MEMS chip structure and etching method

Abstract

The invention relates to the technical field of semiconductor MEMS chip processes, in particular to an MEMS chip structure and an etching method, the chip structure comprises quartz, metal Cr is formed on the surface of the quartz, an inorganic compound is formed on the surface of the metal Cr, and the inorganic compound forms a mask on the metal Cr; the etching method comprises the following steps: after growing an inorganic compound on metal Cr, firstly photoetching a part of the inorganic compound to form an etching groove, then etching the metal Cr by using a dry method of the residual inorganic compound, and finally removing residual silicon bubbles by using a wet method. According to the MEMS chip structure and the etching method, a layer of inorganic compound is generated on the metal Cr to serve as the mask, chlorine and oxygen do not react with the inorganic compound when dry etching is carried out on the metal Cr, external corners generated by the metal layer can be eliminated, angle perpendicularity can be guaranteed as much as possible, and a high-precision MEMS chip can be obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of MEMS chip etching process, and in particular to a MEMS chip structure and an etching method. Background Art

[0002] Ultrasonic sensors based on MEMS chips are sensors that convert ultrasonic signals into other energy signals (usually electrical signals). Ultrasonic waves are mechanical waves with a vibration frequency higher than 20kHz. They have the characteristics of high frequency, short wavelength, small diffraction phenomenon, especially good directionality, and the ability to propagate in a directional manner as rays. Ultrasonic waves have a great ability to penetrate liquids and solids, especially in solids that are opaque to sunlight. When ultrasonic waves encounter impurities or interfaces, they will produce significant reflections to form reflected echoes, and when they encounter moving objects, they can produce the Doppler effect. Ultrasonic sensors are widely used in industry, national defense, biomedicine, etc.

[0003] In the prior art, when metal Cr is etched with photoresist, a positive corner will appear, such as Figure 1 As shown, the performance and accuracy of ultrasonic sensors based on MEMS chips are affected. In addition, in the process of etching metal Cr with photoresist, the selectivity ratio is 5:1 (meaning that etching 1mm of Cr requires 5mm of photoresist), which is costly. Inorganic compounds, the selectivity ratio of SiO to Cr is 1:5, and the selectivity ratio of silicon to Cr is 1:40, which can reduce process costs.

[0004] The invention application with application number 202011529954.3 discloses a closed vibration membrane piezoelectric MEMS speaker and its preparation method. It can be seen from its preparation method that the etching process used for the metal electrode layer will produce positive corners, affecting the finished product quality of the MEMS chip. Summary of the invention

[0005] In view of the above problems, the present invention aims to provide a MEMS chip structure and an etching method. When dry etching is used for metal Cr, the cost is high and the problem of positive corners may occur.

[0006] The purpose of the present invention can be achieved through the following technical solution: a MEMS chip structure includes quartz, a metal layer is grown on the surface of the quartz, an inorganic compound is grown on the surface of the metal layer; the inorganic compound forms a mask on the metal layer.

[0007] As a further embodiment of the present invention, the inorganic compound material is silicon oxide and / or silicon.

[0008] As a further embodiment of the present invention, the inorganic compound has a double-layer structure, wherein the bottom layer is silicon and the top layer is silicon oxide.

[0009] As a further solution of the present invention, the thickness of the silicon oxide is 40-70 nm, the thickness of the silicon is 10-20 nm, and the thickness of the metal layer is 200-300 nm.

[0010] An etching method based on the above chip structure comprises the steps of:

[0011] S1, growing an inorganic compound on the metal layer;

[0012] S2, dry etching part of the inorganic compound by photolithography to form an etching groove;

[0013] S3, using the remaining inorganic compound to form a mask to dry-etch the metal layer;

[0014] S4, a wet process is used to remove the residual silicon of the inorganic compound.

[0015] As a further solution of the present invention, the dry etching of the metal layer in S3 comprises the steps of:

[0016] S31, dry etching the upper part of the metal layer to consume silicon oxide;

[0017] S32, dry etching the lower part of the metal layer to consume silicon.

[0018] As a further solution of the present invention, the dry etching uses chlorine and oxygen gases.

[0019] Beneficial effects of the present invention:

[0020] 1. The MEMS chip structure and etching method of the present invention generate a layer of inorganic compound on the metal Cr as a mask. When the metal Cr is dry-etched, chlorine and oxygen will not react with the inorganic compound, which can eliminate the positive angle generated by the metal layer and ensure that the angle is vertical as much as possible. In fact, the angle θ can be greater than 88°, which is conducive to obtaining high-precision MEMS chips.

[0021] 2. The inorganic compound bottom layer of the present invention uses silicon. When etching the upper part of Cr, the top silicon oxide will be consumed, and when etching the lower part of Cr, part of the silicon will also be consumed. The remaining silicon can be easily removed by soaking it away in a wet method, thereby simplifying the process flow and cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic diagram of a positive angle caused by an existing etching method;

[0023] Figure 2 This is a schematic diagram of the structure of the MEMS chip of the present invention;

[0024] Figure 3 It is a schematic diagram of the MEMS chip etching process flow of the present invention.

[0025] 100, Quartz;

[0026] 200, metal layer;

[0027] 300. Inorganic compounds; 310. Silicon oxide; 320. Silicon. DETAILED DESCRIPTION

[0028] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar symbols throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0029] Embodiment 1:

[0030] like Figure 2 As shown, the present invention discloses a MEMS chip structure, comprising quartz 100, a metal layer 200 and an inorganic compound 300 stacked in sequence. Optionally, the metal layer 200 is composed of metal or metal compound; specifically, the metal layer 200 is metal Cr.

[0031] Metal Cr 200 is grown on the surface of the quartz 100 , and an inorganic compound 300 is grown on the surface of the metal Cr 200 .

[0032] The inorganic compound 300 is made of silicon oxide 320 and / or silicon 310 , etc. The inorganic compound 300 forms a mask on the metal Cr 200 .

[0033] When the existing process uses photoresist as a mask to dry-etch metal Cr200, a positive corner will appear, such as Figure 1 As shown, the accuracy of the MEMS chip is affected.

[0034] After the inorganic compound 300 is formed on the metal Cr200, the inorganic compound 300 is made of silicon oxide 320 and silicon 310, and the inorganic compound 300 forms a mask on the metal Cr200. Chlorine and oxygen are used as dry etching gases. When the metal Cr200 is dry-etched by chlorine and oxygen, the chlorine and oxygen will not react with the inorganic compound, so the positive corner can be effectively eliminated. Figure 1 As shown, the angle θ can actually be guaranteed to be greater than 88°, meeting the use requirements and improving the processing accuracy of the MEMS chip.

[0035] Furthermore, the inorganic compound 300 is a double-layer structure, in which the bottom layer is silicon 310 and the top layer is silicon oxide 320. The thickness of silicon oxide 320 is controlled to be 40-70nm, the thickness of silicon 310 is controlled to be 10-20nm, and the thickness of metal Cr200 is controlled to be 200-300nm. When etching metal Cr200, the selectivity ratio of SiO to Cr in the inorganic compound is 1:5, and the selectivity ratio of silicon to Cr can be 1:40. Appropriate thickness control not only saves costs but also improves etching accuracy.

[0036] Embodiment 2:

[0037] Based on the MEMS chip structure described in Example 1, the present invention further discloses an etching method, which comprises the following steps:

[0038] S1, growing inorganic compound 300 on metal Cr200;

[0039] S2, dry-etching part of the inorganic compound 300 by photolithography to form an etching groove; the etching groove is a small line width etching groove with a width of 200-400 nm.

[0040] S3, using the inorganic compound 300 forming the etching groove as a mask to dry-etch the metal Cr200;

[0041] S4, using a wet process to remove the inorganic compound remaining in the silicon 320.

[0042] like Figure 3 As shown in A, an inorganic compound 300 is used to form a mask on the metal Cr200. When etching the inorganic compound 300, a photolithography process is first used to form an etching groove with a certain line width in the inorganic compound 300, and then the metal Cr200 is etched by a dry process using oxygen and chlorine as the medium.

[0043] Further, when the metal Cr200 is dry-etched using the remaining inorganic compound 300, Figure 3 B, including:

[0044] S31, dry etching the upper portion of metal Cr200, consuming silicon oxide 320;

[0045] S32 , dry etching the lower portion of the metal Cr200 to consume silicon 310 .

[0046] When etching metal Cr200, dry etching uses chlorine and oxygen. Chlorine and oxygen will not react with inorganic compounds, and can effectively eliminate the positive corners of metal Cr200.

[0047] The inorganic compound adopts a double-layer structure, with the bottom layer being silicon 310 and the top layer being silicon oxide 320. The advantage of using silicon 310 for the bottom layer is that it is easy to remove and can be removed by soaking it off using a wet method. When etching the upper part of the metal Cr200, the silicon oxide 320 will be consumed. When etching the lower part of the metal Cr200, a part of the silicon 310 will also be consumed. Finally, the silicon 310 can be removed by a wet method. The wet liquid does not react with silicon oxide 320, which reduces the process steps and also reduces the process cost.

[0048] Compared with the traditional process, the etching process proposed in this embodiment first generates a layer of inorganic compound 300 on the metal Cr200. The material of the inorganic compound 300 is silicon oxide 320 or silicon 310 to form a mask. The inorganic compound 300 is first photoetched to form an etching groove with a certain line width on the inorganic compound 300, and then the metal Cr200 is dry-etched by gas. In this way, when etching the metal Cr200, the inorganic compound 300 on the metal Cr200 serves as a mask. Since chlorine and oxygen will not react with the inorganic compound, the positive angle generated by the metal Cr200 can be eliminated. The angle θ can actually ensure that the angle is greater than 88°, which is conducive to obtaining a high-precision MEMS chip.

[0049] The above are only preferred specific implementation modes of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0050] It should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0051] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0052] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0053] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

Claims

1. A MEMS chip structure, characterized in that: The invention comprises quartz (100), a metal layer (200) is grown on the surface of the quartz (100), an inorganic compound (300) is grown on the surface of the metal layer (200), and the inorganic compound (300) forms a mask on the metal layer (200).

2. The MEMS chip structure according to claim 1, characterized in that: The inorganic compound (300) is made of silicon oxide (320) and / or silicon (310).

3. The MEMS chip structure according to claim 1, characterized in that: The inorganic compound (300) is a double-layer structure, wherein the bottom layer is silicon (310) and the top layer is silicon oxide (320).

4. The MEMS chip structure according to claim 3, characterized in that: Said: The thickness of the silicon oxide (320) is 40-70 nm, the thickness of the silicon (310) is 10-20 nm, and the thickness of the metal layer (200) is 200-300 nm.

5. The etching method of the MEMS chip structure according to any one of claims 1 to 4, characterized in that: Includes steps: S1, growing an inorganic compound (300) on the metal layer (200); S2, dry etching a portion of the inorganic compound (300) by a photolithography process to form an etching groove; S3, using the remaining inorganic compound (300) to form a mask to dry-etch the metal layer (200); S4, removing the silicon (310) remaining in the inorganic compound (300) by a wet process.

6. The etching method according to claim 5, characterized in that: The dry etching of the metal layer (200) in S3 comprises the following steps: S31, dry etching the upper portion of the metal layer (200) to consume the silicon oxide (320); S32, dry etching the lower portion of the metal layer (200) to consume silicon (310).

7. The etching method according to claim 5, characterized in that: The dry etching uses chlorine and oxygen as gases.

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