JPH0722153B2 - Dry etching method and apparatus - Google Patents

Description

TECHNICAL FIELD The present invention relates to a multilayer including an Al or Al-based alloy film and a refractory metal, which are often used for wiring of high-density solid-state devices such as semiconductor integrated circuits (LSI). The present invention relates to a method for dry etching a metal film with high reproducibility and high accuracy, and an apparatus therefor.

[Prior Art] Currently, in order to realize a high-density and high-speed operation LSI, it is necessary to establish a highly reliable fine wiring formation technology.
Conventionally, Al-Si alloys have been used for LSI wiring, but as wiring becomes finer, disconnection due to electromigration and deterioration of bonding due to Al diffusion into the Si substrate become more severe, so wiring materials should be examined. It has been advanced.

In order to improve the heat resistance of wiring and solve these problems, a method of using Al and refractory metal in multiple layers has been proposed (for example, PSHo, T. Kewok; Fig. 16 International Conference on Solid State Materials). EXTENDED ABSTRACTS A-3-5 P55 (1984)
reference). Here, Mo, W, Ti, etc. are candidates as the refractory metal.

By the way, looking at the dry etching technology that holds the key to miniaturization, the development of Al, Al-based alloys and refractory metals has been advanced and put to practical use. However, when a multilayer film of Al and a refractory metal is etched using these devices, severe after-corrosion occurs and a stable pattern cannot be formed.

After-corrosion is a phenomenon in which the Al pattern is gradually corroded after etching, and is also observed in the etching of an Al single layer.The cause is that the etching gas attached to the wafer is decomposed by moisture in the atmosphere. However, it has been thought that it is an acid that corrodes Al. Therefore,
In the etching of Al single layer, after-corrosion is prevented by removing the deposits on the surface by washing with water immediately after etching or by CF ₄ plasma treatment.

However, when etching Al on refractory metal or refractory metal on Al, severe after-corrosion occurs even if such measures are taken, and fine Al patterns are taken within 1 minute after being taken out into the atmosphere. Disappears. The cause and countermeasure of the after-corrosion, which is fatal to the pattern formation, has not been clarified at all, and the prospect of practical application of the multilayer metal wiring has not been obtained so far.

[Problems to be Solved by the Invention] Therefore, an object of the present invention is to provide a dry etching method for a multilayer metal film which does not cause after-corrosion and has excellent reproducibility, and an apparatus for realizing the method. This is to advance the development of high-density and large-capacity LSI.

[Means for Solving Problems] The present inventor has made detailed description of etching characteristics of a multilayer metal composed of Al and a refractory metal, and as a result, has obtained the following findings regarding the cause of after-corrosion. That is, it was confirmed that the after-corrosion in the etching of Al and the refractory metal occurs because the reaction product of the refractory metal is decomposed by moisture to generate an acid.

As shown in Table 1 below, high-melting-point metal halides have a boiling point higher than room temperature and are difficult to evaporate even if they are formed, and even if they evaporate, they easily adhere to the reaction vessel or wafer surface. There is. When etching Al on the refractory metal, after the etching of Al is completed, the exposed refractory metal reacts with the etching gas to generate chloride of the refractory metal. A large amount of this chloride adheres to the surface of the wafer after etching, but it decomposes violently due to moisture and becomes hydrochloric acid, which causes after-corrosion.

There are several kinds of refractory metal chlorides other than those shown in Table 1. For Mo, for example, Mocl ₂ , MoCl ₃ , MoCl ₄ , Mo
It is considered that Cl ₅ is mixed on the wafer surface. Since some of these are soluble in water and others are difficult to dissolve in water, after-corrosion cannot be prevented by washing with water. Further, this chloride is difficult to remove by a weak plasma treatment of CF ₄ , and on the contrary, fluoride may adhere to the surface. This fluoride also decomposes by moisture to generate hydrofluoric acid, which may unexpectedly promote after-corrosion.

The same applies to the case of etching a refractory metal on Al, and after-corrosion occurs due to chlorides and fluorides attached during etching of the refractory metal.

From the above, in order to perform stable etching of a multilayer metal film without aftercorrosion, it is necessary to devise a method for reducing the adverse effects of the reaction product of the refractory metal.

In view of this point, in the present invention, (1) the reaction container for etching the refractory metal is provided separately from the reaction container for etching the other metal, and the influence of the contamination of the container by the reaction product is avoided. prevent.

(2) In etching the refractory metal, the wafer is kept at a high temperature so that reaction products do not adhere to the surface of the wafer on which the refractory metal is deposited.

(3) The transfer is performed in vacuum so that after-corrosion does not occur when the wafer is transferred between separate reaction vessels.

That is, the manufacturing method of the present invention, when dry etching the multilayer metal film in the wafer in which the multilayer metal film including the Al or Al-based alloy layer and the refractory metal layer is dry-etched, Al or Al-based alloy layer is dry-etched. In a first reaction container, a step of transferring the one dry-etched wafer into a second reaction container separate from the first reaction container through a vacuum atmosphere, and a second reaction And a step of dry-etching the refractory metal layer while the wafer is heated in the container.

The manufacturing apparatus of the present invention is capable of accommodating a wafer, and is a plurality of reaction vessels for generating a gas plasma to perform dry etching on the wafer. A chamber for transferring a wafer in a vacuum atmosphere between the containers, and heating provided in at least one reaction container of the plurality of reaction containers and heating the wafer accommodated in the at least one reaction container. It is characterized by having a section and.

[Operation] That is, according to the present invention, a multilayer metal film of Al and a refractory metal can be etched with good reproducibility without causing after-corrosion.

[Examples] Hereinafter, the present invention will be described in detail with reference to the drawings.

An embodiment of the dry etching apparatus of the present invention is shown in FIG. Here, 1 is a first reaction container for dry etching an Al or Al-based alloy layer, and 2 is a second reaction container for dry etching a refractory metal layer. Reference numeral 3 denotes a load lock chamber for loading and unloading the wafer W. The reaction containers 1 and 2 and the load lock chamber 3 are housed in a transfer chamber 4 constituted by a vacuum chamber.

Reference numeral 5 is a table on which the wafer W is placed in the load lock chamber 3. Reference numeral 6 denotes a flat plate discharge electrode which also serves as a table on which the wafer W is placed in the first reaction container 1, and 7 is arranged in parallel to face the flat plate electrode 6 for performing reactive etching in the first reaction container 1. The discharged discharge electrode 8 is a high frequency power source for applying a high frequency voltage between the electrodes 6 and 7.

Reference numeral 9 denotes a flat plate-shaped discharge electrode which also serves as a table on which the wafer W is placed in the second reaction container 2, and 10 is arranged parallel to the flat plate-shaped electrode 9 so as to perform reactive etching in the second reaction container 2. The discharge electrode 11 is a high frequency power source for applying a high frequency voltage between the electrodes 9 and 10.

A wafer chuck arm 12 holds the wafer W and transfers the wafer W from the load lock chamber 3 to the first reaction container 1 or from the first reaction container 1 to the second reaction container 2 in the vacuum transfer chamber 4. The wafer W is transported by rotating as shown by the arrow in the figure.

The second reaction vessel 2 is made of a material having excellent heat resistance, and heated oil is made to flow through the vessel wall and the inside of the discharge electrodes 9 and 10, so that the entire vessel 2 is heated to about 200 ° C. It can be so.

After the wafer W is loaded into the load lock chamber 3, after the load lock chamber 3 is in the same vacuum state as the transfer chamber 4,
The table 5 descends, and the wafer W is clamped by the wafer chuck arm 12. Then, by rotating the arm 12 clockwise or counterclockwise, the wafer W is transferred toward the reaction container 1 or 2 in the transfer chamber 4 in the vacuum state. In the reaction container 1 or 2, the electrode 6 or 9 is lowered in advance, the transferred wafer W is placed on the electrode, and the arm 12 is detached from the reaction container 1 or 2. The wafer W is also transferred between the reaction vessels 2 and 3 in the same manner as described above.

An embodiment in which the dry etching method of the present invention is carried out by using the apparatus of the present invention having the above-described structure will be described. Here, as a sample to be dry-etched, 4 coated with a thermal oxide film was used.
A 1000 Å thick Mo film and a 4000 Å thick Al film were sequentially deposited on an inch Si wafer by a sputtering method, and a resist pattern was formed thereon using a photolithography technique. The wafer W was housed in the load lock chamber 3, and then the wafer W was transferred to the first reaction container 1 by the arm 12. Al was dry-etched in the first reaction container 1, the wafer W was then transferred to the second reaction container 2, and Mo was dry-etched in the second reaction container 2. Cl ₂ is used for dry etching of Al, pressure is 20 Pa, and discharge power is 0.2.
It was performed under the condition of W / cm ² . In the dry etching of Mo, the temperature of the reaction vessel 2 was set to 150 ° C., the pressure was 15 Pa using CBrF ₃ , and the discharge power was 0.3 W / cm ² .

After such dry etching, the wafer was allowed to stand in the laboratory for observation and no after-corrosion occurred even after 3 days.

It can be seen that the present invention has a remarkable effect as a countermeasure against after-corrosion, in comparison with the fact that the fine pattern disappeared within 1 minute after being taken out from the etching apparatus due to after-corrosion in the conventional Al etching apparatus. This is because the apparatus of the present invention separates the reaction vessels 1 and 2 of Al and the refractory metal into separate chambers, and heats the entire vessel 2 during the etching of the refractory metal, so that the reaction product of the refractory metal is This is because it no longer adheres to the wafer surface.

It was confirmed that after-corrosion did not appear at all even when a mixed gas of Cl ₂ and O ₂ was used as an etching gas for Mo. According to the present invention, after-corrosion can be prevented even when another etching gas is used.

Furthermore, contrary to the above sample, 4000 Å on the wafer.
Dry etching of a two-layer metal film in which thick Al is deposited and then 1000 Å thick Mo is deposited, or Mo is deposited on a wafer, Al is deposited on the Mo, and then Mo is deposited on this Al. Similarly, in the case of dry etching of the deposited three-layer metal film, after-corrosion does not occur and a stable pattern can be formed.

[Effects of the Invention] As described above, according to the present invention, a multilayer metal film of Al and a refractory metal is formed without causing after-corrosion.
Can be etched with good reproducibility.

Although Mo is used as the refractory metal in the above-described examples, similar effects can be obtained with other refractory metals such as W, Ti, and Ta. Similar effects were obtained even when Al-based alloys such as Al-Si and Al-Cu were used instead of Al. Further, it is also effective for etching a multi-layer metal containing other metals such as Pt and Ni in addition to Al and refractory metal.

The dry etching method in the first reaction container and the second reaction container is not limited to the reactive ion etching in the above example, but reactive ion beam etching, parallel plate plasma etching, plasma etching, reactive ion shower etching, plasma Various dry etching methods using a reactive gas such as flow etching can be applied.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the configuration of the device of the present invention. 1 ... First reaction container, 2 ... Second reaction container, 3 ... Load lock chamber, 4 ... Vacuum transfer chamber, 5 ... Table, 6,7,9,10 ... Discharge electrode, 8,11 …… High frequency power supply, 12 …… Wafer chuck arm, W …… Wafer.

Claims (2)

[Claims] 1. Dry-etching the Al or Al-based alloy layer in dry-etching the multilayer metal film in a wear in which a multilayer metal film including an Al or Al-based alloy layer and a refractory metal layer is arranged. A step of performing the step in the first reaction container, a step of transferring the dry-etched wafer into a second reaction container separate from the first reaction container through a vacuum atmosphere, and the second reaction container And a step of dry etching the refractory metal layer while heating the wafer. 2. A plurality of reaction vessels capable of accommodating wafers and performing gas dry etching on the wafers by generating gas plasma, the reaction vessels being individually arranged, and the plurality of reaction vessels. A chamber for transferring the wafer in a vacuum atmosphere between the reaction vessels, and a wafer provided in at least one reaction vessel of the plurality of reaction vessels and containing the wafers accommodated in the at least one reaction vessel. A dry etching apparatus comprising a heating unit for heating.