JP2001091364A - Thermoelectric sensor device and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve sensor performance without increasing the size and cost of a thermoelectric sensor device. SOLUTION: Polycrystalline silicon, titanium or Al
A thermoelectric sensor device made of SiCu is shown as a thermocouple made of a material for a thermoelectric sensor device. The feature of the present invention is to select a material such as aluminum, titanium, aluminum alloy, or titanium alloy having a low thermal conductivity as a thermocouple element line, and to use a zigzag structure for the thermocouple element line,
The purpose is to increase the length of the thermocouple element line. Also, to reduce the external dimensions of the thermoelectric sensor module and increase the overall silicon wafer,
Using etching technology on the front side Si bulk,
Etching to create voids in the silicon substrate below the device. At the same time, it is necessary to create a resistor to be treated as a heater on the film for adjusting the device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thermoelectric sensor device and a method for manufacturing the same. More specifically, a method of increasing the length of a thermocouple element line, a method of reducing thermal conductivity by using a thermocouple element line having a zigzag structure or a meandering structure,
And a method of etching a silicon substrate by using front side silicon bulk wet etching. Furthermore, it relates not only to a method for increasing the total die productivity of a silicon wafer, but also to a method of manufacturing a resistor which is a heater on a film structure of a sensor for electrical calibration of a device.

[0002]

2. Description of the Related Art An infrared detector receives infrared rays generated from a target and measures the temperature of the target by counting the intensity of the infrared rays. Execute. Typical applications are, for example, in-situ monitoring of semiconductor process steps, infrared spectroscopy, detection of various gases and liquids in factory process environment, measurement of indoor temperature distribution for air conditioners. Further, there are medical thermography and a thermometer for an eardrum as an application example in the medical field, and a passive intrusion detector as an application example in the security field. The basic principle of operation is that infrared radiation emitted to the detector causes a temperature rise in the radiation absorption region, changing the physical properties of the device,
Then, the change in the physical property is converted into a change in the electrical output. Conventional sensors are known as pyroelectric sensors, bolometers, and thermopile.

[0003] Pyroelectric sensors are formed from ceramics or polymers and require careful handling during assembly and packaging. The manufacturing cost of a pyroelectric sensor is relatively high when compared to a thermoelectric sensor. The reason is that the thermoelectric sensor can be assembled by batch operation using a semiconductor mass production line. On the other hand, bolometer sensors require a bias to measure the change in resistance, and 1 / f noise is generated based on such a bias reading. A thermopile or thermoelectric sensor is a group of thermocouples connected in series. The thermocouple is composed of a pair of different conductors joined at two places. Thus, if the two locations, ie the two junctions, have different temperatures, an electromotive force will be generated based on the thermoelectric effect. Thermoelectric sensors require no additional bias and can be used over a wide range of ambient temperatures. Since the thermoelectric sensor can be assembled by a semiconductor process technology, it can be easily connected to a monolithic IC. Therefore, thermoelectric sensors have great market potential and cost competitiveness.

[0004] In terms of sensor function, if the device includes a thermoelectric detection element and an amplification line, the function and capability of the device will increase and the noise of the signal interface will decrease. This illustrates the advantage of developing compatible thermoelectric sensing elements using a standard CMOS process. That is, to provide a possibility to integrate the thermoelectric detection element and the signal processing line into the monolithic IC sensor. The post-process, i.e., the process in which the prior art thermoelectric sensor usually has an independent film structure formed by backside silicon wet etching, presents the following drawbacks.

FIG. 1 is a sectional view of an edge of a thermoelectric sensor. On a provided silicon substrate 1, a closing film 2, a plurality of first thermocouple element lines 3, an insulating layer 4, a plurality of second thermocouple element lines 5, and a radiation absorbing layer 6 are formed. The radiation absorbing layer 6 insulated from the insulating layer 4 'is connected to the first thermocouple element line 3 and the second thermocouple element line 5. The closure membrane 2, the first thermocouple element line 3, the insulating layer 4, and the second thermocouple element line 5 are symmetric at the edge of the thermoelectric sensor.

FIG. 2 shows the interconnection relationship for the thermoelectric sensor of FIG. 1st thermocouple element line 3
The opening of the second thermocouple element line 5,
The thermal contact H near the radiation absorbing layer 6 is connected for interconnection. Further, the cold junction C is far away from the radiation absorbing layer 6. The first cold junction C of the first thermocouple element line 3 is electrically connected to the first metal pad 7. Final cold junction C of second thermocouple element line 5
Are electrically connected to the second metal pad 7.

[0007] The thermal contact H is located above the closing film 2 and below the radiation absorbing layer 6, and its temperature rises based on the heat transferred from the radiation absorbing layer 6. When the radiation absorbing layer 6 is irradiated with infrared rays, the temperature rises. The cold junction C is located on the silicon substrate 1 and its temperature is equal to the ambient temperature. The reason is that the silicon substrate has high solid conductance, and heat from the cold junction is dissipated via the silicon substrate 1. In order to form the closing film 2, a silicon anisotropic wet etching process is applied, and the silicon substrate under the closing film 2 is removed. When an etching window is formed on the back side of the silicon substrate, the etching solution etches silicon from the back side. Since the crystal planes of silicon have different etching rates, a larger etching window area is needed to define the area of the closure film 2. That is, the overall size of the device is considerably larger than the area of the closure film 2 defined. The reason is that the etching window on the back side is
The size of the device is larger than the defined area of the closing film 2 and the size of the device is larger than the etching window on the back side. However, if an etching window is formed on the front side of the silicon substrate, the resulting cavity is similar to that shown in FIG. That is, the overall size of the device is approximately the same as the area of the closure membrane 2 that is defined. In such a case,
In order to support the structure of the radiation absorbing layer and a group of thermocouples,
Commonly used. Due to the different sizes of devices manufactured by front side or back side silicon anisotropic wet etching, the total die of thermoelectric sensors from wafers manufactured by front side wet etching is manufactured by back side wet etching Larger than the ones.

[0008] In general, a thermoelectric sensor is characterized by a volt /
The responsivity expressed in watts (Rv), Johnson noise (V
J), noise equivalent power (NEP), and ratio detection sensitivity (D
^* ) Is used and expressed. The corresponding equation follows the equation below.

[0009]

(Equation 1)

[0010] N is the number of thermocouples. α is the Seebeck coefficient [V / ° C.]. Gs, Gg and Gr are
The thermal conductivity of solids, gases and radiation, respectively.
k is Boltzmann's constant. T is absolute temperature (° K)
It is. R is the electric resistance. Δf is the bandwidth of the amplifier. A is the area of the radiation absorbing layer.

As described above, the ability of a thermoelectric sensor to measure the temperature of a target depends on the amount of output signal and the sensitivity of the measured target to changes in temperature. The responsivity Rv is an output voltage per input radiation power, and represents the output efficiency of the sensor. The noise equivalent power NEP is the input power when the output voltage of the thermopile is equal to the noise level. The ratio detection sensitivity D ^* is the reciprocal of NEP and is normalized by the radiation absorption area and the signal frequency.
D ^* is a sensor index indicating the minimum value of a detectable signal. The thermal conductivity of the structural material of a thermoelectric sensor is inversely proportional to the values of Rv and D ^* . Therefore, use thermocouple element lines with low thermal conductivity, or
By increasing the length of the thermocouple element line, Rv and D ^* can be improved.

As shown in FIG. 2, the first thermocouple element line 3 and the second thermocouple element line 5
It is a straight line. The thermocouple element line 5 is usually formed from aluminum having high thermal conductivity. However, in a thermoelectric sensor manufactured by a standard semiconductor CMOS process, the first thermocouple element line 3 is polycrystalline silicon and the second thermocouple element line 5 is aluminum. Therefore, the performance of the sensor is limited by the value of the thermal conductivity of the second thermocouple element line 5. The overall thermal conductivity is increased by increasing the length of the thermocouple element line
Although decreasing, the overall resistance of the thermopile increases. Since the resistance of the polycrystalline silicon is large, the resistance of the first thermocouple element line increases rapidly as its length increases. Thus, the overall sensor capabilities are simply:
It does not increase in proportion to the increase in the length of the thermocouple element line. The present invention discloses a zigzag structure of the second thermocouple element line. The zigzag structure reduces the thermal conductivity of the second thermocouple element line. The length of the first thermocouple element line is kept the same. In such an invention, the performance of the sensor can be improved without changing the size of the sensor or the size of the membrane.

A typical thermoelectric sensor measures the ambient temperature using an off-chip temperature sensor such as a thermistor, transistor or diode. The present invention applies the same material to either the first thermocouple element line or the second thermocouple element line to form an on-chip temperature sensitive resistor that can measure ambient temperature. Further, the resistance of the on-chip temperature sensing resistor is set to a value larger than 100 KΩ in order to prevent the temperature of the silicon substrate from rising due to heat power dissipation based on the bias reading of the on-chip temperature sensing resistor.

Further, in the non-contact temperature measurement, the target temperature can be calculated from the output voltage value of the thermoelectric sensor. The output voltage or responsivity decreases or worsens based on the aging of the thermocouple material caused by severe environmental changes and storage damage. This effect will lead to measurement deviations in the long run. Also,
Using expensive electrical circuits to calibrate these effects for merchandise adds to the cost of the manufacturer. The present invention provides a method of using a heater resistor formed in a region adjacent to a thermal junction to adjust the drift effect of a thermocouple material according to an electrical calibration method.

A conventional thermoelectric sensor is constituted by a 4-pin metal can package. The two pins are for a thermoelectric sensor, and the remaining two pins are for an off-chip ambient temperature sensor. The present invention provides a thermoelectric sensor composed of a 5-pin or 6-pin metal can package. That is, two pins for the thermoelectric sensor, two pins for the on-chip temperature sensing resistor, and two pins for the heater resistor. Note that the on-chip temperature sensing resistor and the heater resistor can share the ground. The two pins for the thermoelectric sensor are insulated from the metal can to reduce the effects of noise.

Important patents to define the prior art for thermoelectric sensors are set forth below.

(1) US Pat. No. 4,665,276,
Thomas Elbel, Jurgen Muller, Friedemann Volklein, "Thermoelectric sensors (The
(2) U.S. Pat. No. 5,100,479, Kensal. Kensall D. Wise, Khalil Najati, “Thermopile and Infrared Det with Semiconductor-Supported Rim (Thermopile, Infrared Det)
(3) U.S. Pat. No. 4,456,919, Katsuhiro Tomita, Tatsuo Shimizu, Masai Bando, "Thermocouple detector with temperature sensor for cold junction (Thermo)
pile Type Detector with Temperature Sensor for Col
d Junction). "

US Pat. No. 4,665,276 discloses a thermoelectric sensor having a film structure in which backside wet etching has been performed. This thermoelectric sensor has a thin-film thermopile and uses beryllium and antimony as thermoelectric materials.

US Pat. No. 5,100,479 discloses a thermoelectric sensor having a heavily doped silicon support rim. The rim supports a row of polycrystalline silicon and metal thermocouples. The rim also supports the cold junction and functions as a good thermal conductor for removing heat from the cold junction.

The thermoelectric sensor means according to the above two patents uses a backside wet etching closed film structure. However, the present invention uses an open film structure of front side wet etching.

US Pat. No. 4,456,919 discloses a thermoelectric sensor having an on-chip diode or transistor formed in the same manufacturing process as the thermoelectric sensor. Diodes or transistors are used to detect the ambient temperature and compensate for the temperature. The present invention uses a first thermocouple element line or a second thermocouple element line to form an on-chip temperature sensitive resistor or thermistor. The on-chip temperature sensing resistor can be formed in the same manufacturing process as the thermoelectric sensor.

In this regard, reference is made to the following article:

(1) G. R. Lahiji (GR Lahi
ji) and K. Dee. Wies (KD Wise),
"A batch-fabricated silicon thermopile infrared detector
etector) ”, IEE Transformer. Electon Devices Electron D
evices ED) -29, pp. 14-22, (1982)
Year (2) Earl. R. Lenggenhager,
Etch. H. Baltes, Jay. Pier (J.P.
eer) and M. Forster, CM
Thermoelectric infrared sensor based on OS technology (Thermoelectric i
nfrared sensors by CMOS technology ”, IEEE Ele
ctron Device Letters) 13, 454, (1992)
Year) (3) Tea. T. Akin, Zet. Organ (Z. Olgun), Oh. O. Akar, and etch. H. Kulah, "An integrated thermopile structure with high responsiveness using a standard CMOS process (An integra
ted thermopile structure with high responsivity us
ing any stndard CMOS process), Sensors and Actuators, A (A) 66, 218-224 (1998) (4) Etch. H. Baltes, "CMOS as Sensor Technology", Sensors and Actuato
rs), A (A) 37-38, pp. 51-56 (1
993 (5) eh-planar technique catalog
Of Thermo Sensors (HL-PLANAR Technik Catalog
of Thermosensors) (TS 1006)
0), HL-Planartechnik GmbH, HL-Planartechnik GmbH, Hauer
t) 13 44 227 Dortmund, Germany.

According to the document, Rahizi and Wies propose a closed film structure comprising a thermoelectric material of Au and polycrystalline silicon, wherein the closed film structure is formed using backside silicon anisotropic wet etching. To form Baltes et al. Provide thermoelectric materials of aluminum and polycrystalline silicon, using an open film structure by front side silicon anisotropic wet etching. The radiation absorbing layer is composed of SiO2 and SiN. Have provided a structure in which the open film structure was made by front-side silicon anisotropic wet etching, and the thermoelectric material uses a standard CMOS n-poly and p ⁺ active layer process. However, an electrochemical etch stop technique is needed to protect the p ⁺ active layer from wet etching during the process of removing the underlying silicon substrate.
This approach introduces process complexity and reduces total die productivity.

Furthermore, the method of reference (4) discloses that a heater resistor is disposed on the membrane and used to measure the thermal conductivity of the structure. However, in the present invention, a heater resistor is created in the area near the hot junction and used for electrical calibration of the thermoelectric material over time. Reference material (5) uses an on-chip Ni thermistor as a temperature sensor. On the other hand, the present invention uses the first
Alternatively, the same material as the second thermocouple element line is used. This on-chip temperature sensitive resistor and thermopile structure are made simultaneously.

When the normalized output is obtained for different incident radiation angles, we assume that the 100% normalized output is the radiation at an incident angle that deviates from the normal of the plane of the radiation scattering layer by about ± 10 °. Find out what happened at And 8
A 5% normalized output is observed for an incident angle of about 0 °. This fact indicates that the Si (11
1) Indicates that some of the radiant energy reflected from the surface is being absorbed by the radiation absorbing layer. The present invention is directed to avoiding radiation entering through the front side etching window, impinging on the Si (111) surface, being reflected and incident on the radiation absorbing layer.
A reflective mirror covering a front side etching window is disclosed. This reflective mirror plate is placed at the location of the front side etching window and is made at the same time as making the thermoelectric sensor structure. This reflective mirror plate has aluminum for reflection purposes.

[0027] The present invention provides an economical method. The advantage of a polycrystalline silicon / metal thermocouple is that it is simple because it is made by a standard CMOS process. How to increase total die, productivity, and upgrade sensor capability is the subject of the present invention.

The present invention has been made in order to improve the disadvantages of the prior art described above, and an object of the present invention is to provide a thermoelectric device capable of improving sensor performance without increasing size and cost. It is an object of the present invention to provide a type sensor device and a method for manufacturing the same.

[0029]

The salient features of the present invention are as follows.

(1) A material having a lower thermal conductivity is selected as a thermocouple element line, and a meandering or zigzag structure of the thermocouple element line is formed by using a photolithographic method. This can increase the length of the thermocouple element line, reduce thermal conductivity, and increase the performance of the thermoelectric sensor without increasing sensitivity and die size.

(2) Titanium alloy having a lower thermal conductivity is selected as the material of the thermocouple element line to reduce the solid thermal conductivity.

(3) Create a resistor to be treated as a heater on the area in the vicinity of the thermal contact and use it for electrical calibration against aging of thermoelectrics and other constituent materials and environmental influences; In a long-term operation, the accuracy of non-contact temperature measurement is increased.

(4) Using a titanium thin film and its related alloy, a radiation absorbing layer is formed by process technology in the semiconductor industry.

(5) An etching hole is formed on an independent or floating film of the radiation absorbing layer and the insulating layer to shorten the etching time and increase the productivity.

(6) The silicon substrate located under the open film structure of the thermoelectric sensor is removed by using the front side silicon anisotropic wet etching technique. The hot junction is then floated or thermally insulated from the silicon substrate to increase signal output. The method provides a higher total die, a simpler package, a simpler process over the prior art, and relatively reduces etch time and possible damage to the sensing element.

(7) The same material as the first or second thermocouple element line is selected as the on-chip temperature sensing resistor, and the resistance value of this resistor is greater than 100 KΩ.

(8) Form a reflective mirror to cover the front side etching window to avoid the effects of radiation reflected from the underlying Si (111) surface of the underlying v-shaped globe. This reflecting mirror plate is made at the same time as making the structure of the thermoelectric sensor. This reflective mirror plate has an aluminum film for reflection purposes.

(9) Select a 5-pin or 6-pin metal can.

To achieve the above-mentioned object, the present invention provides:
A method for manufacturing a thermoelectric sensor device having the following steps is provided.

First, a step of supplying a silicon substrate. And forming a first insulating layer on the surface of the silicon substrate. Forming a thermocouple element material layer on a surface of the first insulating layer; This material is, for example, polycrystalline silicon, amorphous silicon or metal. Forming a first thermocouple element line by performing masking definition and etching on the thermocouple element material layer. Forming a second insulating layer on the surface of the first thermocouple element line and the first insulating layer. Patterning and etching a portion of the second insulating layer to form a plurality of contact windows or contact paths. Forming a metal layer on a surface of the second insulating layer. Patterning and etching the portion of the metal layer to form a second thermocouple element line, wherein the second thermocouple element line is connected to the first thermocouple by a plurality of hot contacts and cold contacts by the contact window described above; The stage of joining to the element line. Forming a third insulating layer on the surface of the second thermocouple element line and the second insulating layer. Patterning and etching the third insulating layer and the second insulating layer, thereby exposing the last second thermocouple element line. Then, in the next step, the first thermocouple consisting of the first thermocouple element line is electrically connected to the first metal pad through the connection with the second thermocouple element line. Are linked together. Forming a second metal layer above the third insulating layer; Patterning and etching the second metal layer to form a first metal pad and a second metal pad. Then, an electrical connection between the group of thermocouples and the metal pad is formed. Forming a fourth insulating layer above the third insulating layer and the second metal layer. Forming a third metal layer above the fourth insulating layer, and defining a radiation absorbing layer that absorbs infrared rays during operation by etching or lift-off, that is, reverse masking. Forming a fifth insulating layer on the surfaces of the fourth insulating layer and the radiation absorbing layer. The portions of the fourth insulating layer and the fifth insulating layer are etched, and the first metal pad and the second
Forming a bonding window on the metal pad; Patterning is performed to form the fifth insulating layer, the fourth insulating layer, the third insulating layer, the second insulating layer, and the first insulating layer.
Forming a front side etching window by performing etching through an insulating layer, and exposing a surface of the silicon substrate. Etching the silicon substrate through the front side etching window using a silicon anisotropic wet etching technique to undercut or void the silicon substrate located below the thermocouple film region.

Reference is made to the method described above for making an electrical connection between a group of thermocouples and a metal pad.

Other methods of making an electrical connection include: patterning and etching a portion of the third and second insulating layers, thereby providing a final second thermocouple element. A part of the line and a part of the first thermocouple element line are exposed. A second metal layer is deposited on the third insulating layer. Patterning and etching a portion of the second metal layer, then forming connection lines between the first and second thermocouple elements of each pair, and similarly forming the first and second metal pads. Form. Then, an electrical connection between the group of thermocouples and the metal pad is formed.
A fourth insulating layer is deposited on the third insulating layer and the second metal layer.
Here, the same technique for creating the radiation absorbing layer and the front side etching window and wet etching are used to form the final structure of the thermoelectric sensor.

According to the above process, the signal output of the thermoelectric sensor device is measured between a first metal pad and a second metal pad.

The structure of the thermoelectric sensor comprises the following: a silicon substrate and a first insulating layer formed on the surface of the silicon substrate. Numerous first thermocouple element lines formed on the surface of the first insulating layer. Here, each first thermocouple element line has a hot junction and a cold junction, and the first cold junction is electrically connected to the first metal pad. A second insulating layer formed on a surface of the first thermocouple element line; Numerous second thermocouple element lines formed on the surface of the second insulating layer. Here, the second thermocouple element lines are defined and patterned to have a meandering or zigzag structure, each second thermocouple element line having a hot junction and a cold junction, and The last cold junction is electrically connected to the second metal pad and connected to the hot junction of the first thermocouple element line. A third insulating layer formed on the surface of the second insulating layer and the second thermocouple element line. A second metal layer formed on the first metal pad and the second metal pad. A fourth insulating layer formed on surfaces of the third insulating layer, the first metal pad, and the second metal pad; A radiation absorbing layer formed on a part of the surface of the fourth insulating layer that absorbs infrared rays.
The fifth insulating layer and the fifth insulating layer formed on the surface of the radiation absorbing layer.
Insulating layer. A bonding window formed in the first metal pad and the second metal pad by etching a portion of the fourth and fifth insulating layers; A front side etching window formed in the silicon substrate by etching through the fifth insulating layer, the fourth insulating layer, the third insulating layer, the second insulating and the first insulating layers. Silicon substrate under thermocouple film area that can be wet etched through the front side etching window. Same material as the first or second thermocouple element line, assembled in the area near the hot junction and used for electrical calibration of thermoelectrics and other components over time and environmental effects Use heater registers. 10 manufactured at the same time that a thermoelectric sensor is manufactured by semiconductor process technology
An on-chip temperature sensing resistor using the same material as the first or second thermocouple element line having a resistance greater than 0 KΩ. A reflective mirror that covers the front side etching window to avoid the effects of radiation reflected from the Si (111) surface of the underlying v-shaped globe that is made at the same time as the fabrication of the thermoelectric sensor configuration. Here, the reflection mirror plate has an aluminum film for the purpose of reflection.

[0045]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 3 is a cross-sectional view of the thermoelectric sensor according to the present invention. Here, the thermoelectric sensor includes a silicon substrate 31, a large number of first thermocouple element lines 35, and a large number of second thermocouple elements. Line 36, radiation absorbing layer 3
9, front side etching window 34, lower v-shaped globe cavity 32 formed by anisotropic wet etching, multiple contact windows 4 for thermal contacts
3, first insulating layer 21, second insulating layer 22, third insulating layer 2
Third, fourth and fifth insulating layers 24 and 25 are provided.

FIG. 4 is a diagram in which two thermocouple element lines according to the thermoelectric sensor of FIG. 3 are connected. 3 and 4, the second thermocouple element line 36 is
The thermal contact H via the contact window 43 of the third insulating layer 23
Is in contact with the first thermocouple element line 35 having The last line of the second thermocouple element line 36 is electrically connected to the second metal pad 38. The start line of the first thermocouple element line 35 is electrically connected to the first metal pad 37. The first metal pad 37 and the second metal pad 38 function as output electrodes of the thermoelectric sensor.

FIGS. 7 to 16 are sectional views showing steps of manufacturing a thermoelectric sensor according to the present invention.

First, a silicon substrate 31 is provided, and a first insulating layer 21 is deposited on the surface of the silicon substrate, as shown in FIG. 8, and a part of the silicon substrate 31 below the thermocouple is changed in the next step. It is removed by isotropic wet etching. A first thermocouple element layer made of metal, polycrystalline silicon or amorphous silicon is deposited on the surface of the first insulating layer. In FIG. 9, a part of the first thermocouple element layer is patterned by photolithography and dry etching so as to form the first thermocouple element line 35 on a part of the surface of the first insulating layer 21. . The second insulating layer 22 is placed on the surface of the first thermocouple element line 35 and the first insulating layer 21 to perform planarization and to form a plurality of contact windows 43 for thermal contacts. Partly etched. As shown in FIG. 10, the first thermocouple element line 35 is exposed at the bottom of the contact window 43.

A first metal layer is deposited on the surface of the second insulating layer 22, and the first metal layer fills the contact window 43. After this deposition process, the second insulating layer 22
The first metal layer is patterned to form thermocouple element lines. First thermocouple element line 35
The electrical connection between and the second thermocouple element line 36 is made via a contact window 43, as shown in FIG. The second thermocouple element line 36 contacts the first thermocouple element line 35 at the hot contact H of the contact window 43 and at a cold contact C (not shown) via a contact window (not shown).

After forming the second thermocouple element line 36, the third insulating layer 23 is deposited on the second thermocouple element line 36 and the surface of the second insulating layer 22. This third
The insulating layer 23 and the second insulating layer 22 are etched to form the first
The start line of the thermocouple element line 35 and a part of the last line of the second thermocouple element line 36 are exposed to the cold junction region. The exposed portion of the cold junction at the start line of the first thermocouple element line 35 and the last line of the second thermocouple element line 36 becomes a contact window in the next step of bonding metal pads to form an electrical connection. Then, a second metal layer is deposited on the contact window at the cold junction in the start line of the first thermocouple element line 35 and the last line of the second thermocouple element line 36 and on the third insulating layer 23. The second metal layer is
Filled with contact window. After the deposition process, the second metal layer is connected to the metal pads 37, 38, the starting line of the first thermocouple element line 35 and the electrical connection line of the metal pad 37, and the last line of the second thermocouple element line 36. Metal pad 38 (not shown in FIGS. 11 to 12)
And patterned to form electrical connection lines between them. Thereafter, the last line of the second thermocouple element line 36 is electrically connected to the second metal pad 38. As shown in FIG. 4, the first thermocouple element line 3
The start line 5 is electrically connected to the first metal pad 37.

As shown in FIG. 12, a fourth insulating layer 24 is deposited on the third insulating layer 23 and the second metal layer. Then, a third metal layer is deposited on the fourth insulating layer 24, and a radiation absorbing layer 39 for absorbing incident infrared rays is formed by etching or lift-off as shown in FIG. The material of the radiation absorbing layer is selected from the group consisting of titanium, titanium nitrogen compounds, titanium alloys and other alloys.

After the formation of the radiation absorbing layer 39, a fifth insulating layer 25 is deposited on the surfaces of the fourth insulating layer 24 and the radiation absorbing layer 39. Portions of the fourth insulating layer 24 and the fifth insulating layer 25 are etched to open windows (not shown) on the first metal pad 37 and the second metal pad 38. This exposes the first metal pad 37 and the second metal pad 38, which serve as output electrodes of the thermoelectric sensor. Following the opening of the fourth and fifth insulating layers 24 and 25, the third insulating layer 23, the second insulating layer 22 and the first insulating layer 21 in the front side wet etching window 34 are continuously etched. Is removed. Then, as shown in FIG. 15, the bear surface or the substrate surface of the silicon substrate 31 is exposed. By the method of silicon anisotropic wet etching through the front side wet etching window 34,
The silicon substrate 31 is etched. As a result, FIG.
As shown in FIG. 6, the silicon substrate 31 under the thermocouple film area is undercut or voided.

The above steps of the process are illustrated,
The features or mechanisms of this thermoelectric sensor structure are as follows.

The thermocouple element line will be described.

In the embodiment of the present invention, the second thermocouple element line 36 is formed from titanium or its alloy. The thermal conductivity of titanium (17 W / K) is AlSi
In addition to being significantly smaller than the thermal conductivity of Cu alloys (〜238 W / K), titanium is a good conductor, resulting in improved responsivity (Rv) and specific detection sensitivity (D ^* ). This is because the total resistance of the thermocouple sensor is substantially maintained at the same level, while the total thermal conductivity of the thermocouple sensor is lower. The second thermocouple element line 36 is formed in the contact window 43. As a result, as shown in FIG. 4, the second thermocouple element line 36 serves as a connection line between the first line of the first thermocouple element line 35 and the second line, and the first thermocouple element line 35 , And serves as a connection line to the third line of the second line.

In another embodiment of the present invention, the second metal layer described above replaces the second thermocouple element line 36 as the connection line 40, as shown in the interconnected state in FIG. In this manner, a second metal layer is deposited on the third insulating layer 23 and the contact window on the cold junction. The second metal layer fills the contact window. After the deposition process, connection line 40,
The metal pad 37, the metal pad 38, the electrical connection line between the first line of the first thermocouple element line 35 and the metal pad 37, and the last line of the second thermocouple element line 36 and the metal pad 38 The second metal layer is patterned to form electrical connection lines between them.

In another embodiment of the present invention, the material of the second thermoelectric element layer is used for the first metal pad 37 and the second metal pad 38. In this way, it is possible to avoid forming the third insulating layer 23 and the second metal layer.

According to the mechanism described above, improving the characteristics of the thermocouple sensor is to increase the length of the thermocouple element line, thereby reducing the thermal conductivity by adding the thermocouple element line to the thermocouple element line. A zigzag structure or meandering structure is adopted. Like the structure shown in FIG.
The present invention discloses a structure in which the second thermocouple element line is zigzag to reduce the thermal conductivity of the second thermocouple element line while maintaining the length of the first thermocouple element line the same. I have. In such an invention, the sensor performance can be improved without changing the size of the sensor or the size of the film. The zigzag structure includes a number of geometric configurations, such as a single zigzag layer structure, a multi-layer zigzag structure, a meandering shape structure, or other structures desired by a user. Further, the first thermocouple element line 3
If the material No. 5 has a high thermal conductivity and a low electrical resistivity, the first thermocouple element line 35 can also have a zigzag structure.

Further, the principle of the above-mentioned thermoelectric sensor is that the radiation heat absorbed by the radiation absorbing layer 39 is converted into a temperature difference between the hot junction and the cold junction, and then the output voltage of the thermoelectric sensor is converted by this temperature difference. It is to get. The value of this voltage output is used to calculate the temperature of the object based on Stefan-Boltzmann's law. However,
This output voltage can be reduced or degraded due to aging of the thermocouple material caused by severe environmental changes and storage damage. This voltage can also change due to drift in the characteristics of the readout power distribution circuit. This effect will reduce measurement accuracy in the long run. According to the present invention, there is provided a resistor which is a heater and is formed in a region adjacent to the thermal contact. This heater register
Used to adjust for drift effects based on the following electrical calibration measurements.

The principle of the electrical calibration measurement is outlined as follows. The thermoelectric sensor structure is configured to include a heater resistor on an adjacent area of the thermal junction. A pulse voltage or an AC voltage is applied to the heater register in a state where infrared radiation from the object is shielded, and the output voltage from the thermoelectric sensor at that time is accurately measured. The output voltage of the thermoelectric sensor is only related to the heat input to the heater register from the applied bias. In this way, the output voltage caused by the increasing temperature difference of the thermoelectric sensor when receiving or receiving radiation or radiant energy from the object can be simulated. In other words, the power and the rising temperature of the heater are proportional to the power and the rising temperature of the incident radiant heat. For practical applications, before measuring the temperature of an object such as the human body, the radiation to the thermoelectric sensor is shielded by a shutter in advance, and then the power Wh is supplied to the heater and the output voltage Vh Is measured accurately. After removing the shutter, power W
t is received from the object and radiated or radiated onto the radiation absorbing layer. And the output voltage V of the thermoelectric sensor
t can be accurately measured. The power Wt can be calculated according to the input or default values of Wh and the measured values of Vh and Vt. The calculation formula is as follows.

[0062]

(Equation 2)

Here, k is a constant. This constant may be adjustable when performing precision measurements with a known black body temperature and a known input bias to the heater. The output result of the thermoelectric sensor affects Vh and Vt at the same slope or rate according to the environment, time or drift effect of the readout power distribution circuit. However, V
Since h / Vt is kept the same, the radiation or radiant energy can be accurately measured, and the temperature of the object can be accurately measured.

According to another embodiment of the present invention, the larger apertures in the front side wet etch window 34 provide infrared radiation reflected from the bottom 48 of the anisotropic undercut cavity or the v-shaped glove sidewall 49. Will invite you. Further, the infrared rays are secondarily incident on the back side of the radiation absorbing layer having the thermoelectric structure. To avoid these effects,
As shown in FIG. 23, in the present invention, a reflection mirror 50 including a first metal and / or a second metal to reflect incident infrared rays is proposed. In this way,
The front side wet etch window is defined as a narrow trench.

The package preceding the thermoelectric sensor is a four-pin metal can or metal with two pins serving as output electrodes for the thermoelectric sensor and two pins serving as electrodes for the off-chip room temperature sensor. It has a jacket. According to another embodiment of the present invention, a metal jacket package for a thermoelectric sensor having 5 pins or 6 pins is proposed. In a 6-pin metal jacket, the temperature and heater resistors can share a common ground electrode, while 2 pins are for thermoelectric sensors, 2 pins are for on-chip temperature registers, and 2 pins are Used for heater register. The two pins for the thermoelectric sensor are insulated from the metal jacket to reduce the effects of noise.

The features of the present invention are as follows.

(1) Structure of Second Thermocouple Element Layer The second thermocouple element line has a zigzag or meandering structure in order to reduce the thermal conductivity. It is formed from a material with a low rate. This even allows the use of the AlSiCu material of the standard CMOS process and reduces the thermal conductivity of the solid by 70% to 8% compared to a conventional linear structure.
It can be further reduced to 0%. Therefore,
Sensor performance can be improved without increasing the size and cost of the thermoelectric sensor.

(2) Post-Etching Process The present invention provides a front side Si anisotropic wet etching method instead of the conventional back side Si anisotropic wet etching method. Applying front side wet etching to release the thermocouple and radiation absorbing structure can reduce the device size of the thermoelectric sensor. This increases the total die of the wafer and reduces the wet etch time. As shown in FIGS. 17, 18 and 19, the structure can be a cantilever beam or a cantilever beam, a two-arm bridge and a four-arm bridge.

(3) Radiation Absorption In a preferred embodiment of the present invention, titanium or a titanium alloy is used for the radiation absorbing layer 39. Optimal absorption is obtained by controlling the appropriate thickness at about 34 μg / cm 2. It is helpful that titanium be an available material in standard CMOS processes.

(4) Etching Hole When the film area of the radiation absorbing layer is very large, it is easy to obtain a small hill structure on the bottom of the v-shaped glove after the front side wet etching treatment. As shown in FIG. 20, an etching hole 43 ′ such as an etching window 34 can be etched on the center of the radiation absorbing film 44. The function of the etching hole 43 'is not only to avoid the formation of a silicon hill on the bottom but also to shorten the etching time.

(5) Structure for Performing Electrical Calibration Measurement As shown in FIG.
A register 45 is provided above. This register 45
The third metal pad 46 and the fourth metal pad 47 are electrically coupled. The material of the resistor 45 is made of the material of the first thermocouple element layer or the second thermocouple element layer. Input power between the third metal pad 46 and the fourth metal pad 47 is provided for electrical calibration measurements. The radiated power value and the temperature rise of the thermoelectric sensor are simulated and proportional to the input heat power to the heater resistor and the temperature rise caused by the thermoelectric sensor.

(6) Process The present invention is provided with a compatible CMOS process.
A combined process of iCMOS and thermoelectric sensors has been achieved to reduce the effects of noise in various circuits. It is useful to simplify the process.

(7) Temperature Sensitivity Register for Room Temperature Measurement In general thermoelectric sensors, the room temperature is measured by using an off-chip temperature sensor. In the present invention, the same material as the first thermocouple element line or the second thermocouple element line is applied to form an on-chip temperature sensitive resistor that can be used to measure room temperature. Further, in order to prevent the temperature of the silicon substrate from rising due to the thermal power dissipated from the leading bias of the on-chip temperature sensing resistor, the resistor of the on-chip resistor is set to 100 KΩ or more.

(8) Reflection Mirror Structure In the present invention, in order to prevent the secondary incident infrared rays from being radiated or radiated on the back side of the radiation absorbing layer having the thermoelectric structure, the first metal is used. And / or a reflecting mirror having a second metal is used to reflect incident infrared radiation.

(9) The package of the thermoelectric sensor has five pins or six pins of a metal jacket.

As understood by those skilled in the art,
The above-described preferred embodiments of the present invention are illustrative rather than limiting of the present invention. Various improvements or similar devices falling within the spirit and scope of the claims are included in the present invention, and the claims are intended to cover all such improvements or similar configurations. It should be consistent with the broadest interpretation.

[0077]

According to the present invention, the sensor performance can be improved without increasing the size and cost of the thermoelectric sensor device.

[Brief description of the drawings]

FIG. 1 is a sectional view of an edge of a conventional thermoelectric sensor.

FIG. 2 is a diagram in which the thermoelectric sensors of FIG. 1 are interconnected.

FIG. 3 is a sectional view of a thermoelectric sensor according to the present invention.

FIG. 4 is a diagram in which two layers of thermoelectric element lines related to the thermoelectric sensor of FIG. 3 are connected.

FIG. 5 is a diagram in which three layers of thermoelectric element lines related to the thermoelectric sensor of FIG. 3 are connected.

FIG. 6 is a diagram in which a second thermoelectric element line has a meandering or zigzag structure on a linear first thermoelectric element line according to the thermoelectric sensor of FIG. 3;

FIG. 7 is a cross-sectional view showing processing steps for manufacturing a thermoelectric sensor according to the present invention.

FIG. 8 is a cross-sectional view showing the same processing step.

FIG. 9 is a cross-sectional view showing the same processing step.

FIG. 10 is a cross-sectional view showing the same processing step.

FIG. 11 is a cross-sectional view showing the same processing step.

FIG. 12 is a cross-sectional view showing the same processing step.

FIG. 13 is a cross-sectional view showing the same processing step.

FIG. 14 is a cross-sectional view showing the same processing step.

FIG. 15 is a cross-sectional view showing the same processing step.

FIG. 16 is a cross-sectional view showing the same processing step.

FIG. 17 is a diagram showing a configuration of a cantilever-shaped thermoelectric sensor according to an embodiment of the present invention.

FIG. 18 is a diagram showing a configuration of a four-arm bridge thermoelectric sensor according to an embodiment of the present invention.

FIG. 19 is a diagram showing a configuration of a two-arm bridge thermoelectric sensor according to an embodiment of the present invention.

FIG. 20 is a diagram showing a configuration of a thermoelectric sensor having a wet etching hole on a radiation absorbing layer according to an embodiment of the present invention.

FIG. 21 is a schematic diagram of manufacturing a heater resistor in a region near a thermal junction of a thermocouple film used for electrical calibration according to another embodiment of the present invention.

FIG. 22 is a schematic cross-sectional view of a reflected light path of an incident infrared ray which is affected by radiation reflected from the Si (111) surface of a v-shaped globe located below according to an embodiment of the present invention. .

FIG. 23 illustrates a reflective mirror covering the front side etching window to avoid the effects of radiation reflected from the Si (111) surface of the underlying v-shaped globe according to the preferred embodiment of the present invention. FIG. 4 is a schematic sectional view used.

FIG. 24 is a plan view of a reflection mirror according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 ... 1st insulating layer, 22 ... 2nd insulating layer, 23 ... 3rd insulating layer, 24 ... 4th insulating layer, 25 ... 5th insulating layer, 31 ... Silicon substrate, 32 ... V-shaped glove cavity, 35 ... 1 thermocouple element line, 36 ... second thermocouple element line, 37 ... first metal pad, 38 ... second metal pad, 39 ... radiation absorbing layer, 43 ... contact window, 44 ... radiation absorbing film, 45 ... register, 46: third metal pad, 47: fourth metal pad, 50: reflection mirror, C: cold junction, H: hot junction.

Claims (22)

[Claims] A step of supplying a silicon substrate; a step of forming a first insulating layer on a surface of the silicon substrate; a step of forming a material layer on a surface of the first insulating layer; Forming a first thermocouple element line by patterning and etching, forming a second insulating layer on the surface of the first thermocouple element line and the first insulating layer, and forming the second insulating layer. Forming a plurality of contact windows by patterning a portion of the first metal layer; forming a first metal layer on the surface of the second insulating layer; patterning and etching the portion of the first metal layer to form a plurality of contact windows. Forming a second thermocouple element line;
A thermocouple element line penetrates the contact window to provide a plurality of hot and cold contacts for the first contact.
Bonding to a thermocouple element line, forming a third insulating layer on the surface of the second thermocouple element line and the second insulating layer, and forming a third insulating layer and a portion of the second insulating layer on the surface of the second insulating layer. Etching to expose a last portion of the second thermocouple element line; forming a second metal layer above the third insulating layer; and etching the second metal layer. Forming a first metal pad and a second metal pad, and a last part of the second thermocouple element line is electrically connected to the second metal pad, and A step of electrically connecting a start portion to the first metal pad via the second thermocouple element line; and a fourth insulating layer above the third insulating layer and the second metal layer. Forming a third metal layer above the fourth insulating layer, and defining a radiation absorbing layer that absorbs infrared rays by etching or lift-off, that is, a reverse masking method; Forming a fifth insulating layer on the surface of the radiation absorbing layer; etching the fourth insulating layer and the portion of the fifth insulating layer to form a front side wet etching window to form the first metal pad and Exposing the second metal pad, forming an etching window and an etching hole, forming the fifth insulating layer, the fourth insulating layer, the third insulating layer, the second insulating layer, and the first insulating layer; Through
A step of exposing the surface of the silicon substrate, and a step of etching the silicon substrate through the etching hole by a front-side silicon anisotropic wet etching technique to form a void in the silicon substrate. Manufacturing method of sensor device. 2. The method according to claim 1, wherein the material of the material layer includes a metal and polycrystalline silicon. 3. The method of claim 1, wherein the radiation absorbing layer material is selected from the group consisting of titanium, titanium nitride, titanium alloy, and other alloys. 4. The method of claim 1, wherein the material of the first thermocouple element line and the second thermocouple element line comprises a semiconductor material. 5. The method of claim 1, wherein said first thermocouple element line is connected to said second thermocouple element line at said third metal layer. 6. The method of claim 1, wherein the material of the second thermocouple element line is selected from the group consisting of titanium, aluminum, titanium nitride, titanium alloy, aluminum alloy, and the like. 7. The zigzag structure of the second thermocouple element line has a zigzag structure, a zigzag structure of one layer, a zigzag structure of multiple layers, a meandering structure, or a structure required by a user. When the first thermocouple element line has a high thermal conductivity and a low low efficiency, the line shape of the first thermocouple element line has a zigzag structure or a solid thermal conductance. 2. The method of claim 1, wherein the other structure reduces. 8. The method of claim 1, wherein said first metal pad and said second metal pad are made of a first metal layer, omitting formation of said second metal layer. 9. The method of claim 1, wherein an etching hole is formed on a center of the radiation absorbing layer while the etching window is being formed. 10. A thermoelectric sensor device of a type utilizing a first metal pad and a second metal pad at an output end, wherein: a silicon substrate; a first insulating layer formed on a surface of the silicon substrate; A plurality of first thermocouple element lines formed on a surface of the first insulating layer, each of the first thermocouple element lines having a hot junction and a cold junction, and a cold junction at a start of the first thermocouple element line. A plurality of first thermocouple element lines electrically connected to the first metal pad; a second insulating layer formed on a surface of the first thermocouple element line; A plurality of second thermocouple element lines formed from a first metal layer on the surface, each second thermocouple element line having a hot junction and a cold junction, and a second thermocouple element line. A plurality of second thermocouple element lines formed by electrically connecting a contact to a thermal contact of the first thermocouple element line and a cold junction at a last portion of the second thermocouple element line to the second metal pad. A third insulating layer formed on the surface of the second insulating layer and the second thermocouple element line; a second metal layer forming the first metal pad and the second metal pad; An insulating layer, a fourth insulating layer formed on a surface of the first metal pad and the second metal pad, a radiation absorbing layer formed on a surface portion of the fourth insulating layer and absorbing infrared rays, A fifth insulating layer formed on the surface of the insulating layer and the radiation absorbing layer; and a fifth insulating layer formed above the first metal pad and the second metal pad and passing through the fifth insulating layer and the fourth insulating layer. hand, A bonding pad window on which the first metal pad and the second metal pad are exposed; and a fifth insulating layer, the fourth insulating layer formed on a surface of the fifth insulating layer and extending downward. A thermoelectric sensor device comprising: an etching window passing through the third insulating layer, the second insulating layer, and the first insulating layer, and communicating the silicon substrate so as to come into contact with the outside. 11. The thermoelectric sensor device according to claim 10, wherein said silicon substrate has a CMOS circuit. 12. The thermoelectric sensor device according to claim 10, wherein the silicon substrate has a BiCMOS circuit. 13. The thermoelectric sensor device according to claim 10, which has a cantilever shape. 14. The thermoelectric sensor device according to claim 10, exhibiting a bridge shape having four arms. 15. The first thermocouple element line,
The thermoelectric sensor device according to claim 10, wherein the thermoelectric sensor device has a linear or zigzag structure. 16. The second thermocouple element line,
The thermoelectric sensor device according to claim 10, wherein the thermoelectric sensor device has a zigzag structure. 17. A thermo-sensitive resistor having a resistance value greater than 100 KΩ is applied to the first thermocouple element line or the second thermocouple element line.
4. The thermoelectric sensor device according to 1. 18. On the radiation absorbing layer near the thermal contact,
The thermoelectric sensor device according to claim 10, further comprising a heater register for performing an electrical calibration measurement. 19. The thermoelectric sensor device according to claim 18, wherein a material of the resistor is made of a material of the first thermocouple element line or the second thermocouple element line. 20. The thermoelectric sensor device according to claim 10, wherein the package includes a 5-pin metal can. 21. The thermoelectric sensor device according to claim 10, wherein the package comprises a 6-pin metal can. 22. The etching window defined as a narrow trench, comprising a reflective mirror used to reflect incident infrared radiation and to prevent second incident infrared radiation from being emitted to the backside of the radiation absorbing layer. 2. The reflection mirror includes the first and / or second metal layers.
0. The thermoelectric sensor device according to 0.