JPH0474415A - Selective epitaxial growth method of silicon - Google Patents

Abstract

PURPOSE:To obtain a selective epitaxial growth method, of silicon, which controls the shape of a growth part near an insulating film and which restrains the deformation of a facet by a method wherein a growth temperature is made low or a gas flow rate is increased. CONSTITUTION:When silicon is grown epitaxially, a growth temperature and a gas flow rate are controlled and, thereby, the shape of a selective growth part near an insulating film is controlled. At this time, the growth temperature is changed within a range of 400 to 800 deg.C, and the gas flow rate is changed within a range where the degree of vacuum near the surface of a substrate is at 10<-3>Torr or lower. For example, when the growth temperature is set at 550 deg.C and the gas flow rate is at 50 scums i.e., when the growth temperature is low and the gas flow rate is large, the silicon is grown in a shape that a part near an oxide-film sidewall 13 swells. Consequently, a leakage current generated at the part of a facet is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for selective epitaxial growth of silicon using a gas source, and particularly to a method for controlling the shape of a grown layer near the sidewalls of an insulating film.

(Prior art) In the single crystal growth of silicon using a gas source, when an insulating film such as an oxide film or a nitride film and an exposed silicon part coexist, growth can be performed selectively only on the exposed silicon part. It has been known. The first method used was dichlorosilane and hydrogen chloride, and the growth temperature at this time was 800°C or higher. Then silane,
It has been reported that disilane was used, and the growth temperature was 5.
The temperature dropped to around 00°C. However, in order to achieve selective growth, the gas flow rate must be adjusted so that the partial pressure of disilane near the surface is 1O
It has been carried out under low pressure conditions of −5 Torr or less. Under these conventional growth conditions, surfaces that are difficult to grow, called facets, expand from the sidewall portions of the insulating film as the insulating film grows.

FIG. 7 is a cross-sectional view after selective growth at a growth temperature of 700° C. and a gas flow rate of 5 seconds. In this case, the degree of vacuum near the surface is approximately 10-5 Torr. Silicon substrate 1 when the growth temperature is high and the gas flow rate is low
In the epitaxially grown layer 11 on the oxide film 12, a facet surface 14 is formed from the lower end of the side wall 13 of the oxide film 12, and the original (100) growth surface 15 is flat.

(Problems to be Solved by the Invention) If there are facets, there is a problem that when an element is formed, leakage current increases at the facet portion, causing the element to malfunction. Furthermore, as the thickness of the grown film increases, the facets also grow, which reduces the area of the flat portion and increases the level difference, so the presence of facets becomes a big problem when making fine elements. In the case of FIG. 7, when the thickness of the growth layer 11 is 200 OA, the width W of the face and throat is about 2,500.

An object of the present invention is to suppress deformation of facets by controlling the shape of a grown portion near an insulating film in selective growth of silicon using a gas source.

(Means for Solving the Problems) The present invention controls the shape of a selectively grown portion near an insulating film by controlling the growth temperature and gas supply rate in selective epitaxial growth of silicon using gas. Traditionally - growth temperature 7 has been used for boat fishing
The growth conditions were 0.006C or higher, and the gas flow rate was approximately 10' Torr or lower when converted to pressure near the surface, and under these conditions, facets were formed. As a result of extensive studies, the present inventor found that the epitaxial growth reaction of silicon depends on both the growth temperature and the gas flow rate. It was found that the formation of can be suppressed. Here, the range in which the growth temperature is changed is from 400°C to 800°C, and the range in which the gas flow rate is changed is in a range where the degree of vacuum near the substrate surface is 10-3 Torr or less. Further, by lowering the growth temperature and increasing the gas supply amount, the portion near the insulating film can grow into a raised shape.

(Function) The facets spread out as the growth progresses because the reactivity of the facets is low, so if even a small amount of facets is formed in the early stages of growth, reactive species will rapidly escape from the facets due to migration, etc. This is because the Therefore, the formation of facets can be suppressed by providing conditions in which the growth rate of reactive species is faster than the rate of escape from the proboscis asset surface. There are two approaches to achieving this condition.

One is to lower the growth temperature, and one is to increase the gas flow rate. By lowering the growth temperature, the difference in reactivity due to plane orientation is reduced. Therefore, the difference in growth rate between the facet surface and the growth surface becomes small, and the formation of facets is suppressed. At this time, the growth temperature must be 400°C or higher. This is because substituents such as hydrogen in the gas must be eliminated for growth to proceed, and the elimination reaction is 4
This is because a temperature of 00°C or higher is required. On the other hand, since the rate of escape is constant at the same growth temperature, the growth of facets can be suppressed by increasing the reaction rate on the surface by increasing the gas flow rate. At this time, the gas flow rate is such that the degree of vacuum near the surface of the substrate is 10" Tor.
control within the range below r. If the gas flow rate is increased more than this, the gas molecules will be excited by collisions between them before reaching the surface, making it impossible to maintain selectivity. As described above, the formation of facets can be suppressed by either lowering the growth temperature or increasing the gas flow rate. When the growth temperature is low and the gas flow rate is high, the growth reaction becomes completely rate-limiting. At this time, the temperature near the insulating film side wall increases due to heat radiation from the insulating film side wall, so that the insulating film grows into a swollen shape near the side wall.

(Example) The present invention will be described below using the drawings. FIG. 1 is a schematic explanatory diagram of a silicon epitaxial growth apparatus using a gas source for explaining the present invention in detail. As the substrate 1, a 4-inch n-type 5i (100) wafer having an oxide film pattern with a thickness of 5000 nm on the surface was used. This substrate is loaded into growth chamber 2. The inside of the chamber 2 is made into an ultra-high vacuum and heated to 900°C by the heater 3 on the back side of the substrate.
Heat for 10 minutes. This process cleans 5
An i(100) surface is obtained. The cleanliness of the surface is determined by the observation of a 2×1 surface superstructure characteristic of a clean 5i (100) plane in the diffraction pattern of a reflection high-speed electron diffraction device consisting of a high-speed electron gun 4 and a fluorescent screen 5. confirmed. The growth temperature of the silicon substrate is set at 550° C. to 800° C., and disilane as a source gas is supplied from the gas cell 6 to this clean surface. The disilane gas flow rate supplied from the gas pump 7 through the subchamber 8 was varied from 5 seconds to 101005e. Most of this is evacuated by the subchamber's exhaust pump 9, and approximately one-fifth of this amount is supplied to the substrate from the gas cell.

Figure 2 shows a growth temperature of 700°C and a gas flow rate of 50 sec.
FIG. 3 is a cross-sectional view after selective growth in the case of This is a case where the gas flow rate is increased compared to the conventional example shown in FIG. They can grow into a nearly bonded state. If the grown film thickness is the same as in Figure 7, 2000 people, the facet width W is about 400 people,
The depth D is about 300 people, which is very small compared to the conventional example shown in FIG.

FIG. 3 is a cross-sectional view after selective growth at a growth temperature of 550° C. and a gas flow rate of 5 seconds. When the growth temperature is low and the gas flow rate is small, the oxide film sidewall 13
The side surfaces of the grown layer 11 are joined to each other, no facets are formed, and the oxide film grows into a rounded shape near the side wall 13, as shown by 17a in the figure. Under these growth conditions, the grown film thickness is 2
When there are 000 people, the size of the rounded part 17a is
The height is very small, about 100 people, and the width is also small, about 100 OA. The portion away from the oxide film sidewall 13 is flat.

Figure 4 shows a growth temperature of 550°C and a gas flow rate of 50 sec.
FIG. 3 is a cross-sectional view after selective growth in the case of When the growth temperature is low and the gas flow rate is large, the oxide film sidewall 1
Silicon grows into a raised shape near 3. When the growth condition is a film thickness of 200 OA, the size of the raised portion 17b is very small, 400 OA in height, and the width is also about 200 OA. At this time as well, the portion 7 apart from the oxide film sidewall 13 is flat.

For comparison, experimental results are shown in which the growth temperature was slightly lower and the gas flow rate was slightly higher than in the conventional example shown in FIG. FIG. 5 is a cross-sectional view after selective growth at a growth temperature of 600'C and a gas flow rate of 1105CC.

In this case, the facet grows from the middle of the oxide film side wall 13, and the facet surface 14 is flat, although it becomes slightly smaller. At this time, the upper part of the facet surface becomes slightly raised, and the grown layer separated from the oxide film sidewall 13 is still flat. The width W of the facet is approximately 2000 mm when the grown film thickness is 2000 mm, and it cannot be said that the formation of facets is sufficiently suppressed under this condition.

FIG. 6 shows growth conditions under which the formation of facets is suppressed. The circles shown in the figure are the growth conditions shown in FIGS. 2 to 5, which were explained in the example described in L. The shaded area in the figure is the area where the formation of facets is sufficiently suppressed. Since the required gas flow rate varies depending on the size of the device used, it is recommended to calibrate each device.

(Effects of the Invention) As described in detail above, according to the present invention, in epitaxial growth of silicon using a gas source, the shape of the silicon growth portion near the sidewall of the insulating film is controlled by adjusting the temperature of the substrate and the gas flow rate. Since it is possible to control and suppress the formation of facets, the leakage current generated at the facet portions is reduced. Furthermore, since the facets become smaller, there is no problem when manufacturing minute elements.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a gas-based silicon epitaxial growth apparatus for explaining the present invention in detail. Second
4 is a cross-sectional view of the structure near the side wall of the oxide film after growth when selective growth is performed under the conditions of the present invention, and FIGS. 5 and 7 are under growth conditions other than the conditions. FIG. 6 is a diagram showing growth conditions under which the formation of facets is sufficiently suppressed. In the figure, l is a 4-inch n-type 5i (100) wafer, 2
3 is a silicon epitaxial growth device using gas, 3 is a substrate heater, 4 is a high-speed electron gun for reflected high-speed electron beams, 5 is a fluorescent screen for observing reflected electron beam diffraction patterns, 6 is a gas cell, 7 is a gas cylinder, 8 is a subchamber 9 is a sub-chamber Chamber exhaust pump, 1o is an n-type silicon (IOO) substrate, 11 is a silicon selective epitaxial growth layer, 12 is an oxide film, 13 is an oxide film side wall, 14 is a facet surface, 15
is the silicon (100) surface of the growth layer.

Claims (1)

[Claims] A growth method in which silicon is selectively epitaxially grown using a gas source, in which the shape of the grown region near the sidewalls is controlled during selective growth by lowering the growth temperature or increasing the gas flow rate.