TWI747931B - Method for forming film - Google Patents

Abstract

The present invention relates to a method and device for forming a film. The object is to provide a method for forming a film in a groove and the like by embedding the film in the groove and the like without forming a gap. The method for forming a film according to an embodiment of the present invention includes the following processes: generating plasma of film-forming gas containing silicon on a surface of a substrate having a groove or hole at a bottom and a side wall, so as to form a first semiconductor film containing silicon on the bottom and the side wall. The first semiconductor film formed on the side wall is selectively removed by generating plasma of etching gas containing halogen on the surface of the substrate. Through generating a first plasma on the surface of the substrate, a second semiconductor film is formed on the bottom and the side wall.

Description

Film forming method

The present invention relates to a film forming method and a film forming device.

With the progress of the miniaturization process in recent years, there is a demand for embedding with an insulating film without voids in trenches or holes (hereinafter, trenches, etc.) with a high aspect ratio used in the element isolation region. At this time, a void may be formed in the film formed in the trench or the like. Under such a situation, there is a technique of temporarily opening the voids formed in the film by etching and burying the film again in the opened voids (for example, refer to Patent Document 1).

Prior art literature

Patent literature

Patent Document 1: Japanese Patent Application Publication No. 2012-134288

However, in the technique of temporarily opening the formed void and burying the film in the opened void, the film forming process becomes complicated. Therefore, a technique of burying a film in a trench or the like without forming a void is required.

In view of the above-mentioned circumstances, an object of the present invention is to provide a film forming method and a film forming apparatus for embedding a film in a trench or the like without forming a gap in a film formed in a trench or the like.

In order to achieve the above-mentioned object, a film forming method according to an aspect of the present invention includes the following steps: a first plasma containing a film forming gas containing silicon is generated on the surface of a substrate provided with trenches or holes having a bottom and sidewalls, thereby The bottom and the sidewalls form a first semiconductor film containing silicon.

The first semiconductor film formed on the side wall is selectively removed by generating a second plasma of an etching gas containing halogen on the surface of the substrate.

By generating the first plasma on the surface of the substrate, a second semiconductor film containing silicon is formed on the bottom and the sidewalls.

Thus, for the semiconductor film formed in the trench or the like, the film is formed in the trench or the like without forming a void.

In the above-mentioned film forming method, the process of selectively removing the first semiconductor film formed on the sidewall and forming the second semiconductor film on the bottom and the sidewall may be repeated twice or more.

As a result, the semiconductor film is reliably formed in the trench or the like.

In the above-mentioned film forming method, the time for generating the above-mentioned first plasma may be within 5 minutes.

As a result, trenches and the like are not blocked by the semiconductor film.

In the above-mentioned film forming method, the time for generating the above-mentioned second plasma may be within 5 minutes.

As a result, the semiconductor film formed on the sidewall of the trench or the like is selectively removed.

In the above-mentioned film forming method, the above-mentioned etching gas may contain at least one of _{NF 3} , NCl ₃ , Cl ₂ and H _2.

As a result, the semiconductor film formed on the sidewall of the trench or the like is chemically removed by any one of _{NF 3} , NCl ₃ , Cl _2, and H _2.

In the above-mentioned film forming method, as the first semiconductor film and the second semiconductor film, a film containing silicon and at least one of phosphorus, arsenic, antimony, boron, aluminum, gallium, indium, and germanium is formed as a dopant. At least any one of the silicon film of the miscellaneous agent.

Thereby, the first semiconductor film and the second semiconductor film formed in the trench etc. become a film containing silicon and containing at least one of phosphorus, arsenic, antimony, boron, aluminum, gallium, indium, and germanium as a dopant At least any one of the silicon films of the agent.

In the above-mentioned film forming method, the interface between the first semiconductor film and the second semiconductor film contains a halogen, and the halogen is a halogen contained in the etching gas.

Thus, the interface between the first semiconductor film and the second semiconductor film formed in a trench or the like contains halogen, and the halogen is a halogen contained in the etching gas.

In addition, a film forming apparatus according to an aspect of the present invention includes a vacuum chamber, a support table, a plasma generation source, and a control unit.

The above-mentioned vacuum chamber can be configured to maintain a reduced pressure state.

The above-mentioned support table can place a substrate. Grooves or holes are provided on the substrate. The trenches or holes each have a bottom and sidewalls.

The plasma generating source may generate a first plasma of a film forming gas including silicon introduced into the vacuum chamber to form a semiconductor film including silicon on the bottom and sidewalls. In addition, the plasma generation source may selectively remove the semiconductor film formed on the side wall by generating a second plasma of the halogen-containing etching gas introduced into the vacuum chamber.

The control unit may switch the generation of the first plasma and the generation of the second plasma.

Thus, for the semiconductor film formed in the trench or the like, the film is formed in the trench or the like without forming a void.

In the above-mentioned film forming apparatus, the above-mentioned plasma generation source may be constituted by an inductively coupled plasma generation source.

As a result, semiconductor films with different film qualities are formed on the bottom and sidewalls of trenches, etc., respectively.

The above-mentioned film forming apparatus may further include a first gas supply source and a second gas supply source. The first gas supply source may supply the film forming gas into the vacuum chamber, and may have a first supply port through which the film forming gas is ejected. The second gas supply source may supply the etching gas into the vacuum chamber, and may have a second supply port through which the etching gas is ejected. The position of the second supply port may be different from the position of the first supply port.

As a result, the thickness of the semiconductor film is uniformly formed in the substrate.

According to the present invention, for a film formed in a trench or the like, the film can be buried in the trench or the like without forming a void.

1: substrate

1a: Silicon substrate

1b: Silicon oxide film

1u: upper surface

5: groove

5c: corner

5b: bottom

5w: side wall

10: Vacuum tank

10p: Plasma formation space

11: bottom

12: Cylindrical wall

13: cover

20: Support table

21: Capacity

30: Plasma generation source

31: High frequency coil

32: High frequency power supply

33: Integrated circuit

40, 45: gas supply source

41, 46: nozzle

41h, 46h: supply port

42, 47: gas inlet pipe

43, 48: Flowmeter

50: Control Department

70, 70a, 70b: semiconductor film

71a, 71b, 71c, 71d, 71e, 72a, 72b, 73a, 73b: film

100: Film forming device

S10: Step S10

S20: Step S20

S30: Step S30

α: length

β: length

FIG. 1 is a schematic configuration diagram of a film forming apparatus applied to the film forming method of this embodiment.

Fig. 2 is a schematic flow chart of the film forming method of the present embodiment.

FIGS. A and B of FIG. 3 are schematic cross-sectional views showing the film forming method of the present embodiment.

FIGS. A and B of FIG. 4 are schematic cross-sectional views showing the film forming method of this embodiment.

FIGS. A and B of FIG. 5 are schematic cross-sectional views showing the film forming method of this embodiment.

Fig. 6A is a schematic graph showing the relationship between the etching time and the film thickness when shifting to the etching process using hydrogen plasma without performing dry cleaning after the film forming process. Fig. B is a schematic graph showing the relationship between the etching time and the film thickness when the film forming process is dry-washed and then transferred to the etching process using hydrogen plasma.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, XYZ axis coordinates may be imported.

[Film Forming Device]

FIG. 1 is a schematic configuration diagram of a film forming apparatus applied to the film forming method of this embodiment.

The film forming apparatus 100 shown in FIG. 1 includes a vacuum chamber 10, a support table 20, a plasma generation source 30, gas supply sources 40 and 45, and a control unit 50. The film forming apparatus 100 has both a film forming unit that forms a film (for example, a semiconductor film) on the substrate 1 by a plasma CVD (Chemical Vapor Deposition) method, and an etching unit that removes the film formed on the substrate 1 by dry etching. As the plasma generation source 30, an inductively coupled plasma source is shown as an example. The plasma source of this embodiment is not limited to an inductively coupled plasma source.

The vacuum chamber 10 is a container capable of maintaining a reduced pressure state. The vacuum tank 10 has a bottom 11, a cylindrical wall 12 and a cover plate (cover) 13. To the vacuum tank 10, a vacuum pump (not shown) such as a turbo molecular pump is connected, for example. The atmosphere in the vacuum chamber 10 is maintained at a predetermined pressure by the vacuum pump. The bottom 11 surrounds the support table 20, for example. The cylindrical wall 12 is provided on the bottom 11 and surrounds the nozzles 41 and 46, for example. The cover plate 13 is provided on the cylindrical wall 12 opposite to the support table 20. The bottom part 11 and the cover plate 13 have, for example, a structure including a conductor. The cylindrical wall 12 has a transparent insulating material such as quartz. In addition, the vacuum chamber 10 is provided with a pressure gauge (not shown) that measures the pressure in the vacuum chamber 10.

Inside the vacuum chamber 10, a support table 20 that supports the substrate 1 is provided. The substrate 1 is, for example, any of a semiconductor substrate, an insulating substrate, a metal substrate, and the like. The semiconductor substrate is a silicon wafer, a silicon wafer with an insulating film formed on the surface, or the like. The insulating film is, for example, silicon oxide, silicon nitride, aluminum oxide, or the like. The wafer diameter is, for example, 150 mm or more and 300 mm or less, for example, set to 300 mm. However, the wafer diameter is not limited to this example. In addition, the insulating substrate is a glass substrate, a quartz substrate, or the like.

The support stand 20 has a structure including a conductor, for example. In the support table 20, the surface on which the substrate 1 is placed may be a conductor or an insulator. For example, in the support table 20, an electrostatic chuck may be provided on the surface on which the substrate 1 is placed. When the support table 20 includes an insulator or an electrostatic chuck, even if the support table 20 is grounded, a parasitic capacitance 21 is generated between the substrate 1 and the ground. In addition, a DC power supply or an AC power supply (high-frequency power supply) may be connected to the support table 20 so that a bias potential can be applied to the substrate 1. Furthermore, a heating source for heating the substrate 1 to a predetermined temperature may be built in the support table 20.

The plasma generation source 30 has a high-frequency coil (antenna) 31 for plasma generation, a high-frequency power source 32 connected to the high-frequency coil 31, and an integrated circuit 33. The integrated circuit 33 is provided between the high-frequency coil 31 and the high-frequency power source 32. The high-frequency coil 31 is wound around the outer circumference of the cylindrical wall 12, for example. The number of turns of the high-frequency coil 31 wound around the outer circumference of the cylindrical wall 12 is not limited to the number shown in the figure. The high-frequency power source 32 is, for example, an RF power source. The high frequency power supply 32 may also be a VHF power supply.

The plasma generation source 30 is not limited to an inductively coupled plasma source, and may also be an Electron Cyclotron Resonance Plasma (Electron Cyclotron Resonance Plasma) source, a Helicon Wave Plasma (Helicon Wave Plasma) source, or the like.

When a gas is introduced into the vacuum chamber 10 and a predetermined power is input to the high-frequency coil 31, plasma is generated in the plasma forming space 10p in the vacuum chamber 10. The plasma is formed by inductive coupling. As a result, in the plasma formation space 10p, a low-pressure but high-density plasma (hereinafter, low-pressure high-density plasma) is generated. In addition, by generating high-density plasma in the plasma forming space 10p, it becomes easy to apply a self-bias potential to the substrate 1. Furthermore, since the high-frequency coil 31 is provided outside the vacuum chamber 10, it does not directly contact the plasma generated in the vacuum chamber 10. Therefore, the component (for example, metal) of the high-frequency coil 31 does not fly to the substrate 1 due to being sputtered by the plasma.

When a film forming gas is introduced into the vacuum chamber 10 and plasma is generated in the plasma forming space 10 p by the plasma generation source 30, a film is formed on the substrate 1. In this case, the film forming apparatus 100 functions as a film forming apparatus that forms a film on the substrate 1. In addition, since the plasma is a low-pressure and high-density plasma, for example, when trenches or holes (trenches, etc.) are provided in the substrate 1, it becomes easy to form semiconductor films with different film qualities on the bottom and sidewalls. The reason for this will be described later. In addition, the aspect ratio of the groove etc. is 4 or more, for example.

On the other hand, if an etching gas is introduced into the vacuum chamber 10 and plasma is generated in the plasma formation space 10p by the plasma generation source 30, the film formed on the substrate 1 is removed. In this case, the film forming apparatus 100 functions as an etching apparatus that removes the semiconductor film formed on the substrate 1.

The gas supply source 40 supplies film forming gas into the vacuum chamber 10. The gas supply source 40 has an annular nozzle 41, a gas introduction pipe 42 and a flow meter 43. The nozzle 41 is opposed to the support table 20. The nozzle 41 is provided with a supply port 41h through which the process gas is ejected. The supply port 41h faces the support table 20, for example. For example, in order to obtain a desired film thickness distribution, the diameter of the nozzle 41 or the angle of the supply port 41h toward the support table 20 can be appropriately adjusted. The gas introduction pipe 42 is connected to the nozzle 41. The gas introduction pipe 42 is provided in the cover plate 13, for example. The gas introduction pipe 42 is provided with a flow meter 43 that adjusts the flow rate of the process gas.

As the film forming gas, a gas containing silicon is used. As a result, a semiconductor film containing silicon, for example, is formed on the substrate 1. For example, as the film forming gas, at least any one of _{SiH 4} or Si ₂ H _{6 is used.} In addition, inert gas (Ar, He, etc.) may be mixed with at least any one of _{SiH 4} and Si ₂ H _6. In addition, a gas containing P (phosphorus) or B (boron) may be added to at least any one of _{SiH 4} or Si ₂ H _6.

The gas supply source 45 supplies etching gas into the vacuum chamber 10. The gas supply source 40 has an annular nozzle 46, a gas introduction pipe 47 and a flow meter 48. The nozzle 46 is opposed to the support table 20. The nozzle 46 is provided with a supply port 46h through which the process gas is ejected. The supply port 46h faces the support table 20, for example. example In order to obtain a desired etching distribution, the diameter of the nozzle 46 or the angle of the supply port 46h toward the support table 20 can be adjusted appropriately.

The gas introduction pipe 47 is connected to the nozzle 46. The gas introduction pipe 47 is provided in the cover plate 13, for example. The gas introduction pipe 47 is provided with a flow meter 48 for adjusting the flow rate of the process gas.

Among them, the diameter of the nozzle 46 is smaller than the diameter of the nozzle 41. Thus, the position of the supply port 46h is different from the position of the supply port 41h. For example, when the etching gas is more easily adsorbed on the vacuum chamber 10 than the film forming gas, it is preferable that the diameter of the nozzle 46 is smaller than the diameter of the nozzle 41. As a result, the nozzle 46 is farther away from the vacuum chamber 10 than the nozzle 41, and it becomes difficult for the etching gas to be adsorbed to the vacuum chamber 10. As a result, a desired etching distribution can be obtained.

As the etching gas, a gas containing halogen is used. For example, as the etching gas, a gas containing fluorine or a gas containing chlorine is used. Thereby, for example, the semiconductor film containing silicon formed on the substrate 1 can be etched. For example, as the etching gas, at least one of _{NF 3} , NCl ₃ and Cl _{2 is used.} In addition, _{at least any one of NF 3} , NCl _3, and Cl ₂ may be mixed with inert gas (Ar, He, etc.). In addition to this, as the etching gas, at least any one of _{CF 4} and SF _{6 may be used.} In addition, _{at least any of CF 4} and SF ₆ may be added to at least any of _{NF 3} , NCl ₃ and Cl ₂ .

)結構的孔，能夠對基板1均勻地供給氣體。 In addition, the gas supply source is not limited to the two gas supply sources 40 and 45, and another gas supply source may be further provided. In addition, the gas supply sources 40 and 45 may be shower plate type gas supply sources. In addition, the shower plate may also be provided separately from the gas supply sources 40 and 45, for example, may also be provided between the cylindrical wall 12 and the bottom 11. Furthermore, the shower plate has, for example, a plurality of tree-shaped rows (Japanese:

The holes of the) structure can uniformly supply gas to the substrate 1.

The control unit 50 can switch between the generation of plasma using a film-forming gas and the generation of plasma using an etching gas. The control unit 50 uses hardware elements used in computers such as CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory) and necessary hardware elements used in the computer. Software comes accomplish. Instead of or on the basis of the CPU, it is also possible to use FPGA (Field Programmable Gate Array) and other PLD (Programmable Logic Device), or DSP (Digital Signal Processor, digital signal processor) )Wait.

For example, the control unit 50 sets the flow meter 43 to the on state when plasma using the film-forming gas is generated (at this time, the flow meter 48 is in the off state). Thus, the film forming gas is introduced into the vacuum chamber 10 from the nozzle 41. Then, the control unit 50 drives the high-frequency power supply 32 to generate plasma (first plasma) using a film-forming gas in the vacuum chamber 10. The control unit 50 controls the integrated circuit 33 to stabilize the plasma. In addition, the control unit 50 sets the flow meter 48 to the on state when the plasma using the etching gas is generated (at this time, the flow meter 43 is in the off state). As a result, the etching gas is introduced into the vacuum chamber 10 from the nozzle 46. Then, the control unit 50 drives the high-frequency power supply 32 to generate plasma (second plasma) using an etching gas in the vacuum chamber 10.

In the film forming apparatus 100, by alternately repeating the film forming process and the etching process on the substrate 1, a semiconductor film is formed without forming voids in the trenches or the like having a high aspect ratio formed on the substrate 1.

Due to the difficulty of the miniaturization process in the recent photolithography technology and the structural problems of the semiconductor device that increase the leakage current due to miniaturization, such as FinFET (Fin Field Effect Transistor, fin field effect transistor), Attempt to re-examine the structure of the semiconductor device. Under such circumstances, in the three-dimensional processing of semiconductor devices, a technique of embedding a film in a miniaturized trench or the like is required. However, for the film buried in the miniaturized trench or the like, it is difficult to form without voids in the same way as the insulating film due to differences in reflow characteristics and etching characteristics at the time of temperature rise.

In response to this, the present embodiment solves the above-mentioned situation. Hereinafter, the film forming method of the present embodiment will be described.

[Film forming method]

Fig. 2 is a schematic flow chart of the film forming method of the present embodiment.

For example, the substrate 1 is provided with trenches or holes (trenches, etc.) with a high aspect ratio, and high-density plasma of the film forming gas is generated on the surface of the substrate 1, thereby forming silicon-containing substrates on the bottom and sidewalls of the trenches, etc. Semiconductor film (first semiconductor film) (step S10).

Next, by generating plasma of an etching gas on the surface of the substrate 1, the semiconductor film formed on the side wall is selectively removed (step S20).

Then, step S10 and step S20 are repeated. For example, the process of forming a semiconductor film containing silicon on the bottom and sidewalls of trenches etc. provided in the substrate 1 and the process of selectively removing the semiconductor film formed on the sidewalls are repeated (step S30). For example, the semiconductor film formed on the sidewall of the trench or the like is selectively removed, and in the next film forming step, the process of forming a semiconductor film (second semiconductor film) containing silicon on the bottom and sidewalls of the trench or the like is repeated twice above.

According to such a film forming method, a semiconductor film is formed in a trench or the like without forming a void. Hereinafter, the flow of FIG. 2 will be described in more detail.

3A to 5B are schematic cross-sectional views showing the film forming method of this embodiment.

For example, a film forming process of forming a semiconductor film in a trench provided in the substrate 1 is taken as an example to describe the film forming method of the present embodiment.

As shown in A of FIG. 3, a trench 5 with a high aspect ratio is provided in the substrate 1. Here, the length of "β" (the depth of the groove 5) is set to be 4 times or more the length of "α" (the width of the bottom 5b of the groove 5). In addition, the length of "α" is set to several nm to several tens of nm. In addition, as an example, the substrate 1 is set as a substrate in which a silicon oxide film (SiO ₂ ) 1b is formed on a silicon substrate 1a.

Next, as shown in B of FIG. 3, a semiconductor film 70a containing silicon is formed in the trench 5 and the upper surface 1u of the substrate 1 by plasma CVD. For example, SiH ₄ gas diluted with Ar is introduced from the nozzle 41. As the film forming gas, a gas obtained by diluting _{Si 2} H _{6 with Ar may also be used.} Next, electric power is input to the high-frequency coil 31 through the high-frequency power supply 32. _{In the vacuum chamber 10, a high-density plasma of SiH 4} /Ar gas (first plasma) is generated on the upper surface 1 u of the substrate 1. Thus, the semiconductor film 70a is formed on the bottom 5b of the trench 5, the sidewall 5w of the trench 5, and the upper surface 1u of the substrate 1 (step S10).

An example of film formation conditions is as follows.

Substrate diameter: 300mm

Film forming gas: SiH ₄ /Ar

Film formation time: within 5 minutes

Discharge power: above 300W and below 600W (13.56MHz)

Pressure: 0.05Pa or more and 1.0Pa or less

Substrate temperature: room temperature

The semiconductor film 70 a has, for example, a film 71 a formed on the bottom 5 b of the trench 5, a film 72 a formed on the side wall 5 w of the trench 5, and a film 73 a formed on the upper surface 1 u of the substrate 1. The film 72a is also formed near the corner 5c of the trench 5. In other words, the film 72a includes a portion in contact with the side wall 5w and a portion formed in the portion in contact with the side wall 5w and in contact with the film 73a. In addition, B of FIG. 3 illustrates a configuration in which the film 72a is not in contact with the film 71a in the trench 5, but the film 72a may be in contact with the film 71a in the trench 5.

In the film forming step, the film forming conditions are adjusted so that the upper portion of the trench 5 is not blocked by the semiconductor film 70a. For example, if the film formation time becomes longer than 5 minutes, the films 72a grown from the corners 5c of the both side walls 5w may come into contact with each other, and the upper film 72a of the trench 5 may be blocked. Thus, the film formation time is adjusted to within 5 minutes, and preferably set to 2 minutes.

If the semiconductor film 70a is formed in the trench 5 and the substrate 1 by low-pressure and high-density plasma, the semiconductor film 70a grows while being irradiated with ions in the plasma. The ions pass through the potential difference between the plasma potential and the self-bias potential of the substrate 1, and are incident perpendicular to the substrate 1, for example. At this time, the bottom 5b of the base of the film 71a and the upper surface 1u of the base of the film 73a are orthogonal to the incident direction of ions. As a result, the membrane 71a and the membrane 73a receive the kinetic energy of ions on the bottom 5b and the upper surface 1u while gradually receiving the kinetic energy of the ions. Gradually grow. As a result, the film 71a and the film 73a become films with good crystallinity. For example, the film 71a and the film 73a are denser and denser than the film 72a.

However, the higher the above-mentioned potential difference, the more the energy of the ions irradiating the film 71a and the film 73a increases. For example, if the discharge power becomes less than 300 W, the irradiation energy of ions may decrease, and the crystallinity of the film 71a and the film 73a may decrease. In addition, if the discharge power becomes more than 600 W, the energy becomes too large, and the film 71a and the film 73a become easy to be physically etched. Therefore, the discharge power is preferably 300W or more and 600W or less, preferably 500W.

In addition, if the pressure during film formation is also less than 0.05 Pa, the amount of film formation gas may decrease and discharge may become unstable. In addition, if the pressure during the film formation is greater than 1.0 Pa, the film 71a and the film 73a have poor coverage of the step difference. Therefore, the pressure is preferably 0.05 Pa or more and 1.0 Pa or less, preferably 0.1 Pa.

On the other hand, the film 72a formed on the side wall 5w of the trench 5 does not have a base during film formation. As a result, the film 72a is less likely to receive the kinetic energy of the ions than the film 71a and the film 73a, or a part of the film 72a is formed by the incident ion sputtering the film 71a and the like. Therefore, compared with the film 71a and the film 73a, the film 72a has The crystallinity is not good. Thereby, for example, the film 72a becomes a less dense and less dense film than the film 71a and the film 73a. For example, the film 72a is a film that is less resistant to etching by fluorine than the film 71a and the film 73a. For example, when an etching gas containing fluorine is used, the etching rate of the film 72a is faster than the etching rates of the film 71a and the film 73a.

In this manner, in the film forming step, the film 71a, the film 73a, and the film 72a having different film qualities from the film 71a and the film 73a are formed.

Next, as shown in A of FIG. 4, the film 72a formed on the sidewall 5w of the trench 5 is selectively removed by reactive dry etching (chemical etching) (step S20). For example, NF ₃ gas is introduced from the nozzle 46. Regarding the etching gas, a gas containing at least one of _{NF 3} , NCl ₃ and Cl _{2 may also be used.} Next, electric power is input to the high-frequency coil 31 through the high-frequency power supply 32. In the vacuum chamber 10, a high-density plasma (second plasma) of _{NF 3} gas is generated on the upper surface 1 u of the substrate 1. As a result, the film 72a that is not resistant to etching by the etching plasma is selectively removed. For example, when silicon in the film 72a reacts with fluorine in the plasma, SiF _x and the like _{are generated, and SiF x} and the like are exhausted from the vacuum chamber 10 by a vacuum pump.

An example of etching conditions is as follows.

Substrate diameter: 300mm

Etching gas: NF ₃

Etching time: within 5 minutes

Discharge power: 500W (13.56MHz)

Pressure: 1Pa

Substrate temperature: room temperature

In the etching process, the etching conditions are adjusted so that the film 72a is selectively removed. For example, if the etching time becomes longer than 5 minutes, the film 71a and the film 73a may react with fluorine, and the film 71a and the film 73a may also be removed. Therefore, the etching time is preferably adjusted to within 5 minutes, preferably 20 seconds.

In addition, in the etching process, if physical etching using Ar plasma is used, for example, the film 71a may be etched simultaneously with the film 72a, which is not preferable.

Next, as shown in B of FIG. 4, a semiconductor film 70b containing silicon is formed in the trench 5 and the film 73a by plasma CVD. For example, under the same conditions as the semiconductor film 70a, the semiconductor film 70b is formed in the trench 5 and the film 73a.

The semiconductor film 70 b includes, for example, a film 71 b formed on the film 71 a in the trench 5, a film 72 b formed on the side wall 5 w of the trench 5, and a film 73 b formed on the upper surface 1 u of the substrate 1. The film 72b includes a part in contact with the side wall 5w and a part formed in the part in contact with the side wall 5w and in contact with the film 73b. In addition, in the trench 5, the film 72b may be in contact with the film 71b. In addition, since the film 71a is etched, a trace amount of fluorine may remain at the interface between the film 71a and the film 71b.

In the semiconductor film 70b, the film 72b is also a low-density and less dense film than the film 71b and the film 73b. For example, the film 72b becomes a film less resistant to etching by fluorine than the film 71b and the film 73b.

Next, as shown in A of FIG. 5, the film 72b formed on the sidewall 5w of the trench 5 by reactive dry etching is selectively removed. For example, the film 72b is selectively removed under the same conditions as the conditions for removing the film 72a.

Next, as shown in B of FIG. 5, the film forming process (step S10) and the etching process (step S20) are repeated (step S30). The number of repetitions (5 times as an example in this embodiment) is set to, for example, 2 times or more. Thus, in the trench 5, the film 71a, the film 71b formed on the film 71a, the film 71c formed on the film 71b, the film 71d formed on the film 71c, and the film 71e formed on the film 71d are formed. The film formed on the upper surface 1u of the substrate 1 is removed by, for example, CMP (Chemical Mechanical Polishing). In addition, a small amount of fluorine may remain in the respective interfaces of the film 71a, the film 71b, the film 71c, the film 71d, and the film 71e.

In this manner, the step of forming a semiconductor film containing silicon on the bottom 5b and sidewalls 5w of the trench 5 and the step of selectively removing the semiconductor film formed on the sidewall 5w are repeated to form a semiconductor containing silicon in the trench 5. Film 70 (films 71a, 71b, 71c, 71d, 71e). According to such a film forming method, the semiconductor film 70 is formed in the trench 5 without forming a void. In addition, it is not limited to the trench 5, and in a hole having the same aspect ratio as the trench 5, the semiconductor film 70 is formed in the hole without forming a void.

In addition, a gas containing phosphorus (P), boron (B), germanium (Ge), or the like may be added to the film forming gas to form the semiconductor film 70. For example, the composition ratio of silicon in the semiconductor film 70 formed in the trench 5 is 50 atom% or more, preferably 90 atom% or more, and more preferably 99 atom% or more. That is, as the semiconductor film 70, a silicon film (film containing silicon) containing inevitable impurities and phosphorus (P), arsenic (As), antimony (Sb), boron (B), aluminum (Al), and gallium are formed. At least any one of a silicon film having at least one of (Ga), indium (In), and germanium (Ge) as a dopant. in, "Inevitable impurities" refer to impurities that are not intentionally introduced but are inevitably introduced in the raw material gas or the manufacturing process.

In addition, in the etching process, the higher the reactivity of the etching plasma, the more likely the films 71a, 73a shown in B of FIG. 3 to be damaged by the etching plasma, or the less selective the film 72a Fully obtained. The film 71b, 73b and the film 72b shown in B of FIG. 4 can also cause the same phenomenon.

When such a phenomenon occurs, H ₂ (hydrogen) gas may be used in place of the halogen-based gas in the etching process. An example of etching conditions using H _{2 gas is as follows.}

Substrate diameter: 300mm

Etching time: within 7 minutes

Discharge power: below 1000W (13.56MHz)

Pressure: 5Pa

Substrate temperature: room temperature

_{For example, if plasma of H 2} gas is generated on the upper surface 1 u of the substrate 1, the film 72 a that is less resistant to etching than the films 71 a and 73 a reacts with the hydrogen plasma, and the film 72 a is selectively removed. In this case, the Si contained in the film 72a is changed to SiH _x or the like, and the SiH _x is exhausted from the vacuum chamber 10 or the like by a vacuum pump. After that, the film forming process and _{the etching process using H 2} gas are repeated to form the semiconductor film 70 in the trench 5.

Furthermore, in the present embodiment, a dry washing step may be introduced in which the inside of the vacuum tank 10 is dry washed after the film forming step.

For example, in the film forming process, in addition to the substrate 1, the semiconductor film is attached to the bottom 11 of the vacuum chamber 10, the cylindrical wall 12, the cover plate 13, the support table 20, the nozzles 41, 46, and the like. After that, if hydrogen plasma is exposed to the semiconductor film attached to the bottom 11 of the vacuum chamber 10, the cylindrical wall 12, the cover 13, the support table 20, and the nozzles 41, 46 during the etching process, the semiconductor film may be The hydrogen plasma reacts, and SiH _x and the like are released from the bottom 11 of the vacuum chamber 10, the cylindrical wall 12, the cover plate 13, the support table 20, the nozzles 41, 46, and the like.

For example, if the SiH _x flies in the plasma formation space 10 p and is decomposed by etching plasma, the SiH _x itself becomes a gas for film formation, and a semiconductor film is formed on the substrate 1 again. However, after the film formation process, the semiconductor film attached to the bottom 11 of the vacuum chamber 10, the cylindrical wall 12, the cover plate 13, the support table 20, and the nozzles 41, 46, etc. are removed in a dry cleaning process, and the semiconductor film is transferred to the substrate. Reattachment on 1 is suppressed.

Hereinafter, the state after the etching when the film formation process is transferred to the etching process using hydrogen plasma without dry cleaning and the dry cleaning process after the film formation process is transferred to the etching process using hydrogen plasma will be described. .

A of FIG. 6 is a schematic graph showing the relationship between the etching time and the film thickness when shifting to the etching process using hydrogen plasma without performing dry cleaning after the film forming process. B of FIG. 6 is a schematic graph showing the relationship between the etching time and the film thickness when dry cleaning is performed after the film forming process and then transferred to the etching process using hydrogen plasma.

In A and B of FIG. 6, the horizontal axis represents the etching time, and the vertical axis represents the film thickness of the semiconductor film. A and B of FIG. 6 show the results of repeating the film forming process and the etching process for each cycle. For example, the film thickness when the etching time is 0 seconds corresponds to the film thickness of the semiconductor film formed on the upper surface 1 u of the substrate 1 or the bottom 5 b of the trench 5 after the completion of one film forming process. The film thickness is about 5 nm.

An example of dry washing conditions is as follows.

Dry scrubbing gas: H ₂

Dry washing time: within 7 minutes

Discharge power: below 1000W (13.56MHz)

Pressure: 5Pa

In the dry cleaning process, the inside of the vacuum tank 10 may be cleaned with the substrate 1 after the film formation process placed on the support table 20, or the substrate 1 may be transferred to a vacuum tank different from the vacuum tank 10 Then, the inside of the vacuum tank 10 is washed. However, when the substrate 1 is placed on the support table 20 in the dry cleaning process, the substrate 1 is covered with blinds or the like. The dry washing step may be implemented at the end of each film forming process, or may be implemented at the end of multiple film forming processes.

First, referring to A of FIG. 6, an example in which the film formation step is followed by a dry cleaning and the transition to the etching step using hydrogen plasma will be described.

In this case, if the etching process is performed for 100 seconds with a discharge power of 100 W, the film thickness is reduced from about 5 nm to about 4 nm. Next, if the etching process is performed for 300 seconds with a discharge power of 100 W, the film thickness becomes approximately 2.5 nm. In this way, in the etching process with a discharge power of 100 W, the more the etching time increases, the more the film thickness decreases. That is, at a discharge power of about 100W, the etching amount can be controlled by the etching time.

If the discharge power is increased from 100W to 200W, the film thickness will be reduced to about 2nm by the etching treatment for 300 seconds.

However, at a discharge power of 400 W, the film thickness increased to about 12 nm by the etching treatment for 100 seconds, and the film thickness was reduced to about 2 nm by the etching treatment for 300 seconds. Regarding the temporary increase in the film thickness, the greater the discharge power, the more significant it is. In addition, at a discharge power of 1000 W, the film thickness increased to about 28 nm by the etching treatment for 100 seconds, and the film thickness was reduced to about 3.5 nm by the etching treatment for 300 seconds.

In this way, if the etching process is performed with a discharge power greater than 200 W, the film thickness of the semiconductor film tends to increase compared to the original film thickness when the etching time is about 100 seconds. It is considered that this is due to the adhesion to the bottom 11 of the vacuum chamber 10, the cylindrical wall 12, the cover 13, the support 20, and the nozzle 41 when moving to the etching process using hydrogen plasma without performing dry cleaning after the film formation process. The semiconductor film such as, 46, etc. is decomposed by hydrogen plasma and deposited on the substrate 1 again.

In this way, in the case of adopting the process of shifting to the etching process using hydrogen plasma without performing dry cleaning after the film formation process, when the discharge power is low (for example, 200W or less), although the film formation time and The film thickness of the semiconductor film is controlled by the etching time, but if the discharge power is increased (for example, greater than 200W), the film thickness of the semiconductor film will temporarily increase from the beginning of the etching, and it becomes difficult to control the film formation time and the etching time The thickness of the semiconductor film.

On the other hand, B of FIG. 6 shows the result when the film formation process is followed by dry washing and then the etching process is transferred. In this case, before the etching process, the semiconductor film adhering to the bottom 11 of the vacuum chamber 10, the cylindrical wall 12, the cover plate 13, the support table 20, the nozzles 41, 46, and the like are removed.

In this process, in the etching process at a discharge power of 100W, the film thickness of the semiconductor film is reduced from about 5nm to about 4nm when the etching time is 30 seconds, and the film thickness becomes about 3nm after the etching time is 60 seconds. After the etching time was 75 seconds, the film thickness was further reduced.

Furthermore, at a discharge power of 200 W, the film thickness becomes about 2.5 nm when the etching time is 30 seconds, and the film thickness becomes about 0.5 nm when the etching time is 60 seconds. At a discharge power of 400 W, the film thickness becomes approximately 2.5 nm when the etching time is 30 seconds, and the film thickness becomes thinner than 1 nm when the etching time is 60 seconds. At a discharge power of 1000 W, the film thickness becomes thinner than 1 nm when the etching time is 30 seconds.

In this way, by performing dry cleaning after the film formation process, the phenomenon that the film thickness of the semiconductor film in the etching process temporarily increases is suppressed. That is, it is considered that the semiconductor film attached to the bottom 11 of the vacuum chamber 10, the cylindrical wall 12, the cover plate 13, the support table 20, and the nozzles 41, 46, etc., are removed by dry cleaning before the etching process, so the semiconductor film is on the substrate 1. The phenomenon of upper redeposition is suppressed.

In this way, by adopting a process of performing dry cleaning after the film forming process and then transferring to the etching process, the film thickness of the semiconductor film can be controlled with high accuracy based on the film forming time and the etching time.

In addition, in order to improve the surface flatness of the film formed on the upper surface 1 u of the substrate 1 and the bottom 5 b of the trench 5, a bias potential may be applied to the support table 20 in the etching step. As a result, during etching, for example, an ion bombardment effect on the film surface acts, and the flatness of the film surface is improved. but Yes, if the bias potential becomes too high, the ion bombardment effect becomes excessive, and the film is removed from the upper surface 1u of the substrate 1 and the bottom 5b of the trench 5 by ion irradiation. The bias potential applied to the support table 20 is adjusted to such an extent that the film thickness is not easily reduced and the flatness of the film surface is improved.

As mentioned above, although the embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment, of course, various changes can be added.

S10: Step S10

S20: Step S20

S30: Step S30

Claims (8)

A method of forming a film by generating a first plasma on the surface of a substrate provided with a trench or hole having a bottom and sidewalls, thereby forming a first semiconductor film on the bottom, the sidewalls, and the surface of the substrate, so _{The first plasma is formed by introducing a mixed gas of SiH 4} and Ar at a pressure of 0.05 Pa or more and 1.0 Pa or less, and formed by high frequency. The first semiconductor film is a film containing silicon. _{A second plasma containing an etching gas of NF 3} is generated on the surface to selectively remove the first semiconductor film formed on the side wall, and the first plasma is generated on the surface of the substrate , Thereby forming a second semiconductor film containing silicon on the bottom and the sidewalls. The film forming method according to claim 1, wherein the film containing silicon is a silicon film containing at least one of phosphorus, arsenic, antimony, boron, aluminum, gallium, indium, and germanium as a dopant. A method of forming a film by generating a first plasma on the surface of a substrate provided with a trench or hole having a bottom and sidewalls, thereby forming a first semiconductor film on the bottom, the sidewalls, and the surface of the substrate, so _{The first plasma is formed by introducing a mixed gas of SiH 4} and Ar at a pressure of 0.05 Pa or more and 1.0 Pa or less, and formed by high frequency. The first semiconductor film is a film containing silicon. _{The second plasma of only H 2} etching gas is generated on the surface to selectively remove the first semiconductor film formed on the side wall, and the first plasma is generated on the surface of the substrate As a result, a second semiconductor film containing silicon is formed on the bottom and the sidewalls. The film forming method according to claim 3, wherein: The film containing silicon is a silicon film containing at least one of phosphorus, arsenic, antimony, boron, aluminum, gallium, indium, and germanium as a dopant. The film forming method according to claim 1 or 3, wherein the first semiconductor film formed on the side wall is selectively removed, and the process of forming the second semiconductor film on the bottom and the side wall is performed Repeat 2 more times. The film forming method according to claim 1 or 3, wherein the time for generating the first plasma is within 5 minutes. The film forming method according to claim 1 or 3, wherein the time for generating the second plasma is within 5 minutes. The film forming method according to claim 1, wherein the interface between the first semiconductor film and the second semiconductor film contains fluorine, and the fluorine is fluorine contained in the etching gas.

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