JP4834828B2 - Manufacturing method of semiconductor device - Google Patents

Description

The present invention relates to a method for manufacturing a multi-stage semiconductor device in which the position of germanium dots in the planar direction is artificially controlled.

As materials for light-emitting devices, 3-5 semiconductor materials, which are mainly light-emitting direct transition semiconductors, have been used. If a silicon (Si) -based light-emitting device can be produced, the manufacturing process matches that of a large-scale integrated circuit (LSI) of Si. Therefore, it is expected to realize a high-functional device such as an optical-logic integrated circuit. Furthermore, since Si with abundant resources can be used, Si-based light emitting devices are also expected from the viewpoint of resources. However, since Si and germanium (Ge) are non-light emitting indirect transition semiconductors, they hardly emit light.

However, when fine Ge dots are formed in or on Si, a quantum confinement effect appears, and electrons in Si and holes confined in Ge dots are recombined to emit light. At this time, since light is emitted in the optical communication wavelength band of 1.3 to 1.6 μm, the device using Ge dots is expected to be applied as a light emitting device in the optical communication wavelength band.
When Ge is deposited on Si, it grows epitaxially as a thin film up to about four layers (the atomic spacing in the planar direction of the growing thin film Ge grows in conformity with the atomic spacing of the underlying Si). Ge gathers in a self-organizing manner to form dots. As one method for producing Ge dots, Ge dots self-organized and grown in this way are used.

However, the size and position of Ge dots formed in a self-organizing manner are random. In order to obtain light emission with a high emission intensity and a narrow half-value width, the Ge dots must have the same size. Since Ge as a supply source for forming Ge dots is originally isotropically moved, if the positions of the Ge dots can be formed at regular positions, the size of the Ge dots is also made uniform. For this reason, various techniques for artificially and regularly arranging Ge dots have been studied.
When the surface of the Si substrate is etched to form a trapezoidal (see Non-Patent Document 1) or ridge-like (see Non-Patent Document 2) convex structure, Ge is relatively regularly formed around the trapezoid and on the top of the ridge. Dot is lined up. However, Ge dots need to be regularly arranged in a two-dimensional form as an ultimate form.
A method has also been proposed in which SiO2 is formed on a Si substrate, a window is regularly formed in SiO2 and Ge is deposited, and Ge dots are regularly formed on the Si substrate at the open position of the window. (See Non-Patent Document 3).

Until 2003, it was thought that Ge dots were mainly formed in convex structure portions. However, Suda et al. Reported that Ge dots were formed most stably at the bottom of the inverted pyramidal concave structure. That is, when the convex structure and the inverted pyramid-shaped concave structure coexist on the Si substrate, Ge gathers at the bottom of the inverted pyramid-shaped concave structure at a high temperature. It has been reported that an inverted pyramid-shaped concave structure can be formed at an arbitrary regular position and a Ge dot can be formed at the center of the bottom using this method (see Non-Patent Document 4). Further, after regularly forming windows with resist on the Si substrate, Si at the window position is etched downward in a rectangular parallelepiped shape by reactive ion etching to form Ge dots near the center of the position. A method has been reported (see Non-Patent Document 5).

On the other hand, in order to obtain a sufficiently strong light emission intensity, it is necessary to stack Ge dots in multiple stages across the Si layer and increase the number of Ge dots per unit area. However, after Ge dots are formed, Ge is deposited at a certain substrate temperature with a thin Si layer in between. When Ge is deposited on the thin Si layer, Ge is gathered at the position where the Ge dot is located below. Has been reported (see Non-Patent Document 6). The Si atomic spacing in the Si layer near the position where the Ge dot is located below is distorted to approach the atomic spacing of the lower dot-shaped Ge crystal, and approaches the atomic spacing of the Ge crystal. For this reason, Ge on the Si layer is gathered at a position where it is close to the atomic spacing of the original Ge crystal and becomes stable in terms of energy. Using this method, it has been reported that Ge dots can be formed in multiple stages by sandwiching a thin Si layer on a self-organized Ge dot.

B. Yang, A.A. R. Wall, P.M. Rugheimer, M.M. G. Lagally, Mat. Res. Soc. Symp. Proc. 2002, 715, p. A. 8.5.1-A. 8.5.6 K. L. Wang, J. et al. L. Liu, G.G. Jin, Crystal Growth, 2002, 237-239, p. 1892-2897 E. S. Kim, N.A. Usami, Y. et al. Shiraki, Appl. Phys. Lett. 1998, 72, p. 1617-1619 S. Kaechi, D.H. Kitayama, Y. et al. Suda, Ext. Abs. 2003 Int. Conf. on Solid State and Materials, 2003, p. 96-97 Z. Zhong, A.M. Halilovic, T.W. Fromherz, F.M. Schaffler, G.M. Bauer, Appl. Phys. Lett. 2003, 82, p. 4779-4781 K. L. Wang, J. et al. L. Liu, G.G. Jin, Crystal Growth, 2002, 237-239, p. 1892-2897

In order to use it as a light emitting diode, electrons and hole currents flow by applying a voltage in a direction perpendicular to the surface on which Ge dots are formed. However, in the method of forming a two-dimensional regular window SiO _2, SiO ₂ itself becomes an obstacle to current flow.
By regularly arranging the Si concave structures, Ge dots can be basically formed at the positions. However, in the method of forming Ge dots corresponding to the first stage in the center of the recesses proposed in Non-Patent Document 4 and Non-Patent Document 5, etc., the first-stage Ge dots are formed directly above or as the recesses. A concave portion is formed in a ring shape between the Ge dots. When the first-stage Ge dot is formed in the center of the recess, if the Ge dot is small, an inverted trapezoidal recess is formed on the top. In this case, when a thin Si layer is stacked and irradiated with Ge at a constant temperature, a plurality of second-stage Ge dots are formed in an L-shaped portion corresponding to the bottom of the inverted trapezoidal shape. Even when a concave portion is formed in a ring shape, a plurality of second-stage Ge dots are formed in the ring-shaped concave portion, and in each case, a plurality of second-stage Ge dots are formed near the position of the first-stage Ge dots. It is formed that the second-stage Ge dot is divided and formed near the position of the first-stage Ge dot. Moreover, the second stage Ge dots are non-uniform. In the present invention, when manufacturing Ge dots in multiple stages, the manufacture of a semiconductor device in which Ge dots are formed in multiple stages at the position of the inverted pyramid recess on the Si substrate where the Ge dots are artificially controlled without splitting the Ge dots. It is an object to provide a method.

In order to solve the above-mentioned problems, the first invention includes a first step of forming an inverted pyramid-shaped concave structure surrounded by at least four surfaces by etching on a silicon substrate, and the inverted pyramid-shaped concave A second step of filling germanium so that there are no recesses in the structure; a third step of forming a silicon layer after the step; and forming germanium dots at a position above the silicon layer and below the germanium dots A method of manufacturing a multi-stage semiconductor device, characterized in that it comprises a fourth step.

According to a second aspect of the present invention, there is provided a method for manufacturing a semiconductor device according to the first aspect, wherein germanium dots are stacked in multiple stages by repeating the third step and the fourth step.

A third invention is a method of manufacturing a semiconductor device according to the first or second invention, wherein a step of forming a Si layer is inserted between the first step and the second step.

A fourth invention is a method of manufacturing a semiconductor device according to any one of the first to third inventions, wherein a wet etching method is used as an etching method in the first step.

According to the first invention, at least the inverted pyramid-shaped recess is filled flat with germanium so that the recess is eliminated. Alternatively, by filling germanium more than the volume of the concave portion of the inverted pyramid, the buried germanium rises in a convex shape above the upper surface of the inverted pyramid. When the concave portion disappears in this way, a thin silicon layer is formed above the germanium, and when germanium is deposited at a constant temperature, germanium is gathered at a position where germanium is located below to form a germanium dot. It does not become a split shape.

According to the second invention, by filling the inverted pyramid-shaped concave portion of the substrate at least flatly, the germanium dots are not divided even if the formation of the thin silicon layer and the formation of the germanium dots are repeated above the concave portions. All the upper germanium dots are formed at the position of the inverted pyramid of the substrate in the planar direction.

According to the third invention, by forming a thin silicon layer on the inverted pyramid of the substrate, the defects of the atomic crystal structure of the inverted pyramid surface formed by etching disappear, and the germanium dots embedded in the inverted pyramid Good crystallinity can be maintained. For this reason, crystal defects and dislocations do not propagate upward, and a multi-stage germanium dot having excellent crystallinity is formed.

According to the fourth invention, when the inverted pyramid of the substrate is formed by wet etching, there is little physical damage seen in dry etching, and crystal defects and dislocations caused by physical damage propagate upward. And a multistage germanium dot having excellent crystallinity is formed.

  Si (100) is used for the substrate. A resist pattern in which square holes are regularly and two-dimensionally opened is formed on the surface by lithography. Next, when Si is etched using a wet etching solution that can be anisotropically etched using the resist mask, a recess (pit) is formed in a reverse pyramid shape from a square hole that is regularly opened two-dimensionally. Is formed. A concave structure of the inverted pyramid is surrounded by four (111) planes by anisotropic etching. When Si is thinly formed on the upper portion by a thin film forming technique such as a chemical vapor deposition method (CVD), a molecular beam epitaxy method (MBE) method or a sputtering method, the crystallinity of Si on the surface can be maintained well. After removing the resist pattern, when Ge is grown in a substrate temperature range of 500 to 700 ° C. by a thin film formation technique such as chemical vapor deposition (CVD), molecular beam epitaxy (MBE), or sputtering, the surface of Ge Electrophoresis is also added, Ge gathers inside the inverted pyramid, and Ge is buried in the concave portion of the inverted pyramid. The Ge is buried so that the concave portion disappears and is flattened or the Ge is raised in a convex shape. When the formation of a thin Si layer and the formation of Ge dots are repeated on the upper portion by the same thin film growth method as described above, Ge dots are formed in multiple stages at the position of the inverted pyramid. Finally, a Si cap layer is formed. When forming a light emitting diode, n-type Si is used for the Si of the substrate, and the Si cap layer is doped to form p-type Si. Alternatively, p-type Si is used for the substrate Si, and the Si cap layer is doped to form n-type Si. Doping is not applied to the Si layer between the Si substrate and the Si cap layer.

1 and 2 are diagrams for explaining a method for producing multistage Ge dots according to an embodiment of the present invention. In forming the inverted pyramid in the first step, first, a resist pattern having a square hole was formed by using a lithography technique. Next, an inverted pyramid-shaped recess surrounded by four (111) planes was formed using 25% TMAH (tetramethyl ammonium hydroxide) anisotropic etching solution.
FIG. 1 shows a substrate in which an inverted pyramid-shaped recess is formed on a Si (100) substrate in the first step. FIG. 1 is a front view of FIG. 1 and FIG. 1 is a cross-sectional view taken along line AA ′ across the inverted pyramid. Shown above.
On the p-type Si (100) substrate (1), Ge was grown at a substrate temperature of 500 ° C. using GeH 4 gas as a source gas. The surface of the Ge was added to fill the inverted pyramid-shaped recess, and the GeH4 gas irradiation amount was adjusted to stop the growth of Ge until the Ge filled with the inverted pyramid-shaped recess was raised (2). Between the inverted pyramids, Ge surface migration is added and Ge dots are not formed. Above this, a Si thin film (3) was grown at a substrate temperature of 600 ° C. using Si 2 H 6 gas as a raw material. Thereafter, Ge was grown again using GeH 4 gas as a source gas at a substrate temperature of 500 ° C. to form Ge dots (4). The growth of the Si thin film and Ge dots was repeated 9 times to form a 9-stage multistage Ge dot array. Finally, an n-type Si cap layer (5) was formed. In order to dope n-type, Si 2 H 6 gas and PH 3 gas were used for the growth of the Si cap layer.
For comparison, FIG. 3 shows a cross-sectional view of the case where Ge is not filled flat in the first step. Ge is buried on the Si (100) substrate (6) so that Ge is not buried flat (7). Thereafter, when a thin Si layer (8) is formed, an inverted trapezoidal recess is formed in the upper part of the inverted pyramid. When Ge dots are formed thereafter, the Ge dots are formed in a split shape (9). Therefore, it can be seen that the method according to the present invention shown in FIG. 2 is effective for position control of Ge dots.

It is the figure which showed Si substrate in which the shape of the inverted pyramid was formed after completion | finish of the 1st process of the manufacturing method of the multistage Ge dot based on one Embodiment of this invention (the lower figure is a front view and the upper figure is AA. 'Cross section). It is the figure which showed sectional drawing of the multistage Ge dot array formed in order to show the manufacturing method of the multistage Ge dot based on one Embodiment same as the above. For comparison, it is a diagram showing the formation of split Ge dots that occur when Ge is not filled in the inverted pyramid recess until the recess disappears in the first step.

Explanation of symbols

1. 1. Si (100) substrate Ge filled with a concave in the shape of an inverted pyramid
3. 3. Inserted Si layer 4. Ge dots formed Si cap layer 6. Si (100) substrate 7. 7. Ge dots formed in an inverted-plasma-shaped recess 8. Inserted Si layer Split Ge dots formed

Claims (4)

A first step of forming at least four inverted pyramid-shaped concave portion surrounded by the surface by etching the silicon substrate,
A second step of filling germanium into the recess so as to be flat with respect to the silicon substrate or so as to rise above the upper surface of the silicon substrate ;
A third step of forming a silicon layer after the second step;
A fourth step of forming a germanium dot above the silicon layer and above the recess embedded with the germanium ;
A method for manufacturing a semiconductor device, comprising: The third step and by repeating the fourth step, the method of manufacturing a semiconductor device according to claim 1, characterized in that the germanium dots superimposed in multiple stages. The method of manufacturing a semiconductor device according to any one of claims 1 to 2, characterized in that the insertion of the step of forming a silicon layer between the first step and the second step. The method of manufacturing a semiconductor device according to claim 1, wherein a wet etching method is used as the etching method in the first step.

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