JP2001210601A - Semiconductor manufacturing method and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a silicon film to be doped with phosphorus using PH3 (phosphine) in a batch reaction furnace. SOLUTION: A semiconductor manufacturing method includes a thermal diffusion process, in which phospine or mixed gas that contains phosphine is introduced into reaction furnaces 1 and 3 which thermally treat wafers 5 so as to be diffused into a silicon film on a wafer 5. By conducting thermal diffusion process is carried out, in such a manner in which the wafer 5 is introduced into a reaction furnace which is heated to a temperature (e.g. 350 deg.C) at which anatural oxide film is hardly influenced, and which is lower than a prescribed treatment temperature (e.g. 800 deg.C), phosphine or mixed gas containing phosphine is introduced into the reaction furnace 1 as the reaction furnace is gradually raised to the above treatment temperature (e.g. 800 deg.C) at a prescribed temperature rise rate (e.g. 5 to 20 deg.C/min) by controlling a heater 2, and phosphorus doping is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor manufacturing method comprising a step of diffusing phosphorus into a silicon film such as a polysilicon film or an amorphous silicon film which is a base film formed on a substrate such as glass or a wafer. And an apparatus for performing the method.

[0002]

2. Description of the Related Art Conventionally, to form a polysilicon (Poly-Si) film doped with phosphorus (P), POCl _{3 is used.}
(Phosphorus oxychloride) to diffuse phosphorus into the Poly-Si film, or D-Poly-S by CVD using a silane-based gas such as PH ₃ (phosphine) and SiH 4.
There is a method of forming an i (doped polysilicon) film.

In recent years, with the integration and miniaturization of memories, techniques for miniaturizing and increasing the surface area have been developed. In order to make use of this technology, it has become impossible to cope with the conventional method using POCl ₃ or the CVD method using PH ₃ and a silane-based gas. Therefore, phosphorus doping with PH3 was attempted using a batch-type reactor capable of holding a vacuum.

[0004]

However, after the boat on which the wafer is mounted is inserted into the reaction furnace, the temperature of the substrate is raised,
Even when the conventional sequence of introducing PH ₃ (phosphine) as a P source is performed when the substrate temperature reaches a desired substrate processing temperature (eg, 800 ° C.) and is stabilized, effective phosphorus doping is performed. Was not done.

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides a semiconductor manufacturing method capable of doping phosphorus into a silicon film in a batch-type reactor using PH ₃ (phosphine) and controlling the phosphorus concentration. , And a semiconductor manufacturing apparatus.

[0006]

According to a first aspect of the present invention, a phosphine or a mixed gas containing phosphine is introduced into a reaction furnace for heat-treating a substrate to diffuse phosphorus into a silicon film of the substrate. In the semiconductor manufacturing method having a step, in performing the thermal diffusion step, after inserting the substrate into the reaction furnace at a temperature lower than a predetermined substrate processing temperature, the temperature in the reaction furnace is reduced to the substrate processing temperature by a predetermined amount. It is characterized in that phosphine or a mixed gas containing phosphine is introduced into the reaction furnace while increasing the temperature at a rate of temperature increase.

According to the present invention, after a substrate is inserted into a reaction furnace, the temperature in the furnace is raised to a substrate processing temperature at a predetermined temperature increase rate, and at the same time, phosphine (P) as a phosphorus source is used.
Since a gas mixture containing H ₃ ) or phosphine is introduced into the furnace for thermal diffusion, the silicon film on the substrate can be doped with phosphorus. At this time, the concentration of phosphorus diffused into the silicon film can be controlled by changing the rate of temperature rise (claim 2). In this case, it is desirable that the rate of temperature rise be set in the range of 5 to 20 ° C./min.

According to a fourth aspect of the present invention, there is provided a reaction furnace for thermally diffusing phosphorus into a silicon film of a substrate, and an atmosphere temperature in the reaction furnace is adjusted. A heater, gas introduction means for introducing phosphine or a mixed gas containing phosphine into the reaction furnace, and controlling the heater when a substrate is inserted into the reaction furnace to control the inside of the reaction furnace from a predetermined substrate processing temperature. After the insertion of the substrate, the heater is controlled to increase the temperature in the reaction furnace to the substrate processing temperature at a predetermined temperature increase rate, and the gas introducing means is set. Phosphine or a mixed gas containing phosphine into the reaction furnace.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a semiconductor manufacturing apparatus for performing the semiconductor manufacturing method according to the embodiment. In the figure, reference numeral 1 denotes an external reaction tube, and around the external reaction tube 1, a heater 2 for increasing the ambient temperature in the external reaction tube 1 is arranged. A cylindrical internal reaction tube 3 is provided in the external reaction tube 1, and a reaction chamber is defined by the internal reaction tube 3.
The wafer 5 held by the boat 4 is inserted into a reaction chamber defined in the internal reaction tube 3. The inside of the reaction furnace constituted by the outer reaction tube 1 and the inner reaction tube 3 is airtightly closed by a furnace lid on which the boat 4 is placed.

Phosphine (P) which is a phosphorus (P) source
H ₃ ) is introduced from the reaction gas introduction tube 6 to the inside of the internal reaction tube 3. The reaction gas introduction pipe 6 branches on the way, and from the lower end in the internal reaction pipe 3 and from the reaction gas introduction nozzle 9 arranged inside the internal reaction pipe 3, to the reaction chamber in the internal reaction pipe 3. Supply phosphine. In this case, the introduction flow rate of phosphine is adjusted by flow regulators (mass flow controllers) 11 and 12 provided in the middle of the reaction gas introduction pipe 6. The gas in the reaction chamber defined by the internal reaction tube 3 passes through the upper end of the internal reaction tube 3, passes through a flow path secured between the external reaction tube 1 and the internal reaction tube 3, and The gas is discharged from the reactor through an exhaust port 8 provided at the lower end of the tube 1. The boat 4 is rotated by a rotation mechanism (not shown). The apparatus is provided with control means (not shown).
Furnace temperature control by the heater 2 and supply control of phosphine into the furnace are performed.

Next, a semiconductor manufacturing method performed by this apparatus will be described. When doping the silicon film on the wafer 5 with phosphorus, first, the furnace temperature is controlled to an insertion temperature (for example, about 350 ° C.) where the influence of the natural oxide film is small, and a predetermined number of wafers 5 are removed. The mounted board 4 is inserted (loaded) into the furnace.

After loading the boat 4, the inside of the furnace is maintained at a predetermined pressure (for example, a pressure of about 640 Pa), and the temperature in the reaction furnace is increased at a predetermined temperature increase rate. In the present embodiment, the temperature was raised at a temperature rise rate of about 20 ° C./min. At the same time as the temperature is raised, phosphine (PH ₃ ) as a phosphorus source is supplied into the reactor. The supply amount of phosphine is, for example, 480 (0.5% PH ₃ / He base) scm
m. Even after the temperature in the reactor reaches the substrate processing temperature (about 800 ° C. in the present embodiment), the supply of phosphine as a phosphorus source is continued until the phosphorus diffusion processing is completed.

When the diffusion process is completed, the supply of phosphine is stopped, the residual gas in the reactor is removed, and the pressure in the reactor is returned to the atmospheric pressure. Further, the temperature in the reaction furnace is lowered to a temperature slightly lower than the processing temperature, for example, about 600 ° C. Thereafter, the boat 4 holding the phosphorus-doped wafers 5 is unloaded from the reactor, and
Collect.

As described above, in this embodiment, after the wafer 5 is inserted at the insertion temperature (about 350 ° C.) where the influence of the natural oxide film is small, the phosphorus source is used from the timing when the temperature inside the reaction furnace is started to rise. to supply phosphine PH _3,
In addition, since the temperature is raised to the processing temperature at a predetermined temperature increase rate while supplying phosphine, a desired concentration of phosphorus P can be diffused into the silicon film of the wafer 5. This is at a low temperature by the relationship of H ₂ coverage and P coverage of the surface (400 ° C. or less) in the H ₂ coverage is large,
Increasing the temperature causes hydrogen desorption, which increases the coverage of P and increases the P concentration. 550 ° C
Although P desorption occurs in the above, it is considered that P desorption can be suppressed and PH can be sufficiently diffused by continuing the flow of PH ₃ (P.
If left at 550 ° C or higher without flowing H ₃ , P
The concentration is expected to decrease).

Specifically, phosphorus concentration = average 9.45 × 10
¹⁹atoms / cc, in-plane uniformity = 2.7 to 3.9%
I was able to. After the processing temperature reaches the phosphine
(PH _Three) Is supplied (performed in the conventional sequence)
Case 1) is shown in Table 1 below.

[0016]

[Table 1]

As shown in FIG. 2, the concentration of phosphorus was measured at five predetermined points on the wafer 5 by an X-ray fluorescence analyzer. In other words, there are four points at the center of the wafer 5 having a diameter of φ200 (8 inches) and four equally spaced points in the circumferential direction of 55 mm from the center. The phosphorus concentration measurement range at each point is φ23m centered on each point.
m inside the circle.

Table 2 shows the results when the treatment temperature was set at 750 ° C. and the temperature was increased at two different rates, 5 ° C./min and 10 ° C./min.

[0019]

[Table 2]

Also in this case, the former is based on the phosphorus concentration = 6.0 on average.
5 × 10 ¹⁹ atoms / cc, in-plane uniformity = 6.2 to 5.9
%, The latter being phosphorus concentration = 8.03 × 10 ¹⁹ atoms / cc on average,
As a result, the same excellent result as in-plane uniformity = 1.0 to 4.2% was obtained. According to the above data, the higher the temperature rise rate, the higher the phosphorus concentration,
It can be seen that the in-plane uniformity can be improved. Therefore, it is possible to control the phosphorus concentration by changing the rate of temperature rise.

The temperature rise rate can take any value in the range of 5 to 20 ° C./min. Also, the processing temperature is 75
It is not limited to 0 ° C. or 800 ° C. The gas introduced into the furnace from the processing gas introduction pipe 6 is not limited to phosphine, but may be a mixed gas containing phosphine.

[0022]

As described above, according to the present invention,
After the substrate is inserted into the reaction furnace, the temperature inside the furnace is raised to the substrate processing temperature at a predetermined rate while simultaneously introducing phosphine (PH ₃ ) as a phosphorus source or a mixed gas containing phosphine into the furnace. In this case, thermal diffusion is performed, so that the silicon film on the substrate can be doped with phosphorus without fail. At this time, by changing the rate of temperature rise, the concentration of phosphorus diffused into the silicon film can be controlled. Therefore, high integration of the memory can be realized by using the current batch type reaction furnace.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a semiconductor manufacturing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing measurement points of phosphorus concentration.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 External reaction tube (reactor) 2 Heater 3 Internal reaction tube (reactor) 5 Wafer (substrate) 6 Processing gas introduction tube

Claims (4)

[Claims] 1. A method for manufacturing a semiconductor device comprising a heat diffusion step of diffusing phosphorus into a silicon film of a substrate by introducing phosphine or a mixed gas containing phosphine into a reaction furnace for heat-treating the substrate. In performing the process, after inserting the substrate into the reaction furnace at a temperature lower than a predetermined substrate processing temperature, while increasing the temperature in the reaction furnace to the substrate processing temperature at a predetermined temperature increase rate, A semiconductor manufacturing method, wherein phosphine or a mixed gas containing phosphine is introduced into a reaction furnace. 2. The method according to claim 1, wherein the concentration of phosphorus diffused into the silicon film is controlled by changing the rate of temperature rise. 3. The method according to claim 1, wherein the predetermined temperature rise rate is 5 to 20 ° C./min.
The method according to claim 1, wherein the semiconductor device is set in a range of: 4. A reaction furnace for thermally diffusing phosphorus into a silicon film of a substrate, a heater for adjusting an ambient temperature in the reaction furnace, and a gas introduction for introducing phosphine or a mixed gas containing phosphine into the reaction furnace. Means for controlling the heater when inserting a substrate into the reaction furnace, setting the inside of the reaction furnace to a temperature lower than a predetermined substrate processing temperature, and controlling the heater after inserting the substrate to control the heater. Control means for controlling the gas introduction means to introduce phosphine or a mixed gas containing phosphine into the reaction furnace while raising the internal temperature to the substrate processing temperature at a predetermined temperature increase rate. Characteristic semiconductor manufacturing equipment.