JPH0424920A - Wet type thermal oxidizing apparatus - Google Patents

Abstract

PURPOSE:To efficiently oxidize, to eliminate a distortion at a substrate with economy and to obtain an oxide film of high quality by providing a cooler provided in a superpure water supply passage, a mass flowmeter provided in the cooler and a heater for evaporating the water quantitatively measured by the flowmeter. CONSTITUTION:A superpure water manufacturer 9 is connected to a mass flowmeter 11 through a filter 10 in a steam supply system 8, and connected to a controller 13 for automatically opening and closing a valve 12 in which superpure water measured by the meter 11 is supplied. A heater 14 such as a tape heater for heating the water to be supplied in a constant quantity is mounted at a tube 15 at the end of the flowmeter 11. The flowmeter 11 has an electronic cooler 17 to be temperature-controlled in contact with a fluid passage 18, and three temperature sensors 19, 20, 21 respectively provided in the passage 18 in the cooler 17 or on the outer periphery of the passage 18 and the position on the surface of the cooler.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a wet thermal oxidation apparatus for forming an oxide film on a semiconductor wafer.

[Prior Art] In the manufacture of semiconductor integrated circuit devices, there is a trend toward higher integration, and higher quality is desired in film formation. For oxide film formation, we use a thermal oxidation device that directly oxidizes the silicon substrate,
There is a deposition apparatus that deposits an oxide film on a silicon substrate.

Among these, the thermal oxidation equipment performs heat treatment in an electric furnace that creates an atmosphere of 800 to 1200°C.
Good consistency at the interface between O It is widely used for forming element isolation films, gate films, interlayer insulating films, etc. because it has relatively little variation. There are two types of thermal oxidation equipment: a high-pressure oxidation equipment and an ordinary pressure oxidation equipment. Since the former requires high running costs, an ordinary pressure oxidation equipment is practically used.

[Problem to be solved by the invention] There are two types of atmospheric pressure oxidation equipment: dry type and wet type. Of these, the dry type supplies 02 gas with N2 gas as a carrier while adjusting the flow rate, and oxidizes by controlling the oxidation rate. Perhaps because of this, the oxidation rate was slow and the substrate was easily distorted. In order to increase the oxidation rate and eliminate distortion of the substrate, a wet method is known in which oxidation is performed by supplying 02 gas in the presence of water vapor.

In order to perform wet oxidation, H2 gas and 0° gas are supplied and reacted with an external combustion device to generate water vapor.
The partial pressure of water vapor is controlled by the flow rates of 02 gas and H2 gas, or the partial pressure of water vapor generated by heating pure water made in a pure water production equipment is adjusted to the water temperature of pure water and 0. □、N
2. Controlled by carrier gas such as Ar gas (described in electronic materials).

However, the former external combustion device, which produces steam by reacting 0° gas and H2 gas, is very large-scale and poses safety problems. In addition, when producing water vapor by evaporating the latter pure water, it is difficult to supply a constant amount of water vapor even if it is controlled by the temperature of the pure water and the carrier gas. It was uneconomical because steam was supplied.

In order to eliminate the above-mentioned drawbacks, the present invention aims to provide a wet thermal oxidation apparatus that can perform oxidation efficiently, is economical, and can produce a high-quality oxide film without causing distortion on the substrate. do.

[Means for Solving the Problems] The present invention has been made to achieve the above object, and the wet thermal oxidation apparatus of the present invention uses oxygen gas and water vapor generated from ultrapure water. In a wet thermal oxidation apparatus for forming an oxide film on a semiconductor wafer, a cooling section provided in the supply path of the ultrapure water, a mass flowmeter provided in the cooling section, and a constant amount measured by the mass flowmeter are provided. The apparatus is equipped with a water vapor supply system having a heating device for evaporating the ultrapure water.

[Function] In order to produce steam from ultra-pure water in just the right amount and supply it to the reaction tube, the ultra-pure water produced from the ultra-pure water production equipment is accurately measured with a mass flow meter, and then the water vapor is transferred to the heating device. Heat and evaporate. The amount of pure water supplied to the heating device is commensurate with the work efficiency of the heating device, so just the right amount of pure water is turned into water vapor. A predetermined amount of water vapor produced by controlling the amount of supply is supplied to the reaction tube, and the oxidation reaction of the substrate proceeds together with O2 gas.

This results in a fast oxidation rate and a uniform oxide film.
It is possible to manufacture a high-quality semiconductor wafer 1.

[Example] An example of the wet thermal oxidation apparatus of the present invention will be described with reference to the drawings.

The wet thermal oxidation apparatus O shown in FIG.
Semiconductor sea urchin supported by 0 sheets/X2 or carried in through insertion port 3,
A reaction tube 4 made of quartz is also provided. On the outer periphery of the reaction tube 3, a heater 5 is provided which is divided into 3 or 5 zones to form a soaking zone in the atmosphere where the semiconductor sea urchins are arranged. It has become. Further, the outer periphery of the heater 5 is covered with a heat insulating material such as alumina, and the structure is such that the heat of the heater 5 can efficiently heat one row of semiconductor wafers in the reaction tube 4. Further, a reaction gas inlet 6 is provided near the insertion port 3 of the reaction tube 4, and the inlet 6 has an 02 gas supply body 7.
and the water vapor supply system 8 are the supply paths for ultrapure water.
connected via. The steam supply system 8 is provided with an ultrapure water production device 9 connected to a mass flowmeter 11 via a filter 10, and a valve 12 to which ultrapure water measured by the mass flowmeter 11 is supplied opens and closes automatically. Controller 13
connected to and equipped with. At the other end of the mass flowmeter 11,
A heating device 14 such as a tape heater or the like is attached to piping 15 to heat a fixed amount of ultrapure water. Furthermore, reaction tube 4
On the opposite side of the insertion port 3, an exhaust port 16 is provided connected to an exhaust system (not shown) through which the reaction gas flowing into the reaction tube 4 from the reaction gas inlet 6 is exhausted.

Steam supply system 8 of the wet thermal oxidizer O configured as above
As shown in FIG. 2, the mass flowmeter 11 installed in It is composed of three temperature sensors 19, 20, and 21 provided inside the channel 18 or at the outer periphery of the channel 18 and at the surface of the cooling element. The electronic cooling element 17 is an element made by alternately combining P-type and N-type semiconductor elements, and when a voltage is applied between the electrodes, heat is absorbed on one side and heat is generated on the other side. The endothermic surface can be used as a cooling section, and the temperature of the endothermic surface can be freely controlled by changing the applied voltage. The electronic cooling element 17 is controlled so that there is a constant difference between the signal from the temperature sensor 19 that detects the temperature of the liquid and the signal from the temperature sensor 20 in the electronic cooling element 17, that is, the cooling is performed to a constant temperature difference. In this state, when there is no flow of liquid as shown in FIG. The signals from the temperature sensor 21 become equal, but if there is a flow of fluid, the temperature of the flow path 18 becomes as shown by the dotted line, and the temperature of the flow path 18 and the electronic cooling element 17 become equal.
Heat exchange occurs between the flow path 18 and the temperature of the flow path 18.

At that time, the mass flow rate is determined by converting the difference between the signals of the temperature sensor 20 and the temperature sensor 21 into a flow rate from the output Q shown by the following equation.

Q=-K・-d2・ρ・Cp-Um・△θm However Heat conduction on the surface of the cooling element, etc. Coefficients included d: Channel diameter ρ: density Cp: constant pressure specific heat Um: average flow velocity Δθm: Difference in liquid temperature in the cooling section In the above formula, ρ・−d2・Um is the mass flow rate.

Since a mass flowmeter using such a cooling element is used, the mass flow rate is accurately measured without generating bubbles in the sensor part, unlike mass flowmeters that are heated, and the mass flow rate is accurately measured and supplied to the heating device 14 according to this measurement. The amount of purified water can be controlled and supplied in accordance with the capacity of the heating device 14. Therefore, pure water is completely converted into steam, and this steam is mixed with O2 gas whose supply amount is controlled and supplied to the reaction tube 4.

The operation of the wet thermal oxidation apparatus equipped with the mass flow meter as described above will be explained.

A plurality of semiconductor wafers 2 placed on a support 1 are transferred to a reaction tube 4.
Load it from insertion port 3. The inside of the reaction tube 4 is heated to, for example, 950° C. by the heater 5. The ultrapure water produced by the ultrapure water production device 9 passes through the filter 10 and passes through the mass flowmeter 1.
1 flow path 18. When the mass flow meter 11 detects a predetermined flow rate of ultrapure water, the controller 13 opens the valve 12 and supplies ultrapure water to the heating device 14 . When the ultrapure water passes through the heating device 14 according to the flow rate, it becomes completely steam, and the combined flow rate is controlled and it is mixed with 02 supplied from the 02 gas supply system 7 in the pipe 15, and then flows into the reaction tube 4 from the inlet 6. Supplied.

Then, the semiconductor wafer 2 is heated to 20~ by 02 gas and water vapor.
The oxidation process is carried out at a rate of 30 persons/min, and the excess gas is exhausted from the exhaust port 16, and the exhaust gas is exhausted by the exhaust system.

[Effects of the Invention] As is clear from the above embodiments, according to the wet thermal oxidation device of the present invention, a certain amount of ultrapure water whose flow rate is accurately measured is supplied to the heating device, and the ultrapure water is heated here. In order to efficiently produce steam without shortage, 02 gas and steam are always supplied at a constant ratio, and a uniform oxide film can be quickly obtained. No equipment or large-scale combustion equipment is required, and it is safe, inexpensive, and very economical.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the wet thermal oxidation apparatus of the present invention;
2 is a diagram showing a main part of the embodiment shown in FIG. 1, and FIG. 3 is an explanatory diagram of the main part of FIG. 2. 1... Semiconductor wafer 8... Water vapor supply system 11... Mass flow system 14... Heating device 15... Piping (ultra pure water supply route) O...
...Wet thermal oxidation equipment

Claims (1)

[Claims] In a wet thermal oxidation apparatus that forms an oxide film on a semiconductor wafer from oxygen gas and water vapor generated from ultrapure water, a cooling section provided in the ultrapure water supply path and a cooling section provided in the cooling section are provided. A wet thermal oxidation apparatus comprising: a steam supply system having a mass flow meter and a heating device for evaporating a certain amount of the ultrapure water measured by the mass flow meter.