JPH07335544A - Method for manufacturing high-frequency circuit element - Google Patents

Abstract

PURPOSE:To positively execute a process which can be executed to a part with a high step and a part with a low step in the same process. CONSTITUTION:The step between compound semiconductor layers 2, 3, and 4 on a substrate 1 and AlN layer 6 is buried by resists 10 and 11, SiO 12 is subjected to patterning on the resist 10, the resists 10 and 11 are further subjected to patterning from the opening part with the SiO 12 as a mask, a metal film 25 is formed, lift-off is performed, and then the unneeded metal film 25 on the SiO 12 is eliminated, thus forming an electrode.

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 high-frequency circuit element in which a high-frequency amplifier element having a compound semiconductor layer and a surface acoustic wave element having a piezoelectric layer are manufactured on the same silicon substrate.

[0002]

2. Description of the Related Art In general, a semiconductor device using a compound semiconductor can be operated at a higher speed and a higher frequency than a device using a silicon semiconductor, and therefore its use is gradually expanding.

In particular, it is used as an indispensable element part in radio equipment handling high frequencies, and as mobile radio equipment is made smaller and lighter with the spread of mobile communication represented by mobile phones, it is used as an element part thereof. There is a demand for reduction in size and weight of the compound semiconductor device itself.

The applicant of the present invention has proposed, as one of such high frequency devices, gallium arsenide (GaA) which is a compound semiconductor.
We have developed a high-frequency circuit element in which a high-frequency amplifier element according to s) and a surface acoustic wave filter using a piezoelectric material are manufactured on one silicon substrate (Japanese Patent Application No. 3-366091). This high-frequency circuit element has a GaAs layer on a silicon substrate,
An aluminum nitride (AlN) layer is formed, an active element such as an amplifier is formed on the GaAs layer, and a surface acoustic wave filter is formed on the AlN layer.

This high frequency circuit element has a GaA
Since the s layer and the AlN layer have different thicknesses, the step difference becomes a problem. The GaAs layer formed on the silicon substrate is
An element manufactured on GaAs requires a thickness of about 3 to 5 μm so as not to be affected by the mixing of silicon that is a substrate (change in conductivity of GaAs), whereas a surface acoustic wave filter. Is not affected by the silicon substrate,
Since unnecessarily thickening the film deteriorates the productivity, Al
Since the film thickness of N is less than about 1 μm, there is a step difference of 2 to 3 μm or more. Therefore, the electrodes and wiring of the active element on GaAs and AlN
It cannot be formed at the same time as the electrodes and wiring of the upper surface acoustic wave filter.

Therefore, conventionally, when there is such a step shape, a patterning technique called a multi-layer resist method is used. A typical multi-layer resist method is called a three-layer resist method. In this method, first, a thick first-layer resist required for embedding a step on a work piece having a step on the substrate surface is applied. Then, the surface is flattened and baked to harden the resist surface. An extremely thin SiO ₂ film of about 0.1 to 0.2 μm is formed on the resist surface, and a resist for further patterning is formed thereon. Is applied, the resist is patterned by photolithography, and then the first layer resist and the SiO ₂ film are RI
After patterning with E or the like, the workpiece on the substrate surface is patterned.

[0007]

However, in the high-frequency circuit element described above, the step difference is as large as 3 μm, and the area of the AlN film, which is the low step difference portion, is as large as several mm ^2. , The surface cannot be completely flattened at the time of applying the first layer resist, and it is difficult to simultaneously form a fine pattern of 1 μm or less on a high step portion (GaAs surface) and a low step portion (AlN surface). Is.

Of course, it is possible to fabricate a high-frequency circuit element by separately patterning a high-step portion and a low-step portion by repeating resist coating and photolithography. However, if such a manufacturing method is used, If you do, you have to repeat the process that you only need to do once,
Further, it is not necessary to simply repeat the resist coating, photolithography, and etching of the workpiece, and for example, it is necessary to adjust the depth of focus at the time of photolithography in the high and low steps, However, there is a problem that is not suitable for mass production.

Therefore, an object of the present invention is to provide a method of manufacturing a high-frequency circuit element capable of simultaneously performing the same process on a high portion and a low portion separated by a step.

[0010]

The present invention for achieving the above object comprises a high frequency amplifying device using a compound semiconductor layer,
A method of manufacturing a high-frequency circuit device, wherein a surface acoustic wave device using a piezoelectric layer is manufactured on the same silicon substrate, wherein a compound semiconductor layer is formed on a portion of the silicon substrate where the high-frequency amplification device is formed. And a step of forming an insulating film so as to cover at least the compound semiconductor layer on the result of the above steps, and forming a piezoelectric layer on at least a portion of the silicon substrate where the surface acoustic wave element is formed. And a step of removing at least one electrode of the high-frequency amplification element of the insulating film covering the compound semiconductor layer to form the electrode, and a part of the piezoelectric layer. A step of forming a first resist having a thickness corresponding to a step between the compound semiconductor layer and the piezoelectric layer, and a step of forming a dielectric film on the resultant obtained through the steps, A step of forming a second resist on the electric conductor film, a step of patterning the second resist, and a step of using the second resist patterned by the patterning step as a mask, the dielectric film and the 1 a step of patterning a resist, a step of forming a metal film on a product obtained through the above steps, a step of removing the first resist and the dielectric film, and an unnecessary portion of the metal film thereon. And a step of removing the.

The present invention for achieving the above object is
A method of manufacturing a high-frequency circuit element, wherein a high-frequency amplification element having a compound semiconductor layer and a surface acoustic wave element having a piezoelectric layer are produced on the same silicon substrate, the method comprising forming the compound semiconductor layer on the silicon substrate. A step of removing a part of the compound semiconductor layer to expose the silicon substrate, a step of forming an insulating film on a product obtained through the above steps, and a step of removing a part of the insulating film, A step of exposing a part of the surface of the silicon substrate, a step of forming a piezoelectric layer on the result of the above steps, and a step of removing a part of the piezoelectric layer to expose a part of the insulating film. A step, a step of removing a part of the insulating film exposed by the step to expose a part of the compound semiconductor layer, and the high frequency amplification element on the compound semiconductor layer exposed by the step Source electrode and And forming a drain electrode, on a part of the piezoelectric layer to form a first resist thickness corresponding to the step between the piezoelectric layer and the compound semiconductor layer,
On the step of patterning and the result of the above steps,
A step of forming a dielectric film; a step of forming a second resist on the dielectric film; a step of patterning the second resist; and a step of patterning the second resist by the patterning step. As a mask, the step of patterning the dielectric film and the first resist, the step of depositing a metal film on the product obtained through the above steps, the first resist and the dielectric film are removed, and And a step of removing an unnecessary portion of the metal film above, the method for manufacturing a high-frequency circuit element.

Further, the present invention for achieving the above object is a method for producing a high frequency circuit element in which a high frequency amplifying element having a compound semiconductor layer and a surface acoustic wave element having a piezoelectric layer are formed on the same silicon substrate. A step of forming the compound semiconductor layer on the silicon substrate, a step of removing a part of the compound semiconductor layer to expose the silicon substrate, and an insulating film formed on the result of the above steps. And a step of removing a part of the insulating film to expose a part of the silicon substrate surface, a step of forming a piezoelectric layer on the resultant product after the above steps, and a step of forming the piezoelectric layer. Removing a part of the insulating film, exposing a part of the insulating film exposed by the process, exposing a part of the compound semiconductor layer; Exposed by Forming a source electrode and a drain electrode of the high-frequency amplification element on the compound semiconductor layer, and forming a part of the piezoelectric layer with a thickness corresponding to a step between the compound semiconductor layer and the piezoelectric layer. A step of forming and patterning a first resist, a step of forming an intermediate resist layer on the result of the above steps, a step of forming a dielectric film on the intermediate resist, and a step of forming the dielectric film. A step of forming a second resist on the above, a step of patterning the second resist, and the dielectric film and the first resist using the second resist patterned by the patterning step as a mask. A step of patterning, a step of forming a metal film on the product obtained through the above steps, a step of removing the first resist and the intermediate resist, and a step of forming the dielectric film and the gold on the step. Is a manufacturing method of a high-frequency circuit element characterized by comprising a step of removing unnecessary portions of the film.

[0013]

According to the present invention configured as described above, the first resist is formed on the piezoelectric body so as to have a thickness corresponding to the step between the compound semiconductor layer and the piezoelectric layer, and is patterned to reduce the step. The surface of the substrate is flattened by leaving it only on the piezoelectric layer, which is a portion, and filling the step to have the same height as the surface of the compound semiconductor layer.
A resist is applied, and this second resist is patterned by photolithography. Then, using the patterned second resist as a mask, the dielectric film and the first
Pattern the resist. As a result, the second resist and the dielectric film thereunder serve as a mask material for processing the compound semiconductor on the compound semiconductor layer, and the dielectric film and the first resist on the piezoelectric layer. It serves as a mask material for processing the piezoelectric layer. Then, using this mask material, a metal film is formed on the mask material, and then the structure on the first resist and the dielectric film is removed to remove the high-frequency amplifier element, the surface acoustic wave element electrode, and Wiring for connecting the high frequency amplification element and the surface acoustic wave element is simultaneously formed.

Further, according to the present invention, an intermediate resist is formed on the first resist so that unnecessary portions of the dielectric film and the metal film, which are the subsequent steps, are removed at once by an organic solvent that dissolves the resist. be able to.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In addition, the same number is attached to the member having the same function.

Embodiment 1 FIGS. 1A to 1C are sectional views showing the steps of manufacturing a high frequency integrated circuit device to which the present invention is applied in order of steps. In this manufacturing method, as shown in FIG. 1, first, a non-doped high-purity i-G having a thickness of 1.5 μm is formed as a compound semiconductor layer on a silicon substrate 1 having a specific resistance of 10 to 50 Ωcm.
an aAs layer 2, a non-doped i-AlGaAs layer 3, and
N-GaA doped with impurities such as Si to be an active layer
The s-layer 4 and the s-layer 4 are epitaxially grown by a known two-step growth method. That is, first, a very thin (for example, about 200 Å) i-GaAs layer 2 is grown at a low temperature (400 ° C.), and then grown to a thickness of 1.5 μm at room temperature. When the film thickness reaches 1.5 μm, continue with AlGaA
The s layer 3 is grown at a temperature of 700 ° C. to 1.5 μm.
Further, the n-GaAs layer 4 is grown while introducing a Si impurity source such as silane or disilane. This makes G
aAs layer 2, AlGaAs layer 3, and n-GaAs layer 4
The compound semiconductor layer in which is laminated has a thickness of 3.2 μm.

Next, a mask material is formed by resist coating and photolithography, and the GaAs layer 2 and AlGaAs are formed by a mixed etching solution of hydrofluoric acid and hydrogen peroxide.
A part of the compound semiconductor layer composed of the layer 3 and the n-GaAs layer 4 is removed by mesa etching. Then S on the entire surface
An io ₂ film 5 is formed to a thickness of about 2000 Å by plasma CVD, and photolithography and hydrofluoric acid (H
F) and ammonium fluoride (NH ₄ F) in an aqueous solution to etch only the compound semiconductor layer to form SiO ₂
Leave the membrane 5. Note that FIG. 1 is a cross-sectional view of the state after the steps up to here.

Next, as shown in FIG. 2, ECR (Electr
on Cyclotron Resonance: Electron Cyclotron Resonance) C
The AlN layer 6, which is a piezoelectric layer, is formed by VD to a thickness of about 0.5 μm. Then, resist coating, photolithography, and etching with a NaOH aqueous solution are performed, and A
FE which becomes a high frequency amplification element by removing a part of the 1N layer 6
The SiO ₂ film 5 on the compound semiconductor layer in the portion forming T is exposed.

Next, as shown in FIG. 3, a portion of the resist coating of SiO ₂ film 5 is removed by photolithography and etching, followed by the partial removal of the SiO ₂ film 5 of AuGe / Ni / Au A metal film is vapor-deposited, lifted off (resist removed), and the source electrode 20 of the FET
And a drain electrode 21 are formed, and an alloying heat treatment (45
0 ° C.).

Next, as shown in FIG. 4, a first resist 10 having a thickness corresponding to the step between the compound semiconductor layer and the AlN layer 6 is applied, and the AlN layer 6 is subjected to photolithography.
The first resist 10 is left only on the upper side, and is cured by post baking.

Next, as shown in FIG. 5, an intermediate resist layer 11 and a SiO film 12 which is a dielectric film are applied on the entire surface of the resultant product after the above steps. It suffices if the intermediate resist layer 11 has a thickness of about 2 to 2.5 μm.
Has a thickness of about 1000Å. The intermediate resist layer 11 avoids direct contact with the metal of the source and drain electrodes where the SiO film 12 is already formed and the exposed portion of the AlN layer 6, and in the subsequent steps,
This is for the purpose of facilitating the process when removing the structure formed above this, and is not always necessary.

Next, as shown in FIG. 6, a second resist 13 is applied on the SiO film 12 and patterned into a required pattern by photolithography.

Next, as shown in FIG. 7, the second resist 1
The SiO film 12 is etched through the opening 3 by RIE using CF _{4 as} an etching gas.

Next, as shown in FIG. 8, the second resist 13 and the first resist 10 and the intermediate resist 11 are opened from the openings of the SiO film 12 by RIE using oxygen (O ₂ ) or ozone (O ₃ ). Etching. Here, instead of the asher normally used for resist removal,
The reason why RIE is used is that the first resist is vertically etched by anisotropic etching of RIE as shown in the figure. Although the second resist 13 is completely removed by this step as shown in the drawing, the SiO film 12 is formed by using oxygen or ozone as an etching gas.
Remains unetched at all.

Next, as shown in FIG. 9, in order to form the gate electrode of the FET, the product obtained through the above steps is immersed in a mixed etching solution of hydrofluoric acid and ammonium fluoride,
The exposed part of SiO ₂ is etched. In addition,
Since SiO, AlN, and resist are insoluble in the mixed etching solution of hydrofluoric acid and ammonium fluoride, they are not etched.

Next, as shown in FIG. 10, the n-GaAs layer 5 in the portion where the gate electrode of the FET is formed (the portion where the SiO ₂ film is removed in the above-mentioned step) is applied to about 1000-25.
About 00Å hydrofluoric acid (HF) and hydrogen peroxide solution (H ₂ O ₂ )
Gate recess etching is performed with the mixed etching solution of. In addition, in this step, the FET of this embodiment is MESFE
Because of T.

Next, as shown in FIG. 11, an Al film 25 to be a gate electrode and an electrode of the surface acoustic wave device is deposited.

Next, as shown in FIG. 12, the first resist 10 and the first resist 10 are formed by using an organic solvent such as acetone or alcohol.
The intermediate resist 11 is dissolved, and unnecessary metal films, SiO films, and the like thereon are lifted off and removed. If the intermediate resist layer 11 is not formed, the first resist 10 is removed, and then CF4 or the like is used as an etching gas on the entire surface of the substrate under the condition that only SiO is selectively etched. CDE is preferably performed to etch unnecessary SiO.

As described above, the compound semiconductor FET and the surface acoustic wave device on the AlN layer are formed on one silicon substrate as the high frequency amplifying device, and the electrode thereof is 1 μm or less on the stepped compound semiconductor layer. And on the AlN layer at the same time.

In the above embodiments, the high frequency amplifying element FET is a MESFET, but the present invention is not limited to this, and the layer structure of the compound semiconductor and the compound semiconductor material can be changed as appropriate. It is also possible to manufacture FETs other than MESFET, such as HEMT.

[0031]

As described above, according to the present invention,
When manufacturing a semiconductor element that has a high step and a large area on one side of the step, it is possible to perform the same process at a high step portion and a low step portion at the same time, improving mass productivity in semiconductor element production. To do.

[Brief description of drawings]

FIG. 1 is a cross-sectional view for explaining a method of manufacturing a high-frequency circuit element to which the present invention is applied in order of steps.

FIG. 2 is a cross-sectional view for explaining the method of manufacturing the high-frequency circuit element to which the present invention is applied, following the steps in FIG. 1 in order of steps.

FIG. 3 is a cross-sectional view for explaining the method of manufacturing the high-frequency circuit element to which the present invention is applied, following step order in the order of steps.

FIG. 4 is a cross-sectional view for explaining the method of manufacturing the high-frequency circuit element to which the present invention is applied, in order of steps subsequent to FIG.

FIG. 5 is a cross-sectional view for explaining the manufacturing method of the high-frequency circuit element to which the present invention is applied, in the order of steps, continuing from FIG. 4;

FIG. 6 is a cross-sectional view for explaining the method of manufacturing the high-frequency circuit element to which the present invention is applied, in order of steps, following FIG. 5;

FIG. 7 is a cross-sectional view for explaining the method of manufacturing the high-frequency circuit element to which the present invention is applied, in order of steps, following FIG. 6;

FIG. 8 is a cross-sectional view for explaining the manufacturing method of the high-frequency circuit element to which the present invention is applied, in the order of steps, continuing from FIG. 7;

FIG. 9 is a cross-sectional view for explaining the method of manufacturing the high-frequency circuit element to which the present invention is applied, in the order of steps, continuing from FIG. 8;

FIG. 10 is a cross-sectional view for explaining the method of manufacturing the high-frequency circuit element to which the present invention has been applied, in the order of steps, continuing from FIG. 9;

FIG. 11 is a cross-sectional view for explaining the method of manufacturing the high-frequency circuit element to which the present invention is applied, in the order of steps, continuing from FIG. 10;

FIG. 12 is a cross-sectional view for explaining the method of manufacturing the high-frequency circuit element to which the present invention has been applied, in the order of steps, continuing from FIG. 11;

[Explanation of symbols]

1 ... Silicon substrate, 2 ... i-GaAs layer, 3 ...
i-AlGaAs layer, 4 ... n-GaAs layer, 5 ... Si
O ₂ film, 6 ... AlN layer, 10 ... First resist layer, 11 ... Intermediate resist layer, 12 ... SiO film,
13 ... 2nd resist, 25 ... Al metal film.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01L 29/812 21/338 H03H 3/08 7259-5J

Claims (3)

[Claims] 1. A method of manufacturing a high-frequency circuit element, wherein a high-frequency amplifier element made of a compound semiconductor layer and a surface acoustic wave element made of a piezoelectric layer are manufactured on the same silicon substrate. A step of forming a compound semiconductor layer in a portion where an element is formed, a step of forming an insulating film so as to cover at least the compound semiconductor layer on the result of the above steps, and at least the surface of the silicon substrate A step of forming a piezoelectric layer in a portion where an acoustic wave element is formed, and removing a portion of the insulating film covering the compound semiconductor layer where at least one electrode of the high frequency amplification element is formed, And a step of forming a first resist having a thickness corresponding to a step between the compound semiconductor layer and the piezoelectric layer on a part of the piezoelectric layer, A step of forming a dielectric film on the resultant obtained through the above steps, a step of forming a second resist on the dielectric film, a step of patterning the second resist, and a step of patterning Using the second resist patterned by the process as a mask, the dielectric film and the first
A step of patterning a resist, a step of forming a metal film on a product obtained through the above steps, a step of removing the first resist and the dielectric film, and removing unnecessary portions of the metal film thereon. And a step of removing the high-frequency circuit element. 2. A method of manufacturing a high-frequency circuit device, wherein a high-frequency amplifier device having a compound semiconductor layer and a surface acoustic wave device having a piezoelectric layer are manufactured on the same silicon substrate, wherein the compound semiconductor is formed on the silicon substrate. A step of forming a layer, a step of removing a part of the compound semiconductor layer to expose the silicon substrate, a step of forming an insulating film on a product obtained through the above steps, and a part of the insulating film. Is removed to expose a part of the surface of the silicon substrate, a step of forming a piezoelectric layer on the result of the above steps, a part of the piezoelectric layer is removed, and the insulating film And a step of exposing a part of the insulating film exposed by the step,
Exposing a part of the compound semiconductor layer, forming a source electrode and a drain electrode of the high frequency amplification element on the compound semiconductor layer exposed by the step, and forming a part of the piezoelectric layer A step of forming and patterning a first resist having a thickness corresponding to a step between the compound semiconductor layer and the piezoelectric layer, and a step of forming a dielectric film on the resultant product after the above steps. Forming a second resist on the dielectric film, patterning the second resist, and using the second resist patterned by the patterning process as a mask, the dielectric film and the dielectric film First
A step of patterning a resist, a step of forming a metal film on a product obtained through the above steps, a step of removing the first resist and the dielectric film, and removing unnecessary portions of the metal film thereon. And a step of removing the high-frequency circuit element. 3. A method of manufacturing a high-frequency circuit device, wherein a high-frequency amplifier device having a compound semiconductor layer and a surface acoustic wave device having a piezoelectric layer are manufactured on the same silicon substrate, wherein the compound semiconductor is formed on the silicon substrate. A step of forming a layer, a step of removing a part of the compound semiconductor layer to expose the silicon substrate, a step of forming an insulating film on a product obtained through the above steps, and a part of the insulating film. Is removed to expose a part of the surface of the silicon substrate, a step of forming a piezoelectric layer on the result of the above steps, a part of the piezoelectric layer is removed, and the insulating film And a step of exposing a part of the insulating film exposed by the step,
Exposing a part of the compound semiconductor layer, forming a source electrode and a drain electrode of the high frequency amplification element on the compound semiconductor layer exposed by the step, and forming a part of the piezoelectric layer A step of forming a first resist having a thickness corresponding to a step between the compound semiconductor layer and the piezoelectric layer, and patterning; and a step of forming an intermediate resist layer on the result of the above steps, Patterning by a step of forming a dielectric film on the intermediate resist, a step of forming a second resist on the dielectric film, a step of patterning the second resist, and a step of patterning The dielectric film and the first film are formed using the formed second resist as a mask.
A step of patterning a resist, a step of forming a metal film on a product obtained through the above steps, and a step of removing the first resist and the intermediate resist and removing the dielectric film and the metal film thereon. And a step of removing an unnecessary portion, the method for manufacturing a high-frequency circuit element.