JPS6220331A - Selectively growing method for alumina film - Google Patents

Abstract

PURPOSE:To coat an aluminum wiring layer with a very stable Al2O3 protective film by using an Al2O3 selectively growing method. CONSTITUTION:A substrate is filled in a plasma etching unit, boron trichloride BCl3 is fed as etching gas, gas pressure is maintained 0.2-0.3Torr, a high frequency voltage is applied to perform a plasma etching. The plasma etching with BCl3 has strong selectivity, the surface of partly exposed silicon becomes an activated surface, but does not almost react with an insulating film such as a PSG film. Then, an Al2O3 film is grown by a vapor-phase grown on the surfaces of the activated aluminum and silicon. At this time, the temperature of the substrate is held at approx. 260-320 deg.C, but if the substrate temperature is excessively high to exceed 360 deg.C, the selectivity of the Al2O3 film is lost. The Al2O3 film is not almost grown on the aluminum and silicon surface if the activated surfaces are not exposed.

Description

[Detailed Description of the Invention] [Summary] Alumina (A7!zCh) is known as a chemically extremely stable abrasive material, but it is difficult to grow and process after growth, so it is not suitable for manufacturing semiconductor devices. Not used much. The present invention describes a method that enables selective vapor phase growth of alumina on silicon and aluminum.

[Industrial application field]

The present invention relates to a process for selectively growing alumina on aluminum and silicon.

Aluminum is widely used as a wiring layer for 31'-conductor devices, and physical vapor deposition (
PVD method) is used exclusively.

On the other hand, a drawback of the vapor deposition method is the problem of step coverage in one tank I/window, and a method to solve this problem is the vapor phase epitaxy (CVD) using an organometallic compound, namely TIBA () law) has been developed.

A7! Aluminum layers can now be stacked by vapor phase growth. It is known that O3 can also be grown by adding O2 and N20 in the aluminum vapor phase growth process.
It is difficult to control the process to selectively grow only on the surfaces of aluminum and silicon without growing 12O2, and improvements are desired.

[Conventional technology]

TIBA is represented by the molecular formula A 12 (C4H9) 3, and is thermally decomposed at 250 to 300°C to form A as shown below.
Precipitate β.

Aβ(C,4H9)3→Aβ+3/2H2+3C4He
TIBA is a liquid at room temperature, but to accelerate the reaction, it is heated to about 50°C, He or Ar gas is bubbled through it, and it is introduced into a reaction tank in which a substrate heated to around 300°C is installed. .

By adding oxygen gas 02 and Neo before introducing the above gases into the reaction tank, AA2 replaces Aj2.
03 is deposited on the substrate.

The Aβ,03 precipitation caused by the above reaction is highly dependent on the temperature of the substrate, and when the substrate temperature reaches 340° C. or higher, an Al2203 film is deposited over the entire surface of the substrate.

[Problem that the invention seeks to solve]

The above-described vapor phase growth method using TTBA is applicable to the case where an A7!203 film is laminated over the entire surface of a substrate.

However, once the A1203 film is grown over the entire surface, the process becomes extremely difficult. This is because Aa203 forms an extremely stable film, making subsequent processing extremely difficult.

One of the causes of reduced reliability of semiconductor devices is disconnection in the aluminum wiring layer or short-circuit failure due to spikes occurring on the aluminum surface.

To prevent these problems, a method of covering the PSG film or 5i3Nn film as a passivation film is generally used. If it becomes possible to selectively cover with the Al2203 film, the effect will be great.

[Means for solving problems]

The problem mentioned above is that the substrate is exposed to plasma using boron trichloride gas.
An etching process is performed to expose the activated surfaces of the aluminum and silicon.

AN2 of the present invention, which comprises selectively growing alumina on the activated aluminum and silicon surfaces by a vapor phase growth method using TIBA and oxygen as source gases.
0. The choice of growth method is solved.

[Effect]

Plasma etching using boron trichloride gas selectively etches the aluminum and silicon surfaces to form active surfaces.

Next, the aluminum and silicon were grown by vapor phase growth using a mixed gas of TIBA gas and oxygen gas.

It is possible to selectively grow an alumina layer only on the active surface of the ion.

〔Example〕

An embodiment according to the present invention will be described in further detail. As shown in FIG. 1, an insulating film 3 such as Sing having a deep step 2 is laminated on a substrate 1, and an aluminum wiring layer 4 is formed on this insulating film.

The aluminum wiring layer 4 is formed by vacuum evaporation method or TrBA
It can be obtained by laminating layers using a CVD method and then patterning.

As already explained, the CVD method has better coverage than vacuum deposition. 17 on such a wiring layer!
A method of protection using a 203 film will be described.

The substrate is placed in a plasma etching apparatus, and boron trichloride (BCA3) is introduced as an etching gas.

Plasma etching is performed by maintaining the gas pressure at 0.2 to 0.3 Torr and applying a high frequency voltage.

Plasma etching using BCl2 has strong selectivity, and aluminum and partially exposed silicon surfaces become activated surfaces, but hardly reacts with insulating films such as 5iC12 and PSG films.

Next, Al! is deposited on the activated aluminum and silicon surfaces by vapor phase growth. Grow to3 film. The method is to use a CVD device, maintain the TIBA solution at 50°C, and bubble it through the TIBA solution at a flow rate of 200'sccm.
m and N20 gas are mixed at a flow rate of 50 seconds and introduced into the reaction tank.

At this time, the temperature I:1' of the substrate 1 is maintained at about 260-320°C. This substrate temperature is an important factor when selectively growing an Al2O2 film.
When it exceeds 0°C, Aρ20. l membrane selectivity is lost.

Also, if the activated surface of the aluminum or silicon surface is not exposed, An20. The film hardly grows.

FIG. 2(a), (I)l shows the growth in the XX plane Q in FIG. A cross-sectional view of the substrate after 1r1 is shown.

〔Effect of the invention〕

As explained below, Aff20. of the present invention. The selective growth BuJ method makes it possible to cover the aluminum wiring layer with a very stable AAz(:lh protective film), and since the process is carried out using a gas phase reaction, the coverage of deep steps is also good. There is. - This increases the reliability of semiconductor devices 141
The key is to contribute to each other.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a substrate for explaining the growth method of the present invention, and FIG. 2 is a cross-sectional view for comparing and explaining before and after growing an Al!203 film of the present invention. In the drawings, 2 is a step, 3 is a color border film, 4 is an aluminum wiring layer, and 5 is an A/!203 film.

Claims (1)

[Claims] The method is characterized in that after performing plasma etching treatment on the surface of a silicon substrate or aluminum wiring using boron trichloride gas, an alumina film is grown on the exposed aluminum or silicon surface by vapor phase growth. Selective growth method for alumina film.