JPH02148833A - Selective vapor growth method - Google Patents

Abstract

PURPOSE:To eliminate contamination, etc., of a silicon substrate, and to remote a damaged layer even in an opening having fine and high aspect ratio by removing a damaged layer by RIE of isotropic dry etching method under low pressure before selective vapor growing. CONSTITUTION:When an SiO2 film is etched by a RIE method with resist 3 as a mask to form an opening, a damaged layer 4 is formed on the exposed Si substrate 1. Then, the resist 3 is removed, the exposed substrate 1 is isotropically etched approx. 300Angstrom by a CDE method using (CF4+O2) to remove the layer 4. Since the CDE method uses fluorine radical of low kinetic energy, damage by etching can be ignored as compared with the RIE method. Since the etching rate of Si to SiO2 in the CDE method is 20 or more, the etching of the SiO2 film 2 whole the layer 4 is removed can be ignored. Thereafter, an Si layer 5 is selectively formed in the opening.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a selective vapor phase growth method, and is particularly used in a selective vapor phase growth method for silicon.

(Prior Art) A selective vapor phase growth method is a method in which, for example, a silicon layer is selectively grown in a vapor phase only in an opening of an insulating film formed on a silicon substrate.

Conventionally, openings in insulating films were mainly formed by wet etching or dry etching, but in recent years, R etching, which is anisotropic etching, has been used to form fine openings.
I E (Reactive Jon Etching
) method is increasingly being used.

Although this RIE method allows highly accurate microfabrication, it has the property of forming a damaged layer or the like on the silicon substrate exposed in the opening. Therefore, it is necessary to remove the damaged layer after forming the opening by RIE and before selective vapor deposition, and this is generally done by anisotropic wet etching.

However, since the anisotropic wet etching method uses a chemical solution, there are problems such as contamination of the silicon substrate by impurities in the chemical solution and adhesion of fine particles floating in the chemical solution to the silicon substrate. In addition, a contact embedding technology using selective vapor deposition has been developed, which contributes to the miniaturization of LSIs. However, the dimensions and aspect ratio of the contact hole are 0.51 or less and 2a or more, respectively, making it difficult to fill the inside of the contact hole. Another drawback is that the chemical solution cannot be replaced smoothly, making it difficult to remove the damaged layer.

(Problems to be Solved by the Invention) As described above, conventionally, the damaged layer of a silicon substrate after forming an opening by the RIE method was removed by an anisotropic wet etching method. Therefore, contamination of the silicon substrate,
There were drawbacks such as adhesion of fine particles to the silicon substrate and difficulty in removing the damaged layer due to insufficient replacement of the chemical solution.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a selective vapor phase growth method that does not cause contamination of a silicon substrate and allows removal of damaged layers even in fine and high aspect ratio openings.

[Structure of the Invention] (Means for Solving the Problems and Their Effects) In order to achieve the above object, the selective vapor deposition method of the present invention first forms an insulating layer on, for example, a silicon substrate. And R
A fine opening reaching the silicon substrate is formed in the insulating layer using IE. Then, in order to remove the layer damaged by RIE, the silicon substrate is isotropically etched using, for example, the CDE method. After this, a silicon layer is selectively formed in the opening.

Further, if the area of the semiconductor substrate exposed at the opening is 50% or less of the area of the main surface of the semiconductor substrate,
It is possible to suppress the loading effect and is even more effective.

If such a selective vapor phase growth method is used, the damaged layer of the semiconductor substrate can be removed by low-pressure isotropic dry etching, and the deterioration of selectivity due to contamination and the like and the yield of the selective vapor phase growth process can also be improved.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIGS. 1(a) to 1(h) show the selective vapor phase growth method of the present invention. First, (100)S as shown in figure (a)
i Prepare a (silicon) substrate 1. Next, the Si
A film of about 1 μm is deposited on the surface of the substrate 1 by oxidation or CVD.
An i02 film 2 is formed (see figure (b)). Next, a resist 3 is applied on the SiO2 film 2 (see FIG.
c). Next, the resist 3 is E B (El
It is partially removed using the electron beam (electron beam) drawing method (see figure (d)). Next, using the resist 3 as a mask, the 5i02 film 2 is etched by RIE to form an opening. At this time, a damaged layer 4 is formed on the exposed Si substrate 1 (see FIG. 4(e)). Next, the resist 3 is removed (see figure (f)) and isotropically dry etched using CDE (Chemical Dry Etching) using CF4+02, for example.
The exposed Si substrate 1 is subjected to isotropic etching by about 300 people to remove the damaged layer 4 (see (g) in the figure).

Note that since the CDE method uses fluorine radicals with low kinetic energy, the damage caused by etching can be ignored compared to the RIE method. In addition, Si and 5 in the CDE method
The etching rate ratio with i02 is (S i/S i 0
2) = 20 or more, the etching of the 5iO9 film 2 during the removal of the damaged layer 4 can also be ignored. After this, selective vapor phase growth was performed at 900°C and 120 torr using S i H2Cjl 2 +HCfl +H2,
51 layers 5 are selectively formed in the openings (see FIG. 5(h)).

According to this selective vapor deposition method, the damaged layer 4 is removed by isotropic dry etching without using wet etching, so there is no influence from impurity contamination or fine particles. In addition, since the low-pressure dry etching method is used for fine openings with high aspect ratios, the replacement of fluorine radicals and reaction products at the fine openings is smooth, and good vapor phase growth is possible. .

By the way, in the CDE method, the film to be etched (Si substrate 1)
There is a large change in etching rate (loading effect) depending on the exposed area. Therefore, the area ratio of the Si substrate l exposed at the opening to the main surface of the Si substrate l (hereinafter referred to as "area ratio") is
That's what it means. ) is 50% or less, variations in etching rate can be suppressed, and further improvement in yield in the selective vapor deposition process can be achieved.

Next, a Si layer was grown in vapor phase using the present invention and the conventional vapor phase growth method, and the two were compared and studied. First, (100
) A 5i02 film of approximately one thickness is formed on the surface of the Si substrate, and a 0.3 μ
An opening of 2.0 kun was formed from s. Thereafter, about 300 people etched the exposed Si substrate using the CDE method using CF4 + O2 in the present invention, and the anisotropic wet etching method using ammonia water in the conventional example. And both are S i H2Cp 2+HC,
Vapor phase growth was performed using a selective vapor growth method at 900°C and 20 torr using l) +) (2) so that the Si layer grew to about 1-.
A 5% and a 55% version were prepared.

As a result, in the conventional example, IIA
Although a Si layer with a culm degree was growing, no Si layer growth was observed in the openings with a culm degree of 0.51 or less.

Also, in other openings, 0. A Si layer of On-0.5° was growing irregularly. This is thought to be because the etching solution was not sufficiently replaced in the fine contacts during etching, resulting in insufficient removal of the damaged layer by RIE. In contrast, in the present invention, 0.31
A Si layer of approximately 1 kon was grown in every 2.0 kon opening. Furthermore, the incidence of selectivity deterioration due to t9 dyeing was reduced to 1/10 compared to the conventional example. Furthermore, the area ratio is 4
In the case of 5%, the variation in Si layer thickness was 1/2 compared to that of 55%. The reason why the uniformity of the Si layer thickness is improved is that the loading effect becomes smaller after the area ratio reaches 50%, and the uniformity of the etching rate of the Si substrate is improved.

[Effects of the Invention] As described above, the selective vapor growth method of the present invention provides the following effects.

Since the damaged layer caused by RIE is removed using a low-pressure isotropic dry etching method before selective vapor deposition, there is no contamination of the silicon substrate, and the damaged layer can be removed even from fine and high aspect ratio openings. became possible. Therefore, it has become possible to reduce the incidence of selectivity deterioration and achieve a high yield in the selective vapor phase growth process.

[Brief explanation of the drawing]

FIG. 1 is a sectional view for explaining a selective vapor growth method according to an embodiment of the present invention. ■...Si substrate, 2...5iO7 film, 3...resist, 4...damaged layer, 5...Si layer. Applicant's agent Patent attorney Takehiko Suzue

Claims (2)

[Claims] (1) A step of forming an insulator layer on the main surface of a semiconductor substrate, a step of forming an opening in the insulator layer reaching the semiconductor substrate, and a step of isotropically etching the semiconductor substrate using a dry etching method. , selectively forming a semiconductor layer in the opening. (2) The selective vapor deposition method according to claim 1, wherein the area of the semiconductor substrate exposed through the opening is 50% or less of the area of the main surface of the semiconductor substrate.