JP3135727B2 - Method of forming pad portion of infrared sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a pad portion in a process of manufacturing an infrared sensor for detecting infrared rays by using a change in resistance value with temperature.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventional infrared sensor. A heat insulating film 2 is formed on a substrate 1, and a detection unit 3 is formed thereon. The substrate 1 has a hollow portion below the portion corresponding to the central portion of the detection unit 3, thereby further improving the thermal insulation of the detection unit 3. The heat insulating film 2 is usually composed of a multilayer film in which SiO ₂ layers and Si ₃ N ₄ layers are alternately formed, and at least a part of the surface layer (top layer) is made of Si.
It consists of an O ₂ layer 21. The detection unit 3 is formed by laminating an infrared absorption layer on a thin film thermistor. This thin-film thermistor has a sandwich structure in which a resistor layer 31 made of an amorphous alloy such as amorphous silicon carbide or the like whose resistance value changes according to a temperature change is sandwiched between electrodes 32 and 33 such as Cr from above and below. On this thin-film thermistor, an SiO ₂ film 34 serving as an infrared absorbing layer is formed by lamination. On the left side of the figure, a pad portion 4 is formed on a heat insulating film whose surface layer is an SiO ₂ layer 21.

In forming the pad portion 4, a conductor layer serving as the electrode 32 is formed on the SiO ₂ layer 21 and then formed.
An SiO ₂ film 34 serving as an infrared absorbing layer is formed on the conductor layer, and a portion of the SiO ₂ film 34 above the pad portion 4 is removed by etching to expose a part of the conductor layer serving as the electrode 32. The conductor layer 35 for the pad is formed on the exposed electrode conductor. The conductor layer for the pad is formed of, for example, Al or the like.

[0004]

However, the pad portion 4
In the portion surrounded by the dashed line in the above, there are the following problems. That is, at this time, if a pinhole is formed in the conductor layer because the conductor layer serving as the electrode is thin, etc., when the SiO ₂ film 34 serving as the infrared absorption layer is removed by etching, the etching penetrated from the pinhole occurs. The liquid (etchant, buffered hydrofluoric acid, etc.) is mixed with SiO ₂ under the conductor layer.
As far as the layer 21, this layer 21 is partially eroded.
Therefore, there is a problem that the eroded SiO ₂ layer may be peeled off together with the electrode conductor layer of the pad portion.

Accordingly, an object of the present invention is to provide a method for forming a pad portion in which the above-described peeling of the pad portion does not occur even if the thickness of the conductor layer serving as an electrode is reduced.

[0006]

Means for Solving the Problems] method of forming a pad portion of the infrared sensor according to the present invention, for solving the above problems, a detection portion of the at least some surface layer on the thermal insulating layer of SiO ₂ In manufacturing an infrared sensor formed by laminating a thin film thermistor and an infrared absorption layer,
Wherein forming a conductive layer serving as a thermistor electrode on the SiO ₂ surface layer on, serving as the infrared absorbing layer thereon SiO ₂
After forming the film, the SiO ₂ film is removed by etching to expose a portion serving as a pad portion in the conductor layer, and a conductor layer for a pad is formed on the exposed portion. Before forming a conductor layer made of SiO ₂ , a portion corresponding to the lower side of the pad portion in the SiO ₂ surface layer is removed by etching in advance, and the conductor layer serving as the electrode is made of the SiO ₂ surface layer.
The surface of the SiO ₂ surface layer from inside the etched portion of the layer
It is characterized in that it is formed up to

[0007]

As described above, the Si portion is formed below the portion to be the pad portion.
If there is no O ₂ layer (surface layer of the heat insulating film),
When the SiO ₂ layer (infrared absorbing layer) on the conductor layer serving as an electrode is etched, even if the etching solution reaches the lower side of the pad portion through the pin hole of the conductor layer, the SiO ₂ layer is there. Since there is no erosion, the pad does not peel off.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.
However, the present invention will be described in detail below.
No restrictions are imposed by the examples. First, in FIG.
As shown in (a), thermal insulation deposited on a silicon substrate
SiO in conductive film_TwoWith the lower side of the pad portion of the surface layer (top layer) 21
As shown in FIG. 1 (b), the photolithography
Patterning in the rough process
(Buffered hydrofluoric acid). Then, in FIG.
As shown in (c), when the substrate temperature is room temperature,
The Cr conductor layer, which is to be an electrode by the
_TwoDeposited on the surface layer 21 with a thickness of 1000 Å
Patterning in the photolithographic process
After forming the electrode 32, as shown in FIG.
SiO as infrared absorption layer_TwoGlow discharge decomposition of layer 34
Deposited by the method. Next, as shown in FIG.
And SiO that overlaps the pad_TwoLayer 34
It is patterned and removed by etching in
After exposing the portion of the Cr electrode 32 that will become the pad portion,
As shown in FIG. 1 (f), the state where the substrate temperature was set to room temperature
Then, an electron beam evaporation method is used to form an Al layer (a conductor for pads).
Layer 35 is made of SiO_TwoA film having a thickness of 1 μm on the layer 34;
The pad portion 4 is patterned by a photolithography process.
Formed.

FIG. 2 shows an infrared sensor having a pad formed in this manner. In FIG. 2, the same reference numerals as in FIG. 3 denote the same components as those in the infrared sensor of FIG. Si in pad portion 4
The electrode 32 is formed so as to enter the trace where the O ₂ surface layer 21 is removed.

[0010]

According to the present invention, since the pad does not peel off, the occurrence of defective elements due to the breakage of the pad is suppressed, and the yield of the infrared sensor is improved. Even if the thickness of the conductor layer serving as an electrode is reduced, since the pad portion does not peel off, the electrode can be thinned, and as shown in FIG.
It is also possible to reduce the residual stress of the thin film body when the detecting section 3 has a diaphragm structure.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing each step of a method for forming a pad section according to the present invention.

FIG. 2 is a cross-sectional view of an infrared sensor having a pad formed by the method of the present invention.

FIG. 3 is a sectional view of a conventional infrared sensor.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Thermally insulating film 3 Detecting part 4 Pad part 21 SiO ₂ layer 21 31 Resistor layer 32 Electrode 33 Electrode 34 SiO ₂ film 35 Conductor layer for pad

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takayoshi Awai 1048 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Works, Ltd. 56) References JP-A-2-206733 (JP, A) JP-A-4-215022 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01J 1/02 G01J 5/02 G01J 5/20-5/24 H01L 37/00-37/02

Claims (1)

(57) [Claims] Upon 1. A of at least some surface layer to produce an infrared sensor in which a thin film thermistor and an infrared-absorbing layer as a sensing portion on the thermally insulating layer are laminated form made of SiO _2, on the SiO ₂ surface layer After forming a conductor layer serving as an electrode of the thermistor and forming an SiO ₂ film serving as the infrared absorbing layer thereon, the SiO ₂ film is removed by etching to remove a portion serving as a pad portion in the conductor layer. A method of exposing and forming a conductor layer for a pad on the exposed portion, the method comprising:
A portion below the pad portion in the O ₂ surface layer is removed by etching in advance, and the conductor layer serving as the electrode is
From the inside of the ₂ surface of etched portions SiO ₂ surface layer
A method of forming a pad portion of an infrared sensor, wherein the pad portion is formed over a surface .