JPS5925245A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To inhibit a projection through heat treatment of an Al layer by continuously coating the upper section of a semiconductor substrate with an Al film and an inorganic insulating film, patterning the insulating film, thermally treating the whole at a high temperature and patterning a wiring layer consisting of the Al film. CONSTITUTION:The upper section of the semiconductor substrate 11 is coated with the Al film 12 and the SiO2 film 13. A resist film 14 is applied, only a wiring layer forming section is masked through patterning, and the SiO2 film 13 exposed is removed through dry etching. When the resist film 14 is removed and the whole is thermally treated, the Al projections S are formed in the Al film exposed. The surface is dry-etched while using the SiO2 film 13 as a mask, the Al film 12 is patterned, and the desired Al wiring layer is formed. The substrate 11 is heated, and a PSG film is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, particularly to an improvement in a method for forming an aluminum wiring layer formed on the surface of a semiconductor integrated circuit (IC).

(b) Prior Art and Problems In an IC, a large number of active elements and passive elements are provided on a semiconductor substrate, and these elements are connected to each other through conductive wiring layers.

An aluminum (Al) film is most often used as this conductive distribution layer because aluminum has extremely good electrical conductivity and is an inexpensive material.

Such an aluminum wiring layer usually contains about 1% silicon, etc., and the method for forming it is to deposit it by sputtering or vapor deposition, then form a resist film mask in a photo process, and then The wiring layer is patterned by dry etching using carbon chloride (CCl4) gas. Thereafter, heat treatment is performed at a high temperature of 400 to 500° C. in order to align the crystal atoms of the aluminum wiring layer and improve conductivity. In addition, even if such high-temperature heat treatment is not performed, if a protective film is applied using chemical vapor deposition (CVD) when covering the top surface of an aluminum wiring layer, the aluminum wiring layer can be coated with a protective film. The semiconductor substrate is heated to about 420° C., and this heat treatment also serves to restore conductivity. Such a protective film is naturally an insulating film, for example, a phosphorous silicate glass (PSG) film or a silicon dioxide (SiO2) film is used, and when this protective film is formed with multiple aluminum wiring layers, Similarly, a PSG film or a SiO2 film is used as each interlayer insulating film.

However, when the aluminum wiring layer is subjected to high-temperature heat treatment to align the crystal atoms, the crystals grow abnormally and protrusions form.
For example, for aluminum wiring with a film thickness of 1 μm, the length is 1 μm.
Aluminum protrusions that grow close to 3000 m in length deteriorate the coverage of the protective film, and in the case of multilayer wiring, the insulation between wiring layers deteriorates, causing problems in terms of reliability. . FIG. 1 shows such an aluminum protrusion S, which is generated by forming an aluminum wiring layer 2 on a semiconductor substrate 1 and covering it with a PSG film 3, and the PSG film is thin at the protrusion part. Because it is rusted, it is easy for moisture to enter, causing aluminum to deteriorate.

Therefore, in order to eliminate these problems, for example, after depositing an aluminum film by vapor deposition, boron difluoride (BF2) ions are implanted at a high concentration to increase the hardness of the aluminum film. Ion implantation processing is performed to prevent protrusions from growing externally.

However, at high acceleration voltages and for long periods of time (e.g. 100Ke
Completing the process (V, 1 hour) increases time and man-hours accordingly, and increasing the hardness of the aluminum film too much weakens the adhesive strength during wire bonding. This also raises reliability issues.

(c) Object of the Invention The present invention proposes a manufacturing method for the purpose of suppressing aluminum protrusions caused by such heat treatment of an aluminum wiring layer.

(d) Structure of the Invention The purpose is to successively deposit an aluminum film and an inorganic insulating film on a semiconductor substrate, pattern the inorganic insulating film and heat treat it at high temperature, and then use the inorganic insulating film as a mask. This can be achieved by a method for manufacturing a semiconductor device that includes a step of patterning a wiring layer made of the aluminum film.

(e) Examples of the invention Hereinafter, embodiments will be described in detail with reference to the drawings.

2 to 6 are cross-sectional views of the manufacturing process according to the present invention. First, as shown in FIG. 2, a film of 1% silicon with a thickness of 1 μm is deposited on a semiconductor substrate 11 by a continuous sputtering method. An aluminum film 12 and a silicon dioxide (SiO2) film 13 having a thickness of 1000 to 2000 Å are deposited. The continuous sputtering method refers to sputtering an aluminum film in the first sputtering chamber 21 and sputtering an SiO2 film in the second sputtering chamber 22 using, for example, an RF sputtering device as shown in FIG. Since the load lock chamber 23 is provided and connected, this method allows continuous deposition without exposure to the atmosphere.

Next, as shown in FIG. 3, a resist film 14 is formed on the upper surface.
After coating and patterning to mask only the portion where the wiring layer will be formed, the exposed SiO2 film 13 is dry etched using trifluoromethane (CHF3) gas.
Remove by etching. Next, as shown in FIG. 4, after removing the resist film 14, heat treatment is performed at 450° C. for 40 minutes in an atmosphere of nitrogen gas (containing 5% hydrogen gas), and aluminum protrusions S are formed on the exposed aluminum film surface. . In this case, the heat treatment temperature of 450°C is
Substrate heating temperature 420 to 43 when depositing G film
The temperature is higher than 0° C., which is suitable for alloying the still sputtered aluminum and silicon.

Next, as shown in FIG. 5, using the SiO2 film 13 as a mask, dry etching is performed using a mixed gas of CCl4 and BCl3 (boron trichloride) as an etching agent.
The aluminum film 12 is patterned to form a desired aluminum wiring layer. In this process, unlike the conventional aluminum pattern formation using a resist film as a mask, a wiring layer with a smooth surface is formed without causing the worm-eaten phenomenon on the side surface of the aluminum film. This is considered to be because if a resist film is present, hydrochloric acid gas is generated more easily than CCl4 gas and corrodes the aluminum surface, and if there is no resist film, the reaction is less likely.

Next, as shown in FIG. 6, the substrate is placed in a CVD apparatus (not shown) and heated to 420°C to form a film with a thickness of 1 μm.
A PSG film 15 of about 100 mL is deposited. However, this heating does not cause the growth of aluminum protrusions.

(f) Effects of the Invention As can be seen from the above examples, although the present invention requires an additional process for patterning the SiO2 film, it requires fewer steps than a process such as long-term ion implantation, and the growth of aluminum protrusions is suppressed. In addition, this method greatly contributes to improving the reliability of ICs, as it also has the effect of eliminating moth-eaten surfaces.

Although the above embodiments have been described by taking the SiO2 film as an example of the inorganic insulating film, other inorganic insulating films include silicon nitride (Si3N4) films and the like, and these are not excluded.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an aluminum wiring layer showing the conventional problems, FIGS. 2 to 6 are cross-sectional views of the manufacturing process according to the present invention, and FIG. 7 is a schematic diagram of a continuous sputtering apparatus. In the figure, 1 and 11 are semiconductor substrates, 2 and 12 are aluminum films or aluminum wiring layers, 3 and 15 are PSG films, 1
3 is a SiO2 film, 14 is a resist film, and S is an aluminum protrusion. Figure 1 Figure 2 Figure 31-1 Figure 6 71 River

Claims (1)

[Claims] An aluminum film and an inorganic insulating film are connected and deposited on a semiconductor substrate, the inorganic insulating film is patterned and subjected to high temperature heat treatment, and then a wiring layer made of the aluminum film is patterned using the inorganic insulating film as a mask. 1. A method for manufacturing a semiconductor device, the method comprising the step of: