JP3753986B2 - Semiconductor device manufacturing method and substrate processing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device manufacturing method and a substrate processing apparatus, and more particularly to a semiconductor device manufacturing method and a substrate processing apparatus for depositing polysilicon germanium or amorphous silicon germanium by a low pressure CVD method (chemical vapor deposition method). .
[0002]
[Prior art]
In a process of manufacturing a semiconductor device such as an IC or LSI, a thin film is formed on a substrate by a low pressure CVD method (chemical vapor deposition method). As one of such film formation processes, attempts have been made to form a silicon germanium film by a low pressure CVD method.
[0003]
For silicon germanium, attempts are being made to grow epitaxial silicon germanium in the base region in a heterojunction bipolar transistor (HBT), for example, and to form a polysilicon germanium film in the gate electrode portion in a MOS transistor, depending on the target device. .
[0004]
In polysilicon germanium film formation by a conventional low pressure CVD apparatus, diborane (B ₂ H ₆ ) has been used to dope boron. However, when diborane is used, it is difficult to ensure the uniformity of boron (B) concentration in the silicon germanium film within the wafer surface and between the wafer surfaces in the vertical vacuum CVD apparatus that is a batch process. It was. Therefore, boron trichloride (BCl ₃ ) has been used as an alternative doping gas for diborane. Since boron trichloride is less reactive than diborane, it does not consume much in the gas flow direction, so it is possible to ensure uniformity between boron concentration surfaces. Further, it is known that even when the wafer interval is as narrow as about 5.2 mm pitch, boron trichloride spreads to the center of the wafer and the boron concentration in-plane uniformity is improved.
[0005]
[Problems to be solved by the invention]
The appropriate value of the boron concentration in the silicon germanium film varies depending on the device part to be applied. For example, in the case of a gate electrode, a high concentration of boron is introduced to reduce the resistance. It is known that the boron concentration in the silicon germanium film due to diborane increases monotonically in proportion to the diborane partial pressure. However, the behavior of boron trichloride containing chlorine is not known. Therefore, clarifying the behavior of boron in the silicon germanium film when boron trichloride is used as a doping gas is an important issue in performing boron doping at an appropriate concentration.
[0006]
SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor device manufacturing method and substrate capable of solving the above-described problems and depositing boron-doped polysilicon germanium or boron-doped amorphous silicon germanium having an appropriate boron doping concentration by a low pressure CVD method. It is to provide a processing apparatus.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present invention as described in claim 1,
Manufacture of a semiconductor device using monosilane and monogermane as reaction gases and depositing boron-doped polysilicon germanium or boron-doped amorphous silicon germanium as a gate electrode of a MOS transistor on a substrate by a low pressure CVD method in a reaction furnace In the method, the pressure in the reactor is set to 30 Pa to 120 Pa, boron trichloride is used as a doping gas, the partial pressure of the boron trichloride at the time of film formation is set to 0.2 Pa to 1 Pa, and at the time of film formation The temperature in the reaction furnace is set to 450 ° C. or more and 500 ° C. or less, and the flow ratio of boron trichloride to monosilane during film formation is set to 0.000017 to 0.028. .
[0008]
Further, the present invention provides the following, as described in claim 2.
A substrate processing apparatus for forming boron-doped polysilicon germanium or boron-doped amorphous silicon germanium on a substrate as a gate electrode of a MOS transistor, a reaction tube for processing the substrate, and a heater for heating the substrate in the reaction tube A nozzle for supplying monosilane as a film forming gas into the reaction tube, a nozzle for supplying monogermane as a film forming gas, a nozzle for supplying boron trichloride as a doping gas, and the inside of the reaction tube. The exhaust pipe to be exhausted, the pressure in the reaction tube is set to 30 Pa to 120 Pa , the temperature in the reaction furnace at the time of film formation is set to 450 ° C. to 500 ° C., and the flow ratio of boron trichloride to monosilane at the time of film formation is and 0.000017 to 0.028, 0.2 the partial pressure of the boron trichloride in film formation constituting the substrate processing apparatus characterized by a control device for controlling the a least 1Pa or less.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
As a result of intensive studies, the present inventors have investigated the relationship between the concentration of boron taken into the silicon germanium film and the partial pressure of boron trichloride when boron trichloride is used as a doping gas, and based on the results, Invented.
[0010]
A method for manufacturing a semiconductor device according to the present invention includes a vertical reduced pressure CVD apparatus which is one of the substrate processing apparatuses according to the present invention, wherein monosilane (SiH ₄ ) and monogermane (GeH ₄ ) are used as reaction gases, and three are used as doping gases. Boron chloride is used to deposit boron-doped polysilicon germanium or boron-doped amorphous silicon germanium on the wafer.
[0011]
FIG. 1 shows a schematic diagram of a reactor structure of a hot wall vertical vacuum CVD apparatus which is an example of the vertical vacuum CVD apparatus. In the figure, a quartz outer tube 1 and an outer tube, which are outer cylinders of a reaction furnace 11, are arranged inside a heater 6 that constitutes a hot wall furnace and is divided into four zones (U, CU, CL, and L) for heating a substrate. An inner tube 2 inside the tube 1 is installed, and a vacuum is drawn between the two types of tubes using a mechanical booster pump 7 and a dry pump 8. Therefore, monogermane as a reaction gas from four intermediate supply nozzles 12 inside the inner tube 2, a mixed gas of monosilane and monogermane as a reaction gas from a SiH ₄ + GeH ₄ nozzle 13, and a doping gas as a doping gas from a BCl ₃ nozzle 14. Boron chloride is introduced, and the reaction gas and doping gas rise in the inner tube 2 and descend between the two types of tubes 1 and 2 and are exhausted. The supply flow rate of each gas is controlled by a flow rate control device (not shown) provided in each gas supply system.
[0012]
A quartz boat 3 (for example, for 8-inch wafers, a pitch between wafers of 5.2 mm) is a loading substrate support in which a plurality of wafers 4 are stacked and loaded in a vertical direction. A boron-doped silicon germanium thin film is formed on the wafer 4 by reaction in the gas phase and on the surface of the wafer 4 when placed and exposed to the reaction gas. At that time, in order to control the pressure in the reaction furnace 11, nitrogen (N ₂ ) is introduced into the exhaust system through the N ₂ ballast valve 16, and the flow rate of the nitrogen is determined by the controller 17 from the output signal of the pressure gauge 15. Control based on. The partial pressure of boron trichloride is controlled by adjusting the ratio between the furnace pressure, the total flow rate, and the BCl ₃ flow rate. However, the furnace pressure (growth pressure), so greatly affects the thickness uniformity in the wafer plane, in this embodiment, by increasing or decreasing the flow rate of BCl _3, and controls the BCl ₃ partial pressure . That is, in the present embodiment, a pressure control device including the N ₂ ballast valve 16, the pressure gauge 15, and the controller 17 and a flow rate control device (not shown) for controlling the flow rate of boron trichloride are claimed. 2 is configured to control the partial pressure of boron trichloride.
[0013]
The heat insulating plate 5 is used to insulate between the boat 3 and the lower part of the apparatus. Reference numeral 9 denotes a boat rotation shaft, and reference numeral 10 denotes a stainless steel lid.
[0014]
FIG. 2 shows a film forming procedure using the substrate processing apparatus shown in FIG.
[0015]
First, a plurality of wafers 4 are put into the boat 3, the inside of the reaction furnace 11 is stabilized at the film formation temperature, and then the boat 3 loaded with the wafers 4 is loaded (inserted) into the reaction furnace 11. The inside of the reactor (reactor 11) is evacuated, and N ₂ purge is performed to desorb moisture adsorbed on the boat 3 and the tubes 1 and 2.
[0016]
Thereafter, after performing a leak check in the reactor, the flow rate of each raw material gas is set and stabilized by N ₂ ballast so as to reach a growth pressure while flowing each gas into the reaction furnace 11. At this time, the BCl ₃ partial pressure is determined by the relationship between the growth pressure, the total flow rate, and the ratio of the BCl ₃ flow rate. However, as described above, the growth pressure greatly affects the film thickness uniformity in the surface of the wafer 4. In this embodiment, the BCl ₃ partial pressure is controlled by increasing or decreasing the BCl ₃ flow rate. Then, after the growth pressure in the reactor 11 is stabilized, film formation is performed.
[0017]
After deposition is completed, the flow of the reaction gas is stopped, the pipe was cycle purged with N _2, returning the reactor (reactor 11) with N ₂ to atmospheric pressure. When the pressure returns to atmospheric pressure, the boat 3 is unloaded and the wafer 4 is naturally cooled. Finally, the wafer 4 is taken out from the boat 3.
[0018]
Embodiments are shown below.
[0019]
Boron-doped silicon germanium was deposited on an 8-inch wafer using the substrate processing apparatus shown in FIG.
[0020]
The film formation conditions in this case were a film formation temperature of 450 to 500 ° C., a growth pressure of 30 to 120 Pa, GeH ₄ / SiH ₄ = 0.038, and BCl ₃ / SiH ₄ = 0.000017 to 0.028. These ratios (GeH ₄ / SiH ₄ , BCl ₃ / SiH ₄ ) indicate the flow ratios of GeH ₄ and BCl ₃ to SiH ₄ , respectively.
[0021]
FIG. 3 shows the relationship between boron trichloride partial pressure and boron concentration from 0.05 to 2 Pa of which the partial pressure of boron trichloride is controlled in the range of 1.02 × 10 ⁻⁴ to 2 (Pa). Indicates.
[0022]
As shown in FIG. 3, it was found that the boron trichloride monotonously increased by increasing the boron trichloride partial pressure, and the boron concentration was approximately saturated at the point of boron trichloride partial pressure “a”. This point is in the vicinity of the solid solution limit region of boron taken into the silicon germanium film. Therefore, boron can be doped to the maximum by setting the partial pressure of boron trichloride to the partial pressure at the point “a”, that is, 0.1 Pa or more. Also, it can be seen that an arbitrary boron concentration can be obtained by controlling the partial pressure of boron trichloride.
[0023]
FIG. 4 is a graph showing the relationship between the boron concentration and the resistivity immediately after the formation of the boron-doped silicon germanium film doped with boron trichloride. From the figure, it can be seen that the resistivity decreases as the boron concentration increases. On the other hand, the resistivity increases with a decrease in the boron concentration. If the boron concentration is lower than the “b” point, the resistivity becomes too high, which is not preferable. Further, if the boron concentration is higher than the “c” point, the resistivity tends to increase despite the increase in boron concentration, which is not preferable. From these facts, it can be said that the boron concentration range from the “b” point to the “c” point is a suitable range for a gate electrode that requires a reduction in resistance. Note that the boron concentrations at points “b” and “c” in FIG. 4 correspond to the boron concentrations at points “d” and “e” in FIG. Therefore, the silicon germanium film having a boron concentration range suitable for the gate electrode as described above has a partial pressure of boron trichloride that is a partial pressure at the point “d” in FIG. It can be seen that the film is formed when the pressure is set to 1 Pa or less. Even if the partial pressure of boron trichloride is higher than 1 Pa, the boron concentration in the film only slightly increases as shown in FIG. 3, and as shown in FIG. Since the rate rises, it is not practically advantageous.
[0024]
From this, it is understood that a boron germanium film having a boron concentration suitable for the gate electrode can be obtained by setting the partial pressure of boron trichloride to 0.2 Pa or more and 1 Pa or less. Such a resistivity of the silicon germanium film is realized immediately after film formation at a film formation temperature of 450 to 500 ° C., and therefore, a high temperature (temperature higher than 500 ° C.) annealing process is not used. However, it can be seen that a low-resistance silicon germanium film can be formed only by a low-temperature (500 ° C. or lower) processing step.
[0025]
Note that amorphous or poly film formation is possible if the film formation conditions are appropriately determined.
[0026]
As described above, in the semiconductor manufacturing method and substrate processing apparatus for depositing boron-doped polysilicon germanium or boron-doped amorphous silicon germanium in the vertical reduced pressure CVD apparatus according to the implementation of the present invention, the partial pressure of boron trichloride is increased. A method of manufacturing a semiconductor device and a substrate processing apparatus capable of obtaining a boron concentration suitable for a gate electrode by controlling the temperature and reducing the resistance at a low temperature without using a high temperature annealing process are provided. Can do.
[0027]
【The invention's effect】
By implementing the present invention, it is possible to provide a method of manufacturing a semiconductor device and a substrate processing apparatus capable of forming a boron-doped polysilicon germanium or boron-doped amorphous silicon germanium having an appropriate boron concentration by a low pressure CVD method. it can.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a reaction furnace structure of a vertical reduced pressure CVD apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a film forming procedure by a low pressure CVD method.
FIG. 3 is a diagram showing a relationship between a partial pressure of boron trichloride and a boron concentration in a silicon germanium film during a film forming process.
FIG. 4 is a diagram showing a relationship between a boron concentration in a silicon germanium film and a silicon germanium film resistivity.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Outer tube, 2 ... Inner tube, 3 ... Boat, 4 ... Wafer, 5 ... Heat insulation board, 6 ... Heater, 7 ... Mechanical booster pump, 8 ... Dry pump, 9 ... Boat rotating shaft, 10 ... Stainless steel lid, 11 ... reactor, 12 ... halfway supply nozzle, 13 _... SiH ₄ + GeH 4 nozzle, 14 ... BCl ₃ nozzles, 15 ... pressure gauge, 16 ... _{N 2} ballast valve, 17 ... controller.

Claims (2)

Manufacture of a semiconductor device using monosilane and monogermane as reaction gases and depositing boron-doped polysilicon germanium or boron-doped amorphous silicon germanium as a gate electrode of a MOS transistor on a substrate by a low pressure CVD method in a reaction furnace In the method, the pressure in the reactor is set to 30 Pa to 120 Pa, boron trichloride is used as a doping gas, the partial pressure of the boron trichloride at the time of film formation is set to 0.2 Pa to 1 Pa, and at the time of film formation A method for manufacturing a semiconductor device, wherein a temperature in the reaction furnace is set to 450 ° C. or more and 500 ° C. or less, and a flow ratio of boron trichloride to monosilane during film formation is set to 0.000017 to 0.028 . A substrate processing apparatus for forming boron-doped polysilicon germanium or boron-doped amorphous silicon germanium on a substrate as a gate electrode of a MOS transistor, a reaction tube for processing the substrate, and a heater for heating the substrate in the reaction tube A nozzle for supplying monosilane as a film forming gas into the reaction tube, a nozzle for supplying monogermane as a film forming gas, a nozzle for supplying boron trichloride as a doping gas, and the inside of the reaction tube. The exhaust pipe to be exhausted, the pressure in the reaction tube is set to 30 Pa to 120 Pa , the temperature in the reaction furnace at the time of film formation is set to 450 ° C. to 500 ° C., and the flow ratio of boron trichloride to monosilane at the time of film formation is and 0.000017 to 0.028, 0.2 the partial pressure of the boron trichloride in film formation The substrate processing apparatus characterized by a control device for controlling the a least 1Pa or less.

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