JP2014045143A - Method for forming silicon film, cyclohexasilane packing body, and device for forming silicon film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for forming a silicon film, capable of stably supplying vaporized cyclohexasilane gas even when cyclohexasilane is used, and capable of achieving fast-speed film formation, low-temperature film formation and high-step coverage when a chemical vapor deposition method is applied, and to provide a technique for forming a silicon film, capable of forming a silicon film with high purity.SOLUTION: In a method for forming a silicon film, cyclohexasilane stored in a material tank is sent out through a sending line to a vaporizer, cyclohexasilane is vaporized in the vaporizer, and vaporized cyclohexasilane in a reaction chamber is formed to a silicon film by chemical vapor deposition.

Description

  The present invention relates to a silicon film forming method for forming cyclohexasilane on a silicon film by chemical vapor deposition, a cyclohexasilane package, and a silicon film forming apparatus.

  Silicon thin films (amorphous silicon films, polysilicon films, etc.) used for semiconductors and electronic devices such as thin film transistors and integrated circuits are formed by a chemical vapor deposition method (CVD method) using monosilane, which is a gas material, as a raw material. In recent years, however, it has been required to increase the deposition rate in order to produce a larger amount of silicon thin film. In addition, in order to cope with a complicated device structure, the film is formed under low temperature conditions, and a uniform film on an uneven substrate is formed. There is a demand for film formation.

  Further, as a method of forming a liquid material into a thin film, a method of vaporizing a liquid once and then depositing it, for example, a CVD method is known. As a method for vaporizing a liquid material used in this CVD method, a method of vaporizing a liquid material by bubbling a carrier gas into the liquid material (a bubbling method), a liquid material by heating the liquid material without using the carrier gas, The method of vaporizing (baking method) and the like can be mentioned. In the bubbling method, the vaporization efficiency is increased by heating the liquid material. However, if the thermal stability of the liquid material is low, the vaporized gas discharge line may be clogged. Also in the baking method, the liquid material in the raw material tank is similarly heated to generate vaporized gas. However, if the substance used is sensitive to heat, the vaporized gas discharge line may be clogged.

  For example, in Patent Document 1, as a silicon film manufacturing method using a liquid silane compound, a silicon film is chemically formed on a substrate by applying thermal energy to a cyclic silane compound gasified with a carrier gas under normal pressure. A method of vapor deposition is disclosed. In this method, the cyclic silane compound is introduced into the reaction chamber together with the carrier gas in a normal pressure gas state. However, in the normal pressure CVD, it is difficult to maintain the uniformity of the wafer temperature, and the film thickness uniformity and the coverage property of the thin film are formed. There is a problem that particles such as dust are easily mixed in the silicon film. Patent Document 2 discloses a vaporizer for gasifying water, a CVD liquid raw material, or the like at normal pressure and supplying the gas to a semiconductor manufacturing apparatus. Patent Document 3 discloses a thin film forming apparatus and a thin film forming method for forming a mixed material containing silicon and carbon. A raw material liquid of an organosilane compound is instantaneously atomized by a high-speed carrier gas flow to form silicon. And a thin film containing carbon. Patent Document 4 discloses a liquid material vaporizer that includes a gas-liquid mixing unit that mixes a liquid material and a carrier gas, and a vaporization unit. Patent Document 5 discloses a method of forming a Si-containing film on a substrate by introducing a process gas containing cyclohexasilane into a chamber and chemically depositing cyclohexasilane.

JP 60-26664 A JP 2006-13086 A JP 2007-308774 A JP 2009-79302 A US Patent Application Publication No. 2012/0024223

However, none of the above-mentioned documents disclose that the CVD method is performed by using cyclohexasilane, which is transferred to a vaporizer through a delivery line while being liquid and vaporized. In particular, in Patent Document 5, cyclohexasilane is directly introduced into the chamber by bubbling of a vacuum pump. However, cyclohexasilane is solidified due to heating when bubbling, and the nozzles are clogged. There is a possibility that the amount of vaporized cyclohexasilane cannot be delivered and a high-quality silicon film cannot be formed.
In addition, cyclohexasilane has a low viscosity and is a colorless and transparent liquid. However, it tends to undergo thermal polymerization and photopolymerization. When polymerized, the viscosity tends to increase and the molecular weight tends to increase. There was a problem that a uniform amount of vaporized cyclohexasilane could not be stably supplied to the chamber.

The present invention is a silicon film forming technology that can stably supply vaporized cyclohexasilane gas even when cyclohexasilane is used, and enables high-speed film formation, low-temperature film formation, and high step coverage when a chemical vapor deposition method is employed. It is an issue to provide.
Another object of the present invention is to provide a silicon film forming technique capable of forming a high-purity silicon film.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors use cyclohexasilane, supply cyclohexasilane from the raw material tank to the vaporizer, and further vaporize cyclohexasilane in the vaporizer. It is possible to stably supply vaporized cyclohexasilane gas to the reaction chamber, and when chemical vapor deposition is adopted, high-speed film formation, low-temperature film formation and high step coverage are possible, and a high-purity silicon film can be formed. The headline and the present invention were completed.

  That is, in the silicon film forming method according to the present invention, cyclohexasilane contained in a raw material tank is sent to a vaporizer through a delivery line, cyclohexasilane is vaporized by the vaporizer, and vaporized in the reaction chamber. Is a method of forming a silicon film by chemical vapor deposition.

  The temperature of the raw material tank is preferably maintained at 50 ° C. or lower, and cyclohexasilane is sent from the raw material tank to the vaporizer by pumping or sucking cyclohexasilane with a pressurized inert gas in the delivery line. Is preferred. The liquid flow rate controller inserted in the delivery line may control the delivery amount of cyclohexasilane. Vaporization is preferably carried out through a vaporizing chamber with adjustable pressure and / or a vaporized gas outlet. At the jet outlet, cyclohexasilane is preferably jetted in the form of fine particles or mist, and the temperature of the jet outlet is preferably maintained at 100 ° C. or lower. The pressure in the vaporizing chamber is, for example, less than 5 kPa. The chemical vapor deposition is preferably a low pressure CVD method or a plasma CVD method, and it is preferable to form a silicon film by supplying monosilane gas and cyclohexasilane gas to the reaction chamber.

  The present invention includes a cyclohexasilane package for use in the above method and for filling a raw material tank. The content of each metal element in the cyclohexasilane package is preferably 10 ppm or less.

  Furthermore, the present invention includes a raw material tank for containing cyclohexasilane, a feed line connected to the raw material tank for sending the cyclohexasilane in liquid form from the raw material tank, and connected to the feed line. Also included is a silicon film forming apparatus comprising a vaporizer for vaporizing cyclohexasilane and a reaction chamber for converting the vaporized cyclohexasilane into a silicon film by chemical vapor deposition.

According to the present invention, since cyclohexasilane is vaporized by a vaporizer, vaporized cyclohexasilane gas can be stably supplied, and high speed film formation and low temperature film formation are possible when a silicon film is formed by chemical vapor deposition. It becomes.
Moreover, according to such a method, high step coverage can be achieved and a high-purity silicon film can be formed.

FIG. 1 is a diagram showing an embodiment of the silicon film forming method or silicon film forming apparatus of the present invention. FIG. 2 is a diagram showing another embodiment of the vaporizer in the silicon film forming method or silicon film forming apparatus of the present invention.

<Silicon film formation method>
Hereinafter, one embodiment of the silicon film forming method of the present invention will be described with reference to FIG. 1, but the present invention is not limited to the one embodiment.

  FIG. 1 is a schematic view of an apparatus for explaining an example of the silicon film forming method of the present invention. In this example, cyclohexasilane 2 contained in a raw material tank 1 is directed to a vaporizer 8 through delivery lines 5 and 6. This is characterized in that cyclohexasilane is vaporized by the vaporizer 8 and the cyclohexasilane vaporized in the reaction chamber 13 is formed into a silicon film by chemical vapor deposition.

  More specifically, the raw material tank 1 is provided with an inert gas introduction line 3, and the inert gas pressurized by opening a valve 4 attached to the line 3 is sent to the raw material tank 1. The internal cyclohexasilane 2 itself is pressurized. In the illustrated example, since the inlet of the delivery line 5 opens below the liquid level of the cyclohexasilane 2, the pressurized cyclohexasilane 2 is pumped to the vaporizer 8 through the delivery lines 5 and 6. Further, in the illustrated example, a liquid flow rate controller 7 is inserted on the delivery lines 5 and 6, and an appropriate amount of cyclohexasilane can be delivered to the vaporizer 8 by adjusting the flow rate of cyclohexasilane. . The vaporizer 8 includes a heater 10 capable of adjusting the temperature, a vaporization chamber 8a for securing a vaporization space, and a jet outlet 9 that opens in the vaporization chamber 8a. 6 is connected. And while adjusting the temperature in the vaporization chamber 8a with the heater 10, cyclohexasilane is ejected in a mist form from the ejection port 9 and vaporized. At this time, the carrier gas may also flow into the vaporizing chamber 8a at the same time. The vaporized cyclohexasilane is sent to the reaction chamber 13 through the delivery line 12 from the vaporized gas discharge port 11 provided on the downstream side of the vaporization chamber 8a. Since the reaction chamber 13 in the illustrated example includes a laminated body including the first electrode 14 and the substrate 15 and a second electrode 16 facing the substrate 15, the reaction chamber 13 is provided in the reaction chamber 13 from the delivery line 12. By introducing vaporized cyclohexasilane, a silicon film can be formed on the substrate 15 by chemical vapor deposition. Note that a vacuum pump 17 is connected to the reaction chamber 13 in the illustrated example so that the gas flow can be adjusted, and the temperature, pressure, and the like may be appropriately adjusted.

  According to the above method, since cyclohexasilane is vaporized by the vaporizer 8, the vaporized cyclohexasilane gas can be stably supplied. When a silicon film is formed by chemical vapor deposition, high-speed film formation and low-temperature formation are possible. A membrane is possible. Moreover, according to such a method, high step coverage can be achieved and a high-purity silicon film can be formed.

  It can be said that the feature of the present invention is that cyclohexasilane is vaporized without using the bubbling method or baking method. When vaporization is performed by the vaporizer 8, thermal polymerization of cyclohexasilane due to heating during bubbling is suppressed, and clogging of piping in the raw material tank 1, the delivery lines 5, 6 and the like can be prevented. In addition, cyclohexasilane that is not affected by thermal polymerization is stably supplied to the vaporizer 8, and the injection port 9, vaporized gas discharge port 11, etc. are obtained by solidification by thermal polymerization of cyclohexasilane. The clogging of the piping at can also be suppressed. Finally, vaporized cyclohexasilane that is not excessively polymerized and does not contain solids can be stably supplied to the reaction chamber, and high-speed film formation and low-temperature film formation are possible when the CVD method is adopted. In addition, high step coverage can be achieved, and a high-purity silicon film can be formed.

  The cyclohexasilane 2 may be any one produced by a conventionally known method. For example, cyclohexasilane obtained by coupling diphenyldichlorosilane with a metal to form a 6-membered ring, followed by halogenation and reduction steps. From the viewpoint of forming a high-purity silicon film, a material that has been purified to remove impurities may be used.

  In the raw material tank 1, it is recommended that cyclohexasilane 2 be stably supplied to the vaporizer 8 via the delivery lines 5 and 6 without causing the cyclohexasilane 2 to be thermally polymerized or photopolymerized. For example, the temperature of the cyclohexasilane 2 in the raw material tank 1 may be maintained at a predetermined temperature or lower, preferably 50 ° C. or lower, more preferably 45 ° C. or lower, and further preferably 40 ° C. or lower. If the temperature is lowered too much, the effect of preventing thermal polymerization and photopolymerization is saturated, but if cooled below the melting point, it solidifies and makes it difficult to transfer the liquid. Further, since the cooling cost increases, a lower temperature limit may be set. The lower limit of the temperature of cyclohexasilane 2 is preferably maintained at 15 ° C or higher, more preferably 18 ° C or higher, and further preferably 20 ° C or higher.

  The material of the raw material tank 1 is not particularly limited as long as the cyclohexasilane 2 is a material that does not undergo thermal polymerization or photopolymerization. For example, the material is a light-impermeable high-strength stable material, specifically, , Nickel, molybdenum, manganese, chromium, titanium, copper, aluminum, stainless steel, and alloys thereof. Specifically, the material of the raw material tank 1 is preferably stainless steel (SUS). Moreover, the raw material tank 1 may have a light-shielding property as needed, and may use a light-shielding plate. The raw material tank 1 preferably has pressure resistance from the viewpoint of pumping a liquid material and safely handling cyclohexasilane having pyrophoric properties. It is more preferable that the raw material tank having pressure resistance has 0.05 MPa or more. Further, the raw material tank 1 is required to have a take-out port attached with at least two valves shown in, for example, the delivery lines 5 and 6, etc., but at least one valve is a pressurizing valve or a material filling valve. Preferably, at least one valve is a liquid material transfer valve. In addition, the raw material tank 1 may have two or more outlets for the purpose of tank cleaning. The capacity of the raw material tank is preferably about 50 ml to 100 l, more preferably about 500 ml to 10 l. The shape of the raw material tank is not particularly limited, and examples thereof include a columnar shape, a prismatic shape, and a cylindrical shape.

  The delivery of the cyclohexasilane 2 from the raw material tank 1 toward the vaporizer 8 is not limited to the pressure delivery system as shown in FIG. A delivery method other than pressurization and suction may be used, but in any case, a non-heating delivery device is preferable. Further, in the case of the pressure feeding method, in the example of FIG. 1, the inert gas introduction line 3 is provided in the upper part (particularly the upper surface) of the raw material tank 1, and the flow rate of the inert gas can be adjusted by the valve 4. However, the connection position of the inert gas introduction line 3 can be set as appropriate and may be below the liquid level of the cyclohexasilane 2, but is preferably on the liquid level. The length of the delivery line 5 in the tank can be set as appropriate, but it is desirable that it extends to the vicinity of the tank bottom from the viewpoint of effective utilization of raw materials. The pressure at the time of pumping from the raw material tank 1 may be any pressure as long as the cyclohexasilane 2 is sent out from the raw material tank 1 to the vaporizer 8 while being in a liquid state.

  Examples of the inert gas include nitrogen, helium, neon, and argon. From the viewpoint of versatility and cost, the inert gas is preferably nitrogen, helium, or argon, and more preferably nitrogen or argon.

  In the delivery lines 5 and 6, it is preferable to send the cyclohexasilane 2 from the raw material tank 1 to the vaporizer 8 by a pressure feeding system or a suction system. The pressure feeding method can be achieved by installing an appropriate inert gas introduction line in the raw material tank or the like separately from the delivery lines 5 and 6. Further, at the time of pressure feeding, a mass flow controller may be installed at an appropriate place (for example, on the inert gas introduction line 3 or on the upstream side thereof). On the other hand, the suction method can be achieved by installing an appropriate liquid feed pump (tube pump or the like) between the delivery lines 5 and 6 or the raw material tank 1 and the vaporizer 8. In addition to these, a pressure reducing valve or an orifice may be adopted as the pressure reducing method. In addition, the inlet of the delivery line 5 may be provided downward in the raw material tank from the viewpoint of reducing intrusion of high specific gravity impurities, but the inlet of the delivery line 5 is not limited as long as it is in liquid, for example, Further, it may extend downward around the bottom of the raw material tank. As long as cyclohexasilane is sent in a liquid state, the materials of the delivery lines 5 and 6 can use materials known in the prior art, and may be corrosion-resistant aluminum, stainless steel, or the like. The structure of the delivery lines 5 and 6 is not particularly limited as long as it is a sealed pipe that transfers the liquid material from the raw material tank 1 to the vaporizer 8.

The liquid flow rate controller 7 inserted in the delivery lines 5 and 6 is not essential in the present invention, and appropriate pressure feed force control (including the above-described pressurization valve 4 and the mass flow controller formed in the inert gas introduction line). The delivery amount can be controlled as appropriate by controlling the suction speed or controlling the amount of rotation of the tube pump, but it is preferable to control the delivery amount of cyclohexasilane by the liquid flow rate controller 7. The position of the liquid flow rate controller 7 may be arbitrary as long as it is inserted on the delivery lines 5 and 6 from the raw material tank 1 to the vaporizer 8 and can control the flow rate of cyclohexasilane. The liquid flow rate controller 7 may be an appropriate conventionally known means, for example, a throttle valve (for example, an on-off valve). Preferably, the flow rate can be controlled while measuring a fluid mass flow rate such as a mass flow controller. Equipment is used. According to such a flow rate control device, it is not necessary to perform correction even if the use conditions change, and it is possible to measure the flow rate with high accuracy and control the flow rate. The flow control device is preferably composed of a flow sensor, a bypass, a flow control valve, an electric circuit, and the like. The delivered liquid is first divided into a flow sensor and a bypass, and the flow control valve may be controlled by an electric circuit so as to obtain an appropriate flow rate. Examples of fluid control valves include, but are not limited to, piezo actuator valves, thermal actuator valves, solenoid actuator valves, and the like.
When the liquid flow rate controller 7 is a throttle valve, it is preferable that the throttle valve is also appropriately controlled according to the flow rate. For example, a sensor for measuring the liquid flow rate may be provided on an appropriate place such as in the vaporizer 8 on the delivery line 6, and the opening of the throttle valve may be adjusted by a signal from this sensor.

  Any vaporizer may be used as long as it vaporizes by heating cyclohexasilane under reduced pressure, and a carrier gas may be used. Specifically, in the example of FIG. 1, the vaporizer 8 includes the vaporization chamber 8 a, the jet port 9 provided in the vaporization chamber 8 a, and the vaporized gas discharge port 11. . The cyclohexasilane sent from the delivery lines 5 and 6 toward the vaporizing chamber 8a is vaporized by being ejected from the ejection port 9. It is desirable that the temperature of the vaporizing chamber 8a can be adjusted. Specifically, the heater 10 is disposed in the central portion and / or the outer peripheral portion (the outer peripheral portion in the example of FIG. 1) of the vaporizing chamber 8a, and the internal temperature The distribution can be adjusted (for example, uniformly adjusted). Further, a pressure-reducing pressure reducing pump or the like may be connected to the vaporizing chamber 8a.

  In the vaporizer 8, by appropriately designing the shape of the vaporization chamber 8a and the location of the heater 10, the vaporized gas may be efficiently heated while heating the jet port 9 may be avoided. If heating of the jet port 9 is avoided, clogging of the jet port 9 due to thermal decomposition of cyclohexasilane can be prevented. FIG. 2 is a schematic view showing an example of such a separate heating type vaporizer 24. The vaporizer 24 is used in place of the vaporizer 8 in FIG. 1 and includes a first vaporization chamber 18 and a second vaporization chamber 19. Further, the first vaporization chamber 18 and the second vaporization chamber 19 communicate with each other through a connecting pipe, and the vaporized gas in the first vaporization chamber 18 can be quickly moved to the second vaporization chamber 19. In the vaporizer 24 shown in FIG. 2, a temperature for heating the vaporized cyclohexasilane is formed in the first vaporization chamber 18 by forming a jet port 20 connected to the delivery line (corresponding to the delivery lines 5 and 6 in FIG. 1). An adjustable heater 21 is arranged in the second vaporization chamber 19. Thus, by providing the vaporization chamber for ejection and the vaporization chamber for heating separately, vaporized cyclohexasilane can be stabilized while suppressing the thermal influence on the ejection port 20. A vaporized gas discharge port 23 (corresponding to the vaporized gas discharge port 11 in FIG. 1) for sending vaporized cyclohexasilane to the reaction chamber 13 is provided on the downstream side of the second vaporization chamber. Also in the vaporizer 24 of FIG. 2, it is preferable that a pressure-reducing decompression pump or the like is connected to the second vaporization chamber 19.

  Furthermore, the vaporizer of the present invention may include a carrier gas introduction line 22 as shown in FIG. That is, the carrier gas introduction line 22 may be connected to the upstream of the ejection port 20, and the mixture of cyclohexasilane and carrier gas from the delivery lines 5 and 6 may be ejected from the ejection port 20. By jetting together with the carrier gas, the vaporization efficiency of cyclohexasilane can be increased. This carrier gas can also be used as a carrier gas in chemical vapor deposition. The vaporizer 8 of FIG. 1 may also include a similar carrier gas introduction line.

  In the separate heating type vaporizer, the number of vaporization chambers is not particularly limited as long as the vaporization chamber for ejection and the vaporization chamber for heating are separately provided, and may be three or more. Moreover, even if it is one vaporization chamber, if the spout formation place and the heater installation place are separated, the same effect can be produced. Furthermore, in this invention, it is not necessary to provide a heating means (heater) in the vaporizer for ejecting cyclohexasilane.

  The shape of each of the vaporization chambers 8a, 18, 19 may be, for example, a cylinder, a prism, or an approximate shape thereof. The material of the vaporization chambers 8a, 18, 19 may be aluminum, stainless steel (or Stainless steel) or the like, and a temperature sensor, a pressure sensor, or the like may be attached to the inside of the vaporizing chambers 8a, 18, and 19. The temperature in the vaporizing chambers 8a, 18, and 19 is adjusted by the heaters 10 and 21, but the heaters 10 and 21 are installed in the vaporizing chambers 8a, 18, and 19 as long as cyclohexasilane vaporizes. Alternatively, it may be arranged around the vaporizing chambers 8a, 18, and 19. Since the gas jetted into the vaporizers 8 and 24 has a very high flow velocity, the space in the vaporization chambers 8a, 18 and 19 is further provided with a jet nozzle outlet 9 so that the jetted gas does not concentrate locally. , 20, the volume can be set sufficiently large so that the spray can be easily diffused.

  The cyclohexasilane is preferably ejected in the form of fine particles or mist through the ejection ports 9 and 20, and more preferably in the form of fine particles or mist under reduced pressure. The spouts 9 and 20 are provided on one side of the vaporizers 8 and 24 and normally include a spray nozzle.

  The cross-sectional area or the hole size of the ejection ports 9 and 20 or the ejection nozzle can be adjusted, and can be adjusted so that the ejection can be performed in the best state even when the type and flow rate of the carrier gas change. In the case of using a carrier gas, the liquid material is atomized by the jet energy from the jet outlet of the nozzle body at a flow velocity close to the critical velocity. The size of the atomized spray body is preferably about 1 pl to several μl (for example, less than 10 μl), more preferably 10 pl to several hundred pl (for example, 800 pl or less), and by changing the flow rate of the liquid flow rate controller 7 Or by controlling the size and number of nozzle holes and the input signal.

Important factors that affect liquid atomization include the liquid surface tension, viscosity, density, pressure before and after the carrier gas nozzle, the flow ratio of liquid material to carrier gas (gas-liquid ratio), and temperature. . In order to obtain a stable fine particle size spray, for each of these factors, reduce the surface tension of the liquid, reduce the viscosity of the liquid material, increase the differential pressure across the nozzle of the carrier gas, upstream It is preferable to perform operations such as increasing the pressure and increasing the gas-liquid ratio (decreasing the relative flow rate of the liquid material), thereby improving the atomization efficiency of the nozzle.
As means for vaporizing the liquid material with the vaporizers 8 and 24, introduction and vaporization are sequentially performed by introducing the liquid material into the vaporizers 8 and 24 in a liquid state, and then heating and vaporizing the vaporizers 8 and 24 for vaporization. There is no problem even if it goes by the method. However, from the viewpoint of stable vaporization, the liquid material alone or mixed with the carrier gas is sprayed in a mist form from the jet outlets 9 and 20 into the vaporizers 8 and 24 heated and depressurized as described above. A vaporization method is desirable.

  The temperature of the ejection ports 9 and 20, that is, the ambient temperature in the vicinity of the ejection port is preferably maintained at 100 ° C. or less, more preferably 95 ° C. or less, from the viewpoint of suppressing generation of solids due to thermal polymerization of cyclohexasilane. The temperature is preferably maintained at 50 ° C. or higher, more preferably 60 ° C. or higher. When the ambient temperature near the jet outlet is higher than 100 ° C., cyclohexasilane is thermally polymerized to cause clogging of the jet outlet. When the ambient temperature is less than 50 ° C., the amount of cyclohexasilane vaporized decreases.

  The pressure in the vaporization chambers 8a, 18, and 19 is preferably less than 5 kPa, more preferably 4 kPa or less, still more preferably 3 kPa or less, and even more preferably 1 kPa or less, from the viewpoint of suppressing thermal polymerization of cyclohexasilane. Preferably it is 0.1 Pa or more, More preferably, it is 1 Pa or more, More preferably, it is 10 Pa or more, More preferably, it is 50 Pa or more.

  The chemical vapor deposition is not limited to the apparatus illustrated in FIG. 1 or a method using this apparatus, and any CVD method can be selected. For example, the chemical vapor deposition is preferably a low pressure CVD method or a plasma CVD method. Low-pressure CVD is a chemical vapor deposition method that grows amorphous, polycrystalline, and single crystals by supplying a carrier gas and a compound containing a constituent element as a target deposit onto a substrate as a species having a high vapor pressure. The main reaction is a thermally excited chemical reaction, which means a chemical vapor deposition method in which the gas phase pressure is less than atmospheric pressure. The reaction chamber includes a substrate, a heater, a vacuum pump, a carrier gas supply pipe, and the like, and can thermally decompose the vaporized cyclohexasilane gas to deposit amorphous silicon or a polysilicon thin film on the substrate.

  Examples of the type of reactor in the reaction chamber in the low pressure CVD method include a horizontal type, a vertical type, a cylindrical type, a continuous type, and a tubular furnace type. For example, in the horizontal type, the substrate is placed horizontally and gas is introduced horizontally to the substrate to form a Si-containing film on the substrate. In the vertical type, the substrate is placed horizontally, and gas is introduced from the top or bottom of the reaction chamber to form a Si-containing film on the substrate. In the cylindrical type, the substrate is a cylindrical type, and gas is introduced from the upper or lower part of the reaction chamber to form a Si-containing film on the substrate. In the continuous type, a gas is introduced into the substrate placed on the belt conveyor from the upper part of the reaction chamber to form a Si-containing film on the substrate. In a tubular furnace type, a substrate is placed between a pair of tubular heaters, and a gas is sucked by a vacuum device to form a Si-containing film on the substrate. In the low pressure CVD method, the pressure in the reaction chamber is reduced by a vacuum pump or the like, but a pump such as a mechanical booster pump (MBP) or a turbo molecular pump (TMP) can be combined.

  The temperature of the reaction chamber in the low pressure CVD method is preferably 300 ° C. or higher, more preferably 350 ° C. or higher, more preferably 400 ° C. or higher, preferably 1300 ° C. or lower, more preferably 900 ° C. or lower, and still more preferably 800 ° C. or lower. is there. Further, these temperatures may be reaction temperatures (substrate temperatures) of cyclohexasilane or the like substantially thermally decomposed on the substrate. The pressure in the reaction chamber in the low pressure CVD method is preferably 1 Pa or more, more preferably 5 Pa or more, further preferably 10 Pa or more, preferably 1 kPa or less, more preferably 800 Pa or less, and further preferably 500 Pa or less.

  The flow rate of vaporized cyclohexasilane introduced into the reaction chamber is preferably 0.1 sccm or more, more preferably 0.5 sccm or more, still more preferably 1 sccm or more, preferably 1000 sccm or less, more preferably 500 sccm or less, still more preferably Is 300 sccm or less.

  The flow rate of the carrier gas (for example, nitrogen) introduced into the reaction chamber is preferably 10 sccm or more, more preferably 20 sccm or more, further preferably 30 sccm or more, preferably 10,000 sccm or less, more preferably 5000 sccm or less, and further preferably 3000 sccm. It is as follows.

The growth rate of the silicon film is preferably 1 nm / min or more, more preferably 2 nm / min or more, further preferably 10 nm / min or more, preferably 4000 nm / min or less, more preferably 1000 nm / min or less, and further preferably 500 nm / min. It is below min. In order to improve the growth rate of the film or the uniformity of the film thickness, it is preferable to use a flow in which the convection and stagnation in the reaction chamber are suppressed, and the flow is laminar, that is, the fluid streamline is always parallel to the delivery line 12 axis. What is necessary is just to make it. Including but Reynolds number R _e as the index, R _e is represented by the following general formula.
R _e = duρ / η (d: tube diameter (m), u: flow velocity (m / s), ρ: density (kg / cm ³ ), η: viscosity of Newtonian fluid (kg / m · s))
As this value is lower, turbulent flow is less likely to occur. Therefore, for example, a plurality of gas introduction pipes may be provided.

  The plasma CVD method uses plasma discharge to control the excitation / decomposition of gas gas or chemical reaction, generates a chemically active state by electron impact, etc., and is active at a lower temperature than in the case of thermal energy. It means a chemical vapor deposition method in which seeds and the like are deposited on a substrate. The plasma CVD method will be described with reference to FIG. 1. For example, the reaction chamber 13 may be provided with a first electrode 14, a substrate 15, a second electrode 16, a vacuum pump 17, a heater, and the like. The atoms and molecules of the vaporized cyclohexasilane gas are excited and become chemically active, and these chemically active species can be deposited on the substrate. The vacuum pump 17 is not essential in the present invention. However, the vacuum pump 17 reaches the substrate by reducing the frequency with which the molecules to be deposited collide with another gas molecule before reaching the substrate. Can be used as appropriate so as not to be mixed.

  Bipolar discharge, electrodeless discharge, or the like can be adopted as the type of reactor in the reaction chamber. For bipolar discharge, the reaction chamber preferably comprises a discharge electrode (eg, anode, cathode or first electrode, second electrode) connected to a radio frequency power supply (RF), heater, substrate, substrate holder, and the like. In electrodeless discharge, the reaction chamber preferably includes a high-frequency coil, a quartz tube, a substrate, a substrate holder, a heater, and the like, and the coil and the like may be connected to a high-frequency power source.

  Examples of excitation methods include high frequency plasma CVD, high density plasma (HDP) CVD, ECR plasma CVD, inductively coupled plasma (ICP) CVD, helicon wave plasma CVD, UHF or VHF plasma CVD. In the plasma CVD method, the pressure in the reaction chamber is reduced by a vacuum pump 17 or the like, and a pump such as a mechanical booster pump (MBP) or a turbo molecular pump (TMP) can be combined. In addition to the carrier gas, a gas such as hydrogen may coexist in the chamber. A considerable amount of hydrogen is mixed in the film, and various silicon films can be formed depending on conditions.

  The temperature of the reaction chamber in the plasma CVD method is preferably 200 ° C. or higher, more preferably 220 ° C. or higher, more preferably 250 ° C. or higher, preferably 450 ° C. or lower, more preferably 430 ° C. or lower, more preferably 410 ° C. or lower. is there. In addition, these temperatures may be substantially reaction temperatures (substrate temperatures) of chemically active substances on the substrate. The pressure in the reaction chamber in the plasma CVD method is preferably 0.01 Pa or higher, more preferably 0.1 Pa or higher, still more preferably 1 Pa or higher, even more preferably 10 Pa or higher, preferably 1 kPa or lower, more preferably 700 Pa or lower, Preferably it is 500 Pa or less. Within such a range, the frequency of collision of the active species with the substrate can be increased, so that the film can be formed efficiently.

  The flow rate of vaporized cyclohexasilane introduced into the reaction chamber and the flow rate of the carrier gas (for example, nitrogen) may be the same as described above.

  The growth rate of the silicon film is preferably 1 nm / min or more, more preferably 2 nm / min or more, further preferably 5 nm / min or more, preferably 500 nm / min or less, more preferably 400 nm / min or less, and further preferably 300 nm / min. It is below min.

  A silicon film may be formed by supplying monosilane gas and cyclohexasilane gas to the reaction chamber. By using either one as an additive, different characteristics occur, such as higher film coverage than when used alone, and higher step coverage, and a wide variety of silicon films can be formed. The monosilane gas may be mixed by an introduction line provided from the vaporization outlet of the vaporizer of the vaporized cyclohexasilane gas to the reaction chamber, or directly introduced into the reaction chamber by a line different from the cyclohexasilane gas. May be.

  Between the vaporizer 8 and the reaction chamber 13, a delivery line 12 for supplying vaporized cyclohexasilane gas from the vaporizer to the reaction chamber may be provided. By heating the delivery line 12, the cyclohexasilane gas can be stably supplied to the reaction chamber 13 without being liquefied between the vaporizer and the reaction chamber. This is preferable from the viewpoint of stabilizing the supply amount.

  In addition, after forming the silicon film, the raw material tank used in the silicon film forming method of the present invention, the piping of the delivery line, etc. are decompressed and / or heated to completely remove the remaining liquid material or vaporized gas. Thus, the silicon film may be formed safely and repeatedly.

<Cyclohexasilane package>
The present invention includes a cyclohexasilane package for use in the silicon film forming method and for filling a raw material tank.

  The content of each metal element in the cyclohexasilane package is preferably 10 ppm or less, more preferably 5 ppm or less, still more preferably 1 ppm or less, and even more preferably 0.1 ppm or less. In the present invention, each metal element is derived from impurities contained in the reaction raw material at the time of synthesizing the cyclohexasilane compound or contamination in the production process. Examples of each metal element include lithium and sodium. , Potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, titanium, chromium, manganese, iron, cobalt, nickel, copper, silver, zinc, cadmium, boron, aluminum, gallium, phosphorus, arsenic, etc. In addition, chlorine, bromine and the like may be included in the above definition. The smaller the content of each metal element in the cyclohexasilane package, the higher the purity of the resulting silicon film.

<Silicon film>
The present invention also includes a silicon film formed by the silicon film forming method. The silicon film formed by the silicon film forming method can be formed at high speed and low temperature, can achieve high step coverage, and is a high-purity film. Therefore, it is a semiconductor, electronic device such as a thin film transistor or an integrated circuit, etc. Regardless of whether it is an amorphous silicon film or a polysilicon film, these films can be suitably used in places where they are needed. In addition, since high step coverage can be achieved, it can be suitably used particularly when a film is formed on a substrate having unevenness and a film is buried in a trench structure.

  The silicon film can be widely used as a member of a semiconductor thin film transistor, and various applications such as a three-dimensionally mounted polysilicon electrode are assumed. Moreover, it can be used in a wide range of fields such as solar cells and display members as electronic devices.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention. In the following, “part” means “part by mass” and “%” means “mass%” unless otherwise specified.

Example 1
A silicon film was formed using the apparatus shown in FIG. Specifically, first, cyclohexasilane was produced by a conventionally known method, and 700 mL of the obtained cyclohexasilane (each metal element content: 1 ppm or less) was added to a raw material tank 1 having a volume of 1 L (withstand pressure of 0.05 MPa or more). The temperature of the raw material tank 1 was set to 25 ° C. The raw material tank 1 has an inert gas introduction line 3 installed above the cyclohexasilane liquid level of the raw material tank 1 and an inlet at the lower liquid level of the raw material tank 1, and is external to the raw material tank through the upper part of the raw material tank. The delivery line 5 extending to the carburetor 8 was installed. The valve 4 was opened and the inert gas nitrogen was introduced into the raw material tank 1, and while the raw material tank was slightly pressurized, the cyclohexasilane was pumped out of the raw material tank while still in liquid form.

  Further, a liquid flow rate controller 7 for controlling the amount of cyclohexasilane delivered is inserted on the delivery lines 5 and 6, and the flow rate of cyclohexasilane to the vaporizer 8 is adjusted. The temperature of the vaporizing chamber 8a was set to 100 ° C. (that is, the temperature of the jet port 100 ° C.) by the heater 10 in the vaporizer 8, and the pressure of the vaporizing chamber 8a was set to 0.5 kPa. Cyclohexasilane is sprayed in the form of a mist from an outlet 9 provided in the vaporizing chamber 8a for vaporizing cyclohexasilane, and the vaporized cyclohexasilane is discharged from the vaporized gas discharge port 11, and is sent through a delivery line 12. Then, it was supplied to the reaction chamber 13 to form a film by the plasma CVD method.

The reaction chamber 13 includes a first electrode (lower electrode) 14, a second electrode (upper shower electrode) 16, a heater (not shown), and a substrate 15, and each electrode 14, 16 is an RF outside the reaction chamber. Connected to a power supply (13.56 MHz) (not shown), the reaction chamber 13 was made of aluminum. In the reaction chamber 13, vaporized cyclohexasilane was deposited by chemical vapor deposition under the conditions of a substrate temperature of 400 ° C., a carrier gas (N ₂ ) flow rate of 1000 sccm, a cyclohexasilane (CHS) flow rate of 100 sccm, and an RF power of 200 W. An amorphous silicon film was formed thereon (amorphous silicon film deposition rate of 100 to 110 nm / min). The obtained amorphous silicon film was capable of high-speed film formation and low-temperature film formation, and the silicon film had high purity and high step coverage even on an uneven substrate.

Example 2
An amorphous silicon film was formed by plasma CVD in the same manner as in Example 1 except that the temperature of the raw material tank 1 was 25 ° C. and the temperature of the vaporization chamber 8a was 60 ° C. As a result, the amorphous silicon film formation speed was 90 to 100 nm / min. However, the obtained silicon film can be formed at high speed and low temperature, and the amorphous silicon film has high purity and is uneven. High step coverage even on a substrate with

Comparative Example 1
The inert gas introduction line 3 of the raw material tank 1 is installed below the liquid level or the bottom surface of the raw material tank as the delivery line 5, while the delivery line 5 is installed above the liquid level as the inert gas introduction line 3. In the raw material tank 1, the vaporization method is changed to the bubbling method so that the inert gas can be introduced from the inert gas introduction line 3 and the inert gas and the vaporized cyclohexasilane gas can be sent from the delivery line 5 toward the reaction chamber. changed. An amorphous silicon film was formed by plasma CVD in the same manner as in Example 1 except that the temperature of the raw material tank 1 was 25 ° C. and the vaporizer 8 was not installed. As a result, since cyclohexasilane was not sufficiently vaporized, sufficient and stable vaporized cyclohexasilane could not be supplied to the reaction chamber, and an amorphous silicon film could not be formed.

Comparative Example 2
An amorphous silicon film was formed by plasma CVD in the same manner as in Example 1 except that the raw material tank 1 was changed to the bubbling method and the temperature of the raw material tank 1 was changed to 70 ° C. As a result, when bubbling was performed in the raw material tank 1, solids were generated on the delivery lines 5 and 6 by thermal polymerization of cyclohexasilane, causing clogging of the piping.

Comparative Example 3
An amorphous silicon film was formed by plasma CVD in the same manner as in Example 1 except that the temperature of the vaporizing chamber 8a was set to 130 ° C. As a result, a solid substance of cyclohexasilane adhered to the ejection port 9 of the vaporizer 8, and the resulting amorphous silicon film contained foreign matter.

According to the present invention, it is possible to provide a silicon film formation technique capable of high-speed film formation, low-temperature film formation and high step coverage by chemical vapor deposition, and to provide a high-purity silicon film formation technique. it can.
The obtained silicon film can be widely used as a member of a semiconductor thin film transistor, and various uses such as a three-dimensionally mounted polysilicon electrode are assumed. Moreover, it can be used in a wide range of fields such as solar cells and display members as electronic devices.

1: Raw material tank 2: Cyclohexasilane 3: Inert gas introduction line 4: Valve 5, 6: Delivery line 7: Liquid flow rate controller 8, 24: Vaporizer 8a: Vaporization chamber 9, 20: Outlet 10, 21 : Heater 11, 23: Vaporized gas discharge port 12: Delivery line 13: Reaction chamber 14: First electrode 15: Substrate 16: Second electrode 17: Vacuum pump 18: First vaporization chamber 19: Second vaporization chamber 22: Carrier Gas introduction line

Claims (13)

  A silicon film forming method in which cyclohexasilane contained in a raw material tank is sent to a vaporizer through a delivery line, cyclohexasilane is vaporized by the vaporizer, and the cyclohexasilane vaporized in the reaction chamber is converted into a silicon film by chemical vapor deposition. .   The method according to claim 1, wherein the temperature of the raw material tank is maintained at 50 ° C. or lower.   The method according to claim 1 or 2, wherein in the delivery line, cyclohexasilane is delivered from a raw material tank to a vaporizer by feeding or sucking cyclohexasilane with a pressurized inert gas.   The method according to claim 1, wherein a delivery amount of cyclohexasilane is controlled by a liquid flow rate controller inserted in the delivery line.   In the vaporizer, cyclohexasilane from the delivery line is vaporized through a jet port provided in the vaporization chamber, a vaporization chamber capable of adjusting temperature and / or pressure, and a vaporized gas discharge port. 5. The method according to any one of 4.   The method according to claim 5, wherein cyclohexasilane is ejected in the form of fine particles or mist by the ejection port.   The method according to claim 5, wherein the temperature of the jet outlet is maintained at 100 ° C. or lower.   The method according to claim 5, wherein the pressure in the vaporization chamber is maintained at less than 5 kPa.   The method according to claim 1, wherein the chemical vapor deposition is a low pressure CVD method or a plasma CVD method.   The method according to claim 1, wherein a silicon film is formed by supplying monosilane gas and cyclohexasilane gas to the reaction chamber.   A cyclohexasilane package for use in the method according to claim 1 to fill a raw material tank.   The cyclohexasilane package according to claim 11, wherein the content of each metal element is 10 ppm or less.   A raw material tank for containing cyclohexasilane, a supply line connected to the raw material tank for sending the cyclohexasilane in liquid form from the raw material tank, and connected to the supply line for vaporizing cyclohexasilane And a reaction chamber for converting the vaporized cyclohexasilane into a silicon film by chemical vapor deposition.

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