Semiconductor device epitaxial layer lateral growth rate control method using CBr.sub.4

A semiconductor device epitaxial layer lateral growth rate control method using CBr.sub.4 gas involves regulating an epitaxial layer lateral growth rate in accordance with the CBr.sub.4 amount doped into the epitaxial layer during the epitaxial layer growth occurring on a patterned GaAs substrate by means of a metalorganic chemical vapor deposition (MOCVD) process. The lateral growth rate may be regulated by varying the growth temperature and the V/III doping ratio.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a semicontuctor device epitaxial layer 
growth, and more particularly to a semiconductor device epitaxial layer 
lateral growth rate control method using CBr.sub.4 gas capable of 
regulating a patterned semiconductor device lateral growth rate by doping 
CBr.sub.4 gas into an epitaxial layer which is grown by a metalorganic 
chemical vapor deposition (MOCVD) on a patterned GaAs substrate. 
2. Description of the Conventional Art 
Recently, several studies on photoelectric device fabrication technology in 
relation with compound semiconductor device mechanisms are being 
conducted. However, to fabricate such a photoelectric device, a number of 
complicated fabrication steps are generally required. 
A selective epitaxial growth technology which is one of the active studies 
being made in recent years, retains a strong advantage, in which a desired 
three-dimensional epitaxial layer structure can be obtained by a single 
layer growing process without any other complicated fabrication steps, and 
interface damage which may occur during display fabrication steps other 
than the selective epitaxial growth technology can also be prevented. 
Further, a non-planar growth mechanism which is one of such selective 
epitaxial growth technologies applies to forming a mesa or V-groove type 
substrate and growing an epitaxial layer on the patterned substrate. The 
non-planar growth method favors the fabrication of a semiconductor device 
having a lateral structure, and a low threshold current laser diode 
manufacturing or an optical wave guide fabrication having low wave damage 
can be applicable thereto. 
FIGS. 1A and 1B are cross-sectional views showing common semiconductor 
device structures which adopt the previously described non-planar growth 
method. Specifically, FIG. 1A is a cross-sectional view showing the 
vertical and lateral growth rates of a semiconductor device having a mesa 
pattern, and FIG. 1B is a cross-sectional view showing the vertical and 
lateral growth rates of a semiconductor device having a V-groove pattern. 
As shown in FIGS. 1A and 1B, in order to form a desired device structure on 
a mesa or a V-groove type non-planar substrate 10, although a desired 
vertical growth rate R.sub.ver can be obtained by controlling the growth 
time or the source gas concentration, an appropriate technology for 
regulating a lateral growth rate R.sub.lat has yet to be realized. 
A metalorganic chemical vapor deposition (hereinafter, "MOCVD") enables a 
partial regulation of the previously described growth rates by controlling 
the V/III group doping amount ratio of a fifth group reaction resource gas 
to a third group resource gas and a growth temperature; however, such a 
regulation tends to show a poor reproducibility, and moreover, because the 
rate of the lateral growth to the vertical growth does not exceed 2, a 
substantial lateral growth rate regulation remains difficult to achieve. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a 
semiconductor device epitaxial layer lateral growth rate control method 
capable of easily regulating a lateral growth rate by doping a small 
amount of CBr.sub.4 gas into the epitaxial layer during an MOCVD applied 
epitaxial layer growth. 
To achieve the above-described object, a semiconductor device epitaxial 
layer lateral growth rate control method involves regulating an epitaxial 
layer lateral growth rate in accordance with the CBr.sub.4 gas amount 
being doped into the epitaxial layer when the epitaxial layer is grown by 
an MOCVD on a patterned GaAs substrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A semiconductor device epitaxial layer lateral growth rate control method 
using CBr.sub.4 gas in accordance with the present invention is focused on 
regulating an epitaxial layer lateral growth rate by doping CBr.sub.4 gas 
into an epitaxial layer during the epitaxial layer growth, and the lateral 
growth rate control steps are detailed as follows. 
First, as shown in FIGS. 1A and 1B, an epitaxial layer 20 is grown by means 
of an MOCVD on a (100) oriented GaAs substrate 10 having a single mesa 10a 
which is formed thereon in parallel with a (011) orientation and a 
V-groove array lob which is formed in the surface thereof. Meanwhile, the 
single mesa 10a and the V-groove array are formed by means of a 
photolithography process or a wet etching process. 
To grow the epitaxial layer 20 applied by the MOCVD, high purity hydrogen 
is used at a flow rate of 5 l/min so as to act as a carrier gas. During 
the epitaxial layer growth, trimethylgallium (hereinafter, "TMG") or 
trimethylaluminium (hereinafter, "TMA") is adopted as a third group metal 
organic resource, and AsH.sub.3 gas (Arsine) which is diluted in hydrogen 
at the ratio of 9 hydrogen to 1 ASH.sub.3 is employed as a fifth group 
resource. At this time, the CBr.sub.4 gas concentration varies from zero 
(before CBr.sub.4 gas doping) to 4.6.times.10.sup.-6 mole/min or 0.023 
cc/min, and the epitaxial layer growth temperature is confined from 
600.degree. C. to 800.degree. C. The V/III value changes from 5 to 120 
which is the ratio of the fifth group resource doping amount to the third 
group resource doping amount. 
To perform a minute observation of the GaAs epitaxial layer growth aspect, 
the present invention has been applied to grow a five-sublayer GaAs 
epitaxial layer, in which each sublayer includes a marker composed of a 
400 .ANG.-thickness Al.sub.0.5 Ga.sub.0.5 As epitaxial layer. The thusly 
grown specimen has been observed by a scanning electron microscope. 
Referring to FIG. 2A, the picture taken before CBr.sub.4 gas doping 
exhibits a mesa pattern lateral growth rate which is almost similar to the 
vertical growth rate thereof. 
Meanwhile, as shown in FIG. 2B, the CBr.sub.4 gas doped into the epitaxial 
layer during the layer growth enables a significant lateral growth rate 
increase; the CBr.sub.4 gas doping occurred at 0.0023 cc/min or 
4.6.times.10.sup.-6 mole/min. At this time, the epitaxial layer growth 
temperature T.sub.g was at 750.degree. C. 
FIG. 3 is a graph showing the variations in each of the GaAs epitaxial 
layer vertical growth rate R.sub.ver and lateral growth rate R.sub.lat in 
accordance with CBr.sub.4 flux concentration at the temperature of 
700.degree. C. The V/III ratio in FIG. 3 denotes a mole fraction ratio of 
AsH.sub.3 gas to TMG. CBr.sub.4 ! and TMG! describe the concentrations 
of CBr.sub.4 and TMG respectively. The FIG. 3 also shows CBr.sub.4 
concentration having little influence on the vertical growth rate; 
however, the lateral growth rate exhibits a geometric increase in 
accordance with the CBr.sub.4 concentration. 
As shown in FIG. 4, when the epitaxial layer growth temperature is at 
700.degree. C., and the CBr.sub.4 concentration is at 4.6.times.10.sup.-6 
mole/min, the ratio R.sub.lat /R.sub.ver of the lateral growth rate to 
vertical growth rate can reach up to 26. 
As a result, in accordance with the results shown in FIGS. 3 and 4, the 
selective regulation of the lateral growth rate can be achieved depending 
on the CBr.sub.4 concentration without a noticeable variation in the 
vertical growth rate. 
FIG. 5 is a graph showing the respective dependence of the epitaxial layer 
lateral growth rate and the vertical growth rate on the temperature, in 
which a vertical growth rate is little changed during temperature 
variations, yet the lateral growth shows its highest rate at 700.degree. 
C., and the growth rate decreases at temperatures higher than 700.degree. 
C.; CBr.sub.4 gas doping enables lateral growth rate regulation by means 
of growth temperature variation. The V/III ratio in FIG. 5 denotes the 
mole fraction ratio of AsH3 gas to TMG, and CBr.sub.4 ! and TMG! 
describe the concentrations of CBr.sub.4 and TMG respectively. 
FIG. 6 is a graph showing the variations in the lateral growth rate and the 
vertical growth rate, which occur in the GaAs epitaxial layer. The 
vertical growth rate in FIG. 6 hardly changes despite the increase in the 
V/III ratio; however, the lateral growth increases rapidly until the V/III 
ratio reaches 40, then slows due to saturation. 
FIGS. 7A and 7B are scanning electron microscope pictures showing CBr.sub.4 
doping effect occurring when a GaAs epitaxial layer is grown on a 
V-grooved substrate. The black marker lines in FIGS. 7A and 7B are AlGaAs 
layers which are for effectively observing the epitaxial layer growth. 
FIG. 7A is a scanning electron microscope picture taken cross-sectionally 
before CBr.sub.4 doping; FIG. 7A shows a conventional common property, in 
which the lateral growth rate as well as the vertical growth rate exhibits 
little growth rate variations. 
FIG. 7B is a scanning electron microscope picture taken cross-sectionally 
after the doping of CBr.sub.4 at a rate of 0.023 cc/min or 
4.6.times.10.sup.-6 6 mole/min, in which the epitaxial layer lateral 
growth rate has increased so much that the planarization of the epitaxial 
layers have been already obtained at the first epitaxial layer formed on 
the substrate; the planarization of a semiconductor device can be 
regulated by the CBr.sub.4 gas doping method. 
As detailed above, the semiconductor device epitaxial layer lateral growth 
rate control method using CBr.sub.4 gas in accordance with the present 
invention enables regulating the epitaxial layer lateral growth rate by 
CBr.sub.4 gas doping when an epitaxial layer is grown on a mesa or 
V-groove patterned GaAs substrate employing MOCVD, thus planarizing the 
semiconductor device.