JPH03211427A - Infrared sensor and production thereof - Google Patents

Abstract

PURPOSE:To improve the mechanical strength of a bridge girder part and to provide the above sensor which is smaller in size and higher in accuracy by providing a reinforcing part formed to have the thickness increasing gradually toward the bridge girder part near the end of a bridging part having the bridge girder part. CONSTITUTION:Curved surface parts 9a, 9b having a prescribed curvature is provided in the angle part of the ceiling surface of a cavity part 8 formed between the silicon oxide film 2 and silicon substrate 2 of the bridging part consisting of the silicon oxide film 2, phosphorus silicate glass 3 and silicon oxide film 4 of the bridging structure on the silicon substrate 1. The mechanical strength of the bridging part is improved in this way and, therefore, the IR sensor of the small size and high accuracy for which fine working technology for semiconductor is realized. The reinforcing part 8 may be the reinforcing part of the structure having the slope inclining at a specified angle from the base part of the bridging part consisting of the silicon oxide film 2 to the side face part.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an infrared sensor and a method for manufacturing the same, and particularly an infrared sensor suitable for use in a thermometer that measures temperature such as body temperature without contact, and a method for manufacturing the same. Regarding.

[Prior Art] Conventionally, non-contact thermometers have rarely been manufactured because there is no difference between the background temperature (ambient environment temperature) and body temperature, so it is difficult to extract only the true temperature.

Recently, however, the demand for inexpensive, highly accurate thermometers that take temperature in a short time has been increasing day by day, mainly among nurses at hospitals caring for infants and the elderly. In order to shorten the time required to measure body temperature, predictive thermometers have been put into practical use that estimate the temperature in a thermal equilibrium state from the actual temperature and elapsed time, but they still require a measurement time of about 1 minute.

Infrared radiation thermometers are desirable for realizing thermometers that take temperature in a few seconds.In particular, bolometer-type infrared sensors have the advantage of controlling the amount of self-heating because the temperature-sensing part has a high resistance and the current flowing through the element is suppressed. There is.

Conventionally, such bolometer-type infrared sensors have a structure in which the temperature-sensing part is made of a metal oxide such as manganese (Mn) or nickel (Ni), and this element is suspended by a thin metal wire. there were.

[Problem to be solved by the invention] However, the conventional bolometer type infrared sensor
There is a limit to miniaturization, and the B constant (thermistor constant), which is the temperature coefficient of resistance, is small (as described above, it cannot be said to be sufficient for use in thermometers that require high accuracy).

Therefore, attempts have been made to manufacture a compact and highly accurate infrared sensor having a bridge structure using semiconductor microfabrication technology that has recently advanced greatly.

However, when an infrared sensor was manufactured using this semiconductor microfabrication technology, the following problems occurred. That is, for example, as shown in FIG.
In the case where a sacrificial layer 31 for forming a horizontal structure made of molybdenum or the like is provided on top of the sacrificial layer 31, and a silicon oxide film 32 which becomes a bridge portion is formed on this sacrificial layer 31 by a CVD method (chemical vapor deposition method). , a shadow is formed at the end on the sacrificial layer 31 side, and as a result, the stepped portion of the silicon oxide film 32, as shown by A in the figure,
In other words, the film thickness at the bridge girder becomes thinner, causing breakage,
The mechanical strength of that part may become extremely weak.

The present invention has been made in view of the above problems, and is an infrared sensor that improves the mechanical strength of the bridge girder part of a horizontal structure, and thus realizes a small and highly accurate thermometer etc. using semiconductor microfabrication technology. The purpose is to provide a method for producing the same.

[Means for Solving the Problems] In order to solve the above problems, in the infrared sensor of the present invention, the infrared sensor includes a bridge part having a bridge girder part at the end, and the infrared sensor has The present invention is characterized in that a reinforcing portion is provided whose thickness gradually increases toward the bridge girder.

Specifically, the reinforcing portion includes a curved surface portion that changes at a constant curvature from the bottom surface of the bridge section to the bridge girder section, or an inclined section that slopes at a constant angle from the bottom surface section of the bridge section to the bridge girder section. It is something that you have.

Kiki Shigo Word n Word 2 Extermination Shidaigure Bano + Taigyo Sao Gyoshi -He L= :i I+ -+
- It is preferable to form it with an oxidized film.

Further, the method for manufacturing an infrared sensor of the present invention includes a step of forming a metal film for forming the bridge portion on a support substrate, a step of forming an etching-resistant film having a sacrificial layer pattern on the metal film, etching is performed using the etching-resistant film as a mask to selectively remove the metal film to form a sacrificial layer, and forming curved portions for forming reinforcing portions at the corners of the upper surface of the sacrificial layer, respectively; a step of forming an insulating film for forming a bridge portion on a support substrate including the layer; and a step of providing an opening in the insulating film that reaches the sacrificial layer, and performing etching through the opening to remove the sacrificial layer. Particularly when forming the curved surface portion on the sacrificial layer, it is preferable to apply ultrasonic waves to the etching-resistant film to partially peel off the end portions of the etching-resistant film.

Furthermore, the method for manufacturing an infrared sensor of the present invention includes a step of forming the metal film for forming the bridge portion on the support substrate, a step of forming an etching-resistant film having a sacrificial layer pattern on the metal film, etching is performed using the etching-resistant film as a mask to selectively remove the metal film to form a sacrificial layer, and forming sloped portions for forming reinforcing portions at the corners of the upper surface of the sacrificial layer, respectively; forming an insulating film for forming a bridge portion on a support substrate including the insulating film; and providing an opening in the insulating film that reaches the sacrificial layer, and removing the sacrificial layer by etching through the opening. In particular, it is preferable to form a sloped portion in the sacrificial layer by plasma etching.

[Function] Generally, the thermal balance equation for a thermal infrared sensor is W=C-
It is given by d(δT)/dt +G・δT, and the thermal time constant is = C/G (where W = incident energy, δT =
Temperature change of the light receiving part, C = heat capacity, G = thermal conductance).

Ultimately, in order to improve the sensitivity and responsiveness of a thermal infrared sensor, it is necessary to reduce the thermal conductance and further reduce the heat capacity. (SiO-
The thermal conductivity of the bridge is 0.012J7cm-s, which is about two orders of magnitude smaller), and if the thickness of the bridge is made thinner, the mechanical strength of the bridge structure will become weaker. Another way to reduce thermal conductance is to increase the distance between the heat receiving section (temperature sensing section) and the bridge girder section from which heat flows. If the length between the bridge girders is increased, the mechanical strength of the bridge structure will be reduced, so reinforcement will be required.

In the infrared sensor according to the present invention configured as shown in L, the reinforcing portion having a curved surface or an inclined surface is formed in the bridge girder portion of the bridge portion, so that the mechanical strength of the bridge girder portion is improved, and therefore the semiconductor microstructure is improved. A small and highly accurate infrared sensor can be realized using processing technology.

Further, in the method for manufacturing an infrared sensor according to the present invention, since the curved surface portion or the inclined portion for forming the reinforcing portion is formed in advance at the upper corner portion of the sacrificial layer, it is easy to form the reinforcing portion, and The bridge girder section of the bridge becomes thinner,
There is no step breakage, and therefore the above-mentioned infrared sensor can be manufactured easily.

[Example] Hereinafter, an example of the present invention will be specifically described with reference to the drawings.

FIG. 1 shows a cross-sectional structure of an infrared sensor according to an embodiment of the present invention.

In the figure, reference numeral 1 denotes a semiconductor substrate, such as a silicon substrate, as a supporting substrate. A silicon oxide film (S i O □) 2 having a bridge structure is formed on this silicon substrate 1, and furthermore, a phosphorus-sifcate glass film 3 and a silicon oxide film 4 are sequentially formed on this silicon oxide film 2. As a result, a three-layer bridge structure is formed. Note that a silicon nitride film may be used instead of the phosphorus silicate glass film 3. Also,
A metal layer such as a titanium film 5 is formed as a conductive layer on the silicon oxide film 4, and a silicon film 6 as a temperature sensing part is formed in the center of the bridge on the titanium film 5. An aluminum film 7 is formed on the film 5 at the bridge girder portion as an external lead electrode.

A corner part of the ceiling surface of the cavity 8 formed between the silicon oxide film 2 and the silicon substrate l of the bridge structure, that is, a curved surface part 9a having a predetermined curvature R from the bottom part of the bridge part to the bridge girder part; 9b is formed.

That is, in the infrared sensor of this embodiment, the curved portions 9a, 9b are provided on the bridge girder portion of the bridge portion made of the silicon oxide film 2.
The reinforcing portion 9 is formed to have a reinforcement portion 9, which significantly improves the mechanical strength of the bridge portion. Note that, as shown in FIG.
) may have a structure in which the reinforcing portion 25 has an inclined surface 25a that is inclined at an angle of .

Next, we will discuss the manufacturing method of the infrared sensor with the above structure in the third section.
This will be explained in detail with reference to FIGS. (a) to (r).

First, as shown in FIG. 3A, a silicon substrate 10 as a support is prepared. Then, as shown in the figure (b), a photoresist film 1) with a thickness of 2.0 μm was coated on this silicon substrate 0, exposed, developed and fixed, and then heated at 140±2°C. A heat treatment (pigeon baking) is performed for 90 seconds in a nitrogen atmosphere to form a pattern for the next step of lift-off of the gold film.

Next, sputtering of gold (Au) was performed for 45 seconds in an argon gas atmosphere at a temperature of 1) 0°C or lower to form a gold film 2 with a thickness of 0.6±0.1 μm as shown in Figure (c).
form. Subsequently, the wafer is immersed in a resist stripping solution (acetone) at room temperature to remove the photoresist film 1) and the gold film 12 formed thereon.
), a pattern of a gold film 12a as a reflective film is formed. Thereafter, heat treatment is performed in a nitrogen gas atmosphere at a temperature of 450±5°C.

Next, molybdenum (Mo) is sputtered in an argon gas atmosphere at a temperature of 250±30°C, and as shown in FIG. A molybdenum film 13 with a thickness of .0 μm is formed.

Next, as shown in FIG. 2F, a photoresist film 14 is coated on the molybdenum film 13, exposed, developed and fixed, and then heat-treated for 90 seconds in a nitrogen atmosphere at 140±2°C. hard baking) to form a sacrificial layer pattern.

Subsequently, the wafer was immersed in an etching solution (with a liquid temperature of 35±5℃).
H, PO,: HNO3: 820=5 + 1 :4
) to selectively remove the molybdenum film 13. At this time, the photoresist film 14 is etched during etching.
When ultrasonic waves are applied to
) A smooth curved surface portion 13a is formed as shown in FIG.

Incidentally, instead of applying ultrasonic waves as described above, inclined surfaces may be formed at the corners of the molybdenum film 13 using an ion milling device or a plasma etching device.

Next, in an atmosphere of gas (oxygen gas) flow rate = 50 sec, pressure 5, and OTorr, high-frequency power 50
Ashing (ashing) is performed by applying 0 W, and the photoresist film 14 is removed as shown in FIG.

Next, plasma CV was performed at a temperature of 300±2°C, a pressure of 0.9 Torr, and a gas flow rate of silane (S i H4) = 200 sec and laughing gas (N20) = 4000 sec.
A silicon oxide film 15 having a thickness of 18,000±1,500 wafers is formed on a silicon substrate 10 including a molybdenum film 13 by method D, as shown in FIG. 1(i).

Subsequently, as shown in Figure (j), the temperature was increased to 24°5±0.
A film with a thickness of 550 mm is formed on the silicon oxide film 15 while rotating the wafer using a rotating device in an atmosphere of 5°C.
A photoresist film 16 having a temperature of 0±500°C is formed, and heat treatment is performed at a temperature of 140±2°C. Subsequently, fluorocarbon (cz F
e) = 90 sec, oxygen (Of) = 12 s
Planarization etching is performed using ECM, helium (He) = 50 sec, and trifluoromethane (CHF3) = 20 sec.

Next, in an atmosphere with a gas (oxygen gas) flow rate of 50 seconds and a pressure of 5.0 Torr, a high frequency power of 500 W was applied.
By adding , ashing (ashing) is performed, and the photoresist film 16 is removed as shown in FIG. 3(k). As a result, the surface of the silicon substrate 10 is planarized and the silicon oxide film 15 on the molybdenum film 13 is removed.

Next, as shown in the same figure (I2), the temperature was 300±2°C.
1 Pressure 0.9 Torr, gas flow rate silane (S i H
4) =200sec, laughing gas (N20) = 40
The same figure (i
) As shown in FIG.
Silicon oxide film 17 with a thickness of 9000±1500 on
form.

Next, as shown in FIG.
i H4)=20±1p6i, laughing gas (N20)=2
0±1psi, phosphine (PH,)=22±1ps
i, film thickness 8000±10 by plasma CVD method
A phosphorus silicate glass (PSG) film 18 of 0.00% is formed on the surface of the silicon substrate 10 . Note that the gas flow rate was silane = 20 ± 1 psi, ammonia gas (NH).

)=20 ps i, a silicon nitride film having a thickness of 1500±500 μm may be formed on the surface of the silicon substrate by CVD at a temperature of 800° C.

Next, the plasma CVD method was performed using the plasma CVD method at a temperature of 300±2°C, a pressure of 0.9 Torr, and a gas flow rate of silane (S i H,) = 200 sec and laughing gas (N 20 ) = 4000 sec as shown in the same figure (n). Yorin・
A silicon oxide film 19 having a thickness of 3500±1500 wafers is formed on the silicate glass film 18.

Next, titanium (Ti) was sputtered in an argon gas atmosphere at a temperature of 230±30°C.
As shown in FIG. 0), a film thickness of 0.0. l±
After forming the titanium film 20 with a thickness of 0.05 μm, a titanium electrode pattern is formed by ordinary electrode photolithography.

Subsequently, aluminum (Ar1) is sputtered in an argon gas atmosphere at a temperature of 230±30° C. to form a film with a thickness of 1.5 mm on the titanium film 20, as shown in FIG.
After forming the aluminum film 21 of 0±0.1 μm,
An electrode pattern is formed by ordinary photolithography.

Next, as shown in FIG. 2(q), sputtering is performed using a silicon substrate (resistance 3000 Ω·cm) as a target 2, and a film thickness of 1.0 to 1.0 to A 1.5 μm silicon film 22 is formed, and an acceleration voltage of 120 Ke and a dose of I x 10 ” are formed.
Boron ions are implanted under the condition of 7cm'' to bring the silicon film 22 close to a neutral semiconductor.Next, the silicon film 22 is heated for 30 minutes in a nitrogen atmosphere at a temperature of 1) 00°C.
2. Perform crystallization. As a result, the B constant (thermistor constant) of the silicon film 21 as a temperature sensing portion can be set to about 500, and the sensitivity to temperature changes can be improved. Subsequently, oxygen (0 □) = 45 ± l sec as a reaction gas,
Sulfur hexafluoride (SF, ) = 135 ± 2 sec was flowed, pressure was 400 ± 10 mTorr, high frequency power was 125
By performing plasma etching under the condition of W, the silicon film 22 is selectively removed to form a pattern of the temperature sensing portion.

Next, a photoresist film pattern is formed as photolithography for opening windows in the sacrificial layer, and using this photoresist film as a mask, trifluoromethane (CH) is used as a reactive gas.
F3) = 103sec, oxygen (02): 7s
By performing plasma etching under the conditions of ecm, high frequency power of 300 W, and bias voltage of 500 V, a silicon oxide film 17.19 and a phosphorus silicate glass film 18 are formed.
An opening reaching the molybdenum film 13 is formed. continue,
Phosphoric acid (H3PO4): Nitric acid (HNOs): Water (H20
)=5:1:4 etching solution using the photoresist film as a mask to form a molybdenum film 13 as a sacrificial layer as shown in FIG.
is removed to form the cavity 23. As this etching solution, an etching solution of nitric acid:sulfuric acid water=l:l:3 may be used.

Finally, pressure 5, OTorr, high frequency power 500W
Plasma ashing is performed for 4.5 seconds under the following conditions to remove the photoresist film.

In this way, it is possible to manufacture an infrared sensor element having a reinforcing section 24 having a curved surface section 24a on the bridge girder section of the fruit picking section.

Although the present invention has been described above with reference to Examples, the present invention is not limited to the above-mentioned Examples, and can be modified in various ways without departing from the gist thereof.

For example, in the above embodiment, the bridge part has a three-layer structure of the silicon oxide film I7, the phosphorus silicate glass film 18, and the silicon oxide film 19 to increase its strength.
This may be a single layer structure of the silicon oxide film 17, and the semiconductor material is not limited to silicon, but other materials may also be used.

[Effects of the Invention] As explained above, according to the infrared sensor according to the present invention, since the reinforcing portion having a curved surface or an inclined surface is formed in the bridge girder portion of the bridge section, the mechanical strength of the bridge girder portion is improved. Therefore, it is possible to realize a small and highly accurate infrared sensor using semiconductor microfabrication technology.

Further, according to the method for manufacturing an infrared sensor according to the present invention,
Since a curved surface or an inclined surface for forming the reinforcing part is formed in advance on the upper corner of the sacrificial layer, it is easy to form the reinforcing part, and it also prevents the bridge girder part of the bridge part from becoming thin or breaking. This has the effect that the above-mentioned infrared sensor can be manufactured easily.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an infrared sensor according to one embodiment of the present invention, FIG. 2 is a cross-sectional view of essential parts of an infrared sensor according to another embodiment of the present invention, and FIGS. 3(a) to (r) are FIG. 1 is a cross-sectional view showing the manufacturing process of an infrared sensor, and FIG. 4 is a cross-sectional view of a main part for explaining the problems of a conventional infrared sensor. 1.10...Silicon substrate 2.4, 17.19...Silicon oxide film 3.18...
・Phosphorus silicate glass film 5.20...Titanium film 6.22...Silicon film (temperature sensing part) 13...Molybdenum film (sacrificial layer) 9.24...Reinforcement part

Claims (8)

[Claims] (1) An infrared sensor including a bridge section having a bridge section at an end, in which a reinforcing section is provided near the end of the bridge section so that the thickness gradually increases toward the bridge section. An infrared sensor characterized by: (2) The infrared sensor according to claim 1, wherein the reinforcing part has a curved surface part that changes with a constant curvature from the bottom part of the bridge part to the bridge girder part. (3) The infrared sensor according to claim 1, wherein the reinforcing section has an inclined section that slopes at a constant angle from the bottom surface of the bridge section to the bridge girder section. (4) The infrared sensor according to claim 2 or 3, wherein the reinforcing portion is formed integrally with the bridge portion using a silicon oxide film. (5) The method for manufacturing an infrared sensor according to claim 2, including the step of forming the metal film for forming the bridge portion on the support substrate, and forming an etching-resistant film having a sacrificial layer pattern on the metal film. forming a sacrificial layer by selectively removing the metal film by etching using the etching-resistant film as a mask, and forming curved parts for forming reinforcing parts at the corners of the upper surface of the sacrificial layer. a step of forming an insulating film for forming a bridge portion on a support substrate including the sacrificial layer; providing an opening reaching the sacrificial layer in the insulating film and removing the sacrificial layer by etching through the opening; A method for manufacturing an infrared sensor, comprising the steps of: (6) The method for manufacturing an infrared sensor according to claim 5, wherein when forming the curved surface portion in the sacrificial layer, ultrasonic waves are applied to the etching-resistant film to partially peel off an end portion of the etching-resistant film. (7) The method for manufacturing an infrared sensor according to claim 3, including the step of forming the metal film for forming the bridge portion on the support substrate, and forming an etching-resistant film having a sacrificial layer pattern on the metal film. forming a sacrificial layer by selectively removing the metal film by etching using the etching-resistant film as a mask, and forming sloped portions for forming reinforcing portions at the corners of the upper surface of the sacrificial layer. a step of forming an insulating film for forming a bridge portion on a support substrate including the sacrificial layer; providing an opening reaching the sacrificial layer in the insulating film and removing the sacrificial layer by etching through the opening; A method for manufacturing an infrared sensor, comprising the steps of: (8) The method for manufacturing an infrared sensor according to claim 7, wherein a sloped portion is formed in the sacrificial layer by plasma etching.