JP2007253304A - Forming method of insulating separation structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form an insulating separation structure by a simple manufacturing process. <P>SOLUTION: A linear hole structure 15 is formed by forming a hole arriving at an insulating layer 12 on an active layer 13 at every predetermined interval. The active layer 13 existing between adjacent holes is oxidized by an oxidization process. The insulating separation structure is formed by removing a supporting layer 11 and the insulating layer 12 existing at the lower part of the hole structure 15 by an etching treatment. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for forming an insulating isolation structure for insulating and isolating an active layer of an SOI (Silicon On Insulator) substrate formed by sandwiching an insulating layer between a support layer and an active layer into at least two regions.

In recent years, micromachine technology has been developed as the demand for miniaturization and higher precision of parts having movable parts has increased. As such a micromachine, a tilt mirror element that scans a light beam such as a laser by oscillating a minute mirror portion by an electrostatic force or the like is known, and is used in the field of optical communication, barcode reader, laser reader, area, etc. Widely used in the field of optical equipment such as sensors, projection displays, and optical switches (see Non-Patent Document 1).
"Large deflection Micromechanical Scanning Mirrors for Linear Scans and Pattern Generation, IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL.6, NO.5, P.715

  By the way, in the tilt mirror element that swings the mirror portion in the biaxial direction, it is necessary to form an insulating separation structure for separating the substrate surface into at least two regions. However, in order to form such an isolation structure, a groove structure is formed on the substrate surface, the groove structure is oxidized, and a polysilicon film is formed on the groove structure by LPCVD (Low Pressure Chemical Vopar Deposition) method. A very complicated process of removing the polysilicon film by backfilling and chemical mechanical polishing must be performed. For this reason, according to the conventional method for forming an insulating isolation structure, it is difficult to mass-produce tilt mirror elements.

  The present invention has been proposed in view of the above-described circumstances, and an object of the present invention is to provide a method for forming an insulating isolation structure capable of forming an insulating isolation structure by a simple manufacturing process.

  In order to solve the above-described problems, a feature of the method for forming an insulating isolation structure according to the present invention is that an active layer of an SOI substrate formed by sandwiching an insulating layer between a support layer and an active layer is insulated in at least two regions. A method for forming an insulating isolation structure for isolation, wherein a hole reaching the insulating layer is formed in an active layer at predetermined intervals, and a linear hole structure is formed between adjacent holes by an oxidation process. There is a step of oxidizing the active layer and a step of removing the support layer and the insulating layer existing under the hole structure by an etching process.

  According to the method for forming an insulating isolation structure according to the present invention, the insulating isolation structure can be formed only by the semiconductor manufacturing process, and therefore the insulating isolation structure can be formed by a simple manufacturing process.

  The present invention can be applied to, for example, the formation of an insulating separation structure used in a tilt mirror element that can swing a mirror portion in two axial directions as shown in FIG. The tilt mirror element shown in FIG. 1 has a structure in which the region 3 and the region 4 of the active layer are insulated and separated by the insulating separation structures 1 and 2. Hereinafter, the method for forming the insulating isolation structure according to the embodiment of the present invention will be described with reference to the method for forming the insulating isolation structure 1 in the region A of FIG.

  FIG. 2 shows a top view of the insulating separation structure 1 in the region A shown in FIG. 1, and the insulating separation structure 1 insulates and separates the substrate surface into a region A1 and a region A2. FIG. 3 is a cross-sectional view taken along the line segment X1Y1 shown in FIG. 2, and the substrate under the insulating isolation structure 1 is removed by etching.

  When forming the insulating isolation structure shown in FIGS. 2 and 3, first, an SOI substrate including a support layer 11, an insulating layer 12, and an active layer 13 is prepared, and the active layer 13 is formed as shown in FIG. The resist film 14 is patterned on the surface of the substrate in accordance with the shape of the hole structure 15 described later. Next, as shown in FIG. 3B, the active layer 13 is etched through the mask 14 until the insulating layer 12 is reached by a D-RIE (Deep-Reactive Ion Etching) process, thereby forming a linear hole structure 15. Form.

  In the present embodiment, the hole structure 15 is formed by forming holes reaching the insulating layer 12 in the active layer 13 at predetermined intervals. Further, since the hole structure 15 supports the structure with a hollow structure, the hole structure 15 is formed by changing the shape of the hole forming the hole structure 15 to a square shape or a circular shape with a tapered periphery. It is desirable to increase the strength of.

  Next, after removing the resist film 14 as shown in FIG. 3 (c), the entire substrate is subjected to a thermal oxidation process to oxidize the active layer 11 existing between the holes forming the hole structure 15, As shown in FIG. 3D, an oxide film 16 is formed on both the front surface and the back surface of the substrate. As described above, since the hole structure 15 supports the structure with a hollow structure, a denser oxide film 16 is formed by thermal oxidation treatment.

  The film thickness of the oxide film formed by the normal oxidation treatment is proportional to the square of the oxidation time, and the ratio of the oxidation rate on the substrate surface side to the oxidation rate on the substrate inner side is about 6: 4. Further, in order to form an oxide film having a film thickness of 2 [μm] by a pyro-oxidation process at 1100 [° C.], an oxidation treatment time of about 10 hours is required. Therefore, in order to oxidize all the active layers having a thickness of about 1.5 [μm], an oxidation treatment of about 10 hours or less is required. is not. Therefore, it is desirable that the thickness of the oxide film 16 between the holes forming the hole structure is 1.5 [μm] or less, and thereby has a sufficient withstand voltage in a sufficiently realizable thermal oxidation time. An insulating isolation structure can be formed.

  Next, after patterning a resist film 17 on the hole structure 15 as shown in FIG. 3E, an oxide film on the substrate surface side is etched by using the resist film 17 as a mask as shown in FIG. 16 is removed. Next, after removing the resist film 17 as shown in FIG. 3 (g), the resist film 18 is patterned on the back side of the substrate leaving the lower region portion of the hole structure 16 as shown in FIG. 3 (h). .

  Next, as shown in FIGS. 3 (i) and 3 (j), the oxide film 16 and the support layer 11 below the hole structure 16 are sequentially removed by etching using the resist film 18 as a mask. As shown in (l), the resist film 18, the oxide film 16, and the insulating layer 11 on the back side of the substrate are removed. Thereby, a series of formation processes is completed.

  As is clear from the above description, in the method for forming an insulating isolation structure according to the embodiment of the present invention, the linear hole structure 15 is formed by forming holes reaching the insulating layer 12 in the active layer 13 at predetermined intervals. The insulating separation structure is formed by oxidizing the active layer 13 existing between adjacent holes by an oxidation process and removing the support layer 11 and the insulating layer 12 existing below the hole structure 15 by an etching process. It is possible to form the insulation isolation structure only by the semiconductor manufacturing process, and the insulation isolation structure can be formed by a simple manufacturing process.

  As another embodiment, as shown in FIGS. 4A and 4B, a CVD method having good consistency with an existing semiconductor process is formed between the holes forming the insulating isolation structure and the upper surface of the oxide film 16. A thin film 21 such as a polysilicon film formed by use, a highly insulating TEOS (tetraethoxysilane) film, and an insulating SOG (Spin On Glass) film that can be applied by a simple spin coating method is formed. It may be. According to such a configuration, the strength of the insulating separation structure can be increased. When forming the insulation isolation structure shown in FIGS. 4A and 4B, first, as shown in FIG. 5, patterning processing and D-RIE processing similar to those in FIGS. 3A to 3D are performed. Then, after performing the resist removal process and the thermal oxidation process, a thin film 21 is formed on the substrate surface side as shown in FIG. Next, after patterning the resist film 22 at a position corresponding to the hole structure 15 as shown in FIG. 5F, etching is performed using the resist film 22 as a mask as shown in FIGS. As a result, the thin film 21 and the oxide film 16 other than the position corresponding to the hole structure 15 are removed. Then, as shown in FIG. 5 (i), after removing the resist 22 by an etching process, an insulating separation structure can be formed by performing the same processes as in FIGS. 3 (h) to 3 (l).

  As another embodiment, the insulating isolation structure 1 may be formed in multiple stages as shown in FIG. According to such an insulating isolation structure, it is possible to easily increase the insulating property by simply changing the pattern without adding a process. In addition, since a sufficient withstand voltage can be obtained even if the space between the holes is reduced, an insulating isolation structure can be formed more easily. Also in this embodiment, a thin film may be formed between the holes forming the insulating separation structure and on the upper surface of the oxide film.

  As another embodiment, as shown in FIG. 7, the holes forming the insulating separation structure 1 may be arranged in a wave shape (zigzag shape). According to such an insulating separation structure 1, the strength of the insulating separation structure 1 can be easily increased only by changing the pattern without adding a process. Also in this embodiment, a thin film may be formed between the holes forming the insulating separation structure and on the upper surface of the oxide film.

  As mentioned above, although embodiment which applied the invention made by the present inventors was described, this invention is not limited by the description and drawing which make a part of indication of this invention by this embodiment. That is, it should be added that other embodiments, examples, operation techniques, and the like made by those skilled in the art based on the above-described embodiments are all included in the scope of the present invention.

It is a top view which shows the structure of the tilt mirror element to which this invention is applied. It is the top view and sectional drawing which show the structure of the insulation isolation | separation structure used as embodiment of this invention. FIG. 3 is a cross-sectional process diagram illustrating a method for forming the insulating separation structure illustrated in FIG. 2. FIG. 3 is a top view and a cross-sectional view illustrating a configuration of an application example of the insulating separation structure illustrated in FIG. 2. FIG. 5 is a cross-sectional process diagram illustrating a method for forming the insulating separation structure illustrated in FIG. 4. FIG. 3 is a top view and a cross-sectional view illustrating a configuration of an application example of the insulating separation structure illustrated in FIG. 2. FIG. 3 is a top view and a cross-sectional view illustrating a configuration of an application example of the insulating separation structure illustrated in FIG. 2.

Explanation of symbols

1, 2: Insulating isolation structure 11: Support layer 12: Insulating layer 13: Active layers 14, 17, 18: Resist film 15: Hole structure 16: Oxide film

Claims (5)

A method for forming an insulating isolation structure for insulating and isolating an active layer of an SOI substrate formed by sandwiching an insulating layer between a support layer and an active layer into at least two regions,
Forming a linear hole structure by forming holes reaching the insulating layer at predetermined intervals in the active layer;
Oxidizing the active layer present between the linear pore structures by an oxidation process;
A method for forming an insulating isolation structure, comprising: a step of removing a support layer and an insulating layer existing under a hole structure by an etching process. A method for forming an insulating isolation structure according to claim 1,
A method for forming an insulating separation structure, comprising a step of forming a thin film on the hole structure. A method for forming an insulating separation structure according to claim 1 or 2,
The method for forming an insulating isolation structure, wherein the predetermined interval is 1.5 [μm] or less. A method for forming an insulating separation structure according to any one of claims 1 to 3,
A method of forming an insulating separation structure, wherein the linear hole structure is formed in multiple stages. A method for forming an insulating separation structure according to any one of claims 1 to 4,
A method for forming an insulating separation structure, wherein the holes forming the hole structure are arranged in a wavy pattern.

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