CN114604818A - A kind of MEMS infrared light source based on porous silicon and preparation method thereof - Google Patents

Abstract

The invention relates to the technical field of semiconductor optoelectronic components, and specifically discloses a porous silicon-based MEMS infrared light source and a preparation method thereof. The MEMS infrared light source includes a silicon substrate, a dielectric film, a heating resistor and a black body sequentially arranged from bottom to top Radiation layer, the heating resistor forms a pattern structure through a metal lift-off process, the black body radiation layer is located in the middle area of the heating resistor, the front side of the silicon substrate is located below the black body radiation layer, and a porous silicon structure is formed by etching, the silicon The backside of the substrate is located under the porous silicon structure to form a back hole region by etching. The MEMS infrared light source and its preparation method disclosed in the present invention firstly make a porous silicon structure on a silicon substrate before processing the light source, and then deposit a dielectric film, a heating resistor and a black body radiation layer on the porous silicon structure, and the porous silicon structure has low thermal conductivity. The advantages of high efficiency and high mechanical strength greatly improve the reliability of the MEMS infrared light source.

Description

A kind of MEMS infrared light source based on porous silicon and preparation method thereof

technical field

The invention relates to the technical field of semiconductor optoelectronic components, in particular to a MEMS infrared light source based on porous silicon and a preparation method thereof.

Background technique

The MEMS infrared light source is based on the principle of thermal radiation, by heating the MEMS film to radiate broad-spectrum infrared light. The basic composition of MEMS infrared light source is composed of substrate, supporting film, heating layer and radiation layer. The substrate is used to support the entire thin film as well as the heating and radiating layer structures. The support film is the support structure for the heating layer and the radiation layer. The heating layer is composed of conductive metal, which converts electricity into heat energy by applying a certain voltage. Since the infrared spectrum produced by the radiation of the radiative layer depends on the radiation temperature, the thin film region of the light source heats up to several hundred degrees during normal operation. Then through the principle of thermal radiation, broad-spectrum infrared light is radiated outward.

At present, MEMS infrared light source is manufactured by semiconductor process, starting from a silicon wafer substrate, then depositing a supporting film structure on the silicon wafer, and then fabricating a heating layer and a radiation layer on the film. However, during the working process of the light source, the normal working temperature of the light source is several hundred degrees Celsius, so the film will generate a large thermal stress due to its own thermal expansion, and the thermal stress will make the film unstable and cause the film to rupture and other phenomena . Moreover, in the process of switching the light source, along with the increase and decrease of the temperature of the film, its mechanical strength will be reduced, and the stability of the light source will be reduced.

SUMMARY OF THE INVENTION

In order to solve the above technical problems, the present invention provides a MEMS infrared light source based on porous silicon and a preparation method thereof, so as to make the light source structure have higher mechanical strength and improve the reliability of the MEMS infrared light source.

For achieving the above object, technical scheme of the present invention is as follows:

A MEMS infrared light source based on porous silicon, comprising a silicon substrate, a dielectric film, a heating resistor and a black body radiation layer sequentially arranged from bottom to top, the heating resistor forms a pattern structure through a metal lift-off process, and the black body radiation layer is located in the In the middle area of the heating resistor, the front surface of the silicon substrate is located below the black body radiation layer to form a porous silicon structure by etching, and the backside of the silicon substrate is located below the porous silicon structure to form a back hole area by etching.

In the above solution, the material of the dielectric thin film is selected from at least one of silicon dioxide, silicon nitride, and silicon oxynitride.

In the above solution, the heating resistor is made of platinum.

In the above solution, the material of the black body radiation layer is platinum black, carbon nanotubes or porous silicon.

A preparation method of a porous silicon-based MEMS infrared light source, comprising the following steps:

S1, select a silicon wafer as a silicon substrate;

S2, using an electrochemical etching method to etch the front middle region of the silicon substrate to form a porous silicon structure;

S3, depositing a dielectric thin film on the silicon substrate forming the porous silicon structure by using the thin film growth technology;

S4, depositing a heating resistor on the dielectric film, and forming a pattern structure through a metal stripping process;

S5, deposit a black body radiation layer in the middle area of the heating resistor;

S6 , etching the bottom of the porous silicon structure on the backside of the silicon substrate to form a back hole region.

In the above scheme, in step S2, in the electrochemical etching method, a certain volume fraction of HF and anhydrous ethanol are mixed in a volume ratio of 1:1 and then etched.

In the above solution, in step S3, the thin film growth technology is a PECVD method.

In the above solution, in step S4, the heating resistor is deposited by electron beam evaporation or sputtering process.

In the above scheme, in step S5, the black body radiation layer is deposited by the method of electroplating.

In the above solution, in step S6, the ICP dry etching technique is used to etch to form the back hole region.

Through the above technical solutions, a porous silicon-based MEMS infrared light source and a preparation method thereof provided by the present invention have the following beneficial effects:

The MEMS infrared light source of the present invention is processed into an infrared light source on a silicon substrate. Before processing the light source, a porous silicon structure is first fabricated on a silicon substrate, and then a dielectric film, a heating resistor and a black body radiation layer are deposited on the porous silicon structure. The porous silicon structure has the advantages of low thermal conductivity and high mechanical strength, which greatly improves MEMS. Reliability of infrared light sources.

Description of drawings

In order to illustrate the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that are required in the description of the embodiments or the prior art.

1 is a front cross-sectional view of a porous silicon-based MEMS infrared light source disclosed in an embodiment of the present invention;

2 is a top view of a porous silicon-based MEMS infrared light source disclosed in an embodiment of the present invention;

3 is a process flow diagram of a method for preparing a porous silicon-based MEMS infrared light source disclosed in an embodiment of the present invention;

Figure 4 shows the Raman peaks of 1mW laser scanning porous silicon samples at different temperatures;

Figure 5 is a graph showing the correspondence between the temperature of the porous silicon structure and the Raman peak;

Figure 6 shows the test results of the absorptivity of the black body radiation layer.

In the figure, 1, silicon substrate; 2, dielectric film; 3, heating resistor; 4, black body radiation layer; 5, back hole region; 6, porous silicon structure.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

The present invention provides a MEMS infrared light source based on porous silicon, as shown in FIG. 1 and FIG. 2 , including a silicon substrate 1, a dielectric film 2, a heating resistor 3 and a black body radiation layer 4 sequentially arranged from bottom to top. The resistor 3 forms a pattern structure through a metal lift-off process, the black body radiation layer 4 is located in the middle area of the heating resistor 3, the front surface of the silicon substrate 1 is located below the black body radiation layer 4, and a porous silicon structure 6 is formed by etching, and the back surface of the silicon substrate 1 is located in the porous silicon structure 6. A back hole region 5 is formed under the silicon structure 6 by etching.

In this embodiment, the material of the dielectric film 2 is selected from at least one of silicon dioxide, silicon nitride, and silicon oxynitride.

The heating resistor 3 is made of platinum, and the black body radiation layer 4 is made of platinum black, carbon nanotubes or porous silicon.

A preparation method of a porous silicon-based MEMS infrared light source, as shown in Figure 3, includes the following steps:

S1. Select a silicon wafer as the silicon substrate 1 .

S2. First, use the LPCVD method to deposit a layer of silicon nitride film on the front side of the silicon substrate 1 as an etching mask, and then perform the operation steps of gluing, exposing, developing, and etching on the silicon substrate 1 to form porous silicon in the middle area. In the etching window, an electrochemical etching method is used to etch the front middle area of the silicon substrate 1 to form a porous silicon structure 6; in the electrochemical etching method, a volume fraction of 49% hydrofluoric acid and absolute ethanol are used according to After mixing in a volume ratio of 1:1, etching was performed. During the etching process, a constant current was applied to the silicon substrate 1. Through the weighing method, the porosity of the prepared porous silicon structure 6 was 68.44%.

S3 , depositing a layer of dielectric thin film 2 on the silicon substrate 1 on which the porous silicon structure 6 is formed by using a thin film growth technique (eg PECVD), and measuring the thickness of the deposited dielectric thin film 2 by using an ellipsometer.

S4, the front side of the silicon substrate 1 after the growth medium film 2 is coated with negative photoresist, exposure, development and other steps to form a pattern structure, and a thin layer of titanium metal is deposited by electron beam evaporation or sputtering process as a The transition layer is then deposited with platinum metal, and the heating resistor 3 is formed by a metal lift-off process.

S5, performing operations such as gluing, exposing, developing, etc. on the front side of the silicon substrate 1 after forming the heating resistor 3 structure to form the electroplating window of the black body radiation layer 4, placing the silicon substrate 1 forming the electroplating window into the electroplating solution, and The silicon substrate 1 is connected to the negative electrode of the power supply, and finally a black body radiation layer 4 is deposited in the middle area of the heating resistor 3 by a method of constant current electroplating.

S6, using the double-sided alignment photolithography technology to perform the operation steps of gluing, exposing, developing and the like on the back of the silicon substrate 1 to form a back etching window corresponding to the front porous silicon structure 6, and then adopting the ICP dry etching technology The wafer is etched to form a back hole region 5 .

In the present invention, before processing the light source, a porous silicon structure 6 is first fabricated on the front side of the silicon substrate 1, and then a dielectric film 2, a heating resistor 3 and a black body radiation layer 4 are deposited on the porous silicon structure 6. The silicon preparation process is combined with the semiconductor processing method to prepare a porous silicon support structure with high mechanical strength, which greatly improves the reliability of the MEMS infrared light source.

In the present embodiment, the thermal conductivity of the prepared porous silicon structure 6 is tested by using a Raman spectrometer. The basic principle of Raman spectroscopic testing of thermal conductivity is that the peak of the Raman spectrum will move to the left as the temperature of the measured substance changes. The laser of the Raman spectrometer will increase the temperature of the porous silicon at the corresponding position. According to the corresponding relationship between the temperature rise and the spectral peak, the thermal conductivity of the porous silicon can be deduced. The relationship between the local temperature rise of porous silicon and its thermal conductivity:

(1)

(1)

为多孔硅的导热系数，P为引起温升的激光功率，a为激光束光斑的直径，

为激光引起的温升，

为多孔硅结构6温度。 in,

is the thermal conductivity of porous silicon, P is the laser power that causes the temperature rise, a is the diameter of the laser beam spot,

for the temperature rise caused by the laser,

is the temperature of 6 for the porous silicon structure.

的值。最 终根据公式（1）计算得到多孔硅结构6的导热系数为3.5 W/(mK)。 The porous silicon structure 6 was heated to 35°C, 135°C, 235°C, and 335°C in sequence using a temperature control station. The Raman peaks were scanned sequentially for the above temperatures with a laser power of 1 mW, as shown in Figure 4. From this, the corresponding relationship between the Raman peak y and the temperature x of the porous silicon structure 6 is obtained, as shown in Figure 5. The relationship curve is: y=-0.0245x+519.46, and calculated from this

value of . Finally, according to formula (1), the thermal conductivity of the porous silicon structure 6 is calculated to be 3.5 W/(mK).

The absorption rate of the black body radiation layer 4 was tested by Fourier transform spectrometer (FTIR) to deduce its radiation efficiency. The test results are shown in Figure 6. It can be seen that when the current density is the same, the longer the electroplating time is, the higher the electroplating platinum black radiation is. The absorption rate of the layer is also higher. The test results show that the absorption rate of the black body radiation layer 4 in the spectral wavelength range of 2-14 μm is greater than 99%, which greatly improves the radiation efficiency of the MEMS infrared light source.

The above description of the disclosed embodiments enables any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. a MEMS infrared light source based on porous silicon, is characterized in that, comprises silicon substrate, dielectric film, heating resistance and black body radiation layer that are arranged sequentially from bottom to top, and described heating resistance forms pattern structure by metal stripping process, The black body radiation layer is located in the middle area of the heating resistor, the front side of the silicon substrate is located below the black body radiation layer to form a porous silicon structure, and the back side of the silicon substrate is located below the porous silicon structure to form a back hole region by etching . 2 . The porous silicon-based MEMS infrared light source according to claim 1 , wherein the material of the dielectric film is selected from at least one of silicon dioxide, silicon nitride, and silicon oxynitride. 3 . 3 . The MEMS infrared light source based on porous silicon according to claim 1 , wherein the heating resistor is made of platinum. 4 . 4 . The MEMS infrared light source based on porous silicon according to claim 1 , wherein the black body radiation layer is made of platinum black, carbon nanotubes or porous silicon. 5 . 5. a preparation method of MEMS infrared light source based on porous silicon, is characterized in that, comprises the steps: S1, select a silicon wafer as a silicon substrate; S2, using an electrochemical etching method to etch the front middle region of the silicon substrate to form a porous silicon structure; S3, depositing a dielectric thin film on the silicon substrate forming the porous silicon structure by using the thin film growth technology; S4, depositing a heating resistor on the dielectric film, and forming a pattern structure through a metal stripping process; S5, deposit a black body radiation layer in the middle area of the heating resistor; S6 , etching the bottom of the porous silicon structure on the backside of the silicon substrate to form a back hole region. 6. The method for preparing a porous silicon-based MEMS infrared light source according to claim 5, wherein in step S2, in the electrochemical etching method, a certain volume fraction of HF and absolute ethanol are used at 1:1 The volume ratio is mixed and then etched. 7 . The method for preparing a porous silicon-based MEMS infrared light source according to claim 5 , wherein, in step S3 , the thin film growth technology is a PECVD method. 8 . 8 . The method for preparing a porous silicon-based MEMS infrared light source according to claim 5 , wherein, in step S4 , the heating resistor is deposited by an electron beam evaporation or sputtering process. 9 . 9 . The method for preparing a porous silicon-based MEMS infrared light source according to claim 5 , wherein, in step S5 , the black body radiation layer is deposited by electroplating. 10 . 10 . The method for preparing a porous silicon-based MEMS infrared light source according to claim 5 , wherein in step S6 , ICP dry etching technology is used to etch to form a back hole region. 11 .

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