JPS6254421A - Molecular beam epitaxial growing process and device thereof - Google Patents

Abstract

PURPOSE:To make the intensity of molecular beams and the evenness of film thickness compatible by making the diameter of a substrate holder; the distance between the intersection of the central line of molecular beam source cell with the plane whereto a substrate belongs and the turning center of substrate holder; and the distance from an opening of molecular beam source cell to the surface of substrate meet specified requirements. CONSTITUTION:Assuming the diameter of a substrate holder; the distance between the intersection of the central line of molecular beam source cell with the plane whereto a substrate belongs and the turning center of substrate holder; and the distance from an opening of molecular beam source cell 6 to the plane whereto the substrate belongs on the central line of molecular beam source cell 6 respectively to be D, x and y, the film shall be grown meeting the requirements represented by the expressions shown in figure. Through these procedures, multiple substrates 4 can be fixed on the substrate holder 2 to be grown simultaneously while providing each substrate 4 with excellent evenness of film thickness by revolution only without resort to rotation. Besides, the excellent evenness of film thickness can be assured, even if the distance between the molecular beam source cell 6 and the substrates 4 is short, without complicating the structure of a manipulator 8.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention enables film growth over a wide area by devising the positional relationship between the molecular beam source cell and the substrate holder (in other words, the substrate attached to it). The present invention relates to a molecular beam epitaxy growth method and an apparatus for the same, which can achieve both molecular beam intensity and film thickness uniformity.

[Conventional technology]

FIG. 6 is a side view showing the positional relationship between a conventional molecular beam source cell and a substrate holder. A substrate holder 2 is attached to a manipulator 8 in a vacuum container (not shown), and the substrate holder 2 is rotated by the manipulator 8, for example, in the direction of arrow C in the figure. In this example, one substrate vi, 4 is attached to the substrate holder 2.

A molecular beam source cell 6 that emits a molecular beam 10 is arranged so that its opening 61 faces the surface of the substrate 4 and aims at the vicinity of the center of the substrate 4.

Film growth (epitaxial growth) on the substrate 4 is performed by heating the groups vi and 4 with a heater (not shown) provided in the manipulator 8, for example, while rotating the substrate holder 2 and rotating the substrate 4 with the manipulator 8. This is carried out by heating the molecular beam source cell 6 using a heater (not shown) provided in the radiation source cell 6 to generate a molecular beam 10 therefrom, and depositing the molecular beam 10 on the substrate 4 .

In that case, generally, if the distance between the molecular beam source cell 6 and the substrate 4 is shortened, the intensity of the molecular beam incident on the substrate 4 will increase, but the uniformity of the grown film thickness will deteriorate. Conversely, if the distance between the molecular beam source cell 6 and the substrate 4 is increased, the film thickness uniformity improves, but the molecular beam intensity decreases in inverse proportion to the square of the distance, and the growth rate decreases.

FIG. 8 shows an example of the film thickness distribution in the diameter direction of the substrate 4 when one substrate 4 is attached to the substrate holder 2 as shown in FIG. 6 and a film is grown. Since the density distribution of the molecular beam 10 emitted from the molecular beam source cell 6 generally follows the cosine law (cos'θ law), the film thickness distribution also has a mountain shape. However, it is possible to obtain relatively good film thickness uniformity in a relatively narrow area, for example, a 1 to 2 inch substrate area.

[Problem that the invention seeks to solve]

As described above, the method of attaching one substrate 4 to the substrate holder 2 and growing a film has poor productivity because only one substrate can be grown per growth. For this purpose, the substrate holder 2 can be enlarged and a plurality of substrates 4, for example, four substrates 4 as shown in FIG.
There is an idea to grow multiple plants at the same time by attaching them to a.

However, the film thickness distribution in such a wide area becomes as shown in FIG. 9, for example, and the film thickness uniformity deteriorates. In that case, increasing the distance between the molecular beam source cell 6 and the substrate 4 will improve the film thickness uniformity, but if you do so, the molecular beam intensity will suddenly weaken and the growth rate will decrease. is as described above. In other words, in the conventional method, there is a problem in that molecular beam intensity and film thickness uniformity are not compatible in a wide area such as when growing a plurality of layers.

On the other hand, in the case of growing multiple substrates, there is an idea of rotating each of the multiple substrates 4 on its own axis and revolving the entire substrate in order to improve the film thickness uniformity, but in that case, the manipulator 8 Another problem arises that the structure becomes very complex.

Therefore, an object of the present invention is to achieve both molecular beam intensity and film thickness uniformity when growing a film over a wide area without using the above-mentioned special manipulator.

[Means for solving problems]

The molecular beam epitaxy growth method of the present invention involves attaching one or more substrates to a substrate holder provided in a vacuum atmosphere, and connecting the opening of a molecular beam source cell that emits molecular beams and the surface of the substrate attached to the substrate holder. In this method, the diameter of the substrate holder is set to Let X be the distance between the point where the center line of the molecular beam source cell intersects with the plane to which the surface of the substrate belongs and the rotation center of the substrate holder. If the distance to the plane to which the surface belongs is y, then 0.4D≦x≦0.7D and 0.7D≦y≦1.
It is characterized in that the film is grown under 6D conditions.

The molecular beam epitaxy apparatus of the present invention includes a substrate holder provided in a vacuum container to which one or more substrates can be attached, a manipulator that rotates the substrate holder, and a molecular beam source cell that emits molecular beams. The diameter of the substrate holder is D, and the center line of the molecular beam source cell is the center line of the substrate. When the distance between the point where the surface intersects with the plane to which the surface belongs and the rotation center of the substrate holder is X, and the distance from the opening of the molecular beam source cell to the plane to which the substrate surface belongs on the center line of the molecular beam source cell is y. , X is 0.4D: Sx≦
Set within the range of 0.7D, and y is 0.7D≦y≦
It is characterized by being set within a range of 1.6D.

[Effect]

As a result of simulation calculations, etc., it has been confirmed that by setting the distances X and y within the above ranges, it is possible to achieve both molecular beam intensity and film thickness uniformity even when growing a film over a wide area. Ta.

〔Example〕

FIG. 1 and FIG. 2 are side views for explaining the positional relationship between the molecular vA source cell and the substrate holder in the present invention, respectively. A substrate holder 2 is attached to a manipulator 8 in a vacuum container (not shown), and the substrate holder 2 is rotated by the manipulator 8, for example, in the direction of arrow C in the figure. One or more substrates 4, in this example a plurality of substrates 4, are attached to the substrate holder 2, for example, on the circumference at approximately the same distance from the center of the substrate holder 2 (see FIG. 6). A molecular beam source cell 6 that emits molecular beams (not shown) is arranged such that its opening 61 faces the plane to which the surface of the substrate 4 belongs.

In that case, the direction of the surface of the substrate holder 2, in other words, the surface of the substrate 4, as long as it satisfies the above-mentioned relative relationship with the opening 61 of the molecular beam source cell 6.
It may be directed downward as shown in the figure, diagonally downward as shown in FIG. 2, or even sideways (not shown).

The molecular beam source cell 6 is designed to aim at a location largely eccentric from the center of the substrate holder 2, unlike the conventional one. That is, in this invention, the diameter of the substrate holder 2 is
Let the distance between the point P where the center 'aA of the molecular beam source cell 6 intersects the plane to which the surface of the substrate 4 belongs and the rotation center B of the substrate holder 2 be X, and the center IL of the molecular beam source cell 6 is on the line A. If the distance from the opening 61 of the molecular beam source cell 6 to the plane to which the surface of the substrate 4 belongs is y, then the distance X is 0.4D.
Set within the range of ≦x≦0.7D, and distance y is 0.7
It is set within the range of D≦y≦1.6D, and film growth is performed under such conditions. The reason will be explained later.

Note that the thickness of the substrate 4 on the substrate holder 2 is negligibly small compared to the distance y (generally, for example, O0
Even if the distance y is viewed as the distance from the opening 61 of the molecular beam source cell 6 to the plane to which the surface of the substrate holder 2 belongs, it is substantially the same as in the case described above.

Specifically, the film growth (epitaxial growth) on each substrate 4 is performed by rotating the substrate holder 2 with the manipulator 8 and rotating (revolving) the substrate 4 as a whole.
As in the conventional method, each substrate 4 is heated by a heating means (not shown), and the molecular beam source cell 6 is heated to emit molecular beams, which are incident and deposited on each substrate 4.

Next, the reason why distances ix and y are set within the above ranges will be explained. First, using distance X as a parameter, distance y
The third example shows the tendency of change in film thickness uniformity when changing
As shown in the figure. In this case, the film thickness uniformity is determined by calculating integrally the molecular beam intensity at each point in the diameter direction of the substrate holder 2 when the substrate holder 2 is rotated, and calculating the film thickness distribution. is calculated. In the figure, the film thickness uniformity improves as it approaches the horizontal axis.

The value U1 indicates the upper limit value of the film thickness uniformity that is practically acceptable in this type of device, and is generally selected to be about 1%, for example. Therefore, from this figure, it can be seen that X≧0.
It can be seen that there is a region where good film thickness uniformity can be obtained in the range of 4D and y≧0.7D.

To explain in more detail, the distance y is a value corresponding to the vicinity of point a in Fig. 3 when X = 0.4D (i.e., around 0.7D), and a value corresponding to the point A when x = 0.5D. range from the value corresponding to point e to the value corresponding to point e, if X = 0.6D, point C
In the case of X=0.7D, the film thickness uniformity is better than the above value UI when the value is equal to or greater than the value corresponding to point d.

Next, an example of the tendency of change in molecular beam intensity when distance y is changed using distance X as a parameter is shown by a solid line in FIG. The molecular beam intensity in this case is the average value of the molecular beam intensities at each point on the substrate holder 2 determined by the above calculation. In the figure, the molecular beam intensity increases as it moves away from the horizontal axis.

The region sandwiched between the two dashed lines L+ and Lx in the figure shows the range of distance y that is permissible from the viewpoint of film thickness uniformity in each of the above-mentioned X, and points a' to e' are the third Point a4 in the diagram
They correspond to e. Therefore, the upper limit of the molecular beam intensity is the value M1 corresponding to point a', taking into consideration the permissible film thickness uniformity. On the other hand, the weaker the molecular beam intensity is selected, the more the molecular beam emitted from the molecular beam source cell 6 will be wasted and the economical efficiency will decline.
The lower limit value M2 of the allowable molecular beam intensity is generally selected to be, for example, about M1/3 in this type of apparatus.

Therefore, the region where both good film thickness uniformity and relatively strong molecular beam intensity can be satisfied is within the region between the chain line and L2 and above the lower limit M2 line. Therefore, from this lower limit value M2 side,
Since the conditions of ≦0.7D and y≦1.6D are derived, if we put the above together, the above-mentioned 0, 4D≦x≦0.7
D and within the range of 0.7D≦y≦1.6D.

0.4D≦x≦0.7D and 0.7D5M as above
An example of the film thickness distribution in the diametrical direction of the substrate holder 2 obtained under the condition of ≦1.6D is shown in FIG. Under the above conditions, although there is some unevenness in the film thickness distribution, the tops of the peaks are dispersed, for example, near the center of the substrate 4, which is wider than in the case of the conventional method (see Figure 9). Good film thickness uniformity can be obtained over the area. Moreover, since it is not necessary to increase the distance between the molecular beam source cell 6 and the substrate 4, relatively strong molecular beam intensity can be obtained.

Therefore, according to the above-described means, it is possible to attach a plurality of substrates 4 to the substrate holder 2 and grow them simultaneously, thereby improving productivity.

Of course, in this case, each board 4 revolves without rotating,
That is, good film thickness uniformity can be obtained only by rotating the substrate holder 2 as shown in FIG. 1 or 2, for example.
The structure of the manipulator 8 does not become complicated.

Further, even if the distance between the molecular beam source cell 6 and the substrate 4 is small, good film thickness uniformity can be obtained, so the vacuum container (growth chamber) for film growth does not need to be enlarged too much.

Incidentally, instead of simultaneously growing a film on multiple substrates 4 as described above, it is also possible to attach one large diameter (for example, 6 inch) substrate to the substrate holder 2 and grow a film, and even in that case, the above-mentioned method may be used. It goes without saying that relatively strong molecular beam intensity and good film thickness uniformity can be obtained as well.

〔Effect of the invention〕

As described above, according to the present invention, even when growing a film over a wide area, both molecular beam strength and film thickness uniformity can be achieved.
Relatively strong molecular beam intensity and good film thickness uniformity can be obtained. Therefore, it is possible to simultaneously grow a film on a plurality of substrates or to grow a film on a large diameter substrate. Furthermore, according to the present invention, there is no need to use a special manipulator, and furthermore, there is no need to increase the size of the vacuum vessel for film growth.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are side views for explaining the positional relationship between the molecular beam source cell and the substrate holder in the present invention, respectively. FIG. 3 is a diagram showing an example of the tendency of change in film thickness uniformity when the distance y is changed using the distance X as a parameter. FIG. 4 is a diagram showing an example of the tendency of change in molecular beam intensity when the distance y is changed using the distance X as a parameter. FIG. 5 is a schematic diagram showing an example of the film thickness distribution in the diametrical direction of the substrate holder obtained by the present invention. FIG. 6 is a side view showing the positional relationship between a conventional molecular beam source cell and a substrate holder. FIG. 7 is a front view showing an example in which four substrates are attached to the substrate holder. FIGS. 8 and 9 are schematic diagrams each showing an example of the film thickness distribution in the diametrical direction of a substrate holder obtained by a conventional method. 2... Substrate holder, 4... Substrate, 6... Molecular beam source cell, 61... Opening, 8... Manipulator,
lO...molecular beam

Claims (2)

[Claims] (1) One or more substrates are attached to a substrate holder provided in a vacuum atmosphere, and the opening of the molecular beam source cell that emits molecular beams faces the plane to which the surface of the substrate attached to the substrate holder belongs. In this method, the diameter of the substrate holder is D, and the diameter of the molecular beam source cell is The distance between the point where the center line intersects the plane to which the surface of the substrate belongs and the rotation center of the substrate holder is x, and the distance from the opening of the molecular beam source cell to the plane to which the surface of the substrate belongs on the center line of the molecular beam source cell. If y is 0.4D≦x≦0.7D and 0
．． A molecular beam epitaxy growth method characterized by performing film growth under the condition of 7D≦y≦1.6D. (2) A substrate holder provided in a vacuum container to which one or more substrates can be attached, a manipulator that rotates the substrate holder, and a molecular beam source cell that emits molecular beams, the opening of which is the substrate holder. The diameter of the substrate holder is D, and the point where the center line of the molecular beam source cell intersects with the plane to which the surface of the substrate belongs. If x is the distance between the center of rotation of the substrate holder and
A molecular beam epitaxy apparatus characterized in that x is set within a range of 0.4D≦x≦0.7D, and y is set within a range of 0.7D≦y≦1.6D.