JPH08264636A - Composite semiconductor substrate - Google Patents

Abstract

PURPOSE: To improve the humidity resistance and to reduce the warpage by using silicon, boron and oxygen as main ingredients as glass substance for connecting a composite semiconductor substrate, and specifying the atomic ratio of the silicon to the boron. CONSTITUTION: A plurality of semiconductor single crystalline regions 11 are isolated from each other, and electrically insulated from each other. The periphery of the region 11 is covered with an insulating film 12, and the layer 14 made of semiconductor polycrystal or amorphous semiconductor is brought into contact with the film 12 to connect the plurality of the regions 11 to each other. The warpage of the substrate can be reduced by the layer 14. The regions 11 and the layers 12, 14 for coupling them are supported by a support board 15 via a glass substance layer 13. The layer 13 contains silicon, boron and oxygen as main ingredients in such a manner that the atomic ratio (a) of the silicon to the boron is 1.0<=a<=0.4. Thus, a composite semiconductor substrate which has excellent humidity resistance and small warpage can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite semiconductor substrate including a dielectric isolation substrate for semiconductor devices capable of forming power elements and the like.

[0002]

2. Description of the Related Art Dielectric isolation technology known as a method for isolating semiconductor single crystal regions from each other is
The isolation technology between devices is extremely good compared to the standard junction isolation substrate, and there are few restrictions on the applicable circuit.
Suitable for high withstand voltage and large current power ICs. A typical dielectric isolation method is EPIC (Epitaxial Passivat).
Although the ed integrated circuit) method is known, various other methods are being studied due to problems with large wafer diameters and manufacturing costs. SOI (Silicon On Insulato) that manufactures substrates by bonding multiple semiconductor substrates
r) Technology is one of them. Among them, an excellent method for bonding substrates is disclosed in, for example, JP-A-61-224.
There is a method disclosed in Japanese Patent No. 2033.

In the above-mentioned publication, a soot-like substance obtained by burning a raw material containing silicon tetrachloride as a main component with an oxyhydrogen flame is deposited on the surface of a semiconductor substrate, and after superposing a supporting substrate, helium gas and oxygen gas are deposited. Discloses a method of joining a semiconductor substrate by sintering a soot-like substance which is heat-treated in a mixed atmosphere. This method is an excellent method in that a composite semiconductor substrate having a large wafer diameter with few crystal defects can be manufactured at a relatively low cost. As shown in FIG. 1, a conventional substrate having a plurality of semiconductor single crystal regions manufactured by a bonding method of this kind is usually a semiconductor single crystal island 11 covered with an insulating film 12 such as SiO _2. Are bonded to the support substrate 15 by the glass material layer 13.

However, when a semiconductor substrate is mounted, the semiconductor substrate may be exposed to a harsh environment, so that environmental resistance characteristics, particularly humidity resistance, may become a problem.

Further, recently, a semiconductor substrate having a larger wafer diameter has been demanded, and among the semiconductor substrates bonded by the conventional method described in the above publication, a warp (an outer peripheral portion and a central portion) due to the increase in size of the wafer has been demanded. The difference between the height and the area) becomes large, and as a result, there arise problems that it is difficult to convey in a production line where various devices are formed on a semiconductor substrate, and it is difficult to improve fine photolithography accuracy.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems in the conventional composite semiconductor substrate and to provide a composite semiconductor substrate having excellent moisture resistance and small warpage.

[0007]

The present invention provides a composite semiconductor substrate in which one or a plurality of semiconductor single crystal regions separated from each other and a supporting substrate supporting the same are bonded by a glass material. The present invention relates to a composite semiconductor substrate, wherein the glass substance contains silicon, boron and oxygen as main components, and an atomic ratio (Si / B ratio) a of silicon and boron is 1.0 ≦ a ≦ 4.0.

In the glass material containing silicon, boron and oxygen as the main components of the present invention, if the atomic ratio (Si / B ratio) a of silicon and boron is too large, it is necessary to raise the sintering temperature at the time of bonding. Therefore, the sintering time becomes long, the manufacturing efficiency becomes poor, the warp of the substrate becomes large, and when it is excessively small, the moisture resistance deteriorates. Therefore, the ratio a is 1.
The range of 0 ≦ a ≦ 4.0 is selected. When the Si / B ratio a is 1.4 ≦ a ≦ 3.0, minute voids generated at the bonding surface between the semiconductor substrate and the glass material layer (obtained by sintering the soot-like material). It is preferable because the number of holes is small, the filling state of the groove is good, the moisture resistance is improved, and the warpage is reduced.

The structure of the composite semiconductor substrate of the present invention will be described with reference to FIG. The plurality of semiconductor single crystal regions 11 are separated from each other and electrically insulated from each other. As shown in the figure, the semiconductor single crystal region 1
The periphery of 1 is usually covered with an insulating film 12. In this figure, a layer 14 made of semiconductor polycrystal or amorphous semiconductor is provided so as to be in contact with the insulating film 12 so as to connect a plurality of semiconductor single crystal regions 11 to each other.
It is preferable to provide No. 4 as appropriate because the warp of the substrate can be reduced. The semiconductor single crystal region and each of the above-mentioned layers connecting these are the glass material layer 13
It is supported by the support substrate 15 via.

Silicon is a typical material for the semiconductor single crystal region 11, but GaAs, GaAlAs, In
It may be a compound semiconductor such as P or SiC or a single element semiconductor such as Ge.

The insulating film 12 usually formed is not particularly limited, but a SiO ₂ film is preferably used. The thickness of the insulating film is usually 0.5 to 2.0 μm. The semiconductor polycrystal layer 14 formed as desired to reduce the warp of the substrate is a polycrystal layer of a single element semiconductor such as silicon or Ge, or GaAs or GaAlA.
Examples include a polycrystalline layer of various compound semiconductors such as s, InP, and SiC, and examples of the amorphous semiconductor layer 14 include an amorphous semiconductor layer made of amorphous silicon, silicon germanium, or the like. The thickness of the semiconductor polycrystalline layer or the amorphous semiconductor layer is usually 0.
It is 1 to 100 μm, preferably 1 to 50 μm.

The glass material layer 13 is mainly composed of silicon, boron and oxygen. If the thickness of the glass material layer is too thin, it may not be completely joined, and if it is too thick, the joining strength will decrease.
m, preferably 0.5 to 100 μm. A phosphorus compound or a germanium compound may be added to lower the sintering temperature of the glass material layer.

The supporting substrate 15 has good bondability with glass and is less likely to cause distortion in the bonded surface after bonding, and has a thermal expansion coefficient close to that of the semiconductor single crystal region 11 so that warpage of the composite semiconductor substrate is reduced. Materials are selected. Usually, the same material as the semiconductor single crystal region 11 is selected.

The semiconductor single crystal region 11 in the above description
Or the thickness of the layer may be different between the semiconductor single crystal regions. Further, a part of the semiconductor single crystal region 11 may be directly bonded to the supporting substrate 15, or a part of the supporting substrate may appear on the device surface.

Although the semiconductor single crystal regions are separated from each other in the above description, as shown in FIG. 3, there is one semiconductor single crystal region 11 and the insulating layer 12, semiconductor polycrystal or amorphous semiconductor is used. It may be bonded to the support substrate 15 via the layer 14 and the glass substance 13.

Next, an example of the method for manufacturing the composite semiconductor substrate of the present invention will be described with reference to FIG. First, an isolation groove is formed on the surface of the semiconductor substrate 10 to be the semiconductor single crystal region 11.
Although a V-shaped groove is shown in the drawing, it may be a trench or the like, and can be selected in consideration of a target device and manufacturing cost. As a manufacturing method, a commonly used method such as wet anisotropic etching using KOH or dry etching using SF ₆ gas can be used. The depth of the groove is preferably a little deeper than the thickness of the semiconductor single crystal region 11, and is usually 0.1 μm to
It is about 300 μm.

Since the semiconductor substrate 10 finally becomes the semiconductor single crystal region 11, the material is the same semiconductor as the semiconductor single crystal region.

Next, the insulating film 12 is formed on the surface of the semiconductor substrate 10. A SiO ₂ film is preferably used as the insulating film. The SiO ₂ film is formed by a CVD method or the like, but when the semiconductor substrate 10 is silicon, SiO ₂ obtained by thermally oxidizing the surface is preferably used.

Next, if desired, a semiconductor polycrystal or amorphous semiconductor layer 14 is formed on the insulating film 12. Although the manufacturing method is not particularly limited, for example, in the case of polycrystalline silicon, it can be manufactured by a CVD (chemical vapor deposition) method or the like.

Next, after the glass material layer 13 is formed, the support substrate 15 is overlaid and heat-treated to bond the semiconductor substrate 10 and the support substrate 15 together. The glass material layer contains silicon, boron and oxygen as main components, and can optionally contain phosphorus compounds and germanium compounds. Glass material layer is soot deposition method, C
It can be manufactured by VD, spin coating, or the like. Among them, the soot deposition method is particularly preferable because it is filled with the glass substance even in the entire groove.

The soot deposition method mainly uses SiO ₂ and B ₂ O ₃ obtained by burning a raw material containing a silicon compound such as SiCl ₄ and a boron compound such as BCl ₃ as main components in an oxyhydrogen flame. In this method, a soot-like substance as a component is deposited on the surface of the semiconductor substrate 10, superposed on the support substrate 15, and then heat-treated and sintered to bond the semiconductor substrate 10 and the support substrate 15 together.

Manufacture of composite semiconductor substrate by soot deposition method
The silicon compound used in the
By burning with SiO₂Is a compound that produces
The general formula SiR¹R²R³R^FourCompound represented by
Thing (substituent R¹, R², R³And R^FourAre identical to each other
May be different, halogen, hydrogen, an alkyl group,
It is a substituent selected from an alkyloxy group. ); Jishi
Contains two or more silicon atoms such as roxane and polysiloxane
Siloxane having; silicon such as disilane and polysilane
Examples include silanes containing two or more atoms.
It Among these, the obtained SiO₂Quality and granularity of
From the viewpoint, the general formula SiR is preferable.¹R²R³R^Fourso
A compound represented, wherein the substituent R¹, R², R³And
And R^Four(R¹~ R^FourMay be the same or different from each other
Yes. ) Is chlorine, hydrogen, an alkyl group having 1 to 3 carbon atoms, charcoal
In the case of a substituent selected from alkyloxy groups having a prime number of 1 to 3.
It is the case. Of these, particularly preferred are the above substituents.
R¹, R², R³And R ^Four(R¹~ R^FourAre identical to each other
But it can be different. ) Is chlorine or hydrogen
Is. Specific examples of these silicon compounds include SiCl
_Four, SiH_Four, Si ₂H₆, SiHCl₃, Si (OE
t)_FourAnd Si (OMe)_FourCan be mentioned
It

As the boron compound, boron trichloride, boranes (BH ₃ , B ₂ H ₆ ), BHCl ₂ , B (OE)
Examples thereof include t) ₃ and B (OMe) ₃ , and among these, boron trichloride is preferable because it can be easily supplied.

The phosphorus compound and the germanium compound, which are optionally added to lower the sintering temperature of the soot-like substance, are those which produce oxides of phosphorus and germanium by burning in an oxyhydrogen flame. Any compound may be used. Examples of the phosphorus compound include phosphorus pentachloride, phosphorus oxychloride (POCl ₃ ), phosphine (PH ₃ ), and the germanium compound includes germanium tetrachloride and germane (GeH _4). ) Etc. can be mentioned. Of these, phosphorus pentachloride and phosphorus oxychloride (P
OCl ₃ ) and germanium tetrachloride.

The above raw materials are supplied into the oxyhydrogen flame directly in the oxyhydrogen flame or while being mixed with hydrogen or oxygen while the oxyhydrogen flame is mixed by adjusting the flow rate with a valve if the above raw materials are gases. To supply. If the raw material is a liquid, it is supplied by a spraying device, or hydrogen gas, oxygen gas or an inert gas such as argon gas or nitrogen gas as a carrier, by entraining the vapor of the raw material,
Alternatively, the raw material can be supplied by heating the raw material and pressure-feeding it by the vapor pressure of the raw material itself.

The above-mentioned raw material supplied to the oxyhydrogen flame was subjected to flame addition.
Water decomposed, SiO₂And B₂O ₃Is the main component
This produces a soot-like substance. This soot-like substance is an ultrafine particle of glass
It is a child and has a particle size of about 0.05 to 0.2 μm.
An oxyhydrogen flame is the simultaneous supply of oxygen and hydrogen.
It is a combustion flame obtained by.

The generated soot-like substance is immediately deposited on the surface of the semiconductor substrate to be bonded. The deposition is preferably performed by spraying an oxyhydrogen flame directly onto the semiconductor substrate.

Then, the supporting substrate 15 to be joined is placed on the deposition of soot-like substance, and the soot-like substance is sintered by heat treatment. In the sintering, heat treatment is performed in a mixed gas of oxygen gas and an inert gas in order to prevent the formation of vacancies in the valleys of the grooves provided in the semiconductor substrate 10 as much as possible. The oxygen gas content is 10% or more, preferably substantially in the oxygen gas content. That is, oxygen gas is 90% or more and helium gas is 2%.
% Or less, and other gases that are not reactive with semiconductor substrates are used. In particular, the oxygen gas content is 95% or more, more preferably 99% or more. The heat treatment temperature during sintering is 800 to 1400 ° C. The soot-like substance is vitrified when it is sintered, and the semiconductor substrate 10 and the support substrate 15 are bonded together.

Thereafter, the semiconductor substrate 10 is ground and further polished from the side opposite to the bonding surface to manufacture a composite semiconductor substrate. If the semiconductor substrate used for bonding is a grooved substrate such as a V-shaped groove or trench groove, an island-shaped separated semiconductor single crystal region 11 is obtained through a grinding / polishing process.

[0030]

EXAMPLES The present invention will be described more specifically below, but the present invention is not limited thereto. Example 1 The composite semiconductor substrate shown in FIG. 2 was manufactured as follows. A substrate having a V-shaped recess was manufactured as follows. First, as shown in FIG.
V-grooves were formed at a depth of 50 μm by photolithography and anisotropic etching on the surface of the silicon substrate 10 having a diameter of 0 inch and a diameter of 4 inches and a thickness of 525 μm. The V groove is formed by forming a mask of SiO ₂ by photoetching, and exposing the region of Si to a 20% aqueous solution of KOH 9
0 parts by weight, isopropyl alcohol 5 parts by weight and n-
It was prepared by etching at a temperature of 80 ° C. using a so-called anisotropic etching solution containing 5 parts by weight of butyl alcohol.

Subsequently, SiO ₂ was formed on the surface of the V groove as the insulating film 12 to a thickness of 1.5 μm by thermal oxidation.
Next, polycrystalline silicon was formed in a thickness of 20 μm on the surface having the V groove by CVD.

Then, the gaseous S is adjusted so that the atomic ratio (Si / B) a of silicon to boron of the glass substance becomes 2.0.
iCl ₄ (supply amount 210 ml / min) and gaseous BCl ₃ (supply amount 105 ml / min) were replaced with hydrogen (supply amount 850 ml / min) and oxygen (supply amount 5000 ml / m).
in), and soot-like substances obtained by decomposition are deposited on the surface of the semiconductor substrate 10 in which the V groove is formed. The amount of soot-like substance deposited was adjusted to 20 μm when it was sintered. A 4-inch diameter, 450 μm-thick silicon substrate 15 having a plane orientation (100) plane, which was separately prepared, was superposed on the soot-like substance deposited,
Raise the temperature to 1280 ° C in an oxygen atmosphere in a heating furnace.
When heated for a time, the soot-like substance sinters and the thickness is 20μ.
At the same time, the glass contracted to a volume of m and vitrified, and the two silicon substrates were evenly bonded to each other.

The substrate thus bonded is subjected to an ultrasonic image exploration apparatus (UH Pulse20 manufactured by Olympus Corporation).
When the groove filling state was examined in 0), it was confirmed that there were no holes at all. Furthermore, when the cleaved surface of this substrate was observed with a scanning electron microscope, it was found that glass was filled in every corner of the V-shaped groove. Using a sample prepared under the same conditions to determine the composition ratio of the glass substance, the glass substance was dissolved in an aqueous solution of hydrogen fluoride and quantitatively analyzed by ICP. The atomic ratio a of Si / B was 2. It was 0.

Next, polishing is performed from the surface opposite to the bonding of the silicon substrate 10 and after processing to a predetermined thickness, further polishing is performed using the mechanochemical polishing method, and unnecessary portions are formed until the polycrystalline silicon layer appears on the surface. Was removed to form island-shaped semiconductor regions 11 which were isolated from each other. The warp at this time was such that, when the semiconductor single crystal region was placed on a flat surface, the warp was such that the central portion was convex upward by 80 μm from the periphery. Therefore, there was no trouble during transportation, and the yield in the photolithography process was good.

The sample 1 obtained by cutting this substrate into 5 mm square chips was observed with a scanning electron microscope for the sintered state of the chip cross section. As a result, the semiconductor substrate of the sample 1 and the supporting substrate were evenly bonded. And the bonded state was good. Further, when the filling state of the groove was observed, no minute holes were formed, and no damage such as engraving was observed.

A chip cut out from a bonded substrate produced by the same method as the sample 1 was subjected to a moisture resistance test according to a vapor pressure test described on page 64 of Mitsubishi Semiconductor Reliability Handbook (3rd edition). That is, after being left in a pressurized steam atmosphere at a temperature of 121 ° C. and a humidity of 100% for another 4 hours and 8 hours in addition to the standard conditions of 2 hours,
Observation of the tip surface of the chip with a scanning electron microscope revealed that no damage such as cracks occurred and the chip had excellent moisture resistance.

Various bonded composite semiconductor substrates were prepared in the same manner as in the case of the sample 1, and each sample cut into a 5 mm square chip was observed with a scanning electron microscope for the sintering state of the chip cross section and bonded. The alignment state and the filling state of the groove were examined. Furthermore, each sample was placed at a temperature of 121 ° C and a humidity of 10
After being left in a 0% pressurized steam atmosphere for 2 hours, 4 hours, and 8 hours, the tip end face of each sample was observed with a scanning electron microscope to observe the occurrence of damage such as cracks. Table 1 shows the results of the bonded state, the groove filling state and the moisture resistance test.

[0038]

[Table 1]

In the table, a sample in which partial peeling was observed when the bonded state was observed with a scanning electron microscope before the moisture resistance test was marked with an X, and when the filled state of the groove was observed, voids were observed. The obtained sample was marked with an X, and the sample in which some holes were observed was marked with a Δ. In addition, a sample in which cracks or peeling were observed on the joint surface of the sample end surface after the high temperature and high humidity atmosphere leaving test was marked with x.

[0040]

As described in detail above, the composite semiconductor substrate of the present invention has excellent moisture resistance when cut into chips, is practically useful, and has small warpage even when it has a large wafer diameter. It can be put into a device manufacturing line where strict standards are required, and the accuracy of photolithography can be improved and the yield can be improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a composite semiconductor substrate manufactured by a conventional dielectric isolation technique.

FIG. 2 is a vertical cross-sectional view showing one embodiment of the composite semiconductor substrate of the present invention.

FIG. 3 is a vertical cross-sectional view showing one embodiment of the composite semiconductor substrate of the present invention.

FIG. 4 is a diagram showing a manufacturing process of the composite semiconductor substrate of the present invention.

[Explanation of symbols]

 10 Semiconductor Substrate 11 Semiconductor Single Crystal Region 12 Insulating Film 13 Glass Material Layer 14 Semiconductor Polycrystalline Layer or Amorphous Semiconductor Layer 15 Supporting Substrate

Claims (1)

[Claims] 1. A composite semiconductor substrate in which one or a plurality of semiconductor single crystal regions separated from each other and a supporting substrate supporting the same are bonded by a glass material, wherein the glass material is silicon, boron and oxygen. As the main component,
Atomic ratio of silicon and boron (Si / B ratio) a is 1.0 ≦
A composite semiconductor substrate, wherein a ≦ 4.0.