the Ta.sub.2O.sub.5 high-refractive-index layer and a refractive index of the Nb.sub.2O.sub.5 low-refractive-index layer is greater than or equal to 0.5.

16. The multilayer film structure of claim 7, wherein, the base substrate is one selected from the group consisting of a glass substrate, a crystal substrate and a sapphire substrate.

17. The multilayer film structure of claim 14, wherein, the first raw gas precursor is one selected from the group consisting of SiH.sub.4, SiHCl.sub.3, SiCl.sub.2H.sub.2, SiCl.sub.4, Al(CH.sub.3).sub.3 and Cp.sub.2Mg; the second raw gas precursor is at least one selected from the group consisting of O.sub.2, O.sub.3, CO.sub.2, CO, NO.sub.2, NO, H.sub.2O and F.sub.2; the third raw gas precursor is one selected from the group consisting of TiH.sub.4, TiCl.sub.4, NbCl.sub.5, TaCl.sub.5 and ZrCl.sub.4; and the fourth raw gas precursor is at least one selected from the group consisting of O.sub.2, O.sub.3, CO.sub.2, CO, NO.sub.2, NO, H.sub.2O and F.sub.2.

18. The multilayer film structure of claim 13, wherein, in the multilayer film structure, a number of dots with a size greater than or equal to 1 μm is 0.

19. The multilayer film structure of claim 14, wherein, in the multilayer film structure, a number of dots with a size greater than or equal to 1 μm is 0.

20. The multilayer film structure of claim 15, wherein, in the multilayer film structure, a number of dots with a size greater than or equal to 1 μm is 0.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1 is a schematic diagram of the multilayer film structure of the present invention;

[0035] FIG. 2 is a structural schematic diagram of the CLCC package of the present invention;

[0036] FIG. 3 is a schematic diagram of the cover plate of Embodiment 1 observed under a metallurgical microscope with a 10× ocular lens and a 100× objective lens;

[0037] FIG. 4 is an Atomic Force Microscopy (AFM) image of the surface of the cover plate of Embodiment 1;

[0038] FIG. 5 is a three-dimensional AFM image of the surface of the cover plate of Embodiment 1; and

[0039] FIG. 6 is a schematic diagram of the cover plate of a Comparative Embodiment observed under the metallurgical microscope with the 10× ocular lens and the 100× objective lens.

[0040] Reference numerals: 1, substrate; 2, CMOS; 3, capacitor resistor; 4, driving motor; 5, separation wall base; 6, cover plate.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0041] The present invention will be further described with reference to the drawings and embodiments. The refractive index of the present invention is set to be obtained under the d-line of a helium (He) light source, and a wavelength of the d-line is 587.56 nm.

[0042] A CVD preparation method for minimizing camera module dot defects includes the following steps:

[0043] S1: Ultrasonic cleaning and drying are performed on a base substrate to obtain a pre-treated base substrate.

[0044] S2: The pre-treated base substrate is placed into a reaction chamber, the reaction chamber is evacuated, and nitrogen or inert gas is introduced into the reaction chamber to slightly positive pressure.

[0045] S3: The precursor I and the precursor II are simultaneously introduced at a temperature of 500-700° C. to deposit and form a low refractive index L layer on the base substrate, wherein a flow rate of silane is 10-80 sccm, and a flow rate of oxygen is 20-80 sccm.

[0046] S4: Introduction of the precursor I and the precursor II is halted, and the reaction chamber is purged with nitrogen or inert gas.

[0047] S5: At a temperature of 600-800° C., the raw gas precursor III and precursor IV are introduced to deposit a high-refractive-index H layer on the low-refractive-index L layer, wherein a flow rate of the precursor III is 20-90 sccm, and a flow rate of the precursor IV is 20-60 sccm.

[0048] S6: Introduction of the raw gas precursor III and precursor IV is halted, and the reaction chamber is purged with nitrogen or inert gas.

[0049] S7: The reaction chamber is cooled to room temperature to obtain an optical element with coating films having different refractive indices; wherein the refractive index of the high-refractive-index H layer is greater than the refractive index of the low-refractive-index L layer. The above optical element can be subjected to secondary heating treatment, plasma treatment and the like to further improve the optical performance.

[0050] Further, the above preparation method further includes periodically repeating steps S3-S4 and/or S5-S6.

[0051] Further, in the above preparation method, the coating films of the optical element include: a combination of SiO.sub.2 low-refractive-index L layer and TiO.sub.2 high-refractive-index H layer; a combination of SiO.sub.2 low-refractive-index L layer and Nb.sub.2O.sub.5 high-refractive-index H layer; a combination of SiO.sub.2 low-refractive-index L layer and Ta.sub.2O.sub.5 high-refractive-index H layer; a combination of MgF.sub.2 low-refractive-index L layer and TiO.sub.2 high-refractive-index H layer; a combination of MgF.sub.2 low-refractive-index L layer and Nb.sub.2O.sub.5 high-refractive-index H layer; a combination of Nb.sub.2O.sub.5 low-refractive-index L layer and Ta.sub.2O.sub.5 high-refractive-index H layer; a combination of MgF.sub.2 low-refractive-index L layer, Al.sub.2O.sub.3 high-refractive-index H layer and SiO.sub.2 low-refractive-index L layer; a combination of Al.sub.2O.sub.3 low-refractive-index L layer, H4 high-refractive-index H layer and MgF.sub.2 low-refractive-index L layer; and a combination of Al.sub.2O.sub.3 low-refractive-index L layer, ZrO.sub.2 high-refractive-index H layer and MgF.sub.2 low-refractive-index L layer.

[0052] Further, in the above preparation method, in a two-component material film structure, namely a structure that contains films made of two kinds of materials, the difference between the refractive index of the high-refractive-index H layer and the refractive index of the low-refractive-index L layer is equal to or greater than 0.5. The greater the difference in refractive index between two layers, the better the optical performance.

[0053] Further, in the above preparation method, the base substrate is a glass, crystal or sapphire substrate.

[0054] Further, in the above preparation method, the precursor I is one selected from the group consisting of SiH.sub.4, SiHCl.sub.3, SiCl.sub.2H.sub.2, SiCl.sub.4, Al(CH.sub.3).sub.3 and Cp.sub.2Mg. The precursor II is at least one selected from the group consisting of O.sub.2, O.sub.3, CO.sub.2, CO, NO.sub.2, NO, H.sub.2O and F.sub.2. The precursor III is one selected from the group consisting of TiH.sub.4, TiCl.sub.4, NbCl.sub.5, TaCl.sub.5 and ZrCl.sub.4. The precursor IV is at least one selected from the group consisting of O.sub.2, O.sub.3, CO.sub.2, CO, NO.sub.2, NO, H.sub.2O and F.sub.2.

[0055] A multilayer film structure, as shown in FIG. 1, is prepared by the above CVD preparation method, wherein the number of dots with a size greater than or equal to 1 μm is 0, and a surface roughness Ra of the multilayer film structure ranges from 0.01 nm to 20 nm. The CVD preparation method includes performing bombardment modification on the currently deposited layer with plasma after the completion of the deposition of each layer of the film structure and before the deposition of the next layer of the film structure. The plasma used in the modification has a voltage of 100-1000 V and a current of 100-1000 mA, and the time is preferably 1-2 minutes to avoid affecting the performance and thickness of the deposited film layer.

[0056] A CLCC package cover plate includes a cover plate substrate and a functional film covering the cover plate substrate, and the functional film includes a multilayer film structure. The multilayer film structure is deposited by the above CVD preparation method, which includes performing bombardment modification on the currently deposited layer with plasma after the completion of the deposition of each layer of the film structure and before the deposition of the next layer of the film structure. The conventional CVD deposition process is only suitable for single-layer film deposition. During the deposition of the multilayer film structure, after the previous layer of film is deposited, the next layer of film cannot be successfully deposited due to a change in the deposition surface. In the present invention, the multilayer film is successfully deposited through the surface modification by plasma bombardment after each layer of the film structure.

[0057] A CLCC package, as shown in FIG. 2, includes the substrate 1. The CMOS 2 is attached in the middle of the substrate 1. The capacitor resistor 3 and the driving motor 4 are attached on the edge of the substrate 1. The separation wall base 5 is provided on the substrate 1. A CMOS sensor vacancy, a capacitor resistor vacancy and a driving motor vacancy are provided at positions on the separation wall base 5 corresponding to the CMOS 2, the capacitor resistor 3 and the driving motor 4 on the substrate, respectively. The cover plate 6 is mounted on the upper surface of the CMOS sensor vacancy.

[0058] A camera module, includes the CLCC package as described above.

Embodiment 1

[0059] A camera module, includes a CLCC package. The CLCC package includes the substrate 1. The CMOS 2 is attached in the middle of the substrate 1. The capacitor resistor 3 and the driving motor 4 are attached on the edge of the substrate 1. The separation wall base 5 is provided on the substrate 1. A CMOS sensor vacancy, a capacitor resistor vacancy and a driving motor vacancy are provided at positions on the separation wall base 5 corresponding to the CMOS 2, the capacitor resistor 3 and the driving motor 4 on the substrate, respectively. The cover plate 6 is mounted on the upper surface of the CMOS sensor vacancy. The size of the particle on the surface of the cover plate 6 is less than or equal to 10 nm, and the roughness Ra of the cover plate 6 is 1.135 nm, as shown in FIGS. 3-5.

[0060] The above cover plate is an optical element of the camera module in which a glass substrate is coated with a SiO.sub.2 low-refractive-index L layer and a TiO.sub.2 high-refractive-index H layer. The low-refractive-index L layer has a thickness of 100-200 nm and a refractive index of 1.46-1.50. The high-refractive-index H layer has a thickness of 350-650 nm and a refractive index of 2.28-2.35.

[0061] The above cover plate is prepared by the CVD preparation method, including the following steps:

[0062] Step S1: Pretreatment, the glass base substrate is firstly placed and cleaned in an ultrasonic cleaner for 60 minutes, and dried to obtain a pre-treated base substrate.

[0063] Step S2: The pre-treated glass base substrate is placed in a reaction chamber, the reaction chamber is evacuated to 0.1-5 Torr, and nitrogen or inert gas is introduced.

[0064] Step S3: Then, silane and oxygen are introduced into the reaction chamber in a pulse mode at 650-700° C. at a flow rate of 60 sccm and a flow rate of 30 sccm, respectively, for 0.015 s and 2000 cycles, to deposit SiO.sub.2 on the base substrate to form a low-refractive-index L layer, wherein a thickness of the low-refractive-index L layer is 100-200 nm.

[0065] Step S4: Introduction of the raw gas silane and oxygen is halted, the reaction chamber is purged with nitrogen or inert gas, and surface modification is performed through plasma bombardment.

[0066] Step S5: At 700-800° C., TiCl.sub.4 and O.sub.2 are introduced into the reaction chamber at a flow rate of 30 sccm and a flow rate of 30 sccm, respectively, for 0.015 s and 2000 cycles, to deposit a TiO.sub.2 high-refractive-index H layer on the low-refractive-index L layer through the reaction, wherein the thickness of the high-refractive-index H layer is 350-650 nm.

[0067] Step S6: Introduction of the raw gas TiCl.sub.4 and O.sub.2 is halted, and the reaction chamber is purged with nitrogen or inert gas.

[0068] Step S7: The reaction chamber is cooled to room temperature to obtain an optical element with coating films having different refractive indices.

[0069] In the present embodiment, the products produced in batches have a diameter of 300 mm and 12 substrates are produced in each batch. The particle condition is monitored through the metallographic microscope, no particles with a particle size greater than 1 μm are observed on all the cover plates, and the qualification rate is 100%. The particle size is further observed, and no particles with a particle size greater than 10 nm are observed.

Embodiment 2

[0070] A camera module includes a CLCC package. The CLCC package includes the substrate 1. The CMOS 2 is attached in the middle of the substrate 1. The capacitor resistor 3 and the driving motor 4 are attached on the edge of the substrate 1. The separation wall base 5 is provided on the substrate 1. A CMOS sensor vacancy, a capacitor resistor vacancy and a driving motor vacancy are provided at positions on the separation wall base 5 corresponding to the CMOS 2, the capacitor resistor 3 and the driving motor 4 on the substrate, respectively. The cover plate 6 is mounted on the upper surface of the CMOS sensor vacancy. The size of particle on the surface of the cover plate 6 is less than or equal to 10 nm, and the roughness Ra of the cover plate 6 is 0.433 nm.

[0071] The above cover plate is an optical element of the camera module in which a crystal substrate is coated with a SiO.sub.2 low-refractive-index L layer and a Nb.sub.2O.sub.5 high-refractive-index H layer. The low-refractive-index L layer has a thickness of 20-50 nm and a refractive index of 1.46-1.50. The high-refractive-index H layer has a thickness of 10-100 nm and a refractive index of 2.1-2.3.

[0072] The above cover plate is prepared by the CVD preparation method, including the following steps:

[0073] Step S1: Pretreatment, the crystal base substrate is firstly placed and cleaned in an ultrasonic cleaner for 60 minutes, and dried to obtain a pre-treated base substrate.

[0074] Step S2: The pre-treated crystal base substrate is placed into a reaction chamber, the reaction chamber is evacuated to 0.1-5 Torr, and nitrogen or inert gas is introduced.

[0075] Step S3: Then, at 550-650° C., silane and oxygen are introduced into the reaction chamber at a flow rate of 10 sccm and a flow rate of 20 sccm, respectively, for 0.010 s and 1000 cycles, to deposit SiO.sub.2 on the base substrate to form a low-refractive-index L layer, wherein the thickness of the low-refractive-index L layer is 20-50 nm.

[0076] Step S4: Introduction of the raw gas silane and oxygen is halted, and the reaction chamber is purged with nitrogen or inert gas, and surface modification is performed through plasma bombardment.

[0077] Step S5: At 700-800° C., NbCl.sub.5 and O.sub.3 are introduced into the reaction chamber at a flow rate of 20 sccm and a flow rate of 20 sccm, respectively, for 0.001 s and 1000 cycles, to deposit a Nb.sub.2O.sub.5 high-refractive-index H layer on the low-refractive-index L layer through the reaction, wherein the thickness of the high-refractive-index H layer is 10-100 nm.

[0078] Step S6: Introduction of the raw gas NbCl.sub.5 and O.sub.3 is halted, and the reaction chamber is purged with nitrogen or inert gas.

[0079] Step S7: The reaction chamber is cooled to room temperature to obtain an optical element with coating films having different refractive indices.

[0080] In the present embodiment, the products produced in batches have a diameter of 80*76*0.21 mm and 156 substrates are produced in each batch. The particle condition is monitored through the metallographic microscope, and no particles with a size greater than 1 μm are observed on all the cover plates. The particle size is further observed, and no particles with a size greater than 10 nm are not observed.

Embodiment 3

[0081] A camera module includes a CLCC package. The CLCC package includes the substrate 1. The CMOS 2 is attached in the middle of the substrate 1. The capacitor resistor 3 and the driving motor 4 are attached on the edge of the substrate 1. The separation wall base 5 is provided on the substrate 1. A CMOS sensor vacancy, a capacitor resistor vacancy and a driving motor vacancy are provided at positions on the separation wall base 5 corresponding to the CMOS 2, the capacitor resistor 3 and the driving motor 4 on the substrate, respectively. The cover plate 6 is mounted on the upper surface of the CMOS sensor vacancy. The size of the particle on the surface of the cover plate 6 is less than or equal to 100 nm, and the roughness Ra of the cover plate 6 is 5.962 nm.

[0082] The above cover plate is an optical element of the camera module in which a sapphire substrate is coated with a MgF.sub.2 low-refractive-index L1 layer, an Al.sub.2O.sub.3 high-refractive-index H layer and a SiO.sub.2 low-refractive-index L2 layer. The MgF.sub.2 low-refractive-index L1 layer has a thickness of 10-20 nm and a refractive index of 1.35-1.4. The Al.sub.2O.sub.3 high-refractive-index H layer has a thickness of 100-200 nm and a refractive index of 1.54-1.62. The SiO.sub.2 low-refractive-index L2 layer has a thickness of 200-300 nm and a refractive index of 1.45-1.47.

[0083] The above cover plate is prepared by the CVD preparation method, including the following steps:

[0084] Step S1: Pretreatment, the sapphire base substrate is firstly placed and cleaned in an ultrasonic cleaner for 60 minutes, and dried to obtain a pre-treated base substrate.

[0085] Step S2: The pre-treated sapphire base substrate is placed into a reaction chamber, the reaction chamber is evacuated to 0.1-5 Torr, and nitrogen or inert gas is introduced.

[0086] Step S3: Then, at 500-700° C., Magnesocene (Cp.sub.2Mg) and fluorine (F.sub.2) are introduced to the reaction chamber at a flow rate of 80 sccm and a flow rate of 80 sccm, respectively, for 0.005 s and 800 cycles, to deposit MgF.sub.2 on the base substrate to form a low-refractive-index L1 layer, wherein the thickness of the low-refractive-index L1 layer is 10-20 nm.

[0087] Step S4: Introduction of Cp.sub.2Mg and F.sub.2 is halted, and the reaction chamber is purged with nitrogen or inert gas, and surface modification is performed through plasma bombardment.

[0088] Step S5: At 600-750° C., Al(CH.sub.3).sub.3 and CO.sub.2 are introduced into the reaction chamber at a flow rate of 90 sccm and a flow rate of 60 sccm, respectively, for 0.015 s and 2000 cycles, to deposit an Al.sub.2O.sub.3 high-refractive-index H layer on the low-refractive-index L layer through the reaction, wherein the thickness of the high-refractive-index H layer is 100-200 nm.

[0089] Step S6: Introduction of the Al(CH.sub.3).sub.3 and CO.sub.2 is halted, and the reaction chamber is purged with nitrogen or inert gas.

[0090] Step S7: Then, at 650-700° C., silane and oxygen are introduced into the reaction chamber at a flow rate of 80 sccm and a flow rate of 80 sccm, respectively, for 0.025 s and 3000 cycles, to deposit SiO.sub.2 on the base substrate to form a low-refractive-index L2 layer, wherein the thickness of the low-refractive-index L layer is 200-300 nm.

[0091] Step S8: Introduction of the silane and oxygen is halted, and the reaction chamber is purged with nitrogen or inert gas.

[0092] Step S9: The reaction chamber is cooled to room temperature to obtain an optical element with coating films having different refractive indices.

[0093] In the present embodiment, the products produced in batches have a diameter of 200 mm and 21 substrates are produced in each batch. The particle condition is monitored through the metallographic microscope, and no particles with a size greater than 1 μm are observed on all the cover plates, and the qualification rate is 100%. The particle size is further observed, and no particles with a size greater than 100 nm are observed.

Comparative Embodiment

[0094] The target product of the present embodiment is the same as that of Embodiment 1, and the adopted vacuum thermal evaporation preparation method includes the following steps:

[0095] Step S1: A base substrate glass is firstly placed in a holder, the holder is placed on an umbrella-shaped rack, and the umbrella-shaped rack is placed in a chamber of a coating machine.

[0096] Step S2: SiO.sub.2 and TiO.sub.2 are placed into crucibles at the left side and the right side of the machine chamber, respectively, the door of the machine chamber is closed, the machine chamber is evacuated to 0.0001-0.001 Pa, and the temperature is set within a range of 50-400° C., wherein the internal pressure of the machine chamber is maintained in the evacuation range.

[0097] Step S3: An electronic gun at the position where SiO.sub.2 is located is turned on. The electronic gun, according to a set film thickness, is stopped when the thickness is reached, and the remaining molecules are pumped by the gas after the electronic gun is stopped. An electronic gun at the position where TiO.sub.2 is located is automatically turned on to perform film coating.

[0098] Step S4: The machine performs cycle coating according to the set number of coating film layers.

[0099] For the products of the Comparative Embodiment, the dot condition is monitored by a metallographic microscope, and the result thereof is shown in FIG. 6. The dot defect with a particle size greater than or equal to 5 μm can be observed. After batch testing, the defect rate of the products obtained using the preparation method due to the dot defect (a particle size greater than or equal to 5 μm) is 70%.

[0100] The foregoing embodiments are only used to illustrate the present invention rather than to limit the present invention. Those having ordinary skill in the art can make various changes and transformations without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions belong to the scope of the present invention, and the scope of protection of the present invention shall be defined by the claims.