JPH06276043A - Manufacture of substrate for high frequency circuit - Google Patents

Abstract

PURPOSE:To provide the manufacture of the high frequency circuit substrate which maintains excellent characteristics and complies with the mass-production of products and a demand for high reliability. CONSTITUTION:A p type epitaxial film is formed on the surface of a silicon substrate, an n type layer 3 is formed partially in the p type epitaxial film, which is etched electrochemically to form a step; and a semiconductor thin film 5 is formed at the low part of the step and a dielectric thin film 6 is formed at the high part of the step to manufacture the high frequency circuit substrate on which the top surface of the semiconductor thin film 5 and the top surface of the dielectric thin film 6 are in level with each other without having any step.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a high frequency circuit substrate used for manufacturing a high frequency circuit element.

[0002]

2. Description of the Related Art Mobile phones, MCA (Multi Channel Acces
s) With the spread of mobile radios used in the high frequency range of several hundred MHz to several GHz such as radio, miniaturization of radio equipment,
There is a demand for weight reduction, and inevitably, there is a demand for reduction in size and weight of components used in these wireless devices. In particular, miniaturization of high-frequency amplifier circuits and filters that handle signals in the high-frequency range is not said to be smaller and more quantified than LSIs used for normal signal processing. There is a strong demand for downsizing and weight reduction of parts used in.

In order to reduce the size and weight of high-frequency parts, attention has been paid to surface acoustic wave devices using piezoelectric bodies. This is because it is possible to manufacture a filter element that is smaller and lighter than the coaxial filter and the helical filter that have been used so far. Further, instead of using this surface acoustic wave element as a single filter, a dielectric thin film such as aluminum nitride is formed on a semiconductor substrate having a high frequency amplifier circuit formed in a part thereof to form a surface acoustic wave filter. High frequency integrated circuits have been disclosed (eg Tsubouchi K; IEEE Trans.Sonics.Ultrason.
Vol.32, No.5, P634 (1985)).

However, when a single crystal silicon substrate is used as the substrate and a high frequency amplifier circuit is formed on a part of the surface of the silicon substrate and aluminum nitride is deposited on the surface of the same substrate to form a surface acoustic wave filter, It is difficult to obtain sufficient characteristics with an amplifier circuit formed of silicon as an amplifier circuit used in a high frequency region of several hundred MHz to several GHz. As such an amplifier circuit in the high frequency region, an amplifier circuit formed of a compound semiconductor such as gallium arsenide is usually used. This is because an amplifier circuit formed of gallium arsenide can operate at a higher speed than a silicon amplifier circuit when handling high frequencies.

On the contrary, in order to obtain sufficient characteristics as a high frequency amplifier circuit, a high frequency amplifier circuit is formed on a part of a gallium arsenide substrate, aluminum nitride is formed on the same substrate surface, and a surface acoustic wave is formed. When the filter is formed, the characteristics as a high frequency amplifier circuit are sufficient, but the characteristics as a surface acoustic wave filter, especially the transmission speed of the surface acoustic wave are not sufficient. This is because the velocity of the surface acoustic wave transmitted through gallium arsenide is as small as 3000 m / s or less, so that the surface acoustic wave on the aluminum nitride film formed on the gallium arsenide substrate is also affected by it, and a sufficient velocity cannot be obtained. This is because.

The applicant of the present invention has found that, as shown in FIG. 6, a gallium is formed on a part of the surface of the element substrate 100 as a problem of the element in which the high frequency amplifier circuit and the surface acoustic wave element are integrated on the same substrate. Semiconductor thin film 101 made of arsenic and same substrate 10
A high frequency circuit substrate in which an aluminum nitride thin film 102 is formed on another part of the surface is developed, and a high frequency amplifying element is provided on the semiconductor thin film 101 of this high frequency circuit substrate, and a surface acoustic wave is formed on the aluminum nitride thin film 102. It has been found that the problem can be solved by a high-frequency circuit element formed with the element (Japanese Patent Application No. 3-3660691).

This high-frequency circuit board and the high-frequency circuit element using the same solves the above-mentioned problems as a high-frequency integrated circuit element and achieves the initial object.
Since a semiconductor thin film, an aluminum nitride film, etc. are formed on the surface of the element substrate, a step is created by these, and the metal wiring process between elements is not easy and the mass wiring process is not easy. The problem remained. It is also said from the experience of general integrated circuits that such a step causes breakage of metal wiring and the like, and there is concern about the reliability as an integrated circuit element.

[0008]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a high-frequency circuit substrate on which a high-frequency amplifier circuit and a surface acoustic wave device are formed on one substrate so that the circuit and the device formed exhibit good characteristics. It is another object of the present invention to provide a method for manufacturing a high-frequency circuit board, which is capable of meeting the demand for mass production as a product and high reliability.

[0009]

Means for Solving the Problems The above-mentioned objects are to provide a step of forming a p-type single crystal silicon film on an n-type single crystal silicon substrate by an epitaxial growth method, and an n-type part of the p-type single crystal silicon film. A step of forming a layer, and immersing the n-type single crystal silicon substrate in the potassium hydroxide aqueous solution while applying a potential of -1 V or more with respect to the potential of the potassium hydroxide aqueous solution as a reference, It is characterized by comprising a step of partially etching, a step of forming a semiconductor thin film in a portion where the p-type single crystal silicon film is etched, and a step of forming a dielectric thin film in a portion where the n-type layer is formed. And a method of manufacturing a substrate for a high frequency circuit.

Further, the above-mentioned various objects are a step of forming an n-type single crystal silicon film on an n-type single crystal silicon substrate by an epitaxial growth method, and a p-type single crystal silicon film on the n-type single crystal silicon film by an epitaxial growth method. And a step of forming an n-type layer on a part of the p-type single crystal silicon film, and a potential of -1 V or more on the n-type single crystal silicon substrate, based on the potential of the aqueous potassium hydroxide solution. And a part of the p-type single crystal silicon film is etched by immersing the p-type single crystal silicon film in an aqueous potassium hydroxide solution.
A method for manufacturing a high frequency circuit substrate, comprising: a step of forming a semiconductor thin film in a portion where a mold single crystal silicon film is etched; and a step of forming a dielectric thin film in a portion where the n-type layer is formed. To be achieved.

[0011]

According to the first method of manufacturing a high frequency circuit substrate of the present invention, a p-type single crystal silicon film is formed on an n-type silicon substrate by epitaxial growth, and an n-type layer is formed on the p-type single crystal silicon film. Then, by electrochemically etching the p-type single crystal silicon film other than the part where the n-type layer is formed (p-type part), a step is formed on the silicon substrate leaving only the n-type layer. A high frequency circuit substrate having a flat surface is manufactured as a high frequency circuit substrate after the semiconductor thin film and the dielectric thin film are formed by absorbing the thickness of the semiconductor thin film and the dielectric thin film formed on the silicon substrate. Is.

According to a second method of manufacturing a high-frequency circuit board of the present invention, an n-type single crystal silicon film is formed on an n-type silicon substrate by epitaxial growth, and then a p-type single crystal silicon film is formed in the same manner as above. Is formed by epitaxial growth, and only the p-type portion is selectively electrochemically etched to leave a step on the silicon substrate leaving only the n-type layer. The step causes the semiconductor thin film and the dielectric to be formed on the silicon substrate. By absorbing the thickness of a body thin film, a high frequency circuit substrate having a flat surface is manufactured as a high frequency circuit substrate after a semiconductor thin film and a dielectric thin film are formed. In this manufacturing method, since the n-type single crystal silicon film is once formed by epitaxial growth on the n-type silicon substrate and then the p-type single crystal silicon film is formed by epitaxial growth, the p-type single crystal film is removed by etching. After that, when the semiconductor thin film is formed, the semiconductor thin film is formed on the n-type single crystal silicon film by epitaxial growth, so that the semiconductor thin film having good crystallinity is obtained.

According to the present invention, only the p-type portion can be selectively electrochemically etched and removed, and since the p-type portion to be removed is formed by the epitaxial growth method, the precision is very high. The growth thickness can be controlled by. As a result, a p-type single crystal silicon film having an arbitrary thickness can be formed on the n-type silicon substrate by epitaxial growth, and only the p-type portion can be selectively electrochemically removed by etching. Therefore, the portion removed by etching can obtain a highly accurate step corresponding to the required thickness of the semiconductor thin film according to the characteristic requirements of the circuit or element to be formed later. It is possible to manufacture a high-frequency circuit substrate having a flat surface by forming a thin film.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings. The same members are designated by the same reference numerals.

Example 1 In the first method for manufacturing a high-frequency circuit substrate of the present invention, first,
As shown in FIG. 1a, p is formed on the n-type single crystal silicon substrate 1.
The type single crystal silicon film 2 is formed by an epitaxial growth method. This p-type single crystal silicon film 2 portion is etched to expose a silicon surface which will be a portion where a semiconductor thin film will be formed in the subsequent steps.

The thickness of the p-type single crystal silicon film 2 formed by epitaxial growth is, as will be described later, the height of a step due to a portion removed by etching and a portion left after the n-type layer 3 is formed. become. The step is such that a dielectric thin film is formed on the upper surface separated by the step later and a semiconductor thin film is formed on the lower surface. In general, the dielectric thin film and the semiconductor thin film to be formed need to be thicker than the semiconductor thin film because of the necessity of the high frequency amplification element and the surface acoustic wave element formed therein. Therefore, the height of the step is formed so that the height of the step and the thickness of the dielectric thin film formed on the surface with the higher step are equal to the thickness of the semiconductor thin film. There is a need. For example, when the thickness of the semiconductor thin film to be formed is 4 μm and the thickness of the dielectric thin film is 0.5 μm, the height of the step is 3.5 μm. Since the height of this step corresponds to the thickness of the p-type single crystal silicon film 2 to be etched, the thickness of the p-type single crystal silicon film 2 depends on the thickness of the dielectric thin film and semiconductor thin film to be formed later. Is adjusted appropriately.

For this epitaxial growth, the usual LI
Although it is possible to control the thickness with sufficient accuracy even by the CVD method used in the S manufacturing process, if the molecular beam epitaxy method is used for more precise control, the thickness can be controlled at the molecular level. It is also possible to control the thickness.

Next, as shown in FIG. 1b, an n-type layer 3 reaching the n-type single crystal silicon substrate is formed on a part of the p-type single crystal silicon film 2 formed by the epitaxial growth method. The n-type layer 3 is formed by an ion implantation method or a thermal diffusion method. In the case of using the ion implantation method, a mask having an opening at a portion to be the n-type layer 3 is provided, and ions are implanted therein. In the case of using the thermal diffusion method, a glass-based film containing an n-type impurity, for example, a PSG film or an n-type polysilicon film is formed in a portion to be the n-type layer 3 and heat treatment is performed to reach the substrate 1. Then, the n-type layer 3 is formed.

Next, a method of etching the p-type single crystal silicon film 2 having the n-type layer 3 formed on a part thereof will be described.

First, an outline of an apparatus for performing etching will be described. As shown in FIG. 2, this etching apparatus includes an etching bath 20 for carrying out an aqueous potassium hydroxide solution for etching, a potentiostat 22 for controlling voltage and current, and a microcomputer 26 for monitoring current value and current value. In the etching tank 20, a reference electrode (R
E) 23, a sample electrode (WE) 24 and a counter electrode (CE) 25 provided on the silicon substrate to be etched are installed, and nitrogen for removing oxygen dissolved in the potassium hydroxide aqueous solution is provided in the etching tank 20. A bubbling device (not shown) is provided. A saturated calomel electrode (SCE) is used as RE, and voltage values used in the following description are values based on this RE.

To perform etching, a sample electrode 24 for applying a voltage is provided on the single crystal silicon substrate 1 having the p-type single crystal silicon film 2 having the n-type layer 3 formed on a part thereof by soldering or the like. A coating resin is applied to the electrode portion to protect the electrode portion from the potassium hydroxide aqueous solution, and the electrode portion is immersed in a 40% potassium hydroxide aqueous solution at 60 ° C. in an etching tank to have a potential of -1 V or more, preferably 0 V or more. Voltage is applied so that This results in FIG.
As shown in FIG. 5, the p-type single crystal silicon film 2 formed on the silicon substrate 1 is etched, and the n-type layer 3 part remains and a step is formed.

Next, after a step is formed on the silicon substrate 1 by the above-mentioned electrochemical method, as shown in FIG. 3a, a semiconductor thin film 5, such as gallium arsenide (GaAs), is formed on the lower surface of the step. A compound semiconductor thin film is formed by the CVD method. If necessary, a semiconductor thin film 5 having good crystallinity can be obtained by forming a single crystal silicon film on the silicon surface by an epitaxial growth method before forming the semiconductor thin film 5.

Next, as shown in FIG. 3b, a dielectric thin film 6, for example, aluminum nitride, zinc oxide, lithium tantalate, lead zirconate titanate or the like is formed on the surface having the higher step by the sputtering method or the CVD method. To do. This makes it possible to manufacture a high-frequency circuit substrate in which the surfaces of the semiconductor thin film 5 and the dielectric thin film 6 are uniform and flat.

Example 2 In the second method for manufacturing a high-frequency circuit board of the present invention, first,
As shown in FIG. 4 a, n is formed on the n-type single crystal silicon substrate 1.
The type single crystal silicon film 4 is formed by an epitaxial growth method.

Next, as shown in FIG. 4B, a p-type single crystal silicon film 2 is formed on the n-type single crystal silicon film 4 by an epitaxial growth method.

After that, as in Example 1, an n-type layer 3 is formed on a part of the p-type single crystal silicon film 2 as shown in FIG. 5a, and as shown in FIG. The p-type portion is etched by etching, and a semiconductor thin film 5 is formed on the exposed n-type single crystal silicon film 4 as shown in FIG. 5c. As shown in FIG. 5d, the semiconductor thin film 5 remains after etching. A dielectric thin film 6 is formed on the n-type layer 3 portion.

According to this method, the n-type single crystal silicon film 4 previously formed by the epitaxial growth method exists under the p-type layer portion removed by etching.
Since the silicon surface exposed when the p-type single crystal film 2 is removed is the silicon surface formed by this epitaxial growth, the semiconductor thin film 5 formed thereafter can have good crystallinity.

In the high-frequency circuit substrate of the present invention formed by the above-described manufacturing method, the surface of the semiconductor thin film 5 forming the high-frequency amplifier element and the surface of the dielectric thin film 6 forming the surface acoustic wave element are on the same plane. Therefore, it can be provided to the manufacturing process of the device or the integrated circuit in a state where the entire substrate is flattened. Therefore, in the device or integrated circuit manufacturing process, since there is no unnecessary step on the substrate surface, it is possible to simultaneously pattern the interlayer insulating film, the metal wiring film, etc. on the semiconductor thin film and the dielectric thin film.

[0029]

As described above, according to the method for manufacturing a high-frequency circuit board of the present invention, a high-frequency circuit board in which a semiconductor thin film and a dielectric thin film, which are entirely flat, are formed on a silicon substrate is manufactured. Therefore, when manufacturing a high-frequency circuit element using this high-frequency circuit substrate,
Since the device can be formed on a flat substrate without steps, the wiring process and patterning process can be facilitated when forming an integrated circuit, which contributes to mass production and improved reliability as a high frequency integrated circuit device. You can

[Brief description of drawings]

FIG. 1 is a cross-sectional view for explaining the first method for manufacturing a high-frequency circuit board of the present invention.

FIG. 2 is a diagram for explaining electrochemical etching used in the method of manufacturing a high-frequency circuit substrate of the present invention.

FIG. 3 is a cross-sectional view for explaining the first method for manufacturing the high-frequency circuit board of the present invention, which is subsequent to FIG.

FIG. 4 is a cross-sectional view for explaining the second method for manufacturing the high-frequency circuit board of the present invention.

FIG. 5 is a cross-sectional view for explaining the second method for manufacturing the high-frequency circuit board of the present invention, which follows FIG.

FIG. 6 is a cross-sectional view of a conventional high-frequency circuit board.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Silicon substrate, 2 ... P-type single crystal silicon film 3 ... N-type layer, 4 ... N-type single crystal silicon film 5 ... Semiconductor thin film, 6 ... Dielectric thin film, 20 ... Etching tank,
22 ... Potentiostat, 23 ... Reference electrode,
24 ... Sample electrode, 25 ... Counter electrode,
26 ... Microcomputer, 30 ... Single crystal silicon film, 31
… Silicon oxide film.

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[Procedure amendment]

[Submission date] May 20, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

2. Description of the Related Art Mobile phones, MCA (Multi Channel Acces
s) With the spread of mobile radios used in the high frequency range of several hundred MHz to several GHz such as radio, miniaturization of radio equipment,
There is a demand for weight reduction, and inevitably, there is a demand for reduction in size and weight of components used in these wireless devices. Among them, high-frequency amplifier circuit and miniaturization of the filter that handles signals of the high frequency range is different from the LSI and the like used in the normal signal processing, a small, it can not be said to have progressed light weight, such a high frequency band There is a strong demand for downsizing and weight reduction of parts used in.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] Explanation of code

[Correction method] Change

[Correction content]

DESCRIPTION OF SYMBOLS 1 ... Silicon substrate, 2 ... P-type single crystal silicon film 3 ... N-type layer, 4 ... N-type single crystal silicon film 5 ... Semiconductor thin film, 6 ... Dielectric thin film, 20 ... Etching tank,
22 ... Potentiostat, 23 ... Reference electrode,
24 ... Sample electrode, 25 ... Counter electrode,
26 ... Microcomputer .

Claims (2)

[Claims] 1. A step of forming a p-type single crystal silicon film on an n-type single crystal silicon substrate by an epitaxial growth method, a step of forming an n-type layer on a part of the p-type single crystal silicon film, A part of the p-type single crystal silicon film is etched by immersing the p-type single crystal silicon film in the potassium hydroxide solution while applying a potential of -1 V or more on the basis of the potential of the potassium hydroxide solution. A method of manufacturing a high-frequency circuit substrate, comprising: a step of forming a semiconductor thin film in a portion where a p-type single crystal silicon film is etched; and a step of forming a dielectric thin film in a portion where the n-type layer is formed. . 2. A step of forming an n-type single crystal silicon film on an n-type single crystal silicon substrate by an epitaxial growth method, and a step of forming a p-type single crystal silicon film on the n-type single crystal silicon film by an epitaxial growth method. And a step of forming an n-type layer on a part of the p-type single crystal silicon film, and applying water to the n-type single crystal silicon substrate while applying a potential of -1 V or more with reference to the potential of the aqueous potassium hydroxide solution. A step of immersing in a potassium oxide aqueous solution and etching a part of the p-type single crystal silicon film; a step of forming a semiconductor thin film in the etched part of the p-type single crystal silicon film; and a step of forming the n-type layer. And a step of forming a dielectric thin film on a portion thereof.