CN102942157A - Flow sensor manufacturing method by the way of positive corrosion - Google Patents

Abstract

The invention relates to a method for manufacturing a flow sensor by means of frontal corrosion. In this method, a groove for making a cavity is formed on the front surface of the substrate by reactive ion etching. The depth of the groove determines the thickness of the substrate above the cavity, and then a barrier layer is deposited on the surface of the substrate and the side walls and bottom of the groove. Selectively remove the barrier layer on the surface of the substrate and the bottom of the groove, form a sidewall protective layer on the sidewall of the groove, and use the sidewall protective layer as a mask to continue etching the groove to form a deep groove. Wet etching is used to etch deep grooves to form cavities inside the substrate; then metal-containing heating devices and temperature measuring devices are fabricated in specific areas on the front side, and then a protective layer is deposited. In this way, the thickness-controllable silicon substrate cavity under the specific area where the heating device and the temperature measuring device are located can be obtained with high efficiency and low cost.

Description

Method for manufacturing flow sensor by front-side corrosion

technical field

The invention relates to the technical field of micro-electromechanical system (MEMS) manufacturing, in particular, the invention relates to a method for manufacturing a flow sensor by means of front-side corrosion.

Background technique

In the structure of some temperature-related semiconductor sensors, it is sometimes necessary for the sensor to be on a thin suspended film, and the thickness of the suspended film is relatively thin. After packaging, the substrate below the sensor is not in direct contact with the base of the package. , but suspended in the air and in contact with air or vacuum to achieve the purpose of reducing the interference of the external environment temperature.

In terms of the application of the above sensors, the accuracy of the sensor is closely related to the thickness of the substrate material below the device. In order to achieve higher temperature measurement accuracy and shorter response time, it is necessary to make the thickness of the film above the suspension thinner to reduce the longitudinal heat conduction of the device; of course, on the other hand, it is also necessary to consider the supporting effect of the thinner substrate on the device, the thicker the thickness , the stronger the structure of the sensor, it is ultimately necessary to consider the above factors comprehensively to select an appropriate thickness of the surface film.

For the semiconductor process, most of the current sensor processes require the backside process. These processes are the current mainstream, but they are not compatible with the conventional semiconductor process. Therefore, it is necessary to use a customized sensor processing line, which increases production cost. Moreover, it is also very difficult to obtain an accurate surface silicon thickness through the backside etching process. When processing in a semiconductor factory with a large size and many batches, the uniformity of the devices in the chip and the repeatability of the devices between the chips are more exposed. By adopting the manufacturing method of the present invention, the above-mentioned problems can be well solved, and the quality of the manufactured sensor is obviously higher.

The invention relates to a manufacturing method of a flow sensor, which has good uniformity of devices in a chip and repeatability of devices between chips, and is suitable for mass production.

Contents of the invention

The purpose of the present invention is to provide a method for manufacturing a flow sensor by front-side etching, which is compatible with conventional semiconductor manufacturing processes, simplifies the manufacturing process, and reduces production costs.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical scheme: a method for manufacturing a flow sensor by front-side corrosion, characterized in that: the manufacturing process steps are as follows:

1) Take a silicon substrate, which is covered with a layer of isolation layer, and form grooves for making cavities in the silicon substrate by dry etching;

2) depositing a barrier layer on the surface of the substrate and the sidewalls and bottom of the trench;

3) removing the barrier layer on the surface of the substrate and the bottom of the groove, and forming a sidewall protection layer on the sidewall of the groove;

4) Using the sidewall protective layer as a mask, continue to etch the groove to form a deep groove;

5) Etching the deep groove by wet etching to form a cavity inside the substrate;

6) Filling the isolation and/or filling material between the side wall protection layers of the groove to form a plug structure to isolate the cavity from the outside world;

7) planarizing the surface of the substrate;

8) Depositing an electrothermal layer on the silicon substrate;

9) Patterning the electrothermal layer, forming a heating device, a temperature measuring device and electrodes on the silicon substrate;

10) Depositing a protective layer on the substrate, the protective layer covering the heating device and the temperature measuring device.

Optionally, the method further includes depositing an insulating layer before forming the cavity for forming the cavity.

Optionally, the substrate is silicon with (111) crystal orientation.

Optionally, the shape and/or depth of the grooves are adjustable according to actual needs.

Optionally, the barrier layer is formed by chemical vapor deposition or atomic layer deposition.

Optionally, the barrier layer on the surface of the substrate and the bottom of the groove is removed by an etch-back process.

Optionally, the depth of the deep groove is 0.1-10um.

Optionally, the wet etching method uses an anisotropic etching process to form a cavity inside the substrate.

Optionally, the wet etching solution is KOH and/or TMAH.

Optionally, the shape and/or depth of the cavity is arbitrary.

Optionally, an isolation and/or filling material is filled between the sidewall protection layers of the trench by chemical vapor deposition or atomic layer deposition.

Optionally, the isolation and/or filling material is a single-layer or multi-layer structure.

Optionally, the planarization process includes chemical mechanical polishing and/or etching back.

Optionally, the electrothermal layer is made of metal-containing material.

Optionally, the electrothermal layer is a single-layer or multi-layer structure.

Optionally, the metal-containing material is a temperature-resistant material.

Optionally, the temperature resistance material includes platinum or gold.

Optionally, the shape, layout, line size, thickness and number of turns of the heating device and the temperature measuring device can be adjusted according to different needs.

Optionally, the protective layer is a single-layer or multi-layer structure.

Compared with the prior art, the present invention has the following obvious outstanding substantive features and significant technical progress:

The air flow sensor manufacturing method provided by the present invention adopts a front-side corrosion process compatible with conventional semiconductor processes, and can realize large-scale manufacturing on a general-purpose semiconductor production line, and has the advantages of practicality, economy, and high performance.

Description of drawings

Fig. 1 is a structural schematic diagram of a flow sensor of the present invention.

Fig. 2 is a sectional view at A-A in Fig. 1 .

3 to 16 are structural schematic diagrams of various procedures in the manufacturing process of the flow sensor shown in FIG. 1 .

Detailed ways

Preferred embodiments of the present invention are described in detail as follows in conjunction with accompanying drawings:

FIG. 1 is a schematic plan view of the structure of a temperature resistance sensor manufactured by an embodiment of the present invention. In the plan view of the sensor structure shown in FIG. 1 , a substrate 001 includes a groove 002 forming a cavity, a heating unit 003 , a temperature measuring unit 004 and a cavity 010 . In order to better illustrate the structure of the temperature resistance sensor, a schematic cross-sectional structure diagram of the above-mentioned sensor in the A-A direction is made, as shown in FIG. 2 .

FIG. 2 is a schematic cross-sectional structure diagram of the temperature resistance sensor structure shown in FIG. 1 along the A-A direction in the figure. It can be seen from FIG. 2 that the heating unit 003 and the temperature measuring unit 004 are formed on a base film with a certain thickness, and the film is suspended above the cavity 010. The number 006 in the figure is the filling material, and the numbers 108 and 008 are respectively It is the top protection layer and the groove side wall protection layer, and the label 009 is the isolation layer.

Those skilled in the art should recognize that the above distribution diagrams of the temperature resistance sensor structures shown in FIG. 1 and FIG. 2 are schematic. It should also be understood here that the arrangement and adjustment of the positions of the internal units of the temperature resistance sensor structure can be done at will according to the needs, all of which are within the protection scope of the application of the present invention. In addition, the shape and/or size of the heating unit and the temperature measuring unit in the present invention can also be adjusted arbitrarily as required.

The manufacturing process of the temperature resistance sensor according to the embodiment of the present invention will be further described below in combination with specific embodiments and accompanying drawings.

3 to 16 are schematic cross-sectional structural views of the manufacturing process of the temperature resistance sensor according to an embodiment of the present invention. It should be noted that these and other subsequent drawings are only examples, which are not drawn according to the same scale, and should not be taken as limitations on the protection scope of the actual claims of the present invention.

In this method of manufacturing a flow sensor using a front-side corrosion method, the manufacturing process steps are as follows:

1) As shown in Figure 3, a silicon substrate 001 is taken, and an isolation layer 100 is covered on the substrate, and the isolation layer can be oxide, nitride, etc. Here, silicon (Si) is taken as an example for the substrate 001 , but the substrate material that can be used in the present invention is obviously not limited thereto, and those skilled in the art can make corresponding adjustments according to actual needs.

As shown in FIG. 4 , the substrate 001 is etched to form a groove 002 for making a cavity in the substrate 001 , wherein the shape and/or depth of the groove 002 are adjustable according to actual needs. From a top view (not shown), the projection of the groove 002 can be polygonal (including rectangular), circular, or other shapes, which will not be repeated here.

2) As shown in Figure 5, a layer of barrier layer 101 is deposited on the surface of the isolation layer 100 and the sidewall and bottom of the groove 002 by chemical vapor deposition, or other methods such as atomic layer deposition can also be used Instead, the deposited barrier layer 101 must cover the sidewalls of the trench 002 . Therefore, those skilled in the art should realize that the specific deposition method used depends on whether the method can well cover the sidewall of the groove 002 .

3) As shown in Figure 6, the surface of the isolation layer 100 and the barrier layer 101 at the bottom of the groove 002 are completely removed through the etching-back process, especially to expose the bottom of the groove 002, that is, the barrier layer 101 at the bottom is completely removed. The unremoved part of the barrier layer 101 attached to the sidewall of the groove 002 becomes the sidewall protection layer of the groove 002 .

4) As shown in Figure 7, using the etching process, using the sidewall protection layer 101 as a mask, continue to etch the groove 002 to form a deep groove 102. The depth of the deep groove 102 can be 0.1-100um. , because the sidewall protection layer 101 exists as a hard mask during the etching process to protect other regions, therefore, the selected etching conditions require a better etching selectivity ratio.

5) As shown in Figure 8, the deep groove 102 is etched by wet etching method to form a cavity 010 inside the substrate 001. For example, choose silicon as the substrate, use KOH and/or NaOH and/or EPW and/or TMAH and other wet etching solutions to etch the substrate 001 anisotropically (selectively) when etching its internal cavity, and inside it A cavity 010 is formed. Those skilled in the art may preferably use an anisotropic etching process according to actual needs, and of course other etching methods may also be used. It should be noted that the cavity 010 shown here is a regular rectangle in cross-section. However, it should be pointed out here that the view is only for the convenience of expression, and the shape and/or depth of the cavity 010 actually obtained is arbitrary. Closely related to etching process, substrate and other aspects. Those skilled in the art should understand that the shape and/or depth of the cavity 010 does not limit the content of the present invention.

6) As shown in Figure 9, it is preferable to fill the spacer and/or filling material 103 between the sidewall protection layer 101 of the groove 002 by chemical vapor deposition or atomic layer deposition, such as a single layer or a multilayer Polysilicon, silicon oxide, silicon nitride, etc. are used to isolate the cavity 010 from the outside world, and at the same time, heat insulation materials such as silicon oxide can be used to reduce heat conduction between certain specific areas.

7) After the filling is completed, as shown in Figure 10, planarize the surface of the substrate 001.

8) Deposit the electrothermal layer on the silicon substrate 001.

9) Through patterning, various patterns of metal-containing materials are formed on the isolation layer 100 . A layer of metal-containing material 107 is deposited on the surface of the barrier layer 100 after planarization. This layer of material can be a single layer or a multi-layer. The deposited metal-containing material is characterized in that it is It can be used as the material of the electrothermal device, and as the temperature changes, the material exhibits the characteristic that the resistivity changes with the temperature. The metal-containing material may be a temperature resistance material such as Pt. Then, the patterns for making the heating unit, temperature measuring unit and electrodes are formed by semiconductor photolithography and dry etching technology. The cross-sectional view is shown in FIG. 11a , which is only a schematic diagram, indicating that not only the heating unit 003 but also the temperature measuring unit 004 is formed on the substrate; taking this as an example, the top view of FIG. 11a is shown in FIG. 15 . It can be seen that a heating unit 003 and a temperature measuring unit 004 are formed on the isolation layer, and electrodes 020 are also included. It should be clearly pointed out here that the shape, layout, line size, thickness and number of turns of the heating unit and temperature measuring unit involved in the present invention do not limit the content of the present invention, and can be adjusted according to different needs.

As shown in Figure 11b, the patterning of metal materials can also be achieved by the following methods. A layer of phosphorus-silicate glass (PSG) and a layer of silicon nitride (Si ₃ N ₄ ) are deposited successively on the surface of the barrier layer 100 after planarization; then, it is formed by semiconductor photolithography and dry etching technology Windows for making heating units, temperature measuring units and electrodes. On the premise of precisely controlling the etching time, a buffered silicon oxide etching solution (BOE) is used to form the window 106 as shown in Figure 12; Pt material is deposited as shown in Figure 13, and finally formed by wet chemical stripping The corresponding top view of the structure shown in 14 is shown in Figure 15. As shown in Figure 13, the specific process of wet chemical stripping is to use BOE to remove PSG together with Si ₃ N ₄ and Pt grown on PSG after Pt deposition. It needs to be clearly pointed out here that the two-layer material and etching solution used to form the window in the present invention are obviously not limited to the above-mentioned PSG, Si ₃ N ₄ and BOE, and the key lies in that the selected etching solution is more important to the selected two-layer material. It has high selectivity, that is, it corrodes layer 104 but does not corrode layer 105, and the selected etchant has isotropic corrosion characteristics to the material of 104, so those skilled in the art can make corresponding adjustments according to actual needs.

10) Depositing a protective layer 108, which may be a single-layer or multi-layer structure, as shown in FIG. 16 .

Packaging can be performed on the basis of the structure obtained in FIG. 16 . Because the sensor component will be in direct contact with the substrate of the package through the substrate with better thermal conductivity, the temperature of the sensor will be disturbed by the temperature of the external environment. In this way, background noise will be introduced into the measurement of flow and temperature, resulting in inaccurate measurement , so it is necessary to suspend the sensor device. the

Claims (12)

1. A method for manufacturing a flow sensor by means of frontal corrosion, characterized in that: the manufacturing process steps are as follows: 1) Take a silicon substrate (001), covered with a layer of isolation layer (100) above the silicon substrate (001); use dry etching to form grooves for making cavities in the silicon substrate ; 2) Depositing a barrier layer on the surface of the silicon substrate (001) and the sidewall and bottom of the groove (002); 3) removing the barrier layer on the surface of the silicon substrate (001) and the bottom of the groove (002), and forming a sidewall protection layer (008) on the sidewall of the groove (002); 4) Using the sidewall protection layer (008) as a mask, continue to etch the groove (002) to form a deep groove (102); 5) Etching the deep groove (102) by wet etching to form a cavity (010) inside the silicon substrate (001); 6) filling the isolation and/or filling material (006) between the side wall protection layer (008) of the groove (002) to form a plug structure, and isolate the cavity (010) from the outside; 7) planarizing the surface of the silicon substrate (001); 8) Depositing an electrothermal layer on the silicon substrate (001); 9) Patterning the electrothermal layer, forming a heating device (003), a temperature measuring device (004) and electrodes (020) on the silicon substrate (001); 10) Depositing a protective layer (108) on the silicon substrate (001), the protective layer (108) covering the heating device (003) and the temperature measuring device (004). 2. The method for manufacturing a flow sensor by means of front etching according to claim 1, characterized in that: the deposition barrier layer in the step 2) is formed before the deposition of the groove (002) of the cavity (010) Insulation. 3 . The method for manufacturing a flow sensor by front-side etching according to claim 1 , wherein the silicon substrate is silicon with a (111) crystal orientation. 4 . 4 . The method for manufacturing a flow sensor by front etching according to claim 1 , wherein the barrier layer in step 2) is formed by chemical vapor deposition or atomic layer deposition. 5. The method for manufacturing a flow sensor by front-side etching according to claim 1, characterized in that: in the step 3), the barrier layer on the surface of the silicon substrate and the bottom of the groove (002) is etched back process removed. 6 . The method for manufacturing a flow sensor by front etching according to claim 1 , characterized in that: the depth of the deep groove ( 102 ) in step 4) is 0.1-10 um. 7. The method for manufacturing a flow sensor by front-side etching according to claim 1, characterized in that: the wet etching method in the step 5) adopts an anisotropic etching process on the silicon substrate (001) A cavity (010) is formed inside; the etching solution used in the wet etching is KOH and/or TMAH. 8. The method for manufacturing a flow sensor by front etching method according to claim 1, characterized in that: the filling isolation and/or filling material in the step 6) is by chemical vapor deposition or atomic layer deposition filling the isolation and/or filling material (006) between the side wall protection layers (008) of the groove (002); the isolation and/or filling material (006) has a single-layer or multi-layer structure. 9 . The method for manufacturing a flow sensor by front etching according to claim 1 , wherein the planarization process in step 7) includes chemical mechanical polishing and/or etching back. 10. The method for manufacturing a flow sensor by means of frontal corrosion according to claim 1, characterized in that: the electrothermal layer is a metal-containing material; the electrothermal layer is a single-layer or multi-layer structure; Metal-containing materials are temperature-resistant materials. 11 . The method for manufacturing a flow sensor by front etching according to claim 10 , wherein the temperature resistance material includes platinum or gold. 12 . 12. The method for manufacturing a flow sensor by front-side etching according to claim 1, characterized in that: the protective layer (108) in the step 10) is a single-layer or multi-layer structure.

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