KR20000066010A - Method for manufacturing SOI semiconductor substrate - Google Patents

Abstract

PURPOSE: A method of fabricating a SOI semiconductor substrate is provided to prevent the porous ion from penetrating into a silicon layer by removing boron ion and easily to control the knee voltage CONSTITUTION: In a method of fabricating a SOI(silicon on insulator) semiconductor substrate, a first(11,31) wafer and a second wafer(20,40) is provided, a boron ion layer(12,32) is formed in the first wafer(11,31), a buffer silicon single crystal layer grows on the boron ion layer(12,32), a single silicon crystal layer(12,32) is formed on the boron layer(12,32) and finally the insulating oxide layer(15,21) is formed on the first and second wafer(11,20). Subsequently the insulating oxide layer(15,21) on the first and the second wafer is bonded. Wherein the first wafer is etched down to the depth on the boron ion layer. The boron ion layer, the first wafer ,and the buffer silicon single crystal including the boron ion are etched.

Description

Method for manufacturing SOI semiconductor substrate

The present invention relates to a method for manufacturing a silicon on insulator (SOI) semiconductor substrate, and more particularly, to a method for manufacturing a S.O. semiconductor substrate capable of securing threshold voltage characteristics of a semiconductor device formed on the SOI substrate. It is about.

In general, in the manufacturing process of a CMOS transistor, device isolation is formed to ensure a relatively large area in order to prevent separation between devices and latch-up of the CMOS transistor. However, this device isolation region reduces chip area and becomes a factor of inhibiting high integration.

In order to solve such a problem, a conventional SOI substrate is used instead of a semiconductor substrate.

The SOI substrate is formed by sandwiching a buried insulating layer having a predetermined thickness between the silicon handling substrate and the device silicon substrate. Such an SOI substrate can achieve complete device isolation, thereby preventing the latch-up phenomenon of the CMOS transistor, thereby enabling high-speed operation of the device.

One method of forming such an SOI substrate is the Separation by Implanted Oxygen (SIOX) technique, which injects oxygen ions into a silicon substrate. However, this SIMOX technology is disadvantageous in that dislocation is easily generated in the device formation surface during oxygen ion implantation, and the thickness of the device formation layer cannot be precisely controlled, resulting in a large amount of leakage current. .

In another conventional method, Bond and Etch-back SOI (BESOI) is formed by bonding two silicon substrates having an insulating layer formed on at least one wafer, and then etching back the silicon substrate for the device to form a silicon layer on which the device is formed. There is technology.

In the conventional BESOI technique, as illustrated in FIG. 1A, a first silicon wafer 1 and a second wafer 2 are prepared. The first and second wafers 1 and 2 are both silicon wafers. Boron ions are implanted into the first wafer 1 to a predetermined depth to form the boron ion layer 2. As the boron ion layer 2 is formed, the first wafer 1 is divided into a first silicon layer 1 a and a second silicon layer 1b. The first oxide film 3 for the buried insulating film is deposited on the second silicon layer 1b.

On the other hand, the second oxide film 6 for the buried insulating film is also formed on the second wafer 5.

Then, as shown in FIG. 1B, the first oxide film 3 and the second oxide film 6 are bonded to each other to be brought into contact with each other, and then a thermal process is performed. Then, the first silicon layer 1a is polished until the boron ion layer 2 is exposed. At this time, the first oxide film 3 and the second oxide film 6 become one buried insulating film 7 in the above thermal process.

Thereafter, as shown in FIG. 1C, the boron ion layer 2 is removed through a selective wet etching method so that the second silicon layer 1b remains. At this time, the remaining second silicon layer 1b becomes a semiconductor layer on which a semiconductor device is to be formed.

However, there are the following problems in manufacturing the SOI semiconductor substrate.

That is, when the boron ion layer 2 is formed as an etch stop layer in order to form a uniform semiconductor layer as described above, the boron ions in the boron ion layer 2 act on the second silicon layer 1b acting as a semiconductor layer. Some inflow.

As a result, the impurity concentration of the region in which the semiconductor element is to be formed is substantially increased, thereby making it difficult to control the threshold voltage of the semiconductor element to be formed later.

Accordingly, it is an object of the present invention to provide a method for manufacturing an SOI semiconductor substrate which can remove the boron ions remaining in the semiconductor layer of the SOI substrate, thereby improving the threshold voltage characteristic of the semiconductor element formed on the SOI substrate.

1A to 1C are cross-sectional views for explaining a method of manufacturing a conventional SOH semiconductor substrate.

2A to 2F are cross-sectional views of respective processes for explaining the first embodiment of the present invention.

3A to 3G are cross-sectional views of respective processes for explaining the second embodiment of the present invention.

(Explanation of symbols for the main parts of the drawing)

11,31-First Wafer 12,32-Boron Ion Layer

13,33-Buffered Monocrystalline Silicon Layer 14,34-Monocrystalline Silicon Layer

15,21,36,38,41-Oxide film for investment insulating film

20,40-Second Wafer 37-Capacitor Electrode

In order to achieve the above object of the present invention, the present invention provides a method for preparing a first wafer and a second wafer, forming a boron ion layer at a predetermined depth in the first wafer, and buffering single crystal silicon on the boron ion layer. Growing a layer, growing a single crystal silicon layer on the buffer single crystal silicon layer, forming an oxide film for a buried insulating film on the single crystal silicon layer of the first wafer and the second wafer, respectively, Bonding a first wafer and a second wafer to abut the oxide film for buried insulation, removing the first wafer with the boron ion layer as an etch stop layer, and boron with the single crystal silicon layer as an etch stop layer Removing the ionic layer and the remaining first wafer and the buffer single crystal silicon layer.

The method may further include forming a capacitor electrode to contact the single crystal silicon layer between forming the single crystal silicon layer and forming an oxide film for a buried insulation film on the first wafer.

According to the present invention, the single crystal silicon layer grown on the wafer is used as the semiconductor layer while the boron ion layer is used as the etch stop layer, and the wafer layer on the boron ion layer is not used as the semiconductor layer. As a result, the inflow of boron ions is prevented, and the influence of the boron ions can be reduced, so that the threshold voltage can be easily controlled.

(Example)

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2A to 2F are cross-sectional views for each process for describing the first embodiment of the present invention, and FIGS. 3A to 3G are cross-sectional views for each process for explaining the second embodiment of the present invention.

First, the first embodiment will be described.

Referring to Fig. 2A, a first wafer 11 made of silicon material is prepared. Boron (B) ions are implanted into the first wafer 11 to form the boron ion layer 12. In this case, the boron ion layer 12 is formed by ion implantation of ions of 10 ¹⁴ to 10 ¹⁷ dose / cm 2 with energy of 10 to 200 KeV. Next, the buffer single crystal silicon layer 13 is grown to a thickness of about 100 to 5000 mm 3 on the first wafer 11 on which the boron ion layer 12 is formed. At this time, the buffer single crystal silicon layer 13 is deposited while flowing a SiHCl ₃ or SiH ₂ Cl ₂ solution 0.5 to 3L / min, B ₂ H ₆ solution 0.1 to 5L / min.

Subsequently, as shown in FIG. 2B, the single crystal silicon layer 14 is formed on the buffer single crystal silicon layer 13, and the first oxide film 15 for the buried insulation film is formed thereon. At this time, the single crystal silicon layer 14 is preferably grown to a thickness of about 100 to 2000 kPa while flowing SiHCl ₃ or SiH ₂ Cl ₂ solution at 0.5 to 3 L / min and B ₂ H ₆ solution at about 0.1 to 5 L / min. Here, the single crystal silicon layer 14 is a layer on which a semiconductor device is to be formed, and after forming the buffer single crystal silicon layer 13 as described above in order to secure the film cleanliness of the semiconductor layer, the single crystal silicon layer 14 is formed. It is preferable to form

In addition, the first oxide film 15 may be formed to a thickness of about 1000 to 10000 kPa by chemical vapor deposition, and any one of a BPSG film, an HDP oxide film, a PE-TEOS oxide film, and an SOG oxide film may be used.

Meanwhile, as shown in FIG. 2C, the second wafer 20 is prepared. The second oxide film 21 for the buried insulating film is formed on the second wafer 20. The second oxide film 21 may also be formed by chemical vapor deposition, and may be formed by any one of the oxide films listed above, and the thickness thereof is suitably about 1000 to 10000 Pa.

Then, cleaning is performed for the surface hydrophilization treatment while removing particles on the surface before bonding the first wafer 11 and the second wafer 20. In this case, the cleaning process may be performed using an SC-1 solution or a piranha washing solution or a mixed solution thereof, or may be performed by heat treatment at 700 to 1200 ° C., O ₂ or N ₂ atmosphere for 30 to 120 minutes. have.

Next, as illustrated in FIG. 2D, the first wafer 11 and the second wafer 20 are bonded to abut the first and second oxide films 15 and 21. The bonding process is preferably carried out under a vacuum of 7.5 × 10 ⁻¹ to 7.5 × 10 ⁻⁴ torr. Subsequently, in order to improve the bonding strength between the two wafers 11 and 15, a heat treatment process is performed for a predetermined time. The heat treatment process is performed for 30 to 120 minutes in 700 to 1200 ℃, O ₂ or N ₂ atmosphere.

Thereafter, a large part of the first wafer 11, that is, the first wafer 11 is polished back such that the first wafer 11 remains by a predetermined thickness. At this time, the rotation speed of the polishing chuck wafer at the time of backside polishing is about 50 to 400rpm, and the rotational speed of the spindle is about 1000 to 4000rpm, so that the backside polishing speed is about 10 to 400µm / min.

Thereafter, as shown in FIG. 2E, the boron ion layer 12 is used as an etch stop layer, and the remaining first wafer 11 is removed by a wet etching method. The remaining first wafer 11 is wet-etched with a solution in which HNO ₃ : HF: H ₂ SO ₄ : H ₃ PO ₄ is mixed at 0.5-5: 0.5-2: 0.5-1: 0.5-3, or NH ₄ OH: H ₂ O ₂ : H ₂ O is wet etched with a mixed solution of 1 to 4: 0 to 0.5: 5 to 10.

Subsequently, as shown in FIG. 2F, the boron ion layer 12, the remaining first wafer 11, and the buffer single crystal silicon layer 13 are removed by chemical mechanical polishing using the single crystal silicon layer 14 as a stop layer. do. Here, the chemical mechanical polishing is a rotational speed of the chuck table is 10 to 30rpm, the pressure for pressing the spindle is about 4 to 8psi, and the rotational speed of the spindle is 20 to 40rpm.

Here, the single crystal silicon layer 14 becomes a semiconductor layer on which a semiconductor device is to be formed, thereby completing an SOI semiconductor substrate.

As described above, according to this embodiment, even when the boron ion layer is used as an etch stop layer, the single crystal silicon layer is grown twice over the boron ion layer, and the single crystal silicon layer formed on the surface is used as the semiconductor layer. As a result, boron ions do not remain in the single crystal silicon layer formed on the buffer single crystal silicon layer, so that the threshold voltage can be easily controlled.

Hereinafter, a second embodiment of the present invention will be described with reference to FIGS. 3A to 3. The second embodiment is a method of forming a DRAM device by using the first embodiment.

First, referring to FIG. 3A, a first silicon wafer 31 is prepared. Boron ions are implanted on the first wafer 31 at 10 ¹⁴ to 10 ¹⁷ doses / cm 2 of energy at an energy of 10 to 200 KeV to form the boron ion layer 32 in the first wafer 31. The buffer single crystal silicon layer 33 is grown to a thickness of about 100 to 5000 상 에 on the first wafer 31 on which the boron ion layer 32 is formed. In this case, the buffer single crystal silicon layer 33 is grown while flowing SiHCl ₃ or SiH ₂ Cl ₂ solution by flowing 0.5 to 3 L / min and B ₂ H ₆ solution to about 0.1 to 5 L / min. Next, the single crystal silicon layer 14 is formed on the buffer single crystal silicon layer 13. Here, the single crystal silicon layer 34 is grown to a thickness of about 100 to 2000 microns while flowing SiHCl ₃ or SiH ₂ Cl ₂ solution at 0.5 to 3 L / min and B ₂ H ₆ solution at about 0.1 to 5 L / min.

Next, as shown in FIG. 3B, through the known photolithography process and the etching process, the portion of the low concentration single crystal silicon layer 23 is patterned to expose the predetermined portion of the buffer single crystal silicon layer 33, and the trench is then trenched. A groove (not shown) is formed. Here, the trench grooves are preferably formed in the region where the device is to be separated.

Then, as shown in Fig. 3C, an insulating film is embedded in the trench groove. Hereinafter, the insulating film embedded in the trench groove is called the trench insulating film 35. Next, the first oxide film 36 for the buried insulating film is deposited on the trench insulating film 35 and the single crystal silicon layer 34 by a chemical vapor deposition method with a thickness of about 1000 to 10000 GPa. Here, any one of the BPSG film, the HDP oxide film, the PE-TEOS oxide film, and the SOG oxide film may be used as the first oxide film 25. Thereafter, a predetermined portion of the first oxide film 36 is etched to form a hole (not shown) so that a predetermined portion of the single crystal silicon layer 34, preferably a region where the capacitor electrode is to be formed, is exposed. Thereafter, the capacitor electrode 37 is formed in the hole by a known method so as to be in contact with the exposed single crystal silicon layer 34. Next, a second oxide film 38 for the buried insulation film is formed over the capacitor electrode 37 and the first oxide film 36. In this case, the second oxide film 38 is formed in the same manner as the first oxide film 36 and is formed of any one of a BPSG film, an HDP oxide film, a PE-TEOS oxide film, and an SOG oxide film.

Meanwhile, as shown in FIG. 3D, a second wafer 40 to be bonded to the first wafer 31 is prepared. Thereafter, a third oxide film 41 for buried insulating film is formed on the second wafer 40. At this time, the third oxide film 41 is also formed in the same manner as the first and second oxide films 36 and 38, and any one of the oxide films listed above may be used.

Next, as shown in FIG. 3F, the second oxide film 38 of the first wafer 31 and the third oxide film 41 of the second wafer 40 are bonded to each other. At this time, before bonding the first wafer 31 and the second wafer 40, cleaning is performed for the surface hydrophilization treatment while removing particles on the surface. In this case, the cleaning process may be performed using an SC-1 solution or a piranha washing solution or a mixed solution thereof, or may be performed by heat treatment at 700 to 1200 ° C., O ₂ or N ₂ atmosphere for 30 to 120 minutes. have. Here, the bonding process is preferably carried out under a vacuum of 7.5 × 10 ^-1 to 7.5 × 10 ^-4 torr. Subsequently, in order to improve the bonding strength between the two wafers 31 and 40, a heat treatment process is performed for a predetermined time. The heat treatment process is performed for 30 to 120 minutes in 700 to 1200 ℃, O ₂ or N ₂ atmosphere. Most of the first wafer 11 is, for example, polished back such that the first wafer 31 remains by a predetermined thickness. At this time, the rotation speed of the polishing chuck wafer at the time of backside polishing is about 50 to 400rpm, and the rotational speed of the spindle is about 1000 to 4000rpm, so that the backside polishing speed is about 10 to 400µm / min.

Then, as shown in FIG. 3F, the remaining first wafer 31 is removed by a wet etching method. The remaining first wafer 31 is wet-etched with a solution in which HNO ₃ : HF: H ₂ SO ₄ : H ₃ PO ₄ is mixed at 0.5-5: 0.5-2: 0.5-1: 0.5-3, or NH ₄ OH: H ₂ O ₂ : H ₂ O is wet etched with a mixed solution of 1 to 4: 0 to 0.5: 5 to 10.

Subsequently, as shown in FIG. 3G, the boron ion layer 32, the remaining first wafer 31, and the buffer type single crystal silicon layer 33 are chemically mechanically polished using the single crystal silicon layer 34 as an etch stop layer. Remove it in such a way. In the chemical mechanical polishing, the rotation speed of the chuck table is 10 to 30 rpm, the pressure for pressing the spindle is about 4 to 8 psi, and the rotation speed of the spindle is 20 to 40 rpm.

As described in detail above, according to the present invention, while using the boron ion layer as an etch stop layer, the single crystal silicon layer grown on the wafer is used as the semiconductor layer without using the wafer layer on the boron ion layer as the semiconductor layer. As a result, the inflow of boron ions is prevented, and the influence of the boron ions can be reduced, so that the threshold voltage can be easily controlled.

Claims (20)

Preparing first and second wafers; Forming a boron ion layer at a predetermined depth in the first wafer; Growing a buffer single crystal silicon layer on the boron ion layer; Growing a single crystal silicon layer on the buffer single crystal silicon layer; Forming an oxide film for a buried insulation film on the single crystal silicon layer and the second wafer, respectively, of the first wafer; Bonding the first wafer and the second wafer to abut the oxide film for buried insulation; Removing the first wafer using the boron ion layer as an etch stop layer; And Removing the boron ion layer, the remaining first wafer, and the buffered single crystal silicon layer by using the single crystal silicon layer as an etch stop layer. 2. The method of claim 1, further comprising forming a capacitor electrode in contact with the single crystal silicon layer between forming the single crystal silicon layer and forming an oxide film for a buried insulating film on the first wafer. A method of manufacturing an SOI semiconductor substrate. The method of claim 1 or 2, wherein the boron ion layer is formed by implanting boron ions with 10 ¹⁴ to 10 ¹⁷ doses / cm 2 of ions at an energy of 10 to 200 KeV. The method of claim 1 or 2, wherein the buffer single crystal silicon layer is characterized in that the SiHCl ₃ or SiH ₂ Cl ₂ solution is deposited at a flow rate of 0.5 to 3L / min, B ₂ H ₆ solution at a flow rate of 0.1 to 5L / min A method for producing an SOI semiconductor substrate. 4. The method of claim 3 wherein the buffer single crystal silicon layer is grown to about 100 to 5000 microns thick. The method of claim 1 or 2, wherein the single crystal silicon layer is characterized in that the SiHCl ₃ or SiH ₂ Cl ₂ solution is grown by flowing 0.5 to 3L / min, B ₂ H ₆ solution by flowing about 0.1 to 5L / min Method of manufacturing a SOI semiconductor substrate. 7. The method of claim 6, wherein the single crystal silicon layer is formed to a thickness of 100 to 2000 microns. The method of manufacturing an SOI semiconductor substrate according to claim 1 or 2, wherein the buried insulating oxide film is formed of any one selected from BPSG film, HDP oxide film, PE-TEOS oxide film and SOG oxide film. The method of claim 8, wherein the oxide film is formed to a thickness of about 1000 to 10000 kV by chemical vapor deposition. 3. The fabrication of an SOI semiconductor substrate according to claim 1 or 2, further comprising a cleaning step for a surface hydrophilization treatment while removing particles on the surface before bonding the first and second wafers. Way. The method of claim 10, wherein the cleaning process is performed using an SC-1 solution, a piranha washing solution, or a mixed solution thereof. The method of claim 10, wherein the cleaning process is performed at 700 to 1200 ° C., O ₂ or N ₂ , for 30 to 120 minutes. The method of claim 1, wherein the bonding step is bonded under a vacuum of 7.5 × 10 ⁻¹ to 7.5 × 10 ⁻⁴ torr. The method according to claim 1 or 2, wherein the bonding strength between the bonding of the wafers and the polishing of the first wafer is improved to 30 to 120 in an O ₂ or N ₂ atmosphere at 700 to 1200 ° C. A process for producing an SOI semiconductor substrate, characterized in that it proceeds for minutes. The method of claim 1, wherein the removing of the first wafer using the buffer single crystal silicon layer as an etch stop layer comprises polishing the first wafer to a predetermined thickness and wetting the remaining first wafer. A method of manufacturing an SOI semiconductor substrate comprising the step of etching. The polishing method of claim 15, wherein the polishing of the first wafer by a predetermined thickness comprises rotating the polishing chuck wafer at about 50 to 400 rpm and rotating the spindle at about 1000 to 4000 rpm. A method of manufacturing an SOI semiconductor substrate, wherein the wafer is polished so as to be about µm / min so as to remain by a predetermined thickness. The method of claim 15, wherein the remaining first wafer is wet-etched with a solution in which HNO ₃ : HF: H ₂ SO ₄ : H ₃ PO ₄ is mixed at 0.5-5: 0.5-2: 0.5-1: 0.5-3. SOI semiconductor substrate manufacturing method characterized in that. The SOI semiconductor according to claim 15, wherein the remaining first wafer is wet-etched with NH ₄ OH: H ₂ O ₂ : H ₂ O with a mixed solution of 1-4: 0-0.5-0.5: 5-10. Method of manufacturing a substrate. The method of claim 1, wherein the boron ion layer, the remaining first wafer, and the buffer single crystal silicon layer are removed by chemical mechanical polishing using the single crystal silicon layer as an etch stop layer. 20. The method of claim 19, wherein the high concentration single crystal silicon layer is removed at a rotational speed of the polishing chuck table at 10 to 30 rpm, a pressure for pressing the spindle at about 4 to 8 psi, and a rotational speed of the spindle at 20 to 40 rpm. SOI semiconductor substrate manufacturing method characterized in that.