DE10058861A1 - Infrared sensor for high-resolution infrared detector arrangements and method for its production - Google Patents

Abstract

An infrared sensor for high-resolution infrared detector arrangements has a carrier (20) on which at least one pixel element (30) for detecting infrared radiation is arranged, and a reading electronics or components of such reading electronics integrated in the carrier and coupled to the pixel element (30) is / are. Contact surfaces (2) of the readout electronics or of components of the readout electronics are located inside the carrier (20). The readout electronics or components of the readout electronics and the pixel element (30) are designed in a vertical arrangement. The carrier (20) contains a CMOS-compatible surface micromechanical structure with an integrated cavity (7) below the pixel element (30) and columnar metal structures (6a) that extend vertically and the contact surfaces (2) of the readout electronics with the pixel element (30) electrically connect. In a method for producing the IR sensor, readout electronics or components of the readout electronics and pixel elements (30) are arranged vertically one above the other.

Description

The present invention relates to an infrared sensor according to the preamble of claim 1 and a method for Manufacture of an infrared sensor according to the preamble of Claim 9. The IR sensor is especially for high Solving infrared detector arrangements suitable.

Integrated infrared sensors for high-resolution infrared Detector arrangements include a semiconductor support body or Chip on which a sensor element for measuring the intensity an infrared radiation is configured. Here is the Sen sensor element, for example a pyroelectric capacitor. Is located next to the sensor element or the sensor structure on the chip readout electronics that are ready for processing processing of the signals generated by the sensor structure. The readout electronics and the sensor structure are ne applied to each other on the chip. The readout electronics is integrated in the chip.

However, the known infrared sensors have the disadvantage large space requirement. By arranging selection electronics and sensor structure side by side on the chip with a given detector area or with a given one the number of chips in an integrated sensor array the sensor elements limited.

Add to that the general requirement that the sensors or IR detector arrays stable against mechanical influences  should be from outside. In addition, the infra red sensors can be manufactured inexpensively.

It is therefore the object of the present invention, a Infrared sensor especially for high-resolution infrared To create detector arrays that are very compact or space can be designed to be economical and with the detector rays a dense arrangement of the sensors can be achieved. Furthermore, a high resolution of the IR detector arrays are made possible. In addition, a Method for producing such an infrared sensor be specified, which is relatively inexpensive to carry out.

The task is solved by the infrared sensor according to Pa claim 1 and by the method for producing a Infrared sensor according to claim 9. Further advantageous Features, aspects and details of the invention result from the dependent claims, the description and the drawings gene.

The infrared sensor according to the invention for high-resolution infra red detector arrangements has a support on which at least a pixel element arranged for the detection of infrared radiation is net, and a z. B. integrated in the carrier selection electronics or components of a read-out electronics that the pixel element is coupled / sin, the readout electro nik or the components of the readout electronics and the pixel element are formed in a vertical arrangement and the Trä eng - among other things - contains a micromechanical structure.

The micromechanical structure can be used for thermal insulation of the Serve pixel elements from the substrate material.  

Because of the vertical arrangement of the two parts electronics or readout circuit or components of the readout electronics and pixel element in connection with a microme The sensors can be provided with a mechanical structure in a detector arrangement be arranged much closer together. This allows high-resolution IR detector arrays are created that have a very small footprint and yet one achieve high resolution. The infrared sensor according to the invention is particularly with techniques of surface micromechanics producible, d. H. with a CMOS compatible mic romechanics or surface micromechanics high-resolution IR Detector arrays accessible.

A surface microme is advantageously in the carrier mechanically manufactured support structure provided. This will a particularly high stability against external influences achieved, while still an extremely small footprint ge is guaranteed. The use of the surface micromecha nically manufactured support structures also serves in particular to reduce crosstalk between individual pixels or pixel elements.

Electrical contact from the pixel element to is preferred Readout electronics or the components of the Ausle seelektronik in the support structure or in the support structures integrated. As a result, the space or space requirement is still white ter reduced, without the stability suffers disadvantages. The support structure thus fulfills two functions at the same time NEN, namely on the one hand the provision of the electrical Contacts to the readout circuit or to the readout electronics, and on the other hand the support of the vertical or vertical elements of the infrared sensor arranged one above the other.  

A cavity is advantageously provided in the carrier. because the cavity is preferably evacuated or the cavity Closure process carried out in a vacuum. Through the cavity and especially through the evacuated cavity is the pi xelelement thermally insulated, which improves the qua measurement results or to increase the resolution wearing. Due to this advantageous embodiment the thermal insulation directly in the pixel and the entire chip or infrared sensor can be placed in a subatmospheric pressure existing housing. This saves costs saves, because a vacuum housing in comparison with this Lich higher costs.

The carrier contains e.g. B. a CMOS-compatible micromechanics structure with an in particular vertical of the carrier interior contact made on the carrier surface. This still carries in addition to saving space and increasing stability act at.

The carrier is preferably made of a substrate with a brought layer sequence formed, being in the layer sequence closed cavity with one or more electrically conductive support structures is designed, the selection circuit or the readout electronics or the components the readout electronics with the pixel element (s) the. The carrier or the substrate is in particular a chip. This results in a particularly inexpensive and special space-saving design.

The pixel element can e.g. B. a pyroelectric capacitor include structure or be designed as such, the ins especially through the support structures in the carrier with the readout electronics  or the components of the readout electronics e is electrically connected.

The inventive method for producing an infra red sensor, especially for high-resolution infrared Suitable detector arrangements includes the steps: Be riding a carrier with micromechanically produced Cavities and a readout electronics or components egg ner readout electronics; Applying a pixel element to the Support surface; and making an electrically conductive Connection between the readout electronics or the components the readout electronics and the pixel element; being the Readout electronics or the components of the readout electronics and the pixel element are arranged vertically one above the other, and wherein the electrically conductive connection through the Stretcher stretches.

With the inventive method can be inexpensive How to create a space-saving infrared sensor, which enables high resolution in infrared detector arrays light, but still a high strength or stability of the Infrared sensor is achieved.

In particular, the electrically conductive extends Connection of the readout electronics or the components the readout electronics of the carrier to the carrier surface. there are the contact surfaces of the readout circuit z. B. in In neren of the carrier arranged.

The method according to the invention is advantageously used Techniques of micromechanics or surface micromechanics carried out. This allows z. B. support structures and / or  Insulations to reduce crosstalk between one individual pixels are produced.

In particular, a layer can be used to produce the carrier follow to be applied to the substrate, in the example wise one or more metal structures to support the Trä surface and for electrical contacting of the readout electronics or the components of the readout electronics from the Carrier surface are introduced.

An auxiliary layer within the support is preferably e.g. B. selectively etched below a membrane to create a cavity in the Train carriers. The cavity advantageously becomes closed at a sufficiently low pressure. This can possibly in a vacuum or under vacuum conditions hen. This saves costs that would otherwise be incurred a necessary vacuum housing for the infrared sensor arises would. The pixel elements are through these measures very well thermally insulated, making it even denser order of the infrared sensors in the detector array is possible, but still a good resolution is guaranteed.

A layer sequence is advantageously provided on the carrier Formation of a pyroelectric capacitor applied, the forms the pixel element, the capacitor or the Pi xelelement z. B. a surface micromechanically Herge put support structure inside the beam with the elite electronics or the components of the readout electronics kon is clocked.

The advantages, features and details of the invention, which under Reference to the method of manufacturing the IR sensor are given, of course, also apply to the invention  Infrared sensor itself, as well as advantages and features of the infrared sensor for the invention processes for its manufacture apply.

The following is first the manufacture of a fiction infrared sensor or a high-resolution pyroelectric described IR detector arrays by way of example, and in conclusion, the IR sensor itself is based on the manufactured Structure described as an example. Show

Fig. 1a and 1b a schematic representation of the various steps in the manufacture of the infrared sensor according to a preferred embodiment of the invention it, wherein the structure in each Her position phases A through T is characterized.

In Fig. 1a is assumed that a wafer 1, which is provided with a read-out electronics and read-out circuit or parts thereof. Metallic contact surfaces 2 in the form of pads are formed on the surface of the wafer 1 . The wafer 1 forms a substrate which contains the readout electronics or components of the readout electronics, the contact surfaces 2 serving for contacting the readout electronics or semiconductor circuit or the components of the readout electronics. Further layer sequences can be applied to the wafer provided in this way. (A)

Now a passivation 3 is applied to the surface of the substrate or wafer 1 , the passivation 3 covering the contact surfaces 2 or pads. The passivation 3 is preferably formed by one or more nitride layers or silicon nitride layers. The upper silicon nitride layer of the passivation 3 serves as an etching stop for a later cavity etching above the passivation 3 , so that the underlying substrate 1 is not attacked. (B)

In the process step that follows, an auxiliary layer 4 is applied to the passivation 3 nitride layer, which is, for example, a plasma oxide layer. The plasma oxide layer or auxiliary layer 4 is, for. B. a 0.5 micron thick layer, which is used for the later production of a support structure with an integrated electrical contact or conductor. The auxiliary layer 4 forms a sacrificial layer for the later cavity etching. (C)

Now another layer as membrane 5 is applied to the plasma oxide of auxiliary layer 4 . The membrane layer or membrane 5 is, for example, a Si nitride layer and has, for. B. a thickness of about 0.2 microns. (D)

Subsequently, contact holes 5 a are etched into the layers placed on the substrate or wafer 1 , which reach as far as the aluminum pads or contact areas 2 of the readout electronics and contact them. The respective contact hole 5 a is formed vertically from the top of the membrane 5 downwards perpendicular to the substrate surface. The diameter of the respective contact hole 5 a is for example 1 to 2 microns. (E) and (F)

Subsequently, the contact holes 5 a are filled with an electrically conductive material or a metal, with tungsten being advantageously used before. The tungsten can be deposited, for example, in a CVD process (Chemical Vapor Deposition). The electrically conductive material in the contact holes 5 a extends from the surface of the membrane 5 in a columnar manner down to the surface of the contact surfaces 2 , so that it forms a continuous electrical contact from the surface of the structure thus formed to the contact surfaces 2 located inside the structure , After filling the contact holes with the metal or tungsten metal, there is a metal layer 6 on the surface of the membrane 5 . (G)

Now the metal or tungsten, which is located on the surface of the membrane 5, is removed or structured via an FT. (H)

The next step comprises the etching of further holes 5 b in the membrane 5 made of silicon nitride. The openings or holes 5 b penetrate the membrane 5 completely over their entire thickness, so that a connection is created from the outside to the auxiliary layer. 4 (K)

The next step is a cavity etching, with the auxiliary layer 4 or plasma oxide layer between the silicon nitride layers, ie between the passivation 3 and the membrane 5 above, being partially etched out. The etching process is carried out in such a way that 5 a Si oxide remains in the contact holes around the tungsten. A cavity 7 is formed in the auxiliary layer 4 below the holes 5 b. The tungsten in the contact holes 5 a, which are formed on both sides of the cavity 7 , forms a metal structure 6 a, which serves as a via. The remaining material of the auxiliary layer 4 on the metal structures 6 a protects the metal or tungsten from an etching attack. Now who closed the etching holes 5 b in the membrane 5 with a suitable material by means of the known methods. The closure material forms a closure or membrane layer 8 , on which a wiring of electrical components z. B. can be carried out by means of photo technology. (L)

Due to the etching by the oxide on the tungsten cone clocks or W-plugs results in a very space-saving, CMOS Compatible surface micromechanical structure with one from In Contact made on the wafer surface. The con clock forms an electrical line that is perpendicular to the Extends wafer level and that below the wafer surface located, integrated in the wafer readout relation as their components contacted.

Now the further process steps take place, through which pyroelectric pixels are defined on the provided thermally insulating structures. First, in a first step, a platinum layer, which forms a lower electrode 9, is applied over the entire surface of the membrane layer 8 . Other materials can also be used for the electrode. For example, an Ir layer can be used as the lower electrode 9 instead of a Pt layer. The thickness of the lower electrode 9 is typically in the range between 50 and 300 nm. (M)

A layer 10 of pyroelectric material is applied to the Pt electrode or lower electrode 9 by a sputtering process. PZT (lead zirconate titanate) is used as the pyroelectric material. The ferroelectric PZT layer 10 is applied in an oxygen-containing atmosphere at temperatures between approximately 450 ° C. and 550 ° C. (N)

An upper electrode 11 , which is formed from a CrNi layer, is then applied to the PZT layer 10 using a lift-off process. The CrNi electrode or upper electrode 11 has a thickness of approximately 20-50 nm and optimally absorbs infrared radiation in a wavelength range of 10 micrometers. (O)

The next step involves structuring the ferroelectric PZT layer 10 using an RIE (reactive ion etching) process. This is an anisotropic physical dry etching. The size of a pixel defined in this way is approximately 50 by 50 μm ² , the PZT layer 10 having a thickness of approximately 1 μm. (P).

The lower electrode 9 is also structured using an RIE process. The structured lower electrode 9 , the ferroelectric PZT layer 10 and the upper electrode 11 form a pyroelectric capacitor structure which is applied to the surface structure of the wafer 1 . (Q)

The next steps involve connecting this capacitor to the readout circuit below. For this purpose, an insulator 12 is first attached to the side of the ferroelectric layer 10 . The insulator 12 extends laterally over the edges of the upper electrode 11 and the lower electrode 9 . (R)

Holes 8 a are now etched into the membrane layer 8 , so that the columnar metal structures 6 a or tungsten plugs are opened or exposed. That is, the holes 8 a are arranged directly above the metal structures 6 a. (S)

Subsequently, a metallization 13 is applied to contact the lower and upper electrodes 9 , 11 , which forms an electrically conductive connection of the respective electrodes 9 and 11 to the associated columnar metal structure 6 a. In the schematically shown arrangement shown here, the metallization 13 extends on the one hand between the lower electrode 9 and the metal structure 6 a arranged on the left in the figure, and on the other hand between the upper electrode 11 and the metal structure arranged on the right in the figure 6 a. As a result, electrical contacts are made from the electrodes 9 , 11 to the underlying contact surfaces 2 of the underlying readout electronics or semiconductor circuit or from the components of the readout electronics. The metallizations 13 can, for. B. made of aluminum, Ti / Pt / Au or Cr / Au. The thickness of these contacts, which are structured using the lift-off technique, for example, is in the range between 400 and 600 nanometers. (T)

The infrared sensor shown in section (T) of FIG. 1b comprises a carrier 20 , which is formed by a surface micromechanical structure with contacts guided on the wafer surface. On the carrier 20 , a pixel element 30 is arranged in the form of a pyroelectric capacitor structure, which is formed by the lower and upper electrodes 9 , 11 with the PZT layer 10 arranged therebetween.

A readout electronics or a readout circuit, which is not explicitly shown in the figures, is integrated in the carrier 20 and coupled to the associated pixel element 30 . The readout circuit and the pixel element 30 are arranged one above the other or designed in a vertical arrangement. Vertical electrical lines in the form of columnar metal structures 6 a, which extend through the carrier 20 , connect the readout electronics with the pixel element 30 lying above them. As a result, the contacting of the readout electronics located below the chip surface takes place on the chip surface in the immediate vicinity of the sensor or pixel element 30 lying above it.

The metal structures 6 a each form a support structure, and are used both for supporting the pixel element 30 on the surface of the membrane 8 , and for contacting the respective or associated readout circuit or components thereof. The cavity 7 in the plasma oxide layer 4 or in the carrier 20 serves for thermal insulation of the pixel element 30 and is seen directly below the pixel element 30 .

In an IR detector array, a large number of such IR Sensors arranged in high density, the IR sensors z. B. are configured in a single wafer.

Claims (15)

1. infrared sensor, in particular for high-resolution infrared detector arrangements, with a carrier ( 20 ) on which at least one pixel element ( 30 ) is arranged for the detection of infrared radiation, and
readout electronics or components of such readout electronics integrated in the carrier ( 20 ), which are coupled to the pixel element ( 30 ),
characterized by
that the readout electronics or the components of the readout electronics and the pixel element ( 30 ) are formed in a vertical arrangement, the carrier ( 20 ) containing a micromechanical structure. 2. Infrared sensor according to claim 1, characterized in that in the carrier ( 20 ) a surface micromechanically produced support structure ( 4 , 6 a) is provided to reduce crosstalk between individual pixel elements ( 30 ). 3. Infrared sensor according to claim 1 or 2, characterized in that a metal structure ( 6 a) in the support structure ( 4 , 6 a) is integrated, the vertically guided electrical contact from the pixel element ( 30 ) to the readout electronics or to the components the readout electronics. 4. Infrared sensor according to one of the preceding claims, characterized in that a cavity ( 7 ) for thermal insulation of the pixel element ( 30 ) is provided in the carrier ( 20 ). 5. Infrared sensor according to claim 4, characterized in that the cavity ( 7 ) is evauuiert. 6. Infrared sensor according to one of the preceding claims, characterized in that the carrier ( 20 ) contains a CMOS-compatible surface micromechanical structure with a surface from the carrier interior onto the carrier surface vertically or perpendicularly to the contact surface. 7. Infrared sensor according to one of the preceding claims, characterized in that the carrier ( 20 ) from a substrate ( 1 ) which has a readout electronics or components of a readout electronics, and an applied layer sequence ( 3 , 4 , 5 , 8 ) is, in the layer sequence a closed cavity ( 7 ) with one or more electrically conductive support structures ( 4 , 6 a) is designed, which connect the readout electronics or the components of the readout electronics with the at least one pixel element ( 30 ). 8. Infrared sensor according to one of the preceding claims, characterized in that the Pi xelelement ( 30 ) comprises a pyroelectric capacitor structure which is electrically connected by support structures ( 4 , 6 a) in the carrier ( 20 ) with the readout electronics or the components of the readout electronics. 9. A method for producing an infrared sensor for high-resolution infrared detector arrangements, comprising the steps:
Providing a carrier ( 20 ) with micromechanically produced cavities and with a readout electronics or components of readout electronics;
Applying a pixel element ( 30 ) to the carrier surface; and
Establishing an electrically conductive connection between the readout circuit and the pixel element ( 30 );
characterized,
that the readout electronics or the components of the readout electronics and the pixel element ( 30 ) are arranged vertically one above the other, the electrically conductive connection extending through the carrier ( 20 ). 10. The method according to claim 9, characterized in that it is with Techniques of micromechanics, especially the surface chenmicromechanics, is carried out. 11. The method according to claim 9 or 10, characterized in that for the production of the carrier ( 20 ) a sequence of layers ( 3 , 4 , 5 , 8 ) is applied to a substrate ( 1 ) into which one or more metal structures ( 6 a) are introduced, which serve to support the carrier surface and for electrical contacting of the readout electronics or the components of the readout electronics from the carrier surface. 12. The method according to any one of claims 9 to 11, characterized in that an auxiliary layer ( 4 ) within the carrier ( 20 ) below a membrane ( 5 , 8 ) is selectively etched to form a cavity ( 7 ) in the carrier ( 20 ) , 13. The method according to claim 12, characterized in that the cavity ( 7 ) is closed at a sufficiently low pressure. 14. The method according to any one of claims 9 to 13, characterized in that on a diaphragm layer ( 8 ) of the carrier ( 20 ) a layer sequence ge ( 9 , 10 , 11 ) is applied to form a pyroelectric capacitor which the pixel element ( 30 ) forms. 15. The method according to any one of claims 9 to 14, characterized in that the Pi xelelement ( 30 ) via a surface micromechanically produced support structure within the carrier ( 20 ) with the readout electronics or the components of the readout electronics is contacted.