JP2007150362A - Method of forming film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of plasma treatment capable of significantly suppressing the occurrence of charge-up damage. <P>SOLUTION: A method of plasma treatment generates plasma at an electrode 38 for plasma provided in a treatment vessel 22 which is enabled to be evacuated by supplying predetermined power from a power source for generating plasma, and performs predetermined plasma treatment on a workpiece accommodated in the treatment vessel. The method is configured in such a way that in order to suppress a charge-up voltage generated in a workpiece, when starting the plasma treatment, the power supplied to the electrode for plasma is gradually increased. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a plasma processing method and a film forming method for forming a metal film or the like on a surface of a silicon substrate or the like.

  In general, in order to manufacture a semiconductor integrated circuit, a large number of desired elements are formed by repeatedly performing film formation and pattern etching on a silicon substrate such as a semiconductor wafer. In this case, various heat treatments are performed on the semiconductor wafer. However, in recent manufacturing processes of semiconductor integrated circuits, it is necessary to perform various processes at a low temperature because it is necessary to suppress thermal damage of each element as much as possible. In such a situation, since processing can be performed at a relatively low temperature, processing using plasma has been increasingly adopted.

For example, the wiring connecting each element in the integrated circuit, the lower layer of the wiring layer for making electrical contact with each element, for the purpose of suppressing interdiffusion between the substrate Si and the wiring material, or peeling from the base layer Barrier metal is used for the purpose of preventing corrosion, but as this barrier metal, it is necessary to use a material with excellent corrosion resistance as well as low electrical resistance. In particular, a laminated structure of Ti film / TiN film tends to be frequently used, and plasma CVD processing is performed when the Ti film is formed. That is, a very thin Ti film is formed by plasma CVD, is nitrided, and a TiN film is further formed by thermal CVD. The Ti film is formed by plasma CVD (Chemical Vapor Deposition) using TiCl ₄ (titanium tetrachloride) gas and hydrogen gas as source gases (Patent Document 1).

JP 2001-210713 A

  By the way, when plasma processing such as film formation processing, modification processing, etching processing, etc. is performed on a semiconductor wafer using plasma, the plasma itself is electrically neutral, but due to the action of this plasma, the semiconductor wafer itself In addition, a potential difference, that is, a charge-up voltage is inevitably generated between the semiconductor wafer and the plasma. Such a charge-up voltage is generated immediately after the plasma processing is started, and as a result, the insulating film or the like already formed on the semiconductor wafer is broken down by the charge-up voltage and is subjected to charge-up damage. As a result, there is a problem that the yield of the product is lowered.

In particular, as the wafer size is increased from a diameter of 200 mm to a diameter of 300 mm, and further a thin film thickness and a fine line width are further demanded, an early solution of the above problems is strongly desired.
Further, in connection with the above problem, for example, when a Ti film / TiN film laminated structure is used as the barrier metal, there is a problem that the Ti film is peeled off from the underlayer. That is, recently, when a logic circuit element is mainly manufactured as a semiconductor integrated circuit instead of a DRAM, a NiSi (nickel silicide) film may be used as a contact film because it can operate at high speed. If this NiSi film is not used together with a Ti film or a TiN film, the degree of adhesion is lowered and peeling occurs. Therefore, the Ti film or the TiN film is used together with the NiSi film. For example, when exposed to 600 ° C. or more, the crystal form changes and its resistance increases rapidly. Therefore, it is necessary to always set each process temperature in the subsequent process after forming the NiSi film to 500 ° C. or less. Then, when, for example, a Ti film or a TiN film is formed at a low temperature of 500 ° C. or lower in the subsequent process, the film forming temperature is too low, so that the adhesion of the Ti film or TiN film becomes low. As a result, there arises a problem that the Ti film or TiN film is peeled off from the underlayer as described above.

This point will be described with reference to FIG. In FIG. 7, for example, a case where a TiN film is used as a barrier metal for an element formed on a semiconductor wafer made of a silicon substrate will be described.
First, in FIG. 7A, a semiconductor wafer W as an object to be processed is made of, for example, a silicon substrate, and the entire surface of the semiconductor wafer W made of this silicon substrate is covered with an insulating material made of, for example, SiO _2. Layer 2 is formed. The insulating layer 2 is patterned to form, for example, a hole 4 such as a contact hole, and a silicon portion 6 that is the surface of the silicon substrate is exposed at the bottom of the hole 4. The hole 4 may be a via hole.

  Then, as shown in FIG. 7B, a Ni film 8 is formed on the surface of the wafer W by using, for example, sputtering (Ni film forming step). In this case, the Ni film deposited on the bottom of the hole 4 naturally reacts at the boundary portion with the surface of the silicon portion 6 of the underlying layer, and the NiSi mixed layer 10 made of NiSi is spontaneously formed.

Next, as shown in FIG. 7C, the Ni film 8 is removed while leaving the NiSi mixed layer 10 by etching using, for example, APM (ammonia peroxide) and SPM (sulfuric acid peroxide). (Ni film removing step).
Next, as shown in FIG. 7D, the Ti film 12 is formed on the entire surface of the semiconductor wafer W by performing, for example, plasma CVD as the plasma processing (Ti film forming step). At this time, for example, TiCl ₄ is used as the source gas, and H ₂ gas, Ar gas, or the like is used in addition. In this case, a Ti film is also formed at the bottom of the hole 4, and NiTiSi (titanium-containing nickel silicide) reacts spontaneously at the boundary between the Ti film and the NiSi mixed layer 10 at the bottom of the hole 4. The NiTiSi mixed layer 14 is spontaneously formed.

Next, as shown in FIG. 7E, the TiN film 12A is converted into a TiN film by nitriding the Ti film 12 with plasma using, for example, Ar gas, H ₂ gas, NH ₃ gas, or the like. Is formed (nitriding step).
Next, as shown in FIG. 7F, a TiN film 16 is formed on the entire surface by performing a thermal CVD process using, for example, TiCl ₄ as a source gas and NH ₃ or the like as a reducing gas (see FIG. 7F). TiN film forming step). As a result, a barrier metal made of the TiN films 12A and 16 is formed at the bottom of the hole 4.
Next, as shown in FIG. 7G, for example, by performing a thermal CVD process using WF ₆ and H ₂ or the like, a wiring made of a tungsten film over the entire surface of the wafer W while filling the hole 4. Layer 18 is formed. Thereafter, a predetermined wiring pattern is formed by pattern etching of the wiring layer 18.

In the film formation process as described above, as described above, the NiSi mixed film 10 to be a contact suddenly increases its electrical resistance value when exposed to a high temperature of, for example, 600 ° C. or more, in order to avoid this, The process temperature in all steps from the step shown in FIG. 7B to the step shown in FIG. 7G had to be set to a low temperature of, for example, 500 ° C. or less.
For this reason, the adhesiveness of the TiN film 12A formed at a low temperature of 500 ° C. or lower is lowered, and the TiN film 12A is peeled off from the NiTiSi mixed layer 14 or the insulating layer 2 made of the SiO ₂ film as the underlying layer. There was a problem I took. In this case, it is considered that the reason why the adhesion of the TiN film 12A is lowered is that the TiN film 12A contains a Cl component in TiCl, which is a raw material gas used when depositing the Ti film.

  The present invention has been devised to pay attention to the above problems and to effectively solve them. A first object of the present invention is to provide a plasma processing method capable of greatly suppressing the occurrence of charge-up damage. A second object of the present invention is to provide a film forming method capable of suppressing the occurrence of peeling of a TiN film that is a barrier metal even when film forming is performed at a relatively low temperature.

  According to the first aspect of the present invention, plasma is generated by supplying a predetermined power from a plasma generation power source to a plasma electrode provided in a processing container that can be evacuated, and is stored in the processing container. In a plasma processing method in which a predetermined plasma process is performed on an object to be processed, when the plasma process is started in order to suppress a charge-up voltage generated in the object to be processed, The plasma processing method is characterized in that the power to be supplied is gradually increased.

As described above, when the plasma processing is started, the power supplied to the plasma electrode is gradually increased without supplying large power at a stroke, so that the charge-up voltage is suppressed by reducing the inrush voltage. As a result, it is possible to suppress the occurrence of charge-up damage to the object to be processed.
In this case, for example, as defined in claim 2, the increasing tendency of the electric power supplied to the plasma electrode is set to an increasing tendency such that no charge-up damage occurs to the object to be processed.

Further, for example, as defined in claim 3, the maximum value of the predetermined power is 350 watts, and the power supplied to the plasma electrode at the start of the plasma processing is approximately zero seconds to 350 watts over 5 seconds or more. Increase linearly.
According to a fourth aspect of the present invention, plasma is generated by supplying a predetermined power from a plasma generating power source to a plasma electrode provided in a processing vessel that can be evacuated, and a source gas is provided in the processing vessel. In the plasma processing method in which a predetermined plasma treatment is performed on the object to be processed accommodated in the processing container, the plasma is used to suppress a charge-up voltage generated in the object to be processed. When starting the process, less power than that in the steady process is supplied to the plasma electrode, and the raw material gas having a flow rate lower than that in the steady process is supplied into the processing vessel for a predetermined time. A first process in which only the plasma treatment is performed, and when the power supplied to the plasma electrode is increased to the power in the steady process after the first process is completed. Is a plasma processing method characterized in that it comprises a second step in which to perform the plasma treatment is increased to flow rate at the flow rate constant process of the raw material gas.

Thus, when starting the plasma treatment, in the first step, the plasma electrode is supplied with less power than the power during the steady process, and the source gas is also set to a flow rate less than the flow during the steady process. The plasma treatment is performed for a predetermined time, and then the plasma treatment is performed in the second step by increasing both the power and gas flow rate to the power and flow rate during the steady process. As a result, it is possible to suppress the occurrence of charge-up damage to the object to be processed.
In this case, for example, as defined in claim 5, the power less than the power in the steady process is 2/7 or less of the power in the steady process, and the flow rate less than the flow in the steady process is The flow rate during the steady process is 15/46 or less.

Further, for example, as defined in claim 6, the plasma treatment is a plasma film formation treatment for forming a thin film on the surface of the object to be processed.
For example, as defined in claim 7, the thin film is a metal film.
For example, as defined in claim 8, the metal film is a Ti film.
The invention according to claim 9 is the film forming method for forming a thin film on the surface of the object to be processed which is at least partly or entirely made of a silicon part, wherein the metal film is formed on the entire surface of the object to be processed. Forming a metal silicide layer spontaneously at the boundary portion between the surface of the silicon portion and the metal film, and removing the metal film by etching while leaving the metal silicide layer A film removing step, a Ti film forming step of forming a Ti film on the entire surface and spontaneously forming a titanium-containing metal silicide mixed layer at a boundary portion between the metal silicide layer and the Ti film, and the titanium-containing metal A Ti film removing step for etching and removing the Ti film so as to leave a silicide mixed layer; a TiN film forming step for forming a TiN film over the entire surface; and a wiring layer over the entire surface. A film forming method and having a wiring layer formation step.

  Thus, for example, when the barrier metal is formed, the Ti film containing Cl element is removed by etching, so that the Ti film containing Cl element does not intervene in the barrier metal, and as a result, peeling of the film occurs. It is possible to greatly suppress this.

In this case, for example, as defined in claim 10, a plasma nitriding step of nitriding a metal film is performed between the Ti film removing step and the TiN film forming step.
Further, for example, as defined in claim 11, the surface of the object to be processed immediately before performing the metal film forming step is an insulating layer in which a hole pattern is formed so that the surface of the silicon portion is exposed at the bottom. Covered.
For example, as defined in claim 12, the process temperature of each step after the metal film forming step is set to 500 ° C. or lower.
For example, as defined in claim 13, the metal film is a Ni (nickel) film, and the metal silicide layer is a NiSi (nickel silicide) mixed layer.
For example, as defined in claim 14, when performing the Ti film forming step, the plasma processing method according to any one of claims 1 to 8 is used.

According to the plasma processing method and the film forming method of the present invention, the following excellent operational effects can be exhibited.
According to the invention defined in claims 1 to 3, when starting the plasma processing, the power supplied to the plasma electrode is gradually increased without supplying a large power at a stretch. As a result, the charge-up voltage is suppressed, and as a result, the occurrence of charge-up damage to the object to be processed can be suppressed.
According to the invention defined in claims 4 to 8, when starting the plasma processing, in the first step, the plasma electrode is supplied with less power than the power in the steady process, and the source gas is also in the steady process. Since the plasma processing is performed for a predetermined time by setting the flow rate to be lower than the flow rate, and then the plasma processing is performed in the second step by increasing both the power and gas flow rates to the power and flow rate during the steady process. As the inrush voltage decreases, the charge-up voltage is suppressed. As a result, the occurrence of charge-up damage on the object to be processed can be suppressed.
According to the invention defined in claims 9 to 12, for example, when the barrier metal is formed, the Ti film containing Cl element is removed by etching, so that the Ti film containing Cl element does not intervene in the barrier metal. As a result, it is possible to greatly suppress the occurrence of film peeling.

Hereinafter, an embodiment of a plasma processing method and a film forming method according to the present invention will be described in detail with reference to the accompanying drawings.
<First embodiment>
First, the first invention will be described.
FIG. 1 is a block diagram showing an example of a plasma processing apparatus for carrying out the method of the present invention, FIG. 2 is a graph for explaining the relationship between electric power supplied to a plasma electrode and a charge-up voltage, and FIG. 3 is a graph on a semiconductor wafer. It is a figure which shows distribution of specific resistance. As shown in the figure, the plasma processing apparatus 20 includes a processing container 22 formed in a cylindrical shape by, for example, stainless steel, and the processing container 22 is grounded.
An exhaust port 26 for exhausting the atmosphere in the container is provided at the bottom 24 of the processing container 22, and an exhaust system 30 having a vacuum pump 28 is connected to the exhaust port 26. The inside of the processing container 22 can be evacuated uniformly from the bottom periphery.

  In the processing container 22, a disk-shaped mounting table 34 is provided via a support column 32 made of a conductive material, and a silicon substrate W, for example, can be mounted thereon as an object to be processed. ing. Specifically, the mounting table 34 is made of ceramic such as AlN, and the surface thereof is coated with a conductive material. The mounting table 34 also serves as a lower electrode which is one of plasma electrodes, and is directly attached to the support column 32. It consists of a lower base 34A to be supported and an upper base 34B joined to this upper surface, and a resistance heater 36 is sandwiched between these joint surfaces. The lower base 34A and the upper base 34B are joined by, for example, welding at the joint surface.

  A ceiling plate 40 integrally provided with a shower head 38 which is also used as an upper electrode which is the other of the plasma electrodes is attached to the ceiling portion of the processing vessel 22 in an airtight manner with respect to the side wall of the vessel via an insulating material 42. It has been. The shower head 38 is provided so as to face almost the entire upper surface of the mounting table 34, and a processing space S is formed between the shower head 38 and the mounting table 34. The shower head 38 introduces various gases into the processing space S in a shower shape, and a plurality of injection holes 46 for injecting gas are formed on the injection surface 44 on the lower surface of the shower head 38.

A gas introduction port 48 for introducing gas into the head is provided above the shower head 38, and a supply passage 50 through which gas flows is connected to the gas introduction port 48.
A plurality of branch pipes 52 are connected to the supply passage 50, and each branch pipe 52 has, for example, a TiCl ₄ gas source that stores TiCl ₄ gas as a gas that also serves as a film forming source gas and an etching gas. 54, _{H 2 H 2} gas source 56 that stores the gas, Ar gas source 58 that stores, for example, Ar gas as the plasma gas, NH ₃ gas source 60 and the _{N 2} gas source 62 storing the ammonia are connected. The flow rate of each gas is controlled by a flow rate controller provided in each branch pipe, for example, the mass flow controller 63. Each branch pipe 52 is provided with an on-off valve 64 for supplying and stopping the supply of each gas as necessary. Here, the case where each gas is supplied in a mixed state in one supply passage 50 is shown, but the present invention is not limited to this, and a part or all of the gas is supplied individually into different passages. In addition, a gas transport mode in which the gas is mixed in the shower head 38 or in the processing space S (so-called postmix) may be used.

  The ceiling plate 40 is connected to a matching circuit 68 and a high-frequency power source 70 which is a power source for generating plasma of 450 kHz, for example, via lead wires 66 in order to form plasma when forming the Ti film. Here, in this high frequency power supply 70, the output power is made variable so that power of an arbitrary magnitude can be output. The lead wire 66 is provided with an open / close switch 72 that cuts off the supply of high-frequency power as necessary. A gate valve 74 that can be opened and closed in an airtight manner when the substrate W is loaded and unloaded is provided on the side wall of the processing container 22.

Next, the plasma processing method of the present invention performed using the apparatus configured as described above will be described.
Here, a case where a Ti film is formed as an example of the plasma processing method will be described as an example. The feature of the first invention resides in that, in order to suppress the charge-up voltage, the power supplied to the electrode is gradually increased to increase to the power during the steady process over a certain period of time.
First, at the time of forming the Ti film, the silicon substrate W is introduced into the processing container 22 through the opened gate valve 74, and this is placed on the mounting table 34 to seal the inside of the processing container 22. On the surface of the silicon substrate W, for example, a contact hole for making contact with a transistor on the substrate has already been formed in the previous step.

If the inside of the processing vessel 22 is sealed, the raw material gas TiCl ₄ gas, the reducing gas H ₂ gas, and the plasma gas Ar gas are respectively supplied from the shower head 38 as the upper electrode at a predetermined flow rate. The inside of the processing vessel 22 is evacuated by a vacuum pump 28 and maintained at a predetermined pressure.
At the same time, a high frequency of 450 kHz is applied from the high frequency power source 70 to the shower head 38 as the upper electrode, and a high frequency electric field is applied between the shower head 38 and the mounting table 34 as the lower electrode to supply power. As a result, the Ar gas is turned into plasma, and the reduction reaction between the TiCl ₄ gas and the H ₂ gas is promoted, and a Ti film is formed on the substrate surface. The temperature of the substrate W is maintained at a predetermined temperature by a resistance heater 36 embedded in the mounting table 34.

The important point here is that the electric power supplied between the upper and lower electrodes 38 and 34 does not increase from zero watts to the process electric power (electric power in a steady process) at once, but suppresses the charge-up electric power generated by the wafer W. Therefore, the supply power is gradually increased over a certain period of time to increase the power to the steady process.
The conditions of the steady process here are, for example, when processing an 8-inch substrate, the temperature of the substrate W is, for example, about 350 to 500 ° C., and the process pressure is about 665 Pa (≈5 Torr). Regarding the gas flow rate, TiCl ₄ gas is about 4.6 sccm, H ₂ gas is about 1500 sccm, and Ar gas is about 300 sccm. The entire film formation time is about 60 seconds, and the thickness of the Ti film is about 200 mm.

The power supplied from the plasma generating power supply 70 is, for example, 350 watts during the steady process, and gradually increases from zero watts to, for example, about 5 to 10 seconds, up to 350 watts, which is the maximum power during the steady process. For example, it is increased linearly.
In this way, by gradually increasing the supply power to the power during the steady process over a short time immediately after the start of the plasma treatment, for example, about 5 to 10 seconds, the inrush voltage is suppressed to a low level. The charge-up voltage generated on the wafer W during the period can be suppressed as much as possible, and therefore the occurrence of charge-up damage can be suppressed.

  As described above, even if about 5 to 10 seconds have elapsed, even if the power in the steady process is supplied, that is, the full power is applied, the wafer W is already on the wafer W for a short period of 5 to 10 seconds. Since the Ti film, which is a conductive film, is deposited with a very small thickness, the flow of charge is generated by this extremely thin conductive Ti film, so that almost no charge-up voltage is generated. In addition, the in-plane uniformity of the plasma treatment such as the film thickness can be maintained high.

  Here, the point that the charge-up voltage is lowered in the method of the present invention will be described with reference to FIG. FIG. 2A is a graph showing changes in power supplied to the plasma electrode, and FIG. 2B is a graph showing changes in charge-up voltage Vdc on the semiconductor wafer at that time. In FIG. 2, the supply of electric power to the shower head 38, which is the upper electrode, starts at the point P1, and the plasma processing is started. The characteristic X1 is supplying full power, for example, 350 watts at the same time as the start of the plasma processing, which shows the case of the conventional method. In FIG. 2A, the magnitude of the high-frequency power on the vertical axis is indicated by a scale. For example, the scale 1.7 corresponds to 350 watts.

  On the other hand, the characteristics Y1 and Y2 show the case of the method of the present invention, and the characteristic Y1 is gradually increased linearly over 5 seconds from zero watt to full power (power during steady process). The characteristic Y2 shows a case where the power is gradually increased linearly over 10 seconds from zero watts to full power. The charge-up voltage Vdc at this time is shown in FIG. 2B, and the maximum charge-up voltage reaches -81 volts in the characteristic X1 of the conventional method. On the other hand, in the case of the method of the present invention, the maximum charge-up voltage Vdc is about -64 volts in the characteristic Y1 applied to the full power for 5 seconds, and the maximum charge-up voltage in the characteristic Y2 applied to the full power for 10 seconds. Is about -62 volts, both of which can significantly suppress the maximum charge-up voltage. In this case, the longer the time to increase from zero watts to full power, the smaller the maximum value of the generated charge-up voltage can be made. As a result, in the case of the method of the present invention, it was confirmed that the generation amount of charge-up damage can be greatly suppressed.

Here, if the period during which the power supplied to the showerhead 38 increases from zero watts to full power is set to be smaller than 5 seconds, the effect of suppressing the charge-up voltage cannot be exhibited so much. If the period of increase from zero watts to full power is excessively long, not only will the process period become longer, but also the in-plane uniformity of the film thickness will be reduced, so the maximum value is, for example, about 30 seconds. .
Here, the characteristics Y1 and Y2 are linearly changed. However, the supplied power may be increased so that they have an arc shape that protrudes upward or protrudes downward, or The supply power may be increased stepwise instead of in a straight line. Anyway, any increase in supply power is possible as long as the charge-up voltage generated in the semiconductor wafer W is not excessively increased. An aspect may be sufficient.

Further, here, the case where the supply power in the steady process is 350 watts is described, but when this is, for example, about 200 watts, the voltage is too low, so no charge-up damage occurs even if the method of the present invention is not adopted. . In practice, the magnitude of the charge-up voltage also varies depending on process conditions such as process pressure and gas type, and therefore it is desirable to set a power increase period from zero watts to steady process power for each process.
Here, since the electric power supplied to the shower head 38 is changed during the process, the in-plane uniformity of the Ti film may be lowered. Therefore, the film thickness was examined.

  The result is shown in FIG. Although specific resistance is shown in FIG. 3, the specific resistance reflects the state of the film thickness by 1: 1, so that the film thickness can be known by examining the specific resistance. As shown in the figure, in the case of the conventional method, the deviation of the film thickness was 1.4%, whereas in the case of the method of the present invention, the deviation of the film thickness was 1.6%. As in the case of the conventional method, it was confirmed that a sufficiently high in-plane uniformity can be obtained.

<Modification>
Next, a modification of the first invention will be described.
In the previous embodiment, the power supplied to the plasma electrode was gradually increased from zero watts to the power in the steady process, but this is not a limitation, and the power supply is increased in at least two stages. You may make it make it.
Here, a case where power is increased in two stages from zero watts to power in a steady process will be described as an example.
That is, in this modified example, when starting the plasma processing in order to suppress a charge-up voltage generated in the object to be processed, less power than that in a steady process is supplied to the plasma electrode and the processing is performed. A first process in which the raw material gas having a flow rate smaller than that in a steady process is supplied into the container to perform plasma treatment for a predetermined time, and after the completion of the first process, the plasma electrode is supplied to the plasma electrode. This is a second step in which the plasma processing is performed by increasing the supply power to the power during the steady process and increasing the flow rate of the source gas to the flow during the steady process.

That is, since the power in the steady process is 350 watts here, in the first step, less power, for example, 100 watts is supplied to the plasma electrode (shower head) at the same time, and at the same time, the source gas, that is, TiCl ₄ gas is supplied. The flow rate during the steady process, for example, a flow rate smaller than 4.6 sccm, for example, 1.5 sccm is set, and the plasma film forming process is performed for a short predetermined time, for example, about 10 seconds. During this period, the other gas types are supplied with the same flow rate as in the steady process.

Next, in the second step, the supply power to the plasma electrode is increased to the power during the steady process, and the flow rate of the source gas is also increased to the flow rate during the steady process. In this case, when the power supplied to the plasma electrode is increased in the second step, it may be increased to the power at the time of the steady process, or instead, linearly in a certain short time, or You may increase in steps.
Here, the flow of this modification will be described with reference to the flowchart shown in FIG.

First, TiCl ₄ gas which is a raw material gas is supplied into the processing container 22 together with H ₂ gas and Ar gas (S1). At this time, as described above, this source gas is supplied at a flow rate lower than 4.6 sccm, for example, 1.5 sccm, for example, during a steady process. At the same time, plasma power is supplied between the shower head 38, which is a plasma electrode, and the mounting table 34, and plasma is generated to perform plasma processing, that is, plasma film formation processing (plasma CVD). A film is deposited (S2). At this time, as described above, the power to be supplied is set to a power lower than 350 watts, for example, 100 watts, for example, during a steady process. That is, this 100-watt power is supplied to the plasma electrode at once. Then, the first step is continuously performed for a predetermined time, for example, about 10 seconds (S3).

In this way, when the first step is completed, the process proceeds to the second step. That is, here, the flow rate of the source gas is increased to increase the flow rate during the steady process, for example, 4.6 sccm. At the same time, the supply amount of plasma power is also increased and set to a power during a steady process, for example, 350 watts (S4).
Here, when the plasma supply power is increased to the power during the steady process, it may be increased at once, or may be increased linearly or stepwise over a short period of time, for example, several seconds. May be. If the film forming process is performed for a predetermined time in such a state, the second process is ended (S5), and the entire process is ended. Also in this modification, the same effect as the previous embodiment can be exhibited, that is, the occurrence of charge-up damage can be suppressed while maintaining high in-plane uniformity of plasma processing such as film thickness. .

  Here, since the power supplied to the shower head 38 and the flow rate of the raw material gas are changed during the process, the in-plane uniformity of the Ti film may be lowered. Therefore, the film thickness was examined. The result is shown in FIG. Although specific resistance is shown in FIG. 5, the specific resistance reflects the state of the film thickness by 1: 1, so that the film thickness can be known by examining the specific resistance. In this figure, as a comparative example, the supply power for plasma is changed in two stages, but the data when the flow rate of the steady process is flowed from the beginning without decreasing the supply amount of the source gas is also shown. Show.

  As shown in the figure, the deviation in film thickness was 1.4% in the case of the conventional method, whereas the deviation in film thickness was 4.1% in the case of the modification of the method of the present invention. However, although it increased to some extent compared with the conventional method, it was within the allowable range, and it was confirmed that in-plane uniformity with a high film thickness could be obtained. On the other hand, in the case of the comparative example, the deviation of the film thickness reached 15.7%, and good characteristics could not be obtained. Thus, in order to obtain in-plane uniformity with a good film thickness, it is possible to confirm that it is necessary to reduce not only the plasma supply power but also the supply amount of the source gas in the first step. did it.

In the plasma processing apparatus 20, the case where a high frequency voltage for plasma is applied to the shower head 38 which is the upper electrode has been described as an example. However, the present invention is not limited to this, and the high frequency for plasma is provided on the mounting table 34 side which is the lower electrode. The method of the present invention can also be applied to a device for applying a voltage or a device for applying a high-frequency voltage to both upper and lower electrodes. The method of the present invention can also be applied to a plasma processing apparatus using a magnetic field or an electric field in combination.
Furthermore, although the case where the Ti film is formed by plasma CVD has been described as an example here, not only the case where another metal film or insulating film is formed, but also plasma modification treatment (for example, nitriding treatment), plasma The method of the present invention can also be applied to other plasma processing such as etching processing.

<Second invention>
Next, the second invention will be described.
In the second invention, for example, when various films are deposited on the surface of the semiconductor wafer W made of a silicon substrate, the method of the first invention described above when forming a part of the film is used. In addition to the occurrence of peeling, the occurrence of charge-up damage is suppressed. FIG. 6 is a flowchart showing an example of a film forming method when a TiN film is used as the barrier metal.
Here, a case where a NiSi film is used as a contact and a TiN film is used as a barrier metal in an element formed on a semiconductor wafer made of a silicon substrate will be described as an example. Part of the film formation process here is exactly the same as the steps shown in FIGS. 7A to 7D described above. That is, first, in FIG. 6A, a semiconductor wafer W as an object to be processed is made of, for example, a silicon substrate, and the entire surface of the semiconductor wafer W made of this silicon substrate is made of, for example, SiO ₂ so as to cover it. An insulating layer 2 is formed. The insulating layer 2 is patterned to form, for example, a hole 4 such as a contact hole, and a silicon portion 6 that is the surface of the silicon substrate is exposed at the bottom of the hole 4. The hole 4 may be a via hole.

  Then, as shown in FIG. 6B, for example, a Ni film 8 is formed as a metal film on the surface of the wafer W by using, for example, sputtering (Ni film forming process: metal film forming process). In this case, the Ni film deposited on the bottom of the hole 4 reacts spontaneously at the boundary portion with the surface of the silicon portion 6 of the underlayer, and a NiSi mixed layer (metal silicide layer) 10 made of, for example, NiSi as a metal silicide. Is formed spontaneously. Here, when the temperature of the NiSi mixed layer 10 is higher than, for example, 600 ° C., the crystal structure is changed, and the electric resistance is rapidly increased to increase the contact resistance. Therefore, in all the steps after the step shown in FIG. 6B (FIGS. 6C to 6G), the NiSi mixed layer 10 is prevented from being exposed to a temperature higher than 600 ° C. In order to achieve this, each process temperature is set to 600 ° C. or lower and each process is performed.

Next, as shown in FIG. 6C, the Ni film 8 is removed leaving the NiSi mixed layer 10 by etching using, for example, APM and SPM (Ni film removal step).
Next, as shown in FIG. 6D, the Ti film 12 is formed on the entire surface of the semiconductor wafer W by performing, for example, plasma CVD as the plasma processing (Ti film forming step). At this time, for example, TiCl ₄ is used as the source gas, and H ₂ gas, Ar gas, or the like is used in addition. In this case, a Ti film is also formed at the bottom of the hole 4, and a NiTiSi mixed layer made of NiTiSi reacts spontaneously at the boundary between the Ti film and the NiSi mixed layer 10 at the bottom of the hole 4 ( Titanium-containing metal silicide mixed layer) 14 is spontaneously formed. And when performing this Ti film-forming process, it uses the method of 1st invention demonstrated previously using the plasma processing apparatus 2 as shown in FIG. 1 demonstrated previously. Thereby, it is possible to greatly suppress the occurrence of charge-up damage during the plasma film formation.

Next, as shown in FIG. 6E, the Ti film is removed by etching without using plasma in the same plasma processing apparatus 2 (Ti film removing step). In this case, the NiTiSi mixed layer 14 remains without being removed because of the etching selectivity.
In this etching process, plasma is not used by opening the open / close switch 72 of the plasma processing apparatus 2 and cutting off the supply of the high-frequency power source 70, and only TiCl ₄ gas is supplied into the processing chamber 22 as an etching gas. The process conditions at this time are, for example, that the temperature of the wafer W is in the range of 350 to 500 ° C., the process pressure is about 665 Pa (≈5 Torr), and the flow rate of the TiCl ₄ gas is about 30 sccm at the maximum. As a result, as described above, the Ti film 12 excluding the NiTiSi mixed layer 14 that has reacted with the underlying layer can be removed by etching.

Next, as shown in FIG. 6F, a TiN film 16 is formed on the entire surface by performing a thermal CVD process using, for example, TiCl ₄ as a raw material gas and NH ₃ or the like as a reducing gas (see FIG. 6F). TiN film forming step). Also in this case, the film forming process is continuously performed in the plasma processing apparatus 20 without using plasma. As a result, a barrier metal made of the TiN film 16 is formed at the bottom of the hole 4.
Next, as shown in FIG. 6G, for example, by performing a thermal CVD process using WF ₆ and H ₂ or the like, a wiring made of a tungsten film is formed on the entire surface of the wafer W while filling the hole 4. Layer 18 is formed. The wiring layer 18 may be formed of other metal such as Al. Thereafter, a predetermined wiring pattern is formed by pattern etching of the wiring layer 18.
Thus, the Cl-containing TiN film 12A (see FIG. 7E) formed in the case of the conventional method does not need to be formed in the method of the present invention. As a result, the treatment is performed at a low temperature of, for example, 500 ° C. or lower. Even if the process is performed, the film does not peel off or corrode, and a contact with good electrical characteristics can be obtained.

Moreover, in the said Example, although it shifted to the TiN film | membrane formation process shown in FIG.6 (F) immediately after the Ti film | membrane removal process shown in FIG.6 (E), it is not limited to this, In said FIG.6 (E), Since the Ti film cannot be completely etched in the Ti film removal step shown, and it is predicted that the Ti film remains slightly, after this Ti film removal step, the metal film that may remain, that is, the residual Ti film is nitrided A plasma nitriding treatment may be performed to increase the adhesion by processing. As described above, this plasma nitriding treatment may be performed using plasma in the plasma processing apparatus 2 and using the first invention method of the present invention described above.
In each of the above embodiments, the NiSi film is used as the contact. However, the present invention is not limited to this. For example, a metal silicide film such as a CoSi film or a PtSi film can be used. It should be noted that the process conditions described in the above embodiments are merely examples, and of course are not limited thereto.
Here, the silicon substrate is used as the object to be processed. However, the present invention is not limited to this, and it is needless to say that the method of the present invention can be applied to an LCD substrate or a glass substrate on which a silicon layer or the like is formed.

It is a block diagram which shows an example of the plasma processing apparatus which enforces the method of this invention. It is a graph for demonstrating the relationship between the electric power supplied to the electrode for plasma, and a charge up voltage. It is a figure which shows distribution of the specific resistance on a semiconductor wafer. It is a figure which shows the flowchart of this invention method. It is a figure which shows distribution of the specific resistance on a semiconductor wafer. It is a flowchart which shows an example of the film-forming method when using a TiN film | membrane as a barrier metal. It is a flowchart in the case of using a TiN film as a barrier metal for an element formed on a semiconductor wafer made of a silicon substrate.

Explanation of symbols

2 Insulating layer 4 Hole 6 Silicon part 8 Ni film 10 NiSi mixed layer 12 Ti film 12A TiN film 14 NiTiSi mixed layer 16 TiN film 18 Wiring layer 20 Plasma processing apparatus 22 Processing vessel 34 Mounting table (electrode for plasma)
38 Shower head (Plasma electrode)
70 High-frequency power supply (power supply for plasma generation)
W Semiconductor wafer (object to be processed)

Claims (14)

A plasma is generated by supplying a predetermined power from a plasma generation power source to a plasma electrode provided in a processing chamber that can be evacuated, and a predetermined amount is applied to a target object accommodated in the processing chamber. In the plasma processing method in which plasma processing is performed,
A plasma processing method, wherein power supplied to the plasma electrode is gradually increased when the plasma processing is started in order to suppress a charge-up voltage generated in the object to be processed. The plasma processing method according to claim 1, wherein an increasing tendency of electric power supplied to the plasma electrode is set to an increasing tendency so as not to cause charge-up damage to the object to be processed. The maximum value of the predetermined power is 350 watts, and the power supplied to the plasma electrode at the start of the plasma processing is increased substantially linearly from zero watts to 350 watts over 5 seconds. Item 3. The plasma processing method according to Item 1 or 2. A plasma is generated by supplying a predetermined power from a plasma generating power source to a plasma electrode provided in a processing vessel that can be evacuated, and a raw material gas is supplied into the processing vessel. In a plasma processing method in which a predetermined plasma processing is performed on an object to be processed contained in
In order to suppress a charge-up voltage generated in the object to be processed, when starting the plasma processing, less power than that in a steady process is supplied to the plasma electrode, and the processing container is supplied with power during the steady process. A first step of performing plasma treatment for a predetermined time by supplying the raw material gas at a flow rate lower than the flow rate of
After the first step, the plasma process is performed by increasing the power supplied to the plasma electrode to the power for the steady process and increasing the flow rate of the source gas to the flow rate for the steady process. When,
A plasma processing method comprising: The power less than the power in the steady process is 2/7 or less of the power in the steady process, and the flow rate less than the flow in the steady process has a flow rate of 15/46 or less in the steady process. The plasma processing method according to claim 4. The plasma processing method according to claim 1, wherein the plasma processing is a plasma film forming processing for forming a thin film on a surface of the object to be processed. The plasma processing method according to claim 6, wherein the thin film is a metal film. The plasma processing method according to claim 7, wherein the metal film is a Ti film. In a film forming method for forming a thin film on the surface of an object to be processed at least partially or entirely made of a silicon part,
Forming a metal film on the entire surface of the object to be processed, and forming a metal silicide layer spontaneously at a boundary portion between the surface of the silicon portion and the metal film; and
A metal film removing step of etching and removing the metal film leaving the metal silicide layer;
A Ti film forming step of forming a Ti film on the entire surface and spontaneously forming a titanium-containing metal silicide mixed layer at a boundary portion between the metal silicide layer and the Ti film;
A Ti film removing step of etching and removing the Ti film so as to leave the titanium-containing metal silicide mixed layer;
A TiN film forming step of forming a TiN film on the entire surface;
A wiring layer forming step for forming a wiring layer on the entire surface;
A film forming method comprising: The film forming method according to claim 9, wherein a plasma nitriding step of nitriding a metal film is performed between the Ti film removing step and the TiN film forming step. The surface of the object to be processed immediately before performing the metal film forming step is covered with an insulating layer in which a hole pattern is formed so that the surface of the silicon portion is exposed at the bottom. The film forming method according to 9 or 10. The film forming method according to claim 9, wherein a process temperature in each step after the metal film forming step is set to 500 ° C. or less. The film forming method according to claim 9, wherein the metal film is a Ni (nickel) film, and the metal silicide layer is a NiSi (nickel silicide) mixed layer. The film forming method according to any one of claims 9 to 13, wherein the plasma processing method according to any one of claims 1 to 8 is used when performing the Ti film forming step.

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