JP3173444B2 - Semiconductor device and method of forming inductor in semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a method for forming an inductor in the semiconductor device, and more particularly to an inductor line suitable for a microwave monolithic IC (hereinafter, referred to as MMIC) and a method for forming the same.

[0002]

2. Description of the Related Art FIG. 16 is a diagram of a conventional MMIC as viewed obliquely from above, and FIG. 17 is a sectional view of the inductor of FIG. Conventionally, the inductor line 13 on the MMIC is formed by, for example, Au plating on the GaAs substrate 11 via the insulating film 12. MMICs are typically made on expensive single crystal substrates. Therefore, inexpensive M
In order to provide MIC, miniaturization of MMIC, that is, MM
It is desired to reduce the IC chip area. Further, the MMIC is used, for example, inside a mobile phone terminal, and it is desired to reduce the size of the MMIC to reduce the size of the mobile phone terminal.

[0003] However, the ratio of the inductor area to the total area of the MMIC chip may be 30% or more, and it is necessary to reduce the inductor area in order to reduce the MMIC chip area. JP-A-3-2377
No. 55 proposes a method for reducing the area of an inductor in an MMIC. FIG.
FIG. 19 is a plan view of the inductor proposed in Japanese Patent Publication No. 55, and FIG. 19 is a sectional view of FIG. As described above, there is a method of reducing the area of the inductor by forming the inductor into a two-layer structure.
However, in the inductor of FIG. 18, the direction of the magnetic field generated by the first layer inductance line 14 and the second layer inductance line 1
The direction of the magnetic field created by 5 is reversed, which has the disadvantage that a large inductance cannot be obtained even if the length of the inductance line is long. In addition, Japanese Unexamined Patent Publication
No. 237755 discloses a second layer inductance line 15.
Is formed by vapor deposition. However, a metal film formed by vapor deposition generally has a disadvantage that the film thickness is small, so that a large DC current cannot be passed.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned conventional disadvantages, and in particular, to reduce the ratio of the area occupied by the inductor to the MMIC chip, thereby reducing the area of the expensive semiconductor substrate. A method for forming a semiconductor element and an inductor is provided. Another object of the present invention is to provide a method for forming an inductor having a large current capacity.

[0005]

SUMMARY OF THE INVENTION The present invention basically employs the following technical configuration to achieve the above object. That is, as a first aspect of the semiconductor device according to the present invention, in a semiconductor device in which a spiral or meander-shaped inductor is formed on a semiconductor substrate, a case is formed on the surface of the semiconductor substrate.
A plurality of depressions are formed in a child point shape, and the plurality of depressions and the depressions are formed.
A flat portion of the semiconductor substrate surface where only the
By forming metal wiring so as to cross, the spiral shape
Alternatively, a meander-shaped inductor is formed. As a second aspect, the depression is formed in an inverted pyramid shape. As a third aspect, a tip formed in the inverted pyramid shape is provided. parts to be those that are formed flat portions, as a fourth aspect, the recess is Ru der what is depression formed in a hemispherical shape or a gently curved surface.
A first aspect of the method of forming an inductor in a semiconductor device of the present invention is a method of forming a spiral or meandering inductor on a semiconductor substrate, wherein a photoresist film is formed on the semiconductor substrate. Apply this photo
Forming a grid point-like opening in the resist film, the pre-Symbol semiconductor substrate with the photoresist film as a mask Yuck
Collected by etching, and forming a plurality of recesses, and removing the photoresist film, forming a silicon oxide film on the Mito Kubo said surface of semiconducting <br/> material substrate, wherein
A plurality of depressions and the semiconductor substrate on which the depressions are not formed;
Au plated wiring so as to cross the flat part of the surface of the board
By forming, the spiral or meander- shaped inductor
Forming a spiral or meandering inductor on the semiconductor substrate, wherein the method comprises forming a silicon on the semiconductor substrate.
Depositing an oxide film, a photoresist film on the silicon oxide film is applied, the grid to the photoresist film
Forming a point-like opening ; and
Using the silicon oxide film as a mask,
Etching by an on-etching method to form a plurality of lattice-point-shaped depressions; removing the photoresist film; and forming the plurality of depressions and the depressions.
Not to cross the flat part of the surface of the semiconductor substrate
By forming the Au plating wiring, the spiral or the
Forming a solder-like inductor .

[0006]

Embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, the best mode of the present invention is to form an uneven structure on a semiconductor substrate such as a GaAs substrate 1, form an insulating film such as a silicon oxide film 2 on the substrate 1, and then form an Using metal,
The inductor line 3 is formed on unevenness.

By making the surface of the semiconductor substrate uneven, the length of the inductor line formed thereon can be made longer than when it is formed on a plane. The length of the inductor line changes depending on the shape of the irregularities and their arrangement. By arranging the uneven structure densely, the planar portion on the substrate surface can be reduced. That is, by arranging the concavo-convex structure as densely as possible, the length of the inductor line becomes longer, and the inductance in a certain area can be increased. Further, by changing the shape of the unevenness, the line length of the inductor also changes.

Next, an embodiment of the manufacturing method of the present invention will be described. Irregularities are formed on portions of the semiconductor substrate where inductors are to be formed. The formation method covers a semiconductor substrate surface using a material such as a photoresist, which is difficult to process at the time of processing the semiconductor substrate, as a mask. At this time, instead of covering the entire surface of the semiconductor substrate, the semiconductor substrate is partially opened as shown in FIG.
Thereafter, the semiconductor substrate is processed as shown in FIG. 8 by a method such as dry etching, wet etching, and milling.
In this case, the shape of the unevenness is determined by the processing method and conditions. After processing, the mask covering the surface as shown in FIG. 9 is removed.

Next, as shown in FIG. 10, the surface of the semiconductor substrate is covered with an insulating material such as a silicon oxide film. This insulates the inductor from the semiconductor substrate. Then, as shown in FIG. 11, a metal such as Au is formed in a line shape as an inductor on the insulating material. Many methods such as plating, sputtering, and vapor deposition are conceivable. In the manner described above, an uneven structure can be formed on the surface of the semiconductor substrate, and an inductor can be formed on the uneven structure. You can have.

As described above, according to the present invention, since the line forming the inductor is formed on the irregularities, the line length that can be formed within the same area is longer than the conventional method of forming the line on a plane. Thus, an inductor having a larger inductance than the conventional one can be formed in the same area on the MMIC. That is, inductors having the same inductance can be formed in a smaller area than the conventional method.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific examples of a semiconductor device and a method of forming an inductor in the semiconductor device according to the present invention will be described in detail with reference to the drawings. 1, 2 and 5 to 11
FIG. 3 is a view showing a structure of a first specific example of the present invention. In the figure, in a semiconductor element in which a spiral or meandering inductor 3 is formed on a semiconductor substrate 1, a depression is formed on the surface of the semiconductor substrate 1. A semiconductor element is shown in which a plurality of Rs are formed, and the inductors 3 are continuously formed on the depressions R.

The present invention will be described in further detail. FIG. 1 is a view showing a first embodiment of the present invention, and FIG. 2 is a view of the MMIC viewed from obliquely above, and FIG. 2 is a sectional view of the inductor portion of FIG. is there. In the present invention, a large number of inverted pyramid-shaped depressions are formed on the surface of the GaAs substrate 1, and a silicon oxide film 2 for insulation is grown thinly on the substrate 1, and then the inductor line 3 is formed by Au plating. The inverted pyramid structure can be easily obtained by anisotropically etching the GaAs substrate 1,
When four slopes of the inverted pyramid are formed on the As (111) plane, the apex angle is about 71 degrees as shown in FIG. This angle is determined by the crystal structure of the GaAs single crystal having the Zincblend structure. When the inductor line 3 is formed so as to pass through the top of the inverted pyramid and pass through the (111) plane, the line length is about 1.7 times as long as the line formed on a plane. This length can be obtained from a trigonometric function. At this time, for example, when the line is formed in a spiral shape and used as an inductor,
The area occupied by the inductor is halved, depending on the density of the depressions on the inverted pyramid.

Next, a manufacturing method according to a first embodiment of the present invention will be described with reference to the drawings. First, as shown in FIG.
Is covered with a photoresist film 4. At this time, the photoresist film 4 is exposed and developed so as to open like a lattice point as shown in FIG. The space between the openings 5 is the space between the inverted pyramids. As shown in FIG. 1, it is desirable for the inductor line 3 to pass through the apex of the depression R on the inverted pyramid in order to increase the inductance. Therefore, the interval between the openings 5 is made equal to the interval between the inductor lines 3. Next, wet etching is performed to anisotropically etch the GaAs substrate exposed in the opening 5. HF + as an etchant
H ₂ O ₂ + H ₂ O, HBr + H ₂ O ₂ + H ₂ O, H ₂ S
By using O ₄ + H ₂ O ₂ + H ₂ O or the like, inverted pyramid-type anisotropic etching is performed.

FIG. 7 shows that the sectional structure of the substrate changes depending on the etching time. If the etching time is short, the etching is completed before the etching is completed to the complete inverted pyramid structure. Therefore, as shown in FIG. 7A, a cross section in which a flat portion R ′ is formed at the tip formed in the inverted pyramid shape. Shape. Conversely, if the etching time is long,
As shown in FIG. 7B, the inverted pyramid structure is completed, and furthermore, the etching proceeds obliquely downward, so that the depth of the inverted pyramid becomes deeper, and the pyramids are connected side by side as shown in FIG. FIG. 9 shows a cross-sectional structure after removing the photoresist film 4. FIG. 10 shows a structure after a thin silicon oxide film 2 is deposited as an insulating film on the GaAs substrate 1 of FIG. The silicon oxide film 2 is for insulating the GaAs substrate 1 from the inductor line 3 and has a thickness of 30 mm.
Deposition is performed at 0 Å by a CVD method (chemical vapor deposition). It is difficult to deposit a thinner silicon oxide film on the controllability of the CVD apparatus. Conversely, it is possible and not problematic to deposit a thick silicon oxide film, but 300 Å is sufficient for the purpose of insulating the GaAs substrate from the inductor line.

FIG. 11 shows a cross-sectional structure after Au is formed by plating on the inductor line 3 on FIG. The inductor line 3 is formed spirally using a photoresist. The inductor line 3 is wired so as to pass through the top of the inverted pyramid of the GaAs substrate 1. By doing so, a larger inductance can be obtained. When the inductor line 3 is formed in a spiral shape, the line width of the inductor line 3 is 5 microns, and the line interval is 5 microns. The smaller the line width and spacing, the longer the line within a certain area, that is, a large inductance can be obtained.However, the line width and spacing depend on the workability when forming the inductor line and the amount of current flowing when used as an inductor. Needs to be changed.

Next, a second embodiment of the present invention will be described. 3 and 4 and FIGS. 12 to 15 are views showing a second specific example. FIG. 3 is a view of the MMIC viewed obliquely from above, and FIG. 4 is a cross-sectional view of the inductor portion of FIG. Referring to FIG. 4, the second specific example is different from the first specific example in the shape of the concavities and convexities, and the silicon oxide film 7 on the GaAs substrate 6 is deposited thickly and the silicon oxide film 7 is etched. Recess R 'formed by hemisphere or gentle curved surface
To form It is sufficient that the thickness of the silicon oxide film 7 is not less than the depth of the depression R '. For example, in the case of the depression R' having a depth of 3 microns, the thickness of the silicon oxide film 2 is sufficient to be 4 microns. When the cross-sectional shape of the depression R 'is semicircular and a line is formed so as to pass through the vertex of the semicircle, the line length is π / 2 as compared with the case where the line is formed on a plane. Here, π represents the pi.

Next, the manufacturing method of this embodiment will be described with reference to the drawings. First, a silicon oxide film 7 is deposited on the surface of a GaAs substrate 6 as shown in FIG. It is sufficient that the thickness of the silicon oxide film 7 is equal to or greater than the depth of the concave / convex depression R1 to be formed later. For example, when the depression R1 has a depth of 3 microns, the thickness of the silicon oxide film 7 is 4 microns. It is.

Next, the surface of the silicon oxide film 7 is covered with a photoresist film 9 as shown in FIG. The photoresist film 9 has openings like lattice points like the photoresist film 4 of FIG. Next, dry etching is performed to etch the silicon oxide film 7 exposed in the opening 10. CF ₄
By performing etching by the RIE method (reactive ion etching method) with + H ₂ gas, the etching is performed into a shape having a gentle curve as shown in FIG. FIG.
15 is a cross-sectional structure in which the photoresist film 9 of FIG. 14 is removed and Au is formed as an inductor line 8 by plating.

In the above description, the recess is formed on the semiconductor substrate. However, a plurality of protrusions are formed on the contrary, whereby a predetermined length of the inductor line is continuously formed. Is also good.

[0020]

The present invention is constructed as described above.
An inductor having a line length up to about 1.7 times in the first embodiment and up to π / 2 times in the second embodiment can be formed on the MMIC having the same area as the conventional one.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first specific example.

FIG. 2 is a cross-sectional view of a first specific example.

FIG. 3 is a perspective view showing a second specific example.

FIG. 4 is a cross-sectional view of a second specific example.

FIG. 5 is a diagram showing the apex angle of a depression after anisotropic etching of the first specific example.

FIG. 6 is a diagram showing a state of an opening of a resist serving as an etching mask.

FIG. 7 is a cross-sectional view showing the relationship between the etching time and the shape of a depression in the first specific example.

FIG. 8 is a sectional view of the first specific example after etching.

FIG. 9 is a cross-sectional view of the first specific example after the photoresist is removed.

FIG. 10 is a cross-sectional view after depositing a silicon oxide film of the first specific example.

FIG. 11 is a cross-sectional view after the inductor line of the first specific example is formed.

FIG. 12 is a cross-sectional view after depositing a silicon oxide film of a second specific example.

FIG. 13 is a cross-sectional view after depositing a photoresist according to a second specific example.

FIG. 14 is a sectional view of a second specific example after etching.

FIG. 15 is a cross-sectional view after forming an inductor line according to a second specific example.

FIG. 16 is a perspective view of an inductor portion of a conventional MMIC.

FIG. 17 is a sectional view of an inductor portion of a conventional MMIC.

FIG. 18 is a plan view of a main part of Japanese Patent Application Laid-Open No. 3-237755.

FIG. 19 is a sectional view of the inductor part.

DESCRIPTION OF REFERENCE NUMERALS 1 GaAs substrate 2 Silicon oxide film 3 Inductor line 4 Photoresist film 5 Photoresist opening 6 GaAs substrate 7 Silicon oxide film 8 Inductor line 9 Photoresist film 10 Photoresist opening 11 GaAs substrate 12 Silicon oxide film DESCRIPTION OF SYMBOLS 13 Inductor line 14 1st-layer inductance line 15 2nd-layer inductance line 16 Silicon nitride film 17 Contact part 18 GaAs main surface

Claims (6)

(57) [Claims] 1. A semiconductor device having a spiral or meandering inductor formed on a semiconductor substrate, wherein a plurality of depressions are formed in a lattice point on the surface of the semiconductor substrate.
The plurality of depressions and the semiconductor without the depressions
Metal wiring is formed so as to cross the flat part of the body substrate surface
Thereby forming the spiral or meandering inductor . 2. The semiconductor device according to claim 1, wherein said depression is formed in an inverted pyramid shape. 3. A flat portion is formed at a tip of the inverted pyramid.
The semiconductor element as described in the above. 4. The semiconductor device according to claim 1, wherein the depression is a depression formed in a hemispherical shape or a gentle curved surface. (5)Spiral or meander shape on semiconductor substrate
A method of forming an inductor of A photoresist film is applied on the semiconductor substrate, and
Forming lattice-shaped openings in the photoresist film; Using the photoresist film as a mask, the semiconductor substrate is
Wet etching to form a plurality of depressions; Removing the photoresist film; A silicon oxide film is formed on the recess and the surface of the semiconductor substrate.
The process of The plurality of depressions and the semiconductor without the depressions
Au plating so as to cross the flat part of the surface of the substrate
By forming a line, the spiral or meandering in
Forming a ductor; Forming an inductor in a semiconductor device characterized by including
how to. 6.Spiral or meander shape on semiconductor substrate
A method of forming an inductor of Depositing a silicon oxide film on the semiconductor substrate; A photoresist film is applied on the silicon oxide film,
Photoresist film Step of forming lattice-shaped openings
When, Using the photoresist film as a mask, the silicon acid
Etched by reactive ion etching.
And forming a plurality of lattice point-like depressions, Removing the photoresist film; The plurality of depressions and the semiconductor without the depressions
Au plating so as to cross the flat part of the surface of the substrate
By forming a line, the spiral or meandering in
Forming a ductor; Forming an inductor in a semiconductor device characterized by including
how to.