JP2805396B2 - Beam manufacturing method - 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 manufacturing a beam on a semiconductor substrate.

[0002]

2. Description of the Related Art As a method of manufacturing a beam on a semiconductor substrate, a method of manufacturing a cantilever using anisotropic etching of silicon is known (for example, Kurt. E. Peters).
en “Dynamic Micromechanics”
on Silicon: Techniques an
d Devices ”IEEE vol. ED-2
5, No10 pp1241-1250 Oct.
1978). Hereinafter, a method of manufacturing a cantilever by this method will be described. FIG. 4 is a schematic process sectional view. First, the surface of the silicon substrate 1 having the crystal orientation (100) plane as the main surface is C
A silicon nitride film 3 is formed by a VD method, and is etched into a cantilever pattern (see FIG. 4A). Next, using the silicon nitride film 3 as a mask, anisotropic wet etching of the silicon substrate 1 is performed with an aqueous solution of potassium hydroxide at 80 to 90 ° C. Etching is first performed on Si (100)
The etching proceeds from the surface 12 and the etching is almost stopped when the Si (111) surface 13 comes out. The lower part of the beam is Si (21
1) Side etching is performed from the surface 14 (see FIG. 4B). The formation of the beam ends when the Si (111) plane at the base of the beam is exposed (see FIG. 4C).

This method uses anisotropic wet etching utilizing the fact that the etching rate of the Si (111) plane is several hundredths slower than the etching rate of other planes such as the Si (100) plane. It is. However, it is certain that the Si (111) surface is etched even though the speed is several hundredths, and it is not possible to avoid side etching of the root portion of the beam when forming the cantilever. As a result, the silicon nitride film becomes hollow, stress concentrates on the root portion, and causes damage.

As a method for solving this, the following method has been considered. FIG. 5 is a schematic process sectional view. First, a silicon substrate 1 having a crystal orientation (100) plane as a main surface
A silicon nitride film 3 is formed on the front surface and the back surface by CVD (see FIG. 5A). Next, patterning for the marker hole 15 is performed on the back surface, and the marker hole 15 is formed by anisotropic etching of silicon with a potassium hydroxide aqueous solution heated to 80 to 90 ° C. (FIG. 5).
(B)). At this time, a silicon nitride membrane is formed on the surface of the substrate, and the front surface and the back surface are aligned using the membrane as a marker. Further, patterning for the etching hole 16 is performed on the back surface, and anisotropic etching is performed with a potassium hydroxide aqueous solution heated to 80 to 90 ° C. until the thickness up to the surface remains about 10 μm (FIG. 5).
(C)). Furthermore, the silicon nitride film 3 on the surface is patterned into a cantilever shape (see FIG. 5D).
Finally, the silicon under the beam is removed by dry etching from the back surface to form a beam (see FIG. 5E).

In this method, the hollow shape of the silicon nitride film 3 at the root of the beam on the front surface can be avoided by controlling the pattern shape for the etching holes 16 on the back surface.

[0006]

In the latter conventional example, although the problem of stress concentration existing in the former conventional example has been solved, a new problem has occurred.

First, there is a problem of reproducibility of the size of the etching hole formed on the surface. If the thickness accuracy of the silicon substrate is ± 10 μm, the accuracy of the length of one side of the etching hole formed on the surface is approximately ± 7 μm, and it is difficult to obtain reproducibility.

Second, there is a problem of the size of the opening of the etching hole formed on the back surface of the substrate. For example, thickness 525
If a square hole of 250 μm square is formed on the front surface to form a 200 μm long cantilever on a silicon substrate of μm, an opening of about 1000 μm square is required on the back surface. That is, an extra space of 15 times the area is taken on the surface. Therefore, it is an issue to manufacture a large number of beams on a substrate with high density and high accuracy.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a method of manufacturing a beam showing a method of solving the above-mentioned problems, comprising: a first step of forming and patterning a first layer on a semiconductor substrate;
A second step of forming and patterning a second layer on the semiconductor substrate on which the first step is completed, and removing the first layer of the semiconductor substrate on which the second step is completed by etching. A third step of forming a beam made of the second layer by etching using an etching method depending on the crystal orientation.

FIG. 1 shows a manufacturing procedure and an outline of a manufacturing method of the present invention. First, the first surface of the semiconductor substrate 1
The layer 2 is formed, and is etched except for a portion to be a lower portion of the beam (see FIG. 1A). Next, a second layer 3 is formed on the semiconductor substrate 1 and patterned to leave a beam and a portion to be a supporting portion of the beam (FIG. 1).
(B)). Further, the first layer 2 of the semiconductor substrate 1
Is removed by chemical etching (see FIG. 1C). Finally, by using the second layer 3 as a mask, the semiconductor substrate 1 is etched by an etching method having an etching rate depending on the crystal orientation of the semiconductor substrate 1, thereby forming a beam made of the second layer 3 (FIG. 1 (d)). )reference).

The beam may have any shape as long as it can be obtained by processing the semiconductor substrate 1. For the semiconductor substrate 1, an etching method whose etching rate depends on its crystal orientation (for example, Si, GaAs) can be used.
Etc.). An aqueous solution of potassium hydroxide is typically used as an etching solution at this time, but a solution (eg, an aqueous solution of ammonia water, an aqueous solution of hydrazine, or an aqueous solution of ethylenediamine and pyrocatechol) in which the etching rate is anisotropic depending on the crystal orientation of the semiconductor substrate 1 is used. Etc.) can be similarly applied.

The material of the first layer 2 is a material which can be selectively etched with the semiconductor substrate 1 and the second layer 3 (for example, polycrystalline silicon, various metals, various resist materials, various ceramics, polyimide, etc.). Applicable.

As a material of the second layer 3, a material (for example, silicon nitride, silicon oxide, or the like) that can be selectively etched with the semiconductor substrate 1 can be used.

The first layer 2 and the second layer 3 are formed by a conventionally known technique, for example, a vacuum deposition method, a sputtering method, a chemical vapor deposition method (CVD method) generally used in the semiconductor industry.
Such a thin film manufacturing technology, a photolithographic technology, and an etching technology can be applied, and the manufacturing method is not limited to the present invention.

[0015]

Embodiment 1 An embodiment according to the present invention will be described below. FIG. 1 is a sectional view of the process. A single-crystal silicon substrate (525 μm thick) having a crystal orientation (100) plane as a main surface was used as the semiconductor substrate 1, and aluminum nitride was formed as a first layer 2 on the surface by AC sputtering to a thickness of 700 Å. Aluminum (99.999%) was used as a target, and a mixed gas of argon and nitrogen was used as an atmosphere.

Next, the formed aluminum nitride was patterned into a predetermined shape (corresponding to a cantilever beam portion) (see FIG. 1A). A photoresist was used for patterning, dry-etched with an ion milling device, and then the resist was stripped. Further, as the second layer 3, silicon nitride is applied at 800 ° C. by an LPCVD apparatus.
A 000 Å film is formed and patterned into a cantilever shape (see FIG. 1B). A photoresist was used for patterning, dry-etched with a CF ₄ gas by a reactive ion etching apparatus, and then the resist was peeled off.

The length direction of the cantilever is Si (11
1) It coincides with the direction of intersection of the equivalent surface with the Si (100) surface. The length of the cantilever is 1200 μm and the width is 50 μm.

Finally, the aluminum nitride layer is etched with an aqueous solution of potassium hydroxide (KOH: H ₂ O = 1: 2, weight ratio) at 80 ° C. (see FIG. 1 (c)). Silicon was anisotropically etched to form a cantilever (see FIG. 1D).

Comparative Example 1 Table 1 shows a comparison between the cantilever described in Example 1 and the cantilever according to the prior art shown in FIG.

[0020]

[Table 1] As shown in Table 1, in order to fabricate beams of the same length, etching time of 400 minutes was required in the related art, but it was possible to fabricate the beam in 30 minutes in the present embodiment. Further, by shortening the etching time, the side etching of the root portion of the beam can be reduced to approximately 0 μm.

Embodiment 2 FIG. 2 shows another embodiment according to the present invention. Example 2 is a doubly supported beam. The detailed manufacturing process is the same as in the first embodiment.

Comparative Example 2 In the case of a doubly supported beam, according to the prior art, the longitudinal direction of the beam was Si.
Since it is parallel to the (111) equivalent plane, side etching does not occur below the beam. Therefore, the conventional method cannot manufacture a doubly supported beam, and requires the method of the second embodiment.

Embodiment 3 Another embodiment according to the present invention will be described. The method for manufacturing a beam described below is a method for manufacturing a bimorph-driven cantilever used for driving a transducer probe of a recording / reproducing apparatus. In such a recording / reproducing apparatus, a plurality of microprobes for generating a tunnel current are arranged at minute intervals in opposition to a recording medium, and the work function of the surface of the recording medium is changed by a tunnel current generated from the probe and passing through the recording medium. The information is read out by detecting a change in the tunnel current between the probe media due to a change in the work function as a write record on the surface of the recording medium.

Here, the tunnel current generating probe is
It is manufactured by micromechanics technology and is arranged near the tip of a cantilever provided with a displacement means on a substrate having a semiconductor layer.

As the displacement means, a piezoelectric effect, an electrostatic force or the like is used, and a means using a piezoelectric bimorph is preferably used. Further, since the cantilever is formed on the substrate having the semiconductor layer, a current amplification circuit and a current-voltage conversion circuit for amplifying a current signal generated from the tunnel current generation probe, and a driving driver for the displacement means A semiconductor integrated circuit including a circuit and the like is provided near the cantilever.

An embodiment according to the present invention of a bimorph-driven cantilever used for driving a tunnel current generating probe will be described below. FIG. 3 shows a sectional view thereof.

First, as the semiconductor substrate 1, the crystal orientation (10
0) as the main surface (a thickness of 525 μm).
m) on the surface thereof as a first layer 2 (not shown) C
Polycrystalline silicon is grown by the VD method at 500 ° C. at 1000 ° C., and only 40
It is removed by wet etching using an aqueous solution of potassium hydroxide at ℃. The pattern is formed using a photoresist. Hereinafter, photoresist is used for pattern formation.

Next, 2000 angstrom silicon nitride is formed as the second layer 3 at 800 ° C. by LPCVD, and a pattern of the cantilever portion is formed. On this occasion,
The silicon nitride is dry-etched by a reactive ion etching device.

The length direction of the cantilever is Si (11
1) It coincides with the direction of intersection of the equivalent surface with the Si (100) surface. The length of the cantilever is 1000 μm and the width is 50 μm.

Next, the bimorph driving portion 2
The piezoelectric layers 4, 5 and the three electrode layers 6, 7, 8 are formed. The piezoelectric layer is formed using zinc oxide by an alternating current sputtering method, and a pattern is formed by wet etching using an aqueous acetic acid solution. 3 for the electrode layers 6, 7, 8
Use 1000 Å gold with 0 Å chromium subbed. Chromium and gold are formed by vapor deposition using resistance heating, and chromium is formed by wet etching using an aqueous solution of ceric ammonium nitrate and perchloric acid, and gold is formed by wet etching using an aqueous solution of iodine and potassium iodide. Each electrode has a take-out portion leading to a driving amplifier circuit. To prevent conduction between the electrodes, make the electrode pattern smaller than the piezoelectric pattern,
The pattern shape is such that the covering between the layers is step-shaped. The upper electrode 6 and the lower electrode 8 are each divided into two by the center line in the length direction of the cantilever, and form a cantilever having five electrodes in total, which can be driven in three axial directions.

Further, a protective layer 9 of a driving portion, a probe 10 for generating a tunnel current, and an extraction electrode 11 thereof are formed. As the protective layer 9 in the driving portion, an amorphous silicon nitride film formed by 2,000 angstrom by a CVD method and patterned by dry etching with an RIE apparatus is used. The extraction electrode 11 is formed by forming a chromium film by an evaporation method using resistance heating and forming a pattern. The tunnel current generating probe 10 is formed by depositing gold to a thickness of 2 μm by vapor deposition, leaving the photoresist at the probe portion in a circular shape, and forming the probe by isotropic wet etching using an aqueous solution of iodine and potassium iodide.

Finally, the first layer 2 of the polycrystalline silicon layer is removed with an aqueous potassium hydroxide solution (KOH: H ₂ O = 1: 2, weight ratio) at 80 ° C. The semiconductor substrate 1 is etched by isotropic etching to form a cantilever.

Comparative Example 3 Table 2 shows a comparison between the bimorph-driven cantilever shown in Example 3 and the bimorph-driven cantilever manufactured according to the prior art.

[0034]

[Table 2] As shown in Table 2, in Example 3, the beam was displaced by 30 μm when the beam was displaced at a voltage of 50 V, whereas in the conventional example, when a voltage was applied, the root portion of the beam was broken by the stress of the film.

[0035]

As described above, when manufacturing a beam on a semiconductor substrate, first, a first layer is formed on the surface of the semiconductor substrate.
After patterning, then forming and patterning the second layer, and further removing the first layer, the semiconductor substrate is anisotropically wet-etched to form a beam composed of the second layer. There is an effect that a large number of beams can be manufactured at a high density without a problem of stress.

[Brief description of the drawings]

FIG. 1 is a process sectional view showing a method for manufacturing a cantilever according to one embodiment of the present invention.

FIG. 2 is a diagram of a doubly supported beam according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a bimorph-driven cantilever according to a third embodiment of the present invention.

FIG. 4 is a process chart showing a method for manufacturing a cantilever according to the prior art.

FIG. 5 is a process chart showing a method of manufacturing a cantilever according to a conventional example.

[Description of Signs] 1 Semiconductor substrate 2 First layer 3 Second layer 4, 5 Piezoelectric layer 6, 7, 8 Electrode layer 9 Protective layer of driving part 10 Tunnel current generating probe 11 Extraction electrode 12 Si (100) surface 13 Si (111) surface 14 Si (211) surface 15 Marker hole 16 Etching hole

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 29/84 H01L 21/306 H01L 41/09

Claims (3)

(57) [Claims] In a method of manufacturing a beam obtained by processing a semiconductor substrate, a first step of forming and patterning a first layer on the semiconductor substrate, and a step of forming a first layer on the semiconductor substrate after the first step is completed. A second step of forming and patterning two layers,
After removing the first layer of the semiconductor substrate having completed the second step by etching, the semiconductor substrate is etched by an etching method in which an etching rate depends on a crystal orientation,
And a third step of forming a beam composed of the second layer. 2. The method according to claim 1, wherein the beam is a cantilever. 3. The method according to claim 1, wherein the beam is a doubly supported beam.