JPH04162630A - Semiconductor substrate - Google Patents

Abstract

PURPOSE:To be endowed with sufficient mechanical strength and sufficient flatness and to increase a gettering effect by a method wherein another semiconductor substrate for support use is bonded, via a specific compound film, to the other main face of a semiconductor single-crystal silicon substrate which has a device formation region on one main face. CONSTITUTION:Before a bonding operation, the bonding face of a polycrystalline silicon film 4 is polished. After that, a hydrophilic treatment is executed respectively to it and to a single crystal silicon substrate 5; a phenyl group is attached; they are overlapped in a clean atmosphere. A heating operation is executed; a dehydration treatment is executed; after that, a heat treatment is executed additionally; their bonding strength is increased. The surface 2 of a single-crystal silicon substrate 1 and the rear 7 of the single-crystal silicon substrate 5 are polished. The single-crystal silicon substrate 1 for device formation use and the single-crystal silicon substrate 5 for support use are pasted via the polycrystalline silicon film 4; a structure is formed. The distance between the surface on which a device is formed of the single-crystal substrate 1 and the polycrystalline silicon film 4 for gettering use can be made short without being restricted by mechanical strength.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a semiconductor substrate for forming a semiconductor device.

[Conventional technology]

FIG. 12 shows a conventionally used single crystal silicon substrate. In the figure, one main surface (front surface) 2 of a single-crystal silicon substrate 1 is exposed as it is for forming a device, but the other main surface (back surface) 3 is coated with polycrystalline silicon by a CVD method. A silicon film 4 is formed.

This polycrystalline silicon film 4 is formed for the purpose of a gettering effect that collects and confines minute heat-induced defects and metal contamination that occur during heat treatment when a device is formed on the surface of the single-crystal silicon substrate 1. That is, the part actually required for device formation is the surface 2 side of the single-crystal silicon substrate 1, but if that surface becomes contaminated, the contaminants will diffuse into the inside of the substrate due to heat treatment. The diffusion rate has a unique value for each element, and reaches the back surface 3 of the substrate after a certain period of time. At this time, if polycrystalline silicon 4 exists on the back surface 3, contaminants are gettered and confined by the strain generated at the interface between the back surface 3 and the polycrystalline silicon film 4 and at the grain boundaries inside the polycrystalline silicon film 4. , it is no longer possible to diffuse back toward the surface 2 of the substrate. In this way, the surface 2 of the single crystal silicon substrate 1 can be kept free from contamination.

[Problem to be solved by the invention]

In such a conventional single-crystal silicon substrate, a device formation region is located on the front surface, and a polycrystalline silicon film having a gettering effect is located on the back surface, separated by the thickness of the single-crystal silicon substrate. For this reason, metals with a small diffusion coefficient (AZ).

Regarding contamination such as Ti, etc., there is a problem in that the contamination in the process cannot be completely gettered during the process, especially when heat treatment is performed at a low temperature of 600° C. or less or for a short time. This tendency is getting worse as the diameter of the substrate becomes larger and the thickness is also increasing in order to provide sufficient mechanical strength.

Further, as the degree of integration of devices increases, requirements for substrate flatness are becoming stricter, and in order to obtain high flatness, it is necessary to perform double-sided polishing. However, in the structure in which the polycrystalline silicon film is exposed on the back surface as described above, there is a problem that the polycrystalline silicon film is also polished during double-sided polishing, and the gettering effect is weakened.

An object of the present invention is to bring the device-forming surface of a single-crystal silicon substrate closer to the gettering region while maintaining sufficient flatness and mechanical strength.

[Means to solve the problem]

In the present invention, another support semiconductor substrate is bonded to the back surface of a semiconductor single-crystal silicon substrate via a gettering silicon or silicon compound film to form a single semiconductor substrate.

[For production]

Because the supporting semiconductor substrate provides sufficient mechanical strength, single-crystal silicon substrates can be polished to the extent that polishing precision allows.
It becomes possible to reduce the thickness to the limit required for device fabrication. This makes it possible to significantly reduce the distance between the device-forming surface of the single-crystal silicon substrate and the gettering film on the back surface, and to prevent contamination of metals with small diffusion coefficients. Also, gettering occurs in a short time before it becomes a crystal defect or dislocation.

In addition, because the gettering film is sandwiched between a single crystal silicon substrate and a supporting semiconductor substrate and is not exposed to the outside, it is protected from the effects of double-sided polishing, thermal intensification, cleaning, etching, etc. It is easy to maintain the gettering effect from the initial stage to the final process.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a semiconductor substrate showing an embodiment of the present invention. In the same figure, 1 is a single-crystal silicon substrate;
In order to fabricate various devices on the surface 2, a material having a predetermined oxygen concentration, resistivity, orientation, dopant species, etc. is used. Its front surface 2 and back surface 3 are polished to a mirror surface, and the back surface 3 is coated with a polycrystalline silicon film 4 for gettering.
It is deposited by the VD method at a reaction temperature of 300 to 800°C.

It is sufficient that the thickness of the polycrystalline silicon film 4 is about 0.05 to 5 μm, and even if it is made thicker than that, the effect remains the same even though the cost increases. Through this polycrystalline silicon film 4,
Furthermore, another single crystal silicon substrate 5 is bonded at a bonding surface 6.

The single crystal silicon substrate 5 is used for support to provide mechanical strength, but must be firmly bonded to the polycrystalline silicon film 4. Therefore, before bonding, it is desirable to polish the bonding surface of the polycrystalline silicon film 4 by about 0.01 to 0.50 μm.

Thereafter, each of the polycrystalline silicon substrates 5 is subjected to a hydrophilic treatment to have a phenol group attached thereto, and then superimposed on each other in a clean atmosphere. Then, after dehydration treatment is performed by heating at 200 to 800°C for 2 hours, the adhesive strength is increased by further performing heat treatment at 800 to 1200°C. At this time, an oxygen concentration distribution is formed with the peak at the bonding surface 6. The thickness of this layer is 0.1 μm or less and works to increase the bonding strength, but it is not 5102 mm thick.

Thereafter, the front surface 2 of the single crystal silicon substrate 1 and the back surface 7 of the single crystal silicon substrate 5 are polished. At this time, the thickness of the single-crystal silicon substrate 1 is approximately 30 to 50 μm, and the thickness of the single-crystal silicon substrate 5 is adjusted so that the thickness of the entire semiconductor substrate becomes a standard thickness. Polishing may be done by grinding or etching.

By bonding the single-crystal silicon substrate 1 for device formation and the single-crystal silicon substrate 5 for support through the polycrystalline silicon film 4 to form a structure, a device of the single-crystal silicon substrate 1 is formed. The distance between the surface to be treated and the polycrystalline silicon film 4 for gettering can be shortened without being restricted by mechanical strength.

For example, if this is 50 μm, the thickness of the single-crystal silicon substrate 1, which is normally 500 μm or more in the conventional substrate shown in FIG. The time required to do this is 10
It will be less than one-fold.

Furthermore, since the polycrystalline silicon film 4 is sandwiched between two single-crystalline silicon substrates and is not exposed to the outside, consumption of the polycrystalline silicon film 4 due to polishing, heat treatment, cleaning, etching, etc. in the device process can be eliminated. I can do it. As a result, high gettering ability can be completely maintained from the initial stage of the device process to the final process.

Furthermore, the warpage of the substrate can be reduced.

Conventionally, a structure in which polycrystalline silicon films 4 having different expansion coefficients were simply applied to the back surface 3 of a single-crystalline silicon substrate 1 had a problem of warping, but the polycrystalline silicon film 4 was formed by forming two single-crystalline silicon substrates. By adopting the sandwiching structure, two single crystal silicon substrates 1,
Since the semiconductor substrates 5 are warped in opposite directions, the warpage of the semiconductor substrate as a whole is reduced.

In addition, in the conventional structure in which the polycrystalline silicon film 4 is exposed on the back surface of the single-crystal silicon substrate 1, only one-sided polishing, which is polishing only the front surface 2 of the single-crystal silicon substrate 1, can be performed in order not to damage the polycrystalline silicon film 4. Although planarization was difficult, by sandwiching the polycrystalline silicon film 4 between the single-crystal silicon substrates 1 and 5, the front surface 2 of the single-crystal silicon substrate 1 and the back surface 7 of the single-crystal silicon substrate 5 were polished. It is possible to polish both sides and achieve high flatness.

In the above embodiment, the polycrystalline silicon film 4 was provided at a depth of about 50 μm from the surface 2 of the single crystal silicon substrate 1, but the present invention is not limited to this.
It is sufficient if the thickness is about 5 μm or more.

In particular, as shown in FIG. 2, if the thicknesses of the single crystal silicon films 1 and 5 sandwiching the polycrystalline silicon film 4 are made equal, the warpage of the substrate can be minimized.

Conversely, as shown in FIG.
(Gettering) effect may also be provided. 8 in the figure schematically shows an IG source.

As a support substrate, instead of the single crystal silicon substrate 5,
As shown in FIG. 4, a polycrystalline silicon substrate 9 may be bonded and used. 10 indicates the back side thereof.

In addition, in order to avoid reducing the gettering effect of the single crystal silicon substrate 1 on the device formation side by gettering up to the support substrate side where no gettering is necessary, a polycrystalline silicon film is added as shown in FIG. 4 plus oxide film 1
1 or 6, a nitride film 12 may be provided.

Furthermore, as shown in FIG. 7, layers 1B having different types or concentrations of dopants may be stacked on two surfaces of one single crystal silicon substrate to form the single crystal silicon substrate 1.

2B shows the surface of the shrimp layer 1B. Further, as shown in FIG. 8, an embedded diffusion region 13 may be formed in advance on the back surface 3 on the side to be bonded to the supporting substrate.

Alternatively, as shown in FIG. 9, the polycrystalline silicon film 4 is formed on the mechanically strained layer 14 by damaging the back surface 3 of the single crystal silicon substrate 1 by sandblasting, laser irradiation, or ion implantation. You can.

Further, as shown in FIG. 10, the back surface of the support single crystal silicon substrate 5 may be etched and a gettering process may be performed, such as applying a polycrystalline silicon film roughened by sandblasting. This figure shows an example in which a polycrystalline silicon film 16 is provided on the etched surface 15.

Alternatively, as shown in FIG. 11, the peripheral portion of either the device forming side or supporting side substrate may be removed within a range of about 5 mm or less and then bonded together.

In the example shown in the figure, a single crystal silicon substrate 1 provided with a polycrystalline silicon substrate 4 is chamfered. By doing this, peeling from the chamfered portion can be reduced, and the front and back sides of the semiconductor substrate can be easily washed at a glance.

Note that the gettering film may be an amorphous silicon film, a silicon nitride film, or an oxide film heavily doped with impurities instead of the polycrystalline silicon film.

〔Effect of the invention〕

As described above, according to the present invention, by creating a structure in which a dedicated support substrate is bonded to a single crystal silicon substrate for device formation via a gettering film, a single crystal silicon substrate for device formation can be easily bonded without reducing mechanical strength. By reducing the distance between the device forming surface of the crystalline silicon substrate and the gettering film, it becomes possible to polish both sides without damaging the gettering film. Therefore, a semiconductor substrate having sufficient mechanical strength and flatness and a high gettering effect can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the present invention, FIGS. 2 to 11 are sectional views showing other embodiments, and FIG. 1 is a sectional view showing a conventional example. 1-...Fist single crystal silicon substrate, 2...Surface, 3...
...Back surface, 4... Polycrystalline silicon film for gettering, 5... Single crystal silicon substrate for support, 10...
- Polycrystalline silicon substrate for support.

Claims (1)

[Claims] A semiconductor substrate formed by bonding a semiconductor single-crystal silicon substrate having a device formation region on one main surface to another supporting semiconductor substrate via a gettering silicon or silicon compound film.