JP2914043B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming a multilayer wiring.

[0002]

2. Description of the Related Art Generally, aluminum is often used as a wiring material for LSIs. This is because they are inexpensive, have good workability, and have low electric resistance. However, it has become difficult to satisfy the recent requirements for high integration, high current density, and high reliability for the wiring of LSI with aluminum wiring. Therefore, there has been proposed a technique of forming a wiring by depositing a noble metal film by plating in a groove having a wiring forming pattern provided in a photoresist film or an electron beam resist film (hereinafter referred to as a resist film). For example, when gold is used as a wiring material, there are various advantages as compared with aluminum. That is, the gold wiring has a specific resistance about 20% lower than that of the aluminum wiring, and the life of stress migration and electromigration is several tens times longer. The aluminum wiring is formed into a desired pattern shape by depositing an aluminum film by a sputtering method and then combining an ordinary photolithography technique and an anisotropic etching technique such as RIE (reactive ion etching). However, inconveniences such as reduction in step coverage due to the sputtering method and thinning of the wiring due to side etching due to the RIE method often occur, thereby lowering reliability. On the other hand, noble metal wiring is formed by plating using a resist film as a mask,
The aforementioned problem does not occur.

In forming a noble metal wiring by the plating method, the wiring shape and the wiring pitch are affected by the performance of a resist film used as a plating mask.

Conventionally, a novolak-based positive resist film has been used. However, when a mask pattern of a plating method is formed using a positive resist film, the cross-sectional shape becomes
The positive type resist film has a forward taper as a feature. This tendency becomes more remarkable as the thickness of the resist film increases. In recent years, as the level of integration of LSIs has increased, the level difference between substrates in the wiring process has also increased. Therefore, a resist film used as a plating mask has to be thickened, and its cross-sectional shape has a high forward taper. Therefore, the cross-sectional shape of the wiring formed using this resist film as a mask is an inverted trapezoid. If the cross-sectional shape of the wiring is inverted trapezoidal, there is a problem that voids are generated in the interlayer insulating film formed on the wiring and the accuracy of the width of the wiring is reduced.

To solve this problem, the use of a recently proposed chemically amplified negative resist film was studied. In a chemically amplified negative resist film, an acid is generated from an acid generator in the resist film upon exposure, and the acid serves as a catalyst to promote insolubilization of the resist film. Its features include very high sensitivity and high resolution, and high dry etching resistance. By using this chemically amplified negative resist film, the problem of low resolution of the conventional negative resist film can be solved, and its shape takes advantage of the characteristics of the negative resist film, and its cross-sectional shape is from reverse tapered to slightly forward tapered. Can be controlled to some extent.

FIG. 2 is a sectional view of a semiconductor chip for explaining an example of a conventional method of manufacturing a semiconductor device.

As shown in FIG. 2, an insulating film 2 is provided on a semiconductor substrate 1 having an uneven surface on which elements and basic wiring are formed, and a titanium tungsten film and a gold film are sequentially formed on the insulating film 2. A deposited metal film 3 is formed. Here, the metal film 3 serves as a power supply film in an electroplating method or a deposition film in an electroless plating method. When a noble metal film is plated, a noble metal film is preferable. Next, a chemically amplified negative resist film is applied on the metal film 3 and patterned to form a resist film 6 having a wiring forming pattern. Next, a gold film 7 is formed on the metal film 3 by electroplating using the resist film 6 as a mask.
Is deposited to form wiring.

[0008]

However, in this conventional method for manufacturing a semiconductor device, a chemically amplified negative resist film is applied on a metal film to be a power supply film for electroplating or a deposition film for electroless plating. When patterning by the photolithography technique, there is a problem that the resist film at the portion in contact with the metal film at the concave portion of the step portion is pulled down as shown by the bottom portion 8 in FIG.

[0009] The extent of this skirting sharply increases at a portion deviating from the image plane of the pattern image at the time of exposure. Therefore,
The greater the level difference, the more significant skirting occurs. When a metal film is deposited in the groove by electroplating using the resist film with the tail as a mask as a mask to form wiring,
The cross-sectional shape of the wiring is constricted. This constriction causes voids when an interlayer insulating film is formed on the surface including the wiring, and when the wiring is locally thin, electromigration is likely to occur, and the reliability is reduced. .

[0010]

According to a method for manufacturing a semiconductor device of the present invention, a first insulating film is formed on a semiconductor substrate having an element or the like having an uneven surface, and plating is performed on the first insulating film. Forming a metal film to be a power supply film (or a deposition film) for forming a second insulating film on the metal film by a coating method, and then etching back the second insulating film to form the second insulating film. Exposing the other portion of the metal film while leaving the second insulating film only in the concave portion of the metal film; and applying a chemically amplified negative resist solution to the surface of the metal film including the second insulating film. Patterning to form a resist film having a wiring forming pattern; and forming the second resist film using the resist film as a mask.
And a step of forming a wiring by depositing a noble metal film on the surface of the metal film by plating again using the resist film as a mask.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The background of the present invention is as follows. First, an attempt was made to improve the shape of a chemically amplified negative resist film on a noble metal film using a flat substrate, and the transparency of the resist film, the amount of an acid generator, the prebake temperature, the PEB ( Post Exposure Bake:
By appropriately selecting the temperature of (post-exposure bake), a shape without tailing was obtained. However, when an experiment was performed on a semiconductor substrate having a step on which an element was formed, it was found that the bottom was largely drawn in the concave portion, and it could not be solved by adjusting the conditions for forming the resist film. In view of the fact that the shape of the chemically amplified resist film greatly changes depending on the material of the substrate, changes in the cross-sectional shape of the resist film with respect to films of various materials were investigated. As a result, SOG film, polyimide film, plasma oxide film, plasma nitride film, Ti film, TiN
It was found that the tailing was reduced in the film, and there was no tailing in the SOG film in particular. That is, it has been found that a film made of a material that can easily absorb the acid generated in the resist film as compared with the noble metal film may be selected. Then, a thin SOG film having a thickness of about 10 nm was formed on the entire surface of the noble metal film, and then a chemically amplified negative resist film was applied and patterned. However, this time, the shape of the resist film was narrowed in the flat portion.

In order to solve this problem, it has been devised to partially form an acid absorption film formed on a noble metal film by using a coating method. That is, the thickness of the SOG film formed by the coating method is larger in the concave portion than in the flat portion. Therefore, when the entire surface of the SOG film is etched back, the noble metal film is exposed in the flat portion, and the SOG film can be left only in the concave portion. After having such a structure on the substrate,
The formed resist pattern has SO
The footing was suppressed by the effect of the G film, and the noble metal film was exposed in the flat part, so that a resist film shape without footing and constriction could be obtained. It was also found that similar effects can be obtained by using not only an SOG film but also a polyimide film formed by a coating method.

Next, an embodiment of the present invention will be described with reference to the drawings.

FIGS. 1A to 1C are sectional views of a semiconductor chip shown in the order of steps for explaining an embodiment of the present invention.

First, as shown in FIG. 1A, an element or the like is formed, and an insulating film 2 provided on a semiconductor substrate 1 having a step is provided.
A titanium tungsten film having a thickness of 30 to 100 nm and a gold film having a thickness of 30 to 100 nm are sequentially deposited thereon by sputtering to form a laminated metal film 3. Here, the titanium tungsten film plays a role in maintaining the adhesion between the insulating film 2 and the gold film. Next, an SOG liquid is applied on the metal film 3 and baked to form an SOG film 4 having a thickness of 10 to 30 nm. This S
The OG film 4 is thicker in the recess 5 than in the flat portion.

Next, as shown in FIG. 1B, the SOG film 4 is etched back to remove the SOG film 4 other than the concave portions 5, exposing the surface of the metal film 3 in the flat portion.

Next, as shown in FIG. 1C, a chemically amplified negative resist solution (for example, Tokyo Ohkasha Co., Ltd.) is applied on the metal film 3 including the thin SOG film 4 left on the metal film 3 in the recess 5. Made i
N-200 to which a slight amount of dye is added) is applied to a thickness of 1.6 μm, and then patterned by a photolithography process to form a resist film 6. Next, using the resist film 6 as a mask, the SOG film 4 remaining on the metal film 3 is removed by RIE using O ₂ + CHF ₃ plasma.

Here, the S remaining on the metal film 3 in the recess 5
By absorbing the acid generated by the OG film 4, the footing of the resist film 6 in the concave portion 5 is suppressed, and the pattern accuracy is improved. The same effect can be obtained by using a polyimide film coated and baked instead of the SOG film 4.

Next, using the resist film 6 as a mask, the metal film 3
Is deposited on the metal film 3 by an electroplating method or an electroless plating method as a power supply film or a deposition film to form a wiring.

When the SOG film 4 or the polyimide film is directly formed on the metal film 3 by adhesion, the adhesion between these films and the noble metal film is reduced depending on the film formation conditions, and the formed SO
The G film 4 or the polyimide film may be peeled off from the metal film 3. To overcome such disadvantages, the metal film 3
After forming a silicon nitride film as an adhesion film with a thickness of about 10 nm by plasma CVD thereon, an adhesion can be improved by forming an SOG film or a polyimide film.

[0021]

As described above, the present invention eliminates defects in the cross-sectional shape of a pattern provided in a resist film by selectively forming an insulating film on the surface of a concave portion formed in a power supply film for plating. This has the effect of improving the reliability of the fine noble metal wiring.

[Brief description of the drawings]

FIG. 1 is a sectional view of a semiconductor chip shown in the order of steps for explaining an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a semiconductor chip for describing a conventional method of manufacturing a semiconductor device.

[Explanation of symbols]

 Reference Signs List 1 semiconductor substrate 2 insulating film 3 metal film 4 SOG film 5 concave portion 6 resist film 7 gold film 8 foot

Claims (3)

(57) [Claims] 1. A first insulating film is formed on a semiconductor substrate on which an element or the like is formed and has an uneven surface, and a metal film serving as a power supply film (or a deposition film) for plating is formed on the first insulating film. Forming and, after forming a second insulating film on the metal film by a coating method, etching back the second insulating film to leave the second insulating film only in the concave portion of the metal film. Exposing the other portion of the metal film, and applying a chemically amplified negative resist solution to the surface of the metal film including the second insulating film to form a resist film having a wiring forming pattern. A step of removing the second insulating film using the resist film as a mask, and a step of forming a wiring by depositing a noble metal film on the surface of the metal film by plating using the resist film as a mask again. Manufacture of a semiconductor device characterized by including Construction method. 2. The method according to claim 1, wherein the second insulating film is an SOG film or a polyimide film. 3. The method according to claim 1, wherein the second insulating film is formed on the silicon nitride film by using SO.
2. The method according to claim 1, wherein the semiconductor device has a two-layer structure in which a G film or a polyimide film is deposited.