JPH06232406A - Substrate for semiconductor element - Google Patents

Abstract

PURPOSE:To provide a substrate for a semiconductor element in which the potential of the conductive substrate can be easily controlled by taking out the continuity of electricity of the conductive substrate through a contact hole from a semiconductor layer side in the plural places of the circumferential edge part of the substrate. CONSTITUTION:This substrate is a layered product in which a single crystal Si layer 3 is stuck together to an Si substrate 1 through an SiO2 layer 2, and the other single crystal Si layer and SiO2 layer than the effective region to be used for a semiconductor element all are removed to form an SiO2 layer 2' by oxidizing a gate and to perform the element isolation and a polycrystalline Si is deposited to form a gate electrode 4. At the same time, ions are implanted into the source and the drain of an element and an Si substrate 1. After an insulating layer (SiO2 layer) is formed, contact holes 5, 5' are made in the insulating layer to perform the wirings 6, 6' thereof. Therefore, the plural contact holes 5' are formed in the circumferential edge part of the substrate 1 to take out the continuity of electricity of the conductive substrate 1, thereby being able to more uniformly control the potential of the conductive substrate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor element substrate used in a device having a semiconductor element in a light transmitting region, such as an active matrix driving type liquid crystal display device using a TFT (thin film transistor).

[0002]

2. Description of the Related Art In the technology of SOI (silicon on insulator) in which a single crystal Si layer is formed on an insulating layer, in a semiconductor element substrate, single crystal Si is α (amorphous).
Since it has many advantages over -Si and polycrystalline Si, it has been widely studied and is expected to be used for a thin film transistor (TFT) or the like which has been attracting attention in recent years.

As a method of manufacturing this SOI, for example,
SIMOX (Separat) for separately forming a single crystal Si thin film by ion-implanting oxygen into a single crystal Si substrate (bulk)
Inby Implanted Oxygen) is known.

Further, the present applicant has achieved a method of epitaxially growing single crystal Si on the surface of porous Si as one of the SOI techniques described above. According to this method, a single crystal Si substrate having almost no defects can be obtained.
The method will be briefly described.

FIG. 4 shows a manufacturing process of a single crystal Si substrate using porous Si. First, the surface of the first Si substrate 11 is made porous to form a porous Si layer 12 (a). An Si single crystal 3 is epitaxially grown on the surface of the porous Si layer 12 (b). On the other hand, a Si substrate 1 is prepared, an insulating SiO ₂ layer 2 is formed on the surface thereof, the SiO ₂ layer 2 and the single crystal Si layer 3 are bonded (c), and the porous Si substrate is etched. It is removed to obtain a Si substrate (d).

[0006]

As described above, the SOI is formed on the Si substrate which is a semiconductor via the insulating layer. Therefore, a semiconductor element manufactured using SOI is
The characteristics are deteriorated under the influence of the potential of the Si substrate. In the case of a normal semiconductor element substrate such as an LSI, a conductive layer made of metal or the like is formed on the back surface of a Si substrate, and the potential of the conductive layer is controlled.

However, in mounting the semiconductor element substrate on a display device or the like, it is desirable to take out a contact on the semiconductor element side rather than controlling the potential on the back side of the Si substrate.

Further, the above-mentioned SOI fabrication technique using porous Si achieved by the applicant of the present invention is applied to a liquid crystal panel such as an active matrix type liquid crystal display device using a TFT, which has been attracting attention in recent years. When used in a device having a semiconductor element in the light-transmitting region, as shown in FIG. 3, after a SiO ₂ layer is formed on the surface and bonded to a transparent substrate, as shown in FIG. 13 is formed (a), and the region to be made transparent is removed by etching the Si substrate 1 to form a hollow portion 15 to be a light transmitting region (b). In this hollowing process, the insulating layer 14 such as SiO ₂ or SiN ₄ is formed on the back surface of the Si substrate to serve as a mask for etching. Therefore, the conventional method of contacting from the back surface requires the step of removing the insulating layer. It is complicated.

An object of the present invention is to easily control the potential of a conductive substrate in a semiconductor element substrate having the conductive substrate.

[0010]

The present invention is a semiconductor element substrate having a semiconductor layer formed on a conductive substrate with an insulating layer interposed between the semiconductor layer and the semiconductor layer at a plurality of positions on the periphery of the substrate. The semiconductor element substrate is characterized in that the conduction of the conductive substrate is taken out from the side through a contact hole. The present invention is widely used in the semiconductor field.
The invention is preferably applied to, and is particularly suitable for the SOI described above.

The above-mentioned porous Si will be described in detail. Porous Si is described in 1956 by Uhir et al.
It was discovered in the course of research on electropolishing of semiconductors in the year [A. Uhir, Bell System. Tech.
J. , Vol 35, 333 (1956)]. In addition, Unami et al. Studied the dissolution reaction of Si in anodization and reported that the anodic reaction of Si in HF solution requires holes, and the reaction is as follows [T. ． Unagami: J. Electrochem. Soc. , Vo
l. 127, 476 (1980)].

Si + 2HF + (2-n) e ⁺ → SiF ₂ + 2H ⁺ + ne ^- SiF ₂ + 2HF → SiF ₄ + H ₂ SiF ₄ + 2HF → H ₂ SiF ₆ or Si + 4HF + (4-λ) e ⁺ → SiF ₄ + 4H ⁺ + λe ^- where _{SiF 4 + 2HF → H 2 SiF} 6, e + , e ^-, respectively, represent the holes and electrons. Further, n and λ are the numbers of holes necessary for dissolving Si1 atoms, respectively, and porous Si is formed when the condition of n> 2 or λ> 4 is satisfied.

As described above, holes are required to form porous Si, and P-type Si is more likely to be transformed into porous Si than N-type Si. However, it is known that N-type Si is also transformed into porous Si if holes are injected. [R. P. Holmstrom and J. Y.
Chi. Appl. Phys. Lett. vol. Four
2, 386 (1983)].

The porous Si produced in this way is
By changing the HF solution concentration to 50 to 20% as compared with the density of single crystal Si of 2.33 g / cm ³ , the density can be changed to the range of 1.1 to 0.6 g / cm ^3. . According to observation with a transmission electron microscope, pores having an average diameter of about 600 Å are formed in this porous Si layer. Despite its density being less than half that of single crystal Si, single crystallinity is maintained, and single crystal Si can be epitaxially grown on the upper part of the porous layer.

Generally, when single-crystal Si is oxidized, its volume increases about 2.2 times, but it is possible to suppress the volume expansion by controlling the density of the porous material.
Warpage of the substrate and cracks introduced into the surface residual single crystal layer can be avoided. The volume ratio R of single crystal Si after being oxidized to porous Si can be expressed as follows.

R = 2.2 × (A / 2.33) where A is the density of porous Si. If R = 1,
That is, if there is no volume expansion after oxidation, A = 1.06
(G / cm ³ ), and if the density of porous Si is set to 1.06, volume expansion can be suppressed.

Further, since the porous layer has a large amount of voids formed therein, its density is reduced to less than half. As a result, the surface area increases dramatically compared to the volume,
Its chemical etching rate is significantly enhanced compared to the etching rate of the non-porous Si layer.

The conditions for making the Si substrate porous according to the present invention are not particularly limited. For example, the following conditions are preferably used.

The current density ^{J = 10 -3 ~10 0 A /} cm 2 preferably ¹⁰ -2 ^~10 -1 A / cm ² solution _{= HF (49%): C} 2 H 5 OH: H 2 O porous layer Film thickness = 0.1 to 100 μm, preferably 1 to 10 μm Porosity = 20 to 50%

[0020]

EXAMPLES AND ACTION The present invention will be described in detail below by taking Si as an example.

FIG. 1 shows a manufacturing process of an embodiment of the semiconductor element substrate of the present invention. In the figure, 1 is a Si substrate, 2 to
2 "is a SiO ₂ layer as an insulating layer, 3 is a single crystal Si layer,
Reference numeral 4 is a gate electrode, 5 is a contact hole, and 6 and 6'are wirings. This figure (a) corresponds to the above-mentioned figure 4 (d), the single crystal Si layer 3 through the SiO ₂ layer 2 Si substrate 1
It is a laminated body stuck to. All of the single crystal Si layer and the SiO ₂ layer other than the effective area used for the semiconductor element are removed,
Gate oxidation is performed to form a SiO ₂ layer 2 '(b). Next, element isolation is performed (c), polycrystalline Si is deposited to form the gate electrode 4, and at the same time, ion implantation is performed on the source and drain of the element. At this time, the Si substrate 1 is also ion-implanted at the same time, so that the contact property of the wiring 5 ′ described later can be improved. Next, and after forming the insulating layer (SiO ₂ layer) 2 ″ (d), the contact holes 5 and 5 ′ are drilled in the insulating layer to connect the wirings 6 and 6 ′ (e). In addition, when the unnecessary single crystal Si layer is removed in the steps (a) and (b), the SiO ₂ layer is also removed, so that the element contact hole 5 and the Si substrate contact hole 5 ′ are removed.
Are formed in the insulating layer having the same thickness, and the manufacturing efficiency is good. Therefore, there is no problem in the structure of the present invention even if the SiO ₂ layer 2 is left as it is without being removed.

Further, as shown in FIG. 2, an insulating layer 7 and a pixel electrode 8 are formed on the semiconductor element substrate of the present invention obtained by the process shown in FIG. 1, and the Si substrate 1 is hollowed out in a necessary transparent region. By making it transparent, a drive electrode substrate for a liquid crystal display device can be obtained.

FIG. 3 shows a view of the semiconductor substrate of the present invention viewed from the semiconductor element side. In the figure, A to D are respective semiconductor element substrates, and normally, a plurality of semiconductor element substrates are simultaneously manufactured from one wafer in this way, and are cut and separated by a cut line 10. Reference numeral 9 denotes a Si edge, which is a region where a semiconductor element is formed. In the present invention, as shown in the figure, by forming a plurality of contact holes 5'in the peripheral portion of the substrate and taking out conduction of the conductive substrate, the potential of the conductive substrate can be controlled more uniformly. In particular,
In SOI, since the substrate is a semiconductor and its conductivity is not high, it is difficult to control the potential at only one place, and the potential is likely to be uneven within the same substrate, so the present invention is preferably used.

[0024]

As described above, in the semiconductor element substrate of the present invention, since the back surface potential can be uniformly controlled, the characteristics of the semiconductor elements are uniform in the same substrate, and all the elements can operate stably. Can be done. Therefore, a highly reliable display device can be obtained. Moreover, the conduction of the conductive substrate according to the present invention can be created at the same time in the normal semiconductor element forming process, so that it is not necessary to add a new process in manufacturing, and the manufacturing design and yield of the substrate can be improved. It is also very useful.

[Brief description of drawings]

FIG. 1 is a diagram showing a manufacturing process of an embodiment of a semiconductor element substrate of the present invention.

FIG. 2 is a diagram showing a manufacturing process of a liquid crystal display device using the semiconductor element substrate of the present invention.

FIG. 3 is a view of the semiconductor element substrate of the present invention viewed from the semiconductor element side.

FIG. 4 is a diagram showing a manufacturing process of single crystal Si according to the present invention.

FIG. 5 is a diagram showing a manufacturing process of a liquid crystal display device using single crystal Si according to the present invention.

[Explanation of symbols]

1 Si substrate 2 to 2 "SiO ₂ layer 3 single crystal Si layer 4 gate electrode 5, 5 'contact hole 6,6' wiring 7 insulating layer 8 pixel electrode 9 Si edge 10 cut line 11 Si substrate 12 made porous Si layer 13 semiconductor element 14 insulating layer 15 hollow portion

Claims (2)

[Claims] 1. A semiconductor element substrate comprising a conductive substrate and a semiconductor layer formed on the conductive substrate with an insulating layer interposed between the conductive layer and the semiconductor layer. A semiconductor element substrate characterized by taking out the continuity of the substrate. 2. The semiconductor element substrate according to claim 1, wherein the semiconductor is Si.