JP2015093340A - Semiconductor device manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a semiconductor device having a step formed between a stationary side interdigital electrode and a movable side interdigital electrode, without requiring any special processing such as a stiction pad, by an ordinary photolithography technique.SOLUTION: A semiconductor device manufacturing method comprises: an insulation groove forming step of masking the surface of a first working part 61 formed at a first working part forming step and the surface of a first mask layer 51 with a second mask layer 53 and etching to reach an insulating layer 2, thereby to form an insulating groove 15; and a step forming step of etching an active layer 1 of a movable side interdigital electrode construction 13A thereby to form a step in the thickness direction of a stationary side interdigital electrode 14 and a movable side interdigital electrode 13.

Description

  The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device such as a comb-shaped electrostatic actuator having a comb-tooth structure formed using an SOI (Silicon on Insulator) substrate.

  Conventionally, comb-shaped electrostatic actuators such as electrostatic MEMS mirrors used for acceleration sensors and optical switches are used as semiconductor devices having a comb-tooth structure formed by using SOI substrates that are frequently used in MEMS applications and the like. Has been proposed. Such a comb-shaped electrostatic actuator has a fixed comb electrode fixed to the support layer side, and a movable comb electrode formed on a movable mirror portion supported by a beam.

  When the comb-shaped electrostatic actuator is driven with vertical comb teeth (the movable comb electrode is driven perpendicularly to the fixed comb electrode (in the thickness direction of the SOI substrate)) In addition, it is necessary to provide a step between the two comb electrodes. As a configuration for providing the step, (1) a configuration in which the movable comb teeth and the fixed comb teeth are formed in separate layers, and (2) the movable comb teeth and the fixed comb teeth in the same layer. It is divided roughly into the structure to form. As the configuration of (1), for example, as in Patent Document 1, when forming a fixed comb electrode and a movable comb electrode, a technique for forming comb electrodes on both surfaces of the SOI substrate by photolithography. Is mentioned.

  On the other hand, as the configuration of (2) above, for example, as in Patent Document 2, a stiction pad method (a stiffening pad serving as a weight is coupled to a movable comb electrode by a beam and an insulating layer under the stiction pad is removed In order to provide a step between the comb-teeth electrodes separately from the step of forming the comb-teeth electrode, as in the method of tilting the fixed-side comb-teeth electrode and providing a step between the comb-teeth electrodes). In addition, there is a technique for forming a mechanism for inclining the comb electrode by specially processing the frame coupled to the comb electrode (V-shaped on the support layer side). Furthermore, as disclosed in Patent Document 4, there is a technique in which an initial displacement is caused by the displacement of the fixed comb electrode.

JP 2009-037247 A JP 2006-047897 A JP 2004-219839 A JP 2006-334697 A

  However, in the configuration of (1) above, since the comb electrodes are formed on both surfaces of the SOI substrate by photolithography, the gap between the fixed comb electrode and the movable comb electrode depends on the alignment accuracy on both surfaces. Therefore, it is difficult to form a gap between comb electrodes with high accuracy. For this reason, there is a problem in that the gap interval is increased and the drive voltage is likely to be increased.

  In the configuration (2), the fixed side comb electrode and the movable side comb electrode are formed on the same layer by one photolithography, and therefore, the configuration between the comb electrodes, which is a problem in the configuration (1) above. The problem of gap spacing is eliminated, but a separate process such as a stiction pad structure is required to form a step in the comb electrode, and the process becomes complicated by special processing. There is a problem that the device becomes large due to the pad structure. In order to provide such a stiction pad, it is necessary to remove the insulating layer below the stiction pad, and a general method of removing the stiction pad by wet etching is used, but the stiction pad having a very fine structure is used. It is very difficult to infiltrate the wet etching solution into the lower layer of the action pad structure, and there is also a problem that it is difficult to achieve a stable process.

  Therefore, the present invention has been made paying attention to the above-mentioned problems, and its purpose is to provide a fixed comb electrode and a movable comb electrode without requiring special processing such as a stiction pad. Another object of the present invention is to provide a method for manufacturing a semiconductor device in which a step is formed between the two.

A method of manufacturing a semiconductor device according to an aspect of the present invention for solving the above problems includes a fixed frame in which a support layer, an insulating layer, and an active layer are stacked at least in this order, and an inner peripheral end of the fixed frame. The fixed-side comb-teeth electrode made of the active layer, the mirror part made of the active layer connected to the mirror part fixed frame by at least one pair of beams inside the fixed frame, and the mirror part A method of manufacturing a semiconductor device having a movable comb electrode facing the fixed comb electrode with a gap,
A first mask layer forming step of forming a first mask layer on the surface of the active layer;
On the surface of the first mask layer excluding the first region which is one of the region where the fixed comb electrode is formed and the region where the movable comb electrode is formed, and the second region which is an insulating groove. A first patterning step of forming a mask on the substrate;
Etching the first region and the second region until reaching the active layer to form a first processed portion; and
A second mask layer forming step of forming a second mask layer on the surface of the first mask layer and the surface of the first processed portion;
A second patterning step of forming a mask on the surface of the second mask layer excluding the second region to be the insulating groove;
Etching the second region until reaching the insulating layer to form the insulating groove; and
A second mask layer removing step of removing the second mask layer;
A step forming step of forming a step by etching the active layer of the first processed portion in the thickness direction.

Here, the manufacturing method of the semiconductor device, after completion of the step forming step,
A third mask layer forming step of forming a third mask layer on the surface of the support layer;
A third patterning step of forming the third mask layer for masking the mirror portion fixing frame and the lower portion of the fixing frame;
An etching step of etching the support layer and the insulating layer in a region where the third mask layer is not formed;
Preferably, the method includes a first mask layer and a third mask layer removing step of removing the first mask layer and the third mask layer.
Further, in the method of manufacturing the semiconductor device, in the first patterning step, a region where the movable comb electrode is formed is the first region.
In the step forming step, it is preferable that the active layer of the first processed portion is etched in the thickness direction so that the movable comb electrode is thinner than the fixed comb electrode.
In the method for manufacturing the semiconductor device, the first mask layer is preferably an oxide film or a metal film, and the second mask layer is preferably a resist film.

  As described above, according to the method for manufacturing a semiconductor device of an aspect of the present invention, there is no need for special processing such as a stiction pad and the like between the fixed comb electrode and the movable comb electrode. It is possible to provide a method for manufacturing a semiconductor device in which a step is formed.

It is a top view which shows the structure of a semiconductor device. It is sectional drawing which follows the II-II line of FIG. (A)-(e) is sectional drawing which shows the flow of the manufacturing method of the semiconductor device of a certain aspect of this invention. FIG. 4 is a plan view of FIG. That is, FIG. 3E is a cross-sectional view taken along line IIIe-IIIe in FIG. In this figure, each part is indicated by hatching corresponding to FIG. 3 (e) so that the relationship with FIG. 3 (e) becomes clear. (A)-(d) is sectional drawing which shows the flow of the manufacturing method of the semiconductor device of an aspect with this invention. FIG. 6 is a plan view of FIG. That is, FIG. 5D is a cross-sectional view taken along the line Vd-Vd in FIG. In this figure, each part is indicated by hatching corresponding to FIG. 5 (d) so that the relationship with FIG. 5 (d) becomes clear. (A)-(d) is sectional drawing which shows the flow of the manufacturing method of the semiconductor device of an aspect with this invention. FIG. 8 is a plan view of FIG. 7A is a cross-sectional view taken along line VIIa-VIIa in FIG. In this figure, each part is indicated by hatching corresponding to FIG. 7A so that the relationship with FIG. 7A becomes clear. (A)-(d) is sectional drawing which shows the flow of the manufacturing method of the semiconductor device of an aspect with this invention. FIG. 9D is a cross-sectional view taken along line IXd-IXd in FIG.

A method for manufacturing a semiconductor device according to an aspect of the present invention will be described below with reference to the drawings.
FIG. 1 is a plan view showing a configuration of a semiconductor device (comb-type electrostatic actuator) manufactured by a method for manufacturing a semiconductor device according to an aspect of the present invention. 2 is a cross-sectional view taken along the line II-II in FIG.
As shown in FIG. 1, a semiconductor device manufactured by a method of manufacturing a semiconductor device according to an aspect of this embodiment (hereinafter, simply referred to as a semiconductor device) is an SOI substrate that is often used for MEMS applications and the like. This is a semiconductor device having a basic configuration of (Silicon On Insulator). The SOI substrate is a substrate obtained by bonding an active layer (Si substrate) 1 and a support layer (Si substrate) 3 in FIG. 2 with an insulating layer (SiO ₂ substrate) 2 interposed therebetween.

  As shown in FIG. 1, the comb-shaped electrostatic actuator of the present embodiment includes a fixed frame 17, a fixed comb electrode 14 formed on the inner peripheral end of the fixed frame 17, and an inner side of the fixed frame 17. A mirror part 11 connected to the mirror part fixed frame 16 by at least one pair of beams 12, and a movable side comb electrode 13 formed on the mirror part 11 and facing the fixed side comb electrode 14 with a gap; Have Further, the mirror part fixed frame 16, the mirror part 11, the beam part 12, the movable side comb electrode 13, and the fixed frame 17 and the fixed side comb electrode 14 are insulated by an insulating groove 15. The comb-shaped electrostatic actuator of this embodiment is based on electrostatic force generated by applying a voltage between the movable comb electrode 13 (electrode 41) and the fixed comb electrode 14 (electrode 42). The mirror unit 11 swings. Specifically, as shown in FIG. 2, a comb stepped structure is provided on the movable comb electrode 13. Thus, by forming a step structure on the movable comb electrode 13, the mirror unit 11 can be efficiently vibrated initially.

(Method for manufacturing semiconductor device)
Next, a method for manufacturing the semiconductor device shown in FIGS. 1 and 2 will be described with reference to FIGS. 3 to 9 are cross-sectional views showing a flow of a method for manufacturing a semiconductor device according to an aspect of the present invention.
In the manufacturing method of the semiconductor device of this embodiment, a step is formed in the movable comb electrode with respect to the fixed comb electrode through the following steps (i) to (xiv).
Specifically, the method for manufacturing a semiconductor device according to the present embodiment includes at least a first processed part forming step, an insulating groove forming step, and a step forming step.

(i) Substrate Cleaning Step As shown in FIG. 3A, first, an SOI substrate formed by laminating the support layer 3, the insulating layer 2, and the active layer 1 in this order is cleaned.

(ii) Electrode Formation Step Next, as shown in FIG. 3B, the electrode 41 is formed on the surface of the active layer 1 and the electrode 42 is formed on the surface of the support layer 3. Specifically, the electrodes 41 and 42 are formed by forming a material such as AlSi or Ti / Au by sputtering or vapor deposition and patterning the material by photolithography. Here, the electrode 41 is an electrode that functions as a drive electrode, a detection electrode, and a GND electrode, and the electrode 42 is an electrode that functions as a GND electrode.

(iii) First Mask Layer Forming Step Next, as shown in FIG. 3C, a first mask layer 51, which is a first mask for processing the active layer 1, is formed on the surface of the active layer 1. To do. Here, the material of the first mask layer 51 is preferably a metal or an oxide, but any material other than the metal and the oxide can be used as long as it has a selectivity with respect to a second mask layer 53 (for example, a resist) described later.
(Iv) First Patterning Step In the first patterning step, as shown in FIG. 3D, the first region which is the region where the movable comb electrode of the first mask layer 51 is formed and the first trench that becomes the insulating groove. In this step, a pattern of the resist 52 is formed by photolithography on the surface excluding the two regions.

(v) First Processed Part Forming Process In the first processed part forming process, the first mask layer 51 in the first region and the second region reaches the active layer 1 as shown in FIGS. In this process, the first processed portion 61 is formed by etching until the resist 52 is removed.

(vi) Second Mask Layer Forming Step Next, as shown in FIG. 5A, a second layer mask that processes the active layer 1 on the surface of the first mask layer 51 and the surface of the first processing portion 61. A second mask layer 53 is formed. Examples of the material of the second mask layer 53 include a resist material.

(vii) Second Patterning Step Next, as shown in FIGS. 5B to 5D and FIG. 6, a resist 54 is formed on the second mask layer 53, and the second region to be an insulating groove is removed. A mask pattern made of a resist 54 is formed on the surface by photolithography (FIG. 5C). Next, using the resist 54 as a mask, the second mask layer 53 is etched to form a second processed portion 62, and the resist 54 is removed (FIG. 5D). By this step, as shown in FIGS. 5D and 6, the active layer 1 is exposed on the surface of the second processed portion 62 (second region), and a movable side comb electrode structure 13 </ b> A described later is formed. The active layer 1 on the active layer 1 is covered only with the second mask layer 53, and the active layer 1 in the region to be the mirror part fixed frame 16, the mirror part 11, the beam part 12, the fixed frame 17, and the fixed side comb-teeth electrode 14. The top is covered with a first mask layer 51 and a second mask layer 53. However, when a resist material is used for the second mask layer 53, the step of forming the resist 54 can be omitted.

(viii) Insulating groove forming step In the insulating groove forming step, the surface of the active layer 1 exposed by the second processed portion 62 is etched until it reaches the insulating layer 2 to form the movable comb electrode structure 13A. It is a process to do.

  In this step, as shown in FIGS. 7A and 8, first, the third processed portion 63 is formed by dry etching. By the formation of the third processed portion 63, the movable side comb electrode structure 13A having the second mask layer 53 formed on the upper surface is provided at a location that becomes the movable side comb electrode 13 (see FIG. 1).

(ix) Second Mask Layer Removal Step Next, as shown in FIG. 7B, the second mask layer 53 is removed by O ₂ plasma ashing. Here, in the movable side comb-tooth electrode structure 13A, the active layer 1 is exposed. Further, the upper surface of the movable comb electrode structure 13A and the surface of the active layer 1 on which the fixed comb electrode 14 is formed have substantially the same height in the thickness direction of the SOI substrate. 7B to 7D are movable side comb teeth in cross-sectional views (FIGS. 7B to 7D) cut along the line VIIa-VIIa in FIG. This is a fixed comb electrode 14 adjacent to the electrode 13 in the depth direction of the drawing. Further, the first mask layer 51a shown in FIGS. 7B to 7D is formed as a fixed-side comb electrode in cross-sectional views (FIGS. 7B to 7D) taken along the line VIIa-VIIa in FIG. 14a is a first mask layer 51 formed on 14a.

(x) Step forming step In the step forming step, the movable comb electrode structure 13A in the active layer 1 is etched in the thickness direction so that the fixed comb electrode 14 and the movable comb electrode 13 are in the thickness direction. Is a step of forming a step. In this step, as shown in FIG. 7C, the movable comb electrode teeth 13A having a step in the thickness direction with respect to the surface of the active layer 1 by dry etching the movable comb electrode structure 13A. Electrode 13 is formed. Here, in the present embodiment, “a step is formed (a step is formed)” means that the upper surface of the manufactured movable comb electrode 13 and the upper surface of the fixed comb electrode 14 respectively. This means that the (height) position differs in the thickness direction of the SOI substrate.

(xi) Third Mask Layer Formation Step Next, as shown in FIG. 7D, a third mask layer 55 is formed on the surface of the support layer 3 (the surface on which the electrode 42 is provided).

(xii) Third Patterning Step Next, as shown in FIG. 9A, the pattern of the third mask layer 55 that masks the lower part of the mirror portion fixing frame 16 and the fixing frame 17 (see FIG. 1) is formed by photolithography. Form. The fixed comb electrodes 14a shown in FIGS. 9 (a) to 9 (d) are movable comb teeth in cross-sectional views (FIGS. 9 (a) to (d)) cut along the line IXd-IXd in FIG. This is a fixed comb electrode 14 adjacent to the electrode 13 in the depth direction of the drawing. Further, the first mask layer 51a shown in FIGS. 9A to 9D is a cross-sectional view (FIGS. 9A to 9D) cut along the line IXd-IXd in FIG. It is the 1st mask layer 51 formed on 14a.

(Xiii) Etching Step Next, as shown in FIG. 9B, the fourth processing portion 64 is formed by processing the support layer 3 by dry etching using the third mask layer 55 as a mask. Thereafter, as shown in FIG. 9C, the fifth mask 65 is formed by processing the insulating layer 2 by dry etching using the third mask layer 55 as a mask.

(xiv) First Mask Layer and Third Mask Layer Removal Step Next, as shown in FIG. 9D, the first mask layer 51 and the third mask layer 55 are removed by a dry process. FIG. 9D corresponds to a cross-sectional view taken along line IXd-IXd in FIG.

  The semiconductor device formed in this way is a comb-like electrostatic actuator that has a movable comb tooth by electrostatic force generated by applying a voltage between the fixed comb electrode 14 and the movable comb electrode 13. The electrode 13 can be swung.

  Through the above steps, the comb-shaped electrostatic actuator having a step formed between the movable comb electrode 13 and the fixed comb electrode 14 is subjected to a structure forming step for forming a step with respect to the active layer 1. It can be formed without adding separately.

  Specifically, the fixed-side comb electrode and the movable-side comb electrode formed with the steps by the insulating groove forming step, the second mask layer removing step, and the step forming step are formed by one photolithography. It is possible to form the step between the comb-shaped electrodes without forming a step (stiction pad or the like) for forming the step.

  In addition, the semiconductor manufacturing method according to the present embodiment does not require a separate mechanism for forming a step in a comb-shaped electrode such as a stiction pad. Therefore, the throughput can be improved by downsizing and simplifying the process. . In addition, the step between the comb electrodes can be freely adjusted by the etching amount, and a semiconductor device rich in variations of the steps between the comb electrodes can be provided.

  As mentioned above, although embodiment of this invention has been described, this invention is not limited to this, A various change and improvement can be performed. For example, in the above-described embodiment, a step is formed in the movable comb electrode 13 with respect to the fixed comb electrode 14 in the “(iv) first patterning step”, so that the movable side of the first mask layer 51 is movable. The region for forming the comb-tooth electrode and the region to be the insulating groove are patterned and etched, but the first mask layer 51 is fixed to form a step in the fixed-side comb electrode 14 with respect to the movable-side comb electrode 13. You may pattern and etch the area | region which forms a side comb-tooth electrode, and the area | region used as an insulation groove | channel. That is, in the “(iv) first patterning step”, it can be determined whether the step is provided on either the fixed side comb electrode or the movable side comb electrode. Further, both the region for forming the movable comb electrode and the region for forming the fixed comb electrode may be patterned and etched so as to produce a step in the thickness direction. In addition, the step may be provided in a stepped manner in a stepped manner by stepwise etching at least one of the movable side comb electrode structure 13A and the fixed side comb electrode structure.

DESCRIPTION OF SYMBOLS 1 Active layer 2 Insulating layer 3 Support layer 11 Mirror part 12 Beam part 13 Movable side comb electrode 13A Movable side comb electrode structure 14 Fixed side comb electrode 15 Active layer process part (insulation groove)
16 Fixing frame of mirror part 17 Fixed side electrode fixing frame 41 Electrode 42 Electrode 51 First mask layer 52 Resist mask 53 Second mask layer 54 Resist mask 55 Third mask layer 61 First processing part 62 Second processing part 63 Third Processing part 64 Fourth processing part 65 Fifth processing part

Claims (4)

A fixed frame in which a support layer, an insulating layer, and an active layer are laminated in at least the order; a fixed comb electrode formed of the active layer formed on an inner peripheral end of the fixed frame; and an inner side of the fixed frame A mirror part composed of the active layer connected to a mirror part fixed frame by at least one pair of beams, and a movable side comb electrode formed on the mirror part and facing the fixed side comb electrode with a gap A method of manufacturing a semiconductor device comprising:
A first mask layer forming step of forming a first mask layer on the surface of the active layer;
On the surface of the first mask layer excluding the first region which is one of the region where the fixed comb electrode is formed and the region where the movable comb electrode is formed, and the second region which is an insulating groove. A first patterning step of forming a mask on the substrate;
Etching the first region and the second region until reaching the active layer to form a first processed portion; and
A second mask layer forming step of forming a second mask layer on the surface of the first mask layer and the surface of the first processed portion;
A second patterning step of forming a mask on the surface of the second mask layer excluding the second region to be the insulating groove;
Etching the second region until it reaches the insulating layer to form the insulating groove;
A second mask layer removing step of removing the second mask layer;
A step forming step of forming a step by etching the active layer of the first processed portion in a thickness direction. After completion of the step forming step,
A third mask layer forming step of forming a third mask layer on the surface of the support layer;
A third patterning step of forming the third mask layer for masking the mirror portion fixing frame and the lower portion of the fixing frame;
An etching step of etching the support layer and the insulating layer in a region where the third mask layer is not formed;
2. The method of manufacturing a semiconductor device according to claim 1, further comprising a first mask layer and a third mask layer removing step of removing the first mask layer and the third mask layer. In the first patterning step, a region for forming the movable comb electrode is defined as the first region,
The step forming step includes etching the active layer of the first processed portion in a thickness direction so that the movable comb electrode has a thickness smaller than the fixed comb electrode. Item 3. A method for manufacturing a semiconductor device according to Item 1 or 2.   4. The method of manufacturing a semiconductor device according to claim 1, wherein the first mask layer is an oxide film or a metal film, and the second mask layer is a resist film. 5.

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