JP2734034B2 - Processing method of silicon semiconductor substrate - Google Patents

Description

The present invention relates to a method for processing a silicon semiconductor substrate, and more particularly to a method for forming a defect layer serving as a gettering source.

[Conventional technology]

Techniques for gettering harmful impurities and the like by using a crystal defect layer formed in a silicon semiconductor substrate are roughly classified into an intrinsic gettering (hereinafter abbreviated as IG) technique and an extrinsic getter according to a method of forming the defect layer. There is a ring (hereinafter abbreviated as EG) technology. IG
A typical technique is to form a defect layer inside a silicon semiconductor substrate by depositing dissolved oxygen originally contained in supersaturation in a silicon single crystal pulled by the Czochralski method by heat treatment.

On the other hand, EG technology intentionally introduces lattice strain on the back surface side of the semiconductor substrate, for example, mechanically damages the back surface of the silicon semiconductor substrate, or diffuses impurities such as phosphorus on the back surface of the silicon semiconductor substrate, A lattice mismatch dislocation network is generated, or a lattice is damaged by implantation of ions such as argon, or a silicon nitride film is grown on the back surface of the silicon semiconductor substrate and heat-treated at a high temperature to form a silicon semiconductor substrate and silicon. There is a method of forming a strain field at the interface with the nitride film. Further, a method of growing a polycrystalline semiconductor film on the back surface of a silicon semiconductor substrate and using a crystal grain boundary of the polycrystalline semiconductor film as a gettering source is also included in the EG technology.

[Problems to be solved by the invention]

However, in the conventional gettering technique described above, for example, in the IG technique, since the mechanism of oxygen precipitation includes extremely diverse and complicated factors, complete control of the oxygen precipitation is extremely difficult, and the defect layer is not sufficiently controlled. Formation is not enough,
On the contrary, there is a defect that a defect is generated in an active region that should be defect-free, thereby lowering a manufacturing yield of a semiconductor device.

On the other hand, EG technology often involves deformation and contamination of silicon semiconductor substrates, is generally less effective than IG technology, and has the drawback that the gettering action does not last long during the semiconductor device manufacturing process. .

The purpose of the present invention is mainly IG technology, but EG
Another object of the present invention is to provide a novel method for processing a silicon semiconductor substrate, which can also obtain the effect described above.

[Means for solving the problem]

A processing method according to the present invention includes a step of forming a silicon oxide film on the entire surface or a part of one main surface of a silicon substrate, further applying a silicon nitride film on the entire surface of the one main surface, and heat-treating the silicon substrate. A step of removing supersaturated oxygen to a certain depth by external diffusion on the other main surface of the silicon substrate not covered with the silicon nitride film;
Removing all or a portion of the silicon nitride film, heat treating the silicon substrate to form oxygen precipitation nuclei in the substrate, and removing the silicon nitride film completely or partially to remove the silicon nitride film. A heat treatment in an atmosphere containing oxygen to form stacking faults based on the oxygen precipitation nuclei on the one main surface.

[Action]

In the second step of heat-treating the silicon semiconductor substrate at a high temperature (1050 ° C. or higher), supersaturated oxygen is removed and reduced to a certain depth from one surface (the surface on which a semiconductor element is formed), and the precipitation nuclei during internal crystal formation are formed. To reduce. In this method, since the other surface does not have oxygen diffused outward by the silicon nitride film, a sufficient amount of supersaturated oxygen which gives the IG effect later remains on this surface. Next, at low temperature (less than 1000 ℃, usually 600
In the fourth step of heat treatment at a temperature of about 700 ° C.), oxygen precipitation nuclei can be accurately formed in a region where supersaturated oxygen remains.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 4 show the first embodiment. FIG. 1 shows a first step, in which a silicon semiconductor substrate 1 is shown.
70 nm silicon oxide film 2 on one surface
Then, a 15 nm silicon nitride film 3 is formed on the same surface by the CVD method. The silicon semiconductor substrate 1
It contains interstitial oxygen of 1.4 × 10 ¹⁸ cm ^-3 and has a plane orientation (100).
It has a diameter of 125 mm and a thickness of 600 μm.

Next, FIG. 2 shows a second step, in which the silicon semiconductor substrate 1 is subjected to a heat treatment at 1100 ° C. for 2 hours in a nitrogen atmosphere containing 5% of oxygen.
Of the interstitial oxygen distributed almost uniformly inside the surface of the silicon oxide film 2 and the silicon nitride film 3, the external diffusion 4 occurs from the surface which is not masked. The oxygen concentration during the period becomes lower. This region is used as a device active region. At this time, the stress due to the silicon nitride film 3 is relieved by the silicon oxide film 2, and the silicon semiconductor substrate 1 does not deform.

Subsequently, after a third step of removing the silicon oxide film 2 and the silicon nitride film 3 from the silicon semiconductor substrate 1, a fourth step is performed in a nitrogen atmosphere as shown in FIG.
Heat treatment at 0 ° C. for 4 hours is performed to grow oxygen precipitation nuclei 5 in a region where the interstitial oxygen concentration is high inside silicon semiconductor substrate 1. Next, when this silicon semiconductor substrate 1 is subjected to a heat treatment at 1000 ° C. for 16 hours in a dry oxygen atmosphere, as shown in FIG. 4, oxygen precipitates 6 are formed in regions where oxygen precipitate nuclei 5 are formed. grow up. Oxygen precipitate nuclei 5 are present at high density near the surface first masked by the silicon oxide film 2 and the silicon nitride film 3. , Stacking faults 7 are generated at high density, which acts as a strong EG source. As described above, the process shown in FIG. 4 is not performed at the wafer stage, and a similar effect is often obtained during the manufacturing process of the semiconductor device.

The silicon semiconductor substrate fabricated as described above is
Unlike the one using EG technology, there is no stress that causes the silicon semiconductor substrate to be deformed by heat treatment, etc., and since the EG source uses internal defects exposed to the surface, the gettering source is inexhaustible You can say,
There is no anneal-out or repeated consumption of heat treatment. Further, in the method for manufacturing a semiconductor substrate according to the present invention, there is no fear that the semiconductor substrate is contaminated by harmful impurities or the like.

Furthermore, since the present invention can obtain an extremely strong gettering action by a synergistic effect of the IG technology and the EG technology, it is not necessary to take a danger of forming high-density internal defects near a region to be defect-free. Absent. From these facts, it can be said that the semiconductor substrate manufactured according to the present invention is extremely effective for manufacturing a highly reliable semiconductor device at a high yield.

Next, a second embodiment will be described. First, as shown in FIG. 5, a silicon oxide film 9 having windows arranged in a lattice on a silicon semiconductor substrate 8 is formed. As in the first embodiment, the silicon semiconductor substrate 8 contains interstitial oxygen of 1.4 × 10 ¹⁸ cm ⁻³ , has a diameter of 125 mm, a thickness of 600 μm, and a plane orientation (100). The silicon oxide film 9 is formed to a thickness of 30 nm by a CVD method and then forms a pattern by photoetching. Here, the size of the portion of the silicon oxide film 9 that will be the window is a square having a side of 2 mm, and the distance between these windows is 2 mm. Note that each side of this window corresponds to <11
0> direction is desirable.

Next, a silicon nitride film 10 having a thickness of 40 nm is grown on the same surface of the silicon semiconductor substrate 8 by the CVD method to obtain a structure as shown in FIG. Next, as a second step, as shown in FIG. 7, the silicon semiconductor substrate 8 is subjected to a heat treatment at 1100 ° C. for 2 hours in a nitrogen atmosphere containing 5% oxygen to form a silicon oxide film 9 and a silicon nitride film. External diffusion 10 of interstitial oxygen in a region near the surface not masked by 10 is caused. At this time, dislocations 12 are generated at high density due to thermal stress at the interface where the silicon nitride film 10 is in direct contact with the silicon semiconductor substrate 8 through the window of the silicon oxide film 9.

Then, as a third step, as shown in FIG. 8, the silicon nitride film 10 is removed by a photo-etching method except for a portion where the silicon nitride film 10 is in contact with the silicon semiconductor substrate 8, and the silicon oxide film 9 is further removed. I do. In the fourth step, the silicon semiconductor substrate 8 is subjected to a heat treatment at 650 ° C. for 5 hours in a nitrogen atmosphere to grow oxygen precipitation nuclei 13 as shown in FIG.

When the silicon semiconductor substrate 8 that has been subjected to the above treatment is further subjected to a heat treatment at 1000 ° C. for 16 hours in a dry oxygen atmosphere, oxygen precipitates 14 are formed as shown in FIG. At this time, on the surface on which the pattern of the silicon nitride film 10 is formed, the stacking fault is caused by the growth of the oxygen precipitate 14 and the progress of oxidation of the silicon semiconductor substrate 8 in the portion where the silicon semiconductor substrate 8 is exposed. 15 occur at high density. In this embodiment, the silicon semiconductor substrate 8 and the silicon nitride film 10
An extremely strong gettering action is obtained due to dislocations 12 generated at the interface with silicon, stacking faults 15 generated at portions where the silicon semiconductor substrate 8 is exposed, and oxygen precipitates 14 generated inside the silicon semiconductor substrate. Can be This silicon semiconductor substrate is further less deformed by heat treatment or the like than in the case where a silicon nitride film is grown on one entire surface as in the first embodiment.

〔The invention's effect〕

As described above, according to the present invention, first, only on one surface side of the silicon semiconductor substrate, a fixed region where supersaturated oxygen is removed or reduced is formed, and then a low-temperature heat treatment is performed.
Oxygen precipitation nuclei are formed outside the above-mentioned region. In the certain region, a semiconductor element is formed in a manufacturing process.At this time, the temperature becomes 1000 ° C. or higher, an oxygen precipitate grows in a region of an oxygen precipitate nucleus, and a lattice defect performing an intrinsic gettering action occurs. . This lattice defect generation region can be controlled with high accuracy. In addition, the other surface of the silicon semiconductor substrate (the back surface on which no semiconductor element is formed) has oxygen precipitation nuclei up to the surface, so that stacking faults or dislocations occur on the surface, which is also a strong extrinsic gettering source. Since special surface treatment is not performed unlike the conventional extrinsic gettering, there is no fear of deformation and contamination of the semiconductor substrate, and there is an effect of giving a strong and long-lasting gettering action.

[Brief description of the drawings]

FIG. 1 to FIG. 4 are cross-sectional views showing respective steps of the first embodiment,
FIG. 5 is a view showing a pattern of a silicon oxide film formed on one surface of a silicon semiconductor substrate according to a second embodiment, and FIGS. 6 to 10 are each a figure after forming a silicon oxide film pattern of the second embodiment. It is sectional drawing which shows a process. 1,8 …… Silicon semiconductor substrate, 2,9 …… Silicon oxide film,
3,10: Silicon nitride film, 4,11: External diffusion of oxygen, 5,
14 ... Oxygen precipitate nucleus, 6,13 ... Oxygen precipitate, 7,15 ... Stacking fault, 12 ... Dislocation.

Claims (1)

(57) [Claims] A step of forming a silicon oxide film on an entire surface or a part of one main surface of a silicon substrate and further depositing a silicon nitride film on an entire surface of the one main surface; Removing, by external diffusion, supersaturated oxygen to a predetermined depth on the other main surface of the silicon substrate on which the nitride film is not deposited; removing all or part of the silicon nitride film; Heat-treating the silicon substrate to form oxygen precipitation nuclei in the substrate, and removing all or a part of the silicon nitride film, and then heat-treating the silicon substrate in an atmosphere containing oxygen to obtain a stacking fault based on the oxygen precipitation nuclei. Forming a silicon substrate on the one main surface.