JP2002343792A - Film forming method and device thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for forming films by which the microloading of the film forming speed can be sufficiently improved while suppressing the decrease in the film forming speed when a film containing atoms of nitrogen is formed on a substrate by a CVD method. SOLUTION: The film forming method is a thermal CVD method by which a silicon nitride film is formed on a silicon wafer W. The silicon wafer W is placed on a susceptor 5 in a chamber 2, and NH3 gas and SiH4 gas are supplied into the chamber 2 at a specified flow rate from a gas supplying part 30 while the chamber 2 is depressurized. In this case, the supply and exhaust of the gases is controlled by a controller 80, MfC 31a, 32a and the like in such a way that the retention time of the gases on the silicon wafer W is 8-17 sec, for example. In this way, the generation of Si i-mer on the silicon wafer W is suppressed and the rate controllability of deposition reaction is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for forming a film, and more particularly, to a chemical vapor deposition (hereinafter referred to as "CV").
D)) and a film forming apparatus for forming a film having nitrogen atoms such as a nitride film on a substrate by a method.

[0002]

2. Description of the Related Art A CVD method is widely known as one of film forming methods used for manufacturing semiconductor devices. In general, when an element pattern is formed on a substrate such as a silicon wafer on which a film is to be formed, the size of the surface area varies depending on the density of the pattern. If, for example, a functional film such as a dielectric film, an insulating film, or a protective film or a use film is formed on a region (site) having a different surface area by a CVD method, a large surface area (a high pattern density) may be obtained in some cases. In some cases, the film deposition rate in the region (i.e., region) decreases, that is, the density dependence of the film deposition rate (microloading) becomes significant.

[0003]

The present inventors have conducted detailed studies on various film forming processes applied to the manufacture of semiconductor devices with respect to such micro-loading at a film forming rate. It has been found that when a nitride film such as a silicon nitride film is formed by a thermal CVD method using an NH ₃ ) gas as a nitrogen source, a difference in film formation rate due to pattern density may be remarkable. When such a phenomenon occurs, it becomes difficult to control the film formation, and it becomes difficult to obtain a desired film having excellent uniformity of the film thickness. As a result, the performance required for the semiconductor device may not be sufficiently achieved.

According to the knowledge of the present inventors, as one of the methods for preventing such macro loading of the film formation rate, a method of performing the film formation reaction in a reaction-controlled state is considered. However, as a measure for this, it is necessary to perform film formation under extremely reduced pressure conditions, and there is a concern that the film formation speed itself may be extremely reduced. This is inconvenient, especially when a single-wafer CVD apparatus is used, and there has been a strong demand for an alternative method capable of suppressing the occurrence of microloading without performing film formation under an extremely reduced pressure.

Accordingly, the present invention has been made in view of such circumstances, and when forming a film containing nitrogen atoms on a substrate by a CVD method, it is possible to suppress a decrease in the film forming rate and to form the film. An object of the present invention is to provide a film forming method and apparatus capable of sufficiently improving microloading of a film speed.

[0006]

Means for Solving the Problems In order to solve the above problems, the present inventors have conducted intensive studies and found that a reaction intermediate (intermediate product) formed by various elementary reactions on a substrate in the CVD method ), The formation probability thereof, and the rate-limiting state of the reaction, and the micro-loading effect of the deposition rate, have been found to have a close relationship, and as a result of further research based on this finding, the present invention has been completed. I came to.

That is, the film forming method according to the present invention comprises:
A method for forming a film having nitrogen atoms on a substrate by a VD method, comprising the steps of: (1) forming a first gas containing an NH ₃ gas on a substrate and a first gas capable of reacting with the first gas; A gas supply step of supplying the first gas and the second gas so that the residence time of the first gas and the second gas on the substrate becomes a predetermined value; and (2) a substrate heating step of heating the substrate to a predetermined temperature. And

In the film forming method having such a structure,
When the first gas and the second gas are supplied onto the substrate in the gas supply step, and the substrate is heated to a predetermined temperature in the substrate heating step, a gas phase reaction of the substances constituting both gases substantially immediately above the substrate. Occurs. As a result, a film containing nitrogen atoms is formed on the substrate. At this time, in the gas phase reaction, various reaction intermediates are formed, and their types and production probabilities are presumed to vary variously and subtly depending on equilibrium conditions and reaction kinetic governing factors in the reaction field. .

For this reason, it is often extremely difficult to optimize the film forming conditions, and in particular, a specific optimum such as sufficiently improving only the macro loading of the film forming speed while sufficiently maintaining the film characteristics. The conversion method did not exist conventionally. On the other hand, the present inventors have found that in the gas supply step, the residence time of the first gas and the second gas as the source gas on the substrate (residence time; or
It has been found that process control for setting the passage time) to a predetermined value is extremely effective.

As an example, the case where a monosilane (SiH ₄ ) gas which is a silane-based gas is used as the second gas will be described. The residence time of the first gas and the second gas on the substrate is excessively short. Then, the decomposition of the NH ₃ gas contained in the first gas in the substrate heating step tends to be insufficient. In this case, the probability of reaction between the NH ₃ gas and the SiH ₄ gas is reduced, and the Si ionomer (i−) is formed by the reaction between the SiH ₄ gas which is more easily thermally decomposed than the NH ₃ gas or with the chemical species derived from SiH _4. mer; Si _j H ₂ ) is relatively increased.

As a result, the consumption of the SiH ₄ gas increases and the Si source is depleted. In addition, since the eyemer is generally active and has a large reaction rate constant, the film formation reaction of the silicon nitride film is shifted toward the supply-limiting side. Go leaning. Therefore, the supply of the source gas to a portion having a large pattern density (a narrow portion) on the substrate tends to be delayed, and the film forming speed at that portion is relatively reduced.

On the other hand, if the residence time becomes excessively large, N
H ₃ pyrolysis gas proceeds, SiH ₄ gas between or the SiH ₄
Although a part of the reaction with the derived chemical species is replaced by the reaction between NH ₃ and SiH ₄ , the increase in the probability of producing an eyemer also becomes remarkable, and as a result, the production reaction of the eyemer becomes dominant and the supply The rate control will increase. Therefore, also in this case, microloading of the film forming speed is likely to occur. The operation is not limited to these.

That is, although there is a possibility that it depends on other film forming conditions, there is a suitable range for the residence time of the first gas and the second gas on the substrate. In the present invention,
Since the first gas and the second gas are supplied onto the substrate so as to realize such an effective residence time, the generation of an eyemer is sufficiently suppressed. In addition, since the generation of an eyemer is suppressed by controlling the residence time, it is not necessary to set an extremely reduced pressure around the substrate.

More specifically, although depending on other conditions as described above, the predetermined value of the residence time in the gas supply step is preferably 8 to 17 seconds, more preferably 12 to 13 seconds.
It is preferable that the value be within the range of ec. When the residence time is less than the above lower limit, the decomposition of the NH ₃ gas in the first gas becomes insufficient, and the generation probability of an eyemer generated from a component of the second gas such as the SiH ₄ gas is excessively increased. There is a tendency. On the other hand, even when the residence time exceeds the above upper limit, the film forming reaction tends to be in a supply-limiting state, which is inconvenient.

In the gas supply step, it is more preferable to adjust the discharge rates of the first gas and the second gas from the periphery of the base so that the above-mentioned residence time becomes a predetermined value. Here, the “residence time” in the present invention can be represented by the following equation (1): Rt = V _ch / S (1). Where Rt is the residence time (sec)
And V _ch represents the volume (l) of a predetermined space region on the substrate to which the first gas and the second gas are supplied, and
Indicates a discharge (exhaust) rate (l / sec) of all gases including the first gas and the second gas from the space region.

Normally, in an apparatus using the CVD method, a raw material gas is supplied from a shower head or the like onto a wafer as a substrate, and the volume V _{ch in} this case is specifically determined by a shower head or the like. And the volume of the predetermined space between the substrate and the base. Therefore, by controlling the residence time Rt by adjusting the discharge speed S, it is possible to prevent the generation of the eyemer and the rate-determining of supply to be excessively increased without depending on the apparatus in which the film is formed.

More specifically, in the gas supply step, the supply flow rates of the first gas and the second gas onto the substrate,
Further, it is more preferable to adjust the discharge speed S by adjusting at least one of the pressure around the substrate.

The discharge speed S in the above equation (1) can satisfy the relationship expressed by the following equation (2): Q = P × S (2). In the formula, Q indicates a total supply flow rate (Torr · l / sec) of all gases supplied onto the substrate including the first gas and the second gas, and P indicates a pressure (Torr) around the substrate. . That is, the pressure P and the supply flow rate Q, which are relatively easy to adjust, can adjust and control the discharge speed S and thus the residence time Rt. Therefore, the complexity of process control is effectively suppressed, and
The formation of the eyemer is suppressed, and the film forming reaction is prevented from excessively tilting toward the supply-limiting side.

In the gas supply step, the ratio of the flow rate of the first gas to the flow rate of the second gas is preferably 3
The first gas and the second gas are set so as to be not less than 00, more preferably 300 to 600, and particularly preferably 350 to 550.
Is preferably supplied onto the substrate.

According to the study of the present inventors, the ratio of the flow rate of the first gas to the flow rate of the second gas (hereinafter referred to as “F1 / F”)
It has been found that the above-described control of the residence time Rt functions particularly effectively under a gas supply condition in which the “2 ratio” is 300 or more. That is, the F1 / F2 ratio is 3
When it is not less than 00, suppression of the eyemer that can be generated from the component of the second gas is sufficiently suppressed, and also in this case, the optimum range of the residence time Rt considered to be caused by the same action as the above-described action mechanism is set to Exists.

If the F1 / F2 ratio is too large, the supply of the second gas is insufficient compared to the NH ₃ gas contained in the first gas depending on the process, and the microloading is not always sufficiently improved. Not only that, the deposition rate may be significantly reduced. Therefore, in such a case, although it depends on the type of the second reaction gas, the film formation conditions, and the like, F
By setting the 1 / F2 ratio to 600 or less, a decrease in the film formation rate can be prevented more sufficiently.

Further, as described above, when the second gas contains a silane-based gas such as SiH ₄ gas,
The formation of Si eyemers is likely to occur, and this Si
It is a reaction intermediate having a relatively high production probability and a high reactivity among various eyemers. Therefore, microloading of the film forming speed may be easily generated as compared with the case where another gas including an organic metal gas, a metal halide gas, or the like is used as the second gas. Therefore, the present invention is extremely useful when a gas containing a silane-based gas is used as the second gas.

The film forming apparatus according to the present invention is an apparatus for effectively implementing the film forming method of the present invention,
A film containing a nitrogen atom is formed on the substrate by the method D, wherein (1) a chamber for accommodating the substrate;
(2) a first gas supply source connected to the chamber and including a first gas containing NH ₃ gas;
A gas supply unit having a second gas supply source containing a second gas capable of reacting with the second gas, and (3) the residence time Rt of the first gas and the second gas on the substrate is a predetermined value. And a residence time adjusting unit for adjusting the supply of the first gas and the second gas to the chamber and the discharge of the first gas and the second gas from the chamber, and A substrate heating unit for heating to a predetermined temperature.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. Note that the same components are denoted by the same reference numerals, and redundant description will be omitted. Unless otherwise specified, the positional relationship such as up, down, left, and right is based on the positional relationship shown in the drawings. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

FIG. 1 is a cross-sectional view (partial configuration diagram) schematically showing a preferred embodiment of a film forming apparatus according to the present invention. The CVD apparatus 1 as a film forming apparatus includes a gas supply unit 30 in a chamber 2 in which a silicon wafer W (base) is accommodated.
Are connected. The chamber 2 has a susceptor 5 on which a silicon wafer W is placed. Above the susceptor 5, a shower head 4 having a hollow disk shape is provided.
Is provided.

The susceptor 5 is hermetically provided in the chamber 2 by an O-ring, a metal seal, or the like.
It is provided so that it can be driven up and down by a movable mechanism (not shown). The distance between the silicon wafer W and the shower head 4 is adjusted by the movable mechanism. Further, a heater 51 (substrate heating unit) is provided in the susceptor 5, and thereby the silicon wafer W is heated to a desired predetermined temperature.

On the other hand, the showerhead 4 has a substantially cylindrical shape and has a base plate provided with the gas supply port 9 as an upper wall. The lower end of the body 41 has a plurality of through holes 45a formed therein. The plate-like face plate 45 is combined. Inside the shower head 4, a blocker plate 43 in the form of a perforated plate having a plurality of through holes 43 a is provided substantially in parallel with the face plate 45. A space Sa is defined by the body 41 and the blocker plate 43, and a space Sb is defined by the body 41 and the face plate 45.

An opening 7 is provided below the chamber 2. The opening 7 has an exhaust system 70 having a vacuum pump capable of reducing the pressure inside the chamber 2 and maintaining the inside of the chamber 2 at a predetermined pressure value in accordance with the supply flow rate of each gas described later from the gas supply unit 30. Is connected.

Although not shown, the space inside the chamber 2 on the front side of the silicon wafer W and the space inside the chamber 2 on the back side are gas-sealed with each other. That is, a raw material gas and the like to be described later are supplied to the front side from the gas supply unit 30 through the shower head 4, while a purge gas is supplied to the back side from a back side purge system (not shown). Both gases are prevented from entering the regions on the opposite surfaces.

The gas supply unit 30 includes an NH ₃ gas supply source 31 (first gas supply source), a SiH ₄ gas supply source 32
(A second gas supply source) and supply sources 33 and 34 for a carrier gas or a dilution gas (hereinafter, referred to as “carrier gas or the like”). Each of these gas supply sources 31 to 34 is an MFC (mass flow controller) for controlling the supply flow rate of each gas.
The shower head 4 is connected to the gas supply port 9 via a pipe 10 provided with 31a to 34a. As a result, NH ₃ gas (first gas), SiH ₄ gas (second gas), carrier gas, and the like are introduced into the shower head 4, and are introduced into the chamber 2 via the blocker plate 43 and the face plate 45. Supplied to

Further, the MFCs 31a to 34a and the exhaust system 70 are connected to the control unit 80 by electric wires.
The control unit 80 has an input / output interface (both not shown) capable of bidirectional transmission with an arithmetic device such as a CPU, and controls the gas flow rate signals from the MFCs 31a to 34a and the gas discharge speed in the exhaust system 70 ( (Exhaust flow rate) is input to the arithmetic unit via the input / output interface, and control signals based on these values are output to the MFCs 31a to 34a and the exhaust system 70 via the input / output interface, and the gas supply flow rate and the gas discharge rate Adjustments are made. Thus, the MFCs 31a and 32a, the exhaust system 70, and the control unit 80 constitute a residence time adjusting unit.

An example of the film forming method according to the present invention using the CVD apparatus 1 having such a configuration will be described below. The operations of the CVD apparatus 1 described below are controlled by the control unit 80 or another control system (not shown), or manually, based on an operation by an automatic or operator.

First, the pressure in the chamber 2 is reduced by a vacuum pump. Under this reduced pressure, the silicon wafer W is transferred into the chamber 2 from a predetermined location such as a load lock chamber, another chamber, another wafer preparation chamber, etc.
Place on top and house. Next, a carrier gas or the like is supplied from the gas supply sources 33 and 34 into the chamber 2 through the pipe 10, and the pressure is adjusted so that the inside of the chamber 2 has a predetermined pressure.

After the pressure in the chamber 2 is stabilized at a predetermined value, NH ₃ gas and SiH ₄ gas are supplied as source gases for film formation from the gas supply sources 31 and 32 to the shower head 4 through the pipe 10 respectively ( Gas supply step). In this state, the heater 51 is operated to heat the silicon wafer W to a predetermined temperature (substrate heating step). Thus, on the silicon wafer W, the NH ₃ gas and the SiH ₄ gas are thermally decomposed or dissociated, and various chemically active species are generated.

These chemical species are involved in various elementary reactions (thermochemical reactions) in a complicated manner, and a governing factor depending on an equilibrium and a rate-determining condition depending on a state of a reaction field can be generated. Examples of the reaction product generated by the elementary reaction include various reactions such as the above-mentioned Si eyemer, an intermediate containing a Si atom and an N atom in a molecule such as aminosilane (Si (NH ₂ ) ₄ ), and a silylene derivative. Intermediates are envisioned.

Here, in the present embodiment, SiH ₄
The flow ratio of NH ₃ gas to gas (F1 / F2 ratio)
Preferably 300 or more, more preferably 300 to 60
The control unit 80 adjusts the MFCs 31a and 32a so as to be 0, more preferably 350 to 550. This F
When the 1 / F2 ratio is less than 300, the supply of the NH ₃ gas to the SiH ₄ gas in the chamber 2 becomes too small, and the relative generation ratio of the Si eyer tends to increase significantly. In such a case, the reaction gas is depleted due to the consumption of the SiH ₄ gas, and as a result, the film forming reaction tends to lean toward the supply-limiting side. On the other hand, F1 / F2
When the ratio exceeds 600, the supply rate of the SiH ₄ gas is initially short compared to the NH ₃ gas, so that the reaction probability between the NH ₃ gas and the SiH ₄ gas decreases, and in some cases, the film formation. It is difficult to increase the speed sufficiently.

Further, not only the F1 / F2 ratio is adjusted by adjusting the MFCs 31a and 32a, but also the supply flow rates of the NH ₃ gas and the SiH ₄ gas, and
The FCs 33a and 34a are adjusted to adjust the total gas supply flow rate into the chamber 2. The total gas supply flow rate Q to the chamber 2, the pressure P in the chamber 2, and the gas discharge speed S from the chamber 2 are represented by the following formula (2); Q = P × S (2) Satisfy the relationship. Therefore, by adjusting the total gas supply flow rate Q according to the pressure P, the gas discharge speed S from the chamber 2 can be easily controlled.

Further, the gas discharge speed S from the chamber 2
And the residence time Rt of the NH ₃ gas, the SiH ₄ gas, the carrier gas, and the like on the silicon wafer W are represented by the following equation (1); Rt = V _ch / S (1) Satisfy the relationship.

Here, the silicon wafer W is
Volume V _ch when processing is more precisely, the following formula _{(3); V ch = π} × (r + r a) 2 × H ... (3), can be represented by. Wherein, r is shown the radius of the silicon wafer W, H represents the distance between the top surface Wf of the lower surface 45f and the silicon wafer W of the face plate 45, r _a is 50
mm. That is, the volume V _ch represents the volume of the space V indicated by the hatched broken line in FIG. The units of the radius r and the distance H are determined as needed so that the unit systems on the left side and the right side of Expression (3) match.

Therefore, the residence time Rt can be adjusted to a desired time by appropriately adjusting the gas discharge speed S according to the volume _Vch of the space V in the chamber 2. More specifically, as the residence time Rt, the equation (1)
8 to 17 sec (more strictly, for example, 8.4 to 19.6 sec), more preferably 12 to 13 sec (more strictly, for example, 12.2 sec.)
１２12.8 sec). When the residence time Rt of the NH ₃ gas and the SiH ₄ gas in the space portion V is set to a value within this range, generation of Si immers is suppressed, waste of the SiH ₄ gas is prevented, and Si atoms such as aminosilane are removed. And the production ratio of intermediates containing N atoms is increased. Therefore, while the supply rate control of the film forming reaction on the silicon wafer W is suppressed, the reaction rate control is enhanced.

The intermediate such as aminosilane is excellent in migration on the silicon wafer W,
It tends to be fixed or adhered on the silicon wafer W.
Therefore, it is possible to sufficiently prevent a reduction in the film formation rate. further,
The preferred range of the residence time Rt is as follows.
Although not limited to using H ₄ gas, it is particularly effective for the reaction system of this embodiment (NH ₃ gas and SiH ₄ gas).

Further, the preferred range of the residence time Rt is as follows:
This is extremely useful when the aforementioned F1 / F2 ratio is 300 or more. That is, when the F1 / F2 ratio is increased, the concentration of NH ₃ gas in the reaction field is increased, and NH ₃ gas and SiH ₄
The average equilibrium reaction with gas (the sum of various elementary reactions) tends to shift toward the formation of intermediates such as aminosilane, but, for example, the 'gas flow rate' is too fast and the residence time Rt is excessively shortened. In such a case, it is difficult to reduce the supply rate control of the reaction. This is presumed to be due to the fact that, despite the increased NH ₃ gas concentration, the decomposition of the NH ₃ gas is insufficient, and the generation ratio of Si eyemers is relatively increased. However, the operation is not limited to this.

Next, by performing such gas supply and heating of the silicon wafer W for a predetermined time, a silicon nitride film is deposited and grown on the silicon wafer W. Thereafter, the supply of the NH ₃ gas and the SiH ₄ gas to the chamber 2 is stopped, and the film formation is completed. Then, after purging the gas remaining in the chamber 2 as necessary, the silicon wafer W on which the silicon nitride film is formed is carried out of the chamber 2.

According to the CVD apparatus 1 thus configured and the film forming method of the present invention using the same, the residence time Rt of the NH ₃ gas and the SiH ₄ gas in the space V on the silicon wafer W is set to a desired value. NH ₃
By supplying a gas, a SiH ₄ gas, a carrier gas, and the like into the chamber 2, the generation of Si immers can be suppressed, and the rate control of the film formation reaction of the silicon nitride film can be increased. Therefore, even when a stepped portion such as an element pattern is provided on the silicon wafer W, it is possible to sufficiently suppress the sparse and dense dependence of the deposition rate, that is, the occurrence of microloading.

If the residence time Rt is kept or maintained at a value in the range of 8 to 17 seconds, the generation of Si immers can be sufficiently and reliably suppressed, and the reaction rate-determining property can be surely enhanced. Therefore, it is possible to further improve the microloading of the film forming speed. Further, since the microloading can be improved without extremely reducing the pressure in the chamber 2, a decrease in the film forming speed can be suppressed. Therefore, in forming the silicon nitride film, it is possible to suppress a decrease in throughput and productivity due to a decrease in processing speed, and it is particularly suitable for a process using a single-wafer type film forming chamber such as the CVD apparatus 1. is there.

Further, the control for adjusting the residence time Rt is
The adjustment is performed by adjusting the gas discharge speed S according to the volume _Vch of the space V, and the adjustment of the gas discharge speed S is performed in the chamber 2.
Since the adjustment is performed by adjusting the total gas supply flow rate Q according to the internal pressure P, the process control can be easily performed without complicated processing and labor. Then, since the microloading can be improved without lowering the film forming speed by such a simple control operation, the film forming controllability can be remarkably improved as compared with the related art.

Further, usually, the radius r of the silicon wafer W and the distance shown in FIG. H is often different. Therefore, depending on the chamber, wafer, process, etc., the space V
Volume V _ch of is often fluctuate. On the other hand, in the present invention, the residence time Rt is adjusted by adjusting the gas discharge speed S.
Can be controlled as desired. Therefore, according to the film forming method using the CVD apparatus 1, it is possible to realize a film forming process having extremely excellent versatility, having almost no dependence on a chamber, a wafer, a process and the like.

[0048] Further, with the NH ₃ gas flow rate ratio of (F1 / F2 ratio) over 300 to the flow rate of SiH ₄ gas, SiH ₄ intermolecular or the collision probability between the active species derived from SiH ₄ molecules On the other hand, the probability of collision between NH ₃ molecules and SiH ₄ molecules or their active species is sufficiently increased. As a result, the formation of Si eyemers is further suppressed and S
iH ₄ with waste gases is suppressed, generation probability of the intermediate increases such aminosilane rich migration and fixability.

Therefore, a reduction in the film forming speed can be more reliably suppressed, and the supply-controlled state is easily eliminated, so that the microloading can be further improved. At this time, if the residence time Rt is set to a value within the above preferable range, NH ₃
Since the thermal decomposition of the gas is promoted, the effect of suppressing the microloading of the deposition rate can be further improved.

In the above-described embodiment, the second gas is not limited to the SiH ₄ gas, but may be another silane-based gas, for example, higher silanes such as disilane (Si ₂ H ₆ ) gas, or SiCl 4 gas. A halogenated silane-based gas such as ₂ H ₂ gas or the like may be used alone or as a mixture of two or more. The present invention is also effective when a film forming material gas other than these silane-based gases, for example, an organic metal gas such as methylaluminum or a metal halide gas such as tantalum chloride is used.

[0051]

EXAMPLES Hereinafter, specific examples according to the present invention will be described, but the present invention is not limited to these examples.

Embodiments 1 to 3 CVD apparatus 1 shown in FIG.
Using a film forming apparatus having the same configuration as described above, using NH ₃ gas and SiH ₄ gas as source gases, controlling the residence time Rt in the same manner as the above-described film forming method of the present invention, and forming an element pattern. A silicon nitride film was formed on a silicon wafer having a diameter of 8 inches (200 mm in diameter). At this time, the film formation temperature (substrate heating temperature) was set to 750 ° C., and the chamber pressure was set to 200, 300, and 400 Torr, and the film was formed by changing the supply flow rate of the SiH ₄ gas at each pressure value. Table 1 shows the main film forming conditions.

Note that "N ₂ (BP)" in Table 1 indicates the flow rate of N ₂ gas supplied as a backside purge gas. [SiH ₄ partial pressure] indicates a partial pressure of SiH ₄ gas with respect to the total gas pressure except N ₂ (BP), and [F1 / F2
Ratio] indicates the ratio of the flow rate of the SiH ₄ gas to the NH ₃ gas as described above.

Example 4 A silicon wafer having a diameter of 3
A silicon nitride film was formed in the same manner as in Example 1 except that a film having a thickness of 00 mm was used, the film forming temperature was set to 800 ° C., the pressure in the chamber was set to 240 Torr, and the supply flow rate of each gas was set to the conditions shown in Table 2. The membrane was made. The “total gas flow rate” in Table 2 indicates the total gas supply flow rate excluding N ₂ (BP).

Example 5 A silicon wafer having a diameter of 3 was used.
A silicon nitride film was formed in the same manner as in Example 1 except that a film having a thickness of 00 mm was used, the film forming temperature was set to 800 ° C., the chamber pressure was set to 300 Torr, and the supply flow rate of each gas was set to the conditions shown in Table 2. The membrane was made.

<Embodiment 6> The pressure in the chamber was set to 170 To.
A silicon nitride film was formed in the same manner as in Example 5 except that rr was set as the supply flow rate of each gas and the conditions shown in Table 2.

Reference Example 1 A silicon wafer having a diameter of 3
A silicon nitride film was formed in the same manner as in Example 1 except that a film having a thickness of 00 mm was used, the film forming temperature was set to 800 ° C., the pressure in the chamber was set to 275 Torr, and the supply flow rate of each gas was set to the conditions shown in Table 2. The membrane was made.

<Evaluation of Micro-Loading of Film Deposition Rate> With respect to the silicon wafer on which the silicon nitride film was formed according to Examples 1 to 6 and Reference Example 1, the film thickness of the silicon nitride film at the portion where the density of the element pattern was different was changed. The length was measured by SEM observation. The microloading effect of the film formation rate was evaluated from the measured values of these film thicknesses. FIG.
FIG. 3 is a schematic diagram showing a cross-sectional state of a silicon wafer according to an evaluation index of microloading of a film forming speed, and is a diagram schematically showing an example of a state in which a silicon nitride film is formed.

In the figure, a silicon wafer before film formation has a pattern composed of an oxide film 102 and a gate portion 103 formed on a silicon base layer 101.
A silicon nitride film 104 is formed thereon. The area A is a part with a low pattern density (open space), and the area B is a part with a high pattern density.

Then, the microloading of the film formation rate was evaluated using an index represented by the following formula (4): LE = (Da−Db) / Da × 100 (4) In the equation, LE indicates an index (%) indicating the microloading effect of the film forming rate, Da indicates the thickness of the silicon nitride film portion 104a deposited on a portion having a low pattern density, and Db indicates the thickness of the silicon nitride film portion 104a having a high pattern density. The thickness of the silicon nitride film portion 104b deposited on the portion is shown. The smaller the index LE is, the smaller the degree of macro loading is, which indicates that the film forming property is excellent.

Tables 1 and 2 also show the evaluation results of the silicon wafers obtained in each of the examples and the reference examples. Also,
FIG. 3 is a graph showing a change in the index LE evaluated with respect to the SiH ₄ gas partial pressure for the silicon wafers formed in Examples 1 to 3. In FIG. 3, symbols indicated by diamonds, squares, and triangles indicate the results of Examples 1 to 3, respectively, and each curve in FIG. 3 is obtained by performing a least-squares fitting of a higher-order function to each result. Indicates a reference line.
FIG. 4 is a graph showing a change in the index LE with respect to the total gas flow rate evaluated for the silicon wafer on which the film was formed in Example 4.

[0062]

[Table 1]

[0063]

[Table 2]

From these results, it was confirmed that the index LE of the silicon wafer obtained in each example shows a sufficiently small value. Reference Example 1 (Rt was 6.87 sec)
c) From the comparison between the index LE in the total gas flow rate of 7 slm (Rt is 19.83 sec) in Example 4 and the index LE in the other examples, the residence time Rt was 8 to 17;
The advantage in the case of adjustment and control during the second was confirmed. In particular, in Example 5, the index LE was dramatically improved to 13%, and particularly in Example 6, 11.4% was achieved as the index LE. From these, it is understood that according to the present invention, the effect of suppressing microloading can be significantly improved. From the comparison between Examples 1 to 5 and Example 6, it was confirmed that reducing the pressure in the chamber while maintaining the residence time Rt in the above-described preferable range is extremely effective in improving microloading. Was done.

Further, from the tendency shown in FIG. 3, in order to improve the microloading, the SiH ₄ gas partial pressure, in other words, the ratio of the flow rate of the SiH ₄ gas to the NH ₃ gas (F1 / F2
Ratio) of 350 to 550, further superiority was confirmed. Furthermore, the results of Example 4 shown in FIG. 4 suggest that there is an optimum range for the entire gas flow rate.

[0066]

As described above, according to the film forming method and the apparatus according to the present invention, the raw materials are controlled so that the residence time of the first gas and the second gas supplied onto the substrate becomes a predetermined value. By controlling the gas supply, it is possible to sufficiently improve the microloading of the film formation rate while suppressing a decrease in the film formation rate when forming a film containing nitrogen atoms on the substrate by the CVD method. Become.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view (a partial configuration diagram) schematically illustrating a preferred embodiment of a film forming apparatus according to the present invention.

FIG. 2 is a schematic diagram illustrating a cross-sectional state of a silicon wafer according to an evaluation index of microloading of a film forming speed, schematically illustrating an example of a state in which a silicon nitride film is formed.

FIG. 3 is a graph showing a change in an index LE with respect to a partial pressure of a SiH ₄ gas, which is evaluated for silicon wafers on which films are formed in Examples 1 to 3.

FIG. 4 is a graph showing a change in an index LE evaluated with respect to a total gas flow rate for a silicon wafer on which a film is formed in Example 4.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... CVD apparatus (film forming apparatus), 2 ... chamber, 4 ... shower head, 5 ... susceptor, 30 ... gas supply part, 31
... NH ₃ gas supply source (first gas supply source), 32 ... Si
H ₄ gas supply source (second gas supply source), 31a, 32a
... MFC (residence time adjustment unit), 51 ... heater (substrate heating unit), 70 ... exhaust system (residence time adjustment unit), 80 ... control unit (residence time adjustment unit), W ... silicon wafer (substrate).

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Nobuo Tokai 14-3 Shinzumi, Narita-shi, Chiba Applied Materials Japan Co., Ltd. (72) Inventor Yuji Maeda 14-3 Noizumi, Shin-izumi, Narita-shi, Chiba Within the Applied Materials Japan Co., Ltd. (72) Inventor Kegan Juan 95054, Santa Clara, California, USA, Bowers Avenue 3050 Within Applied Materials, Inc. (72) Inventor Jerry Tao, 95054, California, Santa Clara, USA Bowers Avenue 3050 Applied Materials Inside Luz Inc. (72) Inventor Sir Ann United States of America California State 95054, Santa Clara, Bowers Ave 3050 Applied Materials, Inc. Incorporated (72) Inventor Stephen Achen United States of America California 95054, Santa Clara, Bauer's Avenue 3050 Applied Material Inside F-term (reference) 4K030 AA06 AA13 BA40 CA04 CA12 EA11 FA10 HA15 JA05 JA09 JA10 JA11 JA12 5F045 AA06 AB33 AC01 AC12 AD11 AD12 AE25 EF03 EE07 EE02 AF03 DP03 EE17 GB06 GB15 5F058 BA20 BC08 BF04 BF23 BF30 BG02 BG03 BG04 BG10 BJ01

Claims (7)

[Claims] 1. A film forming method for forming a film having nitrogen atoms on a substrate by a chemical vapor deposition method, comprising: a first gas containing an ammonia gas on the substrate; A gas supply step of supplying a second gas capable of reacting with the first gas so that a residence time of the first gas and the second gas on the substrate becomes a predetermined value; A substrate heating step of heating to a predetermined temperature. 2. The film forming method according to claim 1, wherein in the gas supply step, the predetermined value of the residence time is set to a value within a range of 8 to 17 seconds. 3. In the gas supply step, the discharge speed of the first gas and the second gas from the periphery of the base is adjusted so that the residence time becomes the predetermined value. The film forming method according to claim 1 or 2, wherein: 4. In the gas supply step, at least one of a supply flow rate of the first gas and the second gas onto the substrate and a pressure around the substrate is adjusted. 4. The film forming method according to claim 3, wherein the discharge speed is adjusted. 5. In the gas supply step, the second gas is supplied.
The ratio of the flow rate of the first gas to the flow rate of the first gas is 30.
5. The method according to claim 1, wherein the first gas and the second gas are supplied onto the base so that the value is 0 or more.
The film formation method according to any one of the above. 6. The film forming method according to claim 1, wherein a gas containing a silane-based gas is used as the second gas. 7. A film forming apparatus for forming a film containing nitrogen atoms on a substrate by a chemical vapor deposition method, comprising: a chamber for accommodating the substrate; a chamber connected to the chamber; A first gas supply connected to and including a first gas containing ammonia gas, and a second gas supply including a second gas capable of reacting with the first gas; A gas supply unit, and a supply of the first gas and the second gas to the chamber such that a residence time of the first gas and the second gas on the substrate is a predetermined value. And a residence time adjusting unit for adjusting the discharge of the first gas and the second gas from the chamber; and a substrate heating unit for heating the substrate to a predetermined temperature. Film forming equipment.