An etching process method for regulating the etching slope angle of the sidewall of an etched material

Abstract

The application discloses an etching process method for regulating the etching slope angle of the sidewall of an etched material, which comprises the following steps: step 1, cleaning a to-be-etched flat piece and then spin-coating photoresist; step 2, using a lift-off process to manufacture alignment marks, depositing a Ti / Au film on the sample obtained in step 1 after exposure and development, and then peeling off the photoresist to obtain alignment marks for a subsequent photoetch process; step 3, cleaning the sample obtained in step 2 and then spin-coating photoresist again, performing oblique exposure after using a first mask to align the marks, and then forming a photoresist sidewall inclined surface after development; the sample is further exposed to light multiple times through other masks to align the marks, and then multiple-direction photoresist sidewall inclined surfaces are formed after development; step 4, performing dry etching on the sample obtained in step 3 until the depth reaches a set value; and step 5, placing the sample obtained in step 4 into an acetone solution to remove the remaining photoresist, and then obtaining the sidewall slope angle of the etched material. The application mainly relates to the technical field of semiconductors.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductor micro-nano processing and manufacturing technology, and particularly relates to an etching process method for regulating and controlling the etching slope angle of a side wall of an etched material. BACKGROUND

[0002] In the process of preparing most micro-nano devices, the side wall etching angle is a very important process parameter. Most device processes require the side wall etching morphology to be steep and to reduce the side wall etching phenomenon as much as possible. In contrast, some micro-nano devices have special requirements for the side wall etching angle, such as the MEMS direction using anisotropic wet etching to form a "V" groove and a reflective slope of silicon polycrystal, the flexible tactile sensor field using anisotropic wet etching to prepare an inverted pyramid slope structure, a multi-level metal climbing process, the LIGA direction using an etching process to design a side wall inclined demolding angle for the convenience of separating the plated part from the mold after electroplating, and the micro-fluidic direction designing a channel side wall inclined surface, all of which require angle side wall etching of the etched material.

[0003] The existing process for regulating and controlling the side wall etching slope angle of the etched material has the following problems:

[0004] 1) The process parameters such as ICP ion source power, radio frequency power, etching gas flow, and chamber pressure are regulated and controlled to control the horizontal and vertical etching rates in the etching process, so as to regulate and control the side wall etching slope angle. The main problems of this method for regulating and controlling the side wall etching slope angle include: ① There are too many process control parameters, and each process parameter affects and restricts the etching process, so it is difficult to determine the change of the side wall etching slope angle by a single variable; ② A large number of process test experiments are required to calibrate the horizontal and vertical etching rates; and ③ The regulation and control of the side wall etching slope angle for high aspect ratio etching is limited.

[0005] 2) The ion beam incident angle is regulated and controlled to etch the surface of the substrate in a grazing incidence manner. The main problems of this method for regulating and controlling the side wall etching slope angle include: ① It is difficult to regulate and control the side wall etching slope angle for high aspect ratio etching; and ② The etching selectivity is not high, and the deposits easily contaminate the etched material.

[0006] 3) The thick photoresist mask contact exposure method is used to form a trapezoidal or inverted trapezoidal side wall structure for etching. The main problems of this method for regulating and controlling the side wall etching angle include: ① The regulation and control range of the trapezoidal or inverted trapezoidal side wall slope angle of the photoresist is limited; and ② It is difficult to accurately predict the photoresist side wall slope angle by the edge diffraction exposure method. SUMMARY

[0007] The application provides an etching process method for regulating the etching slope angle of the sidewall of an etched material, so as to solve one or more technical problems in the prior art and at least provide a beneficial selection or create conditions.

[0008] The application provides an etching process method for regulating the etching slope angle of the sidewall of an etched material, comprising the following steps:

[0009] Step 1: after cleaning a wafer to be etched, spin-coating photoresist is performed;

[0010] Step 2: using a lift-off process to manufacture an alignment mark, after exposing and developing the sample obtained in step 1, depositing a Ti / Au film, and peeling off the photoresist, an alignment mark for a subsequent photoetch process is obtained;

[0011] Step 3: after cleaning the sample obtained in step 2, spin-coating photoresist is performed again, and after using a first mask plate to align the mark, oblique exposure is performed, and after development, a photoresist sidewall inclined surface is formed; then, through other mask plates, the mark is exposed multiple times, so that after development, a multi-direction photoresist sidewall inclined surface is formed; wherein the oblique exposure refers to an auxiliary device of a photoetch machine, which can arbitrarily deflect the parallel light beams emitted by the photoetch machine at a right angle to the horizontal stage, so as to form parallel ultraviolet light beams incident at an arbitrary angle to the horizontal stage of the photoetch machine;

[0012] Step 4: dry etching is performed on the sample obtained in step 3 until the depth setting value is reached; wherein the etching gas source is SF6 gas, the passivation gas is C4F8, the source power is selected to be 1500-2300 W, the bias power is 20-50 W, and the He leakage is 2-3 mtorr / min;

[0013] Step 5: the sample obtained in step 4 is placed in an acetone solution to remove the remaining photoresist that has not been etched, and finally the sidewall slope angle of the etched material is obtained.

[0014] Further, in step 1, the cleaning method for the wafer to be etched is to clean with acetone-isopropyl alcohol-deionized water, the ultrasonic power is selected to be 30-50 W, the ultrasonic cleaning time is 5-15 minutes, before spin-coating photoresist, the etched material needs to be dried or pretreated with HMDS (hexamethyldisilazane) vapor, preferably HMDS vapor pretreatment, the HDMS pretreatment temperature is set to be 100-200 DEG C; the photoresist is AZ5214 positive photoresist, the coating speed in the first stage is selected to be 450-650 rpm, the time is 5-7 seconds, the coating speed in the second stage is 2000-4000 rpm, the time is 25-35 seconds, the photoresist thickness is 1.6 microns; the pre-baking condition is to select a hot plate in the range of 90-100 DEG C, and the pre-baking time is 55-65 seconds.

[0015] Further, the cleaning method for the etching flat sheet is cleaned by acetone-isopropyl alcohol-deionized water, the ultrasonic power is 40W, the ultrasonic cleaning time is 10 minutes, and the etched material needs to be pretreated by HMDS (hexamethyl disilazane) vapor before spin coating photoresist, wherein the HDMS pretreatment temperature is 150℃.

[0016] The photoresist is AZ5214 positive photoresist, the first stage rotation speed is 500rpm, the time is 6 seconds, the second stage rotation speed is 4000rpm, and the time is 30 seconds, and the photoresist thickness is 1.6 microns; the pre-baking condition is that the hot plate is 95℃, and the pre-baking time is 60 seconds.

[0017] Further, in step 2, the photoresist exposure dose is 20-30mj; the development uses 2.38% tetramethylammonium hydroxide solution, and the development time is in the range of 30-60 seconds; the Ti / Au thin film is preferably formed by magnetron sputtering, the Ti film related process parameters are argon flow 10sccm, working vacuum 2.4Pa, direct current sputtering power 1000W, and deposition thickness Ni 10nm, the Au film related process parameters are argon flow 5sccm, working vacuum 1Pa, direct current sputtering power 500W, and deposition thickness 50nm; then the method of soaking the photoresist in acetone is used to strip the metal film after plating, and then isopropyl alcohol and deionized water are used for ultrasonic cleaning, the ultrasonic power is 40W, and the ultrasonic time is 5 minutes; finally, an oxygen plasma cleaning machine is used for cleaning to remove organic impurities on the wafer surface, the power is 200W, the oxygen flow is 100sccm, and the cavity pressure is 10pa.

[0018] Further, the photoresist exposure dose is 25mj; the development uses 2.38% tetramethylammonium hydroxide solution (TMAH), and the development time is 45 seconds.

[0019] Further, in step 3, the photoresist is AZ4620 photoresist, the first stage rotation speed is selected in the range of 450-650rpm, the time is selected in the range of 5-7 seconds, the second stage rotation speed is selected in the range of 2000-4000rpm, and the time is selected in the range of 25-35 seconds; the pre-baking condition is that the hot plate is 90-100℃, preferably 95℃, the pre-baking time is 120-180 seconds, preferably 150 seconds; the development liquid ratio is 25% TMAH solution:deionized water=1:8, and the development time is in the range of 90-120 seconds, preferably 110 seconds.

[0020] Further, in step 3, the pre-baking condition is that the hot plate is 95℃, and the pre-baking time is 150 seconds; the development time is 110 seconds.

[0021] The present application has at least the following beneficial effects: the wafer sidewall etching slope angle in different directions can be controlled by adjusting one or two of the three variables, i.e. the exposure beam incident angle, the photoresist thickness and the etching selectivity ratio. BRIEF DESCRIPTION OF DRAWINGS

[0022] The accompanying drawings are included to provide a further understanding of the technical scheme of the present application, and constitute a part of the specification, and are used together with the embodiments of the present application to explain the technical scheme of the present application, and do not constitute a limitation on the technical scheme of the present application.

[0023] Figure 1 is a SEM image of the photoresist sidewall slope after the oblique exposure photolithography and development of the present application;

[0024] Figure 2 is a step profiler test image of the photoresist sidewall slope of the present application;

[0025] Figure 3 is a SEM image of the sidewall etching slope angle of the etched material of the present application;

[0026] Figure 4 is a sidewall etching slope process flow diagram of wafer 1 and wafer 2 under the condition of a certain photoresist thickness and etching selectivity ratio, and different exposure beam incident angles;

[0027] Figure 5 is a sidewall etching slope process flow diagram of wafer 1 and wafer 2 under the condition of a certain exposure beam incident angle and etching selectivity ratio, and different photoresist thicknesses;

[0028] Figure 6 is a sidewall etching slope process flow diagram of wafer 1 and wafer 2 under the condition of a certain exposure beam incident angle and photoresist thickness, and different etching selectivity ratios;

[0029] Figure 7 is a sidewall etching slope process flow diagram of wafer 1 and wafer 2 under the condition of a certain etching rate selectivity ratio and photoresist thickness, and different exposure beam incident angles in different directions. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and do not limit the present application.

[0031] It should be noted that although the functional modules are divided in the system schematic diagram, and the logical sequence is shown in the flowchart, in some cases, the steps shown or described can be used in a manner different from the module division in the system or the sequence in the flowchart. The terms "first", "second", and the like in the specification and claims and the above drawings are used to distinguish similar objects, and do not necessarily describe a specific order or sequence.

[0032] The present application provides a new etching process for preparing a side wall inclined surface. It provides a new design idea for preparing different angle silicon side wall inclined surfaces by using different crystal direction bulk silicon wet etching in the MEMS industry.

[0033] To achieve the above object and other related objects, the technical scheme provided by the present application is as follows: an etching process method for regulating the etching inclined surface angle of the etched material side wall is provided, comprising the following steps:

[0034] (1) After cleaning the single crystal silicon wafer or other to-be-etched flat sheet, spin-coat photoresist;

[0035] (2) The alignment mark mark is made by using the lift-off process, the sample obtained in step (1) is exposed and developed after depositing a Ti / Au thin film, and the photoresist is stripped to obtain the alignment mark mark of the subsequent photoetch process;

[0036] (3) The sample obtained in step (2) is cleaned and spin-coated with photoresist again, and the alignment mark mark is aligned with the first mask, then inclined exposure is performed, and after development, photoresist side wall inclined surface is formed, and then other mask is used to continue to align the mark for multiple times of exposure, so that multiple direction photoresist side wall inclined surface is formed after development, as shown in Figure 1 and Figure 2

[0037] (4) Dry etching is performed on the sample obtained in step (3) to a depth setting value; wherein the etching gas source is SF6 gas, the passivation gas is C4F8, the source power is selected to be 1500-2300W, the bias power is 20-50W, and the He leakage is 2-3mtorr / min;

[0038] (5) The sample obtained in step (4) is placed in an acetone solution to remove the remaining photoresist which is not etched, and the final etched material side wall inclined surface pattern is as shown in Figure 3

[0039] It should be noted that the alignment mark mark of the subsequent photoetch process can be made by plating (the film material can be freely selected), or can be made by etching.

[0040] ​​As a preferred option, the cleaning method of step (1) uses acetone-isopropyl alcohol-deionized water, the ultrasonic power is selected to be 30-50 W, preferably 40 W, the ultrasonic cleaning time is 5-15 minutes, preferably 10 minutes; before spin coating photoresist, the wafer and other etched materials need to be dried or pretreated with HMDS (hexamethyl disilazane) vapor, preferably HMDS vapor pretreatment, the HDMS pretreatment temperature is set to be 100-200°C, preferably 150°C; the photoresist selected is AZ5214 positive resist, the first-stage spin coating speed is selected to be 450-650 rpm, the time is 5-7 seconds, the second-stage spin coating speed is 2000-4000 rpm, the time is 25-35 seconds, preferably the spin coating speed is 500 rpm / 6 s, 4000 rpm / 30 s, and the photoresist thickness is about 1.6 microns; the pre-baking condition is selected to be a hot plate 90-100°C, preferably 95°C, and the pre-baking time is 55-65 seconds, preferably 60 seconds.

[0041] As a preferred option, the photoresist exposure dose of step (2) is selected to be 20-30 mj, preferably 25 mj; the development uses 2.38% tetramethylammonium hydroxide solution (TMAH), the development time is in the range of 30-60 seconds, preferably 45 seconds; the Ti / Au thin film is preferably formed by magnetron sputtering, the Ti film related process parameters are selected to be argon (Ar) flow rate 10 sccm, working vacuum 2.4 Pa, direct current sputtering power 1000 W, and deposition thickness Ni 10 nm, the Au film related process parameters are selected to be argon (Ar) flow rate 5 sccm, working vacuum 1 Pa, direct current sputtering power 500 W, and deposition thickness 50 nm; then the method of acetone immersion is used to strip the photoresist after film plating, followed by isopropyl alcohol and deionized water ultrasonic cleaning, the ultrasonic power is selected to be 40 W, and the ultrasonic time is 5 minutes; finally, an oxygen plasma cleaning machine is used for cleaning to remove organic impurities on the wafer surface, the power is selected to be 200 W, the oxygen flow rate is 100 sccm, and the cavity pressure is 10 Pa.

[0042] As a preferred option, the photoresist of step (3) is selected as AZ4620 photoresist, and the pre-treatment of the wafer to be etched before coating is consistent with the foregoing, the coating speed is selected in the range of 450-650 rpm in the first stage, the time is selected in the range of 5-7 seconds, the speed is selected in the range of 2000-4000 rpm in the second stage, and the time is selected in the range of 25-35 seconds; the pre-baking condition is selected as a hot plate in the range of 90-100°C, preferably 95°C, the pre-baking time is 120-180 seconds, preferably 150 seconds; the developing solution is selected as 25% TMAH solution: deionized water = 1:8, the developing time is in the range of 90-120 seconds, preferably 110 seconds; the oblique exposure is a kind of auxiliary device of a photoetching machine, which can arbitrarily deflect the parallel light beam emitted by the photoetching machine at a right angle to the horizontal wafer table by adjusting the deflection angle of the reflecting mirror, thereby forming a parallel ultraviolet light beam incident at an arbitrary angle to the horizontal wafer table of the photoetching machine, as shown in Figure 1 、 Figure 2 The oblique exposure photoresist side wall inclined plane SEM and step instrument test graph.

[0043] The specific implementation under different conditions is as follows:

[0044] Example 1: This example mainly illustrates that under the condition of fixed photoresist thickness and etching selection, different exposure incident angles, the specific process is as follows:

[0045] (1) After cleaning the surface of two wafers (wafer 1 and wafer 2), spin-coat photoresist;

[0046] (2) Use the lift-off process line to first make a post-etching process alignment mark on the surface of the two wafers (wafer 1 and wafer 2); specifically, after exposure and development, deposit Ti / Au film on the two wafers (wafer 1 and wafer 2), and after stripping the photoresist, the post-etching process alignment mark is obtained; after cleaning, spin-coat photoresist again, and the spin-coater speed is the same, i.e. the thickness of the obtained photoresist is the same, which is H.

[0047] (3) The sample obtained in step (2) is subjected to oblique exposure using a first mask, wherein the oblique exposure incident angle of wafer 1 is θ1 (the angle between the incident light and the wafer plane), and the oblique exposure incident angle of wafer 2 is θ2, and then a second mask is used to align the alignment marks of wafer 1 and wafer 2 respectively, and then subjected to secondary exposure, wherein the ultraviolet light beam is perpendicular to the incident, and the purpose is to eliminate the photoresist inverse slope side wall formed by the oblique exposure of the photoresist side wall inclined plane; as shown in Figure 4 Figure 4 ​Figure A on the left side of the dashed line in the middle of the drawing represents a wafer 1 side wall etching slope process diagram at different exposure beam incident angles under the condition of a certain photoresist thickness and etching selectivity ratio, Figure 4 Figure B on the right side of the dashed line in the middle of the drawing represents a wafer 2 side wall etching slope process diagram at different exposure beam incident angles under the condition of a certain photoresist thickness and etching selectivity ratio.

[0048] After development in the above manner, the wafer 1 photoresist side wall slope angle β1 is β1 = θ1 = arctan (H / L1), wherein θ1 is the angle between the exposure beam and the wafer 1 plane, H is the photoresist thickness, and L1 is the horizontal length of the photoresist side wall slope; the wafer 2 photoresist side wall slope angle β2 is β2 = θ2 = arctan (H / L2), wherein θ2 is the angle between the exposure beam and the wafer 2 plane, H is the photoresist thickness, and L2 is the horizontal length of the photoresist side wall slope; L1 and L2 are also related to the photoresist thickness and the exposure beam incident angle, and are L1 = H*cot (θ1), L2 = H*cot (θ2), H being the photoresist thickness;

[0049] (4) Dry etching is performed on the sample obtained in step (3), and the etching conditions are as follows: the etching gas source is SF6 gas, the passivation gas is C4F8, the source power is 1500-2300 W, the bias power is 20-50 W, and the He leakage is 2-3 mtorr / min. The etching conditions of wafer 1 and wafer 2 are the same, i.e., the etching rate and the etching selectivity ratio are consistent, so that with the passage of etching time, the surface etching morphology of the two wafers will copy the photoresist side wall morphology according to the fixed etching ratio, and finally a certain side wall etching slope angle will be formed. Since the horizontal size of the side wall etching slope is fixed equal to the horizontal size of the photoresist side wall slope, and the etching selectivity ratio of the photoresist to the wafer material to be etched is 1:X, the etching angle γ1 of the wafer 1 side wall etching slope is γ1 = arctan (X*H / L1), and the etching angle γ2 of the wafer 2 side wall etching slope is γ2 = arctan (X*H / L2), while the photoresist side wall slope angle β1 = θ1 = arctan (H / L1), β2 = θ2 = arctan (H / L2), so tan γ1 = X*tan (β1) = X*tan (θ1), tan γ2 = X*tan (β2) = X*tan (θ2).

[0050] From the above formula derivation and Figure 4As shown, when the photoresist thickness and etching selectivity are constant, the relationship between the sidewall etching angle of the wafer material and the incident angle of the ultraviolet exposure beam is: tanγ=X*tan(θ), where γ is the angle between the sidewall etching slope and the horizontal direction, X is the etching selectivity between the etched material and the photoresist in dry etching, and θ is the angle between the exposure beam and the wafer plane; the horizontal length of the sidewall etching slope is equal to the horizontal length L of the photoresist sidewall slope, L=H*cotθ, where H is the photoresist thickness. Therefore, under the condition of constant photoresist thickness and etching selectivity, the angle of the sidewall etching slope of the etched material can be controlled by adjusting the incident angle θ of the exposure beam.

[0051] Example 2 mainly illustrates the process of using a fixed exposure beam incident angle and etching selectivity with different photoresist thicknesses. The specific process is as follows:

[0052] (1) After cleaning the surfaces of the two wafers (wafer1 and wafer2, respectively), spin-coating photoresist is performed.

[0053] (2) Using a lift-off process line, alignment marks for the subsequent photolithography process are first fabricated on the surfaces of two wafers (wafer1 and wafer2, respectively). Specifically, the two wafers (wafer1 and wafer2, respectively) are exposed and developed, and then Ti / Au films are deposited. After the photoresist is stripped off, the alignment marks for the subsequent photolithography process are obtained. After cleaning, the photoresist is spin-coated a second time using different coating speeds, and finally the photoresist thicknesses of wafer1 and wafer2 are H1 and H2, respectively.

[0054] (3) After aligning the samples obtained in step (2) with the first mask and the wafer alignment mark, perform tilt exposure. The incident angle of the tilt exposure on wafer1 and wafer2 is the same, θ (the angle between the incident light and the wafer plane). Then, after aligning the second mask with the alignment mark on wafer1 and wafer2 respectively, perform a second exposure. The ultraviolet light beam of the second exposure is incident perpendicularly. The purpose is to eliminate the photoresist reverse bevel sidewalls formed by the tilt exposure. Figure 5 As shown. Figure 5 Figure A, to the left of the middle dashed line, represents the process flow diagram of sidewall etching of wafer 1 with different photoresist thicknesses under the condition that the incident angle of the exposure beam and the etching selectivity are constant. Figure 5 Figure B to the right of the middle dashed line represents the process flow diagram of sidewall etching slopes with different photoresist thicknesses for wafer 2 under the condition that the incident angle of the exposure beam and the etching selectivity are constant.

[0055] After developing in the above manner, the wafer 1 photoresist sidewall bevel angle β1 is β1 = θ = arctan(H1 / L1), wherein θ is the angle between the exposure beam and the wafer 1 plane, H1 is the photoresist thickness, and L1 is the photoresist sidewall bevel horizontal length; the wafer 2 photoresist sidewall bevel angle β2 is β2 = θ = arctan(H2 / L2), wherein θ is the angle between the exposure beam and the wafer 2 plane, H2 is the photoresist thickness, and L2 is the photoresist sidewall bevel horizontal length; and the relationship between L1, L2, the photoresist thickness, and the incident beam angle is L1 = H1*cot(θ) and L2 = H2*cot(θ);

[0056] (4) Dry etching is performed on the sample obtained in step (3), and the etching conditions are as described above. The etching conditions are as follows: the etching gas source is SF6 gas, the passivation gas is C4F8, the source power is 1500-2300 W, the bias power is 20-50 W, and the He leakage is 2-3 mtorr / min. The wafer 1 and the wafer 2 have the same etching conditions, that is, the etching rate and the etching selectivity ratio are consistent, so as the etching time elapses, the wafer surface etching morphology of the two wafers will copy the photoresist sidewall morphology according to a fixed etching ratio, and finally a certain sidewall etching bevel angle is formed. Since the sidewall etching bevel horizontal size is fixed and equal to the photoresist sidewall bevel horizontal size, and the etching selectivity ratio of the photoresist and the wafer material is 1:X, the etching angle γ1 of the wafer 1 sidewall etching bevel is γ1 = arctan(X*H1 / L1), and the etching angle γ2 of the wafer 2 sidewall etching bevel is γ2 = arctan(X*H2 / L2), while the photoresist sidewall bevel angle β1 = θ = arctan(H1 / L1) and β2 = θ = arctan(H2 / L2) in the previous step, so tanγ1 = X*tan(β1) = X*tan(θ) and tanγ2 = X*tan(β2) = X*tan(θ) are derived.

[0057] As shown by the above formula derivation and Figure 5 Under the condition that the exposure beam incident angle and the etching selectivity ratio are certain values, the sidewall etching bevel angle of the etched wafer material is still tanγ = X*tanθ, wherein γ is the angle between the sidewall etching bevel and the horizontal direction, X is the etching selectivity ratio of the etched material and the photoresist in the dry etching mode, and θ is the angle between the exposure beam and the wafer plane, that is, the sidewall etching bevel angle is a certain value. The sidewall etching bevel horizontal length is equal to the photoresist sidewall bevel horizontal length L, L = H*cotθ, and H is the photoresist thickness. Therefore, under the condition that the exposure beam incident angle and the etching selectivity ratio are certain, the purpose of adjusting the sidewall etching bevel angle to be the same at different etching depths can be achieved by adjusting the photoresist thickness.

[0058] Example 3 mainly illustrates different etching selectivity ratios under fixed exposure beam incident angle and photoresist thickness. The specific process is as follows:

[0059] (1) After cleaning the surfaces of the two wafers (wafer1 and wafer2, respectively), spin-coating photoresist is performed.

[0060] (2) Using a lift-off process line, alignment marks for the subsequent photolithography process are first fabricated on the surfaces of two wafers (wafer1, wafer2). After cleaning, photoresist is spin-coated using the same coating speed, resulting in photoresist thickness H on wafer1 and wafer2.

[0061] (3) After aligning the samples obtained in step (2) with the alignment marks on the wafer using the first mask, perform tilt exposure. The incident angles of the tilt exposures on wafer1 and wafer2 are the same, θ (the angle between the incident light and the wafer plane). Then, after using the second mask to perform a second exposure on the alignment marks on wafer1 and wafer2 respectively, the ultraviolet beam is incident perpendicularly. The purpose of this second exposure is to eliminate the photoresist reverse bevel sidewalls formed by the tilt exposure. Figure 6 As shown. Figure 6 Figure A, to the left of the middle dashed line, represents the process flow diagram of sidewall etching bevels for wafer 1 under the condition of a fixed exposure beam incident angle and photoresist thickness, with different etching selectivity ratios. Figure 6 Figure B to the right of the middle dashed line represents the process flow diagram of sidewall etching slope of wafer2 under the condition that the incident angle of the exposure beam and the thickness of the photoresist are constant, with different etching selectivity ratios.

[0062] After development as described above, the angles of the photoresist sidewall slopes of wafer1 and wafer2 are β1 and β2, respectively, where β1 = β2 = θ = arctan(H / L), θ is the angle between the exposure beam and the wafer plane, H is the photoresist thickness, and L is the horizontal length of the photoresist sidewall slope; at the same time, the horizontal lengths of the photoresist sidewall slopes of wafer1 and wafer2 are the same, L = H * cot(θ).

[0063] (4) Dry etching the sample obtained in step (3), wafer 1 and wafer 2 are selected to have different etching parameter conditions, i.e. different etching rate and etching selectivity. With the elapse of etching time, the etching morphology of the surfaces of the two wafers will replicate the morphology of the photoresist sidewall according to different etching ratios, and finally different sidewall etching bevel angles are formed. Since the horizontal dimension of the sidewall etching bevel is fixed, i.e. equal to the horizontal dimension of the photoresist sidewall bevel, and the etching selectivity of the photoresist and wafer 1 is 1: X1, and the etching selectivity of the photoresist and wafer 2 is 1: X2, then the etching angle γ1 of the wafer 1 sidewall etching bevel is γ1 = arctan (X1*H / L), and the etching angle γ2 of the wafer 2 sidewall etching bevel is γ2 = arctan (X2*H / L), and the sidewall bevel angle β1 = β2 = θ = arctan (H / L) of the photoresist sidewall bevel in the previous step is equal;

[0064] Thus, tan γ1 = X1*tan (β1) = X1*tan (θ), tan γ2 = X2*tan (β2) = X2*tan (θ).

[0065] As shown by the above formula derivation and Figure 6 As shown by the above formula derivation and

[0066] In example 4, the wafer is exposed to different angles of incident light beams in different directions under the same etching rate and photoresist thickness, and the specific process is as follows:

[0067] (1) After cleaning the surfaces of two wafers (wafer 1 and wafer 2), photoresist is spin-coated on the surfaces of the two wafers;

[0068] (2) Using the lift-off process, first mark alignment marks are made on the surfaces of the two wafers (wafer 1 and wafer 2) by using the last photoetching process. After cleaning and spin-coating photoresist, the spin coater has the same speed, i.e. the photoresist thickness is H.

[0069] (3) The sample obtained in step (2) is subjected to oblique exposure after aligning the wafer alignment mark mark using the first mask, as shown in Figure 6 wafer 1 and wafer 2 are subjected to oblique exposure at an incident angle of θ1 (the angle between the incident light and the wafer plane) on the right side, wafer 1 is subjected to secondary exposure using the second mask to align the mark, and the secondary exposure ultraviolet light beam is perpendicular to the incident, which aims to eliminate the inverse bevel of the photoresist bevel formed by the oblique exposure, and the photoresist bevel on the left side of wafer 1 is vertical. Wafer 2 is subjected to secondary exposure using the second mask to align the wafer alignment mark, and the secondary exposure wafer 2 is subjected to exposure with an incident angle of θ2 from the left side of wafer 2, which aims to eliminate the inverse bevel of the photoresist bevel formed by the oblique exposure, and form a photoresist bevel on the left side of wafer 2, as shown in Figure 7 . Figure 7 Figure A on the left side of the dashed line in the middle of the above figure represents a schematic diagram of the sidewall etching bevel process of wafer 1 under the condition of the same etching rate selection ratio and photoresist thickness when the incident angle of the exposure light beam is different in different directions, Figure 7 Figure B on the right side of the dashed line in the middle of the above figure represents a schematic diagram of the sidewall etching bevel process of wafer 2 under the condition of the same etching rate selection ratio and photoresist thickness when the incident angle of the exposure light beam is different in different directions. The photoresist-related sidewall bevel angle is similar to other embodiments and is not derived here;

[0070] (4) The sample obtained in step (3) is subjected to dry etching, and the etching conditions of wafer 1 and wafer 2 are the same, that is, the etching rate and the etching selection ratio are consistent, so that with the passage of etching time, the sidewall etching morphology in different directions on the surface of the two wafers will copy the photoresist sidewall morphology according to a fixed etching ratio, and finally form a determined etching sidewall bevel angle. Since the horizontal dimension of the etching sidewall bevel is fixed and equal to the horizontal dimension of the photoresist sidewall bevel, and since the etching rate and the selection ratio in different directions of the wafer are consistent, it can be known from the related derivation in Embodiment 1 that the angle of the sidewall etching bevel in different directions of the etched material is positively correlated with the incident angle of the exposure light beam in that direction, thereby realizing the control of different bevel angles of the sidewall etching in different directions of the etched material.

[0071] As shown in the above related derivation and Figure 7 , under the condition of a certain photoresist thickness and etching selection ratio, by controlling the different incident angles of the exposure light beam in different directions of the wafer, the control of different bevel angles of the sidewall etching in the corresponding direction of the etched material can be independently and respectively realized.

[0072] The control of the sidewall etching slope angle of the wafer in different directions can be realized simply by adjusting one or two of the three variables, i.e. the incident angle of the exposure light beam, the thickness of the photoresist and the etching selectivity. As shown in Example 1, under the condition that the thickness of the photoresist and the etching selectivity are constant, the sidewall etching slope angle can be controlled by adjusting the incident angle of the exposure light beam. As shown in Example 2, under the condition that the incident angle of the exposure light beam and the etching selectivity are constant, the sidewall etching slope angle can be controlled by adjusting the thickness of the photoresist at different etching depths, thereby realizing the control of the sidewall slope angle of high aspect ratio. As shown in Example 3, under the condition that the incident angle of the exposure light beam and the thickness of the photoresist are constant, the sidewall etching slope angle of the etched material can be controlled by adjusting the etching selectivity of the etched material and the photoresist in the dry etching process, and in this case, only the etching stability of the dry etching equipment needs to be controlled, which avoids the control of the complex control parameters in the etching process to control the sidewall etching slope angle. As shown in Example 4, under the condition that the etching selectivity and the thickness of the photoresist are constant, the sidewall etching slope angle in different directions of the etched material can be controlled independently by adjusting the incident angle of the exposure light beam in different directions.

[0073] The preferred embodiments of the present application are described in detail above, but the present application is not limited to the embodiments described above. Those skilled in the art can make various equivalent modifications or replacements without departing from the spirit of the present application, and these equivalent modifications or replacements are all included in the scope defined by the claims of the present application.

Claims

1. An etching process method for controlling the angle of the etching bevel on the sidewall of the material to be etched, characterized in that, The application comprises the following steps: Step 1, cleaning and spin coating photoresist on a flat piece to be etched; Step 2, using lift-off process to make alignment mark, depositing Ti / Au film after exposing and developing the sample obtained in step 1, and peeling off the photoresist to obtain alignment mark for subsequent photolithography process; Step 3, cleaning the sample obtained in step 2 and spin coating photoresist again, performing oblique exposure after using the first mask to align the mark, forming photoresist side wall inclined surface after development, and then continuing to align the mark by using other masks to perform multiple exposures, thereby forming multi-direction photoresist side wall inclined surface after development; wherein the oblique exposure refers to a kind of auxiliary device of a photoetching machine, which can arbitrarily deflect the parallel light beam emitted by the photoetching machine at a right angle to the horizontal stage, thereby forming a parallel ultraviolet light beam incident at an arbitrary angle to the horizontal stage of the photoetching machine; Step 4, dry etching the sample obtained in step 3 to a depth setting value; wherein the etching gas source is SF6 gas, the passivation gas is C4F8, the source power is selected as 1500-2300 W, the bias power is 20-50 W, and the He leakage is 2-3 mtorr / min; Step 5, placing the sample obtained in step 4 into an acetone solution to remove the remaining photoresist that has not been etched, and finally obtaining the angle of the etched material side wall inclined surface; In step 1, the cleaning of the flat piece to be etched is performed by using acetone-isopropyl alcohol-deionized water, the ultrasonic power is selected as 30-50 W, the ultrasonic cleaning time is 5-15 minutes, the etched material needs to be dried or treated with HMDS (hexamethyldisilazane) vapor before spin coating photoresist, the HDMS pretreatment temperature is set as 100-200 DEG C; the photoresist is AZ5214 positive photoresist, the first stage rotation speed is selected as 450-650 rpm, the time is 5-7 seconds, the second stage rotation speed is 2000-4000 rpm, the time is 25-35 seconds, and the photoresist thickness is 1.6 microns; the pre-baking condition is that the hot plate is selected as 90-100 DEG C, and the pre-baking time is 55-65 seconds.

2. The method of claim 1, wherein the etching process is configured to control the etch slope angle of the sidewall of the etched material. The cleaning of the flat piece to be etched is performed by using acetone-isopropyl alcohol-deionized water, the ultrasonic power is selected as 40 W, the ultrasonic cleaning time is 10 minutes, and the etched material needs to be treated with HMDS (hexamethyldisilazane) vapor before spin coating photoresist, wherein the HDMS pretreatment temperature is set as 150 DEG C; The photoresist is AZ5214 positive photoresist, the first stage rotation speed is selected as 500 rpm, the time is 6 seconds, the second stage rotation speed is 4000 rpm, the time is 30 seconds, the photoresist thickness is 1.6 microns, the pre-baking condition is that the hot plate is selected as 95 DEG C, and the pre-baking time is 60 seconds.

3. The method of claim 1, wherein the etching process is a method of controlling the etching slope angle of the sidewall of the etched material. In step 2, the photoresist exposure dose is selected as 20-30 mj; development is performed using a 2.38% tetramethylammonium hydroxide solution, and the development time is in the range of 30-60 seconds; the Ti / Au thin film is formed by magnetron sputtering, the Ti film related process parameters are selected as argon flow rate 10 sccm, working vacuum 2.4 Pa, direct current sputtering power 1000 W, and deposition thickness Ni 10 nm, the Au film related process parameters are selected as argon flow rate 5 sccm, working vacuum 1 Pa, direct current sputtering power 500 W, and deposition thickness 50 nm; then the metal film after plating is stripped by the method of acetone immersion to strip the photoresist, followed by ultrasonic cleaning using isopropyl alcohol and deionized water, respectively, the ultrasonic power is selected as 40 W, and the ultrasonic time is 5 minutes; finally, an oxygen plasma cleaning machine is used for cleaning to remove the organic impurities on the wafer surface, the power is selected as 200 W, the oxygen flow rate is 100 sccm, and the cavity pressure is 10 Pa.

4. The method of claim 3, wherein the etching process is a method of controlling the etching slope angle of the sidewall of the etched material. The photoresist exposure dose is selected as 25 mj; development is performed using a 2.38% tetramethylammonium hydroxide solution (TMAH), and the development time is 45 seconds.

5. The method of claim 1, wherein the etching process is a method of controlling the etching slope angle of the sidewall of the etched material. In step 3, the photoresist used is AZ4620 photoresist, the coating rotation speed is selected in the range of 450-650 rpm for the first stage, the time is in the range of 5-7 seconds, the second stage rotation speed is selected in the range of 2000-4000 rpm, and the time is in the range of 25-35 seconds; the pre-baking condition is selected as a hot plate 90-100℃, and the pre-baking time is 120-180 seconds; the developing solution ratio is 25% TMAH solution: deionized water = 1:8, and the development time is in the range of 90-120 seconds.

6. The method of claim 5, wherein the etching process is configured to control the etch slope angle of the sidewall of the etched material. In step 3, the pre-baking condition is selected as a hot plate 95℃, the pre-baking time is 150 seconds, and the development time is 110 seconds.

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