Film forming method and film forming apparatus

Abstract

To achieve both improvements in embedding performance and in productivity when embedded into a recessed part using adsorption inhibition.SOLUTION: A film deposition method capable of depositing a film in a recessed part formed on the surface of a substrate comprises the steps of: supplying adsorption inhibition gas to the substrate to form an adsorption inhibition area; supplying silicon-containing gas to the substrate to adsorb the silicon-containing gas in an area except the adsorption inhibition area; and exposing the substrate to nitrogen-containing gas to react the substrate with the adsorbed silicon-containing gas and deposit a silicon nitride film. The step of adsorbing the silicon-containing gas comprises controlling the dose amount of the supplied silicon-containing gas to an amount equal to or more than the adsorption saturation content of the silicon-containing gas adsorbed on the substrate in which the adsorption inhibition area is not formed.SELECTED DRAWING: Figure 9

Description

[Technical field]

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

[0002] There is a demand for filling a film into a recess formed on a substrate without creating voids (vacant holes). However, due to the miniaturization and complexity of device structures, it is becoming more difficult to fill a film without creating voids. For example, if the side wall of a recess has a bowing shape, it is difficult to avoid the creation of voids in the film by simply depositing a film conformally to the recess.

[0003] Therefore, a method of controlling the shape of the film by using an adsorption inhibitor gas has been proposed (for example, Patent Document 1). In Patent Document 1, an adsorption inhibitor gas is adsorbed near the opening of the top part of the recess. This makes the GPC (Growth Per Cycle) of the top part of the recess smaller than the GPC of the bottom part of the recess, thereby suppressing deposition of the film near the opening of the top part and preventing blocking of the opening, and allowing the film to be filled in from the bottom up from the bottom of the recess. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-137369 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure provides a technique that can achieve both improved filling performance and improved productivity in filling recesses using adsorption inhibition. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, there is provided a film formation method for forming a film in a recess formed on a surface of a substrate, the film formation method comprising the steps of: supplying an adsorption-inhibiting gas to the substrate to form an adsorption-inhibiting region; supplying a silicon-containing gas to the substrate to adsorb the silicon-containing gas in a region other than the adsorption-inhibiting region; and exposing the substrate to a nitrogen-containing gas to react with the adsorbed silicon-containing gas to form a silicon nitride film, wherein the step of adsorbing the silicon-containing gas includes controlling a dose of the silicon-containing gas to be supplied to be equal to or greater than an adsorption saturation amount of the silicon-containing gas adsorbed to the substrate not forming the adsorption-inhibiting region. Effect of the Invention

[0007] According to one aspect, in filling a recess using adsorption inhibition, it is possible to achieve both improvement in filling performance and improvement in productivity. [Brief description of the drawings]

[0008] [Figure 1] 13A and 13B are diagrams showing evaluation results of embedding characteristics of a silicon nitride film according to a reference example. [Diagram 2] FIG. 1 is a schematic cross-sectional view showing an example of a film forming apparatus according to an embodiment. [Diagram 3] 3 is a flowchart showing an example of a film forming method according to an embodiment. [Figure 4] 3 is a flow chart showing an example of a process for forming the adsorption-inhibiting region in FIG. 2. [Diagram 5] FIG. 4 is a diagram for explaining an example of an adsorption saturation curve of a silicon-containing gas. [Figure 6] FIG. 13 is a graph showing the relationship between the dose of a silicon-containing gas and GPC depending on the pattern shape. [Figure 7] FIG. 13 is a graph showing an example of the relationship between the number of cycles and the dose amount. [Figure 8] FIG. 1 shows the experimental results of GPC of a silicon nitride film in the absence of adsorption inhibition. [Figure 9] FIG. 13 shows the results of a GPC experiment on a silicon nitride film when adsorption is inhibited. [Figure 10]FIG. 10 shows a GPC obtained by normalizing the evaluation results of FIG. 9 at position Z6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and duplicated descriptions may be omitted.

[0010] [Control of film shape using adsorption inhibitor gas] There is a film formation method that uses an adsorption inhibitor gas to control the shape of the film formed in order to fill the recessed portion formed on the substrate without generating voids (vacancies). For example, in the formation of silicon nitride film (SiN film) by the ALD (Atomic Layer Deposition) method, a silicon-containing gas such as dichlorosilane gas (DCS) is used as the source gas, and a nitrogen-containing gas such as ammonia gas (NH3) is used to nitride the silicon-containing gas. In this case, using chlorine gas (Cl2) as the adsorption inhibitor gas enables bottom-up film formation without generating voids.

[0011] An example of a film forming method using the ALD method will be described as a reference example. A silicon wafer is used as an example of the wafer W, and a trench is formed as a recess in the silicon wafer. The inside of the trench and the surface of the wafer W are made of, for example, silicon or an insulating film, and metal or a metal compound may be partially present.

[0012] In the reference example, chlorine gas is supplied to the wafer W. Chlorine gas is an example of an adsorption inhibition gas. Chlorine gas is adsorbed to the top and the vicinity of the top of the trench formed in the wafer W, and the amount of chlorine gas adsorbed is greater than the amount of chlorine gas adsorbed to the bottom and the vicinity of the bottom. Therefore, the inhibition effect is high at the top of the trench where the amount of chlorine gas adsorbed is large, and low at the bottom where the amount of chlorine gas adsorbed is small. In other words, the top of the trench becomes an adsorption inhibition region, and the bottom becomes a region other than the adsorption inhibition region. The adsorption inhibition region includes a region in the recess of the trench where the adsorption inhibition effect is relatively high, and the region other than the adsorption inhibition region includes a region in the recess where the adsorption inhibition effect is relatively low.

[0013] After forming the adsorption inhibition region with chlorine gas, the chlorine gas is purged. Next, a silicon-containing gas (e.g., DCS) is supplied as a silicon precursor to adsorb the silicon-containing gas into the trench, forming a silicon (Si)-containing layer. The silicon-containing gas is less likely to be adsorbed into the adsorption inhibition region, but is more likely to be adsorbed into regions other than the adsorption inhibition region. Therefore, the bottom of the trench has a greater amount of silicon-containing gas adsorbed than the upper portion.

[0014] Next, after purging the silicon-containing gas, a nitrogen-containing gas (e.g., ammonia gas) is supplied to nitride the silicon-containing layer with the nitrogen-containing gas, forming a silicon nitride film. This allows a silicon nitride film to be formed at the bottom of the trench that is thicker than the upper part. Next, after purging the nitrogen-containing gas, the process returns to the step of supplying chlorine gas to the substrate in which the trench is formed. The steps of supplying chlorine gas, purging chlorine gas, supplying silicon-containing gas, purging silicon-containing gas, supplying nitrogen-containing gas, and purging nitrogen-containing gas are repeated in this order to form a silicon nitride film at the atomic layer level. As a result, bottom-up film formation without voids is possible, improving filling performance.

[0015] The difference in the inhibitory effect of the adsorption inhibitor gas at the top and bottom of the trench can be shown by the difference in GPC (Growth Per Cycle) between the top and bottom. GPC is the amount of film formed per cycle of the ALD method. The larger the difference in GPC, the more difficult it becomes to fill trench structures such as fine trenches and bowing shapes.

[0016] FIG. 1 is a diagram showing the evaluation results of the embedding characteristics of the silicon nitride film in the trench according to the above-mentioned reference examples. Reference Examples 1 to 3 show the change in GPC according to the trench depth when the supply time (s) of the adsorption inhibitory gas is controlled to different values ​​in the adsorption inhibitory gas supply step. The gas dose (Langmuir) is a value indicated by the partial pressure of the gas x the supply time. For example, when the gas supply time is constant, the dose increases when the partial pressure of the gas is increased. Also, for example, when the gas partial pressure is constant, the dose increases when the gas supply time is extended. As a condition of this evaluation, the partial pressure of the adsorption inhibitory gas was controlled to the same pressure in all of Reference Examples 1 to 3. In addition, among Reference Examples 1 to 3, the dose of the adsorption inhibitory gas was increased in Reference Example 1 compared to the dose in Reference Example 2, and the dose was reduced the most in Reference Example 3.

[0017] In Fig. 1(a), among positions Z1 to Z7, position Z1 is the shallowest position, i.e., the upper position in the trench, and position Z7 is the deepest position, i.e., the bottom position in the trench. Fig. 1(b) shows the GPC normalized at position Z7 in all of Reference Examples 1 to 3 shown in Fig. 1(a).

[0018] As shown in FIG. 1(a), in all of Reference Examples 1 to 3, the GPC at the upper part of the trench (where the trench is shallow) is smaller than the GPC at the bottom part of the trench (where the trench is deep). From this result, in all of Reference Examples 1 to 3, the cross section of the silicon nitride film embedded in the trench could be controlled to a V shape. In other words, it was shown that a film with high bottom-up properties can be formed, and the embedding performance can be improved. In addition, as shown in FIG. 1(b), the more the dose of the adsorption inhibitor gas is increased, the larger the difference between the GPC at the upper part of the trench and the GPC at the bottom part of the trench becomes due to the adsorption inhibition of chlorine gas, and the embedding performance is improved.

[0019] From the above, the more the dose of the adsorption inhibitor gas is increased, the film thickness at the top of the trench is relatively lower than that at the bottom due to the adsorption inhibitor effect as shown in Figure 1(b), realizing film formation with high bottom-up effect, eliminating the occurrence of voids, and improving filling performance. On the other hand, the more the dose of the adsorption inhibitor gas is increased, the lower the GPC overall as shown in Figure 1(a), decreasing productivity. Thus, in the film formation method of the reference example, the challenge is a trade-off between the film shape and GPC, that is, achieving both filling performance and productivity.

[0020] Therefore, in this embodiment, a film formation method is provided that can improve both the filling performance and the productivity when filling a trench with an adsorption inhibitor gas. In the following, an example of the configuration of a film formation apparatus according to the embodiment is described, and then a film formation method according to the embodiment that can be performed using the film formation apparatus is described.

[0021] [Film forming equipment] An example of a film forming apparatus 10 according to an embodiment will be described with reference to Fig. 2. The film forming apparatus 10 includes a processing chamber 1, a mounting table 2, a shower head 3, an exhaust unit 4, a gas supply unit 5, an RF power supply unit 8, a control unit 9, and the like.

[0022] The processing vessel 1 is made of a metal such as aluminum and has a substantially cylindrical shape. The processing vessel 1 accommodates a wafer W, which is an example of a substrate. A loading / unloading port 11 is formed in a side wall of the processing vessel 1 for loading or unloading the wafer W. The loading / unloading port 11 is opened and closed by a gate valve 12. An annular exhaust duct 13 having a rectangular cross section is provided on the main body of the processing vessel 1. A slit 13a is formed along the inner peripheral surface of the exhaust duct 13. An exhaust port 13b is formed in the outer wall of the exhaust duct 13. A ceiling wall 14 is provided on the upper surface of the exhaust duct 13 so as to close the upper opening of the processing vessel 1 via an insulating member 16. A seal ring 15 is used to hermetically seal the space between the exhaust duct 13 and the insulating member 16. The partition member 17 partitions the inside of the processing vessel 1 into upper and lower sections when the mounting table 2 (and the cover member 22) is raised to a processing position described later.

[0023] The mounting table 2 horizontally supports the wafer W in the processing chamber 1. A support member 23 for supporting the mounting table 2 is provided on the bottom surface of the mounting table 2. The mounting table 2 is formed in a disk shape having a size corresponding to the wafer W, and is supported by the support member 23. The mounting table 2 is made of a ceramic material such as AlN or a metal material such as an aluminum or nickel alloy, and has a heater 21 embedded therein for heating the wafer W. The heater 21 generates heat when power is supplied from a heater power source (not shown). The output of the heater 21 is controlled by a temperature signal from a thermocouple (not shown) provided near the upper surface of the mounting table 2, thereby controlling the wafer W to a predetermined temperature. The mounting table 2 is provided with a cover member 22 made of ceramic such as alumina so as to cover the outer peripheral region of the upper surface and the side surfaces.

[0024] The support member 23 extends from the center of the bottom surface of the mounting table 2 through a hole formed in the bottom wall of the processing vessel 1 to below the processing vessel 1, and its lower end is connected to a lifting mechanism 24. The lifting mechanism 24 raises and lowers the mounting table 2 via the support member 23 between a processing position shown in FIG. 1 and a transfer position shown by a two-dot chain line below the processing position where the wafer W can be transferred. A flange 25 is attached to the support member 23 below the processing vessel 1. A bellows 26 is provided between the bottom surface of the processing vessel 1 and the flange 25. The bellows 26 separates the atmosphere inside the processing vessel 1 from the outside air, and expands and contracts in accordance with the lifting and lowering operation of the mounting table 2.

[0025] Three wafer support pins 27 (only two shown) are provided near the bottom surface of the processing vessel 1 so as to protrude upward from a lift plate 27a. The wafer support pins 27 are raised and lowered via the lift plate 27a by a lift mechanism 28 provided below the processing vessel 1. The wafer support pins 27 are inserted into through holes 2a provided in the mounting table 2 at the transfer position, and can be protruded and retracted from the upper surface of the mounting table 2. The wafer W is transferred between the transfer mechanism (not shown) and the mounting table 2 by raising and lowering the wafer support pins 27.

[0026] The shower head 3 supplies a processing gas into the processing vessel 1 in a shower-like manner. The shower head 3 is made of metal, is provided to face the mounting table 2, and has approximately the same diameter as the mounting table 2. The shower head 3 includes a main body 31, a shower plate 32, and the like. The main body 31 is fixed to the ceiling wall 14 of the processing vessel 1. The shower plate 32 is connected below the main body 31. A gas diffusion space 33 is formed between the main body 31 and the shower plate 32. A gas introduction hole 36 is provided in the gas diffusion space 33 so as to penetrate the center of the ceiling wall 14 and the main body 31 of the processing vessel 1. A ring-shaped protrusion 34 protruding downward is formed on the periphery of the shower plate 32. A gas discharge hole 35 is formed on the inner flat portion of the ring-shaped protrusion 34. When the mounting table 2 is in the processing position, a processing space 38 is formed between the mounting table 2 and the shower plate 32, and the upper surface of the cover member 22 and the annular protrusion 34 are adjacent to each other to form an annular gap 39.

[0027] The exhaust unit 4 exhausts the inside of the processing vessel 1. The exhaust unit 4 includes an exhaust pipe 41, an exhaust mechanism 42, etc. The exhaust pipe 41 is connected to the exhaust port 13b. The exhaust mechanism 42 has a vacuum pump, a pressure control valve, etc. connected to the exhaust pipe 41. During processing, gas inside the processing vessel 1 reaches the exhaust duct 13 via the slit 13a, passes through the exhaust pipe 41 from the exhaust port 13b, and is exhausted by the exhaust mechanism 42.

[0028] The gas supply unit 5 supplies various process gases to the shower head 3. The gas supply unit 5 includes a gas source 51, a gas line 52, etc. The gas source 51 includes various process gas supply sources, a mass flow controller, a valve (none of which are shown), etc. The various process gases include gases used in the film forming methods of the embodiments described below. The various process gases include an adsorption inhibitor gas, a silicon-containing gas, a nitrogen-containing gas, a purge gas, etc. The various process gases are introduced from the gas source 51 through the gas line 52 and the gas introduction hole 36 into the gas diffusion space 33.

[0029] The adsorption inhibitor gas includes, for example, at least one of chlorine gas (Cl2), nitrogen gas (N2), and a mixed gas of chlorine gas and nitrogen gas (Cl2 / N2). The silicon-containing gas includes, for example, dichlorosilane gas (DCS). The nitrogen-containing gas includes, for example, at least one of ammonia gas (NH3), and a mixed gas of ammonia gas and argon gas (NH3 / Ar). The purge gas includes, for example, argon gas.

[0030] The film forming apparatus 10 is a capacitively coupled plasma apparatus, in which the mounting table 2 functions as a lower electrode and the shower head 3 functions as an upper electrode. The mounting table 2 is grounded via a capacitor (not shown). However, the mounting table 2 may be grounded, for example, without a capacitor, or may be grounded via a circuit combining a capacitor and a coil. The shower head 3 is connected to an RF power supply unit 8.

[0031] The RF power supply unit 8 supplies high frequency power (hereinafter also referred to as "RF power") to the shower head 3. The RF power supply unit 8 includes an RF power source 81, a matching box 82, a power feed line 83, and the like. The RF power source 81 is a power source that generates RF power. The RF power has a frequency suitable for generating plasma. The frequency of the RF power is, for example, within a range from 450 KHz in the low frequency band to 2.45 GHz in the microwave band. The RF power source 81 is connected to the main body 31 of the shower head 3 via the matching box 82 and the power feed line 83. The matching box 82 has a circuit for matching the load impedance to the internal impedance of the RF power source 81. Note that the RF power supply unit 8 has been described as supplying RF power to the shower head 3 serving as the upper electrode, but is not limited thereto. It may be configured to supply RF power to the mounting table 2 serving as the lower electrode.

[0032] The control unit 9 is, for example, a computer, and includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), an auxiliary storage device, etc. The CPU operates based on a program stored in the ROM or the auxiliary storage device, and controls the operation of the film forming apparatus 10. The control unit 9 may be provided inside or outside the film forming apparatus 10. When the control unit 9 is provided outside the film forming apparatus 10, the control unit 9 controls the operation of the film forming apparatus 10 via a communication means such as a wired or wireless communication means.

[0033] [Film forming method] Next, referring to FIG. 3 and FIG. 4, an example of the film forming method of the embodiment will be described using the above-mentioned film forming apparatus 10. First, the control unit 9 prepares the wafer W by loading a wafer W having a trench formed on its surface into the processing vessel 1 and placing it on the mounting table 2 (step S0). The control unit 9 controls the lifting mechanism 24 to lower the mounting table 2 to a transfer position, and opens the gate valve 12. Next, the wafer W is loaded into the processing vessel 1 via the loading / unloading port 11 by a transfer arm (not shown), and placed on the mounting table 2 heated to a predetermined temperature (for example, 600° C. or less) by the heater 21. Next, the control unit 9 controls the lifting mechanism 24 to raise the mounting table 2 to the processing position, and reduces the pressure inside the processing vessel 1 to a predetermined vacuum level by the exhaust mechanism 42.

[0034] (Step S1 of forming an adsorption inhibition region) Next, the step S1 of forming an adsorption inhibition region is performed. In the step S1 of forming an adsorption inhibition region, the wafer W is exposed to plasma generated from an adsorption inhibition gas to form an adsorption inhibition region on the upper part of the trench and on the surface of the wafer W. The adsorption inhibition region is a region that inhibits adsorption of a silicon-containing gas. The step S1 of forming an adsorption inhibition region includes steps S11 and S12, as shown in FIG. 4, for example.

[0035] In step S11, the wafer W is exposed to plasma generated from an adsorption inhibiting gas to form an adsorption inhibiting region mainly on the upper part of the trench and the surface of the wafer W. In this embodiment, the control unit 9 supplies Cl2, N2, or Cl2 / N2 from the gas supply unit 5 into the processing chamber 1 via the shower head 3, and then supplies RF power to the shower head 3 by the RF power supply unit 8. As a result, plasma is generated from Cl2, N2, or Cl2 / N2 in the processing chamber 1, and active species (reactive species) such as chlorine radicals, chlorine ions, nitrogen radicals, and nitrogen ions are supplied into the trench formed on the surface of the wafer W. The active species are physically or chemically adsorbed on the surface. The adsorbed active species have a function of inhibiting the adsorption of a silicon-containing gas (e.g., DCS) in the step S3 of adsorbing a silicon-containing gas, which will be described later, so that the region where the active species are adsorbed becomes an adsorption inhibiting region for the silicon-containing gas. Here, the active species easily reach the surface of the wafer W and the upper part of the trench, but do not reach the depths of the trench, that is, the lower part near the bottom, very much. Since the aspect ratio of the trench is high, most of the active species are adsorbed or deactivated before reaching the depth of the trench. Therefore, the active species are adsorbed at a high density on the surface of the wafer W and on the upper part of the trench, but many unadsorbed portions remain in the lower part of the trench, and the density of the adsorbed active species is low.

[0036] In step S12, the control unit 9 judges whether the number of times step S11 has been performed has reached a set number of times. The set number of times may be one or more. If it is judged in step S12 that the number of times step S11 has been performed has reached the set number of times, the process S1 of forming the adsorption inhibition region is terminated. On the other hand, if it is judged in step S12 that the number of times step S11 has been performed has not reached the set number of times, the process returns to step S11. Note that between steps S11 and S12, a purge step may be performed to remove gas remaining in the processing vessel 1 after step S11.

[0037] In step S1 for forming such an adsorption inhibition region, the wafer W is exposed to plasma generated from Cl2, N2, or Cl2 / N2 (step S11) a set number of times, thereby forming an adsorption inhibition region on the upper part of the trench and on the surface of the wafer W. At this time, the type of adsorption inhibition gas may be the same or different in each of the repeated steps S11.

[0038] For example, if the number of times is set to 2, select Cl2 the first time and Cl 2、 Alternatively, N2 or Cl2 / N2 may be selected. In this case, the step S1 of forming the adsorption inhibition region includes exposing the wafer W to a plasma generated from Cl2, and then exposing the wafer W to a plasma generated from Cl2, N2, or Cl2 / N2. Also, for example, N2 may be selected in the first step and Cl may be selected in the second step. 2、 Alternatively, N2 or Cl2 / N2 may be selected. In this case, the step S1 of forming the adsorption inhibition region includes exposing the wafer W to a plasma generated from N2, and then exposing the wafer W to a plasma generated from Cl2, N2, or Cl2 / N2. Also, for example, Cl2 / N2 may be selected in the first step, and Cl may be selected in the second step. 2、 Alternatively, N2 or Cl2 / N2 may be selected. In this case, step S1 of forming an adsorption inhibition region includes exposing the wafer W to plasma generated from Cl2 / N2, and then exposing the wafer W to plasma generated from Cl2, N2, or Cl2 / N2. Also, for example, one or more of the flow rate, flow rate ratio, plasma exposure time, pressure, and RF power of Cl2, N2, or Cl2 / N2 may be changed between the first and second times.

[0039] In the step S1 of forming the adsorption inhibition region, the wafer W is exposed to plasma generated from Cl2, N2, or Cl2 / N2 because the use of plasma increases reactivity and facilitates adsorption of gases such as Cl2. However, adsorption of adsorption inhibition gases occurs even without using plasma. Therefore, in the step S1 of forming the adsorption inhibition region, the wafer W may be exposed to an adsorption inhibition gas of Cl2, N2, or Cl2 / N2 without using plasma to form the adsorption inhibition region. In this case, RF power is not supplied from the RF power supply unit 8 to the showerhead 3.

[0040] (Purge process S2) Next, a purging step S2 is performed. In the purging step S2, gas remaining in the processing vessel 1 after the step S1 of forming an adsorption inhibition region is removed. In this embodiment, the control unit 9 supplies an inert gas (e.g., argon gas) from the gas supply unit 5 into the processing vessel 1 via the shower head 3, and exhausts the processing vessel 1 using the exhaust unit 4. This allows the adsorption inhibition gas remaining in the processing vessel 1 to be exhausted together with the inert gas. Note that the purging step S2 may be omitted.

[0041] (Step S3 of adsorbing silicon-containing gas) Subsequently, a step S3 of adsorbing the silicon-containing gas is performed. In the step S3 of adsorbing the silicon-containing gas, the silicon-containing gas is supplied to the wafer W, so that the silicon-containing gas is adsorbed in the region other than the adsorption inhibition region to form a silicon (Si)-containing layer. In this embodiment, the control unit 9 supplies the silicon-containing gas (e.g., DCS) from the gas supply unit 5 into the processing vessel 1 via the shower head 3. The silicon-containing gas is not so much adsorbed in the region where chlorine and / or nitrogen having an adsorption inhibition function are present, but is more adsorbed in the region where chlorine and / or nitrogen are not present. Therefore, the silicon-containing gas is adsorbed in a large amount near the bottom of the trench, and the amount of the silicon-containing gas adsorbed on the surface of the wafer W and the upper part of the trench is relatively small compared to the amount of the silicon-containing gas adsorbed near the bottom. In other words, the silicon-containing gas is adsorbed at a high density near the bottom of the trench, and the silicon-containing gas is adsorbed at a low density on the upper part of the trench and on the surface of the wafer W.

[0042] In the present disclosure, in step S3 of adsorbing the silicon-containing gas, the dose amount of the silicon-containing gas to be supplied is controlled to be equal to or greater than the adsorption saturation amount of the silicon-containing gas adsorbed onto the wafer W that does not have an adsorption inhibition region formed thereon. The adsorption saturation amount at which the adsorption amount of the silicon-containing gas onto the wafer W is saturated refers to the maximum value of the silicon-containing gas that can be adsorbed by the adsorption sites on the surface of the wafer W, including the recesses, of the precursor of the silicon-containing gas.

[0043] FIG. 5 is a diagram for explaining an example of an adsorption saturation curve C of a silicon-containing gas. The horizontal axis in FIG. 5 indicates the dose amount of the silicon-containing gas, and the vertical axis indicates GPC, that is, the film formation amount per cycle (Å / cycle). GPC serves as an index of the film formation rate of film C.

[0044] In the example of FIG. 5, in the A period, as the dose amount increases, GPC increases and the film formation rate increases. When the dose amount exceeds a certain amount DA, GPC becomes almost constant. At this time, it is considered that the surface of wafer W is in a state where a precursor of the saturation amount (adsorption saturation amount) is adsorbed. Therefore, in the B period where the dose amount exceeds a certain amount DA, GPC does not increase even if the dose amount is increased. For this reason, in the region where the dose amount is DA or more, GPC hardly changes even if the dose amounts are increased to DB and DC. At this time, the dose amounts of the silicon-containing gas satisfy the relationship DA < DB < DC.

[0045] That is, when a silicon-containing gas is supplied to wafer W that does not form an adsorption inhibition region, the adsorption saturation curve C indicates that once a silicon-containing gas with an adsorption saturation amount (a precursor of the adsorption saturation amount) is adsorbed on wafer W, the film thickness distribution cannot be significantly changed even if more silicon-containing gas is supplied. Note that the adsorption saturation curve draws different curves depending on the type of silicon-containing gas, but in any case, after the period in which the dose amount increases, in the period where the dose amount exceeds a certain amount, the curve is such that GPC hardly increases even if the dose amount is increased. Although there are some that continue to rise slightly, in that case, in the curve of the dose amount (Langmuir) dependence of the average GPC of the entire film, the saturation adsorption amount is determined as twice the dose amount at the inflection point (the dose amount at which the value of the function obtained by second-order differentiating GPC with respect to Langmuir becomes 0). The adsorption saturation curve corresponding to the type of silicon-containing gas is set for each type of silicon-containing gas and is stored in advance in a storage unit such as the RAM of control unit 9.

[0046] In step S3 of adsorbing the silicon-containing gas, the dose amount of the silicon-containing gas to be supplied is controlled to be equal to or greater than the adsorption saturation amount of the silicon-containing gas adsorbed on wafer W that does not form an adsorption inhibition region.

[0047] For example, an adsorption saturation curve corresponding to the type of silicon-containing gas to be supplied is selected from the adsorption saturation curves stored in the storage unit, and the dose of the silicon-containing gas may be controlled for each silicon-containing gas to be adsorbed based on the selected adsorption saturation curve from the adsorption saturation curves stored in advance in the storage unit for each type of silicon-containing gas adsorbed onto the wafer W that does not have an adsorption inhibition region.

[0048] (Purge process S4) Returning to step S4 in FIG. 3, a purging step S4 is subsequently performed. In the purging step S4, the silicon-containing gas remaining in the processing vessel 1 after the silicon-containing gas adsorption step S3 is removed. In this embodiment, the control unit 9 supplies an inert gas (e.g., argon gas) from the gas supply unit 5 into the processing vessel 1 via the shower head 3, and exhausts the processing vessel 1 using the exhaust unit 4. This allows the silicon-containing gas remaining in the processing vessel 1 to be exhausted together with the inert gas. Note that the purging step S4 may be omitted.

[0049] (Nitriding process S5) Subsequently, a nitridation step S5 is performed. In the nitridation step S5, the wafer W is exposed to plasma generated from a nitrogen-containing gas, which reacts with the silicon-containing layer formed on the surface of the wafer W and in the trench to form a silicon nitride film. The control unit 9 supplies, for example, ammonia gas as a nitrogen-containing gas from the gas supply unit 5 into the processing vessel 1 via the shower head 3, and then supplies RF power to the shower head 3 by the RF power supply unit 8. In the processing vessel 1, plasma is generated from the ammonia gas, and active species for nitridation are supplied to the surface of the wafer W and into the trench. The active species react with the silicon-containing layer formed in the trench, and a molecular layer of the silicon nitride film is formed as a reaction product. Here, since the silicon-containing layer is formed in large amounts near the bottom of the trench, a large amount of silicon nitride film is formed near the bottom of the trench.

[0050] In the nitridation step S5, the use of plasma increases reactivity and facilitates adsorption of the nitrogen-containing gas, so the wafer W is exposed to plasma generated from the nitrogen-containing gas to react with the adsorbed silicon-containing gas to form a silicon nitride film. However, gas adsorption can occur even without using plasma. Therefore, in the nitridation step S5, the wafer W may be exposed to the nitrogen-containing gas without using plasma to nitride the silicon-containing layer. In this case, RF power is not supplied from the RF power supply unit 8 to the shower head 3.

[0051] (Purge process S6) Subsequently, a purging step S6 is performed. In the purging step S6, the nitrogen-containing gas remaining in the processing vessel 1 after the nitriding step S5 is removed. In this embodiment, the control unit 9 supplies an inert gas (e.g., argon gas) from the gas supply unit 5 into the processing vessel 1 via the shower head 3, and exhausts the processing vessel 1 using the exhaust unit 4. This allows the nitrogen-containing gas remaining in the processing vessel 1 to be exhausted together with the inert gas. Note that the purging step S6 may be omitted.

[0052] (Judgment step S7) Next, in a determination step S7, the control unit 9 determines whether or not the number of repetitions from step S1 for forming an adsorption inhibition region to step S6 for purging has reached a set number. The set number is determined, for example, according to the shape of the silicon nitride film to be formed. If it is determined in the determination step S7 that the number of repetitions has reached the set number, the process ends. On the other hand, if it is determined in the determination step S7 that the number of repetitions has not reached the set number, the process returns to step S1 for forming an adsorption inhibition region.

[0053] As described above, according to the film forming method of the embodiment, the steps from the step S1 for forming the adsorption inhibition region to the purge step S6 are repeated, and the silicon nitride film is deposited from the bottom side without blocking the opening of the trench. Thus, a silicon nitride film with high bottom-up properties that does not block the opening while forming a V-shaped cross section can be formed. As a result, a high-quality silicon nitride film can be embedded in the trench without generating voids.

[0054] According to the film forming method of the embodiment, the dose of the silicon-containing gas in the step S3 of adsorbing the silicon-containing gas is controlled to be equal to or greater than the adsorption saturation amount of the silicon-containing gas adsorbed to the wafer W that does not have an adsorption inhibition region. This makes it possible to increase the GPC as described below, thereby improving productivity. As a result, it is possible to improve both the embedding performance and the productivity.

[0055] It is also possible to omit the purging steps S2, S4, and S6, and repeat a cycle including the steps of forming an adsorption inhibition region, adsorbing the silicon-containing gas, and forming a silicon nitride film a set number of times.

[0056] In addition, the silicon-containing gas may be adsorbed by changing the dose of the silicon-containing gas according to the number of cycles. For example, the dose of the silicon-containing gas may be increased as the number of cycles increases. For example, the dose of the silicon-containing gas may be decreased as the number of cycles increases. FIG. 6 is a diagram showing the relationship between the dose of the silicon-containing gas and the GPC due to differences in the pattern shape of the wafer. Wa is a flat wafer with no pattern formed, Wb is a wafer having a pattern with a small aspect ratio, and Wc is a wafer having a pattern with a large aspect ratio. In FIG. 6, the dose of the GPC and the silicon-containing gas change according to the pattern shape of the wafer. Therefore, the dose of the silicon-containing gas is changed according to the number of cycles. For example, instead of supplying a constant dose during the cycle as in (a) of the three graphs in FIG. 7, the dose of the silicon-containing gas from the beginning of the film formation ini to the end of the film formation fin is gradually decreased according to the number of cycles as in (b). As a result, the surface area of ​​the wafer W decreases as the film formation progresses, and the GPC can be improved even if the dose required for saturated adsorption changes due to the microloading effect. This is also expected to have the effect of improving productivity and reducing the consumption of silicon-containing gas.

[0057] As described above, according to the film forming method and film forming apparatus of the present embodiment, in the embedding into the recess using adsorption inhibition, it is possible to achieve both improvement in embedding performance and improvement in productivity.

[0058] [Examples of experimental results] FIG. 8 shows the experimental results of GPC for each depth of the trench when a silicon-containing gas is supplied to a wafer W in which an adsorption inhibition region is not formed. D1 and D2 in FIG. 8 show the change in GPC according to the depth of the trench when the dose amount (Langmuir) of the silicon-containing gas is controlled to D1 and D2 (D1 < D2).

[0059] In FIG. 8, among positions Z1 to Z6, position Z1 is the shallowest position, that is, the upper position in the trench, and position Z6 is the deepest position, that is, the lower position in the trench. As shown in FIG. 8, GPC was almost the same at any position at each depth of positions Z1 to Z6 regardless of the difference in the dose amounts D1 and D2. That is, as shown in FIG. 8, GPC did not increase even when the dose amount was increased from D1 to D2. From this, it was found that at least the dose amount is saturatedly adsorbed at a value of D1 or less. Hereinafter, when a silicon-containing gas is supplied to a wafer W in which an adsorption inhibition region is not formed, the minimum value of the dose amount required for saturated adsorption is defined as D1.

[0060] Next, the experimental results of GPC for each depth of the trench when a silicon-containing gas is supplied to a wafer W in which an adsorption inhibition region is formed are shown. FIG. 9 shows the experimental results of GPC for each depth of the trench when a silicon-containing gas is supplied to a wafer W in which an adsorption inhibition region is formed. The change in GPC according to the depth of the trench when the dose amount (Langmuir) of the silicon-containing gas is controlled to D1, D2, and D3 (D1 < D3 < D2) is shown.

[0061] In Fig. 9, when silicon-containing gas is supplied to a wafer W having an adsorption inhibition region formed, the GPC for each depth of the trench is increased by controlling the dose of silicon-containing gas to a dose D3 equal to or greater than the dose D1 of the precursor required for saturated adsorption when no adsorption inhibition region is formed. In addition, when the dose of silicon-containing gas is controlled to a dose D2 greater than the dose D3, the GPC for each depth of the trench is further increased. This is considered to be because the adsorption region (region where Si can be adsorbed) such as NH groups present on the inner surface of the trench becomes difficult to adsorb due to the influence of the adsorption inhibition gas supplied when forming the adsorption inhibition region, and when the Si-containing gas is supplied, the original supply amount is not saturated, and a larger supply amount is required.

[0062] From the above, the inventors have found that the dependency of GPC on the dose amount changes between when an adsorption inhibition region is not formed and when an adsorption inhibition region is formed. Therefore, in the film forming method according to the present embodiment, in the step of supplying a silicon-containing gas to the wafer W after the adsorption inhibition step, the dose amount of the silicon-containing gas is set to be equal to or greater than the adsorption saturation amount of the silicon-containing gas when the silicon-containing gas is supplied to the wafer W without the adsorption inhibition region and the silicon-containing gas is adsorbed on the wafer W. This increases the GPC and improves productivity.

[0063] Fig. 10 is a diagram showing GPC normalized at position Z6 for all of the doses D1, D2, and D3 shown in Fig. 9. According to this, in the silicon-containing gas supplying step after the adsorption inhibition step, the dose is set to be equal to or greater than the dose D1 of the minimum value of the adsorption saturation amount of the silicon-containing gas when the silicon-containing gas is supplied to the wafer W not forming an adsorption inhibition region and the silicon-containing gas is adsorbed onto the wafer W.

[0064] This increases the GPC, improving productivity. Also, the embedding shape is improved. That is, according to FIG. 10, the GPC at the upper part of the trench (where the trench is shallow) is smaller than the GPC at the bottom part of the trench (where the trench is deep). From this result, regardless of whether the dose amount is controlled to D1, D2, or D3, the cross section of the silicon nitride film embedded in the trench can be controlled to a V shape, the embedding performance can be improved, and voids can be eliminated. That is, a silicon nitride film with high bottom-up properties can be formed. However, the difference in GPC between the upper part and the bottom part of the trench was the largest when the dose amount was set to D2, which is the largest among D1, D2, and D3, and the embedding shape was most improved.

[0065] The film forming method and the film forming apparatus according to the embodiments disclosed herein should be considered as illustrative and not restrictive in all respects. The embodiments can be modified and improved in various forms without departing from the scope and spirit of the appended claims. The matters described in the above embodiments can be configured in other ways as long as they are not inconsistent, and can be combined as long as they are not inconsistent.

[0066] In the above embodiment, the adsorption inhibiting gas is chlorine gas (Cl2), nitrogen gas (N2), or a mixed gas of chlorine gas and nitrogen gas (Cl2 / N2), but the present disclosure is not limited to this.

[0067] The adsorption inhibitory gas includes halogen gas and non-halogen gas. Examples of halogen gas include fluorine gas (F2), chlorine gas (Cl2), and hydrogen fluoride gas (HF). Examples of non-halogen gas include nitrogen gas (N2) and silane coupling agents. Examples of silicon-containing gas include gases containing halogens such as chlorine (Cl), bromine (Br), and iodine (I) and silicon (Si).

[0068] For example, the step of forming the adsorption inhibition region includes at least one of exposing to plasma generated from a halogen gas, exposing to plasma generated from a non-halogen gas, exposing to a halogen gas, and exposing to a non-halogen gas. Examples of the adsorption inhibition gas include halogen gas such as fluorine gas (F2), chlorine gas (Cl2), and hydrogen fluoride gas (HF). Examples of the non-halogen gas include nitrogen gas (N2), and a silane coupling agent.

[0069] The step of forming the adsorption-inhibiting region includes exposure to a halogen gas or a plasma generated from a halogen gas, followed by exposure to a non-halogen gas or a plasma generated from a non-halogen gas.

[0070] The step of forming the adsorption-inhibiting region includes exposure to a non-halogen gas or a plasma generated from a non-halogen gas, and then exposure to a halogen gas or a plasma generated from a halogen gas.

[0071] The step of forming the adsorption-inhibiting region includes repeating at least one or more times exposure to a halogen gas or plasma generated from a halogen gas and exposure to a non-halogen gas or plasma generated from a non-halogen gas.

[0072] The step of forming the adsorption inhibition region includes exposing to a mixed gas of a halogen gas and a non-halogen gas, exposing to plasma generated from a mixed gas of a halogen gas and a non-halogen gas, exposing to a halogen gas or a non-halogen gas, or exposing to plasma generated from a halogen gas or a non-halogen gas. The halogen gas includes chlorine gas and the non-halogen gas includes nitrogen gas.

[0073] The silicon-containing gas is not limited to dichlorosilane gas (DCS). For example, the silicon-containing gas may include a gas containing halogen such as chlorine (Cl), bromine (Br), or iodine (I) and silicon (Si).

[0074] The nitrogen-containing gas is not limited to ammonia gas (NH3). For example, the nitrogen-containing gas may be ammonia gas (NH3), hydrazine gas (N2H2), nitrogen gas (N2), or a combination of these. For example, the nitrogen-containing gas may include hydrogen gas (H2).

[0075] In the above embodiment, the purge gas used in the purge steps S2, S4, and S6 is argon gas (Ar), but the present disclosure is not limited to this. For example, the purge gas may be argon gas (Ar), nitrogen gas (N2), or a combination of these. Also, exhaust may be performed in a vacuum state without using a purge gas.

[0076] In the above embodiment, the film forming apparatus is a capacitively coupled plasma apparatus, but the present disclosure is not limited to this. For example, the film forming apparatus may be a plasma apparatus using an inductively coupled plasma, a surface wave plasma (microwave plasma), a magnetron plasma, a remote plasma, or the like as a plasma source.

[0077] In the above embodiment, the case where the film forming apparatus is a single-wafer type apparatus that processes wafers one by one has been described, but the present disclosure is not limited thereto. For example, the film forming apparatus may be a batch type apparatus that processes multiple wafers at once. Also, for example, the film forming apparatus may be a semi-batch type apparatus that revolves multiple wafers placed on a turntable in a processing vessel by the turntable, and processes the wafers by passing them in order through an area where a first gas is supplied and an area where a second gas is supplied. Also, for example, the film forming apparatus may be a multiple-wafer film forming apparatus equipped with multiple mounting tables in one processing vessel. [Explanation of symbols]

[0078] 1 Processing vessel 2. Placement table 3. Shower head 4 Exhaust section 5 Gas supply section 8 RF power supply section 9. Control Unit 10 Film forming device

Claims

1. A film forming method for forming a film in a recess formed on a surface of a substrate, comprising the steps of: supplying an adsorption inhibiting gas to the substrate to form an adsorption inhibiting region; supplying a silicon-containing gas to the substrate to adsorb the silicon-containing gas to an area other than the adsorption inhibition area; and exposing the substrate to a nitrogen-containing gas to react with the adsorbed silicon-containing gas to form a silicon nitride film. The step of adsorbing the silicon-containing gas includes controlling a dose of the silicon-containing gas to be supplied to be equal to or greater than an adsorption saturation amount of the silicon-containing gas adsorbed onto the substrate not forming the adsorption inhibition region.

2. The dose of the silicon-containing gas is The control is performed for each silicon-containing gas to be adsorbed based on an adsorption saturation curve stored in advance in a storage unit for each type of silicon-containing gas adsorbed onto the substrate not forming the adsorption inhibition region. The film forming method according to claim 1 .

3. repeating a cycle including the steps of forming the adsorption inhibition region, adsorbing the silicon-containing gas, and forming the silicon nitride film. The film forming method according to claim 1 or 2.

4. The step of adsorbing the silicon-containing gas includes varying a dose of the silicon-containing gas depending on the number of cycles. The film forming method according to claim 3 .

5. the step of adsorbing the silicon-containing gas includes decreasing a dose of the silicon-containing gas according to the number of cycles; The film forming method according to claim 4.

6. The step of forming the silicon nitride film includes exposing the substrate to a plasma generated from a nitrogen-containing gas to react with the adsorbed silicon-containing gas. The film forming method according to any one of claims 1 to 5.

7. The step of forming the adsorption inhibiting region includes exposing the substrate to plasma generated from the adsorption inhibiting gas. The film forming method according to any one of claims 1 to 6.

8. a processing vessel for accommodating a substrate having a recess formed on a surface thereof; a gas supply unit for supplying an adsorption inhibitor gas, a silicon-containing gas, and a nitrogen-containing gas into the processing vessel; A control unit, The control unit is supplying an adsorption inhibiting gas to the substrate to form an adsorption inhibiting region; supplying a silicon-containing gas to the substrate to adsorb the silicon-containing gas to an area other than the adsorption inhibition area; exposing the substrate to a nitrogen-containing gas to react with the adsorbed silicon-containing gas to form a silicon nitride film; A film forming apparatus, wherein in the step of adsorbing the silicon-containing gas, a dose of the silicon-containing gas to be supplied is controlled to be equal to or greater than an adsorption saturation amount of the silicon-containing gas adsorbed onto the substrate not forming the adsorption inhibition region.

Images