JP3186872B2 - Film forming method by pulse plasma CVD - Google Patents

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 high-quality thin film on a surface of an object by pulse plasma CVD.

[0002]

2. Description of the Related Art Plasma CVD is widely used as a chemical vapor deposition method for forming a film on the surface of an object to be processed. In this plasma CVD method, gas supply and power supply are performed continuously, and the density of plasma energy per area is important. However, the decomposition of the supplied gas is not sufficient with the plasma energy alone, but also depends on the heat of the substrate to be heated. At present, plasma CVD is performed at a film forming temperature of 300 ° C. or higher. However, a substrate such as an alloy tool steel having a film formed at such a temperature becomes dull and decreases in hardness, and is subjected to cold treatment. It cannot be used as a metal mold. Therefore, such applications require a coating temperature of 200 ° C. or less. On the other hand, when trying to obtain a high quality film of TiN as the film forming composition, 500
Since a film formation temperature of not less than ° C. is required, there is a problem that a substrate material to be used is limited.

[0003] A pulse plasma CVD method has also been disclosed in some parts. In this method, an object to be processed and an electrode to which high-frequency power is supplied are arranged at an interval in a reaction chamber, and the reaction chamber is evacuated. , A plurality of reaction gases are introduced, and high-frequency power is intermittently supplied to the electrodes, and the high-frequency power dissociates each reaction gas into its constituent atoms to generate plasma, and these atoms are processed. It forms a thin film by a chemical reaction on an object.

In this method, the ratio of the supply time and the rest time is about 1: 1 to 1: 5 with low power, and gas species are mixed or supplied alternately. Further, in order to increase the plasma energy density, a pulsed plasma C using large power is used.
In the VD method, gas is supplied in a pulsed manner, and high-frequency power is supplied in a pulsed form when the gas is sufficiently diffused into the reaction chamber. In this method, in one cycle, a source gas and a discharge gas are simultaneously supplied, and thereafter, electric power is supplied in a pulse form, then a reaction gas is supplied, and further, electric power is supplied in a pulse form.

[0005]

However, in the above method, the supplied source gas is not heated, and the supplied source gas condenses and adheres to the wall of the reaction chamber. There is a problem that it is difficult to completely decompose, and therefore, undecomposed elements remain in the film and a high-quality film cannot be obtained.

[0006] In view of the above, the inventors of the present invention have an object to provide a film forming method capable of obtaining a good film without leaving undecomposed elements even at a low film forming temperature.

[0007]

That is, according to the first aspect of the present invention, a raw material gas for film formation is introduced into an exhausted and heated reaction chamber.
The discharge gas and the raw material decomposition gas are intermittently introduced while being separately controlled, and a high-frequency power is supplied in a pulsed manner to form a film on the surface of the object to be processed in the reaction chamber by pulsed plasma CVD. In the film forming process, a discharge gas,
A method for forming a film by pulsed plasma CVD comprising supplying a raw material decomposition gas and a high-frequency electric power a plurality of times. The second invention provides a film forming raw material gas and a discharge gas in an exhausted and heated reaction chamber. And controlling the gas for raw material decomposition separately while intermittently introducing them, and supplying high frequency power in a pulsed manner to form a compound film on the surface of the object to be processed in the reaction chamber by pulsed plasma CVD.
In the film forming process, several kinds of film forming source gases constituting the compound thin film are separately and stepwise supplied to the reaction chamber,
Another object of the present invention is to provide a film forming method by pulse plasma CVD characterized by supplying another discharge gas, material decomposition gas and high frequency power every time the film forming material gas is supplied.

[0008]

In a method of forming a film by plasma CVD, a compound is often used as a raw material gas for film formation, but it is very difficult to completely decompose the compound in a reaction chamber. Undecomposed elements remain in the formed thin film, and it cannot be said that the film is a good quality film. In order to remove such undecomposed elements, it is necessary to supply power in a timely manner while supplying a gas that reacts with the undecomposed elements.

According to the present invention, in the film forming step, when a single kind of film forming raw material gas is supplied, a discharge gas, a raw material decomposition gas and a high frequency power are supplied a plurality of times for a single supply. Also, when using several kinds of film forming source gases, these are supplied separately and stepwise, and each time, a discharging gas, a raw material decomposition gas, and a high frequency power are supplied a plurality of times. The source gas is completely decomposed, and a high-quality thin film containing no undecomposed elements can be obtained.

Next, an outline of a pulse plasma CVD film forming apparatus used in the present invention shown in FIG. 1 will be described. In the figure, reference numeral 1 denotes a reaction chamber whose outer periphery is covered by a heater 2. An object to be processed (substrate) 3 is disposed inside the reaction chamber 1 at a lower portion thereof, and the object to be processed 3
The high-frequency electrode 5 is arranged so as to be opposed to the high-frequency electrode 5, and is connected to a pulse high-frequency power supply 7 via a matching box (matching device) 6. The workpiece 3 has a heater 4 below it. The reaction chamber 1 is connected to an oil rotary vacuum pump 10 via a main valve 8 and a roots pump 9.
The inside of the reaction chamber 1 is evacuated by the operation of the oil rotary vacuum pump 10. The oil rotary vacuum pump 10 is connected to an inlet pipe 12 to a waste gas treatment device (not shown), and a branch pipe between the oil rotary vacuum pump 10 and the roots pump 9 is supplied with nitrogen gas by oil. A nitrogen gas introduction valve 11 for supplying to a rotary vacuum pump 10 is provided.

Reference numeral 13 denotes an introduction gas stop valve from which a source gas for film formation, a gas for discharge, a gas for decomposition of the source, and the like are introduced into the reaction chamber 1. That is, Ar gas, H ₂
The gas is sent to the buffer tanks 15 and 18 while controlling the flow rate by the mass flow control valves 14 and 17, from which the piezo valves 16 and 19 are instantaneously opened and closed, and sent from the introduction gas stop valve 13 to the reaction chamber 1. The N ₂ gas used as one of the source gases is sent to the buffer tank 21 while controlling the flow rate by the mass flow control valve 20, from which the piezo valve 22 is opened and closed instantaneously to introduce the introduced gas stop valve 1.
3 to the reaction chamber 1.

Further, when a liquid material at room temperature, such as TiCl ₄ or AlCl ₃ , is used as a raw material, the raw material 26 in the constant temperature bath 27 is heated and vaporized by the heater 28, and the vaporized reaction gas is discharged. Operating the stop valves 29 and 30 to the reaction gas introduction pipe 32 to be supplied to the reaction chamber;
H ₂ gas whose flow rate is controlled by the mass flow control valve 23 used as a carrier gas is supplied to the reaction gas introduction pipe 32 by opening and closing the stop valves 29 and 30, and the reaction gas together with the H ₂ gas is supplied to the buffer tank 24 and the piezo valve. The gas is sent from the introduction gas stop valve 13 to the reaction chamber 1 via 25. In supplying the reaction gas to the reaction chamber 1, in order to prevent the gas from condensing in the reaction gas introduction pipe 32 during the supply,
It is preferable that an introduction pipe heater 33 is attached around the reaction gas introduction pipe 32.

Incidentally, as the carrier gas, Ar, He or the like can be used in addition to H ₂ . Further, NH ₃ gas may be used instead of N ₂ which is one of the reaction gases.
Furthermore, in case of forming an oxide in place of the N ₂ O _2,
N ₂ O and CO can also be used. In the present invention, a Si wafer, a high-speed steel, a die steel, a stainless steel, or the like is used as an object to be processed. The Si wafer having a conductive film, an insulating film, and a barrier film formed on the surface by the method of the present invention is a semiconductor. High-speed steel with an ultra-hard coating formed is used as a device or an electronic component, and is used as a mold, a cutting tool, or a wear-resistant mechanical component.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to FIG. Example 1 (Formation of TiN film) First, after opening the main valve 8 of the pipe connected to the reaction chamber 1 and operating the vacuum pumps 9 and 10 to exhaust the inside of the reaction chamber 1,
The inside of the reaction chamber 1 is previously heated to about 100 ° C. by the heater 2. On the other hand, titanium tetrachloride (TiCl ₄ ) 26, which is a liquefied raw material, housed in a thermostat 27 is heated by a heater 28. Next, the workpiece 3 is heated by the heater 4, and when the temperature reaches 200 ° C., the Ar gas and the H ₂ gas are buffered while adjusting the flow rate by mass flow control valves (hereinafter referred to as MFC) 14 and 17, respectively. After storing in the tanks 15 and 18, the piezo valves 16, 1
9 is opened and closed instantaneously, and the introduction gas stop valve 13 is opened to introduce a pulse into the reaction chamber 1. These introductions
This is performed by repeatedly opening the 7 ms piezo valve at a cycle of 25 ms. The introduction gas stop valve 13
Are kept open from the start of discharge to the end of discharge. Ar gas and H ₂ gas introduced in a pulsed manner
When the pulse is sufficiently diffused, a high frequency power of 40 KW and 13.56 MHz is applied in a pulse form from the pulse high frequency power supply 7 to the high frequency electrode 5 to generate plasma, which adheres to the inner wall surface of the reaction chamber 1 and the workpiece 3. To remove water.

Next, as the first stage of the film forming process, first, the TiCl ₄ gas heated and vaporized in the constant temperature bath 27 is used as a film forming material gas from the stop valves 29 and 30 to the reaction gas introducing pipe 32. introduced, it was introduced into the reaction gas inlet tube 32 by opening and closing the stop valve 29, 30 the H ₂ gas as a carrier gas was adjusted flow rate MFC23 simultaneously, the TiCl ₄ gas with the carrier gas, M
The 7 ms piezo valves 25 and 1 are synchronized with the Ar gas and the H ₂ gas whose flow rates are adjusted by the FCs 14 and 17 at a cycle of 25 ms.
6 and 19 are opened, and this is repeated to introduce the reaction chamber 1 intermittently. When these gases have sufficiently diffused into the reaction chamber 1, the same high frequency power as described above is applied for 150 μs from the pulse high frequency power supply 7 to decompose the TiCl ₄ gas,
The element is deposited as a film on the object.

Further, Ar gas and H ₂ gas whose flow rates have been adjusted by the MFCs 14 and 17 are intermittently supplied by repeating the opening of the 7 ms piezo valve at a cycle of 25 ms for 6 to 7 times,
At the same time, high-frequency power is also intermittently supplied each time, thereby removing the Cl and O elements remaining in the film.

Next, as the second stage of the film forming process, the flow rate of N ₂ gas as a film forming raw material gas is adjusted by the MFC 20 under the same conditions as above with the Ar gas and H ₂ gas from the MFCs 14 and 17. The N ₂ gas reacts with the Ti element on the workpiece by intermittently supplying it two or three times and also supplying high frequency power intermittently a plurality of times. Further, the high frequency power is intermittently supplied 5 to 6 times with the Ar gas and the H ₂ gas almost in synchronism therewith to remove Cl and O elements which tend to remain in the TiN film when the film is formed. Thus, a TiN film was formed on the workpiece.

The time required for the film forming step is 300
~ 500ms, reaction chamber pressure is 0.08 ~ 0.15To
At rr, the deposition rate was 0.5-1.5 μm / h.
The hardness of the obtained film was Knoop hardness (Hk) 1800.
２2500, and as a result of analysis by Auger electron spectroscopy (AES), only 1% and 5% or less of Cl and O elements were recognized, respectively.

Example 2 (Formation of Al film) Instead of TiCl ₄ of Example 1, aluminum chloride (Al
Cl ₃ ) was used as a liquefaction raw material. Further, after the steps up to the removal of the moisture adhering to the inner wall surface of the reaction chamber 1 and the object 3 to be processed are performed in the same manner as in Example 1, first, as a film forming step, the film is heated in a constant temperature bath 27. Al vaporized
Stop valve 2 using Cl ₃ gas as a source gas for film formation
9 and 30 to the reaction gas introduction pipe 32,
The stop valves 29 and 30 are opened and closed and introduced into the reaction gas introduction pipe 32 using the H ₂ gas whose flow rate has been adjusted at C23 as a carrier gas.
_{The 3} gas, the Ar gas and the H ₂ gas whose flow rates were adjusted by the MFCs 14 and 17 were synchronized, and the 7 ms piezo valve was opened at a cycle of 25 ms.
Introduce within. When these gases are sufficiently diffused into the reaction chamber 1, the pulsed high frequency power
KW, applying 13.56 MHz high frequency power several times
The 1Cl ₃ gas is decomposed, and the Al element is deposited as a film on the object.

Further, the Ar gas and H ₂ gas whose flow rates are adjusted by the MFCs 14 and 17 are opened intermittently by opening the 7 ms piezo valve at a cycle of 25 ms and repeating this 12 to 13 times, and at the same time intermittently supplying high frequency power. By supplying, the Cl and O elements remaining in the film were removed to form a pure Al film. The time required for the film forming step in the above is 150 to 300 ms, and the pressure in the reaction chamber is 0.08 to 0.1.
At 5 Torr, the deposition rate was 1.0 to 2.0 μm / h.

In addition, when a SiN film and a SiO ₂ film were formed using the same film forming process as that for forming the TiN film of Example 1, SiH ₄ and N ₂ gases were used as raw material gases in the SiN film. The deposition rate is 1.5 to 2.5 μm / h
Met. In the case of a SiO ₂ film, SiH is used as a source gas.
₄ , O ₂ , and Ar gas are used to form a film at a rate of 2.0 to 3.
It was 0 μm / h.

[0022]

As described above, according to the present invention, a raw material gas for film formation, a discharge gas,
When a raw material decomposition gas is introduced and high-frequency power is applied to form a thin film on the surface of the object to be processed in the reaction chamber, one discharge of the film formation raw material gas and another discharge gas and raw material decomposition Supplying the gas a plurality of times and applying high-frequency power each time, or when using several kinds of film forming material gases, supplying each of these material gases separately and stepwise, and each time using another discharge gas By supplying the gas for raw material decomposition and applying high frequency power, and further maintaining the reaction chamber in a heated state, the condensation of the raw material gas introduced into the reaction chamber is prevented, and the raw material gas is almost completely Therefore, a high-quality thin film containing no undecomposed elements can be obtained on the surface of the object to be processed at a temperature of 200 ° C. or lower by a pulsed plasma CVD method.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one example of a pulse plasma CVD film forming apparatus used in the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 reaction chamber 3 workpiece 5 high-frequency electrode 7 high-frequency power supply 13 introduction gas stop valve 25 piezo valve 26 liquefied raw material 27 constant temperature bath 32 reaction gas introduction pipe

Continuation of the front page (56) References JP-A-4-110757 (JP, A) JP-A-4-361531 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21 / 205 C23C 16/515 H01L 21/31

Claims (2)

(57) [Claims] 1. A film forming source gas, a discharge gas and a source decomposition gas are intermittently introduced into a evacuated and heated reaction chamber while being individually controlled, and high frequency power is supplied in a pulsed manner. In forming a film on the surface of the object to be processed in the reaction chamber by pulsed plasma CVD, a discharge gas, a material decomposition gas, and a high-frequency power are supplied to a single supply of the film forming material gas in the film forming process. A film formation method by pulsed plasma CVD, wherein the film is supplied a plurality of times. 2. A film forming source gas, a discharge gas, and a source decomposition gas are intermittently introduced into the evacuated and heated reaction chamber while being separately controlled, and high-frequency power is supplied in a pulsed manner. In forming a compound thin film on the surface of an object to be processed in the reaction chamber by pulsed plasma CVD, several kinds of film forming source gases constituting the compound thin film are separately and stepwise introduced into the reaction chamber in the film forming process. And supplying a discharge gas, a raw material decomposition gas, and high-frequency power each time the raw material gas is supplied.