JPH04212413A - Epitaxial growth method - Google Patents

Abstract

PURPOSE:To stably manufacture a semiconductor device of high performance. CONSTITUTION:In an epitaxial growth method for forming an epitaxial layer containing both elements of silicon and germanium on a semiconductor substrate, either element of silicon and germanium is supplied on a semiconductor substrate 2 by vacuum evaporation. The other element is supplied on the semiconductor substrate 2, by decomposing hydrogenated or halide gas 12 containing said element. Thereby an epitaxial growth layer 10 is grown. Compound gas which contains dopant elements is previously supplied on the semiconductor substrate 2 for a specified time. Either element of silicon and germanium is supplied on the semiconductor substrate 2 by vacuum evaporation. At the same time, the other element is supplied on the semiconductor substrate 2, by decomposing the hydrogenated or halide gas 12 containing said element. Thereby an epitaxial growth layer 10 is formed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor epitaxial growth method, and more particularly to an epitaxial growth method that is applied to the formation of an epitaxial base layer in a semiconductor device manufacturing process and is used for extremely high-speed semiconductor device manufacturing.

0002

Conventionally, in this type of epitaxial growth method, both elements Si (silicon) and Ge (germanium) are supplied onto a Si substrate by vapor deposition in an ultra-high vacuum, and an epitaxial growth layer containing Si and Ge is formed. (MBE method) was used.

This epitaxial growth method is based on a Si substrate 2 with an oxide film pattern 1 formed on its surface as shown in FIG.
is placed in a vacuum container 3, the natural oxide film 4 on the Si surface is removed in an ultra-high vacuum as shown in FIG. 6 to form a clean Si surface 5, and the Si solid source 6a and as shown in FIG. G
e. Heat the solid source 7a to evaporate Si and Ge, open the shutter 8 and irradiate the Si substrate 2 heated by the heater 9 with the Si molecular beam 6b and the Ge molecular beam 7b,
An epitaxial growth layer 10 containing Si and Ge is formed on a Si substrate 2. Here, a polycrystalline or amorphous layer is formed on the oxide film pattern 1, but this region is removed in a later process or used as an electrode.

0004

However, the conventional epitaxial growth method has a problem in that a high density of interface states is generated at the interface between the Si substrate 2 and the epitaxial growth layer 10 containing Si and Ge. This problem becomes a big problem when a hetero bipolar transistor is manufactured using the epitaxial growth layer 10 containing Si and Ge as a base layer. That is, since a recombination current flows through the interface states, a problem arises in that the fabricated hetero bipolar transistor does not operate at high speed as designed.

In order to solve such problems, based on the above background, a gas source MBE method using a hydrogenation or halide gas containing Si and a hydrogenation or halide gas containing Ge has been carried out. In the following explanation,
"Compound gas" means "hydrogenated or halide gas"
means.

In this method, as shown in FIG. 8, a Si substrate 2 on which an oxide film pattern 1 has been formed is placed in a vacuum container 3, and a natural oxide film 4 on the Si surface is removed in an ultra-high vacuum as shown in FIG. After removing the Si surface 5 to form a clean Si surface 5, as shown in FIG. and is decomposed on the heated Si substrate 2 by the heater 9 to form an epitaxial growth layer 10 containing Si and Ge. Here, a polycrystalline or amorphous layer is formed on the oxide film pattern 1 depending on the growth conditions, but this region is removed in a later step or used as an electrode. Further, depending on the growth conditions, it was also possible to selectively form the epitaxial growth layer 10 containing Si and Ge only on the clean Si surface 5.

In this method, a compound gas 11 containing Si is
Elements such as H, which are normally included in the compound gas 12 containing Ge, play a role in reducing the interface state.

However, when performing epitaxial growth containing Si and Ge by the gas source MBE method as described above, if the pressure of the Si-containing compound gas 11 and the Ge-containing compound gas 12 exceeds 10 −4 Torr, the heater 9 There was a problem in that a film containing Si and Ge was deposited nearby. Therefore, in order to prevent problems such as short-circuiting of the electrodes of the heater 9, it is necessary to expose the inside of the vacuum container 3 to the atmosphere and periodically remove the deposited film. After the inside of the vacuum container 3 is exposed to the atmosphere, a long period of baking and evacuation are required until an ultra-high vacuum is obtained, which poses a problem in that productivity is significantly reduced. Moreover, when the pressure of the compound gas 11 containing Si and the compound gas 12 containing Ge is less than 10 −4 Torr,
Although the problem that a film containing Si and Ge was deposited near the heater 9 was reduced, in this case there was a problem that a practical epitaxial growth rate could not be obtained.

[0009]

[Means for Solving the Problems] In order to solve such problems, the epitaxial growth method according to the present invention is an epitaxial growth method for forming an epitaxial growth layer containing both Si and Ge elements on a semiconductor substrate. One of the elements of Ge is supplied onto the semiconductor substrate by vacuum evaporation, and the other element is supplied onto the semiconductor substrate by hydrogenation or decomposition of a halide gas containing that element to form an epitaxial growth layer. .

0010

[Operation] In the epitaxial growth method of the present invention, one element is supplied onto the semiconductor substrate by decomposition of a compound gas containing the element, so that high-density interface states are less likely to occur. In addition, since the other element is supplied onto the semiconductor substrate by vacuum evaporation, the pressure required to obtain a practical epitaxial growth rate can be lower than 10-4 torr, and a film containing Si and Ge is deposited near the heater for heating the substrate. It becomes difficult to do.

[0011]

Embodiments Hereinafter, embodiments of the present invention will be explained in detail with reference to the drawings. Note that this embodiment is merely an example, and it goes without saying that various changes and improvements can be made without departing from the technical idea of the present invention.

(Example 1) FIGS. 1 to 3 are cross-sectional views of essential parts of an epitaxial growth apparatus for explaining steps according to an embodiment of the epitaxial growth method according to the present invention, and the same parts as in the previous figures are given the same reference numerals. It has been done. In the figure, first, oxide film pattern 1
The Si substrate 2 on which the Si substrate 2 is formed is cleaned using a hydrogen peroxide-based chemical or the like, and a natural oxide film 4 is formed on the Si surface using active oxygen generated from the hydrogen peroxide or the like. here,
A natural oxide film 4 is formed on the Si surface using ozone and ultraviolet irradiation.
may be formed. This treatment has the effect of removing contamination such as organic matter adhering to the surface of the Si substrate 2 and protecting the Si surface. Next, as shown in FIG. 1, the Si substrate 2 is introduced into the vacuum container 3. Here, the vacuum vessel 3 preferably has an ultimate pressure of 10 -9 Torr or less, is equipped with a load lock mechanism, and is capable of introducing the Si substrate 2 without exposing the inner surface of the vacuum vessel 3 to the atmosphere. Next, as shown in FIG. 2, the Si surface is cleaned to form a clean Si surface 5. Here, as a method for forming the clean Si surface 5, the natural oxide film 4 may be removed by heating the Si substrate 2 to 800° C. or higher in a vacuum of 10 −8 Torr or lower using a heater 9 . In addition, by HF treatment etc., a natural oxide film 4 is prepared in advance.
may be removed and the Si substrate 2 is introduced into the vacuum chamber 3 with the Si surface passivated with H or the like, and H or the like may be removed by appropriate heating or ultraviolet irradiation. Next, as shown in FIG. 3, the temperature of the Si substrate 2 is set to an appropriate temperature.
For example, the temperature is controlled to 500 to 700°C by the heater 9, and the Si
Or, by vacuum evaporation of either element Ge, S
The compound gas containing the other element is decomposed and supplied onto the Si substrate 2 to form an epitaxial growth layer 10 containing Si and Ge. Here, a polycrystalline or amorphous layer is formed on the oxide film pattern 1, but this region may be removed in a later step or used as an electrode.

Next, a case will be described in which Si is supplied onto the Si substrate 2 by vacuum evaporation, and Ge is supplied onto the Si substrate 2 by decomposition of the compound gas 12 containing Ge. This case is suitable for the purpose of forming an epitaxial growth layer with a Ge composition of less than 50%. In the vacuum evaporation of Si, a high-purity Si solid source 6a is heated, for example, by an electron beam to evaporate Si, and the shutter 8 is opened and the Si substrate 2 heated by a heater 9 is deposited at a rate of 0.1 to 10 A/min.
It is sufficient to supply Si at a rate of approximately sec. To decompose the compound gas 12 containing Ge, for example, GeH4 gas is heated by the heater 9 through the variable leak valve 13 at an appropriate flow rate, for example, at a flow rate such that the pressure in the vacuum container 3 becomes 10-6 to 10-5 Torr. What is necessary is to supply it onto the Si substrate 2 and decompose it. Here, if the pressure of the GeH4 gas is set to less than 10-4 Torr, film deposition near the heater 9, the solid source 6a, and the heating mechanism of the solid source 6a is negligible, and the inside of the vacuum vessel 3 is kept in the atmosphere for a long period of time. Epitaxial growth can be performed without exposure to

Furthermore, the method of the present invention has the advantage that active adsorption sites are continuously formed on the Si substrate 2 by vapor deposition of Si, so that adsorption and decomposition of GeH4 molecules occur efficiently. H in the GeH4 molecule reduces the interface level that may occur at the interface between the Si substrate 2 and the epitaxial growth layer 10 containing Si and Ge. Si
The composition of Ge in the epitaxial growth layer 10 containing Ge and Ge can be adjusted to any value within the range of 1 to 20%, for example, by controlling the deposition rate of Si and the pressure of GeH4. Epitaxial growth layer 1 containing Si and Ge
It is also possible to continuously change the composition of Si and Ge within a range of 0.

[0015] Furthermore, when introducing impurities such as B, P, and As into the epitaxial growth layer 10 containing Si and Ge, for example, B2 H6, PH3, AsH3, etc.
It is sufficient to introduce a gas such as GeH4 gas together with GeH4 gas. Furthermore, As or the like may be introduced from a Knudsen cell. It is also possible to continuously change the impurity concentration within the epitaxial growth layer 10 containing Si and Ge.

Further, a buffer layer or a layer of Si and Ge may be formed below the epitaxially grown layer 10 containing Si and Ge.
An epitaxial growth layer not containing Ge may be formed as a cap layer on the epitaxial growth layer 10 containing Ge. The buffer layer improves interfacial cleanliness, and the cap layer prevents the formation of unstable Ge oxides.

According to this method, the epitaxial growth layer 10 containing Si and Ge with few interface states is replaced with Si.
It can be stably formed over a long period of time at a practical growth rate on semiconductor substrates such as .

In addition, when Ge is supplied onto the Si substrate 2 by vacuum evaporation and Si is supplied onto the Si substrate 2 by a compound gas containing Si, Ge is evaporated from a Knudsen cell or the like, and SiH4, Si2 H6, etc. By using the Si source gas of , the epitaxial growth layer 10 containing Si and Ge can be similarly formed. This case is suitable for the purpose of forming an epitaxial growth layer having a Ge composition of 50% or more.

Further, the compound gas containing Si or Ge may be a hydrogenated or halide gas of Si or Ge, such as Ax, By, Cz...
(A means Si or Ge, B, C means H, F, Cl, etc., x is an integer of 1 or more, y, z are integers of 0 or more) good.

(Embodiment 2) Next, another embodiment according to the present invention will be described. first,
Clean the Si surface in the same way as in Example 1 to obtain clean S.
After forming the i-surface 5, the temperature of the Si substrate 2 is controlled to an appropriate temperature, for example, 500 to 700° C., by a heater 9. Here, a compound gas containing a dopant element is applied to the Si substrate 2.
For an appropriate time through the variable leak valve 13,
For example, it is supplied onto the Si substrate 2 for 1 to 10 minutes. As the compound gas containing the dopant element, for example, a gas such as B2 H6, PH3, AsH3 diluted with H2 etc. is used at an appropriate flow rate, for example, when the partial pressure of the compound gas containing the dopant element in the vacuum container 3 is 10- 8 Torr～
It is sufficient to supply the gas at a flow rate of 10-7 Torr. Through this step, an appropriate amount of the compound gas containing the dopant element is adsorbed onto the Si substrate 2 and the inner surface of the vacuum vessel 3. Next, the shutter 8 is opened while the compound gas containing the dopant element is being supplied, and Si is supplied onto the Si substrate 2 by vacuum evaporation. At the same time, GeH4 gas is supplied onto the Si substrate 2 through the variable leak valve 13, and Si, Ge ，
An epitaxially grown layer containing a dopant element is formed. Since a suitable amount of the compound gas containing the dopant element is adsorbed on the Si substrate 2 and the inner surface of the vacuum vessel 3, an epitaxial growth layer in which the dopant element rises steeply can be formed.

FIG. 4 is a diagram showing the depth distribution of dopant elements for explaining the effects of Example 2. In the same figure, B is used as a compound gas containing a dopant element in the step.
The B concentration depth direction is shown when the time from supplying 2 H6 to starting Si vapor deposition and GeH4 gas supply is 0 to 10 minutes. Figure 4(a) shows time 0 minutes, that is, Si evaporation and GeH
4. Since it takes several minutes for the surface B concentration on the Si substrate 2 to reach an equilibrium state, a B concentration transition region of about 500 Å exists. FIG. 4(b) shows a case where the time is 5 minutes, and the B concentration transition region is 50 Å or less. FIG. 4(c) shows the case where the time is 10 minutes, and a pile-up of B occurs at the interface between the Si substrate 2 and the epitaxial growth layer 10. By selecting an appropriate time based on FIG. 4, a desired B concentration distribution can be obtained.

By using the epitaxial growth method according to the present invention in the manufacturing process of semiconductor devices, it is possible to stably form the semiconductor device over a long period of time at a practical growth rate, compared to the case where the epitaxial growth method according to the conventional technology is used, and the interface quality can be improved. This enables the production of high-performance semiconductor devices.

[0023]

[Effects of the Invention] As explained above, according to the present invention, one element is supplied onto the semiconductor substrate by decomposition of a compound gas containing that element, so the problem of high density interface states occurring is solved. The pressure that can be avoided and obtains a practical epitaxial growth rate can be lower than 10<-4 >Torr, and the problem of a film containing Si and Ge being deposited near the heater for heating the substrate can be reduced. Further, after supplying a compound gas containing a dopant element onto the semiconductor substrate for a certain period of time in advance, one element is deposited on the semiconductor substrate by vacuum evaporation and the other element is simultaneously applied onto the semiconductor substrate by hydrogenation or decomposition of a halogenated gas containing the element. By supplying B to form the epitaxial growth layer, a desired B concentration distribution can be obtained. Therefore, if the present invention is used in the manufacturing process of semiconductor devices, extremely excellent effects such as the ability to stably manufacture high-performance semiconductor devices can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an epitaxial growth apparatus illustrating an embodiment of an epitaxial growth method according to the present invention.

FIG. 2 is a sectional view of an epitaxial growth apparatus for explaining an embodiment of the epitaxial growth method according to the present invention.

FIG. 3 is a cross-sectional view of an epitaxial growth apparatus for explaining an embodiment of the epitaxial growth method according to the present invention.

FIG. 4 is a distribution diagram of dopant elements in the depth direction for explaining the effects of another embodiment of the epitaxial growth method according to the present invention.

FIG. 5 is a cross-sectional view of an epitaxial growth apparatus for explaining a conventional epitaxial growth method.

FIG. 6 is a cross-sectional view of an epitaxial growth apparatus for explaining a conventional epitaxial growth method.

FIG. 7 is a cross-sectional view of an epitaxial growth apparatus for explaining a conventional epitaxial growth method.

FIG. 8 is a cross-sectional view of an epitaxial growth apparatus for explaining a conventional epitaxial growth method.

FIG. 9 is a cross-sectional view of an epitaxial growth apparatus for explaining a conventional epitaxial growth method.

FIG. 10 is a cross-sectional view of an epitaxial growth apparatus for explaining a conventional epitaxial growth method.

[Explanation of symbols]

1 Oxide film pattern 2 Si substrate 3 Vacuum container 4. Natural oxide film 5. Clean Si surface 6a Si solid source 6b Si molecular beam 8 Shutter 9 Heater 10 Epitaxial growth layer 12 Compound gas containing Ge 13 Variable leak valve

Claims (2)

[Claims] 1. An epitaxial growth method for forming an epitaxial growth layer containing both silicon and germanium on a semiconductor substrate, wherein either the silicon or germanium element is supplied onto the semiconductor substrate by vacuum evaporation, An epitaxial growth method characterized in that the other element is supplied onto the semiconductor substrate by hydrogenation or decomposition of a halide gas containing the element to form the epitaxial growth layer. 2. In an epitaxial growth method for forming an epitaxial growth layer containing both silicon and germanium on a semiconductor substrate, after supplying a compound gas containing a dopant element onto the semiconductor substrate for a certain period of time, Supplying one of the elements of germanium onto the semiconductor substrate by vacuum evaporation, and simultaneously supplying the other element onto the semiconductor substrate by hydrogenation or decomposition of a halide gas containing that element to form the epitaxial growth layer. An epitaxial growth method characterized by: