Etching and stripping process for titanium metal connection layer in MEMS product

Abstract

A kind of etching and stripping process of titanium metal connecting layer in MEMS product includes the following steps: step one, providing the composite film layer to be etched, the composite film layer includes silicon substrate, silicon nitride film layer, titanium film and aluminum film layer;Step two, photoresist is arranged on the aluminum film layer, so that the aluminum film layer of the top layer covered by photoresist and the aluminum film layer of the top layer adjacent to the aluminum film layer covered by photoresist is exposed;Step three, the composite film layer is placed in the first chamber of wet etching, and the exposed part of the aluminum film layer of the top layer is etched in the first chamber;Step four, wet stripping is used;Step five, the composite film layer completed in step four is photoresist arranged, and groove is formed;Step six, the composite film layer completed in step five is placed in the second chamber, and titanium film etching is carried out along the groove;Step seven, stripping in photoresist removal equipment;Step eight, long film is formed on the titanium film and the aluminum film layer to form silicon nitride cover layer.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of semiconductor, and more particularly to a titanium metal connection layer etching and stripping process in a MEMS product. BACKGROUND

[0002] In a MEMS product, titanium metal is often used as a connection layer. The etching and stripping of titanium as a connection layer is an important aspect to be considered in the overall process control of the MEMS product, and needs to be further studied and improved. SUMMARY

[0003] In view of the problems in the background art, the purpose of the present disclosure is to provide a titanium metal connection layer etching and stripping process in a MEMS product, which improves the etching and stripping method of the titanium thin film layer as a titanium metal connection layer in a MEMS product to avoid the impact of titanium oxidation.

[0004] Thus, a titanium metal connection layer etching and stripping process in a MEMS product includes the following steps: Step one, providing a composite film layer to be etched, the composite film layer including a silicon substrate, a bottom silicon nitride film layer, a titanium thin film layer, and a top aluminum film layer arranged in order from bottom to top; Step two, patterning photoresist on the top aluminum film layer to cover part of the top aluminum film layer and expose the top aluminum film layer on both sides adjacent to the part covered by the photoresist; Step three, placing the composite film layer with the completed photoresist of Step two in a first chamber for wet etching, and etching from the exposed part of the top aluminum film layer in the first chamber, with the etching time set to etch until the exposed part of the top aluminum film layer is etched completely and the surface of the corresponding titanium thin film layer is exposed; Step four, placing the composite film layer with the exposed surface of the corresponding titanium thin film layer of Step three in a photoresist stripping device for wet stripping; Step five, patterning photoresist on the composite film layer of Step four to cover the aluminum film layer on the titanium thin film layer and cover the titanium thin film on both sides of the aluminum film layer through the exposed part of the titanium thin film, with the exposed part of the titanium film layer corresponding to the trench formed by the photoresist; Step six, placing the composite film layer of Step five in a second chamber for titanium thin film etching along the trench, with the etching time set to etch until the part of the titanium thin film exposed by the trench is etched completely and the bottom silicon nitride film layer is exposed; Step seven, placing the composite film layer with the exposed bottom silicon nitride film layer of Step six in a photoresist stripping device for stripping; and Step eight, forming a silicon nitride cover layer on the titanium thin film and the aluminum film layer of the composite film layer of Step seven.

[0005] The beneficial effects of the present disclosure are as follows: in the titanium metal connection layer etching and stripping process of the MEMS product of the present disclosure, the stripping in step four adopts a wet method, which avoids the oxidation of the exposed titanium by dry stripping with O2 (the dry stripping is performed at high temperature, so the oxidation speed of the exposed titanium is fast and the oxidation degree is high), the wet stripping in step four is performed before the titanium film layer etching in step six, which avoids the influence of the titanium oxide formed by the dry etching of the exposed titanium film layer in step four on the etching rate, etching uniformity and even the obtained morphology of the subsequent etching of the exposed titanium film layer in step six, in addition, based on the wet stripping in step four, it is beneficial to completely and easily remove the polymer formed in the titanium metal connection layer etching and stripping process, thereby avoiding the negative influence of the polymer residue on the performance, internal structure and the like of the MEMS product composed of the composite film layer. BRIEF DESCRIPTION OF DRAWINGS

[0006] Figure 1 is a schematic view of the composite film layer.

[0007] Figure 2 is a schematic view of the composite film layer.

[0008] Figure 3 is a schematic view of the composite film layer.

[0009] Figure 4 is a schematic view of the composite film layer. Figure 3

[0010] Figure 5 is a schematic view of the composite film layer. Figure 4

[0011] Figure 6 is a schematic view of the composite film layer. Figure 5

[0012] Figure 7 and Figure 8 is a schematic view of the composite film layer. Figure 6

[0013] Figure 9 is a schematic view of the composite film layer. Figure 8

[0014] Figure 10 shows the SEM photo of the part of the MEMS product corresponding to the composite film layer after the completion of step seven of Comparative Example 1. ​​​​​

[0015] Figure 11 A TEM photo of a cross section of a part of the MEMS product corresponding to the composite film layer after completion of step eight of Comparative Example 1 is shown.

[0016] Figure 12 A partial enlarged view of Figure 11 is shown.

[0017] Figure 13 A whole SEM photo of the MEMS device containing the composite film layer after completion of step seven of Comparative Example 1 is shown.

[0018] Figure 14 A SEM photo of a part of the MEMS product corresponding to the composite film layer after completion of step seven of Example 1 is shown.

[0019] Figure 15 A whole SEM photo of the MEMS device containing the composite film layer after completion of step seven of Example 1 is shown.

[0020] Figure 16 The effect of time in air on the etching rate of titanium is shown. DETAILED DESCRIPTION

[0021] The accompanying drawings illustrate embodiments of the present disclosure and, to the extent permitted by applicable laws and regulations, it will be understood that the disclosed embodiments are merely examples of the present disclosure and that the present disclosure can be implemented in various forms, therefore, the specific details disclosed herein should not be interpreted as limiting, but merely as a basis for the claims and as a basis for teaching a person of ordinary skill in the art to implement the present disclosure in various ways.

[0022] [Etching and de-bonding process of titanium metal connection layer in MEMS product]

[0023] Referring to Figures 1 to 9 , the etching and de-bonding process of titanium metal connection layer in MEMS product according to the present disclosure includes the steps of:

[0024] Step one, providing a composite film layer to be etched, the composite film layer including, from bottom to top, a silicon substrate, a bottom silicon nitride film layer, a middle titanium thin film, and a top aluminum film layer, as shown in Figure 1 ;

[0025] Step two, patterning photoresist on the top aluminum film layer to make the photoresist cover part of the top aluminum film layer and make the photoresist expose the part of the top aluminum film layer adjacent to both sides of the part of the top aluminum film layer covered by the photoresist, as shown in Figure 2 ;

[0026] Step three, the completed composite film layer of step two is placed in a first chamber for wet etching, the aluminum film layer of the exposed top layer is etched in the first chamber, the etching time is set to etch the aluminum film layer of the exposed top layer until the corresponding titanium film layer is exposed, as shown in Figure 3 ;

[0027] Step four, the completed composite film layer of step three is placed in a photoresist removing device for wet photoresist removing, as shown in Figure 4

[0028] Step five, the completed composite film layer of step four is patterned with photoresist, the photoresist covers the aluminum film layer on the titanium film layer, and the photoresist covers the titanium film layer on both sides of the aluminum film layer through the exposed titanium film layer, the exposed titanium film layer corresponds to the trench formed by the photoresist, as shown in Figure 5

[0029] Step six, the completed composite film layer of step five is placed in a second chamber for titanium film etching along the trench, the etching time is set to etch the exposed titanium film layer of the trench until the bottom silicon nitride film layer is exposed, as shown in Figure 6

[0030] Step seven, the completed composite film layer of step six is placed in a photoresist removing device for photoresist removing, as shown in Figure 7 and Figure 8

[0031] Step eight, the titanium film layer and the aluminum film layer of the completed composite film layer of step seven are formed with a silicon nitride covering layer, as shown in Figure 9

[0032] In the titanium metal connection layer etching and removing process of the MEMS product of the present disclosure, the photoresist removing of step four is wet photoresist removing, which avoids the oxidation of the exposed titanium by dry photoresist removing with O2 (the dry photoresist removing is performed at high temperature, which makes the oxidation speed of the exposed titanium fast and the oxidation degree high), the wet photoresist removing of step four is performed before the titanium film layer etching of step six, which avoids the influence of the titanium oxide formed by the dry etching of the exposed titanium film layer of step four on the etching rate, etching uniformity, and even the etching pattern of the exposed titanium film layer of step six, in addition, based on the wet photoresist removing of step four, the polymer formed in the titanium metal connection layer etching and removing process can be completely and easily removed, which further avoids the negative influence of the polymer residue on the performance and internal structure of the MEMS product composed of the composite film layer.

[0033] ​​​​​In one example, in step one, the thickness of the silicon substrate is 1-3 μm, the thickness of the bottom layer of silicon nitride film is 0.5-1.5 μm The thickness of the middle titanium film is 0.1-0.3 μm The thickness of the top layer of aluminum film is 0.1-0.3 μm In step eight, the thickness of the silicon nitride cover layer is 0.5-1.5 μm Further, in one example, in step one, the thickness of the silicon substrate is 2 μm, the thickness of the bottom layer of silicon nitride film is 1 μm The thickness of the middle titanium film is 0.2 μm The thickness of the top layer of aluminum film is 0.2 μm In step eight, the thickness of the silicon nitride cover layer is 1 μm The silicon nitride cover layer and the bottom layer of silicon nitride film can be deposited by vacuum vapor deposition, which can be chemical vapor deposition, for example, chemical vapor deposition of SiH4 and NH3 at 250 °C and 2.2 mT. In addition, the silicon nitride cover layer and the bottom layer of silicon nitride film can be grown by multiple step deposition of the film according to the silicon nitride film, i.e. in the same chemical vapor deposition chamber, the number of step deposition of the film can be determined according to the actual production conditions. The middle titanium film and the top layer of aluminum film can be deposited by atmospheric vapor deposition, which can be atmospheric pressure physical vapor deposition (PVD).

[0034] The patterning of the photoresist in steps two and five can be performed by known techniques in the art, for example, the photoresist is patterned by TEL ACT8 photoresist coating and Nikon S205 machine lithography.

[0035] The first chamber in step three can be any suitable known or commercially available wet etching chamber, for example, the wet etching first chamber is the chamber of DNS Screen WS820L machine and the wet etching solution suitable for aluminum etching. For example, the wet etching solution is a mixture of phosphoric acid (H3PO4), nitric acid (HNO3) and acetic acid (CH3COOH), further, a mixture of H3PO4 with a concentration not less than 85% at a volume ratio of (70-80):(1-7):(10-20), HNO3 with a concentration not less than 65% and CH3COOH with a concentration not less than 99.5% can be used, the temperature of the mixture can be 15-40 °C, the flow rate is 50-200 sccm, the rate is 1000-1500 CC / min, the time is 30-50 s, and the standing time of the solution is 48 hours; more specifically, a mixture of H3PO4 (85%), HNO3 (65%) and CH3COOH (100%) at a volume ratio of 70:2:12 at a temperature of 25 °C can be used, the flow rate is 100 sccm, the rate is 1200 CC / min, the time is 40 s, and the standing time of the solution is 48 hours.

[0036] The photoresist removing apparatus chamber of the wet stripping of step four can adopt any suitable known or commercially available apparatus. For example, in step four, the photoresist removing apparatus is a core source KS-S200-6ST wet stripping apparatus. Further, in step four, the wet stripping adopts an organic solvent composed of N-methyl pyrrolidone (NMP) and dimethyl sulfoxide (DMSO), and the mass ratio of N-methyl pyrrolidone (NMP) and dimethyl sulfoxide (DMSO) is 5:1.

[0037] The titanium thin film etching of step six can adopt dry etching or wet etching.

[0038] In one example, in step six, the titanium film is etched in a second chamber without oxygen-containing dry etching gas in a dual-frequency plasma reaction etching gas. The pressure, source power, bias power and etching time of the second chamber are set, and the etching gas introduced into the second chamber is BCl3, Cl2and Ar. The pressure of the second chamber is 8-14 mT, the source power is 500-1200 W, the bias power is 50-200 W, the flow rate of BCl3is 10-180 sccm, the flow rate of Cl2is 10-180 sccm, and the flow rate of Ar is 5-80 sccm. In the dry etching of the titanium film in step six, the etching gas does not contain oxygen (O2) and C / F gas (CHF3, CF4, etc.), and the dry etching gas without oxygen also avoids the influence of the oxidation of titanium to form titanium oxide when the exposed part of the titanium film in the trench is etched by the etching gas containing oxygen. The etching gas does not contain C / F gas, which can avoid the formation of thick polymer during dry etching and avoid the influence of the polymer on the etching rate and etching uniformity of the titanium film. In addition, the source power is the upper electrode power, and the bias power is the lower electrode power. The size of the upper electrode power (i.e. source power) determines the concentration of the plasma. The range of the upper electrode power cannot be too small, otherwise it cannot be normally ignited, which leads to high reflection. Although high reflection can be processed without alarm, it will cause a significant decrease in etching uniformity. The range of the upper electrode power cannot be too large, otherwise the actual output will not match the set value, and the stability is poor, which reduces the service life of the machine. Similarly, the lower electrode power (i.e. bias power) is used to accelerate positive ions and provide vertical physical bombardment. The lower electrode power cannot be too small, otherwise it cannot be ignited or the reflection is high. If it is too large, it will damage the electrostatic chuck (ESC) during warm-up or damage the radio frequency power source. More specifically, in one example, in step six, the pressure of the second chamber is 14 mT, the source power is 500 W, the bias power is 50 W, the flow rate of BCl3is 50 sccm, the flow rate of Cl2is 30 sccm, and the flow rate of Ar is 10 sccm. The second chamber for dry etching in step six can use any known or commercially available metal etching machine that provides a dual-frequency plasma reaction, such as the dry etching chamber of the DPS (decouple plasma source, American Applied Materials Company) Metal machine.

[0039] In another example, in step six, a titanium thin film etching is performed in a wet etching second chamber, the temperature of the wet etching chemical solution is 25 °C, the chemical solution is ammonia water: hydrogen peroxide: water with a volume ratio of 1:1:1, the flow rate is 50 sccm, the rate is 1000 CC / min, the time is 30 s, and the chemical solution standing time is 24 hours. The wet etching second chamber in step six can use any known or commercially available machine that provides titanium wet etching, such as the Ultron S200 from Applied Materials, Inc.

[0040] For the removal of the photoresist in step seven, in one example, in step seven, the photoresist is removed by dry etching using O2 and N2. Further, in step seven, the flow rate of O2 is 40-160 sccm, and the flow rate of N2 is 40-160 sccm. Further, in step seven, the flow rate of O2 is 100 sccm, and the flow rate of N2 is 100 sccm. The removal of the photoresist by dry etching can use the strip chamber of the DPS Metal machine from Applied Materials, Inc., which is a different chamber from the aforementioned dual-frequency plasma reaction chamber.

[0041] Similarly, for the removal of the photoresist in step seven, in another example, in step seven, the photoresist is removed by wet etching. Further, the wet etching uses an organic solvent composed of N-methyl pyrrolidone (NMP) and dimethyl sulfoxide (DMSO). Further, the mass ratio of N-methyl pyrrolidone (NMP) to dimethyl sulfoxide (DMSO) is 5:1. The removal of the photoresist by wet etching can use any suitable equipment, such as the KS-S200-6ST from Chip Source.

[0042] Similarly, for the removal of the photoresist in step seven, in another example, a combination of the aforementioned dry etching and the aforementioned wet etching can be used.

[0043] In addition, as previously described and as shown in FIG. 1, the titanium metal connection layer (i.e., the titanium metal connection layer 110) is formed on the substrate 100. Figures 1 to 9 Figures 1 to 9 ​The manufacturing process of the MEMS product (e.g., the MEMS product with the titanium thin film in the middle) involves the transfer between various steps (i.e., the equipment (i.e., the machine) involved in each step needs to be changed), based on the aforementioned consideration of avoiding the oxidation of the titanium thin film, although the oxidation of titanium by air during the transfer process is much less than the oxidation of titanium by the dry etching with O2 and the stripping with O2, in order to minimize the impact of the oxidation of titanium during the transfer process, the transfer process still needs to be considered. One way is to control the Q-time, specifically, the time point when the surface of the titanium thin film under the aluminum film layer is exposed during etching is recorded as the starting time point of the Q-time, the time point when the part of the titanium thin film exposed by the groove is etched completely in step six is the end time of the Q-time, the time period from the starting time point of the Q-time to the end time of the Q-time is the time period of the Q-time, which is set to be no more than 3 hours, of course, the shorter the better in actual production. Another way is to place the composite film layer in the nitrogen cabinet during the transfer process between different steps from step three to step eight.

[0044] In the etching and stripping process of the titanium metal connection layer in the MEMS product of the present disclosure, the starting time point and the end time involved in the Q-time can be automatically captured by the spectrometer.

[0045] [TEST]

[0046] First part: etching and stripping process of titanium metal connection layer in MEMS product

[0047] Comparative Example 1

[0048] The etching and stripping process of the titanium metal connection layer in the MEMS product adopts the following steps:

[0049] Step one, providing a composite film layer to be etched, the composite film layer includes a silicon substrate, a bottom silicon nitride film layer, a titanium thin film in the middle, and an aluminum film layer on the top, which are arranged in order from bottom to top, wherein the thickness of the silicon substrate is 2 μm, the thickness of the bottom silicon nitride film layer is The thickness of the titanium thin film in the middle is The thickness of the aluminum film layer on the top is The bottom silicon nitride film layer is formed by chemical vapor deposition of SiH4 and NH3 twice at 250°C and 2.2 mT, the first deposition The second deposition

[0050] Step two, patterning the photoresist on the top aluminum film layer to make the photoresist cover part of the top aluminum film layer and expose the part of the top aluminum film layer adjacent to the two sides of the part covered by the photoresist, wherein TEL ACT8 is used to coat the photoresist, and Nikon S205 machine is used for photolithography to pattern the photoresist;

[0051] Step 3: placing the composite film layer with the photoresist set in step 2 into the first chamber of wet etching, etching from the exposed top aluminum film layer in the first chamber, and setting the etching time to etch until the top aluminum film layer exposed by the photoresist is completely etched and the surface of the corresponding titanium film is exposed. The first chamber of wet etching is the chamber of DNSScreen WS820L machine, and the wet etching solution adopts a mixture of H3PO4 (85%), HNO3 (65%), and CH3COOH (100%) with a volume ratio of 70:2:12 and a temperature of 25°C, with a flow rate of 100sccm, a rate of 1200CC / min, a time of 40s, and a standing time of 48 hours;

[0052] Step 4: Place the composite film layer with the surface of the titanium film exposed in step 3 in a photoresist removal device for dry stripping. The photoresist is removed using O2 and N2 at a flow rate of 2500 sccm and a flow rate of 1000 sccm. The dry stripping uses a stripping chamber of a DPS Metal tool from Applied Materials, Inc., USA.

[0053] Step 5: Patterning the composite film layer completed in step 4 with a photoresist so that the photoresist covers the aluminum film layer on the titanium film layer, and covers the titanium films on both sides of the aluminum film layer via the exposed portions of the titanium film, with the exposed portions of the titanium film layer corresponding to the grooves formed by the photoresist. The photoresist is applied using a TEL ACT8 and patterned using a Nikon S205 machine for photolithography.

[0054] Step 6: Place the composite film layer completed in step 5 in a second wet etching chamber, and etch the titanium film along the groove in the second chamber. The etching time is set to etch until the titanium film exposed in the groove is completely etched and the underlying silicon nitride film layer is exposed. The wet etching solution temperature is 25° C., and the solution is a 1:1:1 volume ratio of ammonia water: hydrogen peroxide: water, with a flow rate of 50 sccm, a rate of 1000 cc / min, a time of 30 seconds, and a standing time of 24 hours. The second wet etching chamber uses a chamber of a Pure Technology Ultron S200 machine.

[0055] Step seven, the composite film layer exposing the underlying silicon nitride film layer after step six is placed in a photoresist removal device to remove the photoresist, the photoresist removal device adopts dry photoresist removal first and then wet photoresist removal, the dry photoresist removal adopts O2 and N2, the flow rate of O2 is 100 sccm, the flow rate of N2 is 100 sccm, and the photoresist removal cavity of the DPS metal etching machine of American Applied Materials Company is adopted; the wet photoresist removal adopts an organic solvent composed of N-methyl pyrrolidone (NMP) and dimethyl sulfoxide (DMSO), the mass ratio of N-methyl pyrrolidone (NMP) to dimethyl sulfoxide (DMSO) is 5:1, and the core source KS-S200-6ST is adopted;

[0056] Step eight, a silicon nitride cover layer is formed on the titanium film and the aluminum film layer of the composite film layer after step seven, the silicon nitride cover layer is formed by chemical vapor deposition of SiH4 and NH3 at 250°C and 2.2 mT for multiple times, and the total deposition thickness is 1000 nm.

[0057] Figure 10 The SEM photo of the part of the MEMS product corresponding to the composite film layer after step seven is shown, Figure 11 The TEM photo of the cross section of the part of the MEMS product corresponding to the composite film layer after step eight is shown, Figure 12 The partial enlarged view of Figure 11 is shown. As can be seen from Figure 10 , the Ti in the trench part is not etched completely. As can be seen from Figure 11 and Figure 12 , the part of the titanium film covered and protected by the aluminum film layer does not appear titanium oxidation, while the part of the titanium film not covered and protected by the aluminum film layer appears titanium oxidation.

[0058] Figure 13 The overall SEM photo of the MEMS device containing the composite film layer after step seven is shown, the part in the upper part of the photo corresponds to the composite film layer after step seven (step eight is not performed), and it can be seen that Figure 12 The upper part of the photo is distributed with thick polymer.

[0059] Example 1

[0060] Except that the wet photoresist removal (the wet photoresist removal adopts an organic solvent composed of N-methyl pyrrolidone (NMP) and dimethyl sulfoxide (DMSO), the mass ratio of N-methyl pyrrolidone (NMP) to dimethyl sulfoxide (DMSO) is 5:1, and the core source KS-S200-6ST is adopted) is different from that in Comparative Example 1.

[0061] Figure 14 The SEM photo of the part of the MEMS product corresponding to the composite film layer after step seven is shown, and the correspondingFigure 10 Compared with Figure 14 Titanium is etched clean at the site of the trench.

[0062] Figure 15 The overall SEM photo of the MEMS device containing the composite film layer after step seven is shown. The upper part of the photo corresponds to the composite film layer after step seven (step eight is not performed). It can be seen that Figure 15 The surface of the upper part of the photo is clean without polymer. Figure 13 Compared with

[0063] Second part: Influence of air oxidation during different steps of transfer

[0064] Influence of Q-time on titanium etching

[0065] Titanium film layers were grown on a silicon substrate using atmospheric pressure physical vapor deposition Every 3h, a piece was taken out. The three pieces were placed in the Ultron S200 machine of Zhiqing Technology to perform wet etching. The temperature of the etching solution was 25°C. The etching solution was ammonia water: hydrogen peroxide: water with a volume ratio of 1:1:1. The flow rate was 50sccm, the rate was 1000CC / min, the time was 20s, the lifetime of the etching solution was 72h, and the starting time point of Q-time was counted from the time when the three pieces were taken out from the atmospheric pressure physical vapor deposition. After being taken out, they were placed in the air for the corresponding time to terminate the calculation of the time period experienced by Q-time.

[0066] Table 1: Relationship between etching rate and Q-time

[0067]

[0068]

[0069] In Table 1, piece 3 was placed in the air for 0.5h, piece 2 was placed in the air for 3.5h, and piece 1 was placed in the air for 6.5h.

[0070] Based on Table 1, the Figure 16 It can be seen that as the Q-time increases, the ER will slow down. The rate decreases by about The rate decreases by about This shows that as the Q-time increases, the Ti oxidation starts quickly, and the Ti oxidation gradually slows down in the later period.

[0071] The foregoing detailed description has set forth various exemplary embodiments of the systems and techniques via the use of a number of particular examples and urposes, but other embodiments of the systems and techniques herein disclosed can be employed in each particular case to embody the principles thereof, and this application is intended to be limited only by the claims, properly construed following full interpretation of this specification. Accordingly, unless otherwise indicated herein, the various features of the described embodiments can be combined in any suitable combination, only a portion of which can be used in a particular case.

Claims

1. A process for etching and stripping a titanium metal connection layer in a MEMS product, characterized in that, The method comprises the following steps: Step 1: providing a composite film layer to be etched, the composite film layer comprising, from bottom to top, a silicon substrate, a bottom silicon nitride film layer, a middle titanium film layer, and a top aluminum film layer; Step 2: patterning photoresist on the top aluminum film layer to cover part of the top aluminum film layer and expose the top aluminum film layer on both sides of the part covered by the photoresist; Step 3: placing the composite film layer with the photoresist set in step 2 in a first chamber for wet etching, etching the exposed part of the top aluminum film layer in the first chamber, and setting the etching time to be sufficient to etch the exposed part of the top aluminum film layer and expose the surface of the corresponding titanium film layer; Step 4: placing the composite film layer with the exposed surface of the corresponding titanium film layer in step 3 in a photoresist removing device for wet photoresist removal; Step 5: patterning photoresist on the composite film layer to cover the aluminum film layer on the titanium film layer and cover the titanium film layers on both sides of the aluminum film layer through the exposed part of the titanium film layer, the exposed part of the titanium film layer corresponding to a groove formed by the photoresist; Step 6: placing the composite film layer in step 5 in a second chamber for titanium film etching along the groove, and setting the etching time to be sufficient to etch the part of the titanium film layer exposed by the groove and expose the bottom silicon nitride film layer; Step 7: placing the composite film layer with the exposed bottom silicon nitride film layer in step 6 in a photoresist removing device for photoresist removal; Step 8: forming a silicon nitride cover layer on the titanium film layer and the aluminum film layer of the composite film layer in step 7.

2. The etching and photoresist removing process for the titanium metal connecting layer in the MEMS product according to claim 1, wherein in step 3, a mixed solution with a volume ratio of 70-80:1-7:10-20 and a concentration of phosphoric acid not less than 85%, nitric acid not less than 65%, and acetic acid not less than 99.5% is used, the temperature of the mixed solution is 15-40℃, the flow rate is 50-200sccm, the rate is 1000-1500CC / min, the time is 30-50s, and the standing time of the solution is 48 hours.

3. The etching and photoresist removing process for the titanium metal connecting layer in the MEMS product according to claim 2, wherein in step 3, a mixed solution with a volume ratio of 70:2:12 and a concentration of 85% H3PO4, 65% HNO3, and 100% CH3COOH is used, the temperature of the mixed solution is 25℃, the flow rate is 100sccm, the rate is 1200CC / min, the time is 40s, and the standing time of the solution is 48 hours.

4. The etching and photoresist removing process for the titanium metal connecting layer in the MEMS product according to claim 1, wherein in step 4, the wet photoresist removal uses an organic solvent composed of N-methyl pyrrolidone (NMP) and dimethyl sulfoxide (DMSO), and the mass ratio of N-methyl pyrrolidone (NMP) to dimethyl sulfoxide (DMSO) is 5:

1. ​ ​ ​ 5. The etching and stripping process of the titanium metal connecting layer in the MEMS product according to claim 1, wherein, in step six, titanium film etching is performed in a wet etching second chamber, the temperature of the wet etching solution is 25℃, the wet etching solution is ammonia water: hydrogen peroxide: water with a volume ratio of 1:1:1, the flow rate is 50sccm, the rate is 1000CC / min, the time is 30s, and the solution standing time is 24 hours.

6. The etching and stripping process of the titanium metal connecting layer in the MEMS product according to claim 1, wherein, in step seven, dry stripping is first used, followed by wet stripping.

7. The etching and stripping process of the titanium metal connecting layer in the MEMS product according to claim 6, wherein, in the dry stripping of step seven, O2 and N2 are used, the flow rate of O2 is 40sccm-160sccm, and the flow rate of N2 is 40sccm-160sccm; in the wet stripping of step seven, an organic solvent composed of N-methyl pyrrolidone (NMP) and dimethyl sulfoxide (DMSO) is used, and the mass ratio of N-methyl pyrrolidone (NMP) to dimethyl sulfoxide (DMSO) is 5:

1.

8. The etching and stripping process of the titanium metal connecting layer in the MEMS product according to claim 7, wherein, in the dry stripping of step seven, the flow rate of O2 is 100sccm, and the flow rate of N2 is 100sccm.

9. The etching and stripping process of the titanium metal connecting layer in the MEMS product according to claim 1, wherein, the time point when the surface of the titanium film under the aluminum film layer is exposed during etching is recorded as the starting time point of Q-time; the ending time of Q-time is the time point when the part of the exposed titanium film in the groove is etched completely in step six; the time period from the starting time point of Q-time to the ending time of Q-time is the time period of Q-time, which is set to be no more than 3 hours.

10. The etching and stripping process of the titanium metal connecting layer in the MEMS product according to claim 1, wherein, during the transfer process between different steps from step three to step eight, the composite film layer is placed in a nitrogen cabinet for storage.

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