JPS6033352A - Vacuum cvd apparatus - Google Patents

Abstract

PURPOSE:To form a thin SiO2 film with a uniform thickness onto a wafer, in forming the thin SiO2 film to the surface of the wafer by a vacuum CVD apparatus, by introducing reactive gas into a reaction tube, in which a large number of wafers are arranged in a vertical state, so as to flow the same along the surfaces of said wafers. CONSTITUTION:A large number of wafers 5 are arranged vertically in the inner reaction tube 10 within a double reaction tube apparatus made of quartz consisting of an outer reaction tube 9 and the inner reaction tube 10. The space between the inner and outer reaction tubes 9, 10 are divided left and right by a flange 11 so as to be partitioned into a reactive gas supply side 14 and a reactive gas exhaust side 15. A large number of nozzles 12, of which the lengths are different, are provided to the reactive gas supply side 14 and a gaseous mixture 2 consisting of O2 or NO2 and carrier gas He and SiH4-gas 3 are supplied to the nozzles 12. These gases enter the inner reaction tube 10 from a large number of perforations in a uniform concn. and are flowed along the surfaces of the wafers 5 to form a thin SiO2 film formed by the reaction of SiH4 and O2 or NO2 in a uniform thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a low-pressure OVD apparatus that forms a thin film on a substrate (wafer) by utilizing thermal decomposition or chemical reaction in a gas phase under reduced pressure.

It is well known that silicon oxide (SiO2) and phosphorus silicate glass (PEIG) films are used as interlayer insulating films and passivation films, but thin film formation technology is difficult and hot wall (hot wall)
Even when using a reduced pressure OVD device of the type
The maximum number of sheets to be processed per batch is 40 to 50 sheets.

A feature of a hot wall type low pressure CVD apparatus is that it can process a large number of wafers at once compared to a vertical Pelger type normal pressure OVD apparatus or a single wafer type CVD apparatus.

The present invention is characterized by a furnace structure that further enhances this advantage and enables processing of a larger number of wafers.

First, a conventional device and its drawbacks will be explained.

Figures 1 and 2 show the furnace nozzle of a conventional reduced-pressure OVD device: 1 no.
Nii J-H4z,! -); 3゜The apparatus shown in Figure 1 is an example using a single reaction tube, and 1 in the figure is a quartz reaction tube,
2 is an oxygen (02) or carbon dioxide ff1 (No2) gas injection port, and a carrier helium (He) gas injection port;
6 is a gas nozzle for supplying GtH4, 4 is a quartz boat on which the wafer 5 is placed, and 6 is an exhaust gas to a vacuum pump. The reaction gas SiH4 flows into the reaction tube 1 from the nozzle 3, and the other reaction gas O2 or No2 and carrier gas He2 flow from 2 near the furnace mouth. These reaction gases form a mixed reaction I near the wafer 5.
- forming a thin film on the wafer; However, in such a heavy reaction tube, the concentration of the reactant gas is different between the furnace opening and the exhaust side, so the film tends to be thicker on the furnace opening side and thinner on the exhaust side. Generation] The processing amount in the two types is Si
For O2 and PSG films, the limit was 40 to 50 sheets. For this reason, a device with a perforated tube structure as shown in FIG. 2 was developed.

In FIG. 2, 2 to 6 are the same as in FIG. 1, 7 is a quartz porous (inner) tube, and 8 is a quartz outer reaction tube.

In the perforated pipe device as shown in Fig. 2, the reaction gas 02,
N02, carrier gas He, etc. are injected into the inlet 2 at the furnace mouth.
The reaction gases Sf and H4 flow inside the nozzle tube 6 which has a large number of nozzles formed along the tube axis between the porous tube 7 and the external reaction tube. Since the holes are opened along the periphery of the multiple tubes 70 near the position of the group of wafers, the SiH4 gas reaches the vicinity of the wafers through these holes and reacts to form a thin film. Several nozzle tubes may be used to improve the film thickness distribution between wafers. In such a porous tube device 19, the uniformity of the film thickness distribution between wafers can be improved by adjusting the concentration of the reaction gas supplied to the wafer surface. Because the reaction gas flows into the exhaust gas 1141I, the film thickness on the exhaust side tends to be thicker than on the furnace mouth side, making this adjustment difficult. Since the distance between 7 and Ueno has an effect on the film thickness distribution on the wafer, it is necessary to make the distance constant depending on the size of the wafer, which is difficult in practice. The present invention was made to prevent the above-mentioned drawbacks, and will be described in detail below.

The present invention is characterized in that the flow of the reaction gas is made to flow parallel to the surface of the tube instead of perpendicular to it, and therefore the film thickness distribution has almost no effect on the distance between the surface of the tube and the porous tube. This method has the advantage that the diameter of the wafer can be arbitrarily selected without being affected by Furthermore, if the reaction gas flows from one direction as shown in Figure 1, the concentration of the reaction gas is C-=Oo(exp
-kt) (where co is the initial concentration and k is the reaction rate constant), it decreases greatly depending on the residence time t. In the present invention, since the reaction gas is flowed perpendicularly to the reaction tube, that is, in the cross-sectional direction, and parallel to the surface of the wafer, the residence time is short and variations in concentration can be reduced.

FIG. 6 is a cross-sectional view showing the configuration of the furnace body of the device of the present invention;
The figure shows a perspective view of the internal reaction tube in Fig. 6, Fig. 5 shows a cross-sectional view of the internal reaction tube perpendicular to the tube axis, and Fig. 6 shows not only the furnace body but also a system configuration diagram as a reduced pressure OVD device. be. 6th
In the figure, the furnace body is surrounded by a J-shaped heater 16 having six heating zones (six divisions) to make the temperature of the wafer uniform. (Hot wall type) Low temperature Sio2. The formation temperature for forming a film such as PSG varies depending on the reaction gas, but is approximately 550 to 550°C. Reactant gas is supplied using Remasu cylinder 17J: Remas flow controller (MF).
C) The flow rate is controlled through 18. In addition, exhaust is normally performed using a combination of 19 mechanical booster pumps (MBP) and 200 rotary pumps (RP). The inside of the furnace consists of an outer reaction tube 9 made of quartz and an inner porous reaction tube 1°, the details of which will be explained with reference to FIGS. 6 to 5.

FIG. 3 is a sectional view of the furnace body, and the internal reaction tube 10 is supplied with gas from one side and exhausted from the opposite side when viewed in FIG. 5, which is a sectional view perpendicular to this. FIG. 4 is a perspective view of an example of an internal reaction tube. On the outside of the reaction tube 1o, a plurality of nozzle tubes 12 each having a large number of nozzles formed along the tube axis are provided at appropriate intervals. In order to achieve uniform thickness distribution, nozzle pipes are arranged corresponding to each heating zone as shown in the figure, and the gas flow rate can be adjusted in each heating zone by a mass flow controller 18. Reference numeral 11 designates flanges provided above and below the reaction tube 10, and as shown in FIG. The exhaust side 150 is divided into two parts. The wafer 5 is directly loaded onto the quartz boat 4 and inserted into the internal reaction tube, so that the reaction gas flows in one direction along the surface of the wafer 5 as shown in FIG.

Next, the operation of the device of the present invention will be described. The inside of the reaction tube is initially evacuated to a degree of vacuum of about 0.66 Pascal (Pa). After stabilizing the temperature inside the furnace body to a set value, a reaction gas is supplied through MF018 to begin film formation on the wafer. The degree of vacuum during film formation is approximately 66 Pa to 530 Pa.
It is between. After the generation is completed, the inside of the furnace body is evacuated again.
Replace with an inert gas such as nitrogen (IJ2) or argon (Ar). Furthermore, it is a well-known procedure to return the inside of the furnace to atmospheric pressure, then pull the boat out of the reaction tube and take out the wafer.

Finally, the present invention will be explained in detail.

(1) Since the concentration of the reaction gas on the wafer surface can be made uniform, it has become possible to process about 100 wafers. In conventional equipment, the wafers are arranged perpendicular to the gas flow direction, so the effects of differences in gas concentration distribution cannot be avoided, but in the present invention, the gas flow is parallel to the wafer surface. Therefore, it is easy to adjust the gas flow rate from the nozzle to make the gas concentration distribution uniform.

(2) Since the gas flow is parallel to the wafer, the distance between the wafer and the internal reaction tube has almost no relation to the film thickness distribution within the wafer, so wafers of various diameters can be processed without changing the internal reaction tube. A remarkable effect can be obtained.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views showing an example of the structure of the furnace body of a conventional low-pressure CVD apparatus, FIG. 5 is a cross-sectional view showing an example of the structure of the furnace wood of the apparatus of the present invention, and FIG. Perspective view of internal reaction tube,
FIG. 5 is a sectional view perpendicular to the tube axis of the internal reaction tube, and FIG. 6 is a side view of the system configuration of the apparatus of the present invention. DESCRIPTION OF SYMBOLS 1... Reaction tube, 2... Reaction gas, carrier gas inlet, 6... SiH supply nozzle, 4... Quartz boat, 5... Wafer, 6... Exhaust, 7... Quartz porous tube, 8.9... Quartz external reaction tube, 10... Internal porous reaction tube, 11... Flange, 12... Nozzle (plurality), 14... Gas supply side, 15...・Gas exhaust side,
16...Furnace heater, 17...Gas cylinder, 18
... Mass flow controller, 19 ... Mechanical pump pump, 20 ... Rotary pump. Patent applicant Kokusai Denki Co., Ltd. agent: Oita, 1 external person

Claims (1)

[Claims] The reaction tube of the furnace body has a double structure consisting of an outer reaction tube and an inner porous reaction tube housed inside the outer reaction tube and having multiple gas inflow and outflow holes in the tube wall, and the inner porous reaction tube. In addition, a nozzle tube with a plurality of nozzles formed along the tube axis is provided at appropriate intervals, and a flange is provided along the tube axis to create a space between the internal porous reaction tube and the external reaction tube. A reduced-pressure OVD characterized by being divided into two chambers, in which a reaction gas and a gear gas are fed into one chamber, and the gas flowing out into the other chamber along the surface of each sea urchin is discharged from an exhaust port. Device.