JP3218405B2 - Cantilever displacement element 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 an electrostatically driven cantilever-shaped displacement element formed on a semiconductor substrate and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, a semiconductor pressure sensor, a semiconductor acceleration sensor, and a microactuator using a semiconductor as a mechanical structure in the background of semiconductor process technology.
Attention has been paid to mechanical electric elements (micromechanics) such as.

[0003] The features of such an element include that a small and high-performance mechanical mechanism part can be provided, and the element and an electric circuit can be integrated on a Si wafer because a wafer is used. Further, an improvement in productivity by batch processing of a semiconductor process can be expected. In particular, as a small displacement element, a cantilever-shaped (cantilever) element utilizing a piezoelectric effect, electrostatic force, or thermal deformation is used. Since this element can control extremely delicate movement, It is applied to a scanning tunneling microscope (hereinafter, referred to as STM) that can directly observe the level and molecular level. Further, using this STM technique, observation and evaluation of atomic order and molecular order of semiconductor or polymer material, and fine processing (EE Erichs, Proceeding).
s of 4th International Con
reference on Scanning Tune
ling Microscopy / Spectrosc
optics, '89, S13-3), and applications to various fields such as recording devices.

An example of a cantilever-shaped micro displacement element is a cantilever driven by a piezoelectric effect. For example Sutanfo - de University eat _et - using the proposed micro-displacement element by tiger STM pro - Bed (IEEE Mic
ro Electric Mechanical Sy
stems, pp. 188-199, Feb. 199
Reference numeral 0) denotes a cantilever-shaped actuator having a piezoelectric bimorph structure, which is manufactured on a silicon substrate by using an existing photolithographic technique, a film forming technique, an etching technique and the like.

[0005] A cantilever driven by electrostatic force has also been devised. In this method, a cantilever manufactured by processing a semiconductor substrate is driven by electrostatic force acting between the cantilever and an electrode portion on the substrate. Among them, as a method of driving the cantilever in a direction parallel to the substrate, a method of processing the substrate material itself to form a cantilever structure has been devised. At that time, the cantilever is made of Si (10
0) a method such as anisotropic etching or reactive ion etching or focused ion beam etching of the substrate, and
It is formed using a method such as sacrificial layer etching or etching stop by impurity doping. Also, cantilever
The electrodes for driving are formed by depositing a film by vapor deposition or sputtering, or by doping impurities on electrode portions of the cantilever and the substrate facing each other.

The amount of displacement of the cantilever having such a structure.
X is represented by the following equation using the length l of the hinge, the length L of the beam, the thickness a of the beam, the width w of the beam, the gap g between the electrodes, and the potential difference V.

ΔX = (2ε ₀ Ll ³ V ² ) / (g ² w ³ E) Here, ε ₀ is a dielectric constant of vacuum, and E is a cantilever.
Is the Young's modulus. According to the above formula, in order to increase the displacement amount in the X direction, it is effective to reduce the width of the beam, increase the length of the beam, and reduce the gap between the electrodes.

[0008]

However, in the above conventional example, it was difficult to reduce the gap between the electrodes due to the etching shapes of the electrode portions of the substrate and the cantilever. For example, in the case of dry etching, even those having a large aspect ratio are rounded and do not become smooth parallel electrodes (see FIG. 6A). Further, in a crystal anisotropic etching using a Si (100) substrate which is usually used, smooth but parallel electrodes cannot be formed (see FIG. 6B).

In view of the above problems, an object of the present invention is to reduce the gap between the electrodes and to provide a cantilever-like displacement in which smooth and parallel electrodes (see FIG. 6 (c)) are manufactured with high precision. An object of the present invention is to provide an element and a manufacturing method thereof.

[0010]

That is, the present invention is directed to a cantilever formed by processing a semiconductor substrate, wherein the cantilever is driven by an electrostatic force acting between the cantilever and an electrode portion on the substrate. In the displacement element, the cantilever and the electrode portion on the substrate facing the cantilever have a plane orientation (1).
10) The single-crystal silicon substrate surface processing to be made, prior to
The electrode part and the side of the cantilever facing it are the substrate
It is formed with a (111) plane perpendicular to the (110) plane of the surface,
The side surface of the cantilever support portion of the substrate is other than the (111) plane
And a crystal plane other than the (111) plane in the step of manufacturing the cantilever-shaped displacement element.
Etching is applied to the substrate to form it on the side of the substrate.
Forming a bump region, and (110)
Anisotropic etching to form a (111) plane perpendicular to the plane
And a step of producing the cantilever-shaped displacement element.

The cantilever according to the present invention has a plane orientation (1).
10) The surface is obtained by processing a single-crystal silicon substrate, and is driven by electrostatic force acting between the substrate and an electrode portion. Further, integrated with the semiconductor process, wiring electrodes on the cantilever and the substrate, an integrated circuit for driving the cantilever, and the like are mounted on the same substrate.

In the step of forming a gap between the electrode portion of the substrate and the cantilever, the substrate is etched using an etching method (anisotropic etching) depending on the crystal orientation of the (110) plane single crystal silicon substrate. I do. At this time, the plane orientation of the electrode is (11), (1), (1).
1) Patterning is performed so as to match any one of the azimuth planes of (1). This makes it perpendicular to the substrate surface,
In addition, a parallel electrode having a smooth surface can be formed with high precision. However, when the etching opening pattern for forming the gap is rectangular, it is known that the side surfaces of the etched surfaces other than the two surfaces that become the electrodes advance obliquely during the etching. . For this reason, it is necessary to provide an etching stop region according to the shape of the cantilever.

Methods of forming the cantilever portion other than the gap between the electrodes include methods such as anisotropic etching, reactive ion etching, and focused ion beam etching, and sacrificial layer etching and etching stop by impurity doping. It is formed using a method.

The electrode portion for driving the cantilever is provided on the electrode portions of the cantilever and the substrate facing each other.
It is formed by vapor deposition or sputtering, or by doping impurities.

Conventional methods for producing wiring electrodes on the cantilever and on the substrate, integrated circuits for driving the cantilever, and the like use conventional photolithography techniques, film forming techniques such as vacuum evaporation and sputtering. The method is not a limitation of the present invention.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. Example 1 is a reference example.

Embodiment 1 FIG. 1 is a view of a substrate surface of a cantilever according to this embodiment. In the figure, the length of cantilever-2 is 1000 μm and the width is 5
μm, the thickness is 10 μm, and the gap 3 between the electrodes is 1 μm.

FIG. 2 is a sectional view for explaining a manufacturing process of the cantilever according to the present embodiment. The first manufacturing method
Then, 2000 nm of silicon nitride to be an etching mask and an insulating layer 7 is formed on both surfaces of a 400 μm thick Si (100) substrate 6 by low pressure CVD. Second, after the silicon nitride 7 on the back surface is patterned by dry etching using CF ₄ , the Si substrate in the cantilever portion is anisotropically etched with an aqueous potassium hydroxide solution heated to 100 ° C. (FIG. 2). (A)). Third, the silicon nitride 7 on the substrate surface is removed by reactive ion etching (RIE) using CF ₄ gas. Fourth, Si (11) having a thickness of 400 μm serving as a material for cantilever-2 is used.
0) The substrate 1 is anodically bonded to the surface of the substrate 6,
The Si (110) substrate is polished to a thickness of 10 μm. Fifth, a 2000Å silicon nitride film 7 is formed on both surfaces of the bonded substrates 1 and 6 by a low pressure CVD method. Sixth, the silicon nitride 7 on the substrate surface is patterned into the shape of the cantilever 2 and the electrode gap 3, and RIE using CF ₄ gas is performed.
Etching. At this time, the plane orientation of the electrode is (1)
1) Match the plane orientation of any one of (1), (11) and (1). Seventh, cantilever
In order to shape the Si substrate, the Si substrate in the cantilever portion is anisotropically etched with an aqueous solution of potassium hydroxide heated to 110 ° C. (see FIG. 2B). Eighth, SiH ₄ ,
By the CVD method using O ₂ and B ₂ H ₆ , B
An SG (boron silicate glass) film is formed at 5000 °. Thereafter, annealing is performed at 1200 ° C. for 10 hours, and boron is diffused to a depth of 10 μm to form a p-type region (drive electrode 4) . Ninth, after the BSG film is removed using hydrofluoric acid, patterning is performed by lift-off, and chromium 50 °
Electrode extraction 9 and wiring 10 are formed by vapor deposition of aluminum 3000 °. Finally, the silicon nitride on the back
Cantilever-2 after removal by RIE using F ₄ gas
(See FIG. 2C).

According to this embodiment, an electrostatically driven cantilever-shaped displacement element having a smooth electrode surface and a gap width between electrodes of 1 μm could be manufactured.

Embodiment 2 In this embodiment, another embodiment of the cantilever-shaped displacement element according to the manufacturing method of the present invention will be described. FIG. 3 is a perspective view of the cantilever according to the present embodiment.

In this figure, the cantilever 2 is manufactured by being supported on the single crystal silicon substrate 1 by a hinge 5 in order to increase the amount of displacement. Si facing Cantilever-2
The drive electrode 4 is formed on the substrate portion. By applying a voltage to the drive electrode 4, the cantilever 2 can be operated. Cantilever-2 length is 10
00 μm, width 100 μm, length of hinge 5 100 μm
m, width is 5 μm, thickness of cantilever-2 and hinge 5 is 1
The gap 3 between the electrodes is 1 μm. Although not shown, electrode wiring and a circuit for driving a silicon beam are mounted on a Si substrate.

[0022] Figure 4 is cantilever shown in FIG. 3 - is a sectional view for explaining the manufacturing process. The first manufacturing method
Then, 2000 nm of silicon nitride to be an etching mask 7 is formed on both surfaces of an n-type Si (110) substrate 1 having a thickness of 400 μm by a CVD method. Second, the silicon nitride 7 on the substrate surface is patterned, and the BSG film 8 is
After forming the film at 2,000 ° C., annealed at 1200 ° C. for 10 hours,
Etching stop 1 by diffusing boron 10 μm deep
1 (see FIG. 4A). Third, BS
After removing the G film 8 using hydrofluoric acid and patterning the silicon nitride 7 on the substrate surface, the Si (110) substrate 1 is anisotropically etched with an aqueous solution of potassium hydroxide heated to 100 ° C. , An electrode gap 3 is formed. Fourth,
The silicon nitride 7 on the surface of the substrate is removed by RIE using CF ₄ gas, and the silicon nitride to be used as an etching mask and the insulating layer 7 is formed again by the CVD method at 2000Å, patterned, and then electrolytically etched with heated potassium hydroxide. Unlawful
The important area of the etching stop 11 (the area in FIG. 5)
Region 12) is selectively removed (see FIG. 4b). Fifth,
The silicon nitride 7 on the surface of the substrate is patterned, a BSG film 8 is formed at 5000 ° C. by a CVD method, and then annealed at 1200 ° C. for 10 hours to diffuse boron to a depth of 10 μm to form a p-type region for the electrode 4. Sixth, after removing the BSG film 8 using hydrofluoric acid, patterning is performed by lift-off, and chromium is deposited at 50 ° and aluminum is deposited at 3000 ° to form the electrode take-out 9 and the wiring 10 shown in FIG. . Seventh, silicon is etched from the back surface of the substrate by wet etching with hydrofluoric acid, nitric acid, and water, and RIE dry etching using CF ₄ and O ₂ to a thickness of 10 μm.
Is formed (see FIG. 4C). According to the present embodiment, the electrode portion and the side surface of the cantilever facing the electrode portion are formed by the (111) surface perpendicular to the (110) surface of the substrate surface, and the side surface 13 of the cantilever support portion of the substrate is (11).
1) An electrostatically driven cantilever-shaped displacement element having a crystal plane other than the plane, a smooth electrode plane and a gap width between electrodes of 1 μm was produced.

[0023]

According to the present invention, cantilever-shaped displacement elements having a small gap between the electrodes, having smooth surfaces and being parallel to each other are realized. In addition, it is thin (in the embodiment, the thickness is 10 mm).
μm) A cantilever-shaped displacement element is realized.

[Brief description of the drawings]

FIG. 1 is a diagram of a substrate surface of a cantilever according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view for explaining a manufacturing process of the cantilever according to the first embodiment of the present invention.

FIG. 3 is a perspective view of a cantilever according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a step of manufacturing a cantilever according to a second embodiment of the present invention.

FIG. 5 is a view of a substrate surface showing an intermediate state of a manufacturing process of a cantilever according to a second embodiment of the present invention.

FIG. 6 is a sectional view of a driving electrode of a cantilever according to a conventional example and the present invention.

[Explanation of symbols]

Reference Signs List 1 substrate or Si (110) substrate 2 cantilever 3 electrode gap 4 drive electrode 5 hinge 6 Si (100) substrate 7 etching mask and insulating layer 8 BSG film 9 electrode extraction 10 wiring 11 etching stop 12 area to be selectively removed 13 Side view of substrate cantilever support

Continuation of the front page (72) Inventor Keisuke Yamamoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-2-98971 (JP, A) JP-A-3-178172 ( JP, A) WO 91/12497 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 29/84 G01B 7/34 G01P 15/00 G11B 9/00

Claims (2)

(57) [Claims] A cantilever fabricated by processing a semiconductor substrate is a cantilever-shaped displacement element driven by an electrostatic force acting between the cantilever and an electrode portion on the substrate. The cantilever and the substrate facing the cantilever An upper electrode portion is formed by processing a single crystal silicon substrate having a plane orientation of (110), and is opposed to the electrode portion.
The side of the cantilever is perpendicular to the (110) plane of the substrate surface
(111) formed by the cantilever support of the substrate
A cantilever-shaped displacement element, wherein a side surface of the cantilever comprises a crystal plane other than the (111) plane . 2. In the step of manufacturing the cantilever-shaped displacement element according to claim 1, a crystal plane other than the (111) plane is formed on a side surface of the substrate.
Forming an etching stop region on the substrate
(111) perpendicular to the (110) plane of the substrate surface
Performing an anisotropic etching for forming a surface .