JP2018206896A - Compound semiconductor integrated circuit and manufacture method thereof - Google Patents

Abstract

To provide a compound semiconductor integrated circuit provided with an adhesion improving film capable of preventing moisture from penetrating into a circuit and ensuring moisture resistance in an integrated circuit chip.SOLUTION: A compound semiconductor integrated circuit according to the present invention formed on a semiconductor substrate and having an internal circuit covered with an inorganic insulating protective film includes a bonding pad including gold, an adhesion improving film that is formed in contact with a peripheral region on the bonding pad and includes titanium, an organic interlayer insulating film in which a partial region is formed on a peripheral region of the bonding pad, and the inorganic insulating protective film formed on the organic interlayer insulating film and partly on the adhesion improving film.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a semiconductor integrated circuit using a compound semiconductor, and more particularly to a semiconductor integrated circuit having a structure in which an internal circuit is covered with a protective film made of an inorganic insulating material so as to obtain moisture resistance.

  An organic insulating film such as polyimide or benzocyclobutene (BCB) having a low dielectric constant is often used for an interlayer insulating film of a high-speed compound semiconductor integrated circuit for the purpose of reducing wiring delay. However, compared to inorganic insulating films such as silicon oxide and silicon nitride conventionally used for interlayer insulating films, organic insulating films have high hygroscopicity and water permeability, and it is difficult to obtain good moisture resistance. For this reason, in compound semiconductor integrated circuits in which an organic insulating film is used as an interlayer insulating film, expensive hermetic sealing mounting such as a ceramic package is often used, which has been a major obstacle to cost reduction.

  However, in recent years, there has been an increasing demand for cost reduction in compound semiconductor integrated circuits for ultra-high speed applications, and the application of inexpensive plastic packages has become an issue. In the case of using a plastic package, it is indispensable to ensure moisture resistance in the semiconductor integrated circuit chip itself because airtightness cannot be ensured by the package.

As shown in FIG. 1, when ensuring moisture resistance in a compound semiconductor integrated circuit having an organic interlayer insulating film 3 using an organic film as an interlayer insulating film on a semiconductor substrate 1, silicon nitride or the like that hardly transmits water is used. In general, a portion other than the bonding pad 5 is covered with a protective film (inorganic insulating protective film 4) made of an inorganic insulating material. The bonding pad 5 portion needs to be connected to an external circuit (not shown) by wire bonding, so that it is made of a metal that is not easily oxidized, such as gold, to ensure moisture resistance. The bonding pad 5 portion is connected to an external circuit through the metal wiring 2.

  As a method for improving the adhesion between the bonding pad and the protective film, the Au wiring protective film has a two-layer structure, the upper layer is a silicon nitride film having good moisture resistance, and the lower layer is more adhesive to gold than the silicon nitride film. There is a method using good silicon oxide nitride (see Patent Document 1).

JP-A-5-166803

  As shown in FIG. 1, when the surface of the bonding pad is made of gold, the gold material itself has an advantage in terms of moisture resistance, which is difficult to oxidize. On the other hand, gold generally has good adhesion to inorganic insulating films such as silicon nitride. Is known to be difficult to obtain. If sufficient adhesion is not obtained between the bonding pad and the protective film, water will enter from a portion with insufficient adhesion. Once moisture enters the inside of the inorganic insulating protective film, the internal organic interlayer insulating film has high water permeability, so the water easily reaches the internal circuit side, so that it has sufficient moisture resistance. There arises a problem that cannot be secured.

  Further, even if a silicon nitride film having good moisture resistance is formed on the upper layer of the compound semiconductor described in Patent Document 1 and a protective film using silicon oxide nitride having better adhesion to gold than the silicon nitride film is formed on the lower layer, In addition to the fact that the adhesion between the silicon oxide nitride and the gold is not sufficiently high, there is a problem that moisture may enter from the side surface of the silicon oxide nitride.

  In order to solve these problems, an object of the present invention is to provide a compound semiconductor integrated circuit provided with an adhesion improving film capable of preventing moisture from entering the circuit and ensuring moisture resistance in the integrated circuit chip itself. Will be provided.

One aspect of the compound semiconductor integrated circuit according to the present invention is:
In a compound semiconductor integrated circuit formed on a semiconductor substrate and having a structure in which an internal circuit is covered with an inorganic insulating protective film,
A bonding pad formed on the semiconductor substrate and containing gold;
An adhesion improving film formed in contact with a peripheral region on the bonding pad and containing titanium;
An organic interlayer insulating film in which a partial region is formed on a peripheral region of the bonding pad;
The inorganic insulating protective film formed on and in contact with the adhesion improving film on the organic interlayer insulating film; and
It is characterized by having.

  The inorganic insulating protective film contains silicon nitride.

  The organic interlayer insulating film includes a photosensitive material.

  The bonding pad is connected to the internal circuit through a metal wiring containing gold.

One aspect of a method for manufacturing a compound semiconductor integrated circuit according to the present invention is as follows.
In a method for manufacturing a compound semiconductor integrated circuit formed on a semiconductor substrate and having an internal circuit covered with an inorganic insulating protective film,
Forming a bonding pad containing gold on the semiconductor substrate;
Forming an adhesion improving film containing titanium so as to be in contact with the bonding pad;
Forming a photosensitive organic interlayer insulating film on a peripheral region of the bonding pad;
Forming the inorganic insulating protective film on the organic interlayer insulating film and in contact with a part of the adhesion improving film;
Exposing the bonding pad by etching the adhesion improving film and the inorganic insulating protective film;
It is characterized by having.

  The adhesion improving film is formed by vapor deposition and a lift-off method.

The bonding pad is formed simultaneously with metal wiring including gold,
The internal circuit is formed so as to be connected to the bonding pad through a metal wiring including the gold.

  In the compound semiconductor integrated circuit according to the present invention, the inorganic insulating film having poor adhesion and gold are not in direct contact with each other, and both gold and titanium, and the inorganic insulating film and titanium have good adhesion. Good adhesion can be realized by sandwiching an adhesion improving film made of a metal material. In order to prevent water from entering from the side of the adhesion improving film, the exposed side is immediately oxidized by moisture and becomes titanium oxide, which is known as a very stable substance, preventing further penetration of moisture. Sufficient moisture resistance is ensured.

  This configuration makes it possible to prevent moisture from entering the circuit even in high-speed compound semiconductor integrated circuits that use an organic material with high water permeability for the interlayer insulating film, ensuring moisture resistance in the integrated circuit chip itself. Therefore, the cost can be reduced by applying a plastic package.

It is a figure which shows the cross section of the conventional compound semiconductor integrated circuit. It is a figure which shows the cross section of the compound semiconductor integrated circuit of this invention. 5 is a diagram showing a manufacturing process of the compound semiconductor integrated circuit of the present invention according to Embodiment 1. FIG. 5 is a diagram showing a manufacturing process of the compound semiconductor integrated circuit of the present invention according to Embodiment 1. FIG. 5 is a diagram showing a manufacturing process of the compound semiconductor integrated circuit of the present invention according to Embodiment 1. FIG. 5 is a diagram showing a manufacturing process of the compound semiconductor integrated circuit of the present invention according to Embodiment 1. FIG. 5 is a diagram showing a manufacturing process of the compound semiconductor integrated circuit of the present invention according to Embodiment 1. FIG.

  Hereinafter, embodiments of the compound semiconductor integrated circuit of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the description of the embodiments described below, and it is obvious to those skilled in the art that various changes in form and details can be made without departing from the spirit of the invention disclosed in this specification and the like. is there. Further, the configurations according to the different embodiments can be implemented in combination as appropriate. Note that in the structures of the invention described below, the same portions or portions having similar functions are denoted by the same reference numerals, and repetitive description thereof is omitted.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a cross-sectional view showing a configuration in the vicinity of the bonding pad of the compound semiconductor integrated circuit according to the embodiment of the present invention.

[Embodiment 1]
For example, a metal wiring 2 mainly composed of gold is formed on the semiconductor substrate 1. The metal pad 2 connects the bonding pad 5 and an internal circuit (not shown). The internal circuit includes, for example, a compound semiconductor transistor, a thin film resistor, an MIM capacitor, a metal wiring, an interlayer insulating film, and the like. Although only one layer of the metal wiring 2 is shown in FIG. 2, a multilayer wiring structure may be used. In FIG. 2, for example, an organic interlayer insulating film 3 such as polyimide, BCB, or WPR (manufactured by JSR Corporation) is formed on the metal wiring 2 and the semiconductor substrate 1. An inorganic insulating protective film 4 made of, for example, silicon nitride is formed on the semiconductor substrate 1 so as to cover the metal wiring 2, the organic interlayer insulating film 3, and the internal circuit. However, as for the bonding pad 5, the surface of the bonding pad is exposed in a region for connecting to an external circuit by wire bonding. For this reason, there is no problem if the bonding pad itself is made of gold which is required to have moisture resistance but is not easily corroded.

  In the present invention shown in FIG. 2, an adhesion improving film 6 made of titanium is inserted between the bonding pad 5 and the inorganic insulating protective film 4. Since the adhesion between the inorganic insulating film such as titanium and silicon nitride and the adhesion between titanium and gold are both high, it is possible to prevent a problem related to adhesion in this embodiment.

  As shown in FIG. 1, if the inorganic insulating protective film 4 is formed directly on the bonding pad 5, an adhesion problem occurs between the bonding pad 5 and the inorganic insulating protective film 4. If there is a part with insufficient adhesion, moisture will penetrate from the part, and the moisture will reach the inside of the circuit through the organic interlayer insulating film 3, which will hinder circuit operation. This embodiment can prevent such a problem from occurring.

  Next, a manufacturing method of a compound semiconductor integrated circuit provided with the adhesion improving film 6 which is a feature of the present embodiment will be described with reference to FIGS.

  First, as shown in FIG. 3, after the metal wiring 2 and the bonding pad 5 are formed, an adhesion improving film 6 made of a titanium thin film is formed on the entire surface of the bonding pad by vapor deposition and a lift-off method. The metal wiring 2 is formed so as to be connected to an internal circuit (not shown).

  Next, as shown in FIG. 4, an organic interlayer insulating film 3 made of a photosensitive material such as photosensitive polyimide, photosensitive BCB, or photosensitive WPR is formed on the entire surface of the semiconductor substrate using a spin coat method.

  Next, as shown in FIG. 5, the organic interlayer insulating film in the region where the exposed portion 8a on the bonding pad 5 and the scribe line for separating the individual integrated circuits are formed by a photolithography technique using a stepper. After that, the organic interlayer insulating film 3 is fixed by curing using an oven or the like. A part of the organic interlayer insulating film 3 is formed on the peripheral region of the bonding pad 5.

  Next, as shown in FIG. 6, an inorganic insulating protective film 4 made of silicon nitride is deposited on the entire surface by using a plasma CVD apparatus or the like.

  Next, as shown in FIG. 7, by photolithography using a stepper, the region 9 inside the region where the organic interlayer insulating film 3 on the bonding pad is not deposited and the region 10 other than the region 10 where the scribe line is formed are photo-exposed. In the state covered with the resist 7, the exposed inorganic insulating protective film 4 and the adhesion improving film 6 are continuously etched using a dry etching technique such as reactive ion etching.

  Thereafter, the photoresist is removed using an organic solvent or the like, thereby forming a region 8b for connecting a bonding wire to the bonding pad 5, as shown in FIG. In contact with each other, the inorganic insulating protective film 4 is formed.

  Thus, the compound semiconductor integrated circuit according to the present embodiment in which the adhesion improving film 6 made of titanium is inserted between the bonding pad 5 and the inorganic insulating protective film 4 is manufactured.

  In the process of the present embodiment, as shown in FIG. 5, the patterning of the organic interlayer insulating film 3 is performed by a photolithography technique using a photosensitive material, but the patterning of the organic interlayer insulating film 3 is In general, reactive ion etching is often performed using a non-photosensitive organic insulating film. However, when reactive ion etching is applied to the patterning of the organic interlayer insulating film 3 having the structure of the present invention, the lower adhesion improving film 6 is easily etched when the organic interlayer insulating film 3 is etched. Application of the organic insulating film is difficult. Therefore, it is preferable to use a photosensitive organic insulating film for manufacturing the structure according to the present invention.

  Further, in order to confirm the effect of improving the moisture resistance, a moisture resistance test was conducted on the sample of the bonding pad structure according to the present embodiment shown in FIG. 2 and the sample of the conventional bonding pad structure of FIG. The test conditions were a storage test at an environmental temperature of 85 ° C. and a humidity of 85%. As a result, in the conventional bonding pad structure, it was confirmed that the film lifted from the bonding pad of the inorganic insulating protective film by silicon nitride in 200 hours. On the other hand, in the sample of the structure according to the present invention, no film lift was observed even after 2000 hours, and the effect of the present invention was confirmed.

  The present invention relates to a semiconductor integrated circuit using a compound semiconductor, and can be applied particularly to a semiconductor integrated circuit requiring moisture resistance.

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Metal wiring 3 Organic interlayer insulation film 4 Inorganic insulating protective film 5 Bonding pad 6 Adhesion improvement film 7 Photoresist 8a Exposed part 8b on bonding pad 9 Connection area for bonding wire 9 Organic interlayer insulation on bonding pad Area 10 inside area where film 3 is not deposited Area where scribe line is formed

Claims (7)

In a compound semiconductor integrated circuit formed on a semiconductor substrate and having an internal circuit covered with an inorganic insulating protective film,
A bonding pad formed on the semiconductor substrate and containing gold;
An adhesion improving film formed in contact with a peripheral region on the bonding pad and containing titanium;
An organic interlayer insulating film in which a part of the region is formed on a peripheral region of the bonding pad;
The inorganic insulating protective film formed on and in contact with the adhesion improving film on the organic interlayer insulating film; and
A compound semiconductor integrated circuit comprising: The compound semiconductor integrated circuit according to claim 1,
The compound semiconductor integrated circuit, wherein the inorganic insulating protective film contains silicon nitride. The compound semiconductor integrated circuit according to claim 1 or 2,
A compound semiconductor integrated circuit, wherein the organic interlayer insulating film contains a photosensitive material. The compound semiconductor integrated circuit according to any one of claims 1 to 3,
The compound semiconductor integrated circuit, wherein the bonding pad is connected to the internal circuit through a metal wiring containing gold. In a method for manufacturing a compound semiconductor integrated circuit formed on a semiconductor substrate and having an internal circuit covered with an inorganic insulating protective film,
Forming a bonding pad containing gold on the semiconductor substrate;
Forming an adhesion improving film containing titanium so as to be in contact with the bonding pad;
Forming a photosensitive organic interlayer insulating film on a peripheral region of the bonding pad;
Forming the inorganic insulating protective film on the organic interlayer insulating film and in contact with a part of the adhesion improving film;
Exposing the bonding pad by etching the adhesion improving film and the inorganic insulating protective film;
A method for manufacturing a compound semiconductor integrated circuit comprising: In the manufacturing method of the compound semiconductor integrated circuit of Claim 5,
The method for producing a compound semiconductor integrated circuit, wherein the adhesion improving film is formed by vapor deposition and a lift-off method. In the manufacturing method of the compound semiconductor integrated circuit according to claim 5 or 6,
The bonding pad is formed simultaneously with metal wiring including gold,
The method of manufacturing a compound semiconductor integrated circuit, wherein the internal circuit is formed so as to be connected to the bonding pad through a metal wiring containing gold.

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