JP3191502B2 - Semiconductor manufacturing method and manufacturing apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention is, your method of manufacturing a semiconductor
The present invention relates to a semiconductor device and a manufacturing apparatus, and is preferably applied to, for example, manufacturing of a compound semiconductor device.

[0002]

2. Description of the Related Art Conventionally, a liquid organometallic compound is used as a source gas source, and is vaporized by, for example, a bubbling method using an inert gas or hydrogen gas as a carrier gas to obtain a source gas. Metal-organic pyrolysis (MOVPE, MOCV) to grow compound semiconductor crystals by transporting
D, OMVPE or hybrid VPE) method or a method similar to that described above to obtain a vapor of a component element serving as a dopant,
There is known an organometallic open-tube gas-phase diffusion method in which impurity diffusion is performed using the diffusion source as a diffusion source.

When crystal growth or impurity diffusion is performed by the above-described method, the gas flow can be accelerated by reducing the pressure in the reaction tube, thereby improving uniformity and speeding up gas switching. For example, controllability can be improved. Further, under reduced pressure, an effect such as suppression of an intermediate reaction comes to be recognized due to dilution of the source gas.

[0004] However, when depressurizing the reaction system, there is no clear guideline as to which region the pressure of the raw material system located upstream is to be set. Are also considered to have advantages and disadvantages. In particular, when an organometallic compound having a high vapor pressure is used as a source gas source, the supply amount of the source gas is controlled.
For example, controlling the temperature of a constant temperature bath to keep the raw material cylinder containing the organometallic compound at a constant temperature or controlling the flow rate of the carrier gas for bubbling cannot control or reproduce even the low concentration range. The sex is bad. Therefore, a resistor such as a needle valve is inserted between the reaction system under reduced pressure and the raw material system so as not to be directly affected by the pressure fluctuation in the reaction tube which is one of the unstable factors under reduced pressure. In many cases, measures are taken to set the pressure of the raw material system at or near normal pressure. That is, a piping method of providing a buffer-like resistance between the raw material system and the reaction system to apply a differential pressure is often used. By doing so, even if an accidental sudden pressure increase occurs on the reaction tube side, it is possible to prevent the piping system from being contaminated by backflow of an organometallic compound or the like, and conversely, even when the pressure suddenly drops, The bumping or drawing in of the liquid material can be suppressed.

[0005] In order to suppress the fluctuation of the ultimate pressure in the reaction tube from the target value when the pressure in the reaction tube is controlled to be reduced, generally a valve capable of adjusting the conductance in front of the vacuum pump, for example, a valve. A so-called automatic pressure control (APC) system in which a variable opening / closing type butterfly valve or the like is provided to adjust the exhaust speed according to the pressure in the reaction tube is employed. The APC system includes a pressure gauge for measuring a pressure in a reaction tube, a controller for adjusting an opening / closing rate of a butterfly valve according to an output of the pressure gauge,
And a butterfly valve. According to this,
When the flow rate of the gas introduced into the reaction tube changes due to switching of the source gas or the like, the APC system works quickly to adjust the exhaust speed, and the pressure in the reaction tube is returned to the set value. The response speed at this time can be increased to some extent by adjusting the PID coefficient of each controller according to each device. In this case, only the attenuation of the pressure fluctuation is increased, and the pressure fluctuation itself is reduced. It cannot be eliminated. Even if a constant flow rate of gas flows, a pressure fluctuation of about the fluctuation of the opening / closing rate of the butterfly valve should occur in the entire system, and thus only a quasi-static stable state is maintained. Since the pressure fluctuation in the reaction tube naturally accompanies the fluctuation of the partial pressure of the component elements,
In order to improve the controllability of the process, it is important to minimize the influence of the pressure fluctuation in the reaction tube regardless of the size.

[0006] For example, Journal of Crystal Growth
94 (1989) pp. 481-487, the vapor pressure (partial pressure) of a specific component element in the reaction tube is directly measured, and the measurement result is fed back to the mass flow controller to obtain the vapor of the component element vapor in the reaction tube. Although the possibility of controlling the pressure is discussed, it is not yet an established method.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a gas for a component element in a reaction tube such that the vapor pressure of the component element is always constant without being affected by the ultimate pressure in the reaction tube. It is an object of the present invention to provide a method for manufacturing a semiconductor, which can supply impurities and thereby perform impurity diffusion into a semiconductor or crystal growth of the semiconductor with good controllability and reproducibility.

[0008] The above and other objects of the present invention will become apparent from the following description of the present specification.

[0009]

Means for Solving the Problems To achieve the above object, a first invention of the present invention is to provide a reaction tube having a reduced pressure.
The raw material gas is transported from the raw material system through piping to the reaction tube.
Diffusion of impurities into semiconductors or crystal growth of semiconductors
In the semiconductor manufacturing method described above, the pressure P
_sou depends on the ultimate pressures P _rea and P _rea in the reaction tube
Pressure difference Δp between the reaction tube and the raw material system due to the resistance of the piping.
Configure the piping system as represented as (P _rea) and controllable pressure difference Delta] p _cont and the _{P sou = P rea + Δp (} P rea) + Δp cont, pressure ratio _{α = P rea / P sou (} 0 < α ≦ 1) is almost constant
The feature is that Δp _cont is controlled so that
Is what you do.

In a preferred embodiment of the semiconductor manufacturing method according to the first invention, a liquid or solid raw material (S) is used.
And the raw material gas is obtained by vaporizing the raw material (S). The raw material (S) is, for example, an organometallic compound or a metal halide compound.

A second invention according to the present invention is directed to a pressure reducing state
Raw material gas from the raw material system
Impurity diffusion into the semiconductor or reaction of the semiconductor in the reaction tube.
In a semiconductor manufacturing apparatus that performs crystal growth,
The pressure P _{sou of the} raw material system is the ultimate pressures P _rea and P
between the reaction tube and the raw material system due to the resistance of the piping depending on _rea
The differential pressure Δp (P _rea) and controllable pressure difference Delta] p _cont between
The piping system is configured so that P _sou = P _rea + Δp (P _rea ) + Δp _cont, and the pressure ratio α = P _rea / P _sou (0 <α ≦ 1) is substantially constant.
The feature is that Δp _cont is controlled so that
Is what you do.

In a preferred embodiment of the semiconductor manufacturing method according to the second invention, a liquid or solid raw material (S) is used.
And the raw material gas is obtained by vaporizing the raw material (S). The raw material (S) is, for example, an organometallic compound or a metal halide compound.

[0013]

According to the present invention configured as described above , an example is provided.
For example, using a piezo valve to control the pressure of the raw material system in a loop
By controlling, the ultimate pressure in the reaction tube and the pressure of the raw material system
Can always be almost constant, which
Therefore, even if there is pressure fluctuation in the reaction tube,
(Partial pressure) can always be controlled to be constant. Sand
That is, if there is a pressure fluctuation in the reaction tube,
Depending on the pressure, the supply amount of the component element vapors is constant (1/1 /
α) to compensate for pressure fluctuations in the reaction tube.
Fluctuations in the vapor pressure (partial pressure) of the constituent elements in the reaction tube
It can be suppressed effectively.

[0014]

[0015]

Embodiments of the present invention will be described below with reference to the drawings. In all the drawings of the embodiments, the same or corresponding portions are denoted by the same reference numerals.

FIG. 1 shows a vacuum diffusion / crystal growth apparatus used in the first embodiment of the present invention. Here, for simplicity, the raw material system has only one raw material cylinder, and illustration and description of piping such as a vent line are omitted. FIG.
As shown in FIG. 1, in this reduced pressure diffusion / crystal growth apparatus, a liquid material S such as an organometallic compound is placed in a material cylinder (bubble) 1. The material cylinder 1 is placed in a thermostat 2 for keeping the material cylinder 1 at a constant temperature. Reference numeral 3 denotes piping, 4, 5, and 6 denote mass flow controllers,
PG ₁ denotes a pressure gauge for measuring the pressure of the feed system.

Reference numeral 7 denotes a reaction tube. A substrate (not shown) on which impurity diffusion or crystal growth is to be performed is placed in the reaction tube 7. Carrier gas and various source gases are transported into the reaction tube 7. These gases are adjusted to a constant flow rate by the mass flow controllers 4, 5, and 6, respectively. In addition, this reaction tube 7
Is provided with an electric furnace 8 for maintaining the atmosphere in the reaction tube 7 at a required process temperature.

The inside of the reaction tube 7 is evacuated by a rotary pump 9 to thereby reduce the pressure.
In this case, the ultimate pressure (P _rea ) in the reaction tube 7 is determined by the pressure gauge PG ₂ for measuring the pressure in the reaction tube 7 and the pressure gauge PG ₂
A controller 10 for controlling the opening and closing rate of the butterfly valve BV below in accordance with the _second output, butterfly valve B
The control value is controlled to a set value by an APC system constituted by V.

In the vacuum diffusion / crystal growth apparatus configured as described above, the carrier gas adjusted to a certain flow rate (Q _sou ) by the mass flow controller 6 is maintained at a constant temperature by the thermostat 2. The liquid is introduced into the raw material S in the raw material cylinder 1 and bubbling is performed. As a result, the amount of the component element vapor determined by the vapor pressure (P _vap ) of the raw material S determined only by the temperature of the raw material cylinder 1 and the pressure (P _rea + Δp) of the raw material system at that time is _introduced into the reaction tube 7 through the pipe 3. Be transported. A substrate (not shown) previously placed in the reaction tube 7 and maintained at a required process temperature by an electric furnace 8
Is subjected to impurity diffusion or crystal growth.

In the first embodiment, in order to keep the component element vapor pressure (partial pressure) in the reaction tube 7 constant even if the pressure fluctuates in the reaction tube 7, the first embodiment ,
The pipe 3 is configured so that the resistance of the pipe 3 between the reaction tube 7 and the raw material system is reduced as much as possible, and the pressure difference between the reaction tube 7 and the raw material system due to this resistance becomes substantially zero. The reason why the above-described effects can be obtained by setting the pressure difference between the reaction tube 7 and the raw material system to substantially zero will be described in detail below.

As shown in FIG. 1, a resistance R serving as a buffer, for example, a needle valve, is inserted in the pipe 3 between the raw material system and the reaction system.
It is assumed that a pressure difference + Δp is generated between the pressure and the raw material system. In this case, the total flow rate (Q _rea ) of the gas flowing into the reaction tube 7 is
The sum of the flow rate Q _{1 of} the mass flow controller 4, the flow rate Q ₂ of the mass flow controller 5, and the flow rate Q _sou of the mass flow controller 6, that is, Q ₁ + Q ₂ + Q
_sou .

[0022] In this system, the vapor pressure (partial pressure) of the component elements of the reaction tube 7 when obtained by calculation of P _s, is as follows.

The carrier gas (flow rate Q _sou ) introduced into the raw material cylinder 1 contains a bubbling efficiency η (0 ≦ η).
If ≦ 1) is 1, P _vap / (P _rea + Δ) per unit volume
The vapor of the raw material S is contained in the ratio of p). Therefore, the supply amount of the raw material S into the reaction tube 7 is Q _sou ·
P _vap / (P _rea + Δp). Since the total flow rate in the reaction tube 7 is Q _rea , the partial pressure P _s is expressed as follows: P _s = Q _sou · P _vap · P _rea / Q _rea (P _rea + Δp) (1)

Now, the pressure _Prea in the reaction tube 7 is (+ ξ)
Assume that some fluctuations have occurred. However, it is assumed that the total flow rate of the gas introduced into the reaction tube 7 is completely controlled to a set value (Q _rea ) by the three mass flow controllers 4, 5, 6, and the pressure fluctuation in the reaction tube 7 is ( _Meta -stable state) is caused only by the fluctuation of the exhaust flow rate (Q _ex ). In this case, the exhaust gas flow rate Q _ex is the supply flow rate Q _rea
Is equal to, the pressure _Prea in the reaction tube 7 is kept constant.

Here, the pressure in the reaction tube 7 after the fluctuation (P
_{When rea} + ξ) is written as P _rea ′, it is apparent from Boyle's law that P _rea ′ = P _rea · Q _rea / Q _ex (2) holds.

At this time, the partial pressure P _s ′ of the vapor of the raw material S in the reaction tube 7 is as follows: P _s ′ = Q _sou · P _vap · (P _rea + ξ) / Q _rea (P _rea + ξ + Δp) (3) expressed.

Here, when the pressure difference Δp caused by the resistance R inserted in the pipe 3 between the reaction system and the raw material system is made as close as possible to zero (Δp → 0), the pressure inside the reaction tube 7 after the pressure fluctuation is changed. partial pressure P _s of the vapor of the material S 'may be expressed as _{P s'~Q sou · P vap ·} (P rea + ξ) / Q rea (P rea + ξ) (4). In other words, the _{P s'~Q sou · P vap /} Q rea (5).

Equation (5) indicates that the raw material S when there is no pressure fluctuation
In the formula (1) of the partial pressure of steam it is equivalent to a value obtained by placing a Delta] p = 0, therefore P _{s'~P s} (6) is established. That is, it can be seen that even after the pressure fluctuation occurs in the reaction tube 7, the partial pressure of the vapor of the raw material S does not change from the value before the fluctuation.

As described above, the piping 3 between the reaction system and the raw material system
Is reduced as much as possible so that the pressure difference Δp between the reaction tube 7 and the raw material system becomes substantially zero due to this resistance. It can be seen that the component element vapor pressure (partial pressure) can be constantly controlled.

Next, the condition values used in the actual experiment are substituted into the above-mentioned equations (1) and (3), and the component element vapor pressure (partial pressure) P with respect to the pressure fluctuation (+ ξ) in the reaction tube 7 is calculated. _A description will be given of a result of calculating a change in _s (P _s → P _s ′) using a pressure difference Δp caused by a resistance R of the pipe 3 between the reaction system and the raw material as a parameter. However, in this calculation, for example, the vapor pressure (P _vap ) of the raw material S made of an organometallic compound in the raw material cylinder 1 is set to 12 Torr (1.58 kPa).
It is assumed that the flow rate (Q _sou ) of the carrier gas introduced into the raw material cylinder 1 is always set to 200 sccm by the mass flow controller 6. It is assumed that the total flow rate (Q _rea ) of the gas introduced into the reaction tube 7 is a total of 5 slm of the flow rates of the mass flow controllers 4, 5, and 6.

Now, when the set value of the ultimate pressure (P _rea ) in the reaction tube 7 is 50 Torr (6.58 kPa),
It is assumed that a pressure fluctuation of ξ = 3 Torr (0.39 kPa) has occurred in the reaction tube 7 on the positive pressure side. At this time, the reaction tube 7
Partial pressure P _s of the vapor of the material S of the inner changes as shown in FIG. 2 in accordance with the pressure difference Δp between the reaction system and the raw material system. From FIG. 2, it can be seen that the pressure P _s before the fluctuation and the pressure P _s ′ after the fluctuation decrease with almost the same tendency depending on the differential pressure Δp, but the component element vapor pressure (+ ξ) due to the pressure fluctuation (+ ξ) Partial pressure)
When the ratio of the change (P _s ′ −P _s ) is normalized by the partial pressure P _s before the change and plotted, it is apparent that the ratio clearly increases depending on Δp. Furthermore, especially on the low resistance side,
That is, the side where the differential pressure Δp is small (Δp ≦ 200 Torr)
(〜26 kPa)) is remarkable.

As is clear from the above, the differential pressure Δ
By close to zero as possible to p, it is possible to remarkably suppress the variation of component elements the vapor pressure in the reaction tube 7 (partial pressure) P _s.

FIGS. 3 and 4 show calculation results when the pressure fluctuation (+ ξ) in the reaction tube 7 is greatly emphasized at 10 Torr (1.32 kPa). Here, FIG.
FIG. 4 shows that the pressure in the reaction tube 7 is set to 100 Torr (13.
15 kPa). As component elements the vapor pressure (partial pressure) P _s is so suffer the effects of pressure in the reaction tube 7 in the reaction tube 7 is reduced, by bringing the pressure difference Δp to 0, similarly to the above partial pressure it can be seen that it is possible to obtain the effect of suppressing the variation of P _s.

In the first embodiment, an example of minimizing the resistance of the pipe 3 between the reaction system and the raw material system and realizing the pressure difference Δp → 0 between the reaction system and the raw material system is as follows. The pipe 3 between the reaction system and the raw material system is a straight pipe having a diameter of, for example, 1/4 inch, and has a standard configuration in which a stop valve, a needle valve, and the like are added to the straight pipe, and Δp <1 Torr (0.13 kPa ) And Δp = 0.

As described above, according to the first embodiment,
Since the pressure difference Δp between the reaction tube 7 and the raw material system is made substantially zero by minimizing the resistance of the reaction system, that is, the pipe 3 between the reaction tube 7 and the raw material system, the reaction tube in a reduced pressure state Even if a pressure fluctuation occurs in the reaction tube 7, the supply amount of the vapor of the raw material S into the reaction tube 7 changes in a self-compensating manner with respect to the pressure fluctuation. The pressure (partial pressure) can always be controlled to a set value. Thus, impurity diffusion or crystal growth on the substrate in the reaction tube 7 can be stably performed with good controllability and reproducibility.

The magnitude of the differential pressure (Δp) generated between the reaction tube 7 and the raw material system due to the resistance of the pipe 3 depends on the type and temperature of the gas flowing through the pipe 3 and the shape of the flow path of the pipe 3. In addition, it is largely controlled by the flow velocity in the pipe. In particular, even in a case where the inside of the reaction tube 7 is provided with a pipe in which realization of the differential pressure Δp → 0 does not matter at all in a somewhat low vacuum region (P _rea > 0.1 atm), In a high vacuum region where the pressure is 0.1 atm or less, a pressure distortion (shift) between the reaction tube 7 side and the raw material piping becomes remarkable as the fluid speeds up, and the resulting differential pressure Δp is ignored. The inventor's research has clarified that it is no longer possible.

FIG. 5 shows that the pressure (P _sou ) on the outlet side of the raw material cylinder 1 when the pipe 3 is formed as shown in FIG.
The results obtained by measuring how the pressure changes depending on the ultimate pressure (P _rea ) in the reaction tube 7 with an actual device are shown. The apparatus used in this experiment employs a typical 1/4 inch diameter stainless steel pipe with a VCR fitting, and the pneumatically operated valve, hand valve, etc. used in combination with this are resistance components. . The gas used in the experiment is hydrogen gas often used as a carrier gas.

As shown in FIG. 5, when the ultimate pressure in the reaction tube 7 reaches a degree of vacuum of about 100 Torr (13.16 kPa), pressure distortion (shift) occurs due to the resistance of the pipe 3.
As a result, the differential pressure Δp is present at about 6% of the set pressure, and the pressure of the raw material system is thereby reduced to 106 Torr (13.9).
5 kPa). Further, by the ultimate pressure in the reaction tube 7 20Torr (2.63kPa) down to further increased pressure distortion (shifting),
The differential pressure Δp increases to 20 Torr, almost 100% of the set pressure.
In addition , the pressure of the raw material system is no longer about 40 Torr, which is about twice the set pressure.
It can be seen that control cannot be performed at a low pressure of r (5.26 kPa) or less.

Here, taking the case where the ultimate pressure in the reaction tube 7 is set to 20 Torr (2.63 kPa) in an actual apparatus as an example, the above-mentioned equations (1) and (3) are used as the condition values used in actual experiments. substituting, pressure fluctuations (+ xi]) change in component elements the vapor pressure (partial pressure) P _s for the (P _s → P _s ') and P _s rate of change of _{(P s'-P s)} / P s, FIG. 6 shows the result of calculation using the pressure difference Δp between the reaction system and the raw material system as a parameter. In this calculation, P _vap = 12
Torr (1.58 kPa), Q _sou = 200scc
m, Q _rea = 5 slm, and ξ = 3 in the reaction tube 7
It was assumed that a pressure fluctuation of Torr (0.39 kPa) occurred on the positive pressure side.

[0040] From FIG. 6, the pressure fluctuation (+ xi]) according to component elements the vapor pressure (partial pressure) the rate of change of _{P s (P s'-P} s) /
P _s is P _rea = 2 where the differential pressure Δp = 20 Torr exists.
For the 0 Torr process, it can be seen that it is about 7% before and after the pressure fluctuation. If the same calculation is performed on the assumption that the pressure fluctuation in the reaction tube 7 is ξ = 10 Torr (1.32 kPa), the rate of change in the partial pressure becomes about 20%.

As described above, the increase in the differential pressure Δp when the inside of the reaction tube 7 is in the high vacuum region is caused by the change in the ultimate pressure in the reaction tube 7 due to the fluctuation of the ultimate pressure in the reaction tube 7 (partial pressure).
Results in the fluctuation of

Now, the differential pressure Δp between the reaction system and the raw material system in this apparatus is represented by Δp = 41.2027−7.5226ln (P _rea ) (7) by exponential regression of the numerical values in FIG. Can be. In general, in which pressure region the pressure difference Δp becomes remarkable is determined by individual devices according to a gas system, a piping system, and the like to be used. However, as long as the pressure distortion due to the resistance of the pipe 3 and therefore the differential pressure Δp is expressed in the form including the term of the pressure (P _rea ) in the reaction tube 7 as in the equation (7), the differential pressure Δp In a pressure region where is a problem, as described below, a method of controlling the ratio between the ultimate pressure in the reaction tube 7 and the pressure of the raw material system to be substantially constant is effective in solving the above problem.

The vapor pressure (partial pressure) P _s of the raw material S in the reaction tube 7
Is a function Δp depending on the ultimate pressure P _rea in the reaction tube 7.
When expressed in a form including (P _rea ), the partial pressure P _s is given by the following equation. P _s = Q _sou · P _vap · P _rea / Q _rea (P _rea + Δp (P _rea )) (8)

Here, for the purpose of controlling the pressure of the raw material system,
As will be described later, a closed loop control system using, for example, a piezo valve is added, and a controllable differential pressure term Δp is newly added to the term (P _rea + Δp (P _rea )) of the raw material system pressure in the denominator of the equation (8). Construct a piping system with _cont added. At this time, the controlled partial pressure P _s is represented by P _s = Q _{sou .P vap .P rea} / (Q _{rea .P sou} ) (9) Here, P _sou = P _rea + Δp (P _rea ) + Δp _cont (10)

At this time, the pressure (P _sou ) of the raw material system is not controlled completely independently of the pressure (P _rea ) in the reaction tube 7, but a pressure ratio α = P _rea / P _sou (0 <α ≦ 1) It is important that Δp _cont is feedback-controlled so that is always constant.

The term Δp _{cont on} the right side of the equation (10) is, of course, a function of the ultimate pressure _Prea in the reaction tube 7. That is, the partial pressure P _s ′ after the pressure fluctuation (+ ξ) occurs in the reaction tube 7 is P _s ′ = Q _{sou .P vap.} (P _rea + ξ) / (Q _{rea .P sou} ′) (11) The pressure term (P _sou ′) of the raw material system is expressed as _follows : P _sou ′ = P _rea + ξ + Δp (P _rea ) + Δp _cont = (P _rea + ξ) / α = P _rea ′ / α (12) By controlling Δp _cont so that P _{s ′} to P _s (13) can always be realized.

The value of the pressure ratio α needs to be set so that P _rea / α ≧ P _rea + Δp (P _rea ) (14) is satisfied in the lower pressure range (high vacuum side). Where the expression (1
The left side (P _rea / α) of 4) is nothing but the raw material system pressure (P _sou ). For example, the case of α = ２ will be described with reference to FIG. 5.
= P _rea / P _sou = 2/3) is maintained up to 30 Torr (3.95 kPa) on the low pressure side. That is, 30 Torr
In the pressure reduction process up to, it is sufficient that α is not more than ／.

FIG. 7 shows a reduced pressure diffusion / crystal growth apparatus used in the second embodiment of the present invention, in which a closed loop control system is provided for controlling the pressure of the raw material system as described above.

That is, as shown in FIG. 7, in this reduced pressure diffusion / crystal growth apparatus, for example, a pressure gauge PG ₁ which is a pressure sensor for measuring the pressure of a raw material system, a controller 11 of a piezo valve PV described later, and 0~5V is configured closed-loop control system by the piezo valve PV is a fast response variable flow valve operable by the control input of the raw material system by controlling the piezo-valve PV by using the output of the pressure gauge PG ₁ The feedback control which controls the pressure of is possible.

On the other hand, the output of the pressure gauge PG ₂ for measuring the pressure in the reaction tube 7 is fed to the computer 12, the output of the computer 12 are sent to the controller 11.

In the reduced pressure diffusion / crystal growth apparatus configured as described above, when the ultimate pressure (P _rea ) in the reaction tube 7 deviates from the APC control of the exhaust system and fluctuates to P _rea ′,
Alternatively, if there is an intentional pressure change, the pressure gauge PG ₂
The value of P _rea '/ α is immediately calculated by the computer 12 in accordance with the output of the controller 11 and a pressure setting signal corresponding to the result is transmitted to the controller 11. Then, the piezo valve PV is controlled by the controller 11, the raw material system pressure is controlled to a desired value, and α = P _rea / P _sou is constantly controlled to be constant. Here, the response of the piezo valve PV is
Since it is instantaneous (within 0.5 seconds) according to the control voltage, the action described above is almost free from the effects of pressure change due to gas switching and other causes.
The vapor pressure (partial pressure) of a specific component element in the reaction tube 7 can be controlled as set.

As described above, according to the second embodiment,
By controlling the ratio α = P _rea / P _sou between the ultimate pressure P _rea in the reaction tube 7 and the pressure P _{sou of the} raw material system to be constant, the pressure in the reaction tube 7 in a reduced pressure state is reduced. Even if the fluctuation occurs, the supply amount of the component element vapor to the reaction tube 7 changes at a constant rate (1 / α) depending on the pressure in the reaction tube 7, and the pressure fluctuation in the reaction tube 7 can be compensated. Therefore, even in a process in a low pressure (high vacuum) region where the pressure difference Δp between the reaction system and the raw material system increases, similarly to the first embodiment, the target component element in the reaction tube 7 can be obtained. The vapor pressure (partial pressure) can always be controlled to a set value. Thus, impurity diffusion or crystal growth on the substrate in the reaction tube 7 can be stably performed with good controllability and reproducibility. Further, by positively performing the same control as described above with α as a variable, it is possible to effectively control the component element vapor pressure (partial pressure) in the reaction tube 7 to an arbitrary value.

The method according to the second embodiment is effective even when the pressure in the reaction tube 7 is within a pressure range (high vacuum) of 0.1 atm (10 kPa) or less.

Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications based on the technical idea of the present invention are possible.

For example, in the first and second embodiments described above, the generation of the source gas in the source system is performed by the bubbling method, but the generation of the source gas is performed by, for example, the vapor pressure difference control method. Is also good.

Further, in the second embodiment, when a situation occurs in which the limit of the response speed of the piezo valve PV when the pressure fluctuation in the reaction tube 7 occurs becomes a problem, particularly the pressure fluctuation due to gas switching or the like. Is known in advance in the sequence, for example, the history data is stored by a sampling oscilloscope or the like, and the piezo valve PV can be controlled with a time difference of 0. Further, the present invention can be applied not only to the case where the impurity is diffused into the semiconductor substrate but also to the case where the impurity is diffused into the semiconductor simultaneously with the crystal growth of the semiconductor.

[0057]

As described above, according to the present invention, the vapor pressure (partial pressure) of each component element in the reaction tube can be kept constant even if the pressure in the reaction tube is reduced. Thereby, impurity diffusion into the semiconductor or crystal growth of the semiconductor can be performed with good controllability and reproducibility.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a reduced pressure diffusion / crystal growth apparatus used in a first embodiment of the present invention.

[Figure 2] of the partial pressure P _s and the partial pressure P _s change (P _s'-
Is a graph showing an example of P _s) / P _s calculation results of change due to the differential pressure Δp of.

[Figure 3] of partial pressure P _s and the partial pressure P _s change (P _s'-
Is a graph showing an example of P _s) / P _s calculation results of change due to the differential pressure Δp of.

FIG. 4 shows partial pressure P _s and changes in partial pressure P _s (P _s ′-
Is a graph showing an example of P _s) / P _s calculation results of change due to the differential pressure Δp of.

FIG. 5 is a graph showing an example of measurement results of changes in the raw material system pressure P _sou and the differential pressure Δp due to the reaction tube pressure P _rea .

[6] of the partial pressure P _s and the partial pressure P _s change (P _s'-
Is a graph showing an example of P _s) / P _s calculation results of change due to the differential pressure Δp of.

FIG. 7 is a schematic diagram showing a reduced pressure diffusion / crystal growth apparatus used in a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Raw material cylinder S Raw material 3 Piping 4,5,6 Mass flow controller 7 Reaction tube 8 Electric furnace 10,11 Controller BV butterfly valve PV piezo valve

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/205 C30B 25/14 H01L 21/223

Claims (8)

(57) [Claims] 1. A method for manufacturing a semiconductor, comprising: transporting a source gas from a source system through a pipe into a reaction tube in a reduced pressure state, and performing impurity diffusion into a semiconductor or crystal growth of the semiconductor in the reaction tube. The pressure P _{sou of the} raw material system is the ultimate pressure P in the reaction tube.
_The above _{countermeasures} due to the resistance of the pipe depend on _rea and _Prea.
Controllable with the pressure difference Δp (P _rea ) between the pipe and the raw material system
The piping system is configured such that P _sou = P _rea + Δp (P _rea ) + Δp _cont by the effective differential pressure Δp _cont, and the pressure ratio α = P _rea / P _sou (0 <α ≦ 1) is approximately Constant
A method of manufacturing a semiconductor, characterized in that Δp _cont is controlled to be as follows . 2. After the pressure fluctuation + ξ occurs in the reaction tube.
Of 'when a, P _sou' the pressure in the stock system P _sou characterized in that so as to control the _{= P rea + ξ + Δp (} P rea) + Δp cont = (P rea + ξ) / α become so Delta] p _cont
2. The method of manufacturing a semiconductor according to claim 1, wherein 3. A cloth for controlling the pressure of the raw material system.
Fidoba the Δp _cont by Zudorupu control system
Tsu claim 1, wherein it has to be click Control
Semiconductor manufacturing method. 4. Japanese that P _rea is less than 0.1 atm
2. The method for manufacturing a semiconductor according to claim 1, wherein: 5. A pipe through a reaction tube in a reduced pressure state.
Transports raw material gas from raw material system to semiconductor in the above reaction tube
Impurity diffusion or semiconductor crystal growth
In the semiconductor manufacturing apparatus, the pressure P _{sou of the} raw material system is _equal to the ultimate pressure P in the reaction tube.
_The above _{countermeasures} due to the resistance of the pipe depend on _rea and _Prea.
Controllable with the pressure difference Δp (P _rea ) between the pipe and the raw material system
The piping system is configured such that P _sou = P _rea + Δp (P _rea ) + Δp _cont by the effective differential pressure Δp _cont, and the pressure ratio α = P _rea / P _sou (0 <α ≦ 1) is approximately Constant
The feature is that Δp _cont is controlled so that
Semiconductor manufacturing equipment. 6. After a pressure fluctuation + ξ occurs in the reaction tube.
Of 'when a, P _sou' the pressure in the stock system P _sou characterized in that so as to control the _{= P rea + ξ + Δp (} P rea) + Δp cont = (P rea + ξ) / α become so Delta] p _cont
The semiconductor manufacturing apparatus according to claim 5, wherein 7. A filter for controlling the pressure of the raw material system.
Closed loop control system.
Δp _cont Feedback control
It was to so The semiconductor device according to claim 5, wherein
manufacturing device. 8. P _rea Is less than 0.1 atm Specially
6. The semiconductor manufacturing apparatus according to claim 5, wherein: