Film forming apparatus and film forming method

Abstract

To reduce damage occurring in a base for a titanium metal film when the titanium metal film is formed by a plasma ALD method.SOLUTION: A method for depositing a titanium metal film on a substrate, includes a step of forming the titanium metal film by an atomic layer deposition (plasma ALD) method that conducts an adsorption stage and a reaction stage alternately. In the adsorption stage, a raw material gas is supplied into a processing vessel housing the substrate and adsorbed on the surface of the substrate. In the reaction stage, a reaction gas is supplied into the processing vessel, converted into plasma, and reacted with the raw material gas adsorbed on the surface of the substrate. In the reaction stage, the reaction gas is converted into plasma using high-frequency power of a frequency of 38 MHz or higher and 60 MHz or lower.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a film forming apparatus and a film forming method. [Background technology]

[0002] Patent Document 1 describes a method for forming a film on the surface of a substrate.

[0003] Patent Document 2 describes a substrate processing apparatus that performs a film formation process on a substrate surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-59173 A [Patent Document 2] JP 2017-155292 A Summary of the Invention [Problem to be solved by the invention]

[0005] The technology disclosed herein reduces damage to a substrate underlying a titanium metal film when the titanium metal film is formed by plasma ALD. [Means for solving the problem]

[0006] One aspect of the present disclosure is a method for forming a metal titanium film on a substrate, the method including: forming a metal titanium film by an atomic layer deposition (plasma ALD) method that alternately performs an adsorption step of supplying a source gas into a processing vessel containing the substrate and adsorbing the source gas onto a surface of the substrate; and a reaction step of supplying a reactive gas into the processing vessel, converting the reactive gas into plasma, and reacting the source gas adsorbed onto the surface of the substrate with the plasma-converted reactive gas, wherein in the reaction step: As power for plasma generation High-frequency power with a frequency between 38MHz and 60MHz Using chisels The reactive gas is turned into plasma. Effect of the Invention

[0007] According to the present disclosure, when a titanium metal film is formed by plasma ALD method, damage to the base of the titanium metal film can be reduced. [Brief description of the drawings]

[0008] [Figure 1] 1 is a vertical sectional side view of a film forming apparatus according to an embodiment of the present invention. [Diagram 2] 2 is a timing chart of a film forming process in the film forming apparatus of FIG. [Diagram 3] FIG. 13 is a diagram showing the results of a backside SIMS analysis of a Ti film formed by the PEALD method. [Figure 4] FIG. 13 is a diagram showing the results of a backside SIMS analysis of a Ti film formed by the PEALD method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] For example, in a manufacturing process of semiconductor devices, etc., a metal titanium film (hereinafter sometimes referred to as a "Ti film") may be formed on a semiconductor wafer (hereinafter referred to as a "wafer"). In the Ti film formation process, the film is formed by a chemical vapor deposition (CVD) method or an atomic layer deposition (ALD) method. As an ALD method, a plasma enhanced ALD (PEALD) method is known, which alternately performs a step of adsorbing a source gas onto the surface of the wafer W and then a step of reacting a plasmatized reactive gas with the source gas adsorbed onto the surface of the wafer W (see Patent Documents 1 and 2).

[0010] By the way, in the CVD method, if the temperature is not relatively high during film formation, the impurity concentration in the film becomes high. In contrast, in the PEALD method, it is possible to form a film with a low impurity concentration even at a relatively low temperature. For these reasons, the PEALD method is being considered for use in forming Ti films. However, the PEALD method may reduce damage that occurs to the substrate under the Ti film when the Ti film is formed by the PEALD method.

[0011] Therefore, the technology disclosed herein reduces damage that occurs to the base of the titanium metal film when the titanium metal film is formed by plasma ALD method.

[0012] Hereinafter, a film forming method and a film forming apparatus according to the present embodiment will be described with reference to the drawings. In this specification and the drawings, elements having substantially the same functional configurations are denoted by the same reference numerals, and duplicated description will be omitted.

[0013] <Film forming equipment> FIG. 1 is a vertical cross-sectional view that illustrates a film forming apparatus according to the present embodiment. The film forming apparatus 1 in the figure is a single-wafer type apparatus. The film forming apparatus 1 forms a Ti film on a wafer W as a substrate. Specifically, the film forming apparatus 1 forms the Ti film by the PEALD method. In the PEALD method, the following adsorption stage and reaction stage are alternately performed. In the adsorption stage, a source gas is supplied into a processing vessel 10 (described later) in which the wafer W is accommodated, and the source gas is adsorbed onto the surface of the wafer W. In the reaction stage, a reaction gas is supplied into the processing vessel 10, and the reaction gas is turned into plasma, and the source gas adsorbed onto the surface of the wafer W is reacted with the plasma-turned reaction gas.

[0014] The film forming apparatus 1 includes a process chamber 10 that can be depressurized and that accommodates a wafer W therein. The processing vessel 10 has a vessel body 11 formed in a cylindrical shape with a bottom. An opening 11a, which is an opening for loading / unloading the wafer W, and a gate valve 12 for opening / closing the opening 11a are provided on a side wall of the container body 11. In addition, an exhaust duct 17, which forms a part of the side wall of the processing container 10 and will be described later, is provided on the container body 11.

[0015] A mounting table 20 for mounting a wafer W thereon is provided within the processing vessel 10. The mounting table 20 constitutes a lower electrode. A heater (not shown) is built into the mounting table 20 as a heating mechanism for heating the wafer W, and this allows the wafer W mounted on the mounting table 20 to be heated to a predetermined temperature. A high frequency bias power is supplied to the mounting table 20 from a high frequency power supply 30 provided outside the processing chamber 10 via a matching box 30a. The high frequency power supply 30 may be omitted so that no high frequency bias power is supplied to the mounting table 20 .

[0016] A cylindrical cover member 21 is provided on the mounting table 20 so as to surround the mounting table 20, and the upper end of a support column 22 extending in the vertical direction is connected to the center of the lower surface of the cover member 21. The lower end of the support column 22 extends to the outside of the processing vessel 10 through an opening 11b provided in the bottom of the processing vessel 10 and is connected to a lifting mechanism 23. The mounting table 20 can be moved up and down between a transfer position indicated by a dashed line and a processing position above the transfer position by driving the lifting mechanism 23. The transfer position is a position where the mounting table 20 waits when the wafer W is transferred between a transfer mechanism (not shown) for the wafer W entering the processing vessel 10 from the opening 11a of the processing vessel 10 and support pins 26a described later. The processing position is a position where the wafer W is processed.

[0017] A flange 24 is provided on the outer side of the processing vessel 10 at the support 22. A bellows 25 is provided between the flange 24 and the penetration portion of the support 22 in the bottom wall of the processing vessel 10 so as to surround the outer periphery of the support 22. This keeps the processing vessel 10 airtight.

[0018] A wafer lifting member 26 having a plurality of, for example, three, support pins 26a is provided below the mounting table 20 in the processing chamber 10. The wafer lifting member 26 is movable up and down by a lifting mechanism 28. In addition, by moving up and down, the support pins 26a protrude and retract from the upper surface of the mounting table 20 through through holes 20a formed in the mounting table 20 in order to transfer the wafer W.

[0019] An annular insulating support member 13 is provided above exhaust duct 17 in processing vessel 10. A shower head support member 14 made of quartz is provided on the lower surface side of insulating support member 13. A shower head 15, which is a gas inlet for introducing processing gas into processing vessel 10 and constitutes an upper electrode, is supported on shower head support member 14.

[0020] The shower head 15 has a disk-shaped head body 15a and a shower plate 15b connected to the head body 15a, and a gas diffusion space S1 is formed between the head body 15a and the shower plate 15b. The head body 15a and the shower plate 15b are made of metal. The head body 15a has two gas supply paths 15c and 15d that communicate with the gas diffusion space S1, and the shower plate 15b has a large number of gas discharge holes 15e that communicate with the gas diffusion space S1. Further, high frequency power for generating plasma is supplied to the shower head 15 from a high frequency power supply 31 provided outside the processing chamber 10 via a matching box 31a.

[0021] Furthermore, an annular member 16 is provided inside the processing vessel 10, with the inner wall of the processing vessel 10 protruding above the opening 11a. The annular member 16 is disposed close to the outer side of the cover member 21 of the mounting table 20 at the processing position and surrounding the cover member 21. An exhaust duct 17 curved in an annular shape is provided at the upper part of the side wall of the processing vessel 10. The inner peripheral surface side of the exhaust duct 17 opens in the circumferential direction on the annular member 16, and the processing space S2 can be exhausted through a gap 18 formed between the cover member 21 and the lower peripheral portion of the shower plate 15b.

[0022] An exhaust mechanism 40 that exhausts the inside of the processing vessel 10 is connected to the exhaust duct 17. The exhaust mechanism 40 has an exhaust pipe 41 and a vacuum exhaust pump 42. One end of the exhaust pipe 41 is connected to the exhaust duct 17, and the other end of the exhaust pipe 41 is connected to the vacuum exhaust pump 42. An APC valve 43 and an opening / closing valve 44 are provided in this order from the upstream side in the exhaust pipe 41 between the exhaust duct 17 and the vacuum exhaust pump 42.

[0023] Furthermore, a gas supply mechanism 50 that supplies raw material gases and reactive gases to the processing vessel 10 is connected to the aforementioned gas supply paths 15c and 15d, and more specifically, the downstream ends of gas flow paths 51 and 61 of the gas supply mechanism 50 are connected thereto, respectively.

[0024] The upstream end of the gas flow passage 51, which is a source gas flow passage, is connected to a valve V1 and a flow rate regulator 52, which are connected in this order from the downstream side, to supply the source gas TiCl 4 It is connected to a gas source 53 . The flow rate adjusting unit 52 is composed of a mass flow controller, and is configured to adjust the amount of TiCl from a supply source 53. 4 The flow rate adjusters 55, 62, and 65 described later are configured similarly to the flow rate adjuster 52, and adjust the flow rate of gas supplied to the downstream side of the flow path. The valve V1 is opened and closed to supply TiCl from the supply source 53 to the processing vessel 10. 4The gas supply is cut off. valve V 2, V4, V5 The supply and cut-off of gas from each of the supply sources 56, 63, and 66 to the processing vessel 10 is performed by opening and closing the corresponding valves.

[0025] The downstream end of a gas flow path 54 is connected to the downstream side of the valve V1 in the gas flow path 51. The upstream end of the gas flow path 54 is connected to an Ar gas supply source 56 via a valve V2 and a flow rate regulator 55 in this order from the downstream side. The Ar gas from the supply source 56 is mixed with TiCl 4 It is supplied into the process vessel 10 for dilution of the gas.

[0026] Next, the gas flow path 61 connected to the gas supply path 15d of the processing chamber 10 will be described. The upstream end of the gas flow passage 61, which is a reaction gas flow passage, is connected to a valve V 4 , and the reaction gas H 2 It is connected to a gas source 63 .

[0027] Valve V in gas flow path 61 4 The downstream end of the gas flow passage 64 is connected to the downstream side of the valve V. 5 , via a flow rate adjusting unit 65 in this order from the downstream side, and is connected to an Ar gas supply source 66. The Ar gas from the supply source 66 is supplied into the processing vessel 10 for plasma generation.

[0028] The film forming apparatus 1 configured as above is provided with a control unit 100. The control unit 100 is configured by, for example, a computer equipped with a CPU, a memory, and the like, and has a program storage unit (not shown). The program storage unit stores information about the heater (not shown) in the mounting table 20, the gate valve 12, the valve V1, and the like. , V2, V4, V5The control unit 100 stores therein programs and the like for controlling each device, such as the APC valve 43, and flow rate adjustment units 52, 55, 62, and 65, to realize wafer processing, which will be described later, in the film forming apparatus 1. The above programs may be recorded in a computer-readable storage medium and installed from the storage medium into the control unit 100. Also, a part or all of the programs may be realized by dedicated hardware (circuit board).

[0029] <Film formation method> Next, the wafer processing in the film forming apparatus 1 will be described with reference to Fig. 2. Fig. 2 is a timing chart of the wafer processing in the film forming apparatus 1.

[0030] (Step S1: Wafer loading) First, valve V1 , V2, V4, V5 The gate valve 12 is opened with the gate valve 12 closed. Next, a transfer mechanism (not shown) holding the wafer W is inserted from a transfer chamber (not shown) in a vacuum atmosphere adjacent to the processing vessel 10 through the opening 11a into the processing vessel 10 previously evacuated by the exhaust mechanism 40. Next, the wafer W is transferred to above the mounting table 20 located at the transfer position described above. Then, the wafer W is transferred onto the raised support pins 26a, and then the transfer mechanism is removed from the processing vessel 10 and the gate valve 12 is closed. At the same time, the support pins 26a are lowered and the wafer W is placed on the mounting table 20. The mounting table 20 is adjusted in advance to a predetermined film formation temperature, for example, 300° C. to 450° C., by an internal heater (not shown). After the wafer W is placed on the mounting table 20, the mounting table 20 is moved to the processing position described above, a processing space S2 is formed, and the pressure inside the processing vessel 10 is adjusted to a desired vacuum pressure by the APC valve 43.

[0031] (Step S2: Start supplying base gas) Next, valve V 4 , V 5 was opened, and H was used as the reaction gas. 2Gas is supplied from a supply source 63 through a gas passage 61 to the processing chamber 10, and Ar gas as a plasma generating gas is supplied from a supply source 66 through a gas passage 64 to the processing chamber 10. H 2 Ar gas as a gas for generating plasma and H gas as a reactive gas are continuously flowing during the deposition process. 2 The flow rate of the gas is, for example, 3500 sccm to 7000 sccm, and the flow rate of Ar gas as a plasma generating gas is, for example, 300 sccm to 3500 sccm. During the film formation process including the following steps S3 to S6, the pressure inside the process vessel 10 is adjusted by the APC valve 43 to a desired vacuum pressure, for example, 500 mTorr or more and 5 Torr or less.

[0032] (Step S3: Adsorption) After a preset time has elapsed since the start of supplying the reactive gas and the plasma generating gas, the valves V1 and V2 are opened. 4 A gas is supplied from a supply source 53 through a gas passage 51 to the processing vessel 10, and an Ar gas as a dilution gas is supplied from a supply source 56 through a gas passage 54 to the processing vessel 10. 4 The flow rate of the gas is, for example, 5 sccm to 15 sccm, and the flow rate of the Ar gas as the dilution gas is, for example, 300 sccm to 3500 sccm. This adsorption step is performed for, for example, 0.05 seconds to 0.1 seconds.

[0033] (Step S4: Discharge of raw material gas, etc.) After the adsorption stage is completed, valves V1 and V2 are closed and TiCl 4 The supply of Ar gas as the reaction gas and the dilution gas was stopped, and the supply of H 2 The supply of H gas and Ar gas for plasma generation was continued. 2 The gas and plasma generation of Ar gas were used to generate TiCl 4 Gases and the like are discharged (purged) from the processing vessel 10. In this manner, H 2The Ar gas for generating the gas and plasma is also used as a purge gas. The process of discharging the raw material gas and the like is carried out for, for example, 0.4 to 1 second.

[0034] (Step S5: Reaction) After a preset time has elapsed since the valves V1 and V2 were closed, the high frequency power supply 30 supplies high frequency power for bias and the high frequency power supply 31 supplies high frequency power for plasma generation. As a result, H 2 The Ar gas for generating the plasma was turned into a plasma, and the reaction gas and TiCl 4 Specifically, the H gas generated by the plasma reaction is reacted with the 3 + TiCl adsorbed on the wafer W is removed by active species such as ions. 4 is reduced to metallic titanium. In this reaction stage, the frequency of the high frequency power for plasma generation supplied from the high frequency power source 31 is 38 MHz or more and 60 MHz or less. This reaction stage is carried out for, for example, 1 to 4 seconds.

[0035] (Step S6: Discharge of active species) After the reaction stage is completed, the supply of high frequency power for bias from the high frequency power source 30 and the supply of high frequency power for plasma generation from the high frequency power source 31 are stopped, and H 2 The supply of H gas and Ar gas for plasma generation continues. 2 The gas and the Ar gas for generating plasma exhaust the active species remaining in the processing vessel 10. This process of exhausting the active species is performed for, for example, 0.3 to 1 second.

[0036] If the above steps S3 to S6 are regarded as one cycle, this cycle is repeated to deposit a Ti atomic layer on the surface of the wafer W, thereby forming a Ti film.

[0037] (Step S7: Unloading) Then, after the above cycle is performed a predetermined number of times and a Ti film having a desired thickness is formed, the wafer W is unloaded from the processing vessel 10 in the reverse order to the loading procedure into the processing vessel 10. This completes a series of wafer processing steps.

[0038] As described above, the film formation method according to the present embodiment includes a step of forming a Ti film by the PEALD method in which the adsorption step and the reaction step are alternately performed. In the reaction step, the reaction gas is turned into plasma using high-frequency power having a frequency of 38 MHz to 60 MHz.

[0039] In this embodiment, the frequency of the high-frequency power for turning the reactive gas into plasma, i.e., the high-frequency power for generating plasma, is 38 MHz or higher. Therefore, as will be described later, damage to the base of the Ti film during formation of the Ti film by the PEALD method can be greatly reduced.

[0040] In addition, in this embodiment, the frequency of the high frequency power for plasma generation is 60 MHz or less, and therefore the following effect is obtained. That is, since the impedance of the high frequency power supply circuit for bias including the mounting table 20 as the lower electrode cannot be sufficiently reduced, as the frequency of the high frequency power for plasma generation increases, the proportion of the generated plasma directed toward the side wall of the container body 11 increases, and the plasma density in the vicinity of the mounting table 20 decreases. In contrast, in this embodiment, the frequency of the high frequency power for plasma generation is 60 MHz or less, so the proportion of the generated plasma directed toward the side wall of the container body 11 is small, and the plasma density in the vicinity of the mounting table 20 is sufficiently high, so that the Ti film formation efficiency does not decrease.

[0041] In other words, in this embodiment, since the frequency of the high-frequency power for generating plasma is 38 MHz or more and 60 MHz or less, damage to the base of the Ti film when forming the Ti film by the PEALD method can be suppressed without impairing productivity.

[0042] Also, according to the inventors' intensive research, since the frequency of the high frequency power for plasma generation is 38 MHz or more, the surface roughness of the Ti film can be reduced compared to when the frequency is less than 38 MHz. Furthermore, by lowering the output of the high frequency power for plasma generation while keeping the frequency of the high frequency power for plasma generation at 38 MHz or more, the surface roughness of the Ti film can be further reduced.

[0043] As described above, the reason why the damage to the Ti film substrate can be greatly reduced by setting the frequency of the high frequency power for plasma generation to 38 MHz or more is considered to be as follows: By increasing the frequency of the high frequency power for plasma generation, (A) the density of H radicals in the plasma increases, and the relative amount of H 3 + The ion density is reduced and (B)H 3 + The energy of the ions decreases. As a result, H 3 + This is thought to be because the amount and depth of ions implanted into the Ti film base are reduced, making it difficult for nitrogen, oxygen, etc. to be incorporated.

[0044] <Experimental Example> While changing the frequency of the high frequency power for generating plasma, a Ti film was formed on a Si wafer W by the PEALD method in the same manner as described above, and a backside SIMS (Secondary Ion Mass Spectrometry) analysis was performed. The results are shown in Figures 3 and 4. In Figures 3 and 4, the horizontal axis represents frequency. Also, the vertical axis of Figure 3 represents the nitrogen concentration in the Si wafer W on which the Ti film was formed when the nitrogen concentration was 10 20 atms / cm 3 The vertical axis of FIG. 4 shows the thickness of the portion where the oxygen concentration is 10 20 atms / cm 3 The thickness of the portion where the thickness is equal to or greater than this (hereinafter referred to as the oxygen diffusion depth) is shown. Note that the output of the high frequency power for plasma generation was the same when forming the Ti film at each frequency.

[0045] As shown in Fig. 3, when a Ti film was formed on a Si wafer W by the PEALD method, the nitrogen diffusion depth decreased with an increase in the frequency of the high frequency power for plasma generation. Furthermore, when the frequency of the high frequency power for plasma generation was 38 MHz or higher, the nitrogen diffusion depth was half or less compared to when it was 450 kHz. In addition, as shown in FIG. 4, when a Ti film is formed on a Si wafer W by the PEALD method, as the frequency of the high frequency power for plasma generation increases, oxygen The diffusion depth of the oxygen The diffusion depth was also half or less when the frequency of the high frequency power for plasma generation was 38 MHz or more, compared to when it was 450 kHz.

[0046] From the results shown in Figures 3 and 4, it can be seen that when a Ti film is formed on a Si wafer W by the PEALD method, the degree of diffusion of nitrogen and oxygen in the depth (thickness) direction can be reduced by increasing the frequency of the high frequency power for generating plasma. In particular, it can be seen that the degree of the diffusion can be significantly reduced by setting the frequency of the high frequency power for generating plasma to 38 MHz or higher. In other words, when a Ti film is formed by the PEALD method, damage to the underlying Si wafer W can be significantly reduced by setting the frequency of the high frequency power for generating plasma to 38 MHz or higher.

[0047] <Other applications> The embodiments disclosed herein should be considered as illustrative and not restrictive in all respects. The above-described embodiments may be omitted, substituted, or modified in various forms without departing from the scope and spirit of the appended claims. [Explanation of symbols]

[0048] 1 Film deposition equipment 11 Container body 31 High frequency power supply 100 Control section W wafer

Claims

1. 1. A method for depositing a titanium metal film on a substrate, comprising the steps of: The method includes a step of forming a titanium metal film by an atomic layer deposition (plasma ALD) method, which alternately performs an adsorption step of supplying a source gas into a processing vessel in which the substrate is accommodated and adsorbing the source gas on the surface of the substrate, and a reaction step of supplying a reactive gas into the processing vessel, converting the reactive gas into plasma, and reacting the source gas adsorbed on the surface of the substrate with the plasma-converted reactive gas, In the reaction stage, the reactive gas is turned into plasma using only high frequency power having a frequency of 38 MHz or more and 60 MHz or less as power for generating plasma.

2. The source gas is TiCl ４ and the reactive gas comprises H ２ The film forming method according to claim 1 ,

3. 3. The film forming method according to claim 1, wherein a pressure in the processing vessel in the step of forming the titanium metal film is equal to or higher than 500 mTorr and equal to or lower than 5 Torr.

4. An apparatus for forming a titanium metal film on a substrate, comprising: a processing vessel for accommodating the substrate; a gas supply mechanism for supplying a source gas and a reaction gas into the processing chamber; a high frequency power source that outputs high frequency power for generating plasma in the processing chamber; A control unit, The control unit is a reaction step of supplying a reactive gas into the processing vessel, converting the reactive gas into plasma, and reacting the reactive gas with the raw material gas adsorbed on the surface of the substrate; and a reaction step of supplying a reactive gas into the processing vessel, converting the reactive gas into plasma, and reacting the raw material gas adsorbed on the surface of the substrate with the plasma. The film formation apparatus controls the gas supply mechanism and the high frequency power source so that the reactive gas is converted into plasma using only high frequency power having a frequency of 38 MHz or more and 60 MHz or less as power for generating plasma during the reaction step.

5. The gas supply mechanism supplies TiCl ４ and H as the reaction gas. ２ The film forming apparatus according to claim 4 ,

6. an exhaust mechanism for exhausting the inside of the processing vessel; 6. The film forming apparatus according to claim 4, wherein the control unit controls the gas supply mechanism and the exhaust mechanism so that a pressure in the processing chamber is equal to or higher than 500 mTorr and equal to or lower than 5 Torr in the step of forming the metal titanium film.

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