KR940010412B1 - Method of forming thin film - Google Patents

Abstract

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Description

Thin Film Formation Method

1 is a schematic configuration diagram of a CVD apparatus used in an embodiment according to the present invention.

2A and 2B are schematic views of a thin film forming method according to an embodiment of the present invention.

3 and 4 are graphs comparing the effects of the prior art of the present invention.

5A to 5C and 6A to 6C are diagrams showing an embodiment in which the thin film forming method according to the present invention is applied to the selective CVD method.

* Explanation of symbols for main parts of the drawings

1: quartz reaction tube 2: heater

3 to 6: gas supply system 8: vacuum pump

9: substrate 10: quartz boat

11-14: valve 21, 54, 63: tungsten film

22, 55, 64: tungsten nitride film 51: polysilicon wiring layer

52, 62: contact hole 53, 61: SiO ₂ film

60: silicon substrate

[Industrial use]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film formation method, and more particularly, to a thin film formation method of forming a high quality high melting point metal film on a surface of a substrate by a vapor phase growth method (hereinafter referred to as a CVD method).

[Traditional Technology and Problems]

Recently, a thin high melting point metal film is used as a fine metal wiring material of a high density integrated circuit. Such high melting point metal groups include Ti, W, Mo, and Ta. In the following description, tungsten (W) has been described as an example, and the same can be used for other high melting point metals.

와 같다. 상기와 같은 기상반응에서 텅스텐(W) 박막은 적당한 촉매표면을 제공하는 금속이나 반도체와는 전혀 다른, 예컨대 SiO₂와 같은 절연막은 상반응을 촉진하는데 적당한 촉매표면을 제공하지 못하기 때문에 절연막상에 성장시키는 어렵다.By the way, for example, WF ₆ and H ₂ are used as source gases in the gas phase field using the CVD method for tungsten thin film formation. This gas phase reaction

Same as In such a gas phase reaction, a tungsten (W) thin film is completely different from a metal or semiconductor that provides a suitable catalyst surface, for example, an insulating film such as SiO ₂ does not provide a suitable catalyst surface to promote a phase reaction. It is difficult to grow.

Therefore, since the tungsten thin film can be selectively formed only in a predetermined region of the substrate surface, it is possible to form a fine tungsten wiring pattern without going through the patterning step. Such a specific formation method is called selective CVD method.

와 같다.However, when the tungsten thin film is formed by the above CVD method, serious problems are caused, in particular, the selectivity of tungsten thin film formation is not complete. In particular, where virtual growth is continued for a long time at a reaction temperature (substrate temperature) of 400 [deg.] C. or more, a small amount of tungsten is deposited on the insulating film. In particular, where the insulating film is formed, it is formed by vapor phase reaction performed at high temperature, for example, SiO ₂ and HF, which react with SiO ₂ to easily deposit SiF ₄ on tungsten to improve the selectivity of tungsten film formation. Is degraded. This reaction is

Same as

However, where the tungsten thin film wiring layer is formed on the semiconductor substrate by, for example, the selective CVD method, the processing time of each wafer is shortened, and therefore, the selectivity reduction of each wafer is relative because each wafer is replaced with a new wafer. Will be lowered.

On the other hand, when the CVD apparatus is used repeatedly over a long time, for example, in the diffusion furnace type CVD apparatus, tungsten deposition continues on the inner wall of the quartz (SiO ₂ ) reaction tube for longer than the reaction time. In detail, when the CVD operation is performed for a long time, the fine tungsten particles are mainly deposited on the inner wall of the reaction tube, and thus, the stacked fine tungsten particles provide a catalyst surface for the aforementioned tungsten growth reaction. From then on, rapid tungsten lamination is induced. At this time, the tungsten thin film equipment on the semiconductor surface is rapidly lowered depending on the amount of tungsten deposition on the inner wall of the reaction tube. This not only makes it impossible to form a rapid tungsten film at a high temperature, but also makes it impossible to control the thickness of the tungsten thin film. In addition, the tungsten particles deposited on the inner wall of the reaction tube are weakly attached to the surface, thereby causing a problem of peeling off the wall during the vapor phase growth step. Therefore, the tungsten particles in question fall off the substrate, so that a particulate defect appears in the growth film of the thin film on the substrate. Indeed, these combinations cause serious problems that must be solved for fine circuit formation in high density integrated circuits.

The above problems occur not only in the diffusion type CVD apparatus but also in the stainless steel CVD apparatus called the cold wall type. On the other hand, this is because tungsten particles tend to be deposited on the surface of the stainless steel itself, so that the wall of the reaction tube is cooled in the cold wall type CVD apparatus to prevent tungsten deposition on the wall. However, tungsten particles are deposited on the support surface by installing a heater to heat the substrate to a temperature that can cause a gas phase growth reaction in the support object mounted on the substrate. In another type of cold-walled CVD apparatus, the substrate installed in the support metabolism is heated by infrared radiation through the window of the reaction tube. In this case, the support and the inner wall of the reaction tube are also partially radiated by the infrared rays. Therefore, the radiated portion is heated to generate tungsten, so that a problem such as a significant reduction in the tungsten film growth ratio in the diffusion furnace type CVD apparatus also occurs in the cold wall type CVD apparatus.

[Purpose of invention]

The present invention has been invented in view of the above, and a thin film forming method which enables to form a high quality thin film effectively by preventing the deposition of high melting point metal on the inner wall of the reaction tube even if the CVD operation is continuously performed for a long time. The purpose is to provide.

[Configuration of Invention]

In order to achieve the above object, the present invention provides a thin film forming method for forming a high melting point metal thin film on the surface of a substrate disposed in a CVD reaction tube by a CVD method. At least a part of the member disposed in the reaction tube is characterized by being applied with a metal nitride film.

[Action]

The present invention configured as described above is a method of forming a thin high melting point metal film on the surface of a substrate located in a CVD reaction tube by the CVD method, in the inner wall of the CVD reaction tube and at least in the CVD reaction tube in the process of performing the CVD operation. The surface of a portion of the fittings installed is coated with a metal nitride film, which member supports, for example, supporting rods, baffles and quartz boats used in diffusion furnace type CVD apparatuses. And susceptors used in cold wall CVD devices. In addition, in the present invention, a metal nitride film is formed on the inner wall of the CVD apparatus by introducing a nitrogen-containing gas such as ammonia gas into the reaction tube. In this case, the reaction tube is heated so that the desired portion of the metal surface is nitrided. . On the other hand, the metal nitride film may be laminated on a desired surface by a CVD method using any one of a metal containing gas and a nitrogen containing gas. In this case, the metal contained in the source gas is preferably used for forming a thin film on the substrate while having a high melting point type.

On the other hand, the final metal nitride film is in the form of an interstitial alloy in which nitrogen atoms are intercalated between the metal crystal lattice, so that the stoichiometric mass ratio between the metal forming the metal nitride and the nitrogen atoms becomes unclear. For example, tungsten nitride, which is a compound containing W ₂ N and WN, is represented by the chemical formula WNx. In the following description, tungsten nitride is used as a typical tungsten nitride. However, the following description is not limited to this, but also applies to tungsten nitride of another formula. As described above, the nitride of the high melting point metal forming the thin film is in the form of an invasive alloy, and the thin film on which such a series of nitride is formed becomes an electrical conductor.

In the present invention, the metal nitride film is formed on the inner surface of the quartz reaction tube in advance so that the particles of the high melting point metal laminated on the inner wall of the reaction tube are covered with the metal nitride film. In the present invention, it is difficult to deposit tungsten particles on a metal nitride film as well as a quartz (SiO ₂ ) film by the CVD method in the selective formation of a tungsten film on a substrate using a mixed gas composed of WF ₆ and H ₂ . As a result, undesired lamination of a new metal film on the inner wall of the reaction tube or the like is suppressed in the present invention. This makes it possible to prevent the source gas from being consumed on the inner wall of the reaction tube and the corrosion of the inner wall of the reaction tube by the gaseous reactants.

In addition, the method according to the present invention can form a desired high melting point metal thin film on a substrate at high temperature and accurately, for example, metal particles deposited on the inner wall of the reaction tube are no longer provided when the metal nitride film is coated with the metal nitride film. It is possible to prevent the film from growing. Therefore, it is possible to substantially prevent the metal film from falling off the inner wall of the reaction tube, thereby forming a high quality thin film free of particulate defects.

EXAMPLE

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a diffusion furnace type CVD apparatus according to an embodiment of the present invention, which comprises a quartz reaction tube 1 and a quartz reaction tube for heating the reaction region in the quartz reaction tube 1. It consists of the heater 2 provided in the exterior of (1), the vacuum pump 8, and the gas supply system 3-6 connected to the said quartz reaction tube 1. As shown in FIG. The gas supply from the gas supply system 3 to 6 to the quartz reaction tube 1 is controlled by the valves 11 to 14, and the plurality of substrates 9 on which the thin film is formed are located in the quartz reaction tube 1. It is supported on the quartz boat 10. It is also installed in a quartz reaction tube 1 such as a quartz support (not shown) for moving the quartz boat 10 into and out of the quartz tube and a quartz heat baffle (not shown) for maintaining a constant temperature distribution. The tungsten thin film is formed by the CVD method using the apparatus of FIG.

Example 1

After washing the quartz reaction tube 1, the quartz boat 10 supported by the plurality of substrates 9 is placed in the reaction region in the quartz reaction tube 1 as shown in FIG. Heated to 350 to 600 [° C]. Thereafter, when the inside of the quartz reaction tube 1 was evacuated by the vacuum pump 8 and the atmospheric pressure of the reaction zone was reduced to 0.1 to 1.0 [Torr], WF ₆ gas and H from each gas supply system 3 and _{4 were} discharged. ₂ Inject gas inside. Under such a state, as shown in FIG. 2A, a tungsten film 21 having a thickness of, for example, 0.1 to 1.0 [mu m] is vapor-grown on each of the substrates 9, in which case the tungsten particles are tungsten film 15. As shown in FIG. A small amount, however, is deposited on the inner wall of the quartz reaction tube 1, the quartz boat 10, the quartz support, and the thermal baffle.

After the tungsten film 15 is formed, the valves 11 and 12 are closed to stop the gas inflow from the gas supply systems 3 and 4, and then the gas supply system when the temperature in the quartz reaction tube 1 drops. Ar gas flows into the quartz reaction tube 1 from (5). At this time, after removing the substrate 9 from the quartz boat 10, as shown in FIG. 2b, the quartz boat 10 is again placed in the quartz reaction tube 1, and the inside of the quartz reaction tube 1 is removed. Exhaust. Again, the reaction zone was heated to 350-1000 [deg.] C. and ammonia (NH ₃ ) gas was introduced from the gas supply system 6 into the quartz reaction tube 1 under such conditions, for example, for 30 minutes. The fine tungsten particles 15 attached to the inner wall of 1) and the surface of the quartz boat 10 or the like are nitrided to form the tungsten nitride (W ₂ N) film 22.

Then, in the case of forming the tungsten film on another substrate again, it is not necessary to clean the quartz reaction tube 1 and the quartz boat 10 in advance, and in particular, the other substrate mentioned above is applied to the nitrided quartz boat 10. After arranging and placing in the quartz reaction tube 1 again, the above-described tungsten film forming process and nitriding process may be repeated.

Example 2

In the first embodiment, the tungsten nitride film 22 is formed by nitriding with ammonia gas, but the tungsten nitride film can be formed directly by the CVD method described later. In particular, in Example 2, a tungsten film 21 is formed on the substrate 9 as in Example 1, and the WF ₆ gas is injected into the quartz reaction tube 1 together with the ammonia gas to form the tungsten film 21. And then tungsten nitride was attached using a predetermined CVD reaction. As a result, a tungsten nitride film 22 was formed on the surface of the inner wall of the quartz reaction tube 1 and on the quartz boat 10. The tungsten film 21 was covered with the tungsten nitride film 22 as in the first embodiment. do.

Then, when forming a tungsten film on another substrate again, it is not necessary to clean the quartz reaction tube 1 and the quartz boat 10 in advance as in Example 1, and in particular, another substrate mentioned above is nitrided. After arranging on the quartz boat 10 and again in the reaction tube 1, the series of tungsten film forming steps and nitriding steps may be repeated.

Example 3

According to the present invention, after forming the tungsten film 21, the tungsten nitride film 22 can be formed without removing the substrate 9 from the quartz reaction tube 1, in which case the tungsten film 21 is implemented. The tungsten nitride film 22 is first formed on the substrate 9 as in the method of Example 1, and the tungsten nitride film 22 is continuously formed on the substrate 9 left in the quartz reaction tube 1 as in the first or second embodiment. Therefore, in the third embodiment, it is possible to form a laminated structure composed of a tungsten film 21 and a tungsten nitride film 22 on the substrate 9.

As described in Examples 1 to 3 above, in the method of the present invention, the tungsten nitride film is formed on the inner surface of the quartz reaction tube 1 so that the operation for forming the tungsten film while maintaining the high lamination ratio of the tungsten film on the substrate can be maintained. Can be repeated. On the other hand, in the related art, the increase in the number of operations (or time) for forming the tungsten film causes the tungsten film stacking ratio on the substrate to be significantly reduced.

This will be described in more detail with reference to FIG. 3.

3 shows the tungsten stacking ratio with respect to the time carried out at 600 [deg.] C. in accordance with the method of the present invention, and also shows the conventional case where tungsten stacking was carried out without undergoing a nitriding step.

As shown in FIG. 3, in the prior art, when the number of operations (each operation is continued for 1 hour) required for stacking the tungsten film exceeds four times, the stacking ratio is significantly reduced, even though the reaction is performed at 350 [deg.] C. Even if performed, it can be seen that in about five operations, it is significantly reduced to 1/2 of the initial stacking ratio. In addition, in the related art, when the reaction temperature is set to 600 [° C.], the initial stacking ratio may be maintained for 2 hours, and after about 2.5 hours, it may fall to “0” to form a thin film. However, in the present invention, even if 20 laminations are performed, the reduction of the lamination ratio can be suppressed to within 5% of the initial ratio.

Figure 4 shows the change in the average lamination ratio according to the reaction temperature of the present invention and the prior art, it can be seen in the prior art that the lamination ratio is significantly lowered when the reaction temperature exceeds 400 [° C]. In order to promote the deposition of tungsten on the inner wall of the quartz reaction tube, the following reaction occurs to reduce the deposition ratio.

However, in the present invention, since the CVD operation is performed so that the tungsten nitride film is attached to the inner wall of the reaction tube, even if the reaction temperature is raised to 700 [° C.], the average lamination ratio is substantially increased.

Further, in Examples 1 to 3, since tungsten particles laminated on the inner wall of the reaction tube can be prevented from falling off the inner wall, a high quality tungsten film having a low particulate defect density can be obtained. For example, if the reaction temperature is set at 350 [deg.] C. and the CVD operation is repeatedly performed for 10 hours, in the prior art, the final tungsten defect density of the surface of the final tungsten film is 50 pieces / cm ² in the present invention but 10 pieces / It can be seen that it is cm ² . In addition, in the conventional method, the problem of particulate defects increased with the increase in the number of CVD operations, but in the present invention, the density of defects was about 12 / cm ² even after performing 20 CVD operations.

5 and 6 are cross-sectional views of the fabrication of a semiconductor device using the selective CVD method, which is the method according to the present invention, in which a tungsten film is formed in a contact hole before the formation of the wiring layer, thereby improving the application step of the wiring layer. do.

On the other hand, the technical gist of the present invention can be used in the multi-layered wiring of the first embodiment of FIG. 5, after forming the first polysilicon wiring layer 51 on the silicon substrate 50, as shown in FIG. A quartz film 53 having contact holes 52 is formed so that a part of the polysilicon wiring layer 51 is exposed, and under such a state, as shown in FIG. 5B, by the selective CVD method in the contact holes 52. The tungsten film is laminated to form the tungsten film 54. At this time, the contact hole 52 is filled with a tungsten film, which can improve the application step of the second wiring layer on the tungsten film.

Further, in the first embodiment of FIG. 6, the quartz film 61 is formed on the silicon substrate 60 by thermal oxidation or the like, and is etched by RIE or the like so that a part of the silicon substrate 60 is exposed. To form. 6B is a cross-sectional view in which the tungsten film 63 is formed on the silicon substrate 60 formed as described above on the silicon substrate 60 by the selective CVD method. On the other hand, when the method of Example 3 is applied to the processes of FIGS. 5 and 6, a remarkable effect is obtained. In particular, the surfaces of the tungsten films 54 and 63 filling the contact holes 52 and 62 are covered over the tungsten nitride films 55 and 64, respectively. This is very important when polycrystalline silicon is used to form the wiring layer. If the tungsten nitride film in question is not formed, silicon (Si) in the second wiring layer is diffused into the tungsten films 54 and 63 in the form of tungsten silicide, thereby increasing the sheet resistance of the film by about 10 times, and also deforming the tungsten silicide. By reducing the volume of silver by about 30%, cracking occurs. However, in the present invention, since the surfaces of the tungsten films 54 and 63 are coated with the tungsten nitride films 55 and 64, respectively, diffusion of silicon (Si) can be prevented. Indeed, the above drawbacks do not occur in the present invention. In addition, since tungsten nitride is a conductor, even if the tungsten nitride film is not removed, the problem of electrical conductivity is not caused.

Furthermore, since the tungsten nitride film exhibits high resistance by oxidation, for example, after the selective CVD process, it is necessary to perform an oxidation treatment in a state where the surface of the tungsten film is exposed to the outside, and the tungsten nitride film is protected by the rest.

In the above embodiment, the tungsten nitride film is formed every time the tungsten film is formed on the substrate, and moreover, the object of the present invention can be achieved by performing two or more consecutive operations for forming the tungsten film and then forming the tungsten nitride film. have. Further, in the above embodiment, the initial operation for forming the tungsten film was performed without forming the tungsten nitride film in advance, but in this case, the tungsten nitride film can be formed before the initial operation for forming the tungsten film on the substrate. Moreover, materials such as reaction tubes and boats need not be limited to quartz, and a metal having a high melting point such as tungsten can be used to form the reaction tube. In this case, the tungsten nitride film is formed by the nitriding treatment or the CVD method as the initial operation preparation for the formation of the tungsten film on the substrate, even when a cold wall CVD apparatus is used.

[Effects of the Invention]

As described above, according to the present invention, it is possible to prevent unwanted lamination of a new metal film on the inner wall of the reaction tube or the like. In addition, it is possible to form a desired high melting point metal thin film on the substrate at high temperature and accurately, for example, metal particles deposited on the inner wall of the reaction tube can prevent further metal film from growing when coated with the metal nitride film. It becomes possible. Therefore, it is possible to substantially prevent the metal film from falling off the inner wall of the reaction tube, thereby forming a high quality thin film free of particulate defects.

Claims (16)

In the thin film formation method of forming a high melting point metal thin film by the CVD method on the surface of the substrate 9 disposed in the CVD reaction tube 1, the CVD reaction tube 1 inner wall and the CVD reaction in the process of performing the CVD operation At least a part of the member arrange | positioned in the tube (1) is apply | coated with the metal nitride film, The thin film formation method characterized by the above-mentioned. The gas containing nitrogen atoms according to claim 1, before forming the high melting point metal thin film to nitride the metal surface existing on at least part of the inner wall of the CVD reaction tube 1 and the members disposed in the CVD reaction tube 1. A thin film formation method, comprising introducing a CVD reaction tube and heating the reaction tube to form a metal nitride film. 3. The process for forming a thin film according to claim 2, wherein in the step before forming the high melting point metal thin film, the high melting point metal particles laminated on at least part of the inner wall of the CVD reaction tube 1 and the members disposed in the CVD reaction tube 1 are thin film forming processes. Thin film formation method, characterized in that to be nitrided in. The thin film formation method according to claim 2, wherein the gas containing nitrogen atoms is ammonia gas. 2. A gas according to claim 1, which differs from a gas containing at least nitrogen atoms to deposit metal nitride on at least a portion of the inner wall of the CVD reaction tube 1 and the members disposed in the CVD reaction tube 1 before forming the high melting point metal film. A method for forming a thin film, characterized in that a gas containing a metal is introduced into a CVD reaction tube (1) for CVD. The method of claim 5, wherein the high-melting-point metal particles deposited on at least a portion of the inner wall of the CVD reaction tube 1 and the members disposed in the CVD reaction tube 1 in the process before forming the high-melting-point metal thin film before the thin film forming process. A thin film forming method, characterized in that to be applied to the metal nitride film. The thin film forming method according to claim 5 or 6, wherein the gas containing nitrogen atoms is ammonia gas, and the gas containing other metal atoms is metal fluoride. The high melting point metal before the thin film forming process according to claim 1, wherein the metal nitride film is left in the CVD reaction tube (1) and at least a part of the members disposed in the inner wall of the CVD reaction tube (1) and the CVD reaction tube (1). A thin film formation method, characterized in that the film is formed continuously on the substrate. The member disposed in the inner wall of the CVD reaction tube 1 and the CVD reaction tube 1 after the metal nitride film is removed from the CVD reaction tube 1 before the metal thin film forming process is performed. Thin film formation method, characterized in that formed on at least a portion. The method of claim 1, wherein the high melting point metal film is selected from the group consisting of a tungsten film and a molybdenum film. The method of claim 1, wherein the metal nitride film is a nitride film of a high melting point metal. The method of claim 1, wherein the CVD reaction tube (1) is a diffusion furnace type CVD reaction tube. The method according to claim 12, wherein the reaction tube (1) is made of quartz. The method according to claim 13, wherein the member provided in the reaction tube (1) is composed of a quartz boat (10) for supporting a substrate, a support for the boat (10), and a heat batch. The method according to any one of claims 1 to 5, wherein the CVD reaction tube (1) is a cold wall CVD reaction tube. The substrate 9 according to any one of claims 1 to 5, wherein the substrate 9 is an electrically conductive substrate on which an insulating pattern is formed, and a high melting point metal film is selectively formed on the conductive surface of the substrate on which the insulating pattern is not applied. Thin film formation method characterized in that the.

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