JP3938877B2 - Manufacturing method of semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device in which polysilicon germanium or amorphous silicon germanium is formed 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]
Conventionally, silicon has been used for the gate electrode portion of the MOS transistor. However, with the recent thinning of the gate insulating film, the gate is depleted when the gate is biased, and the boron electrode is used in the heat treatment process. The penetration into the channel portion has been a major problem that deteriorates the device characteristics. It has been found that the above problems are greatly improved by using boron-doped polysilicon germanium instead of boron-doped polysilicon.
[0005]
In addition, in the formation of polysilicon germanium 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.
[0006]
[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.
[0007]
Also, the main method of forming a boron-doped polysilicon film used for the current gate electrode part is to first form a non-doped polysilicon film, and then boron is doped by ion implantation, and then boron is activated and polycrystallized. Therefore, it is necessary to perform heat treatment at about 1000 ° C. At this time, boron that penetrates through the gate insulating film and diffuses into the channel portion is one factor that deteriorates device characteristics.
[0008]
An object of the present invention is to solve the above problems, by low pressure CVD method, it possible to deposit boron-doped polysilicon germanate Niu arm proper boron doping concentration, reducing thermal history by activating the boron at a low temperature It is another object of the present invention to provide a method of manufacturing a semiconductor device that can activate boron (reducing the resistivity to 2 × 10 ⁻³ [Ω · cm]).
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present invention as described in claim 1,
The reaction using monosilane and monogermane as a gas, using boron trichloride as the doping gas, in the reaction furnace, the method of manufacturing a semiconductor device for forming a boron doped polysilicon germanium film by low pressure CVD method, the low pressure CVD method A method for manufacturing a semiconductor device is provided, which is performed at a deposition temperature of 450 ° C. or higher and 500 ° C. or lower .
Further, the present invention provides the following, as described in claim 2.
2. The semiconductor device according to claim 1, wherein the reaction furnace is a hot wall furnace, and the boron-doped polysilicon germanium film is formed on a plurality of wafers stacked vertically in the reaction furnace. Configure the manufacturing method.
[0010]
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.
[0011]
The method of manufacturing a semiconductor device according to the present invention uses a monosilane (SiH ₄ ) and a monogermane (GeH ₄ ) as reaction gases and boron trichloride as a doping gas in a vertical reduced pressure CVD apparatus. the silicon germanium Niu beam is intended to be formed.
[0012]
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.
[0013]
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 and 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 .
[0014]
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.
[0015]
FIG. 2 shows a film forming procedure using the substrate processing apparatus shown in FIG.
[0016]
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.
[0017]
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.
[0018]
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.
[0019]
Embodiments are shown below.
[0020]
Boron-doped silicon germanium was deposited on an 8-inch wafer using the substrate processing apparatus shown in FIG.
[0021]
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.
[0022]
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. The film forming temperature at this time is 475.degree.
[0023]
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.
[0024]
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. The film forming temperature at this time is 475.degree. 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.
[0025]
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.
[0026]
In addition, the change in crystallinity when boron is doped at about 3 × 10 ²⁰ [cm ⁻³ ] to 3 × 10 ²¹ [cm ⁻³ ] at a relatively low temperature of 450 ° C. is observed when boron is not doped (non-doped). , Non-dope), the results of investigation by XRD (X-ray diffraction method) are shown in FIG. The figure shows the relationship between the diffraction angle θ (indicated by twice that in the figure) and the diffraction intensity for the plane orientations (111), (220) and (311) of the silicon germanium film. In any plane orientation, no diffraction peak is observed when boron is not doped, and the crystallinity of the film is completely amorphous, whereas boron is about 3 × 10 ²⁰ [cm ⁻³ ] to When 3 × 10 ²¹ [cm ⁻³ ] is doped, a diffraction peak is observed in any plane orientation, and it can be seen that it is polycrystallized.
[0027]
Furthermore, regarding the activation of boron at a relatively low temperature, the dependence of the resistivity of the boron-doped polysilicon germanium film formed at 450 ° C. on the heat treatment temperature is shown in FIG. The heat treatment time is 60 minutes, and the abscissa as-depo indicates a state after the film formation and before the heat treatment. The resistivity decreased to about 2.2 × 10 ⁻³ [Ω · cm] at the time of as-depo (before heat treatment), and it can be seen that no significant change in the resistivity was observed even after heat treatment. This shows that boron is considerably activated at a relatively low temperature of 450 ° C. without performing heat treatment.
[0028]
Note that when the temperature during film formation is lower than 450 ° C., the growth rate is lower than 3 nm / min and the throughput is lowered, which is not practical. When the temperature is higher than 500 ° C., the resistivity in-plane uniformity is about ± 5% compared to ± 1% at 450 ° C., and there is a problem that the resistivity in-plane uniformity is deteriorated. Therefore, the deposition temperature is preferably 450 ° C. or higher and 500 ° C. or lower.
[0029]
For this reason, the resistivity of the silicon germanium film is realized immediately after film formation at a film formation temperature of 450 to 500 ° C., and it is possible to use a high temperature (temperature higher than 500 ° C.) annealing process. It can be seen that a low-resistance silicon germanium film can be formed only by a low-temperature (500 ° C. or lower) treatment process.
[0030]
Note that amorphous or poly film formation is possible if the film formation conditions are appropriately determined.
[0031]
As described above, by the practice of the present invention, in a semiconductor manufacturing process for forming a boron-doped polysilicon germanate Niu arm in vertical decompression CVD apparatus, by selecting the deposition temperature to 450 ° C. or higher 500 ° C. or less, It is possible to provide a method of manufacturing a semiconductor device that can reduce resistance at a low temperature without using a high-temperature annealing process.
[0032]
【The invention's effect】
By practice of the present invention, by a low pressure CVD method, it possible to deposit boron-doped polysilicon germanate Niu arm proper boron concentration, the polycrystalline thin film is obtained at a relatively low temperature without additional heat treatment, it should be noted and Even without heat treatment, boron can be activated (resistivity can be reduced to 2 × 10 ⁻³ [Ω · cm]).
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a reactor structure of a vertical reduced pressure CVD apparatus used in 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.
FIG. 5 is a diagram showing a change in crystallinity of a silicon germanium film when boron is doped with about 3 × 10 ²⁰ (cm ⁻³ ) to 3 × 10 ²¹ (cm ⁻³ ).
FIG. 6 is a diagram showing the heat treatment temperature dependence of the resistivity of a boron-doped polysilicon germanium film formed at 450 ° C.
[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)

The reaction using monosilane and monogermane as a gas, using boron trichloride as the doping gas, in the reaction furnace, the method of manufacturing a semiconductor device for forming a boron doped polysilicon germanium film by low pressure CVD method, the low pressure CVD method A method for manufacturing a semiconductor device, which is performed at a deposition temperature of 450 ° C. or higher and 500 ° C. or lower .   2. The semiconductor device according to claim 1, wherein the reaction furnace is a hot wall furnace, and the boron-doped polysilicon germanium film is formed on a plurality of wafers stacked vertically in the reaction furnace. Production method.

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