JP2005085794A - Method of forming thin film and method of manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming thin film by which the occurrence of particles can be reduced during the course of forming a thin film on the surface of a substrate without giving any variation to the thin film. <P>SOLUTION: The method of forming thin film includes a step (S2) of inserting a boat 2 on which the substrate 1 is placed in the main body 100 of a furnace and hermetically sealing the main body 100, a step (S3) of maintaining the inside of the main body 100 in an atmospheric state until the thermal expansion of the substrate 1 is saturated, and steps (S4 and S5) of evacuating the inside of the main body 100. The method also includes a step (S8) of forming the thin film on the surface of the substrate 1 through a chemical reaction by supplying a gas which becomes the film forming material into the main body 100. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thin film generation method in which generation of particles when forming a thin film on a substrate is reduced. The present invention also relates to a method for manufacturing a semiconductor device including the thin film generation method.

  Conventionally, when a silicon-containing compound such as silicon nitride, silicon oxide, or polysilicon or a semiconductor thin film is formed on the surface of an insulating substrate such as a glass substrate or a quartz substrate or a substrate such as a silicon wafer, it is well known. Vertical vacuum CVD (Chemical Vapor Deposition) apparatus is used.

  A conventional process for forming a film on the surface of a substrate using a vertical reduced pressure CVD apparatus will be described with reference to the flowchart shown in FIG.

  First, the substrate is transported, and the substrate is transported to a boat (BOAT) that is waiting at a position that is not easily affected by the radiant heat from the CVD device below the CVD device in order to be processed at a time by the low pressure CVD device. Charge (step S21).

  Next, after charging a predetermined number of substrates into the boat, they are raised and inserted into the CVD apparatus and sealed (step S22).

  Then, after the boat is set in the CVD apparatus, the vacuum pump is operated to gently evacuate the furnace (Slow) (step S23).

  After that, after the inside of the furnace is reduced to the set pressure, vacuuming is performed in earnest to further depressurize and exhaust the inside of the furnace (Main) (step S24).

  When the inside of the furnace is reduced to the set pressure, the operation of the decompression pump is once stopped, and the inside pressure of the furnace is monitored to check for leakage (step S25).

  If no leak is detected, the inside of the furnace is adjusted to a set pressure (step S26).

  Next, a gas as a raw material for film formation is supplied into the furnace, and a thin film is generated on the surface of the substrate by a chemical reaction (step S27).

  Then, after a predetermined thin film is formed on the surface of the substrate, the reaction gas in the furnace is scavenged by a cycle purge process (step S28).

  Thereafter, the inside of the furnace is opened to the atmosphere, the inside of the furnace is raised to atmospheric pressure, and then the boat is lowered and taken out from the furnace. (Steps S29 and S30).

  The substrate is cooled, and after predetermined cooling, the substrate is taken out of the boat and transferred to the next process (discharge) (steps S31 and S32).

  By the way, since the inside of the furnace is always heated by the heater, when the substrate loaded on the boat is inserted into the furnace in step S22, the substrate exposed to the high temperature atmosphere in the furnace is thermally expanded. When the inside of the furnace is evacuated in steps S23 and S24, vibration is generated in the substrate.

  As a result, as shown in FIG. 9, the claw portion 2 a of the boat 2 on which the substrate 1 is placed is scratched by the influence of thermal expansion and vibration of the substrate 1. Since a deposition film is deposited on the quartz boat, the deposition film deposited on the claw portion 2a is peeled off and the particles P are generated when it is rubbed by the substrate 1.

  The particles P fall in a sealed furnace and adhere to the surface of the substrate 1 loaded below.

  If the particles P adhering to the surface of the substrate 1 are taken into the thin film during the film formation process, the particles P cannot be removed even if the substrate 1 is cleaned in the subsequent cleaning process. Although it does not necessarily immediately become defective due to the adhesion of the particles P, in the subsequent formation of the circuit pattern or generation of the interlayer insulating film, the thin film portion surrounded by the particles P swells up, resulting in a final product defect. There is a possibility of becoming.

As a technique for suppressing the generation of particles P, for example, in JP-A-5-112870, an adsorbent is disposed in the upper space of the boat to adsorb the film precursor radicals generated in the upper space of the boat, and A technique for reducing the number of particles adhering to the substrate is disclosed.
Japanese Patent Laid-Open No. 5-112870

  However, in the technique disclosed in Japanese Patent Application Laid-Open No. 5-112870, the generation of particles at the upper part of the boat can be suppressed, but the number of particles generated by peeling of the deposit film is reduced below that. It is not possible.

  Furthermore, the flow of airflow in the furnace is likely to change due to the adsorbent, and the thin film distribution generated on the surface of each substrate tends to vary. Further, when a semiconductor device is manufactured by a conventional method, there are many defects due to the above-mentioned particles, and there is a problem that yield and reliability are lowered.

  In view of the above circumstances, the present invention provides a thin film generation method and a semiconductor device manufacturing method capable of reducing the generation of particles in a film formation process without causing variations in the thin film generated on the surface of the substrate. Objective.

  In order to achieve the above object, the present invention provides a thin film generating method for inserting a boat having a plurality of substrates into a furnace body and generating a thin film on the substrate, wherein the boat is erected on a boat base. A step of placing the substrate on the substrate, a step of raising the boat base and inserting the boat into the furnace body and sealing the furnace body, and after sealing the furnace body, A step of maintaining an atmospheric pressure state for a set time; a step of evacuating the furnace body after the set time has elapsed; and a raw material gas for forming a thin film on the surface of the substrate with respect to the furnace body. And a supplying step.

  In such a configuration, after the boat on which the substrate is placed is inserted into the furnace body and sealed, the substrate is first thermally expanded by holding it at atmospheric pressure for a set time without immediately evacuating it. Therefore, in the subsequent evacuation, the substrate does not move due to thermal expansion, and the deposition film deposited on the boat is difficult to peel off, and the generation of particles can be reduced.

  In this case, the set time is defined as the time from when the substrate placed under the boat is inserted into the furnace body until the thermal expansion reaches the saturation region. A vacuum can be drawn after the thermal expansion of reaches the saturation region.

  Furthermore, by shortening the time required for the evacuation by the time for maintaining the inside of the furnace body in the atmospheric pressure state, the film forming process can be performed in substantially the same time as the conventional one.

  In addition, a method for manufacturing a semiconductor device according to the present invention includes the thin film generation method described above.

  With such a configuration, it is possible to improve yield or reliability when manufacturing a thin film transistor or the like on a substrate.

  According to the present invention, it is possible to reduce the generation of particles in the film forming process without giving variation to the distribution of the thin film generated on the surface of the substrate.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic view of a vertical vacuum CVD apparatus.

  The furnace main body 100 of the vertical reduced pressure CVD apparatus shown in the figure has a quartz tube 101. The tube 101 includes an outer tube 101a and an inner tube 101b. The inside of the outer tube 101a is maintained at a predetermined temperature (for example, 600 ° C.) by a heater 102 disposed on the outer periphery thereof, and is formed by a source gas supplied from the outside to the substrate 1 installed in the inner tube 101b. Perform membrane treatment. Note that the inside of the furnace body 100 is evacuated during the film forming process.

  An opening 103 at the lower end of the tube 101 is an insertion / discharge port for the substrate 1. On the boat base 104 that opens and closes the lower end opening 103 of the tube 101, a quartz boat 2 on which a plurality of substrates 1 are placed is erected. The boat 2 is formed of four pillars, and a plurality of claw portions 2a for placing the substrate 1 are formed on each pillar at predetermined intervals. In this embodiment, it is possible to place a maximum of 140 substrates 1 on the boat 2, but the upper and lower regions are regions where it is difficult to perform uniform film formation, and dummy substrates In general, the film forming process is performed with about 120 sheets.

  Further, the boat 2 is guided to the inside and outside of the inner tube 101b by the raising and lowering operation of the boat base 104 (load / unload). Then, the opening 103 of the tube 101 is sealed at the rising end of the boat base 104.

  In addition, a gas pipe 106 for supplying a raw material gas and the like communicates with the tube 101, and an exhaust port 107 is opened. A decompression pump (not shown) is communicated with the downstream side of the exhaust port 107. .

  Next, a process of forming a film on the substrate 1 using the vertical reduced pressure CVD apparatus having such a configuration will be described with reference to the flowchart shown in FIG.

  As shown in FIG. 2, the boat base 104 in the standby state is lowered to a position where it is hardly affected by the radiant heat from the heater 102.

  In this state, first, in step S1, the substrate 1 is transferred to the boat 2 standing on the boat base 104 in a standby state in order to transfer the substrate 1 and process it at once in the vertical reduced pressure CVD apparatus. Charge.

  In step S2, a predetermined number of substrates 1 are charged into the boat 2, then lifted, inserted into the tube 101, and sealed.

  In step S3, the inside of the furnace main body 100 is maintained at atmospheric pressure for a predetermined time. The holding time is set as a target until the thermal expansion of the substrate 1 reaches the saturation region, and is approximately 20 minutes in this embodiment. Since the boat 2 is inserted into the tube 101 at a relatively loose speed, the substrate 1 placed on the upper portion of the boat 2 has a thermal expansion as compared with the substrate 1 placed on the lower end side. Will start sooner. Therefore, the holding time set here is set to a value corresponding to the time when the thermal expansion of the substrate 1 placed on the lower end side of the boat 2 reaches the saturation region after the tube 101 is sealed with the boat base 104. Has been.

  As shown in FIG. 4, the expansion rate δ of the substrate 1 is substantially proportional to the temperature rise. Therefore, as shown in FIG. 5, the temperature inside the furnace body 100 is maintained at To ° C. (for example, 600 ° C.). In this case, when the substrate 1 is inserted into the furnace and reaches a predetermined time to, the thermal expansion becomes saturated.

  Therefore, in this embodiment, since the evacuation is not started until the thermal expansion of almost all the substrates 1 mounted on the boat 2 reaches the saturation region, the substrate 1 vibrates under the influence of the evacuation. However, since only the thermal expansion moves with respect to the claw part 2a, the deposit film deposited on the claw part 2a is difficult to peel off, and the generation of particles P (see FIG. 9) can be reduced.

  Then, after the atmospheric pressure holding time has elapsed, the same control as in the prior art is performed after step S4. Steps S4 to S13 correspond to steps S23 to S32 shown in FIG.

  The process after step S4 will be briefly described.

  Step S4: The vacuum pump is operated to gently evacuate the furnace body 100 (Slow).

  Step S5: After the inside of the furnace main body 100 is reduced to the set pressure, vacuuming is performed in earnest to further reduce the pressure inside the furnace main body 100 and exhaust (Main).

  When the inside of the furnace body 100 is evacuated, since the thermal expansion of the substrate 1 has already reached the saturation region, the substrate 1 is only vibrated by evacuation. Therefore, the substrate 1 does not give vibration to peel off the deposited deposit film to the claw portion 2a on which the substrate 1 is placed, and the generation of particles P (see FIG. 9) is also generated in this process. Can be reduced.

  Step S6: When the inside of the furnace main body 100 is reduced to the set pressure, the operation of the decompression pump is once stopped, the pressure inside the furnace main body 100 is monitored, and the presence or absence of a leak is checked.

  Step S7: When no leak is detected, the inside of the furnace body 100 is adjusted to a set pressure.

  Step S8: A gas as a film forming material is supplied into the furnace body 100, and a thin film is generated on the surface of the substrate 1 by a chemical reaction.

  Step S9: After forming a thin film on the surface of the substrate 1, the reaction gas in the furnace body 100 is scavenged by a cycle purge process.

  Step S10: After that, the inside of the furnace body 100 is opened to the atmosphere.

  Step S11: The boat 2 is lowered and taken out from the furnace body 100.

  Step S12: The boat 2 is left for a while to cool the substrate 1.

  Step S13: After predetermined cooling, the substrate 1 is taken out from the boat 2 and transferred to the next process (discharge).

  As described above, in this embodiment, since the thermal expansion of the substrate 1 and the vibration generated by evacuation are shifted in time, they act synergistically and deposit on the claw portion 2a on which the substrate 1 is placed. The vibration that peels off the deposited film is not generated, and the generation of particles P can be reduced.

  As a result, as shown by hatching in FIG. 7, in the present embodiment, the number of particles is significantly reduced as compared with the conventional one shown by a white frame, and the product defect rate can be reduced correspondingly. 7A shows the number of particles attached to the lower surface of the boat 2, FIG. 7B shows the middle portion, and FIG. 7C shows the number of particles attached to the surface of the monitor substrate placed on the upper portion.

  By the way, in this embodiment, since the atmospheric holding time is set in step S3, the processing time becomes longer as compared with the conventional film forming process, but the amount is controlled in, for example, step S5. Adjustment is possible by shortening the main evacuation time, or by shortening both the main evacuation time and the slow evacuation time controlled in step S4.

  In addition, according to the present embodiment, since the structure of the CVD apparatus has not been changed, the airflow generated during the film forming process does not change, and the distribution of the thin film generated on the surface of each substrate 1 varies. It does not occur.

  Further, if the thin film generation method of the present invention is used in a method for manufacturing a semiconductor device having a plurality of thin film transistors and the like on a substrate such as an electro-optical device, an improvement in yield and an improvement in reliability can be realized.

It is the schematic of a vertical reduced pressure CVD apparatus. 1 is a schematic view of a vertical reduced pressure CVD apparatus in which a boat is in a standby state. It is a top view of a boat. It is a graph which shows the thermal expansion coefficient of a board | substrate. It is a graph which shows the thermal expansion characteristic of a board | substrate. It is a flowchart which shows a film-forming process process. It is a chart which shows the number of particles which occur. It is a flowchart which shows the conventional film-forming process process. It is the schematic which shows the generation principle of a particle.

Explanation of symbols

1 substrate, 2 boat, 2a claw part, 100 furnace body, 101 tube, 102 heater, 103 lower end opening, 104 boat base, P particle

Agent Patent Attorney Susumu Ito

Claims (4)

A thin film generation method for inserting a boat in which a plurality of substrates are arranged in a furnace body and generating a thin film on the substrate,
Placing the substrate on the boat standing on the boat base;
Raising the boat base and inserting the boat into the furnace body and sealing the furnace body;
After sealing the furnace body, maintaining the furnace body at atmospheric pressure for a set time;
After the set time has elapsed, evacuating the furnace body; and
And a step of supplying a raw material gas for generating a thin film on the surface of the substrate into the furnace body.   2. The thin film according to claim 1, wherein the set time is a time from when the substrate placed under the boat is inserted into the furnace body until thermal expansion reaches a saturation region. Generation method.   3. The method for producing a thin film according to claim 1, wherein a time required for the evacuation is shortened by a time for maintaining the inside of the furnace body in an atmospheric pressure state.   A method for manufacturing a semiconductor device, comprising the method for producing a thin film according to claim 1.

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