JPS6254462A - Manufacture of semiconductor substrate - Google Patents

Abstract

PURPOSE:To built a single-crystal layer without degrading the flatness of an insulating layer by a method wherein a heat-rejecting layer is provided in a gap in an insular semiconductor layer for the prevention of heat from reaching the substrate during a process of fusion and recrystallization. CONSTITUTION:The surface of an Si substrate 1 is exposed to heat for oxidation. On the resultant oxide film 2, a polycrystalline Si layer is formed, which is subjected to patterning. Si islands 3 are linked with each other by Si joints 4 and the direction of their linkage is designed to correspond to the direction of recrystallization to follow a later process of zone melting. A column of Si islands 3 is separated from a neighboring column of Si islands 3 by an oxide film formed between the linked islands 3 and by the groundwork oxide film 2. The entire surface is covered with an SiO2 film 20, whereafter zone melting recrystallization is accomplished. The polycrystalline Si islands 3 and Si joints 4 melt to absorb heat and the gaps created by the SiO2 layer 5 between the Si islands 3 are small, which prevents the transfer to the substrate 1 of so much heat as to cause the substrate 1 to melt. This design results in single- crystal semiconductor islands built on a flat-surface substrate after recrystallization.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a substrate having a single crystal semiconductor layer of high crystal quality on an insulator, a so-called SOI (5 silicon I).
The present invention relates to a method of manufacturing a (n5ulator) substrate.

[Background of the invention]

One of the known methods for forming a single crystal semiconductor of high crystal quality on an insulating substrate is to melt and recrystallize a polycrystalline or amorphous conductor layer deposited on an insulating substrate. There is.

For example, [IFiEE electron device letters (IFiEE glectronD
evice Letters) J EDL-Volume 2, 1
B published on page 241 of No. 0 (1981),
[MO8FBT (MO8FFiT) fabricated in silicon formed by recrystallizing coated polycrystalline silicon on an insulating substrate by zone melting.
's on 5iliconPrepared by
Moving Melt Zone Recrysta
ll-ization of Encapsulate
dPolycrystallineSilicon
on an Ir+sulating
The zone melting method described in J. 5Ubstrate is one method of melt recrystallization. According to this method.

Crystallization 8i with (100) plane orientation is obtained.

Here, the melt recrystallization method will be briefly explained.

FIGS. 2(a), 2(b), and 2(c) are schematic diagrams showing the zone melting recrystallization process used by the present inventors.

Six long slender protrusions are provided at the center of the carbon susceptor 6, which is a heating element for high-position wave induced heat, and a thin carbon plate 7 as a heat shield is placed in the recessed part, and the surface of the carbon susceptor 6 is The temperature distribution of is as shown in Figure 2 (C),
It has a high temperature peak part 9 in the center.

Therefore, when the insulating substrate 8 having a polycrystalline silicon (8i) film on the surface is placed on the carbon susceptor 6 and slid, the polycrystalline Si layer on both temperature peaks 9 melts and the wafer 8 moves (arrow 1o direction), the m-melting portion 11 moves relatively, and zone melting recrystallization progresses.

In addition, [Journal of the Electrochemical Society]
electrochemical 5ociety)
rMO by Y. Kobayashi et al., published in Jl Vol. 31, No. 5 (1984), p. 1188.
RF recrystallization of polycrystalline silicon on m-fused silica for 8FETs
PolycrystallineSiliconF
usedSilicaforMO8FgTDevice
s) Connection pattern (con) as described in J.
(ne-cted 1sland pattern), an island of single crystal silicon with a (100) plane orientation is obtained.

However, this Shiojima pattern was developed using zone melting using an 8i (silicon) substrate (an insulating layer was formed on the surface by oxidizing the surface of the Si substrate) instead of an insulating substrate made of quartz. When applied.

Heat is easily transmitted from the gap where the connecting part is not placed to the 81 substrate side, melting the Si substrate under the insulating layer, and the Si underlying the single-crystal connecting part tends to melt.
It has been found that there is a new problem in that significant unevenness occurs in the 81.
Polycrystalline S disposed on substrate 1 with oxide film 2 interposed therebetween.
The i islands 3 (or their connecting parts 4) are not densely patterned - in other words, the polycrystalline Si islands 3 are sparsely arranged, and where there are no Si islands 3 there is an insulating layer (e.g. , 8i02 layer 5 and Cv by partial thermal oxidation of Si
Suppose that it is covered by 8i0,20 due to D.

Heating during zone melting recrystallization is shown in Figure 3 (a).
This is done from above, as shown by arrow 12. Therefore, in the area where the polycrystalline Si island 3 is located, as the polycrystalline Si island 3 melts, heat corresponding to its latent heat is removed.
The heat applied to the Si substrate 1 through the underlying oxide film 2 decreases and does not melt 8i on the substrate side.

However, in the absence of the Si island 3, the heat is only slightly reduced as it is conducted through 8i0°1x5 and 20, so that sufficient heat is provided to the Si substrate 1 to melt it. Therefore, the 81 substrate is melted from a place where such a Si island 3 is not present. and.

The melt 8i has irregularities due to surface tension, and when the recrystallization process is completed, it loses its flatness as shown in FIG. 3(b). In addition, in FIG. 3(b), 13 is a recrystallized Si island.

It is clear that if the underlying Si loses its flatness and becomes uneven, it will become a major hindrance in the subsequent device fabrication process. for example.

Decrease in resolution in one step of Hol-IJ lithography.

The accompanying deterioration of dimensional accuracy, @ line, etc. at stepped portions is likely to occur. [Object of the Invention] The object of the present invention is to Another object of the present invention is to provide a method for forming the single crystal layer while maintaining the flatness of the insulator.

[Key points of invention]

As mentioned earlier, when zone melting recrystallization is performed using the connection pattern using an oxidized SI substrate surface as an insulator, the substrate S1 under the oxide film melts and the flatness of the underlying layer is reduced. However, due to zone melting, the recrystallized layer forms a layer of polycrystalline Si that covers the entire surface of the substrate.
If it was a layer.

The difference is that the flatness is almost maintained.

As a result of examining the cause of the difference between the two, the present inventors arrived at the idea that it is due to a difference in the heat cage applied to the Si substrate underlying the insulator.

In other words, if the entire surface of the substrate is covered with polycrystalline 8i, when the polycrystalline Si melts, it absorbs latent heat, and the oxidized M underneath it absorbs latent heat.
The heat applied to the (insulator) and the substrate Si below it is reduced, making it difficult for the substrate SL to melt.

On the other hand, when the polycrystalline Si on the oxide film forms a connection pattern, the latent heat is taken away in the island part, but the latent heat is not taken away in the part without the island, so a large amount of heat is transferred to the substrate Si through the oxide film. , its temperature will rise too much and it will melt.

Therefore, in order to prevent the underlying substrate Si from melting, it is found that it is necessary to provide a layer that absorbs heat (7:l) or blocks heat conduction in areas where there are no connecting parts. . The present invention provides such a heat absorption or heat conduction blocking layer to prevent the underlying layer from melting and planarize it.

[Embodiments of the invention]

The present invention will be described in detail below with reference to the drawings. Embodiment 1 FIG. ) in A-B
FIG.

The surface of a Si substrate 1 with a thickness of 400 μm is oxidized by thermal oxidation to form an oxide film 2 with a thickness of 1 pfn on the 1 surface.

Furthermore, on top of that, polycrystalline 8i with a thickness of 0.5 μm is deposited by CVD.
(Chemical Vapor Deposit
on: formed by chemical vapor deposition).

Thereafter, a LOGOS island is formed by photolithography or the like, and a polycrystalline 8i layer is patterned as shown in FIG. 1(a). In addition, in FIG. 1(a),
The Si island 3 can become a region in which a semiconductor element will be formed later.

The Si islands 3 are connected to each other by a Si connecting portion 4. The direction of this connection is, of course, made to coincide with the direction of subsequent recrystallization by zone melting. In addition, as shown in FIG. 1(b), each row of connecting portions has an oxide film (Si02) 5 formed between adjacent rows of connecting portions (3, 4) and an underlying oxide film 2. The structure is separated by

After creating such a pattern, the entire surface is coated with CVD8i02
It is coated with a film 20 and subjected to zone melting recrystallization treatment. In this embodiment, as can be seen from FIG. 1(a), the polycrystalline Si islands 3 and the connecting portions 4 are densely arranged.

Therefore, by melting the polycrystalline island 3 and the connecting portion 4, not only the heat is removed by the amount of latent heat, but also the SiO□
The gap between the Si islands 3 separated by the layer 5 is several microns wide.
Because it is narrow from m to several tens of prB, the lower layer Si substrate l
The amount of heat required to melt is not transferred. That is,
The Si substrate l is not melted and maintains its original flatness.

After the recrystallization process, the polycrystalline portion 8i (Si islands 3 and Si connections 4) in FIG. 1(a) is recrystallized to become single crystal FN.

Therefore, the area necessary for element formation was left as is.

The entire unnecessary region or the boundary portion is thermally oxidized until it reaches the base oxide film 2, and 8i0. It is possible to inactivate it by doing this.

Actual #A Example 2 In the above-mentioned Example 1, l! ! I took as an example a pattern in which Yushimas are arranged closely and regularly. However, the dimensions of the element arrangement vary, and as shown in Figure 1, S
It is often difficult to line up the i-islands.

FIG. 4 is an example of a pattern in which elements having various sizes and shapes are arranged. Polycrystalline Si
Island 3 is the same as in Example 1.

They are connected by connecting parts 4 of polycrystalline 8i, and these 8i
Island 3 is a region where elements are formed after single crystallization.

Polycrystalline 5irii3.4 is present only at these joints, and the joints in contact with Ill are wide apart.

As is clear from the above-mentioned C, the lower substrate side 8i melts during zone melting recrystallization. Therefore, in this embodiment, as shown in the figure, a very narrow insulating layer (5i02) 5 is left between the connecting parts, and a polycrystalline 5i
It is filled with 414.

After forming such a pattern, the entire surface was covered with a CVD5iO□ film, and the same recrystallization treatment as in Example 1 was performed. In this case as well, except for the divided portion by the insulating layer (S i02 ) 5, polycrystalline Sil! 3 and 4.14 covered the entire surface of the Si substrate, the amount of latent heat was reduced by melting the polycrystalline Si layer, and the underlying Si substrate was not melted and its flatness was maintained.

Furthermore, in such a case, the polycrystalline 5ifWI additionally provided to prevent melting of the Si substrate is
As shown in the figure, they do not necessarily have to be continuous,
It may also be discontinued as indicated by reference numeral 15 in FIG. Also, as shown in 16 in the same figure, the polycrystalline S
The i layer 16 may be connected to the Si island 3 of the connecting portion.

In this case as well, unnecessary portions after recrystallization may be oxidized to the base oxide film.

Example 3 As mentioned earlier, after the recrystallization treatment, the underlying Si
The reason why the flatness of the substrate deteriorates is that the Si substrate is overheated and melted from the region where there are no Si islands. Therefore, S
i A heat absorbing layer or a heat conduction blocking layer that prevents the substrate from being overheated above its melting point is provided on the Si substrate.
It is sufficient to provide it in an area where no i island exists.

In Examples 1 and 2, this is the same polycrystalline 8i as the connection.
Although it was @, it is not limited to -.

Figures 6 and 7 show the depth direction from the top surface of a wafer 81 in which a (base) oxide film is provided on the substrate and (polycrystalline) Si islands are formed on it during recrystallization processing. This shows the relationship between distance and temperature.

In FIG. 6(a), as shown in FIG. 6(b), a (base) oxide film 2 is provided on an 8i substrate 1, and a (polycrystalline) Si island 3 on the (base) oxide film 2 is This is the temperature distribution along the straight line IJx at a location where the non-existent portion is simply covered with insulations 1-5 and 20.

7(a), as shown in FIG. 7(b), a (base) oxide film 2 is provided on the Si substrate 1, and a (polycrystalline) Si island 3 is formed on the (base) oxide film 2. The straight line
The temperature distribution is along the .

The surface of the wafer is now heated to a temperature higher than the melting point of Si, and as shown in FIG. ) If the Si substrate is heated only through the oxide film 2, the temperature distribution will be as shown in FIG. 6(a). In this state, the Si substrate is heated above its melting point and melted.

On the other hand, if a layer 17 having a large heat capacity and absorbing heat is provided on the (underlying) oxide film 2 as shown in FIG. 7(b), the temperature distribution as shown in FIG. 7(a) will occur. This can be realized, and since the temperature at the interface between the (underlying) oxide film 2 and the Si substrate 1 is below the melting point of 81, the Si substrate does not melt.

Alternatively, the high temperature peak portion 9 (
It is possible to realize a temperature distribution as shown in FIG. 7(b) in which the Si substrate is not heated to its melting point while passing through the Si substrate (FIG. 2).

In the embodiments described above, the Si islands 3 serving as the element regions are connected by the connecting portions 4, but it goes without saying that the present invention is applicable even when the Si islands 3 are not connected.

Furthermore, the object of recrystallization was polycrystalline Si.

Amorphous 81 may also be used.

Furthermore, other semiconductor layers, Ge, GaAs, G
arb.

GaP, InAs, InSb
, InP, GaAAAs
, Zn5e.

Any material such as ZnTe may be used. Further, these semiconductor materials can also be used in place of the Si substrate.

〔Effect of the invention〕

According to the present invention, a layer that prevents heat transfer to the substrate during recrystallization is provided on an insulating layer of a substrate having an insulating layer on its surface, in a region where no semiconductor island is present, so that recrystallization is possible. Single-crystal islands of recrystallized semiconductor can be obtained on a flat substrate surface without melting the underlying substrate such as a semiconductor during crystallization.

[Brief explanation of the drawing]

FIG. 1(a) is a plan view showing a pattern of polycrystalline Si according to an embodiment of the present invention, and FIG. 1(b) is an A--
2(a), (b), and (c) are a schematic plan view, a side view, and a temperature distribution diagram for explaining an example of a zone melting recrystallization processing apparatus, and FIG. 3 is a sectional view taken along line B. (-)
(b) is a cross-sectional view for explaining that unevenness is produced on the substrate in the conventional method; FIGS. 6(a) and (b) are diagrams for explaining the temperature distribution in the depth direction of the substrate in the conventional method, and FIGS. 7(a) and (b) are diagrams for explaining the temperature distribution in the depth direction of the substrate in the present invention 2. FIG. l...Si substrate, 2...(base) oxide film, 3...
(Polycrystalline) Sl island, 4... Sl connection part, 5...
- Insulating layer, 6... Carbon susceptor, 7... Carbon plate, 8... Insulating substrate having polycrystalline silicon film, 9
...High temperature peak part, 11...Melting (Si) part, 1
3... Recrystallized Sl island, 14, 15.16... Polycrystalline Si layer, 17... Material with large heat capacity 1 Agent Patent attorney Michihito Hiraki Figure 1 (Q) (b) Figure 2 Figure 3 (Q) Figure 4 Figure 5 Figure 6 O Figure 7

Claims (5)

[Claims] (1) In a method for manufacturing a semiconductor substrate, in which an island-shaped semiconductor layer is formed on the insulating layer of a substrate having an insulating layer on the surface, and the semiconductor layer is melted and recrystallized by heating from above, the island-shaped semiconductor layer A method for manufacturing a semiconductor substrate, comprising providing a layer in a gap portion to prevent heat transfer to the substrate during melting and recrystallization. (2) The method of manufacturing a semiconductor substrate according to claim 1, wherein the layer for inhibiting heat transfer is polycrystalline or amorphous silicon. (3) The method of manufacturing a semiconductor substrate according to claim 1, wherein the layer for preventing heat transfer is made of a material having a large heat capacity. (4) The method of manufacturing a semiconductor substrate according to claim 1, wherein the layer for blocking heat transfer is made of a material with low thermal conductivity. (5) The method of manufacturing a semiconductor substrate according to claim 1, wherein the layer for preventing heat transfer is made of a substance that liquefies or vaporizes when heated during melting and recrystallization.