KR19990002894A - Oxide film formation method of semiconductor device - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method for forming an oxide film of a semiconductor device, by improving the diffusion length value of minority carriers in a silicon substrate by adjusting the temperature of the wafer loading step in forming an oxide film of the semiconductor device.

2. Technical problem to be solved by the invention

The present invention seeks to reduce the width of the minority carrier diffusion length reduction in the silicon substrate when forming the oxide film of the semiconductor device.

3. Summary of Solution to Invention

SUMMARY OF THE INVENTION In the method of forming an oxide film of a semiconductor device, it is desirable to reduce the minority carrier diffusion length reduction width in a silicon substrate by adjusting the temperature of the wafer loading step to 750 to 850 ° C.

4. Important uses of the invention

The present invention can be applied to oxide film formation of all semiconductor devices produced by the thermal oxidation method.

Description

Oxide film formation method of semiconductor device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming an oxide film of a semiconductor device, and in particular, by adjusting the temperature of a wafer loading step at the time of forming an oxide film to reduce a decrease in the minority carrier diffusion length in a silicon substrate and to improve life time. The present invention relates to a method for forming an oxide film of a semiconductor device.

In general, as the degree of integration of semiconductors increases, defects or metallic impurities, which act as recombination centers in the substrate, reduce the refresh characteristics of the integrated device and reduce reliability. . Therefore, in order to overcome this problem, it is necessary to increase the thickness control ability of the oxide film during the thermal oxidation process and to prevent the inflow of contaminants from the outside. In order to prevent such contamination, the temperature of the wafer is loaded at 650 ° C. The oxide formation process is described below with reference to FIG. 1.

1 is a process chart showing a conventional method for forming a thermal oxide film. After a wafer is loaded into a reactor at a temperature of 650 ° C., a purge process of supplying about 30 [square liter per minute (SLM) nitrogen gas is performed. Remove contaminants Then, the temperature is gradually raised to the oxidation temperature at a rate of temperature increase of about 5 ° C./min (first ramp-up step). Flowing a small amount of pure oxygen while increasing the temperature can increase the flatness of the gate oxide film. In addition, it is possible to prevent the occurrence of defects or particles by exporting the impurities generated in accordance with the process conditions. On the other hand, the oxidation temperature is about 800 ℃, and the oxidation gas is a dry oxidation method using pure oxygen, and a mixture of oxygen and hydrogen oxidizes hydrogen to generate moisture to flow oxygen and moisture together to increase oxidation rate. Oxidation methods can be used. After the oxidation process is completed, a nitrogen purge process is performed to remove the oxidizing gas, and then the temperature is increased for the annealing process. At this time, the annealing temperature is suitable for about 20 minutes at about 900 ℃ but if it proceeds too long, the life is reduced by the occurrence of defects due to the high temperature thermal process rather than the annealing effect. After the annealing process is completed, the wafer is unloaded by lowering the temperature to about 800 ° C. or less at a rate of temperature rise of about 3 ° C./min. The annealing process is an option step, and may be omitted if necessary.

However, the above method reduces the diffusion length of minority carriers, which is a factor that indicates damage or silicon contamination in silicon bulk, thereby impairing the reliability of the oxide film. In addition, since the recombination position of the minority carriers increases due to the external contamination of the silicon substrate during the oxidation process, it adversely affects the device characteristics. Therefore, in order to compensate for this, there has been a demand for the development of a method for reducing the reduction in the diffusion length of minority carriers in the silicon bulk after the thermal oxidation process.

Accordingly, the present invention improves the characteristics of the silicon substrate by reducing the diffusion length of minority carriers in the silicon substrate by adjusting the temperature of the wafer loading step, thereby increasing the reliability of the semiconductor device to form an oxide film of the semiconductor device. The purpose is to provide a method.

In order to achieve the above object, the present invention provides a method for forming an oxide film of a semiconductor device by sequentially performing a wafer loading step, a temperature stabilization step, an oxidation step, a ramp-down step, and an unloading step. It is characterized by advancing at a temperature of 750-850 degreeC.

1 is a thermal oxidation process for forming an oxide film of a conventional semiconductor device.

2 is a thermal oxidation process for forming an oxide film of a semiconductor device according to an embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings the present invention will be described in detail.

2 is a thermal oxidation process diagram for forming an oxide film of a semiconductor device according to an embodiment of the present invention.

The wafer is placed in a reactor maintained at a temperature of 750 ° C to 850 ° C, and a wafer loading step of waiting for a predetermined time is performed. After loading the wafer, a purge process is performed to supply nitrogen gas of about 30 [square liter per minute (SLM)] to remove contaminants.

The oxidation step is carried out from the loading step through a temperature stable step. The temperature stabilization step proceeds in a nitrogen (N ₂ ) atmosphere of 30 [SLM]. On the other hand, the oxidation temperature is about 800 ℃, and the oxidation gas is a dry oxidation method using pure oxygen, and a mixture of oxygen and hydrogen oxidizes hydrogen to generate moisture to flow oxygen and moisture together to increase oxidation rate. Oxidation methods can be used.

The annealing process proceeds from the oxidation step to a ramp-up step, a purge step and a ramp-down step. This annealing process can be omitted as a selection process and can proceed directly from the oxidation step to the ramp-down step. The ramp-down step proceeds in an atmosphere of 20 [SLM] nitrogen (N ₂ ) until the temperature is about 800 ° C., the unloading temperature, at a rate of 3 to 5 ° C./min. Thereafter, after waiting for a predetermined time at a temperature of 800 ℃ proceeds to the unloading step to release the wafer.

As described above, the present invention makes the temperature at a high temperature of 750 ° C to 850 ° C in the wafer loading step. When the oxide film is formed under such a condition, the decrease in the diffusion length of the minority carriers in the silicon substrate is reduced, which will be described with reference to the following table.

[table]

Wafer loading temperature [℃] Diffusion length before oxide film formation (1 m) diffusion length after oxide film formation (1) m) Diffusion length reduction width X [1] before and after oxide film formation m] 650 552 339 213 ↓ 750 543 354 189 ↓ 800 546 375 171 ↓

[Table] shows the measurement of the minority carrier diffusion length in the silicon substrate using SPV (Surface Photo Voltage) equipment while changing the temperature of the wafer loading step when forming the oxide film.

As can be seen from the above table, when the loading temperature was 600 ° C. as in the prior art, the diffusion length reduction width was the maximum at 213 [SLM]. However, increasing the temperature of the wafer loading step reduced the decrease in the diffusion length. When the temperature of the wafer loading step was 800 ° C., the decrease in diffusion length was the lowest at 171, and when it was at 750 ° C., the reduction in diffusion length was 189.

According to the result of such a measurement value, when the temperature of a wafer loading step is set to 800 degreeC, the spreading | diffusion length reduction width of a minority carrier can be made minimum.

As described above, the present invention can increase the temperature of the wafer loading step when forming the oxide film by thermal oxidation, thereby minimizing the decrease in the minority carrier diffusion length in the silicon substrate, thereby improving the refresh characteristics. There is an excellent effect of improving the reliability of the integrated device by minimizing the degree of contamination of the material generated during the thermal oxidation process.

Claims (2)

A method of forming an oxide film of a semiconductor device by sequentially performing a wafer loading step, a temperature stabilization step, an oxidation step, a ramp-down step and an unloading step, And the oxidation step is performed after setting the temperature of the wafer loading step to 750 to 850 ° C. such that a diffusion length is formed. The method of claim 1, wherein the rate of temperature rise in the ramp-up step is 5 to 10 ° C./min.