JP2006170895A - Manufacturing method for infrared detecting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for an infrared detecting element of high productivity by making a side etching angle in etching of a MgO substrate as larger as possible. <P>SOLUTION: In this manufacturing method for an infrared detecting element D, a thin film pyroelectric substance 4 is provided in a condition sandwiched by a lower electrode 2 and an upper electrode 3 in a surface 1a side of the substrate 1 (1'), an infrared absorption film 6 is provided on the upper electrode 3 via an insulating film 5, and a cavity part 15 is provided in a substrate area R corresponding to the pyroelectric substance 4, by etching the substrate 1 (1') from a reverse face 1b side, using a mask 12. The mask 12 comprising a material having a satisfactory close-contacting property with the substrate 1 (1') is used in the manufacturing method. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a method for manufacturing an infrared detection element.

At the time of manufacturing a pyroelectric infrared detecting element, a method is used in which after a thin film pyroelectric body is formed on the front surface side of the substrate, the substrate is etched from the back surface side using a mask. For example, as shown in FIG. 4A, a thin pyroelectric body 4 is provided between the lower electrode 2 and the upper electrode 3 on the surface 1 a side of the MgO substrate 1, and the upper electrode is interposed via the insulating film 5. The substrate region corresponding to the pyroelectric body 4 is provided by performing the etching of the MgO substrate 1 from the substrate back surface (the surface opposite to the pyrosensor light receiving portion surface) 1b using the mask 7. A pyroelectric infrared detection element is configured by providing a cavity (diaphragm) 8 in R for improving sensitivity and the like. The cavity 8 is formed by removing the back surface of the MgO substrate 1 by etching using a mask 7 so as to have a predetermined shape. Then, for example, a wafer-like MgO substrate 1 ′ having a length of 40 mm × width of 40 mm × thickness of 300 μm is diced and divided into individual sensor chips 9 (see FIG. 4B). Become.

Conventionally, a wafer-like MgO substrate 1 ′ is etched from the back surface of the substrate using polyimide as a mask material. However, with this method, the angle θ ₁ (hereinafter referred to as a side etching angle) of the substrate etching end face 1c becomes gentle, the individual sensor chip 9 becomes larger, and the sensor thin film portion (circular in plan view) with respect to each sensor chip 9 The proportion of the membrane having a diameter of 1.0 mm is reduced. That is, a wafer-like MgO substrate 1 ′ having a length of 40 mm × width of 40 mm × thickness of 300 μm is prepared, and the number of sensor chips 9 produced from this 40 mm square wafer-like MgO substrate 1 ′ is reduced. There were drawbacks.

For example, in one sensor chip 9 after dicing, an attempt is made to obtain a sensor thin film having a circular shape in plan view and a diameter of 1.0 mm on an MgO substrate 1 having a thickness d of 300 μm (etching conditions of the MgO substrate) In the case where the polyimide film 7 is used as an etching mask, side etching proceeds at a side etching angle θ ₁ of 30 ° with respect to the horizontal direction of the MgO substrate 1, and the sensor chip 9 having a square shape in plan view is formed. The required minimum required size b ₁ is 2.04 mm.

The present invention has been made in consideration of the above-mentioned matters, and an object of the present invention is to provide a method for manufacturing an infrared detection element with high productivity by making a side etching angle as large as possible when etching an MgO substrate. It is.

In order to achieve the above object, a manufacturing method of an infrared detecting element according to the present invention includes a thin film pyroelectric body provided between a lower electrode and an upper electrode on the surface side of a substrate, and the upper electrode is interposed through an insulating film. In the method of manufacturing an infrared detecting element in which an infrared absorption film is provided and a cavity is formed in a substrate region corresponding to a pyroelectric body by etching the substrate from the back side using a mask, adhesion to the substrate A mask made of a good material is used (claim 1).

  In the present invention, the substrate is preferably MgO or sapphire, and the mask material is preferably Cr or Ti.

  In the present invention, it is preferable to use a metal sputtered film as a mask.

In the present invention, as shown in FIG. 2A, for example, on a wafer-like MgO substrate 1 ′ having a thickness d of 300 μm and a 40 mm square, the same etching conditions as those in the past (MgO substrate etching conditions, phosphoric acid 10%: In the case of obtaining a sensor thin film with a diameter of 1.0 mm having the same configuration as shown in FIG. 4B at 80 ° C. (see FIG. 2B), for example, a Cr metal Since the Cr film has good adhesion to the MgO substrate when the sputtered film is used as a mask, it has been found that the side etching angle can be up to 45 °. Therefore, the minimum required size b ₂ required for each sensor chip 19 is 1.6mm.

  In the present invention, it is considered that side etching during substrate etching can be suppressed by using a mask made of a material having good adhesion to the substrate as a mask during etching. As a result, it is required for a sensor chip. The minimum required size can be reduced compared to the conventional one, and each substrate size of the infrared detection element can be reduced accordingly, and the light receiving area relative to the chip size can be increased. The number of picks can be increased.

  Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited thereby.

  1 to 3 show an embodiment of the present invention. FIG. 1 shows a pyroelectric infrared detecting element obtained by the present invention, FIG. 2 shows a minimum required size required for the sensor chip, and FIG. 3 shows a manufacturing process of the pyroelectric infrared detecting element. 1 to 3, the same reference numerals as those shown in FIG. 4 are the same or equivalent.

  In this invention, by using a mask made of a material having good adhesion to the substrate, the minimum required size required for the sensor chip (substrate region corresponding to the pyroelectric body) can be reduced as compared with the prior art. The other structure of the pyroelectric infrared detecting element is the same as that of the conventional example shown in FIG.

  In FIG. 1, a pyroelectric infrared detecting element D is provided with a thin pyroelectric body 4 sandwiched between a thin film lower electrode 2 and an upper electrode 3 on the surface 1a side of the MgO substrate 1, and a thin insulating film 5 An infrared absorption film 6 made of, for example, gold black is provided on the upper electrode 2 through the substrate, and further, the pyroelectric body 4 is formed by etching the MgO substrate 1 from the back surface 1b side using a mask 12 described later. A cavity 15 is provided in the corresponding substrate region R (see FIG. 2A). The pyroelectric material 4 is made of a ferroelectric material such as PZT [lead zirconate titanate] (hereinafter, the pyroelectric material 4 is referred to as PZT). The insulating film 5 is made of polyimide, for example, and is a thin film having a thickness of about 1.0 to 5.0 μm. Each of the lower electrode 2 and the upper electrode 3 is made of, for example, a platinum thin film and has a thickness of about 0.1 to 0.5 μm. PZT4 has a thickness of about 1.0 to 5.0 μm. The infrared absorption film 6 is made of a thin film obtained, for example, by vacuum deposition of gold black.

  A method for forming the pyroelectric infrared detection element D will be described with reference to FIG. The following shows a case where one pyroelectric infrared detection element D is manufactured.

(1) In order to obtain a plurality of pyroelectric infrared detection elements D simultaneously, for example, a wafer-like MgO substrate 1 ′ having a length of 40 mm × width of 40 mm and a thickness d of 300 μm is prepared. FIG. 3A shows the MgO substrate 1 in one pyroelectric infrared detection element D. In FIG. 3B, first, the lower electrode 2 is patterned on the surface 1a of the MgO substrate 1 using an appropriate mask. The thickness of the lower electrode 2 at this time is about 0.1 to 0.5 μm. Next, the lower electrode 2 surface by low pressure CVD method, a pyroelectric, its composition to obtain a PZT4 of Pb _x La _y Ti _z Zr _w a O ₃ PZT4 thin film expressed as by epitaxially growing a predetermined shape. At this time, the PZT 4 is shaped as shown in FIG. 3B using an appropriate mask. The thickness of PZT4 is about 1.0 to 5.0 μm. Subsequently, the upper electrode 3 is patterned on the surface of the PZT 4 using an appropriate mask, and the PZT 4 is provided between the lower electrode 2 and the upper electrode 3. The thickness of the upper electrode 3 at this time is about 0.1 to 0.5 μm.

  (2) Subsequently, as shown in FIG. 3C, an insulating film 5 is patterned on the surface 1a of the MgO substrate 1 including the lower electrode 2, the PZT 4, and the upper electrode 3. The insulating film 5 is formed so as to cover the upper electrode 3 and the PZT 4 using an appropriate mask and to cover a part of the lower electrode 2 and the surface 1 a of the MgO substrate 1. After forming the insulating film 5, as shown in FIG. 3C, a contact hole 5 a is formed in the insulating film 5 to expose the surface of the upper electrode 3.

  (3) Subsequently, as shown in FIG. 3D, the lead electrode 11 connected to the upper electrode 3 through the contact hole 5a is formed. The extraction electrode 11 is made of, for example, Au—Cr material and is formed so as to cover a part of the insulating film 5 and a part of the surface 1 a of the MgO substrate 1 using an appropriate mask.

  (4) Subsequently, as shown in FIG. 3E, a thin Cr film 12 serving as a mask for isotropic etching is formed on the back surface 1b of the MgO substrate 1 by sputtering, and the opening 13 is formed. Form. The Cr film 12 and the opening 13 are formed using an appropriate mask.

  (5) Subsequently, as shown in FIG. 3F, an infrared absorption film 6 is formed on the upper electrode 3 with the insulating film 5 interposed therebetween. The infrared absorption film 6 is provided so as to cover the insulating film 5 on the upper electrode 3 and the portion of the extraction electrode 11 that covers the contact hole 5a. Thereafter, as shown in FIG. 3F, an etching protective film 14 is formed on the entire surface of the wafer-like MgO substrate 1 ′ (on the pyrosensor light-receiving portion side). An organic resin material (resist material) is used as the etching protective film 14. In this state, isotropic etching is performed through the opening 13 using the Cr film 12 as a mask from the back surface (the surface opposite to the pyrosensor light-receiving surface) 1b of the wafer-like MgO substrate 1 ′ to penetrate the MgO substrate 1 ′. A cavity 15 reaching the back surface 2b of the lower electrode 2 is formed. For example, the back surface 1b of the wafer-like MgO substrate 1 'is dug by isotropic etching with 10% phosphoric acid etchant at 80 ° C. to form the cavity 15 as shown in FIG.

  (6) Subsequently, as shown in FIG. 3G, the etching protective film 14 is removed and the Cr film 12 is removed.

  As described above, a plurality of pyroelectric infrared detection elements D are obtained on one wafer-like MgO substrate 1 '. By dicing this, each sensor chip 19 is divided into pyroelectric infrared detecting elements D as shown in FIG.

The pyroelectric infrared detection element D formed as described above has the following effects.
That is, conventionally, etching of the MgO substrate 1 (1 ′) was performed using polyimide as a mask material, but side etching progressed at an angle of 30 ° with respect to the horizontal direction of the MgO substrate 1 (1 ′). For example, when a sensor thin film portion having a diameter of 1.0 mm is formed on an MgO substrate 1 (1 ′) having a thickness d of 300 μm, a minimum of 2.04 mm square (when the sensor thin film portion is 1.0 mm, side etching is performed). A sensor chip area of 0.52 × 2 mm is required. However, when the Cr film 12 is used as a mask as in the present invention, the Cr film 12 has good adhesion to the MgO substrate 1 (1 ′), and therefore can be suppressed to side etching at an angle of 45 °. In order to form a sensor thin film portion having a diameter of 1.0 mm, the pyroelectric infrared detection element D can be formed with a sensor chip area of 1.6 mm square. That is, the minimum area ratio at the time of creating the pyroelectric infrared detection element is 45 °: 30 ° = 1: 1.63, which is the same as that of the conventional wafer-shaped wafer having a length of 40 mm × width of 40 mm and a thickness d of 300 μm. The pyroelectric infrared detection element D can be obtained 1.63 times in the area of the MgO substrate 1 ′, and productivity can be improved.

  Further, since polyimide is used as a mask material, the chip size is increased by etching only from the back surface of the MgO substrate, so that the problems that occur in the comparative example in which etching is performed from both surfaces of the MgO substrate can also be solved. That is, when etching is performed from both sides of the MgO substrate, patterning of both the front and back surfaces of the MgO substrate is necessary, and there is a process complexity and etching variation from the front and back surfaces of the MgO substrate. The variation in (etching hole size) was large. However, in the present invention, by using the Cr film 12 as a mask, patterning of only the MgO substrate surface 1a becomes possible, variation in the cavity size (etching hole size) is reduced, man-hours are reduced, and sensor yield is reduced. Can contribute to improvement.

  Furthermore, when the polyimide is provided on the back surface of the MgO substrate, it is necessary to bake for drying after applying the polyimide resin, and this took about half a day. Therefore, the formation of the mask 12 by the sputtering method takes about one hour and has the advantage that the time required for manufacturing can be shortened. The present invention also has the advantage that the sputtering method used in the present invention has better adhesion to the MgO or sapphire substrate than the Cr or Ti mask material is formed by vapor deposition.

  The present invention is not limited to the above-described embodiment. For example, the pyroelectric material 4 as a ferroelectric thin film is not limited to the PZT.

It is composition explanatory drawing which shows the infrared detection element obtained by one Embodiment of this invention. (A) is composition explanatory drawing which shows the middle of manufacture in the said embodiment. (B) is a figure which shows the magnitude | size of a sensor chip in the said embodiment. It is manufacturing process explanatory drawing which shows the said embodiment. (A) is composition explanatory drawing which shows the middle of manufacture in a prior art example. (B) is a figure which shows the magnitude | size of a sensor chip in a prior art example.

Explanation of symbols

1 (1 ') Substrate 1a Substrate surface 1b Substrate back surface 2 Lower electrode 2b Lower electrode back surface
3 Upper electrode 4 Pyroelectric body 5 Insulating film 6 Infrared absorbing film 12 Mask 15 Cavity R Substrate region D Infrared detector

Claims (3)

  A thin film pyroelectric body is provided on the surface side of the substrate sandwiched between the lower electrode and the upper electrode, an infrared absorption film is provided on the upper electrode through an insulating film, and etching of the substrate is performed on the back side using a mask. In a method for manufacturing an infrared detection element in which a cavity is provided in a substrate region corresponding to a pyroelectric material by using a mask, a mask made of a material having good adhesion to the substrate is used. .   The method for manufacturing an infrared detection element according to claim 1, wherein the substrate is MgO or sapphire, and the mask material is Cr or Ti. The manufacturing method of the infrared detection element of Claim 1 or Claim 2 which uses the metal sputtered film as a mask.

Images