JPH06177055A - Manufacture of polycrystalline silicone layer - Google Patents

Abstract

PURPOSE:To reduce crystal defect by supplying atom-shaped hydrogen generated separately from a compound feed gas to the surface of a substrate and then supplying the compound feed gas to the surface of the substrate for depositing a polycrystalline silicon layer on the surface of the substrate alternately. CONSTITUTION:In a process for depositing poly-Si: H layer 12, hydrogen molecule gas which is formed while SinH2 polymer grows is thermally released from a deposition layer. Then, combination hydrogen forming Si-H combination lurking inside near the surface of a deposition layer is released chemically from Si network at a low temperature by operating active atom-shaped hydrogen or atom-shaped deuterium which is supplied from the inside of a vapor without using operation by heating. Then, it is formed as H2 molecule and at the same time is thermally released from the deposition layer, thus recombining silicon atoms which exist in proximity after losing combination hydrogen atom for relaxing structure. By repeating it for a plurality of times, crystallization can be promoted and at the same time generation of a grain boundary can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ULSI equipped with a Bi-CMOS device having both low power consumption and high speed, a three-dimensional structure device in which functional devices such as a sensor device, a calculation device, and a memory are stacked, and an electronic exchange. (Silicon On Insula), which is the next-generation semiconductor integrated circuit technology for high-voltage devices such as electric discharge type printers and power transistors for plasma displays.
The present invention relates to a method for producing a polycrystalline silicon layer used in the fields of forming technology and micromachining technology, and particularly to a method for producing a low defect polycrystalline silicon layer having device quality on an amorphous insulator film. .

[0002]

2. Description of the Related Art Conventionally, polycrystalline and monocrystalline functional films such as semiconductor films, insulating films, photoconductive films, magnetic films, and metal films have been individually selected from the viewpoint of desired physical characteristics and intended use. A suitable forming technique is adopted.

For example, a recrystallization method, an epitaxial growth method, an insulating film burying method, a bonding method and the like are known as a method of manufacturing a polycrystalline silicon semiconductor layer in the SOI forming technique, and they are appropriately selected depending on the device structure to be formed. It is generally done. In particular, the epitaxial growth method has already been used as a method for producing a single crystal silicon layer on a single crystal silicon (hereinafter abbreviated as “c-Si”) substrate, and also on a single crystal material other than silicon or an insulating material. Crystalline silicon (hereinafter abbreviated as “poly-Si”. In the present application, microcrystalline silicon “μc-Si: H.
D "and amorphous silicon" a-Si: HD "are poly
-Do not fall into the category of Si. ) Is widely used as a layer manufacturing technique.

[0004]

Recently, in order to prevent the use of low-resistivity wiring materials and the deterioration of the characteristics of the devices formed in the lower layers due to the auto-doping and the outward diffusion, as the integration of LSIs has increased in recent years, Realization of low process temperature is desired. Moreover, since it is used as a semiconductor layer of an integrated circuit in an SOI structure, it is desired in practical use that semiconductor characteristics such as electron and hole mobilities are as high as that of a single crystal. It is desirable that the density of crystal defects such as grains and sub-grain boundaries is as low as that of a single crystal. In addition, it is desired in practical use that the threshold dispersion due to crystal anisotropy is small and the characteristic variation is small, and it is preferable that the crystal orientation is controlled.

A method for producing polycrystalline silicon at low temperature and
Then, for example, Classen (W.A.P.
en) et al. magazine “Journal Electrochemical So
Society (J. Electrochem. So
c. ) ”Vol. 128, No. 6 (1981) 1353-
There is a method announced on page 1359. According to this
Pressure phase growth method (Low Pressure-CVD method,
(Hereinafter abbreviated as LP-CVD method)
Monosilane (SiH_Four) As water as carrier gas
By using the element, even at a low temperature of about 600 ℃
Silicon oxide (Si₃N _Four) Selective growth on the film is possible
And high crystal nucleation density has been reported.
It Monosilane gas is currently a by plasma CVD method
Widely used in the semiconductor industry as a raw material for forming Si: H films
Has been used in Near the substrate in the LP-CVD method
By pyrolyzing this side by side, SiH as a precursor₂Boom
Are generated. SiH₂Radicals are c-Si substrates
If the substrate surface is covered with Si atoms,
Adsorbed on SiH₂-Si bond formation. One of the substrate surface
Part is Si₃N_FourSiH if covered with layers₂La
Zical is preferentially adsorbed on surface nitrogen atoms, forming Si nuclei.
Increases density. On the other hand, SiO₂When covered with layers
Hydrogen molecules are preferentially adsorbed on Si atoms and Si-
SiH for coating with OH group₂Prevents radical adsorption
Been Si₃N_FourSelectivity occurs between layers. At low temperature
The growing poly-Si layer is hydrogen
Su (H₂) Is emitted while Si_nH₂(N is an integer) Poly
Grows as a mer, but combines with Si atoms in the growth layer
These hydrogen atoms are not removed at low temperature, so these crystals
Even if the nuclei coalesce to form a poly-Si layer, hydrogen atoms
A large amount of hydrogenated polycrystalline silicon compound (hereinafter referred to as "p
"Oly-Si: H". ) Form a layer. this
As a result, a large amount of bound hydrogen exists at the interfaces such as grain boundaries.
A low-quality poly-Si layer with many pits is formed.

In order to remove these crystal defects, generally, after forming the poly-Si layer, annealing treatment is carried out in a high temperature atmosphere of about 1000 ° C. to thermally desorb the bonded hydrogen and to relax the structure between Si atoms. It has been generally attempted to promote it, but needless to say, it is not preferable for the purpose of a low temperature process. On the other hand, plasma C
By heating the a-Si: H film deposited by the VD method to a temperature of 370 ° C. or higher, the contained hydrogen molecules are desorbed to the outside of the film, and when heated to a temperature of 600 ° C. or higher, Si dangling bonds are compensated. It is known that the hydrogen atoms in the film are also dissociated and gradually released to the outside of the film, and the hydrogen in the film disappears completely at a temperature of 800 ° C. or higher. Therefore, a-Si: H
Attempts have been made to anneal the film at a low temperature of about 400 to 600 ° C. to promote crystallization.
Under the present circumstances, since the hydrogen atom bonded to the i atom cannot be completely removed, the hydrogen atom is contained and the region of the microcrystalline structure is not exited. In addition, there is a problem that the device in the lower layer is damaged by the ions from the plasma. Further, there are some examples such as the molecular beam epitaxy method (MBE method) which has already been proved to be capable of crystal growth at a low temperature, but it is a forming method in an ultra-high vacuum chamber and has a cost problem. .

When used as a semiconductor device, it is preferable that the crystal orientation of the poly-Si layer formed as described above is uniform. In the epitaxial growth, there is a phenomenon in which the Si crystal nuclei growing due to the temperature at the time of formation freely rotate in the plane around the crystal axis shared with the site and take many orientations. When the nucleation surface used has an amorphous structure, this problem is more serious because the sites exposed on the surface have no regularity. It is known that almost 100% of Si crystal nuclei have a (110) plane orientation when the temperature at the time of formation becomes a low temperature of about 610 ° C. or less, but annealing at a high temperature again or the temperature at the time of formation is 700 ° C. About half (10
It is known to grow as crystal nuclei having a 0) plane orientation. Therefore, if the temperature at the initial stage of nucleation is set to 610 ° C. or lower, there is a possibility that the plane orientation can be controlled to (110). However, under the condition that the nucleation density is relatively low, there is a problem that the grain boundaries are generated because the nuclei generated from the individual sites grow before the coalescence between the crystal nuclei is achieved. However, as introduced earlier, S as a nucleation surface
When SiH ₄ —H ₂ based source gas is pyrolyzed on the i ₃ N ₄ film to grow nuclei, the nucleation density increases as the temperature decreases and reaches about 10 ¹¹ cm ⁻² at about 600 ° C. Has been reported. On the contrary, the nucleation density on the SiO ₂ film is 10
^It drops to about ⁸ cm ^-2 . However, as described above, at such a low temperature, there is a problem that only a low-quality poly-Si: H layer containing hydrogen and having many crystal defects can be formed.

[0008]

In order to solve the above-mentioned problems, the present invention provides a substrate installed in the reaction vessel by thermally decomposing a compound source gas containing silicon as a main constituent element in the reaction vessel. In the method for producing a polycrystalline silicon layer, wherein a polycrystalline silicon layer is deposited on the substrate surface, the step of supplying atomic hydrogen or atomic deuterium generated separately from the compound source gas to the surface of the substrate; And a step of supplying the compound source gas and depositing a polycrystalline silicon layer on the surface of the substrate are alternately performed.

[0009]

The present invention will be described below based on embodiments.

In this embodiment, 400 to 6 in the reaction vessel are used.
In the vicinity of the substrate surface heated and held at a temperature of 50 ° C. (more preferably 450 to 610 ° C.), the silane-based source gas is thermally decomposed to generate a SiH ₂ precursor, and the SiN 2 layer is formed on the surface of the substrate. selectively adsorbing the Si _n H ₂ polymer is nucleated, coalescing this poly-Si: H
In the process of depositing layers, to thermally release hydrogen molecules gas conversion while Si _n H ₂ polymer grows from該堆laminate (first step). Next, this deposition is interrupted, and dissociation is performed at the temperature (400 to 650 ° C.) at which the deposition is presented,
Bonded hydrogen forming a Si-H bond, which is hidden inside the vicinity of the surface of the deposited layer, which is not released, is reacted with active atomic hydrogen or atomic deuterium supplied from the gas phase without using the effect of heating at low temperature. By chemically cutting off from the Si network and forming it as H ₂ molecule and simultaneously releasing it from the deposited layer, the adjacent hydrogen atoms that have lost the bonded hydrogen atoms are recombined to relax the structure ( Second step).

It should be noted that the dissociation of hydrogen molecules requires a high temperature of 1000 ° C. or higher. Therefore, as the active atomic hydrogen used here, one obtained by thermally decomposing the hydrogen gas introduced as the carrier gas together with the raw material gas is insufficient in its action. Here, apart from the source gas, hydrogen gas can be pyrolyzed at a high temperature and excited at a high frequency, but in terms of its energy and atomic hydrogen production density, it was excited by a microwave to be formed. It is most preferable to use one.

In this embodiment, by repeating the first step and the second step a plurality of times, crystallization promotion and prevention of grain boundary generation are achieved at the same time, and low defect poly-Si is obtained.
This is to realize a compound semiconductor layer. The thickness of the deposited layer formed at one time is the same as that of the Si _n H ₂ polymer.
It is desired that the thickness is such that the network does not solidify, and at the same time the atomic hydrogen penetrates and the molecular hydrogen that forms is passed through between the polymers and desorbed. Experimentally, it is preferable that the thickness of the silicon crystal is about several atomic layers in terms of the crystal plane spacing. More specifically, the film thickness of the polycrystalline silicon layer deposited per cycle is preferably 10 Å or less. The film thickness does not have to be the same for each cycle. For example, since the film thickness deposited in the first cycle acts as a seed layer, it may be a thickness of about a monoatomic silicon layer to several atomic layers, and from the second cycle it is formed as a polycrystalline silicon layer. The thickness of the polycrystalline silicon layer to be deposited may be changed for each cycle such that the film is deposited with a film thickness of the cycle or more.

The supply of atomic hydrogen to the surface of the substrate at the initial stage of nucleation exerts a special action other than the above. In general, the mobility of the precursor on the surface of the substrate decreases at low temperatures, so that defects due to abnormal growth tend to occur. Covering the surface of the substrate with hydrogen enhances the mobility of the precursor on the surface of the Si ₃ N ₄ film, makes it easier to reach the most stable site, and acts to help the formation of complete crystal nuclei. On the other hand, since the occupation of stable sites is promoted on the SiO ₂ film, it has an action of preventing adsorption of the SiH ₂ precursor and preventing nucleation.

Further, as described above, nucleation on a Si ₃ N ₄ film at a low temperature of 610 ° C. or lower using a silane-based source gas is effective for controlling the crystal orientation. However, if the temperature is 650 ° C. or lower, Si crystal nuclei whose crystal orientation is controlled to some extent can be obtained. Increase the number of surface stable sites, increase the degree of supersaturation of the precursor supplied,
The increase in the surface mobility of the precursor due to the surface hydrogen coating promotes the growth and coalescence by the closely-closed two-dimensional nuclei that take the easy orientation of the (110) plane in the early stage of nucleation, and even if the (100) plane orientation is Even if the crystal nuclei possessed by it appear, it has a function of rearranging it on the (110) plane. This allows
A monoatomic layer of Si (110) surface grows on the Si ₃ N ₄ seed and becomes a Si nucleation surface of Si epitaxial growth perpendicular to the subsequent surface. As a result, even if a nucleation surface made of an amorphous material is used, low defect poly-
A Si layer can be formed.

That is, the material for the nucleation surface, the source gas, the substrate temperature, and the repeated treatment with atomic hydrogen are important requirements for achieving the object of the present invention.

Since the epitaxial deposition in the present embodiment example is carried out on the amorphous silicon nitride film, the substrate material is not limited to the single crystal silicon substrate, but a substrate material that can withstand the processing temperature of the present invention. However, a single crystal GaAs substrate or a heat-resistant glass substrate having a different lattice constant from silicon may be used. The present invention is not limited to the case where the poly-Si layer is formed on the amorphous silicon nitride film. For example, the present invention is also applied to the case where a poly-Si layer is formed on a substrate such as a c-Si substrate in which a thin μc-Si film or an a-Si film is formed on a SiO ₂ coating film.

The compound raw material gas is typically a silane-based gas, preferably monosilane (SiH ₄ ) gas, S.
iD ₄ gas can be used, and if necessary, an inert gas such as hydrogen (H ₂ ) gas, deuterium (D ₂ ) gas, or argon can be used as a carrier gas.

[0018]

Embodiments of the present invention will be described in detail below with reference to the drawings. (Embodiment 1) In carrying out the present invention, first, as shown in FIG. 2, Si is formed on a (100) plane c-Si wafer 1.
_{The 3} N ₄ film 2a was vapor-deposited to prepare the substrate 3a. The substrate 3
After cleaning a, a disc type LP-CVD as shown in FIG.
Set on the susceptor 5 of the furnace 4, and set the entire furnace to 10 ^-5 Torr.
Then, the high frequency coil 6 was simultaneously energized to heat the susceptor 5 to heat and hold the substrate 3a at 550 ° C. Then, hydrogen gas is supplied from the hydrogen gas supply pipe 7 to the applicator type microwave discharge tube 8 at a rate of about 500 cc / min, and the microwave oscillator 9 is energized to generate hydrogen plasma in the discharge tube 8 to dissociate the hydrogen gas. To produce atomic hydrogen. This atomic hydrogen is emitted from the discharge nozzle 10 at 2 × 10 ⁻¹ T
It was introduced into the CVD furnace 4 adjusted to a vacuum degree of orr and sprayed onto the surface of the substrate 3a. After being exposed to atomic hydrogen for 20 seconds, the supply of hydrogen gas is interrupted, and then silane gas and hydrogen gas are supplied from the source gas supply pipe 11 at a rate of 30 minutes per minute, respectively.
0 and 100 cc of each are mixed and supplied into the CVD furnace 4, and thermally decomposed near the surface of the substrate 3a to form the poly-Si: H layer 1.
2 is deposited to a film thickness of 10Å. Next, the supply of the raw material gas is stopped and the atomic hydrogen is supplied again. By processing for 20 seconds, the bound hydrogen in the film is released to the outside of the film as hydrogen gas and desorbed to form the poly-Si layer 13. These operations were repeated 600 times to deposit a poly-Si layer having a thickness of about 5000Å. In Figure 1, poly-S
The layer structure during the deposition of the i film is shown. In the figure, 13 indicates each poly-Si layer from which hydrogen molecules have been released, and 12 indicates a poly-Si: H layer deposited on the poly-Si layer containing in-film bound hydrogen. After the atomic hydrogen treatment of the top layer is completed, pol
The y-Si film deposition process is completed. After cooling, it was taken out into the atmosphere and evaluated for crystal quality. The crystal structure had a Raman scattering half-value width of about 8 cm ⁻¹ and was oriented in the (220) plane. Moreover, a clear Kikuchi line was observed, and Si having good crystallinity was formed. In addition, crystal defects such as fine twins and sub-grain boundaries were not observed by cross-sectional TEM (transmission electron microscope) observation from the cross-sectional direction. Also, no crystal defect was observed at the Si ₃ N ₄ interface. In addition, in the measurement by the FT-IR method (infrared absorption spectroscopy), it was confirmed that a low-defect poly-Si film was formed because the presence of bonded hydrogen in the film was not confirmed. (Example 2) Next, selective growth by the substrate material was examined. As shown in FIG. 4 instead of the substrate shown in FIG.
After the Si ₃ N ₄ film 2b was vapor-deposited and patterned on the surface c-Si wafer 1, the substrate 3b was prepared by further vapor-depositing the SiO ₂ film 14 and patterned. Next, a poly-Si layer was formed by the same process as in Example 1. pol
The y-Si layer 13b slightly covers the region of the SiO ₂ film 14, but the y-Si layer 13b is formed by ELO (epitaxial lateral 1).
In contrast to the appearance observed with polycrystalline silicon compound layers deposited in the over-growth method, Si
_It was grown almost vertically on the ₃ N ₄ film 2b. Figure 6
-The layer shape in the middle of Si film deposition is shown. When this was observed by a cross-sectional TEM in the same manner as in Example 1, it was found to be pol.
No crystal defect was observed in the y-Si layer. This is because the formation of Si crystal nuclei on the SiO ₂ film was prevented by the atomic hydrogen treatment, and the Si atomic layer formed on the Si ₃ N ₄ film at the initial stage of deposition forms the (110) plane. It is considered that (100) having a high growth rate does not become a facet, and vertical (110) side faces are obtained. (Embodiment 3) Further, the effect of the atomic deuterium treatment was examined by using the substrate 3b of the same type as that of Embodiment 2. In this case, the same steps and operations as in Example 2 were carried out except that deuterium gas was passed through the applicator type microwave discharge tube 8 to excite it. The deposited poly-Si layer had the same shape as in Example 2, and no defect was confirmed.

Further, in order to investigate the effect of the substrate temperature at the time of depositing the poly-Si layer, the substrate was heated and held at 350 ° C. and 700 ° C. respectively, and the same steps and operations as in Example 1 were performed on the Si ₃ N ₄ film. A poly-Si layer was deposited on. 35
When deposited at 0 ° C., hydrogen in the film was not confirmed by measurement by FT-IR method, and columnar S was observed by cross-sectional TEM observation.
The i crystal was growing. Similarly, in the poly-Si layer deposited at a substrate temperature of 700 ° C., although hydrogen in the film was not confirmed, countless crystal defects were observed.

[0020]

As described in detail above, according to the present invention, a low defect polycrystalline silicon layer having a crystal structure as close as possible to single crystal silicon at low temperature can be laminated on an insulating film. . Moreover, since the silane-based gas is used as the raw material gas, it can be manufactured at a low cost as compared with the conventional epitaxial growth of Si single crystal silicon at a high temperature. Moreover, the substrate surface is covered with the Si ₃ N ₄ film and Si.
It is also possible to selectively deposit a low-defect polycrystalline silicon layer in a desired region by patterning and covering with an O ₂ film, which is a main process for manufacturing future ULSI and high breakdown voltage devices. It is extremely effective in realizing the forming technology at low temperatures.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a poly-Si film showing a deposition process of the present invention.

FIG. 2 is a schematic sectional view of a substrate used in Example 1 of the present invention.

FIG. 3 is a schematic sectional view of an LP-CVD furnace suitable for carrying out the present invention.

FIG. 4 is a schematic cross-sectional view of a substrate used in another embodiment 2 of the present invention.

FIG. 5 is a schematic cross-sectional view showing a state of deposition of a poly-Si film.

[Explanation of symbols]

1 c-Si wafers 2a, 2b Si ₃ N ₄ film 3a, 3b substrate 4 LP-CVD furnace 5 susceptor 6 high frequency coil 7 hydrogen gas supply pipe 8 microwave discharge tube 9 microwave oscillator 10 discharge nozzle 11 source gas supply pipe 12 poly-Si: H layer 13 poly-Si layer 14 SiO ₂ film

Claims (13)

[Claims] 1. A method for producing a polycrystalline silicon layer, which comprises thermally decomposing a compound source gas containing silicon as a main constituent element in a reaction vessel and depositing the polycrystalline silicon layer on a substrate placed in the reaction vessel. A step of supplying atomic hydrogen or atomic deuterium generated separately from the compound source gas to the surface of the substrate,
A method for producing a polycrystalline silicon layer, which comprises alternately performing the step of supplying the compound source gas to the surface of the substrate to deposit the polycrystalline silicon layer on the surface of the substrate. 2. The method for producing a polycrystalline silicon layer according to claim 1, wherein the temperature of the substrate is heated and maintained in the range of 400 to 650 ° C. 3. The method according to claim 1, wherein atomic hydrogen or atomic deuterium is supplied to the surface of the substrate for processing before the step of depositing the polycrystalline silicon layer is started. Method for manufacturing polycrystalline silicon layer. 4. The method for producing a polycrystalline silicon layer according to claim 1, wherein a silane-based gas is used as the compound source gas. 5. A silane-based gas is used as the compound raw material gas, and a hydrogen-based gas or an inert gas is introduced as a carrier gas.
A method for producing a polycrystalline silicon layer as described. 6. The thickness of a deposition layer deposited at one time in the step of supplying the compound source gas to deposit a polycrystalline silicon layer on the surface of the substrate is 10 Å or less. A method for producing a polycrystalline silicon layer as described. 7. The method for producing a polycrystalline silicon layer according to claim 1, wherein the atomic hydrogen or atomic deuterium is produced by exciting hydrogen gas or deuterium gas with microwave energy. Method. 8. The method of manufacturing a polycrystalline silicon layer according to claim 1, wherein the substrate is a substrate whose surface is coated with a silicon nitride layer. 9. The method for producing polycrystalline silicon according to claim 1, wherein the surface of the substrate is patterned and covered with a silicon nitride film and a silicon oxide film. 10. The method for producing a polycrystalline silicon layer according to claim 9, wherein the silicon nitride film and the silicon oxide film covering the substrate have an amorphous structure. 11. The silicon nitride film and the silicon oxide film which cover the substrate are deposited on the substrate by a vapor phase growth method prior to the manufacturing step of the polycrystalline silicon layer. Method for manufacturing polycrystalline silicon layer. 12. The method for producing a polycrystalline silicon layer according to claim 9, wherein the substrate whose surface is coated with a patterned silicon nitride film and a silicon oxide film is a single crystal substrate. 13. The method for producing a polycrystalline silicon layer according to claim 1, wherein the substrate whose surface is coated with a patterned silicon nitride film and a silicon oxide film is a heat-resistant glass substrate.