JP3188956B2 - Film processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a film forming apparatus.

[0002]

2. Description of the Related Art Generally, in processing semiconductor wafers,
When the wafer reacts with oxygen in the air, a natural oxide film is formed on the wafer surface.
In order to increase the gate oxide film and the contact resistance, it is necessary to remove the natural oxide film before the next film formation or to suppress the formation thereof.

[0003] Conventionally, therefore, in a washing station,
The cleaning process is performed by immersing the wafer in a chemical solution such as hydrofluoric acid, or by blowing a carrier gas into the hydrofluoric acid solution to obtain hydrofluoric acid vapor and bringing it into contact with the wafer to remove the natural oxide film. The subsequent wafer is transferred to, for example, a film forming processing station.

When the film forming process is performed at a high temperature, air is caught in the furnace by convection when loaded into the processing furnace. As a result, the wafer reacts with oxygen in the air at a high temperature. The formation of a natural oxide film is promoted. Therefore, recently, it has been studied to load and unload the wafer boat, for example, by setting an area below the vertical processing furnace to an inert gas atmosphere.

[0005]

As described above, even if the natural oxide film is removed by washing the wafer in advance, and the growth of the natural oxide film at a high temperature is suppressed during the film forming process. When the natural oxide film grows again while being transported from the cleaning station to the film forming processing station, and the wafer after cleaning is caused to stand by due to a difference in processing timing of each station, The degree is even greater.

The re-grown natural oxide film is considerably thinner than a natural oxide film formed when a wafer is loaded into a processing furnace, and thus has not been a problem in the past. High integration is progressing rapidly,
For example, when the DRAM is going to achieve a capacity of 4 M to 16 M or 32 M or more, the thickness of the oxide film must be controlled more precisely. In such a situation, it is necessary to remove even a very thin native oxide film.

The present invention has been made under such a background, and an object of the present invention is to provide a film forming apparatus capable of minimizing regrowth of a natural oxide film.

[0008]

SUMMARY OF THE INVENTION The present invention provides a vertical film-forming processing furnace for mounting a plurality of objects on a vertically movable boat to collectively form a film, and this film-forming furnace. An inert gas atmosphere is provided below the processing furnace, and the object to be processed is
A processing object mounting / dismounting chamber for mounting and demounting the processing object, and an airtight connection to the processing object mounting / dismounting chamber via a gate valve ;
A workpiece transfer chamber to be an inert gas atmosphere, in the workpiece transfer chamber gate - coupled hermetically through the Tobarubu, non
A gas chamber having an active gas atmosphere, a stage provided in the gas chamber, in which a cassette for accommodating a plurality of objects to be processed is placed, and a loading / unloading port through which the cassette is loaded / unloaded with the outside. A gate door, a cleaning device for cleaning an object to be processed and removing a natural oxide film on the surface thereof, a heating unit for mounting the cleaned object on a mounting table and heating the same; An object to be processed is transferred from a cassette on the stage to the cleaning device provided in the chamber.
At the same time, the object to be processed is placed on the heating unit from the cleaning device.
A transfer arm for receiving the table, and a transfer chamber for the object to be processed.
The object to be processed, which is provided in the
Ball - and a transfer mechanism for transferring the bets, the washing
The equipment consists of a sealed processing tank and a rotatable
Vignetting, a holding plate for holding the processing member, the processing bath dense
Means for closing and releasing, provided in the processing tank
Open / close the chemical storage tank and the gas phase of this chemical storage tank,
The vapor of the chemical in the liquid storage tank is held by the holding plate
To remove the native oxide film by supplying it to the workpiece
Valve and means for replacing atmosphere in the processing tank
And characterized in that:

[0009]

FIG. 1 is a cross-sectional plan view showing a film forming apparatus according to an embodiment of the present invention, and FIG. 2 is a vertical side view taken along line AA. Film forming furnace 1
And a wafer loading / unloading chamber 2 located below the film forming furnace 1 for loading / unloading semiconductor wafers from / to a wafer boat, which will be described later. A wafer transfer chamber 3 and a spare chamber 4 airtightly connected to the transfer chamber 3 via a gate valve G2;
A natural oxide film removing device 5 according to the embodiment of the present invention is connected to the preliminary chamber 4.

The film forming furnace 1 includes a reaction vessel 11 in which a wafer film forming area is formed, and the reaction vessel 1.
A heater 12 and the like are arranged so as to surround the outer periphery of the reactor 1, and a process gas is introduced into the reaction vessel 11 to perform a film forming process such as CVD.

A ball screw 21 is provided in the wafer loading / unloading chamber 2.
There are provided a boat elevator 22 which is raised and lowered by, for example, and a wafer boat 23 mounted on the elevator 22 and capable of storing, for example, 99 wafers W.

The transfer chamber 3 is provided with a first transfer mechanism 31 comprising an articulated arm having a degree of freedom of up, down, rotation, and expansion and contraction, and an orientation flat alignment mechanism 32 for aligning an orientation flat of a wafer. And a second transfer mechanism 41 similar to the transfer mechanism 31 is also installed in the preliminary chamber 4.

Here, the wafer loading / unloading chamber 2, the wafer transfer chamber 3 and the preliminary chamber 4 are connected to a gas introduction pipe and an exhaust pipe (not shown), and a load lock chamber for obtaining an atmosphere of an inert gas such as nitrogen gas. Is configured as

The natural oxide film removing apparatus 5 includes a gas chamber 51 for setting an inert gas atmosphere. The gas chamber 51 includes a loading / unloading stage 52 serving as a wafer storage section and a hydrofluoric acid vapor. Cleaning device 6 for removing the natural oxide film on the surface of the wafer by means of
A third transfer mechanism 53 composed of a multi-joint arm having the same configuration as that of the first and fourth configurations 41 and 41 and the heating unit 7 are provided.

The gas chamber 51 is provided with a gas introduction pipe 51a and an exhaust pipe 51b for introducing an inert gas, for example, nitrogen gas, and a gate door for keeping airtight with the outside (atmosphere). D is provided. V1 and V2 are valves. Two wafer cassettes 54 containing, for example, 25 wafers to be cleaned before being cleaned are loaded into the loading / unloading stage 52 through the gate door D, and the processed wafers are returned to the cassette 54. It is carried outside through the rear gate door D.

The third transfer mechanism 53 takes out the uncleaned wafer from the cassette 54 on the loading / unloading stage 52 and transfers it to the cleaning device 6, transfers the cleaned wafer to the heating unit 7, and It has a role of returning processed wafers transferred from the preliminary chamber 4 into the cassette 54.

As shown in FIG. 3, the heating section 7 has wafer loading / unloading ports 71 and 72 on both sides, respectively, and a housing 73 in which the loading / unloading port 72 is opposed to the gate valve G3. A wafer mounting table 74 is provided, and three infrared lamps 75 as heating means are provided in parallel above the mounting table 74 so as to heat the surface to be cleaned of the wafer W on the mounting table 74. The reason for providing the heating means in this way is that, as will be described later, when the wafer is cleaned with hydrofluoric acid in the cleaning apparatus 6, by-products containing water as a main component are attached to the wafer surface. This is for decomposing by-products by heating.

The cleaning device 6 is configured as shown in FIG. 4, for example. Next, the cleaning device 6 will be described in detail.

Reference numeral 8 denotes a processing tank, and a storage tank 82 for storing, for example, a 1 to 5% hydrofluoric acid solution is disposed below the processing tank via an opening / closing valve 81.

The ceiling of the processing tank 8 is raised and lowered by a lifting mechanism (not shown) to seal and release the processing tank 8.
3 in the center of the lid 83,
Rotating shaft 8 that is rotated around a vertical axis by drive unit 831
32 is inserted into the treatment tank 8 via the magnetic seal part 833. At the lower end of the rotating shaft 832, a holding plate 84 that holds the wafer W by suction or gripping by a gripping claw is attached.

The processing tank 8 is provided with an exhaust port 85 which is opened and closed by a shutter S to suppress the diffusion of hydrofluoric acid vapor in the processing tank 8 when the lid 83 is opened. The outside of the exhaust port 85 is set to a negative pressure by a vacuum pump (not shown).

On the lid 83 and the side wall of the processing tank 8,
An introduction hole 86 and an exhaust hole 87 for nitrogen gas are formed, respectively. By passing nitrogen gas through the introduction hole 86 and the exhaust hole 87, the magnetic seal portion 833 is protected against hydrofluoric acid vapor and When the processing tank 8 is evacuated by opening the shutter S, the gas is replaced.

In cleaning the wafer W,
First, after holding the wafer W on the holding plate 84 with the surface to be etched facing downward, the lid 83 is closed to seal the inside of the processing tank 8, and then the holding plate 84 is moved together with the wafer W by the driving unit 831. The opening / closing valve 81 is opened after reaching, for example, 500 rpm. As a result, the hydrofluoric acid vapor in the storage tank 82 is caught on the surface of the wafer W,
The natural oxide film on the surface of the substrate is removed. After the etching is completed, the shutter S is opened, the gas in the processing tank 8 is replaced to some extent, and the lid 83 is raised to the position indicated by the dashed line, and is replaced with the next wafer. Next, the operation of the above embodiment will be described. First, two cassettes 54 containing, for example, 25 wafers W before cleaning are loaded into the loading / unloading stage 52 in the natural oxide film removing apparatus 5 through the gate door D from the outside.
After closing the door D, the gas introduction pipe 51a and the exhaust pipe 51b
Is used to replace the air in the gas chamber 51 with nitrogen gas.

Next, the wafer W before cleaning is taken out of the cassette 54 by the arm of the transfer mechanism 53 and the cleaning device 6
Is held by the holding plate 84 (see FIG. 4) at the dashed line position. Next, the lid 83 of the cleaning device 6 is closed, and the wafer is cleaned to remove the natural oxide film on the wafer surface as described above, and then the lid 83 is opened.

Thereafter, the cleaned wafer is received from the holding plate 84 by the arm of the transfer mechanism 53 and is mounted on the mounting table 74 of the heating unit 7 (see FIG. 3). Then infrared lamp 7
5, a power of, for example, 500 W in total is applied, thereby heating the wafer until, for example, the surface is near 70 ° C.
The heating time depends on the distance between the wafer W and the infrared lamp 75 and the like, but is, for example, about 1 minute. However, by this time, the inside of the wafer loading / unloading chamber 2, the wafer transfer chamber 3, and the preliminary chamber 4 is once set to a vacuum atmosphere by an exhaust pipe (not shown).
Nitrogen gas is introduced from a gas introduction pipe (not shown) to form a nitrogen gas atmosphere having a low water content and a high clean degree. Then, with the gate valve G2 closed, the gate valve G3
Is opened, the wafer W on the mounting table 74 is received by the second transfer mechanism 41, and is loaded into the preliminary chamber 4;
After closing the gate valve G3, the gate valve G2 is opened and transferred to the orientation flat aligning mechanism 32.

The gate valve G1 is opened before the orientation flat alignment by the orientation flat alignment mechanism 32 is completed, and the wafer W on which the orientation flat alignment is completed is transferred to the first transfer mechanism 3
The arm 1 transfers it to a boat 23 in the wafer loading / unloading chamber 2. The holding of the wafer by the respective arms of the transfer mechanisms 31, 41, 53 is performed by, for example, a vacuum chuck.

On the other hand, after the second transfer mechanism 41 transfers the wafer to the orientation flat aligning mechanism 32, the gate valve G2 is closed, and the gate valve G3 is opened to prepare for loading of the next wafer. In this case, since the inside of the gas chamber 51 of the natural oxide film removing apparatus 5 is an inert gas atmosphere having a low degree of cleanness, which is substantially replaced with air and nitrogen gas and contains a considerable amount of moisture, etc. In order to prevent gas from entering the preliminary chamber 4, it is desirable to open the gate valve G3 immediately before loading the wafer. By repeating such an operation, a predetermined number of wafers W are mounted on the boat 23 in the loading / unloading chamber 2.

Thereafter, the boat is loaded into the reaction vessel 11 by the elevator 22, and the wafer W is positioned in the film formation processing area, and a film formation process such as CVD is performed. After the film forming process is completed, the boat 23 is lowered into the loading / unloading chamber 2, the gates G1 and G2 are opened, and the boat is moved by the first transfer mechanism 31.
The wafer W on the wafer 23 is transferred to the second transfer mechanism 41 using, for example, the orientation flat aligning mechanism 32 as a relay point. Then, the gate valve G2 is closed and the gate valve G3 is opened, and the wafer is transferred to the transfer mechanism 53 with the mounting table 74 of the heating unit 31 as a relay point, and returned to the original cassette 54. By repeating such operations sequentially, all the processed wafers are returned to the original cassette 54.

According to such an embodiment, the wafer is placed in an inert gas atmosphere after the natural oxide film is removed, introduced into the reaction vessel without being exposed to the air, and heated by a heat treatment in the middle. Since residual by-products at the time of cleaning are decomposed and removed, film formation is performed on the wafer surface in a very clean state.

In the above, the present invention can be variously modified in accordance with the layout of the entire system, the processing timing of each station, and the like. For example, a carry-out port is provided in the wafer transfer chamber 3 or the preliminary chamber 4, and through these, The processed wafer may be carried out, or an area for storing a large number of wafer cassettes may be secured in the gas chamber 51 of the natural oxide film removing device 5.

According to the experiment by the present inventors, when the wafer was washed and then placed in an inert gas atmosphere, the regrowth of the natural oxide film was hardly observed until several tens of hours had passed, but the growth of air was not observed. When placed inside, the regrowth of the natural oxide film can be seen after 1-2 hours at the earliest, so if the film is left for a long time until the film forming process is performed after cleaning for the convenience of the system, etc. It is very effective to store many wafers after cleaning.

In the above-described embodiment, the inert gas in the gas chamber 51 having a low clean degree is prevented from entering the wafer loading / unloading chamber 2 and the wafer transfer chamber 3 in the inert gas atmosphere having a high clean degree. Although the preliminary chamber 4 is provided in the present invention, it is not always necessary to provide the preliminary chamber 4 in the present invention.

In the present invention, if the gas chamber 51 is configured to be movable using, for example, a caster, and the gas introduction pipe 51a and the exhaust pipe 51b are made detachable, there are a plurality of film formation processing stations. It can be used sequentially for convenience. Further, the heating means for heating the wafer after cleaning is not limited to an infrared lamp, and a hot plate or the like may be used.

If such a heating means is used, by-products remaining on the wafer surface after cleaning can be decomposed and removed, so that the wafer surface becomes very clean. However, in the present invention, the heating means is not necessarily used. Not required.

Further, the cleaning apparatus is not limited to the use of hydrofluoric acid vapor .

[0036]

As described above, according to the present invention, the object to be cleaned is placed in an inert gas atmosphere without being exposed to the air after the natural oxide film is removed, so that the natural oxide film is regrown. As a result, a film forming process can be performed on a clean surface of the object to be cleaned. Therefore, for example, for a semiconductor device, the thickness of the gate oxide film can be controlled with high accuracy, or a required contact resistance can be reliably obtained, so that high integration can be supported.

In addition, since the heating means is provided in the gas chamber, by-products remaining on the surface of the object to be cleaned after cleaning can be decomposed by heating, so that a film is formed on a cleaner surface. be able to.

[Brief description of the drawings]

FIG. 1 is a cross-sectional plan view schematically showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is an explanatory diagram illustrating an example of a heating unit.

FIG. 4 is a cross-sectional view illustrating an example of a cleaning device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Processing furnace 2 Wafer attaching / detaching room 3 Wafer transfer mechanism 31 41 53 Transfer mechanism 5 Natural oxide film removal device 52 Loading / unloading stage 6 Cleaning device W Wafer

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/205 H01L 21/304 641

Claims (1)

(57) [Claims] 1. A vertical type film forming furnace for mounting a plurality of objects on a vertically movable boat and performing a film forming process collectively, and a lower position of the film forming process furnace. An inert gas atmosphere, and a processing object mounting / dismounting chamber for mounting and demounting the processing object with respect to the boat, and an airtightly connected to the processing object mounting / dismounting chamber via a gate valve. a workpiece transfer chamber which is inactive gas atmosphere, the gate to the workpiece transfer chamber - coupled hermetically via Tobarubu, a gas chamber is an inert gas atmosphere, arranged in the gas chamber Where a cassette for accommodating a plurality of objects to be processed is placed.
A gate door for opening / closing a loading / unloading opening for loading / unloading a cassette from / to the outside; a cleaning apparatus for cleaning a workpiece to remove a natural oxide film on its surface; and a cleaned workpiece. A heating unit for mounting the object on a mounting table and heating the object; and transferring the object to be processed from the cassette on the stage to the cleaning device.
The object to be processed is received from the cleaning device on the mounting table of the heating unit.
And a transfer arm for transferring heat to the object to be processed.
Transfer mechanism for transferring the processed object to the boat
When, wherein the cleaning device includes a sealed processing tank, rotates in the treatment tank
A holding plate that is provided freely and holds the object to be processed;
Means for hermetically closing and opening the treatment tank;
The opened chemical storage tank and the gas phase of this chemical storage tank are opened.
Closed and the vapor of the chemical in the chemical storage tank is held by the holding plate.
To remove the native oxide film
To replace the atmosphere in the processing tank with a valve for
Means for forming a film.