JP2000331830A - Planar magnetic element integrated semiconductor device - Google Patents

Abstract

(57) [Problem] To provide a planar magnetic element-integrated semiconductor element having a small number of manufacturing steps and a high yield rate. SOLUTION: In order to electrically connect a planar magnetic element 22 to an integrated circuit 21 to form an integrated type, when both are joined via an insulating film having a contact hole 6, a side wall of the contact hole 6 is provided. By making the shape have a forward inclination, the number of processes is reduced, and the yield rate is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar magnetic element such as a planar inductor (thin film inductor) or a planar transformer manufactured by utilizing a surface micromachining technology and an IC manufacturing technology, and more particularly, to a planar magnetic device. The present invention relates to a planar magnetic element integrated semiconductor device in which such a planar magnetic element is electrically connected to an integrated circuit.

[0002]

2. Description of the Related Art In recent years, miniaturization of various electronic devices such as multimedia devices typified by notebook personal computers and mobile phones has been actively promoted. Along with this, research on the miniaturization of the power supply section is also being actively conducted, and in order to realize the miniaturization of magnetic elements such as inductors and transformers, which are the main components, these magnetic elements are surface micromachining technology. Many attempts have been made to produce flat and thin film types using IC manufacturing technology.

The most common example of a planar inductor is shown in FIG. 1A shows an exploded view, and FIG. 1B shows a sectional view. That is, an insulating film is formed on a substrate such as silicon (Si) (not shown),
The lower magnetic film 4, the lower insulating film 5, the planar coil (conductor portion) 8, the insulating film 10, and the upper magnetic film 11 are formed in this order, and a so-called planar coil is sandwiched between magnetic films. Yes, it is called a laminated planar inductor. Further, since the magnetic material is located outside the coil and the coil is inside the magnetic film, it is also called an outer iron type or an inner coil type inductor.

As the shape of the planar coil, various patterns such as a zigzag type, a meander type, and a spiral type are used. Among these coil patterns, since the spiral type can maximize the inductance value per unit area, it can be said that the spiral type that can be further reduced is the most suitable to obtain the same inductance value. . The planar inductor having such a configuration needs to have a sufficiently high Q value in a used frequency band. The Q value of the planar inductor is represented by R for the coil resistance, L for the inductor, and ω = 2πf.
(F: frequency), it is represented by Q = ωL / R. In order to increase the Q value of the inductor, it is necessary to lower (reduce) the resistance of the coil and increase the inductance.

The factors that determine the inductance are:
The size of the coil and the number of turns are important, and a planar inductor generally requires a size of several mm square or more. Further, in order to reduce the resistance, it is necessary to increase the thickness of the coil when the size and the number of turns of the coil are constant. In recent years, as a planar inductor that meets such demands, one side of the coil is 4 mm square or more, and in order to reduce the DC resistance of the coil, a copper film is formed in a spiral type by electrolytic plating, and a thick coil conductor of 30 μm or more is formed. There have been many reports of plating-type inductors having the following characteristics (for example, Japanese Patent Application Laid-Open No. 4-363006, IEICE Tech.
6-14).

A planar inductor is, for example, a main element of a power supply circuit. By using a planar inductor instead of a conventional inductor element using a bulk magnetic material, the power supply circuit is made thinner and smaller. Examples have been reported. When such a planar inductor is used in a power supply circuit, a method of externally mounting a control IC, a MOSFET, a diode, a capacitor, and the like that constitute the power supply circuit on, for example, a plastic substrate, and externally attaching the planar inductor in the same manner as other elements. (Hybrid method) is generally used.

To further reduce the size of the power supply circuit, the control I
It is necessary to integrally form a magnetic element with an integrated circuit such as C or MOSFET. 5. As such a magnetic element integrated semiconductor device, a film thickness of a coil formed by forming a film of aluminum (Al) by sputtering and processing it into a coil shape by etching.
An example of an oscillation circuit in which a laminated planar inductor having a thickness of 1 μm and a magnetic film thickness of 1.4 μm is formed on an integrated circuit has also been reported (see the 22nd Annual Meeting of the Applied Magnetic Society, 22aB-4).

[0008]

As described above, in order to reduce the DC resistance of the planar inductor, it is desired that the coil conductor be thick. However, forming a thick coil conductor by the above-described etching method of the Al sputtered film causes warpage of the substrate due to the stress of the sputtered film and a reduction in coil occupancy due to the etching method. It is not suitable as a planar inductor forming method. To form a thick coil conductor, a thick-film photoresist or photosensitive polyimide is patterned on a substrate on which a plating seed layer has been sputtered with a thin film, and is formed by an electrolytic plating method using the same as a plating mold. The method is appropriate. In this case, an insulating film is required between the integrated circuit and the magnetic element, and a contact hole needs to be formed to electrically connect the two elements. FIG. 5 shows a conventional contact hole forming procedure. In this method, a contact hole 14 is formed by an etching method using a mask 13 or the like, and the contact hole is plated to be electrically connected. 1 denotes a semiconductor substrate, 2 denotes an electrode, 3 denotes an insulating film, and 4 denotes a magnetic film.

However, the method shown in FIG. 5 has the following problem. A new process for forming a mask pattern is required. The mask material is limited by the electrode material on the integrated circuit. The side wall of the contact hole has a curved R shape as shown in FIG. 5 (4) or (5). Electrode corrosion due to wraparound occurs, and the yield rate decreases. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a planar magnetic element integrated semiconductor device having a high yield rate with a small number of steps.

[0010]

According to the first aspect of the present invention, a spiral planar coil, an insulator and the spiral planar coil are formed on an integrated circuit formed on a semiconductor substrate. A planar magnetic element formed by laminating soft magnetic thin films sandwiched therebetween is formed via an insulating film having a contact hole, and the sidewall shape of the contact hole has a forward slope. Claim 1
According to the invention, the contact hole can be formed by a dry etching method of a photosensitive insulating material (the invention of claim 2).

[0011]

FIG. 1 is a structural view showing a first embodiment of the present invention. FIG. 1 (a) is a perspective view and FIG. 1 (b) is a sectional view. That is, an insulating film 3 having contact holes indicated by reference numeral 6 in FIG. 1B for electrically connecting to an integrated circuit 21 formed on the upper surface of a semiconductor substrate as shown in FIG. When the planar magnetic element 22 is formed through the through hole, the side wall shape of the contact hole 6 is formed to have a forward inclination to improve the coverage of the sputtered film serving as a plating seed layer on the contact hole. .

FIG. 2 is an explanatory diagram of the manufacturing procedure. First, an insulating film 3 is formed on a substrate 1 on which an integrated circuit has been formed. As the insulating film, an insulating film such as a silicon oxide film or a silicon nitride film, which can be formed by a film formation method such as sputtering or vacuum evaporation, or a polyimide resin is used. These insulating films need to be made of a material that can be etched in a later step. Next, the lower magnetic film 4 is formed and patterned by etching or the like. Next, a contact hole 6 is formed.

FIG. 3 is a detailed diagram of a procedure for forming a contact hole. First, a photosensitive insulating material such as photosensitive polyimide is patterned to form an insulating film 5. At this time,
A hole pattern 6a for forming a contact hole 6 for electrically connecting the electrode 2 of the integrated circuit and the inductor is formed. The side wall shape of the hole pattern 6a can be formed into a shape having a forward taper (forward inclination) by shortening the exposure time. Thereafter, by performing isotropic dry etching, the insulating film 3 below the hole pattern for forming a contact hole is etched to form a contact hole 6b.
To form

The inclination of the side wall of the contact hole reflects the inclination of the hole pattern 6a of the insulating film 5 as it is, and since the upper edge portion 6c is isotropically etched, R is necessarily formed. Is done. In addition, in this contact hole forming method, if the thickness of the insulating film 5 is increased, the insulating film 5 can be used as an interlayer insulating film between the lower magnetic film 4 and the coil conductor 8, so that there is no need to peel off the mask material. . That is, not only is the process saved, but also the electrode material on the integrated circuit is hardly limited.

Next, the coil conductor 8 is formed by electrolytic plating. First, a current-carrying layer 7 of electrolytic plating is formed and patterned to form a coil shape. Next, the photosensitive polyimide is patterned, a plating mold 9 is formed, and the coil conductor 8 is formed by electrolytic plating. As a method for forming the coil conductor, a plating method using a photoresist as a plating type may be used instead of the photosensitive polyimide. Next, polyimide or the like is applied on the coil conductor 8 to form an upper insulating film 10.
To form If you need to remove the electrode from the coil,
The electrode outlet 12 is formed by patterning. At this time, if a photosensitive polyimide or the like is used, the electrode outlet and the insulating film can be formed simultaneously. Finally, the upper insulating film is formed by the same process as the lower insulating film to form a planar inductor integrated semiconductor device. By using the above-described contact hole forming method, when forming a planar magnetic element on an integrated circuit, even when using an electrolytic plating method, corrosion of an electrode material does not occur, and a stable device can be formed in a small number of steps. Can be obtained.

[Embodiment] Next, an embodiment will be described. First, an integrated circuit is formed using a semiconductor substrate.
Here, a substrate on which a control IC for a power supply and a MOSFET are formed is used. Polyimide is applied and baked as an insulating film on the semiconductor substrate after the completion of IC fabrication. The film thickness may be arbitrary, but in order to make the surface of the IC substrate flat, 5 μm is used here.
m.

Next, a magnetic film is formed by sputtering and patterned by etching. The thickness of the magnetic film is 9 μm. Next, a photosensitive insulating material such as photosensitive polyimide is patterned to form an insulating film between the magnetic film and the coil conductor and a hole pattern for forming a contact hole. The film thickness was 15 μm. The side wall shape of the hole pattern at this time is
Conditions were set to have a forward taper of about 45 degrees. Subsequently, a contact hole for electrically connecting the planar inductor to the integrated circuit is formed on the electrode formed on the integrated circuit by performing dry etching by plasma etching using oxygen and chlorofluorocarbon. The side wall shape at this time was also about 45 degrees.

Titanium and gold serving as a seed layer at the time of electrolytic plating of the coil conductor are formed by sputtering, and are patterned into a coil shape by etching. At this time, the throwing power of the sputtered film was good. The photosensitive polyimide is patterned according to the coil pattern of the plating seed layer to form a coil conductor plating mold. The plating mold has a thickness of 35 μm. A coil conductor is formed by electrolytic plating. The film thickness of the coil was about 35 μm including the plating type. A photosensitive polyimide is patterned thereon to form an interlayer insulating film with the upper magnetic film. The thickness of the interlayer insulating film is 10 μm. An upper magnetic film is sputtered thereon and patterned by etching. Thus, the thin-film reactor is completed. A not electrically connected to reactor
The l pad was exposed by performing deep etching of polyimide by plasma.

Finally, heat treatment in a rotating magnetic field is performed to suppress variations in the magnetic film characteristics depending on the location of the magnetic film in the wafer, and heat treatment in a static magnetic field is performed to induce uniaxial magnetic anisotropy. Done. The number of turns of the manufactured inductor is 16 turns, the coil conductor width is 93 μm, the coil thickness is 35 μm, the coil interval width is 20 μm, the size of the coil portion is 4 × 4 mm, the total thickness of the coil portion is 53 μm, control IC, M
The size of the semiconductor device including the OSFET is 4 × 5 mm
It is. The electrical connection between the planar inductor and the electrodes of the integrated circuit was good, and phenomena such as electrode corrosion did not occur.
Miniaturization and thinning have been achieved at the same time.

In this embodiment, a planar inductor is used as an example, but a planar transformer and the like can be formed by the same manufacturing method. Further, the present invention can be applied to all devices that form a coil by an electrolytic plating method regardless of the presence or absence of a magnetic film.
Further, it is needless to say that the present invention is not limited to an integrated circuit for a power supply, but can be applied to a general semiconductor device requiring a magnetic element such as a filter circuit.

[0021]

According to the present invention, when a planar inductor is formed on an integrated circuit, the shape of the side wall of the contact hole for electrically connecting the two is made to have a forward slope. A highly efficient magnetic element integrated semiconductor device can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory view of a manufacturing process of FIG. 1;

FIG. 3 is a detailed view of a procedure for forming a contact hole in FIG. 2;

FIG. 4 is a configuration diagram illustrating a general example of a planar magnetic element.

FIG. 5 is an explanatory view of a manufacturing process in FIG. 4;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2 ... Electrode, 3, 5, 10 ... Insulating film,
4,11 ... magnetic film, 6,6b ... contact hole, 6a
... hole pattern, 6c ... edge part, 7 ... conductive layer of plating, 8 ... coil conductor, 9 ... plating type, 12 ... electrode outlet, 21 ... integrated circuit, 22 ... planar magnetic element.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H01L 27/04 H01L 27/04 L 21/822

Claims (2)

[Claims] A planar magnetic element comprising a spiral planar coil, an insulator, and a soft magnetic thin film sandwiching the spiral planar coil is laminated on an integrated circuit formed on a semiconductor substrate, and has a contact hole. A planar magnetic element-integrated semiconductor device formed through an insulating film and having a contact hole having a forward slope in a side wall shape. 2. The planar magnetic element-integrated semiconductor device according to claim 1, wherein said contact hole is formed by a dry etching method of a photosensitive insulating material.