JPH01300527A - Oxidizing method - Google Patents

Abstract

PURPOSE:To form a homogeneous thin oxide film onto the surface of a body to be treated by bringing the inside of a furnace to an oxidizing atmosphere, inserting a wafer into the furnace from an anteroom and accurately setting the treating period of film formation. CONSTITUTION:A furnace 21 oxidizing and treating bodies to be treated 36 and anterooms 22, 23, which are connected and mounted to the furnace 21 and pressure of which is elevated to the pressure of the furnace, are installed. The inside of the furnace is brought to an oxidizing atmosphere and the bodies to be treated 36 are inserted into the furnace 21 from the anterooms 22, 23 and oxidized on oxidizing treatment. Accordingly, a temperature is not disturbed by the variation of pressure, and the bodies to be treated are oxidized and treated at stable pressure and temperature, thus forming a homogeneous thin oxide film onto the surfaces of the bodies to be treated.

Description

[Detailed description of the invention] [Object of the invention] (Industrial application field) The present invention relates to an oxidation method.

(Prior Art) A pressure oxidation method has conventionally been used as a method for forming an oxide film on the surface of a semiconductor.

This is a method in which the wafer is placed in a pressurized atmosphere of about 8 atmospheres and heated to a temperature of about 900°C to heat the surface.Since the oxidation rate and pressure are proportional, oxidation under normal pressure It has the advantage that the oxidation rate of the wafer surface is faster than that of the wafer, and the oxide film can be formed in a short time.

In this pressure oxidation method, the process of forming an oxide film on the wafer is carried out in the sequence shown in FIG. In FIG. 3, p-lines and t-lines indicate changes in pressure and temperature inside the processing furnace. A wafer is placed inside a furnace, and in step 1, oxygen is supplied to the inside of the furnace to increase the pressure inside the furnace, and the temperature inside the furnace is raised using a heater provided in the furnace. Next, in step 2, the pressure inside the furnace rises to a predetermined level, for example 8 atmospheres, and becomes stable, and further, in Stella f3, the temperature inside the furnace stabilizes at a predetermined level, for example 900°C.

Thereafter, in step 4, the oxygen inside the furnace is exhausted to the outside, and heating by the heater is stopped. Each of these steps 1, 2, ? And every fourth step, each surface of the wafer is oxidized to form an oxide film. This explanation refers to dry pressurized oxidation, but in the case of wet oxidation, hydrogen is supplied together with oxygen to the inside of the furnace.

(Problem to be Solved by the Invention) However, in the method of forming an oxide film by pressure-oxidizing the wafer through such a sequence, the most important issues are the quality and thickness of the oxide film, which will be described below. There's a problem. Looking at the growth process of the oxide film formed on the surface of the wafer through the above sequence, as shown in Figure 4, in step 1, a large amount of oxygen is supplied to increase the pressure inside the furnace. The temperature increase line is disturbed, and a rough oxide film 12 is formed on the surface of the wafer 11. In Stella f2, the pressure inside the furnace is stabilized, but the temperature is not yet stable and is in an unstable state around a predetermined height value, so that coarse oxide a13 is formed. Then, in step 3, the pressure and temperature inside the furnace are stabilized, so that a homogeneous oxide film 14 is formed. Furthermore, in Stella F4, a large amount of oxygen is discharged from the furnace in the opposite situation to step 1, so
A rough oxide film 15 is still formed. According to the above sequence, a rough oxide film is formed in steps 1.2 and 4, and a homogeneous film is obtained only in step 3, so that a uniform and good oxide film is formed on the wafer surface as a whole. is difficult to form.

In the above sequence, oxygen is supplied into the furnace to perform oxidation treatment on the wafer, and then an oxide film is formed on the surface of the wafer at each step f1 to f4 until the oxygen gas is discharged from the furnace. is formed and the oxide film grows sequentially,
As a result, the thickness of the oxide film formed on the surface of Ueno is between 1000K and 20000K, and the film thickness below that is
For example, it is difficult to obtain an oxide film with a thickness of 1000^. However, recently, there has been a demand for a thin oxide film of about 100 OX to be formed on the surface of a wafer, and it is necessary to be able to form such a thin oxide film using the pressure oxidation method as well. It is becoming.

The present invention has been made based on the above-mentioned circumstances, and an object of the present invention is to provide an oxidation method capable of forming a homogeneous and thin oxide film on the surface of an object to be processed.

[Configuration of the Invention (Means for Solving the Problems) In order to achieve the above object, the oxidation method of the present invention includes a furnace for oxidizing an object to be treated, and a furnace connected to the furnace to reduce the pressure of the furnace. When performing oxidation treatment using an apparatus equipped with a preparation chamber that is raised to a height of be.

(Function) Since the wafer is inserted into the furnace from the preparation room after the furnace has been made into an oxidizing atmosphere, the process period for film formation can be accurately set.

(Example) An example in which the method of the present invention is applied to a high-pressure oxidation method for semiconductor wafers will be described below with reference to FIG.

First, the device will be explained. In this embodiment, preparation chambers 22 and 23 are connected to both ends of the wafer entrance and exit of the horizontal furnace 21.

The horizontally arranged furnace 21 #i is a cylindrical pressure vessel that can withstand high pressure, and is equipped with a cylindrical electric heater 24 inside. A reaction tube 25 made of quartz is inserted horizontally into the heater 24 in the furnace 21 . The reaction tube 25Fi accommodates a boat 37 on which wafers 36, which are objects to be processed, are placed at predetermined intervals, and is accessed through openings at both ends, which are closed with lids 26 and 26 after the wafers 36 are inserted. be done. Further, an oxygen gas pipe 27 and a hydrogen gas pipe 28 are connected to the reaction tube 25 from the outside.
Further, a nitrogen gas pipe 29 is connected to the furnace 2111C.

Communication ports 30 and 30 are formed in both end walls of the furnace 1, respectively, and the preparation chambers 22 and 23 provided at both ends of the furnace 21 communicate with the furnace 2 through the communication ports 30 and 30. . Communication port 3
0.30 is a lid automatically controlled from the outside, 91, 3
1 is occluded. The preparation room 22.23 is a pressure vessel and has an access port 32.32 for the boat 37. Access to and from the boat 37 32.3211-1 is closed by an automatically controlled lid 33°33. In addition, the preparation room 22,
23KFi oxygen gas supply pipe 34.34 and exhaust pipe 35°3
5 is connected.

A case in which Ueno is oxidized under pressure using the pressure oxidation apparatus configured as described above will be described.

First, both heat openings of the reaction tube 25 provided in the furnace 21 are connected to the lid 26.
6, and oxygen (02) gas is fed into the reaction tube 25 through the gas tube 27 to raise the pressure to a level required for pressure oxidation treatment, for example, 8 atmospheres. 1. Electric heater 2
In step 4, the reaction tube 25 is heated to raise the internal temperature to a level required for the pressure oxidation treatment. Note that nitrogen (N2) gas is fed into the furnace 1 through the gas pipe 29 to increase the pressure.
The pressure balance inside and outside the reaction tube 25 is maintained. On the other hand 1
For example, the entrance to the preparation room 22? 2. Open the lid 33 that was previously closed and place multiple ueno 36 in an upright position. Air is sucked and exhausted from the inside of the preparation chamber 22 through the exhaust v35, and oxygen gas is sent into the preparation chamber 22 through the gas pipe 34f, so that the surface of the wafer 36 in the preparation chamber 22 is not oxidized at this stage. .

In this state, the lid 3 that had closed the opening 30 at one end of the furnace 21 was opened, and the lid 26 that had closed one end of the reaction tube 25 was removed, and the boat 37 was opened.

Close 26. The wafers are loaded onto boat 37!
36 is a pressurized oxidizing atmosphere (8
The wafer 3
An oxide film is formed on the surface of 6. In this case, the wafer 36
The mixture is transferred from the preparation chamber 22, which has been pressurized to 8 atmospheres in advance, to the reaction tube 25, which has a pressurized oxidizing atmosphere, and immediately under stable pressure and temperature as shown in Figure 2. A homogeneous oxide film 38 can be formed on the surface of the wafer 36. After the time required to form an oxide film of a predetermined thickness, for example, 100OX, the lid 26 and the lid 3 are opened and the wafer 36'fL-reaction tube 25 is transferred to the preparation chamber 22, and the lid 26 and the lid 3 are removed again. Close 3.

In this case, the preparation chamber 22 is at a pressure of 8 atmospheres, and the wafer 2
The surface of No. 6 is not oxidized. Furthermore, the lid 33 is opened and the sea urchin 36 is taken out of the preparation chamber 22.

Therefore, the temperature of the wafer 36 is not disturbed due to the rise and fall of pressure.
A homogeneous and thin oxide film can be formed on the surface.

(9) The use of oxygen gas is economical because only the preparation chamber 22 is used to constantly take in and out oxygen gas, and oxygen gas is only initially introduced into the reaction tube 25. Since oxygen gas is sent into the preparation chamber 22 to replace the atmosphere, it is possible to prevent the atmosphere from entering the furnace 1.

By using one preparation chamber 22 to perform pressure oxidation treatment on a wafer 36, and using the other preparation chamber 23 to prepare another wafer 36 for pressure oxidation treatment, Pressure oxidation treatment can be carried out continuously and efficiently.

Furthermore, since there is no need to increase or decrease the pressure in the reaction tube each time the oxidation treatment is performed, gas consumption is small and the 7'' process interval can be shortened.

In addition, continuous operation is possible, and the inside of the reaction tube is always separated from the atmosphere, resulting in less pollution.

In the above-mentioned embodiment, a wet pressure oxidation treatment can be performed by feeding the sample to the dry pressure oxidation treatment.

The wafers can not only be subjected to pressure oxidation treatment in an upright state, but also can be treated in the partially vertical furnace of the furnace 21, in which the wafers are lined up horizontally.

[Effects of the Invention] As explained above, according to the oxidation method of the present invention, the oxidation treatment is performed on the object to be treated under stable pressure and temperature without any disturbance in temperature due to rise and fall of pressure. A thin, homogeneous oxide film can be formed on the surface of the body.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a wafer high-pressure oxidation apparatus used in an embodiment of the method of the present invention, FIG. 2 is a cross-sectional view showing an oxide film on a wafer formed in the same embodiment of the present invention, and FIG. FIG. 4 is an explanatory diagram showing the process of pressure oxidation treatment, and FIG. 4 is a cross-sectional view showing an oxide film on a wafer formed by conventional pressure oxidation treatment. 21...Furnace, 22.23...Semi-semi-chamber, 25...Reaction tube, 36...Wafer. Applicant's agent Patent attorney Takeshi Suzue 2nd day

Claims (1)

[Claims] When performing oxidation treatment using a device that includes a furnace for oxidizing the object to be treated and a preparation chamber connected to the furnace and raised to the pressure level of the furnace, the inside of the furnace is made into an oxidizing atmosphere. An oxidation method characterized in that the object to be processed is then inserted into the furnace from the preparation chamber and oxidized.