JPS5944875A - Semiconductor device having beam structure - Google Patents

Abstract

PURPOSE:To unnecessitate the positioning of super high accuracy by a method wherein a supporting base composed of poly Si is formed on an insulation film, and a movable beam composed of poly Si is supported thereon. CONSTITUTION:A fixed electrode layer 13 is formed on the surface of the semiconductor substrate 11 by a diffused layer 14 of the reverse conductive semiconductor as the substrate 11 or by a conductive thin film. Next, the surface of the substrate 11 is coated with the alkali etching resistant insulation film 12, and the supporting base 14 composed of alkali etching poly Si is formed at a fixed position on the insulation film. Then, the movable beam composed of alkali etching resistant poly Si doped with a P type impurity 15 at high density is so constructed on this supporting base as to be supported in an integral body.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides the following methods: 1. A beam capable of vibration is formed on a semiconductor substrate;
:Relating to a semiconductor device having a beam structure.

This type of beam (111) A semiconductor device (1) is basically supported at one end or both ends on a semiconductor substrate, the vibrating part is almost parallel to the surface of the board, and the vibrating part is integrally connected to the vibrating part. The semiconductor device includes a movable beam including an electrode layer, and a fixed electrode layer provided on the surface of the semiconductor substrate opposite to the movable beam and forming a condenser together with the electrode layer.

Regarding this semiconductor device, Akane Tetsu, the inventor of the present invention, first developed and tested a device with the structure shown in FIG.

The preceding example of a semiconductor device based on the beam 1111 structure shown in FIG. 1 will be explained in order of its manufacturing process. This device uses an N-type (100) 3i substrate 1. First, P''1Ff2, in which 1]-type impurities are buried at a high fAIσ, is formed at a predetermined position on the substrate 1, and then the entire surface of the single substrate 1 is An N-type (100) SiIFJ3 is formed by epitaxial growth, and then a thermally oxidized 3iQz film 4 is coated on the - face of the epitaxial 1N layer 3, and then a contact layer 1 is formed to reach the P+ layer 2. ~ Holes 7 are drilled and soched (permanently installed), and then ΔU is deposited on the entire surface side of the substrate 1, and unnecessary portions of ΔU are removed by goutsbung to form a predetermined pattern of Δ11 electrode wiring 55. !, and then remove 3 i 021!+!4 around the forming part of the movable beam 6 by etching.After that, 41'/, +! Ruru N type (10
0) Remove the St epitaxial layer 3 by etching and notching,
To form the digging part 8, J, S, SiO2 film 4 and △1
A movable beam 6 having a two-layer structure of one electrode 5 is left in a cantilevered state.

The formation of the ten-dimensional digging portion 8 will be described in detail. N type (100)
Etching of the St epitaxial layer 3 is carried out using a J alkaline etching solution (for example, a mixture of ethylenediamine, 1,000 pyrocatechol and water) which exhibits remarkable anisotropy. 1', I
FIG. 2 shows how the J beam 6 is formed.

FIG. 2 is a plan view of the movable beam 6 and its surrounding area.

As shown in FIG. 2, an etched window portion formed by removing the S + 02 film 4 in a square shape is formed around the portion that is to become the movable beam 6. Each side of this =1 character shape]-touching window is made of <110> directions. Regarding the depth direction, when the 1'-cutting reaches the P+ buried layer 2, the etching speed in the depth direction becomes extremely slow, and the P+ buried layer 2 acts as a ]-etching stopper. Also < 1
10 :> direction.

The etched side surface along the side becomes a (111) plane, and the etching speed becomes slow. When etching progresses to a certain extent, a (100) plane appears at the tip of the movable beam 6, and a (100) plane appears at the tip of the movable beam 6.
The speed of the 00) plane is about 3 that of the (111) plane.
It is 0 times larger, and because of A, it is etched in the direction of the arrow from the tip of the beam C3 to the two directly below the movable beam 6. A completely hollow trench 8 is formed right below the JJ beam 6, resulting in a cantilevered structure. IJ beam 6 is completed.

However, in the previous example of a semiconductor device in which 1 is connected, the fixed electrode layer also serves as an etching speed bar.
-) Formed with 10 buried layers 2, etched all 4 Schiller layers 3 with an anisotropic alkaline etching solution to form trenches 8, and left movable beams 6. As such, the following problems arise.

First, since one bitaxitol layer is required, manufacturing costs are high. In addition, since the 3i square plate is limited to the (100) plane, and each side of the pattern of the single-cutting window that makes the movable beam must be precisely aligned in the <110> direction, -1 (It is necessary to set the reference side (orientation flat) with a high precision of 1.5 degrees ( ), which makes manufacturing complicated. Furthermore, as explained in detail in Figure 2, 1 bitaxial layer 3 directly below the movable beam 6 as shown in FIG.
is not etched only from the tip direction of the movable beam 6, so the alkaline etching solution is
Even with an etching rate of 7' μm, it takes a long time of about 10 hours to make a movable beam with a length of, for example, 300 μm. For this reason, it is not possible to use a Δ℃ film as an electrode material for an inexpensive 4 film with an etching rate of 0.1 to 0.2 film 1 m/hour for an alkaline etching solution, and as explained earlier, Au is used as an electrode material Y1. This also increases the cost of the device.

This invention was made in view of the above-mentioned conventional problems, and its purpose is to use Si (100
) Not limited to substrates, -1″ pitaxitol is not required,
There is no need for ultra-high precision positioning U'' that matches the anisotropy of etching, and the T etching time for forming a movable beam is short.
Cheap A1 etc. can also be used as a monthly electrode charge, making it a more reasonable option. It is an object of the present invention to provide a semiconductor device having a beam IM body that can be rotated from one side to the other.

In order to quickly achieve the above object, the present invention (1) made the surface of a semiconductor substrate on which a fixed electrode layer was formed with an aluminum-resistant material.
In addition to coating with an insulating film R, a support base made of alkali-etchable polysilicon is formed at a predetermined position to ensure insulation, and P-type impurities are added to the top surface of this support base at high temperature to provide alkali etch resistance. It is characterized in that it is constructed so that the II moving beam made of polysilicon is integrally supported.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 3 is a diagram showing the manufacturing process of a semiconductor device for a beam structure to which the present invention is applied, and FIG. 4 is a diagram showing the semiconductor device according to the present invention completed through the manufacturing process of FIG. 3. There is. Below, each process (A) to (+-
1) will be explained in order.

(A)...First, for example, resistivity 5-8 ΩcmGl)
Prepare an N-type 81 substrate 11, oxidize its surface, form a thermally oxidized Si02 film 12 of, for example, about 5,000 layers over the entire surface, form the above-mentioned fixed electrode layer, and remove Si02 in the exposed area.
The film 12 is removed by 1 tweezing, and the removed part is 10
00 level thermal oxidation S! At the same time as the 02 film is formed, a thin F) type layer 13 is formed by implanting boron[1] into the surface of the 3i substrate 11 in that area by ion implantation.

(B)...Next above) Hot thermal oxidation S! After removing the 02 film with hydrofluoric acid, the surface is oxidized again to give a
Insulating film 121 on thermally oxidized Si 02 film
) to form. After that, for example, reduced pressure CV]] Law J:
5il-I4 is pyrolyzed at about 620"C'r, e.g.
An impurity-free polysilicon layer 14 of ~5 μm is formed. By this heat treatment during oxidation of one culm, the ICP type layer 13 with a depth of 1 μm or more is formed.
It becomes b.

(C)...Next, for example, by ion implantation, boron is implanted into 5X10+6 pieces/CI Pi at an acceleration voltage of 60 KeV.
! The surface of the above-mentioned polysilicon IH14 was injected with 1×102
0/Gl♂ or more [] type layer phase polysilicon = ln layer 1
5 to a thickness of 0.5 μm culm.

(1) )...Next, the polysilicone layer 14J3J in the portion other than the movable beam forming area and the P-type polysilinine layer 15 on the surface thereof are removed by -■- twisting.

In the example shown in Figure D, nipping is performed twice) to form two stages on the outer periphery of the polysilicon Fi1/I.
: is being written.

([)...Next, add 8l to the entire surface, for example 1,! 5
After evaporating to a thickness of IIm, remove unnecessary portions of A from A1 to J, and remove Δ that connects to ijJ moving beam.
! A Δl wiring 17 is formed which connects the wiring 16 and the one-film type layer 131) which is a fixed electrode layer. ]] The reason why two steps fJ are provided around the polysilicon layer 14 as shown in the figure is to prevent the Δ° C. wiring 16 from being disconnected.

(F)...Next, the entire surface is coated with 3i by CVD method, for example.
After low-temperature oxidation of l-14 at about 400° C. and phosphorus being added thereto to deposit a PSG film 18 with a thickness of, for example, 1.5 fzm, a bonding pad is applied to the film l-1 with J. And PS G If 180 in the town moving beam area) The film thickness is 3000 = 5000 culm thinner. .

(G)...The PSG film 18 is further etched to completely remove the SG film in the movable beam area. In this case, there is a thin P S on the supporting end side of the jj1 moving beam.
G film 19 is left.

(+-1)...Next, add a strong alkaline aqueous solution (e.g. ethylenediamine-pyrocatechol→-water mixture) to J
- Dip the entire body in I-Tsting liquid. Then,
Due to the impurity dependence during etching of 3i, the polysilicon 14 is etched, leaving a P-type deep polysilicon layer 15 with a high concentration of boron 15 remaining as the movable beam 1511.
Gahigiru. In addition, the polysilicon layer 14 is not entirely etched away; 1) the portion of the polysilicon layer 14 that is masked by the SG film 18 remains, and this portion is made of polysilicon with a P wall height of a ii) The support stand 1411 of the J moving beam 15h remains.

Bonding pad and 1IiJI beam 15h at most
The PSG film 18 is etched over the entire surface of the thinned portion 50 (1) of the 19th part of the SG film (), and the semiconductor device shown in FIG. 4 is completed.

The shape of the movable beam 151) is the same as the one-culm frame A1 in the figure [].
~ Can be made freely by etching. For example, q(
The shape of the movable beam 1511 can be covered so that the center of gravity shifts to the tip side in the longitudinal direction, or the shape of the movable beam 1511 can be
An elongated hole is opened in the center in the length direction of 511, and when etching one culm in Figure 1-1, the alkaline etching solution permeates through hole 11, and the I-nitching of the polysilicon layer 14 directly under the movable beam i51+ is performed. Shorten the time J: You can also do this.

Here, the application of the semiconductor device shown in FIG. 4 will be briefly explained. For example, if the mechanical vibration in the device is JJI, and its frequency is equal to the number of 0J per vibration of the movable beam 15h,
The movable beam 1511 resonates greatly, and the distance between the movable beam 1511 and the P-type layer 13b changes greatly.

The movable beam 1511 made of a P-type layer-concentrated polysilicon layer itself becomes an electrode layer, and the P-type layer 131) is a fixed electrode layer opposing it. is formed. Then move the movable beam 1511
When the vibration occurs and the distance from the mold layer 13b increases, the capacitance of the capacitor also changes according to the vibration amplitude. Also, as a matter of course, even if a vibration that deviates significantly from the natural frequency of the movable beam 1511 is applied, the R15II will not resonate, and therefore the capacitance of the capacitor will change (less than 5%).

Therefore, if a circuit is provided to detect the capacitance change between the movable beam 1 and the E5 II type layer 1311, the output of the circuit will cause the movable beam 1511 to vibrate at a frequency corresponding to its natural frequency. It is possible to overturn the judgment of whether or not the addition -) is present.

This capacitance change detection circuit can be integrally formed on the semiconductor device that supports the beam structure.

As shown in (a) above, the semiconductor device according to the present invention can be used, for example, as a vibration analysis device, and one specific example of its application is considered to be application to the detection of knocking in an automobile engine. When knocking occurs, the engine generates a noticeable vibration of about 7 Kfiz, but the natural frequency of the movable beam is increased to about 7 + 17. If you set it to 11, you can set this knocking detection to 11. Approximately 7K
For a movable beam with a vibration frequency of +12, when C polysilicon is used as in the present invention, the thickness of the beam is 0.55 μm, and the length of the beam is approximately 330 μm. It is. In this way, it is possible to realize a device that performs the functions and frequency discrimination functions of a mechanical type air converter directly on a microscopic semiconductor device. Another application example - C is
By detecting changes in capacitance due to acceleration and centrifugal force perpendicular to the water height part of the J moving beam, it is possible to apply this method to detect acceleration errors and rotation errors.

As explained in detail above, the semiconductor device having the predetermined structure according to the present invention has a fixed electrode layer on the surface of the semiconductor single plate, with a substrate and a semi-conductive diffusion layer or a conductive layer ++q. A support base made of alkali-etchable polysilicon is formed at a predetermined position on the insulating layer, and a support base made of alkali-etchable polysilicon is formed on the top surface of the support base. High i1i of P-type impurities! It is constructed so that a movable beam made of polysilicon that is resistant to alkaline earth and is added at the same time is integrally supported/)1
1 et al., the semiconductor '3 of the prior example shown in FIGS. 1 and 2
There is no need for an epitaxial layer like in the A-neck, and the semiconductor substrate is not limited to a Si (100) substrate; the area directly below and around the movable beam is polysilicon, and this polysilicon is etched in all directions with an alkaline etching solution. Since etching progresses from the beginning, even a beam with a length of 100μ
This can be formed by etching for about an hour.

This J: Since it requires a much shorter J etching time, it is possible to easily use ∆℃ as an electrode material, which has a slight elatinating gray level of 1 compared to an alkaline etching solution.In the same sense, an inexpensive PSG film can be used as a protective film material ! It can be used as l'31. Furthermore, since the anisotropy of etching is not used to form the movable beam, there is no need to provide ultra-high precision reference sides on each beam. As described above, according to the present invention, Yorigo J! A semiconductor device having a beam structure can be realized at low cost with the desired beam C1 hiss.

[Brief explanation of the drawing]

Figure 1 shows the end of the 31' conductor device located one inch to the right of the beam 414 structure.
Figure 2 is a cross-sectional view showing an example of J3 LJ in the device shown in Figure 1.
FIG. 3 is a partial plan view showing the process of forming a beam according to the present invention, and FIG. 1r1j is a cross-sectional view of the semiconductor device according to the present invention. FIG. 11... Semiconductor substrate 12, 121)... Oxide film 13, . 13b...[] type layer 14...Polysilicon layer 15...P type layer 8F 1 degree polysilicon layer 15h
......Movable beam 1411...Support stand 18...A℃ wiring electrode patent applicant [1san Jidosha Co., Ltd.

Claims (1)

[Claims] (1) The surface of the semiconductor substrate is coated with an alkali-resistant niche insulating film, and a support base made of alkaline earth, polysilicon, and bamboo is formed at a predetermined position on the insulation film. 1] A semiconductor device having a beam structure characterized in that a movable beam made of polycrystalline silicon resistant to high temperatures and doped with type impurities is integrally supported.