CN1851950A

CN1851950A - Micromechanical thermalelectric-stack infrared detector compatible with co-complementive metal oxide semiconductor technology and preparing method

Info

Publication number: CN1851950A
Application number: CNA2006100262917A
Authority: CN
Inventors: 李铁; 刘义冬; 王翊; 熊斌; 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: 2006-04-29
Filing date: 2006-04-29
Publication date: 2006-10-25
Anticipated expiration: 2026-04-29
Also published as: CN100423310C

Abstract

This invention relates to a micro-mechanical thermopile infrared detector structure compatible with a complementary metal-oxide semiconductor, (CMOS) and its execution method characterizing in utilizing the erosion property of the anisotropy of a monocrystal silicon and applying a front specific open-end to realize a large area micro-mechanical thermopile structure by the front erosion, the character of the infrared detector is that a frame and a middle suspended infrared absorption region constitute a cold junction region and a hot junction region of the thermopile, a bracket arm is connected with the frame, the infrared absorption region and carries the thermopile and a long open-end covers the entire infrared absorption region.

Description

Micromachined thermopile infrared detector and manufacture method with the CMOS (Complementary Metal Oxide Semiconductor) technology compatibility

Technical field

The present invention relates to micromachined thermopile infrared detector structure of a kind of and complementary metal oxide semiconductors (CMOS) (CMOS) compatibility and preparation method thereof, be specially adapted to the manufacturing of big array infrared detector.The invention belongs to the Infrared Detectors field.

Background technology

In recent years, Infrared Detectors is concerned by people day by day in the application of the aspects such as real-time heat detection of public safety, medical diagnosis, environmental monitoring, safety system, astronomical research, driver assistance and chip.Universal day by day along with what use, strong day by day to miniature, sensitive, exquisite, the concealed and highly reliable also requirement of infrared detection system.Compare with traditional light quantity subtype sensitive detection parts, the non-refrigeration type infrared technique adopts ripe day by day at present MEMS technology, utilize light-Re-electricity to transform and survey infrared light, owing to do not need refrigeration machine and sweep mechanism, having reduced weight, complexity, power consumption, the cost of complete machine, is the mainstream development direction of infrared technique low cost, miniaturization.

Thermoelectric type infrared detector is by incident light is changed into heat, and then measures.Thermopile IR detector and array thereof are to study the earliest and one of the electrothermic type infrared imaging device of practicability, it by measuring metal or semiconductor because the thermoelectric potential that Seebeck effect produces is surveyed infrared radiation.In the past, thermopile IR detector all is to use the method manufacturing of vacuum coating, and the device size that produces like this is bigger, and not can manufacture.Along with the development of large scale integrated circuit, the especially development of MEMS technology, the manufacturing technology of infrared thermopile is upgraded rapidly.At present, the micromechanics infrared thermopile generally adopts back of the body etch, the method that in " Infrared thermopile sensors withhigh sensitivity and very low temperature coefficient " literary composition, adopts as J Schieferdecker etc., etching time is long, need tow sides to aim at exposure, poor with the CMOS processing compatibility, increased technology difficulty, manufacturing cost is also higher.Some micromechanics infrared thermopiles have also adopted the method for Surface Machining in the recent period, in " the front etch method is made novel micromechanics infrared thermopile detector ", adopt positive processing to obtain thermopile IR detector as Xu Zhengyi etc., but because the restriction of process, it can not obtain big INFRARED ABSORPTION area, duty ratio is less, is unfavorable for raising, the array of device performance.

Summary of the invention

The object of the present invention is to provide a kind of and cmos compatible front etch micromechanics infrared thermopile structure and preparation method thereof.

The present invention's micromachined thermopile infrared detector is＜100〉to make on the silicon chip of crystal orientation, structure comprises framework 1 as shown in Figure 1, thermoelectric pile 2, support arm 3, INFRARED ABSORPTION district 4, five parts such as strip opening 5 grades.Wherein, framework 1 and the middle INFRARED ABSORPTION district that suspends 4 constitute the cold junction district and the thermojunction district of thermoelectric piles 2, and support arm plays the purpose of connecting frame 1 and INFRARED ABSORPTION district 4 and carrying thermoelectric pile 2.Support arm 3 and INFRARED ABSORPTION district are made of the silica of deposit on silicon chip and silicon nitride composite membrane.Support arm 3 can be bilateral to draw or four limits to pull-up structure, (a) four support arm structures as shown in Figure 2, (b) double bracing arm configuration and (c) four limits to widening the support arm structure.Thermoelectric pile 2 can adopt with the P type polysilicon of CMOS process compatible, N type polysilicon, materials such as Al, Au in any two kinds of combinations make.Strip opening 5 is corrosion windows of etching in INFRARED ABSORPTION district 4, and it is to utilize the characteristic of (100) face Silicon Crystal Anisotropic Etching to design along＜100〉direction.To form with the opening after the corrosion is diagonal, the square bottom surface terrace with edge shape hole along＜110〉crystal orientation, as shown in Figure 3.Oblong openings 5 can cover by the suitable distribution of design.The distribution design of oblong openings 5 as shown in Figure 4, be that to overlook the square that obtains with each opening be the unit, select the square of suitable size, consider the width of support arm 3 and the size and the stress in INFRARED ABSORPTION district 4, cover whole INFRARED ABSORPTION district 4, when support arm discharged like this, the rapid release that can reach entire device was shaped.

The manufacture method that the present invention adopts is as shown in Figure 5, and is specific as follows:

1. get＜100〉crystal orientation two throw silicon chips and carry out oxidation after, with the method double-sided deposition silicon nitride/polysilicon layer of low-pressure chemical vapor deposition (LPCVD), and then the growing silicon oxide layer.

2. photoetching and etching window use the method for ion injection or the method for diffusion that polysilicon is carried out p type or the doping of p/n type and makes high-temperature annealing activation.

3. photoetching and etch the polysilicon resistance bar is as thermoelectric pile galvanic couple material.

4. at polysilicon resistance bar superficial growth silicon oxide layer.

5. lithography fair lead figure on oxide layer, form fairlead with hydrofluoric acid corrosion oxidation silicon, at the front depositing metal layers, and make metal wire by lithography, the polysilicon strip of bonding jumper and doping is realized ohmic contact by fairlead, form p/n type polysilicon or polysilicon, metal fever couple, become the primary structure of thermoelectric pile.

6. on the composite membrane in front, make corrosion window by lithography, remove silicon nitride, silica in the window, use anisotropic etchant, corrode as Tetramethylammonium hydroxide (TMAH) or potassium hydroxide (KOH), discharge fully to infrared absorption layer and support arm, promptly obtained infrared thermopile detector.

Advantage of the present invention is as follows:

1. adopt front etch of the present invention to discharge the method for thermoelectric pile structure, can discharge the broad area device structure in the short time rapidly, improve rate of finished products, reduce production costs;

2. manufacture craft and existing CMOS process compatible.Because needed thin-film material all is in conventional IC process materials scope in the device, and has adopted body silicon front etch releasing structure layer process different from the past, device integrated artistic and CMOS compatibility, cost is lower;

3. the design of suspension film makes that INFRARED ABSORPTION district area duty ratio is big, helps device performance and improves.

In sum, the thermopile IR detector that the present invention proposes adopts specific front openings structure to carry out wet etching to discharge the thermoelectric pile structure, its effective INFRARED ABSORPTION area can account for about 50% unit pixel area, have that duty ratio is big, etching time is short, rate of finished products is high, cost is low, good with the CMOS compatibility, be fit to characteristics such as array.

Description of drawings

Fig. 1 is the micromechanics polysilicon thermopile IR detector structural upright schematic diagram of the present invention's the compatible front etch of CMOS.

Fig. 2 is three kinds of design diagrams of micromechanics polysilicon thermopile IR detector structure of the present invention's the compatible front etch of CMOS.(a) being four support arm structures, (b) is two support arm structures, (c) is wide support arm structure.

Fig. 3 is strip open design (a) and the Corrosion results schematic diagram (b) thereof along＜100〉direction.

Fig. 4 is the present invention's strip open design schematic illustration.

Fig. 5 is the micromechanics polysilicon thermopile IR detector structure fabrication process of the present invention's the compatible front etch of CMOS.(a) film growth, (b) the graphical doping, (c) thermoelectric pile is shaped, and (d) passivation layer is made, (e) interconnection line, (f) structure discharges.

Fig. 6 is the device stereoscan photograph that specific embodiment 1 is made.

1 is framework among the figure, and 2 is thermoelectric pile, and 3 is support arm, and 4 is the INFRARED ABSORPTION district, and 5 is the strip opening

Embodiment 1:

The present embodiment structure is referring to Fig. 1.Its manufacture craft is as follows:

1. LPCVD deposits one deck SiO on (100) monocrystalline silicon ₂/ Si ₃N ₄Two-layered medium membrane structure, total film thickness are about 5000 .Grow the thereon then polysilicon of about 4000  of a bed thickness, about 1000  silica of then growing are shown in Fig. 5-(a).

2. through photoetching, BOE (Buffered Oxide Etch, the buffer oxide layer corrosive agent) etc. technology is after the surface forms the silica graph window, utilize photoresist to inject masking layer as ion, P, B plasma inject polysilicon, form the polysilicon resistance bar, as thermoelectric pile galvanic couple material, shown in Fig. 5-(b).

3. after the photoetching post bake, the silica of all the other polysilicon surfaces of BOE wet etching, the polysilicon that ion dry etching resistance bar figure is outer, the removing of photoresist by plasma, 1000 ℃ of high-temperature annealing activation ions form the thermoelectric pile figures, shown in Fig. 5-(c).

4. at grow silica about 2000  of polysilicon resistance bar surface PECVD, as the polysilicon passivation protection layer of last silicon anisotropic etching technology, shown in Fig. 5-(d).

5. through exposing polysilicon resistance bar lead-in wire contact hole after the technologies such as photoetching, BOE.Metals such as sputter 2000  aluminium or titanium are as the lead-in wire between the resistance, adopt the graphical metal lead wire of band glue stripping technology, shown in Fig. 5-(e).

6. ion dry etching SiO ₂/ Si ₃N ₄The two-layered medium film forms corrosion window, and adopting concentration is that 25% TMAH anisotropic etch solution discharges the free standing structure film heat insulating construction, and 80 ℃ of water-baths can be finished structure in 3 hours and discharge, and carries out the dehydration of alcohol drying then and obtains device, shown in Fig. 5-(f).

See Fig. 6 through obtained device photo after the above step flow.

Embodiment 2:

Present embodiment structure vertical view is referring to Fig. 2-(b), all the other are with embodiment 1.

Embodiment 3:

Present embodiment structure vertical view is referring to Fig. 2-(c), all the other are with embodiment 1.

Claims

1. the micromachined thermopile infrared detector with the CMOS process compatible is characterized in that framework (1) and the middle INFRARED ABSORPTION district (4) that suspends constitute the cold junction district and the thermojunction district of thermoelectric pile (2); Support arm (3) connecting frame (1) and INFRARED ABSORPTION district (4) and carrying thermoelectric pile (2); Strip opening (5) covers whole INFRARED ABSORPTION district (4).

2. by the described micromachined thermopile infrared detector with the CMOS process compatible of claim 1, it is characterized in that described support arm (3) for bilateral to draw or four limits to pull-up structure.

3. by the described micromachined thermopile infrared detector with the CMOS process compatible of claim 2, it is characterized in that support arm (3) is that four support arm structures, double bracing arm configuration or four limits are to widening the support arm structure.

4. by the described micromachined thermopile infrared detector with the CMOS process compatible of claim 1, it is characterized in that strip opening (5) is a corrosion window of going up etching in INFRARED ABSORPTION district (4), square bottom surface terrace with edge shape hole along＜100〉crystal orientation.

5. by the micromachined thermopile infrared detector of claim 1 or 4 described and CMOS process compatibles, it is characterized in that the corrosion of strip opening obtains square shaped cells.

6. by the described micromachined thermopile infrared detector with the CMOS process compatible of claim 1, it is characterized in that described support arm (3) and INFRARED ABSORPTION district (4) are that silica and silicon nitride composite membrane by deposit on silicon chip constitutes.

7. make the method for the micromachined thermopile infrared detector of as claimed in claim 1 and CMOS process compatible, it is characterized in that processing step is:

(a) get＜100〉crystal orientation two throw silicon chips and carry out oxidation after, with the method double-sided deposition silicon nitride/polysilicon layer of low-pressure chemical vapor deposition, and then the growing silicon oxide layer;

(b) photoetching and etching window use the method for ion injection or the method for diffusion that polysilicon is carried out p type or the doping of p/n type and makes high-temperature annealing activation;

(c) photoetching and etch the polysilicon resistance bar is as thermoelectric pile galvanic couple material;

(d) at polysilicon resistance bar superficial growth silicon oxide layer;

(e) lithography fair lead figure on oxide layer, form fairlead with hydrofluoric acid corrosion oxidation silicon, at the front depositing metal layers, and make metal wire by lithography, the polysilicon strip of bonding jumper and doping is realized ohmic contact by fairlead, form p/n type polysilicon or polysilicon, metal fever couple, become the primary structure of thermoelectric pile;

(f) on the composite membrane in front, make corrosion window by lithography, remove silicon nitride, silica in the window, use anisotropic etchant to corrode, infrared absorption layer and support arm are discharged fully, promptly obtained infrared thermopile detector.

8. by the manufacture method of the described micromachined thermopile infrared detector with the CMOS process compatible of claim 7, it is characterized in that described anisotropic etchant is Tetramethylammonium hydroxide or potassium hydroxide.