JP3388207B2 - Thermoelectric sensor device and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD 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 the thermocouple element line, a method of reducing the thermal conductivity by using a thermocouple element line having a zigzag structure or a meandering structure,
And a method for etching a silicon substrate by using front side silicon bulk wet etching. Further, it relates not only to a method for increasing the productivity of the total die of a silicon wafer, but also to a method for producing a resistor, which is a heater, on the sensor film structure for electrical calibration of the 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, so-called non-contact temperature measurement. Run. Typical applications are, for example, in-situ monitoring of semiconductor process steps, infrared spectroscopy, detection of various gases and liquids in factory process environments, measurement of indoor temperature distribution for air conditioners. Further, there are medical thermography and tympanic thermometer 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, changes in physical properties are converted into changes in electrical output. Conventional sensors are known as pyroelectric sensors, bolometers and thermopile.

Pyroelectric sensors are made of ceramics or polymers and require careful handling during assembly and packaging. The manufacturing cost of the pyroelectric sensor is relatively high as compared with the thermoelectric sensor. The reason is that thermoelectric sensors can be assembled in batch operations using semiconductor mass production lines. Bolometer sensors, on the other hand, require a bias to measure the change in resistance, and 1 / f noise is generated based on such bias readings. 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 locations. Therefore, when two points, or two junctions, have different temperatures, electromotive force is generated based on the thermoelectric effect. Thermoelectric sensors require no additional bias and can be used in a wide range of ambient temperatures. Since the thermoelectric sensor can be assembled by the semiconductor process technology, it can be easily connected to the monolithic IC. Therefore, thermoelectric sensors have great market potential and cost competitiveness.

In terms of sensor functionality, if the device includes thermoelectric sensing elements and amplification lines, the functionality and capabilities of the device are increased and the signal interface noise is reduced. This illustrates the advantage of developing a compatible thermoelectric sensing element using a standard CMOS process. That is, to provide the possibility of integrating the thermoelectric detection element and the signal processing line into a monolithic IC sensor. Subsequent steps, that is, prior art thermoelectric sensors, which typically have a separate film structure formed by backside silicon wet etching, exhibit the following drawbacks.

FIG. 1 is a sectional view of an edge portion of a thermoelectric sensor. A closed 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 on the provided silicon substrate 1. 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 symmetrical at the edge of the thermoelectric sensor.

FIG. 2 shows the interconnection relationships for the thermoelectric sensor of FIG. First thermocouple element line 3
The opening of the second thermocouple element line 5 and the end,
The thermal contact H near the radiation absorbing layer 6 is connected for interconnection. The cold junction C is far away from the radiation absorption 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 the second thermocouple element line 5
Are electrically connected to the second metal pad 7.

The heat contact H is located above the closing film 2 and below the radiation absorbing layer 6, and its temperature rises due to the heat transferred from the radiation absorbing layer 6. The temperature of the radiation absorbing layer 6 rises when it is irradiated with infrared rays. The cold junction C is located on the silicon substrate 1 and its temperature is the same as the ambient temperature. The reason is that the silicon substrate has high solid conductance, and the heat from the cold junction is dissipated through the silicon substrate 1. To form the closure film 2, a silicon anisotropic wet etching process is applied and the silicon substrate under the closure 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 defined area of the closure membrane 2. The reason is that the etching window on the back side is
This is because the area 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 will be similar to that shown in FIG. That is, the overall size of the device is approximately the same as the defined area of the closure membrane 2. In such cases,
The cantilever structure or the four-arm bridge structure supports the structure of the radiation absorption layer and the group of thermocouples,
Commonly used. Due to the different size of the device manufactured by front side or back side silicon anisotropic wet etching, the total die of thermoelectric sensor from the wafer manufactured by front side wet etching is manufactured by back side wet etching. Greater than anything.

Generally, the characteristic of the thermoelectric sensor is that the bolt /
Response in watts (Rv), Johnson noise (V
J), noise equivalent power (NEP), and specific detection sensitivity (D
^* ) Is used and expressed. The corresponding formula follows the formula below.

[0009]

[Equation 1]

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 a Boltzmann constant. T is the absolute temperature (° K)
Is. R is an electric resistance. Δf is the bandwidth of the amplifier. A is the area of the radiation absorption layer.

As explained above, the ability of a thermoelectric sensor to measure the temperature of a target depends on the amount of output signal and its sensitivity to changes in the temperature of the measured target. 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 thermoelectric sensor's structural material is inversely proportional to the values of Rv and D ^* . Therefore, use a thermocouple element line with low thermal conductivity, or
Rv and D ^* can be improved by increasing the length of the thermocouple element lines.

As shown in FIG. 2, the first thermocouple element line 3 and the second thermocouple element line 5 are
It is a straight line. The thermocouple element line 5 is usually made of aluminum having a 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 capacity 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 reduced, the overall resistance of the thermopile is increased. Since the resistance of polycrystalline silicon is high, the resistance of the first thermocouple element line increases sharply as its length increases. Therefore, the overall sensor capability is 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 for the second thermocouple element line. The zigzag structure reduces the thermal conductivity of the second thermocouple element line. The lengths of the first thermocouple element lines are kept the same. In such an invention, the sensor capability can be improved without changing the sensor size or membrane size.

A typical thermoelectric sensor utilizes an off-chip temperature sensor such as a thermistor, transistor or diode to measure ambient temperature. 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 capable of measuring ambient temperature. Further, in order to avoid the temperature rise of the silicon substrate due to the dissipation of the thermal power based on the bias reading of the on-chip temperature sensitive resistor, the resistance of the on-chip temperature sensitive resistor is set to a value larger than 100 KΩ.

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 responsiveness 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 commercial products increases manufacturer costs. The present invention provides a method of using a heater resistor formed in an area adjacent to a thermal contact to adjust the drift effect of thermocouple material according to an electrical calibration method.

A conventional thermoelectric sensor is composed of a 4-pin metal can package. 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, there are two pins for the thermoelectric sensor, two pins for the on-chip temperature sensitive resistor, and two pins for the heater resistor. The on-chip temperature sensitive resistor and the heater resistor can share the ground. The two pins for the thermoelectric sensor are isolated from the metal can to reduce the effects of noise.

Important patents are given below to define the prior art relating to thermoelectric sensors.

(1) US Pat. No. 4,665,276,
Thomas Elbel, Jurgen Muller, Friedemann Volklein, “Thermoelectric Sensor (The
rmoelectric Sensor) "(2) US Pat. No. 5,100,479, Kensal. Kensall D. Wise, Khalil Najati, “Thermopile and Infrared Det detectors with a semiconductor-supported rim.
(3) US Pat. No. 4,456,919, Katsuhiro Tomita, Tatsuo Shimizu, Masaichi Bando, “Thermocouple detector with a temperature sensor for cold junctions (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 is performed. This thermoelectric sensor has a thin film thermocouple array 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 carries a row of polycrystalline silicon and a metal thermocouple. The rim also supports the cold junction and acts as a good heat conductor for removing heat from the cold junction.

The thermoelectric sensor means according to the above two patents uses a backside wet etching closure membrane structure. However, the present invention uses an open film structure for 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 ambient temperature and compensate for temperature. The present invention uses the first thermocouple element line or the second thermocouple element line to form an on-chip temperature sensitive resistor or thermistor. The on-chip temperature sensitive resistor can be formed in the same manufacturing process as the thermoelectric sensor.

In this regard, the following papers are referred to:

(1) G. R. GR Lahi
ji) and K. Dee. Wies (KD Wise),
"A batch-fabricated silicon thermopile infrared detector
etector) ”, Ie Ee trance. Elect on Devices Easy (IEEE Trans. Electron D
evices ED) -29, pp. 14-22, (1982
Year (2) are. R. Lenggenhager,
Etch. H. Baltes, Jay. Pier (J.P.
eer) and M. Foster (M. Forster), "CM
Thermoelectric infrared sensor based on OS technology (Thermoelectric i
nfrared sensors by CMOS technology) ", IEEE Eleon Devices Letters (IEEE Ele
ctron Device Letters) 13, 454, (1992)
Year) (3) Tea. T. Akin, Zet. Z. Olgun, Oh. Oka Akar, and Etch. H. Kulah “Highly Responsive Integrated Thermocouple Structure Using Standard CMOS Process (An integra
ted thermopile structure with high responsivity us
ing any stndard CMOS process ”, Sensors and Actuators, A (66), 218 to 224 (1998) (4) Etch. H. Baltes "CMOS as Sensor Technology", Sensors and Actuato
rs), A (A) 37-38, pages 51-56 (1
993 (5) Etch-Planar Technique Catalog
Of Thermo Sensors (HL-PLANAR Technik Catalog
of Thermosensors) (TS 1006)
0), H-Planartechnik GmbH, Hauert
t) 13 44 227 Dortmund, Germany.

According to the above-cited document, Raheji and Wies have proposed a closed film structure comprising thermoelectric materials of Au and polycrystalline silicon, using backside silicon anisotropic wet etching. To form. Barthes et al. Provide thermoelectric materials of aluminum and polycrystalline silicon and use an open film structure by front side silicon anisotropic wet etching. The radiation absorbing layer is composed of SiO2 and SiN. Klaha et al. Provide a structure in which the open film structure is made by front side silicon anisotropic wet etching, and the thermoelectric material uses standard CMOS n-poly and p ⁺ active layer processes. 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.

Further, the method of reference (4) discloses that a heater resistor is placed in the membrane and used to measure the thermal conductivity of the structure. However, in the present invention, a heater resistor is made in the area near the thermal contact 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, according to the present invention, since the on-chip temperature sensitive resistor is formed,
Alternatively, the same material as the second thermocouple element line is used. The on-chip temperature sensitive resistor and thermopile structure are made simultaneously.

When normalized outputs are obtained for different incident radiation angles, we have found that 100% normalized output is for radiation at incident angles that deviate from the normal to the plane of the radiation-diffusing layer by approximately ± 10 °. Find out what happened in. And 8
A 5% normalized output is observed for an incident angle of about 0 °. This fact is due to the Si (11
1) Indicates that some of the radiant energy reflected from the surface is absorbed by the radiation absorbing layer. The present invention provides for radiation to enter through the front side etching window and to avoid being incident on the Si (111) plane and reflected back into the radiation absorbing layer.
A reflective mirror is disclosed that covers a front side etching window. This reflective mirror plate is placed at the position of the front side etching window and is made at the same time as the thermoelectric sensor structure is made. The reflective mirror plate has aluminum for reflective purposes.

The present invention provides an economical method. The advantage of polycrystalline silicon / metal thermocouples is that they are simple because they are made by standard CMOS processes. Methods for improving total die, productivity, and upgrading sensor capabilities are the subject matter of the present invention.

The present invention has been made in order to improve the above-mentioned disadvantages of the prior art, and an object of the present invention is to improve thermoelectric performance capable of improving sensor performance without increasing size and cost. Type sensor device and its manufacturing method.

[0029]

The salient features of the present invention are as follows.

(1) A material having lower thermal conductivity is selected as the 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 lines as well as reduce the thermal conductivity and increase the performance of the thermoelectric sensor without increasing sensitivity and die size.

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

(3) A resistor which is treated as a heater is formed on a region in the vicinity of the heat contact, and is used for electrical calibration with respect to a change with time of thermoelectricity and other constituent materials and an influence of environment. And, in long-term operation, the accuracy of non-contact temperature measurement is increased.

(4) A titanium thin film and its related alloy are used to form a radiation absorbing layer from the process technology of the semiconductor industry.

(5) The etching time is shortened and productivity is increased by forming an etching hole on the independent or floating film of the radiation absorbing layer and the insulating layer.

(6) The front side silicon anisotropic wet etching technique is used to remove the silicon substrate underlying the open film structure of the thermoelectric sensor. The hot contact is then suspended or thermally isolated from the silicon substrate to increase the 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) As the on-chip temperature sensitive resistor, the same material as that of the first or second thermocouple element line is selected, and the resistance value of this resistor is larger than 100 KΩ.

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

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

In order to reach the above-mentioned object, the present invention provides
Provided is a method of manufacturing a thermoelectric sensor device having the following steps.

First, the 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 the surface of the first insulating layer. This material is, for example, polycrystalline silicon, amorphous silicon or metal. Masking and etching the portion of the thermocouple element material layer to form a first thermocouple element line. Forming a second insulating layer on the surfaces 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 passages. Forming a metal layer on the surface of the second insulating layer. Patterning and etching a portion of the metal layer to form a second thermocouple element line, the second thermocouple element line having a plurality of hot and cold junctions through the contact window described above. The step 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 portions of the third insulating layer and the second insulating layer, thereby exposing portions of the final second thermocouple element line. Then, in a next step, it is electrically connected to the second metal pad, and 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 a portion of 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 light during operation by etching or lift-off or reverse masking methods. Forming a fifth insulating layer on the surfaces of the fourth insulating layer and the radiation absorbing layer. Etching is performed on the portions of the fourth insulating layer and the fifth insulating layer, and the first metal pad and the second metal pad
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 etching through the insulating layer and exposing the 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 membrane 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 the electrical connections include: patterning and etching a portion of the third and second insulating layers, which results in the final second thermocouple element. Part of the line and part of the first thermocouple element line are exposed. A second metal layer is deposited on the third insulating layer. A portion of the second metal layer is patterned and etched, and then connecting lines between the first and second thermocouple elements of each pair are formed, as well as 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 the first metal pad and the second metal pad.

The construction of the thermoelectric sensor consists of the following: a silicon substrate and a first insulating layer formed on the surface of this silicon substrate. A large number of 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 the surface of the first thermocouple element line. A large number of second thermocouple element lines formed on the surface of the second insulating layer. Here, the second thermocouple element lines are defined and patterned so as to have a meandering structure or a zigzag structure, and each second thermocouple element line has a hot contact and a cold contact, and the heat contact is A first thermocouple element line is connected to the hot contact and a final cold contact is electrically connected to the second metal pad. A third insulating layer formed on the surfaces 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 the 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.
Fifth formed on the surfaces of the fourth insulating layer and the radiation absorbing layer
Insulation layer. A bond window formed in the first metal pad and the second metal pad by etching a portion of the fourth insulating layer and the fifth insulating layer. 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 layer and the first insulating layer. Silicon substrate under the thermocouple membrane region that can be wet etched through the front side etching window. The same material as the first or second thermocouple element line, assembled in the area near the thermal contacts and used to perform electrical calibration for thermoelectric and other component materials over time and environmental impact Heater register using. The thermoelectric sensor is manufactured at the same time as the semiconductor process technology. 10
An on-chip temperature sensitive 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 influence of radiation reflected from the Si (111) surface of the v-shaped globe located at the same time as the thermoelectric sensor structure is manufactured. Here, the reflection mirror plate has an aluminum film for the purpose of reflection.

[0045]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3 is a cross-sectional view of a thermoelectric sensor according to the present invention, in which 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 of thermal contacts
3, first insulating layer 21, second insulating layer 22, third insulating layer 2
The third, fourth insulating layer 24 and fifth insulating layer 25 are provided.

FIG. 4 is a diagram in which two thermocouple element lines related to the thermoelectric sensor of FIG. 3 are connected. 3 and 4, the second thermocouple element line 36 is
Through the contact window 43 of the third insulating layer 23, the thermal contact H
Is in contact with the first thermocouple element line 35. 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.

7 to 16 are sectional views showing the steps of manufacturing the thermoelectric sensor according to the present invention as the above-mentioned structure.

First, a silicon substrate 31 is provided, and as shown in FIG. 8, a first insulating layer 21 is deposited on the surface of this silicon substrate, and a part of the silicon substrate 31 under the thermocouple is changed in the next step. It is removed by anisotropic wet etching. A first thermocouple element layer 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 that the first thermocouple element line 35 is formed 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 the planarization and to form the multiple contact windows 43 of the thermal contacts of the second insulating layer 22. Etch a part. 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 contact window 43 is filled with the first metal layer. After this deposition process, the second insulating layer 22 has a second
The first metal layer is patterned to form the thermocouple element lines 36. First thermocouple element line 35
The electrical connection between the second thermocouple element line 36 and the second thermocouple element line 36 is formed through a contact window 43, as shown in FIG. The second thermocouple element line 36 contacts the first thermocouple element line 35 with the heat contact H of the contact window 43 and with 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 surfaces of the second thermocouple element line 36 and the second insulating layer 22. This third
The insulating layer 23 and the second insulating layer 22 are etched to form a first
The starting 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 portions of the cold junctions in the starting line of the first thermocouple element line 35 and the last line of the second thermocouple element line 36 become contact windows in the next step of joining metal pads to form an electrical connection. Then, a second metal layer is deposited on the contact window at 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 and the third insulating layer 23. The second metal layer is
Fill the contact window. After the deposition process, the second metal layer forms the metal pads 37, 38, the start 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. 11-12)
Patterned to form electrical connection lines between and. Then, 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 starting line of 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 an etching method or a lift-off method 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 forming the radiation absorbing layer 39, the 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 the 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. And removed. Then, as shown in FIG. 15, the bearer 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,
As shown in FIG. 6, the silicon substrate 31 under the thermocouple film region is undercut or voided.

The steps of this process are illustrated,
The features or mechanism 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 made of titanium or its alloy. The material of the second thermocouple element line is
Titanium, aluminum, titanium nitrogen compound, titanium compound
Group consisting of gold, aluminum alloys, and similar mixtures
Can be selected more. Thermal conductivity of titanium (17W / K)
Is considerably smaller than the thermal conductivity (˜238 W / K) of the AlSiCu alloy, and since titanium is a good conductor, the responsivity (Rv) and the specific detection sensitivity (D *) are improved. This is because the total resistance of the thermocouple sensor is almost 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 connecting line to the second line of the first line in the first thermocouple element line 35, and at the same time, the first thermocouple element line 35. It serves as a connecting line from the second line to the third line in.

In another embodiment of the present invention, the second metal layer previously described replaces the second thermocouple element line 36 as the connecting line 40, as shown in the interconnected state in FIG. In this manner, the 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, the connecting 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 there between.

Further, in another embodiment of the present invention, the material of the second thermoelectric element layer is used as the first metal pad 37 and the second metal pad 38. By doing so, 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 thermoelectric sensor is to increase the length of the thermocouple element line, thereby reducing the thermal conductivity of the thermocouple element line. It adopts a zigzag structure or a meandering structure. Like the structure shown in FIG.
The present invention discloses a zigzag structure for the second thermocouple element line to reduce the thermal conductivity of the second thermocouple element line while maintaining the same length of the first thermocouple element line. There is. In such an invention, the sensor performance can be improved without changing the size of the sensor or the size of the membrane. The zigzag structure described above includes multiple geometric configurations such as, for example, a single zigzag layer structure, a multilayer zigzag structure, a serpentine shaped structure, or other structure desired by the user. Further, the first thermocouple element line 3
If the material of 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 thermoelectric sensor is that the radiant 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. 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 read distribution circuit. This effect reduces the measurement accuracy in the long term. According to the present invention, the heater is provided with the resistor formed in the area adjacent to the heat contact. This heater register is
Used to adjust the drift effect based on the following electrical calibration measurements.

The principle of the electrical calibration measurement is as follows. The thermoelectric sensor structure is constructed to include a heater resistor on the adjacent area of the thermal contact. A pulse voltage or an AC voltage is applied to the heater resistor with the infrared radiation from the object 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 into 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 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 application, before measuring the temperature of an object such as a human body, the shutter is used to shield the radiation to the thermoelectric sensor in advance, and then the power Wh is supplied to the heater to output the output voltage Vh. To measure accurately. After removing the shutter, power W
t is received from the object and emitted or radiated on the radiation absorbing layer. Then, 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 value of Wh, the measured values of Vh and Vt. The calculation formula is as follows.

[0062]

[Equation 2]

Here, k is a constant. This constant can be adjustable when performing a precision measurement with a known blackbody temperature and a known input bias to the heater. The output result of the thermoelectric sensor affects Vh and Vt with the same slope or ratio according to the environment, time or drift effect of the readout distribution circuit. However, V
Since h / Vt is kept the same, the temperature of the object can be precisely measured by accurately measuring the radiant energy or the radiant energy.

According to another embodiment of the present invention, the larger apertures in the front side wet etching window 34 allow infrared radiation reflected from the bottom 48 of the anisotropic undercut cavity or the v-groove sidewall 49 to be reflected. Will be invited. Further, this infrared ray is secondarily incident on the back side of the radiation absorption layer having the thermoelectric structure. To avoid such effects,
As shown in FIG. 23, the present invention proposes a reflection mirror 50 including a first metal and / or a second metal for reflecting incident infrared rays. In this way
The front side wet etch window is defined as a narrow trench.

The previous package of the thermoelectric sensor is a metal can or metal with four pins, two pins serving as output electrodes for the thermoelectric sensor and two pins serving as electrodes for the off-chip room temperature sensor. Have a jacket. According to another embodiment of the present invention, a metal jacket package of a thermoelectric sensor having 5 or 6 pins is proposed. The 6-pin metal jacket allows the temperature resistor and heater resistor to share a common ground electrode, while 2 pins are for thermoelectric sensors, 2 pins are for on-chip temperature resistors, and 2 pins are It is for heater registers. 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) Regarding the structure of the second thermocouple element layer The second thermocouple element line has a zigzag or meandering structure in order to reduce the thermal conductivity, and for example, a thermal conductive material such as titanium or titanium alloy is used. It is made of a material with a low rate. This allows even standard CMOS process AlSiCu materials to be used, with solid body thermal conductivity of 70% -8% compared to conventional linear structures.
It can be further reduced to 0%. Therefore,
It is possible to improve sensor performance 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 A preferred embodiment of the present invention is to use titanium or a titanium alloy for the radiation absorption layer 39. Optimal absorption is obtained by controlling the appropriate thickness at about 34 μg / cm 2. It is helpful that titanium is an available material in standard CMOS processes.

(4) About Etching Holes When the film area of the radiation absorbing layer is very large, it is easy to obtain a mound structure on the bottom of the v-shaped globe after the front side wet etching process. As shown in FIG. 20, an etching hole 43 ′ such as the etching window 34 may be etched on the center of the radiation absorbing film 44. The function of this etching hole 43 'is not only to prevent the formation of silicon hills on the bottom, but also to shorten the etching time.

(5) As to the structure for carrying out the electrical calibration measurement, as shown in FIG. 21, the radiation absorbing film 44 of the present invention is used.
It has a register 45 on top. This register 45 is
It is electrically coupled to the third metal pad 46 and the fourth metal pad 47. The material of the resistor 45 is 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, CMOS, B
A combined iCMOS and thermoelectric sensor process is achieved to reduce the effects of noise in various circuits. It is useful to simplify the process.

(7) Temperature Sensitive Resistor for Measuring Room Temperature In a general thermoelectric sensor, the room temperature is measured by using an off-chip temperature sensor. The present invention applies the same material as the first thermocouple element line or the second thermocouple element line 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 sensitive resistor, the register of this on-chip resistor is set to 100 KΩ or more.

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

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

As will be 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. Further, various modifications and similar devices falling within the spirit and scope of the claims are included in the present invention, and the claims include all such modifications and similar configurations. It should agree 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 drawings]

FIG. 1 is a sectional view of an edge portion 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.

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

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

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

FIG. 7 is a cross-sectional view showing processing steps for manufacturing the 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 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 the 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 wet etching holes on a radiation absorption layer according to the embodiment of the present invention.

FIG. 21 is a schematic view of manufacturing a heater resistor in a region near a thermal contact 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 optical path of incident infrared rays affected by radiation reflected from the Si (111) surface of the v-shaped globe located below according to the embodiment of the present invention. .

FIG. 23 shows a reflection mirror covering a front side etching window in order to avoid the influence of radiation reflected from the Si (111) surface of the lower v-shaped globe according to the preferred embodiment of the present invention. It is a typical sectional view used.

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

[Explanation of symbols]

21 ... First insulating layer, 22 ... a second insulating layer, 23 ... Third insulating layer, 24 ... Fourth insulating layer, 25 ... Fifth insulating layer, 31 ... Silicon substrate, 32 ... V-shaped glove cavity, 35 ... First thermocouple element line, 36 ... Second thermocouple element line, 37 ... First metal pad, 38 ... second metal pad, 39 ... Radiation absorption layer, 43 ... contact window, 44 ... Radiation absorbing film, 45 ... Register, 46 ... Third metal pad, 47 ... fourth metal pad, 50 ... Reflective mirror, C ... cold junction, H ... thermal contact.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01K 7/02 H01L 35/32 H01L 35/34

Claims (19)

(57) [Claims] 1. A step of supplying a silicon substrate, a step of forming a first insulating layer on the surface of the silicon substrate, a step of forming a material layer on the surface of the first insulating layer, and a portion of the material layer. Patterning and etching to form a first thermocouple element line, forming a second insulating layer on the surface of the first thermocouple element line and the first insulating layer, and the second insulating layer To form a plurality of contact windows on the surface of the first insulating layer, to form a first metal layer on the surface of the second insulating layer, and to pattern and etch the portion of the first metal layer to form a first metal layer. 2 thermocouple element lines are formed and the second
A thermocouple element line penetrates the contact window to allow the first and
Joining 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 on the surface of the third insulating layer and the second insulating layer. Etching to expose the last part of the second thermocouple element line, forming a second metal layer above the third insulating layer, and etching the second metal layer. And forming a first metal pad and a second metal pad, and the last portion of the second thermocouple element line is electrically connected to the second metal pad, the method comprising part of the start portion is electrically connected to the front Symbol first metal pad, forming a fourth insulating layer to the upper than the third insulating layer and the second metal layer, the fourth insulating layer Above Chapter 3
Forming a metal layer and defining a radiation absorbing layer that absorbs infrared rays by etching or lift-off, that is, reverse masking, and forming a fifth insulating layer on the surfaces of the fourth insulating layer and the radiation absorbing layer If, etched in a portion of the fourth insulating layer and the fifth insulating layer, the steps of pre-Symbol first metal pad and the second metal pad is exposed, to form a front side wet etching windows, the first 5 insulating layers, the fourth insulating layer, the third insulating layer, the second insulating layer and the first insulating layer,
By exposing the surface of the silicon substrate and using the front side silicon anisotropic wet etching technique, the front side wet etching process is performed.
Etching the silicon substrate through a dough to void the silicon substrate, and a method for manufacturing a thermoelectric sensor device. 2. The material of the material layer is metal or multi-layered
The method of claim 1 comprising crystalline silicon . 3. The method of claim 1, wherein the radiation absorbing layer material is selected from the group consisting of titanium, titanium nitrogen compounds, and titanium alloys . Wherein the material of the first thermocouple element line A method according to claim 1 having a semiconductor material. 5. The method of claim 1, wherein the material of the second thermocouple element line is selected from the group consisting of titanium, aluminum, titanium nitrogen compounds, titanium alloys, and aluminum alloys. 6. The line shape of the second thermocouple element line has a zigzag structure, and the zigzag structure is a one-layer zigzag structure, a multilayer zigzag structure, or a meandering structure. The method described in. 7. The method of claim 1, wherein the first metal pad and the second metal pad are made of a first metal layer, omitting the formation of the second metal layer. 8. The method of claim 1, wherein an etching hole is formed on the center of the radiation absorbing layer while the front side wet etching window is being formed. 9. A thermoelectric sensor device of a type using a first metal pad and a second metal pad as an output terminal, comprising: a silicon substrate; a first insulating layer formed on a surface of the silicon substrate; A plurality of first thermocouple element lines formed on the surface of the first insulating layer, wherein each first thermocouple element line has a hot contact and a cold contact, and the first thermocouple element line has a cold portion at the beginning 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, and a second insulating layer. A plurality of second thermocouple element lines formed from the first metal layer on the surface, each second thermocouple element line having a hot junction and a cold junction, The point is joined to the heat contact of the first thermocouple element line, the cold junction of the second thermocouple element line is joined to the cold contact of the first thermocouple element line, and the cold portion of the last portion of the second thermocouple element line is joined. The cold junction includes a plurality of second thermocouple element lines electrically connected to the second metal pad, a second insulating layer, and a third insulating layer formed on a surface of the second thermocouple element line. A second metal layer forming the first metal pad and the second metal pad; a fourth insulating layer formed on the surfaces of the third insulating layer, the first metal pad and the second metal pad; A radiation absorbing layer formed on the surface of the fourth insulating layer to absorb infrared rays, a fifth insulating layer formed on the surfaces of the fourth insulating layer and the radiation absorbing layer, the first metal pad and the front. A bonding pad window formed above the second metal pad and passing through the fifth insulating layer and the fourth insulating layer to expose the first metal pad and the second metal pad; and the fifth insulating layer. The silicon substrate is formed on the surface of the layer and extends downward to pass through the fifth insulating layer, the fourth insulating layer, the third insulating layer, the second insulating layer and the first insulating layer, And a v-shaped globe cavity formed by etching the silicon substrate through the front side wet etching window, and a thermoelectric sensor device . 10. The thermoelectric sensor device according to claim 9, wherein the silicon substrate has a CMOS circuit. 11. The thermoelectric sensor device according to claim 9, wherein the silicon substrate has a BiCMOS circuit. 12. The first thermocouple element line comprises:
The thermoelectric sensor device according to claim 9, which has a linear or zigzag structure. 13. The second thermocouple element line,
The thermoelectric sensor device according to claim 9, which has a zigzag structure. 14. The thermoelectric sensor device according to claim 9, wherein a temperature sensitive resistor having a resistance value of more than 100 KΩ is applied to the first thermocouple element line or the second thermocouple element line. 15. A radiation absorbing layer in the vicinity of the thermal contact,
The thermoelectric sensor device according to claim 9, further comprising a heater register for performing electrical calibration measurement. 16. The thermoelectric sensor device according to claim 15, wherein the material of the resistor is made of the material of the first thermocouple element line or the second thermocouple element line. 17. The thermoelectric sensor device according to claim 9, further comprising five pins serving as output electrodes and a metal jacket. 18. The thermoelectric sensor device according to claim 9, further comprising six pins serving as output electrodes, and a metal jacket. 19. A reflective mirror wherein the front side wet etching window is defined as a narrow trench and is used to reflect incident infrared radiation and to avoid second incident infrared radiation from radiating to the backside of the radiation absorbing layer. And the reflecting mirror comprises the first and / or second
The thermoelectric sensor device according to claim 9, comprising a metal layer.