JPH06196441A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve the reliability of a semiconductor device by a method wherein, when semi-fused aluminum is embedded in a semiconductor device where a hole is made, the density of impurities in a film-forming atmosphere is set below one ppm using the processing gas of impurity density of below one ppm and aluminum. CONSTITUTION:An oxide film 21 is formed on an Si substrate 20, a contact hole is provided there, a polysilicon film is thinly formed, and aluminum 22 is sputtered. At this time, when the entering of impurity gas into the film and production of oxidation are prevented while the sputtering is being conducted using Ar gas passing through a refining device in which the impurity gas pressure is suppressed to one ppm or lower, the aluminum 22 is turned to a semi- fused state, and the hole is filled with it. As a result, the embedding of metal by sputtering having excellent process consistency can be conducted at a low temperature, the reliability can be improved and the cost can be cut down.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device.

[0002]

2. Description of the Related Art Conventionally, a base pressure of 10 is used for burying an Al alloy by sputtering in a wiring forming process.
-With an ⁸ Torr device, the substrate temperature is raised to 500 ° C or higher without controlling the impurity gas pressure during film formation, and Al-
A Si or Al-Si-Cu alloy was formed into a film by a sputtering method and embedded. However, in this method, the surface is oxidized during film formation, which hinders the Al alloy from being in a semi-molten state and filling holes. In order to perform burying in a state where the impurity gas concentration is high, it is necessary to increase the fluidity of the Al alloy during film formation.
It was necessary to raise the temperature to ℃ or above.

When an Al alloy such as Al-Si-Cu is used for electrodes and wirings, if the substrate heating temperature exceeds 500 ° C., a lump of Si is deposited in the fine wiring and the portion has a very high resistance. Will end up. In particular, in the case of fine wiring having a width of about 0.2 μm, when the substrate heating temperature exceeds 500 ° C., the large amount of deposited Si reduces the reliability.

Further, when TiN is deposited by reactive sputtering, the water vapor existing in the chamber becomes an obstacle, and in order to control this, hydrogen is sensed to quantify the water vapor amount, and when the water vapor amount increases. There is a method of increasing the partial pressure of the reactive gas (N ₂ ) accordingly (Japanese Patent Laid-Open No. 63-60277). However, in this method, the absolute value of the amount of water vapor is not reduced, and when applied to the filling of contact holes, the Al surface is oxidized during film formation, and the fluidity deteriorates. It was necessary to raise the temperature to 500 ° C or higher.

[0005]

The impurity gas in the process gas reacts with the Al alloy and is taken into the film, or is taken into the film as it is. In particular, if the partial pressure of water or the partial pressure of oxygen is high, the Al alloy is oxidized during film formation to form an oxide film having a very high melting point, so that the Al alloy is unlikely to be in a semi-molten state and filling of holes is difficult. There is a problem that it becomes difficult. Even if the amount of water vapor is sensed and the amount of process gas is adjusted, if the absolute amount of impurity gas in the process gas is not reduced, incorporation of impurities into the film and surface oxidation will occur, making embedding difficult. When the substrate temperature is set to a high temperature of 500 ° C. or higher in order to ensure the filling, the Al alloy reacts with an impurity gas such as water and oxygen to cause surface roughening, and especially in the case of a multilayer wiring structure. Had a problem that the lower layer wiring was affected and the electrical characteristics became unstable.

[0006]

SUMMARY OF THE INVENTION The present invention is a method of filling a hole in a semiconductor device in which Al or Al alloy is in a semi-molten state to fill the hole with an impurity concentration of pp.
A method for manufacturing a semiconductor device is characterized in that an impurity concentration of a film forming atmosphere is set to be equal to or lower than ppm by using a process gas and an Al alloy which are controlled to be equal to or lower than m.

[0007]

By controlling the gas pressure of the impurities to be not more than ppm, it is possible to prevent the impurities from being taken into the film during the sputtering and to suppress the surface oxidation. As a result, there is nothing that obstructs the fluidity of Al due to burying by high temperature sputtering, so that it is possible to lower the substrate temperature than before and bury holes, and device reliability is improved.

[0008]

Embodiments of the present invention will be described with reference to the drawings.

[0009] sputtering apparatus used base pressure is 1 × 10 ^- is an ultra vacuum sputtering apparatus capable evacuated to ^{1 0} Torr. In this device, in addition to the main exhaust cryopump, the set temperature of the cryopump is set to about 70K, and Ar, which is the process gas, is not exhausted during sputtering, but other cryogenic impurities such as water can be exhausted. A pump is installed so that the partial pressure of the impurity gas during sputtering can be reduced.

Ar, which is a process gas, is passed through a refining device, and its outlet is set so that water, hydrocarbons, nitrogen and the like are in a ppm or less. The target used was pure Al, and the target had a lower oxygen concentration than the conventional one.

For gas analysis during sputtering, water, nitrogen, carbon oxides, and hydrocarbons were simultaneously monitored to a ppb level by a differential exhaust system.

Embedding of pure Al by high temperature sputtering was performed under the above conditions. The substrate temperature is 400 to 500 ° C., and the sputter power is 10 kw. The buried hole has a depth of about 1.1 μm and a hole diameter of 0.15 to 0.8.
A film having a thickness of μm and 500 A of polysilicon laid as a base film was examined. This polysilicon melts into pure Al during high temperature sputtering to form an Al-Si alloy. Also,
In order to compare the case where the impurity gas concentration was lowered to ppm or less and the case where it was not, the experiment containing a large amount of the impurity gas used Ar gas directly supplied from the cylinder. Figure 1
Partial pressure of water vapor, which is an impurity in Ar gas when passing through the refining equipment in Fig. 1 (a), and A directly supplied from the cylinder.
The partial pressure of the same water vapor in the r gas is shown in FIG. It can be seen that there is a difference of about two digits between the partial pressures of water in (a) and (b). Since water is contained in Ar, the partial pressure of water also changes in accordance with the change in the partial pressure of Ar in (b). In addition, hydrocarbons are also higher in the direct supply from the cylinder than in the gas passed through the refiner. An embedding experiment was conducted using these two kinds of gases. FIG. 2 shows the results of embedding with respective gases at a substrate temperature of 470 ° C. An oxide film 21 was formed on the Si substrate 20, the above-mentioned contact hole was opened therein, and a thin layer of polysilicon (not shown) pure aluminum 22 was sputtered.
When Ar gas that has passed through the refining device with the impurity gas pressure suppressed to less than ppm is used, the impurity gas is not taken into the film or oxidized during sputtering, so Al becomes a semi-molten state and holes are filled. (FIG. 2 (a)) contains a large amount of impurity gas, the fluidity of Al is hindered even at the same substrate temperature, and voids 23 are generated, resulting in poor filling (FIG. 2 (b)).

This phenomenon is caused by Al--Si--Cu and Al--S.
Even if other Al alloys such as i are used, silicide,
The same is true when using a base film such as various barrier metals such as nitride.

[0014]

As described above, according to the present invention, it is possible to embed metal by sputtering, which has good process consistency with the conventional one, at a temperature lower than that of the conventional one, and to improve reliability.
There is also an effect that the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a measurement result of gas analysis performed for explaining an example of a semiconductor device of the present invention. (A) shows the case where the gas is passed through the gas purifier, and (b) shows the case where the gas is directly supplied from the cylinder.

FIG. 2 (a) is a result of filling holes when a purified gas in which the impurity gas pressure is suppressed to ppm or less is used, (b)
FIG. 6 is a diagram showing a result of embedding with a gas directly supplied from a cylinder.

[Explanation of symbols]

 20 Si substrate 21 Oxide film 22 Aluminum 23 Void

Claims (1)

[Claims] 1. Al on a semiconductor device having holes formed therein.
Alternatively, in the method of filling the hole by making the Al alloy in a semi-molten state, the process gas and the Al alloy having the impurity concentration of ppm or less are used, and the impurity concentration of the film forming atmosphere is p
A method of manufacturing a semiconductor device, characterized in that it is set to pm or less.