A MEMS dry etching method, device and MEMS device

Abstract

The application relates to the technical field of micro electromechanical systems, and discloses a MEMS dry etching method, a MEMS dry etching device and a MEMS device. The method comprises the following steps: providing a wafer, wherein the wafer has an adsorption surface and an etching surface, and the adsorption surface and the etching surface are a set of opposite surfaces; using a pre-prepared mask plate to manufacture an adsorption structure on the adsorption surface; the adsorption structure is matched with a lifting column pattern of an electrostatic chuck or matched with an adsorption chuck print pattern generated when the adsorption surface is electrostatically adsorbed; the lifting column of the electrostatic chuck is controlled to be in butt joint with the adsorption structure, and the electrostatic chuck is controlled to adsorb the adsorption structure after the lifting column retracts the electrostatic chuck; and MEMS dry etching is carried out on the etching surface. The application solves the problem of chuck print defects generated on the wafer surface due to uneven adsorption force of the electrostatic chuck.

Description

Technical Field

[0001] This application relates to the field of microelectromechanical technology, and in particular, to a MEMS dry etching method, apparatus, and MEMS device. Background Technology

[0002] Dry etching is one of the most frequently used and crucial processes in MEMS sensor fabrication, playing a key role in the performance, reliability, and mass production yield of the final device. During the dry etching process, due to the vacuum environment, the substrate wafer is typically fixed to the chuck of the dry etching equipment cavity using electrostatic adsorption (ESC).

[0003] However, the current method of dry etching using electrostatic chucks and electrostatic adsorption is prone to producing chuck marks on the wafer. These chuck marks affect the detection accuracy of MEMS sensors and, in severe cases, can even cause the wafer to break, leading to device failure. Summary of the Invention

[0004] The purpose of this application is to provide a MEMS dry etching method, equipment and MEMS device, which solves the problem of chuck imprint defects on the wafer surface caused by uneven electrostatic chuck adsorption force.

[0005] Other features and advantages of this application will become apparent from the following detailed description, or may be learned in part from practice of this application.

[0006] According to one aspect of the embodiments of this application, a MEMS dry etching method is provided, the method comprising: providing a wafer having an adsorption surface and an etching surface, the adsorption surface and the etching surface being a set of opposing surfaces; using a pre-fabricated mask to fabricate an adsorption structure on the adsorption surface; the adsorption structure matching the rising and falling column pattern of an electrostatic chuck, or matching the chuck imprint pattern generated on the adsorption surface during electrostatic adsorption; controlling the rising and falling column of the electrostatic chuck to dock with the adsorption structure, and controlling the electrostatic chuck to adsorb the adsorption structure after the rising and falling column retracts into the electrostatic chuck; and performing MEMS dry etching on the etching surface.

[0007] In some embodiments, the method for manufacturing the mask includes: obtaining the size of the lifting column of the electrostatic chuck or the size of the suction cup imprint generated by the adsorption surface during electrostatic adsorption, and manufacturing the mask according to the size of the lifting column or the size of the suction cup imprint.

[0008] In some embodiments, after providing the wafer, the method further includes: obtaining the sensitivity of the adsorption surface to the electrostatic chuck; the step of using a pre-fabricated mask to fabricate an adsorption structure on the adsorption surface includes: when the sensitivity is greater than or equal to a first preset threshold, fabricating the adsorption structure using a photoresist mask; and when the sensitivity is less than the first preset threshold, fabricating the adsorption structure using a cutout mask.

[0009] In some embodiments, fabricating the adsorption structure using a photoresist mask includes: preparing a MEMS structure film layer on the adsorption surface, the MEMS structure film layer being used for signal interaction with the outside world; preparing a coating film on the upper surface of the MEMS structure film layer; forming a photoresist pattern on the coating film using the photoresist mask; the etching groove pattern of the photoresist mask being the same as the rising column pattern; etching the coating film including the photoresist pattern; and removing the photoresist pattern after etching to obtain the adsorption structure.

[0010] In some embodiments, the preparation of the coating film on the upper surface of the MEMS structure film layer includes using one of PVD, CVD and sol-gel processes to prepare the coating film on the upper surface of the MEMS structure film layer, wherein the thickness of the coating film ranges from 0.2 μm to 5 μm.

[0011] In some embodiments, fabricating the adsorption structure using a perforated mask includes: preparing a MEMS structure film layer on the adsorption surface, the MEMS structure film layer being used for signal interaction with the outside world; attaching the perforated mask layer onto the MEMS structure film layer, the filling groove pattern of the perforated mask layer being complementary to the lifting column or the suction cup imprint; preparing a coating film within the filling groove of the perforated mask layer; and removing the perforated mask layer to obtain the adsorption structure.

[0012] According to one aspect of the embodiments of this application, a MEMS dry etching apparatus is provided. The apparatus includes an electrostatic chuck, an etching component, and a controller. The controller is configured to: fabricate an adsorption structure on the adsorption surface of a wafer using a pre-fabricated mask; the adsorption structure matches the rising and falling column pattern of the electrostatic chuck, or matches the chuck imprint pattern generated on the adsorption surface during electrostatic adsorption; control the rising and falling column of the electrostatic chuck to dock with the adsorption structure, and control the electrostatic chuck to adsorb the adsorption structure after the rising and falling column retracts into the electrostatic chuck; control the etching component to perform MEMS dry etching on the etching surface of the wafer; the adsorption surface and the etching surface are a set of opposing surfaces of the wafer.

[0013] According to one aspect of the embodiments of this application, a MEMS device is provided, including a wafer, a device layer, and an adsorption structure; the wafer has an adsorption surface and an etched surface, the adsorption surface and the etched surface being a set of opposing surfaces; the device layer is disposed on the etched surface, the adsorption structure is disposed on the adsorption surface, and the adsorption structure matches the rising column pattern of an electrostatic chuck, or matches the chuck imprint pattern generated by the adsorption surface during electrostatic adsorption.

[0014] In some embodiments, the adsorption structure includes a MEMS structure film and a coating film; the MEMS structure film is located between the adsorption surface and the coating film, and is used for signal interaction with the outside world; the pattern of the coating film matches the pattern of the rising column.

[0015] In some embodiments, the MEMS structure film and the coating film partially or completely cover the adsorption surface.

[0016] Compared with the prior art, the significant advantages of the technical solution of this application are as follows: This invention processes the adsorption surface of the wafer to match the adsorption structure with the lifting column pattern of the electrostatic chuck, or with the chuck imprint pattern generated during electrostatic adsorption. This adsorption structure, matching the lifting column pattern or chuck imprint pattern, can influence the induced charge distribution on the wafer surface, thereby regulating the electric field distribution on the electrostatic chuck surface, reducing local adsorption force, and making the adsorption force distribution of the electrostatic chuck more uniform. This solves the problem of chuck imprint defects on the wafer surface caused by uneven adsorption force of the electrostatic chuck, and avoids key issues such as dimensional distortion of MEMS sensor chip structures, uneven local etching thickness, color difference, and substandard chip performance. Furthermore, due to its high flexibility, this invention can adjust process parameters to improve the problem-solving effect for different MEMS product structures, making it highly applicable. Compared with traditional solutions involving customized equipment components or equipment upgrades, this invention shortens problem-solving time, significantly reduces costs, and facilitates product iteration and rapid mass production.

[0017] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0018] The above and other features and advantages of this application will become more apparent from the detailed description of exemplary embodiments thereof with reference to the accompanying drawings.

[0019] Figure 1 A flowchart of a method for uniformly distributing electrostatic adsorption forces according to an embodiment of this application is shown;

[0020] Figure 2A flowchart illustrating the fabrication of an adsorption structure using a photoresist mask according to one embodiment of this application is shown;

[0021] Figure 3 A flowchart illustrating the fabrication of an adsorption structure using a perforated mask according to an embodiment of this application is shown;

[0022] Figure 4 A schematic diagram of the connection between the lifting column and the adsorption structure according to an embodiment of this application is shown;

[0023] Figure 5 A schematic diagram of a MEMS dry etching structure according to an embodiment of this application is shown;

[0024] Figure 6 A schematic diagram of the surface structure of an electrostatic chuck according to another embodiment of this application is shown;

[0025] Figure 7 A schematic diagram of the mask surface structure according to another embodiment of this application is shown.

[0026] The reference numerals in the attached figures are explained as follows: 1. Wafer; 2. MEMS structural film layer; 3. Coated film; 4. Photoresist mask; 5. Hollowed-out mask; 6. Electrostatic chuck; 7. Dry etching cavity; 8. Adsorption structure; 9. Lifting column; 10. Device layer; 11. Chuck pattern. Detailed Implementation

[0027] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided to make this application more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art.

[0028] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this application. However, those skilled in the art will recognize that the technical solutions of this application can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this application.

[0029] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0030] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily need to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0031] The method for uniform distribution of electrostatic adsorption force in MEMS dry etching according to embodiments of this application is briefly described below:

[0032] Currently, some existing technologies often increase the electric field strength and electrostatic adsorption force by increasing the electrode plate voltage of the ESC (Electrostatic Discharge Machining) to achieve better adsorption tightness. However, this is accompanied by the problem of uneven adsorption force. The voltage adjustment range is generally 400-4000 volts, varying between different dry etching equipment, and the adjustable precision also varies. However, increasing the ESC voltage often results in excessive local adsorption force, which can adversely affect the wafer (e.g., chuck marks, causing device failure) or even wafer breakage. In addition, frequent adjustments to the ESC voltage of the etching equipment increase the difficulty of chip manufacturing line management and preventing material mixing; furthermore, the voltage adjustment range of some older equipment is limited, requiring equipment upgrades, which are expensive.

[0033] Some existing technologies achieve this by upgrading equipment components or the entire device. Examples include customizing ESC chucks, replacing ESC insulation materials, or optimizing the electrode pattern of the ESC chuck. However, this approach has two main limitations: first, customizing dry etching equipment or components is time-consuming and typically expensive; second, MEMS sensor chips are diverse, and customized equipment components often cannot meet the diverse requirements of products and the rapid iteration cycles.

[0034] To solve the above problems, according to some embodiments, such as Figure 1 , Figure 4 , Figure 5 As shown, this application provides a MEMS dry etching method, the method comprising:

[0035] Step 101: Provide wafer 1, which has an adsorption surface and an etching surface, wherein the adsorption surface and the etching surface are a pair of opposing surfaces;

[0036] Step 102: Using a pre-made mask, an adsorption structure 8 is made on the adsorption surface; the adsorption structure 8 matches the pattern of the lifting column 9 of the electrostatic chuck 6, or matches the chuck imprint pattern generated on the adsorption surface during electrostatic adsorption.

[0037] Step 103: Control the lifting column 9 of the electrostatic chuck 6 to dock with the adsorption structure 8, and after the lifting column 9 retracts the electrostatic chuck 6, control the electrostatic chuck 6 to adsorb the adsorption structure 8.

[0038] Step 104: Perform MEMS dry etching on the etched surface.

[0039] Based on the above embodiments, when MEMS dry etching is not performed, the lifting column 9 of the electrostatic chuck 6 is in the raised state. When MEMS dry etching is performed, the lifting column 9 of the electrostatic chuck 6 is in the lowered state. The lifting column 9, also known as a PIN pin or PIN foot, is used for positioning the electrostatic chuck 6.

[0040] This application fabricates an adsorption structure 8 on the adsorption surface of wafer 1, matching the lifting post 9, before performing MEMS dry etching; or, before performing MEMS dry etching, fabricates an adsorption structure 8 on the adsorption surface of wafer 1, matching the chuck imprint. The adsorption surface of wafer 1 is the surface used to form the adsorption structure 8, and can be considered the front side of wafer 1; the etched surface of wafer 1 is the surface opposite the adsorption surface, and can be considered the back side of wafer 1. The chuck imprint is the imprint left on the adsorption surface of wafer 1 during electrostatic adsorption. The groove of the adsorption structure 8 has the same or approximately the same shape as the lifting post 9, and the groove size of the adsorption structure 8 is slightly larger than the size of the lifting post 9, allowing the adsorption structure 8 to mate with the lifting post 9. Figure 4 As shown.

[0041] After fabricating the adsorption structure 8, when starting MEMS dry etching, such as Figures 4 to 5 As shown, MEMS dry etching is performed within the dry etching chamber 7. The adsorption structure 8 on wafer 1 is aligned with the lifting column 9, and the adsorption structure 8 is inserted into the lifting column 9. Then, the lifting column 9 is lowered until it is flush with the surface of the electrostatic chuck 6. Finally, the electrostatic chuck 6 is controlled to electrostatically adsorb the adsorption structure 8 of wafer 1, and MEMS dry etching is performed on the back side of wafer 1 opposite to the adsorption surface. Specifically, the back side of wafer 1 opposite to the adsorption surface faces upwards. The back side of wafer 1 is first photolithographically etched using a photoresist mask 4, and then dry etched using a reactive plasma gas. Since the adsorption surface of wafer 1 forms a pattern that matches the electrostatic chuck 6, the adsorption structure 8 can affect the induced charge distribution on the surface of wafer 1 during the back-side dry etching process, thereby adjusting the electric field distribution on the surface of electrostatic chuck 6, reducing local adsorption force, and making the adsorption force of electrostatic chuck 6 uniformly distributed. This avoids the problem of chuck mark defects caused by uneven adsorption force damaging wafer 1, and avoids key problems such as chip structure size distortion, uneven local etching thickness, color difference, and substandard chip performance in MEMS products such as MEMS sensors.

[0042] Furthermore, the dry etching method provided in this embodiment can adjust process parameters to improve problem-solving effectiveness for different MEMS product structures, making it highly applicable. Compared to traditional solutions involving customized equipment components or equipment upgrades, this invention shortens problem-solving time, significantly reduces costs, and facilitates product iteration and rapid mass production.

[0043] To enable those skilled in the art to better understand this application, the following will be combined with Figures 1 to 7 The details of this application are described in detail.

[0044] According to some embodiments, the method for manufacturing the mask plate includes:

[0045] Obtain the dimensions of the lifting column 9 of the electrostatic chuck 6 or the dimensions of the suction cup imprint generated by the adsorption surface during electrostatic adsorption, and fabricate the mask plate according to the dimensions of the lifting column 9 or the dimensions of the suction cup imprint.

[0046] Based on the above embodiments, the dimensions of the lifting column 9 are as follows: Figure 4 As shown, Figure 4 Here is a cross-sectional view of the lifting column 9, as shown below. Figure 6 As shown, Figure 6 This is a schematic diagram of the surface structure of an electrostatic chuck according to another embodiment. The method for obtaining the size of the suction cup imprint is as follows: First, the lifting column 9 of the electrostatic chuck 6 is controlled to retract, bringing the adsorption surface of the wafer 1 into contact with the surface of the electrostatic chuck 6. The electrostatic chuck 6 is then controlled to electrostatically adsorb the wafer 1. After the electrostatic adsorption reaches a first set time, the electrostatic adsorption is turned off, and the wafer 1 is removed. A suction cup imprint will be left on the adsorption surface of the wafer 1. The size of the suction cup imprint can be obtained by measuring it.

[0047] According to some embodiments, after providing wafer 1, the method further includes:

[0048] The sensitivity of the adsorption surface to the electrostatic chuck 6 is obtained;

[0049] The process of fabricating the adsorption structure 8 on the adsorption surface using a pre-fabricated mask includes:

[0050] When the sensitivity is greater than or equal to the first preset threshold, the adsorption structure 8 is fabricated using a photoresist mask 4; when the sensitivity is less than the first preset threshold, the adsorption structure 8 is fabricated using a perforated mask 5.

[0051] The first preset threshold can be set according to actual needs.

[0052] According to some embodiments, such as Figure 2 As shown, the fabrication of the adsorption structure 8 using a photoresist mask 4 includes:

[0053] A MEMS structure film layer 2 is prepared on the adsorption surface, and the MEMS structure film layer 2 is used to interact with the outside world.

[0054] A coating film 3 is prepared on the upper surface of the MEMS structure film layer 2;

[0055] A photoresist pattern is formed on the coated film 3 using the photoresist mask 4; the etching groove pattern of the photoresist mask 4 is the same as the pattern of the lifting column 9;

[0056] The coating film 3, which includes the photoresist pattern, is etched. After etching, the photoresist pattern is removed to obtain the adsorption structure 8.

[0057] The function of the MEMS structure film layer 2 is determined according to the product design, and it can be used for signal transmission, signal isolation, and signal switching, etc.

[0058] Based on the above embodiments, the MEMS structure film layer 2 includes a first non-metallic layer, a second non-metallic layer, an active layer, and a metal layer. The active layer is disposed between the first and second non-metallic layers. The first non-metallic layer, the second non-metallic layer, and the active layer are disposed between the adsorption surface of the wafer 1 and the metal layer. The metal layer and the active layer are electrically connected. The active layer and the metal layer are used for signal switching and signal transmission.

[0059] The thickness of the coating film 3 can be adjusted to control the electrostatic adsorption force, and the thickness of the coating film 3 can be set according to actual needs.

[0060] The photolithography process on the photoresist mask 4 includes the following steps in sequence: resist coating, exposure, and development. After the photolithography process is completed, the etching groove of the photoresist mask 4 has the same shape as the lifting column 9 of the electrostatic chuck 6. For example... Figure 7 As shown, Figure 7 For the corresponding Figure 6 A schematic diagram of the mask surface structure of another embodiment.

[0061] The coated film 3 is etched through the etching tank of the photoresist mask 4. Etching can be performed using either wet or dry etching. The adsorption structure 8 pattern on wafer 1 has a large linewidth and no special requirements for the cross-section, allowing for batch wet etching, which is beneficial for increasing output and reducing production costs.

[0062] After etching, a groove structure with the same shape as the lifting post 9 of the electrostatic chuck 6 is obtained. At this time, the photoresist is removed to obtain the adsorption structure 8 of the wafer 1 corresponding to the lifting post 9 or the chuck imprint. Figure 2 As shown, Figure 2 A flowchart for fabricating an adsorption structure using a photoresist mask, such as... Figure 6 As shown, Figure 6This is a schematic diagram of the surface structure of an electrostatic chuck according to another embodiment.

[0063] In this process, the aforementioned MEMS structure film 2 and coating film 3 completely cover the adsorption surface of wafer 1. When the sensitivity of the adsorption surface of wafer 1 to the electrostatic chuck 6 is above a first preset threshold, the aforementioned photoresist mask 4 can be used to fabricate the adsorption structure 8 of wafer 1. Due to the specific adsorption structure 8 of the adsorption surface, the adsorption force is distributed more evenly, preventing the adsorption surface structure of wafer 1 from being damaged or affected.

[0064] Furthermore, in addition to the methods mentioned above, such as Figure 3 As shown, the adsorption structure 8 is fabricated using a perforated mask plate 5, comprising:

[0065] A MEMS structure film layer 2 is prepared on the adsorption surface, and the MEMS structure film layer 2 is used to interact with the outside world.

[0066] The perforated mask 5 is attached to the MEMS structure film layer 2, and the filling groove pattern of the perforated mask 5 is complementary to the lifting column 9 or the suction cup imprint.

[0067] A coating film 3 is prepared in the filling groove of the hollow mask plate 5;

[0068] Remove the perforated mask plate 5 to obtain the adsorption structure 8.

[0069] The function of the MEMS structure film layer 2 is determined according to the product design, and it can be used for signal transmission, signal isolation, and signal switching, etc.

[0070] Based on the above embodiments, the MEMS structure film layer 2 includes a first non-metallic layer, a second non-metallic layer, an active layer, and a metal layer. The active layer is disposed between the first and second non-metallic layers. The first non-metallic layer, the second non-metallic layer, and the active layer are disposed between the adsorption surface of the wafer 1 and the metal layer. The metal layer and the active layer are electrically connected. The active layer and the metal layer are used for signal switching and signal transmission.

[0071] In this process, the MEMS structure film 2 and the coating film 3 cover a portion of the adsorption surface of the wafer 1, while the other portion of the adsorption surface of the wafer 1 is exposed. When the sensitivity of the adsorption surface of the wafer 1 to the electrostatic chuck 6 is below a first preset threshold, the aforementioned cutout mask 5 can be used to fabricate the adsorption structure 8 of the wafer 1. Since the linewidth is large in order to form an adsorption structure 8 that matches the electrostatic chuck 6, the cutout mask 5 technology can be used, and obvious benefits can be obtained, including a shorter process flow and lower cost.

[0072] Furthermore, the higher the sensitivity of the adsorption surface of wafer 1 to the electrostatic chuck 6, the easier it is for wafer 1 to be electrostatically adsorbed; conversely, the lower the sensitivity, the less easily it is adsorbed. A thicker coating film 3 reduces the adsorption force of the wafer 1's adsorption surface to the electrostatic chuck 6, while a thinner coating film 3 increases the adsorption force. Therefore, when the sensitivity of the wafer 1's adsorption surface to the electrostatic chuck 6 is low, a perforated mask 5 is used to prepare the coating film 3, covering part of the adsorption surface of wafer 1 while exposing the other part. When the sensitivity of the wafer 1's adsorption surface to the electrostatic chuck 6 is high, a photoresist mask 4 is used to prepare the coating film 3, completely covering the adsorption surface of wafer 1 with the MEMS structure film layer 2 and the coating film 3. The thickness of the coating film 3 can be adjusted according to the actual sensitivity.

[0073] The sensitivity is obtained by first observing the complexity of the suction cup pattern 11 on the surface of the electrostatic chuck. The more complex the suction cup pattern 11, the higher the electrostatic attraction force on the adsorption surface of the wafer 1. Secondly, before step 101, the lifting column 9 of the electrostatic chuck 6 is retracted, bringing the adsorption surface of the wafer 1 into contact with the surface of the electrostatic chuck 6. The electrostatic chuck 6 is then controlled to electrostatically adsorb the wafer 1. After a second set time, the electrostatic adsorption is stopped, and the wafer 1 is removed. A suction cup imprint is left on the adsorption surface of the wafer 1, and the depth of the imprint is measured. The deeper the imprint, the higher the electrostatic attraction force and the higher the sensitivity of the wafer 1; the shallower the imprint, the lower the electrostatic attraction force and the lower the sensitivity of the wafer 1.

[0074] According to some embodiments, the preparation of the coating film 3 on the upper surface of the MEMS structure film layer 2 includes using one of the physical vapor deposition (PVD) process, chemical vapor deposition (CVD) process, and sol-gel process to prepare the coating film 3 on the upper surface of the MEMS structure film layer 2, wherein the thickness of the coating film 3 ranges from 0.2 μm to 5 μm.

[0075] In some specific embodiments, the diameter of the electrostatic chuck 6 is 210 mm. The dimensions of the lifting column 9 of the electrostatic chuck 6, or the dimensions of the chuck imprint appearing on the wafer 1 during electrostatic adsorption, are 10 mm wide and 100 mm long. The dimensions of the cutout mask 5 are 8–16 mm wide and 80–120 mm long, and the cutout mask 5 is consistent with or similar to the electrostatic chuck 6. The photomask is fabricated using laser direct writing technology according to the drawn drawings. The photomask uses a quartz glass substrate with a thickness of 1.0–2.5 mm and a square size of 4–9 inches. The metal thin film of the photomask is made of chromium with a thickness of 0.1–0.6 μm.

[0076] Wafer 1 is used for MEMS microphone products. Wafer 1 has a diameter of 5-9 inches, preferably 8 inches. A back-side cavity needs to be fabricated on the back side of wafer 1 using deep silicon etching (DRIE). Before dry etching, the adsorption surface (front side) needs to be treated with the process of this invention to avoid adsorption marks caused by uneven electrostatic field strength of the electrostatic chuck 6 of the DIRE device. First, a MEMS structure film layer 2 is fabricated on the adsorption surface of wafer 1, and then a protective coating layer is fabricated. Preferably, the coating layer is a silicon dioxide thin film deposited using PECVD process, with a thickness of 0.5-5 μm, preferably 2.5 μm.

[0077] Then, photoresist is prepared by coating, exposing, and developing the coated layer to obtain photoresist mask 4. Preferably, a positive photoresist with a thickness of 1.5–6 μm is used. A proximity lithography machine is preferably used for exposure, as the linewidth of photoresist mask 4 is relatively large and the requirements are not high.

[0078] Next, the protective film on the front side of wafer 1 is dry etched. Reactive ion etching (RIE) is used to etch the unprotected silicon dioxide film (coating layer). Preferably, the etching depth is 0.7 μm, leaving a layer thickness of 1.8 μm. It should be noted that the selected etching depth affects the surface stress distribution when the adsorption surface is adsorbed by the electrostatic chuck 6. Therefore, the process can be adjusted and optimized accordingly for different scenarios. Immediately after the silicon dioxide (coating layer) etching is complete, the wafer enters the resist removal chamber for resist removal.

[0079] After completing the above steps, the pretreatment process before the DIRE dry etching process on the back side of MEMS microphone wafer 1 is finished, ensuring a uniform distribution of electrostatic adsorption forces. Next, wafer 1 is placed into the DIRE dry etching equipment for deep silicon etching on the back side. Because the adsorption surface (front side) of wafer 1, which contacts the electrostatic chuck 6, has a protective layer formed by a specific coating layer of adsorption structure 8, chuck marks caused by uneven electrostatic forces are avoided. Theoretical analysis suggests that the adsorption structure 8 of the protective layer and its thickness variations affect the induced charge distribution on the surface of wafer 1, thereby regulating the electric field distribution on the surface of the electrostatic chuck 6 and reducing localized adsorption forces.

[0080] Finally, wafer 1 is fed into subsequent process steps to complete product preparation.

[0081] The MEMS dry etching apparatus of this application embodiment is briefly described below:

[0082] According to some embodiments, this application provides a MEMS dry etching apparatus, the apparatus including an electrostatic chuck 6, an etching assembly, and a controller, the controller being configured to:

[0083] Using a pre-made mask, an adsorption structure 8 is made on the adsorption surface of wafer 1; the adsorption structure 8 matches the pattern of the lifting column 9 of the electrostatic chuck 6, or matches the chuck imprint pattern generated on the adsorption surface during electrostatic adsorption.

[0084] Control the lifting column 9 of the electrostatic chuck 6 to dock with the adsorption structure 8, and control the electrostatic chuck 6 to adsorb the adsorption structure 8 after the lifting column 9 retracts the electrostatic chuck 6.

[0085] The etching assembly is controlled to perform MEMS dry etching on the etching surface of the wafer 1; the adsorption surface and the etching surface are a set of opposite surfaces of the wafer 1.

[0086] The MEMS devices of the embodiments of this application are briefly described below:

[0087] According to some embodiments, this application provides a MEMS device, including a wafer 1, a device layer 10, and an adsorption structure 8; the wafer 1 has an adsorption surface and an etched surface, the adsorption surface and the etched surface being a set of opposing surfaces; the device layer 10 is disposed on the etched surface, the adsorption structure 8 is disposed on the adsorption surface, and the adsorption structure 8 matches the pattern of the lifting column 9 of the electrostatic chuck 6, or matches the chuck imprint pattern generated by the adsorption surface during electrostatic adsorption.

[0088] According to some embodiments, the adsorption structure 8 includes a MEMS structure film layer 2 and a coating film 3; the MEMS structure film layer 2 is located between the adsorption surface and the coating film 3, and is used for signal interaction with the outside world; the pattern of the coating film 3 matches the pattern of the lifting column 9.

[0089] Based on the above embodiments, the thickness of the coating film 3 can adjust the electrostatic adsorption force, and the thickness of the coating film 3 can be set according to actual needs. The electrostatic chuck 6 is used to electrostatically adsorb the wafer 1 through the adsorption structure 8, and MEMS dry etching is performed on the back side of the wafer 1 opposite the adsorption surface. For example... Figures 4 to 5 As shown, the back side of wafer 1 faces upwards, with the adsorption surface opposite the back side. The back side of wafer 1 is first photolithographically etched using a photoresist mask 4, and then dry etched using a reactive gas plasma.

[0090] Furthermore, in some embodiments, one side of the MEMS structure film layer 2 and one side of the coating film 3 completely cover the adsorption surface of the wafer 1.

[0091] Based on the above embodiments, when the sensitivity of the adsorption surface of wafer 1 to the electrostatic chuck 6 is above a first preset threshold, the photoresist mask 4 can be used to fabricate the adsorption structure 8 of wafer 1 so that the adsorption surface of wafer 1 is completely covered. Due to the specific adsorption structure 8 of the adsorption surface, the adsorption force is distributed more evenly, avoiding damage or impact on the adsorption surface structure of wafer 1.

[0092] In other embodiments, one side of the MEMS structure film 2 and one side of the coating film 3 cover a portion of the adsorption surface of the wafer 1, while the other portion of the adsorption surface of the wafer 1 is exposed.

[0093] Based on the above embodiments, when the sensitivity of the adsorption surface of wafer 1 to the electrostatic chuck 6 is below a first preset threshold, the aforementioned cutout mask 5 can be used to fabricate the adsorption structure 8 of wafer 1, so that another part of the adsorption surface of wafer 1 is exposed. Since the linewidth is large in order to form an adsorption structure 8 that matches the electrostatic chuck 6, the cutout mask 5 technology can be used, and obvious benefits can be obtained, including a shorter process flow and lower cost.

[0094] According to some embodiments, the MEMS structure film layer 2 includes a first non-metallic layer, a second non-metallic layer, an active layer, and a metal layer. The active layer is disposed between the first non-metallic layer and the second non-metallic layer. The first non-metallic layer, the second non-metallic layer, and the active layer are disposed between the adsorption surface of the wafer 1 and the metal layer. The metal layer is electrically connected to the active layer.

[0095] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the embodiments disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein.

[0096] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A MEMS dry etching method, characterized in that, The method includes: A wafer is provided, the wafer having an adsorption surface and an etched surface, the adsorption surface and the etched surface being a set of opposing surfaces; An adsorption structure is fabricated on the adsorption surface using a pre-made mask; the adsorption structure matches the rising column pattern of the electrostatic chuck, or matches the chuck imprint pattern generated on the adsorption surface during electrostatic adsorption. Control the lifting column of the electrostatic chuck to dock with the adsorption structure, and control the electrostatic chuck to adsorb the adsorption structure after the lifting column retracts the electrostatic chuck; MEMS dry etching is performed on the etched surface.

2. The method according to claim 1, characterized in that, The method for manufacturing the photomask includes: Obtain the dimensions of the lifting column of the electrostatic chuck or the dimensions of the suction cup imprint generated by the adsorption surface during electrostatic adsorption, and fabricate the mask plate according to the dimensions of the lifting column or the dimensions of the suction cup imprint.

3. The method according to claim 1, characterized in that, After providing the wafer, the method further includes: The sensitivity of the adsorption surface to the electrostatic chuck is obtained; The process of fabricating an adsorption structure on the adsorption surface using a pre-fabricated mask includes: When the sensitivity is greater than or equal to a first preset threshold, the adsorption structure is fabricated using a photoresist mask; when the sensitivity is less than the first preset threshold, the adsorption structure is fabricated using a perforated mask.

4. The method according to claim 3, characterized in that, The adsorption structure is fabricated using a photoresist mask, including: A MEMS structure film is fabricated on the adsorption surface, and the MEMS structure film is used to interact with the outside world. A coating film is prepared on the upper surface of the MEMS structure film layer; Using the photoresist mask, a photoresist pattern is formed on the coated film; the etching groove pattern of the photoresist mask is the same as the rising column pattern; The coating film including the photoresist pattern is etched, and after etching, the photoresist pattern is removed to obtain the adsorption structure.

5. The method according to claim 4, characterized in that, The preparation of a coating film on the upper surface of the MEMS structure film layer includes... The coating film is prepared on the upper surface of the MEMS structure film layer using one of the following processes: PVD, CVD, and sol-gel. The thickness of the coating film ranges from 0.2 μm to 5 μm.

6. The method according to claim 3, characterized in that, The adsorption structure is fabricated using a perforated mask, including: A MEMS structure film is fabricated on the adsorption surface, and the MEMS structure film is used to interact with the outside world. The perforated mask is attached to the MEMS structure film layer, and the filling groove pattern of the perforated mask is complementary to the lifting column or the suction cup imprint. A coating film is prepared in the filling groove of the perforated mask plate; Remove the perforated mask plate to obtain the adsorption structure.

7. A MEMS dry etching apparatus, characterized in that, The device includes an electrostatic chuck, an etching assembly, and a controller, wherein the controller is configured to: An adsorption structure is fabricated on the adsorption surface of a wafer using a pre-made mask; the adsorption structure matches the rising column pattern of an electrostatic chuck, or matches the chuck imprint pattern generated on the adsorption surface during electrostatic adsorption. Control the lifting column of the electrostatic chuck to dock with the adsorption structure, and control the electrostatic chuck to adsorb the adsorption structure after the lifting column retracts the electrostatic chuck; The etching assembly is controlled to perform MEMS dry etching on the etching surface of the wafer; The adsorption surface and the etching surface are a set of opposite surfaces of the wafer.

8. A MEMS device, characterized in that, It includes a wafer, a device layer, and an adsorption structure; the wafer has an adsorption surface and an etched surface, the adsorption surface and the etched surface being a set of opposing surfaces; the device layer is disposed on the etched surface, the adsorption structure is disposed on the adsorption surface, and the adsorption structure matches the lifting column pattern of the electrostatic chuck, or matches the chuck imprint pattern generated by the adsorption surface during electrostatic adsorption.

9. The MEMS device as described in claim 8, characterized in that, The adsorption structure includes a MEMS structure film and a coating film; the MEMS structure film is located between the adsorption surface and the coating film, and is used for signal interaction with the outside world; the pattern of the coating film matches the pattern of the rising column.

10. The MEMS device as described in claim 9, characterized in that, The MEMS structure film and the coating film partially or completely cover the adsorption surface.

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