阅读说明：本技术 一种多频cmut器件的制造方法及多频cmut器件 (Manufacturing method of multi-frequency CMUT device and multi-frequency CMUT device ) 是由 王久江 余远昱 旷江明 徐晶 杨济宁 张双 李尧 刘益和 于 2020-05-20 设计创作，主要内容包括：本申请提供一种多频CMUT器件的制造方法及多频CMUT器件,包括选用高浓度掺杂的硅晶圆作为基底制作硅基层；在所述硅基层的上表面设置绝缘层；在所述绝缘层的上表面沉积非晶硅制备牺牲层并定义CMUT单元；所述牺牲层包括圆形主体和与所述圆形主体连接的多个释放通道；在所述CMUT单元上沉积振动薄膜；在各个所述释放通道的开孔位置开设腐蚀孔,对牺牲层进行释放,形成空腔；在所述牺牲层释放完毕后密封所述腐蚀孔；利用光刻蚀工艺围绕所述圆形主体形成的空腔刻蚀预设宽度的支撑壁；深腐蚀操作至硅基层,以便沉积底电极；沉积电极及器件之间的连接导线,同时在所述振动薄膜的上表面沉积顶电极。(The application provides a manufacturing method of a multi-frequency CMUT device and the multi-frequency CMUT device, which comprises the steps of selecting a high-concentration doped silicon wafer as a substrate to manufacture a silicon substrate; arranging an insulating layer on the upper surface of the silicon-based layer; depositing amorphous silicon on the upper surface of the insulating layer to prepare a sacrificial layer and define a CMUT unit; the sacrificial layer comprises a circular body and a plurality of release channels connected with the circular body; depositing a vibrating membrane on the CMUT cell; opening corrosion holes at the positions of the openings of the release channels, and releasing the sacrificial layer to form a cavity; sealing the corrosion hole after the sacrificial layer is released; etching a supporting wall with a preset width by using a cavity formed around the circular main body by using a photoetching process; etching back to the silicon base layer to deposit the bottom electrode; and depositing a connecting wire between the electrode and the device, and simultaneously depositing a top electrode on the upper surface of the vibration film.)

1. A method of fabricating a multi-frequency CMUT device, comprising:

s1, selecting a high-concentration doped silicon wafer as a substrate to manufacture a silicon substrate layer;

step S2, arranging an insulating layer on the upper surface of the silicon-based layer;

step S3: depositing amorphous silicon on the upper surface of the insulating layer to prepare a sacrificial layer and define a CMUT unit; the sacrificial layer comprises a circular body and a plurality of release channels connected with the circular body;

step S4: depositing a vibrating membrane on the CMUT cell;

step S5: opening corrosion holes at the positions of the openings of the release channels, and releasing the sacrificial layer to form a cavity;

step S6: sealing the corrosion hole after the sacrificial layer is released;

step S7: etching a supporting wall with a preset width by using a cavity formed around the circular main body by using a photoetching process, and performing thinning operation to recover the thickness of the vibration film;

step S8: etching back to the silicon base layer to deposit a bottom electrode;

step S9: and depositing a connecting wire between the electrode and the device, and simultaneously depositing a top electrode on the upper surface of the vibration film.

2. The method of manufacturing of claim 1, wherein the relief channel comprises an opening to an L-shaped channel and an etch hole; the first end of the L-shaped channel is communicated with the sacrificial layer; the second end of the L-shaped channel is communicated with the corrosion hole opening part; the corrosion hole forming part is used for forming corrosion holes.

3. The method of manufacturing of claim 2, wherein a thickness of the L-shaped channel is consistent with a thickness of the circular body.

4. The method of claim 2, wherein the etch hole opening is square in shape.

5. The method of claim 1, wherein the step S6 is performed by sealing the etch holes with silicon nitride.

6. The manufacturing method according to claim 1, wherein the vibration film is a low residual stress silicon nitride film.

7. The manufacturing method according to claim 1, characterized by further comprising: the width of the supporting walls is increased according to the requirements of the eigenfrequency of the CMUT device.

8. A multi-frequency CMUT device is characterized by comprising a silicon substrate, an insulating layer, a cavity, a vibration film, a top electrode and a supporting wall; the insulating layer is arranged on the upper surface of the silicon base layer; the cavity is circular; the shape of the vibration film is matched with that of the cavity, and the cavity is arranged between the vibration film and the insulating layer; the support wall is disposed around an edge of the cavity; the top electrode is arranged on the upper surface of the vibration film.

Technical Field

The present invention relates to the technical field of ultrasonic sensor manufacturing, and in particular, to a method for manufacturing a multi-frequency CMUT device and a multi-frequency CMUT device.

Background

The ultrasonic probe plays a key role in ultrasonic imaging; the ultrasonic sensor is a key component of an ultrasonic probe, the early ultrasonic sensor generally adopts lead zirconate titanate ceramic (PZT), and along with the development of the technology, the capacitive micromachined ultrasonic sensor (CMUT) has the advantages of wide frequency band, easy integration of an integrated circuit, easy processing and the like, and has the advantages of replacement. The eigenfrequency of the CMUT can determine the imaging accuracy, and generally methods for raising the eigenfrequency of the CMUT include methods of reducing the radius of the membrane, increasing the thickness of the membrane, changing the material of the membrane, and the like. However, the methods of adjusting the radius of the film, increasing the thickness of the film, changing the material of the film, etc. require adjusting the layout of at least two layers of design layouts, which makes the production flow more complicated. It is therefore desirable to provide a solution to facilitate increasing the eigenfrequencies of CMUTs more conveniently in case only one layer of the design layout is changed.

Disclosure of Invention

The present application provides a method for manufacturing a multi-frequency CMUT device and a multi-frequency CMUT device, so as to achieve the technical effect of more conveniently improving the eigenfrequency of the CMUT by only changing one layer of design layout.

In a first aspect, an embodiment of the present application provides a method for manufacturing a multi-frequency CMUT device, including

S1, selecting a high-concentration doped silicon wafer as a substrate to manufacture a silicon substrate layer;

step S2, arranging an insulating layer on the upper surface of the silicon-based layer;

step S3: depositing amorphous silicon on the upper surface of the insulating layer to prepare a sacrificial layer and define a CMUT unit; the sacrificial layer comprises a circular body and a plurality of release channels connected with the circular body;

step S4: depositing a vibrating membrane on the CMUT cell;

step S5: opening corrosion holes at the positions of the openings of the release channels, and releasing the sacrificial layer to form a cavity;

step S6: sealing the corrosion hole after the sacrificial layer is released;

step S7: etching a supporting wall with a preset width by using a cavity formed around the circular main body by using a photoetching process, and performing thinning operation to recover the thickness of the vibration film;

step S8: etching back to the silicon base layer to deposit a bottom electrode;

step S9: and depositing a connecting wire between the electrode and the device, and simultaneously depositing a top electrode on the upper surface of the vibration film.

Further, the release channel comprises an opening part which is communicated with the L-shaped channel and the corrosion hole; the first end of the L-shaped channel is communicated with the sacrificial layer; the second end of the L-shaped channel is communicated with the corrosion hole opening part; the corrosion hole forming part is used for forming corrosion holes.

Further, the thickness of the L-shaped channel is consistent with the thickness of the circular body.

Further, the shape of the corrosion hole opening part is square.

Further, the material used in sealing the etch hole in step S6 is silicon nitride.

Further, the vibration film is a low residual stress silicon nitride film.

Further, the manufacturing method further includes: the width of the supporting walls is increased according to the requirements of the eigenfrequency of the CMUT device.

In a second aspect, an embodiment of the present application provides a multi-frequency CMUT device, including a silicon-based layer, an insulating layer, a cavity, a vibrating membrane, a top electrode, and a supporting wall; the insulating layer is arranged on the upper surface of the silicon base layer; the cavity is circular; the shape of the vibration film is matched with that of the cavity, and the cavity is arranged between the vibration film and the insulating layer; the support wall is disposed around an edge of the cavity; the top electrode is arranged on the upper surface of the vibration film.

The beneficial effect that this application can realize is: in the traditional process of manufacturing the CMUT device by adopting a sacrificial layer release method, the thickness of the supporting wall is generally not considered, but the thickness of the supporting wall has great influence on the intrinsic frequency of the CMUT device.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments of the present application will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and that those skilled in the art can also obtain other related drawings based on the drawings without inventive efforts.

Fig. 1 is a schematic flow chart of a method for manufacturing a multi-frequency CMUT device according to an embodiment of the present application;

fig. 2 is a schematic diagram of a first mask structure when a multi-frequency CMUT device is fabricated according to an embodiment of the present application;

fig. 3 is a schematic diagram of a second mask structure when a multi-frequency CMUT device is fabricated according to an embodiment of the present application;

fig. 4 is a schematic diagram of a third mask structure for fabricating a multi-frequency CMUT device according to an embodiment of the present application;

fig. 5 is a schematic cross-sectional structure diagram of a multi-frequency CMUT device according to an embodiment of the present application.

Icon: 10-multi-frequency CMUT devices; a 100-si base layer; 200-an insulating layer; 300-a cavity; 400-vibrating the membrane; 500-a top electrode; 600-a support wall; 700-first layer mask; 710-a circular body; 720-L-shaped channel; 730-etching hole forming part; 800-a second layer of mask; 900-third level mask.

Detailed Description

The technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures. Meanwhile, in the description of the present application, the terms "first", "second", and the like are used only for distinguishing the description, and are not to be construed as indicating or implying relative importance.

Referring to fig. 1, fig. 2, fig. 3 and fig. 4, fig. 1 is a schematic flow chart illustrating a method for manufacturing a multi-frequency CMUT device according to an embodiment of the present application; fig. 2 is a schematic diagram of a first mask structure when a multi-frequency CMUT device is fabricated according to an embodiment of the present application; fig. 3 is a schematic diagram of a second mask structure when a multi-frequency CMUT device is fabricated according to an embodiment of the present application; fig. 4 is a schematic diagram of a third mask structure in the fabrication of a multi-frequency CMUT device according to an embodiment of the present application.

The applicant researches and discovers that the common methods for increasing the eigenfrequency of the CMUT include methods of reducing the radius of the membrane, increasing the thickness of the membrane, changing the material of the membrane, and the like. However, methods such as reducing the radius of the thin film, increasing the thickness of the thin film, and changing the material of the thin film need to adjust the layout of the design layout, and the production process is more complicated, so a scheme needs to be provided to more conveniently improve the eigenfrequency of the CMUT under the condition that only one layer of the layout of the design layout is changed, and the specific production steps are as follows.

S1, selecting a high-concentration doped silicon wafer as a substrate to manufacture a silicon substrate layer;

the silicon substrate 100 can be made of a high-concentration doped silicon wafer (the purity of silicon is 99.999%) before production, and the shape of the silicon substrate 100 can be made into a round shape or a square shape.

Step S2, arranging an insulating layer on the upper surface of the silicon-based layer;

after the silicon substrate 100 is formed, the insulating layer 200 is deposited on the silicon substrate 100, and the insulating layer 200 may be silicon nitride (Si)₃N₄) Low Pressure Chemical Vapor Deposition (LPCVD) may be used for the Deposition.

Step S3: depositing amorphous silicon on the upper surface of the insulating layer to prepare a sacrificial layer and define a CMUT unit; the sacrificial layer comprises a circular body and a plurality of release channels connected with the circular body;

after depositing the insulating layer 200 on the silicon based layer 100, a sacrificial layer may be prepared by depositing amorphous silicon on the insulating layer 200 using a first layer mask 700 as shown in figure 2, while defining the CMUT cells. The sacrificial layer prepared using the first layer mask 700 includes a circular body 710 and a plurality of release channels connected to the circular body 710. The sacrificial layer can also be deposited using LPCVD.

In one embodiment, the release channel includes a channel that is aligned with the L-shaped channel 720 and the etch hole opening 730; a first end of the L-shaped channel 720 communicates with the circular body 710; the second end of the L-shaped channel 720 is communicated with the etch hole opening part 730; the etch hole opening portion 730 is used to open an etch hole. In order to improve the efficiency of sacrificial layer release, the thickness of the L-shaped channel 720 is consistent with that of the circular body 710; meanwhile, in order to facilitate the start of etching, the etching hole opening portion 730 is provided in a square shape. However, the shape of the etch hole opening portion 730 is not limited to the square shape, and may be a circle, a triangle, or another polygonal shape.

Step S4: depositing a vibrating membrane on the CMUT cell;

after the CMUT cell is defined, the vibration membrane 400 may be deposited on the CMUT cell, and the vibration membrane 400 may be a low residual stress silicon nitride membrane.

The vibration film 400 may be a silicon oxide film, a silicon film, or the like.

Step S5: opening corrosion holes at the positions of the openings of the release channels, and releasing the sacrificial layer to form a cavity;

when etching the etch holes, the second layer mask 800 shown in fig. 3 may be used, and openings corresponding to the shapes and positions of the etch hole openings 730 are formed in the second layer mask 800, and the openings are smaller than the etch hole openings 730 and located in the central region of the etch hole openings 730. After the second mask 800 is arranged, an etch hole can be formed at the opening by using potassium hydroxide to release the sacrificial layer, thereby forming a cavity.

Step S6: sealing the corrosion hole after the sacrificial layer is released;

and after the sacrificial layer is completely released, sealing the corrosion hole by using a sealing material. Silicon nitride may be deposited in the etch holes by LPCVD during sealing.

Step S7: etching a supporting wall with a preset width by using a cavity formed around the circular main body by using a photoetching process, and performing thinning operation to recover the thickness of the vibration film;

after the etch hole sealing is completed, a predetermined width of the support wall 600 is etched around the cavity formed by the circular body 710 of the sacrificial layer using a photolithography process. The width of the support walls 600 corresponds to the thickness of the support walls 600 of the finished device. Specifically, the supporting walls 600 can be prepared by using the third layer mask 900 as shown in fig. 4, and meanwhile, the third layer mask 900 can be modified according to the requirement of the eigenfrequency of the multi-frequency CMUT device 10 in the using process, so as to increase the width of the supporting walls 600, thereby increasing the eigenfrequency of the CMUT device. A variety of CMUT devices with different eigenfrequencies are fabricated. During manufacturing, only the width of the supporting wall 600 needs to be changed, and the design layout does not need to be completely modified, so that the supporting wall can be manufactured more conveniently. The third layer mask 900 is also provided with a pattern to protect the etch holes, which may be better sealed.

Step S8: etching back to the silicon base layer to deposit the bottom electrode;

after the support wall 600 is prepared, the etch back operation may be continued to the silicon substrate to deposit the bottom electrode, which may be circular, rectangular, etc. The material of the top electrode 500 may be aluminum or gold.

Step S9: and depositing a connecting wire between the electrode and the device, and simultaneously depositing a top electrode on the upper surface of the vibration film.

After the bottom electrode deposition is completed, the connection wires between the electrodes and the devices can be deposited, and then the top electrode 500 is continuously deposited on the vibration film 400, wherein the top electrode 500 can be arranged in the central area of the vibration film 400, and the shape can be round, rectangular, and the like. The material of the top electrode 500 may be aluminum or gold.

Referring to fig. 5, fig. 5 is a schematic cross-sectional structure diagram of a multi-frequency CMUT device according to an embodiment of the present application.

The embodiment of the present application further provides a multi-frequency CMUT device 10, the multi-frequency CMUT device 10 includes a silicon-based layer 100, an insulating layer 200, a cavity 300, a vibrating membrane 400, a top electrode 500, and a support wall 600; the insulating layer 200 is disposed on the upper surface of the silicon substrate 100; the cavity 300 is circular; the shape of the vibration film 400 matches the shape of the cavity 300 and the cavity 300 is disposed between the vibration film 400 and the insulating layer 200; the support wall 600 is disposed around the edge of the cavity 300; the top electrode 500 is disposed on the upper surface of the vibration film 400. When the eigenfrequency of the multi-frequency CMUT device 10 of this type needs to be raised, only the thickness of the supporting wall 600 needs to be increased, and the original design layout does not need to be modified completely.

In summary, the present application provides a method for manufacturing a multi-frequency CMUT device and a multi-frequency CMUT device, including step S1 of selecting a highly doped silicon wafer as a substrate to fabricate a silicon substrate; step S2, arranging an insulating layer on the upper surface of the silicon-based layer; step S3: depositing amorphous silicon on the upper surface of the insulating layer to prepare a sacrificial layer and define a CMUT unit; the sacrificial layer comprises a circular body and a plurality of release channels connected with the circular body; step S4: depositing a vibrating membrane on the CMUT cell; step S5: opening corrosion holes at the positions of the openings of the release channels, and releasing the sacrificial layer to form a cavity; step S6: sealing the corrosion hole after the sacrificial layer is released; step S7: etching a supporting wall with a preset width by using a cavity formed around the circular main body by using a photoetching process, and performing thinning operation to recover the thickness of the vibration film; step S8: etching back to the silicon base layer to deposit a bottom electrode; step S9: and depositing a connecting wire between the electrode and the device, and simultaneously depositing a top electrode on the upper surface of the vibration film. By the mode, the eigen frequency of the CMUT can be improved more conveniently under the condition that only one layer of design layout is changed, the manufacturing process is more convenient, and the production cost is also reduced.

The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.