JP4110623B2 - Thin film thermistor device and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thin film thermistor device including a plurality of temperature sensing parts and using a semiconductor thin film for each temperature sensing part, and a method for manufacturing the same.
[0002]
[Prior art]
In recent years, development of infrared detection elements that can measure temperature in a non-contact manner has become active. In particular, it is known that a thermistor-type infrared detection element can obtain a high DC output and is suitable for miniaturization and high integration, and thermistors are widely used as temperature sensors for various devices. By the way, in order to detect the weak infrared rays radiated from the detection target with high accuracy, the infrared detection element is generally provided with at least two temperature sensing units, that is, an infrared detection unit and a temperature compensation unit. . Here, the temperature sensitive part of the small thermistor type infrared detecting element is formed of a polycrystalline material such as polycrystalline silicon. In thermistor-type infrared detection element, in order to increase the thermal response (to reduce the thermal time constant), it is desired to reduce the thermal capacity of the element, and the film thickness of the temperature sensitive part Is set to 0.1 μm to 1 μm.
[0003]
In addition, an infrared image sensor in which a number of thermistors are two-dimensionally arranged to detect the temperature distribution has been proposed. When this type of infrared image sensor is used, the temperature distribution can be handled in the same way as image information. become.
[0004]
A small thermistor element used for an infrared image sensor or the like cannot be manufactured by a conventional method of sintering a metal oxide, so a semiconductor thin film made of polycrystalline silicon is formed on a substrate by a CVD method, It is considered that this semiconductor thin film functions as a temperature sensitive part. Here, after the polycrystalline silicon is deposited at 600 ° C. or higher by a low pressure CVD method or the like, the dopant is activated by implanting the dopant with an ion implantation apparatus and further annealing at 1000 ° C. or higher.
[0005]
[Problems to be solved by the invention]
By the way, in the above-described infrared detection element, if the sensitivity (B constant) of the thermistor varies between the infrared detection unit and the temperature compensation unit, that is, if there is variation in sensitivity between the temperature sensing units, the compensation accuracy of the environmental temperature is increased. There is a problem that the temperature is lowered, and in the infrared image sensor, each temperature sensing part constitutes each pixel, and thus there is a problem that variations in sensitivity between the temperature sensing parts cause image noise.
[0006]
On the other hand, in each of the above conventional configurations, the temperature sensitive portion is made of polycrystalline silicon, but as described above, it is deposited at 600 ° C. or higher by the low pressure CVD method or the like, and the dopant is implanted by an ion implantation apparatus and annealed at 1000 ° C. or higher. The formed polycrystalline silicon is composed of crystal grains having a grain size of 1 μm to 3 μm, and crystal grains of various sizes gather to form a semiconductor thin film.
[0007]
Therefore, when the film thickness of the temperature sensitive part is reduced, crystal grains 8a larger than the film thickness of the temperature sensitive part 8 are present in a large number of crystal grains 8a constituting the temperature sensitive part 8 as shown in FIG. In other words, the ratio of the crystal grain boundary 8b in the element area of each temperature sensitive portion 8 varies depending on the position where the crystal grains 8a larger than the film thickness exist and the number thereof, and the sensitivity varies. It is necessary to separately provide a correction means for controlling the ambient temperature of the infrared image sensor to be substantially constant, which causes a problem that the apparatus becomes complicated, becomes larger, and becomes expensive.
[0008]
The present invention has been made in view of the above reasons, and an object of the present invention is to provide a low-cost thin film thermistor device with small variations in sensitivity among a plurality of temperature sensing parts and a method for manufacturing the same.
[0009]
[Means for Solving the Problems]
The invention of claim 1, in order to achieve the above object, a thin film thermistor equipment manufacturing method using the semiconductive thin film of polycrystalline silicon for each temperature sensing unit comprises a plurality of temperature sensing portion, The semiconductor thin film is formed by a low pressure CVD method at a film formation temperature of 600 ° C. to 650 ° C., and doping is performed at the time of the film formation. can be formed of a semiconductor thin film made of small polysilicon diameter, moreover, by performing doping during deposition, ion implantation, ion implantation and subsequent annealing process, such as in the prior art becomes unnecessary, semiconductors Compared to conventional thin film thermistor devices using polycrystalline silicon that contains crystal grains with a grain size larger than the thickness of the semiconductor thin film as a thin film , the sensitivity variation between temperature sensing parts is different. Small crack It is possible to provide a low-cost thin-film thermistor device.
[0012]
The invention of claim 2 is a thin film thermistor device having a plurality of temperature sensing parts and using a semiconductor thin film for each temperature sensing part, wherein each semiconductor thin film is made of amorphous silicon or amorphous SiC. Compared with the case where polycrystalline silicon is used for each semiconductor thin film, it is possible to reduce the variation in sensitivity between the temperature sensitive parts, and it is not necessary to provide a separate correction means as in the past, so the cost is reduced. Can be achieved. Further, the temperature sensitive part can be formed at a film formation temperature lower than the film formation temperature of polycrystalline silicon .
[0015]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
The thin film thermistor device of the present embodiment is an infrared image sensor, and a plurality of thin film thermistors 10 are two-dimensionally arranged on a support substrate 1 made of a single crystal silicon substrate as shown in FIG. Is connected to _two wirings L ₁ and L ₂ via a switching element S made of a MOS transistor as shown in FIG. In order to read the change in resistance value of the thin film thermistor 10, it is only necessary to apply a voltage to the wiring L ₁ to turn on the switching element S and read out the wiring L ₂ .
[0016]
The configuration of each thin film thermistor 10 be the same, as shown in FIG. 2, thin film 4 consisting of a S ₃ N ₄ film 2 on the supporting substrate 1 the S ₃ N ₄ film 2 on the SiO ₂ film 3 which Formed on top. Here, the thin film portion 4 is formed by providing a recess 6 in the support substrate 1 from the back side of the support substrate 1. The thin film thermistor 10 includes a lower electrode 11 a made of a chromium (Cr) film formed on the thin film portion 4, a temperature sensing portion 8 made of a polycrystalline silicon thin film formed on the lower electrode 11 a, and the temperature sensing portion 8. And an upper electrode 11b made of a Cr film. A SiON film 12 is formed on the thin film thermistor 10.
[0017]
Hereinafter, a method for manufacturing the thin film thermistor 10 will be described.
[0018]
First, after forming a Si ₃ N ₄ film on each of the main surface and the back surface of the support substrate 1 and subsequently forming a SiO ₂ film, the recess 6 is formed using a photolithography technique and an etching technique. Thereafter, a Cr film is formed on the entire surface of the SiO ₂ film 3 on the main surface side of the support substrate 1 by a vapor deposition apparatus (for example, an EB vapor deposition apparatus) or the like, and a lower portion made of a Cr film having a predetermined shape by a photolithography technique and an etching technique. The electrode 11a is formed. Next, a semiconductor thin film made of polycrystalline silicon is formed so as to cover the entire surface on the main surface side by low pressure CVD, and unnecessary portions of the semiconductor thin film (polycrystalline silicon) are removed by photolithography technique and etching technique. After forming the temperature sensing portion 8, a Cr film is formed so as to cover the entire main surface side of the support substrate 1, and an upper electrode 11b made of a Cr film having a predetermined shape is formed by a photolithography technique and an etching technique. Thereafter, a SiON film 12 is formed so as to cover the entire main surface side of the support substrate 1, and unnecessary portions of the SiON film 12 are removed by a photolithography technique and an etching technique. In the present embodiment, the element size of each temperature sensing unit 8 is 50 μm × 50 μm.
[0019]
By the way, in the present embodiment, the polycrystalline silicon constituting the temperature sensing portion 8 is formed by the low pressure CVD method in which the film formation temperature is 600 ° C. to 650 ° C. As other film formation conditions, the pressure is 0.2 Torr to 1 Torr, and 100% to 20% (N ₂ diluted) SiH ₄ is used as the source gas. Further, in the present embodiment, the conventional ion implantation process and the annealing process after ion implantation are unnecessary by performing doping at the time of film formation. The crystal grain size of the temperature sensing portion 8 formed under the above conditions is 0.03 μm to 0.3 μm. For example, when the film formation temperature is 630 ° C., the crystal grain size is 0.1 μm. Thus, there is little local variation in particle size, and a film with good film uniformity can be obtained as compared with a film forming temperature of 700 ° C.
[0020]
In short, as shown in FIG. 1, the present embodiment is characterized in that each temperature sensing portion 8 is made of polycrystalline silicon composed of crystal grains 8a having a smaller particle size than the thickness of the temperature sensing portion 8. is there. Thus, in the present embodiment, as compared with the conventional case where polycrystalline silicon that includes crystal grains 8a having a grain size larger than the film thickness of the temperature sensing portion 8 is used as the temperature sensing portion 8. The ratio of the crystal grain boundaries 8b to the element area of the temperature sensitive part 8 is substantially constant in all the temperature sensitive parts 8, and the ratio of carriers trapped at the crystal grain boundaries 8b is substantially constant between the temperature sensitive parts 8. Therefore, even if the film thickness of the temperature sensing portion 8 is 1 μm or less, the sensitivity variation among the plurality of temperature sensing portions 8 can be reduced, and there is no need to separately provide a correction means as in the prior art. Can be achieved. In addition, as shown in FIG. 5, by arranging the grain sizes of the crystal grains 8 a, the variation in the average grain size of the crystal grains of each temperature sensing unit 8 can be reduced, and the sensitivity variation among the temperature sensing units 8. Can be further reduced. Note that the sensitivity variation between the temperature sensing parts 8 and the temperature resolution have a relationship as shown in FIG. 6, and if the sensitivity variation increases, the temperature resolution deteriorates. It is desirable to reduce the variation in the average grain size of the crystal grains of the temperature sensitive portion 8.
[0021]
In the present embodiment, doping is performed when the temperature-sensitive portion 8 is formed by the low pressure CVD method. However, ion implantation may be performed after the film formation, and in this case, the grain size of the crystal grains 8a is What is necessary is just to determine annealing conditions so that it may become smaller than the film thickness of the temperature sensing part 8 (it should just make annealing temperature low).
[0022]
(Embodiment 2)
The basic configuration of the thin film thermistor device of the present embodiment is substantially the same as that of the first embodiment, and is different in that the semiconductor thin film constituting the temperature sensing unit 8 is amorphous.
[0023]
Therefore, in this embodiment, since the semiconductor thin film which comprises each temperature sensing part 8 is amorphous, there is no crystal grain like a polycrystal and compared with the case where a polycrystal is used for each semiconductor thin film. The variation in sensitivity between the units 8 can be reduced, and it is not necessary to separately provide a correction means as in the prior art, so that the cost can be reduced.
[0024]
In order to form the semiconductor thin film constituting the temperature sensitive portion 8, the mixed gas of SiH ₄ and H ₂ may be decomposed by glow discharge by the plasma CVD method. Therefore, the film forming temperature of the temperature sensing portion 8 can be 350 ° C. or lower, and the temperature sensing portion 8 can be formed with lower energy than in the conventional example or the first embodiment. That is, the film forming temperature can be lowered as compared with the low pressure CVD method, and an ion implantation process or an annealing process is not required.
[0025]
Alternatively, an amorphous compound such as amorphous SiC (hereinafter referred to as a-SiC) may be formed as the temperature sensing portion 8 by mixing a gas such as CH ₄ into the source gas. In order to form a p-type a-SiC: H thin film, a mixed gas of monosilane (SiH ₄ ) and methane (CH ₄ ) is used as a source gas, and hydrogen gas (H ₂ is used as a gas for diluting the source gas. ) And diborane (B ₂ H ₆ ) diluted with H ₂ may be used as the dopant gas. As an example of film formation conditions in this case, in the plasma CVD apparatus, the substrate temperature (film formation temperature) is 270 ° C., the pressure is 0.9 Torr, the dilution gas is H ₂ , the flow rate of SiH ₄ is 50 sccm, and the flow rate is CH ₄ . 170 sccm, and B ₂ H ₆ having a concentration of 0.5% diluted with H ₂ may be 200 sccm.
[0026]
(Reference example)
The basic configuration of the thin film thermistor device of the present reference example is substantially the same as that of the first embodiment, except that the semiconductor thin film constituting the temperature sensing portion 8 is microcrystalline silicon in which an amorphous phase and a crystalline phase are mixed.
[0027]
In this reference example, since the temperature sensitive part 8 is a microcrystalline phase in which an amorphous phase and a crystalline phase are mixed, there is no crystal grain boundary, the film uniformity is high, and each temperature sensitive part 8 has polycrystalline silicon. Compared to the conventional example using the temperature sensor, variations in sensitivity between the temperature sensing portions 8 can be reduced, and it is not necessary to separately provide a correction means as in the prior art, so that the cost can be reduced. In addition, the temperature sensitive portion 8 can be formed at a film formation temperature lower than the film formation temperature of polycrystalline silicon. Further, by using microcrystalline silicon for the temperature sensing portion 8, the conductivity can be improved by two orders of magnitude or more compared to the case of using amorphous silicon.
[0028]
By the way, the mobility of the amorphous phase is about two orders of magnitude lower than that of the crystalline phase, and the various characteristics of the microcrystalline phase are determined by the volume ratio of the amorphous phase to the crystalline phase. By making it constant, the variation in sensitivity between the temperature sensing parts 8 can be further reduced.
[0029]
As for the conditions for forming microcrystalline silicon, FIG. 7 shows an example in which the SiH ₄ gas / H ₂ gas flow ratio and the high-frequency power are changed. FIG. 7 is May 1994 from Baifukan Co., Ltd. This is described on page 95 of “Amorphous Semiconductor” issued on the 20th. The substrate temperature is 350 ° C. and the pressure is 50 mTorr. In FIG. 7, the diameter of the open 3/4 circle represents the average grain size of the microcrystal grains contained in the produced film, and the area of the black 1/4 circle represents the volume fraction of the microcrystal. Represents. In the lower left of FIG. 7, the case of a particle size of 10 nm and a volume fraction of 100% is shown. In FIG. 7, A represents “amorphous”, which indicates that the film produced under this plasma condition was amorphous. That is, the film produced under the plasma conditions in the range surrounded by A in FIG. 7 is μc-Si: H. In order to form microcrystalline silicon, it is only necessary to increase the hydrogen dilution rate, lower the high-frequency power density, or increase the film formation temperature than the film formation conditions for amorphous silicon.
[0030]
In each of the above embodiments form state and the reference example, a thin film thermistor device has been described infrared image sensor, is not limited to the infrared image sensor, it is sufficient that comprises a plurality of temperature sensing portion, for example, The infrared detection element provided with two temperature sensing parts, such as an infrared detection part and a temperature compensation part as described in the conventional example, may be used.
[0031]
【The invention's effect】
The invention according to claim 1, a thin film thermistor equipment manufacturing method using the semiconductive thin film of polycrystalline silicon in the temperature sensitive portion comprises a plurality of temperature sensing portion, 600 deposition temperature semiconductor thin film The film is formed by a low pressure CVD method at a temperature of 650 ° C. to 650 ° C., and doping is performed at the time of film formation, and each temperature-sensitive portion is made of polycrystalline silicon having a crystal grain size smaller than the film thickness. can be formed of a semiconductor thin film, moreover, by performing doping during deposition, as in the prior art ion implantation steps and ion implantation after the annealing step is not required, the conventional semiconductor thin film as a semiconductor thin film large particle size as compared grains in the thin film thermistor device using the polycrystalline silicon, such as including a plurality of sensitivity between the temperature sensing portion Baratsu outs small, low-cost thin film thermistor than the thickness of the It is possible to provide a location.
[0034]
The invention of claim 2 is a thin film thermistor device having a plurality of temperature sensing parts and using a semiconductor thin film for each temperature sensing part, and each semiconductor thin film is made of amorphous silicon or amorphous SiC. Compared to the case of using polycrystalline silicon, it is possible to reduce the variation in sensitivity between the temperature sensing parts, and it is not necessary to separately provide a correction means as in the prior art, so that the cost can be reduced. There is. Further, there is an effect that the temperature sensitive part can be formed at a film forming temperature lower than the film forming temperature of the polycrystalline silicon .
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a main part of a first embodiment.
FIG. 2 is a cross-sectional view of the thin film thermistor of the above.
FIG. 3 is a schematic configuration diagram of the above.
4 is an explanatory diagram of a main part of FIG. 3;
FIG. 5 is an explanatory diagram of a main part of the above.
FIG. 6 is a diagram illustrating the relationship between sensitivity variation and temperature resolution.
FIG. 7 is an explanatory diagram of film formation conditions for microcrystalline silicon.
FIG. 8 is an explanatory diagram of a main part of a conventional example.
[Explanation of symbols]
8 Temperature Sensitive Section 8a Crystal Grain 8b Grain Boundary

Claims (2)

A plurality of temperature sensing portion comprises manufacturing method of a thin film thermistor equipment using semiconductive thin film of polycrystalline silicon in the temperature sensing portion, the semiconductor thin film was to not 600 ° C. The deposition temperature 650 ° C. under reduced pressure was deposited by a CVD method, and a thin film thermistor equipment manufacturing method which is characterized in that the doping during the deposition. To each temperature sensing unit comprises a plurality of temperature sensing portion A thin film thermistor device using a semiconductor thin film, the semiconductor thin film, the thin film thermistor device you characterized by consisting of amorphous silicon or amorphous SiC.

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