JP2002026010A - Multilayer wiring for bare chip mounting and its manufacturing method - Google Patents

Abstract

[Problem] To provide a highly reliable multilayer wiring for bare chip mounting and an excellent method of using an organic film as an interlayer film and a protective film, having excellent moisture resistance, good adhesion to a main metal of the wiring, and high reliability. provide. A semiconductor substrate having an electronic device and at least one lower layer wiring has a contact hole portion connecting the lower layer wiring and the upper layer wiring, and a predetermined moisture content (preferably 1 to 5 wt. %), An interlayer film made of an organic material (for example, a polyimide-based material) having a property of confining moisture and hardly exuding moisture to the outside of the film is provided.
By improving the adhesion of the wiring to the main metal layer, depositing a base metal layer (for example, WSiN-based) made of a metal compound having an amorphous structure, which is difficult for oxygen atoms to penetrate, and depositing the main metal layer of the wiring thereon To form a multilayer wiring structure in which an upper layer wiring pattern is formed and a protective film made of an organic material is provided on the upper layer wiring pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer wiring compatible with bare chip mounting in a semiconductor integrated circuit such as a GaAs-based and Si-based communication IC / hybridized microwave circuit, which can be applied to bare chip mounting, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In the wiring of a semiconductor integrated circuit such as a 1C / hybrid microwave circuit for GaAs and Si communication, a large number of wiring layers are formed through a VIA through an insulating film using a thick organic material.
(Via contact) A multilayer wiring structure formed by connection is effective for miniaturization and multifunctionalization of a circuit.

A conventional semiconductor chip having this type of wiring has been used in a completely sealed case made of ceramic or the like, so that the moisture resistance characteristics of the wiring portion did not matter at all.
In addition, since organic materials have higher hygroscopicity than inorganic materials such as a silicon oxide film and a silicon nitride film, it has generally been considered that moisture resistance is poor and sufficient reliability cannot be obtained. For this reason, studies for applying to applications requiring high moisture resistance have not been made much.

[0004]

In recent years, with the rapid growth of communication equipment, it has been desired to reduce the cost of the above-mentioned semiconductor devices. In addition, the cost of device fabrication has been reduced, and the cost of packages has become noticeable, and demand for low-cost bare chip mounting has increased.

However, although inorganic materials are considered to be effective in terms of moisture resistance, there is a problem that it is extremely difficult to form a thick interlayer film using inorganic materials.

A method of depositing an inorganic film having excellent moisture resistance as a protective film on the organic interlayer film is also considered. However, since the organic film and the inorganic film have significantly different thermal expansion coefficients, the inorganic film is cracked. There is a problem that it is easy and sufficient reliability cannot be obtained.

On the other hand, regarding the wiring metal, Au (gold), which is the main metal of the wiring, has no problem with respect to the moisture resistance, but the W (tungsten) -based metal has low adhesion with respect to the underlying metal layer of the wiring. Although W has advantages such as high deposition by sputtering and easy processing by dry etching, W has a low resistivity and is resistant to oxidation, but has a problem of easily causing electromigration.
Si (tungsten silicide) metal has a problem that it has a relatively low resistivity but is easily oxidized.

Further, since Ti (titanium) -based metal has poor workability and is difficult to remove by dry etching, there is a problem that Ti atoms are apt to remain after processing and the withstand voltage characteristic is easily deteriorated. ) The system metal has poor adhesion and has a problem that the pad is easily peeled off during bonding.

An object of the present invention is to solve the above-mentioned problems in the prior art, to use an organic film having a specific water content as an interlayer film or a protective film, to have good adhesion to a main metal layer of a wiring, and to provide oxygen. It is an object of the present invention to provide a highly reliable bare chip mounting multilayer wiring excellent in moisture resistance of a wiring portion having a base metal layer having an amorphous structure in which atoms do not easily penetrate, and a method of manufacturing the same.

[0010]

Means for Solving the Problems In order to achieve the above object of the present invention, the present invention is configured as described in the claims. That is, as described in claim 1, on a semiconductor substrate having an electronic device and at least one lower layer wiring, a contact hole portion connecting the lower layer wiring and the upper layer wiring is provided, and a predetermined amount of water is contained inside the film. An interlayer film made of an organic material having a property of confining moisture at a high rate and hardly exuding moisture is provided outside the film. On the interlayer film, adhesion between the wiring and the main metal layer is improved, and oxygen atoms enter the film. A bare chip comprising: depositing a base metal layer made of a metal compound having a difficult amorphous structure, depositing a main metal layer of wiring thereon, forming an upper wiring pattern, and providing at least a protective film on the upper wiring pattern. This is a multilayer wiring for mounting.

Further, as described in claim 2, claim 1
In the above, the base metal layer is a multi-layer wiring for a bare chip mounting made of a tungsten silicon nitride (WSin) metal compound.

Further, as described in claim 3, claim 1
Wherein the interlayer film or the protective film, or the interlayer film and the protective film, is a bare chip mounting-compatible multilayer wiring made of a polyimide organic material having a moisture content of 1 to 5% by weight.

According to a fourth aspect of the present invention, on a semiconductor substrate on which an electronic device and at least one lower layer wiring are formed, moisture is confined inside the film at a predetermined moisture content, and moisture is contained outside the film. A step of depositing an interlayer film using a polyimide-based organic material having a property that is difficult to exude, a step of forming a contact hole portion connecting the lower wiring and the upper wiring in the interlayer film made of the organic material, On top, W for improving the adhesion of the wiring to the main metal layer is formed.
Depositing a base metal layer having an amorphous structure made of a SiN-based metal compound, depositing a plating electrode layer for plating a main metal layer of wiring on the base metal layer, and forming the main metal layer by electrolytic plating; And after forming a resist mask having a wiring pattern using a resist material on the surface of the main metal layer of the wiring,
Using the mask, a milling method is used to remove unnecessary main metal portions and underlying metal portions to process and form an upper wiring, and after removing the resist mask, reactive ions using a fluorine-based gas are removed. A step of etching and removing underlying metal atoms slightly remaining on the surface of the interlayer film by etching; and forming the same organic material as the interlayer film or another protective organic material on the surface of the main metal layer and the surface of the interlayer film. Depositing a protective film using a material, forming a resist mask having a pad pattern for wiring on the protective film, forming a pad region for wiring using the mask, and removing the resist mask And a method for producing a multilayer wiring for bare chip mounting.

The multilayer wiring for bare chip mounting and the method of manufacturing the same according to the present invention have the following two improvements. That is, (1) Conventionally, the moisture content (hygroscopicity) of an organic material has been regarded as a problem with respect to the moisture resistance of a multilayer wiring. However, since a material having a low moisture content cannot contain moisture inside, the moisture permeability is low. Is very high on the contrary. For this reason, the amount of water required for the corrosion of the metal wiring passes through sufficiently, and the moisture resistance deteriorates. (2) On the other hand, a material having a moderate moisture content of, for example, 1 to 5% has a property of firmly retaining moisture inside the membrane, and therefore has very low moisture permeability. Therefore, the latter is more suitable as moisture resistance.

FIG. 2 shows that WSi (tungsten silicide) metal, which is very susceptible to corrosion, is replaced with BCB [benzocyclobutene (B) having a low hygroscopicity, for example, a water content of 0.2%.
enzocyclobutene)] The rate of change of resistance [resistance R / initial resistance Ro] indicating the corrosion state of a sample coated or covered with a suitable hygroscopic property, for example, a polyimide having a moisture content of 1 to 5%. Shows the relationship. The test conditions are 8
5 ° C., 85% RH. For comparison, the result of a sample in which metal (WSi) is exposed without coating is also shown.

FIG. 2 shows that BCB having low hygroscopicity (moisture content)
Polyimide coating with moderate hygroscopicity has better R than coating.
The value of / Ro was almost constant, there was no change in resistance, and good moisture resistance was exhibited. The moisture content of the polyimide is preferably 1 to 5% by weight, and more preferably 2 to 3% in terms of moisture resistance of the wiring.

According to the present invention, a WSiN-based metal compound having an amorphous structure which does not easily penetrate moisture while having the advantage of a W (tungsten) -based metal is used as a base metal, and the WSiN-based metal compound as a base metal is milled. In the processing step, W is reliably removed and the remaining W
In order to prevent short-circuit failure due to movement of atoms, a reactive ion etching step of fluorine-based gas is further introduced.

Since the WSiN-based metal compound forming the base metal layer has an amorphous structure in which the gap between W atoms is filled with Si and N without any gap, it is very difficult for oxygen to cause oxidation to penetrate. It can be said that it is a metal compound having excellent moisture resistance. In addition, since it has an amorphous structure, it is difficult to move atoms, so that electromigration hardly occurs.

W constituting the WSiN-based metal compound,
The atomic ratio of Si and N does not necessarily have to be a stoichiometric amount, and even if there is a slight variation in the amount of constituent elements, an amorphous structure in which Si and N fill the gap between W atoms without gap. As long as it can be used, it can be applied as the base metal layer of the present invention.

FIG. 3 shows the relationship between the resistance change rate (corrosion state) of various metals and metal compounds and the test time. This is a bare sample without a protective film on the metal. The test conditions are 85 ° C. and 85% RH. It can be seen that the WSiN-based metal compound has the best corrosion resistance to moisture and is suitable for the underlying metal layer.

However, it is difficult to completely remove the W-based compound by a mechanical removal method such as milling. The remaining W atoms do not cause any problem when the humidity is low, but easily move under high temperature and high humidity because they are single metal atoms and cause a short-circuit failure. For this reason, in the method for manufacturing a multilayer wiring according to the present invention, after the milling process, for example, a reactive ion etching step of a fluorine-based gas is added, and the remaining W atoms are almost completely removed. Thus, it is possible to realize a highly reliable multilayer wiring compatible with bare chip mounting having excellent moisture resistance without causing a short circuit failure due to the above.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a method for manufacturing a multilayer wiring for bare chip mounting according to the present invention will be exemplified.
This will be described in more detail with reference to the drawings. FIG. 1 is a process chart showing a process of manufacturing a multilayer wiring for bare chip mounting exemplified in the embodiment of the present invention.

As shown in FIG. 1A, an interlayer film 3 made of an organic material such as polyimide is deposited on a semiconductor substrate 1 having a lower wiring 2.

Next, a resist mask 4 having a hole pattern 5 is formed using a material such as a resist, and O ₂ (oxygen) / CF ₄ (carbon tetrafluoride) is formed using the resist mask 4.
(Reactive ion etching) using a mixed gas of
Thereby, a hole pattern 5 reaching the surface of the lower wiring 2 is formed in the interlayer film 3 (FIG. 1B).

Next, the resist mask 4 is removed by an oxygen plasma treatment (ashing treatment) or the like (FIG. 1C).

Next, the interlayer film 3 including the inside of the hole pattern 5 is formed.
First, a thin underlayer of Au (gold) is continuously formed by sputtering as a base metal layer 6 made of a WSiN-based metal compound for improving adhesion and a thin electrode 7 for plating. Next, using the plating electrode 7, Au
The main metal wiring layer 8 is deposited by electroplating (FIG. 1D).

Next, the hole pattern region and the desired wiring pattern region are covered with a photoresist 9, and the unnecessary portions of the main metal wiring layer 8, the plating electrode 7, and the base metal layer 6 are removed by milling [FIG. (E)].

After that, the photoresist 9 is removed by oxygen plasma treatment (ashing treatment) or the like, and then a small amount of W atoms remaining on the interlayer film 3 by RIE using SF ₆ (sulfur hexafluoride) gas or the like. Is removed [FIG. 1 (f)].

Next, a protective film 1 made of an organic material such as polyimide is used.
Deposit 0. Next, a resist mask 11 having a pad pattern 12 is formed using a material such as a resist (FIG. 1 (g)).

Next, using the resist mask 11, O ₂
The protective film 10 on the pad portion 13 of the wiring is removed by RIE using a mixed gas of / CF ₄ , and then the resist mask 11 is removed by an oxygen plasma treatment (ashing treatment) or the like, and the multilayer for bare chip mounting is removed. A wiring structure is manufactured (FIG. 1H).

As described above, in the method for manufacturing a multilayer wiring according to the present invention, after the milling process, for example, a reactive ion etching step of a fluorine-based gas is added, and the remaining W atoms are completely removed. A highly reliable multi-layer wiring for bare chip mounting with excellent moisture resistance and capable of suppressing short-circuit failure due to movement or the like was realized.

In the present embodiment, a thin film obtained by sputtering Au is used as the plating electrode 7, and the main metal wiring layer 8 is made of A
Although the electroplated layer of u is used, an Au alloy can be used instead of Au, or Cu (copper) or a Cu alloy can be used, and a metal having a predetermined performance as a main metal wiring layer can be used. Of course, if it is an alloy, it can be applied to the present invention.

[0033]

According to the multilayer wiring for bare chip mounting and the method of manufacturing the same according to the present invention, an organic film such as polyimide excellent in moisture resistance is used as an interlayer film and a protective film, and the adhesion of the wiring to the main metal is improved. By providing a base metal layer of a WSiN-based metal compound having an amorphous structure that is less likely to penetrate oxygen atoms, a multilayer wiring structure excellent in moisture resistance can be realized.

Further, according to the method for manufacturing a multilayer wiring of the present invention, after the milling process, for example, a reactive ion etching step of a fluorine-based gas is added, and the remaining W atoms are completely removed. It is possible to manufacture a highly reliable multi-layer wiring for bare chip mounting, which is excellent in moisture resistance and can suppress a short circuit failure due to movement of the semiconductor chip, by a simple process. This can contribute to cost reduction and improvement in reliability of semiconductor integrated circuits such as GaAs-based and Si-based communication ICs and hybrid microwave circuits.

[Brief description of the drawings]

FIG. 1 is a process chart showing a method for manufacturing a multilayer wiring compatible with bare chip mounting exemplified in the embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a resistance change rate (corrosion state) of a sample and a test time when a WSi metal is coated with BCB or a polyimide organic material having low water absorption.

FIG. 3 is a diagram showing the relationship between the resistance change rate (corrosion state) of various metals and metal compounds and the test time.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Lower wiring 3 ... Interlayer film 4 ... Resist mask 5 ... Hole pattern 6 ... Base metal layer 7 ... Plating electrode 8 ... Main metal wiring layer 9 ... Resist mask 10 ... Protective film 11 ... Resist mask 12 ... Pad Output pattern 13 ... Pad part of wiring

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference)

Claims (4)

[Claims] An electronic device and a semiconductor substrate having at least one lower layer wiring, a contact hole connecting the lower layer wiring and the upper layer wiring, and confining moisture at a predetermined moisture content inside the film, In addition, an interlayer film made of an organic material having a property of preventing moisture from oozing out is provided outside the film. On the interlayer film, a metal compound having an amorphous structure that has good adhesion to a main metal layer of wiring and has a low penetration of oxygen atoms. A base metal layer, and a main metal layer of wiring thereon, forming an upper wiring pattern, and at least a protective film provided on the upper wiring pattern. Multi-layer wiring. 2. The multilayer wiring for bare chip mounting according to claim 1, wherein said base metal layer is made of a tungsten silicon nitride (WSiN) based metal compound. 3. The bare chip mounting according to claim 1, wherein the interlayer film or the protection film, or the interlayer film and the protection film are made of a polyimide organic material having a moisture content of 1 to 5% by weight. Corresponding multilayer wiring. 4. A polyimide organic material having a property of confining moisture at a predetermined moisture content inside a film and preventing water from oozing out of the film on a semiconductor substrate on which an electronic device and at least one lower wiring layer are formed. A step of depositing an interlayer film by using, a step of forming a contact hole portion connecting the lower layer wiring and the upper layer wiring in the interlayer film made of the organic material, and forming a main metal layer of the wiring on the interlayer film. Depositing a base metal layer having an amorphous structure made of a WSiN-based metal compound to improve the adhesion of the substrate; and depositing a plating electrode layer for plating a main metal layer of the wiring on the base metal layer. Depositing the main metal layer by electrolytic plating, and after forming a resist mask having a wiring pattern using a resist material on the surface of the main metal layer of the wiring, Using the mask to remove unnecessary main metal portions and underlying metal portions by milling to form an upper layer wiring; and, after removing the resist mask, reactive ions using a fluorine-based gas. Etching the base metal atoms slightly remaining on the surface of the interlayer film by etching; and forming the same organic material as the interlayer film or another protective organic material on the surface of the main metal layer and the surface of the interlayer film. Depositing a protective film using a material, forming a resist mask having a pad pattern for wiring on the protective film, forming a pad region for wiring using the mask, and removing the resist mask A method for manufacturing a multilayer wiring for bare chip mounting, comprising: