JP3008092B2 - Growth substrate having growth nuclei made of diamond or diamond-like carbon and provided on a growth surface, and method for uniform nucleation of growth substrates - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a growth substrate made of diamond or diamond-like carbon and having a growth nucleus provided on the growth surface, and a method for uniform nucleation of the growth surface.

[0002]

2. Description of the Related Art Such a growth substrate and a nucleation method are as follows.
Dissertation Wolter et al. , "Nucleati
on of high oriented diamond
ndon silicon via an alter
naming current substrat b
ias ", Appl. Phys. Lett. Vol.
8, No. 25, 17 June 1996, pp 3
558-3560. From this document, an AC voltage is used in a plasma CVD process for nucleation of a growth substrate which has been placed in an evacuated reactor made of diamond with growth nuclei of diamond or diamond-like carbon and which has been pretreated. It is known to apply a bias voltage of the form: By this means, a high nucleus density of a growth nucleus having a highly accurate orientation can be obtained on the growth substrate as compared with a DC bias voltage under conditions which are otherwise comparable. The high-precision bearing is the Miller index (h,
(k, l) means a growth nucleus having an orientation different from the crystal orientation defined by the growth substrate by 10 ° or less. Despite the high nuclear density, nucleation is highly heterogeneous. That is, remarkable lateral fluctuations appear in the density of the growth nuclei having a high precision orientation over the entire growth surface of the growth substrate.

It is known from International Patent Application No. WO09 / 08076 to pretreat a silicon growth substrate for nucleation of the silicon growth substrate and subsequently to nucleate it from the gas phase by a plasma CVD method. For pre-treatment, the growth substrate is placed in a reactor, the reactor is evacuated to below 10 ⁻⁹ mbar as much as possible, and the growth substrate is heated to above 950 ° C.
Alternatively or additionally, the growth surface is plasma-treated, preferably with a near 100% hydrogen plasma at a substrate temperature of 300 to 1100 ° C.
In this case, +50 to -300 V, particularly about-
It is advantageous to apply a bias voltage of 50V. After purification, nucleation is started in a known manner, with the bias voltage being advantageously maintained. For example, CO and CH ₄ , C ₂ H ₅ OH, acetylene and acetone or, for example, CF ₄ and methane can be used as process gases. A preferred combination is hydrogen and methane.

[0004] Although the nuclei density obtained by this method is high, nucleation is highly non-uniform because few or no growth nuclei with high precision orientation are formed at the center of the growth substrate.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to produce a growth substrate having a growth surface with a more uniform nuclear density than in the prior art.

[0006]

According to the invention, in order to solve this problem, according to the invention, the nucleus density between the center of the growth substrate and a point 15 mm away from this center varies by up to 80%. . According to the present invention with respect to the manufacturing method, the frequency of the bias voltage is 0.5 to 50%.
A frequency of 0 Hz is set, and a negative peak voltage of the bias voltage is selected to be smaller than -30 V, and a bias voltage is applied at a value smaller than -30 V for a predetermined operation time in one cycle, and specified in the same cycle. -30V during idle time
Apply a bias voltage with a larger value .

Further advantageous embodiments of the invention can be found in the dependent claims. The invention is further described below by way of examples shown in the figures.

[0008]

Detailed Description of the Preferred Embodiments The nucleation of a growth substrate shown below is performed in an evacuated reactor under substantially the same CVD process conditions. The only difference is the frequency of the AC bias voltage.

[0009] The principle process step is plasma etching for cleaning the growth surface. For this, the reactor is evacuated by approximately 10 ⁻⁸ mbar and plasma etching is carried out in a H ₂ plasma at a substrate temperature of 810 ° C. without a bias voltage.

Following the plasma etching, a pre-bias treatment is performed. In this case, a periodic alternating voltage of 0.5 to 500 Hz with a maximum amplitude of 230 V is applied to the substrate. H ₂ , CH ₄ , N ₂ and O ₂ are used as process gases. In particular, a growth substrate formed from silicon is heated to a temperature of 870 to 890 ° C. Si
When sufficient nucleation by diamond is detected on the growth surface of the growth substrate by increasing the value of the average bias current, the bias pretreatment is terminated.

The bias pretreatment is followed by the growth of the diamond layer, where the growth parameter α is set to a value between 2 and 3 according to the following equation: α = √3 · v ₁₀₀ / v ₁₁₁ Where V ₁₀₀
Is the growth rate in the <100> direction, and _V111 is the <11>
The growth rate in the 1> direction, where <a, b, c> corresponds to the Miller index in crystallography.

FIG. 1 shows the time course of an alternating voltage (Ac) bias voltage applied during nucleation of a silicon growth substrate (see FIG. 2). In order to realize this bias voltage, a sine wave voltage having a frequency of 50 Hz is full-wave rectified. The maximum voltage applied to the growth substrate is 0V
And the minimum voltage is -200V. Therefore, the maximum value of the voltage is 200V.

FIG. 2 shows that the portion of the growth surface nucleated with the bias voltage according to FIG.
It is shown at 10,000 mm magnification at a distance of mm.

The small percentage of growth nuclei formed differs well, ie, 1 to the crystal axis defined by the growth substrate.
Since the crystal axes differ only by 0 ° or less,
Nucleation quality is relatively poor. The sample after nucleation is coated for one hour under growth conditions α = 2. Subsequently, by scanning electron microscopy (REM), the nucleus having an in-plane misorientation of 10% or less is manually counted to determine the nucleus density. 80% of oriented nuclei
That is all. Since the size of the nucleus is related to the coating time, information about this size is not very useful.

FIG. 3 shows the time course of an alternating voltage (AC) bias voltage as applied during the nucleation of the silicon growth substrate according to FIG. A normal sinusoidal voltage with a frequency of 50 Hz is used as the bias voltage. Each maximum voltage applied to the growth substrate is 200
V, the minimum voltage is -200V. Therefore, the maximum value of the voltage is 200V.

FIG. 4 shows that a part of the growth surface nucleated by the bias voltage according to FIG.
It is shown at 10,000 mm magnification at a distance of mm.
Since the percentage of highly oriented nuclei formed is high,
The nucleation quality is better than that of the embodiment of FIG.

FIG. 5 shows the time course of an alternating current (AC) voltage-like bias voltage as applied during the nucleation of the silicon growth substrate according to FIG. In order to realize this bias voltage, a sine wave voltage having a frequency of 50 Hz is half-wave rectified, so that only a negative half wave is used. The maximum voltage applied to the growth substrate is 0V, and the minimum voltage is -200V. Therefore, the maximum value of the voltage is 200V.

In this preferred waveform of the bias voltage, the negative peak voltage is smaller than -30 V, especially smaller than -50 V, and each of the operation times t which can be specified in one cycle.
_It is particularly advantageous to set the waveform such that the bias voltage for _on is applied at a value less than -30 V and the bias voltage for a particular dwell time t _off is at -30 V intervals within the same period. is there.

FIG. 6 shows that a part of the growth surface nucleated by the bias voltage according to FIG.
It is shown at 10,000 mm magnification at a distance of mm. The nucleation quality is the best ever obtained. The percentage of growth nuclei formed is the highest.

Five examples (samples 1 to 5) of similar waveforms of the bias voltage but nucleated at different frequencies are shown below. Sample 1 has a frequency of 0.5
Hz, the frequency of sample 2 is 5 Hz, the frequency of sample 3 is 50 Hz, and the frequency of sample 4 is 500 Hz. The value of the bias voltage is 0 to 200 V for all the samples 1 to 4, and the voltage is 0 V during the dwell time t _off.
It is. To match the rest time t _off approximately operation duration of the time t _on, the waveform of the bias voltage is set.

FIGS. 7 and 8 show portions of the growth surface at different distances from the center of the growth surface of sample 1, respectively. A bias voltage of 0.5 Hz is applied to sample 1 for nucleation, which satisfies the criteria described above and, in manner, approximately corresponds to FIG. 7 and 8 show a 10,000-fold magnification.

Table 1 shows the conditions for nucleation of Sample 1 by the plasma CVD method.

[Table 1]

Nucleation in the center area of the growth surface of sample 1 is limited to small islands, as shown in FIG. Nucleation of the growth surface at 10 mm from the center of the growth surface is shown in FIG. 8 and is improved compared to nucleation at the center.

[0024] Figure 17 is a nuclear density of the oriented nuclei on the growth surface of the sample 1 is shown in relation to distance from the center, the nucleus density is entered in cm ² per 10 ⁸ nuclei, The distance from the center of the growth surface of the growth substrate of Sample 1 is indicated in mm.

[0025] As can be seen from the diagram according to FIG. 17, the nuclear density of the sample 1 is improved with increasing distance from the center, where the center distance of about 14～15Mm, cm ² per about 2.
And with the highest point with a nuclear dense length of 2 · 10 ⁸ of the nucleus.
Following nucleation density is decreased again, but with a nuclear density also at a distance of about 20mm Note cm ² per 1.1 · 10 ⁸ nuclei. The nuclear density at the center of the sample 1 is not worth mentioning in a given unit.

As a whole, the uniformity of the nucleus density over the growth surface of the sample 1 has a good value only at a distance of 10 to 20 mm from the center, and is poor in the center range up to 10 mm away.

In order to produce the diagrams according to FIGS. 17 and 18 to 21, the nuclear density is determined by evaluation of REM photography. Therefore, all the crystals having an orientation tilted or rotated by 100 ° or less with respect to the growth substrate are referred to as having a fixed orientation by hand.

FIGS. 9 and 10 show portions of the growth surface at different distances from the center of the growth surface of sample 2, respectively. Here, unlike the sample 1, nucleation is performed at a frequency of a bias voltage of 5 Hz. 9 and 1
0 is again magnified 10,000 times.

The conditions for the nucleation of sample 2 by plasma CVD are as follows.

[Table 2]

The nucleation in the center area of the growth surface of the sample 2 is good as shown in FIG. The nucleation of the growth surface at 10 mm away from the center is shown in FIG. 10 and is further improved with respect to nucleation at the center. FIG. 18 shows that the nuclei density of oriented nuclei on the growth surface of sample 2 is
Shown in relation to the distance from the center, the nucleus density is entered at 10 ⁸ nuclei per cm ² and the distance from the center of the growth surface of the growth substrate of sample 2 is entered in mm.

[0032] As can be seen from the diagram according to FIG. 18, the nuclear density of the sample 2 in the center is with a value per cm ² 3.6 · 10 ⁸ nuclei. Again, the nuclear density increases continuously with increasing distance from the center, about 14 to 1 from the center.
At a distance 5 mm, and with the highest point with a nuclear density per cm ² to about 4, 8, 10 ⁸ nuclei. Then the nuclear density suddenly
Reduced to intense, about 0 · per cm ² is at a distance of about 20mm
Nuclear density of 2 · 10 ⁸ of the nucleus not only with. Sample 2, the difference between the nuclear HisokaRyo and maximum nuclear Dedo in the center is about 1, 2, 10 ⁸ nuclei accordance connexion about 25% per cm ^2. Overall, the uniformity over the growth surface of Sample 2 has the best results of Samples 1-4.

FIGS. 11 and 12 show portions of the growth surface at different distances from the center of the ash-long surface of sample 3, respectively. Unlike Samples 1 and 2, nucleation of Sample 3 is performed at a frequency of 50 Hz bias voltage.
11 and 12 are again magnified 10,000 times.

The conditions for the nucleation of sample 3 by plasma CVD are as follows.

[Table 3]

The nucleation in the center area of the growth surface of sample 3 is better in sample 1 but worse in sample 2 as shown in FIG. Nucleation of the growth surface 10 mm away from the center is shown in FIG. 12 and is an improvement over nucleation at the center.

[0036] Figure 19 is a nuclear density of the oriented nuclei of the growth surface of the sample 3 is shown in relation to distance from the center, the nucleus density is entered in cm ² per 10 ⁸ nuclei, the sample The distance from the center of the growth surface of the growth substrate No. 3 is written in mm.

[0037] As can be seen from the diagram according to FIG. 19, the nuclear density of the sample 3 at the center is has a value of about 1 · 10 ⁸ nuclei per cm ^2. The nuclear density increases continuously and continuously with increasing distance from the center, and at a distance of about 14 to 15 mm from the center, it has the highest point with a nuclear density of about 4.4 · 10 ⁸ nuclei per cm ² ing. Followed by nuclear density decreases again rapidly, and with the nuclear density of about 20mm away still cm ² per about 2.2 · 10 ⁸ nucleus in place. The decrease in nuclear density after the maximum is less than in Sample 2. As a whole, the uniformity of the nuclear density is worse than that of the sample 2, but it can be regarded as good especially in the range of about 0.5 to 20 mm away from the center.

FIGS. 13 and 14 show portions of the growth surface at different distances from the center of the growth surface of sample 4, respectively. Unlike the samples 1 to 3 which have been used up to now, the nucleation of the sample 4 is performed at a frequency of a bias voltage of 500 Hz. Figures 13 and 14 again show 10,000
It has been magnified 0 times.

The conditions for nucleation of sample 4 by plasma CVD are as follows.

[Table 4]

The nucleation in the area of the ash-long surface of Sample 4 is limited to individual islands that are partially joined together at the edges, as shown in FIG. In principle, nucleation is sample 1
It looks like (see FIG. 7), but is better because there is a higher nuclear density here. The nucleation of the growth surface at 10 mm from the center is shown in FIG. 14 and is an improvement over nucleation at the center.

FIG. 20 shows the nuclear density of oriented nuclei on the growth surface of sample 4 as a function of the distance from the center. The nuclear density is plotted at 10 ⁸ nuclei per cm ^2. The distance from the center of the growth surface of the growth substrate of No. 4 is entered in mm.

[0042] As can be seen from the diagram according to FIG. 20, the nuclear density of the sample 4 at the center, in cm ² per 1 · 10 ⁸ units are having not worth mentioning value. The nucleus density increases very strongly continuously with increasing distance from the center, about 3.15 mm from the center, about 3.15 per cm ² .
And with the highest point with a nucleus density of nuclei 4-10 ^8. Subsequently, the nucleus density again decreases sharply, and still has a nucleus density of about 0.8 · 10 ⁸ per cm ² at a distance of about 20 mm. In general, the uniformity of the nuclear density is
Worse at 2 and 2, but about 0.5 to 2 from center
A range of 0 mm away can be regarded as acceptable. Generally, the uniformity of the nuclear density of the sample 4 is better than the uniformity of the sample 1.

FIGS. 15 and 16 show portions of the growth surface at different distances from the center of the growth surface of sample 5, respectively. Nucleation takes place at a frequency of a bias voltage of 10 Hz. Figures 15 and 16 again show 10,0
It is enlarged by 00 times.

The conditions for the nucleation of sample 5 by plasma CVD are as follows.

[Table 5]

As can be seen from Table 5, the results for Sample 5 are not directly comparable to the results for Samples 1-4. This is because the plasma dimensions are slightly different and the sample is subsequently coated, ie 5 hours after the original nucleation.

As can be seen from FIG. 21, a very good radial uniformity of the nuclei density in a fixed orientation is again very clearly evident here. The absolute value of the nuclear density has shifted to a slightly smaller value compared to the previous sample, which is attributable to the larger layer thickness.

The nucleation in the center area of the sample 5 is good as shown in FIG. Blocking of the growth surface at a distance of 10 mm from the center is equally good as shown in FIG.

FIG. 21 shows the nucleus density of the growth surface of the sample 5 in relation to the distance from the center. The nucleus density is entered at a nucleus density of 10 ⁸ nuclei per cm ² , The distance from the center of the growth surface of the substrate is entered in mm. Similarly, in the diagram, the total nuclear density is indicated by dots, and the nuclear density of highly oriented nuclei is also indicated by square points.

[0049] As can be seen from the diagram according to FIG. 21, the nuclear density of the oriented nuclei of the sample 5 has a value of nuclei per cm ² to about 2.4 · 10 ⁸ in the center, the total nuclear density cm ² is the core of per about 3.4 · 10 ^8. Previous samples 1 to 4
Unlike this, no maximum of the nuclear density is formed here.
The nucleus density in a fixed orientation at a distance of 20 mm from the center is c
There are about 3.8 · 10 ⁸ nuclei per m ² and the total nuclear density is c
is the core of m ² per about 5.8 · 10 ^8. Overall, the uniformity of nucleus density over the growth surface of sample 5 is good,
Starting from 10 to 15 mm away from the center, the total nuclear density increases more strongly than the oriented nuclear density.

In summary for Samples 1-5, the uniformity of nuclear density is a function of frequency, with improvement seen with increasing frequency up to about 500 Hz, with best results in the frequency range near 5 Hz.

Instead of a growth substrate made of crystalline silicon, a growth substrate made of crystalline β silicon carbide (β-SiC) can be selected.

[Brief description of the drawings]

FIG. 1 shows a sine wave voltage that is full-wave rectified as a bias voltage.

2 shows a growth surface of a silicon growth substrate nucleated with a bias voltage according to FIG. 1;

FIG. 3 shows a sine wave voltage as a bias voltage.

4 shows a growth surface of a silicon growth substrate nucleated with a bias voltage according to FIG. 3;

FIG. 5 shows a half-wave rectified sine wave voltage as a bias voltage.

6 shows a growth surface of a silicon growth substrate nucleated with a bias voltage according to FIG. 5;

FIG. 7 shows the center of a growth surface nucleated with diamond at a half-wave rectified bias voltage of 0.5 Hz.

FIG. 8 shows the growth surface of the growth substrate of FIG. 7 at a distance of about 10 mm from the center.

FIG. 9 shows the center of the growth surface nucleated with diamond at 5 Hz half-wave rectified bias voltage.

FIG. 10 shows the growth surface of the growth substrate of FIG. 9 at a distance of about 10 mm from the center.

FIG. 11 shows the center of the diamond nucleated growth surface at 50 Hz half-wave rectified bias voltage.

FIG. 11 shows a position about 10 mm away from the center;
3 shows a growth surface of a growth substrate of FIG.

FIG. 13 shows the growth surface of a diamond nucleated growth substrate at 500 Hz half-wave rectified bias voltage.

FIG. 14 is a view of FIG.
3 shows a growth surface of a growth substrate of FIG.

FIG. 15 shows the growth surface of a diamond nucleated growth substrate at 10 Hz half-wave rectified bias voltage.

FIG. 16 at about 10 mm away from the center
3 shows a growth surface of a growth substrate of FIG.

FIG. 17 shows the evolution of the nuclear density as a function of the distance from the center in the growth substrate according to FIG.

18 shows the evolution of the nuclear density in relation to the distance from the center in the growth substrate according to FIG.

19 shows the evolution of the nuclear density in relation to the distance from the center in the growth substrate according to FIG.

20 shows the evolution of the nuclear density in relation to the distance from the center in the growth substrate according to FIG.

21 shows the evolution of the nuclear density in relation to the distance from the center in the growth substrate according to FIG.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Gundtmar Schürz, Germany Bluffingen Hopfengarten 21 (72) Inventor Reinhard Saashayi, Gunzburg am Huarenberg 5a, Germany (72) Inventor Peter Bodo Gruissier Neu-Ulm Katsuse, Germany 56 Renensichturasse 56 (72) Inventor Erhard Korn Ulm-Leah Rad Gebweig 21 (72) Inventor Paul Twimann Erbatsch, Germany Brenau Tufenweg 36 (56) References Special Tables Hei 8-504479 (JP, A) D. Wolter et al. , "The nucleation of highly oriente d diamond on silicon on via an alternating current substrate biases", Applied Physics Letters, Vol. 68, no. 25, 17 June 1996, pp. 3558-3560 (58) Field surveyed (Int. Cl. ⁷ , DB name) C30B 29/04

Claims (17)

(57) [Claims] 1. A growth substrate wherein the orientation of 50% or more of the growth nuclei differs from the crystal orientation defined by the growth nuclei by 10 ° or less according to the Miller index (h, 1,1). A growth substrate comprising a growth nucleus made of diamond or diamond-like carbon and provided on a growth surface, characterized in that the nucleus density between the center and 15 mm away from the center varies by up to 80%. 2. The center of the growth substrate and 15 mm from this center
2. The growth substrate according to claim 1, characterized in that the nucleus density between remote locations varies by up to 50%. 3. The center of the growth substrate and 15 mm from the center
2. The growth substrate according to claim 1, characterized in that the nucleus density with a distance varies by up to 30%. 4. The center of the growth substrate and 15 mm from the center
The growth substrate according to claim 1, characterized in that the nucleus density between the remote locations varies by up to 20%. 5. The nucleus density at the center of the growth substrate is cm ²
Wherein the contact is at least 1 · 10 ^8,
The growth substrate according to claim 1. 6. The nucleus density at the center of the growth substrate is cm ^2.
Wherein the contact of at least 3 · 10 ^8,
The growth substrate according to claim 1. 7. The center of the growth substrate and 15 mm from the center
The nucleus density between distant places is 1.10 per cm <sup>2
2. The</sup> method according to claim 1, wherein the number is from ⁸ to 5.108.
A growth substrate according to claim 1. 8. The center of the growth substrate and 15 mm from the center
3.5 Nuclear density per cm ² between the away
Wherein the 10 ⁸ to a 5-10 ^8, the growth substrate according to claim 1. 9. A method for uniformly nucleating a growth surface having diamond or diamond-like carbon from a gas phase, said method being provided in an evacuated reactor and pretreated to form growth nuclei. A bias voltage in the form of an AC voltage is applied to the grown substrate, and a normal process gas is supplied to the growth surface of the grown substrate. The bias voltage is set to a frequency of 0.5 to 500 Hz. negative chosen smaller than -30V peak voltages, respectively predetermined operating time within one period of (t _on)
A bias voltage is applied between -30V smaller value, is at -30V greater than during a particular dwell time within the same period (t _off) and applying a bias voltage, a growth substrate uniform Nucleation method. 10. The method according to claim 9, wherein the bias voltage during the pause time (t _off ) is applied at an interval of ± 30 V or less. 11. The method according to claim 9, wherein a frequency between 1 and 100 Hz is selected. 12. The method according to claim 9, wherein a frequency of 1 to 10 Hz is selected. 13. A bias voltage is applied at a value less than -30 V for a specific operation time (t _on ) in one cycle, and a specific pause time (t _off ) in the same cycle.
The method according to claim 9, wherein a bias voltage is applied at an interval of ± 30 V or less, and the operation time (t _on ) is set to be approximately equal to the pause time (t _off ). 14. One cycle in each specific body stop time a bias voltage is applied with -30V smaller value between _{(t on),} between ± 30 V for a particular dwell time within the same period _{(t off)} 10. The method according to claim 9, wherein the bias voltage is applied at intervals of less than or equal to, and the sum of the operating time and the idle time is selected as the duration of this cycle. 15. A bias voltage is applied for a specific time (t _on ) within one period, and the bias voltage is applied for a specific time (t _on ).
_off ) blocking. 16. The method according to claim 9, wherein a growth substrate made of silicon is selected. 17. The method according to claim 9, wherein a growth substrate made of β silicon carbide (β-SiC) is selected.