JP3162097B2 - Thermal infrared sensor and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal infrared sensor for measuring the temperature of an object to be measured in a non-contact manner and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, various techniques have been developed for producing a thermal infrared sensor suitable for use in a non-contact thermometer or the like by utilizing a semiconductor fine processing technique. The thermal infrared sensor has a structure in which a bridge portion is formed on a support substrate, and a temperature sensitive portion is further formed on the bridge portion. That is, an infrared ray is received by the temperature sensing section, and a temperature rise due to the infrared ray is measured by a change in electric resistance to know an infrared ray amount (heat amount).

In this thermal infrared sensor, the temperature sensitive portion has a small heat capacity with respect to a minute amount of infrared rays, and the smaller the amount of heat transmitted from the temperature sensitive portion to the outside, the greater the temperature rise and the higher the response sensitivity. For this reason, in general,
The thermal capacity is reduced by making the temperature sensitive portion a small cross-linked structure or a thin diaphragm structure, thereby improving the sensitivity. The temperature-sensitive portion is composed of a temperature-sensitive film formed on the bridge portion, an electrode formed on the sensitive film, and wiring from the electrode to the bonding pad. Here, not only the temperature sensitive part, but also the electrodes and wiring contribute to heat capacity and heat transfer,
These also need to be contrived to make them as small, fine and thin as possible.

Conventionally, the electrodes and wirings of the temperature-sensitive film are formed by superposing an electrode on a part of the temperature-sensitive film and superposing a wiring on a part of the electrode to make electrical contact. I have.

[0005]

However, when the electrode and the wiring are superimposed on the temperature-sensitive film as described above,
Steps of unevenness were generated in the portion, and the electrode and the wiring were apt to be disconnected, and the product yield was poor.

In general, metal is used for the electrode and the wiring. However, in the overlapping portion between the temperature-sensitive film and the electrode, and between the electrode and the wiring, physical shape defects such as disconnection do not occur. Must be in an electrically ideal contact (ohmic contact) state. However, since a high-resistance semiconductor is more sensitive to a temperature-sensitive film, it is difficult to form an ohmic contact with a conventional metal electrode using a high-resistance temperature-sensitive film. further,
Metals for electrodes that can make electrical ideal contact are generally
It is easy to penetrate deep into this sensitive film by making an alloy with the temperature sensitive film, so the dimensions between the electrodes are not as designed,
This also caused a variation in the resistance value.

The present invention has been made in view of the above-mentioned problems, and can prevent the occurrence of disconnection between a temperature-sensitive film and an electrode, eliminate contact failure at the interface, and reduce the dimension between the electrodes. It is an object of the present invention to provide a thermal infrared sensor capable of improving the yield of products as designed, and a method of manufacturing the same.

[0008]

SUMMARY OF THE INVENTION A thermal infrared sensor according to the present invention comprises a support formed of a semiconductor material, an electrically insulating bridge formed on the support, and a bridge formed at the bridge. a temperature-sensitive film in which the first ion implantation is made across Rutotomoni, Rutoto formed in the temperature-sensitive in the film
In addition, an electrode portion composed of a high-concentration impurity region formed by the second ion implantation of the same conductivity type as the first ion implantation region, and a wiring directly taken out from the electrode portion and passing over the bridge portion are formed. Have.

In the thermal infrared sensor according to the present invention, a high-concentration impurity region is formed in the temperature-sensitive film and this is used as the electrode portion. Therefore, a step between the conventional electrode portion and the temperature-sensitive film is reduced. Disappears. Therefore, the wiring portion whose resistance has been reduced by the addition of the high-concentration impurities can be directly taken out of the temperature-sensitive film, so that step disconnection can be reduced and the wiring can be taken out in a region shifted from the high-resistance temperature-sensitive film. The electrode spacing (dimension of the high resistance region) can be specified with high accuracy. In addition, the problem of poor contact at the interface between the temperature-sensitive film and the electrode portion is also solved, making it easy to make ohmic contact, improving response sensitivity and improving product yield. In the case where an electrode made of a metal such as aluminum is formed, a process such as etching is not required, but such a process is simplified. Further, conventionally, for example, when an aluminum electrode was formed on a temperature-sensitive film, the infrared rays incident at that portion were reflected and the sensitivity was reduced accordingly, but the present invention eliminates the need for a metal electrode. Such a fear disappears. In addition, since the metal electrode is not required, the heat capacity of the sensitive part is reduced accordingly, and the sensitivity is improved.

The impurities previously implanted into the entire temperature-sensitive film are as follows:
This is for compensating the film itself to be close to the intrinsic semiconductor and for imparting conductivity for adjusting the resistance value. When this film is formed to be p-type, the impurity region of the electrode portion is also changed to p-type. A high concentration p ⁺ -type region is formed by using impurities. On the other hand, when the impurity implanted in advance is formed to be n-type with arsenic (As) or the like, the impurity region of the electrode portion is also formed of an n-type impurity to be a high-concentration n ⁺ -type region.

The wiring connected to the electrode portion in the temperature-sensitive film may be either a p ⁺ type or an n ⁺ type impurity region of the electrode portion.
If aluminum (Al), titanium (Ti), or the like is selected and sintering is performed, the contact with the p ⁺ -type and n ⁺ -type regions becomes ohmic contact, and the contact state is improved.

Further, in the method of manufacturing a thermal infrared sensor according to the present invention, a first ion implantation step of implanting ions into the entire temperature-sensitive film formed on the cross-linking portion, during said sensitive film by ion implantation of an ion implantation region of the same conductivity type, through a second ion implantation step of forming a high-concentration impurity regions serving as the electrode portion, the bridge portion wirings
Directly from the temperature-sensitive film .

In the method of manufacturing a thermal infrared sensor according to the present invention, it is easy to adapt to the process of forming a temperature-sensitive film, which is desirably minute and as thin as possible. In other words, the impedance of the temperature-sensitive film is designed by the width and distance of the electrode part due to the restriction of electrical measurement. However, the patterning accuracy of the electrode part such as photolithography and etching and diffusion and alloying by heat treatment (sintering, etc.) Causes a manufacturing error. The ion implantation method has a relatively small lateral diffusion and diffusion depth as compared with the thermal diffusion method and can perform diffusion at a low temperature (room temperature), so that such a manufacturing error can be eliminated. In addition, the exact dose of impurities (addition amount)
And the depth of introduction, the controllability of the thermistor constant and the electrical resistance value of the temperature sensitive film is good, the response sensitivity is improved, and the reproducibility of the electrical characteristics is improved.

The conditions for ion implantation into the temperature-sensitive film are as follows. The first ion implantation step is for making the temperature-sensitive film sensitive to the temperature, and adjusts the kind of ions and the dose thereof so as to be as close as possible to an intrinsic semiconductor after the heat treatment. When a subsequent heat treatment is performed without ion implantation, the temperature-sensitive film
If it becomes a mold, it is better to ion-implant an n-type impurity to compensate for this. For example, 1 μm thick silicon (Si)
The thin film is a temperature sensitive film, and the concentration of the actor is 1 × 10 ¹⁶
Pcs / cm ³ , the phosphorus (P) is 1 × 1
If ions are implanted at a dose of 0 ¹³ / cm ^3, a compensated intrinsic semiconductor will be obtained. If ions are implanted slightly more than this dose, an n-type semiconductor will be obtained. Actually, in the case of silicon, since the resistance is too large for a perfect intrinsic semiconductor and is difficult to handle, it is better to adjust the resistance value so that, for example, the intrinsic value becomes a somewhat n-type semiconductor. In the second ion implantation step, the ohmic contact is made with the thermistor part, which is a part (temperature-sensitive part) immediately below the ion implantation mask in the high-resistance temperature-sensitive film formed in the first ion implantation step. This is for forming a high-concentration impurity region to be an electrode portion. In order to obtain an ohmic contact with the thermistor portion, it is necessary to have the same conductivity type. Therefore, as a result of the first ion implantation step, if the thermistor portion is n-type, ions serving as n-type impurities may be implanted. In order to reduce the resistance, a large amount of impurities may be implanted. In the second ion implantation, for example, when the temperature-sensitive film is silicon having a thickness of 1 μm, phosphorus (P) or arsenic (As) is used as an n-type impurity at 1 × 10 ¹⁷ at 280 keV.
The dose may be performed at a dose of pieces / cm ³ . This corresponds to a high impurity concentration of 1 × 10 ²⁰ / cm ³ when the doping efficiency is set to 100% and a uniform distribution is made in the thickness direction by heat treatment. At this time, heat treatment at 1100 ° C. for one hour is sufficient.

The temperature-sensitive film is made of amorphous silicon (a-Si) or amorphous germanium (a-Si).
Ge) can be formed by a sputtering method or a CVD method, and is preferably formed as a thin film having a thickness of 0.5 to 3 μm.

As the substrate, a semiconductor substrate such as silicon or germanium is used, but it is preferable to use a single crystal silicon substrate which can be easily and inexpensively obtained. Further, it is preferable to use a silicon oxynitride (SiOxNy) film as the cross-linking portion. This silicon oxynitride film has the properties of both a silicon oxide film and a silicon nitride film, and therefore has a good stress balance and can form a stable crosslinked structure. The thickness of this silicon oxynitride film is 0.1
It is preferable to set it to 50 μm. If it is less than 0.1 μm, it is too thin to obtain a sufficient strength, while if it is more than 50 μm, the heat capacity becomes large and the sensitivity is lowered. Specifically, the silicon oxynitride film is formed, for example, by a plasma CVD method. In this method, the gas used is monosilane (Si
H _4), nitrogen (N ₂₎ and laughing gas (N ₂ O) is used. Here, the gas flow ratio between N ₂ and N ₂ O (N ₂ / (N
₂ + N ₂ O)), the stoichiometric composition x, y of the silicon oxynitride film can be controlled, and the difference in the coefficient of thermal expansion between the supporting substrate, especially the silicon substrate, can be substantially reduced. Thus, damage due to stress can be prevented.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 2 schematically shows a planar structure of a thermal infrared sensor according to an embodiment of the present invention, and FIG. 1 is a perspective view showing a temperature sensitive portion which is a main portion thereof. In this thermal infrared sensor, for example, a cavity 13 is formed at the center of a silicon substrate 11 serving as a support,
On the surface of the silicon substrate 11, a width of 10
Two crosslinked portions 12 having a thickness of 2 μm, a length of 2 mm, and a thickness of 2 μm
a, silicon oxynitride film 12 having 12a
Are formed. A temperature-sensitive film 14 is formed on the upper part of the center of each of the bridges 12a. This temperature sensitive film 14 is made of, for example, amorphous silicon (a-
Si), and is doped with an impurity such as arsenic (As) to impart conductivity. Further, two electrode portions 15a and 15b are provided in the temperature-sensitive film 14.
Are formed facing each other. These electrode parts 15
a and 15b are formed of, for example, high concentration impurity regions of arsenic. One end of a wiring 16 is connected to each of the electrode portions 15a and 15b.
The other end of 6 is connected to bonding pads 17 at both ends of bridge 12a. These wirings 16 are formed of, for example, aluminum (Al).

In this thermal infrared sensor, the electric resistance of the temperature-sensitive film 14 changes in accordance with the amount of incident infrared light (the amount of heat), and the electrode portion 15 changes in accordance with the change in the resistance.
The amount of infrared rays can be detected by measuring a current value flowing through a, 15b and the wiring 16 or a voltage value between the bonding pads 17 by a signal processing circuit (not shown).

FIGS. 3A to 3D and FIGS.
(G) shows a manufacturing process of the thermal infrared sensor. First, a silicon substrate 11 having a plane orientation (110) as shown in FIG. 3A was prepared. Next, a silicon oxynitride film 12 having a thickness of 2 μm was formed on the silicon substrate 11 by a plasma CVD method as shown in FIG. That is, the silicon substrate 11 was heated to 450 ° C., the pressure was set to 0.45 torr, the high-frequency output was set to 400 W, and the reaction gas was monosilane (SiH).
₄ ) was flowed at 15 SCCM, nitrogen (N ₂ ) at 203 SCCM, and laughing gas (N ₂ O) at 32 SCCM, and silicon oxynitride was vapor-phase grown on the silicon substrate 11.

Subsequently, sputtering was performed using silicon as a target to form a temperature-sensitive film 14 made of amorphous silicon (a-Si) on the silicon oxynitride film 12, as shown in FIG. In this sputtering, the gas flow rate was set to argon (Ar) = 2 SCC
M, hydrogen (H ₂ ) = 1 SCCM, deposition pressure 3 × 10 ⁻³ Tor
r, The high frequency pressure was set to 200 W for 10 minutes.

Next, as a first ion implantation step, for example, phosphorus (P) 19 is added to the temperature-sensitive film 14 at 1 × 10 ^13.
Ions / cm ^{3 at} a dose of
Heat treatment was performed at a temperature of 0 ° C. for 1 hour.

Subsequently, as shown in FIG. 3D, the temperature sensitive film 14 was patterned by reactive ion etching (RIE).

Next, as shown in FIG. 4E, patterning is carried out with a photoresist 18, and phosphorus (P) 20, which is the same ion species as in the first ion implantation, is 1 × 10 ¹⁷ / c.
The second ion implantation is performed at a dose of m ³ , and the electrode portions 15 a and 15 b made of high-concentration impurity regions are formed in the temperature-sensitive film 14.
Was formed.

Thereafter, the photoresist 18 was removed, and a wiring 16 of an aluminum thin film was formed so that one end was connected to each of the electrodes 15a and 15b, as shown in FIG.

Next, in order to protect the temperature-sensitive film 14 and the wiring 16 from an aqueous hydrazine solution described later, FIG.
A silicon oxynitride film 21 was formed as shown in FIG.

Next, the silicon oxynitride film 1
Patterns 2 and 21 were formed to form the pattern of the crosslinked portions 12a and 12a as shown in FIG. This patterning was performed by, for example, reactive ion etching (RIE) until the underlying silicon substrate 11 was exposed.
In this etching, methane trifluoride (CHF ₃ ), Freon 14 (CF ₄ ) and oxygen (O ₂ ) are used as etching gases.
And the flow rate was CHF ₃ = 30 SCCM, CF ₄ = 8 SC
CM, O ₂ = ₂ SCCM, pressure during etching is 0.08
Torr, high frequency output 300W, etching time 4
0 minutes. Finally, the silicon substrate 11 below the bridge portions 12a, 12a is selectively etched away to remove the hollow portion 1a.
3 was formed. This etching was performed by anisotropic etching using a hydrazine aqueous solution. The anisotropic etching may be performed using an aqueous solution of potassium hydroxide.

As described above, in this embodiment, the high-concentration impurity region is formed in the temperature-sensitive film
5a and 15b, and the wiring 16 is directly taken out of the temperature-sensitive film 14.
a, 15b and the step between the temperature sensitive film 14 are eliminated,
The occurrence of disconnection is reduced. At the same time, the problem of poor contact at the interface between the temperature-sensitive film 14 and the electrode portions 15a and 15b is also resolved, making it easier to make ohmic contact, improving response sensitivity and improving product yield. it can.

In this embodiment, the temperature sensitive film 1
Since the ion implantation method is used, which has a relatively small diffusion depth as compared with the thermal diffusion method, when introducing the impurity into 4, the impurity can be diffused at a low temperature. Therefore, it is easy to adapt to the process of forming the temperature-sensitive portion having a minute and thin cross-linking structure, and the dose amount and the introduction depth of the impurity can be accurately set. Therefore, the controllability of the thermistor constant and the electric resistance value is improved, the response sensitivity is improved, and the reproducibility of the electric characteristics is improved.

The present invention has been described with reference to the embodiments.
The present invention is not limited to the above embodiment, but can be variously modified without changing the gist of the invention. For example, in the above embodiment, the ion implantation into the temperature-sensitive film 14 is performed, and then the anisotropic etching is performed to form the crosslinked portion 12a. However, the ion implantation is performed after the crosslinked portion 12a is formed. It may be. Further, in the above embodiment, the second ion implantation for forming the electrode is performed after the first ion implantation step. However, after the electrode portion is formed first, ions are further implanted and the temperature sensitive portion is formed. Needless to say, it is possible to form
The above embodiment is more advantageous.

[0031]

As described above, according to the thermal infrared sensor according to the first aspect, the high concentration impurity region is formed in the temperature sensitive film and this is used as the electrode portion. The step between the film and the temperature-sensitive film is eliminated, and the disconnection of the step is reduced. In addition, the problem of poor contact at the interface between the temperature-sensitive film and the electrode portion is also solved, making it easy to make ohmic contact, improving response sensitivity and improving product yield.

Further, according to the manufacturing method of the thermal-type infrared sensor according to claim 2, wherein, in the step of forming the step and the electrode portions to introduce a pre-impurities to a temperature-sensitive film, the diffusion depth as compared to the thermal diffusion method Since a relatively small amount of ion implantation is used, the manufacturing process is simplified, diffusion can be performed at a low temperature, controllability of the thermistor constant and electric resistance value is improved, and response sensitivity is improved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a temperature sensing unit of a thermal infrared sensor according to one embodiment of the present invention.

FIG. 2 is a plan view showing an overall configuration of a thermal infrared sensor according to one embodiment of the present invention.

3 (a) to 3 (d) are longitudinal sectional views showing manufacturing steps of the thermal infrared sensor along the line AA in FIG. 2, respectively.

4 (e) to 4 (g) are longitudinal sectional views each showing a manufacturing process of the thermal infrared sensor along the line AA in FIG. 2;

[Explanation of symbols]

 11 silicon substrate 12 silicon oxynitride film 12a bridging part 13 cavity part 14 temperature sensitive film 15a, 15b electrode (high concentration impurity region) 16 wiring

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-53-42580 (JP, A) JP-A-50-113278 (JP, A) JP-A-3-41330 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01L 37/02 G01J 1/02 G01J 5/02

Claims (2)

(57) [Claims] 1. A support formed of a semiconductor material, an electrically insulating bridge formed on the support, and a temperature at which the first ion implantation is performed on the bridge and entirely. and the sensitive film, the temperature-sensitive film is formed in the Rutotomoni, an electrode portion made of the high concentration impurity region formed by the second ion implantation of the first ion implantation region of the same conductivity type, directly from the electrode portion A thermal infrared sensor comprising: a wiring that is taken out and passes over the bridge portion. 2. The method for manufacturing a thermal infrared sensor according to claim 1, wherein a first ion implantation step of performing ion implantation on the entire temperature-sensitive film formed on the bridge portion; A second ion implantation step of performing ion implantation of the same conductivity type as that of the ion implantation region in the ion-implanted temperature-sensitive film to form a high-concentration impurity region serving as an electrode portion; A step of directly extracting the infrared ray from the temperature-sensitive film.