A method for improving the uniformity of large-diameter plasma etching by using a curved electrode

Abstract

The present invention relates to a method for improving the uniformity of large-diameter plasma etching by using a curved electrode, which solves the problems of uneven etching rate distribution and difficulty in improving the etching uniformity during the large-diameter plasma etching process. The method includes the following steps: measuring the initial etching rate distribution function; placing m micro-planar electrodes with different thicknesses h on the surface of the lower electrode plate respectively, and performing plasma etching on an unprocessed sample piece respectively; measuring the average etching rate; calculating the functional relationship between the thickness of the micro-planar electrode and the average etching rate; obtaining the thickness distribution of the curved electrode; placing the curved electrode coaxially with the lower electrode plate, and performing plasma etching on an unprocessed sample piece on the workpiece. The method for improving the uniformity of large-diameter plasma etching by using a curved electrode provided by the present invention can design the shape of the curved electrode according to the initial etching rate distribution, has high flexibility, and can effectively improve the uniformity of plasma etching quickly and efficiently.

Description

Technical Field

[0001] The present invention belongs to the manufacturing field of plasma etching processing, and particularly relates to a method for improving the uniformity of large-diameter plasma etching by using a curved surface electrode. Background Art

[0002] In the regulation method of plasma etching processing uniformity, generally, the airflow distribution of reaction gas in the chamber is adjusted by improving the structure or distribution of the air inlet of the shower plate of the etching equipment; or the distribution of plasma is adjusted by optimizing radio frequency (RF) frequency, the number of RF sources, driving power, air pressure, electrode spacing and their related process parameters; or the flow field distribution of the etching gas is adjusted by changing the gas inlet and outlet mode, and then the uniformity of the etching rate is adjusted. Since plasma etching processing is often under constant pressure conditions, the method of improving the structure of the shower plate or changing the gas inlet and outlet mode has a weak ability to regulate etching uniformity. In addition, the influence of different process parameters on plasma is mutually coupled. Therefore, the method of optimizing process parameters is neither flexible and efficient nor easy to implement. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to use a curved surface electrode to improve the uniformity of large-diameter plasma etching processing, and achieve low-cost, efficient and flexible uniform etching of the full diameter plasma. The present invention provides a method for improving the uniformity of large-diameter plasma etching by using a curved surface electrode.

[0004] To achieve the above object, the technical solutions adopted by the present invention are as follows:

[0005] A method for improving the uniformity of large-diameter plasma etching by using a curved surface electrode, comprising the following steps:

[0006] Step 1: Place the tooling with the sample on the surface coaxially with the lower electrode plate, perform plasma etching processing on the sample, and measure the initial etching rate distribution function E = f1(x, y) on the surface of the sample; where E is the etching rate, and (x, y) is the coordinate point on the surface of the sample;

[0007] Step 2: Place m micro planar electrodes with different thicknesses h on the surface of the lower electrode plate respectively, and place them coaxially with the lower electrode plate, and perform plasma etching processing on an unprocessed sample respectively;

[0008] Step 3: When using the m micro planar electrodes with different thicknesses h respectively, measure the average etching rate of the surface area covered by the vertical projection of the micro planar electrode on the sample as where ψ is the coordinate range of the surface area, S(ψ) is the area of the surface area, and f2(x, y) is the etching rate distribution function of the surface area;

[0009] Step 4: Obtain the average etching rate through mathematical fitting And the functional relationship with the thickness h of the micro planar electrode And calculate the thickness h of the micro planar electrode and the average etching rate Of the functional relationship

[0010] Step 5: Calculate the initial etching rate difference ET = f1(x, y) - f1(0, 0) between each part of the surface of the sample piece and the central region of its surface, and obtain the thickness distribution H(x, y) of the curved surface electrode = f3 - 1 (ET) - min(f3 - 1 (ET)); where f1(0, 0) is the etching rate at the center of the surface of the sample piece, and min(f3 -1 (ET)) is the minimum value of f3 -1 (ET);

[0011] Step 6: Place the curved surface electrode with the thickness distribution of H(x, y) coaxially with the lower electrode plate, and perform plasma etching on an unprocessed sample piece on the tooling. After the etching is completed, take out the sample piece to achieve plasma uniform etching of the large-diameter component.

[0012] Furthermore, in the said Step 1, the material of the said sample piece includes a rigid optical substrate or a flexible optical film. The said rigid optical substrate is silica, glass-ceramics, acrylic, silicon or silicon carbide, and the said flexible optical film is polyimide or polyethylene terephthalate; the said lower electrode plate is the lower flat electrode of the plasma etching equipment.

[0013] Furthermore, in the said Step 1, the measuring method for measuring the initial etching rate distribution function on the surface of the said sample piece is laser interferometer measurement, step gauge measurement, profiler measurement or coordinate measuring machine measurement.

[0014] Furthermore, in the said Step 2, the value range of m is 20 ≥ m ≥ 5.

[0015] Furthermore, in the said Step 2, the thickness h of the said m micro planar electrodes forms an arithmetic sequence, the first term of the thickness value is 1 mm, and the last term of the thickness value is 20 mm; the diameters of the said m micro planar electrodes are all not greater than 100 mm.

[0016] Furthermore, in the said Step 3, the measuring method for the said average etching rate is laser interferometer measurement, step gauge measurement, profiler measurement or coordinate measuring machine measurement.

[0017] Furthermore, in the said Step 4, the said Is The inverse function of.

[0018] Further, in the step 5, the lower surface of the curved surface electrode is a plane and is in contact with the lower electrode plate.

[0019] Further, in the step 6, the outer diameter of the curved surface electrode is not greater than the inner diameter of the tooling, and its maximum thickness is not greater than the height of the tooling.

[0020] The advantages of the present invention compared with the prior art are as follows:

[0021] (1) The present invention can avoid mechanical modification of the spraying structure of the plasma etching equipment, which helps to maintain the reliability of the plasma etching equipment and the stability of the processing technology.

[0022] (2) The present invention can reduce the process complexity brought about by the method of improving etching uniformity by optimizing process parameters or modulating multiple radio frequency sources.

[0023] (3) The method of the present invention for improving plasma etching uniformity by using a curved surface electrode, the shape of the curved surface electrode is derived from the initial etching rate distribution when the curved surface electrode is not used. The implementation path of this method has good robustness and high flexibility, which further broadens the application scope of the present invention in realizing the improvement of large-aperture plasma etching uniformity. Description of the Drawings

[0024] Figure 1(a) is a schematic diagram of the measurement steps of the initial etching rate distribution;

[0025] Figure 1(b) is a schematic diagram of the measurement steps of the average etching rate of the micro planar electrode;

[0026] Figure 1(c) is a schematic diagram of the uniform etching steps of the curved surface electrode.

[0027] Wherein: 1 - sample wafer; 2 - tooling; 3 - lower electrode plate; 4 - micro planar electrode; 5 - surface area covered by the vertical projection; 6 - curved surface electrode. Detailed Embodiments

[0028] The present invention will be further described below in conjunction with the drawings and specific embodiments.

[0029] Some process conditions in the embodiment are set as follows: the material of the sample wafer to be processed is silicon dioxide, the equipment used for etching is a capacitively coupled plasma etching equipment, the reaction gases are oxygen and carbon tetrafluoride, the flow ratio is 1:2, the etching power is 500 watts, and the etching chamber pressure is 1.5 Pa.

[0030] As Figures 1(a) - 1(c) shown, the specific process includes:

[0031] Step 1: Place the tooling 2 with the sample piece 1 on its surface coaxially with the lower electrode plate 3 of the plasma etching equipment, perform plasma etching on the sample piece 1, and measure the initial etching rate distribution function E = f1(x, y) on the surface of the sample piece 1 using a laser interferometer;

[0032] Step 2: Place 7 micro planar electrodes 4 with thicknesses h of 2 mm, 5 mm, 8 mm, 11 mm, 14 mm, 17 mm, and 20 mm respectively and a diameter of 50 mm on the surface of the lower electrode plate 3, and place them coaxially with the lower electrode plate 3, and perform plasma etching on an unprocessed sample piece 1 respectively;

[0033] Step 3: Use a laser interferometer to measure the average etching rate of the surface area 5 covered by the vertical projection of the micro planar electrode 4 on the sample piece 1 when using 7 micro planar electrodes 4 with different thicknesses h respectively where f2(x, y) is the etching rate distribution function of the surface area 5, and (x, y) is the coordinate point of the surface area 5;

[0034] Step 4: Through mathematical fitting, obtain the functional relationship between the average etching rate and the thickness h of the micro planar electrode 4 and calculate the thickness h of the micro planar electrode 4 and the average etching rate of the function where is the inverse function of;

[0035] Step 5: Calculate the initial etching rate difference ET = f1(x, y) - f1(0, 0) between each part of the surface of the sample piece 1 and its surface central region, and obtain the thickness distribution H(x, y) of the curved surface electrode 6 = f3 -1 (ET) - min(f3 -1 (ET)); where f1(0, 0) is the etching rate at the center of the surface of the sample piece 1, and min(f3 -1 (ET)) is the minimum value of f3 -1 (ET);

[0036] Step 6: Place the curved surface electrode 6 with the thickness distribution of H(x, y) coaxially with the lower electrode plate 3, and perform plasma etching on an unprocessed sample piece 1 on the tooling 2. After the etching is completed, take out the sample piece 1 to achieve plasma uniform etching of large-diameter components;

[0037] Obviously, the above embodiments are merely examples given for clear illustration and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. And the obvious changes or modifications derived therefrom still fall within the protection scope of the present invention.

Claims

1. A method for improving the uniformity of large - diameter plasma etching by using a curved surface electrode, characterized in that, The following steps are involved: Step 1: Place a tool (2) with a sample (1) on its surface coaxially with a lower electrode plate (3), perform plasma etching on the sample (1), and measure an initial etching rate distribution function E=f1(x, y) on the surface of the sample (1); wherein E is the etching rate and (x, y) is a coordinate point on the surface of the sample (1); Step 2: m micro-planar electrodes (4) with different thicknesses h are respectively placed on the surface of the lower electrode plate (3) and coaxially placed with the lower electrode plate (3), and a piece of unprocessed sample (1) is plasma etched respectively; Step 3: When measuring respectively the mean etching rate of the surface area (5) covered by the vertical projection of the micro planar electrode (4) on the sample piece (1) when using the m micro planar electrodes (4) with different thicknesses h, it is where ψ is the coordinate range of the surface area (5), S(ψ) is the area of the surface area (5), and f2(x, y) is the etching rate distribution function of the surface area (5); Step 4: Obtain the average etching rate through mathematical fitting Function relation with the thickness h of the micro planar electrode (4) And calculate the function relation between the thickness h of the micro planar electrode (4) and the average etching rate of the function relation Step 5: Calculate the initial etching rate difference ET = f1(x, y) - f1(0, 0) between each part of the surface of the sample piece (1) and its central region on the surface, and obtain the thickness distribution H(x, y) of the curved surface electrode (6) = f3 -1 (ET) - min(f3 -1 (ET)); where f1(0, 0) is the etching rate at the center of the surface of the sample piece (1), and min(f3 -1 (ET)) is the minimum value of f3 -1 (ET); Step 6: Place a curved electrode (6) having a thickness distribution of H(x, y) coaxially with the lower electrode plate (3), and perform plasma etching on an unprocessed sample (1) on the tooling (2). After the etching is completed, take out the sample (1) to achieve plasma uniformity etching of large-diameter components.

2. The method of improving the uniformity of large-aperture plasma etching by using a curved electrode according to claim 1, characterized in that: In step 1, the material of the sample (1) includes a rigid optical substrate or a flexible optical film, the rigid optical substrate is silicon dioxide, microcrystalline glass, acrylic, silicon or silicon carbide, and the flexible optical film is polyimide or polyethylene terephthalate; the lower electrode plate (3) is the lower plate electrode of a plasma etching device.

3. The method of improving large-aperture plasma etching uniformity by using curved electrodes according to claim 1, characterized in that: In the step 1, the measurement method of the initial etching rate distribution function on the surface of the measurement sample (1) is laser interferometer measurement, step profiler measurement, profilometer measurement or three-coordinate measurement.

4. The method of improving large-aperture plasma etching uniformity by using curved electrodes according to claim 1, characterized in that: In step 2, the value range of m is 20≥m≥5.

5. The method of improving large-aperture plasma etching uniformity using curved electrodes according to claim 1, characterized in that: In step 2, the thickness h of the m micro-planar electrodes (4) is an arithmetic progression, the first term of the thickness value is 1 mm, and the last term of the thickness value is 20 mm; and the diameter of the m micro-planar electrodes (4) is no greater than 100 mm.

6. The method of improving large-aperture plasma etching uniformity using curved electrodes according to claim 1, characterized in that: In the step 3, the method for measuring the mean etching rate is laser interferometer measurement, step profiler measurement, profilometer measurement or three-coordinate measurement.

7. The method of improving large-aperture plasma etching uniformity by using curved electrodes according to claim 1, characterized in that: In the said step 4, the is inverse function of.

8. The method of improving large-aperture plasma etching uniformity by using curved electrodes according to claim 1, characterized in that: In the step 5, the lower surface of the curved electrode (6) is a plane and is in contact with the lower electrode plate (3).

9. A method for improving the uniformity of large-diameter plasma etching by using a curved electrode according to claim 1, characterized in that: In the step 6, the outer diameter of the curved electrode (6) is not greater than the inner diameter of the tooling (2), and its maximum thickness is not greater than the height of the tooling (2).

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