JP4234839B2 - Deposition method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention forms a silicon film on a substrate having a recess formed on the surface, such as a semiconductor wafer.Deposition methodAbout.
[0002]
[Prior art]
As one of the manufacturing processes of a semiconductor wafer (hereinafter referred to as “wafer”), there is a process of forming an electrode by forming silicon (Si) in a recess formed on the wafer surface. This process includes, for example, a mounting table for mounting a wafer, a gas supply unit called a shower head provided 10 mm above the wafer so as to face the mounting table, and heating for heating the wafer. In a single wafer type film forming apparatus, a film deposition gas, for example, SiH4 gas is supplied from a shower head toward the wafer while heating the wafer, and a CVD (chemical vapor deposition) method is used. This is done by forming a silicon film on the wafer surface.
[0003]
[Problems to be solved by the invention]
By the way, when the silicon film is formed by the above-described apparatus, the step coverage is deteriorated when the aspect ratio of the concave portion is increased, and for example, a void tends to be generated in the case of embedding. At this time, if the film formation rate is low, good step coverage can be obtained, and in the case of embedding, it is possible to embed without voids, but from the viewpoint of improving throughput, the film formation rate is set to 300 Å / min or more. Desirably, such a high film formation rate deteriorates the embedding property in the recess.
[0004]
The reason for this is assumed to be caused by reactive species mainly composed of SiH2, which is a decomposition product of SiH4 gas in the gas phase, as will be described later. Therefore, an early solution is required.
[0005]
  The present invention has been made under such circumstances, and its object is to provide a substrate having a recess.Polysilicon filmWhen film is formed, silicon can be satisfactorily embedded in the recess.Deposition methodIs to provide.
[0006]
[Means for Solving the Problems]
  For this reason, the film forming apparatus of the present invention is formed on the substrate.Opposite the substrateGas is supplied into the reaction space to the planar portion that defines the reaction space.Numerous gas injection holes for formedGas supply unitTheIn the processing chamber provided, from the gas supply unitMonosilane gas as a film forming gasSupplied to the surface of the substrate, with a film forming speed of 300 angstroms / minute or more on the substrate having a recess formed on the surfacePolysilicon film by thermal CVDFilm formation to formMethodIn
  The distance between the substrate and the surface of the planar portion facing the substrate surfaceThe5mm to 18mmThe total flow rate of the gas supplied from the gas supply unit is set to 500 sccm or more and 5000 sccm or less, and the total pressure is 1.33 × 10 6. ^Four Film formation is performed at a Pa (100 Torr) or lowerIt is characterized by that.
[0009]
  hereThe gas supplied from the gas supply unit preferably contains a dilution gas for reducing the partial pressure of the monosilane gas.It is desirable to use a gas containing hydrogen gas as the dilution gas,In this case, the partial pressure of the monosilane gas is 1.33 × 10 ³ If it is set to Pa (10 Torr) or less, step coverage is improved.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a side cross-sectional view showing an embodiment of a film forming apparatus according to the present invention. In FIG. 1, reference numeral 11 denotes a chamber forming a processing chamber for storing wafers W to be processed one by one. 11, an opening 10 larger than the wafer W is formed in the center of the floor, and a wafer insertion opening 12 is formed in the side wall. The wafer insertion port 12 is closed by a gate valve 13, and when the gate valve 13 is opened, it is connected to the inside of a load lock chamber (not shown).
[0011]
In the chamber 11, a mounting table 21 for mounting the wafer W almost horizontally is provided so as to close the opening 10. A holding arm 22 for holding the wafer W and mounting it on the mounting table 21 and a lifter 23 for moving it up and down are provided outside the mounting table 21 in the chamber 11. A groove portion (not shown) corresponding to the holding arm 22 is formed in the mounting table 21 and enters the groove portion when the holding arm 22 holding the wafer W is lowered. The wafer W is delivered to the top. A load arm (not shown) for transferring the wafer W is provided in the load lock chamber. Between the transfer arm and the holding arm 22 when the gate valve 13 is opened. The wafer W is transferred.
[0012]
A gas supply unit 31 called a shower head or the like is provided on the ceiling of the chamber 11 above the wafer W placed on the mounting table 21, for example, 5 mm to 18 mm so as to face the mounting table 21. It has been. The gas supply unit 31 supplies a film forming gas or the like when the apparatus is used for a film forming process by a CVD (chemical vapor deposition) method. For example, the apparatus is used to animate the film in an inert gas atmosphere. In the case of carrying out the gas treatment, an inert gas is supplied.
[0013]
The gas supply unit 31 is configured to supply, for example, the gas supplied from the gas supply pipes 32 and 33 into the chamber 11 from a number of gas injection ports 35 of the gas diffusion unit 34, and the gas diffusion unit The lower surface of 34 forms a planar portion that partitions the reaction space on the wafer W. The gas supply unit 31 is configured such that the outer edge of the gas blowing region (gas supply region), which is the formation region of the gas injection port 35, and the size of the wafer W are substantially aligned, that is, the ratio of the size of the gas blowing region to the wafer W. Is set so that (the diameter of the outer edge of the gas blowing region) / (the diameter of the wafer W) = 0.8 to 1.2. Further, a fluid passage 36 is formed in the side wall portion of the gas supply unit 31 and the gas diffusion unit 34 for allowing a temperature adjusting fluid to flow therethrough. The gas supplied by such a gas supply unit 31 is exhausted through an exhaust means (not shown) provided in the chamber 11.
[0014]
Further, on the lower side of the mounting table 13 of the opening portion 10 of the chamber 11, for example, a transmission for transmitting heat rays from a heating means to be described later so as to close the opening portion 10 from the lower side across the bottom wall of the chamber 11. A window 41 is formed. The space surrounded by the mounting table 13 and the transmission window 41 is configured such that an inert gas, for example, nitrogen gas, can be supplied by an inert gas supply means (not shown) through an inert gas supply port 42. For example, when this apparatus is used as a CVD apparatus, a film is formed from the inside of the chamber 11 by supplying nitrogen gas uniformly to the vicinity of the lower surface of the wafer W through the gas holes 43a of the buffer plate 43. Gas or the like is prevented from flowing into the transmission window 41 side, and film formation does not occur on the surface of the transmission window 41.
[0015]
On the lower side of the transmission window 41 of the chamber 11, for example, a heating unit 5 including a lamp group 51 is disposed. The lamp group 51 is arranged on, for example, a rotating table 53 that is rotationally driven by a motor 52, and has, for example, three concentric circles centered on a point corresponding to the center point of the wafer W and having different radii. It is arranged along the circumference of each. At this time, for example, two lamps 51A are provided along the innermost circumference, for example, six lamps 51B are provided along the middle circumference, and for example, 15 lamps are provided along the outermost circumference. The lamp 51C is provided. The number of concentric circles and the number of lamps 51A, 51B, 51C on each circumference are not limited to the numbers described above.
[0016]
In addition, the lamp group 51 can control the heating amount per unit area independently for each circumference or one by one. For example, three annular heating regions are formed. Then, the heating per unit area is gradually performed from the center of the wafer W toward the outer periphery by controlling the heating amount per unit area to increase toward the outermost annular heating region by a control device (not shown). The amount is increased and the in-plane temperature distribution of the wafer W is controlled to be uniform.
[0017]
Next, the operation of the above embodiment will be described. First, a wafer W having a size of, for example, 200φ having a recess formed on the surface in the previous process is loaded into the chamber 11 by a transfer arm (not shown) and transferred onto the holding arm 22 of the lifter 23. Then, the chamber 11 is evacuated by an evacuation unit (not shown), and the wafer W is heated to, for example, about 600 ° C. by the lamp group 51, and a gas containing silane as a film forming gas, such as SiH 4 gas, is heated by the gas supply pipes 32 and 33. Diluting gas such as H2 gas and N2 gas are introduced into the chamber 11 through the gas supply unit 31, respectively, and a polysilicon film is formed on the surface of the wafer W at a film forming speed of, for example, 300 angstroms / minute or more under normal pressure. Form.
[0018]
At this time, the total flow rate of the introduced gas is preferably 500 sccm to 5000 sccm, the total pressure of the introduced gas is preferably 100 Torr or less, and the partial pressure of the SiH4 gas is preferably low. For example, the total pressure of the introduced gas is set to 100 Torr, the partial pressure of SiH4 gas is set to 25 Torr, and the flow rate ratio of SiH4 gas and H2 gas is set to 1: 1, for example.
[0019]
The film forming apparatus of the present invention, when forming a silicon film at a film forming speed of 300 angstroms / minute or more on the surface of the wafer W formed with a recess using a gas containing silane as a film forming gas, The ratio of the gas blowing area of the gas supply unit 31 to the size of the wafer W is set so that (the diameter of the outer edge of the gas blowing area) / (the diameter of the wafer W) = 0.8 to 1.2, The distance between the lower surface of the gas supply unit 31 and the surface of the wafer W is set to, for example, 5 mm to 18 mm. By setting in this way, the silicon film is embedded on the surface of the wafer W while the silicon film is satisfactorily embedded in the recess. Can be formed.
[0020]
Here, the background that led to the present invention will be described. First, when a polysilicon film is formed by using SiH4 gas as a film forming gas, the film forming reaction shown in the following formula (1) is the reaction in which SiH4 gas is directly decomposed on the substrate, and the following (2). It is presumed that the reaction is carried out by the reaction accompanied by the intermediate SiH2 * shown in the formula and the formula (3). Here, the intermediate SiH2 * is a decomposition product of SiH4 gas, and the substrate reactions (1) and (3) are reactions occurring on the surface of the substrate, and the gas phase reaction (2) is the gas in the gas supply unit 31. This is a reaction that occurs in the area between the blowing area and the wafer W.
[0021]
SiH4 → Si (s) + 2H2 ... Substrate reaction (1)
SiH4 → SiH2 * + H2 ... Gas phase reaction (2)
SiH2 * → Si (s) + H2 ... Substrate reaction (3)
By the way, step coverage refers to the film formation rate distribution in the recess, and is determined by the aspect ratio of the recess and the adhesion probability of the film forming species. In other words, regardless of the type of film formation, if the aspect ratio of the recesses is small, a certain degree of satisfactory embedding can be performed. Further, in relation to the adhesion probability of the film formation species, if the adhesion probability of the film formation species is high, for example, as shown in FIG. Originally, it is difficult for the seeds to enter the inside of the recess 61, so that the seeds are deposited so that the shoulder of the recess 61 protrudes inward, and the entrance of the recess 61 is further narrowed. The film formation is performed in such a state that the concentration difference between the film formation species increases and a large void is formed in the recess 61.
[0022]
On the other hand, in film formation with a film formation species with a low adhesion probability, as shown in FIG. 2B, for example, the film formation seed diffuses without adhering as it is even if it contacts the wall surface of the substrate. For this reason, the film forming species easily enter the concave portion 61 and the concentration gradient of the film forming species in the concave portion 61 is small. Therefore, the film formation is performed in a state where the formation of voids in the concave portion 61 is suppressed.
[0023]
Here, when the contribution ratio of SiH4 and SiH2 to the deposition of the polysilicon film was calculated, the result was that the SiH2 adhesion probability was 100,000 times that of SiH4, and step coverage in the deposition of the polysilicon film was obtained. It was found that SiH2 is a factor that worsens the temperature.
[0024]
Therefore, when the characteristics of SiH2 were examined, it was found that the generation amount increased as the volume of the gas phase reaction space increased. Therefore, in order to reduce the gas phase reaction space and suppress the gas phase reaction, It was studied to reduce the area between the gas blowing area of the gas supply unit 31 and the wafer W, which is the gas phase reaction space of the film apparatus. When various experiments were conducted focusing on reducing the volume of the gas phase reaction space by reducing the distance between the lower surface of the gas supply unit 31 and the surface of the wafer W, the distance was, for example, 5 mm to 18 mm. The result is desirable to set.
[0025]
Further, in order to shorten the gas residence time on the wafer to suppress the decomposition reaction to SiH2, and to suppress the reverse diffusion of SiH2 generated on the outer periphery of the wafer onto the wafer, the gas blowing region of the gas supply unit 31 is used. And adjusting the gas flow rate accordingly, (outer edge diameter of gas blowing area) / (wafer W diameter) = 0.8 to 1.2 is set. It was confirmed that the gas phase reaction concentration on the wafer can be suppressed by setting the gas flow rate to 500 sccm to 5000 sccm.
[0026]
Here, an experimental example performed by the present inventors will be described. Using the apparatus shown in FIG. 3, while introducing SiH4 gas at a flow rate of 1000 sccm and heating the wafer W to 620 [deg.] C., the wafer W having recesses with aspect ratios of 1.25, 1.67, and 2.5 On the other hand, a polysilicon film was formed. Here, the inclusion 21b is put on the lower surface of the flange portion 21a of the mounting table 21, and the distance L between the wafer W mounted on the mounting table 21 and the gas supply unit 31 is changed within a range of 5 to 40 mm, thereby forming the polysilicon film. Then, the embedded state of the polysilicon film in the recess was observed with a scanning electron microscope. The apparatus shown in FIG. 3 is configured in the same manner as the apparatus shown in FIG. 1 except that the inclusion 21b is provided.
[0027]
The result is shown in FIG. In this case, the embedding characteristics are evaluated in three stages, ◯, △, and ×. If the step coverage is 0.95 or more, ◯, 0.9 or less and less than 0.95, △ or 0.9 or less. The case was marked with x. Here, the step coverage is represented by Y / X, where X is the film thickness on the upper side of the recess and Y is the film thickness on the bottom of the recess, as shown in FIG. When the step coverage is 1, it is the most ideal state, and the larger the step coverage, the better the embedded state.
[0028]
Thus, when the aspect ratio of the recess is 1.25, the distance L is in the range of 5 to 30 mm, and when the aspect ratio of the recess is 1.67, the distance L is in the range of 5 to 18 mm. Is 2.5, the distance L is in the range of 5 to 14 mm, the step coverage is 0.9 or more and the embedding characteristics are good, and the embedding state becomes severe as the aspect ratio increases. However, it was confirmed that the embedding characteristic is improved by optimizing the distance L. From these results, the aspect ratio tends to exceed 1.5 with the recent miniaturization of devices, but by forming the distance L in the range of 5 to 18 mm, voids are formed even in such recesses. It can be understood that good embedding can be performed while suppressing the above.
[0029]
In the present invention, the total flow rate of the introduced gas is set to 500 sccm to 5000 sccm and the total pressure is set to 100 Torr or less, so that the silicon film can be embedded in the recess more favorably. If the total flow rate of the introduced gas is less than 500 sccm, the gas residence time on the wafer becomes long and the decomposition reaction to SiH2 is promoted, and the total flow rate is 5000 sccm. A larger amount is preferable for suppressing a gas phase reaction, but is not preferable because of high running cost and a large load of abatement equipment. On the other hand, if the total pressure of the introduced gas exceeds 100 Torr, the gas residence time on the wafer is increased, and the decomposition rate into SiH2 is increased, which is not preferable.
[0030]
In the above, the present invention can also be applied to a film forming apparatus having the configuration shown in FIG. This film forming apparatus is different from the above-described film forming apparatus in that a heater is used instead of a lamp as a heating means. In this apparatus, the opening portion 10 is not provided in the chamber 11, and a mounting table 7 provided with a heater 71 made of, for example, a resistance heating element is disposed in the center of the bottom of the chamber 11. A wafer W is placed on the upper surface. Here, the mounting table 7 is configured to be movable up and down, and incorporates, for example, three protruding pins (not shown) that protrude from the upper surface of the mounting table when the mounting table 7 is raised. The wafer W is mounted on the mounting table 7 for cooperative operation (not shown). Other configurations are the same as those of the above-described film forming apparatus. Next, a simulation experiment will be described. The present invention can be achieved as a result of examination based on the knowledge obtained by this experiment. Here, the calculation of the gas phase reaction uses Chemkin's SENKIN, and the base reaction rate data set is P.I. Those described in Ho et al. [1] were used. The surface reaction was evaluated in the above SENKIN calculation using the S / V ratio equivalent to the gas phase reaction assuming a complete mixing tank.
[0031]
Specifically, when a molecular species containing Si collides with He, it is treated as being deactivated and disappears. For example, in the case of SiH2,
SiH2 + He → SiH2 (B) + He
(SiH2 (B) is an inert substance that does not react any more), and this gas phase reaction rate was defined as follows in order to evaluate the effect of disappearance due to surface reaction on the substrate surface or the like.
[0032]
-D [SiH2] / dt = ks S / V [SiH2] = kg [SiH2] [He]
From this relationship, the gas phase reaction rate constant kg is calculated and used in the simulation. However, in the case of SiH2, etc., the surface reaction rate is too fast, so actually kd (mass transfer coefficient) is not ks. KG was used to evaluate. In the case of SiH4 and Si2 H6, the surface reaction rate is low and the surface reaction rate is limited. Therefore, ks was evaluated using ks.
[0033]
The simulation was performed for film formation speed and step coverage. The film formation speed (speed at which molecular species contribute to film formation) depends on the surface reaction speed to the concentration of each molecular species predicted from the calculation result of the gas phase reaction. Alternatively, it was calculated by multiplying by the mass transfer coefficient, and at this time, the value of crystal was used as the density of silicon. The step coverage is represented by the sum of the step coverage of each molecular species. At this time, the film formation from SiH4 and Si2 H6 is 100% coverage, and the other molecular species is 1% coverage.
[0034]
First, in order to confirm the influence of the surface reaction (S / V ratio), the reaction temperature was 873 K, the deposition gas was SiH4 gas, the dilution gas was He gas and N2 gas, respectively, and the total pressure of the introduced gas was 76 Torr, SiH4. The simulation was performed for the case where the gas partial pressure was 1.0 Torr and the He gas partial pressure was 0.0 Torr, 0.1 Torr, 1.0 Torr, and 10.0 Torr.
[0035]
Here, the S / V ratio means that S is a reaction area corresponding to the wafer area, and V is a reaction volume obtained by (wafer area) × (distance between the wafer and the gas supply unit). The V ratio is 1 / (distance between the wafer and the gas supply unit). In this simulation, when He gas is introduced as a diluent gas, the concentration of SiH4 gas changes, which corresponds to changing the S / V ratio, so that the S / V ratio is changed by changing the partial pressure of He gas. The influence of the V ratio was considered.
[0036]
The results are shown in FIGS. 6 to 9 when the partial pressure of He gas is 0.0 Torr, 0.1 Torr, 1.0 Torr, and 10.0 Torr, respectively. The figure shows the flow of gas under the above conditions at time 0, and the generation and increase of molecular species such as SiH2 in the gas phase with time, with the horizontal axis representing time and the left vertical axis Shows the deposition rate of each molecular species that contributes to the film generated in the gas phase, the right vertical axis shows the step coverage, and the step coverage is closer to 1, as described above, the better the embedded state is Is shown.
[0037]
Also, in this simulation result, the step coverage is 1 at time 0 and decreases with the passage of time. This is because SiH4 is introduced at time 0, and the only molecular species present at this time is SiH4. Since SiH4 does not deteriorate the step coverage, the step coverage is in an ideal state of 1, and when time passes, SiH4 reacts in the gas phase to generate molecular species such as SiH3 and SiH2, and this is the step coverage. It is because it becomes a cause to worsen.
[0038]
From this simulation result, it has been found that when the partial pressure of He gas is increased to increase the S / V ratio, the deposition rate is reduced and the step coverage is improved. Accordingly, it is presumed that the step coverage is improved when the distance between the wafer and the gas supply unit is reduced.
[0039]
Subsequently, in order to confirm the influence of the partial pressure of SiH4 gas, the reaction temperature was 873 K, SiH4 gas was used as the film forming gas, H2 gas, He gas and N2 gas were used as the dilution gas, respectively, and the total pressure of the introduced gas was 76 Torr. The simulation was performed by changing the partial pressures of SiH4 gas, H2 gas, He gas, and N2 gas.
[0040]
When this result is used as a dilution gas, He gas and N2 gas are used, that is, the partial pressure of SiH4 gas is 1.0 Torr, the partial pressure of H2 gas is 0.0 Torr, the partial pressure of He gas is 1.0 Torr, and the partial pressure of N2 gas. FIG. 8 shows a case where the pressure is 74.0 Torr. The partial pressure of SiH4 gas is 0.1 Torr, the partial pressure of H2 gas is 0.0 Torr, the partial pressure of He gas is 1.0 Torr, and the partial pressure of N2 gas is 74. In the case of 9 Torr, FIG. 10 shows the case where the partial pressure of SiH4 gas is 10.0 Torr, the partial pressure of H2 gas is 0.0 Torr, the partial pressure of He gas is 1.0 Torr, and the partial pressure of N2 gas is 65.0 Torr. FIG. 11 shows the case where the partial pressure of SiH4 gas is 25.0 Torr, the partial pressure of H2 gas is 0.0 Torr, the partial pressure of He gas is 1.0 Torr, and the partial pressure of N2 gas is 50.0 Torr. Show.
[0041]
When He gas and H2 gas are used as the dilution gas, that is, the partial pressure of SiH4 gas is 10.0 Torr, the partial pressure of H2 gas is 65.0 Torr, the partial pressure of He gas is 1.0 Torr, and the partial pressure of N2 gas is The case of 0.0 Torr is shown in FIG. 13. The partial pressure of SiH4 gas is 1.0 Torr, the partial pressure of H2 gas is 74.0 Torr, the partial pressure of He gas is 1.0 Torr, and the partial pressure of N2 gas is 0.0 Torr. FIG. 14 shows a case where the partial pressure of SiH4 gas is 25.0 Torr, the partial pressure of H2 gas is 50.0 Torr, the partial pressure of He gas is 1.0 Torr, and the partial pressure of N2 gas is 0.0 Torr. Respectively.
[0042]
As a result of this simulation, He gas (partial pressure 1 Torr) and N2 gas (partial pressure determined according to the partial pressure of SiH4 gas) are used as the dilution gas, and the partial pressure of SiH4 gas is 0.1 Torr to 25.0 Torr. In the case of changing within the above range (FIGS. 8 and 10 to 12), it was found that increasing the partial pressure of the SiH4 gas improves both the deposition rate and step coverage.
[0043]
When He gas (partial pressure 1 Torr) and H2 gas (partial pressure is determined according to the partial pressure of SiH4 gas) are used as the dilution gas, and the partial pressure of SiH4 gas is changed within the range of 1.0 Torr to 25.0 Torr. (FIGS. 13 to 15) show that when the partial pressure of the SiH4 gas is reduced, the film forming speed is reduced, but the step coverage is improved. In particular, when the partial pressure of the SiH4 gas is 10 Torr or less. The knowledge that step coverage is 0.9 or more and embedding is performed well was obtained. This is presumably due to the following reasons. That is, in the gas phase reaction of the silicon film, the H2 desorption reaction of the above formula (2) occurs, and the step coverage deteriorates when the amount of SiH2 produced by this reaction increases, but if H2 gas is used as the dilution gas, Since the gas phase becomes an atmosphere rich in H2, the reverse reaction (SiH2 + H2-> SiH4) of the formula (2) occurs. Therefore, if the partial pressure of H2 gas is increased and the partial pressure of SiH4 is lowered, the SiH2 concentration is lowered, so that step coverage is considered to be improved.
[0044]
On the other hand, when N2 gas is used as the dilution gas, if the partial pressure of N2 gas is lowered and the partial pressure of SiH4 is increased without causing the reverse reaction, SiH2 recombines with SiH4 and Si2 H6. (SiH 2 + SiH 4 → Si 2 H 6) occurs. Here, Si2 H6 does not deteriorate the step coverage. Therefore, lowering the partial pressure of N2 gas to increase the partial pressure of SiH4 improves the step coverage, and increasing the partial pressure of N2 gas to increase the partial pressure of SiH4. It is thought that step coverage deteriorates if it is lowered.
[0045]
Subsequently, in order to confirm the influence of the partial pressure of H2, the reaction temperature is 873 K, the deposition gas is SiH4 gas, the dilution gas is H2 gas, He gas, and N2 gas, respectively, and the total pressure of the introduced gas is 76.0 Torr. The simulation was performed by changing the partial pressure of the H2 gas and the N2 gas while setting the partial pressure of the SiH4 gas to 10.0 Torr and the partial pressure of the He gas to 1.0 Torr.
[0046]
The results are shown in FIG. 13, where the partial pressure of H2 gas is 65.0 Torr, the partial pressure of N2 gas is 0.0 Torr, and the partial pressure of H2 gas is 1.0 Torr and the partial pressure of N2 gas is 64.0 Torr. FIG. 16 shows the case where the partial pressure of H2 gas is 10.0 Torr and the partial pressure of N2 gas is 55.0 Torr, respectively.
[0047]
From this simulation result, it has been found that increasing the partial pressure of H2 gas, which is a dilution gas, decreases the deposition rate and improves the step coverage. For this reason, it is presumed that step coverage is improved by setting the partial pressure of SiH4 gas to 10 Torr or less by using H2 gas as a dilution gas.
[0048]
In order to confirm the temperature dependence, simulation was performed using SiH4 gas (flow rate 250 sccm) as a film forming gas and changing the reaction temperature in the range of 600 ° C to 680 ° C. The results are shown in FIG. 18. In the figure, the horizontal axis represents time, the left vertical axis represents the deposition rate of each molecular species that contributes to the film formed in the gas phase, and the right vertical axis represents step coverage. ● indicates the deposition rate after 1 second, ○ indicates the deposition rate after 10 seconds, □ indicates the step coverage after 1 second, and ■ indicates the step coverage after 10 seconds. From this simulation result, it was found that although the deposition rate increases as the reaction temperature increases, the step coverage hardly changes, and therefore the reaction temperature does not significantly affect the step coverage.
[0049]
Further, in order to confirm the concentration dependency, a simulation was performed using SiH4 gas as a film forming gas, a reaction temperature of 680 ° C., and changing the partial pressure of SiH4 gas in the range of 1 Torr to 10 Torr. The results are shown in FIG. 19, where the horizontal axis represents time, the left vertical axis represents the deposition rate of each molecular species contributing to the film formed in the gas phase, and the right vertical axis represents step coverage. ● indicates the deposition rate after 1 second, ○ indicates the deposition rate after 10 seconds, □ indicates the step coverage after 1 second, and ■ indicates the step coverage after 10 seconds. From this simulation result, it was found that when the partial pressure of SiH4 gas is increased and the concentration of silane is increased, the deposition rate is increased, but the step coverage is deteriorated.
[0050]
In the above, the silicon film referred to in the present invention includes a doped silicon film and a non-doped silicon film. In addition to SiH4 gas, Si2 H6 gas, Si3 H8 gas, or the like can be used as a film forming gas containing silane. In addition to H2 gas, N2 gas, Ar gas, He gas, etc. can be used as the dilution gas. Further, when forming a doped silicon film, AsH3 gas, PH3 gas, B2 H6 gas or the like can be used as a dopant gas.
[0051]
Further, in the film forming apparatus of the present invention, for example, as shown in FIG. 20, the planar portion that partitions the reaction space on the substrate is constituted by the inner wall 81 of the ceiling portion of the chamber 8, and the gas supply nozzle is formed on the side wall portion of the chamber 8. 82 may be provided so that gas is supplied from the gas supply nozzle 82 to the reaction space. In this case, the gas supply nozzle 82 corresponds to a gas supply unit.
[0052]
【The invention's effect】
According to the present invention, when silicon is deposited on a substrate having a recess, the silicon can be satisfactorily embedded in the recess.
[0053]
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of an embodiment of a film forming apparatus of the present invention.
FIG. 2 is a cross-sectional view for explaining step coverage.
FIG. 3 is a cross-sectional view showing a film forming apparatus used in an experimental example.
FIG. 4 is a characteristic diagram showing a relationship between a distance L and an embedding characteristic, and a sectional view for explaining step coverage.
FIG. 5 is a cross-sectional view showing another example of the film forming apparatus of the present invention.
FIG. 6 is a characteristic diagram showing a simulation result of film forming speed and step coverage.
FIG. 7 is a characteristic diagram showing simulation results of film formation speed and step coverage.
FIG. 8 is a characteristic diagram showing a simulation result of film formation speed and step coverage.
FIG. 9 is a characteristic diagram showing a simulation result of film formation speed and step coverage.
FIG. 10 is a cross-sectional view showing another example of the film forming apparatus of the present invention.
FIG. 11 is a characteristic diagram showing simulation results of film formation speed and step coverage.
FIG. 12 is a characteristic diagram showing a simulation result of film formation speed and step coverage.
FIG. 13 is a characteristic diagram showing a simulation result of film forming speed and step coverage.
FIG. 14 is a characteristic diagram showing a simulation result of film forming speed and step coverage.
FIG. 15 is a cross-sectional view showing another example of the film forming apparatus of the present invention.
FIG. 16 is a characteristic diagram showing simulation results of film formation speed and step coverage.
FIG. 17 is a characteristic diagram showing simulation results of film formation speed and step coverage.
FIG. 18 is a characteristic diagram showing a simulation result of temperature characteristics.
FIG. 19 is a characteristic diagram showing a simulation result of density characteristics.
FIG. 20 is a cross-sectional view showing still another example of the film forming apparatus of the present invention.
[Explanation of symbols]
11,8 chamber
21,7 mounting table
31 Gas supply unit
35 Gas outlet
5 Heating means
51 lamp
71 heater
82 Gas supply nozzle
W Semiconductor wafer

Claims (5)

In the processing chamber provided with a gas supply unit for a large number of gas injection ports are formed for supplying gas to the planar portion and the reaction space for partitioning the substrate opposed to the reaction space on the substrate, Film formation for forming a polysilicon film by thermal CVD at a film formation rate of 300 Å / min or more on a substrate having a recess formed on the surface by supplying monosilane gas as a film formation gas from the gas supply unit In the method
Set the distance to 5mm or 18mm or less between the substrate and the planar portion and the substrate surface and the opposing surfaces of the total flow rate of the gas supplied from the gas supply portion is set lower than 5000sccm than 500 sccm, the total pressure film forming method, wherein a forming a film by setting the 1.33 × 10 ⁴ Pa (100Torr) or less. The film forming method according to claim 1, wherein the gas supplied from the gas supply unit includes a dilution gas for reducing a partial pressure of the monosilane gas. The film forming method according to claim 2, wherein the dilution gas contains hydrogen gas. The partial pressure of monosilane gas is 1.33 × 10 ³   The film forming method according to claim 3, wherein the film thickness is Pa (10 Torr) or less. The substrate is a semiconductor wafer, and the ratio of the gas blowing area of the gas supply unit to the size of the semiconductor wafer (the diameter of the outer edge of the gas blowing area) / (the diameter of the semiconductor wafer) is 0.8 to 1.2. The film forming method according to claim 1, wherein the film forming method is provided.

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