JP2735150B2 - Method for manufacturing composite semiconductor substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates to a semiconductor substrate and a manufacturing method thereof, and more particularly to a bonding method of a semiconductor substrate for element formation substrate suitable for fabricate the high performance or high-performance semiconductor devices.

[0002]

2. Description of the Related Art A dielectric isolation technique, which is known as a method of isolating semiconductor single crystal regions from each other, has extremely good insulation isolation between devices as compared with a standard junction isolation technique, and limits the application circuit. Therefore, it is suitable for a power IC having a high withstand voltage and a large current. A typical dielectric isolation method is EPIC (Epitaxial Passivated Integrated Circuit).
Although the cuit) method is known, there are problems in handling large-diameter wafers and manufacturing costs, and various other methods are being studied. SOI (Silicon On Insulator) technology for manufacturing a substrate by bonding a plurality of semiconductor substrates is one of them. As a method of bonding substrates, for example, Japanese Patent Application Laid-Open No. 61-242033 and Japanese Patent Application Laid-Open No. 62-17793
No. 8 discloses a method. Of these,
Japanese Patent Application Laid-Open No. 1-242033 discloses that a soot-like substance obtained by burning a raw material containing silicon tetrachloride as a main component in a oxyhydrogen flame is deposited on a surface of a semiconductor substrate, and a holding substrate is overlapped with the helium gas and oxygen gas. Discloses a method of bonding a semiconductor substrate by sintering a soot-like substance by heat treatment in a mixed gas atmosphere. This method is excellent in that a large-diameter composite semiconductor substrate having few crystal defects can be manufactured at a relatively low cost.

[0003]

However, Japanese Patent Application Laid-Open No.
Manufacturing a composite semiconductor substrate having a plurality of semiconductor single crystal regions as shown in FIG. 1 according to the bonding method described in Japanese Patent No. 242033 may cause some problems. As shown in FIG. 2, this manufacturing process uses a soot-like substance 130 obtained by burning a raw material containing silicon tetrachloride as a main component in an oxyhydrogen flame to form a semiconductor substrate 10 having a V-groove. After bonding with the support substrate 15,
The semiconductor substrate 10 is polished to form semiconductor single crystal regions 11 which are insulated and separated from each other. However, in this manufacturing method, cracking or chipping occurs at the time of polishing, or minute movement of the island-shaped semiconductor single crystal region 11 occurs during a process of forming an element in the semiconductor single crystal region 11, and furthermore, However, there is a problem that peeling frequently occurs between the bonded semiconductor substrates. Another problem is that a large amount of expensive helium gas must be used.

An object of the present invention is to eliminate the above-mentioned disadvantages in the conventional method for manufacturing a composite semiconductor substrate, to improve the yield,
It is another object of the present invention to provide a method for manufacturing a composite semiconductor substrate at low cost.

[0005]

Means for Solving the Problems The present inventors have investigated in detail the above problems, namely, the causes of cracks and chips during polishing, and the minute movements of island-like semiconductor single crystal regions. As a result, it has been found that such a problem is caused by the presence of minute holes as defects at the joint surface between the semiconductor substrate and the glass layer (obtained by sintering the soot-like substance). It has been found that such holes are likely to be formed particularly in the valleys of the grooves of the grooved substrate. The inventors of the present application have conducted research to find a manufacturing method that does not generate the above-mentioned voids, and as a result, have completed the present invention. That is, the present invention provides a step of depositing a soot-like substance containing SiO ₂ as a main component obtained by burning a raw material containing a silicon compound as a main component in an oxyhydrogen flame on a surface of a semiconductor substrate ; Placing another holding substrate to be bonded on the deposition of the particulate matter, performing heat treatment in an atmosphere substantially consisting of oxygen gas, and sintering the deposit of the soot-like substance. And a method for manufacturing a composite semiconductor substrate .

Further, the present invention relates to a method for manufacturing a composite semiconductor substrate , characterized by using a raw material obtained by adding at least one of a boron compound, a phosphorus compound and a germanium compound to the silicon compound.

Hereinafter, the present invention will be described in detail. The silicon compound used in the present invention may be any compound that generates SiO ₂ by burning in an oxyhydrogen flame, and may be a compound represented by the general formula SiR ¹ R ² R ³ R ⁴ (substituent R ¹ , R ² , R ³ and R ⁴ may be the same or different and each is a substituent selected from halogen, hydrogen, an alkyl group and an alkyloxy group.); Two silicon atoms such as disiloxane and polysiloxane Silanes containing two or more silicon atoms such as disilane and polysilane. Among them, preferred from the viewpoint of the quality and particle size of the obtained SiO ₂ are compounds represented by the general formula SiR ¹ R ² R ³ R ⁴ , wherein the substituents R ¹ , R ² , R ³ and R ^Four
(R ^{1 to} R ⁴ may be the same or different from each other)
Is chlorine, hydrogen, an alkyl group having 1 to 3 carbon atoms, 1 carbon atom
This is the case where the substituent is a substituent selected from the above-mentioned alkyloxy groups. Among them, particularly preferred are the substituents R
¹ , R ² , R ³ and R ⁴ (R ^{1 to} R ⁴ may be the same or different) are chlorine or hydrogen.

In the present invention, it is preferable to supply a raw material obtained by further adding at least one of a boron compound, a phosphorus compound and a germanium compound to the above-mentioned silicon compound into an oxyhydrogen flame. This is because the temperature at which the soot-like substance is sintered can be lowered by adding these compounds. The boron compound, the phosphorus compound and the germanium compound may be compounds that generate oxides of boron, phosphorus and germanium by burning in an oxyhydrogen flame, respectively.
Examples include boron trichloride and borane (BH ₃ , B ₂ H ₆ ). Examples of the phosphorus compound include phosphorus pentachloride, phosphorus oxychloride (POCl ₃ ), and phosphine (PH ₃ ). Further, examples of the germanium compound include germanium tetrachloride and germane (GeH ₄ ). Of these, boron trichloride, phosphorus pentachloride, phosphorus oxychloride (POCl ₃ ), and germanium tetrachloride are preferred because they are easily supplied.

If the raw material is supplied to the oxyhydrogen flame, the raw material is a gas, while the flow rate is adjusted with a valve or the like, directly into the oxyhydrogen flame, or mixed with hydrogen or oxygen into the oxygen flame. Supply and do. If the raw material is a liquid, it is supplied by a spraying device, or by using an inert gas such as hydrogen gas, oxygen gas or argon gas or nitrogen gas as a carrier, and accompanying the vapor of the raw material,
Can be supplied.

The raw material supplied to the oxyhydrogen flame is flame-hydrolyzed to form a soot-like substance mainly composed of SiO ₂ . This soot-like substance is ultrafine glass particles having a particle size of about 0.05 to 0.2 μm. The oxyhydrogen flame is a combustion flame obtained by simultaneously supplying oxygen and hydrogen.

The soot-like substance produced is immediately deposited on the surface of the semiconductor substrate to be bonded. Preferably, the deposition is performed by blowing an oxyhydrogen flame directly onto the semiconductor substrate. The semiconductor substrate used here can be selected depending on the purpose of use, but is usually a single crystal substrate of a semiconductor such as silicon. The shape of the surface of the substrate is
Although the substrate may be flat, the effect of the present invention is particularly exhibited in a substrate having a groove such as a V-shaped groove or a trench on the surface. This is because voids are likely to be formed particularly in the valleys of the grooves. It is preferable that the surface of the semiconductor substrate is covered with an insulating film such as silicon oxide as necessary.

Next, another holding substrate to be bonded is placed on the soot-like material stack. It is preferable that the holding substrate used here has a thermal expansion coefficient close to that of the semiconductor substrate. This is because if the thermal expansion coefficients are significantly different, the joint surface may be distorted or the joined substrate may warp.

Next, the soot-like substance is sintered by heat treatment. In the present invention, this step is performed substantially in oxygen gas. That is, the atmosphere contains 90% or more of oxygen gas and 2% or less of helium gas, and does not include other gases that are reactive with the semiconductor substrate or the like. Preferably, the oxygen gas content is 95% or more, more preferably 99% or more. This is because the effect of the present invention increases as the oxygen gas content increases. That is, conventionally, such sintering has been commonly performed in a mixed gas of oxygen gas and helium gas. However, when the present inventors heat-treat in substantially oxygen gas to perform sintering, surprisingly, the above-mentioned vacancies are not generated at all, or even if they are generated, the generation rate is extremely small or minute. I found something.

The heat treatment temperature during sintering is 800 ° C. to 140 ° C.
0 ° C. The larger the amount of the boron compound, the phosphorus compound and the germanium compound to be added, the lower the temperature.

As described above, the soot-like substance is vitrified when sintered, and the semiconductor substrate and the holding substrate are bonded to each other. Then, the composite semiconductor substrate is manufactured by grinding and polishing the semiconductor substrate from the side opposite to the bonding surface. If the semiconductor substrate used for bonding is a substrate having a groove such as a V-shaped groove or a trench groove, an island-shaped separated semiconductor single crystal region can be obtained through a grinding / polishing process.

[0016]

According to the present invention, as described above, sulfur obtained by burning a raw material containing a silicon compound as a main component in an oxyhydrogen flame is used.
After depositing a soot-like substance containing iO ₂ as a main component on the surface of the semiconductor substrate, another holding substrate is placed, and heat treatment is performed in an atmosphere substantially composed of oxygen gas. It is possible to prevent the occurrence of voids between the glass layer and the glass layer. This effect cannot be obtained by sintering in a mixed gas of oxygen gas and helium gas.

[0017]

EXAMPLES The present invention will be described more specifically below, but the present invention is not limited thereto.

First, a substrate having a concave portion processed into a V-shape was manufactured as follows. As shown in FIG. 3, a V-groove was formed at a depth of 50 μm by photolithography and anisotropic etching on the surface of a silicon substrate 10 having a (001) plane and a diameter of 4 inches and a thickness of 525 μm.
To form the V-groove, a mask of SiO ₂ was prepared by photoetching, and the region where Si was exposed
It was prepared by etching at a temperature of 80 ° C. with a so-called anisotropic etching solution to which 90 parts by weight of an aqueous solution, 5 parts by weight of isopropyl alcohol and 5 parts by weight of n-butyl alcohol were added. Subsequently, SiO ₂ was formed as an insulating film 12 on the surface of the V groove by thermal oxidation (FIG. 3C).

Gaseous SiCl ₄ (supply amount 210 ml /
min) and gaseous BCl ₃ (supply rate 105 ml / m
in) is introduced into a central tube 20 of a quartz burner, and supplied into a combustion flame (oxyhydrogen flame) composed of hydrogen (0.85 l / min) and oxygen (5 l / min), soot obtained by decomposition. The material was deposited on the surface of the semiconductor substrate with the V-groove (FIGS. 4 and 3 (d)).

A silicon substrate 15, which is a supporting substrate prepared separately, is superimposed on the soot-like substance, and heated to 1280 ° C. in an oxygen atmosphere in a heating furnace. Then, the volume shrunk to a thickness of 20 μm, and at the same time vitrified uniformly, and the two silicon substrates were uniformly bonded to each other (FIG. 3E).

The substrate thus bonded is connected to an ultrasonic image probe (UH Pulse 20 manufactured by Olympus Corporation).
Inspection in 0) confirmed that no holes were present. Further, when the cleaved surface of this substrate was observed with a scanning electron microscope, it was found that the glass was filled in every corner of the V-shaped groove.

Next, grinding is performed from the opposite side of the bonding of the silicon substrate 10 to a predetermined thickness, and further, is polished by using a mechanochemical polishing method. An area was formed (FIG. 3
(F)). At this time, the substrate could be manufactured with good yield without cracking or chipping of the substrate during polishing. In addition, the composite semiconductor substrate manufactured in this manner is subjected to a process including heat treatment for forming an element,
There was no problem such as minute movement of the island-shaped semiconductor single crystal region.

COMPARATIVE EXAMPLE In the example, when the soot-like substance was vitrified by heating in a heating furnace, oxygen
The example was repeated except that a gas mixture consisting of 0% and 40% helium was used. After bonding as in the example, an ultrasonic image search device (UHPulse manufactured by Olympus Corporation)
Inspection by (200) revealed that holes existed everywhere on the substrate as shown in FIG. Further, when the cleaved surface of this substrate was observed with a scanning electron microscope, as shown in FIG.
Voids existed in the portion of the letter-shaped groove. Furthermore, cracking and chipping may occur during polishing.

[0024]

According to the method of manufacturing a composite semiconductor substrate of the present invention, cracks or chips occur during polishing, and an island-shaped semiconductor single crystal region is formed during a process of forming an element in a semiconductor single crystal region. Since there is no problem that the eleventh minute movement occurs, a composite semiconductor substrate can be manufactured with high yield. In addition, since it is not necessary to use expensive helium gas, there is an effect that the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 shows a composite semiconductor substrate having a plurality of semiconductor single crystal regions.

FIG. 2 is a diagram showing a state of bonding of a composite semiconductor substrate.

FIG. 3 is a diagram illustrating one embodiment of a manufacturing process of the composite semiconductor substrate.

FIG. 4 shows a step of depositing a soot-like substance on a grooved semiconductor substrate.

FIG. 5 is a diagram showing a distribution of holes when a composite semiconductor substrate obtained by a conventional manufacturing method is observed with an ultrasonic image search device. This is an enlargement of a portion that becomes one chip. It should be noted that the portion 50 in which a hole is generated does not indicate the size or shape of the hole itself, but illustrates the region where the hole exists. In addition, most of the island-shaped semiconductor single crystal regions are not shown.

FIG. 6 is a diagram showing the presence of holes when a composite semiconductor substrate obtained by a conventional manufacturing method is cleaved and its fracture surface is observed with a scanning electron microscope.

[Explanation of symbols]

10 Semiconductor substrate 11 Semiconductor single crystal region In FIG. 5, other semiconductor single crystal regions are not shown. Reference Signs List 111 Part where semiconductor single crystal region is formed 12 Insulating film (SiO ₂ film) 13 Soot-like substance after sintering 130 Deposit of soot-like substance 131 Soot-like after sintering filled in groove valley part Substance 15 Support substrate 20 Quartz burner 50 Portion where vacancy is generated 51 Vacancy

Claims (2)

(57) [Claims] A step of depositing a soot-like substance containing SiO ₂ as a main component obtained by burning a raw material containing a silicon compound as a main component in an oxyhydrogen flame on a surface of a semiconductor substrate; Placing another holding substrate to be bonded on the material deposition, performing a heat treatment in an atmosphere substantially consisting of oxygen gas, and sintering the soot-like material deposit. A method for manufacturing a composite semiconductor substrate , characterized by: 2. A boron compound to the silicon compound, method for manufacturing a composite semiconductor substrate according to claim 1, characterized by using a raw material obtained by adding at least one of the phosphorus compound and germanium compound.