JPS6272130A - Vapor reaction method and vapor reaction device directly used therefor - Google Patents

Abstract

PURPOSE:To prevent a natural oxide film from being formed using purge gas in case of feeding and discharging wafers to and from a furnace by lowering the furnace temperature excluding the film forming time by a method wherein oxidation preventing gas is fed to a reaction furnace from the inner part thereof simultaneously feeding cooling gas in case of feeding and discharging wafers to and from the reaction furnace. CONSTITUTION:When a cover 3 of a reaction tube 1 is opened to feed wafers thereto, gas such as N2 etc. is fed to the tube 1 from a purge gas inlet 7 causing no trouble to prevent a natural producing film from being formed on the surface of wafers. Besides, the furnace temperature is kept at low temperature of T1 in case of feeding and discharging the wafers to restrain the natural oxide film from growing. When the wafer feeding is finished, the furnace temperature is rapidly raised up to the vapor reaction temperature to be kept for specified time so that coating film may be grown on the wafers using reaction gas fed from a gas inlet 4. Later the temperature of heater is lowered simultaneously to be quenched down to the low temperature T1 using the gas fed from a cooling gas inlet 6. Finally purge gas is fed from the inlet 7 to the reaction tube 1 to open the cover 3 thereof for discharging the wafers.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a natural oxide film (SiO□) formed during a gas phase reaction process, and particularly to the natural oxide film (SiO□) formed before and after deposition. Regarding reduction.

〔overview〕

In the present invention, when a necessary film is formed on a semiconductor wafer by a gas phase reaction, when the semiconductor wafer is carried into a reactor, an antioxidant gas is sent from deep inside the reactor to lower the temperature inside the reactor. The formation of a natural oxide film is suppressed by raising the temperature to form a film, lowering the temperature inside the reactor, and transporting the semiconductor wafer while flowing anti-oxidation gas from deep inside the reactor.

[Conventional technology]

The furnace shown in FIG. 3 is a conventional gas phase reactor.

The inside of the quartz reaction tube 1 is exhausted by an exhaust device 5.

A large number of wafers can be loaded into the quartz reaction tube 1 by opening the lid 3 of the reaction tube. The quartz reaction tube 1 is heated to a gas phase reaction temperature by a heater 2, and the temperature is kept constant during loading and unloading of wafers and during film formation. A gas phase reaction gas is introduced into the reaction tube 1 through the gas introduction port 4, and the pressure inside the tube is adjusted by the flow rate of the reaction gas. This low-pressure CVD method is particularly effective for deposition on large-diameter wafers and for mass processing, and is a highly economical method with excellent uniformity in film thickness and film quality, and is often used in the semiconductor industry.

[Problem that the invention seeks to solve]

As LSIs become finer, the presence of a natural oxide film at the interface, which has not been a problem in the past, has become a major problem in submicron manufacturing.

Conventionally, LP-CVD (low pressure CVD) furnaces typically use horizontal diffusion furnaces. 10 to 30 natural oxide films (SiO□) were formed when Si substrates were taken in and out of the furnace.

The structure of the furnace was such that sufficient uniform heating was achieved, as shown in Figure 3, and the temperature was always set at a constant value.

The purge to prevent air from getting in was from the front flange, so there was some air getting in, and the prevention was not sufficient.

In addition, purging tends to cause turbulence, which tends to kick up dust and products and contaminate the silicon substrate.

Oxygen and water that are physically or chemically adsorbed on the silicon substrate become oxidizing species even at medium temperatures (600 to 800°C).

[Means for solving problems]

When carrying semiconductor wafers into and out of the reactor, an anti-oxidation gas is sent from the back of the reactor to prevent the formation of a natural oxide film, to enable ramping of the reactor, and to allow cooling gas to flow. The above problem was solved by making it possible to raise and lower the temperature of the reactor in a short time.

[Effect]

Since the furnace used in the present invention has a lower insulation effect and can be rapidly cooled by flowing cooling gas, the temperature of the furnace can be lowered except during film formation to suppress the formation of a natural oxide film. I can do it.

Furthermore, when wafers are transported into and out of the furnace, a purge gas is flown to prevent the formation of a natural oxide film.

〔Example〕

FIG. 1 shows the reactor of the present invention. The inside of the quartz reaction tube 1 is exhausted by an exhaust device. The reaction tube 1 is heated by a heater 2 and cooled by cooling gas introduced from a cooling gas inlet 6. When the reaction tube lid 3 is opened and a group of wafers are carried into the reaction tube 1, a purge gas such as N2 is flowed from the purge gas introduction lower to an extent that does not cause turbulence in the tube, forming a naturally occurring film on the wafer surface. prevent the formation of Moreover, the temperature of the furnace is maintained at a low temperature T when the wafer is loaded into and unloaded from the reaction tube 1, thereby suppressing the growth of a natural oxide film. The reactor of the present invention has a lower adiabatic effect than conventional reactors, so it is easier to ramp.

When the loading of the wafer group is completed as described above, the temperature inside the furnace is raised twice in succession to reach the gas phase reaction temperature.

The quartz reaction tube 1 is maintained at the reaction temperature for a required period of time, and a reaction gas is introduced from the reaction gas inlet 4 to grow a film on the wafer. After the film is formed, the temperature of the heater 2 is lowered, and at the same time cooling gas is flowed through the cooling gas inlet 6 to cool the reaction tube 1.
is rapidly cooled to temperature T1. A purge gas is flowed into the tube from the introduction lower, the lid 3 of the reaction tube is opened, and the wafer group is carried out from the reaction tube 1.

〔Effect of the invention〕

FIG. 2 shows data showing the effects of the present invention.

Five points were defined in the diametrical direction on a 5-inch CZON type wafer, and the state of natural oxide film formation for each manufacturing method was measured. (d) shows the natural oxide film produced by the conventional manufacturing method, when neither back purging nor ramping is employed.

(c) shows the state of a natural oxide film that occurs when T1 is set to 610° C. and bank purge is used but ramping is not used. (b) shows the case where T is set to 420° C., bank purge is employed, and ramping is not employed. (a) shows the occurrence of a natural oxide film when T1 is 610° C. and both back purging and ramping are used. In this case, it can be seen that the occurrence of natural oxide film is reduced by more than one order of magnitude compared to (b).In this way, according to the present invention, by simple improvement of the conventional furnace, the gas phase reaction process can be completed. It was possible to completely remove the natural oxide film formed at the interface of the middle Si substrate.

The following effects can also be observed in terms of the specific manufacturing of the device.

(i) In the case of a process in which polycrystalline Sj is made amorphous and solid-phase growth is performed again, reliable growth can be performed because there is no natural oxide film at the interface.

(ii) Since the natural oxide film, which was a cause of variation in the contact resistance of polycrystalline Si, can be removed, the yield is improved.

(iii) When trying to increase the capacitance of 5iJ4, the dielectric constant does not decrease even if the film is made thinner, and the value as designed can be obtained.

[Brief explanation of drawings]

FIG. 1 shows a reactor according to the invention. FIG. 2 is a diagram showing the effects of the present invention. FIG. 3 is a diagram showing a conventional reactor. FIG. 4 is a diagram showing the conventional effect. 1...Quartz reaction tube 2...Heater 3...
Reaction tube lid 4...Reaction gas inlet 5...Exhaust device 6...Cooling gas introduction lower...Purge gas inlet

Claims (1)

[Claims] 1. In a gas phase reaction method for forming a predetermined film on a semiconductor wafer, oxidation prevention is carried out from the back of the reactor as seen from the semiconductor wafer loading/unloading port to the semiconductor wafer loading/unloading port. a step of transporting the semiconductor wafer into the reactor while supplying gas; a step of raising the temperature in the reactor to a temperature suitable for a gas phase reaction to perform a gas phase reaction; A gas phase reaction method comprising the steps of lowering the temperature of the semiconductor wafer, and transporting the semiconductor wafer out of the furnace while sending an antioxidant gas from the inner part of the furnace to the semiconductor wafer loading/unloading port. 2. A gas phase reaction device having an outlet for an antioxidant gas from the inner part of the furnace as seen from the semiconductor wafer loading/unloading port to the semiconductor wafer loading/unloading port.