JP5605464B2 - Film forming apparatus and cleaning method thereof - Google Patents

Description

  The present invention relates to a film forming apparatus for forming a polymer thin film such as a polyimide thin film on the surface of a semiconductor wafer or the like and a cleaning method therefor.

In general, in order to manufacture a semiconductor integrated circuit or the like, various processes such as a film forming process, an etching process, and an oxidation process are repeatedly performed on a semiconductor wafer made of a silicon substrate or the like. In general, inorganic insulating films such as SiO ₂ films are the mainstream as insulating films used in the semiconductor integrated circuits. However, since the manufacturing process and process conditions have been relatively simple, Polymer thin films made of organic substances have been studied (Patent Documents 1, 2, 3 and Non-Patent Document 1).

  For example, this polymer thin film typified by a polyimide thin film has been studied for use as an interlayer insulating film in a semiconductor integrated circuit, a liquid crystal alignment film in a liquid crystal display device, or the like. In addition, the polymer thin film is attracting attention as an inter-chip insulating film when mounting so-called chips on which integrated circuits are formed, three-dimensionally stacked and mounted as another application. As a method for forming this polymer thin film, a so-called wet method in which a raw material monomer is dissolved in a solvent, and this is spin-coated on a semiconductor wafer and polymerized, or the polymer thin film is formed into a film in advance to form a wafer. A film method that is bonded to the surface, a vapor deposition polymerization method in which a raw material monomer is evaporated and polymerized in a vacuum vessel in a reduced pressure atmosphere, and the like are known.

JP-A 61-261322 Japanese Patent Laid-Open No. 9-143681 JP 2000-21867 A "Electrical, thermal and mechanical properties of polyimine thin films pre-prepared by high-temperature vapor deposition polymerization," High Perm. 5 (1993) 229-237 pp. ]

  By the way, in the above wet method, not only is it difficult to reduce the film thickness sufficiently, but the adhesion between the thin film and the substrate (semiconductor wafer) is not sufficient, and impurities are added during the addition and removal of the solvent. There are drawbacks such as easy mixing and pinholes or the like where the volatile components of the solvent are removed. In addition, the film method has a drawback that when a recess is present on the wafer surface, it cannot be embedded in the recess.

  On the other hand, the vapor deposition polymerization method is a relatively preferable method because it can eliminate all the disadvantages of the wet method described above. However, in this vapor deposition polymerization method, a large amount of unnecessary film adheres to the inner wall surface of the processing vessel or the wafer boat that holds the wafer. However, a cleaning method for removing this unnecessary film has been sufficiently established. The current situation was not.

  The present invention has been devised to pay attention to the above problems and to effectively solve them. An object of the present invention is to use a fluorine-based gas as a cleaning gas when removing unnecessary polymer thin film adhering to the inside of a processing container by a cleaning process, thereby providing a holding means for holding the processing container itself or an object to be processed. It is an object of the present invention to provide a film forming apparatus capable of selectively and efficiently removing only unnecessary polymer thin films without causing damage and a cleaning method therefor.

Invention, vertical quartz processing barber vessel polyimide thin film or a polyurea film on the surface of the object held by the holding means to the processing chamber while evacuating by a vacuum evacuation system a according to claim 1 In the method for cleaning a film forming apparatus for forming a polymer thin film, the film is formed in the processing container while maintaining the processing container at a predetermined temperature after performing the film forming process of the polymer thin film using a plurality of source gases. And a cleaning method for a film forming apparatus, wherein a cleaning process is performed by flowing an F ₂ gas, which is a fluorine-based gas, as a cleaning gas in the vacuum exhaust system .
Thus, when the polymer thin film made of an unnecessary polyimide thin film or polyurea thin film adhering to the film forming apparatus is removed by the cleaning process, by using F ₂ gas which is a fluorine-based gas as the cleaning gas , In addition, it is possible to selectively and efficiently remove not only the unnecessary polymer thin film attached to the vacuum exhaust system.
請Motomeko 6 engaging Ru invention is a film forming apparatus for forming a polymer thin film made of polyimide thin film or polyurea film on the surface of the object to be processed, the vertical processing container for accommodating a plurality of workpiece and A holding means having a plurality of stages for holding the object to be processed in the processing container, a vacuum exhaust system for evacuating the processing container, and the polymer into the processing container A gas supply means for supplying a plurality of raw material gases for the thin film, a cleaning gas supply means for supplying F ₂ gas, which is a fluorine-based gas, as a cleaning gas into the processing container, a container heating means for heating the processing container, formed, characterized in that it and a device control unit for controlling to implement the cleaning method of the film formation apparatus according to claim 1乃optimum 5 gall deviation or claim controls the operation of the entire apparatus It is a membrane device.
In a film forming apparatus for forming a polymer thin film made of a polyimide thin film or the polyurea thin film on a surface of an object to be processed, a vertical processing container that accommodates a plurality of the objects to be processed; A holding unit having a plurality of stages for holding the object to be processed in the processing container, a vacuum exhaust system for evacuating the processing container, and the polymer thin film into the processing container Gas supply means for supplying a plurality of source gases, cleaning gas supply means for supplying F ₂ gas, which is a fluorine-based gas, as a cleaning gas into the processing container, container heating means for heating the processing container, and the entire apparatus And a device control unit for controlling the operation of the film forming apparatus.

In this way, when the polymer thin film made of an unnecessary polyimide thin film or polyurea thin film adhering to the inside of the processing container of the film forming apparatus is removed by the cleaning process, by using F ₂ gas which is a fluorine-based gas as the cleaning gas. Only the unnecessary polymer thin film can be selectively and efficiently removed without damaging the processing container itself or the holding means for holding the object to be processed.

In this case, the said equipment controller For example, the fluorinated polymer film is in the cleaning gas, excessively enforce time the cleaning operation of the length to the vicinity of the surface which is fluorinated comes to volatilize It is characterized by doing.
Further, characterized by having a temperature control unit for controlling the temperature during the cleaning process in the range of 150 to 300 ° C. In example embodiment.

Further, the processing vessel In example embodiment is characterized in that it is made of quartz.

The plurality of raw material gas when forming the polyimide thin film if example embodiment is characterized in that the more the pyromellitic dianhydride (PMDA) 4,4'-diaminodiphenyl ether (ODA).
The plurality of raw material gas when forming the polyurea film if example embodiment, the feature to become more and 4,4'-diphenylmethane diisocyanate (MDI) and 4,4'-diaminodiphenylmethane (MDA) To do.

Related art of the present invention is a method of cleaning the film deposition apparatus that is used to form a polymer thin film made of polyimide thin film or polyurea film on the surface of the object, as a cleaning gas into the treatment Barber vessel A cleaning method for a film forming apparatus, wherein a cleaning process is performed by supplying F ₂ gas, which is a fluorine-based gas.

In this case, the cleaning process if example embodiment, the polymer thin film is fluorinated in the cleaning gas, excess and characterized in that near the surface that is fluoride is carried the length of time until the volatilized To do.
The temperature during the cleaning process For example is characterized in that it is in the range of 150 to 300 ° C..

The plurality of raw material gas when forming the polyimide thin film if example embodiment is characterized in that the more the pyromellitic dianhydride (PMDA) 4,4'-diaminodiphenyl ether (ODA).

The plurality of raw material gas when forming the polyurea film if example embodiment, the feature to become more and 4,4'-diphenylmethane diisocyanate (MDI) and 4,4'-diaminodiphenylmethane (MDA) To do.

Yet another related art of the present invention, when cleaning the film forming apparatus, and controls the film deposition apparatus to carry out the above cleaning method, that was to store readable program in a computer This is a characteristic storage medium.

According to the film forming apparatus and the cleaning method thereof according to the present invention, the following excellent operational effects can be exhibited.
According to the present invention, when removing a polymer thin film made of an unnecessary polyimide thin film or polyurea thin film attached to the film forming apparatus by a cleaning process, by using F ₂ gas which is a fluorine-based gas as a cleaning gas , process not vessel only only obsolete polymer film adhering to the inside of the vacuum exhaust system selectively and can be efficiently removed.
According to the related art of the present invention, when a polymer thin film made of an unnecessary polyimide thin film or polyurea thin film adhering to a processing container of a film forming apparatus is removed by a cleaning process, F ₂ that is a fluorine-based gas is used as a cleaning gas. By using the gas, it is possible to selectively and efficiently remove only the unnecessary polymer thin film without damaging the processing container itself or the holding means for holding the object to be processed.

It is a section lineblock diagram showing the film deposition system concerning the present invention. It is a cross-sectional view which shows the wafer boat which is a holding means. It is the elements on larger scale which show a wafer boat. Is a graph showing the selectivity of the etching of the F ₂ gas to polyimide thin film and the quartz. It is a graph which shows the element concentration of the film thickness direction of the polyimide thin film (PI) formed on the silicon substrate. The electron micrograph of the film thickness direction of the polyimide thin film (PI) formed on the silicon substrate is shown. It is a figure which shows the fluorine concentration at the time of an etching, and temperature dependence.

Hereinafter, an embodiment of a film forming apparatus and a cleaning method thereof according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a sectional view showing a film forming apparatus according to the present invention, FIG. 2 is a transverse sectional view showing a wafer boat as holding means, and FIG. 3 is a partially enlarged view showing the wafer boat. Here, a case where a polyimide thin film, which is a polyimide resin thin film, is formed as an example of the polymer thin film will be described.

  As shown in the figure, this film forming apparatus 2 has a vertical processing container 4 having a ceiling with a lower end opened and having a predetermined length in the vertical direction and having a cylindrical shape. For example, quartz having high heat resistance can be used for the processing container 4. A wafer boat 6 as a holding means on which a plurality of semiconductor wafers W as processing objects are placed at a predetermined pitch over a plurality of stages from below the processing container 4 is removably inserted and removed. The structure of the wafer boat 6 will be described later. When the wafer boat 6 is inserted into the processing container 4, the opening 4 </ b> A at the lower end of the processing container 4 is closed and sealed with a metal lid portion 8 made of, for example, aluminum or aluminum alloy.

  At this time, a seal member 10 such as an O-ring is interposed between the lower end portion of the processing container 4 and the peripheral portion of the lid portion 8 in order to maintain airtightness. The lid 8 may be formed of a stainless plate. The wafer boat 6 is attached and fixed to the upper surface side of the lid portion 8. The lid portion 8 is attached to the tip of an arm 12A extending from an elevating mechanism 12 such as a boat elevator, for example, so that the wafer boat 6 and the lid portion 8 can be integrally raised and lowered.

  The side of the processing container 4 is provided with a container heating means 14 made of, for example, a carbon wire heater that surrounds the processing container 4, and the quartz processing container 4 and the object to be processed are disposed inside the processing container 4. A certain semiconductor wafer W can be heated. And this container heating means 14 is connected to the heater power supply 15 which supplies electric power to this. Further, a heat insulating material 16 is provided on the outer periphery of the container heating means 14 to ensure this thermal stability.

  A temperature sensor 18 made of, for example, a thermocouple is provided in the vicinity of the container heating unit 14, and measures the temperature of the processing container 4 close to the container heating unit 14. A gas supply means 20 for supplying a predetermined gas into the processing container 4 is provided on the lower side wall of the processing container 4. Specifically, the gas supply means 20 includes a first source gas supply system 22 and a second source gas supply system for supplying a plurality of source gases for film formation, here two types of source gases. 24 and a cleaning gas supply system 26 for supplying a cleaning gas.

Actually, although not shown, an inert gas supply system for supplying a rare gas such as N ₂ gas or Ar or He as a purge gas or a dilution gas as necessary is also provided. The first source gas supply system 22, the second source gas supply system 24, and the cleaning gas supply system 26 are respectively made of quartz first provided so as to penetrate, for example, the lower side wall of the processing vessel 4. , Second and third gas nozzles 22A, 24A, 26A. Here, straight straight tubes are used as the first, second and third gas nozzles 22A, 24A and 26A.

  Each of these gas nozzles 22A, 24A, and 26A is actually provided in the flange portion 4B having a thickness at the lower end portion of the processing container 4. Further, instead of this structure, a stainless steel cylindrical manifold may be provided at the lower end of the processing container 4, and the gas nozzles 22A, 24A, and 26A may be provided in the manifold.

  Gas passages 22B, 24B, and 26B are connected to the first, second, and third gas nozzles 22A, 24A, and 26A, respectively, and supply source gases and cleaning gases whose flow rates are controlled. It is like that. Further, the gas passages 22B and 24B for the raw material gas are provided with winding heaters 22C and 24C such as tape heaters, for example, and the vapor pressure is increased by heating each passage. It is designed to prevent liquefaction and solidification during the flow of the source gas. On the way of the gas passages 22B, 24B, and 26B, on-off valves 22D, 24D, and 26D for supplying and stopping the supply of the gases are provided, respectively. Here, for example, pyromellitic dianhydride (hereinafter also referred to as “PMDA”) and 4,4′-diaminodiphenyl ether (hereinafter also referred to as “ODA”) are used as the two kinds of source gases.

Since the PMDA is solid at room temperature, it is sublimated by heating to about 250 ° C., for example, and the generated gas is transferred together with a carrier gas whose flow rate is controlled. Further, since the ODA is solid at room temperature, it is liquefied by heating, and vapor is generated by bubbling this liquid with a carrier gas whose flow rate is controlled, and is transferred together with the carrier gas. As the carrier gas, for example, N ₂ gas which is an inert gas is used here, but a rare gas such as He may be used instead. As the cleaning gas, a fluorine-based gas is used. Here, for example, 4% concentration of F ₂ (fluorine gas) is used as the fluorine-based gas.

  Further, an exhaust port 28 bent in an L shape in the lateral direction is provided in the ceiling portion of the processing container 4. A vacuum exhaust system 30 for evacuating the inside of the processing container 4 is connected to the exhaust port 28. Specifically, the vacuum exhaust system 30 has an exhaust passage 32 connected to the exhaust port 28. The exhaust passage 32 includes a pressure control valve 32A such as a butterfly valve, and a reaction in the exhaust gas. A trap mechanism 32B and a vacuum pump 32C for sequentially collecting by-products and unreacted raw material gas are respectively provided.

  Here, the wafer boat 6 as a holding means for holding the wafer W will be described. As shown in FIGS. 2 and 3, the wafer boat 6 includes a plurality of columns, three columns 36A, 36B, and 36C in the illustrated example, and a plurality of stages along the longitudinal direction of the columns 36A to 36C. It is mainly composed of a plurality of fixed mounting tables 38. The wafer boat 6 is provided with an internal cooling means 40 (see FIG. 1) for cooling the wafers W held by the wafer boat 6.

  Specifically, the entire wafer boat 6 is formed of a metal that does not cause contamination of the wafer W, such as aluminum or an aluminum alloy. The three struts 36A to 36C forming a part of the wafer boat 6 are provided upright from the lid portion 8 that seals the opening 4A at the lower end of the processing container 4, and each of the struts 36A to 36C is provided. The upper ends are connected to each other by a top plate 42 (see FIG. 1). The mounting table 38 is formed in a disk shape having a predetermined thickness, and is supported on the back surface of the mounting table 38 in an L shape extending in the center direction from the three columns 36A to 36C. The distal ends of the arms 44A, 44B and 44C are connected and fixed to support the mounting table 38 (see FIG. 2). Then, the wafer W is directly mounted on the upper surface side of the mounting table 38. The pitch P1 of the mounting table 38 is, for example, about 8 mm, but is not particularly limited.

  Here, the diameter of the mounting table 38 is set to be slightly smaller than the diameter of the wafer W, for example, about several centimeters, and as shown in FIG. 2, a bifurcated fork 46 for transferring the wafer W is provided. Thus, the lower surface of the peripheral portion of the wafer W is supported and can be lifted or lowered.

  A transfer mechanism (not shown) having the fork 46 is provided in a loading area below the processing container 4. Further, as shown in FIG. 2, the three columns 36A to 36C are arranged at equal intervals on a substantially semicircular circumferential portion on the opposite side to the direction in which the fork 46 enters, and the wafer is transferred. The time fork 46 and each of the columns 36A to 36C do not interfere with each other. In the case shown in FIG. 1, seven mounting tables 38 are provided. However, depending on the size of the processing container 4 in the height direction, about 25 to 100 are actually provided.

  On the other hand, the internal cooling means 40 for cooling the wafer W is mainly constituted by a refrigerant passage 48 formed in the wafer boat 6 and a refrigerant circulation portion 50 for circulating the refrigerant through the refrigerant passage 48. Specifically, the refrigerant passage 48 includes two strut passages 52A and 52C formed along the two struts 36A and 36C among the three struts 36A to 36C, and the two struts 36A. 36C, arm passages 54A, 54C formed in the support arms 44A, 44C extending from 36C, and a mounting base passage 56 formed in, for example, a meandering manner in the mounting base 38 over the entire surface thereof. Yes.

  In each mounting table 38, the arm internal passage 54A, the mounting base internal passage 56, and the arm internal passage 54C are connected in series, and each of the internal arm passages 54A and 54C is connected to the two post internal passages 52A and 52C. They are connected to each other. As a result, the refrigerant can be allowed to flow to the placement table passage 56 of each placement table 38.

  Further, as shown in FIG. 1, the strut passages 52 </ b> A and 52 </ b> C and the refrigerant circulation section 50 are connected by a bellows-like expansion / contraction tube 58 that can be expanded and contracted. The expansion and contraction tube 58 can follow the up-and-down movement of the wafer boat 6 while circulating the refrigerant. As the internal cooling means 40 formed in this way, for example, a chiller (registered trademark) can be used. A temperature sensor 60 made of, for example, a thermocouple for measuring the wafer temperature (mounting table temperature) is provided on a part of the mounting table 38 of the wafer boat 6.

  The refrigerant circulation unit 50 and the heater power supply 15 are controlled by a temperature control unit 62 made of, for example, a computer. Specifically, the temperature control unit 62 receives both outputs of the temperature sensor 18 that detects the temperature of the processing container 4 and the temperature sensor 60 that detects the temperature of the mounting table 38. And the mounting table 38 are controlled so that the temperature difference is not less than a predetermined temperature difference, for example, not less than 50 ° C. That is, the temperature of the side wall of the processing container 4 is controlled to be higher by 50 ° C. or more than the mounting table 38.

  The operation of the entire apparatus, for example, the start and stop of the supply of each gas, the pressure control in the processing container 4, the operation command to the temperature control unit 62, and the like are controlled by a device control unit 64 such as a computer. . The apparatus control unit 64 stores a storage medium 66 such as a flexible disk, a flash memory, a hard disk, a CD-ROM, or a DVD for storing a program that can be read and written by a computer for controlling the operation of the entire apparatus. have.

  Next, the film forming method performed using the film forming apparatus 2 configured as described above and the cleaning method of the present invention will be described. As described above, the operation described below is performed based on the program stored in the storage medium 66.

  First, the film forming method will be described. For example, when the semiconductor wafer W made of a silicon wafer is in an unloaded state and the film forming apparatus 2 is in a standby state, the processing container 4 is maintained at a process temperature or a lower temperature. A wafer boat 6 on which a large number of wafers W, for example, 50 wafers W are placed, is loaded into the processing container 4 which has been brought into a hot wall state by the container heating means 14 from above and loaded, and the lid 8 By closing the opening 4A at the lower end of the processing container 4, the inside of the processing container 4 is sealed.

Then, the inside of the processing container 4 is evacuated by the evacuation system 30 and maintained at a predetermined process pressure, and the power supplied to the container heating means 14 is increased to increase the temperature of the processing container 4 itself and the wafer temperature. Then, the temperature is raised to the process temperature for film formation and stabilized.
Further, the internal cooling means 40 provided in the wafer boat 6 is driven in advance in the wafer boat 6 so that the refrigerant flows in the refrigerant passage 48, and each mounting table 38 is set to a predetermined temperature.

  That is, the refrigerant supplied from the refrigerant circulation section 50 passes through one of the telescopic pipes 58 and ascends in the intra-post passage 52A provided in the post 36A of the wafer boat 6, and from the intra-post passage 52A to each arm passage 54A. It branches and flows into the mounting base channel | path 56 of each mounting base 38 through this, and this mounting base itself is cooled. The refrigerant flowing in the mounting table passage 56 passes through the other arm inner passage 54C and joins in the pillar inner passage 52C provided in the other pillar 36C, and the joined refrigerant passes through the other telescopic pipe 58. It will return to the circulation part 50. In this way, the refrigerant circulates in the wafer boat 6 and cools the mounting tables 38 and the wafers W mounted thereon.

  Then, in this state, the gas supply means 20 is driven to introduce the PMDA transported together with the carrier gas from the first gas supply system 22 into the processing container 4 and from the second gas supply system 24 to the carrier. The ODA transported together with the gas is introduced into the processing container 4, and the pressure in the processing container 4 is maintained at a predetermined process pressure by the vacuum exhaust system 30. As a result, the raw material gases are polymerized to deposit or deposit a thin film made of a polyimide thin film on the surface of the wafer W.

  During the film formation process by this polymerization reaction, the process pressure in the processing container 4 is maintained within a range of 1 to 10 Torr (133.3 to 1333 Pa), for example. The temperatures of the processing container 4 and the mounting table 38 are detected by temperature sensors 18 and 60, respectively, and input to the temperature control unit 62. During the film formation process, the temperature control unit 62 sets the wafer temperature. While maintaining the process temperature, the heater power supply 15 and / or the refrigerant circulating unit 50 are controlled to control the temperature between the side wall of the processing vessel 4 and the mounting table 38 which is a part of the wafer boat 6. The difference is controlled so as to be a predetermined temperature difference or more, specifically 50 ° C. or more.

  In other words, when the cooling means is not provided on the mounting table 38, the mounting table temperature is raised to the same temperature as the side wall of the processing container 4, and therefore the internal cooling means 40 is provided on the mounting table 38 side. The temperature of the processing container 4 is controlled to be higher by 50 ° C. or more than the temperature of the mounting table 38. Here, the temperature of the wafer W mounted on the mounting table 38 is heated to substantially the same temperature as the temperature of the mounting table 38. The temperature of each part at this time is set such that, for example, the temperature of the side wall of the processing container 4 is 250 ° C. or higher, and the temperature of the mounting table 38, that is, the wafer W is set to 200 ° C.

  In this case, the temperature of the side wall of the processing vessel 4 and the temperature of the mounting table 38 are both set higher than the temperature at which PMDA and ODA, which are raw material gases for film formation, are resolidified or reliquefied. And ODA are set within a temperature range in which neither of them is thermally decomposed, but in a temperature range in which both raw material gases as monomers undergo vapor deposition polymerization. In this case, the sublimation temperature of the PMDA is, for example, about 203 ° C., and the thermal decomposition temperature is about 400 ° C. The ODA liquefaction temperature is, for example, about 187 ° C., and the thermal decomposition temperature is about 400 ° C.

  As described above, by providing a temperature difference of 50 ° C. or more between the side wall of the processing container 4 and the mounting table 38, that is, the wafer W, both gaseous PMDA and ODA as raw material monomers are heated by thermophoresis. Is attracted mainly to the lower wafer W side, and a polyimide thin film is formed on the surface of the wafer W as a thin film by vapor deposition polymerization. Further, when the temperature difference is smaller than 50 ° C., the effect of attracting the raw material gas by thermophoresis becomes thin, and the Brownian motion is mainly used, and the thin film is almost evenly formed on the surface of the wafer W and the side wall of the processing container 4. Is not preferable.

  In this way, PMDA and ODA, which are source gases, are difficult to be attracted to the side wall of the processing container 4 having a high temperature, so that it is possible to prevent or suppress the deposition of a thin film on the side wall.

  In the above embodiment, the temperature of the wafer W is set to 200 ° C., and the temperature of the side wall of the processing container 4 is set to 250 ° C. or more. As long as the attraction of the material significantly occurs even at a temperature difference smaller than 50 ° C., the temperature difference may be made smaller. However, by setting the wafer temperature to 200 ° C. or higher, it is possible to reliably evaporate the moisture adhering to the surface and improve the film quality of the polyimide thin film.

  In any case, the temperature of the side wall of the processing container 4 and the temperature of the wafer W (mounting table 38) are maintained at the above temperature difference, the two source gases maintain the vaporized state, do not undergo thermal decomposition, and cause vapor deposition polymerization. Keep within the temperature range. Thus, the container heating means 14 is provided on the processing container 4 side, the internal cooling means 40 is provided on the wafer boat 6 side as the holding means, and the temperature difference between the side wall of the processing container and the holding means is a predetermined temperature. Since the temperature difference is controlled to be greater than the difference, for example, 50 ° C. or more, a polyimide thin film having a good film quality can be formed on the surface of the wafer W while suppressing the deposition of an unnecessary adhesion film on the side wall of the processing container 4. it can.

  Now, when the batch-type film forming process as described above is repeatedly performed, the deposition of an unnecessary adhesion film on the inner wall surface or the like of the processing container 4 is suppressed. It is inevitable that unnecessary adhesion films that cause particles will gradually accumulate on the surface of the substrate, the surface of the mounting table 38, and the like.

  Therefore, when a plurality of batches of wafers W are formed, a cleaning process for removing the unnecessary adhesion film (polyimide thin film) is performed regularly or irregularly. Here, fluorine gas, specifically, 4% concentration fluorine gas is used as the cleaning gas. In this cleaning process, if the temperature in the processing container 4 is increased, the etching reaction is promoted and the cleaning speed is generally improved. However, the heat resistance of the constituent materials of the processing container 4 and the constituent materials of the wafer boat 6 and the mounting table 38 is increased. And selectivity for etching gas must be considered.

  The material of the processing container 4 is quartz, which has high heat resistance. However, the material constituting the wafer boat 6, which is a holding means, for example, each of the columns 36A to 36C, the support arms 44A to 44C, and the mounting table 38 is higher than that of quartz. The upper limit of the cleaning temperature is set to about 300 ° C. for this reason.

At the same time, the above materials and the polyimide thin film which is an unnecessary thin film must have high selectivity with respect to the cleaning gas. The fluorine-based gas can be etched relatively easily by optimizing the temperature. Furthermore, aluminum, aluminum alloy, and quartz have strong resistance to the fluorine-based gas. It becomes possible to selectively remove only. For this reason, as described above, a fluorine-based gas such as F ₂ gas is used here as the cleaning gas.

  First, at the time of cleaning, the semiconductor boat W is emptied without placing any semiconductor wafer W on the wafer boat 6, and the wafer boat 6 in such a vacant state is inserted into the processing container 4 to seal the inside. . In this state, the processing container 4 and the wafer boat 6 themselves are heated by the container heating means 14 to maintain these temperatures at about 200 ° C., for example. In this case, since the heat absorption rate is different between quartz forming the processing vessel 4 and aluminum alloy forming the wafer boat 6, the refrigerant circulation part 50 of the internal cooling means 40 is driven into the wafer boat 6 as necessary. The wafer boat 6 is maintained at a desired temperature, for example, about 200 ° C. by flowing a coolant or the like.

At the same time, the cleaning gas supply system 26 of the gas supply means 20 is operated to introduce F ₂ gas, which is a cleaning gas, from the third gas nozzle 26A into the processing container 4 while controlling the flow rate. The F ₂ gas introduced into the processing container 4 is an unnecessary film that has been deposited on the surface of the wafer boat 6 and the mounting table 38 and the inner wall surface of the processing container 4 while rising in the processing container 4. It reacts in contact with a certain polyimide thin film, which is fluorinated and etched away.

  The etching is optimized by maintaining each temperature of the wafer boat 6 including the processing container 4 and the mounting table 38 at, for example, about 200 ° C., so that the processing container 4 and the wafer boat 6 are damaged. In addition, only the polyimide thin film which is an unnecessary thin film can be selectively and efficiently removed.

In this case, the temperature of the processing container 4 and the temperature of the wafer boat 6 including the mounting table 38 are set within a temperature range of 150 to 300 ° C., and preferably within a temperature range of 200 to 250 ° C. When the temperature of the wafer boat 6 including the mounting table 38 is set to be higher than 300 ° C., the aluminum or aluminum alloy itself constituting these has sufficient resistance to F ₂ gas, It is not preferable because it will be damaged.

In addition, when the temperature of the quartz forming the processing container 4 is higher than 300 ° C., the selectivity for the polyimide thin film deteriorates rapidly, and not only the polyimide thin film but also the quartz itself is severely scraped by the F ₂ gas. This is not preferable. In addition, when the temperature of the processing container 4 and the temperature of the wafer boat 6 including the mounting table 38 are lower than 150 ° C., the etching rate of the polyimide thin film is drastically reduced, and a long time is required for the cleaning process. The throughput is greatly reduced, which is not preferable.

As described above, in the present invention, when removing an unnecessary polymer thin film, for example, a polyimide thin film, attached to the inside of the processing container 4 of the film forming apparatus by the cleaning process, a fluorine-based gas, for example, F ₂ gas is used as the cleaning gas. As a result, only the unnecessary polymer thin film can be selectively and efficiently removed without damaging the processing vessel itself or the wafer boat 6 which is a holding means for holding the object to be processed.

<Evaluation of etching selectivity>
Here, an experiment was conducted on the selectivity of F ₂ gas during etching with respect to the polyimide thin film and quartz, and the evaluation results will be described. FIG. 4 is a graph showing the selectivity during etching of F ₂ gas with respect to the polyimide thin film and quartz. Here, the horizontal axis represents the etching (cleaning) time, the left vertical axis represents the PI (polyimide thin film) etching film thickness, and the right vertical axis represents the quartz etching film thickness. It should be noted that the left vertical axis and the right vertical axis are different by two digits here.

In the etching, 4% concentration of F ₂ gas is used as an etching gas (cleaning gas), the temperature of the object to be etched is set to 200 ° C., and the pressure is set to 150 Torr. As is apparent from this figure, it can be understood that the etching film thickness of quartz increases linearly with the passage of time, and the etching rate is always constant. In this case, the etching rate is about 0.3 nm / min, which is very small.

  On the other hand, it can be understood that the etching film thickness of the polyimide thin film (PI) is small at the beginning of the etching, but gradually increases with time, for example, in a quadratic curve. In this case, for example, the etching rate up to about 10 minutes at the beginning of etching is about 20 nm / min, whereas the etching rate for 10 minutes from 20 to 30 minutes after the start of etching rapidly increases to about 75 nm / min. It has increased. The reason for this is considered to be that the reaction mechanism when the polyimide thin film is etched consists of two steps of “film fluorination” and “volatilization in the vicinity of the excessively fluorinated surface”.

That is, at the beginning of etching, F ₂ gas is consumed for fluorination of the film and the film deteriorates. When the fluorination progresses to a certain extent, the fluorinated film is rapidly sublimated and taken out to delay the etching. After that, etching proceeds while maintaining a rapid sublimation state.

  In any case, from the graph shown in FIG. 4, in the region where the processing time is 20 minutes or more, the etching rate of quartz can be suppressed to a value that is about two orders of magnitude lower than the etching amount of the polyimide thin film or the etching rate. As a result, it can be seen that the polyimide thin film can be selectively removed without cutting the quartz. In other words, it can be seen that the polyimide thin film can be removed more efficiently by about two orders of magnitude (100 times) than quartz.

  Then, the element concentration in the film thickness direction at this time was examined, and a cross section of the film thickness was taken in the photograph, and the result is shown. FIG. 5 shows the element concentration in the film thickness direction of the polyimide thin film (PI) formed on the silicon substrate, and FIG. 6 shows an electron micrograph in the film thickness direction of the polyimide thin film (PI) formed on the silicon substrate. . The element concentration was measured using XPS (X-ray photoelectron spectroscopy). In FIG. 5, the horizontal axis indicates the depth of the film thickness from the film surface, the vertical axis indicates the element concentration, and in the figure, carbon (C), fluorine (F), oxygen (O), nitrogen (N ), And the concentration of each element of silicon (Si) is shown.

  As shown in FIG. 5, from the film surface to a depth of about 800 nm, the F concentration is high, and the film is fluorinated to form a fluorinated polyimide thin film (F-PI film). When the depth exceeds 800 nm, the C concentration increases rapidly, while the F concentration decreases rapidly. This portion becomes a pure polyimide thin film (PI film) that is not fluorinated. Yes. It can be understood that when the depth exceeds 1600 nm and the depth further increases, the Si concentration rapidly increases and reaches the Si substrate.

  FIG. 6 shows an electron micrograph at this time, and it can be seen from the lower side that it has a three-layer structure of a Si substrate, a PI film and a fluorinated PI film. Here, the total film thickness of the PI film and the fluorinated PI film is about 1601 nm, and the initial value of this film thickness is about 1600 nm, and the formation of F is proceeding before the film is taken out.

<Evaluation of fluorine concentration and temperature dependency>
Next, since the fluorine concentration and temperature dependency during etching were examined, the evaluation results will be described. FIG. 7 is a diagram showing the fluorine concentration and temperature dependency during etching, and shows the etching rate of the polyimide film (PI), the etching rate of the SiO ₂ film (quartz), and the selectivity between them. Here, the process pressure at the time of etching is set to 400 Torr (53320 Pa).

As shown in FIG. 7, in the case of the fluorine concentration-dependent experiment, all the process temperatures are set to 200 ° C., and the F ₂ concentration is changed over three types of 1.5%, 8%, and 20%. ing. According to this, the selection ratio between the PI film and the SiO ₂ film is two digits or more as long as it is within the above F ₂ concentration range. Even when the F ₂ concentration is 1.5%, which is the lowest, the etching rate of the PI film is 0.03 μm / min, which is a sufficiently large value and is an effective concentration. However, in order to remove the PI film more efficiently, it is preferable to set the F ₂ concentration to 8% or more and the etching rate to 0.31 μm / min or more. In this case, the higher the F ₂ concentration is, the higher the etching rate of the PI film is.

In the case of the temperature dependence experiment, two types of F ₂ concentrations of 8% and 20% were used, and the process temperature was three types of 150 ° C., 200 ° C., and 250 ° C. with respect to each concentration. In this case, the selection ratios are large values of two digits or more except for “77” when the F ₂ concentration is 20% and the temperature is 250 ° C. All the selection ratios show preferable results. You can see that

In addition, when the temperature is 150 ° C., the etching rate of the PI film is 0.03 μm / min when the F ₂ concentration is 8%, and 0.12 μm / min when the F ₂ concentration is 20%. On the other hand, when the temperature is 200 ° C. and 250 ° C., it is 0.31 μm / min to 1.6 μm / min even when the F ₂ concentration is 8%. It is quite high and it can be seen that it exhibits excellent properties. Therefore, the optimum temperature at the time of etching (cleaning) is 150 ° C. or higher, preferably 200 ° C. or higher at which the etching rate of the polyimide thin film becomes larger.

  Further, as described above, the upper limit of the temperature at the time of cleaning is 300 ° C. which is the heat resistance temperature of aluminum or aluminum alloy which is a constituent material of the wafer boat 6 including the mounting table 38, and preferably a margin for heat resistance is expected. Set to 250 ° C or lower. From the above results, each temperature of the processing container 4, the wafer boat 6 and the mounting table 38 at the time of cleaning is set within the range of 150 to 300 ° C., more preferably within the range of 200 to 250 ° C. as described above. To.

In the above embodiment, F ₂ gas is used as the fluorine-based gas used for the cleaning gas. However, the present invention is not limited to this, and the fluorine-based gas is selected from the group consisting of F ₂ , NF ₃ , ClF ₃ , and C ₂ F _6. One or more selected gases can be used. In the present embodiment, the case where an organic polyimide thin film is formed as a polymer thin film will be described as an example. However, the present invention is not limited to this, and the present invention is also applied to a case where a polyurea thin film is formed as an organic thin film. Can be applied. As a plurality of source gases for forming the polyurea thin film, for example, 4,4′-diphenylmethane diisocyanate (MDI) and 4,4′-diaminodiphenylmethane (MDA) can be used.

  Furthermore, the polymer thin film formed by the monomer polymerization process is not limited to an organic thin film, and the present invention can also be applied to the case where a polymer thin film made of an inorganic thin film is formed. Examples of such an inorganic thin film include a SiO film and a SiN film, and further include an organic / inorganic hybrid film such as a SiOCH film and a SiNCH film.

  Further, here, a so-called batch type film forming apparatus that processes a plurality of wafers at a time has been described as an example. However, the present invention is not limited to this, and the heights of the processing vessel 4 and the wafer boat 6 that is a holding means are respectively set. The present invention can also be applied to a so-called single-wafer type film forming apparatus that is set to be small and processes wafers one by one.

  Although the semiconductor wafer is described as an example of the object to be processed here, the semiconductor wafer includes a silicon substrate and a compound semiconductor substrate such as GaAs, SiC, GaN, and the like, and is not limited to these substrates. The present invention can also be applied to glass substrates, ceramic substrates, and the like used in display devices.

2 Deposition device 4 Processing vessel 6 Wafer boat (holding means)
DESCRIPTION OF SYMBOLS 8 Cover part 12 Elevating mechanism 14 Container heating means 20 Gas supply means 22 1st raw material gas supply system 24 2nd raw material gas supply system 26 Cleaning gas supply means 30 Vacuum exhaust system 36A-36C Support | pillar 38 Mounting stand 40 Internal cooling means 44A to 44C Support arm 48 Refrigerant passage 50 Refrigerant circulation part 52A, 52C In-post passage 54A, 54C In-arm passage 56 Placement base passage 58 Telescopic tube 62 Temperature control part 64 Device control part 66 Storage medium W Semiconductor wafer (object to be processed) )

Claims (6)

Forming a vertical quartz processing barber vessel polymeric thin film made of polyimide thin film or polyurea film on the surface of the object held by the holding means to the processing chamber while evacuating by a vacuum exhaust system of In the cleaning method of the film forming apparatus,
F, which is a fluorine-based gas as a cleaning gas in the processing container and the vacuum exhaust system while maintaining the processing container at a predetermined temperature after the polymer thin film is formed using a plurality of source gases cleaning method of a film forming apparatus is characterized in that to perform the cleaning process by flowing ₂ gas. 2. The film formation according to claim 1, wherein the plurality of source gases when forming the polyimide thin film are composed of pyromellitic dianhydride (PMDA) and 4,4′-diaminodiphenyl ether (ODA). How to clean the device. 2. The plurality of source gases for forming the polyurea thin film are composed of 4,4′-diphenylmethane diisocyanate (MDI) and 4,4′-diaminodiphenylmethane (MDA). The film-forming apparatus cleaning method as described. The film forming apparatus cleaning method according to claim 1, wherein the predetermined temperature is in a range of 150 to 300 ° C. 5. 5. The film forming apparatus cleaning method according to claim 1, wherein when the cleaning process is performed, the empty holding unit is inserted into the processing container. 6. In a film forming apparatus for forming a polymer thin film made of a polyimide thin film or a polyurea thin film on the surface of an object to be processed,
A vertical processing container containing a plurality of the objects to be processed;
Holding means having a mounting table provided in a plurality of stages for holding the object to be processed in the processing container;
An evacuation system for evacuating the inside of the processing vessel;
Gas supply means for supplying a plurality of source gases of the polymer thin film into the processing vessel;
Cleaning gas supply means for supplying F ₂ gas, which is a fluorine-based gas, into the processing container as a cleaning gas;
Container heating means for heating the processing container;
A device controller for controlling to implement the cleaning method of the film forming apparatus according to any one of claims 1乃optimum 5 controls the operation of the entire apparatus,
A film forming apparatus comprising:

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