JP2001250823A - Method and device for forming insulating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a less-contaminated, composition-controlled, and compact insulating film which is suitable for mass production, contains extremely few defects and grain boundaries, and has a superior insulation characteristic and the structure of which is controlled in the depth direction. SOLUTION: A method of forming the insulating film includes a step of supplying gaseous molecules containing Al, Si, Ta, or Ti to the surface of a substrate, after the molecules are adsorbed to the surface, discharging remaining molecules and a step of independently or combinedly supplying gaseous molecules containing at least one kind selected from among O, N, and F to the surface of the substrate, and, after the molecules are adsorbed to the molecules adsorbed to the surface of the substrate in the preceding step, discharging remaining molecules so as to form the insulating film by causing chemical reactions between the molecules adsorbed in the steps.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a thin, high-performance insulating film having high insulation properties and a film forming apparatus therefor. The film forming method and the film forming apparatus can be used in the fields of a gate insulating film for a semiconductor, a capacitor film, a gap layer for a magnetic head, a tunnel GMR (TMR) and an insulating layer for a SQUID.

[0002]

2. Description of the Related Art Conventional gate insulating films for semiconductors, capacitor films, gap layers for magnetic heads, tunnels GMR and S
The insulating layer for QUID and the like has been formed exclusively by sputtering, heat or plasma CVD, or a reaction in an oxidizing atmosphere (O ₂ , H ₂ O, air, etc.) by natural or heating after forming the metal layer.

[0003]

In the field of film formation, the performance has been improved, and at present, an extremely thin and high-performance insulating film of about 20 ° is required. However, in the conventional film forming method, although a high-quality ultra-thin insulating film can be provided by natural oxidation or thermal oxidation in an oxidizing atmosphere of the metal layer, the time required for the reaction is as long as about 24 hours, and the mass production is completely impossible. There was a problem that it was not suitable.

SUMMARY OF THE INVENTION The present invention provides an insulating film which is suitable for mass production, has a small amount of contamination, has a controlled composition, is dense, has very few defects and grain boundaries, has a structure controlled in the depth direction, and has good insulating characteristics. It is an object to provide a method for forming a film and a film forming apparatus for the method.

[0005]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have proposed to replace each of two or more elements constituting an insulating film with at least one kind of gaseous molecules containing these elements. By alternately adsorbing them on the substrate surface, they were alternately stacked at the atomic layer level, and subsequently reacted to form a desired insulating film, thereby completing the present invention. This concerns so-called molecular layer epitaxy.

The method of forming an insulating film according to the present invention comprises the following two main steps.

In the first step, Al, Si, Ta, or T
This is to supply gaseous molecules containing i to the surface of the substrate, adsorb them, and then exhaust excess molecules.

In the second step, gaseous molecules containing at least one selected from O, N, and F are supplied to the substrate surface alone or in combination, and the gaseous molecules are adsorbed in the first step. The remaining molecules are exhausted after being adsorbed on the existing molecules.

A chemical reaction occurs between the molecules adsorbed in the first and second steps, and AlO _x N _y , SiO _x N _y , SiO 2
_{x F z, SiO x N y} F z, TaO x N y, TiO x N y (0 ≦
x, y, z ≦ 2.5) and so on.

In the second step, for example, a plurality of gaseous molecules may be supplied simultaneously, or one or more gaseous molecules may be supplied sequentially and continuously, or supplied / adsorbed.・ After reacting / exhausting, the others may be supplied / adsorbed / reacted / exhausted.

The order of the first step and the second step is not limited, and the second step may be performed after the first step as described above, or vice versa.

The gaseous molecules containing Al, Si, Ta, or Ti are hydrides, fluorides, chlorides,
A metal compound such as bromide, iodide, alkoxide, or alkyl metal is desirable. The gaseous molecules containing at least one selected from the group consisting of O, N and F are O ₂ , O ₃ , H ₂ O, H ₂ O ₂ , N ₂ O, N ₂ , N ₂
Desirably, it is H ₃ , F ₂ , HF, NF ₃ , or ClF ₃ .

The first and second steps are defined as one cycle.
By repeating this, these films grow, and an insulating film having a desired film thickness can be obtained depending on the number of times of the repetition.

If necessary, between each step or each cycle, an inert gas or a reducing gas is introduced and then exhausted, that is, so-called purging is performed, so that the exhaust of the raw material active gas is made more reliable. At the same time, the surface can be cleaned. As for an inert gas or a reducing gas used as a purge gas when exhausting gaseous molecules, for example, He, Ne, Ar, Xe, Kr, or N is used as an inert gas.
There are ₂ gas or the like, there is H ₂ or the like as a reducing gas.

Further, since the amount of adsorption of the source gas changes depending on the substrate temperature, the composition and structure of the obtained insulating film changes. Therefore, if an appropriate substrate temperature range is selected according to the type of a target film, a desired insulating film having high insulating properties can be obtained. For example, as gaseous molecules containing Al,
When H ₂ O is used as a molecule containing Al (CH ₃ ) ₃ and O, as shown in Examples, the substrate temperature is from room temperature to 300 ° C.
Preferably, by keeping the temperature in the range of room temperature to 240 ° C., good insulating properties can be obtained.

According to the present invention, there is provided an insulating film forming apparatus comprising: a process chamber in which a film is formed; a substrate provided below the process chamber; a heating unit for controlling a temperature of the substrate; A film introduction apparatus having a gas introduction system for introducing a gas, and an exhaust system having a high vacuum exhaust pump and a low vacuum exhaust pump for exhausting the process chamber, and an exhaust reservoir tank. Si, Ta,
Or supplying gaseous molecules containing Ti to the substrate surface using the gas introduction system, adsorbing the gaseous molecules, and exhausting the gas using the exhaust system, and removing at least one selected from O, N, and F. Supplying the gaseous molecules containing the gas molecule alone or in combination to the surface of the substrate using the gas introduction system, adsorbing the gas molecules, and exhausting the gas using the exhaust system. It is for.

[0017]

EXAMPLES Next, examples of the present invention will be described, but the present invention is not limited by these examples.

FIG. 1 shows a film forming apparatus used for forming an insulating film in the following embodiments. In FIG. 1, reference numeral 1 denotes a process chamber for forming a film, 2 denotes a substrate provided in the process chamber on which a film is formed, and 3 denotes a hot plate which is a heating means for adjusting the temperature of the substrate 2. By appropriately controlling the gas introduction system including the valve or the mass flow controller 4, the reservoir tank 5, and the mass flow controller 6, the pressure in the process chamber 1 can be increased to a predetermined pressure in a short time. The substrate transfer chamber 7 is connected to the process chamber 1, and the substrate 2 is moved into and out of the process chamber 1 by a robot. Further, an exhaust reservoir tank 8 is provided so as to be connected to the process chamber 1, and by using this tank 8, high-speed exhaust is possible. A cold trap may be provided in the reservoir tank 8. The exhaust in the process chamber 1 is performed by an exhaust system including a reservoir tank 8, a pump 9 for high vacuum exhaust, and a pump 10 for low vacuum. In FIG. 1, the gas removal equipment 11 is connected to the low vacuum pump 10, but this equipment is not required depending on the type of supply gas used.

Embodiment 1 An example in which an insulating film is formed using Al (CH ₃ ) ₃ as a gas containing Al and H ₂ O as a gas containing O will be described. The film forming procedure was performed as shown in "film forming process 1" in the flow sheet of FIG.

That is, as shown in FIG. 2, after performing cleaning, baking and the like on the substrate as a pretreatment, the substrate 2 is loaded from the substrate transfer chamber 7 into the process chamber 1 and the substrate temperature is reduced by the hot plate 3. 120 ° C
After the temperature was adjusted, the film formation was started. The pressure in the process chamber 1 before gas introduction was 1 × 10 ⁻³ Torr.

First, as a first step, Al (CH ₃ ) ₃ was introduced into the process chamber 1 and was adsorbed on the surface of the substrate 2. The introduction pressure and time are each 1 × 10 ⁻¹ Torr
r, 2 sec. Met. After the introduction and adsorption of the gas, the excess Al (CH ₃ ) _{3 is} passed through the reservoir tank 8 to the pump 1.
0, the pump 9 was evacuated to a low vacuum, and the pump 9 was evacuated to a high vacuum.
0 sec. To 5 × 10 ⁻³ Torr. If the pumping speed is high, the reservoir tank 8 becomes unnecessary.

Next, as a _second step, H ₂ O is added to 1 × 1
2 sec. At 0 ^-1 Torr. Then, after adsorbing on the molecules adsorbed in the first step, the gas was exhausted in the same manner as described above. About 50 sec. And exhausted to 5 × 10 ⁻³ Torr.

After repeating the above steps 100 times, the substrate 2 was taken out, and the cross section of the formed film was observed by SEM. As shown in FIG. 3, it was found that the film had grown to about 400 °. As shown in FIG. 3, it can be seen that the hyphenation property at the step portion of the substrate, that is, the step coverage is extremely excellent. The obtained film was analyzed by Auger electron spectroscopy (AES).
_x (x = 1.4 to 1.6), and the film was almost stoichiometric, and impurities such as C were below the detection limit.

Next, in order to evaluate the insulating properties of the film to be formed, the first and second steps were repeated 50 times.
An insulating film of about 200 ° was formed on a conductive Si substrate, and an Al electrode was deposited thereon by 1 mmφ × 5000 ° to prepare a sample. For this, VI characteristics were evaluated, and the results are shown in FIG. As apparent from FIG. 4, when the breakdown voltage is expressed by an electric field strength reaching 10 ⁻⁶ A / cm ² , in this case, it is 5 MV / cm, which indicates that good insulation characteristics are exhibited.

Further, the substrate temperature is changed from room temperature to 300 ° C., and room temperature, 70 ° C., 120 ° C., 180 ° C., 240 ° C.
At each temperature of 300 ° C. and 300 ° C., the above process was repeated 50 times, and the formed film was evaluated for dielectric strength in the same manner as described above. FIG. 5 shows the relationship between the substrate temperature and the insulation resistance, and FIG. 6 shows the relationship between the substrate temperature and the film thickness at this time. As for the insulating properties, good characteristics of 3 MV / cm or more were obtained when the substrate temperature was between room temperature and 240 ° C. The film thickness was almost constant (between 150 ° and 225 °) between room temperature and 180 ° C., but decreased sharply below room temperature, and increased sharply above 180 ° C.

Example 2 The procedure of Example 1 was repeated, except that a step of introducing and exhausting Ar was added after the steps of introducing, adsorbing, and exhausting H ₂ O in Example 1. That is, a film was formed according to the procedure shown in “film formation process 2” in the flow sheet of FIG.

According to this method, the H ₂ O exhaust time can be reduced. H ₂ O at 1 × 10 ⁻¹ Torr
2 sec. For 10 sec. During the evacuation, the air could be exhausted to 5 × 10 ^-2 Torr.
Next, Ar was added at 1 × 10 ⁻¹ Torr for 2 sec. When the gas was introduced for 10 seconds and exhausted. Between 5 × 10 ^-3 To
It was able to exhaust to rr. Therefore, by using Ar, the evacuation time could be reduced to about 1/2 or less. As is clear from FIG. 5, the insulation characteristics were the same as in Example 1.

Example 3 O ₃ was introduced in place of H ₂ O used in Example 1, and the steps of Example 1 were repeated to form a film in the same manner as in Example 1. As is clear from FIG.
Was the same as

[Brief description of the drawings]

FIG. 1 is a schematic side view of an embodiment of a film forming apparatus according to the present invention.

FIG. 2 is a flow sheet for explaining an embodiment of a film forming method according to the present invention.

FIG. 3 is a cross-sectional view showing a film formation state of an insulating film obtained based on the embodiment of the present invention.

FIG. 4 is a graph showing VI characteristics of an insulating film obtained based on an example of the present invention.

FIG. 5 is a graph showing the substrate temperature dependence of the dielectric strength of the insulating film obtained based on the embodiment of the present invention.

FIG. 6 is a graph showing a relationship between a substrate temperature and a film thickness of an insulating film obtained based on an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Process room 2 Substrate 3 Hot plate 4, 5, 6 Gas supply system 7 Substrate transfer room 8 Reservoir tank 9 High vacuum pump 10 Low vacuum pump 11 Detoxification device

Continued on the front page (72) Inventor Yasuhiro Taguma 523 Yokota, Yamatake-cho, Yamatake-gun, Chiba Japan Nippon Vacuum Engineering Co., Ltd. (72) Inventor Yasushi Higuchi 523 Yokota, Yamatake-cho, Yamatake-gun, Chiba Japan Nippon Vacuum Technology Co., Ltd. (72) Inventor Takeshi Sahoda 523, Yamatake-cho, Yamatake-gun, Chiba Prefecture Japan Vacuum Engineering Co., Ltd. (72) Inventor Satoshi Ikeda 523 Yokota, Yamatake-cho, Yamatake-gun, Chiba Japan Vacuum Engineering (72) Inventor Kabun Ota 523 Yokota, Yamatake-cho, Sanmu-gun, Chiba Prefecture Japan Vacuum Engineering Co., Ltd. (72) Nobuaki Seki 2500, Hagizono, Chigasaki-shi, Kanagawa Japan Vacuum Technology Co., Ltd. (72) Inventor Hisazo Nakamura 2500 Hagizono, Chigasaki-shi, Kanagawa Japan F-term (reference) 5F045 AA06 AA15 AB31 AB34 AC02 AC08 AC11 AC12 AD04 AD05 AD06 AD07 BB04 BB16 BB17 EB08 EB13 EE14 EG01 EG03 EG05 EG08 EN04 5F058 BA06 BC11 BC20 BE01 BF04 BF24 BF27 BF29 BF30 BF34 BF37 BG02

Claims (9)

[Claims] A step of supplying gaseous molecules containing Al, Si, Ta, or Ti to the surface of the substrate, adsorbing the gaseous molecules, and exhausting the gaseous molecules; Supplying the molecules alone or in combination to the surface of the substrate, adsorbing the molecules, and exhausting the molecules. 2. The method according to claim 1, wherein the gaseous molecule containing Al, Si, Ta, or Ti is a hydride, fluoride, chloride, bromide, iodide, alkoxide, or alkyl metal of the metal. A method for forming an insulating film. 3. The gaseous molecule containing at least one kind selected from O, N and F is O ₂ , O ₃ , H ₂ O, H
₂ O ₂ , N ₂ O, N ₂ , NH ₃ , F ₂ , HF, NF ₃ , or C
The method for forming an insulating film according to claim 1, wherein the method is 1F ₃ . 4. The method for forming an insulating film according to claim 1, wherein the temperature of the substrate is kept in a range from room temperature to 300 ° C. 5. The method for forming an insulating film according to claim 1, wherein an inert gas or a reducing gas is used as a purge gas when the gaseous molecules are exhausted. 6. The inert gas is He, Ne, Ar, X
e, Kr, or a N _2, deposition method of the insulating film of claim 5, wherein said reducing gas is H _2. 7. The method according to claim 1, wherein the step of supplying gaseous molecules containing Al, Si, Ta, or Ti to the surface of the substrate, adsorbing the gaseous molecules, and exhausting the gaseous molecules is performed first. 3. The method for forming an insulating film according to item 1. 8. The method according to claim 1, wherein the step of supplying gaseous molecules containing at least one selected from O, N and F to the surface of the substrate, adsorbing the gaseous molecules, and exhausting the gaseous molecules is performed first.
7. The method for forming an insulating film according to any one of items 1 to 6. 9. A process chamber for forming a film, a substrate provided below the process chamber, a heating unit for adjusting a temperature of the substrate, and a gas introduction system for introducing a source gas into the process chamber. And an exhaust system having a high-vacuum pump and a low-vacuum pump and an exhaust reservoir tank for evacuating the process chamber, wherein the insulating film is formed of Al, Si, Ta, or Supplying a gaseous molecule containing Ti to the substrate surface using the gas introduction system, adsorbing the gaseous molecule, and exhausting the gas using the exhaust system, and at least one selected from O, N and F Supplying the gaseous molecules alone or in combination to the substrate surface using the gas introduction system, adsorbing the gaseous molecules, and exhausting the gas using the exhaust system. Of the insulating film Deposition equipment for