JPH0744161B2 - Method for manufacturing semiconductor device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a semiconductor device in which a high melting point metal material thin film is selectively formed on a semiconductor substrate.

<Prior Art> In order to obtain an electrical connection between a semiconductor substrate and a wiring material in a semiconductor device, conventionally, a direct electrical contact was formed between the wiring material and the semiconductor substrate. FIG. 3 is a sectional view of a MOS transistor manufactured by using such a method. In FIG. 3, 31 is a semiconductor substrate, 32 is a source part, 33 is a drain part, 34 is a gate part,
35 is a LOCOS oxide film, 36 is a field oxide film (insulating film), 3
7 is a wiring material such as aluminum or its alloy. In this MOS transistor, a direct electrical contact is formed between the wiring material 37 and the source portion 32 and the drain portion 33 in the insulative film opening portion 38 of the source portion 32 and the drain portion 33.

<Problems to be Solved by the Invention> However, in the above-mentioned conventional method, the step coverage is poor, the alignment margin in the photolithography process is small with the miniaturization of the element, and the wiring with the increase in the aspect ratio is formed. There was a problem of reduced reliability.

Therefore, recently, by using a contact plug technique for forming a high melting point metal material thin film as a contact plug on a fine contact portion, the above-mentioned insulating film opening portion (contact opening portion) is formed on the substrate. A method has been adopted in which a high melting point metal material thin film is formed and a wiring material is formed thereon.

By the way, in the conventional contact plug technology, after the dry etching of the insulating film for forming the contact opening, the plasma etching for removing the damaged layer by the etching of the substrate material and the natural oxide film of the contact opening are formed. Wet cleaning for removal was performed, and then a high-melting-point metal material thin film was formed on the substrate in the contact opening portion. However, in this method, since the exposure is performed to the atmosphere between the step of forming the metal material thin film and the step before that, the elapsed time until the processing is performed to form the refractory metal material thin film in a single plate method Due to the difference, it is difficult to obtain the reproducibility of the surface condition of the contact opening portion of the semiconductor substrate immediately before the metal material thin film is formed. Therefore, the condition of the interface between the semiconductor substrate surface and the refractory metal material thin film is favorable. There are drawbacks such that reproducibility cannot be obtained, the electric contact resistance varies, and the electric contact resistance increases. In addition, carbon tetrafluoride (CF ₄ ) gas or nitrogen trifluoride (NF ₃ ) gas is generally used for the above etching, but since it damages the substrate, sulfur hexafluoride (SF ₆ ) is less likely to be damaged. Gas tends to be used. However, since discharge at a low applied voltage is unlikely to occur in the SF ₆ gas alone, stable etching cannot be performed, and structural instability such as film peeling occurs. Since it is performed after etching for the holes, the insulating film is not opened because it may be exposed to the atmosphere due to movement between the equipment before forming the high melting point metal material thin film, and it may take time to form the high melting point metal material thin film. There is a drawback that contamination of the holes cannot be avoided.

Therefore, an object of the present invention is to provide a method for manufacturing a semiconductor device which can reduce the electrical contact resistance between a high melting point metal material thin film and a semiconductor substrate, and which does not cause film peeling of the high melting point metal material thin film. To provide.

<Means for Solving the Problems> In order to achieve the above object, a method for manufacturing a semiconductor device according to the present invention is configured to partially expose a surface of a semiconductor substrate covered with an insulating film by etching and remove a natural oxide film. After that, in a method for manufacturing a semiconductor device in which a high-melting-point metal material thin film is selectively formed only on the exposed portion of the surface of the semiconductor substrate, in the same reaction chamber as the reaction chamber in which the high-melting-point metal material thin film is formed. The temperature of the semiconductor substrate is kept at room temperature to 80 ° C., the damaged layer formed on the exposed portion of the surface of the semiconductor substrate by the etching, using a mixed gas obtained by adding an inert gas to sulfur hexafluoride gas. It is characterized in that the refractory metal material thin film is formed on the exposed portion of the surface of the semiconductor substrate without exposing the semiconductor substrate to the air, by etching. There.

It should be noted that the room temperature is 25 ° C which is usually set in a semiconductor manufacturing factory.
It means a temperature of ± 2 ° C.

<Operation> Since the natural oxide film is removed, the damaged layer formed on the exposed portion of the surface of the semiconductor substrate is removed by etching using a mixed gas of sulfur hexafluoride gas and an inert gas. As compared with the case where only sulfur hexafluoride gas is used, the partial pressure of sulfur hexafluoride gas is lowered, discharge is more likely to occur and uniform, and stable etching is performed. Further, since the temperature of the semiconductor substrate is kept at room temperature to 80 ° C. during this etching, the etching rate can be suppressed to a relatively low level and the damaged layer can be removed with high accuracy.

Subsequently, since the high melting point metal material thin film is formed in the exposed portion of the surface of the semiconductor substrate in the same reaction chamber without exposing the semiconductor substrate to the atmosphere, the damage layer is removed and the high melting point metal material thin film is formed. Is continuously performed for each processing substrate. Therefore, the variation in the film formation state among the respective processed substrates is reduced, and as a result, the refractory metal material thin film is not removed. Further, since the refractory metal material thin film is formed immediately after removing the damaged layer, the electrical contact resistance is reduced.

<Example> Hereinafter, the present invention will be described in detail with reference to illustrated examples.

FIG. 1 is a process sectional view for explaining a method for manufacturing a semiconductor device according to an embodiment of the present invention.

As shown in FIG. 1A, first, the insulating film 2 on the contact portion of the semiconductor substrate 1 is etched to form a contact opening portion 5 of 0.8 μm square or less. Then, when the natural oxide film 3 formed on the surface of the semiconductor substrate in the contact opening 5 is removed by wet cleaning (including etching), the state shown in FIG. 1B is obtained. At this time, a damaged layer due to etching is formed in the exposed portion of the surface of the semiconductor substrate 1. Next, as shown in FIG. 1 (c), SF ₆ gas and an inert gas (for example, helium) are placed in the same reaction chamber as the reaction chamber in which the high melting point metal material thin film is selectively formed in the contact openings 5. The mixed gas with the gas causes the semiconductor substrate of the contact opening 5 to be about 50Å to 300Å from the surface (4 in the figure).
The portion shown by) is etched to remove the damaged layer. The suitable substrate temperature during etching was from room temperature to around 80 ° C. Subsequently, in the same reaction chamber, as shown in FIG. 1D, the refractory metal material thin film 6 is selectively formed only on the substrate surface of the contact opening portion 5, and the insulating film 2 is formed.
To a thickness corresponding to the thickness of.

The high melting point metal material thin film thus formed does not cause film peeling, and the electrical contact resistance value is reduced to about 1/2 to 1/5 as compared with that formed by the conventional method. It has been confirmed.

FIG. 2 is a sectional view of a MOS-FET to which the manufacturing method of this embodiment is applied. Here, 21 is a semiconductor substrate, 22 is a source part, and 23
Is a drain part, 24 is a gate part, 25 is a LOCOS oxide film, 26 is a field oxide film (insulating film), 27 is a wiring material such as aluminum or its alloy, and 28 is a refractory metal material thin film as a contact plug. This MOS-FET is a normal MO
In the S manufacturing process, as described with reference to FIG. 1, the insulating film 26 on the source part 22 and the drain part 23 is etched to form the contact opening 29, and only the opening 29 is selectively elevated. The melting point metal material thin film 28 is formed to a thickness corresponding to the thickness of the insulating film 26. After that, a wiring material 27 is formed, and the wiring material 27 and the source part are formed through the high melting point metal material thin film 27.
22 and the drain portion 23 are electrically connected.

As described above, since the contact plug having a small electric contact resistance and a stable structure is formed so as to obtain the electric connection between the wiring material and the substrate, as in the conventional example of FIG. There is no problem such as reduction in reliability of wiring due to miniaturization of the element, the reliability of the element is improved, high integration can be easily achieved, and a highly functional device can be realized.

<Effects of the Invention> As is apparent from the above, according to the method of manufacturing a semiconductor device of the present invention, after removing the natural oxide film, the damage layer generated on the exposed portion of the surface of the semiconductor substrate is changed to sulfur hexafluoride gas. Since it is removed by etching using a mixed gas with an inert gas added, the partial pressure of sulfur hexafluoride gas is lower than that when only sulfur hexafluoride gas is used, and discharge is more likely and uniform. Therefore, stable etching can be performed. In addition, since the temperature of the semiconductor substrate is kept at room temperature to 80 ° C. during this etching, the etching rate can be kept relatively low and the damaged layer can be removed with high accuracy. In the same reaction chamber,
Since the refractory metal material thin film is formed on the exposed portion of the surface of the semiconductor substrate without exposing the semiconductor substrate to the atmosphere, the removal of the damaged layer and the formation of the refractory metal material thin film are continuously performed for each processing substrate. Will be performed. Therefore, variations in the film formation state among the respective processed substrates are reduced, and as a result, film peeling of the refractory metal material thin film does not occur. Further, since the refractory metal material thin film is formed immediately after removing the damaged layer, the electrical contact resistance is reduced. Therefore, the reliability of the element can be improved, the integration can be increased, and a highly functional device can be realized.

[Brief description of drawings]

FIG. 1 is a process sectional view for explaining a method of manufacturing a semiconductor device according to an embodiment of the present invention, FIG. 2 is a sectional view of a MOS-FET manufactured by the above manufacturing method, and FIG. It is sectional drawing of MOS-FET produced using the manufacturing method. 1 ... Semiconductor substrate, 2 ... Field oxide film (insulating film), 3 ... Natural oxide film, 4 ... Etched portion, 5 ...
… Contact hole, 6 …… High melting point metal material thin film.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyasu Otake 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (56) Reference JP-A-62-291918 (JP, A) JP-A-SHO 63-41014 (JP, A) JP-A-63-125681 (JP, A) JP-A-62-11227 (JP, A)

Claims (1)

[Claims] 1. A surface of a semiconductor substrate covered with an insulative film is partially exposed by etching to remove a natural oxide film, and then a high melting point metal material thin film is formed only on the exposed portion of the surface of the semiconductor substrate. In the method for manufacturing a semiconductor device that is selectively formed, the temperature of the semiconductor substrate is maintained at room temperature to 80 ° C. in the same reaction chamber as the reaction chamber in which the refractory metal material thin film is formed, The damaged layer formed on the exposed portion of the surface by the etching is removed by etching using a mixed gas of sulfur hexafluoride gas and an inert gas, and then the semiconductor substrate is exposed without exposing the semiconductor substrate to the atmosphere. A method of manufacturing a semiconductor device, comprising: forming the high melting point metal material thin film on an exposed portion of a surface of a semiconductor substrate.