JP4236707B2 - Chemical vapor deposition method and chemical vapor deposition apparatus - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a novel chemical vapor deposition (CVD) method capable of forming a thin film with good coverage in a fine depressed structure, and an apparatus for realizing the same.
[0002]
[Prior art]
In the CVD method, one or more raw material (chemical) vapors generated in a raw material system are transported to a reactor maintained at a constant pressure, mixed, and chemically reacted on a substrate held at a high temperature. It is a method of depositing. Since the film formation mechanism is derived from a chemical process, it does not require high temperatures such as thermal oxidation, and high vacuum conditions such as physical vapor deposition (PVD) such as sputtering and resistance wire heating deposition. It is not necessary. Therefore, even a large-scale film forming apparatus can be realized at a relatively low cost. Already, as a means for forming a metal film, a dielectric film, and a semiconductor thin film, this film forming method is used in a wide range of industries.
[0003]
PVD is based on the physical process of supplying and agglomerating physical vapor with a high adhesion probability in a high vacuum state to form a film. . On the other hand, CVD supplies chemical vapor with a relatively low adhesion probability to the substrate in a low vacuum state (or normal pressure), so that the vapor wraps around the shadow area. For this reason, as a general tendency, CVD exhibits a coating property that is remarkably superior in geometric steps as compared with PVD.
[0004]
Whether the step coverage is good or bad becomes a problem when a film is formed on a substrate having a depression. Typical and important applications are found in semiconductor integrated circuit manufacturing technology. As is well known, a semiconductor integrated circuit (substrate) has a small area in which minute recesses such as contact holes, via holes, capacitor grooves and the like, and stepped parts such as field steps, wiring steps, gate steps and the like are concentrated in a small area. Yes. In the manufacturing process of a semiconductor integrated circuit, an insulating film (SiO ₂ And Si _Three N _Four ), Various Si-based thin films such as a semiconductor film (poly-Si) and an electrode film (impurity-added poly-Si) with good coverage are indispensable basic technologies. Therefore, in the manufacturing process of a semiconductor integrated circuit, there are various types of CVD that have better wraparound than PVD.
[0005]
[Problems to be solved by the invention]
Recent progress in super-integration (= large scale and high density) of semiconductor integrated circuits is remarkable, and I do not know where it will stay even today. For example, the storage capacity of a typical semiconductor integrated circuit DRAM (anytime read / write memory) increases four times every three years, and the pattern dimension is reduced by about 70%. While progress in super-integration promotes device performance improvement and cost reduction, it leads to downsizing and complication of the device structure, and all processing technologies are constantly required to be changed.
[0006]
CVD is no exception. Today, the strong demand for CVD to be achieved in integrated circuit manufacturing technology is the formation of non-Si based material films on the integrated circuit substrate. As an example, as a method for simplifying the capacitor structure of a memory cell that is too complicated in a DRAM, conventional SiO ₂ And Si _Three N _Four Derivative film Ta with higher dielectric constant ε than ₂ O _Five (Tantalum pentoxide) and BST (barium strontium titanate) are being studied. Alternatively, a completely new concept cell using a ferroelectric PZT (lead zirconate titanate) thin film has been proposed in order to drastically improve the number of times of rewriting in an electrically writable / erasable nonvolatile memory. However, when these non-Si-based new materials are formed by the conventional CVD method, there is a problem that good step coverage as obtained with a Si-based film cannot be obtained.
[0007]
This problem will be described in more detail with a specific example. A diameter of 1.8 μm as shown in FIG. 9 and an aspect ratio (defined here as a ratio of the diameter and depth of the opening) formed in the Si substrate is 1: When a 100nm thin film is formed in the hole 5 by low pressure CVD, SiH _Four (Silane) and NH _Three Si-based dielectric film Si using (ammonia) as a raw material _Three N _Four When the film is formed, a step coverage of η = 0.9 or more can be obtained. Here, the step coverage η is a value obtained by dividing the minimum film thickness inside the hole by the film thickness on the substrate surface. However, in the same hole TaCl _Five And O ₂ Non-Si dielectric film Ta ₂ O _Five When the film is formed, the step coverage is as low as η = 0.20. Such low values of step coverage are Ta ₂ O _Five It is widely recognized not only for films but also for non-Si materials, and when introducing new material films into semiconductor integrated circuits, it has become a major obstacle for further integration of semiconductor integrated circuits. Yes.
[0008]
[Means for Solving the Problems]
The present invention was made for the purpose of solving the problems of the conventional CVD method, and this purpose is “to supply at least one raw material intermittently with a method of supplying a raw material to a reactor”. And Above `` Before or after the raw material supply period, the supply of all raw materials is stopped, and a vacuum exhaust period for exhausting the residual gas in the reactor is set. '' Above In order to achieve the supply method, it can be achieved by “the CVD apparatus structure is an apparatus structure in which intermittent material supply means and intermittent vacuum exhaust means are added to a conventional CVD apparatus”.
[0009]
That is, in the chemical vapor deposition method of the present invention, one or more raw material vapors are transported to a reactor, chemically reacted at or near the substrate in the reactor, and a thin film is synthesized on the substrate. In vapor deposition, A raw material supply period in which a film is formed on the substrate while increasing the pressure in the reactor by controlling the flow rate of the raw material vapor; , Above Introduce and stop the raw material vapor and stop everything in the reactor of A desired film was synthesized by repeatedly performing one cycle including one or several pairs with a vacuum exhaust period for discharging the residual gas. In this chemical vapor deposition method, the vapor raw material used in the one cycle is desired to be obtained. Thin film These constituent elements may contain at least all the elements, and the pressure increase rate of the reactor internal pressure during the raw material supply period may be 0.1. Torr / sec or more, 20 Torr / sec or less, the pressure reduction rate of the reactor internal pressure during the evacuation period may be 20 Torr It may be less than / sec.
[0010]
In the chemical vapor deposition apparatus of the present invention, one or a plurality of vapor inlets for introducing the raw material vapor, a susceptor for supporting the substrate, an exhaust port for discharging the generated gas and the raw material vapor, Above A closed reactor equipped with a heating means for a substrate or a susceptor, a raw material introduction system connected to the vapor inlet, generating raw material vapor, and intermittently introducing it into the reactor at a predetermined pressure increase rate, and generation The exhaust system is configured to exhaust gas and unreacted raw material vapor from the reactor intermittently and at a pressure increase speed equal to or lower than a predetermined pressure increase speed.
[0011]
[Action]
In order to explain the operation of the present invention in an easy-to-understand manner, first, the reason why the step coverage of the conventional CVD deteriorates at a depression or the like will be described with reference to the case of the hole in FIG.
[0012]
Conventional CVD, whether atmospheric pressure CVD or low pressure CVD, performs film formation while supplying the raw material to the reactor and at the same time exhausting exhaust gas and unreacted raw material from the reactor while keeping the pressure constant. Under such circumstances, since the flux of the raw material flying on the substrate surface (= total amount of raw material passing through a predetermined area per unit time) is considered to be approximately constant regardless of the position, the hole opening portion S _A Flux entering the S and S _A Substrate flat part S having the same area as _B The flux incident on is the same. S _B All fluxes that reached _B It can contribute to film formation only on the surface. However, the opening S _A Since the flux entering the hole is distributed to the entire inner surface (side and bottom) of the hole, the net flux reaching the unit surface area inside the hole is greatly reduced, and the material concentration is reduced, so the film thickness inside the hole is It decreases compared to the flat part. This is the first cause that the step coverage is deteriorated due to a depression or the like.
[0013]
The second cause is related to the sticking probability of the raw material. Here, the adhesion probability is a value obtained by dividing a flux portion actually formed into a film by a total flux in a certain area. SiH, the main raw material for Si-based thin film materials _Four And SiH ₂ Cl ₂ The (dichlorosilane) raw material has a low adhesion probability, and the non-Si-based material has a high adhesion probability. As the adhesion probability increases, the rate at which the raw material is consumed in the vicinity of the opening (= becomes a film) increases, and the tendency of the raw material flux reaching the deep part of the hole to decrease rapidly increases. The decrease in raw material flux immediately appears as a decrease in film thickness.
[0014]
A third cause of the deterioration of the step coverage is related to the local exhaust speed of the exhaust gas generated as a byproduct. It is well known that the retention of product gas decreases the production efficiency in a chemical reaction that generally involves the generation of gas as a product. The inside of the hole as shown in FIG. 9 having only one entrance and a narrow opening and deep depth tends to cause the exhaust gas generated by the film formation reaction to stay locally, and its generation efficiency is lower than that of the substrate surface B or the like. To do. This is particularly noticeable under a constant pressure.
[0015]
The reason why the step coverage of the non-Si thin film is inferior to the step coverage of the Si thin film is probably the result of the above factors intertwined with each other.
[0016]
The present invention has been brought about as a result of diligently identifying the factors that deteriorate the step coverage and organizing it as described above, and repeating the trial many times. The operation of the present invention will be described below.
[0017]
Basically, the present invention is based on a clear technical idea of trying to cancel the above three factors simultaneously. The exact principle is still in the process of being elucidated, but is thought to be based on the following principle.
[0018]
The first factor was a factor born as a result of being bound by the physical principle that the flux flying under a certain pressure is constant everywhere if the area is the same. In order to solve this factor, in the present invention, the pressure is not constant during film formation but is variable. That is, a process of repeatedly introducing a raw material vapor into a vacuum reactor until a predetermined pressure was reached was repeated. When the raw material vapor is introduced into the vacuum, a gas flow occurs so that all pressure differences inside the reactor become zero. This is not an exception for the depressions such as holes shown in FIG. 9, and excess flux equal to the volume of the holes flows into the interior from the front so that the pressure inside the holes becomes the same as the external pressure. That is, in the present invention, a much larger amount of raw material flux can flow into the hole as compared with the flat portion A. Therefore, unlike the conventional CVD, the decrease in the film thickness inside the hole is greatly relieved. More preferably, even if the hole depth becomes deeper, the volume of the hole also increases proportionally, so that the excess flux also increases at the same time, and this effect is automatically guaranteed.
[0019]
The second factor is also mitigated by the present invention. The sticking probability is strongly controlled by the raw material vapor adsorption rate and the chemical reaction rate between the adsorbed raw materials. In general, adsorption is different from aggregation, and only one molecular layer is possible. Therefore, unless the adsorbed raw material molecules (vapor) react and turn into a solid, new adsorption does not occur. In the present invention, immediately after the raw material is introduced in the flat portion and the depressed portion, a high concentration raw material flux flows in instantaneously. . As a result, the adsorption rate is reduced, and the adhesion probability is relatively lowered as compared with the case where a film is formed by the conventional CVD method. Thus, in the present invention, even a material having a high adhesion probability by conventional CVD can be handled.
[0020]
In addition, since the film forming method of the present invention includes a step of evacuating the atmosphere in the reactor before or after intermittent supply of the raw material vapor, during this periodic evacuation, the holes such as those shown in FIG. The atmosphere inside the fine depression is also periodically exhausted at the same time. In the method of the present invention, the problem that the exhaust gas stays in the depression and locally inhibits the film formation reaction does not occur. Thus, the method of the present invention can also eliminate the third factor.
[0021]
The present invention solves the problem of the conventional CVD method by alleviating the above three factors, that is, the problem that a non-Si thin film having a good step coverage cannot be realized with a fine recess. It can be done.
[0022]
【Example】
Hereinafter, the CVD method of the present invention and an apparatus for realizing the same will be described with reference to examples. Since the present invention can be applied to various CVD raw materials and film types, the following description will be given with generality. In the following, it is assumed that a plurality of raw materials A, B, C,... The effects of the embodiments and specific film formation examples based on the embodiments will be described later in the section “Specific Examples”.
[0023]
Example 1
FIG. 1 is a view for explaining a first embodiment of the CVD method of the present invention (referred to as “first embodiment of film formation method”, hereinafter the same). This figure shows the change in pressure in the apparatus reactor as a function of process time. A and B are raw material vapors necessary to obtain a desired thin film. The first embodiment of the method proceeds by repeating one cycle consisting of one raw material introduction period and one evacuation period.
[0024]
To explain over time, first, in the raw material introduction period, the vapor raw materials A and B used for film formation are introduced into the reactor in a sufficiently high vacuum. At this time, the vacuum evacuation is stopped, or at least at an exhaust flow rate sufficiently lower than the total flow rate of the steam raw material. The pressure in the reactor increases with time. When the flow rate of the raw material vapor and the exhaust gas flow rate are constant (this is most easily achieved technically), the pressure rise is linear as shown in FIG. The pressure increase need not be linear, but in any case the instantaneous pressure increase rate PR of the reactor is 20 Torr / sec Care must be taken to control the flow rate of the raw material vapor and the exhaust gas flow rate so as not to exceed. When the PR exceeds this value, a violent turbulent flow occurs in the reactor, and there is a risk that the dust in the reactor is wound up and the film formation surface of the substrate is contaminated with dust. On the other hand, if the pressure increase rate is too small, the time for one cycle becomes longer, and gradually the normal CVD (PR = 0 Torr / sec ), The effects described in the section of action are gradually lost. Therefore, in practice, PR = 0.1 Torr / sec It is necessary to be above, and a value as high as possible is desirable. The two points to be noted regarding PR are not limited to the present embodiment, and are commonly applied to all embodiments described later.
[0025]
When the pressure in the reactor reaches a predetermined pressure (or when the raw material introduction period reaches a predetermined time), one raw material introduction period ends. As is clear from FIG. 1, the pressure in the reactor reaches its maximum at the end of the raw material introduction period.
[0026]
Subsequently, when the evacuation period starts, the introduction of all raw materials is immediately stopped, and the generated gas and the remaining raw material vapor are discharged from the reactor. At this time, the inside of a fine depression such as a hole of the semiconductor substrate is similarly exhausted. It is desirable that the exhaust speed ER is always 20 Torr / sec or less during the period. This is because if the ER exceeds this value, a violent turbulent flow occurs in the reactor, and the dust accumulated in the reactor is wound up, and the film formation surface of the substrate may be contaminated with dust. The evacuation period ends when the pressure in the reactor drops to at least 1/100 or less of the maximum pressure during the raw material introduction period, preferably 10 mTorr or less.
[0027]
When one cycle consisting of one raw material introduction period and one evacuation period ends as described above, a thin film of less than several molecular layers is formed on the substrate. Thereafter, when a similar cycle is repeated, a thin film having an arbitrary thickness is generated.
[0028]
(Example 2)
FIG. 2 is a diagram for explaining a second embodiment of the CVD method of the present invention (referred to as “second embodiment of film formation method”, hereinafter the same). This figure shows the relationship between the pressure in the apparatus reactor and the process time. A and B are raw material vapors necessary to obtain a desired thin film. In the second embodiment of the method, the film formation proceeds digitally by repeating one cycle consisting of two raw material introduction periods and two evacuation periods. The feature of the second embodiment of the present method is that the raw materials A and B are introduced alternately.
[0029]
First, there is a first raw material introduction period. During this period, the vapor raw material A used for film formation is introduced into the reactor that is sufficiently high in vacuum. At this time, the evacuation is stopped, or at least the exhaust flow rate is sufficiently lower than the total flow rate of the steam raw material. When the pressure in the reactor increases with time and both the raw material vapor flow rate and the exhaust flow rate are constant, the pressure increase becomes linear. Although it is not always necessary to make the pressure rise linear, in any case, the instantaneous pressure rise rate PR of the reactor should not exceed 20 Torr / sec so that dust in the reactor does not roll up. To. When the pressure in the reactor reaches a predetermined pressure (or when the raw material introduction time reaches a predetermined time), the first raw material introduction period ends.
[0030]
Subsequently, when the first evacuation period starts, the introduction of the raw material vapor A is immediately stopped, and the generated gas and the remaining raw material vapor are discharged from the reactor. At this time, the inside of a fine depression such as a hole is similarly exhausted. Here again, it is desirable that the exhaust speed ER is always 20 Torr / sec or less during the period in order to prevent the dust in the reactor from rolling up. The first evacuation period ends when the reactor pressure drops to at least 1/100 or less of the maximum pressure during the raw material introduction period, preferably 10 mTorr or less.
[0031]
When the process has progressed so far, two states can occur on the flat surface and the depression surface of the substrate. One is a state in which the raw material vapor remains unreacted (or becomes an intermediate species) and is adsorbed less than one atomic layer. The other is a state in which the raw material vapor is decomposed and deposited as a thin film. Although the actual state varies depending on the reaction system, in the system in which the latter occurs, the A raw material supply amount is suppressed during the first raw material supply period so that the thickness of the deposited layer does not exceed one atomic layer. There is a need.
[0032]
When the first evacuation period ends and the second raw material supply period starts, the steam raw material B is introduced. At this time, the vacuum evacuation is stopped, or at least at an exhaust flow rate sufficiently lower than the total flow rate of the steam raw material. The pressure in the reactor increases with time. At this time, the instantaneous pressure rise rate PR of the reactor should not exceed 20 Torr / sec so that dust in the reactor does not roll up. When the pressure in the reactor reaches a predetermined pressure (or when the raw material introduction time reaches a predetermined time), the second raw material introduction period ends.
[0033]
Subsequently, when the second evacuation period starts, the introduction of the raw material vapor B is stopped, and the generated gas and the remaining raw material vapor are discharged from the reactor. At this time, the inside of a fine depression such as a hole is similarly exhausted. Here again, it is desirable that the exhaust speed ER is always 20 Torr / sec or less during the period in order to prevent the dust in the reactor from rolling up. The second evacuation period ends when the pressure in the reactor drops to at least 1/100 or less of the maximum pressure during the raw material introduction period, preferably 10 mTorr or less.
[0034]
When one cycle consisting of the two raw material introduction periods and the two evacuation periods ends as described above, a thin film of less than one molecular layer is formed on the substrate. Thereafter, when a similar cycle is repeated, a thin film having an arbitrary thickness is generated.
[0035]
In addition, when the raw material system in which the B raw material forms a precipitate specific to the B raw material by thermal decomposition alone is used, the B raw material of one atomic layer or more is a substrate in the second raw material supply period and the second evacuation period. It is necessary to suppress the supply amount of the B raw material so that it does not precipitate on the surface. Methods for suppressing include methods such as lowering the supply concentration of the raw material, lowering the maximum pressure, or shortening the raw material supply time.
[0036]
Examples of other methods will be described below. For the sake of brevity, symbolic notation is defined here. The raw material vapor supply period will be expressed as “(A + B)” with the type of vapor enclosed in parentheses. That is, (A + B) is a series of steps in which the raw material vapors A and B are simultaneously introduced into the reactor, the pressure is increased at a rate of 20 Torr / sec or less, the raw material supply is stopped at a predetermined pressure or a predetermined time, and the process is completed. The raw material supply period consisting of In addition, the evacuation period is simply expressed as “→”. This → means a series of steps in which the residual gas in the reactor is exhausted at a speed of 20 Torr / sec or less, and the exhaust is stopped when a predetermined pressure or a predetermined time is reached.
[0037]
When such a notation is used, the first embodiment (FIG. 1) of the film forming method can be simply expressed as “(A + B) →...”. Here, “...” means repetition. Similarly, the second embodiment (FIG. 2) of the film forming method can be simply expressed as “(A) → (B) →.
[0038]
Hereinafter, an example of the film forming method of the present invention in the case of using three or more kinds of raw material vapor will be described using this new notation.
[0039]
(Example 3)
The third embodiment of the CVD method of the present invention is applied when a thin film is produced from three kinds of raw materials. Expressed in the above notation,
(A) → (B + C) → ・ ・ ・
It is. One cycle of film formation includes a step of supplying and exhausting the A raw material alone and a step of supplying and exhausting the B raw material and the C raw material simultaneously.
[0040]
(Example 4)
The fourth embodiment of the CVD method of the present invention is also applied when a thin film is produced from three kinds of raw materials. Expressed in the above notation,
(A + B) → (B + C) → ...
It is. One cycle of film formation includes a process of supplying and exhausting A raw material and C raw material, and a process of supplying and exhausting B raw material and C raw material simultaneously.
[0041]
(Example 5)
The fifth embodiment of the CVD method of the present invention is also applied when a thin film is formed from three kinds of raw materials. Expressed in the above notation,
(A) → (B) → (C) → ・ ・ ・
It is. One cycle of film formation includes a step of supplying and exhausting the A raw material alone, a step of supplying and exhausting the B raw material alone, and a step of supplying and exhausting the C raw material alone.
[0042]
(Example 6)
The sixth embodiment of the CVD method of the present invention is also applied when a thin film is produced from three kinds of raw materials. Expressed in the above notation,
(A) → (C) → (B) → (C) →.
It is. One cycle of film formation is a process of supplying and exhausting the A raw material alone, a process of supplying and exhausting the C raw material alone, a process of supplying and exhausting the B raw material alone, and again supplying the C raw material alone. And evacuating.
[0043]
(Example 7)
The seventh embodiment of the CVD method of the present invention is also applied when a thin film is produced from three kinds of raw materials. Expressed in the above notation,
(A + B + C) → ・ ・ ・
It is. One cycle of film formation is simple, and includes a step of supplying and exhausting A raw material, B raw material and C raw material simultaneously.
[0044]
(Example 8)
As can be seen from the respective examples using the two or three kinds of raw material vapors as described above, each of the film forming methods of the present invention is one cycle (period) in which a plurality of pairs of the raw material supply period and the subsequent evacuation period are combined. And is characterized in that the pressure is not kept constant during the raw material supply period, and the pressure is constantly increased while being supplied. In the raw material supply method, there are a case where one kind of raw material is supplied alone and a case where two or more kinds of raw materials are supplied simultaneously, and which one is selected is appropriately selected in consideration of the film forming reaction system. . What is important is whether all the raw material species necessary for forming a desired thin film are supplied without omission at the end of one cycle. As long as these principles are observed, the CVD method of the present invention can be applied to four or more types of film forming reaction systems. For example, as the eighth embodiment of the film forming method,
(A + B + C) → (C + D) → ...
and so on. However, this is only an example, and all other possible combination patterns are possible in principle.
[0045]
Example 9
Next, examples of the CVD apparatus of the present invention will be described.
FIG. 3 shows a first embodiment of the apparatus of the present invention, and schematically shows the configuration thereof. Reference numeral 10 denotes a cold wall reactor. Inside the reactor 10, there is a susceptor 12 that supports the substrate 11 and holds it at a predetermined temperature Tg. In addition to this, the reactor 10 includes one or a plurality of raw material vapors (A, B, C...) Used for film formation, steam inlets 13 a, 13 b, 13 c. Are provided with an exhaust port 14 for discharging the reaction vapor to the outside of the vessel and a pressure gauge 15 for measuring the pressure inside the vessel.
[0046]
16a, 16b, 16c,... Are raw material steam generators that can generate the plurality of raw material vapors at a predetermined concentration and flow rate, and are stainless steel pipes, reactor inlet valves 17a, 17b, 17c,. .. Are connected to the first vacuum exhaust device 19 via the reactor bypass valves 18a, 18b, 18c... And 13a, 13b, 13c.
[0047]
On the other hand, the exhaust port 14 of the reactor 10 is connected to the second vacuum exhaust device 22 by a stainless steel pipe through a pair of exhaust main valve 20 and exhaust sub valve 21 arranged in parallel. The exhaust sub-valve 21 is designed to have a sufficiently smaller opening diameter than the exhaust main valve 20, and the exhaust speed ER is always devised to be 20 Torr / sec or less. Instead of using the pair of exhaust main valve 20 and sub valve 21, one valve with an exhaust speed adjusting function may be used. In this case, it is assumed that the exhaust speed is designed to be 20 Torr / sec or less. The gas discharged from the first evacuation device 19 and the second evacuation device 22 is purified by a detoxification device (not shown) and then discharged to the atmosphere.
[0048]
23 is a valve control for precisely controlling the opening / closing timing of the reactor inlet valves 17a, 17b, 17c,..., The reactor bypass valves 18a, 18b, 18c,. Device. The valve control device 23 may have a function of reading and determining the pressure value P measured by the pressure gauge 15 and reflecting it in the valve control.
[0049]
Now that the overall structure of the CVD apparatus has been described, the raw material vapor generators 16a, 16b, 16c,. The raw material used for film formation may be a gas from the beginning, or a liquid or solid may be vaporized to form a vapor. FIG. 4 shows an example of raw material vapor generators 16a, 16b, 16c,... In the case of a gaseous raw material (a liquid material that can be easily vaporized in a cylinder such as propane is also included in this category). Reference numeral 24 is a raw material cylinder filled with a gas raw material, 25 is a pressure regulator for making the outlet pressure of the raw material cylinder 24 constant, and 26 is a mass flow controller. The source gas in the source cylinder 24 is adjusted in pressure by the pressure regulator 25, adjusted to a predetermined flow rate by the mass flow rate regulator 26, and transported to the reactor 10 or the first vacuum exhaust device 19. The important film formation parameters in the gaseous raw material steam generator of FIG. 4 are (1) dilution rate (= pure gas / (pure gas + dilution gas)) and (2) of the raw material gas charged in the raw material cylinder 24. Mass flow rate F.
[0050]
FIG. 5 shows an example of raw material vapor generators 16a, 16b, 16c... When the raw materials are liquid and solid. 27 is Ar, He, N ₂ A cylinder filled with an inert carrier gas such as 28, a pressure regulator 28 for making the outlet pressure of the cylinder 27 constant, 29 is a mass flow controller, and 30 is a raw material container having a temperature regulating function. The raw material container 30 is filled with the raw material used from the filling port 31 in advance. After the pressure of the carrier gas in the cylinder 27 is adjusted by the pressure regulator 28, the carrier gas is adjusted to a predetermined flow rate by the mass flow controller 29, enters the raw material container 30 from the carrier gas inlet 32, and the raw material stays in the raw material container 30. Steam is taken in and exits from the raw material steam outlet 33. Thereafter, the raw material vapor and the carrier gas are transported to the reactor 10 or the first vacuum exhaust device 19. The important film formation parameters in the raw material steam generators 16a, 16b, 16c... In FIG. 5 are (1) the carrier gas mass flow rate S and (2) the raw material container temperature Ts.
[0051]
Although not shown in the figure, the pipe connecting the raw material vapor generators 16a, 16b, 16c... And the reactor 10 in the case of liquid and solid is provided with a temperature control function, and at least during the film formation, It is assumed that the temperature is maintained higher than the set temperature of the raw material container 30. This is to prevent vaporized raw material vapor from aggregating in the pipe. In addition, the reactor 30 is provided with an inert gas introduction mechanism for making the internal pressure atmospheric pressure for the purpose of taking the substrate 11 out of the reactor (also not shown in the figure). .
[0052]
(Example 10)
Next, another embodiment of the present CVD apparatus will be described.
FIG. 6 shows a second embodiment of the apparatus of the present invention. Reference numeral 40 denotes a hot wall type reactor, which includes a sealed quartz tube 41 and a cylindrical electric furnace 42 that surrounds the quartz tube 41 and heats it at a predetermined temperature Tg. During film formation, a susceptor (or boat) 42 that supports the substrate 11 is placed inside the quartz tube 41. One end of 41 is provided with steam inlets 13a, 13b, 13c... For introducing one or more raw material vapors (A, B, C...) Used for film formation, and the other end is generated gas. And an exhaust port 14 for discharging unreacted reaction vapor to the outside of the vessel and a pressure gauge 15 for measuring the pressure in the pipe.
The other parts of the second embodiment of the device of the present invention are the same as those of the first embodiment of the device in terms of configuration and function (the same reference numerals are given), and will not be described.
[0053]
As described above, when the configurations of the first and second embodiments of the device of the present invention have been completed, the operation of the embodiments of both devices will be described together. As is apparent from the configurations of FIGS. 4 and 6, the first embodiment of the apparatus is the same because the embodiments of both apparatuses are essentially the same in structure with only slight differences in the method of heating the reactor substrate. It is sufficient to explain the operation with an example.
[0054]
Both embodiments of the apparatus of the present invention can realize all of the first to seventh embodiments of the film forming method of the present invention described above. However, it will not be explained here that the operation of the embodiment of the whole film forming method is possible. If anything, as described above, the film forming method of the present invention is a periodic film forming method in which a plurality of pairs of a material supply period to be supplied while being gently pressurized and a subsequent evacuation period are combined. This is because the raw material supply method basically has only a case where one type of raw material is supplied alone and a case where two or more types of raw materials are supplied simultaneously. A third embodiment of the film forming method of the present invention having both a raw material supply period for supplying A vapor alone and a raw material supply period for simultaneously supplying B vapor and C vapor can realize both embodiments of the present apparatus. It would be enough to explain.
[0055]
As already described, one cycle of the third embodiment of the film forming method includes four steps, and is expressed as follows in a simplified notation. (A) → (B + C) →. Hereinafter, how these four steps are realized in the first embodiment of the film forming apparatus of the present invention will be described in sequence. As a premise, the substrate 11 has already been maintained at a predetermined temperature Tg. It is assumed that it is placed in the reactor 11 in a high vacuum state (in a standby state). Further, immediately before the start of film formation, the exhaust main valve 20 and the exhaust sub-valve 21 are closed, the raw material reactor inlet valves 17a, 17b, 17c... Are all closed, and the bypass valves 18a, 18b, 18c. All of the raw material steam generated by the raw material steam generators 16a, 16b, 16c,... Are first passed through the corresponding bypass valves 18a, 18b, 18c,. It is assumed that the vacuum exhaust device 19 is discharged.
[0056]
(A), that is, the step of introducing the A raw material vapor while gradually increasing the pressure in the reactor 10 (= raw material first supply period) is performed by closing the bypass valve 18a and opening the reactor inlet valve 17a. Can be achieved. At this time, the A raw material vapor is introduced into the reactor 10 in a sealed state from the vapor inlet 13a, and the pressure of the reactor 10 is determined by the volume of the reactor 10 and the mass flow rate of the A raw material vapor (or carrier gas). It keeps rising at a pressure increase rate (constant). Predetermined time ts ₁ After the time elapses, the reactor inlet valve 17a is closed, the bypass valve 18a is opened, and (A) ends. At the same time, the first evacuation period is started without any delay.
[0057]
First, the exhaust sub-valve 21 is opened, and the product gas and unreacted A raw material vapor staying in the reactor 10 are exhausted to the outside at a moderate exhaust speed. When the pressure in the reactor is sufficiently lowered, this time, The exhaust main valve 20 is opened and the remaining gas and the like are exhausted strongly. This two-stage exhaust operation, in which the exhaust main valve 20 is opened at intervals after opening 21, is a device for preventing dust in the reactor 10 from rolling up. Predetermined time tv ₁ After that, the exhaust main valve 20 and the exhaust sub-valve 21 are closed, and the first vacuum exhaust period “→” ends.
[0058]
The next raw material second supply period (B + C) can be achieved by closing the bypass valves 18b and 18c and opening the reactor inlet valves 17b and 17c. At this time, the B raw material vapor and the C raw material vapor are simultaneously introduced into the reactor 10 in a sealed state from the steam inlets 13b and 13c, respectively, and the pressure of the reactor 10 depends on the volume of the reactor 10 and the B raw material vapor (or carrier). Gas) and C raw material vapor (or carrier gas) continue to rise at a predetermined pressure increase rate (constant) determined by the sum of mass flow rates. Predetermined time ts ₂ After the time elapses, the reactor inlet valves 17b and 17c are closed, the bypass valves 18b and 18c are opened, and (B + C) ends. Here, too, the second evacuation period “→” is started without any delay.
[0059]
The operation of the second evacuation period “→” is the same as that of the first evacuation period. That is, the exhaust sub-valve 21 is opened, and when the internal pressure is sufficiently lowered, the exhaust main valve 20 is opened to exhaust the remaining gas and the like strongly. Predetermined time tv ₂ After that, the exhaust main valve 20 and the exhaust sub-valve 21 are closed, and the first vacuum exhaust period “→” ends. Thus, one cycle of the third embodiment of the film forming method of the present invention is completed.
[0060]
In order to obtain a thin film having a desired thickness on the substrate 11, the above cycle may be repeated as appropriate. When the film reaches a desired film thickness, the temperature of the susceptor (or electric furnace) is lowered, an inert gas is introduced into the reactor 10 to atmospheric pressure, and the substrate 11 is taken out of the reactor 10.
[0061]
As described above, after the embodiments of the film forming method and the film forming apparatus of the present invention have been described, the effects of this embodiment will be described. In order to show as concretely as possible, various films of about 100 nm are formed in the holes having the structure shown in FIG. 9 by the CVD method of the present invention and the conventional CVD method. Evaluate and compare (defined). Film formation by the conventional method is a low-pressure CVD method that is considered to have good step coverage, and film formation is performed under typical conditions using the same raw materials and reactor as those of the method according to the present invention.
[0062]
1) Specific example 1 of film formation
This example uses the first embodiment (FIG. 3) of the film forming apparatus of the present invention and the first embodiment (FIG. 1, (A + B) →. ₂ This is an example of forming a film. Raw material is TiCl _Four (= A raw material vapor, room temperature liquid) and O ₂ (= B raw material vapor, dilution rate 0%). TiCl _Four Is contained in a stainless steel raw material container maintained at a temperature Ts = −10 ° C. Carrier gas is 99.999% purity Ar gas, and its mass flow rate is F _A = 200cc / min, F _B = 100cc / min. The length of the raw material supply period is ts ₁ = 10 sec, length of vacuum evacuation period tv ₁ = 5 sec. The film formation temperature (susceptor temperature) Tg = 450 ° C., and the volume of the reactor was about 5 liters. When film formation is performed under these conditions, TiO with a thickness of average GR = 0.2 nm / cyc in one cycle ₂ A film is deposited.
[0063]
On the other hand, the conditions by the conventional CVD method performed for comparison are TiCl _Four Carrier gas mass flow F _A = 200cc / min, container temperature Tso = -10 ° C, O ₂ Mass flow rate F _B = 100 cc / min, film forming temperature Tg = 450 ° C., film forming pressure P = 2 Torr.
[0064]
The present invention and the conventional CVD conditions are summarized in FIG.
[0065]
TiO in the conventional method and the method of the present invention ₂ As a result of the film formation, the conventional method showed a tendency for the film thickness to decrease sharply from the opening of the hole toward the bottom. Flat part S of substrate _B When the film thickness is 100 nm, the hole bottom film thickness is approximately 15 nm, and according to the definition at the beginning, the step coverage in this case is η = 0.15. In contrast, TiO deposited by the method of the present invention ₂ The film still tended to decrease in thickness from the opening toward the bottom, but the gradient was much milder, η = 0.85.
[0066]
From the above experimental results, it has been shown that the CVD method of the present invention can greatly improve the excellent step coverage in a depressed structure such as a fine hole as compared with the conventional CVD method.
[0067]
2) Specific example 2 of film formation
This example is an example of synthesizing a TiN film used as a barrier film at a contact interface between an Al wiring and a Si substrate (or polysilicon film) in a Si integrated circuit. Since these interfaces are usually located at the bottoms of minute recesses such as contact holes and via holes provided in a PSG (phosphosilicate glass) film, it is an important issue to ensure step coverage.
[0068]
Raw material is A raw material vapor is TiCl _Four (Ar carrier) and B raw material vapor are NH _Three Gas. The first embodiment (FIG. 3) of the film forming apparatus and the second embodiment ((A) → (B) →...) Of the film forming method were applied to the film formation. The film forming conditions of the present invention CVD and the conventional CVD used for the test are as shown in FIG. It should be noted that description of each parameter of the film formation that has been defined in the specific example of film formation is omitted in the following specific examples including this specific example.
[0069]
In the embodiment of the present invention, a propulsion speed of approximately GR = 0.3 nm / cyc is obtained. The step coverage η = 0.89, which is a good value. TiCl _Four + NH _Three When a film is formed by a conventional CVD method using a raw material system, not only is the step coverage η = 0.15 bad, but both raw materials react strongly in the gas phase, and a fine powdery intermediate product is generated. It was difficult to obtain a smooth film. However, in the example of this film formation method, TiCl _Four And NH _Three Are introduced alternately, so that they do not mix in the gas phase, so that such a problem does not occur and a high-quality film can be formed.
[0070]
3) Specific example 3 of film formation
In this example, a PbO film is formed by combining the first embodiment (FIG. 3) of the film forming apparatus and the first embodiment (FIG. 1) of the film forming method. A raw material vapor is Ar gas transported 4-ethyl lead Pb (C ₂ H _Five ) _Four (Normal temperature liquid) and B raw material vapor are O ₂ It is. The film forming conditions are as shown in FIG. In the present CVD method, a growth rate of GR = about 0.41 nm / cyc is obtained under these conditions.
The step coverage was η = 0.85 in the present CVD method and η = 0.45 in the conventional CVD method. The superiority of the present invention is also evident in this example.
[0071]
4) Specific example 4 of film formation
This example is a Ta capacitor that has been developed recently as an LSI capacitor material. ₂ O _Five This is an example of forming a film. As the raw material, A raw material vapor is Ta (OC ₂ H _Five ) _Five (Liquid at normal temperature, Ar carrier transport) and B raw material vapor are O ₂ It is. In the CVD method of the present invention, the second embodiment (FIG. 6) of the hot wall type film forming apparatus and the first embodiment ((A + B) →...) Of the film forming method were applied for film formation. The diameter of the quartz tube of the reactor was 100 mm and the total length was 1500 mm. The present invention CVD and the conventional CVD conditions used in the test are as shown in FIG. In the embodiment of the present invention, a propulsion speed of approximately GR = 0.8 nm / cyc is obtained.
[0072]
The step coverage was η = 0.92 by the present CVD method and η = 0.82 by the conventional CVD method. The superiority of the present invention is also evident in this example. Ta with high step coverage ₂ O _Five It has been confirmed that the film (η is slightly different) can be obtained by using the first embodiment of the apparatus of the present invention or by using the second embodiment of the film forming method of the present invention.
[0073]
5) Specific example 5 of film formation
This example shows ferroelectric PbTiO _Three This is an example in which a (lead titanate) film is synthesized using the first embodiment (FIG. 2) of the film forming apparatus and the fourth embodiment ((A + C) → (B + C) →...) Of the film forming method. A Raw material vapor = Ti (i-OC _Three H ₇ ) _Four (Titanium tetraisopropoxide, room temperature liquid, Ar carrier transport), B raw material vapor = Pb (C ₂ H _Five ) _Four (Ar carrier transport), C raw material vapor = O ₂ It is. The film forming conditions of the present CVD method and the conventional CVD method are as shown in FIG. An average growth rate GR = 0.42 / cyc was obtained.
[0074]
The step coverage was η = 0.85 in the present CVD method and η = 0.42 in the conventional CVD method. Compared with the conventional CVD method, the present invention is superior in step coverage. It has been confirmed that even if the sixth embodiment or the seventh embodiment of the film forming method of the present invention is used, a film having a much higher step coverage can be obtained as compared with the prior art.
[0075]
6) Specific example 6 of film formation
This example shows ferroelectric Pb (Zr _0.5 Ti _0.5 ) O _Three (Lead titanium zirconate: commonly called PZT) film is synthesized using the first embodiment of the film forming apparatus (FIG. 3) and the seventh embodiment of the film forming method ((A + D) → (B + C + D) →...) It is an example. A Raw material vapor = Ti (i-OC _Three H ₇ ) _Four , B raw material vapor = Zr (t-OC _Four H ₉ ) _Four (Zircon tetratertiary propoxide, room temperature liquid, Ar carrier transport), C raw material vapor = Pb (C ₂ H _Five ) _Four (Ar carrier transport), D raw material vapor = O ₂ It is. The film forming conditions of the present CVD method and the conventional CVD method are as shown in FIG. In FIG. 7, parameters having the subscripts A, B, C, and D are related to the A raw material, the B raw material, the C raw material, and the D raw material, and the subscripts 1 and 2 are the first and second raw material supply periods (or vacuums). Exhaust period) is a parameter. An average growth rate GR = 0.42 / cyc was obtained.
[0076]
The step coverage was η = 0.84 in the present CVD method and η = 0.42 in the conventional CVD method. The superiority of the present invention in the step coverage is obvious compared with the conventional CVD method.
[0077]
【The invention's effect】
As described above, according to the chemical vapor deposition method of the present invention, the film formation method of the chemical vapor deposition method includes the raw material supply period in which the raw material vapor is introduced into the reactor while constantly increasing the pressure, and the raw material By adopting a system in which one cycle including a pair or several pairs with the evacuation period for introducing and stopping the steam and discharging the residual gas in the reactor is repeated, the raw material steam having a high adhesion probability must be used. Even in such a case, it is possible to obtain an effect that a desired thin film can be formed with good coverage in a fine depression.
[0078]
Furthermore, in a synthesis reaction system using a plurality of raw material vapors, the film forming method of the present invention has the flexibility to supply a specific raw material species separated in terms of time or mixedly supplied. Therefore, (1) film formation in which gas phase reaction between specific raw material species is prohibited, and (2) film formation in which gas phase reaction between specific raw material species is allowed, under conditions that could not be realized by conventional CVD methods. It becomes possible to form a film. A typical example utilizing the advantage of (1) can be seen in the above-mentioned specific example 2.
[Brief description of the drawings]
FIG. 1 is a diagram showing a first embodiment of a film forming method according to the present invention.
FIG. 2 is a view showing a second embodiment of the film forming method according to the present invention.
FIG. 3 is an overall view showing a first embodiment of a film forming apparatus according to the present invention.
FIG. 4 is a configuration diagram showing an example of a raw material vapor generator of the first embodiment of the film forming apparatus.
FIG. 5 is a configuration diagram showing another example of the raw material vapor generator of the first embodiment of the film forming apparatus.
FIG. 6 is an overall view showing a second embodiment of the film forming apparatus according to the present invention.
FIG. 7 is a diagram showing film forming conditions of an embodiment of the present invention and a conventional example used in the description of specific examples 1 to 3.
FIG. 8 is a diagram showing film forming conditions of an embodiment of the present invention and a conventional example used in the description of specific examples 4 to 6;
FIG. 9 is a cross-sectional view of a main part showing an example of a substrate having a fine depression.
[Explanation of symbols]
10,40 reactor
11 Substrate
12,42 Susceptor
13a-13c ... Steam inlet
14 Exhaust vent
15 Pressure gauge
16a-16c ... Raw material steam generator
17a-17c ... Reactor inlet valve
18a to 18c: Bypass valve
19 First vacuum exhaust device
20 Exhaust main valve
21 Exhaust auxiliary valve
22 Second vacuum exhaust device
23 Valve control device
24 Raw material cylinder
25, 28 Pressure regulator
23, 29 Mass flow controller
27 Carrier gas cylinder
30 Raw material container
31 Filling port
32 Carrier gas inlet
33 Material gas outlet
41 Quartz tube
T _s Raw material container temperature
F Mass flow rate of source gas or carrier gas
T _g Deposition temperature
t _s Raw material supply period length
t _v Vacuum exhaust period length

Claims (4)

In a chemical vapor deposition method in which one or a plurality of non-Si-based thin film raw material vapors are transported to a reactor, chemically reacted at or near the substrate in the reactor, and a thin film is synthesized on the substrate,
A raw material supply period for controlling the flow rate of the non-Si-based thin film raw material vapor and generating a film on the substrate while increasing the pressure in the reactor at a pressure increase rate of 0.1 Torr / sec or more and 20 Torr / sec or less; It is characterized in that a desired film is synthesized by repeatedly performing one cycle including a pair or several pairs with a vacuum pumping period in which the supply of steam is stopped and all residual gas in the reactor is exhausted. Chemical vapor deposition.   2. The chemical vapor deposition according to claim 1, wherein the non-Si-based thin film raw material vapor used in one cycle contains at least all the constituent elements of a desired thin film to be obtained. Law. The chemical vapor deposition method according to claim 1 or 2, wherein the pressure reduction rate of the reactor internal pressure during the evacuation period is 20 Torr / sec or less. In a chemical vapor deposition apparatus in which one or a plurality of non-Si-based thin film raw material vapors are transported to a reactor, chemically reacted at or near the substrate in the reactor, and a thin film is synthesized on the substrate,
A raw material supply period for controlling the flow rate of the non-Si-based thin film raw material vapor and generating a film on the substrate while increasing the pressure in the reactor at a pressure increase rate of 0.1 Torr / sec or more and 20 Torr / sec or less; It is characterized in that a desired film is synthesized by repeatedly performing one cycle including a pair or several pairs with a vacuum pumping period in which the supply of steam is stopped and all residual gas in the reactor is exhausted. Chemical vapor deposition equipment.

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