JPH0235710A - Forming method for thin film semiconductor layer - Google Patents

Abstract

PURPOSE:To simplify a process and form a selective oxide film free from bird's beak by simultaneously performing the crystal growth of an active layer and the formation of the selective oxide layer for element isolation. CONSTITUTION:On an insulative substrate 1, a polycrystalline or amorphous non-single crystalline thin film semiconductor layer 2 is formed; an oxidation resistant film 4 like Si3N4, is formed selectively on the semiconductor layer 2; then by projecting an energy beam, like excimer laser, on the whole surface in an oxidizing atmosphere, the exposed semiconductor layer 2 is selectively oxidized, and the semiconductor layer 2 under the oxidation resistant film 4 is subjected to thermal treatment. Hence a region, where the oxidation resistant film 4 of the non-single crystalline thin film semiconductor layer 2 being an active layer is not formed, is selectively oxidized; and in this part, a selective oxide layer 6 turning to an element isolation region is formed; at the same time, the non-single crystalline thin film layer 2 turning to the active layer under the oxidation resistant film 4 is subjected to solid growth in the simultaneous processing. In the above solid growth, the oxidation resistant film 4 acts as a capping layer, so that the forming process of capping layer can be omitted. Further, bird's beak phenomenon is controlled, and the selective oxide layer 6 free from bird's beak is formed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to thin II? The present invention relates to a semiconductor-like forming method.

[Summary of the invention]

The present invention is a method for forming a thin film semiconductor layer, in which a non-single crystal thin film semiconductor layer is formed on an insulating substrate, and an oxidation-resistant film is selectively formed on the semiconductor IW4. After that, the entire surface is irradiated with an energy beam in an oxidizing atmosphere to oxidize the exposed semiconductor j-, and the semiconductor layer under the anti-oxidation film is heat-treated to form a solid phase of the semiconductor layer that becomes active J@. Selective oxidation (LO
This makes it possible to form a GO3') layer and to form a selective oxidation layer without birthmarks.

[Conventional technology]

Generally, when forming a semiconductor device, especially a thin film semiconductor device, Si3N bifurcated material is used as a gate insulator, a capacitor, or an oxidation-resistant mask during element isolation. This S+3N4 film has a large dielectric constant and excellent oxidation resistance and chemical resistance, and is accepted for the above-mentioned applications. Furthermore, when using the gate insulator as a capacitor, S iJ 4 C is not used alone, but a sandwich structure of 5iO2SijN4Sif2 is often used.

In addition, as the dimension of element separation in a semiconductor construction circuit,
The so-called Locus method (selective oxidation method) uses SS102Si3N4 as an oxidation-resistant mask to thermally oxidize areas other than the element part.
has become mainstream.

In addition, the activation of polycrystalline silicon in thin film semiconductor devices
Excimer laser light is used as a method to improve the crystallization of -4.j
A method of growing crystals by cutting is also known.

(Problems to be Solved by the Invention) By the way, when using the above-mentioned SiSi3N4 as a gate insulating film or adhesive in a semiconductor device, the 5i
The structure is O2Si3N+ 5i02, but the upper 5i (b 1%j is SisN4M
! It is formed by thermally oxidizing the Q surface at about 1100°C. Since this thermal oxidation treatment is usually carried out in a salt air furnace, there are disadvantages such as defects occurring in the monocrystalline silicon precipitate, which is active JfJ, and impurities diffusing during this thermal oxidation.

On the other hand, in element isolation using the 1. ocos method, there is a problem of so-called bird's beak, and it is desired to form a selective oxidation layer without bird's beak.

Regarding crystal growth of the active layer by excimer laser irradiation, 5i (b
It is necessary to camp in Shin etc.

The present invention has been made in view of these points, and its purpose is to simultaneously grow the crystals of the active layer and form the selective oxidation layer for element isolation, thereby simplifying the process. Another object of the present invention is to provide a method for forming a thin film semiconductor layer that enables selective oxidation formation without bird's beaks.

[Means to solve the problem]

The method for forming a 1WIIW semiconductor layer of the present invention is to form a polycrystalline or amorphous non-single crystal thin film semiconductor In on an insulating substrate (1).
+21 and selectively S on the S conductor layer (2).
i) Form an oxidation-resistant film (4) such as N4. after that,
In an oxidizing atmosphere, the exposed semiconductor layer (2) is selectively oxidized by irradiating the entire surface with a mechanical beam such as an excimer laser.
21 was heat-treated.

[Effect]

According to the above-described formation method of the present invention, since the energy beam is irradiated at high temperature and for a short time in an oxidizing atmosphere, the non-single crystal thin film semiconductor rf4 (oxidation-resistant film (4) of 21) which is the active layer
The regions where the oxidation-resistant film (4) is not formed are selectively oxidized, and a selective oxidation layer (61) which becomes an element isolation region is formed therein, and at the same time, a non-single crystal thin film semiconductor layer (2) which becomes an active layer under the oxidation-resistant film (4) is formed. ) becomes a solid phase.During this phase growth,
Since the oxidation-resistant film (4) acts as a camper (-), the step of forming a capping layer is omitted.

In addition, since the energy beam is irradiated in a straight line and only the irradiated portion is oxidized, the bird's beak phenomenon is controlled and a selective oxidation layer (6) without bird's beak is formed.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to FIG.

FIG. 1 is a stage diagram showing a method for forming a thin film semiconductor device according to this embodiment. The process will be explained below.

On the other hand, although this example describes a P-channel thin film transistor, the present invention can also be applied to an N-channel thin film transistor.

First, as shown in Figure A, an insulator made of 5i02 (
1) Polycrystalline silicon Kiyoaki with, for example, P-type on top (2)
is grown by, for example, the CVD method.

Next, as shown in Figure B, a polycrystalline silicon thin film (2) is formed.
A 5t02viI film (3) for a gate is formed by thermally oxidizing the surface. After that, the 5i02 oxidized crotch (3) (same as above) J'lJノSiaN4MII9! '+41
is grown by CVD method or the like.

Next, for element isolation, Si3N
4 thin film (4) and a part of the 5i02 oxide layer (3) were etched away using photolithography technology, and the polycrystalline silicon 'a MIj! that existed in the underlying layer was removed. +2) part (
2A) Expose.

Next, as shown in the same figure, in an oxidizing atmosphere, for example, 0
2 or 03 atmosphere, the entire surface including the Si3N4 thin film (4) and the exposed polycrystalline silicon portion (2^) is irradiated with an excimer laser (5) to perform heat treatment at high temperature and for a short time.
Field insulation layer (6) of 5i02 reaching insulation +1+ by thermal oxidation of polycrystalline silicon part (2A)
At the same time, the surface of the Si3N4 thin film (4) is simultaneously thermally oxidized to form a 5T(h oxide film (7)).

This field insulating layer (6) becomes an element isolation region.

Further, at the same time, the irradiation with the excimer laser (5) causes crystal growth of the polycrystalline silicon film (2) which becomes the active layer of the Si3N4 thin layer (4). In this case, 5iiN+
M membrane (4) is active 1i! (2) excimer laser (
5) It plays a kind of camping effect against the irradiation.

On the other hand, in the field insulating layer (6), the excimer laser (
By direct irradiation and short-time irradiation in 5), only the irradiated polycrystalline silicon portion (2A) is thermally oxidized, resulting in an active area of 7m +
Since thermal oxidation does not proceed to the 21 side, the so-called birthbeak phenomenon does not occur.

Next, as shown in Figure E, a polycrystalline silicon layer (8) doped with an impurity (for example, an n-type impurity) that will become the gate electrode is grown on the entire surface by CVD, and then as shown in Figure D. , polycrystalline silicon layer (8), 5i (h oxidation 1i+
71. Si3N+ *film (4) and 5i02 oxide film (
3) is sequentially selectively etched to form a polycrystalline silicon layer (8).
Gate electrode (9) and 5t (h oxide film (3), 5itN + thin film (4) and 5i02 oxide 11!J (71
At the same time, a gate insulating film (10) consisting of the active J* (21) is formed, and the surface area of the active J* (21) and the area other than the gate area are exposed.

After that, as shown in figure G, field insulation 1m (
Active layer (2) using 61 and gate electrode (9) as a mask.
P-type impurity (13) is ion-implanted into the source region (
11) and a drain region (12) to form a P-channel thin film transistor.

In the above embodiment, the active layer 1iJ (21) was formed of polycrystalline silicon, but it may be formed of other polycrystalline silicon.

In addition, in the upper tide, 5i (b oxidation 11J +31 and Si3N
+ crotch (4) and 5i (h oxide film (7) to gate insulation film (
10), but after the process of the first drawing, these Ill (31(41(7)) were removed and 5i
(It is also possible to form a gate insulating film using H.

According to the method for forming a thin film transistor described above, after forming an S i =N 4 thin film (4) selectively on the polycrystalline silicon thin film (2) via a 5i02 oxide layer (3), heat treatment is performed by excimer laser irradiation. By applying this, selective oxidation to form the field insulating layer (6) and crystallization of the polycrystalline silicon layer (2) which will become the active layer under the 5izN+ thin film (4) are performed simultaneously. In this case, the Si3N4 S film (4), which serves as an oxidation-resistant mask during selective oxidation, also serves as a capping layer during crystal growth of the polycrystalline silicon thin film (2), so it is necessary to add a new capping process. There is no.

Further, by irradiation with the excimer laser (5), the surface of the 5iJ4 thin film (4) is thermally oxidized to form a 5i(h oxide film (7)), and a gate insulating film (10) (or other bonding film) can be formed. ζ5iO2−
A sandwich structure of Si)N4Si(h) can be formed at the same time. Therefore, the manufacturing process of the thin film transistor can be simplified.

On the other hand, when forming the field insulating layer (6) by selective oxidation, unlike the conventional thermal oxidation at 1100°C for a long time, heat treatment is performed at a high temperature and for a short time by excimer laser irradiation. 5) is irradiated straight ahead and only the irradiated portion (2A) is thermally oxidized, so the generation of bird's beak is suppressed and a field insulating layer (6) without bird's beak can be formed;
It is possible to increase the density of elements.

〔Effect of the invention〕

In the method for forming a semiconductor device according to the present invention, a non-single crystal thin film semiconductor layer is formed on an insulating substrate, and an oxidation-resistant film is selectively formed on the semiconductor layer. After that, we irradiated the entire surface with an energy beam in an oxidizing atmosphere to oxidize the exposed semiconductor, and also heat-treated the semiconductor layer under the oxidation-resistant crotch, so that the selective oxidation 1 which becomes the 1iSli region for each element - can be formed at the same time as the crystalline improvement of the semiconductor layer which becomes the active layer of the oxidation-resistant crotch, and can suppress the occurrence of bird's beak phenomenon during selective oxidation, as well as capping the lithium layer during beam irradiation. Therefore, the manufacturing process can be simplified, and the semiconductor device can be highly integrated.

[Brief explanation of the drawing]

FIG. 1 is a stage diagram showing a method for forming a thin film semiconductor device according to this embodiment. (1) is a 5i02 insulator, (2) is a polycrystalline silicon layer (
Active layer), f3) HaS+02v film,! 4) HaS
i, +N 4 thin films, (5) is excimer laser, (6) is field insulating layer, (7) is 5i (h oxide film, (8) is polycrystalline silicon layer, (9) is gate electrode, (10) is a gate insulating film, (11) is a source region, and (12) is a drain region.

Claims (1)

[Claims] A step of forming a non-single crystal thin film semiconductor layer on an insulating substrate, a step of selectively forming an oxidation-resistant film on the semiconductor layer, and a step of irradiating the entire surface with an energy beam in an oxidizing atmosphere. A method for forming a thin film semiconductor layer, comprising the steps of oxidizing the exposed semiconductor layer and heat-treating the semiconductor layer under the oxidation-resistant film.