Method for forming metal film and metal film forming apparatus

Abstract

The present disclosure relates to a metal film forming method and a metal film forming apparatus that form a metal film while suppressing an influence on a semiconductor layer exposed on a bottom surface of a recess. When a metal film is formed in a recess formed on a surface of a substrate, a metal raw material gas containing the metal is supplied to the substrate on which a surface of a semiconductor layer containing a dopant is exposed on a bottom surface of the recess, and in parallel therewith, a reaction gas used to react with the metal raw material gas to obtain the metal film is continuously supplied to the substrate. Furthermore, high-frequency power is continuously applied to a space through which the metal raw material gas and the reaction gas flow to plasmaize the metal raw material gas and the reaction gas. Furthermore, when the metal raw material gas is supplied, the supply of the metal raw material gas is alternately repeated with the stop of the supply of the metal raw material gas after the continuous supply of the metal raw material gas.

Description

Technical Field

[0001] This disclosure relates to a method for forming a metal film and an apparatus for forming a metal film. Background Technology

[0002] In the manufacturing process of semiconductor devices, a process is performed to form a metal film on a semiconductor wafer (hereinafter also referred to as "wafer") that serves as a substrate.

[0003] For example, Patent Document 1 describes a technique in which, when forming a titanium film in a recess formed on the surface of a substrate, titanium raw material gas is supplied to the substrate while high-frequency electricity is applied to plasmaize the titanium raw material gas. According to Patent Document 1, a titanium film with uniform thickness is formed by alternately switching the applied high-frequency electricity on and off and stopping the application of high-frequency electricity multiple times.

[0004] Furthermore, Patent Document 2 describes a technique in which, during the formation of a Ti film, a first step and a second step are alternately repeated multiple times. The first step involves generating a first plasma while simultaneously introducing a Ti compound gas and a reducing gas, and the second step involves stopping the Ti compound gas and generating a second plasma while simultaneously introducing a reducing gas. The document states that by repeating these steps, the reduction effect of the Ti compound is enhanced, the concentration of residues in the film is reduced, and a good film with low resistivity is obtained.

[0005] On the other hand, none of these patent documents 1 and 2 disclose a film-forming method that takes into account the impact of the metal film forming process on the lower layer of the substrate to be processed.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2023-55111

[0009] Patent Document 2: Japanese Patent Application Publication No. 2004-232080 Summary of the Invention

[0010] The problem the invention aims to solve

[0011] This disclosure provides a technique for forming a metal film while suppressing the influence on the semiconductor layer exposed on the bottom surface of the recess.

[0012] Solution for solving the problem

[0013] This disclosure discloses a method for forming a metal film, used to form a metal film in a recess formed on the surface of a substrate, the method comprising the following steps:

[0014] A metal raw material gas containing the metal is supplied to the substrate on the bottom surface of the recess, where a semiconductor layer containing a dopant is exposed.

[0015] In parallel with the process of supplying the metal raw material gas, a reaction gas for reacting with the metal raw material gas to obtain the metal film is continuously supplied to the substrate; and

[0016] High-frequency electricity is continuously applied to the space in which the metal raw material gas and the reactant gas flow to plasmaize the metal raw material gas and the reactant gas.

[0017] The process of supplying the metal raw material gas includes:

[0018] The first step involves continuously supplying the metal raw material gas; and

[0019] The second step involves alternately and repeatedly supplying and stopping the metal raw material gas after the first step has been performed.

[0020] Invention Effects

[0021] According to this disclosure, a metal film can be formed while suppressing the influence on the semiconductor layer exposed on the bottom surface of the recess. Attached Figure Description

[0022] Figure 1 This is an enlarged longitudinal cross-sectional view of the area near the surface of the wafer where the Ti film is formed.

[0023] Figure 2 It is a timeline related to the gas supply during Ti film formation in the existing method.

[0024] Figure 3 This is a photograph of the surface of a wafer on which a Ti film has been formed using existing methods.

[0025] Figure 4 This is an illustrative diagram showing the characteristics of a Ti film formed by conventional methods.

[0026] Figure 5 This is a time graph related to the gas supply during Ti film formation in the improved method.

[0027] Figure 6 This is an explanatory diagram showing the characteristics of the Ti film formed through the improved method.

[0028] Figure 7 This is an explanatory diagram showing the resistivity characteristics of Ti films formed by different methods.

[0029] Figure 8 This is a timeline related to the gas supply during Ti film formation in the first verification method.

[0030] Figure 9 is a timing diagram related to gas supply during Ti film formation in the second verification mode.

[0031] Figure 10A is a schematic diagram showing the region near the surface of the silicon layer exposed at the bottom surface of the recess.

[0032] Figure 10B is an explanatory diagram showing the effect of hydrogen plasma on the dopant contained in the silicon layer.

[0033] Figure 11A is an explanatory diagram showing a state after a boron concentration-reduced region is formed in the silicon layer.

[0034] Figure 11B is an explanatory diagram showing a state after a boron-deficient region is formed in the silicon layer.

[0035] Figure 12 is an explanatory diagram showing the boron concentration distribution in the silicon layer.

[0036] Figure 13 is a timing diagram related to gas supply during Ti film formation in the present embodiment.

[0037] Figure 14 is a longitudinal side view showing a structural example of a film forming apparatus for forming a Ti film.

[0038] Figure 15 is an explanatory diagram showing the influence of the pressure during film formation on the selectivity of Ti film formation at the bottom surface / side wall surface of the recess. DETAILED DESCRIPTION OF EMBODIMENTS

[0039] <Formation of Ti Film>

[0040] First, refer to Figure 1 to describe a structural example of a substrate to which the metal film forming method according to the embodiment is applied. In the following example, a case where a titanium (Ti) film 61 is formed as the metal film will be described.

[0041] Figure 1 schematically shows the structure of the region near the surface of the wafer W of the substrate that is the target for forming the Ti film 61. A silicon layer 64 is formed on the surface of the wafer W. The silicon layer 64 is a semiconductor layer containing a dopant for forming carriers, and the surface of the silicon layer 64 is covered by a SiO₂ layer 63 as an insulating film. A recess 60 on which the Ti film 61 is to be formed is provided in the SiO₂ layer 63.

[0042] The recess 60 is configured as a contact hole with an opening diameter of, for example, 40 nm in the range of 30 nm to 50 nm and a depth of 120 nm in the range of 90 nm to 200 nm. A TiN film 62, serving as a barrier film to inhibit the diffusion of metal (e.g., Ti) into the SiO2 layer 63, may also be formed on the sidewall of the recess 60. The surface of the underlying silicon layer 64 is exposed on the bottom surface of the recess 60.

[0043] Conventionally, Ti films 61 have been formed, for example, using plasma CVD (Chemical Vapor Deposition). In plasma CVD, a Ti feedstock gas (metal feedstock gas) and a reactant gas that reacts with the Ti feedstock gas are supplied, and a high-frequency electric current is applied to the space through which these gases flow. By applying the high-frequency electric current, the gases are plasma-generated to generate active species, and Ti is deposited in the recess 60 by reacting these active species, thus forming a Ti film 61.

[0044] Examples of Ti feedstock gases include titanium tetrachloride (TiCl4) gas containing chlorine atoms, and examples of hydrogen (H2) gas are examples of reactant gases. Additionally, argon (Ar) gas may be added to these gases to assist in plasma formation.

[0045] <Existing Methods and Problems>

[0046] Figure 2 A timeline is shown relating to the gas supply during the formation of the Ti film 61 in the conventional manner. (The following description...) Figure 2 , 5 In the time graphs for 8, 9, and 13, the horizontal axis represents time. The vertical axis uses "On" to indicate the supply of TiCl4 gas, H2 gas (including Ar gas, the same below), or the application of high-frequency power (RF), and "Off" to indicate the cessation of these gas supplies and the application of RF.

[0047] according to Figure 2 In the existing method, the timing diagram shows that the supply of TiCl4 gas and H2 gas to wafer W and the application of RF are started simultaneously. Moreover, after a specified time (e.g., 360 seconds), the supply of TiCl4 gas and H2 gas and the application of RF are stopped simultaneously.

[0048] In order to further suppress the impact on wafer W during the formation of Ti film 61, the inventors of this case studied reducing the processing temperature during the formation of Ti film 61, for example, at 450°C. A target processing temperature, for example, 400°C, can be exemplified in the range of 390°C to 410°C.

[0049] However, it is known that when the processing temperature is lowered, Figure 2 The existing method for forming the Ti film 61 described herein has the following two problems.

[0050] The first problem is that the Ti film 61 at the bottom surface of the recess 60 becomes too thin. In the recess 60, for example, where a contact hole is formed, it is desirable to form the film in a way that increases the thickness T2 of the Ti film 61 at the bottom surface, while preventing the thickness T1 of the film on the sidewalls from becoming excessively thick. However, as experimental results are shown in the comparative example described later, it is known that... Figure 2 When TiCl4 gas, H2 gas and RF are continuously supplied and applied in the recorded time chart, the film thickness T2 on the bottom surface becomes significantly thinner as the processing temperature decreases.

[0051] Next, as the second question, we can cite the reduction in membrane quality. Figure 3 This is an enlarged photograph of the surface of wafer W placed in an atmospheric atmosphere after a Ti film 61 was formed at a processing temperature of 400℃. According to... Figure 3 It was confirmed that a blackened, discolored area was formed on the surface of wafer W. When this area was visually examined on the actual wafer W, surface roughness and film expansion were observed.

[0052] Reference Figure 4 To explain the mechanism that is estimated to be the reason for the reduced film quality of such Ti film 61. Figure 4 (a) schematically shows the state during the formation of Ti film 61. Active species of TiCl4 obtained through RF-based plasma treatment react with active species of H2 to precipitate Ti, forming Ti film 61. At this point, when the processing temperature is lowered to 400°C, the reduction of TiCl4 by H2 does not progress sufficiently, and the amount of chlorine (Cl) remaining in Ti film 61 increases.

[0053] Figure 4 (a) schematically shows the state of Ti film 61 after the formation of Ti film 61 is completed and the wafer W is removed from the processed apparatus. Cl remaining in Ti film 61 readily combines with moisture in the atmosphere. As a result, Ti film 61 expands, causing uneven film thickness within the wafer W plane and a decrease in film quality. Furthermore, a portion of Ti film 61 that reacts with moisture in the atmosphere exhibits liquefaction and deliquescence. Moreover, the combination of Cl and H2O, and the hydrogen chloride (HCl) generated by the reaction of this combination, is corrosive and is a major cause of roughness caused by corrosion on the surface of Ti film 61. Based on this viewpoint, it can be said that TiCl4 gas contains atoms (Cl) that, if remaining in Ti film 61, react with moisture in the atmosphere to form corrosive substances.

[0054] <Improvement Methods and New Problems>

[0055] In addressing the two problems described above, the inventors believed that it was necessary to ensure sufficient time for the active species of TiCl4 to react with the active species of H2, and sufficient time for the residual Cl in the Ti film 61 to detach completely. Based on this viewpoint, alternative methods were used... Figure 2 The method described herein, which involves the continuous supply of TiCl4 gas and H2 gas and the application of RF, was investigated. Figure 5 The improved method is shown. In the improved method, while the supply of H2 gas and the application of RF are continuously performed, the supply and stopping of TiCl4 gas are alternately repeated.

[0056] When considering the setting of supply / stop time in the case of alternatingly repeating the supply and stop of TiCl4 gas, the supply time can be 6 seconds, which is in the range of 1 to 10 seconds, and the stop time can be 4 times the supply time, which is in the range of 1 to 5 times (in the case of a supply time of 6 seconds, the stop time is 24 seconds). Moreover, these supply / stop cycles are repeated in such a way that the cumulative value of the TiCl4 gas supply time reaches a preset target value (240 seconds in the embodiment described later).

[0057] By setting the period for stopping the supply of TiCl4 gas in this way, H2 gas is sufficiently distributed to the bottom surface of the recess 60, and the reaction time between the active species of TiCl4 and the active species of H2 is ensured. As a result, as shown in the embodiments described later, it can be confirmed that... Figure 2 Compared to the time-mapping pattern, the selectivity of Ti film 61 formation on the bottom surface of the concave portion 60 is higher.

[0058] In addition, by ensuring sufficient reaction time between the active species of TiCl4 and the active species of H2, such as Figure 6 As schematically shown in (a), the active species of H2 formed by plasma (hereinafter also referred to as "plasmized H2 gas") comes into contact with the Ti film 61, thereby releasing Cl atoms that generate HCl, which is the corrosive substance. As a result, the amount of Cl remaining in the Ti film 61 is reduced, and the amount of H2O taken into the Ti film 61 can be suppressed. By suppressing the amount of H2O taken into the Ti film 61, the expansion of the Ti film 61 can be suppressed, thus maintaining the uniformity of the film thickness within the W plane of the wafer, suppressing the deliquescence of a portion of the Ti film 61, and suppressing the occurrence of surface roughness of the Ti film 61 with the release of HCl. Figure 6 (b)

[0059] As explained above, based on Figure 5The time-mapping method for forming the Ti film 61 shown can improve the selectivity of Ti film 61 formation at the bottom surface of the recess 60 and improve the film quality. On the other hand, new problems arise that lead to the following description.

[0060] Figure 7 This is a chart comparing the resistivity characteristics of wafer W with a Ti film 61 formed under various variations in the TiCl4 supply method. The resistivity characteristics of wafer W were determined by measuring the contact resistance ρc of wafer W along the thickness direction of the Ti film 61 using the Kelvin method and comparing the values ​​of the contact resistance at the 50% film thickness position. As described later, the heating temperature (processing temperature) of wafer W during Ti film 61 formation was uniformly 400°C, and the processing pressure was uniformly 133.3 Pa (1 Torr).

[0061] exist Figure 7 In the chart, through Figure 2 The contact resistance value of the wafer W with Ti film 61 formed by the existing method shown is (1). Additionally, through... Figure 5 The improved method of alternating supply / stop of TiCl4 gas, as shown, forms a Ti film 61 on wafer W with a contact resistance value of (4). Next, (2) is as follows... Figure 8 (First verification method) shows that after only 750 seconds of H2 gas supply and RF application, the following was achieved: Figure 2 The contact resistance value of wafer W is shown in the case where the Ti film 61 is formed using the existing method. Furthermore, (5) is as follows... Figure 9 (Second verification method) shows that after passing Figure 2 The contact resistance value of wafer W after forming Ti film 61 in the conventional manner is shown under the condition of H2 gas supply for only 750 seconds and RF application. In addition, the method for forming Ti film 61 related to (3) is described later.

[0062] Here, when comparing the existing method (1) with the improved method (4), the contact resistance value of the improved method of forming Ti film 61 by repeatedly supplying / stopping TiCl4 gas increases. This result is not limited to the location of 50% of the film thickness of Ti film 61, but shows the same tendency throughout the entire Ti film 61.

[0063] Furthermore, observing other film formation methods, in verification method (2) which involves only H2 gas supply and RF application before the formation of Ti film 61, the contact resistance value of wafer W deteriorates significantly. On the other hand, in verification method (5) which involves only H2 gas supply and RF application after the formation of Ti film 61, the contact resistance value of wafer W is almost the same as that of the existing method.

[0064] When comparing the resistance characteristics of these wafers W with Ti films 61 formed by different methods, it can be confirmed that they are based on... Figure 8 The time map shows that the contact resistance value of (2) related to the first verification method of Ti film 61 is significantly high. In the first verification method, H2 gas supply and RF application are performed before the formation of Ti film 61, and the wafer W in the state not covered by Ti film 61 is directly exposed to plasma-generated H2 gas.

[0065] On the other hand, compared with based on Figure 9 The time-mapping diagram formed the second verification method of Ti film 61, and the contact resistance value of (5) related to the formation was the same as that of the second verification method. Figure 2 Compared to Ti film 61 (1) in the existing method shown, no significant increase in contact resistance value was confirmed.

[0066] Based on the large differences in contact resistance values ​​caused by the different timing of H2 gas supply and RF application ((2): before the formation of Ti film 61, (5): after the formation of Ti film 61), the reasons for the deterioration of resistance characteristics are estimated as follows.

[0067] Here, in the case that the silicon layer 64 of wafer W is a p-type semiconductor, it contains a group III element (e.g., boron (B), indium (In), gallium (Ga)) as a dopant, acting as an impurity. In the case that it is an n-type semiconductor, it contains a group V element (e.g., phosphorus (P), arsenic (As), antimony (Sb)) as a dopant, acting as an impurity. In these cases, the silicon layer 64 can be, for example, a structure in which a SiGe region containing approximately 30 at% to 50 at% Ga in silicon contains dopants other than Ga. Below, as... Figure 10A The diagram illustrates an example where a boron-containing region 65, containing boron as a dopant, is formed in the vicinity of the surface of wafer W. Figure 1 In the example shown, the boron-containing region 65 is exposed on the bottom surface of the recess 60 before the Ti film 61 is formed.

[0068] Consider the wafer W in its state before being covered by the Ti film 61 and with the boron-containing region 65 exposed. Figure 11B The diagram illustrates the application of RF to supply plasma-generated H2 gas. For clarity, in... Figure 10B In this context, the state of the H2 gas supplied for plasmaization is recorded as "H2+RF".

[0069] The plasma-enhanced H2 gas is highly reactive. On the other hand, no plasma-enhanced TiCl4 is supplied to the wafer W, thus preventing the reaction that forms the Ti film 61 from progressing. Therefore, the plasma-enhanced H2 directly acts on the boron-containing region 65, and a portion of it propels the reaction that causes boron to detach from the boron-containing region 65.

[0070] The result, such as Figure 11A As shown, a low boron concentration reduction region 65a is formed on the surface of wafer W, or as... Figure 11B As shown, a portion of the exposed area on the surface of wafer W forms a missing region 65b that contains almost no boron. Moreover, the presence of these reduced concentration regions 65a and missing regions 65b is the main reason for the increase in the contact resistance of wafer W on which the Ti film 61 is formed.

[0071] Figure 12 To verify the above estimation mechanism, the concentration distribution of B, which is a dopant, was measured along the depth direction of wafer W before and after treatment with plasma-generated H2 gas. The concentration analysis of B was performed using secondary ion mass spectrometry (SIMS). Boron-containing region 65 is formed in the SiGe region. Before the treatment with plasma-generated H2 gas, wafer W underwent a COR (Chemical Oxide Removal) treatment, which involved supplying hydrofluoric acid (HF) and ammonia (NH3) gas to remove the silicon oxide film.

[0072] Figure 12 The horizontal axis represents the depth of wafer W from the surface, and the vertical axis is the logarithmic representation of the boron number concentration. Figure 7 The dashed lines represent the boron concentration distribution on wafer W before processing, while the solid lines represent the boron concentration distribution after processing with plasma-generated H2 gas. Furthermore, before and after the COR processing, the concentration changes are almost identical to those before processing, except for a slight decrease in the B concentration in the region near the surface of wafer W (approximately 0.1 nm to 0.3 nm), and therefore are omitted from the illustration.

[0073] according to Figure 12 The results shown, spanning the entire depth range measured, exhibit a tendency for a decrease in boron concentration after treatment compared to before treatment with plasma-generated H2 gas. In particular, regions with significantly reduced boron concentrations after treatment were confirmed within a depth range of approximately 0.5 nm to 2.0 nm. This indicates that... Figure 11A The low boron concentration region 65a shown is formed near the surface of wafer W.

[0074] As studied above, if plasma-generated H2 gas is supplied to the wafer W uncovered by the Ti film 61, the dopant is released, potentially leading to a deterioration in resistivity. This is considered to be related to the development of... Figure 5The same tendency is also shown in the case of Ti film 61 formation in the time diagram. That is, due to the repeated supply and stop of TiCl4 gas for short periods of time, plasma-enhanced H2 is supplied to the wafer W where Ti film 61 is not sufficiently formed. As a result, although no significant increase in contact resistance was found to the extent of (2) when plasma-enhanced H2 was supplied to the wafer W where Ti film 61 was not formed at all, it is considered that the contact resistance value of (4) is higher than that of the existing method of (1).

[0075] Based on the estimation mechanism described above, such as Figure 10B As shown, due to the supply of plasma-generated H2 gas to the boron-containing region 65 exposed on the surface of wafer W, the dopant is released, and the resistance characteristics deteriorate. Therefore, it is believed that if the surface of the boron-containing region 65 is covered by a Ti film 61, the deterioration of resistance characteristics caused by the release of dopant can be suppressed. However, based on a film suitable for low-temperature film deposition... Figure 5 During the formation of the Ti film 61 in the time-mapping diagram, due to the short supply time of TiCl4 gas in each period, the surface of the boron-containing region 65 is in contact with plasma-generated H2 gas before being covered by the Ti film 61.

[0076] <Method for forming Ti film according to the embodiments>

[0077] Based on these problems, the inventors in this case designed, as follows Figure 13 The method shown divides the TiCl4 gas supply process (the process of supplying the metal raw material gas) into two steps. In this method, TiCl4 gas is continuously supplied in the first step, so that the surface of the boron-containing region 65 is covered with a Ti film 61. In the second step, the supply and stop of TiCl4 gas are alternately repeated, thereby forming a Ti film 61 with high selectivity and good film quality for the bottom surface of the recess 60.

[0078] On the other hand, the supply of H2 gas and the application of RF are carried out in parallel and continuously with the implementation of the first and second processes, just like in the existing methods (the process of continuously supplying the reaction gas and the process of continuously applying high-frequency electricity).

[0079] In the first step, TiCl4 gas is continuously supplied for, for example, 30 to 120 seconds, to form a Ti film 61 covering the boron-containing region 65 on the wafer W. If the TiCl4 gas supply time in the first step is less than 30 seconds, it is possible to supply only plasma-enhanced H2 for an extended period of time while the Ti film 61 is not sufficiently formed. Furthermore, if the TiCl4 gas supply time in the first step exceeds 120 seconds, the period for forming the Ti film 61 using the same method as in existing processes becomes longer, making it difficult to achieve the effect of improving selectivity for the bottom surface of the recess 60 and forming a Ti film 61 with good film quality.

[0080] In addition, in the second process, in order to use Figure 5 The Ti film 61 is formed using almost the same method as described in the time diagram. That is, the supply time of TiCl4 gas can be 6 seconds, which is in the range of 1 to 10 seconds, and the stop time can be 4 times the supply time, which is in the range of 1 to 5 times (when the supply time is 6 seconds, the stop time is 24 seconds). Moreover, these supply / stop cycles are repeated in such a way that the cumulative value of the TiCl4 gas supply time for the entire first and second processes reaches a predetermined target value (240 seconds in the embodiment described later).

[0081] In the formation of the Ti film 61, including these first and second processes, the processing temperature (the heating temperature of the wafer W) is set, for example, to 410°C within the range of 390°C to 410°C. Furthermore, as shown in the embodiments described later, regarding the formation of the Ti film 61, when the processing pressure is reduced, there is a tendency for increased selectivity in the formation of the Ti film 61 towards the bottom surface of the recess 60. Based on this viewpoint, based on... Figure 13 The formation of Ti film 61 in the time diagram shown can be illustrated under pressure conditions in the range of 106.7 Pa to 200 Pa (0.8 Torr to 1.5 Torr).

[0082] Based on the above-described method for forming Ti film 61, based on Figure 13 The time-mapping diagram shown indicates that Ti film 61 was formed, and the contact resistance at the location where the film thickness is 50% becomes... Figure 7 The value shown in (3) is equivalent to the resistance characteristics of Ti film 61 formed based on the time diagram of the existing method.

[0083] Here, the formation conditions of Ti film 61 related to (3) are: processing temperature 400°C, processing pressure 133.3 Pa (1 Torr), first process duration 80 seconds, TiCl4 gas supply time in the second process 6 seconds, TiCl4 gas stop time 24 seconds (4 times the supply time), and TiCl4 gas supply / stop repetition 50 times. Therefore, the cumulative value of TiCl4 gas supply time obtained by combining the first and second periods is 240 seconds.

[0084] <Film Forming Device>

[0085] An example of the structure of the apparatus (film forming apparatus 1) used to implement the method for forming Ti film 61 according to the present embodiment described above will be described. Figure 14 This is a longitudinal side view of the film-forming apparatus 1 in this example. The film-forming apparatus 1 is configured based on the use of... Figure 13 The timeline described describes an apparatus for supplying TiCl4 gas and H2 gas to the surface of wafer W, and forming a Ti film 61 by plasma CVD.

[0086] The film-forming apparatus 1 includes a generally cylindrical processing container 10 made of grounded metal that is resistant to chlorine corrosion. Wafer W is processed within the space of this processing container 10. A cylindrical exhaust chamber 11, protruding downwards, is formed at the center of the bottom surface of the processing container 10, and an exhaust passage 12 is connected to the side of the exhaust chamber 11. A vacuum exhaust section 13, including a pressure regulating valve such as a butterfly valve, is connected to the exhaust passage 12, configured to reduce the pressure inside the processing container 10 to a preset vacuum pressure (e.g., 106.7 Pa to 200 Pa (0.8 Torr to 1.5 Torr) as described above). The exhaust passage 12 and the vacuum exhaust section 13 correspond to the pressure regulating section in this example.

[0087] A loading / unloading outlet 14 is formed on the side of the processing container 10 for loading and unloading wafer W between it and a vacuum transfer chamber (not shown). This loading / unloading outlet 14 is configured to be freely opened and closed by a gate valve 15. Furthermore, a heater 16 for regulating the temperature of the processing container 10 is embedded in the wall of the processing container 10.

[0088] Additionally, a stage 2 for holding the wafer W approximately horizontally is provided within the processing container 10. The stage 2 is supported by a support portion 21 extending from the bottom of the exhaust chamber 11. A heater 20, serving as a heating element, is embedded in the stage 2, capable of heating the wafer W to a set temperature. In this example, the heating temperature of the wafer W is set to, for example, 400°C, within the range of 390°C to 410°C.

[0089] Furthermore, the stage 2 is connected to a high-frequency power supply 23, which supplies high-frequency power for attracting ions, via a matching device 22. The stage 2 is also equipped with a lifting pin (not shown) for holding and raising / lowering the wafer W on the stage 2. By raising and lowering the lifting pin, the wafer W can be transferred between the stage 2 and an external (not shown) transport mechanism.

[0090] Additionally, a disc-shaped, flat spray head 3 for supplying substrate processing gas to the wafer W is provided on the top surface of the processing container 10. The spray head 3 is mounted to the processing container 10 via an insulating member 17.

[0091] A diffusion chamber 31 for gas diffusion is formed inside the spray head 3. Additionally, a large number of ejection holes 32 for ejecting gas onto the wafer W are distributed on the bottom surface of the spray head 3. Furthermore, a heater 35 is embedded on the upper surface of the spray head 3.

[0092] The aforementioned spray head 3 is connected to a high-frequency power supply 34, which supplies high-frequency power for plasma formation, via a matching device 33. That is, the film formation apparatus 1 of this disclosure comprises a parallel-plate type plasma processing apparatus consisting of a spray head 3 forming an upper electrode and a mounting stage 2 forming a lower electrode. A wafer W is placed in the space between these spray heads 3 and the mounting stage 2, and TiCl4 gas, H2 gas, etc., are supplied and high-frequency power is applied, thereby ionizing these gases to form plasma.

[0093] The high-frequency power supply 34 can be configured to supply high-frequency power at any of the following frequencies: 450 kHz, 13.56 MHz, 915 MHz, or 2.45 GHz. Additionally, high-frequency power of up to 300 W, within the range of 0 W to 2000 W, can be supplied from the high-frequency power supply 34. The high-frequency power supply 34 corresponds to the high-frequency power supply unit in this example.

[0094] Additionally, a downstream end of a gas supply path 40 is connected to the diffusion chamber 31 of the spray head 3. Upstream of this gas supply path 40, a TiCl4 gas supply pipe 41 and an H2 gas supply pipe 43 merge. The TiCl4 gas supply pipe 41 is a flow path for supplying TiCl4 gas, which serves as the titanium raw material gas, and the H2 gas supply pipe 43 is a flow path for supplying H2 gas, which serves as the reaction gas. Furthermore, an Ar gas supply pipe 42 is connected to the gas supply path 40; this Ar gas supply pipe 42 is a flow path for supplying Ar gas added to generate plasma.

[0095] A TiCl4 gas supply source 410 is connected to the upstream end of the TiCl4 gas supply pipe 41, and a flow regulating unit M41 and a valve V41 (raw material gas supply unit) are sequentially arranged from the upstream side. Similarly, an Ar gas supply source 420 is connected to the upstream end of the Ar gas supply pipe 42, and a flow regulating unit M42 and a valve V42 are sequentially arranged from the upstream side. Furthermore, an H2 gas supply source 430 is connected to the upstream end of the H2 gas supply pipe 43, and a flow regulating unit M43 and a valve V43 (reaction gas supply unit) are sequentially arranged from the upstream side.

[0096] These TiCl4 gas, H2 gas and Ar gas flow into the diffusion chamber 31 of the spray head 3 in a mixed state through the gas supply path 40, and are supplied into the processing container 10 through the spray hole 32.

[0097] like Figure 3 As shown, the film-forming apparatus 1 with the above-described structure includes a control unit 100. The control unit 100 is composed of a computer including a storage unit storing a program, a memory, and a CPU. The program is programmed with commands (steps) to execute each step of forming the Ti film 61 by outputting control signals from the control unit 100 to each part of the film-forming apparatus 1, thereby controlling the supply of each gas and the supply of high-frequency power. The program is stored in the computer's storage unit, such as a floppy disk, optical disk, hard disk, MO (optical disk), or non-volatile memory, and is read from this storage unit and installed in the control unit 100.

[0098] <Function of film-forming device>

[0099] The function of the film-forming apparatus 1 with the structure described above will be explained.

[0100] First, the gate valve 15 is opened, and the wafer W is transported into the vacuum transport chamber via the inlet / outlet 14 by a transport mechanism (not shown). The transported wafer W is transferred from the transport mechanism to the mounting stage 2 via a lifting pin (not shown), and placed on the upper surface of the mounting stage 2. Next, the transport mechanism is retracted from the processing container 10, the gate valve 15 is closed, and the vacuum exhaust section 13 performs vacuum exhaust in the processing container 10, adjusting the pressure inside the processing container 10 to a preset level. Additionally, the heater 20 heats the wafer W to the previously described 400°C.

[0101] Then, based on Figure 13The timeline shown illustrates the first step, which involves the continuous supply of H2 gas, the application of RF, and the continuous supply of TiCl4 gas. After this first step, which lasts for a predetermined time, the process switches to a second step, where the supply of TiCl4 gas is alternately supplied and stopped. During this second step, the continuous supply of H2 gas and the application of RF continue. Furthermore, in this example, AR gas is also continuously supplied during the application of RF, and the supply of AR gas stops when the application of RF is stopped.

[0102] By following this method Figure 13 The timeline shown illustrates the execution of the first and second processes, forming a Ti film 61 of a predetermined thickness. Next, the supply of TiCl4 gas and H2 gas is stopped, and the application of RF is terminated; heating of wafer W also ceases. Afterward, wafer W is removed from the processing container 10 in the reverse process of wafer loading, awaiting the loading of the next wafer W.

[0103] <Effect>

[0104] According to the embodiment described above, the following effects are achieved. The TiCl4 gas supply process, which serves as the Ti raw material gas, is divided into two steps. In the first step, TiCl4 gas is continuously supplied. As a result, the release of boron (B) as a dopant from the boron-containing region 65 due to exposure to plasma-generated H2 gas alone can be suppressed, and the surface of the boron-containing region 65 is covered by a Ti film 61. Next, by performing a second step of alternately repeating the supply / stop of TiCl4 gas, a Ti film 61 with high selectivity and good film quality for the bottom surface of the recess 60 is formed. Thus, the Ti film 61 can be formed while suppressing the influence on the silicon layer 64 exposed on the bottom surface of the recess 60.

[0105] <Variation Example>

[0106] In the above embodiments, the case where Ti film 61 is formed as a metal film has been described, but based on Figure 13 The timeline for the metal film formed by supplying the metal feedstock gas is not limited to this. For example, it can also be applied to the formation of tungsten films (W films) using tungsten hexafluoride (WF6) gas or tungsten pentachloride (WCl5). The halogen (fluorine, chlorine) atoms contained in these tungsten feedstock gases (W feedstock gases) can also be atoms that react with moisture in the atmosphere to form corrosive substances (HF, HCl).

[0107] The embodiments disclosed herein should be considered illustrative rather than restrictive in all respects. The above embodiments may be omitted, substituted, or modified in various ways without departing from the appended claims and their spirit.

[0108] Example

[0109] (Experiment 1)

[0110] based on Figure 5 The timeline involved in the improvement method shown (equivalent to) Figure 13 The second step of the timeline involved in the implementation method) and Figure 2 The time-map involved in the existing method shown forms Ti film 61, and the selectivity of film formation is confirmed.

[0111] A. Experimental conditions

[0112] (Example 1) Based on Figure 5 The recorded timeline shows that a Ti film 61 was formed on a wafer W with a recess 60 having an opening diameter of 40 nm and a depth of 120 nm. The processing temperature was 400 °C, and the processing pressure was 133 Pa (1 Torr). Furthermore, the supply time of TiCl4 gas for one cycle was set to 6 seconds, and the stop time was set to 24 seconds, and this was performed 40 times (the cumulative supply time of TiCl4 gas was 240 seconds).

[0113] (Comparative Example 1) Based on Figure 2 The timeline shown is for a Ti film 61 formed on the same wafer W as in Example 1. The processing temperature was 400°C, and the processing pressure was 1200 Pa (9 Torr). Additionally, the TiCl4 gas was continuously supplied for 360 seconds.

[0114] (Refer to Example 1) Except that the processing temperature was set to 450°C, a Ti film 61 was formed under the same conditions as in Comparative Example 1.

[0115] B. Experimental Results

[0116] Regarding Example 1, Comparative Example 1, and Reference Example 1, the film thicknesses of the Ti films 61 formed on the sidewall and bottom surfaces of the recess 60 are shown in Table 1. Furthermore, regarding the TiCl4 gas supply time in Table 1, the cumulative value of the supply time is shown for Example 1, and the continuous supply time is shown for Comparative Example 1 and Reference Example 1.

[0117] (Table 1)

[0118]

[0119] According to the results shown in Table 1, compared with Reference Example 1, although Example 1 had a lower processing temperature and pressure and a shorter TiCl4 gas supply time, the Ti film 61 formed on the bottom surface of the recess 60 was thicker. On the other hand, the Ti film 61 formed on the sidewall surface of the recess 60 in Example 1 and Reference Example 1 were almost the same thickness. Therefore, it can be confirmed that Example 1 is a method for forming a Ti film 61 with high selectivity for the bottom surface of the recess 60.

[0120] In contrast, in Comparative Example 1, where only the processing temperature was reduced from the Ti film 61 formation conditions in the Reference Example, the film thickness on the bottom surface of the recess 60 became thinner as the processing temperature decreased.

[0121] (Experiment 2)

[0122] The pressure conditions for forming the Ti film 61 were varied, and the selectivity of film formation on the sidewall / bottom surface of the recess 60 was confirmed.

[0123] A. Experimental conditions

[0124] (Example 2-1) The processing pressure was set to 200 Pa (1.5 Torr), and the number of repetitions of supplying TiCl4 gas for 2 seconds and stopping for 1 second was changed to 140 times, 120 times, and 100 times (the cumulative value of TiCl4 gas supply time was 280 seconds, 240 seconds, and 200 seconds) to form Ti film 61.

[0125] (Example 2-2) Except that the processing pressure was set to 133 Pa (1.0 Torr), a Ti film 61 was formed under the same conditions as in Example 2-1.

[0126] (Examples 2-3) Except that the processing pressure was set to 107 Pa (0.8 Torr), Ti film 61 was formed under the same conditions as in Example 2-1.

[0127] B. Experimental Results

[0128] The results of Examples 2-1 to 2-3 are shown in Figure 15 . Figure 15 The horizontal axis represents the film thickness of the Ti film 61 on the bottom side of the recess 60, and the vertical axis represents the film thickness on the sidewall side. The results of Example 2-1 (processing pressure 200 Pa) are represented by plot points marked with crosses, the results of Example 2-2 (same as 133 Pa) are represented by plot points marked with hollow triangles, and the results of Example 2-3 (same as 107 Pa) are represented by plot points marked with hollow circles.

[0129] Based on these results, regarding the film thickness of Ti film 61, it can be confirmed that as the processing pressure decreases, the film thickness selectively changes in the direction that the film thickness on the bottom side becomes thicker than the film thickness on the sidewall side of the recess 60.

[0130] Explanation of reference numerals in the attached figures

[0131] W: Wafer

[0132] 1: Film forming device

[0133] 10: Handling Containers

[0134] 2: Platform

[0135] 3: Spray head

[0136] 34: High-frequency power supply

[0137] 410: TiCl4 gas supply source

[0138] 430: H2 gas supply source

[0139] 60: Concave

[0140] 61: Ti film

Claims

1. A method for forming a metal film, used to form a metal film in a recess formed on the surface of a substrate, the method comprising the following steps: A metal raw material gas containing the metal is supplied to the substrate on the bottom surface of the recess, where a semiconductor layer containing a dopant is exposed. In parallel with the process of supplying the metal raw material gas, a reaction gas for reacting with the metal raw material gas to obtain the metal film is continuously supplied to the substrate; and High-frequency electricity is continuously applied to the space in which the metal raw material gas and the reactant gas flow to plasmaize the metal raw material gas and the reactant gas. The process of supplying the metal raw material gas includes: The first step involves continuously supplying the metal raw material gas. as well as The second step involves alternately and repeatedly supplying and stopping the metal raw material gas after the first step has been performed.

2. The method for forming a metal film according to claim 1, wherein, The metal raw material gas contains atoms that, if remaining in the metal film, would react with moisture in the atmosphere to generate a corrosive substance. In the second step, during the period when the supply of the metal raw material gas is stopped, the metal film comes into contact with the plasma-enhanced reactive gas, thereby releasing the atoms that generate the corrosive substance.

3. The method for forming a metal film according to claim 1, wherein, In the first step, the continuous supply period of the metal raw material gas is in the range of 30 seconds to 120 seconds. In the second step, the following cycle is repeated: the supply of the metal raw material gas is carried out for a period of 1 second to 10 seconds, and the supply of the metal raw material gas is stopped for a period of 1 to 5 times the supply time of the metal raw material gas in the second step.

4. The method for forming a metal film according to claim 1, wherein, The metal film is a titanium film, the metal raw material gas is titanium tetrachloride, and the reaction gas is hydrogen.

5. The method for forming a metal film according to claim 4, wherein, The semiconductor layer is a silicon layer containing boron as the dopant.

6. The method for forming a metal film according to claim 1, wherein, The metal film is formed at a temperature range of 390°C to 410°C.

7. The method for forming a metal film according to claim 1, wherein, The metal film is formed under pressure conditions ranging from 106.7 Pa to 200 Pa.

8. A metal film forming apparatus for forming a metal film in a recess formed on the surface of a substrate, the metal film forming apparatus comprising: A processing container that houses the substrate on the bottom surface of the recess, where a semiconductor layer containing dopant is exposed. A raw material gas supply unit supplies a metallic raw material gas containing the metal to the processing container; A reaction gas supply unit supplies the processing container with reaction gas for reacting with the metal raw material gas to obtain the metal film. A high-frequency power supply unit is used to apply high-frequency power to the space where the metal raw material gas and the reactant gas flow; and Control Department in, The control unit is configured to perform the following steps: supplying a metal raw material gas containing the metal to the substrate within the processing container; continuously supplying a reaction gas to the substrate for reacting with the metal raw material gas to obtain the metal film, in parallel with the process of supplying the metal raw material gas; and applying the high-frequency power to plasmaize the metal raw material gas and the reaction gas. In the step of supplying the metal raw material gas, the control unit outputs control signals for performing a first step and a second step, wherein the first step is a step of continuously supplying the metal raw material gas, and the second step is a step of alternately repeating the supply and cessation of the metal raw material gas after performing the first step.

9. The metal film forming apparatus according to claim 8, wherein, The metal feedstock gas contains atoms that, if remaining in the metal film, would react with atmospheric moisture to generate a corrosive substance. In the second step, during the period when the supply of the metal feedstock gas is stopped, the metal film comes into contact with the plasma-enhanced reactive gas, thereby releasing the atoms that generate the corrosive substance.

10. The metal film forming apparatus according to claim 8, wherein, In the first step, the continuous supply period of the metal raw material gas is in the range of 30 seconds to 120 seconds. In the second step, the following cycle is repeated: the supply of the metal raw material gas is carried out for a period of 1 second to 10 seconds, and the supply of the metal raw material gas is stopped for a period of 1 to 5 times the supply time of the metal raw material gas in the second step.

11. The metal film forming apparatus according to claim 8, wherein, The metal film is a titanium film, the metal raw material gas is titanium tetrachloride, and the reaction gas is hydrogen.

12. The metal film forming apparatus according to claim 11, wherein, The semiconductor layer is a silicon layer containing boron as the dopant.

13. The metal film forming apparatus according to claim 8, wherein, The device includes a heating element that heats the substrate during the formation of the metal film, thereby bringing the substrate to a temperature within the range of 390°C to 410°C.

14. The metal film forming apparatus according to claim 8, wherein, The device includes a pressure regulating unit that regulates the pressure during the formation of the metal film so that the pressure inside the processing container is within the range of 106.7 Pa to 200 Pa.

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