Manufacturing method of MEMS pressure sensor cavity

Abstract

The invention provides a manufacturing method of an MEMS pressure sensor cavity, and the method comprises the steps: providing a wafer which comprises a chip region and a non-chip region which are formed on a substrate, and the chip region comprises a pressure device formed on the substrate; the manufacturing method of the cavity comprises the steps that S1, a plurality of monitoring areas are formed on a non-chip area on the front face of a wafer, each monitoring area comprises a preset position, a plurality of grooves with preset depths are formed in the vertex of the preset position, and specific materials are arranged at the bottoms in the grooves; s2, etching at the preset position and the corresponding position, mapped to the back surface of the wafer, of the pressure device through a wet etching process to form a cavity, when etching liquid of the wet etching process is in contact with the specific material, etching is stopped, at the moment, the thin film arranged above the cavity is a sensitive film, and the sensitive film is arranged on the back surface of the wafer; the thickness of the sensitive film is the same as the preset depth. According to the invention, the cost is low, and the etching depth of the cavity can be accurately controlled.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for manufacturing a MEMS pressure sensor cavity. Background Art

[0002] With the development of semiconductor technology and the growth of the consumer electronics market, silicon piezoresistive pressure sensors manufactured using micro-electromechanical systems (MEMS) technology have been widely used in commercial and industrial fields due to their small size, high precision and batch production through silicon micromachining technology. The preparation of the back cavity is an important part of the preparation of the pressure sensor chip. When the cavity is obtained, the sensitive film is obtained on the top. The cavity etching depth has a decisive influence on the thickness of the sensitive film, and the thickness of the sensitive film has an important influence on the sensitivity of the pressure sensor. Therefore, the etching depth of the pressure sensor must be strictly controlled.

[0003] In addition, in the pressure sensor, the relative position of the back cavity and the front pattern such as the resistance bar has a great influence on the zero offset and linearity of the pressure sensor. Therefore, it is also necessary to detect and judge the alignment accuracy of the back cavity and the front pattern of the wafer.

[0004] Therefore, the depth control and alignment of the etched cavity during the pressure sensor manufacturing process has become a technical problem that technical personnel in this field need to solve urgently. Summary of the invention

[0005] The purpose of the present invention is to provide a method for manufacturing a cavity of a MEMS pressure sensor, so as to solve the problems of depth control and alignment of the etched cavity during the manufacturing process of the pressure sensor.

[0006] To achieve the above object, the present invention provides a method for manufacturing a MEMS pressure sensor cavity.

[0007] A wafer is provided, wherein the wafer includes a chip area and a non-chip area formed on a substrate, wherein the chip area includes a pressure device formed on the substrate; and the method for manufacturing the cavity includes:

[0008] Step S1: forming a plurality of monitoring areas on the front non-chip area of ​​the wafer, wherein the monitoring area includes a preset position, a plurality of grooves with a preset depth are formed at the apex of the preset position, and a specific material is disposed at the bottom of the groove;

[0009] Step S2: A cavity is formed by etching at the preset position and at the corresponding position where the pressure device is mapped to the back side of the wafer through a wet etching process. When the etching liquid of the wet etching process contacts the specific material, the etching stops. At this time, the thin film arranged above the cavity is a sensitive film, and the thickness of the sensitive film is the same as the first preset depth.

[0010] Optionally, a plurality of grooves with a preset depth are formed at the vertices of the preset positions, and a specific material is disposed at the bottom of the grooves, specifically comprising:

[0011] Spin coating a first photoresist layer on the front side of the wafer;

[0012] Exposing and developing the first photoresist layer to form the first photoresist with the groove pattern at the vertex of the preset position;

[0013] Using the first photoresist patterned with the groove as a mask, etching the wafer to form the groove having the preset depth;

[0014] forming a specific material layer of a preset thickness on the front side of the wafer;

[0015] The patterned first photoresist is removed to form the specific material with the preset thickness at the bottom of the groove.

[0016] Optionally, after completing step S1 and before step S2, the method further includes:

[0017] forming a protective layer on the front and back sides of the wafer, wherein a mask layer of the cavity is formed on the protective layer on the back side of the wafer by etching;

[0018] Spin coating a second photoresist layer on the back protection layer;

[0019] exposing and developing the second photoresist layer to form a second photoresist patterned on the back mask layer at the preset position and at a corresponding position where the pressure device is mapped to the back side of the wafer;

[0020] The protective layer on the back side of the wafer is etched to form the protective layer patterned by the back side mask layer.

[0021] Optionally, the protective layer is one of SiN / SiO2 or a combination of the two.

[0022] Optionally, the protective layer has a thickness of 12.5 nm to 5.3 μm.

[0023] Optionally, the step S2 further includes: using a detection device to detect the etching endpoint; the specific material includes a material that can react with the etching liquid, the specific material contacts and reacts with the etching liquid to form ions to be detected, and the detection device detects the ions to be detected and stops etching.

[0024] Optionally, the specific material has a thickness greater than 0.7 μm; the specific material includes at least one of Al, Zn, Al2O3, ZnO, Ge, and As; and the etching liquid is one of a TMAH solution and a KOH solution.

[0025] Optionally, the specific material includes a material that can dissolve in the etching liquid and change its color; when the etching liquid in the cavity begins to change color, etching is stopped; wherein the specific material includes one of an acid-base indicator, a dye, a coating, and a sprayable glass paint.

[0026] Optionally, the cross-section of the cavity is polygonal, the number of the grooves is multiple, and the center of each groove corresponds to a vertex of the cavity.

[0027] Optionally, after completing step S2, step S3 is also included:

[0028] by removing the second photoresist;

[0029] removing the protective layer and the specific material;

[0030] The deviation between the center of the groove in the monitoring area and the corresponding edge of the cavity is measured.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] The present invention proposes a method for manufacturing a MEMS pressure sensor cavity, by setting a plurality of monitoring areas on the front side of a non-chip area of ​​a wafer, setting a groove of a preset depth at a preset position in the monitoring pre-take, and setting a specific material in the groove, and wet etching the back cavity corresponding to the preset position and the back cavity corresponding to the chip area resistance structure. When the wet etching liquid contacts the specific material, some real-time identifiable information is detected to determine that the wet etching has reached the expected depth, and the etching stops. The technical solution for forming contact holes provided by the present invention can monitor whether the cavity prepared by wet etching has reached the etching depth at a low cost, thereby avoiding over-etching, thereby controlling the thickness deviation of the sensitive film to be small. When a sensitive film pressure sensor is manufactured in this way, the sensitivity and stability of the pressure sensor can be improved. Furthermore, the relative offset between the bottom of the groove and the top of the cavity can be measured to characterize the alignment accuracy of the cavity in the chip area of ​​the wafer and the resistance structure in the pressure device, thereby improving the yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1It is a schematic diagram of a process of manufacturing a MEMS pressure sensor cavity provided by an embodiment of the present invention;

[0035] Figure 2-11 It is a cross-sectional view of different process stages of a method for manufacturing a MEMS pressure sensor cavity provided by an embodiment of the present invention;

[0036] Fig.12 It is a top view of a wafer prepared according to a method for manufacturing a MEMS pressure sensor cavity provided in one embodiment of the present invention;

[0037] Fig.13 yes Fig.11 A schematic diagram of the structure enlarged at A;

[0038] Fig.14 is a schematic diagram of the resistor structure and monitoring area. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0041] At present, the mainstream methods for preparing cavities are wet etching and dry etching. Among them, dry etching mainly uses SOI wafers as substrates, uses Bosh process to etch silicon, and uses buried oxide layer as stop layer. This method can obtain cavities with high etching accuracy and controllable etching depth. However, due to the high cost of Bosh process, long processing time and slow processing efficiency. Therefore, in order to reduce costs and improve work efficiency, wet etching is the first choice to obtain cavity structure, and wet etching cavity is mainly based on two phase-differentiated etching solutions, KOH and TMAH. The improved method also uses SOI wafers as substrates, etches silicon with KOH or TMAH etching solutions, and uses buried oxide layer as stop layer, which can obtain cavities with controllable etching depth in large quantities. Although this method reduces the process cost, SOI wafers need to be customized, so the cost is still high. In order to further reduce costs, the industry uses Si wafers as substrates and etches silicon multiple times with KOH or TMAH etching solutions to obtain cavities of the expected depth. Due to the lack of a stop layer, the cavity obtained by this method cannot achieve self-stopping of etching, resulting in uncontrollable etching depth, making it difficult to control the thickness of the sensitive film. In addition, none of the above schemes have set up a detection of the alignment accuracy of the cavity and the front pattern. It is very difficult to measure the alignment accuracy of the cavity located on the back of the wafer and the front pattern of the wafer.

[0042] Therefore, if you want to use low-cost wet etching to prepare the cavity, you need to have a suitable method to control the cavity etching depth and its alignment accuracy. In view of this, in order to solve the above problems, the inventors of this application proposed a method for making a MEMS pressure sensor cavity, such as Figure 1 As shown, Figure 1 : is a process flow chart of a method for manufacturing a MEMS pressure sensor cavity of the present invention, the method comprising:

[0043] Step S0: providing a wafer, wherein the wafer comprises a chip region and a non-chip region formed on a substrate, wherein the chip region comprises a pressure device formed on the substrate;

[0044] Step S1: forming a plurality of monitoring areas on the front non-chip area of ​​the wafer, wherein the monitoring area includes a preset position, a plurality of grooves with a preset depth are formed at the apex of the preset position, and a specific material is disposed at the bottom of the groove;

[0045] Step S2: A cavity is formed by etching at the preset position and at the corresponding position where the pressure device is mapped to the back of the wafer through a wet etching process. When the etching liquid of the wet etching process contacts the specific material, the etching is stopped. At this time, the thickness of the sensitive film is the same as the preset depth.

[0046] The present invention provides a method for manufacturing a MEMS pressure sensor cavity, which includes setting a plurality of monitoring areas on the front side of a non-chip area of ​​a wafer, setting a groove of a preset depth at a preset position in the monitoring pre-take, and setting a specific material in the groove. When the back cavity corresponding to the preset position and the back cavity corresponding to the chip area resistance structure are wet-etched, the etching stops when the wet etching liquid contacts the specific material. The technical solution for forming a contact hole provided by the present invention can monitor whether the cavity prepared by wet etching reaches the etching depth at a low cost, thereby avoiding over-etching, and controlling the thickness deviation of the sensitive film to be small. When a sensitive film pressure sensor is manufactured in this way, the sensitivity and stability of the pressure sensor can be improved.

[0047] The technical solution of the present invention is described in detail with specific embodiments below. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0048] A method for manufacturing a MEMS pressure sensor cavity according to an embodiment of the present invention will be described in detail below in conjunction with the above drawings. Figures 2 to 11 The present invention is a schematic cross-sectional structural diagram of a method for manufacturing a MEMS pressure sensor cavity according to an embodiment of the present invention.

[0049] Please refer to Figure 2 , performing step S0: providing a wafer 1, the wafer 1 comprising a chip area 11 and a non-chip area 12 formed on a substrate, the chip area 11 comprising a pressure device formed on the substrate. A resistor structure 14 and an electrical connection structure 13 are provided on the chip area 11.

[0050] In a specific implementation, wafers of specifications such as 6 inches, 8 inches, and 12 inches may be selected.

[0051] In one embodiment, the process of forming a pressure device on the wafer 1 specifically includes: providing a wafer; obtaining a pressure device on one side of the wafer using conventional processes such as photolithography, etching, and doping. Specifically, the resistor structure 14 is formed on the wafer through photolithography and ion implantation processes, silicon oxide is deposited on the front of the wafer through PECVD, and through holes are dry-etched at both ends of the resistor structure, a circuit pattern is formed through a photolithography process, and metal is deposited on the pattern, and a circuit is formed after a stripping process. The metal deposition process can be selected from electron beam evaporation, magnetron sputtering coating, and the like. In a specific example, the wafer is a Si wafer. The formation process of the pressure device should be known to those skilled in the art, and the present invention will not be elaborated here.

[0052] Please refer to Figure 1, executing step S1: forming a plurality of monitoring areas 9 on the front non-chip area 12 of the wafer 1, the monitoring area including a preset position, forming four grooves 3 with a preset depth at the vertex of the preset position, and a specific material 5 is arranged at the bottom of the groove 3. The cross-sectional view of the process of forming the grooves with a preset depth and a specific material arranged at the bottom is shown as follows Figures 3 to 6 As shown, the chip area is not shown in the figure, and only one monitoring area of ​​the non-chip area is shown, including:

[0053] Spin coating a first photoresist layer on the front side of wafer 1;

[0054] The first photoresist layer is exposed and developed to form a first photoresist 2 with a pattern of a groove 3 at a vertex of a preset position, such as Figure 3 As shown;

[0055] Using the first photoresist 2 patterned with the groove 3 as a mask, the wafer 1 is etched to form a groove 3 with a preset depth, such as Figure 4 Specifically, the monitoring area 9 is located in the non-chip area 12 on the front side of the wafer 1. The monitoring area 9 can be placed in any number and position on the non-chip area 12 of the wafer. For specific arrangement, please refer to Fig.12 The number and position of the corresponding monitoring area can be selected by those skilled in the art according to the specific situation, and no limitation is made here. The preset position of the non-chip area 12 corresponds to the area size surrounded by the resistor structure 14 of the pressure device of the chip area 11, refer to Fig.14 , a groove 3 is set at the vertex of the preset position. The etching of the groove 3 can be selected as dry etching or wet etching, and the etching depth is controlled by controlling the etching time. Since the depth of the groove 3 is much smaller than the depth of the cavity 4, preferably, the preset depth of the front groove 3 is 1 / 30 to 1 / 20 of the cavity etching depth. Therefore, compared with the cavity etching, the etching time of the groove etching is shorter and the depth control deviation is smaller. A specific material layer of a preset thickness is formed on the front side of the wafer 1, such as Figure 5 As shown; removing the patterned first photoresist 2, forming a specific material 5 having a preset thickness at the bottom of the groove 3, such as Figure 6 As shown. The first photoresist 2 can be stripped by dry stripping or wet stripping. The first photoresist 2 here covers the position outside the groove 3.

[0056] As an embodiment, the specific material 5 includes a material that can react with the etching liquid 8. Once the specific material 5 contacts and reacts with the etching liquid 8, it can form the ions to be detected. Specifically, the specific material is a metal such as Zn, Al2O3, ZnO and its metal oxide, amphoteric substances such as Ge, As or other dyes, etc. The specific material can be formed in the groove by a deposition process, and its preset thickness is less than the preset depth of the groove. It is not limited here. Those skilled in the art can select the material and the formation process according to the specific implementation situation.

[0057] In one embodiment, the etching liquid 8 is a TMAH solution or a KOH solution. The specific material 5 includes at least one of Al, Zn, Al2O3, ZnO, Ge, and As. Preferably, the specific material 5 located at the bottom of the groove 3 is Al, and the thickness of the Al layer is greater than 0.7 μm. When depositing amphoteric materials such as Al on the front of the wafer 1, it can be prepared by magnetron sputtering, electron beam evaporation, etc. After deposition, the specific material in the non-groove area is removed by photolithography and etching processes. There is no limitation here, and those skilled in the art can select the material and the process of formation according to the specific implementation situation.

[0058] Please refer to Figure 1 After completing step S1 and before executing step S2, the method further includes step S12:

[0059] A protective layer 7 is formed on both the front and back sides of the wafer 1. Figure 7 The mask layer 70 of the cavity 4 is formed by etching on the protective layer 7 on the back of the wafer 1, which specifically includes:

[0060] Spin coating a second photoresist layer on the back protection layer 7;

[0061] The second photoresist layer is exposed and developed to form a second photoresist 6 patterned on the back mask layer at a preset position mapped to the corresponding position on the back side of the wafer 1 and the position of the cavity in the chip area, such as Figure 8 As shown;

[0062] The protective layer 7 on the back side of the wafer 1 is etched to form a patterned mask layer 70 of the back side mask layer, such as Fig. 9 shown.

[0063] The protective layer 7 formed on the front side of the wafer is used to protect the pressure device and the specific materials in the groove of the wafer front monitoring area, so as to prevent the pressure device from being damaged during the wafer cavity etching process and ensure the device performance; it also prevents the specific materials in the groove from being damaged during the wafer cavity etching process, so that it cannot be used as the stop point of the cavity etching in the wet etching. On the other hand, since wet etching is isotropic etching, the protective layer 7 patterned on the back mask layer is used as the mask layer 70 for the wafer back cavity etching to protect the substrate outside the wafer back cavity from being etched by the etching solution.

[0064] The protective layer 7 is one of SiN / SiO2 or a combination of the two. The silicon oxide and silicon nitride layers can be prepared by LPCVD (low pressure chemical vapor deposition) or PECVD (plasma enhanced chemical vapor deposition) and other methods.

[0065] The thickness of the protective layer 7 is 12.5nm to 5.3μm. When the protective layer 7 is made of silicon oxide (SiO2), its thickness is 4.2 to 5.3μm; when the protective layer 7 is made of silicon nitride (SiN), its thickness is 12.5 to 15.6nm; when the protective layer 7 is made of both silicon oxide and silicon nitride, the protective layer 7 includes a silicon oxide film and a silicon nitride layer sequentially deposited on the front and back sides of the wafer, the thickness of the silicon oxide film is 12.5 to 15.6nm, and the thickness of the silicon nitride layer is greater than 20nm.

[0066] Please refer to Figure 1 , execute step S2:

[0067] The cavity 4 is formed by etching at the preset position and the corresponding position where the pressure device is mapped to the back of the wafer 1 through a wet etching process. Fig.10 When the etching liquid 8 of the wet etching process contacts the specific material 5, the etching stops. At this time, the thin film arranged above the cavity is a sensitive film, and the thickness of the sensitive film is the same as the preset depth, which specifically includes:

[0068] When etching the cavity on the back of the wafer, the mask pattern corresponding to the photolithography process includes the area enclosed by the resistor structure of the pressure device in the chip area and the pattern corresponding to the preset position. The photolithography process and etching process are performed on the back of the wafer. Due to the presence of the groove 3 at the vertex of the preset position on the front of the non-chip area, when etching reaches the bottom of the groove 3, the etching stops, and cavities of the same depth and size are formed in the chip area and the non-chip area. The cavity on the back of the chip area corresponds to the area enclosed by the resistor structure of the pressure device in the chip area, and the cavity on the back of the non-chip area corresponds to the preset position. At this time, the film arranged above the cavity is a sensitive film, and the groove depth is equal to the thickness of the sensitive film, which is equal to the preset depth of the groove, that is, equal to the wafer thickness minus the cavity depth.

[0069] The etching of the back cavity of the non-chip area and the groove at the vertex of the front preset position is stopped, and the thickness of the sensitive film can be controlled. In the prior art, the cavity etching depth error of the method of multiple wet etching of Si wafers to obtain the cavity is generally more than 10%. Compared with the method of multiple wet etching, the error of the cavity etching depth in the present invention is determined by the accuracy of the front groove etching depth and the speed at which the detection system detects the specific signal, and the front groove etching depth is 1 / 30 to 1 / 20 of the cavity etching depth. Therefore, the cavity etching depth error of this method can be controlled to less than 10%, shortening the process time, and can greatly reduce the cavity etching depth error, and improve the accuracy of the device; further, the thickness of the required pressure sensor sensitive film can be controlled by controlling the depth of the front preset position groove, thereby accurately controlling the thickness of the sensitive film of the sensor with different ranges. On the other hand, by aligning the groove at the vertex of the front preset position of the non-chip area and the back cavity, the alignment monitoring of the front resistance pattern and the back cavity of the chip area can be achieved.

[0070] In one embodiment, step S2 further comprises using a detection device to detect the etching endpoint: the specific material comprises a material that can react with the etching liquid, the specific material contacts and reacts with the etching liquid to form ions to be detected, the detection device detects the ions to be detected, and stops etching, for example, using graphite furnace atomic absorption spectroscopy to detect the ions to be detected. During the wet etching process, the detection device detects whether the ions to be detected appear in the etching liquid 8 in the cavity 4. When the cavity 4 is etched to a certain depth, the etching liquid 8 contacts the bottom of the front groove 3, and the specific material 5 reacts with the TMAH or KOH solution to release gas to form metal ions (such as Al, Zn, etc.) or other special ions (such as Ge, As, etc.), the detection device detects these signals at this time, then the etching depth of the cavity 4 reaches the requirement, and the etching is stopped. At this time, the thin film arranged above the cavity is a sensitive film, and the thickness of the sensitive film is consistent with the depth of the groove 3. In this embodiment, since the specific material 5 located at the bottom of the groove 3 is Al, when the specific material 5 reacts with the TMAH or KOH solution to form Al ions, the detection equipment detects the signal of the Al ions, and the etching depth of the cavity 4 reaches the requirement, the wafer 1 needs to be taken out immediately and the etching is stopped.

[0071] Among them, the cross section of the cavity 4 is polygonal, and the center of each groove 3 corresponds to each vertex of the cavity 4. In this embodiment, the cross section of the cavity 4 is square (because the sensitive membrane of the pressure sensor is a rectangular membrane, it is beneficial to obtain high sensitivity, so the main flow of the cavity bottom surface is mostly square), and the number of grooves 3 is four and corresponds to the four vertices of the cavity 4 respectively. The cross section of the groove 3 is square, and its length and width can be selected to be 10-50 microns. In addition, the cross section of the groove 3 can also adopt other graphics, such as triangle, rhombus, cross, etc., as long as the graphic is conducive to the filling of the specific material 5, and it is convenient to detect the deviation between the position of the back cavity 4 and the position of the front graphic.

[0072] By detecting the metal ion concentration, it is determined whether the wet etching has reached the expected depth, and whether the cavity 4 prepared by wet etching has reached the etching depth can be monitored at a low cost, thereby avoiding over-etching and making the thickness deviation of the sensitive film smaller. When a sensitive film pressure sensor is manufactured in this way, the sensitivity and stability of the pressure sensor can be improved.

[0073] After completing step S2, you need to perform step S3:

[0074] removing the second photoresist on the wafer;

[0075] removing the protective layer and the specific material;

[0076] Measuring the deviation between the center of the groove 3 in the monitoring area and the edge of the corresponding cavity 4;

[0077] Specifically, after the etching of the cavity 4 is stopped, the second photoresist layer on the back of the wafer is removed, and the protective layer on the front and back of the wafer and the specific material in the groove are removed, such as Fig.11 As shown. The process of removing the photoresist layer should be known to those skilled in the art, and the present invention will not be described in detail here; the protective layer and the specific material can be removed by using a wet etching process, and the etching liquid used can be a BOE solution (buffered oxide etchant, a mixture of ammonium fluoride and hydrofluoric acid buffers). Those skilled in the art can select the process according to the actual situation, and are not limited here. After the photoresist layer, the protective layer and the specific material are removed, the deviation between the center of the groove 3 and the edge of the cavity 4 is measured by automatic optical inspection or optical microscope detection to characterize the alignment accuracy of the groove pattern in the front monitoring area and the cavity pattern on the back of the wafer, and then characterize the alignment accuracy of the back cavity in the chip area and the front pressure device, so as to achieve the characterization of the alignment accuracy of the cavity in the wafer chip area and the resistor structure in the pressure device, and determine whether the obtained device meets the requirements; further, control can be carried out at this stage so that samples with unqualified alignment accuracy do not flow into the next normal process, and unqualified samples are scrapped or reworked to improve the yield.

[0078] Example 2

[0079] The difference from Example 1 is that the specific material 5 is a material that can dissolve in the etching liquid 8 and change its color. When the cavity 4 is etched to a certain depth, the etching liquid 8 contacts the bottom of the front groove 3, and the specific material 5 at the bottom of the groove 3 contacts the etching liquid 8 in the cavity 4, so that the etching liquid 8 begins to change color. The etching depth of the cavity 4 reaches the requirement and the etching is stopped. The specific material 5 includes one of an acid-base indicator, a dye, a coating, and a sprayable glass paint.

[0080] By detecting the color change in the etching liquid 8, it is determined whether the wet etching has reached the expected depth, and whether the cavity 4 prepared by wet etching has reached the etching depth can be monitored at a low cost, thereby avoiding over-etching and making the thickness deviation of the sensitive film smaller. When a sensitive film pressure sensor is manufactured in this way, the sensitivity and stability of the pressure sensor can be improved, and the alignment accuracy of the front and back patterns of the wafer can be characterized, thereby improving the yield.

[0081] In summary, by judging the etching stop of the back cavity of the non-chip area and the groove at the vertex of the front preset position through the information released by the specific material, the thickness of the sensitive film can be controlled to improve the accuracy of the device; further, the thickness of the required pressure sensor sensitive film can be controlled by controlling the depth of the groove at the front preset position, thereby accurately controlling the thickness of the sensitive film of sensors with different measuring ranges. On the other hand, by aligning the groove at the vertex of the front preset position of the non-chip area and the back cavity, the alignment monitoring of the front resistance pattern of the chip area and the back cavity can be achieved, improving the alignment accuracy of the front and back sides of the wafer, thereby improving the yield.

[0082] The present invention has been described above in conjunction with the best embodiments, but the present invention is not limited to the embodiments disclosed above, but should cover various modifications and equivalent combinations based on the essence of the present invention.

Claims

1. A method for manufacturing a MEMS pressure sensor cavity, characterized in that: Provide a wafer, the wafer comprising a chip area and a non-chip area formed on a substrate, the chip area comprising a pressure device formed on the substrate; The method for making the cavity comprises: Step S1: forming a plurality of monitoring areas on the front non-chip area of ​​the wafer, wherein the monitoring area includes a preset position, a plurality of grooves with a preset depth are formed at the apex of the preset position, and a specific material is disposed at the bottom of the groove; Step S2: A cavity is formed by etching at the preset position and at the corresponding position where the pressure device is mapped to the back side of the wafer through a wet etching process. When the etching liquid of the wet etching process contacts the specific material, the etching stops. At this time, the thin film arranged above the cavity is a sensitive film, and the thickness of the sensitive film is the same as the preset depth.

2. The method for manufacturing a MEMS pressure sensor cavity according to claim 1, characterized in that: A plurality of grooves with a preset depth are formed at the vertices of the preset positions, and a specific material is arranged at the bottom of the grooves, specifically comprising: Spin coating a first photoresist layer on the front side of the wafer; Exposing and developing the first photoresist layer to form the first photoresist with the groove pattern at the vertex of the preset position; Using the first photoresist patterned with the groove as a mask, etching the wafer to form the groove having the preset depth; forming a specific material layer of a preset thickness on the front side of the wafer; The patterned first photoresist is removed to form the specific material with the preset thickness at the bottom of the groove.

3. The method for manufacturing a MEMS pressure sensor cavity according to claim 1, characterized in that: After completing step S1, before proceeding to step S2, the following further includes: forming a protective layer on the front and back sides of the wafer, wherein a mask layer of the cavity is formed on the protective layer on the back side of the wafer by etching; Spin coating a second photoresist layer on the back protection layer; exposing and developing the second photoresist layer to form a second photoresist patterned on the back mask layer at the preset position and at a corresponding position where the pressure device is mapped to the back side of the wafer; The protective layer on the back side of the wafer is etched to form the protective layer patterned by the back side mask layer.

4. The method for manufacturing a MEMS pressure sensor cavity according to claim 3, characterized in that: The protective layer is made of SiN / SiO2 or a combination of the two.

5. The method for manufacturing a MEMS pressure sensor cavity according to claim 3, characterized in that: The thickness of the protective layer is 12.5 nm to 5.3 μm.

6. The method for manufacturing a MEMS pressure sensor cavity according to claim 1, characterized in that: The step S2 also includes: using a detection device to detect the etching endpoint; the specific material includes a material that can react with the etching liquid, the specific material contacts and reacts with the etching liquid to form ions to be detected, and the detection device detects the ions to be detected and stops etching.

7. The method for manufacturing a MEMS pressure sensor cavity according to claim 6, characterized in that: The thickness of the specific material is greater than 0.7 μm; the specific material includes at least one of Al, Zn, Al2O3, ZnO, Ge, and As; and the etching liquid is one of TMAH solution and KOH solution.

8. The method for manufacturing a MEMS pressure sensor cavity according to claim 1, characterized in that: The specific material includes a material that can dissolve in the etching liquid and change its color; when the etching liquid in the cavity begins to change color, etching is stopped; wherein the specific material includes one of an acid-base indicator, a dye, a coating, and a sprayable glass paint.

9. The method for manufacturing a MEMS pressure sensor cavity according to claim 3, characterized in that: The cross section of the cavity is polygonal, the number of the grooves is multiple, and the center of each groove corresponds to each vertex of the cavity.

10. The method for manufacturing a MEMS pressure sensor cavity according to claim 9, characterized in that: After completing step S2, step S3 is also included: removing the second photoresist; removing the protective layer and the specific material; The deviation between the center of the groove in the monitoring area and the corresponding edge of the cavity is measured.

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