JP3193898B2 - Coating film formation method - 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, for example, an insulating film by applying a coating solution in which particles or colloid of a starting material of a film forming component are dispersed in a solvent to a surface of a substrate.

[0002]

2. Description of the Related Art As a method for forming an interlayer insulating film of a semiconductor device, there are a CVD method, a thermal oxidation method, and the like, and another method called a sol-gel method. This method can be performed, for example, using TEOS (tetraethoxysilane; Si (C
A coating solution in which a colloid of 2 H5 O) 4) is dispersed in an organic solvent such as an ethanol solution is applied to the surface of a semiconductor wafer (hereinafter simply referred to as a wafer), and the coating film is gelled and dried to form a silicon oxide film. Is a technique for obtaining
-162450 and JP-A-8-59362.

FIG. 10 schematically shows the state of modification of a coating film in this method. First, when a coating liquid is first applied to a wafer, TEOS particles or colloid 100 are dispersed in a solvent 200. (FIG. 10 (a)
TEOS) by exposing the coating film to an alkaline atmosphere or by heating.
Condensation polymerization and hydrolysis are promoted to gel the coating film, and T
The network structure of the EOS 300 is formed (see FIG. 10B). Then, in order to remove water in the coating solution, the solvent in the coating film is removed by another solvent 40 having a low boiling point and a low surface tension.
0 (see FIG. 10C), and then dried to obtain a coating film of a silicon oxide film. FIG. 10 (c)
In the solvent replacement step shown in (1), in addition to the purpose of removing water, a solvent having a lower surface tension than ethanol is used, and a large force is not applied to the TEOS network structure when the solvent evaporates. It also has the purpose of keeping the structure from collapsing.

To apply such a sol-gel method to an actual production line, a coating unit for applying a coating liquid to a wafer, and a wafer at a predetermined temperature (for example, 100 ° C.).
Aging unit for heating the applied film to gel the coated film and a replacement unit for replacing the solvent in the coated film with another solvent are required, and further perform pretreatment such as hydrophobic treatment on the wafer. And a baking unit for drying the wafer are required, and the apparatus is provided with a transfer mechanism for transferring the wafer between these units.

When the coating film is gelled, it is necessary to suppress evaporation of the solvent from the coating film so that the gelation of TEOS is not hindered. for that purpose,
Rather than performing gelation in an open system as in the past,
The gelation treatment may be performed in a closed container in an atmosphere filled with the vapor of the solvent. That is, the wafer may be placed in a state of being laid down on the mounting table at a predetermined temperature in the closed container, and a gas containing a solvent vapor may be introduced into the closed container.

Therefore, the present inventors are studying the use of an aging unit 3 having a structure as shown in FIG. 11 , for example, to perform a gelling treatment. This aging unit 3
A ceramic heating plate 30 having a built-in heater 31a, and a hermetically sealed container which is in close contact with the peripheral edge of the heating plate 30 via a seal member 32 and defines a processing chamber S together with the heating plate 30, constitute a heater. A lid 33 provided;
A gas introduction path 34 in which a slit-like gas introduction port 34a is formed outside the heating plate 30 along the peripheral edge of the wafer W, and an exhaust path 35 in which an exhaust port 35a is formed in the center of the lid 33. It has. The aging unit 3 is provided with, for example, three elevating pins 36 for elevating and lowering the wafer W between the heating plate 30 and a position above the heating plate 30.

As the gas used here, a gas of a solvent component, for example, vapor of ethylene glycol is used to suppress evaporation of the solvent in the coating film because the processing atmosphere is heated. The gas introduction path 34 is provided through the heating plate 30, and is heated to a temperature equal to or very close to the temperature (for example, about 100 ° C.) in the closed container, and is then inserted into the closed container. It is being introduced. At that time, the concentration of the ethylene glycol vapor is set to a concentration that is equal to the saturated vapor pressure at the processing temperature (for example, about 100 ° C.). Further, in addition to ethylene glycol, a gas which promotes gelation, for example, an ammonia gas may be introduced at the same time.

[0008]

However, when the introduction of gas into the closed container is started, there is a possibility that the concentration and temperature of the gas may fluctuate until the gas supply becomes steady. In addition, as described above, the wafer is kept at a predetermined temperature (for example, 1
In the case of processing at a temperature of about 00 ° C., when a normal-temperature wafer is directly loaded into a closed vessel at a predetermined temperature, a gas of a solvent component having a saturated vapor pressure comes into contact with the wafer to lower the temperature, resulting in supersaturation and dew condensation. There is a fear. If, for example, ethylene glycol is condensed on the wafer, the film thickness at that portion increases, resulting in a non-uniform insulating film.

The present invention has been made under such circumstances, and an object of the present invention is to suppress fluctuations in concentration and temperature at the start of gas introduction into an airtight container and to place a substrate such as a wafer in the airtight container. It is an object of the present invention to provide a technique capable of preventing dew condensation of a gas of a solvent component immediately after carrying in, thereby obtaining a high-quality thin film, for example, an interlayer insulating film.

[0010]

According to the present invention, there is provided a coating film forming method for forming a coating film by applying a coating liquid in which particles or colloid of a starting material of a film forming component are dispersed in a solvent to the surface of a substrate. A step of carrying the substrate into a temperature-controlled airtight container and then gelling the particles or colloid in the coating film while supplying a gas containing a vapor of the solvent component into the airtight container. A gelation step, wherein the gelation step is a first step of performing the treatment in a state where the average concentration of the solvent component in the gas is low, and then the average concentration of the solvent component in the first step And a second step of performing processing in a state higher than the average density. In this case, it is preferable that the temperature of the gas introduced into the closed container is adjusted to a temperature near the inside of the closed container.

According to the present invention, when the substrate is carried into the closed container and the temperature of the substrate has not yet risen to the predetermined temperature, the average concentration of the components of the solvent is lowered and the temperature of the substrate is raised. Since the concentration of the solvent component is sometimes increased, dew condensation of the solvent component gas immediately after the substrate is carried into the closed container can be prevented.

Before the substrate is carried into the closed container, it is preferable to generate a mixed gas of the vapor of the solvent component and the carrier gas and exhaust the mixed gas. In addition, fluctuations in the concentration of the solvent component and the temperature at the start of gas introduction can be suppressed.

To enumerate specific examples of the present invention,
The step of gelling particles or colloids in the coating film is a step of heating the substrate. The gas supplied into the closed container is generated by mixing the vapor of the carrier gas and the component of the solvent, and the first step is performed by adjusting at least one of the flow rates of the vapor of the carrier gas and the component of the solvent. Further, the mixture of the carrier gas and the vapor of the solvent component is performed by a vaporizer for vaporizing the liquid of the solvent component, and the first step is performed by adjusting the flow rate of the liquid of the solvent component guided to the vaporizer.

In this case, the first step includes a step of continuously changing the concentration of the vapor of the solvent component. The first step includes a step in which the vapor of the solvent component is intermittently mixed with the carrier gas. In the gelling step, before transporting the substrate into the closed container and before performing the first step, the average concentration of the vapor of the solvent component is higher than the average concentration in the first step in the closed container. Supplying a gas.

[0015]

FIG. 1 is a plan view schematically showing the entire structure of an example of a coating film forming apparatus used for carrying out the method of the present invention. Reference numeral 11 denotes an input / output port for a wafer serving as a substrate. The transfer arm 12 takes out the wafer W from the cassette C placed on the cassette stage CS and transfers it to the main arm 13. On one side of the transport path (guide rail) 14 of the main arm 13, the coating unit 2 which is a coating unit which is a main part of this embodiment is an aging unit 3 which is a gelling unit and a solvent replacement unit. It is arranged along with the solvent replacement unit 4 in this order. Processing units U1 to U4 are also arranged on the other side of the transport path 14, and for these processing units U1 to U4, a hydrophobic treatment, a cooling treatment, and a coating film are applied to the substrate before the application liquid is applied to the substrate. A unit for performing a heat treatment (bake treatment) after the formation is assigned to each.

The overall operation of the embodiment using this coating film forming apparatus will be described. FIG. 2 schematically shows the flow of the coating film forming process in order. The unprocessed wafer W taken out of the cassette C of the cassette stage CS by the main arm 13 is stored in the coating unit 2. Then, the coating liquid T is dropped on the surface of the wafer W in the coating unit 2 (FIG. 2A). As the coating solution, for example, a solution obtained by dispersing colloids and / or particles of TEOS in a solvent containing ethylene glycol, ethyl alcohol, water and a small amount of hydrochloric acid is used. Subsequently, the wafer W is rotated at a high speed in a state where the inside of the coating unit 2 is filled with a solvent vapor, for example, ethylene glycol, and the coating liquid spreads on the wafer surface to form a coating film F (FIG. 2).
(B)).

Next, the wafer W is placed on the heating plate 31 of the aging unit 3 and sealed by the lid 33. At that time, the wafer W is heated to a predetermined temperature (for example, about 100 ° C.) by the heating plate 31. Then, a vapor of ethylene glycol and a carrier gas are introduced into the aging unit 3 to gel the coating film (FIG. 2).
(C)).

Next, in the solvent replacement unit 4, solvent replacement of the gelled coating film is performed using ethyl alcohol, HMDS (hexamethyldisilane) and hebutane. Thereby, the water in the coating film is replaced with ethyl alcohol. Further, the hydroxyl groups in the coating film are removed by HMDS. Further, the solvent in the coating film is replaced with heptane. The reason for using heptane is that a solvent having a low surface tension is used to form a porous structure, that is, TEOS.
This is to reduce the force applied to the net-like structure so that it does not collapse. The state so far is shown in FIG. Thereafter, the wafer W is baked in a baking unit, for example, for one minute. Thus, an interlayer insulating film made of, for example, a 6000 angstrom silicon oxide film is formed on the surface of the wafer W.

FIG. 3 shows an example of the aging unit (gelling section) 3 and gas supply means 5 which are main parts of the present embodiment. As shown in the figure, the gas supply means 5 is connected to a gas introduction path 34 of the aging unit 3 and is provided with a flow rate of a carrier gas such as nitrogen gas or ammonia gas supplied from a carrier gas supply device (not shown). Flow controller 5 for adjusting gas
1, a liquid mass flow controller 52 for adjusting the flow rate of a solvent such as ethylene glycol supplied from a solvent supply device (not shown), and a gas mass flow controller 5
A vaporizing device 53 for vaporizing the solvent whose flow rate has been adjusted by the liquid mass flow controller 52 using the carrier gas whose flow rate has been adjusted by 1 and an aging unit for supplying a gas containing the vapor of the solvent component vaporized by the vaporizing device 53 to the aging unit. Three-way valve 54 for switching between chamber side 3 and exhaust side 3
And a pipe or tube connecting them.

The aging unit 3 has the same configuration as the unit shown in FIG. 11, and therefore, a detailed description of the aging unit 3 is omitted. The gas from the gas introduction path 34 is dispersed in the dispersion chamber 34a, and is introduced into the processing space from the gas introduction port 34b formed in the circumferential direction as a slit.

Next, the flow of the gelling process will be described.
FIG. 4 shows a flowchart of the gelation process.
First, the three-way valve 54 is switched to the exhaust side. Then, a carrier gas and a solvent are supplied from a carrier gas supply device (not shown) and a solvent supply device (not shown), and the vaporizer 5 is supplied.
In step 3, a mixed gas of the vapor of the solvent component and the carrier gas is generated. The generated mixed gas is exhausted through the three-way valve 54 (Step S1).

When the generation state such as the concentration and the temperature of the mixed gas is stabilized, the wafer W on which the coating film is formed in the coating unit 2 is placed on the heating plate 31 having a predetermined temperature and the lid 33 is placed.
Is closed (step S2).

Then, the three-way valve 54 is switched to the chamber side. For a while after switching to the chamber side, that is, until the inside of the gas introduction path 34 of the aging unit 3 and the processing chamber S are filled with the mixed gas, the concentration of the solvent component in the mixed gas at the processing temperature, for example, 100 ° C. The concentration is adjusted so as to become the saturated concentration (see FIG. 5, period A).
Then, the temperature of the wafer W gradually increases from room temperature, and after the inside of the processing chamber S is filled with the mixed gas, the solvent component in the mixed gas is maintained until the temperature of the wafer reaches a predetermined temperature (T0, for example, about 100 ° C.). (See FIG. 5,
B period). During this low solvent concentration period, the concentration of the solvent component is continuously increased as the wafer temperature increases. Preferably, the concentration of the solvent component is adjusted to a concentration such that the partial pressure of the solvent component is always equal to the saturated vapor pressure at the wafer temperature, that is, 100% (step S3).

The concentration of the solvent component may be adjusted by adjusting the flow rate of the carrier gas by the gas mass flow controller 51, or by adjusting the liquid mass flow controller 52. You may do both of them.

When the temperature of the wafer reaches a predetermined temperature, the concentration of the solvent component is adjusted to a saturated concentration (100%) (step S4). Then, the state is maintained until the gelling treatment of the coating film is completed (see the period C in FIG. 5). Thereafter, the three-way valve 54 is switched to the exhaust side, and the mixed gas sent from the vaporizer 53 is exhausted ( Step S5). Then, the lid 33 of the aging unit 3 is opened, and the wafer W is carried out of the aging unit 3 (Step S6). This completes the gelling process.

According to the above embodiment, the mixed gas is supplied into the closed vessel of the aging unit 3 after the generation state of the mixed gas is stabilized. Is suppressed. Further, after the wafer is loaded into the closed container, the gas concentration of the solvent component in the mixed gas gradually increases in accordance with the wafer temperature until the temperature of the wafer reaches a predetermined processing temperature. The dew condensation of the solvent component gas can be prevented immediately after the substrate is carried in, so that a high-quality thin film, for example, an interlayer insulating film can be obtained.

FIG. 6 shows another example of the gas supply means. As shown in the figure, the gas supply means 6 includes a gas mass flow controller 61 for adjusting a flow rate of a carrier gas composed of a nitrogen gas, an ammonia gas, or the like supplied from a carrier gas supply device (not shown), and a gas mass flow controller. A two-way valve 62 for switching supply and stop of the carrier gas whose flow rate has been adjusted by 61 to the chamber of the aging unit 3, a container 63 storing a solvent such as ethylene glycol, and a heater 64 for heating the solvent;
A supply pipe 65 for passing a bubbling gas such as nitrogen gas (N ₂ gas) supplied from a bubbling gas supply device (not shown) into a solvent, for example, an ethylene glycol solution;
Gas mass flow controller 66 for adjusting the flow rate of the solvent vapor generated by vessel 63 which is a heating bubbler
And a two-way valve 66a for supplying and stopping the solvent vapor whose flow rate has been adjusted by the mass flow controller 66, a two-way valve 67 for switching between exhausting and stopping the solvent vapor generated by the heating bubbler, and A connecting pipe or tube is provided. The carrier gas and the solvent vapor are mixed and then supplied to the chamber 3.

When the gas supply means 6 shown in FIG. 6 is used, the two-way valves 62 and 66a are opened, the two-way valve 67 of the solvent vapor line is closed, for example, and one or both of the mass flow controllers 61 and 66 are connected. By operating
The concentration of the solvent component in the mixed gas can be continuously changed. However, if the flow rate of the bubbling gas (N ₂ ) is constant, the two-way valve 67 may be opened and the required flow rate may be controlled by the mass flow controller 66 while evacuating the steam. In this case, the pressure in the vessel 63 is stable. There is an advantage of doing so. Also, the two-way valve 67 of the solvent vapor line
, And by squeezing the two-way valve 66a to make the flow rate zero, the supply of the solvent vapor to the chamber 3 can be stopped. The mass flow controllers 61 and 66
The two-way valves 62, 66
a may not be present.

In the example shown in FIG. 6, the concentration of the solvent component in the mixed gas can be continuously adjusted according to the wafer temperature. For example, the concentration of ethylene glycol is adjusted as shown in FIG. Before the wafer is loaded, the solvent vapor of ethylene glycol is generated and exhausted in the same manner as in the above example. Therefore, fluctuations in the concentration and temperature of the solvent component at the start of gas introduction can be suppressed, and dew condensation of the solvent component gas due to the low-temperature wafer W can be prevented, and a high-quality thin film, for example, an interlayer insulating film can be obtained.

The gas supply means 7 shown in FIG. 7 is obtained by removing the mass flow controller 61 of the carrier gas line from the gas supply means 6 shown in FIG. 6, and the other components are the same as those of the gas supply means 6 shown in FIG. Is the same. In this case, in order to adjust the concentration of the solvent component in the mixed gas,
With the two-way valve 62 of the carrier gas line opened and the flow rate of the solvent vapor adjusted by the mass flow controller 66, the opening and closing of the two-way valve 67 of the solvent vapor line may be switched as appropriate.

That is, as shown in FIG.
After the wafer W is loaded into the chamber and the gas introduction path 34 and the processing chamber S are filled with the mixed gas, the temperature of the wafer is reduced to a predetermined temperature (T
0, for example, about 100 ° C.) (B in FIG. 8).
), The two-way valve 67 is intermittently switched to the chamber 3 side. Thereby, the time average concentration of the solvent component in the gas atmosphere in the chamber 3 can be adjusted. At this time, as shown in FIG. 8, by gradually increasing the time during which the two-way valve 67 is switched to the chamber 3 side in the period B, the average concentration of the solvent component in the gas atmosphere in the chamber 3 is reduced to the wafer temperature. Can be adjusted so as to have an appropriate concentration corresponding to the increase in the concentration. In FIG. 8, the conductance of the gas flow path is ignored, and the gas concentration is changed in accordance with the switching of the valve 67.

Also in this case, it is preferable to generate and exhaust a solvent vapor before carrying in the wafer. Also in this example, fluctuations in the concentration and temperature of the solvent component at the start of gas introduction can be suppressed, and the dew condensation of the solvent component gas due to the low-temperature wafer W can be prevented. Can be. Further, in the example shown in FIG. 7, a temperature-controlled buffer chamber 71 may be provided to smooth out a change in the concentration of the solvent vapor.

The gas supply means 8 shown in FIG. 9 is different from the gas supply means 7 shown in FIG. 7 in that the solvent vapor is supplied to one of the chamber 3 and the exhaust side instead of the mass flow controller 66 and the two-way valve 67 of the solvent vapor line. It is provided with a three-way valve 81 that flows to one side. By appropriately switching the supply destination of the solvent vapor to the chamber 3 side or the exhaust side by the three-way valve 81, the solvent vapor is intermittently supplied to the chamber 3 as shown in FIG. The concentration of the solvent component therein can be adjusted to an appropriate concentration corresponding to the rise in the wafer temperature.

In the present invention described above, the means for generating the solvent vapor is not limited to the heating bubbler, and the gas supply means 6 and 7 shown in FIGS. 6 and 7 may not have a carrier gas line. When there is no carrier gas line, the concentration of the solvent and the flow rate of the bubbling gas may be adjusted in the heating bubbler. The substrate to be processed is not limited to a wafer, but may be a glass substrate for a liquid crystal display.

[0035]

As described above, according to the present invention, fluctuations in the concentration and temperature of the solvent component at the start of gas introduction can be suppressed, and dew condensation of the solvent component gas immediately after the substrate is carried in can be prevented. Thereby, a high-quality thin film, for example, an interlayer insulating film can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view showing an overall schematic configuration of an example of a coating film forming apparatus used for carrying out a method of the present invention.

FIG. 2 is an explanatory diagram illustrating a flow of a coating film forming process using the coating film forming apparatus.

FIG. 3 is a schematic view showing an example of an aging unit and gas supply means in the coating film forming apparatus.

FIG. 4 is a flowchart showing an example of the flow of a gelling process according to the method of the present invention.

FIG. 5 is a characteristic diagram showing a change over time in a wafer temperature and a concentration of a solvent vapor in a gelation process according to the method of the present invention.

FIG. 6 is a schematic view showing another example of the gas supply means.

FIG. 7 is a schematic view showing another example of the gas supply means.

8 is a characteristic diagram showing a change over time of a wafer temperature and a concentration of a solvent vapor in a gelling process when the gas supply unit shown in FIG. 7 is used.

FIG. 9 is a schematic view showing another example of the gas supply means.

FIG. 10 is an explanatory diagram showing a state of denaturation of a coating film in a sol-gel method.

FIG. 11 is a schematic diagram showing an example of an aging unit studied by the present inventors.

[Explanation of symbols]

 F Coating film S Processing chamber T Coating liquid W Semiconductor wafer (substrate) 2 Coating unit 3 Aging unit 4 Solvent replacement unit 5, 6, 7, 8 Gas supply means 51, 61, 66 Gas mass flow controller 52 Liquid mass flow controller 53 Vaporizer 54, 81 Three-way valve 62, 67 Two-way valve 63, 64, 65 Heating bubbler 71 Buffer chamber

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoji Mizutani 5-3-6 Akasaka, Minato-ku, Tokyo Tokyo Electron Limited (56) References JP-A-6-23315 (JP, A) JP-A-3 -175616 (JP, A) JP-A-10-70121 (JP, A) JP-A-11-176825 (JP, A) JP-A-11-26443 (JP, A) (58) Fields studied (Int. . ^7, DB name) H01L 21/316 H01L 21/31

Claims (9)

(57) [Claims] 1. A coating step in which a coating liquid in which particles or colloids of a starting material of a film forming component are dispersed in a solvent is coated on a surface of a substrate to form a coating film. A gelling step of gelling the particles or colloid in the coating film while supplying a gas containing a vapor of the component of the solvent into the closed container, and the gelling step, A first step of performing processing in a state where the average concentration of the solvent component in the gas is low, and a second step of performing processing in a state where the average concentration of the solvent component is higher than the average concentration in the first step And a method for forming a coating film. 2. The method for forming a coating film according to claim 1, wherein the temperature of the gas introduced into the closed container is adjusted to a temperature near the inside of the closed container. 3. Before the substrate is carried into the closed container,
A mixed gas of the vapor of the solvent component and the carrier gas is generated, the valve is switched to the exhaust side to exhaust the mixed gas, and after the substrate is carried into the closed container, the valve is switched to seal the mixed gas. 3. The method for forming a coating film according to claim 1, wherein the coating film is introduced into a container. 4. The method of forming a coating film according to claim 1, wherein the step of gelling particles or colloids in the coating film is a step of heating the substrate. 5. The gas supplied into the closed container is generated by mixing a vapor of a carrier gas and a component of a solvent, and the first step is to adjust at least one of a flow rate of the vapor of the carrier gas and a component of the solvent. The method according to any one of claims 1 to 4, wherein the method is performed. 6. The mixing of the carrier gas and the vapor of the solvent component is performed by a vaporizer that vaporizes a liquid of the solvent component.
The method according to any one of claims 1 to 4, wherein the first step is performed by adjusting a flow rate of a liquid of a solvent component guided to the vaporizer. 7. The method according to claim 1, wherein the first step includes a step of continuously changing the concentration of the vapor of the solvent component. 8. The method for forming a coating film according to claim 1, wherein the first step includes a step of intermittently mixing the vapor of the solvent component with the carrier gas. 9. The gelation step is a state in which the average concentration of the vapor of the solvent component is higher than the average concentration in the first step before the first step is performed after the substrate is carried into the closed container. 9. The method for forming a coating film according to claim 1, further comprising a step of supplying a gas into the closed container.