JPH08134650A - Formation of cvd film and device therefor - Google Patents

Abstract

PURPOSE: To flatten a CVD film only through film formation by allowing a specified film forming material to react with active oxygen in a non-plasma atmosphere kept at specified pressure and temp. CONSTITUTION: Liq. hydrogen peroxide is stored in a tank 60 and sent to liq. MFC 62 under pressure by utilizing a pressurized gas from a pipe 61. The hydrogen peroxide is decomposed into oxygen and H2 O in a vaporizer 64, a part of H2 O is trapped in a cooler 67, and the remainder is sent under pressure to a mixer 68. A liq. film forming material is stored in a tank 70 and sent to a liq. MFC 72. The film forming gas in a vaporizer 74 is mixed with the active oxygen, vaporized H2 O and the film forming gas in the mixer 68, and the mixture is sent to a plasma CVD device. The gaseous film forming material is selected from among a group of SiH4 , Si2 H6 , TEOS and TMOS. The gaseous film forming material is allowed to react with the active oxygen in a non- plasma atmosphere kept at 1-760 Torr and 300-400 deg.C to form a film. Consequently, the flattening by an SOG film is not needed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CVD film forming method. More specifically, the present invention relates to a CVD film forming method that does not require the formation of an SOG film for planarization.

[0002]

2. Description of the Related Art In manufacturing a semiconductor IC, there is a step of forming a thin film of silicon oxide on the surface of a substrate. Chemical vapor deposition (CVD) is used as a method of forming a thin film. There are three CVD methods, an atmospheric method, a decompression method and a plasma method, but the plasma method is attracting attention as a suitable method for a recent ultra LSI that requires a high quality and highly accurate thin film. .

In the plasma method, a high-frequency voltage is applied to a reaction gas injected in a vacuum to form a plasma, and energy required for the reaction is obtained. Therefore, a uniform film thickness and a good film quality can be obtained. Moreover, it is excellent in many respects such as a high film formation speed.

For example, SiH ₄ or the like has been used as a material for forming a silicon oxide film by the plasma method. However, a decrease in step coverage (step coverage) has become a problem with the miniaturization of semiconductor devices. Liquid tetraethylorthosilicate (TEOS) [Si (OC ₂ H ₅ ) ₄ ] has recently been used in place of this monosilane gas. This is because TEOS can form a dense film having excellent step coverage. When a silicon oxide film is formed using TEOS, TEOS is heated and vaporized to form TEOS gas, which is mixed with oxygen gas and supplied to the reaction furnace.

FIG. 2 is a schematic configuration diagram of an example of a conventional plasma CVD apparatus 1. In the figure, a reaction furnace (chamber) 10 is made airtight, a metal nozzle portion 30 is fixed to a lid plate 102 of the reaction furnace 10, and an aluminum lower portion is provided therewith, and a large number of minute holes 41 penetrating from the upper surface to the lower surface are provided. The disk-shaped shower electrode 40 is supported by the insulating ring 103. This is the upper electrode 32. A high frequency power supply 7 that applies a high frequency voltage to the shower electrode 40 is provided.

A lower electrode 20 is provided so as to face the upper electrode 32. The lower electrode 20 is supported by columns 25. The susceptor 22 is arranged on the upper part of the pillar 25,
A heater unit 21 is provided below the susceptor 22, and a heater cover 23 is provided around the susceptor 22 and the heater unit 21.

In the reaction process, the side surface 1 of the reaction furnace 10 is used.
05, the gate 51 of the loading / unloading path 50 is opened, the substrate 6 is loaded by the carriage 52, and the susceptor 2 is loaded.
It is placed on the upper surface of the No. 2 approximately at the center. After the gate is closed and the duct 104 is evacuated to bring the inside of the reaction furnace to a predetermined degree of vacuum, the heater unit 21 heats the susceptor 22, and when the substrate 6 placed on the susceptor 22 reaches a predetermined temperature, the inlet is closed. 34 to a predetermined reaction gas (for example, TE
OS and oxygen gas) are fed into the reaction furnace. The gas passes through the nozzle portion 30 and is jetted toward the substrate through the minute holes 41 of the shower electrode 40.

Since the conventional plasma TEOS film has no fluidity, it is formed along the recesses existing between the wiring patterns on the substrate. If you leave this recess as it is,
A new wiring pattern cannot be formed on the plasma TEOS film. For this reason, the plasma TE having a recess is conventionally used.
A spin-on-glass (SOG) film is formed on the OS film and the plasma TEOS film is flattened.

However, in the formation of an interlayer insulating film of a highly integrated chip of 64 M DRAM (dynamic random access memory) or more, there is a limit to the planarization of the three-layer interlayer using the plasma TEOS film and the SOG film. In high-integrated chips such as 64M, the spacing between wiring patterns is too small,
When a recess is formed in the first-layer plasma TEOS film, S
This is because flattening by the OG film cannot be performed.

[0010]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for forming a CVD film which does not require a planarization process using an SOG film.

[0011]

The above-mentioned problems can be solved by feeding active oxygen together with a film forming material gas into a reaction furnace and reacting in a high temperature non-plasma atmosphere to form a CVD film.

[0012]

The mixed gas of the film forming material gas and the active oxygen causes a thermal reaction due to the rise of the gas temperature, and produces an intermediate product such as (Si (OH) ₄ ) _n . Since this intermediate product has self-fluidity, it flows between the patterns even after reaching the substrate surface, forming a CVD film while filling the gap. Therefore, if a film having a certain thickness is formed, the film can be flattened only by forming the film.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings.

FIG. 1 is a schematic diagram of a gas supply system in an example of a CVD film forming apparatus used for carrying out the CVD film forming method of the present invention. The CVD film forming apparatus itself is shown in FIG.
The conventional device shown in can be used as it is.
A feature of the invention is the use of hydrogen peroxide. Liquid hydrogen peroxide is stored in the tank 60, and the pipe 61
A pressurized gas is fed into the tank 60 to be pressure fed to the liquid MFC (mass flow controller) 62. The tank 60 filled with liquid hydrogen peroxide is contained in a constant temperature bath 63 that can be controlled at a temperature in the range of −10 ° C. to + 40 ° C. in order to suppress the deterioration of the material, and keeps the hydrogen peroxide at a constant temperature. The hydrogen peroxide whose flow rate is controlled by the liquid MFC 62 is decomposed into active oxygen and H ₂ O by the vaporizer 64 and is gasified. Carrier gas is fed from the pipe 65. The flow rate of the carrier gas is controlled by the MFC 66, and the active oxygen and H ₂ O gasified by the vaporizer 64 are sent to the cooler 67. Cooler 67 pipe wall temperature is controlled to trap a portion of H ₂ O were gasified reactor 10 controls of H ₂ O amount sent to (see FIG. 2), it is pumped into mixer 68. The trapped H ₂ O is discarded from the drainage line 69.

Similarly, the liquid film-forming material is stored in the tank 70, and a pressurized gas is sent into the tank 70 through a pipe 71 so as to be sent under pressure to a liquid MFC (mass flow controller) 72. The liquid film forming material whose flow rate is controlled by the liquid MFC 62 is gasified by the vaporizer 74. Pipe 75
Carrier gas is fed from. Carrier gas is MFC
The flow rate is controlled by 76, and the film forming gas gasified by the vaporizer 74 is pressure-fed to the mixer 68. Active oxygen with mixer 68,
The vaporized H ₂ O and the film forming gas are mixed and fed from the inlet 34 into the reaction furnace 10 (see FIG. 2). In addition, in order to prevent reliquefaction of vaporized gas, the inlet 3
A coil heater 77 is wound around the supply pipe up to 4.

Referring to FIG. The mixed gas sent from the inlet 34 passes through the nozzle portion 30 and the shower electrode 4
It is evenly dispersed through the small holes 41 of 0 and flows toward the substrate 6 on the susceptor 22. The substrate 6 is the heater unit 21.
Is heated to an arbitrary temperature by means of, and a CVD film having self-fluidity is formed on the substrate 6 by a thermal reaction.

Since the conventional plasma CVD apparatus is used as is in the apparatus shown in FIG. 1, the high frequency power source 7 is connected to the upper electrode 32. However, since the CVD film forming method of the present invention is performed in a non-plasma atmosphere, a high frequency voltage is not applied to the shower electrode 40.

Since the method of the present invention is carried out in a non-plasma atmosphere, the pressure in the reaction furnace 10 when carrying out the film formation reaction is within the range of 1 Torr to 760 Torr. Also,
The substrate heating temperature by the susceptor 22 is preferably in the range of about 300 to 400 ° C. If the temperature is lower than 300 ° C., the thermal reaction of the mixed gas becomes insufficient, and a CVD film having a desired film quality cannot be obtained. On the other hand, if the temperature exceeds 400 ° C., a CVD film having self-fluidity cannot be obtained, which is not preferable.

As the film forming material gas, SiH ₄ , Si ₂
Liquid materials such as silane-based materials such as H ₆ and silicate-based materials such as TEOS and TMOS can be used. In order to embed a fine pattern, T with excellent self-fluidity
Liquid materials such as EOS are particularly preferred.

As the carrier gas, argon, nitrogen,
Gases such as helium, oxygen, nitrous oxide, and ammonia can be appropriately used, but oxygen, nitrogen, or helium gas is preferable from the viewpoint of gas danger and ease of handling. Further, as the pressurized gas, argon, nitrogen, helium, oxygen gas or the like can be used, but it is preferable to use helium in order to suppress dissolution in the liquid material.

The mixing ratio of the film forming material gas and the active oxygen in the mixed gas is not particularly limited. Generally, 1: 3 to 1: 2
It is preferred to have the ratio in the range of 0. If the amount of active oxygen is increased, the reaction in the gas phase proceeds, which causes problems such as a decrease in the deposition rate and the generation of foreign matter. On the other hand, if the amount of active oxygen is small, the reaction does not proceed, so that a fluid film and desired film quality cannot be obtained.

Generally, when 100 ml of liquid hydrogen peroxide is pressure-fed to the vaporizer 64 and vaporized therein, about 30 vol% of active oxygen can be taken out. The vaporizer can take out a higher concentration of active oxygen than when using an ozonizer. As a result, conventional ozone-TE
It is possible to obtain a film of better quality than when using an OS mixed gas. With the conventional ozonizer, ozone can be extracted only at a concentration of at most about ten and several wt%.
Further, in the present invention, only the vaporizer is used instead of the conventional ozonizer, so that the entire apparatus can be downsized.

Since hydrogen peroxide is used, a very small amount of vaporized H ₂ O is entrained together with active oxygen. The presence of this vaporized H ₂ O in the mixed gas has effects such as obtaining a film having better fluidity than ozone-TEOS. However, even if vaporized H ₂ O does not exist in the mixed gas at all, there is no particular adverse effect on the film quality itself of the formed CVD film. It is generally preferred that the amount of vaporized H ₂ O entrained is in the range of 1-15. If it is less than 1, the desired effect cannot be obtained. On the other hand, if it exceeds 15, inconveniences such as deterioration of film quality occur, which is not preferable.

Although the exact mechanism by which active oxygen is used to form a fluid film is not clear, for example, a mixed gas of TEOS and active oxygen undergoes a thermal reaction due to an increase in gas temperature, [Si ( It forms an intermediate product such as OH) ₄ ] _n . Since this intermediate product is like liquid glass and has self-fluidity, it seems to flow between the patterns on the substrate surface even after reaching the substrate surface, and form a CVD film while filling the gaps between the patterns. Be done. Therefore, if the film thickness is formed to some extent, the flattening can be performed only by the film forming process, and the conventional SOG film and the operation for forming the film are not necessary. The film thickness can be controlled by controlling the film formation time. The film formation time can be appropriately determined by considering factors such as the degree of integration of chips, the distance between patterns, and the depth of trenches.

The method of the present invention uses conventional atmospheric or reduced pressure CVD.
It can also be implemented by a device. However, it is preferably carried out in a plasma CVD apparatus as shown in FIG. Plasma C
A conventional plasma TEOS film can be produced using a VD apparatus, and the method of the present invention can be performed in a non-plasma atmosphere. Further, after the method of the present invention is carried out, the CVD film formed and attached in the reaction furnace can be easily removed by plasma dry etching with fluorine radicals.

[0026]

As described above, according to the present invention,
By reacting the active oxygen and the CVD film forming material gas at a temperature of 300 to 400 ° C., an intermediate product such as liquid glass having fluidity is formed. Since this intermediate product has self-fluidity, it flows between the patterns even after reaching the substrate surface, forming a CVD film while filling the gap. Therefore, if a film having a certain thickness is formed, the film can be flattened only by forming the film. As a result, the flattening process with the SOG film, which has been performed with the conventional plasma CVD film, becomes unnecessary.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a gas supply system in an example of a CVD film forming apparatus used for carrying out a CVD film forming method of the present invention.

FIG. 2 is a schematic configuration diagram of an example of a conventional plasma CVD apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma CVD apparatus 6 Substrate 7 High frequency power supply 10 Reactor 20 Lower electrode 21 Heater unit 22 Susceptor 23 Heater cover 25 Strut 32 Upper electrode 60 Liquid hydrogen peroxide tank 62, 72 Liquid mass flow controller 63 Constant temperature bath 64, 74 Vaporizer 65, 75 Carrier Gas Inlet Pipe 66, 76 Carrier Gas Mass Flow Controller 67 Cooler 68 Mixer 69 Drain Line 70 Liquid Film Forming Material Tank 77 Coil Heater

Claims (6)

[Claims] 1. SiH ₄ , Si ₂ H ₆ , TEOS and T
A CVD method characterized in that a film forming material gas selected from the group consisting of MOS and active oxygen are reacted in a non-plasma atmosphere at a pressure in the range of 1 Torr to 760 Torr and a temperature in the range of 300 to 400 ° C. Film forming method. 2. The method of claim 1, wherein the active oxygen is provided by vaporizing liquid hydrogen peroxide. 3. The method of claim 2 wherein the active oxygen is accompanied by a trace amount of vaporized H ₂ O. 4. The method according to claim 1, wherein the film forming material gas is TEOS gas. 5. A CVD apparatus for forming a CVD film by reacting a film forming material gas and active oxygen in a reaction furnace, and a vaporizer for vaporizing liquid hydrogen peroxide,
A cooler for cooling active oxygen and vaporized H ₂ O generated by vaporizing liquid hydrogen peroxide and condensing a part of the vaporized H ₂ O and discharging the liquid, and a small amount of vaporized H ₂ O are accompanied. And a mixer that mixes active oxygen with a film forming material gas, and the mixer is connected to a reaction furnace by a pipe. 6. The apparatus according to claim 5, wherein the film forming material gas and the active oxygen accompanied by a slight amount of vaporized H ₂ O are carried to the mixer and the reaction furnace by a carrier gas.