CN1400486A

CN1400486A - Chip for photomodulation thermoimaging system and its making method

Info

Publication number: CN1400486A
Application number: CN 02136625
Authority: CN
Inventors: 熊斌; 冯飞; 王跃林
Original assignee: Shanghai Institute of Microsystem and Information Technology of CAS
Current assignee: Shanghai Institute of Microsystem and Information Technology of CAS
Priority date: 2002-08-23
Filing date: 2002-08-23
Publication date: 2003-03-05
Anticipated expiration: 2022-08-23
Also published as: CN1173220C

Abstract

The invention refers to a chip applied in the light-modulation hot-imaging system as well as the making method, belonging to the field of as to the micro-electronic mechanical system. The chip is made up of the filtering piece, the half lens, and the micro-lens array. Its character lie in that the micro-lens reflecting surface and the half-lens surface make up two reflecting surfaces of the F-P cavity whose distance is one fourth of the radiant wavelength of incient infrared. The making character is as follows: select the thickness-appropriate silicon film ans SOI silicon slide of SiO2 film; photoetch the micro-lens array pattern, corrode the silicon film and the SiO2 film, reheat the silicon oxide and evaporate the aluminium film on it, which makes the total thickness of the two layers of films equal to that of the SiO2 film in the original SOI silicon piece.

Description

A kind of chip and method for making that is used for photomodulation thermoimaging system

Technical field

The present invention relates to a kind of chip and method for making that is used for photomodulation thermoimaging system, belong to the microelectromechanical systems field.

Background technology

Infrared imaging system can be divided into thermal imaging system and quantum type imaging system.In 800～3000 meters scope, thermal imaging system is the best non-visible light imaging system of observation effect, and is available round the clock, is the important tool that realizes round-the-clock operation in the future war, also is widely used aspect civilian in addition.The thermal imaging system biggest advantage is and can at room temperature works that not resembling the quantum type imaging system needs heavy refrigeration system.Thermal imaging system requires high to heat-proof quality, micro-electronic mechanical skill (MEMS) has special advantages at the hanging structure of making excellent heat insulating performance, development along with the MEMS technology, heat-resistor-type, as Nadim Maluf, An Introduction to Microeletromechanical SystemEngineering, London:Artech house Boston London, 1999,134～135; Heat-capacitor type is as Samoffdevelops micromachined low noise infrared imaging array (http://www.sarcon.com/news_﹠amp; _ info/micromachined060197.htm); Thermocouple type, as D.T.Chang, D.M.Chen, F.H.Lin, W.J.Kaiser, O.M.Stafsudd, CMOS Integrated Infrared Sensor, Proceedings of the 1997Intemational Conference on Solid-State Sensors and Actuators (Transducers ' 97), vol.2, pp.1259-1262,1997 thermal imaging systems such as grade all are in the news in succession, and its common feature is to utilize infrared thermal effect, with the sensitive element of MEMS fabrication techniques excellent heat insulating performance, they are earlier infrared signal to be converted into electric signal, obtain picture signal thereby detect electric signal with cmos circuit at last.But complicated signal read circuits makes the price of device further to reduce, make people begin to seek the emerging substitute technology of exploitation, photomodulation thermoimaging system (LMTID) becomes new research and development focus, as Zhang Liuqiang, optical modulation thermal imaging device research based on micromechanics, Shanhai Institute of Metallurgy, Chinese Academy of Sciences's doctorate paper, in June, 1999; And S.R.Manalis, et al, Two-dimensioned Micromechical BimorphArrays for Detection of Thermal Radiation, Appl.Phys.Lett., Vol.70, pp.3311-3313,1997.

Photomodulation thermoimaging system (LMTID) is to utilize the thermal effect of infrared light that visible light intensity is modulated, thereby infrared image is converted into a kind of device of visible light.At present, it mainly is the chip that the growth sacrifice layer is made LMTID on silicon chip, the method of this surface micro mainly contains two difficulties when making the LMTID chip: the one, and the distance (in order to improve the absorption of micro mirror array to the incident infrared radiation, this distance should be 1/4th incident infrared wavelengths) between two reflectings surface of very difficult accurately control Fabry-Perot interferometer (F-P chamber); The 2nd, the method for application surface micromechanics is difficult to produce satisfactory double mirror.This has influenced the performance of device undoubtedly.

Summary of the invention

The objective of the invention is to propose a kind of chip that is used for photomodulation thermoimaging system and method for making and above-mentionedly making two difficulties that the LMTID chip processes is run into to overcome, it can not only control the distance between two reflectings surface in F-P chamber exactly, and can also produce satisfactory double mirror easily.

The object of the present invention is achieved like this: silicon on the insulation course (SOI) silicon chip is made up of thick silicon base and thin silicon dioxide, silicon fiml, select the silicon dioxide of suitable thickness, the soi wafer of silicon fiml, make the thickness of silicon fiml equal distance between two reflectings surface in F-P chamber, silicon dioxide thickness equals the thickness of the micro mirror that will make.During making, photoetching micro mirror array pattern at first, corrosion silicon fiml, silicon dioxide film, again aluminium film in thermal oxidation silicon, the steaming, and should make the gross thickness of this two tunic equal the thickness of silicon dioxide in the original soi wafer, photoetching then also etches the micro mirror pattern, make silicon-glass bonding subsequently one time, two faces in F-P chamber (micro mirror array and glass semi-permeable mirror) are bonded together, guaranteed that so not only the distance between two reflectings surface in F-P chamber meets the demands, simultaneously also produced satisfactory double mirror comparatively easily, whole technological process is also uncomplicated.

In the present invention, the LMTID chip is made up of semi-permeable mirror, micro mirror array and optical filter, and wherein the reflecting surface of the reflecting surface of micro mirror and semi-permeable mirror has constituted two reflectings surface in F-P chamber, and the distance between them is 1/4th of an incident infrared radiation wavelength.The target infrared radiation is from optical filter one side incident, because infrared thermal effect has caused the displacement of micro mirror, changed the distance between two reflectings surface in F-P chamber, thereby can be to modulating from the monochromatic visible light of semi-permeable mirror 1 one side incidents, the visible light of modulating is produced on retina or with the CCD camera through semi-permeable mirror 2 interference imagings, so finished the conversion of infrared image to visible images.

From Fig. 2, can be clear that the structure of a pixel in the micro mirror array.Minute surface is enclosed in the little silicon frame, and the top of minute surface is the semi-permeable mirror 1 that is bonded on the silicon frame, and minute surface is being supported by the composite beam of four bendings, and an end of composite beam is fixed on the minute surface, and the other end is fixed on the silicon frame.Minute surface is accepted infrared radiation, its temperature will rise, and (beam is owing to the area of accepting infrared radiation is too little all around, the infrared radiation of being accepted can be left in the basket), the result thermograde occurred at the two ends of composite beam, thereby caused the displacement of composite beam, changed the distance between minute surface and the semi-permeable mirror 1, thereby to modulating from the incident visible light of semi-permeable mirror 1 one sides.The infrared radiation that the displacement of micro mirror is accepted by micro mirror and the heat sensitivity of composite beam determine jointly.Composite beam one end connects the minute surface high-temperature region, and an other end is fixed on the silicon frame low-temperature space, and position, beam two ends can be decided as the case may be, is not subjected to the restriction of Fig. 2.The length that increases composite beam can greatly improve the heat sensitivity of composite beam, and this also is to adopt among Fig. 2 along the beam of minute surface both sides bending not adopt along the reason of the monolateral straight beam of minute surface.In order further to improve the heat sensitivity of composite cantilever, can also further increase the length of beam, as adopting along the U-shaped beam of minute surface three spring songs even along the bent beam on minute surface four limits; Perhaps adopt along monolateral folded beam of minute surface etc., also can adopt under the less demanding or larger-size situation of minute surface in sensitivity along the monolateral straight beam of minute surface.

Among the present invention, selecting silicon film thickness for use is the soi wafer of 1～10 μ m, and oxidate temperature is 1050 ℃-1150 ℃, and aluminium film (or golden film) is 0.1～1 with the ratio of silicon oxide thickness, and aluminium film (or golden film) is 0.2～1 with the ratio of silicon nitride thickness.Minute surface and composite beam or be composited by aluminium film (or golden film) and monox or aluminium film (or golden film) and silicon nitride or aluminium film (or golden film) and silicon nitride and monox also can mirror sections be formed (seeing embodiment 3 for details) with the composite beam zone by different composite beds.Should attention when replacing the aluminium film with golden film with silicon nitride or silicon oxide thickness than different.

Description of drawings

Fig. 1 is the LMTID systematic schematic diagram.

Fig. 2 is the stereographic map of pixel.

Fig. 3 is the sectional view of a pixel in the LMTID chip of embodiment 1.

Fig. 4 is the process chart of embodiment 1 shown in Figure 3.

Concrete technological process is: a photoetching → b corrosion silicon → c corrode silicon dioxide → d removes photoresist → e thermal oxide → f evaporation of aluminum → g etching micro mirror pattern → h bonding → i etching back side silicon

Fig. 5 is the pixel sectional view of embodiment 2.

Fig. 6 is the pixel sectional view of embodiment 3.

Among the figure:

1-optical filter 2-silicon frame

3-semi-permeable mirror 2 4-semi-permeable mirrors 1

The crooked composite beam of 5-micro mirror array 6-

7-minute surface 8-silicon fiml

9-aluminium film or golden film 10-silicon oxide film

The 11-photoresist

Embodiment

Embodiment 1

In embodiment shown in Figure 31, micro mirror (composite beam around comprising) is the composite membrane (beam) that silicon dioxide and aluminium film constitute, the thickness of composite membrane (beam) equals the thickness of silicon dioxide in the soi wafer, by silicon-glass bonding, micro mirror array and semi-permeable mirror 1 are bonded together, micro mirror and semi-permeable mirror 1 have constituted the F-P chamber, and the thickness in chamber equals the thickness of silicon fiml in the soi wafer.

Below in conjunction with the technological process of embodiment shown in Figure 41, the invention will be further described.

(1) selecting silicon fiml thick is 2.5 μ m, and the silicon dioxide thickness is about the soi wafer of 1 μ m, and photoetching micro mirror array figure is shown in Fig. 4 a;

(2) corrosion silicon fiml and silicon dioxide film and remove photoresist is shown in Fig. 4 b, c, d;

(3) carry out 1050 ℃ of thermal oxides, photoetching is floated unnecessary monox with HF solution and is formed silicon oxide layer thin shown in Fig. 4 e;

(4) evaporation of aluminum, H is used in photoetching ₃PO ₄Solution floats unnecessary aluminium, on silicon oxide layer, form aluminium film shown in Fig. 4 f, the thickness of aluminium film and silicon oxide thickness can be decided according to growth technique, but its thickness ratio will guarantee that about 0.14, the gross thickness of two membranes is about the thickness of the silicon dioxide film in the soi wafer;

(5) etching micro mirror pattern is shown in Fig. 4 g;

(6) bonding glass semi-permeable mirror is shown in Fig. 4 h;

(7) etching back side silicon discharges hanging structure, shown in Fig. 4 i.

Embodiment 2

The difference of embodiment 2 shown in Figure 5 and embodiment 1 shown in Figure 3 is that minute surface among the embodiment 2 and composite beam are to be made of aluminium and silicon nitride film, rather than are made of aluminium and silicon dioxide film.In process chart, also to make corresponding changes, replace thermal oxide with deposit silicon nitride.

Embodiment 3

The difference of embodiment 3 shown in Figure 6 and embodiment 1 shown in Figure 3 is that minute surface among the embodiment 3 and composite beam are to be composited for three layers, rather than to be made of aluminium and silicon dioxide film by aluminium, silicon nitride, silicon dioxide.In process chart, also to make corresponding changes, also want deposit silicon nitride, evaporation of aluminum then after the thermal oxide.

In embodiment 3, can also do following change.Promptly be composited for three layers by aluminium, silicon nitride, silicon dioxide, and constitute by aluminium, silicon dioxide in the composite beam zone in mirror sections.Also will make corresponding changes in process chart, i.e. deposit silicon nitride after the thermal oxide etches the silicon nitride of mirror sections, last evaporation of aluminum subsequently.

In three above embodiments, all can replace the aluminium film, but will notice that its thickness is than different with golden film; In the shape of above three embodiment central sills are beams (as shown in Figure 2) along the bending of minute surface both sides, if but the heat sensitivity of composite beam is had higher requirements, can also further increase the length of beam, as adopting along the U-shaped beam of minute surface three spring songs even along the bent beam on minute surface four limits; Perhaps adopt along monolateral folded beam of minute surface etc., can adopt under the less demanding or larger-size situation of minute surface in sensitivity along the monolateral straight beam of minute surface.

Claims

1, a kind of chip that is used for photomodulation thermoimaging system, form by optical filter, semi-permeable mirror and micro mirror array, it is characterized in that the reflecting surface of the reflecting surface of micro mirror and semi-permeable mirror constitutes two reflectings surface in F-P chamber, the distance between them is 1/4th of an incident infrared radiation wavelength.

2, by the described chip that is used for photomodulation thermoimaging system of claim 1, it is characterized in that minute surface is enclosed in the silicon frame in the described micro mirror array, the top is the semi-permeable mirror that is bonded on the silicon frame, minute surface is supported by the composite beam of four bendings, the one end is fixed on the minute surface, and the other end is fixed on the silicon frame.

3, by the described chip that is used for photomodulation thermoimaging system of claim 2, it is characterized in that composite beam length is relevant with the sensitivity of composite beam, it or adopt along the bilateral bent beam of minute surface or along the U-shaped beam on minute surface three limits or along the bent beam on minute surface four limits; Or adopt, or adopt along the monolateral straight beam of minute surface along the monolateral folded beam of minute surface.

4,, it is characterized in that minute surface and composite beam or aluminium film or golden film and silicon oxide film composition by claim 1 or the 2 or 3 described chips that are used for photomodulation thermoimaging system; Or aluminium film or golden film and silicon nitride film composition; Or aluminium film or golden film and silicon oxide film and silicon nitride film composition.

5,, it is characterized in that described mirror sections is made up of different composite beds with the composite beam zone by the described chip that is used for photomodulation thermoimaging system of claim 4.

6, a kind of chip that is used for photomodulation thermoimaging system, comprise photoetching, steam film, corrosion silicon, corrode silicon dioxide, remove photoresist, thermal oxide, evaporation of aluminum or gold process process, it is characterized in that:

(1) selects the silicon dioxide of suitable thickness, the soi wafer of silicon fiml, make the thickness of silicon fiml equal the distance between two reflectings surface in F-P chamber; Silicon dioxide thickness equals the thickness of micro mirror;

(2) photoetching and etch the micro mirror pattern is bonded together two faces in F-P chamber silicon, glass bonding.

7,, it is characterized in that the silicon film thickness of selecting for use is the soi wafer of 1～10 μ m by the described chip that is used for photomodulation thermoimaging system of claim 6; Oxidate temperature is 1050 ℃～1150 ℃.

8, by the described chip that is used for photomodulation thermoimaging system of claim 6, it is characterized in that aluminium film or golden film and the ratio of silicon oxide thickness are 0.1～1, aluminium film or golden film are 0.2～1 with the ratio of silicon nitride thickness.