JPH0799196A - Method for forming metal film for integrated circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] In the pretreatment of electroless metal plating used for semiconductor wiring formation, by activating only the semiconductor element formation surface in the liquid phase, metal deposition on the back surface is prevented, and as a result , Prevent contamination in the next process. A semiconductor element forming wafer 11 having a contact hole 18 in which a barrier metal 14 is deposited is pretreated while being rotated on a spin coater 12, and only the semiconductor element forming surface is activated. By immersing the wafer 11 thus surface-treated in the plating bath 13,
The wiring metal 15 is deposited only on the entire surface of the semiconductor element formation surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring forming method for forming semiconductor elements and integrated circuits, and more particularly to forming a metal film by electroless plating.

[0002]

2. Description of the Related Art Heretofore, a sputter deposition method or a CVD method has been used for depositing a metal film for forming wiring of a semiconductor element or an integrated circuit. In these methods, a large amount of energy is applied to a metal compound to release the metal or decompose the metal compound to deposit a metal film on the semiconductor element formation surface. However, the sputtering method has a big problem that sufficient coverage cannot be taken in the uneven portion.
Further, these methods have a problem that the metal is deposited under a vacuum condition, resulting in enormous cost and process complexity. As a method for solving these problems, deposition of a metal film by a plating method has recently attracted attention.

The plating methods are roughly classified into two types, electroplating and electroless plating (chemical plating).
However, in electroplating, since metal deposition depends on the electric field distribution, it is difficult to distribute an electric field similar to that on a flat surface in a fine buried groove or a contact hole. Can not. Therefore, a method of applying an electroless plating method of depositing a metal by chemically utilizing a reduction reaction on the surface of a substrate to depositing a metal film for forming a wiring has been recently studied.

In this electroless plating, a salt of a metal (eg, copper or silver) which is autocatalytically deposited by a reduction reaction,
This is a method of plating by immersing an object to be plated in a plating solution composed of a complexing agent that prevents a metal salt from becoming a hydroxide in a solvent and precipitating, a reducing agent, and a pH adjusting agent. However, the electroless plating method requires a nucleus for depositing the first plated metal, and the activating process that forms an activator (mainly palladium chloride in an acidic aqueous solution) that becomes the nucleus of metal deposition is activated. Required for processing.

At the present stage, the activation treatment is carried out by immersing the whole semiconductor element forming wafer in a pretreatment liquid, and the whole activated wafer is immersed in a plating bath to deposit metal. The method of doing is.

[0006]

However, this method has the following major problems.

Since the whole object to be plated is dipped in the pretreatment liquid, a portion other than the semiconductor element forming surface to be plated is also activated, so that the metal is also deposited on the back surface. The metal on the back surface causes contamination (cross-contamination) in the subsequent steps, which is a serious problem in the semiconductor process. Further, in order to remove the metal on the back surface, it is necessary to employ a method of treating only the back surface with a strong acid capable of dissolving the metal, which results in an increase in one-step process.

As means for solving this problem, a method of depositing palladium which is an activator by a sputtering method or a method of burying it near the surface by an ion implantation method has been proposed so far. However, these methods have problems of low throughput and high cost, and are not practical.

Therefore, an object of the present invention is to provide a method for forming a metal film for an integrated circuit, which can perform an activation treatment in a liquid phase for activating only a portion where a metal film is desired to be deposited.

[0010]

In order to achieve the above object, the present invention is directed to a substrate on which a metal film is to be formed. In the liquid phase, at least the activation treatment for plating is performed only on one main surface of the substrate. The method includes the steps of: performing the activation treatment, placing the activation-treated substrate in an electroless plating treatment tank, and forming a metal film only on the activation-treated surface.

Further, it is desirable to use a method of performing activation treatment by spin coating in the step of subjecting the activation treatment to only one main surface.

Further, in the present invention, it is desirable that at least a groove, a base material, or a contact hole for connecting wiring is formed on one main surface of the substrate.

Further, as the activation processing according to the present invention,
It is desirable to use a palladium compound or a tin compound.

[0014]

In the present invention, in the pretreatment step, only one main surface can be activated, and the metal is selectively deposited on the activation layer. Therefore, the metal film is prevented from being deposited on the portion other than the main surface. You can Therefore, the step of removing the metal film deposited on the back surface is not required, and cross contamination in the semiconductor process can be prevented. Also, activation in the liquid phase is easier than activation using vacuum technology,
Inexpensive wiring can be formed.

Therefore, the use of the present invention is effective in forming a wiring which is simple in process and inexpensive.

[0016]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a method for forming a wiring metal film by the electroless plating method of the first embodiment.

First, in FIG. 1A, the contact hole 1
The semiconductor element forming surface of the semiconductor element forming wafer 11 in which titanium nitride 14 was deposited as a barrier metal on the insulating film 19 having 8 was faced up and set on the spin coater 12. Then, in order to degrease the surface of the semiconductor element, acetone is brought into contact with the wafer 11 from the nozzle for 1 minute while rotating the wafer 11 at a speed of 200 rpm, and then 3000 rpm is applied to dry the acetone. Let After that, the rotation is stopped, and in order to remove the natural oxide film on the titanium nitride surface, BHF is discharged from the nozzle.
The (HF: NH ₄ F = 1: 20) solution was applied on the wafer 11 and immersed for 20 seconds. After 20 seconds, 1000 revolutions /
The wafer 11 was rotated at min for completely removing BHF, and then washed with water for 1 minute. After washing with water, in order to facilitate adsorption of the activator, while rotating the wafer 11 at a speed of 200 rpm, a 10% tin chloride solution was discharged from the nozzle for 5 minutes to perform sensitizing, and then at the same speed. It was washed with water for 30 seconds. Then 10
% Palladium chloride solution was activated from the nozzle for 5 minutes while rotating the wafer 11 at the same speed, and then rinsed with water for 30 seconds in the same manner.

Next, in FIG. 1 (b), the wafer 11 pretreated in this way was prepared with 150 ml / L formalin, 10 g / L ethylenediamine, a small amount of thiourea, 29 g of copper sulfate, and 40 g / L of sodium hydroxide. When immersed in the copper plating bath 13 for 30 minutes while stirring with air, about 1μ
It was possible to deposit the copper film 15 on the entire surface of the semiconductor element formation surface with a film thickness of m (FIG. 1C).

Then, in FIG. 1 (d), a resist is applied on the copper-plated semiconductor element forming wafer 11,
A desired resist wiring pattern 16 was formed using ultraviolet rays, and the silver film 15 was etched using the resist resist pattern 16 as a mask to form a copper wiring (FIG. 1).
(E)).

(Embodiment 2) FIG. 2 is a diagram showing a method for forming a wiring metal film by an electroless plating method according to a second embodiment.

First, in FIG. 2A, a semiconductor element forming wafer 21 having a groove formed in a silicon oxide film 28 on which a titanium-tungsten barrier metal 24 is deposited and a contact hole 27 is exposed with the semiconductor element forming surface as a front side. It was set on the coater 12. Then, while rotating the wafer 21 at a speed of 200 rotations / min, acetone is flown on the wafer 21 from the nozzle for 1 minute to degrease the surface of the semiconductor element. 3000 rpm /
Acetone was dried to a minimum. After that, the rotation is stopped, and palladium chloride 5 mg / L, 12M is discharged from the nozzle.
HCl 0.1 ml, HF (50: 1) 250 ml / L
The solution was cast on the wafer 21 for 20 seconds. 20 seconds later, 1
The wafer 21 is rotated at 000 rotations / min to perform PdC
After the l ₂ -HF solution was completely removed, it was washed with water for 1 minute. By this step, the removal of the natural oxide film on the surface of the semiconductor element and the activating process are simultaneously performed.

Next, in FIG. 2 (b), the wafer 21 pretreated in this way was prepared in the proportions of formalin 150 ml / L, ethylenediamine 10 g / L, a small amount of thiourea, copper sulfate 29 g / L and sodium hydroxide 40 g / L. The wafer 21 is agitated while being agitated in the prepared electroless copper plating bath 23.
Approximately 1 μm when immersed for 1 hour while gently rocking
It was possible to plate the copper film 25 on the entire surface of the semiconductor element formation surface with the thickness of (2) (FIG. 2C).

Then, in FIG. 2 (d), chemical mechanical polishing (CMP) was carried out to remove the copper 25 in the excess portion other than the buried groove, whereby a copper buried wiring could be formed.

Similar good wiring could be formed by a flattening method (etchback method) using dry etching instead of CMP. The portion to be plated may be the entire surface on the groove portion formed in the silicon oxide film. In this case, tungsten or the like is previously deposited and buried in the contact hole portion.

Although the first and second embodiments have been described using copper deposition, the same good results can be obtained with silver, nickel, cobalt and gold.

In the first and second embodiments, the activation process is performed by spin coating in the step of performing the activation process on only one main surface. However, in addition to this method, for example, the main surface portion is used. It is possible to cover the other parts with a resist so as not to carry out the activation treatment, or to use a method in which only the main surface portion is brought into contact with the liquid surface of the activation treatment liquid. It is not limited to.

[0028]

As described above, according to the present invention, by activating only one main surface on which the semiconductor element of the object to be plated before electroless metal plating is activated and immersing the wafer in the plating bath, The metal film can be deposited only on the main surface. Further, by performing the activation treatment on the spin coater, other pretreatments can be continuously performed on the spin coater, and the treatment time can be shortened.

Therefore, according to this method, the wiring can be formed by an inexpensive process without the problem of cross contamination.

The present invention is intended to reduce the process cost and simplify the process by replacing the metal film deposition by the CVD or sputtering technique with the plating technique.

[Brief description of drawings]

FIG. 1 is a process diagram for explaining a method for forming a wiring metal film by an electroless metal plating method according to a first embodiment of the present invention.

FIG. 2 is a process drawing for explaining a method for forming a wiring metal film by an electroless metal plating method according to a second embodiment of the present invention.

[Explanation of symbols]

 11,21 Semiconductor element forming wafer 12 Spin coater 13,23 Copper plating bath 14 Barrier metal (titanium nitride) 24 Barrier metal (titanium tungsten) 15,25 Copper film 16 Resist pattern 17 Copper wiring pattern 26 Copper embedded wiring

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shin Hashimoto 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A step of performing at least a liquid phase activation treatment for plating on a substrate on which a metal film is to be formed, only on one main surface of the substrate; A method of forming a metal film for an integrated circuit, which comprises a step of installing the metal film only on a surface which is placed in an electroless plating treatment tank and subjected to an activation treatment. 2. The method of forming a metal film for an integrated circuit according to claim 1, wherein in the step of performing the activation treatment, only one main surface of the substrate is activated by using a spin coating method. 3. The method for forming a metal film for an integrated circuit according to claim 1, wherein at least a groove, a base element, or a contact hole for connecting a wiring is formed on one main surface of the substrate. 4. The method for forming a metal film for an integrated circuit according to claim 1, wherein a palladium compound or a tin compound is used for the activation treatment.