JP5575299B2 - Film forming method and film forming apparatus - Google Patents

Description

  The present invention relates to a film forming method and a film forming apparatus for forming a silicon nitride film (SiN film) on an object to be processed such as a semiconductor wafer, and more particularly to a semiconductor processing technique. Here, the semiconductor processing means that a semiconductor layer, an insulating layer, a conductive layer, and the like are formed in a predetermined pattern on a target object such as a semiconductor wafer or a glass substrate for an FPD (Flat Panel Display) such as an LCD (Liquid Crystal Display). This means various processes performed to manufacture a structure including a semiconductor device, a wiring connected to the semiconductor device, an electrode, and the like on the object to be processed.

  In a semiconductor device manufacturing sequence, there is a film forming process for forming a silicon nitride film (SiN film) as an insulating film on a semiconductor wafer typified by a silicon wafer. In such a SiN film forming process, a vertical batch type heat treatment apparatus that forms a film on a plurality of semiconductor wafers by chemical vapor deposition (CVD) is often used.

In recent years, with the progress of miniaturization and integration of semiconductor devices, it has been required to form a SiN film having good characteristics at a temperature lower than the film formation temperature in conventional CVD. In a vertical batch-type heat treatment apparatus, as a technique capable of realizing this, an ALD (alternatively repeating film formation at an atomic layer level or a molecular layer level while alternately supplying Si source gas and nitriding gas) A technique for forming a SiN film by atomic layer deposition has been proposed (for example, Patent Document 1). For example, dichlorosilane (DCS; SiH ₂ Cl ₂ ) having good adsorptivity is used as the Si source, and ammonia (NH ₃ ) is used as the nitriding gas.

JP 2006-49809 A

  However, when the film is formed by ALD at 500 ° C. or less using DCS as the Si source, the wet etching rate of the obtained SiN film is extremely large, and the film quality is poor.

  An object of the present invention is to provide a film forming method and a film forming apparatus capable of forming a silicon nitride film with better film quality by ALD.

According to a first aspect of the present invention, there is provided a film forming method for forming a product film made of a silicon nitride film in a processing container capable of maintaining a vacuum, wherein the product film is formed on a workpiece for processing in the processing container. The film forming process to be formed is repeated a plurality of times, and then the cleaning process for removing the reaction product adhering to the processing container by the film forming process is not accommodated in the processing container. Performing in a state, and then performing a coating process for coating the inside of the processing container with a coating film made of a silicon nitride film in a state in which the product to-be-processed object is not accommodated in the processing container, Performing the film forming process for forming the product film on a product target object in the processing container, and the film forming process includes an adsorption process and a nitriding process with a purge process interposed therebetween. Multiple cycles including alternating Repeatedly, in the adsorption step, monochlorosilane gas is supplied as Si source gas into the processing vessel, and in the nitriding step, nitrogen-containing gas is supplied as nitriding gas into the processing vessel by ALD (atomic layer deposition). And the coating process is repeated a plurality of times including alternately a first supply process and a second supply process with a purge process in between. In the first supply process, the Si source gas is introduced into the processing container. Dichlorosilane gas is supplied, and the second supply step is performed by ALD supplying nitrogen-containing gas as nitriding gas into the processing vessel.

A second aspect of the present invention is a computer-readable storage medium that operates on a computer and stores a program for controlling a film forming apparatus, and the program is executed when the first viewpoint is executed. The film forming apparatus is controlled by a computer so that the film forming method is performed.

According to a third aspect of the present invention, there is provided a film forming apparatus for forming a silicon nitride film on a plurality of objects to be processed, the vertical processing container capable of maintaining a vacuum, and the objects to be processed in a plurality of stages. A holding member that is held in the processing container in a held state, a heating mechanism that heats the object to be processed provided on the outer periphery of the processing container, and an Si source gas supply that supplies Si source gas into the processing container A mechanism, a nitrogen-containing gas supply mechanism that supplies a nitriding gas into the processing container, and a control unit that controls the operation of the film forming apparatus, the control unit operating on the computer and the computer And a computer-readable storage medium of the second viewpoint in which the program for controlling the device is stored.

  According to the present invention, while forming a film by the ALD method using monochlorosilane as the Si source, the coating process in the processing container is performed in a mode different from the film forming process, and the concentration of chlorine in the coating film is increased. As a result, a silicon nitride film with good film quality can be formed.

It is a longitudinal cross-sectional view which shows an example of the film-forming apparatus for semiconductor processing concerning embodiment of this invention. It is a cross-sectional view of the film forming apparatus shown in FIG. It is a timing chart which shows the timing of supply of gas in the film-forming method concerning the embodiment of the present invention. It is a graph which shows the relationship between 1000 / T (K) and the logarithm of the film-forming rate (cycle rate) per cycle about the case where MCS is used as Si source, and DCS is used. It is a graph which shows the relationship between the flow time of Si source in each temperature at the time of using MCS as Si source, and the logarithm of a cycle rate. It is a graph which shows the relationship between the film-forming temperature and a cycle rate about the case where MCS is used as Si source, and the case where DCS is used. It is a graph which shows the relationship between the film-forming temperature and the refractive index of a SiN film | membrane about the case where MCS is used as Si source and DCS is used. It is a graph which shows the relationship between the film-forming temperature and the etching rate of the SiN film by dilute hydrofluoric acid (1% DHF) when MCS is used as the Si source and when DCS is used. It is a graph which shows the oxidation resistance of the film | membrane outermost surface in the SiN film | membrane formed into a film at 450 degreeC using DCS at 450 degreeC, 550 degreeC, 600 degreeC, and 630 degreeC, and the SiN film | membrane formed into a film using 450 degreeC. It is a graph which shows Cl content in the SiN film | membrane formed by plasma ALD and thermal ALD.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, components having substantially the same function and configuration are denoted by the same reference numerals, and redundant description will be given only when necessary.
FIG. 1 is a longitudinal sectional view showing an example of a film forming apparatus for semiconductor processing according to an embodiment of the present invention, and FIG. 2 is a cross sectional view showing the film forming apparatus of FIG. In FIG. 2, the heating mechanism is omitted.

  The film forming apparatus 100 includes a cylindrical processing container 1 having a lower end opened and a top closed. The entire processing container 1 is made of, for example, quartz, and a quartz ceiling plate 2 is provided in the vicinity of the upper end portion in the processing container 1, and a lower region thereof is sealed. In addition, a manifold 3 formed in a cylindrical shape from, for example, stainless steel is connected to the lower end opening of the processing container 1 via a seal member 4 such as an O-ring.

  The manifold 3 supports the lower end of the processing vessel 1, and a quartz wafer boat 5 on which a large number of, for example, 50 to 100 semiconductor wafers W can be placed in multiple stages as objects to be processed from below the manifold 3. Can be inserted into the processing container 1. The wafer boat 5 has three columns 6 (see FIG. 2), and a large number of wafers W are supported by grooves formed in the columns 6.

  The wafer boat 5 is placed on a table 8 via a quartz heat insulating cylinder 7, and the table 8 passes through a lid 9 made of, for example, stainless steel that opens and closes the lower end opening of the manifold 3. It is supported on the rotating shaft 10.

  And the magnetic fluid seal | sticker 11 is provided in the penetration part of this rotating shaft 10, for example, and the rotating shaft 10 is supported rotatably, sealing airtightly. Further, a sealing member 12 made of, for example, an O-ring is interposed between the peripheral portion of the lid portion 9 and the lower end portion of the manifold 3, thereby maintaining the sealing performance in the processing container 1.

  The rotary shaft 10 is attached to the tip of an arm 13 supported by an elevating mechanism (not shown) such as a boat elevator, for example, and moves up and down the wafer boat 5 and the lid 9 etc. integrally. 1 is inserted into and removed from the inside. The table 8 may be fixedly provided on the lid 9 side, and the wafer W may be processed without rotating the wafer boat 5.

Further, the film forming apparatus 100 includes a nitrogen-containing gas supply mechanism 14 that supplies a nitrogen-containing gas used as a nitriding gas, for example, ammonia (NH ₃ ) gas, into the processing container 1, and a mono-source Si gas into the processing container 1 An Si source gas supply mechanism 15 that supplies chlorosilane (MCS) gas and a purge gas supply mechanism 16 that supplies an inert gas such as N ₂ gas as a purge gas into the processing container 1 are provided.

The nitrogen-containing gas supply mechanism 14 is connected to the nitrogen-containing gas supply source 17, the gas pipe 18 for introducing the nitrogen-containing gas from the gas supply source 17, and the gas pipe 18, and penetrates the side wall of the manifold 3 inwardly. And a gas dispersion nozzle 19 made of a quartz tube bent in the direction and extending vertically. A plurality of gas discharge holes 19 a are formed in the vertical portion of the gas dispersion nozzle 19 at a predetermined interval over the length in the vertical direction corresponding to the wafer support range of the wafer boat 5. A nitrogen-containing gas, for example, NH ₃ gas, can be discharged from the gas discharge holes 19a in a horizontal direction toward the processing container 1 substantially uniformly.

  The Si source gas supply mechanism 15 is connected to the Si source gas supply source 20, a gas pipe 21 that guides the Si source gas from the gas supply source 20, and the gas pipe 21, and penetrates the side wall of the manifold 3 inward. And a gas dispersion nozzle 22 made of a quartz tube bent in a direction and extending vertically. Here, two gas distribution nozzles 22 for the Si source gas are provided (see FIG. 2). A plurality of gas discharge holes 22 a are formed at predetermined intervals in the vertical portion of each gas dispersion nozzle 22 over the length in the vertical direction corresponding to the wafer support range of the wafer boat 5. The MCS gas as the Si source gas can be discharged almost uniformly into the processing container 1 in the horizontal direction from each gas discharge hole 22a. Note that the number of Si source gas gas dispersion nozzles 22 may be only one.

The purge gas supply mechanism 16 includes a purge gas supply source 23, a gas pipe 24 that guides the purge gas from the gas supply source 23, and a gas nozzle that is connected to the gas pipe 24 and includes a short quartz pipe provided through the side wall of the manifold 3. 25. As the purge gas, an inert gas such as N ₂ gas can be preferably used.

  The gas pipes 18, 21, 24 are provided with on-off valves 18a, 21a, 24a and flow controllers 18b, 21b, 24b such as mass flow controllers, respectively. As a result, the nitrogen-containing gas, the Si source gas, and the purge gas can be supplied while controlling their flow rates.

  A plasma generation mechanism 30 that forms plasma of a nitrogen-containing gas used as a nitriding gas is formed on a part of the side wall of the processing vessel 1. This plasma generation mechanism 30 is airtight on the outer wall of the processing container 1 so as to cover the opening 31 formed vertically from the outside by scraping the side wall of the processing container 1 with a predetermined width along the vertical direction. And has a plasma compartment wall 32 welded thereto. The plasma partition wall 32 has a concave cross-sectional shape and is elongated vertically, and is made of, for example, quartz.

  The plasma generation mechanism 30 includes a pair of elongated plasma electrodes 33 disposed on the outer surfaces of both side walls of the plasma partition wall 32 so as to face each other in the vertical direction, and a power supply line 34 provided to the plasma electrode 33. And a high frequency power supply 35 for supplying high frequency power. A plasma of nitrogen-containing gas can be generated by applying a high frequency voltage of 13.56 MHz, for example, from the high frequency power source 35 to the plasma electrode 33. Note that the frequency of the high-frequency voltage is not limited to 13.56 MHz, and other frequencies such as 400 kHz may be used.

  By forming the plasma partition wall 32 as described above, a part of the side wall of the processing container 1 is recessed outward in the shape of a recess, and the internal space of the plasma partition wall 32 is integrated with the internal space of the processing container 1. Will be in a state of communication. The internal space of the plasma partition wall 32 and the opening 31 are formed long enough in the vertical direction so that all the wafers W held by the wafer boat 5 can be covered in the height direction.

The gas dispersion nozzle 19 for the nitrogen-containing gas is bent outward in the radial direction of the processing container 1 in the middle of extending upward in the processing container 1, and is the innermost part (processing container in the plasma partition wall 32). (The portion farthest from the center of 1)). For this reason, when the high frequency power supply 35 is turned on and a high frequency electric field is formed between the electrodes 33, a nitrogen-containing gas, for example, NH ₃ gas injected from the gas injection holes 19a of the gas dispersion nozzle 19 is converted into plasma. It flows while diffusing toward the center of the processing container 1.

  An insulating protective cover 36 made of, for example, quartz is attached to the outside of the plasma partition wall 32 so as to cover it. In addition, a refrigerant passage (not shown) is provided in the inner portion of the insulating protective cover 36, and the plasma electrode 33 can be cooled by flowing a cooled nitrogen gas, for example.

  The two gas distribution nozzles 22 of the Si source gas are provided upright at a position sandwiching the opening 31 on the inner wall of the processing container 1. MCS gas can be discharged as the Si source gas from the plurality of gas injection holes 22a formed in the gas dispersion nozzle 22 toward the center of the processing vessel 1.

  On the other hand, an exhaust port 37 for evacuating the inside of the processing container 1 is provided at a portion opposite to the opening 31 of the processing container 1. The exhaust port 37 is formed in an elongated shape by scraping the side wall of the processing container 1 in the vertical direction. An exhaust port cover member 38 having a U-shaped cross section so as to cover the exhaust port 37 is attached to a portion corresponding to the exhaust port 37 of the processing container 1 by welding. The exhaust port cover member 38 extends upward along the side wall of the processing container 1, and defines a gas outlet 39 above the processing container 1. The gas outlet 39 is evacuated by an evacuation mechanism VEM including a vacuum pump and the like. A cylindrical heating mechanism 40 for heating the processing container 1 and the wafer W therein is provided so as to surround the outer periphery of the processing container 1.

  Control of each component of the film forming apparatus 100, for example, supply / stop of each gas by opening / closing valves 18a, 21a, 24a, control of gas flow rate by mass flow controllers 18b, 21b, 24b, exhaust control by vacuum exhaust mechanism, and high frequency The temperature control of the wafer W by the on / off control of the power source 35 and the control of the heating mechanism 40 is performed by a controller 50 made of, for example, a microprocessor (computer). That is, the controller 50 functions as a gas supply control mechanism, a temperature control mechanism, and the like. Connected to the controller 50 is a user interface 51 including a keyboard for an operator to input commands for managing the film forming apparatus 100, a display for visualizing and displaying the operating status of the film forming apparatus 100, and the like. Yes.

  A storage unit 52 is connected to the controller 50. The storage unit 52 is a program for realizing various processes executed by the film forming apparatus 100 under the control of the controller 50, and for causing each component of the film forming apparatus 100 to execute processes according to the processing conditions. A program or recipe is stored. The recipe is stored in a storage medium in the storage unit 52, for example. The storage medium may be a fixed type such as a hard disk or a semiconductor memory, or may be a portable type such as a CD-ROM, DVD, or flash memory. Moreover, you may make it transmit a recipe suitably from another apparatus via a dedicated line, for example.

  Then, the recipe is read from the storage unit 52 according to an instruction from the user interface 51 or the like as necessary, and the controller 50 executes processing according to the read recipe, whereby the film forming apparatus 100 is A desired process is performed under the control of the controller 50.

  Next, a method of forming a SiN film according to the present embodiment performed using the film forming apparatus configured as described above will be described with reference to FIG. FIG. 3 is a timing chart showing gas supply timing in the film forming method according to the embodiment of the present invention.

  First, at normal temperature, for example, the wafer boat 5 on which 50 to 100 semiconductor wafers W are mounted is loaded into the processing container 1 controlled in advance at a predetermined temperature by raising it from below. Next, the inside of the processing container 1 is made into a sealed space by closing the lower end opening of the manifold 3 with the lid 9. An example of the semiconductor wafer W is 300 mm in diameter, but is not limited thereto.

  Then, the inside of the processing container 1 is evacuated to maintain a predetermined process pressure. At the same time, the power supplied to the heating mechanism 40 is controlled to increase the wafer temperature and maintain it at the process temperature. Then, the film forming process is started with the wafer boat 5 rotated.

As shown in FIG. 3, the film forming process at this time is performed by so-called plasma ALD in which the step S1 and the step S2 are alternately repeated. In step S <b> 1, MCS gas as Si source gas is supplied to the processing container 1 and is adsorbed on the wafer W. In step S2, a nitrogen-containing gas that is a nitriding gas, for example, NH ₃ gas, is converted into plasma and supplied to the processing chamber 1, and the Si source gas adsorbed on the wafer W is nitrided. Between these steps S1 and S2, steps S3a and S3b for removing the gas remaining in the processing vessel 1 from the processing vessel 1 are performed.

  Specifically, in step S1, MCS gas is supplied as Si source gas from the gas supply source 20 of the Si source gas supply mechanism 15 into the processing container 1 from the gas discharge hole 22a through the gas pipe 21 and the gas dispersion nozzle 22. Supply for period T1. Thereby, MCS is adsorbed on the semiconductor wafer. The period T1 at this time is exemplified by 2 to 30 sec. Further, the flow rate of the Si source gas is exemplified by 1 to 5 L / min (slm). Moreover, the pressure in the processing container 1 at this time is 66.65 to 666.5 Pa (0.5 to 5 Torr), preferably 266.6 to 600 Pa (2 to 4.5 Torr).

In step S <b> 2, for example, NH ₃ gas is discharged as a nitrogen-containing gas from the gas supply source 17 of the nitrogen-containing gas supply mechanism 14 through the gas discharge hole 19 a through the gas pipe 18 and the gas dispersion nozzle 19. At this time, the high-frequency power source 35 of the plasma generation mechanism 30 is turned on to form a high-frequency electric field, and nitrogen-containing gas, for example, NH ₃ gas is converted into plasma by this high-frequency electric field. The nitrogen-containing gas that has been converted into plasma is supplied into the processing container 1. Thereby, MCS adsorbed on the semiconductor wafer W is nitrided to form SiN. The period T2 of this process is exemplified by a range of 5 to 120 seconds. The flow rate of the nitrogen-containing gas varies depending on the number of semiconductor wafers W mounted, but in the case of NH ₃ gas, 0.5 to 10 L / min (slm) is exemplified. Moreover, although the frequency of the high frequency power supply 35 is not specifically limited, 13.56 MHz is illustrated and power is 5-1000W, Preferably 10-200W is employ | adopted. Moreover, the pressure in the processing container 1 at this time is 13.33 to 266.6 Pa (0.1 to 2 Torr), preferably 13.33 to 120 Pa (0.1 to 0.93 Torr).

In this case, examples of the nitrogen-containing gas include NH ₃ gas, N ₂ gas, N ₂ H ₄ gas, and the like, which are converted into plasma by a high-frequency electric field and used as a nitriding agent.

Further, in steps S3a and S3b performed between step S1 and step S2, gas remaining in the processing container 1 is removed after step S1 or after step S2 to cause a desired reaction in the next step. It is a process. Here, an inert gas such as N ₂ gas is supplied into the processing vessel 1 as a purge gas from the gas supply source 23 of the purge gas supply mechanism 16 through the gas pipe 24 and the gas nozzle 25 while evacuating the inside of the processing vessel 1. Examples of the periods T3a and T3b of the steps S3a and S3b include 2 to 15 sec. The purge gas flow rate is exemplified by 0.5 to 15 L / min (slm). Note that, in steps S3a and S3b, if the gas remaining in the processing container 1 can be removed, the evacuation is continuously performed with the supply of all gases stopped without supplying the purge gas. May be. However, the residual gas in the processing container 1 can be removed in a short time by supplying the purge gas.

  In this manner, the step S1 for supplying the MCS gas as the Si source gas and the step S2 for supplying the nitrogen-containing gas excited by the plasma are sandwiched between the steps S3a and S3b for removing the gas from the processing vessel 1. In this case, it is repeatedly supplied alternately. As a result, a thin SiN film can be repeatedly laminated one layer at a time to form a SiN film having a predetermined thickness. The number of repetitions at this time is appropriately determined depending on the thickness of the SiN film to be obtained.

  Regarding the temperature of the wafer during film formation (film formation temperature), the upper limit is a temperature at which ALD can be performed, and the lower limit is a temperature at which a high-quality film can be formed by ALD. Specifically, it is set to a range of 150 to 550 ° C.

  Next, an experiment in which plasma ALD film formation is performed in the apparatus shown in FIG. 1 will be described. First, the film forming temperature will be described in detail below.

  A SiN film was formed when MCS was used as the Si source and when DCS was used. In this experiment, the film formation temperature was changed, but the plasma generation time was constant. With respect to the SiN film thus formed, the following characteristics were evaluated with reference to FIGS.

  FIG. 4 is a graph showing the relationship between 1000 / T (K) and the logarithm of the film formation rate (cycle rate) per cycle when MCS is used as the Si source and when DCS is used. In FIG. 4, the horizontal axis represents 1000 / T (K), and the vertical axis represents the logarithm of the cycle rate. The plot points in FIG. 4 are 630 ° C., 600 ° C., 550 ° C., 500 ° C., 480 ° C., 450 ° C., 400 ° C., 350 ° C., 300 ° C. in the DCS group, and in the MCS group, in order from the high temperature side. They are 600 degreeC, 520 degreeC, 500 degreeC, 450 degreeC, 400 degreeC, 350 degreeC, and 300 degreeC.

  FIG. 5 is a graph showing the relationship between the flow time of the Si source and the logarithm of the cycle rate at each temperature when MCS is used as the Si source. FIG. 5 shows the Si source flow time on the horizontal axis and the logarithm of the cycle rate on the vertical axis.

  As shown in FIG. 4, the cycle rate was remarkably higher in the case of MCS than in the case of DCS at a film forming temperature of 600 ° C. Further, as shown in FIG. 5, the cycle rate in the case of MCS increased rapidly with an increase in the flow time when the film formation temperature was 550 ° C. Thus, when the cycle rate rapidly increases depending on the flow time, it becomes difficult to control the film thickness in the ALD process, particularly to control the film thickness uniformity between wafers in the same batch. Up to a film forming temperature of 550 ° C., the cycle rate when MCS was used was equal to or lower than that when DCS was used. When the film formation temperature was 550 ° C., the plasma ALD using DCS was possible. Considering these, the upper limit of the film forming temperature when MCS is used is 550 ° C.

  However, ALD is preferably performed in a region where the change in film thickness with time is small from the viewpoint of film thickness controllability. ALD is ideally performed in a saturated ALD region where the film thickness does not substantially change with time. From such a viewpoint, the film forming temperature when MCS is used is preferably 520 ° C. or lower as shown in FIG.

  FIG. 6 is a graph showing the relationship between the film forming temperature and the cycle rate when MCS is used as the Si source and when DCS is used. FIG. 6 shows the film formation temperature on the horizontal axis and the cycle rate on the vertical axis. From this figure, it was confirmed that the film could be formed up to 150 ° C. when MCS was used. For this reason, the lower limit of the film formation temperature when MCS is used is set to 150 ° C. From the viewpoint of obtaining a higher quality film, the film forming temperature is preferably 300 ° C. or higher, more preferably 400 ° C. or higher.

  Further, in the apparatus for supplying the processing gas from the gas dispersion nozzles 19 and 22 in which the plasma generation mechanism 30 is integrally provided with the processing container 1 and extends along a plurality of wafers as shown in FIG. Even at a low temperature, a higher ALD cycle rate (deposition rate) and better film quality can be obtained. For example, as shown in FIGS. 6 and 4, the cycle rate when using MCS at a processing temperature of less than 500 ° C., for example, 300 ° C., 350 ° C., 400 ° C., 450 ° C. is practical. From the viewpoint of film thickness controllability in the ALD process, it is desirable that the processing temperature when MCS is used is lower than 450 ° C. as shown in FIG.

  Thus, the range of the film formation temperature when using MCS is set to 150 to 550 ° C. In the case where importance is attached to the film quality and the film forming speed, the film forming temperature range is preferably 400 to 520 ° C. In addition, while maintaining the film quality to some extent, when the film thickness controllability and the burden on the apparatus are emphasized, the film forming temperature range is preferably 150 to 450 ° C, more preferably 200 to 400 ° C, and more preferably 300 to 400 ° C. Further preferred. In addition, when processing temperature shall be 300-400 degreeC, the period T1 of the above-mentioned adsorption process S1 is set to 2-20 sec, Preferably it sets to 3-9 sec. In addition, the period T2 of the above-described nitriding step S2 is set to 10 to 90 sec, preferably 20 to 70 sec. In this case, T2 / T1 is set to 0.5 to 45, preferably 2.2 to 23.

FIG. 7 is a graph showing the relationship between the deposition temperature and the refractive index of the SiN film when MCS is used as the Si source and when DCS is used. FIG. 7 shows the film formation temperature on the horizontal axis and the refractive index on the vertical axis. The refractive index 2 is a stoichiometric SiN film (Si ₃ N ₄ ), and the closer to 2, the closer to the stoichiometric SiN film is formed. As shown in FIG. 7, the SiN film formed using MCS was closer to the stoichiometric SiN film than the SiN film formed using DCS under the same film formation conditions. From this, it is considered that MCS is a Si source that is more easily nitrided than DCS. For this reason, it is presumed that MCS can form a film at a lower temperature.

  In addition, MCS is a Si source that is easily nitrided as described above, and an SiN film having a good film quality can be obtained even at low temperature film formation. Further, the amount of Cl per molecule is smaller than that of DCS, and the residual amount of Cl is low even at low temperature film formation. Therefore, the SiN film formed using MCS has better chemical resistance when compared at the same film formation temperature than the SiN film formed using DCS. Small reduction in resistance.

  FIG. 8 is a graph showing the relationship between the film formation temperature and the etching rate of the SiN film with dilute hydrofluoric acid (1% DHF) when MCS is used as the Si source and when DCS is used. This dilute hydrofluoric acid (100: 1 DHF) is a chemical solution generally used for wet etching. FIG. 8 shows the film formation temperature on the horizontal axis and the etching rate normalized as follows on the vertical axis. Note that the normalized etching rate is a value expressed by assuming that the etching rate of the SiN film formed using DCS at 760 ° C. with dilute hydrofluoric acid (100: 1 DHF) is 1. As shown in this figure, when DCS is used as the Si source, the chemical resistance rapidly decreases when the film forming temperature is lower than 500 ° C., whereas when MCS is used as the Si source, It had good chemical resistance even at 450 ° C.

In addition, when the low temperature film formation lower than 500 ° C. is performed using DCS as the Si source, the outermost surface of the obtained SiN film is easily oxidized, but when MCS is used as the Si source, the low temperature film formation is performed. The oxidation resistance of the film surface obtained with the film is significantly improved. The oxidation of the outermost surface is caused by moisture in the air at the time of unloading of the wafer. The degree of oxidation of the outermost surface depends on the wet etching rate (R _S ) of the outermost surface of the film and the inside of the film ( It is considered that it can be expressed by the difference (R _S −R _B ) from the wet etching rate (R _B ) of the “bulk”.

FIG. 9 is a graph showing the oxidation resistance of the outermost surface of the SiN film formed at 450 ° C., 550 ° C., 600 ° C., and 630 ° C. using DCS and the SiN film formed at 450 ° C. using MCS. is there. In Figure 9, it shows the oxidation resistance of these films by the value of _R S -R _B. As shown in this figure, in the case of using the DCS, in the film forming temperature 450 ° _C., while significantly large value of R S -R _B, when using the MCS is a film forming temperature 450 ° C. forming values of R _S -R _B of the film (oxidation resistance) were comparable to the case of film formation at 550 ° C. or higher using a DCS. This is presumably because MCS has a smaller amount of chlorine per molecule than DCS, and the concentration of chlorine remaining on the surface is lower.

By the way, after the film forming process as described above is repeated for a predetermined number of batches of wafers W, a cleaning process is performed. In the cleaning process, the wafer boat 5 on which product wafers are not mounted in the processing container 1 is placed on the heat insulating cylinder 7, and then loaded into the processing container 1 heated in advance to a predetermined temperature from below. To do. Next, the inside of the processing container 1 is made into a sealed space by closing the lower end opening of the manifold 3 with the lid 9. Next, a fluorine-containing gas such as HF gas or F ₂ gas is supplied into the processing container 1 as a cleaning gas while exhausting the processing container 1.

  Thereby, the reaction product adhering to the inner wall of the processing container 1, the wafer boat 5, the heat insulating cylinder 7, and the gas dispersion nozzles 19 and 22 is removed. The temperature in the processing container 1 during the cleaning process is preferably in the range of 300 to 500 ° C, more preferably in the range of 300 to 450 ° C. For the cleaning process, a cleaning gas supply mechanism 41 can be connected to the processing container 1 as indicated by a virtual line in FIG. The cleaning gas supply mechanism 41 includes a cleaning gas supply source 42 and a gas pipe 43 extending from the gas supply source 42. The gas pipe 43 branches in the middle and is connected to the gas pipe 18 and the gas pipe 21.

  After the cleaning process and before the next film forming process, a coating process in the processing container 1 is performed in a state where the wafer boat 5 on which product wafers are not mounted is placed on the heat insulating cylinder 7, and the inner wall of the processing container 1 Cover the surface of a wafer boat or the like. This is to prevent particles from these members (made of quartz) and contaminants such as Na from scattering and contaminating the product film. Conventionally, in a film forming apparatus for forming a product film by plasma ALD, this coating process is also performed by plasma ALD using the same processing gas as the film forming process in order to increase the controllability and yield. ing.

  However, when a coating film is formed by plasma ALD using MCS, Na contamination to the product film is more likely to occur than when DCS is used. When MCS is used, it is considered that the concentration of chlorine (derived from the Si source gas) contained in the formed film is lowered as described above. That is, from the viewpoint of semiconductor device performance, the concentration of chlorine as a contaminant in the product film is preferably low, but the concentration of chlorine in the coating film exhibits a Na trap effect, so that it is at a certain level. Is preferred.

  From this point of view, the present inventors have conducted research and found that when MCS is used as the Si source gas, it is preferable to perform the coating process by thermal ALD even when the product film is formed by plasma ALD. It was issued. By performing the coating process by thermal ALD, the chlorine concentration in the coating film can be increased, and a coating film having a sufficient thickness can be formed from the bottom to the top in the processing container 1.

  FIG. 10 is a graph showing the Cl content in a SiN film formed by plasma ALD and thermal ALD. This data uses DCS as the Si source gas, but it has been confirmed that similar results can be obtained when MCS is used. As shown in FIG. 10, there is a clear significant difference in Cl concentration depending on the presence or absence of plasma. Since thermal ALD has a higher Cl concentration in the film, a higher Na trap effect due to Cl can be expected by coating with thermal ALD.

Specifically, the thermal ALD alternately repeats an adsorption process for supplying MCS gas and a nitridation process for supplying nitriding gas, as in the timing chart shown in FIG. 3, except that plasma is not generated. By doing. In the adsorption process, MCS, which is a Si source gas, is supplied to the processing container 1 and is adsorbed on the inner surface of the processing container 1 or the like. In the nitriding step, NH ₃ gas, which is a nitriding gas, is supplied to the processing vessel 1 without being converted to plasma, and the Si source gas adsorbed on the inner surface or the like of the processing vessel 1 is nitrided. A purge process for removing the gas remaining in the processing container 1 from the processing container 1 is performed between the adsorption process and the nitriding process.

  In this coating process, the heating temperature in the processing container 1 is set higher than in the film forming process. A specific heating temperature is set to 300 to 630 ° C, preferably 500 to 630 ° C. Regarding other conditions, it can be performed under substantially the same conditions as the plasma ALD for film formation for forming a product film. In addition, the length of the process in the coating process can be in the same range as the length of the process in the film forming process, but the length of the purge process may be shortened.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation is possible. For example, in the above-described embodiment, the present invention is applied to a batch-type film forming apparatus in which a plurality of semiconductor wafers are mounted and collectively formed. However, the present invention is not limited to this. The present invention can also be applied to a single-wafer type film forming apparatus for forming a film.

In the above embodiment uses NH ₃ gas as the nitrogen-containing gas is a nitriding gas is not limited thereto, as described above, N ₂ gas, other nitrogen-containing gas such as N ₂ H ₄ gas Can be used.

  Furthermore, in the above-described embodiment, the example in which the plasma generation mechanism is integrated into the processing container has been described. However, the present invention is not limited to this, and the plasma generation mechanism is provided separately from the processing container to process the nitrogen-containing gas. You may use the remote plasma apparatus which plasmifies beforehand outside a container and introduce | transduces into a processing container.

Furthermore, in the above-described embodiment, the NH ₃ gas that is a nitrogen-containing gas is used after being made into plasma, but depending on the nitrogen-containing gas, it is not necessarily required to be turned into plasma.

Furthermore, in the above-described embodiment, the MCS gas and the NH ₃ gas are completely and alternately supplied. However, it is not always necessary to supply the MCS gas and the NH ₃ gas completely alternately.

  Furthermore, the object to be processed is not limited to a semiconductor wafer, and the present invention can be applied to other substrates such as an LCD glass substrate.

1; processing vessel 5; wafer boat 14; nitrogen-containing gas supply mechanism 15; Si source gas supply mechanism 16; purge gas supply mechanism 19; nitrogen-containing gas dispersion nozzle 22; Si source gas dispersion nozzle 30; 35; high frequency power supply 40; heating mechanism 100; film forming apparatus W; semiconductor wafer (object to be processed)

Claims (7)

A film forming method for forming a product film made of a silicon nitride film in a processing container capable of maintaining a vacuum,
Repeating the film forming process for forming the product film on the product to be processed in the processing container a plurality of times;
Next, performing a cleaning process for removing a reaction product adhering to the processing container by the film forming process in a state where the product object is not stored in the processing container;
Next, a coating process for coating the inside of the processing container with a coating film made of a silicon nitride film is performed in a state where the product target is not stored in the processing container;
Next, performing the film forming process for forming the product film on the product object to be processed in the processing container;
Comprising
The film forming process repeats a cycle including an adsorption process and a nitridation process alternately with a purge process in between, and in the adsorption process, a monochlorosilane gas is supplied as an Si source gas into the processing container, The nitriding step is performed by ALD (atomic layer deposition) for supplying a nitrogen-containing gas as a nitriding gas into the processing vessel;
In the coating process, a cycle including a first supply process and a second supply process are repeated a plurality of times with a purge process in between. In the first supply process, dichlorosilane gas is introduced into the processing container as a Si source gas. Supplying the second supply step by ALD supplying a nitrogen-containing gas as a nitriding gas into the processing vessel;
A film forming method characterized by the above. The processing container is configured to arrange a plurality of workpiece in a plurality of stages, wherein said processing container includes a quartz part, characterized in that Na as a contaminant may occur here Item 2. The film forming method according to Item 1 . The film forming process, sets the processing temperature of 150 to 550 ° C., according to claim 1 or claim and sets the process pressure when supplying the 66.65~666.5Pa the Si source gas 2. The film forming method according to 2 . The film forming process is a plasma ALD in which the Si source gas is supplied into the processing container without being converted into plasma, and the nitriding gas is supplied in a plasma state by a plasma generation mechanism attached to a side wall of the processing container. the film deposition method according to any one of claims 1 to 3, characterized in that to perform. Wherein the nitrogen-containing gas, film deposition method according to any one of claims 1 to 4, characterized in that a NH ₃ gas. A storage medium that operates on a computer and stores a program for controlling the film forming apparatus, wherein the program is executed by the film forming method according to any one of claims 1 to 5. As described above, a computer-readable storage medium that causes a computer to control the film forming apparatus. A film forming apparatus for forming a silicon nitride film on a plurality of objects to be processed,
A vertical processing container capable of holding a vacuum;
A holding member that holds the object to be processed in a plurality of stages in the processing container;
A heating mechanism for heating the object to be processed provided on the outer periphery of the processing container;
A Si source gas supply mechanism for supplying Si source gas into the processing vessel;
A nitrogen-containing gas supply mechanism for supplying a nitriding gas into the processing vessel;
A control unit for controlling the operation of the film forming apparatus;
The control unit includes: a computer; and a computer-readable storage medium according to claim 6 , wherein the computer operates on the computer and stores the program for controlling the device. A vertical film forming apparatus.

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