JPS6134930A - Growing process of selective type crystal - Google Patents

Abstract

PURPOSE:To make it feasible to selectively grow the single crystal of three dimensional structure by a method wherein gaseous molecule containing crystal component is introduced into an ultrahigh vacuum vessel to make the single crystal grow subject to the dimensional precision of monomolecular layer order utilizing the chemical reaction on the surface of substrate. CONSTITUTION:After etching a GaAs substrate 12, an Si3N4 film 16 is formed and then a resist pattern of photoresist 17 is formed to be etched while a mask pattern of film 16 is formed. The substrate 12 so far formed is mounted in a growing vessel 1 to be vacuumed by an ultrahigh vacuum pump 3 for introducing TMG8 while being heated by a heater 10. When, after vacuuming the gas inside growing vessel 1, AsH3 9 is introduced, single crystal of GaAs may be grown at least as monomolecular layer and then monomolecular layers may be grown one after another on a substrate 12 of no mask only without growing GaAs at all while a GaAs single crystal growing layer 18 may be grown subject to the dimensional precision of monomolecular layer by means of repeating said procedures.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a selective crystal growth method for selectively forming a crystal layer.

[Prior technologies and their problems] In recent years 1 With the increase in speed of communication and control, three-terminal elements, various diodes, etc. that exhibit high performance in the microwave to millimeter wave band, and semiconductor devices in the light wave band (laser, light emitting, There is an increasing demand for photodetectors (e.g., photodetectors), and a selective epitaxial method that has a three-dimensional structure with dimensional accuracy on the order of a monomolecular layer in the thickness direction is strongly desired.

Metal-organic vapor phase epitaxy (hereinafter referred to as MO-
CVD method), molecular beam epitaxy method (hereinafter referred to as MB
These include the atomic layer epitaxy method (hereinafter referred to as the +ALE method) invented in Finland. However, in the MO-CVD method, a group III or V compound as a source is simultaneously introduced into a reaction chamber using hydrogen gas or the like as a carrier, and the growth is caused by thermal decomposition, so that the quality of the grown layer is poor. Furthermore, it is difficult to control the monolayer order. Furthermore,
Even if an attempt is made to form a selective epitaxial growth layer on a substrate according to a mask pattern, selective epitaxy is difficult because crystals grow even on the mask material.

On the other hand, the MBE method, which is well known as a crystal growth method using an ultra-high vacuum, uses physical adsorption as the first step, so the quality of the crystal is inferior to the vapor phase growth method using a chemical reaction. Also,
When growing a compound semiconductor between groups 1 and 2, such as GaAs, a group III or group V element is used as a source, and the source itself is placed in a growth chamber. Therefore, it is difficult to control the amount of emitted gas and evaporation by heating the source, and to replenish the source, making it impossible to keep the growth rate constant for a long time. Furthermore, vacuum equipment such as evacuation of evaporated matter becomes complicated. Furthermore, it is difficult to precisely control the stoichiometric composition (stoichiometry) of the compound semiconductor, and as a result, it is impossible to obtain high-quality crystals. Furthermore, M.O.
- Similar to the CVD method, selective epitaxy is difficult because crystals grow on a mask pattern made of a material different from that of the substrate on the substrate.

Furthermore, the ALE method was developed by T, Sur+tola et al. [1,S,
P, NQ4058430 (1977), the MBE method is modified to alternately supply each of the semiconductor elements in a pulsed manner to deposit monoatomic layers alternately on the substrate.
It grows a thin film atomic layer by atomic layer, and has the advantage of being able to control the film thickness with atomic layer precision, but it is an extension of the MBE method.
Like BE, it has poor crystallinity. Also, the grown thin film is C
It is limited to II-IV group compound semiconductors such as dTe and ZnTe, and has not been successful with Si and GaAs, which are currently the mainstay of semiconductor devices such as VLSI. Attempts have been made to improve ALE to adsorb a molecular layer and use chemical reactions on the surface for growth, but this is a growth of an amorphous thin film of polycrystalline Ta 20 s of ZnS and is not a single-crystal growth technique. do not have. Therefore, it is extremely difficult to perform selective epitaxy only on a semiconductor substrate using an insulator or the like as a mask material.

As described above, none of the conventional methods described above can achieve selective epitaxy, and it is difficult to form high-quality crystals that satisfy the stoichiometric composition on the order of a monomolecular layer using the MO-CVD method or MBE method. On the other hand, the ALE method has the drawback that a single crystal cannot be obtained.

[Purpose of the Invention] The present invention eliminates the drawbacks of the above-mentioned prior art and provides selective crystal growth that enables selective growth of a single crystal with a three-dimensional structure that can be controlled with dimensional accuracy on the order of a monolayer in the thickness direction. The purpose is to provide a method.

[Summary of the Invention] Therefore, the present invention introduces gaseous molecules containing crystal component elements into an ultra-high vacuum chamber, and in some cases generates a single crystal by using a chemical reaction on the heated substrate surface while irradiating it with light. It is characterized by achieving selective growth by growing with dimensional accuracy on the order of a monomolecular layer.

[Embodiment of the Invention] Figure 1 shows a configuration diagram of a selective crystal growth apparatus according to an embodiment of the present invention, in which 1 is a growth tank made of metal such as stainless steel, 2 is a gate valve, and 3 is a growth tank made of metal such as stainless steel. is an exhaust device for evacuating the inside of the growth tank 1 to an ultra-high vacuum.

4.5 is a nozzle that introduces mg of the ■-■ group compound semiconductor and a gaseous compound of a component element of the V group; 6 and 7 are nozzles 4;
, 5 is a valve that opens and closes, 8 is a gaseous compound containing a component element of the group ■, 9 is a gaseous compound containing a component element of the group ■, 10 is a heater for heating the substrate, and tungsten ( W) wire, and electric wires and the like are not shown. 11 is a thermocouple for temperature measurement, 12 is a semiconductor substrate, 13
is a pressure gauge to measure the degree of vacuum inside the growth tank. Also,
14 is a light source, and 15 is a window for guiding light from the light source to the substrate 12.

With the above configuration, a method for selectively growing a GaAs single crystal on the GaAs substrate 12 is carried out as follows. That is,
First, a mirror-polished GaAs substrate 12 is etched by about 1 to 2 μm using a normal etching method, and then a uniform Si s layer is etched on the GaAs substrate 12 as shown in FIG.
The Na film 16 was deposited using the plasma CVD method to approximately 2,000 ni.
A (200 nm) thickness is formed, and then photoresist 1 is formed.
Apply 7. Next, by the usual photoetching method,
A resist pattern is formed as shown in FIG. 2(b). After that, buffer etchant HF:H20=1:
After etching the Si 3 N 4 film 16 using etching film 5, the resist 17 is removed to form a mask pattern of the Si 3 N 4 film 16 on the substrate 12 as shown in FIG. 2(c).

The first surface was further cleaned, and the GaAs was etched using a GaAa etching solution containing an organic alkali, THAH (trialky-2-1 hydroxyalkylammonium hydroxide).
After etching the surface of the substrate 12 by about 10 OA, it is washed and dried.

After the substrate 12 on which the mask pattern has been formed is placed on the heater 10 in the growth tank 1 shown in FIG. is discharged to about 10-7 to 10-@Pagcal (hereinafter abbreviated as Pa). Next, the GaAs substrate 12 is heated, for example, to about 300 to 800° C. by the heater 10, and TMG()-limethylgallium) 8 is added as the Ga-containing gas at a pressure in the growth tank 1 of 10-1 to 10'.
The valve 6 is opened for 0.5 to 10 seconds and the water is introduced within the range of Pa. After that, after closing the valve 6 and discharging the gas in the growth tank 1, this time, AsH39 is added as a gas containing As for 2 to 200 seconds in a range where the pressure in the growth tank 1 is 10''1 to 1O-7Pa. Open 7 and install.

As a result, GaAs is selectively applied only to the areas without a mask.
A single crystal can be grown to at least a monolayer.

Furthermore, by repeating the above operation, the image shown in Fig. 2(d) is obtained.
As shown in FIG.
By growing monolayers one after the other only on the maskless substrate 12 without growing any GaA
s Single crystal growth layer can be grown with the dimensional accuracy of a monomolecular layer.

Then, with a buffer etchant, Si s N
When the four films 16 are removed, as shown in FIG. 2(e),
A selectively grown layer of GaAs single crystal having a desired thickness is obtained on the substrate 12 in a desired region according to the mask pattern.

In this process, as well as heating the substrate 12, the light source 14
By irradiating the substrate 12 with ultraviolet rays from above, the growth temperature can be lowered to 400° C. or less, and the crystal quality can be improved.

The selective growth method described above has not yet been fully elucidated theoretically, but was obtained based on experimental results.

Figure 3 shows an example of this experiment, where the introduced gas was
T at a growth temperature of 600°C when using TMG and AsHs
FIG. 3 is a diagram showing the relationship between the number of times MG and AsH3 are alternately introduced and the thickness of the GaAs epitaxial growth layer. For example, when gases 8 and 9 are introduced alternately 400 times, the thickness of the growth layer is 2.
000 people, 1 for 2000 and 4000 deployments
μm and 2 μl. In this way, the relationship between the number of gas introductions and the grown film thickness showed very good linearity, and it was confirmed that the growth layer thickness could be controlled by controlling the number of gas introductions.

FIG. 4 shows another embodiment of the present invention, which is for doping impurities into a selectively grown layer. 20.
21 is a nozzle for introducing a gaseous compound used for adding impurities, 22.23 is a valve that opens and closes the nozzle 20.21, 24 is a gaseous compound containing a component element of the group (2);
5 is a gaseous compound containing a component element of group (1). Since the parts other than the addition of impurities are the same as the embodiment shown in FIG. 1, their explanation will be omitted.

When forming a P-type selective growth layer with this configuration, the introduced gas is TM[;, ()limethylgallium)8, As
Hs, (arsine)9 and Z as an added impurity gas
Three gases, MZn (dimethylzinc) 24, are introduced in a circulating manner. Also, as another method, TMG8 and ZMZn
24 at the same time and alternately with AsHa 9, or AsHa
Impurities can be added by simultaneously introducing H39 and ZMZn24 alternately with TMG8.

In addition, the impurity gases include ZMCd (dimethyl cadmium), ZMMg (dimethyl magnesium), and 5it (
a (monosilane), GeH4 (germane), etc. may also be used.

Next, to form an n-type selective growth layer, ZMSo21 (dimethyl selenium) was added as an impurity gas to T'MG8,
AsHs 9 is introduced in a circular manner. Another method is T
Impurities can be added by simultaneously introducing MG8 and 2MSe25 and alternately introducing TMG8.

In addition, the impurity gases at this time include XMS (dimethyl sulfur), H2S (hydrogen sulfide), and 8258 (hydrogen selenide).
etc. can be used.

In this case, the flow rate of impurity gas introduced is AsHs 9, TM
A molecular layer epitaxial growth layer having a desired impurity concentration distribution in the thickness direction can be formed by making the impurity smaller than G8 by, for example, 10 -3 to 10 -6 and setting the introduction time to about 0.5 to 10 seconds. In addition, by adjusting the amount and time of the impurity gas added, it is possible to improve the structure of pn junctions, non-uniform impurity density distributions, bipolar transistor structures such as npn, npin, pnp, pnip, etc.
Of course, it is possible to realize field effect transistors such as n0 structure, electrostatic induction transistors, pnpn thyristor structures, etc.

In the examples described above, GaAs was mainly used as the gas used for crystal growth, but InP, A
Of course, it can be applied to other m-v group compounds such as ΩP and GaP. Furthermore, the substrate is not limited to Ga1-xAflxAs, but may be formed by heteroepitaxial growth on other compound substrates. Of course, it is also possible to grow crystals of single-element semiconductors, such as semiconductors of group Ⅰ.

In this case, for Si, SiCΩ4 is used as a reactive gas,
Crystal growth can be performed by a combination of chloride such as 5iHCA s or 5iH2Cfl 2 and 112 gas.

[Effects of the Invention] As described above, according to the present invention, a single crystal of a desired thickness can be selectively grown in a desired region on a substrate with dimensional accuracy on the order of a monomolecular layer. Further, at this time, impurities can be added layer by layer, and a very steep impurity concentration distribution can be obtained, which exhibits excellent effects in manufacturing semiconductor devices.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a selective crystal growth apparatus according to an embodiment of the present invention, FIGS. FIG. 4 is a diagram showing the relationship between the growth film thickness and the number of times gas is introduced in the apparatus shown in FIG. 4, and FIG. 4 is a configuration diagram of a selective crystal growth apparatus according to another embodiment of the present invention. 1... Growth tank, 2... Gate valve, 3... Exhaust device, 4, 5, 20. 21... Nozzle, 6, 7, 22
．． 23... Valve, 8,9,24.25... Gaseous compound, 10... Heater, 11... Thermocouple, 1
2... Board, 13... Pressure gauge, 14... Light source, 1
5... Window, 16... Sis Na proboscis, 17...
・Photoresistor. Figure 1 Figure 2 (a) (b) (C) (d) (e) Figure 3 (1 + scale)

Claims (3)

[Claims] (1) A mask pattern made of a material different from that of the substrate is formed on a crystalline substrate, and after cleaning and drying, it is placed in a growth tank, and after evacuating the growth tank to a predetermined degree of vacuum, the substrate is heated. , a gaseous molecule containing a component element of the semiconductor is introduced at a predetermined pressure for a predetermined period of time, and after being evacuated, reacts with a gaseous molecule containing another component element of the semiconductor or a gaseous molecule containing a component element of the semiconductor. By introducing a gas at a predetermined pressure for a predetermined time and evacuating it, a monomolecular layer is grown, and by repeating the above steps, a semiconductor single crystal thin film of a desired thickness is selectively formed only on the substrate. A selective crystal growth method characterized by growing with monomolecular layer precision. (2) A method for growing a selective crystal according to claim 1, wherein the crystalline substrate is made of a III-V group compound semiconductor, and the material molecules as a growth source gas are made of group III or V elements. (3) In claim 2, the mask pattern material is Si_xN_y or Si_xO_y.
Alternatively, a selective crystal using one of the composite films of Si_xN_y and Si_xO_y and using a liquid containing THAH (trialkyl 2-1 hydroxyalkylammonium hydroxide) as a component for cleaning and etching the substrate before growth. How to grow.