JP2000124212A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method with which a semiconductor device having a silicon oxide film, which has superior time-zero dielectric breakdown(TZDB) characteristic and a superior time-dependent dielectric breakdown(TDDB) characteristic, can reduce defects in a semiconductor substrate. SOLUTION: A method for manufacturing a semiconductor device includes a first step of forming a silicon oxide film 13 in an elements-forming region on the surface of a substrate 10, which contains silicon in at least its surface by heat-treating the substrate 10 in an atmosphere containing hydrogen chloride gas in the range of 300-800 deg.C, a second step of removing the silicon oxide film 13 which was formed in the first step in a hydrogen or hydrofluoric acid atmosphere, and a third step of forming another silicon oxide film 14 on the surface of the substrate 10, from which the silicon oxide film 13 is removed at 750 deg.C or higher. By the first step, the TZDB characteristic of a gate oxide film composed of the silicon oxide film 14 is improved by removing metallic impurities M, and the yield of a MOS transistor is improved. With the second step, the dried oxide film 1, which is considered normally to have poor quality and adheres to the substrate 10 at a low temperature, is removed. With the third step, in addition, the silicon oxide film 14 which can be maintained in a highly reliable state over a long period can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming a silicon oxide film on a surface of a silicon substrate which is preferably used as a gate insulating film of a MOS transistor.

[0002]

2. Description of the Related Art In manufacturing a MOS semiconductor device, it is necessary to form a gate insulating film made of a silicon oxide film or another insulating material on a semiconductor substrate. As this kind of gate insulating film, for example, there is a silicon oxide film, and as a method of forming the silicon oxide film, a dry oxidation method and a humidification oxidation method can be given. The dry oxidation method is a method of forming a silicon oxide film on the surface of a silicon substrate by supplying sufficiently dried high-purity oxygen to a heated silicon substrate. In addition, the humidification oxidation method is a method of forming a silicon oxide film on the surface of a silicon substrate by supplying a high-temperature gas containing water vapor to the silicon substrate. In particular, as one of the dry oxidation methods, HCl, Cl ₂ , C
Cl ₄ , C ₂ HCl ₃ , CH ₂ Cl ₂ , C ₂ H ₃ Cl ₃
There is a method of forming a silicon oxide film by adding a compound containing chlorine or another halogen element, such as, to an oxygen atmosphere. This formation method is called a hydrochloric acid oxidation method. (A) Time-Zero breakdown (Time-Zero) by removing heavy metal contaminants such as iron and cobalt in a silicon oxide film.
Improvement of Dielectric Breakdown (TZDB) characteristics, (B)
There are effective points such as neutralization or gettering of alkali metal impurities in the silicon oxide film and (C) reduction of stacking faults. Among them, the most expected of the hydrochloric acid oxidation method is generally the advantage (A). This is because the time zero dielectric breakdown (TZDB) characteristic of the silicon oxide film is an index directly related to the yield. Further, as the device becomes finer, the gate insulating film needs to be made thinner. However, when the device is made thinner, it is generally more susceptible to heavy metal contamination. Therefore, expectations for the hydrochloric acid oxidation method are increasing year by year.

[0003]

As an index of long-term reliability of a gate insulating film, in addition to the above-mentioned TZDB characteristics, a time-dependent dielectric breakdown (Time Dependent Dielectric Breakdown) is used.
kdown: TDDB) characteristic. This aging dielectric breakdown
This is a phenomenon in which the gate insulating film does not break down at the moment when a current stress or a voltage stress is applied, but dielectric breakdown occurs in a gate insulating film after a certain time has passed after the stress is applied. So this T
Comparing the respective oxidation methods with respect to the DDB characteristic and the TZDB characteristic, the silicon oxide film formed by the humidification oxidation method has better TDDB characteristics than the silicon oxide film formed by the dry oxidation method. That is, it can be said that the silicon oxide film formed by the humidification oxidation method has higher long-term reliability. It is said that this is due to minute crystal defects existing in the dry oxide film. It is considered that this defect distorts the electric field distribution and locally intensifies the current, thereby deteriorating long-term reliability. However, the silicon oxide film formed by this humidification oxidation method has a T
There is a problem that the ZDB characteristic is lower than that of the silicon oxide film formed by the hydrochloric acid oxidation method. On the other hand, the hydrochloric acid oxidation method, which is one type of the dry oxidation method, contributes to the improvement of the TZDB characteristics, but has a problem that the TDDB characteristics cannot be improved. In addition, this hydrochloric acid oxidation method has a problem that it is difficult to control an apparatus and conditions for forming an oxide film, and it is difficult to form a high-quality silicon oxide film with good reproducibility.

To solve this problem, a method of forming a silicon oxide film by combining a humidifying oxidation method and a hydrochloric acid oxidation method is disclosed in, for example, Japanese Patent Application Laid-Open No. 8-279502. This silicon oxide film forming method is characterized in that after a silicon oxide film is formed by a humidifying oxidation method, a heat treatment is performed in an inert gas atmosphere containing a halogen element.
However, in this method, since the heat treatment with the halogen element is performed after the formation of the silicon oxide film, there is a problem that the effect of removing heavy metal contamination attached to the silicon substrate in the step before the formation of the silicon oxide film is weak. Moreover, in general, heavy metal impurities are more likely to adhere before the formation of the silicon oxide film than during the formation of the silicon oxide film or after the formation of the silicon oxide film. Therefore, the attached heavy metal contaminants may remain, and it is considered that the TZDB characteristics are not sufficiently improved.

In a September 1995 issue of the US Micro Magazine, there is a report describing oxidation pretreatment with hydrogen chloride (HCl) and dichloroethylene (C ₂ H ₂ Cl ₂ ) before oxidation. According to this method, heavy metal contamination can be efficiently removed at a low temperature of about 600 degrees. However, it is also described that in this method, an oxide film of about 15 Å is formed by the pretreatment. It is known that an oxide film formed at a low temperature generally deteriorates the TDDB characteristics of the oxide film.

As described above, it is difficult to form a silicon oxide film as a gate insulating film that can satisfy both TZDB characteristics and TDDB characteristics by the conventional dry oxidation method or humidification oxidation method. Therefore, an object of the present invention is to provide a method for forming a silicon oxide film which is excellent in TZDB characteristics and TDDB characteristics and can reduce defects included in a semiconductor substrate in a region where a gate insulating film is formed, and a semiconductor including such a silicon oxide film. It is intended to provide a method of manufacturing the device.

[0007]

According to the method of manufacturing a semiconductor device of the present invention, in particular, the method of forming a silicon oxide film as a gate insulating film, a substrate having at least a surface of silicon is coated on a substrate.
A first step of forming a silicon oxide film on the surface of the substrate by heat treatment in an atmosphere containing hydrogen chloride gas at a temperature in the range of 00 to 800 degrees, and a first step in a hydrogen or hydrofluoric acid atmosphere Second to remove the deposited silicon oxide film
And a third step of forming a silicon oxide film at a temperature of 750 ° C. or more on the surface of the substrate from which the silicon oxide film has been removed.

According to the present invention, metal impurities are removed by the first step of performing heat treatment of a silicon semiconductor substrate by generating hydrogen chloride and oxygen. Thereby, the TZDB characteristic of the gate oxide film is improved, and the yield of the MOS transistor is improved. Next, in a second step of removing the silicon oxide film adhered during the pretreatment, the dry oxide film adhered at a low temperature, which is generally considered to be poor in film quality, is removed. Further, the third step of forming an oxide film having a desired film quality and thickness at a high temperature makes it possible to form a gate oxide film having excellent long-term reliability.

[0009]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing an embodiment in which the present invention is applied to a method for manufacturing a MOS transistor, particularly an embodiment in which a method for forming a silicon oxide film according to the present invention is applied to a gate insulating film of a MOS transistor. First, as shown in FIG. 1A, a silicon nitride film 11 as an oxidation-resistant film is selectively formed on the surface of a silicon substrate 10, and the silicon oxide film is used as a mask by a so-called LOCOS (selective oxidation) method. The surface of the silicon substrate 10 is selectively oxidized to form an element isolation oxide film 12 made of a thick silicon oxide film. The element isolation oxide film 12 defines an element formation region where a capacitor or a transistor is to be formed. Thereafter, the silicon nitride film 11 is removed.

Next, as shown in FIG. 1B, after washing with an acid-based aqueous solution, a silicon oxide film 13 is formed on the surface of the silicon substrate 10 in the element formation region. In addition,
FIG. 2 is a diagram in which the temperature-time characteristics in the subsequent processing and the processing gas at that time are shown in a diagram, and will be described with reference to FIG. That is, as shown in FIG. 1B, the silicon substrate 10 is put on a quartz boat (not shown) and carried into a furnace of a vertical diffusion device. The inside of the furnace is at normal pressure and 300 ° C. Then, the inside of the furnace is heated at 100 ° C. per minute in an atmosphere of 5 liters of oxygen per minute and 15 liters of nitrogen per minute, and the inside of the furnace is heated to 700 ° C. Next, hydrogen chloride and oxygen are introduced into the furnace, and a temperature in the range of 300 to 800 ° C, here 700 ° C,
Pre-oxidize for 30 minutes. Here, the flow rate of hydrogen chloride is 0.5 liter per minute, and the flow rate of oxygen is 5 liter per minute. By this processing, a silicon oxide film 13 having a thickness of about 15 ° is formed on the surface of the silicon substrate 10.

Then, as shown in FIG. 1 (c), the inside of the furnace was purged with nitrogen at 20 liters per minute for 5 minutes, the temperature of the furnace was raised to 800 ° C., and hydrogen was introduced into the furnace every minute. Reduction is performed by flowing 5 liters for 10 minutes to remove the silicon oxide film 13 formed on the surface of the silicon substrate in the previous step.
Subsequently, as shown in FIG.
Purging at a flow rate of 20 liters per minute for 20 minutes, then keeping the inside of the furnace at a high temperature of 750 ° C. or more, here 800 ° C., by pyrogenic method, into the furnace by 10 liters of oxygen and 10 liters per minute. Of hydrogen, ie, water vapor, and a 40 ° silicon oxide film 14 is formed on the surface of the silicon substrate 10 by humidification and oxidation. Thereafter, the temperature in the furnace is lowered to about 300 ° C. at −50 ° C./min while supplying 20 liters of nitrogen per minute to complete the formation of the silicon oxide film 14.

Thereafter, as shown in FIG. 1E, a gate electrode 15 is selectively formed on the silicon oxide film 14,
The source and drain regions 16 are formed by ion-implanting impurities into the silicon substrate 10, an interlayer insulating film 17 is formed, a contact hole is opened, and a contact electrode 18 is formed. A MOS transistor using oxide film 14 as a gate insulating film is formed.

As described above, in the manufacturing method of the above-described embodiment, in the step of FIG. 1B, the silicon oxide film 13 is formed in an atmosphere of hydrogen chloride and oxygen, so that the metal impurity on the surface of the silicon substrate 10 is formed. M is a silicon oxide film 1
3 and is removed together with the silicon oxide film 13 in the step of FIG. Thereby, the TZDB characteristics of the gate insulating film made of the silicon oxide film 14 formed on the surface of the silicon substrate 10 in the subsequent steps are improved, and the yield of the MOS transistors is improved. In the step of FIG. 1C, the silicon oxide film 13 formed in the previous step, that is, the dry oxide film 13 formed at a low temperature, which is generally considered to have poor quality, is removed. In the step (d), by forming the silicon oxide film 14 having a desired film quality and thickness at a high temperature, the amount of metal impurities is extremely small, and at the same time, the number of crystal defects in the oxide film is small. When used as a gate oxide film, it is possible to form a gate oxide film which has both high yield and high reliability and is excellent in long-term reliability.

Here, in the process of the embodiment,
It is preferable that at least the first to third steps are continuously performed in the same furnace.

In the step of FIG. 1B, as a method of supplying hydrogen chloride gas to be supplied into the furnace, hydrogen chloride may be directly supplied by a cylinder, but CCl ₄ and C ₂ H ₂ may be supplied.
Cl ₂ , C ₂ HCl ₃ , CH ₂ Cl ₂ , C ₂ H ₃ Cl ₃
A compound containing chlorine may be reacted with oxygen in a furnace to generate hydrogen chloride. According to this method, there is an advantage that the piping on the upstream side does not corrode because hydrogen chloride is not generated on the upstream side of the apparatus.

In the step of FIG. 1C, hydrogen is used to remove the silicon oxide film formed in the previous step, but hydrofluoric acid vapor may be used instead.
However, in this case, Kiyoei dissolves with hydrofluoric acid vapor,
A quartz jig cannot be used in the furnace, and it is necessary to use a material such as silicon carbide as the jig.

[0017]

As described above, the present invention improves the TZDB characteristics of a gate oxide film by removing metal impurities by a first step of performing heat treatment of a silicon semiconductor substrate by generating hydrogen chloride and oxygen, Improve the yield of MOS transistors. In the second step of removing the silicon oxide film adhered at the time of the pretreatment, the dry oxide film adhered at a low temperature, which is generally considered to be poor in film quality, is removed. Further, the third step of forming an oxide film having a desired film quality and thickness at a high temperature makes it possible to form a silicon oxide film having excellent long-term reliability. As a result, the silicon oxide film formed by the method for manufacturing a semiconductor device of the present invention has very few metal impurities and at the same time has few crystal defects in the oxide film. It is possible to have both high yield and high reliability.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the present invention in the order of steps.

FIG. 2 is a diagram showing a relationship between a temperature-time correlation and a processing gas in the manufacturing process of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Silicon substrate 11 Silicon nitride film 12 Element isolation oxide film 13 Silicon oxide film (dry oxide film) 14 Silicon oxide film (humidified oxide film) 15 Gate electrode 16 Source / drain region 17 Interlayer insulating film 18 Contact electrode

Claims (6)

[Claims] A first step of heat-treating a substrate having at least a surface of silicon in an atmosphere containing hydrogen chloride gas in a temperature range of 300 to 800 ° C. to form a silicon oxide film on the surface of the substrate; A second step of removing the silicon oxide film formed in the first step in a hydrogen or hydrofluoric acid atmosphere, and applying a silicon oxide film at a temperature of 750 ° C. or more on the surface of the substrate from which the silicon oxide film has been removed. Forming a semiconductor device. 2. The semiconductor device according to claim 1, wherein in the third step, the silicon oxide film is formed by a humidifying oxidation method of supplying a high-temperature gas containing water vapor to the surface of the substrate. Production method. 3. The method according to claim 1, wherein in the first step, CCl ₄ , C
₂ H ₂ Cl ₂ , C ₂ HCl ₃ , CH ₂ Cl ₂ , C ₂ H <sub>3
3. The</sub> method according to claim 1, wherein a compound containing chlorine such as Cl.sub.3 is reacted with oxygen to generate the hydrogen chloride gas. 4. The method of manufacturing a semiconductor device according to claim 1, wherein the first to third processes are performed by a rapid heating apparatus of a lamp heating type. 5. The method according to claim 1, wherein the thickness of the silicon oxide film formed in the third step is 40 Å or less. 6. The method according to claim 5, wherein a MOS transistor is manufactured using the silicon oxide film formed in the third step as a gate insulating film.