JP2553590B2 - Method and apparatus for selectively depositing metal - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method and apparatus for selectively depositing a metal on a non-oxide surface by a chemical vapor deposition method (hereinafter referred to as a CVD method). .

Conventional technology A refractory metal such as tungsten (hereinafter referred to as W) or molybdenum (hereinafter referred to as Mo) is deposited on a certain film such as a non-oxidized surface of silicon (hereinafter referred to as Si) by a CVD method. Only selective deposition methods are already known,
It is playing an increasingly important role in manufacturing VLSI devices.

For example, the case of filling the contact hole on the Si layer with W will be described. The surface of the Si layer is thermally oxidized in advance to form a SiO ₂ film, and the SiO ₂ film is dry-etched to form a contact hole. Further, a wafer preliminarily cleaned by wet etching in diluted HF is prepared in advance, and this wafer 5 is transferred to a preliminary chamber P capable of vacuum evacuation as shown in FIGS. After decompressing the chamber P, the wafer W is transferred to the reaction chamber R by communicating with the reaction chamber R in a decompressed state, and the temperature of the wafer W is controlled to 300 to 500 ° C.
By introducing a mixed gas of ₆ and H ₂ , W is selectively deposited on the exposed surface of Si, that is, in the contact hole.

The problem to be solved by the invention is that even after the Si surface is exposed by dry etching the SiO ₂ film to expose the Si layer, the wafer W after cleaning is not cleaned.
Since the Si surface is exposed to the outside air while being transported into the preliminary chamber P, it is unavoidable that a natural oxide film of about 20 to 30 Å is formed, and that the oxide film is formed unevenly. Since there are many W layers, the growth of W layer is not uniform, and the selectivity is deteriorated due to distorted formation, and the erosion of the Si surface due to the reduction of WF ₆ spreads laterally to form warm holes.
There is a problem that the device structure itself may be disturbed.

In view of the above-mentioned conventional problems, the present invention is a method of selectively depositing a metal capable of forming a metal film having a uniform thickness, in which erosion of a non-oxide surface due to the growth of a metal film is uniform, a warm hole or the like is hard to be formed, and The purpose is to provide the device.

Means for Solving the Problems In order to achieve the above object, the selective deposition apparatus of the first invention of the present invention comprises a wafer mounting means, a vacuum evacuation means, a metal phase and a vapor phase at a process temperature or lower. In a chemical vapor deposition apparatus having a reaction chamber having a gas introduction unit for introducing a gas of molecules existing as the above, and a heating unit capable of controlling temperature, an upper position and a standby position on the side of the placing unit. It is characterized in that a high-frequency electrode movable between them and a means for supplying a halogen gas containing fluorine for plasma etching are provided.

According to the apparatus of the present invention, by supplying a halogen gas containing fluorine while discharging from the high frequency electrode to the wafer in the reaction chamber, the natural oxide film can be removed by the plasma etching, and after the removal. The metal can be immediately deposited and high selectivity is obtained.
Further, even if the halogen gas containing fluorine is toxic and corrosive, the reaction chamber is originally configured to cope with it, so that the apparatus does not become complicated.

Embodiment Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 and 2.

In FIG. 1 and FIG. 2, reference numeral 1 is a reduced pressure vapor phase growth apparatus, which comprises a reaction chamber 2 and a preliminary chamber 3 capable of maintaining a sealed state. Reference numeral 4 denotes a wafer table on which a wafer 5 to be transferred to and from the preliminary chamber 3 is placed. An unprocessed wafer 5 is supplied to the wafer table 4 by a loader 6, and the wafer table 4 is placed on the wafer table 4. The processed wafer 5 is taken out by the unloader 7.

An exhaust means 8 for exhausting the inside of the reaction chamber 2 to a decompressed state is connected to one side of the reaction chamber 2, and a mixed gas of WF ₆ and H _{2 in} the reaction chamber 2 on the other side of the reaction chamber 2 or A gas introducing means 9 for introducing CF ₄ gas is connected. Further, in the center of the reaction chamber 2, there is provided a support base 10 on which a wafer 5 is placed, which can be driven to rotate, and a sheath heater 11 arranged below the support base 10 and a lamp heater arranged above. At 12, the wafer 5 on the support base 10 can be heated and controlled at 300 to 500 ° C.

The preliminary chamber 3 is connected to an exhaust means 13 for reducing the pressure inside the preliminary chamber 3. Further, the wafer 5 is supported in the auxiliary chamber 3, and the wafer 5 is supported between the auxiliary chamber 3 and the wafer table 4 and between the auxiliary chamber 3 and the support 10.
A transfer means 14 for transferring the wafer is provided, and gate valves 15 and 16 are provided on the wall surface between the preliminary chamber 3 and the reaction chamber 2 and the wall surface of the preliminary chamber 3 facing the wafer table 4. There is. Although the description of the details of the transfer means 14 is omitted, an arbitrary structure can be applied, and as a specific example, the one disclosed in JP-A-60-98628 is preferably applied. You can

A support base is provided on the support base 10 of the reaction chamber 2.
A high frequency electrode 17 is provided on a swing rod 18 so as to be movable between a position directly above 10 and a standby position on the side thereof. A high frequency power source 19 having a matching box is connected to the high frequency electrode 17.

Next, the operation will be described. Operate the exhaust means 8 and 13,
While maintaining both the reaction chamber 2 and the auxiliary chamber 3 in a depressurized state, the gate valve 15 is opened and the unprocessed wafer 5 is transferred by the transfer means 14.
After the wafer 5 is transferred from the preliminary chamber 3 onto the support 10 of the reaction chamber 2 and simultaneously the processed wafer 5 is transferred to the preliminary chamber 3, the gate valve 15 is closed.

Next, in the reaction chamber 2, the sheath heater 11 is turned on to start heating the wafer 5 from the lower surface of the support base 10, while the high-frequency electrode 17 is moved to a position directly above the support base 10 and the high-frequency power source 19 is operated. By applying a high frequency voltage and introducing CF ₄ gas from the gas introducing means 9, the surface of the wafer 5 is plasma-etched to remove the natural oxide film formed in the contact hole which is the Si exposed portion of the wafer 5. In this plasma etching, for example, 13.5MH
50 to 500 W of effective value of high frequency voltage of z is applied and CF ₄ gas is reduced to 0.
By introducing it so that the pressure is 3 Torr,
The oxide film can be removed in about 30 seconds.

After that, the high-frequency electrode 17 is moved to the standby position, the lamp heater 12 is turned on to heat the wafer 5 also from the surface thereof, and the temperature of the wafer 5 is controlled to a predetermined temperature in the range of 300 to 500 ° C. The mixed gas of WF ₆ and H ₂ is introduced from the introducing means 9 so as to be in a pressure state of 0.5 to 5 Torr. Then, first, WF ₄ is rapidly reduced by Si according to the following equation,
W is selectively formed on top.

2WF ₄ + 3Si = 2W + 3SiF ₄ ↑ When the thin W layer thus defined covers the Si surface, the W layer reduces the transport of WF ₄ to Si and prevents the above reaction. Then, when the W layer is formed on the Si surface, the hydrogen reduction reaction of WF ₄ of the following formula starts and W is deposited at a certain growth rate.

WF ₄ + 3H ₂ = W + 6HF ↑ In this hydrogen reduction on the W layer, there is a driving force for continuing selective growth, and W is selectively deposited as it is. The deposition rate is about 500 to 1000Å / min, and the W layer of about 5000Å to 1 μm is filled in the contact hole of the wafer 5 by the reaction for 10 to 20 minutes.

On the other hand, during this reaction, after introducing N ₂ gas into the preliminary chamber 3 to bring it to atmospheric pressure, the gate valve 16 is opened, and the processed wafer 5 taken out into the preliminary chamber 3 by the transfer means 14 is used as a wafer. At the same time when the wafer 5 is sent out onto the table 4, the unprocessed wafer 5 on the wafer table 4 is inserted into the preliminary chamber 3, and then the gate valve 16 is closed and the exhaust means 13 depressurizes the wafer.

Further, the processed wafer 5 on the wafer table 4 is taken out by the unloader 7, and the unprocessed wafer 5 is supplied onto the wafer table 4 by the loader 6.

After that, when the processing in the reaction chamber 2 is completed, the wafers 5 can be sequentially processed by repeating the above operation.

In the above-mentioned first embodiment, the plasma etching for removing the natural oxide film is performed in the reaction chamber 2 before the deposition of the W layer, but the second embodiment shown in FIG. 3 and FIG.
As in the embodiment, it may be performed in the auxiliary chamber 3.

In FIG. 3 and FIG. 4, a high-frequency electrode 20 is arranged at a position directly above the transfer means 14 in the preliminary chamber 3, a high-frequency power source 19 provided with a matching box is connected, and the upper surface of the wafer 5 is evenly arranged. A gas supply means 22 including a gas supply passage 21 formed in the high-frequency electrode 20 is provided to supply CF ₄ gas to the.

In this embodiment, during the waiting time during which the selective deposition of the W layer is carried out in the reaction chamber 2, the unprocessed wafer 5 is inserted into the preliminary chamber 3 and evacuated, and then the high frequency electrode 20 is irradiated with a high frequency wave. By applying a voltage and supplying CF ₄ gas to the wafer 5 by the gas supply means 22 and removing the natural oxide film by plasma etching, the processing time becomes longer due to the natural oxide film removal step. Can be prevented.

The present invention is not limited to the above embodiments.
For example, CF is used as a gas during plasma etching.
_{Although four} gases are illustrated, halogen gas containing fluorine may be generally used. Moreover, although the example applied to the selective deposition of W has been described, the present invention can be similarly applied to the selective deposition by the reduction reaction of the halide of another refractory metal such as Mo. Further, the present invention can be applied not only to burying contact holes but also to selective deposition on gate electrodes, formation of contact barriers, and the like.

EFFECTS OF THE INVENTION According to the metal selective deposition apparatus of the present invention, the natural oxide film is removed by the plasma etching by supplying the halogen gas containing fluorine while discharging from the high frequency electrode to the wafer in the reaction chamber. In addition, the metal can be deposited immediately after the removal, and high selectivity can be obtained. Further, even if the halogen gas containing fluorine is toxic and corrosive, the reaction chamber is originally configured to cope with it, so that the apparatus does not become complicated.

[Brief description of drawings]

FIG. 1 is a plan view showing a schematic configuration of a first embodiment of the present invention,
2 is a front view, FIG. 3 is a plan view showing a schematic configuration of a second embodiment of the present invention, FIG. 4 is a front view thereof, and FIG. 5 is a plan view showing a schematic configuration of a conventional example. FIG. 6 is a front view of the same. 1 ... Reduced pressure vapor phase growth apparatus 2 ... Reaction chamber 3 ... Preliminary chamber 5 ... Wafer 8, 13 ... Exhaust means 9 ... Gas introduction means 10 ... Support 13 ... Exhaust means 14 ... Transfer Means 17, 21 ... high-frequency electrode 19 ... high-frequency power source 22 ... gas supply means.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 62-11227 (JP, A) JP 60-53013 (JP, A) JP 62-107062 (JP, A) Actual 60- 88540 (JP, U)

Claims (1)

(57) [Claims] 1. A wafer mounting means, a vacuum evacuation means, a gas introduction means for introducing a gas of molecules containing a metal and existing as a gas phase at a process temperature or lower, and a heating means capable of controlling temperature. In a chemical vapor deposition apparatus comprising a reaction chamber having, a chemical vapor deposition apparatus for selectively depositing a metal on a non-oxide surface, a high frequency electrode movable between an upper position and a lateral standby position of the placing means, A selective deposition apparatus for metal, which is provided with a means for supplying a halogen gas containing fluorine for plasma etching.