JPS6245129A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a thin oxide film with excellent controllability in a short time by irradiating a semiconductor substrate by halogen lamp beams in an oxidizing atmosphere. CONSTITUTION:Halogen lamp devices 3 are arranged to upper and lower sections on the outside of a core tube 2, on the inside thereof an silicon substrate 1 to which a semiconductor element is shaped is placed and which is formed by quartz. Parabolic reflecting mirrors 5 are each fitted to respective halogen lamp 4. When an oxide film is shaped by using the device 3, the tube 2 is not heated and is kept under a cold wall state from the difference of the optical absorptivity of the substrate 1 and the core tube 2 while the substrate 1 is heated in a short time at a high temperature. Since the tube 2 is kept at a low temperature, the mixing of impurities into the tube 2 is inhibited, thus forming the excellent oxide film.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device in which a thin and dense oxide film is formed on the surface of a semiconductor substrate.

[Summary of the invention]

This invention is a method for forming an oxide film on the surface of a semiconductor substrate forming a semiconductor device, in which a dense oxide film with excellent controllability is formed by irradiating halogen lamp light in an oxidizing atmosphere. be.

[Conventional technology]

Generally, in semiconductor devices such as MOS memory,
Oxidation treatment is performed to form a gate oxide film and the like.

Here, to explain the conventional oxide film forming process, as shown in FIG. 6, a semiconductor substrate 11 to be oxidized is
is housed in a core tube 12 made of a material such as quartz, and heated by a coil 13 or the like in a predetermined gas atmosphere. The heating time during this oxidation step is about 10 minutes to 20 minutes.

[Problem that the invention seeks to solve]

Recent MOS memories are becoming increasingly finer, and gate oxide films and the like are becoming thinner in accordance with the scaling law. For example, the thickness of the oxide film in a DRAM with 256 bits is 100 mm.
~120 people, and 80 for IM Hinode DRAM
~100 people will be required. Similarly, 200 Å or less is required for SRAM, and 1M bit SRAM
150A or less is required.

Furthermore, in addition to the demand for thinner films, there is also a demand for higher quality oxide films. That is, forming an oxide film free from the adverse effects of impurities and the like leads to higher performance of elements such as transistors.

However, conventional oxide film forming methods cannot necessarily meet the above requirements. With conventional oxidation methods, it is easy to form a thick oxide film, but it is difficult to control the formation of a thin oxide film as described above. That is,
The oxidation process requires about 10 to 20 minutes to obtain controllability, and if the oxidation time is shortened to form a thin oxide film, there may be problems such as variations in the oxide film thickness. cause problems. On the other hand, there are also known methods of performing oxidation at a lower oxidation rate.
Even when a low-pressure oxidation method or a low-temperature oxidation method that lowers the effective oxygen partial pressure is used, there are similar problems in controllability of the oxide film thickness, and furthermore, the process is complicated. Further, the shorter the time possible, the greater the advantage in terms of the process.

Furthermore, in the case of this conventional method of forming an oxide film, there is a concern that the interface state, breakdown voltage, etc. may decrease due to the problem of density.

For example, in the conventional oxide film forming method, heating is performed using coil heating or the like, and the furnace core tube is also heated at the same time. Therefore, impurities from the outside or from the inner wall (for example, H20,
(Na, etc.) are mixed into the atmosphere inside the furnace core tube, and when an oxide film is formed, these impurities are taken into the oxide film and have an adverse effect on the film quality.

In view of the above-mentioned problems, the present invention performs heat treatment in a short time, forms a thin oxide film with good controllability in response to the miniaturization of semiconductor devices, and prevents impurities from entering the furnace atmosphere. It is an object of the present invention to provide a method for manufacturing a semiconductor device that does not cause harmful effects such as diffusion.

[Means for solving problems]

The present invention solves the above-mentioned problems by using a method for manufacturing a semiconductor device in which a semiconductor substrate is irradiated with halogen lamp light in an oxidizing atmosphere to form an oxide film on the surface of the semiconductor substrate.

[Effect]

A halogen lamp beam is irradiated onto the half-shaped display board in an oxidizing atmosphere. Therefore, due to the heating performance of the halogen lamp beam, the heat treatment can be carried out in a short time of about 10 to 20 seconds. The oxidizing atmosphere is, for example, Dry 02. Wet 02. Steam 02゜03 (ozone), N2±0
2. This is done using dry air, etc. Because of the high temperature and short time, a silicon oxide film with excellent film quality can be formed with good controllability of film thickness.

Further, as shown in the schematic diagram of FIG. 1, the wavelength distribution D1 of the halogen lamp light is in the range of 0.4 μm to 4.0 μm. Here, the furnace core tube is made of a material such as quartz, and from the wavelength dependence of the light absorption coefficient α, it is 0.4 μm to 4.0 μm.
In the range of 0 μm, the value of the light absorption coefficient α0 of quartz, that is, silicon oxide is small. Therefore, when irradiated with halogen lamp light, heating of the furnace core tube can be suppressed.
Since it is possible to lower the temperature of the furnace core tube, impurities (such as H2O) from the outside or from the inner wall.

It is possible to suppress the incorporation of Na, A*, etc.) into the furnace and prevent adverse effects. Furthermore, when the wavelength of light is in the range of 2.5 μm or less, absorption by silicon oxide, which is the material of the furnace core tube, decreases. Therefore, by irradiating with a light source that emits wavelengths in the range of 0.25 μm or less,
It is possible to prevent impurities from entering the furnace core tube.

On the other hand, when a silicon substrate, for example, is used as the semiconductor substrate, the silicon substrate has a large light absorption coefficient α1 in the range of 0.4 μm to 4.0 μm, and the silicon substrate is efficiently heated. As described above, due to the wavelength dependence of the light absorption coefficient α of silicon oxide and silicon, when a halogen lamp light beam is used, the light is not absorbed by the furnace core tube but is effectively absorbed only by the semiconductor substrate. Therefore, heat treatment can be carried out efficiently in a short time, and moreover, adverse effects such as contamination with impurities can be prevented.

〔Example〕

Preferred embodiments of the present invention will be described based on experimental examples.

First, the irradiation device will be explained with reference to FIG. 5. The halogen lamp device 3 consists of a furnace core tube 2 made of quartz, in which a silicon substrate l forming a semiconductor element is placed. They are placed on the top and bottom of the outside. This halogen lamp device 1 is equipped with a plurality of halogen lamps 4 that emit continuous incoherent light with a wavelength of 0.4 to 4.0 μm, and each halogen lamp 4 is equipped with a parabolic reflecting mirror 5. installed. The silicon substrate 1 is supported in the air by frame-shaped suspenders 6, and the bidirectional surfaces of the silicon substrate 1 are irradiated with continuous incoherent light from each halogen lamp 4.

When forming an oxide film using this halogen lamp device 3, the furnace core tube 2 is not heated due to the difference in light absorption rate α between the silicon substrate 1 and the furnace core tube 2 shown in FIG. 1, resulting in a so-called cold wall. On the other hand, the silicon substrate 1 is heated at a high temperature in a short time. Since the furnace core tube 2 is maintained at a low temperature, it is possible to prevent impurities from entering the furnace core tube 2 and form a high-quality oxide film.

The present inventors conducted an experiment on forming a thin oxide film using such an apparatus. That is, silicon substrate (CZ (1
00) ; n-type, 2 to 3 ohm-cm), and infrared irradiation heating was performed with a halogen lamp 4 in a dry 02 atmosphere as an oxidizing atmosphere. The experimental data for this experiment is shown in Table 1.

(Hereinafter in the margin) Table 1 Figures 2 to 3 are graphs based on this experimental data.
It is a diagram. As shown in FIG. 2, compared with the data obtained by the conventional oxidation method (indicated by four straight lines on the right side in the second section), the formation of the oxide film according to this example 2
Indicated by ○ in the figure. ) is on the straight line of conventional oxide film formation, and this shows that a similar oxide film was formed in a short time, demonstrating the validity of oxide film formation using halogen lamp light. In Figure 2, the vertical axis represents the oxide film thickness (person).
The horizontal axis shows the oxidation time (seconds and minutes).

Further, as shown in FIG. 3, the relationship between the oxidation temperature and the oxide film thickness is a linear relationship. Therefore, as the oxidation temperature increases, the oxide film thickness also increases, and by performing oxidation treatment at a predetermined temperature, an oxide film with a predetermined thickness can be formed.

In this way, the halogen lamp light (0.4~(1°0μ
m, peak wavelength 1.15. +1m) and oxidation is performed in an oxidizing atmosphere, it is possible to control the film thickness on the order of 10 people, and it is possible to easily form a thin oxide film of 50 to 150 people with good controllability. I can do it. As mentioned above, since the furnace core tube 2 is not heated and is in a cold wall state, diffusion of impurities can be suppressed, and since the temperature is high, a dense and high-quality oxide film can be easily formed. .

Incidentally, it is generally known that when high-temperature impurities are introduced into a semiconductor substrate such as a silicon substrate, the so-called accelerated oxidation effect increases the thickness of the formed oxide film.

Therefore, in order to determine the accelerated oxidation effect of the semiconductor device manufacturing method of this example, the present inventor conducted an experiment similar to the above-mentioned example (annealing a silicon substrate into which BF2+ was ion-implanted at 50 keV at 1000°C for 20 minutes). After applying
1150℃, 10 seconds.

Oxidize under the conditions of dry O2: 4β/min and measure the oxide film thickness. ), as shown in Figure 4,
When the semiconductor device manufacturing method of this example is used, a constant oxide film thickness can be obtained at least in the range of lX1013 to 2x1015/cIA, and the oxide film can be formed with good reproducibility and controllability. It shows.

Therefore, the method for manufacturing a semiconductor device of this embodiment is also effective for semiconductor substrates such as silicon substrates into which impurities are introduced, and a thin oxide film can be formed with good controllability in a short time.

〔Effect of the invention〕

The method for manufacturing a semiconductor device of the present invention can easily form a thin oxide film in response to higher integration and miniaturization of semiconductor devices. That is, in the method for manufacturing a semiconductor device of the present invention, since the semiconductor device is irradiated with halogen lamp light in an oxidizing atmosphere, it is possible to heat the semiconductor device to a high temperature in a short time. Further, due to the difference in light absorption between the semiconductor substrate and the furnace core tube, only the semiconductor substrate can be heated, and it is possible to prevent impurities from entering the furnace core tube. Therefore, a thin oxide film can be formed in a short time with good control, and since diffusion of impurities is prevented, it is possible to easily form a high-quality oxide film with excellent interfacial properties. It is.

[Brief explanation of drawings]

Figure 1 shows the wavelength distribution of halogen lamp light and Si and 5
FIG. 2 is a schematic diagram showing the wavelength dependence of optical absorption of i02;
The figure is a characteristic diagram showing the time dependence of the oxide film thickness in the conventional method and the time dependence of the oxide film thickness in the case of using the method of manufacturing a semiconductor substrate of the present invention. FIG. 4 is a characteristic diagram showing the relationship between oxide film thickness, FIG. 4 is a characteristic diagram showing the change in oxide film thickness when impurities are introduced into the silicon substrate according to the present invention, and FIG. FIG. 6 is a schematic cross-sectional view showing an example of a halogen lamp device used in the manufacturing method of FIG. 1...Semiconductor substrate 2...Furnace core tube 3...Halogen lamp device 4...Halogen lamp patent applicant Sony Corporation representative Patent attorney Koba Mima Tamura Sakae - `` Utaka Do← Ichitoba-saba Ichitoba-uke

Claims (1)

[Claims] A method of manufacturing a semiconductor device, which comprises irradiating a semiconductor substrate with halogen lamp light in an oxidizing atmosphere to form an oxide film on the surface of the semiconductor substrate.