JPS6214424A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a flattened electrode and to obtain a flat wiring by a method wherein growths of the metal film and etchings are alternately repeated and the electrode window to be opened on the insulating film is thus filled with the laminated metal film. CONSTITUTION:An electrode window 3 is opened on an insulating film 2 to be formed on an Si substrate 1. A metal film 10 is adhered inside the electrode window 3. The metal film 10 begins to grow on the insulating film 2 as well when the film thickness thereof becomes thicker in about 3,000Angstrom or more. At that point, the growth is stopped and the metal film 10 on the insulating film 2 is etched away by an ion milling method. A metal film 10 is again adhered in the electrode window 3. The metal film 10 on the insulating film 2 is etched away. Lastly the electrode window 3 is filled up with the metal film 10 to be grown. A wiring layer 11 is formed on the metal film 10. By this way, the flattened electrode is formed, thereby enabling to obtain a flat wiring.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of forming an electrode.

2. Description of the Related Art As semiconductor devices such as ICs have become highly integrated, multiple wiring layers have been formed to connect a large number of elements. However, the more layers are laminated, the more uneven the substrate surface becomes, and the disadvantage is that the surface of the substrate becomes more uneven and steps are formed, making it easier for disconnections and short circuits to occur in the wiring layers.

Therefore, flattening the surface of a semiconductor substrate is currently an important issue, but the formation of electrodes is a major cause of inhibiting flattening. is requested.

[Prior art and problems to be solved by the invention] FIG. 2(a) is a diagram showing a conventional method of forming an electrode, in which 1 is a silicon substrate, 2 is an insulating film made of silicon dioxide (Si02) film, 3 is an electrode window, and 4 is a wiring layer (for example, an aluminum film). As shown in the figure, the wiring layer 4 is directly attached to the electrode window 3.
If a wiring layer is formed, the wiring layer will be depressed due to the step at the electrode window portion, and wire breakage will easily occur at that portion. Furthermore, when an insulating film is deposited on top of the insulating film for the purpose of forming a second wiring layer (not shown), the insulating film becomes thinner at the electrode portion, and the second wiring layer formed thereon becomes thinner. A problem arises in that the wiring layer 4 in the figure is likely to be short-circuited.

Therefore, various methods have been devised for flattening the electrode window. For example, the most widely used measures include:
One method is to round the shoulders of the insulating film at the electrode window part to make the difference in level gentle. However, as it has become more highly integrated and miniaturized in recent years, this alone is no longer sufficient.
The problem that the unevenness becomes more severe as the layers are stacked has not been resolved, and the risk of the above-mentioned wire breakage and short circuit has increased. As a solution to this problem, for example, a selective growth method in which the electrode window is buried is being considered.

The selective growth method is a method in which a grown film is selectively deposited depending on the underlying material.For example, tungsten hexafluoride (WF6)
This is a growth method in which when tungsten (W) is thermally decomposed, tungsten (W) is deposited only on the silicon substrate 1 and not on the 5i02 film 2.

However, with such a selective growth method, it is currently difficult to selectively grow until the electrode window is buried, and the film thickness of selective growth is at most 3000 degrees or more, and beyond that, the film begins to be deposited non-selectively and indiscriminately. . Therefore, if the wiring layer 6 is formed on the tungsten film 5 as shown in FIG. It is difficult to achieve sufficient flatness.

In addition, as shown in Fig. 2 fc), polycrystalline silicon II
! A method of planarizing the electrode wiring is known, in which J7 is selectively grown and buried only in the electrode window, and the wiring layer 8 is formed thereon. Chlorine-based reactive gas, such as silicon tetrachloride (S
When pyrolyzed and deposited with iC14) or trichlorosilane (SiHCl2), 5iO211! j! In this case, the electrode window can be buried with a polycrystalline silicon film.

However, even if the polycrystalline silicon film 7 is made of doped polycrystalline silicon to provide conductivity, its electrical resistance is relatively high, and it is not sufficiently satisfactory as a wiring layer of a microdevice.

The present invention proposes a flattening method for forming electrodes that eliminates these problems.

[Means for solving the problem] The problem is that a metal film is selectively grown in a vapor phase in an electrode window in which a window is opened in an insulating film, and then a metal film is grown in a vapor phase on the non-selectively deposited insulating film. The problem is solved by a method of manufacturing a semiconductor device, which includes the step of removing the metal film by etching, and then alternately repeating the growth and etching of the metal film to bury the electrode window with the metal film.

[Operation] That is, the metal film is deposited until it no longer selectively grows, and when it begins to deposit on the insulating film, the growth is stopped and the entire surface is etched to expose the insulating film. The electrode window is buried by repeating this growth and etching process.

By doing so, the wiring layer connected to the electrode is flattened, and even if the number of laminated layers on the substrate is increased, the unevenness will not increase.

[Example] Hereinafter, embodiments will be described in detail with reference to the drawings.

FIGS. 1A to 1E are sequential cross-sectional views of the electrode forming process according to the present invention. First, as shown in FIG. An electrode window 3 having a size of 1.5 μm square is provided.

Next, as shown in FIG. 1 (bl), a tungsten film 10 with a thickness of about 3,000 layers is deposited.The deposition method is chemical vapor deposition (CVD) using a neutral gas such as helium (He). WF6 gas is introduced as a carrier gas, hydrogen gas is added thereto, and the mixture is thermally decomposed at a temperature of several hundred degrees Celsius in a reduced pressure air stream.The reaction formula is as follows.

WF6 +)i2-W+HF Then, the tungsten film 10 is deposited only on the silicon substrate within the electrode window 3, but when the film thickness is increased to about 3000 or more, the selectivity is lost and the tungsten film 10 is deposited only on the silicon substrate within the electrode window 3. It also begins to grow upwards, but at that point it stops growing. The reason for this loss of selectivity is thought to be due to the surface condition of the insulating film.

Next, as shown in FIG. 1C, the tungsten film IO deposited on the 5iO2P22 is etched away by ion milling. To do this, the entire surface is ion-milled, and the etching is stopped when there is no more tungsten film on the 5iO7 film. This is what is called control etch. Then, the 5i02 film is further etched and etched with hydrofluoric acid to adjust the surface condition.

Next, as shown in FIG. 1 (dl), the process in FIG. 1 (bl) above is repeated again, and tungsten [9!
10 is applied. Thereafter, the process shown in FIG. As shown in FIG. 1 (fe), the inside of the electrode window 3 is completely buried with a tungsten film 10, and a wiring layer 11 is formed thereon.

In this way, the wiring layer 11 is flattened, and thus the wiring layer is formed on a flat surface without increasing unevenness even if multilayer wiring is stacked on the substrate.

[Effects of the Invention] As is clear from the above description, according to the present invention, flattened electrodes are formed, flat wiring can be obtained, and the reliability of the IC can be improved. be.

[Brief explanation of drawings]

1a) to 1(e) are sectional views of the electrode according to the present invention in the order of forming steps, and FIG. 2 (aJ, (bl), (C1 is a sectional view of the conventional electrode formation process. Substrate, 2 is S+02 film, 3 is electrode window, 4.6, 8.11 is wiring layer, 10 is tungsten film

Claims (1)

[Claims] A metal film is selectively grown in a vapor phase in an electrode window in which an insulating film is opened, and then the metal film on the insulating film non-selectively deposited is removed by etching, thus growing the metal film. A method of manufacturing a semiconductor device, comprising the step of burying the electrode window with a metal film by alternately repeating and etching.