Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – On insulating substrate or layer
Reexamination Certificate
2001-04-24
2002-11-19
Elms, Richard (Department: 2824)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
On insulating substrate or layer
C438S162000
Reexamination Certificate
active
06482687
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a technique for subjecting semiconductors to each kind of annealing by irradiating the semiconductors with laser light.
2. Description of the Prior Art
Heretofore, techniques are known for subjecting semiconductors to each kind of annealing by irradiating the semiconductors with laser light. For example, the following techniques are known; a technique for transforming an amorphous silicon film (a-Si film) formed on a glass substrate by the plasma CVD into a crystalline silicon film by irradiating the amorphous silicon film with laser light; and an annealing technique after impurity ion doping, or the like. As each kind of annealing technique using such laser light and an apparatus for laser light irradiation, there is a technique described in Japanese Unexamined Patent Application No. Hei 6-51238 filed by the applicant of the present invention.
Since each kind of annealing treatment using laser light does not cause thermal damage to a base substrate, the treatment becomes a useful technique in the case where a material that is weak to heat such as a glass substrate or the like is used as the substrate. However, there is a problem in that it is difficult to keep the annealing effect on a constant level at all times. Further, when an amorphous silicon film is crystallized by irradiating the amorphous silicon film with laser light, it is difficult to constantly obtain a favorable crystallinity that is required. Thus, a demand has been made on a technique for stably obtaining a crystalline silicon film having a more favorable crystallinity.
SUMMARY OF THE INVENTION
An object of the present invention is to solve at least one or more of the problems described in the following items:
(1) to enable providing a constant effect at all times in techniques of annealing semiconductors by irradiating the semiconductors with laser light; and
(2) to further heighten the crystallinity of a crystalline silicon film obtained by irradiating an amorphous silicon film with laser light.
A first embodiment of the invention disclosed herein is a method comprising the steps of: heat-treating an amorphous silicon film to crystallize it; and irradiating the crystallized silicon film with laser light. This method is characterized in that during the irradiation of the laser light, the sample is maintained within ±100° C. of the temperature of the heat-treatment.
In the first embodiment constructed as described above, the temperature of the heat treatment performed during the crystallization step can be selected to be 450-750° C.
The upper limit of this temperature is restricted by the highest tolerable temperature of the substrate. Where a substrate made of glass is used, the upper limit is about 600° C. Where the productivity is taken into account, this temperature is preferably above 550° C. Therefore, where a glass substrate is employed, it is desired to perform a heat treatment at a temperature of about 550-600° C.
During the laser irradiation, the heating temperature is preferably set to about 550-600° C. Heating starting from a temperature of about 450° C. can be put into practical use. Accordingly, the heating temperature preferably lies in the range of 550° C.±100° C.
A second embodiment of the invention disclosed herein is a method comprising the steps of: heat-treating an amorphous silicon film at a temperature lower than 600° C. to crystallize the amorphous silicon film; and irradiating the crystallized silicon film with laser light. This method is characterized in that during the laser irradiation, the sample is maintained within ±100° C. of the temperature of the heat treatment.
A third embodiment of the invention disclosed herein is a method comprising the steps of: heat-treating an amorphous silicon film to crystallize it; implanting impurity ions into at least a region of the crystallized silicon film; and irradiating the ion-implanted region with laser light. This method is characterized in that during the laser irradiation, the sample is maintained within ±100° C. of the temperature of the heat treatment.
A fourth embodiment of the invention disclosed herein is a method comprising the steps of: heat-treating an amorphous silicon film to crystallize it; implanting impurity ions into at least a region of the crystallized silicon film; and irradiating the ion-implanted region with laser light. This method is characterized in that during the laser irradiation, the sample is maintained within ±100° C. of the temperature of the heat treatment.
A fifth embodiment of the invention disclosed herein is a method comprising the steps of: irradiating an amorphous silicon film with a laser beam having a linear cross section while moving the laser beam in steps from one side of the amorphous silicon film to opposite side to crystallize irradiated regions in succession. This method is characterized in that the laser irradiation is performed while heating the irradiated surface above 450° C.
In the fifth embodiment constructed as described above, the laser beam of the linear cross section is moved in steps and made to impinge on the film. Consequently, the required regions can be effectively irradiated with the laser light. Normally, the temperatures of irradiated surfaces are limited to about 600° C. However, these temperature are restricted by the material of the substrate. Higher temperatures may also be used.
A sixth embodiment of the invention disclosed herein is a method comprising the steps of: introducing a metal element for promoting crystallization into an amorphous silicon film; heat-treating the amorphous silicon film to crystallize it; and irradiating the crystallized silicon film with laser light. This method is characterized in that during the laser irradiation, the sample is maintained within ±100° C. of the temperature of the heat treatment.
In the sixth embodiment constructed as described above and in the following seventh through tenth embodiments, the metal element for promoting crystallization is one or more elements selected from the group consisting of Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu, Zn, Ag, and Au. Among these metal elements, nickel is the element producing the most conspicuous effect.
In the above-described configurations, the heat treatment temperature can be selected to lie within the range of from 450° C. to 750° C. The upper limit of this temperature is restricted by the highest tolerable temperature of the substrate. Where a glass substrate is used, the upper limit is roughly 600° C. Where the productivity is taken into consideration, this temperature is preferably higher than 550° C. Accordingly, where a glass substrate is employed, the heat treatment is preferably performed at a temperature of about 550-600° C.
Furthermore, during the laser irradiation, the heat treatment temperature is preferably about 550-600° C. Heating starting from a temperature of about 450° C. can be put into practical use. In consequence, it is desired to heat the substrate within the temperature range of from 550° C.±100° C.
A seventh embodiment of the invention disclosed herein is a method comprising the steps of: introducing a metal element for promoting crystallization into an amorphous silicon film; heat-treating the amorphous silicon film at a temperature lower than 600° C. to crystallize it; and irradiating the crystallized silicon film with laser light. This method is characterized in that during the laser irradiation, the sample is maintained within ±100° C. of the temperature of the heat treatment.
An eighth embodiment of the invention disclosed herein is a method comprising the steps of: introducing a metal element for promoting crystallization into an amorphous silicon film; heat-treating the amorphous silicon film to crystallize it; implanting impurity ions into at least a region of the crystallized silicon film; and irradiating the ion-implanted region with laser light. This method is characterized in that during the laser irradiation,
Hamatani Toshiji
Miyanaga Akiharu
Ohtani Hisashi
Teramoto Satoshi
Yamazaki Shunpei
Elms Richard
Robinson Eric J.
Robinson Intellectual Property Law Office P.C.
Semiconductor Energy Laboratory Co,. Ltd.
Wilson Christian D.
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