DE102008041587A1 - Microstructured temperature sensor element for spatially resolved detection of infrared radiation, has infrared radiation absorbing layer arranged on passivation layer, where absorbing layer is isolated from gas phase - Google Patents

Abstract

The sensor element has an N-doped epitaxial layer (7') with electrical characteristics changing value of the epitaxial layer depending on temperature. A dielectric layer (12), and an infrared radiation absorbing layer (21) is arranged on a passivation layer, where the absorbing layer is isolated from a gas phase. The absorbing layer is doped and/or undoped with silicon, silicon-germanium, silicon carbide and/or silicon dioxide. The epitaxial layer has a monocrystalline layer (8) with a pn-junction between a P-channel region (11) and an N-channel region (10). An independent claim is also included for a method for manufacturing a sensor element.

Description

State of the art

The The present invention relates to a microstructured sensor element, comprising a layer sequence of a doped semiconductor layer with a value of its temperature dependent changing electrical Property, a dielectric layer, a passivation layer and an IR radiation absorbing layer. It continues to apply a method for producing such a sensor element and a sensor array for spatially resolved detection of infrared radiation comprising such sensor elements.

Semiconductor sensors can change temperature, for example, through Infrared radiation, about the electrical properties of semiconductor devices such as diodes detect. To improve the Performances of these sensors, the sensor elements, which take over the task of temperature detection, be provided with infrared (IR) radiation absorbing layers. Usually These absorber layers are made using thick-film technology in paste printing realized. However, a disadvantage of this is the need for separate Process steps in the production. Continue lets the crystallinity of the absorber layer by thick-film process only limited. Furthermore, through this technique not as small structures as in other methods in semiconductor structuring be achieved. In addition, the paste printing process becomes mechanical acted on the sensor element. This can be done with the existing ones sensitive structures for damage and thus failure lead the sensor. Consequently, this is another one Miniaturization of the sensor elements contrary.

Sensors that can benefit from alternative ways of applying IR-absorbing layers are DE 10 2006 028 435 A1 disclosed. Described is a sensor, in particular for spatially resolved detection, comprising: a substrate, at least one microstructured sensor element with a temperature-dependent changing their electrical property and at least one membrane above a cavern, wherein the sensor element is arranged on the underside of the at least one membrane and wherein the sensor element is arranged on the underside of the at least one membrane, and wherein the sensor element is contacted via leads which run in, on or under the membrane. In particular, a plurality of sensor elements can be formed as diode pixels in a monocrystalline, epitaxially formed layer. In the membrane suspension springs can be formed, which receive the individual sensor elements elastic and insulating.

Disclosure of the invention

According to the invention, a microstructured sensor element is proposed, comprising the following layer sequence:
a doped semiconductor layer having a temperature-dependent changing value
electrical property;
a dielectric layer; and
a passivation layer;
wherein on the passivation layer further a vapor deposited layer of infrared radiation absorbing material is arranged.

microstructured Sensor elements in the context of the present invention are in this case Sensor elements whose functional structures are dimensions in the micrometer range exhibit. For example, these functional structures a length, height and / or width of ≥ 1 μm to ≤ 500 microns have.

A temperature-dependent variable electrical property in the doped semiconductor layer, inter alia, the electrical Resistance, the current flowing through the sensor element Current or the voltage drop across the sensor element.

The Dielectric layer on the semiconductor layer may, for example by thermal oxidation or by tetraethoxysilane oxidation (TEOS oxidation) the semiconductor layer can be obtained. She can be next to her electric insulating task also perceive mechanical functions, for example to a connection between the sensor element and a sensor element ultimately produce supporting substrate.

The Passivation layer preferably comprises silicon oxide and / or Silicon nitride. It can be as a layer or as a sequence be executed several layers.

According to the invention provided that on the passivation layer one from the gas phase deposited layer of infrared radiation absorbing material is arranged. This layer converts infrared radiation during sensor operation in heat, for example by electrically active dopants in the layer. This can be obtained by thin-film techniques become.

In one embodiment of the sensor element, the infrared radiation absorbing layer comprises silicon, silicon germanium, silicon carbide and / or silicon dioxide and these materials are doped and / or undoped. Such materials are compatible with conventional processes in semiconductor surface technology and can be understood by Mas Structured precisely from the gas phase deposition. The material can be monocrystalline, polycrystalline or amorphous. It is also advantageous that these materials, even after deposition, can also be structured by means of dry etching processes. The elements used for doping are preferably selected from the group comprising boron, aluminum, nitrogen, phosphorus, arsenic and / or antimony. The doping elements can be present, for example, in an atomic concentration, based on the material of the infrared-absorbing layer, of ≥ 10 ¹² / cm ³ to ≦ 10 ¹⁹ / cm ³ or preferably of ≥ 10 ¹⁵ / cm ³ to ≦ 10 ¹⁸ / cm ³ . In another alternative, the concentration of doping elements is chosen so high that it comes within the range of an alloy. Here, the concentration of the doping elements can be ≥ 10 ¹⁹ / cm ³ to ≦ 10 ²³ / cm ³ or preferably from ≥ 10 ²⁰ / cm ³ to ≦ 10 ²² / cm ³ .

In a further embodiment of the sensor element the thickness of the infrared radiation absorbing layer ≥ 1 μm to ≤ 15 μm. The thickness can be advantageous also ≥ 2 microns to ≤ 10 microns. Absorber layers of this thickness have low thermal insulation so that the response of the sensors during temperature changes is faster.

In a further embodiment of the sensor element, the doped semiconductor layer comprises a monocrystalline layer having at least one pn junction between a positively doped region and a negatively doped region. Here, it is preferred that the monocrystalline layer comprises epitaxially grown n-doped silicon and the pn junction is formed by p ⁺ - and n ⁺ -doped silicon. By forming the sensor elements in an epitaxial and thus monocrystalline layer, the signal noise can be kept very low. This is particularly advantageous in the formation of diodes. The n ⁺ region may serve to establish the connection between metallic contact lines to the semiconductor layer. This avoids the formation of a Schottky contact between the metal and the heavily doped region. The actual diode is formed between the n-doped region and the p ⁺ -doped region, which also does not form a Schottky contact with the metal due to its high doping.

In a further embodiment of the sensor element is the Sensor element above a bearing in which the sensor element Substrate formed cavern arranged. That's the way it is Sensor element thermally decoupled from the substrate. This allows Warming of the substrate as during the Operation of an electrical component occur, the temperature measurement less influence on the sensor element. Each sensor element can be assigned to a cavern or it can be several sensor elements lie over a common cavern.

• a) Bereitstellen einer dotierten Halbleiterschicht mit einer ihren Wert temperaturabhängig ändernden elektrischen Eigenschaft;
• b) Auftragen einer dielektrischen Schicht auf die Halbleiterschicht;
• c) Auftragen einer Passivierungsschicht auf die dielektrische Schicht;
• d) Auftragen einer Infrarotstrahlung absorbierenden Schicht aus der Gasphase auf die Passivierungsschicht;
• e) Auftragen einer Maskierungsschicht auf die Infrarotstrahlung absorbierende Schicht, wobei vorbestimmte Bereiche der Infrarotstrahlung absorbierenden Schicht von der Maskierungsschicht nicht bedeckt werden;
• f) Ätzen der nicht durch die Maskierungsschicht abgedeckten Bereiche der Infrarotstrahlung absorbierenden Schicht.

The invention likewise provides a method for producing a sensor element according to the present invention, comprising the steps:

• a) providing a doped semiconductor layer having a value whose temperature varies depending on the electrical property;
• b) applying a dielectric layer to the semiconductor layer;
• c) applying a passivation layer to the dielectric layer;
• d) applying an infrared radiation absorbing layer from the gas phase to the passivation layer;
• e) applying a masking layer to the infrared radiation absorbing layer, wherein predetermined areas of the infrared radiation absorbing layer are not covered by the masking layer;
• f) etching the areas of the infrared radiation absorbing layer not covered by the masking layer.

In An embodiment of the method is the infrared radiation absorbing layer by sputtering, plasma enhanced chemical vapor deposition and / or low-pressure chemical Applied vapor deposition. Thus, in particular a Silicon, silicon germanium and / or silicon carbide Layer are applied. By applying these thin-film techniques For example, the thickness of the coated layer may be in one Range from ≥ 1 μm to ≤ 15 μm or advantageously also ≥ 2 μm to ≤ 10 μm lie.

In In a further embodiment of the method, the etching takes place the infrared radiation absorbing layer by means of a plasma etching process. An advantage of this is that the same etching medium as in other structuring steps in the manufacture of the sensor element can be used and so the process does not continue is complicated. Preferably, the etching is carried out in a sulfur hexafluoride plasma process.

In In a further embodiment of the method, the etching takes place the infrared radiation absorbing layer in the same process step such as etching a portion of the doped semiconductor layer. Also This shows the advantage of simplified process control.

Another object of the invention is a sensor array for the spatially resolved detection of Infrared radiation comprising sensor elements according to the present invention.

The Invention will be further explained with reference to the drawings, but without being limited thereto. Hereby show:

1 to 3 the production of a sensor element according to the invention

1 shows the starting situation in which a doped semiconductor layer is provided with a value dependent on the temperature-dependent changing electrical property. The manufacturing steps up to this stage can be carried out according to DE 10 2006 028 435 A1 respectively. On a substrate 1 there is a sensor element area 2 and a circuit area 3 to control the sensor and to process its signals. The material of the substrate may comprise, for example, p-doped silicon.

In the substrate 1 can be between the detector area 2 and the circuit area 3 for example, by p ⁺ doping a trench-shaped lower insulation layer in cross-section 4 be formed, which is supplemented in a later process step up and the isolation of the detector area 2 from the circuit area 3 serves. The insulation layer 4 can still through the insulation layer 19 be supplemented. From the production of the cavern 5 stirs an n- or n ⁺ -doped annular region 6 her, which represents a limit for Kavernenätzung.

The layer 7 is an epitaxial layer of n-doped silicon. In the course of growth or application, there is a thermal rearrangement of left over after etching or porosification material in the area from which the cavern 5 arises. This material may prove to be a monocrystalline layer 8th on the bottom of the epitaxial layer 7 knock down. Depending on the choice of conditions can also temporary support points 9 be left, which will be removed in a later step.

On the n-doped epitaxial layer 7 suitable structures are formed, which is both in the detector area 2 as well as in the circuit area 3 can be carried out. In the circuit area 3 For example, different implantation or diffusion process steps can be used to form the circuits in a manner known per se. In the detector area 2 be in the corresponding section of the n-doped epitaxial layer 7 ' for every later pixel an n ⁺ -region 10 and a p ⁺ region 11 formed by implantation and / or diffusion. This forms in the layer 7 ' with the p ⁺ region 11 a diode. Furthermore, one or more dielectric layers 12 formed, for example, by oxidation to SiO ₂ , wherein at least in the detector area 2 locally thicker LOCOS gain ranges through a LOCOS process 13 be formed. For this purpose, in the SiO ₂ layer 12 achieved by appropriate masking a stronger oxidation with a corresponding volume increase and thus thickening in the vertical direction. The LOCOS gain ranges 13 especially at the edge of the later pixels, ie above the edges of the cavern 5 educated. Corresponding LOCOS gain ranges 13 can also in the circuit area 3 be formed.

The one or more dielectric layers 12 will continue in the circuit area 3 as well as in the detector area 2 structured. In the circuit area 3 become, for example, different components 14 structured. Again, LOCOS reinforcements 13 be formed.

In a backend circuit process, metallizations and passivations, for example a metallization layer, are used 15 with contact pad 16 , and one or more passivation layers 17 applied. The metallization layer 15 made of, for example, aluminum contacts in recessed access holes of the dielectric layer 12 the n ⁺ region 10 and the p ⁺ region 11 , The metallization layer 15 is accordingly also in the circuit area 3 for contacting the components formed there 14 , used for supply lines and possibly also for other components. Advantageously, through the metallization layer 15 also connection lines 18 between the detector area 2 and the circuit area 3 designed so that an integrated component with detector area 2 and circuit area 3 is trained.

Here, one or more metallization layers 15 made of, for example, aluminum. The n ⁺ region 10 only serves for contacting with the metallization layer 15 so that no Schottky contact is formed between the metal and the heavily doped region. The actual diode is between the epitaxial layer 7 ' and the p ⁺ region 11 formed, which also due to its high doping no Schottky contact with the metallization layer 15 formed.

In the shift 7 . 7 ' are in dashed lines areas 20 shown, which illustrate the area of a later etching.

In 2 you can see how first the infrared radiation absorbing layer 21 is uniformly deposited by vapor deposition. Subsequently, a resist mask 22 applied. The contacts 16 and the sacrificial layer etching gears are omitted here.

3 shows the state after the etching and the removal of the resist mask 22 , By etching, the cavern becomes 5 finished, the areas 20 etched and thus the electrical insulation to the circuit area 3 realized. In particular, the jetty became 9 away. The dielectric layer 12 serves as a membrane 23 and provides for the connection of the sensor element to the substrate 1 , In other words, the sensor element is above the cavern 5 arranged it only over membrane 23 is mechanically coupled to the substrate. This ensures electrical insulation and thermal decoupling.

In the same etching step, not only the silicon of the substrate becomes 1 and the epitaxial layer 7 . 7 ' etched, but also the infrared radiation absorbing layer 21 not in the mask 22 covered areas. This is preferably done by means of the Bosch process. As shown here, also the contact pads 16 optional. The infrared radiation absorbing layer 21 can, as shown here, be opened a little larger than in the etching of the silicon.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 102006028435 A1 [0003, 0021]

Claims (10)

Microstructured sensor element comprising the following layer sequence: a doped semiconductor layer ( 7 ' ) with a temperature-dependent changing their electrical value property; a dielectric layer ( 12 ); and a passivation layer ( 17 ); characterized in that on the passivation layer ( 17 ) further comprises a vapor-deposited layer of infrared radiation absorbing material ( 21 ) is arranged. Sensor element according to claim 1, wherein the infrared radiation absorbing layer ( 21 ) Silicon, silicon germanium, silicon carbide and / or silicon dioxide and wherein these materials are doped and / or undoped. Sensor element according to claim 1 or 2, wherein the thickness of the infrared radiation absorbing layer ( 21 ) ≥ 1 μm to ≤ 15 μm. Sensor element according to one of claims 1 to 3, wherein the doped semiconductor layer ( 7 ' ) a monocrystalline layer having at least one pn junction between a positively doped region ( 11 ) and a negatively doped area ( 10 ). Sensor element according to one of claims 1 to 4, wherein the sensor element above a in the sensor element supporting the substrate ( 1 ) cavern ( 5 ) is arranged. Method for producing a sensor element according to one of Claims 1 to 5, comprising the steps of: a) providing a doped semiconductor layer ( 7 ' ) with a temperature-dependent changing their electrical value property; b) applying a dielectric layer ( 12 ) on the semiconductor layer; c) applying a passivation layer ( 17 ) on the dielectric layer; d) applying an infrared radiation absorbing layer ( 22 ) from the gas phase to the passivation layer ( 17 ); e) applying a masking layer ( 22 ) on the infrared radiation absorbing layer ( 21 ), wherein predetermined regions of the infrared radiation absorbing layer ( 21 ) from the masking layer ( 22 ) are not covered; f) etching not through the masking layer ( 22 ) covered areas of the infrared radiation absorbing layer ( 21 ). Method according to claim 6, wherein the infrared radiation absorbing layer ( 21 ) is applied by sputtering, plasma enhanced chemical vapor deposition and / or low pressure chemical vapor deposition. A method according to claim 6 or 7, wherein the etching of the infrared radiation absorbing layer ( 21 ) takes place by means of a plasma etching process. Method according to one of claims 6 to 8, wherein the etching of the infrared radiation absorbing layer ( 21 ) takes place in the same method step as the etching of a part of the doped semiconductor layer. Sensor array for the spatially resolved Detection of infrared radiation comprising sensor elements according to a of claims 1 to 5.