JPH05152288A - Manufacture of semiconductor device and manufacturing device of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a method for improving oxidation velocity of a silicon nitride film and for forming a thick silicon oxide film on the silicon nitride film and a method and a device for forming a good oxide film of low interface level density on a silicon substrate. CONSTITUTION:In a semiconductor volume insulating film constituted of a silicon nitride film 6/a silicon oxide film 8, the silicon nitride film 6 is oxidized at 750 to 1200 deg.C with ozone of 2 to 20% added to an oxidizer; thereby, an upper silicon oxide film 8 of a specified film thickness can be acquired at a low temperature in a short time. A good gate oxide film of low interface level density is provided by thermally oxidizing a silicon substrate in an ozone-added oxidizing atmosphere.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitive insulating film for DRAM (Dynamic Random Access Memory), EEPR.
OM (Electrically Erasable and Programmable Read Only Memory) tunnel insulation film and control gate insulation film, EPROM (Electrically Programmable Read Only Memory) and FPGA
The present invention relates to a method and an apparatus for manufacturing a semiconductor device having an antifuse insulating film of (field programmable gate array) and a gate insulating film of a MOS device.

[0002]

2. Description of the Related Art While the area of a capacitance insulating film constituting a memory cell is reduced due to high integration of a memory device, especially a DRAM, a film having a high dielectric constant and high reliability is required for the capacitance insulating film. The structure of the device has been three-dimensionally advanced from the conventionally used flat plate type capacitor to the groove type and laminated type capacitors, and further to the groove type laminated capacitor. For this reason, it has become difficult to secure sufficient capacitance and reliability with a silicon oxide film that has been conventionally used as a flat-plate capacitance insulating film. Therefore, recently, a silicon nitride film having a dielectric constant about twice that of a silicon oxide film has been attracting attention. However, although the silicon nitride film itself has a high dielectric constant, the leak current flowing through the film is large, and many defects are present in the silicon nitride film, and there are still problems with insulation properties and reliability. Therefore, the silicon nitride film is not used alone, but the so-called ONO3 layer film of silicon oxide film / silicon nitride film / silicon oxide film or the so-called ON of silicon nitride film / silicon oxide film.
It is generally used as a composite film such as a two-layer film. In this step, the lower oxide film is generally formed by ordinary thermal oxidation, and the intermediate silicon nitride film is generally formed by the low pressure chemical vapor deposition method. In addition, 900 silicon is generally used for forming a silicon oxide film on a silicon nitride film.
Thermal oxidation in a dry oxygen atmosphere or steam atmosphere at ˜1100 ° C. has been used. It is known that the film thickness and film quality of the silicon oxide film on the silicon nitride film have a great influence on the electrical characteristics and dielectric breakdown reliability of these composite oxide films.

FIG. 8 shows the relationship between the film thickness of the silicon oxide film on the silicon nitride film and the leak current flowing through the composite film. If the silicon oxide film on the silicon nitride film is thin,
Since the injection of holes from the upper electrode cannot be blocked, the leak current increases. As the upper silicon oxide film becomes thicker,
Leakage current is reduced. On the other hand, FIG. 9 shows the relationship between the upper silicon oxide film thickness and the capacity and reliability. The capacity decreases as the thickness of the upper oxide film increases, but the reliability has an extreme value. That is, the leakage current of FIG. 8 and the leakage current of FIG.
There is a trade-off between the capacity and reliability of the. Here, let us consider thermal oxidation in a dry oxygen atmosphere which is generally used conventionally. When thermal oxidation is performed on the silicon nitride film at 900 ° C. for 30 minutes in a dry oxygen atmosphere, a silicon oxide film of about 0.8 nm grows. At this time, a 13 nm silicon oxide film is grown on the silicon substrate under the same conditions. In such an upper oxide film, the leakage current cannot be sufficiently suppressed, and although the capacitance is slightly large, the reliability is not satisfactory. On the other hand, in order to obtain the oxide film thickness, the oxidation time is set to 9
Even when the distance is extended to zero, the thickness of the silicon oxide film on the silicon nitride film is about 1.1 nm and hardly increases. At this time, the silicon oxide film thickness on the silicon substrate was 25 nm, and the oxidation rate on the silicon oxide film was not reflected at all on the silicon nitride film. Therefore, in thermal oxidation in dry oxygen, it is very difficult to obtain the optimum upper oxide film thickness which maximizes the reliability shown in FIG. 9, even if the oxidation time is extended. This is because the oxidation mechanism of the silicon nitride film is controlled by the diffusion rate of oxygen molecules in a dry oxygen atmosphere, and the diffusion rate of oxygen molecules is sufficiently slow in the silicon nitride film. Therefore, in order to improve the diffusion rate of oxygen molecules, oxidation at high temperature is effective, but in this case, the amount of heat treatment is the product of temperature and time. It is impractical because it is totally unacceptable for integrated devices.

It is well known that in an oxide film on a silicon substrate, dangling bonds (broken bonds) existing near the interface between silicon and the silicon oxide film adversely affect the electrical characteristics of the silicon oxide film. ing. In order to prevent this dangling bond, oxidation in a hydrogen-free oxidizing atmosphere and in a dry oxygen atmosphere at a high temperature in order to increase reactivity and prevent unbonding are promising. However, even in this case, the amount of heat treatment is increased, which is not a practical solution for a highly integrated device.

In order to grow a relatively thick silicon oxide film on the silicon nitride film, it is sufficient to efficiently supply the oxidizer to the silicon nitride film / silicon oxide film interface through the silicon nitride film. For this purpose, an oxidizer having a high diffusion rate in the silicon nitride film may be used. That is, if oxidizer is OH by steam oxidation or the like, a higher diffusion rate can be obtained.

[0006]

However, in the above conventional structure, in the case of heat treatment at a high temperature for a long time, or in the case of steam oxidation, residual hydrogen or the like adversely affects the electrical characteristics of the capacitive insulating film, resulting in a leakage current. There is a problem of getting bigger.

An object of the present invention is to solve the above problems, and an object thereof is to provide a method and an apparatus for manufacturing a semiconductor device having an insulating film having a low interface state density and a low trap density.

[0008]

To achieve the above object, the first aspect of the present invention is to provide a semiconductor substrate having at least a silicon nitride film formed thereon in an oxidizing atmosphere containing oxygen and 2 to 20% of ozone. 8. A structure having at least a step of forming a silicon oxide film on the silicon nitride film by performing heat treatment in a temperature range of 750 to 1200 ° C.
Comprises a chamber provided with a lamp heating section, an ozone generating section, and an ozone introducing nozzle for efficiently and evenly feeding the ozone from the ozone generating section into the chamber.

[0009]

With the above structure, the diffusion rate of the oxidant inside the silicon nitride film is significantly increased as compared with the conventional thermal oxidation using dry oxygen, which is lower in temperature and shorter than the conventional method using dry oxygen as the oxidant. A silicon oxide film having a predetermined film thickness can be formed on the silicon nitride film in a certain period of time, and thus formed of silicon oxide film / silicon nitride film / silicon oxide film or silicon nitride film / silicon oxide film. Low leakage current, large capacity and high reliability can be easily realized with the semiconductor capacitor using the composite insulating film, and the capacitor insulating film of high-performance highly integrated DRAM, tunnel insulating film of EEPROM and antifuse of control gate insulating film FPGA. An insulating film can be formed. Further, by using the oxidation method as in the present invention to form a silicon oxide film on a silicon substrate or a polycrystalline silicon substrate, a high quality silicon oxide film with few unbonded portions at the silicon substrate / silicon oxide film interface can be easily formed. It can be formed and is very effective as a gate oxide film of a highly integrated MOS device.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. 1 showing a method of manufacturing a semiconductor device having a capacitive insulating film of DRAM. First, as shown in FIG. 1A, a P-type well 2 is formed on a P-type silicon substrate 1, and an N-type high-concentration diffusion layer connected to a separation region 3 and a selection transistor is further provided in the P-type well 2. on 4, the lower polycrystalline silicon film 5 containing phosphorus atoms 3 × 10 ²⁰ / cm ² to 400nm is deposited by low pressure chemical vapor deposition method where a known technique, which is the lower electrode of the capacitor. Next, as shown in FIG. 1B, a silicon nitride film 6 is deposited to a thickness of 11 nm on the lower polycrystalline silicon film 5 by a known low pressure chemical vapor deposition method. Strictly speaking, in this step, about 2 to 3 n is formed on the lower polycrystalline silicon film 5.
Since the m natural oxide film 7 grows, a two-layer structure of silicon oxide film / silicon nitride film is already formed at this point. Subsequently, as shown in FIG. 1C, a temperature of 900 ° C. for oxidizing the silicon nitride film 6 and a dry oxygen flow rate of 8 per minute.
Thermal oxidation is performed for 60 minutes at a flow rate of 400 cc / min for liter and ozone. As a result, about 2.6 nm is formed on the silicon nitride film 6.
A silicon oxide film 8 having a film thickness of is formed. Then, FIG.
As shown in (d), the upper polycrystalline silicon film 9 containing 3 × 10 ²⁰ / cm ² of phosphorus atoms is again formed by the low pressure chemical vapor deposition method.
00 nm is deposited, and this is used as an upper electrode. This allows
A natural oxide film 7, a silicon nitride film 6 and a silicon oxide film 8 are formed between a lower polycrystalline silicon film 5 electrically connected to the source electrode of the select transistor 10 and an upper polycrystalline silicon film 9 which is a cell plate. A semiconductor capacitor is formed via the composite capacitor insulating film. In order to oxidize the silicon nitride film 6, a horizontal or vertical hot wall type electric furnace is usually used. Such an electric furnace has a large heat capacity, a long gas introduction pipe, and a further process. Since the gas is exposed to a high temperature after the gas is introduced into the tube, it is difficult to efficiently and uniformly convey ozone to the wafer surface. Therefore, in this example, a special ozone heat treatment apparatus as shown in FIG. 2 was used. 11 is a halogen lamp heating unit, 1
2 is an ozone generator, 13 is an introduction nozzle capable of efficiently feeding ozone into the chamber, 14 is a reflector,
15 is Quartz Wound, 16 is a silicon wafer, 1
7 is a quartz pin, 18 is an exhaust port, 19 is a radiation temperature type, 20
Is the platen. Usually, this device is a single-wafer type and can raise the temperature from room temperature to 900 ° C. in a few seconds. FIG. 3 is an enlarged detailed view of the introduction nozzle of FIG.
Is a gas piping system diagram used in the ozone heat treatment apparatus of FIG.
The same parts as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted.
21 is a pump, 22 is a reaction chamber, and 23 is a lamp house. FIG. 5 shows a processing sequence in the ozone heat treatment of FIG. After the cycle purge, exposure to ozone at room temperature realizes effective supply of ozone. Normally, the ozone heat treatment apparatus as shown in FIG. 2 has complete atmosphere control and water can be easily removed from the chamber, so that the influence of hydrogen is small and ozone can be supplied safely. Further, since the supplied ozone is rapidly heated and decomposed on the wafer surface, the loss during the transportation of ozone is small and the ozone can be effectively transported to the wafer surface and can contribute to the reaction on the wafer surface effectively. . Further, since the present apparatus is a single-wafer type, the throughput is remarkably reduced under the conditions of the present embodiment, but the oxidation temperature is 1100 ° C to 1150 ° C.
The processing time per sheet is 30 seconds to 60
It is about a second, and the throughput can be improved. In addition, since this apparatus uses a lamp as a heat source, the rate of temperature rise and temperature drop is significantly faster than that of the conventional electric furnace, and there is no problem in the amount of heat treatment in the above high temperature treatment. Needless to say, the present apparatus is effective not only for oxidizing the silicon nitride film 6 as in this embodiment but also for forming a silicon oxide film on a general silicon substrate and a polycrystalline silicon substrate.

FIG. 6 shows a silicon oxide film / silicon nitride film / silicon oxide film (3.0 / 11.0 / 2.6n) formed by the ozone heat treatment apparatus of FIG. 2 based on the embodiment of FIG.
m) and a conventional silicon oxide film / silicon nitride film / silicon oxide film (3.0 / 11) having an oxide film on a silicon nitride film formed at 900 ° C. in dry oxygen for 90 minutes at an oxidation flow rate of 8 liters / min. It shows a leakage current characteristic of 0.0 / 1.1 nm). In the conventional method, a sufficient silicon oxide film thickness cannot be obtained on the silicon nitride film and the leak current is large, whereas in the present embodiment, a sufficiently low leak current is achieved. In FIG. 7, the horizontal axis represents the stress voltage and the vertical axis represents the life until dielectric breakdown, and the data of the conventional example and this example are plotted. From FIG. 7, the life of the insulating film of this embodiment has a large dependence (large slope) on the voltage. Therefore, the result of the high electric field such as the measurement range of FIG. 7 is extrapolated to the low electric field which is normally used. In this case, the life of the insulating film is significantly longer than that of the conventional method, and it can be seen that a highly reliable insulating film can be formed.

In the present embodiment, the ozone addition oxidation under normal pressure was shown, but by performing this oxidation under a high pressure of 2 to 500 atm, the treatment temperature can be further lowered and the treatment time can be shortened. Needless to say. in this case,
Even in the apparatus as shown in FIG. 2, processing under high pressure is possible. Further, the oxidation rate is further improved by adding 1-1-1 trichloroethane and 1-1-2 trichloroethane in addition to ozone. These effects are not limited to the capacitance insulating film of DRAM, but are applicable to a semiconductor device manufacturing process using oxidation of a silicon nitride film, a silicon substrate having a silicon substrate and a polycrystalline silicon film formed, or a semiconductor device including oxidation of a polycrystalline silicon substrate. It can be applied to manufacturing processes and the like. Needless to say, a conventional electric furnace can be used as an ozone heat treatment apparatus, although the efficiency is low.

[0013]

As is apparent from the above examples, according to the present invention, a semiconductor substrate on which at least a silicon nitride film is formed is heated at a temperature of 750 to 1200 ° C. in an oxidizing atmosphere containing oxygen and 2 to 20% of ozone. Since the structure has at least a step of forming a silicon oxide film on the silicon nitride film by heat treatment in a range, a silicon oxide film having a predetermined thickness can be obtained on the silicon nitride film at low temperature and in a short time. By applying the present invention to the upper oxidation of a film-type composite insulating film, a semiconductor capacitor with low leakage current and high reliability can be easily realized, and a capacitor insulating film of DRAM,
It is possible to provide a semiconductor device having a high-quality insulating film as a tunnel insulating film of a EEPROM, a control gate insulating film, and an antifuse insulating film of an FPGA, and at the same time, the present invention can be applied to the oxidation of general semiconductor substrates and polycrystalline semiconductor substrates. By using it, it is possible to provide a semiconductor device having a very high quality oxide film as a gate oxide film having a low interface state density and a low trap density.

[Brief description of drawings]

FIG. 1 is a process sectional view showing a method for manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a semiconductor manufacturing apparatus used in the method of manufacturing the semiconductor substrate of FIG.

3 is an enlarged perspective view of an ozone introduction nozzle portion of the semiconductor manufacturing apparatus of FIG.

FIG. 4 is a gas piping system diagram used in the semiconductor manufacturing apparatus of FIG.

5 is a diagram showing an ozone heat treatment sequence using the semiconductor manufacturing apparatus of FIG.

FIG. 6 is a characteristic diagram of leakage current with respect to applied voltage of the composite insulating film of the semiconductor device according to the present invention in FIG.

7 is a graph showing the relationship between the stress voltage and the life of the composite insulating film of the semiconductor device according to the present invention in FIG.

FIG. 8 is a diagram showing a relationship between a thickness of an upper silicon oxide film on a silicon nitride film of a conventional semiconductor device and a leak current.

FIG. 9 is a diagram showing a relationship between an upper silicon oxide film on a silicon nitride film of a conventional semiconductor device and reliability and capacitance.

[Explanation of symbols]

 1 P-type silicon substrate (semiconductor substrate) 2 P-type well 3 Isolation region 4 N-type high-concentration diffusion layer 5 Lower polycrystalline silicon film 6 Silicon nitride film 7 Natural oxide film 8 Silicon oxide film 9 Upper polycrystalline silicon film 10 Select transistor

Claims (7)

[Claims] 1. A semiconductor substrate having at least a silicon nitride film formed thereon is heat-treated at a temperature range of 750 to 1200 ° C. in an oxidizing atmosphere containing oxygen and 2 to 20% of ozone,
A method of manufacturing a semiconductor device, comprising at least a step of forming a silicon oxide film on the silicon nitride film. 2. A semiconductor device according to claim 1, wherein a semiconductor substrate having at least a silicon nitride film formed thereon is replaced with a semiconductor substrate having at least a silicon nitride film which is one of capacitive insulating films. Production method. 3. The semiconductor device according to claim 1, wherein a semiconductor substrate, a semiconductor substrate having a polycrystalline silicon film formed thereon, or a polycrystalline semiconductor substrate is used in place of the semiconductor substrate having at least a silicon nitride film formed thereon. Production method. 4. The method of manufacturing a semiconductor device according to claim 1, wherein the oxidizing atmosphere is an oxidizing atmosphere of 2 to 500 atm. 5. The method of manufacturing a semiconductor device according to claim 1, 2 or 3, wherein the oxidizing atmosphere further contains water vapor. 6. The method of manufacturing a semiconductor device according to claim 1, wherein the oxidizing atmosphere further contains 1-1-1 trichloroethane and 1-1-2 trichloroethane. 7. A chamber having a lamp heating section, an ozone generating section, and an ozone introducing nozzle for efficiently and evenly feeding ozone from the ozone generating section into the chamber. Semiconductor device manufacturing equipment.