JP3194547B2 - Method for manufacturing polycrystalline silicon layer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-dimensional structure device in which functional elements such as an ULSI, a sensor device, an arithmetic element, and a memory are mounted on which a Bi-CMOS device having both low power consumption and high speed is mounted, and an electronic switching device. SOI (Silicon On Insula), a next-generation semiconductor integrated circuit technology for high-voltage devices such as power-transistors, discharge-type printers, and power transistors for plasma displays
The present invention relates to a method for manufacturing a polycrystalline silicon layer used in the field of tor) forming technology and micro-machining technology, and more particularly to a method for manufacturing 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 a semiconductor film, an insulating film, a photoconductive film, a magnetic film, and a metal film are individually formed from the viewpoint of desired physical characteristics and applications. Suitable forming techniques are employed.

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

[0004]

In recent years, as the degree of integration of LSIs has increased, the use of low-resistivity wiring materials and the manufacture of devices formed in lower layers to prevent deterioration in characteristics due to auto-doping and outward diffusion have been promoted. It is desired to realize a low temperature process. In addition, since the SOI structure is used as a semiconductor layer of an integrated circuit, 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 crystal grains and sub-grain boundaries is as low as that of a single crystal. It is also desirable in practical use that the dispersion of the threshold value due to crystal anisotropy is small and the variation in characteristics is small, and it is preferable that the crystal orientation is controlled.

A method for producing polycrystalline silicon at a low temperature and
For example, Klassen (WAP Class)
en) et al. published the magazine “Journal Electrochemical So
Society (J. Electrochem. So
c. Vol. 128, No. 6 (1981), 1353-
There is a method published on page 1359. According to this
Low pressure-CVD method,
(Hereinafter abbreviated as LP-CVD method)
Monosilane (SiH_Four) With water as carrier gas
By using nitrogen, even at a low temperature of about 600 ° C,
Silicon (Si)_ThreeN _Four) Selective growth on film is possible
And high nucleation density.
You. Monosilane gas is currently available by plasma CVD.
-Widely used in the semiconductor industry as a raw material for forming Si: H films
Used in Near the substrate in LP-CVD
When this is pyrolyzed nearby, SiH is used as a precursor._TwoBoombox
Is generated. SiH_TwoRadicals are c-Si substrates
If the substrate surface is covered with Si atoms,
Adsorbed on SiH_Two-Form Si bonds. One of the substrate surface
Part is Si_ThreeN_FourSiH if covered by a layer_TwoLa
Dical preferentially adsorbs to nitrogen atoms on the surface, forming Si nuclei
Density increases. On the other hand, SiO_TwoWhen covered with layers
Means that hydrogen molecules are preferentially adsorbed on Si atoms and
SiH to cover with OH group_TwoBlocks radical adsorption
Being Si_ThreeN_FourSelectivity occurs between layers. At low temperatures
The poly-Si layer that grows and grows
(H_Two) While releasing Si_nH_Two(N is an integer)
Grow as a mer, but bond with Si atoms in the growth layer
Hydrogen atoms are not removed at low temperatures,
Even if the nuclei unite to form a poly-Si layer,
Hydrogenated polycrystalline silicon compounds containing a large amount (hereinafter referred to as "p
poly-Si: H ". ) Form a layer. this
Crystal defects due to the presence of a large number of bonded hydrogen at interfaces such as grain boundaries
A low-quality poly-Si layer having many defects is formed.

In order to remove these crystal defects, generally, after forming a poly-Si layer, annealing is performed in a high-temperature atmosphere of about 1000 ° C. to thermally desorb bonded hydrogen and to relax the structure of Si atoms. Acceleration is generally attempted, but needless to say, is not desirable for purposes of low temperature processing. On the other hand, plasma C
When the a-Si: H film deposited by the VD method is heated to a temperature of 370 ° C. or more, the contained hydrogen molecules are desorbed outside the film, and when heated to a temperature of 600 ° C. or more, the Si dangling bond is compensated. It is known that the bonded hydrogen atoms in the film are also dissociated and gradually released out of the film, and the hydrogen in the film completely disappears at a temperature of 800 ° C. or more. Therefore, a-Si: H
Attempts have been made to promote crystallization by annealing the film at a low temperature of about 400 to 600 ° C.
At present, since hydrogen atoms bonded to i atoms cannot be completely removed, they contain hydrogen atoms and do not leave a region of a microcrystalline structure. In addition, there is a problem that the lower device is damaged by ions from the plasma. Further, there is an example in which crystal growth at a low temperature is already possible as in a molecular beam epitaxy method (MBE method), 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 poly-Si layers formed as described above have the same crystal orientation. In the epitaxial growth, there is a phenomenon that a Si crystal nucleus that grows freely rotates in a plane around a crystal axis shared with a site depending on a temperature at the time of its formation, and takes many orientations. When the nucleation surface to be used has an amorphous structure, this problem is more serious because 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. If you raise it to about half, about half (10
0) It is known that they grow as crystal nuclei having a plane orientation. Therefore, if the temperature at the initial stage of nucleation is 610 ° C. or lower, there is a possibility that the plane orientation can be controlled at (110). However, under the condition that the nucleation density is relatively low, there is a problem that nuclei generated from individual sites grow before coalescence between crystal nuclei is achieved, so that grain boundaries are generated. However, as introduced earlier, S as a nucleation surface
When a nucleus is grown on an i ₃ N ₄ film by pyrolyzing a SiH ₄ —H ₂ -based source gas, the nucleation density increases as the temperature decreases, reaching about 10 ¹¹ cm ^-2 at about 600 ° C. Have been reported. Conversely, 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-grade poly-Si: H layer containing hydrogen and having many crystal defects can be formed.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is directed to a method of thermally decomposing a compound raw material gas containing silicon as a main constituent element in a reaction vessel to form a substrate provided in the reaction vessel. In a method of manufacturing a polycrystalline silicon layer on which a polycrystalline silicon layer is deposited, the substrate has a surface formed of silicon nitride.
And a temperature of the substrate is from 400 ° C. to 650 ° C.
℃ range, the polycrystalline silicon layer is deposited
Prior to starting the stacking step, the silicon nitride layer
Supplying atomic hydrogen or atomic deuterium to the surface
Perform processing and supply the compound source gas to the substrate surface
Depositing a polycrystalline silicon layer on the surface of the substrate
And atomic hydrogen or atomic deuterium on the surface of the substrate.
And alternately performing the step of supplying the liquid crystal.

[0009]

The present invention will be described below based on embodiments.

[0010] In this embodiment, 400 to 6
In the vicinity of the substrate surface heated and held at a temperature of 50 ° C. (more preferably 450 to 610 ° C.), a silane-based source gas is thermally decomposed to generate a SiH ₂ precursor, and the surface of the silicon nitride layer formed on the substrate is formed. Selectively adsorb to nucleate the Si _n H ₂ polymer, which is combined to form poly-Si: H
In the process of depositing the layer, hydrogen molecule gas that forms during the growth of the Si _n H ₂ polymer is released from the deposited layer by heat (first step). Next, the deposition is interrupted, and dissociation occurs at a temperature of about the suggested value (a temperature of 400 to 650 ° C.).
The bonded hydrogen forming a Si-H bond lurking in the vicinity of the surface of the deposited layer that is not released is reacted with active atomic hydrogen or atomic deuterium supplied from the gas phase without using the action of heating at a low temperature. By chemically dissociating from the Si network, forming it as H ₂ molecules, and simultaneously releasing it from the deposited layer, the adjacent silicon atoms that have lost the bonded hydrogen atoms are recombined and relaxed ( Second step).

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 hydrogen gas introduced together with the raw material gas as a carrier gas is insufficient in its function. Here, apart from the source gas, it is possible to thermally decompose hydrogen gas at a high temperature or to excite it at a high frequency.However, in terms of its energy and atomic hydrogen generation density, it was formed by microwave excitation. It is most preferred to use one.

In this embodiment, the first step and the second step are repeated a plurality of times, thereby simultaneously promoting crystallization and preventing the generation of grain boundaries, thereby achieving low defect poly-Si.
This realizes a compound semiconductor layer. The thickness of the deposited layer formed at a 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 thickness is such that the atomic hydrogen penetrates and the formed molecular hydrogen passes through the polymer and is released. Experimentally, it is preferable that the silicon crystal has a thickness of about several atomic layers at a crystal plane interval. More specifically, the thickness of the polycrystalline silicon layer deposited per cycle is desirably 10 ° or less. It is not necessary that the film thickness in each cycle be the same. For example, since the film thickness deposited in the first cycle acts as a seed layer, it may have a thickness of about a monoatomic layer of silicon to about several atomic layers. The thickness of the polycrystalline silicon layer deposited in each cycle may be changed such that the film is deposited with a film thickness of the cycle or more.

The supply of atomic hydrogen to the substrate surface at the beginning of nucleation also exerts a special action other than the above. Generally, the mobility of the precursor on the substrate surface decreases at a low temperature, so that defects due to abnormal growth are likely to occur. Covering the substrate surface with hydrogen increases the mobility of the precursor on the surface of the Si ₃ N ₄ film, facilitates reaching the most stable site, and helps to form a complete crystal nucleus. On the other hand, since the occupation of stable sites is promoted on the SiO ₂ film, it has an effect of preventing nucleation by preventing adsorption of the SiH ₂ precursor.

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

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

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

The compound source gas is typically a silane-based gas, preferably a monosilane (SiH ₄ ) gas,
An 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 below in detail with reference to the drawings. (Embodiment 1) In carrying out the present invention, first, as shown in FIG.
The ₃ N ₄ film 2a is deposited, was prepared substrate 3a. The substrate 3
a, and then disc-type LP-CVD as shown in FIG.
It is set on the susceptor 5 of the furnace 4 and the whole furnace is 10 ^-5 Torr
Then, the high-frequency coil 6 was energized to heat the susceptor 5, and the substrate 3a was heated and maintained at 550 ° C. Next, a 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 electricity is supplied to the microwave oscillator 9 to generate hydrogen plasma in the discharge tube 8 to dissociate the hydrogen gas. To produce atomic hydrogen. This atomic hydrogen is discharged from the discharge nozzle 10 to 2 × 10 ⁻¹ T
It was introduced into the CVD furnace 4 adjusted to a vacuum degree of orr and sprayed on the surface of the substrate 3a. After exposure to atomic hydrogen for 20 seconds, the supply of hydrogen gas was interrupted, and then silane gas and hydrogen gas were supplied from the raw material gas supply pipe 11 at a rate of 30 minutes per minute.
The poly-Si: H layer 1 is mixed at a rate of 0, 100 cc and supplied into the CVD furnace 4 and thermally decomposed near the surface of the substrate 3a.
2 is deposited to a thickness of 10 °. Next, supply of the source gas is stopped, and atomic hydrogen is supplied again. By performing the treatment for 20 seconds, the bound hydrogen in the film is released as a hydrogen gas out of the film 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 5000 °. In FIG. 1, poly-S
The layer configuration during the deposition of the i film is shown. In the drawing, reference numeral 13 denotes each poly-Si layer from which hydrogen molecules have been released, and reference numeral 12 denotes a poly-Si: H layer containing a bonded hydrogen in a film deposited thereon. After the atomic hydrogen treatment of the top layer is completed, pol
The step of depositing the y-Si film is completed. After cooling, it was taken out into the atmosphere and the crystal quality was evaluated. The crystal structure had a half-width of Raman scattering of about 8 cm ^-1 and was oriented in the (220) plane. Moreover, a clear Kikuchi line could be observed, and Si having good crystallinity was formed. Further, no crystal defects such as fine twins and sub-grain boundaries were observed by cross-sectional TEM (transmission electron microscope) observation from the cross-sectional direction. No crystal defects were observed at the Si ₃ N ₄ interface. In addition, in the measurement by the FT-IR method (infrared absorption spectroscopy), the presence of bonded hydrogen in the film was not confirmed, so that it was confirmed that a low defect poly-Si film was formed. (Example 2) Next, selective growth using a 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 deposited and patterned on the surface c-Si wafer 1, the substrate 3b was prepared by depositing the SiO ₂ film 14 and patterning. Next, a poly-Si layer was formed in the same process as in Example 1. pol
The y-Si layer 13b slightly covers the region of the SiO ₂ film 14, but has an ELO (epitaxial latera 1).
Unlike the appearance observed with a polycrystalline silicon compound layer deposited in the over-growth method,
It is grown substantially vertically on ₃ N ₄ film 2b. FIG. 5 shows poly.
-Shows the layer shape during the deposition of the Si film. This was observed with a cross-sectional TEM from the cross-sectional direction in the same manner as in Example 1.
No crystal defects were 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. This is probably because (100) having a high growth rate does not become a facet and a vertical (110) side surface is obtained. Example 3 The effect of the atomic deuterium treatment was examined using a substrate 3b of the same type as that of Example 2. In this case, the same steps and operations as those in Example 2 were performed, except that deuterium gas was supplied to the applicator-type microwave discharge tube 8 to excite the same. The deposited poly-Si layer had the same shape as in Example 2, and no defects were confirmed.

Further, in order to examine the effect of substrate temperature during the poly-Si layer deposition, 350 ° C. and same process as in Example 1 by heating and holding the substrate respectively 700 ℃, Si ₃ N ₄ film by the operation Was deposited with a poly-Si layer. 35
When deposited at 0 ° C., no bonded hydrogen was found in the film when measured by the FT-IR method.
An i crystal was growing. Similarly, in the poly-Si layer deposited at a substrate temperature of 700 ° C., no bonded hydrogen was confirmed in the film, but countless crystal defects were observed.

[0020]

As described above in detail, according to the present invention, a low-defect polycrystalline silicon layer having a crystal structure as close as possible to single-crystal silicon can be formed on an insulating film at a low temperature. . In addition, since a silane-based gas is used as a raw material gas, it can be manufactured at an extremely low cost as compared with the conventional high temperature epitaxial growth of single crystal silicon. In addition, the substrate surface is made of 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, and SOI, which is a main process for manufacturing future ULSIs and high breakdown voltage devices, will be described. It is extremely effective in realizing the forming technique at a low temperature.

[Brief description of the drawings]

FIG. 1 is a schematic 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 Embodiment 1 of the present invention.

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

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

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

[Explanation of symbols]

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

Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) H01L 21/205 C30B 25/14 H01L 21/84 H01L 27/12

Claims (6)

(57) [Claims] 1. A compound source containing silicon as a main constituent element.
Gas is decomposed by heating in a reaction vessel and installed in the reaction vessel.
To deposit a polycrystalline silicon layer on a patterned substrate
In the method for manufacturing a capacitor layer, the substrate has a silicon nitride layer on a surface thereof, and the temperature of the substrate is low.
The substrate is heated to a temperature in the range of 400 ° C. to 650 ° C., and before the step of depositing the polycrystalline silicon layer is started, atomic hydrogen or atomic deuterium is supplied to the surface of the silicon nitride layer. Performing a process , supplying the compound source gas to the substrate surface,
Depositing a polycrystalline silicon layer on the surface and adding atomic water
Supplying elemental or atomic deuterium to the surface of the substrate
And a step of alternately performing the steps . 2. A compound source containing silicon as a main constituent element.
Gas is decomposed by heating in a reaction vessel and installed in the reaction vessel.
To deposit a polycrystalline silicon layer on a patterned substrate
The method of manufacturing a Con layer, the substrate surface is coated and patterned with silicon nitride film and a silicon oxide film, wherein the compound feed gas is separately generated atomic hydrogen
Or supplying atomic deuterium to the surface of the substrate;
Supplying the compound source gas to the substrate surface and nitriding
Step of depositing a polycrystalline silicon layer on a silicon film surface
And polycrystalline silicon characterized by alternately performing
The method of manufacturing the layer. 3. The method for producing a polycrystalline silicon layer according to claim 2, wherein the substrate silicon nitride film and a silicon oxide film covering the can and having an amorphous structure. The method according to claim 4, wherein the substrate silicon nitride film and a silicon oxide film covering the polycrystalline prior to the manufacturing process of the silicon layer by a vapor growth method according to claim 2, characterized in that deposited on said substrate A method for manufacturing a polycrystalline silicon layer. 5. A substrate coated with the surface patterned silicon nitride film and a silicon oxide film, method for producing polycrystalline silicon layer according to claim 2, characterized in that the single crystal substrate. 6. The method according to claim 2 , wherein the substrate whose surface is covered with a patterned silicon nitride film and a silicon oxide film is a heat-resistant glass substrate.