JPH077748B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] In forming a semiconductor layer (SOI: Semiconductor On Insulator) on an insulating layer using a SIMOX method, group IV semiconductor ion implantation to a surface layer of a silicon substrate is added. This improves the crystallinity of the formed SOI.

[Industrial application field]

The present invention relates to a semiconductor device manufacturing method, and more particularly to a SIMOX
The present invention relates to a method of forming an SOI using the method.

SOI has been variously studied for its formation method, as it enables complete separation of elements such as transistors to be formed and high speed.

The SIMOX method, which is one method of forming SOI, is
I has the characteristic that the process of formation is simple, but the formed S
OI has some drawbacks, so improvement is desired.

[Conventional technology]

The conventional method of SOI formation using the SIMOX method is as shown in the side views (a) and (b) of FIG.

That is, first, as shown in FIG. 3A, a large amount of oxygen is deeply ion-implanted into the silicon substrate 1 to form an oxygen-implanted layer 2 in the substrate 1, and then heat treatment is performed to form the oxygen-implanted layer 2 in FIG. The buried silicon dioxide layer 3 is changed as shown. Then, a silicon layer 4 made of SOI using the silicon dioxide layer 3 as an insulating layer is formed.

The conditions for the ion implantation are, for example, that the acceleration energy is 15
The concentration distribution of the implanted oxygen in the substrate 1 at that time is 0 KeV and the dose amount is 2 × 10 ¹⁸ / cm ² , and is as shown by the curve A in FIG. 2 (concentration distribution diagram). The silicon dioxide layer 3 is a portion having a concentration of about 10 ²² / cm ³ , and the silicon layer 4 has a thickness of about 0.2 μm.

[Problems to be solved by the invention]

As can be seen from FIG. 2, the silicon layer 4 of SOI thus formed has an oxygen concentration of approximately 10 ²⁰ / cm ³ near the surface.
The crystallinity is not good because it reaches to.

Therefore, when a transistor is formed, if it is directly formed on the silicon layer 4, the characteristics of the transistor are deteriorated.
As shown in FIG. 5 in which an S-transistor is taken as an example, a deposited silicon layer 5 having a thickness of several μm is added on the silicon layer 4,
Often formed there.

However, in the MOS transistor (S is a source region, D is a drain region, G is a gate electrode) shown in FIG. 5, the depletion layer DL may not reach the silicon dioxide layer 3 during operation, which is a characteristic of utilizing SOI. There is a problem that speedup cannot be obtained.

[Means for solving problems]

In order to solve this problem, it is not necessary to add the deposited silicon layer 5, that is, the crystallinity of the SOI should be improved so that a transistor can be directly formed on the SOI formed by using the SIMOX method. Good.

According to the present invention, a group IV semiconductor ion implantation for a surface layer of a substrate is added to a conventional oxygen ion implantation, and a combination of oxygen implanted by heat treatment and a crystallization of the implanted group IV semiconductor are performed to form an SOI. It is achieved by the manufacturing method of.

[Action]

By the group IV semiconductor ion implantation, the oxygen concentration in the surface layer of the substrate becomes relatively lower than in the conventional case. Further, since the crystal of the group IV semiconductor (silicon, germanium, etc.) has the same diamond shape as the crystal of the substrate, it is incorporated into the crystal of the substrate by the heat treatment after the implantation.

Thus, the SOI crystal formed by the method of the present invention has improved crystallinity and reduces the deterioration of the characteristics of the transistor formed therein as compared with the SOI crystal formed by the conventional method. Therefore, the deposited silicon layer 5 described in FIG. No need to add.

〔Example〕

An embodiment of the method of the present invention will be described below with reference to FIGS. 1 and 2, and an example of use of the method of the present invention will be described with reference to FIG. The same reference numerals denote the same objects throughout the drawings.

An embodiment of the method of the present invention for forming SOI using SIMOX method is as shown in the side views (a) to (c) of FIG.

That is, first [see FIG. (A)], oxygen is ion-implanted into the silicon substrate 1 (acceleration energy 150 KeV,
The oxygen injection layer 2 is formed in the substrate 1 with a dose amount of 2 × 10 ¹⁸ / cm ² ). The concentration distribution of implanted oxygen in the substrate 1 is
It is like curve A in the figure. Here, the oxygen concentration is approximately 10 ²² / cm
The region ³ becomes the oxygen injection layer 2.

Next, referring to FIG. 2B, silicon is ion-implanted into the surface layer of the substrate 1 to form a silicon-implanted layer 6. The implantation conditions are an acceleration energy of 30 KeV and a dose of 2 × 10.
^{It is 15} / cm ² . The concentration distribution of the implanted silicon in the substrate 1 by this implantation is as shown by the curve B in FIG. 2, and the concentration in the vicinity of the surface of the substrate 1 exceeds 10 ²¹ / cm ³ and is several tens of times the oxygen concentration.

Next, see Fig. (C)!
Heat treatment for 10 hours. Then, the oxygen injection layer 2 is changed to the silicon dioxide layer 3, and on the silicon dioxide layer 3,
A silicon layer 4a in which the implanted silicon of the silicon implantation layer 6 is incorporated into the crystal of the substrate 1 is formed. The silicon layer 4a made of SOI has a lower oxygen concentration and improved crystallinity than in the conventional method.

FIG. 3 is a schematic side sectional view showing a MOS transistor formed by using the above method.

This transistor is directly formed on the silicon layer 4a. Therefore, the lower surfaces of the source region S and the drain region D almost reach the silicon dioxide layer 3. Therefore, in this transistor, the depletion layer DL during operation reaches the silicon dioxide layer 3 completely, and the high speed, which is a characteristic of using SOI, is secured. For other properties, silicon layer 4a
Since the crystallinity is improved, it is comparable to the transistor shown in FIG.

A silicon layer formed as SOI using the SIMOX method
4a can be used as it is for forming a bipolar transistor due to the improved crystallinity.

Further, in the above embodiment, silicon is used for ion implantation into the surface layer of the substrate 1. However, if it is a group IV semiconductor, other semiconductors such as germanium may be used to lower the oxygen concentration of SOI in the same manner, and It is easy to understand that it is advantageous for formation.

〔The invention's effect〕

As described above, according to the structure of the present invention, in the formation of SOI on the insulating layer using the SIMOX method, the crystallinity of the formed SOI can be improved, and the transistor can be directly formed on the SOI. For example, the SIMOX method can be applied to the formation of a high-speed MOS transistor, which is a characteristic of SOI.

[Brief description of drawings]

FIG. 1 is a side view (a) showing a process sequence of an embodiment of the method of the present invention
(C), FIG. 2 is a concentration distribution diagram of ion implantation in the substrate, FIG. 3 is a schematic side sectional view showing an example of a transistor formed by using the method of the present invention, and FIG. 4 is a process order showing a conventional method. Side views (a) and (b), and FIG. 5 are explanatory views of problems when the conventional method is used. In the figure, 1 is a silicon substrate, 2 is an oxygen injection layer, 3 is a silicon dioxide layer, 4 and 4a are silicon layers (SOI), 5 is a deposited silicon layer, 6 is a silicon injection layer, A and B are concentration distribution curves, DL is the depletion layer.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical indication H01L 27/12

Claims (1)

[Claims] 1. An oxygen ion implantation step for forming an oxygen implantation layer in a silicon substrate, a group IV semiconductor ion implantation step for the surface layer of the substrate, a combination of the implanted oxygen and an implanted group IV semiconductor crystal. And a heat treatment step for forming the semiconductor device.