JP2009076608A - Thin film thermistor and manufacturing method of thin film thermistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin film thermistor and a manufacturing method thereof such that the thermistor can be made compact and its resistance value can be adjusted with high precision without damaging a thermistor thin film itself. <P>SOLUTION: The thin film thermistor comprises a silicon substrate 3 having an SiO<SB>2</SB>layer 2 formed on a surface, the thermistor thin film 4 pattern-formed on a top surface of the SiO<SB>2</SB>layer 2, a pair of thin film upper electrodes 5 pattern-formed on the thermistor thin film 4, an insulating protection film 6 formed on a top surface of the silicon substrate 3 to cover the thermistor thin film 4 and thin film upper electrodes 5, a pair of through holes 8, having conductive films reaching the pair of thin film upper electrodes 5, formed on internal surfaces of through holes bored in the protection film 6, and a pair of upper lead-out electrodes 9 formed on the protection film 6 and having their one-end sides connected to the pair of through holes 8, wherein the resistance value is adjusted by partially removing the pair of upper lead-out electrodes 9. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a thin film thermistor used for an infrared detection sensor, for example, and a method for manufacturing the thin film thermistor.

  In recent years, development of infrared detection elements that can measure temperature in a non-contact manner has become active. Infrared detectors are often used to detect weak infrared rays emitted from objects and human bodies, and are required to have high sensitivity. There are three types of infrared detection elements: a thermopile type in which thermocouples are connected in series, a pyroelectric type using the pyroelectric effect of a specific material, and a thermistor type using the resistivity temperature dependence of a specific metal oxide. .

  Among these, thermistor-type infrared detection sensors, which have a thermistor thin film formed on a substrate such as a semiconductor substrate and are provided with various wirings, are products that have been on the trend of miniaturization, higher performance, and lower prices. It has begun to attract attention. A general structure of the infrared detection sensor using the thermistor thin film is as follows: an insulating substrate or a substrate on which an insulating layer is formed, a thermistor thin film formed on the insulating substrate or the upper surface of the insulating layer, and an upper surface of the thermistor thin film. And a pair of electrodes formed mainly on each other.

In the infrared detection sensor configured as described above, when the temperature of the thermistor thin film changes when the irradiated infrared light is received, the resistance of the thermistor thin film changes. It can be detected.
The thermistor thin film used in this infrared detection sensor is formed on an insulating substrate such as an Si substrate having an SiO ₂ layer (insulating layer) formed on the surface thereof, an alumina substrate, or a quartz substrate.

Various thin film thermistors used as the above-described infrared detection sensors and the like are currently provided. For example, Patent Documents 1 and 2 are provided with excellent thermal responsiveness.
In such a thin film thermistor, a method of performing laser trimming is known in order to improve the resistance value yield. For example, Patent Document 3 proposes a technique in which a trimming portion is provided in an electrode portion in order to adjust a resistance value. Patent Document 4 proposes a technique of adjusting a resistance value by providing a thermistor portion for resistance value and cutting a line connected to the portion to adjust the resistance value.
Thus, as a resistance value adjusting means, conventionally, a resistance value adjusting resistor or electrode is connected in series to a thin film thermistor and the resistance value is adjusted by laser trimming, or the thermistor thin film itself is trimmed. ing.

JP-A 61-160902 JP-A-61-242002 JP 2000-348911 A JP-A-9-283305

However, the following problems remain in the conventional thin film thermistor.
That is, among the above conventional techniques, the method of separately providing a resistance value adjusting resistor or electrode generates a region requiring an occupied area in addition to the thermistor thin film, which inevitably increases the chip size. There is. Further, in the method of trimming the thermistor thin film itself, the resistance value of the thermistor thin film itself is significantly increased by the heat generated by laser irradiation, so it is difficult to adjust the trimming distance while measuring the resistance value. In addition, trimming the thermistor thin film damages the thermistor thin film itself, and there is a possibility that electrical characteristics such as withstand voltage may deteriorate.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a thin film thermistor that can be downsized and whose resistance value can be adjusted with high accuracy without damaging the thermistor thin film itself, and the thin film thermistor. It is to provide a manufacturing method.

The present invention provides the following means in order to solve the above problems.
A thin film thermistor according to the present invention includes a substrate or an insulating substrate having an insulating layer formed on a surface thereof, a thermistor thin film patterned on the upper surface of the insulating layer or the insulating substrate, and a pair of patterns formed on the thermistor thin film. A thin film upper electrode, an insulating protective film formed on an upper surface of the insulating layer or the insulating substrate to cover the thermistor thin film and the thin film upper electrode, and an inner surface of a through hole formed in the protective film. A pair of through holes in which a conductive film reaching a pair of thin film upper electrodes is formed, and a pair of upper lead electrodes formed on the protective film and connected at one end to the pair of through holes. A part of the upper lead electrode is removed and the resistance value is adjusted.

  In addition, the method for manufacturing a thin film thermistor according to the present invention includes a thin film forming step for patterning a thermistor thin film on an insulating layer on a substrate or an upper surface of the insulating substrate, and a thin film for patterning a pair of thin film upper electrodes on the thermistor thin film. Forming an upper electrode, a protective film forming step of covering the thermistor thin film and the thin film upper electrode on the upper surface of the insulating layer or the insulating substrate, and forming a through hole in the protective film; Forming a conductive film reaching the pair of thin film upper electrodes on the inner surface to form a pair of through holes, and forming a pair of upper lead electrodes having one end connected to the pair of through holes as the protective film An upper lead electrode forming step formed on the upper lead electrode; and a resistance value adjusting step of adjusting a resistance value by removing a part of the upper lead electrode. That.

  In these thin film thermistors and thin film thermistor manufacturing methods, the resistance value is adjusted by removing a part of the upper lead electrode on the protective film connected to the thin film upper electrode through a through hole penetrating the protective film. Therefore, since the upper lead electrode to be trimmed is laminated on the protective film, it is possible to reduce the size, and the thermistor thin film itself is not trimmed, so that the thermistor thin film itself is not damaged and the resistance value variation during trimming can be reduced. The resistance value is adjusted with high accuracy. In addition, since the upper lead electrode is directly trimmed as compared with the case where the internal electrode is trimmed from above the protective film, the influence on the protective film can be greatly reduced.

In the thin film thermistor according to the present invention, the pair of upper lead electrodes connect the pad portion for electrical connection with the outside, the pad portion and the through hole, and are narrower than the pad portion. And a lead portion that is partially removed by the resistance value adjustment.
In the method of manufacturing the thin film thermistor according to the present invention, in the upper lead electrode forming step, the upper lead electrode is electrically connected to a pad portion for external connection, and the pad portion and the through hole are connected. And a lead portion extending narrower than the pad portion, and a part of the lead portion is removed in the resistance value adjusting step.

  In these thin film thermistors and thin film thermistor manufacturing methods, the lead portion extending narrower than the pad portion is trimmed, so that the resistance value can be clearly adjusted with a smaller trimming amount than trimming the wide portion. It becomes possible.

  The thin film thermistor manufacturing method of the present invention is characterized in that, in the resistance adjustment step, a part of the upper extraction electrode is removed by irradiating a laser beam. That is, in this thin film thermistor manufacturing method, trimming is performed to remove a part of the upper extraction electrode by irradiating a laser beam, so that local removal can be performed with high positional accuracy and high-precision resistance adjustment. Is possible. In addition, since the upper lead electrode is directly irradiated with laser light, the output of the laser light can be suppressed and the influence on the underlying protective film can be further reduced as compared with the case where the internal electrode is irradiated through the protective film. be able to.

The present invention has the following effects.
That is, according to the thin film thermistor and the manufacturing method thereof according to the present invention, the upper lead electrode on the protective film connected to the thin film upper electrode through the through hole penetrating the protective film is partially removed to provide resistance. Since the value is adjusted, the size can be reduced and the resistance value can be adjusted with high accuracy without damaging the thermistor thin film itself.

  Hereinafter, an embodiment of a thin film thermistor and a thin film thermistor manufacturing method according to the present invention will be described with reference to FIGS. In each drawing used in the following description, the scale of each member is appropriately changed in order to make each member recognizable or easily recognizable.

Thin film thermistor 1 according to this embodiment, as shown in FIGS. 1 and 2, a silicon substrate (substrate) 3 SiO ₂ layer (insulating layer) 2 is formed on the surface, the pattern formed on the upper surface of the SiO ₂ layer 2 The thermistor thin film 4 formed, a pair of thin film upper electrodes 5 patterned on the thermistor thin film 4, and the insulating property formed on the upper surface of the SiO ₂ layer 2 of the silicon substrate 3 so as to cover the thermistor thin film 4 and the thin film upper electrode 5 A protective film 6, a pair of through-holes 8 in which a conductive film 7 reaching the pair of thin film upper electrodes 5 is formed on the inner surface of the through-hole formed in the protective film 6, and a pair of protective films 6 formed on the protective film 6 A pair of upper lead electrodes 9 having one end connected to the through hole 8.

The thin film upper electrode 5 is formed of a metal material other than a noble metal such as Cr, and a pair of internal bonding layers 5a patterned on the upper surface of the SiO ₂ layer 2, and Au patterned on the internal bonding layers 5a. , Pt and the like, and a pair of internal conductive layers 5b made of a noble metal.
The pair of upper lead electrodes 9 is also made of a metal material other than a noble metal such as Cr, and a pair of upper bonding layers 9a patterned on the protective film 6, and Au patterned on the upper bonding layer 9a, And a pair of upper conductive layers 9b made of a noble metal such as Pt.

  Further, the upper lead electrode 9 connects the pad portion 10 for electrical connection with the outside by a lead wire (not shown) by wire bonding, the pad portion 10 and the through hole 8, and from the pad portion 10. And a lead portion 11 that extends in a narrow line shape and is partially removed by resistance value adjustment. That is, in the thin film thermistor 1 of this embodiment, a part of the lead portion 11 in the upper lead electrode 9 is removed by laser trimming and the resistance value is adjusted. In addition, the code | symbol T in FIG. 1 has shown the removal part of the upper extraction electrode 9. FIG.

The SiO ₂ layer 2 is formed by thermally oxidizing the surface of the silicon substrate 3, and has a thickness of 0.1 μm or more and 1.5 μm or less, for example. The SiO ₂ layer 2 of the present embodiment has a layer thickness of 500 nm.
The thermistor thin film 4 is made of Mn—Co based composite metal oxide (for example, Mn ₃ O ₄ —Co ₃ O ₄ based composite metal oxide) or Mn—Co based composite metal oxide with Ni, Fe, or Cu. It is a composite metal oxide film made of a composite metal oxide (for example, Mn ₃ O ₄ —Co ₃ O ₄ —Fe ₂ O ₃ composite metal oxide) containing at least one element, and has a crystal plane (100) It has a spinel crystal structure oriented in the plane, and has a columnar crystal structure extending in the film thickness direction.

The thermistor thin film 4 of this embodiment is formed by patterning the upper surface of the SiO ₂ layer 2 in a substantially square shape in a plan view by a sputtering method, and thereafter annealed for a predetermined time.

  The molar ratio of Mn to Co is suitably about 4: 6. When Fe is included, the molar ratio of Mn: Co: Fe is (20-60) :( 2-65) :( 9-40) is appropriate. The thermistor thin film 4 has the properties of a semiconductor, and has a negative characteristic in which resistance decreases as the temperature rises, that is, a so-called NTC thermistor (Negative Temperature Coefficient Thermistor) property.

The inner bonding layer 5a and the upper bonding layer 9a are respectively formed on the SiO ₂ layer 2 and the protective film 6 with a metal material other than the noble metal (for example, Cr, Ti, or an alloy thereof). The internal bonding layer 5a and the upper bonding layer 9a are the underlayers of the internal conductive layer 5b and the upper conductive layer 9b on the SiO ₂ layer 2 and the protective film 6, respectively. The bonding strength between the _second layer 2 and the protective film 6) is made of a metal material higher than the noble metal material of the inner conductive layer 5b and the upper conductive layer 9b.

The inner conductive layer 5b and the upper conductive layer 9b are formed in the same pattern on the inner bonding layer 5a and the upper conductive layer 9b with a noble metal material (for example, Au, Pt, etc.).
The internal bonding layer 5a and the internal conductive layer 5b are formed in the same pattern in a comb shape.
The protective film 6 is, for example, a SiO ₂ film or SiN ₄ membrane. However, the present invention is not limited to this, and a film made of glass, heat-resistant resin, or the like may be used as long as it is insulating and can block the external atmosphere.

  Next, a method for manufacturing the thin film thermistor 1 configured as described above will be described with reference to FIGS.

First, as shown in FIG. 3A, the SiO ₂ layer 2 having the above thickness is formed on the surface of the silicon substrate 3 by thermal oxidation. Next, as shown in FIG. 3B, a thin film forming step is performed for patterning the thermistor thin film 4 on the upper surface of the SiO ₂ layer 2. That is, the above-described composite metal oxide film is formed on the entire surface of the SiO ₂ layer 2 by a sputtering method under predetermined sputtering conditions. In the thermistor thin film 4 of the present embodiment, a thin film having a spinel structure of (Mn _0.4 Co _0.6 ) ₃ O ₄ was formed with a layer thickness of 200 nm.

Subsequently, a photoresist film is patterned on the upper surface of the composite metal oxide film on the region where the thermistor thin film 4 is formed by photolithography. Then, the unmasked composite metal oxide film is selectively removed by wet etching using a predetermined solution (such as dilute hydrochloric acid solution) using the photoresist film as a mask. Then, the photoresist film used as the mask is removed. Thereby, the thermistor thin film 4 whose outer shape is substantially square in a plan view can be patterned on the upper surface of the SiO ₂ layer 2.
Thereafter, annealing treatment is performed for a predetermined time in the range of 300 ° C. to 900 ° C., more preferably in the range of 600 ° C. to 900 ° C. in order to improve heat resistance. For example, annealing is performed at 600 ° C. for 1 hour. Thereby, the thermistor thin film 4 with high reliability of resistance value and B constant is obtained.

Next, a thin film upper electrode forming step is performed in which a pair of internal bonding layers 5 a and internal conductive layers 5 b are formed on the upper surface of the thermistor thin film 4 to form thin film upper electrodes 5. First, a photoresist film is formed on the entire surface of the thermistor thin film 4 and the entire surface of the SiO ₂ layer 2, and patterning is performed by partially removing the photoresist film in a region to be the internal bonding layer 5 a.

  Then, Cr that forms the internal bonding layer 5a is formed on the entire surface by sputtering. For example, a Cr thin film having a layer thickness of 10 nm is formed as the internal bonding layer 5a. Further thereon, Au is formed as an internal conductive layer 5b by sputtering. For example, an Au thin film having a layer thickness of 190 nm is formed as the internal conductive layer 5b. Next, the Cr thin film and the Au thin film on the photoresist film 12 are removed by using a lift-off method, and the internal bonding layer 5a and the internal conductive layer 5b are formed in a predetermined pattern (comb-like shape) as shown in FIG. Pattern).

Next, as shown in FIG. 3D, a protective film forming step for forming a protective film 6 for sealing the thermistor thin film 4, the internal bonding layer 5a and the internal conductive layer 5b inside is performed. That is, a SiO ₂ thin film is formed on the entire surface by sputtering, for example, with a layer thickness of 600 nm.
Thereafter, as shown in FIG. 4 (a), a through hole H is formed in the protective film 6, and as shown in FIG. 4 (b), the conductive material reaches the thin film upper electrode 5 on the inner surface of the through hole H. A through-hole forming step for forming the film 7 to form the through-hole 8 is performed. That is, a photoresist film is patterned on the protective film 6, and through holes H are formed in the protective film 6 on the internal conductive layer 5b by wet etching using hydrofluoric acid using the photoresist film as a mask. Further, as shown in FIG. 4B, a conductive film 7 is formed on the inner surface of the through hole H by sputtering or the like using Au, Pt, or the like, thereby forming a through hole 8 that is electrically connected to the thin film upper electrode 5.

  Next, as shown in FIG. 4C, an upper lead electrode forming step is performed in which an upper lead electrode 9 having one end connected to the through hole 8 is formed on the protective film 6. That is, a photoresist film 12 is patterned on the protective film 6, and after that, for example, a Cr thin film having a thickness of 10 nm and an Au thin film having a thickness of 200 nm are formed in this order by sputtering, and then unnecessary using a lift-off method. The Cr thin film and the Au thin film are removed, and the upper bonding layer 9a and the upper conductive layer 9b are patterned to form the upper lead electrode 9.

  Further, a resistance value adjustment process for finely adjusting the resistance value is performed. That is, as shown in FIG. 2, trimming is performed to locally remove the upper bonding layer 9a and the upper conductive layer 9b by irradiating a part of the lead portion 11 of the upper lead electrode 9 with YAG laser light L as shown in FIG. At this time, the resistance value is measured by bringing the tip of the resistance value measuring probe into contact with the pad portion 10 while trimming, and when the desired resistance value is reached, the trimming is finished. Note that the power of the YAG laser light L is, for example, about 0.8 W, and the Q rate is about 2 kHz.

By the above process, a large number of thin film thermistors 1 are formed on one substrate, and the thin film thermistors 1 are formed by cutting the substrate.
The resistance value adjusting step may be performed after the thin film thermistor 1 of one chip is cut.

  Thus, in this embodiment, the resistance value is adjusted by removing a part of the upper lead electrode 9 on the protective film 6 connected to the thin film upper electrode 5 through the through hole 8 penetrating the protective film 6. Therefore, since the upper lead electrode 9 to be trimmed is laminated on the protective film 6, the size can be reduced, and the thermistor thin film 4 itself is not trimmed, so that the thermistor thin film 4 itself is not damaged and is being trimmed. The resistance value fluctuation is suppressed and the resistance value is adjusted with high accuracy. In particular, since the lead portion 11 extending narrower than the pad portion 10 is trimmed, the resistance value can be clearly adjusted with a smaller trimming amount than trimming a wide portion.

In addition, since the upper lead electrode 9 is directly trimmed as compared with the case where the internal electrode is trimmed from above the protective film 6, the influence on the protective film 6 can be greatly reduced.
Furthermore, since trimming is performed to remove a part of the upper extraction electrode 9 by irradiating the laser beam L, local removal can be performed with high positional accuracy, and highly accurate resistance value adjustment can be performed. Further, since the upper extraction electrode 9 is directly irradiated with the laser beam L, the output of the laser beam L can be suppressed as compared with the case where the inner electrode is irradiated through the protective film, and the influence on the underlying protective film 6 is reduced. Can be further reduced.

Thus, the thin film thermistor 1 having a high resistance yield can be obtained by the trimming.
Therefore, when the thin film thermistor 1 of this embodiment is used as an infrared detection sensor, for example, it can be suitably used as a small and highly accurate sensor.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

For example, in the above-described embodiment, the case where the silicon substrate 3 having the SiO ₂ layer 2 formed on the surface is used as an example. However, the present invention is not limited to the silicon substrate 3, but other semiconductor substrates or plate-like metals such as Al and Cu. The material may be used. In addition to the semiconductor substrate, an insulating substrate such as an alumina substrate or a quartz substrate may be used. In this case, a thermistor thin film may be formed directly on the upper surface of the insulating substrate.

In the manufacturing process, the thermistor thin film 4 is formed by performing an annealing process after patterning, but conversely, the patterning may be performed after the annealing process is performed after the film formation.
Further, the trimming is performed by irradiating the YAG laser light L, but laser light having other wavelengths (for example, ultraviolet laser light) may be irradiated.

1 is an overall perspective view of a thin film thermistor showing an exploded protective film in an embodiment of a thin film thermistor and a manufacturing method thereof according to the present invention. It is sectional drawing which shows the principal part from a through hole to an upper extraction electrode in the thin film thermistor and its manufacturing method of this embodiment. In the thin film thermistor and its manufacturing method of this embodiment, it is principal part sectional drawing shown in order of a manufacturing process. In the thin film thermistor and its manufacturing method of this embodiment, it is principal part sectional drawing shown in order of a manufacturing process.

Explanation of symbols

1 ... film thermistor, 2 ... SiO ₂ layer (insulating layer), 3 ... silicon substrate (substrate), 4 ... thermistor thin film, 5 ... film on the electrode, 5a ... inner bonding layer, 5b ... inner conductive layer, 6 ... protective film 7 ... conductive film, 8 ... through hole, 9 ... upper lead electrode, 9a ... upper bonding layer, 9b ... upper conductive layer, 10 ... pad part, 11 ... lead part, H ... through hole, L ... laser beam, T ... removal part

Claims (5)

A substrate with an insulating layer formed on the surface or an insulating substrate;
A thermistor thin film patterned on the top surface of the insulating layer or the insulating substrate;
A pair of electrodes on the thin film patterned on the thermistor thin film;
An insulating protective film formed on the upper surface of the insulating layer or the insulating substrate so as to cover the thermistor thin film and the electrode on the thin film;
A pair of through holes in which a conductive film reaching the pair of thin film upper electrodes is formed on the inner surface of the through hole formed in the protective film;
A pair of upper lead electrodes formed on the protective film and connected at one end to the pair of through holes,
A thin film thermistor, wherein a part of the pair of upper lead electrodes is removed to adjust a resistance value. The thin film thermistor according to claim 1,
The pair of upper lead electrodes, a pad portion for electrical connection with the outside;
A thin film comprising: a lead portion connecting the pad portion and the through-hole and extending narrower than the pad portion and partially removed by the resistance value adjustment Thermistor. A thin film forming step of patterning a thermistor thin film on the insulating layer on the substrate or the upper surface of the insulating substrate;
An on-thin film electrode forming step of patterning a pair of thin film upper electrodes on the thermistor thin film;
A protective film forming step of forming an insulating protective film covering the thermistor thin film and the thin film upper electrode on the upper surface of the insulating layer or the insulating substrate;
A through hole forming step of forming a through hole in the protective film and forming a conductive film reaching the pair of thin film upper electrodes on the inner surface thereof to form a pair of through holes;
Forming a pair of upper lead electrodes, one end of which is connected to the pair of through holes, on the protective film;
And a resistance value adjusting step of adjusting a resistance value by removing a part of the upper lead electrode. In the manufacturing method of the thin film thermistor of Claim 3,
In the upper lead electrode forming step, the upper lead electrode has a pad portion for electrical connection with the outside,
The pad portion and the through hole are connected to each other, and the lead portion extends narrower than the pad portion.
A method of manufacturing a thin film thermistor, wherein in the resistance value adjusting step, a part of the lead portion is removed. In the manufacturing method of the thin film thermistor of Claim 3 or 4,
A method of manufacturing a thin film thermistor, wherein, in the resistance adjustment step, a part of the upper extraction electrode is removed by irradiating a laser beam.

Images