JP2001326188A - Selective growth method of solid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform selective growth of a solid on a fine scale of nano meter with high accuracy in a short time, by readily conducting drawing of a high resolution pattern at a high speed and a low cost, when a solid s selectively grown on a substrate surface. SOLUTION: In this method for growing a solid selective in a defined region on a basic material 1, a silicon nitride film 2 formed on the substrate surface 1 is oxidized locally, according to a desired pattern until the basic material 1 is reached to form a locally oxidized part 3, the locally oxidized part 3 is removed by etching, to form a recessed region 9 exposing the substrate surface 1 on the bottom part 9a thereof, the surfaces of at least the recessed region 9 and the silicon nitride film 2 in the vicinity thereof are coated with silicon dioxide 5 to forma two layer mask, the substrate surface is exposed as a defined region on the bottom part 9a of the recessed region 9, and a solid is selectively grown in the defined region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for selectively growing a solid in a specified area on a substrate.

[0002]

2. Description of the Related Art The solid selective growth method is a technique for selectively growing a solid thin film only in a specified region on a semiconductor substrate such as silicon or gallium arsenide in a semiconductor manufacturing process. In the solid selective growth process, the substrate surface is coated with a mask that has the property of inhibiting growth outside the solid growth area. As a material for the mask, silicon dioxide formed by thermal oxidation of silicon or vapor deposition is widely used. After a resist is applied to these masks to form a pattern by lithography, the mask is partially removed by etching to expose the base material, thereby defining a region where a solid is selectively grown.

In recent years, with the miniaturization of semiconductor devices, it has become necessary to reduce the size of the selective growth region from submicron to nanometer scale. To achieve this, a technique has been proposed in which an ultrathin mask having a thickness of 10 nm or less is used, and a pattern for selective growth is directly drawn using an electron beam without applying a resist thereto. (For example, DS Hwan
get et al. , Japanese Journal
of Applied Physics, Part
2, vol. 37, p. 1087 (1998) and Japanese Patent No. 3015822). In particular, this patent 301
The ultra-thin mask having a two-layer structure in which silicon dioxide is stacked on silicon nitride, which is described in Japanese Patent No. 5822, has a better thermal and electron beam stability than a single-layer silicon dioxide mask. Shows sex.

[0004]

However, the above-described method of directly drawing a pattern using an electron beam has a problem that it is not suitable for an actual semiconductor manufacturing process because the drawing speed is generally low.

In the case of drawing using an electron beam,
There is an inherent disadvantage that the resolution is limited by the diameter of the electron beam and the secondary electron effect.

Further, an apparatus for drawing by using an electron beam is expensive and has problems that the performance is not easily maintained and the drawing process is complicated.

[0007] The present invention has been proposed in view of the above,
When a solid is to be selectively grown on a substrate, it is easy to draw a pattern at high speed and with high resolution and at low cost. It is an object of the present invention to provide a solid selective growth method that can be performed in a short time.

[0008]

According to a first aspect of the present invention, there is provided a solid selective growth method for selectively growing a solid in a defined area on a substrate. The silicon nitride film formed on the material is locally oxidized into a locally oxidized portion according to a desired pattern, and the locally oxidized portion is removed by etching to form a concave region where the base material is exposed at the bottom. Forming a two-layer mask by covering the surface of the silicon nitride film for suppressing the growth of the recessed region and the solid with silicon dioxide, exposing a base material to the bottom of the recessed region to form a defined region; The method is characterized in that a solid is selectively grown in a region.

According to a second aspect of the present invention, in addition to the configuration of the first aspect of the present invention, local oxidation of the silicon nitride film is controlled by controlling an excitation source. The method is characterized in that it is carried out using the ion species or the chemically active species generated in the above.

According to a third aspect of the present invention, in addition to the configuration of the first aspect of the present invention, the local oxidation of the silicon nitride film is performed by connecting a conductive needle to the silicon nitride film. The method is characterized in that a voltage is applied to the needle while the needle is in contact with or in proximity to the surface.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is an explanatory view showing each step of the solid-state selective growth method of the present invention. In the solid-state selective growth method of the present invention, a silicon nitride layer (silicon nitride film) 2 is first formed on a substrate 1 as shown in FIG. The film thickness ranges from 1 nm to 20 nm, but the optimum film thickness is around 5 nm. The silicon nitride layer 2 is formed by a vapor deposition method,
Alternatively, when the substrate 1 is silicon, it is formed by a nitriding reaction. In order to enhance the reproducibility of patterning, it is effective to anneal the silicon nitride layer at about 1000 ° C. in advance.

Next, a pattern is directly drawn by performing local oxidation on the silicon nitride layer 2. That is,
As shown in FIG. 1B, the silicon nitride film 2 formed on the base material 1 is locally oxidized according to a desired pattern,
A locally oxidized portion 3 is formed on the silicon nitride film 2. There are the following two methods for performing this local oxidation.

First, the first method will be described. In general, silicon nitride is known to exhibit oxidation resistance to thermal oxidation, but is relatively easily oxidized when ionic species or chemically active species are present, such as in plasma. Such ionic species and chemically active species are supplied to the excitation source (plasma,
Since light can be locally generated by controlling light and charged particle beams, silicon nitride can be locally oxidized. For example, in an atmosphere where oxygen exists, light,
Active oxygen or oxygen ions are locally supplied to the silicon nitride surface by excitation with plasma or an electron beam or by irradiation with a beam of oxygen ions, and local oxidation is performed.

As a second technique, a technique has recently been reported in which a pattern is formed by locally oxidizing silicon nitride using an atomic force microscope (AFM) capable of applying a voltage (FSS). Chen et al., Applie.
d Physics Letters, vol. 76,
p. 360 (2000)), a technique for oxidizing using this technique. This F. S. S. In the literature of Chen et al.
An AFM conductive probe is brought into contact with the surface of a sample in which a silicon nitride layer having a thickness of about 5 nm is formed on a silicon substrate,
By applying a voltage of +4 V to +10 V to the sample, the silicon nitride layer is locally oxidized, and 100 n
A pattern with a width of about m has been successfully formed.

In the second method, specifically, for example, a conductive needle is placed in a silicon nitride 2 under an atmosphere in which moisture is present.
Local oxidation is performed by applying a voltage to the needle in a state of contacting or approaching the surface of the needle. At this time, the needle
When a tip having a tip shape equivalent to that used in an atomic force microscope is used, a line width of about 100 nm can be easily drawn. The voltage applied to the needle is adjusted to achieve the desired oxidation rate and line width. Its value is usually about + 4V to + 10V. This method can be performed in the atmosphere, and has an extremely high initial oxidation rate of 1 μm / s. Further, since the oxidation reaction is induced by a voltage applied to a sharply pointed probe, a high resolution of about 100 nm can be easily obtained. It is believed that the oxidation mechanism involves moisture in the air condensed between the needle and the sample surface.

After the local oxidized portion 3 is formed in the silicon nitride layer 2 as described above, the local oxidized portion 3 is subsequently removed by etching, and a concave region 9 where the base material 1 is exposed at the bottom 9a is formed (FIG. FIG. 1 (c)). This locally oxidized portion 3 can be selectively removed by etching using a hydrogen fluoride (HF) aqueous solution. At this time, the etching rate of silicon nitride in a hydrogen fluoride solution is:
Since the etching rate of the oxide in the locally oxidized portion 3 is small, only the oxide is selectively etched. There is no limitation on the concentration of the aqueous hydrogen fluoride solution to be used, but from the viewpoint of the etching rate, an aqueous solution having a concentration of about 1.0% by weight is easy to use. When the locally oxidized portion reaches the substrate as shown in FIG. 1B, as a result of this selective etching, the underlying substrate 1 is exposed according to the locally oxidized pattern (FIG. 1C). ). When the locally oxidized portion does not reach the base material, the base material 1 on the bottom of the concave portion is continuously placed on the silicon nitride layer having the concave portion formed by the selective etching.
By etching until the silicon is exposed, FIG.
The structure of (c) is formed.

The silicon nitride layer 2 patterned as described above can itself serve as a mask for selective growth. However, depending on the material to be selectively grown and the growth method, the silicon nitride layer 2 may be formed on the surface of the silicon nitride whose growth is to be suppressed. Silicon nitride is not optimal as a material for the selective growth mask because solid growth occurs. Among substances that function as selective growth masks, silicon dioxide has the most excellent growth suppressing effect.

Therefore, the entire surface of the silicon nitride layer 2 in which the recessed regions 9 are formed is covered with silicon dioxide.
As shown in (d), a mask having a two-layer structure including a silicon nitride layer 2 and a layer mainly containing silicon dioxide (hereinafter, referred to as “silicon dioxide layer”) 5 is formed. This silicon dioxide layer 5 may be formed by vapor deposition, but from the viewpoint of controlling the film thickness, the oxidation of the silicon nitride layer 2 is simple. In particular, since thermal oxidation of silicon nitride is slow, it is effective to generate oxygen atoms, ozone, or oxygen ions by plasma or ultraviolet light excitation to perform oxidation. The thickness of the oxide layer (silicon dioxide layer 5) is set to a thickness that can provide a sufficient growth suppressing effect in desired solid selective growth, and oxidation is performed until the thickness is reached. When silicon is selectively grown, its thickness is about 0.5 nm. However, the upper limit of the oxide film thickness is not limited as long as the pattern (concave region 9) already drawn is not disturbed.

At this time, since the exposed surface of the substrate 1 (the bottom 9a of the concave region 9) is also oxidized and covered with the oxide film 6, an appropriate heat treatment or etching is performed prior to the selective growth. Exposing the clean surface of the substrate 1 again,
The state shown in FIG.

When the substrate 1 is made of silicon, the sample is placed in an ultra-high vacuum or in an inert gas or hydrogen gas stream.
By heating to a temperature of not less than ° C., the oxide film 6 formed on the surface of the substrate 1 can be thermally desorbed. The reaction formula at that time is expressed as SiO ₂ + Si = 2SiO, and the substrate 1
Is consumed and silicon monooxide is desorbed into the gas phase, thereby removing silicon dioxide (oxide film 6). At this time, no desorption occurs in the silicon dioxide layer 5 on the silicon nitride layer 2 because there is no silicon necessary for generating silicon monooxide by the above-mentioned reaction formula.

When the substrate 1 is not silicon, the substrate 1
The above oxide (for example, if substrate 1 is gallium arsenide, G
axAsyOz) and silicon dioxide on silicon nitride, utilizing the difference in chemical or physical properties, by a selective desorption reaction or etching reaction depending on the type of the base material 1, The surface of the material is exposed.

Finally, the exposed surface of the base material is defined as a defined area, and a desired solid 7 is selectively grown in the defined area (FIG. 1 (f)). When the solid 7 is silicon, selective growth can be performed in a specified region by growth under molecular flow conditions using silane or disilane, or by chemical vapor deposition using chlorosilane. In order to grow a solid having good crystallinity, the steps of (e) and (f) in FIG.
It is necessary to perform it in an ultra-high vacuum or in a high-purity gas stream.

As described above, in the embodiment according to the present invention, the silicon nitride layer 2 is locally oxidized to draw a pattern, and the locally oxidized portion 3 is removed to form the concave region 9. In this oxidation, an excitation source (plasma, light,
(Charged particle beam) to control oxidation using ion species or chemically active species that can be generated locally. Can be oxidized well. Since the removal of the locally oxidized portion 3 is performed by utilizing the difference between the etching rate of the silicon nitride and the etching rate of the locally oxidized portion 3, only the locally oxidized portion 3 is accurately and smoothly removed. can do. That is, in this embodiment, pattern writing in the case where a solid is selectively grown on the base material 1 can be easily performed at high speed and with high resolution and at low cost by utilizing the properties of the underlying silicon nitride layer 2. The selective growth of the solid can be performed with sufficient selectivity by utilizing the properties of the upper silicon dioxide layer 5. As a result, the selective growth of a solid on a nanometer fine scale can be performed with high accuracy and in a short time.

Further, compared with the conventional electron beam drawing apparatus, the apparatus is simple and low in cost and easy to operate, so that drawing can be performed easily at low cost.

Further, since the local oxidation of the silicon nitride layer 2 is performed using a conductive needle, the pattern can be drawn more directly, at a higher speed and with a higher resolution.

Furthermore, since the surface of the two-layer mask (2, 5) is covered with the silicon dioxide layer 5, it exhibits the same growth suppressing effect as the silicon dioxide single-layer mask in the selective growth reaction. Further, since the silicon nitride layer 2 is provided as a lower layer, it can be thermally stable.

Next, as an example, FIG. 1 is used together with a case where a silicon (001) wafer is used as the base material 1 and silicon is selectively grown on the base material 1 to form a dot pattern. I will explain.

First, in the step of FIG. 1A, the silicon nitride layer 2 was formed by a chemical vapor deposition method using dichlorosilane and ammonia as raw materials, and its thickness was set to about 5 nm.

Next, in the step of FIG. 1 (b), local oxidation was performed using an atomic force microscope equipped with platinum-coated conductive tips, and the pattern was drawn according to a dot-like pattern. . The oxidation was performed by applying +10 V to the sample for 200 ms for each dot in the atmosphere.

Subsequently, in the step of FIG. 1C, the selective etching of the dot-shaped locally oxidized portion 3 was performed using a 1.0% by weight hydrogen fluoride solution to form a concave region 9.

In the step shown in FIG. 1D, the silicon dioxide layer 5 was formed by plasma oxidation at room temperature. That is, oxygen diluted to 5% with helium is used as a plasma gas, and 25 mW at a total pressure of 300 mTorr.
The plasma oxidation was performed by exciting the capacitively coupled plasma at a power density of / cm ² for 20 seconds. Oxide film thickness is about 0.5
nm.

Thereafter, in the step shown in FIG. 1E, the sample is heated under ultra-high vacuum at 1000 ° C. for 3 minutes to thermally desorb silicon dioxide, so that the selective growth region (the concave region 9 The silicon dioxide formed on the bottom 9a) was removed.

Finally, in the step of FIG. 1F, silicon was grown in the selective growth region by a chemical vapor deposition method. The conditions were a disilane pressure of 0.08 mTorr, a substrate temperature of 580 ° C., and a growth time of 600 seconds.

FIG. 2 shows an atomic force microscope image of the sample surface prepared by the above procedure. It is observed that silicon grows in the form of dots on the surface of the silicon substrate 1, which indicates that selective growth can be actually performed by the method of the present invention.

FIG. 3 shows the result of tracking the change in the chemical composition of the sample surface prepared by the above procedure by Auger electron spectroscopy. The horizontal axis in FIG. 3 is the Auger electron energy (e
V), the vertical axis is the Auger electron differential intensity (dN / dE), and here is the LVV peak of silicon. FIGS. 3A and 3B show the surface chemical composition at the time when the step of FIG. 1C is completed, that is, when the bottom 9a of the concave region 9 is exposed. (A) is a result measured on the surface of the silicon nitride layer, and a peak derived from silicon nitride is observed at 83 eV. (B) is a measurement of the exposed substrate (the bottom 9a of the concave region 9 in FIG. 1 (c)). Observation of a silicon peak at 92 eV indicates that a clean silicon surface is exposed.

FIGS. 3C and 3D show FIG. 1F
Is the surface chemical composition at the time when the selective growth step is completed. (C) is a measurement of the selectively grown solid 7 (silicon). Since a silicon peak is observed at 92 eV, it can be confirmed that the grown solid is silicon. (D) is a result measured on the surface of the two-layer mask. Reflecting that the silicon nitride surface was coated with silicon dioxide by plasma oxidation,
Compared to (a), the shape of the spectrum around 75 eV changes. Also, the small peak seen at 92 eV is
This is due to nuclei of silicon generated on the mask.

[0038]

Since the present invention has the above-described configuration,
The following effects can be obtained.

According to the first and second aspects of the present invention, the silicon nitride film is locally oxidized using, for example, an ion species or a chemically active species which can be locally generated by controlling an excitation source. By drawing a pattern by that, the local oxidized part was removed to form a concave area, and then the silicon nitride surface was covered with silicon dioxide to grow a solid in the concave area. The pattern writing in the case of selectively growing a solid on top can be easily performed at high speed, with high resolution, and at low cost by utilizing the properties of the underlying silicon nitride film. It can be performed with sufficient selectivity by utilizing the properties of silicon. As a result, the selective growth of a solid on a nanometer fine scale can be performed with high accuracy and in a short time.

According to the third aspect of the present invention, since the local oxidation of the silicon nitride film is performed using a conductive needle, the pattern can be drawn more directly.
It can be performed at high speed and with high resolution. In addition, the device is simpler and easier to operate than an electron beam drawing device, and therefore, drawing can be performed easily at low cost.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing each step of a selective solid growth method of the present invention.

FIG. 2 is a diagram showing an atomic force microscope image of a sample surface prepared according to the procedure of the present invention.

FIG. 3 is a diagram showing a result of tracking a change in a chemical composition of a sample surface manufactured according to a procedure of the present invention by Auger electron spectroscopy.

[Explanation of symbols]

 Reference Signs List 1 base material 2 silicon nitride layer 3 locally oxidized portion 5 silicon dioxide layer 6 oxide film 7 solid, silicon 9 concave region 9a bottom

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/318 H01L 21/318 B (72) Inventor Tetsuji Yasuda 1-4-1 Higashi Tsukuba, Ibaraki Pref. Industrial Technology Institute of Industrial Science and Technology (72) Inventor Satoshi Yamazaki 1-4-1 Higashi, Tsukuba, Ibaraki Pref. Institute of Industrial Science and Technology (72) Inventor Naoshi Hana Taiwan Sinchu 300 National Shin-Ha University Department Of Physics F term (reference) 4K030 AA06 BA40 BA44 BB13 CA04 CA12 DA08 5F045 AB02 AC01 AD09 AE13 AF03 AF20 DB02 5F058 BA20 BC02 BD01 BD04 BF63 BF70 BF73 BF76 BF78 BJ01

Claims (3)

[Claims] In a solid-state selective growth method for selectively growing a solid in a defined region on a substrate, a silicon nitride film formed on the substrate is locally oxidized according to a desired pattern. A locally oxidized portion by etching, removing the locally oxidized portion by etching to form a concave region where the base material is exposed at the bottom, and forming the concave region and the surface of the silicon nitride film to suppress the growth of solids by silicon dioxide. Forming a two-layer mask by exposing the substrate to a defined region by exposing the base material to the bottom of the concave region, and selectively growing a solid in the defined region. 2. The method according to claim 1, wherein the local oxidation of the silicon nitride film is performed using ionic species or chemically active species locally generated by controlling an excitation source. The selective solid growth method according to the above. 3. The method according to claim 1, wherein the local oxidation of the silicon nitride film is performed by applying a voltage to the needle while the conductive needle is in contact with or close to the surface of the silicon nitride film. Item 2. The method for selective solid growth according to Item 1.