JP2009094321A - Method of forming polysilazane film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming a polysilazane film, which can reduce a change in processing rate of wet processing in a short time even after heat treatment is conducted at a low temperature. <P>SOLUTION: The method of forming a polysilazane film includes: a step (step 1) wherein a substrate with a coating film containing polysilazane formed on the front surface thereof is heat-treated at 150-600°C to reform the coating film into a polysilazane film; and a step (step 2) of bringing water into contact with the obtained polysilazane film. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polysilazane film forming method for forming a polysilazane film on a substrate such as a semiconductor wafer.

As an element isolation film and an interlayer insulating film used in a semiconductor device formed by an STI (Shallow Trench Isolation) method, a BPSG (borophosphosilicate glass) method or an ozone TEOS (tetraethyl orthosilicate) method has been conventionally used. In addition, a SiO ₂ film formed by a USG (undoped silicate glass) method, a high density plasma enhanced deposition (HDP) method, or the like is used.

  By the way, recently, the miniaturization has progressed along with the high integration of semiconductor devices, and the aspect ratio of the recesses such as contact holes and via holes has become very high. The SiO 2 film formed by the above-described method such as the BPSG method, the ozone TEOS method, or the HDP method has a problem that the recess filling property is very poor.

  Therefore, in order to improve the embedding property in the concave portion having a high aspect ratio, a polysilazane film formed by applying a polysilazane coating solution to a wafer as a substrate to be processed and then modifying it by heat treatment is formed as described above. Use as a separation film, an interlayer insulation film, etc. is examined (for example, patent document 1 etc.).

  Such reforming conditions of the polysilazane film vary depending on the target device and usage pattern. For example, when the polysilazane film is etched at a constant speed regardless of the density of the pattern, or when there is a limitation on the thermal budget of the device, it is necessary to process at a low temperature.

However, the polysilazane film processed at a low temperature does not have a stable film quality immediately after the process. Therefore, when a wet process is performed such that CMP is performed and then etching back is performed by wet etching, the CMP rate and the wet etching rate vary. In particular, the film quality variation on the wafer edge side is large, and if wet etching is performed immediately after the heat treatment, the difference in wet etch rate within the wafer surface becomes very large. It takes about one day to stabilize the film quality, and the total processing time becomes long.
JP 2005-116706 A

  The present invention has been made in view of such circumstances, and it is intended to provide a method for forming a polysilazane film that can reduce variation in the wet processing rate in a short period of time even after heat treatment at a low temperature. Objective.

  In order to solve the above-described problems, the present invention provides a process of heat-treating a substrate on which a coating film containing polysilazane is formed at 150 to 600 ° C. to modify the coating film to form a polysilazane film. And a step of bringing water into contact with the polysilazane film.

  In the present invention, the step of bringing the water into contact can be performed as a film quality stabilization process of the polysilazane film. The step of bringing water into contact with the polysilazane film is preferably performed by immersing a substrate having a polysilazane film in water. The step of bringing water into contact with the polysilazane film is preferably performed for 1 hour or longer. In the modifying step, it is preferable to perform heat treatment while supplying water vapor into a processing vessel in which a substrate is disposed.

  According to the present invention, a substrate on which a coating film containing polysilazane is formed is heat-treated at a low temperature of 150 to 600 ° C. to modify the coating film to obtain a polysilazane film, and then water is added to the obtained polysilazane film. Therefore, the effect of accelerating the stabilization of the film quality that has been achieved by leaving it for a long time can be obtained. The variation in the etching rate can be suppressed, and the in-plane uniformity of the wet etch rate can be improved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
First, an example of processing to which the method for forming a polysilazane film of the present invention is applied will be described. FIG. 1 is a diagram for explaining an element isolation film forming process to STI (shallow trench isolation) to which the polysilazane film forming method of the present invention is applied. First, a thermal oxide film 2 is formed on a silicon substrate 1, and a silicon nitride film 3 serving as a stopper for CMP performed later is formed thereon. Then, a pattern is formed on the substrate 1 by photolithography or the like, and the silicon nitride film 3, the silicon thermal oxide film 2, and the silicon substrate 1 are sequentially etched by the RIE process using the formed pattern as a mask, and the shallow trench is formed on the silicon substrate 1. Form. Next, after the unnecessary film is removed, the inside of the shallow trench is thermally oxidized to form a silicon thermal oxide film 4, whereby an isolation groove 5 having an isolation width as shown in FIG. It is formed.

  A polysilazane film 6 is formed on the entire surface of the silicon substrate 1 by spin coating using a coating liquid containing polysilazane (FIG. 1B). Thereafter, processing such as film modification is performed as described later.

  Next, the polysilazane film 6 is polished by CMP using the silicon nitride film 3 as a stopper, and the polysilazane film 6 is left only in the isolation groove 5 (FIG. 1C).

  Next, the polysilazane film 6 is etched back in preparation for the next filling of the HDP silicon oxide film by wet etching using 1% diluted hydrofluoric acid ((d) in FIG. 1).

  Thereafter, a desired semiconductor device is formed through an HDP silicon oxide film filling process and an element forming process.

  In such a manufacturing process, the process of forming the polysilazane film 6 shown in FIG. 1B is performed by inserting a plurality of wafers, which are silicon substrates coated with the polysilazane film 6, into a vertical furnace and performing heat treatment. Is called.

  FIG. 2 shows a vertical heat treatment apparatus for performing such heat treatment. The vertical heat treatment apparatus 10 includes a cylindrical heat insulator 12 having a ceiling portion and a heater 13 which is a heating means provided along the inner wall surface of the heat insulator 12, and a lower end portion of the vertical heat treatment device 10 is a base. A vertical heating furnace 11 fixed to 14 is provided. The heater 13 is configured so that the processing region (heat treatment atmosphere) is divided into a plurality of zones in the upper and lower directions and individual heating control can be performed for each zone. The heating furnace 11 is provided with a reaction tube 16 which is a vertical reaction vessel made of, for example, quartz, whose upper end is closed and in which a heat treatment atmosphere is formed. The reaction tube 16 is fixed to the base 14.

  A wafer boat 17 that is a holder for holding a plurality of, for example, 100 wafers W in a shelf shape can be inserted into the reaction tube 16 from below, and the wafer boat 17 includes a heat insulating cylinder 18 and a heat insulating material. It is inserted into the reaction tube 16 in a state of being placed on the lid 20 via the turntable 19. The lid 20 is for opening and closing the opening at the lower end of the reaction tube 16, and is provided in the boat elevator 21. Further, the boat elevator 21 is provided with a rotation mechanism 22 so that the wafer boat 16 rotates together with the turntable 19. The wafer boat 17 is carried in and out of the reaction tube 16 by moving the boat elevator 21 up and down.

In the vicinity of the bottom of the side wall of the reaction tube 16, a gas supply pipe 24 is provided so as to extend from the outside to the inside. For example, the gas supply pipe 24 extends vertically upward in the reaction tube 17, and the tip thereof is the reaction tube. In the vicinity of the center of the upper end portion of 17, it is bent so as to blow process gas toward the ceiling. An upstream side of the gas supply pipe 24 outside the reaction pipe 17 is branched into a first gas supply pipe 25 and a second gas supply pipe 26, and a steam generator 27 is provided in the first gas supply pipe 25. It has been. The upstream side of the water vapor generator 27 in the first gas supply pipe 25 is branched into an oxygen (O ₂ ) gas supply pipe 28 and a hydrogen (H ₂ ) gas supply pipe 29, and the proximal end of the oxygen gas supply pipe 28 The side is connected to an oxygen gas supply source 32 via a flow rate controller 31 such as a valve 30 and a mass flow controller, and the proximal end side of the hydrogen gas supply pipe 29 is hydrogen via a flow rate controller 34 such as a valve 33 and a mass flow controller. The gas supply source 35 is connected. The proximal end side of the second gas supply pipe 26 is connected to a nitrogen gas supply source 38 which is an inert gas supply source via a valve 36 and a flow rate controller 37 such as a mass flow controller.

  A valve 42 is provided on the downstream side of the water vapor generator 27 in the first gas supply pipe 25, and the first gas supply pipe 25 and the part of the gas supply pipe 24 from the water vapor generator 27 to the reaction tube 16 are provided. A heater, for example a tape heater 43, is wound as a heating means for heating so that water vapor is not condensed. The steam generator 27 is provided with a heating means for heating the gas passing through it, and a catalyst such as platinum is provided in the gas flow path, and oxygen gas and hydrogen gas are heated to a predetermined temperature of, for example, 500 ° C. or lower. The catalyst is brought into contact with the catalyst while being heated, and water vapor is generated by the reaction of oxygen gas and hydrogen gas under the catalyst. According to the water vapor generator 27, for example, the concentration of water vapor with respect to water vapor and oxygen gas can be set to a concentration of about 1 to 90% in the decompressed reaction tube 16.

  Further, an exhaust pipe 44 having a diameter of, for example, 3 inches is connected to the vicinity of the bottom of the side wall of the reaction tube 16, and a vacuum pump 45 serving as a decompression unit is connected to the base end side of the exhaust pipe 44. The exhaust pipe 44 is provided with a pressure adjusting mechanism 46. The pressure adjusting mechanism 46 includes a main valve that opens and closes the exhaust pipe 44 in addition to a device that adjusts the pressure, such as a butterfly valve.

  The vertical heat treatment apparatus 10 includes a control unit 50 having a computer that controls each component, for example, a drive mechanism such as valves, a mass flow controller, a heater power supply, and a boat elevator. The valves 30, 33, and 36 and the mass flow controllers 31, 34, and 37 perform supply / disconnection and flow rate adjustment of each gas. Actually, control signals are sent from the control unit 50 to these valves and the mass flow controller via a controller (not shown). Is given. The control unit 50 includes a storage unit that stores a recipe describing processing parameters and processing procedures of processing in the vertical heat treatment apparatus 10 and a program for reading out the recipe.

  In such a vertical heat treatment apparatus 10, first, the temperature in the reaction tube 16 is set to, for example, 150 ° C., and the valves 30 and 42 are opened in a state in which the water vapor generating device 27 is not operated, and the reaction tube 16 is filled with oxygen gas. Purge with. In this state, a wafer transfer machine, which is a substrate transfer means (not shown), transfers the wafer W from the wafer carrier C, which is a wafer storage container, to the wafer boat 17, and, for example, 100 wafers W are mounted thereon. In the previous step, the wafer W is coated with a coating liquid containing a component of polysilazane {-(SiR1-NR2) n-: R1, R2 is an alkyl group} and a solvent by a spin coating method in a coating unit (not shown). Thus, a coating film is formed, and then, for example, a baking treatment is performed at a temperature of about 150 ° C. for 3 minutes to remove the solvent in the coating solution.

  After the transfer of the wafer W is completed, the wafer boat 17 is raised and loaded into the reaction tube 16, and the lower end opening in the reaction tube 16 is closed by the lid 14. During this time, the reaction tube 16 is evacuated (reduced pressure), and the pressure in the reaction tube 16 is set to, for example, 6665 to 53320 Pa (50 to 400 Torr). Then, after the wafer boat 17 is loaded, the valves 42, 30, 33 are opened and the water vapor generator 27 is operated, and oxygen gas and hydrogen gas are reacted in the presence of the catalyst in the water vapor generator 27 to generate moisture. The water vapor is introduced into the reaction tube 16. With respect to the flow rates of oxygen gas and hydrogen gas, for example, 0.75 to 15 L / min (slm) are respectively provided so that water vapor in an amount necessary for baking the polysilazane film formed on the wafer W is supplied in the reaction tube 16. And 1 to 20 L / min (slm). As a result, the moisture concentration in the processing region in a reduced-pressure atmosphere is, for example, 80%.

  Then, pretreatment is performed as necessary, with the pressure and gas supply state kept unchanged. In the preliminary processing, the heater 13 is controlled, the temperature in the reaction tube 16 is set to 150 to 600 ° C., for example, the pressure is set to 6665 to 53320 Pa (50 to 400 Torr), and this state is maintained for about 30 minutes to perform the processing. . By performing the pretreatment in this way, the solvent and impurities remaining in the polysilazane coating film on the surface of the wafer W are removed. That is, this pretreatment process is performed as a supplement to the baking process in the coating unit. In this case, the water concentration in the reaction tube 16 is desirably set to 1 to 90%.

  Subsequently, the pressure and gas supply state are left as they are, the heater 13 is controlled, the inside of the reaction tube 16 is set to 150 to 600 ° C., and heat treatment for modifying the polysilazane coating film is started. By such heat treatment, impurities such as nitrogen (N), carbon (C), and hydrogen (H) are removed and modified to form a polysilazane film skeleton. In addition, it is preferable to set the processing time at this time to 5 to 60 minutes, the pressure in the reaction tube to 6665 to 53320 Pa (50 to 400 Torr), and the moisture concentration to 1 to 90%, respectively. Here, the heat treatment condition is set to a relatively low temperature of 150 to 600 ° C. when the device to be applied needs to etch the polysilazane film at a constant speed regardless of the density of the pattern or when the thermal budget is limited. Is taken into account. The device shown in FIG. 1 requires that the polysilazane film 6 be etched at a constant speed by wet etching.

  However, when the heat treatment for modifying such a polysilazane coating film to a polysilazane film is performed at 150 to 600 ° C., the film quality becomes unstable. The wet processing rate, particularly the wet etching rate, varies. If the film is left as it is for 24 hours, the film quality is stabilized, but this makes the total processing time longer.

  Therefore, in the present embodiment, as shown in FIG. 3, the polysilazane coating film is modified to form a polysilazane film by performing the heat treatment at 150 to 600 ° C. as described above (Step 1), and then the obtained polysilazane film is formed. Stabilization treatment is performed by bringing moisture into contact (step 2). By bringing water into contact with the polysilazane film obtained by such modification, the stabilization of the film quality that has been realized by standing for a long time can be accelerated and the stabilization process can be significantly shortened. That is, only by performing a relatively low temperature heat treatment at 150 to 600 ° C., the reforming process does not proceed sufficiently, and a stable film quality can be obtained only by standing for a long time after that, but it was obtained by the reforming process. When water is brought into contact with the polysilazane film, the film quality is stabilized by water in a short time. For this reason, after the reforming process at a low temperature, the film quality is stabilized without passing for a long time, and the fluctuation of the rate at the time of the wet process such as CMP or wet etching performed thereafter can be reduced.

  As shown in FIG. 4, in the step 2 of bringing the polysilazane film into contact with water, water (pure water) 61 is stored in the immersion bath 60 and a plurality of wafers W are supported by the support member 62 therein. It can carry out by making it immerse in the made state.

  Further, as shown in FIG. 5, water (pure water) 64 may be sprayed from the nozzle member 65 onto the wafer W supported by the support member 63.

  Further, when the single wafer processing is allowed, as shown in FIG. 6, a spin chuck 67 is provided in the cup 66 as in a normal single wafer cleaning apparatus, and the wafer W is horizontally attracted to the spin chuck 67. Then, water (pure water) 70 may be supplied from the nozzle 69 positioned above while rotating the wafer W by the motor 68.

  In these, the method of immersing the wafer W in the water in the immersion tank 60 is preferable from the viewpoint of simplicity. As such a dipping bath 60, a water washing bath mounted in a wet etching apparatus can be used, so that it is not necessary to use additional equipment, which is advantageous from that point.

  Such a step of contacting with water is effective even for an extremely short time of several minutes, but it is preferable to carry out for 1 hour or longer in order to obtain a reliable effect. In consideration of processing variations, 3 hours or less is preferable.

  In the application shown in FIG. 1 described above, CMP is performed after the polysilicon film forming step, and then etching back is performed by wet etching. Of these, the rate is likely to vary particularly during wet etching. Therefore, when the CMP rate fluctuation does not become a problem, the second step of contacting with water may be performed after CMP.

Next, an experiment for confirming the effect of the present invention will be described.
The wafer on which the polysilazane coating film is formed is heat-treated at a temperature of 300 ° C., a pressure of 26660 Pa (200 Torr), and a water vapor concentration of 80% by a vertical heat treatment apparatus as shown in FIG. The membrane was modified. Next, the wet etching rate is uniform between the sample that was left for 1 hour and then wet etched, and the sample that was wet etched after being immersed in water (pure water) in the immersion bath for 1 hour. Seeking sex. The result is shown in FIG. The vertical axis in FIG. 7 represents the wet etching rate of the polysilazane film normalized with the wet etching rate of the thermal oxide film set to 100. As shown in this figure, when left after heat treatment, the wet etching rate fluctuates greatly even after 1 hour. It was confirmed that the fluctuation of the etching rate can be suppressed.

  Further, after the heat treatment of the polysilazane coating film, the time is changed depending on whether it is normally left or immersed in water, and the center (one point) in the subsequent wet etching process, the radius from the center is 48 mm. The wet etch rate in the subsequent wet etching was determined for the above circle (average), the circle 97 mm from the center (average), and the circle 145 mm from the center (average). The result is shown in FIG. As shown in FIG. 8, with respect to those left after the heat treatment, the wet etching rate fluctuates greatly even after 3 hours, and the wet etching rate tends not to decrease particularly at the outer peripheral portion of the wafer W. However, it was confirmed that the wet etching rate was stable even when the immersion treatment was performed for a short time of 1 hour when immersed in water after the heat treatment.

  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 wafers are mounted and film formation is performed collectively. The present invention can also be applied to a single-wafer type film forming apparatus for forming a film.

Further, the object to be processed is not limited to a semiconductor wafer, and the present invention can also be applied to other substrates such as an LCD glass substrate.
It can be widely used for applications such as an insulating film between the gate and the gate.

The figure for demonstrating the element isolation film formation process to STI (shallow trench isolation) to which the formation method of the polysilazane film | membrane of this invention is applied. Sectional drawing which shows the vertical heat processing apparatus for performing the modification | reformation process of a polysilazane coating film. The block diagram which shows the process of the formation method of the polysilazane film | membrane of this invention. The figure which shows an example of embodiment of the process which makes a polysilazane film | membrane contact a water | moisture content. The figure which shows the other example of embodiment of the process of making a polysilazane film | membrane contact a water | moisture content. The figure which shows the further another example of embodiment of the process of making a polysilazane film | membrane contact a water | moisture content. The figure which shows the in-plane fluctuation | variation of the wet etching rate at the time of performing wet etching after that when it is left to stand for 1 hour after heat processing of a polysilazane coating film, and what was immersed in water for 1 hour. After the heat treatment of the polysilazane coating film, the results obtained by determining the wet etch rate depending on the position of the wafer during the subsequent wet etching process by changing these times in the case of normal standing and when immersed in water. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Silicon substrate 6; Polysilazane film | membrane 10; Vertical heat processing apparatus 11; Heating furnace 12; Heat insulator 13; Heater 16; Reaction tube 17; Wafer boat 24, 25, 26, 28, 29; vessel 30,33,36,42; valve 31,34,37; mass flow controller 32; an oxygen gas supply source 35; hydrogen gas supply source 38; _{N 2} gas supply source 43; tape heater 44; an exhaust pipe 45; a vacuum pump 46 Pressure adjusting mechanism 50; control unit 60; immersion bath 61; water 62; support member W; wafer (object to be processed)

Claims (5)

A step in which a substrate on which a coating film containing polysilazane is formed is heat-treated at 150 to 600 ° C. to modify the coating film to form a polysilazane film;
And a step of bringing water into contact with the obtained polysilazane film.   The method for forming a polysilazane film according to claim 1, wherein the step of bringing the water into contact is a film quality stabilization process of the polysilazane film.   The method of forming a polysilazane film according to claim 1 or 2, wherein the step of bringing water into contact with the polysilazane film is performed by immersing a substrate having the polysilazane film in water.   The method for forming a polysilazane film according to any one of claims 1 to 3, wherein the step of bringing water into contact with the modified polysilazane film is performed for 1 hour or more.   5. The method for forming a polysilazane film according to claim 1, wherein in the modifying step, heat treatment is performed while supplying water vapor into a processing vessel in which a substrate is disposed.

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