JPH0565065B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing microscopic cavities made of Si single crystal. More specifically, for example, a diaphragm is formed on the surface of a Si wafer, and one surface of the diaphragm is a pressure-receiving surface.
The present invention relates to a method for manufacturing microscopic hollow chambers, which is applied when forming hollow chambers on a wafer.

(Prior Art) Conventionally, as a method for manufacturing a diaphragm and a hollow chamber using Si crystal, for example, the
of Transducer´85.1985, pp182-185 HH
Busta, JFDetry, “LASER−
RECRYSTALLIZED
PIEZORESISTIVE MICRO−DIAPHRAGM
There is a method described in ``SENSOR.'' This method produces a microscopic hollow chamber of about 1.25 μm between the Si substrate and the Si diaphragm by recrystallizing polycrystalline Si using a laser. It is something.

(Problems to be Solved by the Invention) However, in the method of manufacturing fine hollow chambers using such a method, it is difficult to sufficiently reduce the number of grain boundaries, and when recrystallizing with a laser, Since a part of the substrate or the hollow space is locally heated, there is a problem in that residual strain, migration, and grain boundaries are generated, which deteriorates the electrical and mechanical properties of the Si crystal.

The present invention was made in view of these problems, and its purpose is to form fine hollow spaces while maintaining complete crystallinity and without deteriorating residual strain or properties of Si crystals. The aim is to provide a manufacturing method.

(Means for Solving the Problems) FIG. 1 is a flowchart showing the steps of the method of the present invention. The method of the present invention involves creating fine hollow chambers on a silicon crystal substrate through the following steps.

Step 1: Forming an oxide film on the silicon crystal substrate and removing the oxide film at the corresponding position where a microscopic hollow chamber is created to form a first hole. Step 2: Forming the first hole on the silicon crystal substrate. Step 3: growing a first epitaxial layer to fill the hole; Step 3: removing the oxide film to form a second hole in contact with the first epitaxial layer and communicating with the silicon crystal substrate; Step 4: Step 5: growing a second epitaxial layer to fill the second hole and cover the surface of the first epitaxial layer; Step 6: removing a portion of the oxide film to form a third hole communicating with the epitaxial layer; Step 6: removing the first epitaxial layer from the third hole by etching; Step 7: Third hole. A step of sealing the hole with a third layer.

(Function) Initially, the first layer was formed on a silicon substrate.
portions of the epitaxial layer are selectively removed by etching to produce microscopic cavities on the silicon substrate surrounded on top by a second epitaxial layer.

(Example) FIG. 2 is an explanatory diagram showing an example of the method of the present invention. Here, a case is illustrated in which a fine hollow chamber having a diaphragm as one wall is manufactured on a silicon crystal substrate.

First, as shown in (a), (100), P-type silicon substrate (boron impurity concentration B is ¹⁰²⁰ pieces/cm2 ^or more)
1, an oxide film 2 of SiO ₂ is formed,
The oxide film at the corresponding position where the microscopic hollow chamber is to be created is removed, and the hole 3 is formed.

Next, as shown in (b), a first epitaxial layer L1 is formed to fill the hole 3. This first
The epitaxial layer of, for example, _H2 carrier,
It can be formed by growing SiH ₄ +HCl at 1000°C to 1100°C.

Next, as shown in (c), the SiO ₂ oxide film 2 is removed and a hole 4 is formed so as to be in contact with the first epitaxial layer L1 and to communicate with the silicon substrate 1.

Next, as shown in (d), a second epitaxial layer L2 is formed to fill the hole 4 and cover the surface of the first epitaxial layer L1. This second
The epitaxial layer L2 is made of, for example, an H ₂ carrier,
It is formed of SiH ₄ +HCl+B ₂ H ₆ and grown until the boron impurity concentration B becomes 10 ²⁰ impurities/cm ² or more.

Next, as shown in (E), a SiO ₂ oxide film 2 is formed so as to be in contact with the second epitaxial layer L2 and the silicon substrate 1 and to communicate with the first epitaxial layer L1.
A hole 5 is provided by removing a portion of the hole 5.

Next, as shown in (F), N ₂ H ₄ · H ₂ O, 110°C
Then, the first epitaxial layer L1 is selectively etched through the hole 5.

Next, as shown in (g), the SiO ₂ oxide film 2 provided on the silicon substrate 1 is removed by etching.

Finally, as shown in (h), the hole 5 is sealed with the third epitaxial layer L3. This third epitaxial layer L3 is composed of, for example, an H ₂ carrier,
It can be formed by growing SiH ₄ at 1000°C to 1100°C.

By the above-described procedure, a fine hollow chamber 6 can be created on the silicon substrate 1. Here, the size and shape of the hollow chamber 6 can be arbitrarily determined depending on the thickness and shape of the first epitaxial layer L1.

FIG. 3 is an explanatory diagram showing another example of the method of the present invention. In this example, the steps (a) to (f) are the same as those in FIG. 2, but in (g), the hole 5 used for etching the epitaxial layer L1 in FIG. A third layer L3 is formed by sputtering SiO ₂ for sealing. next,
As shown in (h), by patterning, unnecessary portions (portions other than those covering the holes 5) of the sputtered film (third layer) L3 are etched and removed.

As a result, a fine hollow chamber (vacuum level) surrounded by the second epitaxial layer L2 is formed on the silicon substrate 1.
10 ^-3 Torr).

In addition, in each of the above embodiments, the hole 5 may be sealed by vapor deposition or CVD in addition to the above-mentioned method.
(Chemical Vapor Deposition)
It may be made of Si ₃ N ₄ , polycrystalline Si, amorphous Si, silicide metal, or the like.

FIG. 4 and FIG. 5 are structural sectional views showing an example of application of the method of the present invention.

The one in FIG. 4 is applied to a pressure sensor, in which a hollow chamber 6 surrounded by a second epitaxial layer L2 is formed on a silicon substrate 1, and a pressure guiding hole communicating with this hollow chamber 6 is formed. 7. A pressure P to be measured is introduced into the hollow chamber 6 through a pressure guiding hole 7, and a pressure P to be measured is introduced into the second epitaxial layer L.
2 acts as a diaphragm, and a strain change occurring in this diaphragm is detected by a diffusion strange gauge 8 provided there.

The one in FIG. 5 is applied to a vibration type transducer, and the second epitaxial layer L
A vibrator 9 is installed in a hollow chamber 6 surrounded by 2. The vibrator 9 can be made by etching the silicon substrate 1, for example, and can be installed in the hollow chamber 6 completely isolated from external fluid. Here, the third layer L3
When forming and sealing the hollow chamber 6, the pressure is reduced.
If a CVD device is used, the pressure inside the hollow chamber 6 can be lowered, and a vibrating transducer with a high Q can be obtained.

(Effects of the Invention) As explained above, the method of the present invention has the following advantages:
The second epitaxial layer is formed, the first epitaxial layer is removed by etching, and the hollow chamber is sealed by the third layer, thereby creating a fine hollow chamber on the silicon substrate. Therefore, according to the method of the present invention, fine hollow chambers can be created on a silicon substrate with few grain boundaries, the same crystallinity as a silicon substrate, and no residual strain or deterioration of the properties of Si crystals. be able to. Moreover, if the hollow chamber is sealed by vapor deposition or sputtering, the hollow chamber can be easily maintained at a high degree of vacuum.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the procedure of the method of the present invention, FIG. 2 is an explanatory diagram showing an example of the method of the present invention,
FIG. 3 is an explanatory diagram showing another example of the method of the present invention;
5 and 5 are configuration diagrams showing an example of application of the method of the present invention. 1...Silicon substrate, 2...SiO ₂ oxide film, 3,
4, 5...hole, 6...hollow chamber, L1, L2, L3
...epitaxial layer.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a microscopic hollow chamber, in which a microscopic hollow chamber is formed on a silicon crystal substrate through the following steps (a) to (g). (b) Forming an oxide film on the silicon crystal substrate and removing the oxide film at corresponding positions where microscopic hollow chambers are to be formed to form a first hole; (b) forming the first hole on the silicon crystal substrate; (c) removing the oxide film and growing a second epitaxial layer in contact with the first epitaxial layer and communicating with the silicon crystal substrate;
(d) growing a second epitaxial layer to fill the second hole and cover the surface of the first epitaxial layer; (e) forming a second epitaxial layer and silicon; (f) forming a third hole by removing a portion of the oxide film in contact with the crystal substrate and communicating with the first epitaxial layer; (f) etching the first epitaxial layer from the third hole; (g) A step of sealing the third hole with the third layer. 2. A method for manufacturing a microscopic hollow chamber according to claim 1, wherein the third layer is an epitaxial layer. 3. The method for manufacturing micro hollow chambers according to claim 1, wherein the third layer is formed by vapor deposition or sputtering.