JP3387047B2 - Solid selective growth method - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art A solid-state selective growth method is a technique for selectively growing a solid thin film only in a defined region on a semiconductor substrate such as silicon or gallium arsenide in a semiconductor manufacturing process. In the solid-state selective growth process, the substrate surface is covered with a mask having the property of suppressing growth outside the region where the solid is grown. 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 a lithographic technique, the masks are partially removed by etching to expose the base material, thereby defining a region in which a solid is selectively grown.

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

[0004]

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

In addition, when drawing with an electron beam,
There is an essential drawback 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 a problem that the performance is not easily maintained and the drawing process becomes complicated.

The present invention has been proposed in view of the above,
Patterns for selective growth of solids on a substrate can be drawn easily at high speed with high resolution and at low cost, and selective growth of solids can be performed with high precision and short time on a nanometer scale. It is an object to provide a solid-state selective growth method that can be performed in time.

[0008]

In order to achieve the above object, the invention according to claim 1 provides a solid selective growth method for selectively growing a solid in a defined region on a substrate, wherein According to a desired pattern, the silicon nitride film formed on the material is locally oxidized to form a locally oxidized portion, and the locally oxidized portion is removed by etching to form a concave region where the base material is exposed at the bottom. , The concave area on the substrate is
The formed surface of the silicon nitride film was coated with silicon dioxide to form a two-layer mask, according to the silicon dioxide
It is characterized in that the base material is exposed again at the bottom of the concave region simultaneously oxidized by the coating to form a defined region, and the solid is selectively grown in the defined region.

According to a second aspect of the invention, in addition to the structure of the first aspect, the local oxidation of the silicon nitride film is controlled by controlling the excitation source. It is characterized in that it is carried out by using ionic species or chemically active species generated in.

In addition to the structure of the invention described in claim 1, the invention described in claim 3 is such that local oxidation to the silicon nitride film is prevented and a conductive needle is attached to the silicon nitride film. It is characterized in that it is performed by applying a voltage to the needle while the needle is in contact with or in the vicinity of the surface.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is an explanatory view showing each step of the solid selective growth method of the present invention. In the solid selective growth method of the present invention, first, as shown in FIG. 1A, a silicon nitride layer (silicon nitride film) 2 is formed on a base material 1. The film thickness is in the range of 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 base material 1 is silicon, it is formed by a nitriding reaction. In order to improve the reproducibility of patterning, it is effective to anneal the silicon nitride layer in advance at about 1000 ° C.

Next, the silicon nitride layer 2 is locally oxidized to directly draw a pattern. 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. It is generally known that silicon nitride is resistant to thermal oxidation, but it is relatively easily oxidized in the presence of ionic species or chemically active species such as in plasma. Such ionic species and chemically active species are excited sources (plasma,
Since it can be generated locally by controlling light and charged particle beam), it is possible to locally oxidize silicon nitride. For example, under an atmosphere of oxygen, light,
Active oxygen or oxygen ions are locally supplied to the silicon nitride surface by excitation with plasma or an electron beam or irradiation with a beam of oxygen ions to locally oxidize.

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

In the second method, specifically, for example, the conductive needle is attached to the silicon nitride 2 under an atmosphere containing water.
The local oxidation is performed by applying a voltage to the needle while being in contact with or in the vicinity of the surface of. At this time, the needle is
If a tip having a tip shape equivalent to that used in an atomic force microscope is used, it is possible to easily draw a line width of about 100 nm. 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 carried out in the atmosphere, and the initial oxidation rate is extremely fast at 1 μm / s. Further, since the oxidation reaction is induced by the applied voltage to the sharply pointed probe, a high resolution of about 100 nm can be easily obtained. It is considered that the moisture in the air condensed between the needle and the sample surface is involved in the oxidation mechanism.

When the locally oxidized portion 3 is formed on the silicon nitride layer 2 as described above, the locally oxidized portion 3 is subsequently removed by etching to form the concave region 9 where the base material 1 is exposed at the bottom 9a ( FIG. 1 (c)). This locally oxidized portion 3 can be selectively removed by etching with a hydrogen fluoride (HF) aqueous solution. At this time, the etching rate of silicon nitride in the hydrogen fluoride solution is
Since the etching rate of the oxide of 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 used, but from the viewpoint of etching rate, an aqueous solution having a concentration of about 1.0 wt% 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 silicon nitride layer in which the recess is formed by this selective etching is continuously used as the base material 1 on the bottom of the recess.
By etching until the
The structure of (c) is formed.

The silicon nitride layer 2 thus patterned can function as a mask for selective growth by itself. However, depending on the material to be selectively grown and the growth method, the silicon nitride layer 2 also serves as a surface for the growth of the silicon nitride to be suppressed. Silicon nitride is not the optimum material for the selective growth mask because it causes solid growth to occur. Of the materials that function as a selective growth mask, silicon dioxide has the best effect of suppressing growth.

Then, the entire surface of the silicon nitride layer 2 in which the concave region 9 is 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 5 containing silicon dioxide as a main component (hereinafter referred to as “silicon dioxide layer”) 5 is formed. The silicon dioxide layer 5 may be formed by vapor deposition, but the oxidation of the silicon nitride layer 2 is easy from the viewpoint of controlling the film thickness. In particular, since the thermal oxidation of silicon nitride is slow, it is effective to generate oxygen atoms, ozone, or oxygen ions by plasma or ultraviolet light excitation for oxidation. The thickness of the oxide layer (silicon dioxide layer 5) is set to a film thickness that provides a sufficient growth suppressing effect in desired solid selective growth, and oxidation is performed until the film thickness is reached. When silicon is selectively grown, its film thickness is about 0.5 nm. However, the upper limit of the oxide film thickness is not limited as long as it does not disturb the already drawn pattern (concave region 9).

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

When the base material 1 is silicon, the sample is kept in an ultrahigh vacuum or in an inert gas or hydrogen gas stream for 900
By heating at a temperature of not less than 0 ° C., the oxide film 6 formed on the surface of the base material 1 can be thermally desorbed. The reaction formula at that time is expressed as SiO ₂ + Si = 2SiO, and the substrate 1
The silicon dioxide (oxide film 6) is removed by consuming the above silicon and desorbing silicon monooxide into the gas phase. At this time, desorption does not occur in the silicon dioxide layer 5 on the silicon nitride layer 2 because there is no silicon necessary to generate silicon monooxide by the above reaction formula.

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

Finally, the exposed surface of the substrate is defined as a defined region, and a desired solid 7 is selectively grown in the defined region (FIG. 1 (f)). When the solid 7 is silicon, selective growth can be performed in a prescribed region by growth under a molecular flow condition using silane or disilane or chemical vapor deposition using chlorosilane. In order to grow a solid having good crystallinity, the steps of (e) and (f) of FIG.
It is necessary to carry out under 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. During this oxidation, the excitation source (plasma, light,
By controlling the charged particle beam), it is possible to oxidize by using ionic species or chemically active species that can be generated locally, so it is generally possible to accurately localize silicon nitride, which is resistant to thermal oxidation. Can oxidize well. Since the removal of the locally oxidized portion 3 is performed by utilizing the difference between the etching rate of silicon nitride and the etching rate of the locally oxidized portion 3, only the locally oxidized portion 3 is removed accurately and smoothly. can do. That is, in this embodiment, the pattern drawing in the case of selectively growing a solid on the substrate 1 can be easily performed at high speed with high resolution and at low cost by utilizing the property of the lower silicon nitride layer 2. The selective growth of the solid can be performed with sufficient selectivity by utilizing the property of the upper silicon dioxide layer 5. As a result, selective growth of a solid on a nanometer scale can be performed with high precision and in a short time.

Further, as compared with the conventional electron beam drawing apparatus, the apparatus is simpler, lower in cost, and easier to operate, and thus drawing can be performed easily at low cost.

Further, since the local oxidation to the silicon nitride layer 2 is performed by using the conductive needle, the pattern can be drawn more directly, at high speed and with high 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 the lower layer, it can be thermally stable.

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

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

Next, in the step of FIG. 1B, local oxidation was carried out by using an atomic force microscope equipped with a probe coated with platinum to make it conductive, and drawing was performed according to a dot pattern. . The conditions were as follows: In the air, +10 V was applied to each sample for 200 ms for each dot to perform oxidation.

Subsequently, in the step of FIG. 1C, the dot-shaped locally oxidized portion 3 was selectively etched using a 1.0 wt% hydrogen fluoride solution to form a concave region 9.

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

Thereafter, in the step of FIG. 1E, the sample is heated at 1000 ° C. for 3 minutes under ultrahigh vacuum to thermally desorb the silicon dioxide, whereby the selective growth area (recessed area 9) is formed in the previous step. 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 the 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 produced by the above procedure. It is observed that silicon grows in a dot shape on the surface of the silicon base material 1, and it can be seen that the selective growth is actually possible by the method of the present invention.

FIG. 3 shows the result of tracking the change in the chemical composition of the sample surface produced by the above procedure by Auger electron spectroscopy. The horizontal axis of FIG. 3 is the Auger electron energy (e
V), the vertical axis represents Auger electron differential intensity (dN / dE), which is the LVV peak of silicon here. 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 measured on the surface of the silicon nitride layer, and a peak derived from silicon nitride is seen at 83 eV. (B) is a measurement of the exposed substrate (bottom 9a of the concave region 9 in FIG. 1C). Since a peak of silicon is observed at 92 eV, it can be seen that a clean silicon surface is exposed.

3 (c) and 3 (d) are shown in FIG. 1 (f).
The chemical composition of the surface at the time when the selective growth step of is finished. (C) is measured on the selectively grown solid 7 (silicon). Since a peak of silicon is observed at 92 eV, it can be confirmed that the grown solid is silicon. (D) is 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 the silicon nuclei generated on the mask.

[0038]

Since the present invention has the above-mentioned structure,
The effects described below can be achieved.

According to the first and second aspects of the present invention, the silicon nitride film is locally oxidized by using, for example, an ionic species or a chemically active species that can be locally generated by controlling an excitation source. By drawing a pattern by this, the locally oxidized portion was removed to form a concave region, and then the silicon nitride surface was covered with silicon dioxide to grow a solid in the concave region. The pattern drawing in the case of selectively growing a solid on the upper surface can be easily performed at high speed, high resolution, and low cost by utilizing the property of the lower silicon nitride film. It can be performed with sufficient selectivity by taking advantage of the properties of silicon. As a result, selective growth of a solid on a nanometer scale can be performed with high precision and in a short time.

Further, in the third aspect of the invention, since the local oxidation to the silicon nitride film is performed by using the conductive needle, the pattern drawing can be performed more directly.
It can be performed at high speed and high resolution. Further, the device is simpler and easier to operate than the electron beam drawing device, and therefore, drawing can be performed easily at low cost.

[Brief description of drawings]

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

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

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

[Explanation of symbols]

1 base material 2 Silicon nitride layer 3 Locally oxidized part 5 Silicon dioxide layer 6 oxide film 7 Solid, Silicon 9 concave area 9a bottom

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification symbol FI H01L 21/318 H01L 21/318 B (72) Inventor Satoshi Yamazaki 1-4-1 Higashi, Tsukuba-shi, Ibaraki Industrial Technology Institute Area Research Institute (72) Inventor Kaoru Taiwan Taiwan Xinchu 300 National Shin-Ha University Department of Physics (56) References JP-A-11-260811 (JP, A) JP-A-4-290232 (JP, A) JP-A-2-33918 (JP, A) JP-A-1-259526 (JP, A) JP-A-2-105441 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/205 B82B 3/00 C23C 16/30 H01L 21/316 H01L 21/318

Claims (3)

(57) [Claims] 1. A solid selective growth method for selectively growing a solid in a defined region on a base material, wherein a silicon nitride film formed on the base material is locally oxidized according to a desired pattern. To form a locally oxidized portion, and the locally oxidized portion is removed by etching to form a concave region where the base material is exposed at the bottom, and the surface of the silicon nitride film having the concave region formed on the base material is silicon dioxide. To form a two-layered mask, expose the base material again to the bottom of the recessed region simultaneously oxidized by the coating with silicon dioxide to form a defined region, and selectively grow a solid in the defined region. A solid-state selective growth method characterized by: 2. The local oxidation to the silicon nitride film is carried out by using an ionic species or a chemically active species locally generated by controlling an excitation source. The solid-state selective growth method described. 3. The local oxidation to 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 solid selective growth method according to Item 1.