JPH05129213A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide an inside of a doping material with concentration distribution of impurities in a doping method of conductivity deciding impurities by energy beam. CONSTITUTION:A semiconductor film 5 containing conductivity deciding impurities is applied and formed on a doping material 2 which is doped with the conductivity deciding impurities in a fixed film thickness, a film thickness of the doping material is changed by a desired pattern and energy beam 6 is irradiated to these laminated films. Thereby, low concentration distribution is provided to a part of thick doping material and high concentration distribution is provided to a part of thin doping material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device in which a semiconductor is doped with a conductivity type determining impurity by irradiation with an energy beam.

[0002]

2. Description of the Related Art Conventionally, as a method for doping a semiconductor material with a conductivity determining impurity, the semiconductor determining material is placed in an atmosphere containing the conductivity determining impurity and subjected to a high temperature heat treatment to add the conductivity determining impurity to the semiconductor material. A so-called laser in which a conductivity type determining impurity is diffused in a semiconductor material by forming a film containing the conductivity type determining impurity on a semiconductor material and irradiating it with an energy beam such as a laser.・ There are doping methods.

In a semiconductor device using a thin film semiconductor in recent years, even if a substrate material to be used has a drawback of poor heat resistance, it is desired to use an inexpensive material at a relatively low temperature. The latter laser doping method, which can be manufactured, is frequently used.

FIG. 5 is a manufacturing process diagram of a thin film transistor by a conventional laser doping method.

In the first step shown in FIG. 1 (a), polycrystalline silicon (52) formed by a conventionally known low pressure CVD method is formed in an island shape on an insulating substrate (51), and then, An n-type amorphous silicon (53) containing phosphorus which is a conductivity type determining impurity is formed by a well-known plasma CVD method.

Next, in a second step shown in FIG. 2B, the n-type amorphous silicon (53) is removed by etching with respect to the portion (53a) of the polycrystalline silicon (52) which becomes the channel of the thin film transistor. .

In the third step shown in FIG. 1C, the polycrystalline silicon (52) and the n-type amorphous silicon (53) are irradiated with the laser (54) from the film forming surface side. In the portion where n is laminated, phosphorus contained in the n-type amorphous silicon (53) diffuses into the polycrystalline silicon (52) and n
It becomes the type polycrystalline silicon (56) (56).

On the other hand, in the portion where the n-type amorphous silicon (53) is not laminated, such diffusion does not occur and the polycrystalline silicon (55) remains as it is.

Then, in the fourth step shown in FIG.
A gate insulating film (57) made of a silicon oxide film, a gate electrode (58) made of a metal film, a drain electrode (59d) and a source electrode (59s) are formed to complete the device.

In the case of such laser doping, as shown in the second step, only a portion of polycrystalline silicon (52) which is planned as a portion to be doped in advance has a constant film thickness n. Formed amorphous silicon (53) is patterned and desired doping is performed.

Regarding such a doping method, for example,
JapaneseJournal Applied Physics Vol.126 (1987), pp.L
It is described in detail in 1678-L1680 and the like.

[0012]

However, in such a conventional method, the concentration of the conductivity determining impurity doped in the polycrystalline silicon (52) is different in each part, that is, in the above-mentioned example. It was always constant in the n-type polycrystalline silicon (56) portion, and it was not possible to provide a fine concentration distribution in the plane of the polycrystalline silicon (52).

As a structure for providing a fine concentration distribution,
For example, n-type polycrystalline silicon (5
There is a case where the concentration is changed near the polycrystalline silicon (55) in 6).

Therefore, in order to provide a distribution of the concentration of the conductivity type determining impurities in the film plane, it is necessary to repeat the same laser doping process a plurality of times according to the conventional method.

That is, in the case of forming a semiconductor device having two kinds of distributions, a low concentration part and a high concentration part,
It is necessary to perform the step of forming a semiconductor film having each concentration and performing laser doping twice.

According to such a conventional manufacturing method, the process is complicated, and in the subsequent diffusion process, the re-diffusion of the conductivity type determining impurities already diffused in the previous diffusion process is considered in advance. There was a problem.

[0017]

The method of manufacturing a semiconductor device according to the present invention is characterized in that the film thickness of the material to be doped is set in advance in a desired pattern, and a semiconductor film containing conductivity determining impurities is added to the film. By depositing a constant film thickness, and by irradiating this semiconductor film with an energy beam, the doping material is subjected to a concentration distribution of conductivity type determining impurities corresponding to the size of the film thickness of the pattern,
In addition, a material to be doped and a plurality of semiconductor films having different concentrations of conductivity determining impurities are formed on at least a part of one surface of the material to be doped, and the semiconductor film is irradiated with an energy beam to cause the conductivity A semiconductor film containing a conductivity-determining impurity having a film thickness different in a desired pattern and a doping material are deposited to form a semiconductor film. And irradiating the material with a conductivity type determining impurity by irradiating the material with an energy beam.

[0018]

[Function] When a semiconductor film containing conductivity determining impurities is formed to a constant thickness on a material to be doped having a locally different film thickness and is irradiated with an energy beam, a unit volume is increased in a portion where the film thickness of the material to be doped is large. The amount of conductivity-determining impurities per hit is smaller than that in the thin portion.

Therefore, by providing a local variation of the film thickness of the material to be doped in a pattern along the film surface in advance, a concentration distribution of the conductivity determining impurities can be provided in the material to be doped.

Further, a material to be doped and a plurality of semiconductor films having different concentrations of the conductivity type determining impurities are formed so as to overlap with each other, and the semiconductor device is irradiated with an energy beam.
In the portion of the material to be doped having the semiconductor film formed in an overlapping manner, the conductivity determining impurities contained in these semiconductor films diffuse into the material to be doped, and a portion having a large concentration of the conductivity determining impurity is formed. it can.

On the other hand, in the non-overlapping portion, only the conductivity type determining impurities contained in any one of the semiconductor films are doped in the material to be doped, and the portion has a low impurity concentration.

Further, a semiconductor film containing a conductivity determining impurity whose film thickness is changed in a pattern along the film surface is formed on a material to be doped, and this is irradiated with an energy beam, whereby the film thickness of the film is reduced. It is possible to provide the material to be doped with a concentration distribution of the conductivity determining impurities corresponding to the change.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 and FIG. 2 are element structure diagrams for each step of a thin film transistor for explaining a method for manufacturing a semiconductor device according to a first embodiment of the present invention.

In the first step shown in FIG. 3A, doping of polycrystal silicon or the like formed on the insulating substrate (1) such as ceramics or quartz by the low pressure CVD method or the atmospheric pressure CVD method is performed. Material (2) (Thickness 1000Å ~ 3000
Å) is formed, and subsequently a protective film (3) composed of a silicon nitride film or a silicon oxide film (film thickness 250 Å ~ 1000
Å) form.

Then, in the second step shown in FIG.
The material to be doped (2) formed on the insulating substrate (1) is patterned into an island shape, and then the protective film (3) is left in the central portion of the surface of the material to be doped. This protective film (3) has a function of protecting polycrystalline silicon which is a material (2) to be doped which becomes a channel of the present semiconductor device.

Next, in the third step shown in FIG. 3C, the material to be doped (2) is etched to a desired depth using the protective film (3) as a mask, and then the protective film (3) is removed. A resist (4) for lift-off is patterned on the surface. In this example, as the etching of the material to be doped (2), 500
Etching was performed so that a depth of Å to 1000Å was produced.
As a result, the material to be doped (2) can be provided with a desired pattern of large and small film thickness.

In the fourth step shown in FIG. 3D, the resist is used.
After etching the protective film (3) exposed from (4), a semiconductor film containing 10 ¹⁸ to 10 ²⁰ / cm ³ of phosphorus as a conductivity type determining impurity, specifically, n-type amorphous silicon (5 Is deposited on the entire device with a constant film thickness (film thickness 50Å to 500Å).

By etching the protective film (3) exposed from the resist (4) in this step, a portion deposited on the n-type amorphous silicon (5) of the material (2) to be doped is formed. Has a thick portion (2a) and a thin portion (2b).

Then, in the subsequent fifth step of FIG. 2 (e), the resist (4) is lifted off and the n-type amorphous silicon (5) existing on the resist (4) is removed to thereby form a protective film.
After exposing (3), the entire element is irradiated with laser light (6) which is an energy beam.

The laser light (6) used in this example is an ArF excimer laser (wavelength 193 mm), and its irradiation intensity is about 300 mJ / cm ² .

As a result, the conductivity determining impurities in the n-type amorphous silicon (5) are doped in the material to be doped (2).

In such doping, doping in the film thickness direction is a problem, and doping in the film surface direction is hardly a problem. This is because the film thickness is on the order of several thousand Å, while the film thickness in the lateral direction is as large as several μm, and doping in the lateral direction does not usually pose a problem.

Next, in a sixth step shown in FIG. 3F, the protective film (3) on the surface of the material to be doped (2) is removed.
Further, in the same figure, the change of the film quality due to the irradiation of the energy beam (6) is shown, and in the part (2a) where the film thickness of the material to be doped is large, the concentration of the conductivity determining impurity is small because the film thickness is large. Become. On the other hand, in the portion (2b) having a small film thickness, the concentration of the conductivity type determining impurity is high.

As a result, the doping material can be provided with a concentration distribution of the conductivity type determining impurities corresponding to the pattern of the thickness of the doping material.

Then, in the seventh step of FIG. 7G, an insulating film (7) (thickness 1000 Å to 2000 Å) such as a silicon oxide film for a gate insulating film or a silicon nitride film is formed.

Finally, in the eighth step of FIG. 3H, after the contact holes (8s) (8d) for the source and the drain are opened, the gate metal film (9g), the source metal film (9s), and The drain metal films (9d) were each formed to have a film thickness of about 5000Å to 10000Å.

Particularly, in the manufacturing method of the present invention, since the magnitude of the conductivity type determining impurity concentration can be determined by the etching depth of the material (2) to be doped in the third step (c), the characteristics are stable. The device formation can be performed.

As a concrete result in this embodiment,
The thickness of the portion (2a) having a large thickness of the material to be doped (2a) is set to 1000Å and that of the portion (2b) having a small film thickness is set to 500Å.
₄ gas flow rate 5 SCCM, PH ₃ gas flow rate 100 SCCM, provided that PH ₃ gas was diluted to 2% with hydrogen and the film thickness was 200 Å under substrate temperature of 80 ° C.

When the energy beam was irradiated 8 times with a pulse having an irradiation intensity of 250 to 300 mJ / cm ² under such conditions, the sheet resistance of the portion (2a) having a large film thickness was 1.2 k.
Ω / □, on the other hand, it became 300Ω / □ in the small part (2b).

In this example, an etching method is used as a means for forming a pattern in which the material to be doped has a film thickness change, but the present invention is not limited to this and, for example, when forming the material to be doped. What has a change in film thickness may be used as the material to be doped.

Further, in the embodiment, after forming the material to be doped (2) having different film thicknesses in a desired pattern, a semiconductor film containing a conductivity determining impurity having a constant film thickness is formed.
(5) was formed and irradiation with an energy beam was performed, but the present invention also obtains the same effect by forming the doped material (2) after forming the semiconductor film (5) in addition to this. be able to.

Next, a method of manufacturing the semiconductor device according to the second embodiment of the present invention will be described with reference to FIGS.

In the first step shown in FIG. 3A, a material to be doped (32) (32) (made of ceramics or polycrystalline silicon formed on an insulating substrate (31) such as quartz by a low pressure CVD method or the like. A film thickness of 1000Å to 3000Å) is formed, and subsequently, a protective film (33) (film thickness of 250Å to 1000Å) made of a silicon nitride film or a silicon oxide film is formed.

Then, in the second step shown in FIG.
The material (32) to be doped and the protective film (33) formed on the insulating substrate (31) are patterned into an island shape.

Next, in a third step shown in FIG. 3C, a first resist (34) for lift-off is patterned in the center of the island-shaped material to be doped (32) to form a protective film ( After etching 33), a first semiconductor film (35) containing conductivity determining impurities is deposited on the entire device. In this example, the conductivity type determining impurity concentration of the first semiconductor film (35) is 10 ¹⁷ to 1
The thickness is 0 ¹⁸ cm ^-3 and the film thickness is 50 to 500 Å.

In the fourth step shown in FIG. 3D, the resist is used.
By removing (34), a part of the first semiconductor film (35) is removed.

Then, in the fifth step shown in FIG.
The size of the second resist (3
After patterning and forming 6), a second semiconductor film (37) containing conductivity determining impurities is deposited on the entire surface of the device.

The conductivity type determining impurity concentration of the second semiconductor film (37) is 10 ¹⁹ to 10 ²⁰ cm ^-3 or more, and the film thickness thereof is 5.
It is 0Å to 500Å.

By this step, a portion (37a) in which the first semiconductor film (35) and the second semiconductor film (37) are formed to overlap each other is formed.

In the sixth step shown in FIG. 6F, after removing the second semiconductor film 37 formed on the resist 36 by removing the second resist 36. ,
A laser beam (38), which is an energy beam, is applied to the entire device.

As the laser beam (38) in this example, the same laser as that used in the above-mentioned embodiment was used with the same intensity.

As a result, the first semiconductor film (35) and the second semiconductor film (35)
The portion (32a) located immediately below the portion (37a) where the semiconductor film (37) is formed so as to be overlaid will be doped with a large amount of conductivity type determining impurities. On the other hand, in the portion (32b) which is not overlapped and is irradiated with the laser beam (38), only the conductivity type determining impurities contained in the first semiconductor film (35) are doped. Since it is not done, the concentration will be low.

Next, in a seventh step shown in FIG. 7G, an insulating film 39 such as a silicon oxide film for a gate insulating film or a silicon nitride film (thickness 1000Å to 2000Å) is formed.

Finally, in the eighth step of FIG. 6H, the insulating film
Contact holes (40s) for source and drain in (39)
After opening (40d), gate metal film (41g), source metal film
(41s) and a drain metal film (41d) is formed. The respective film thicknesses of these metal films are the same as those in the above-mentioned embodiments.

Therefore, according to the manufacturing method of the present invention, a semiconductor device having a desired pattern of impurity concentration distribution can be manufactured by superposing a plurality of semiconductor films having different conductivity type determining impurity concentrations.

In particular, the manufacturing method of the present invention is optimum for forming a semiconductor device which requires a large concentration distribution that cannot be followed by the change in the film thickness of the material to be doped in the case of the other invention described above. .

This is because the content of the conductivity determining impurity can be easily made by providing a large difference between the semiconductors.

The concentration distribution of the conductivity type determining impurities contained in the first semiconductor film (35) and the second semiconductor film (37) in the second embodiment can be made to be the same. it can. In this case, when a semiconductor film having a constant conductivity type determining impurity concentration is formed on the material to be doped by changing the film thickness of the semiconductor film within the film surface, the concentration corresponding to the change in the film thickness It is possible to provide the material to be doped with a distribution.

It is needless to say that the present invention is not limited to the silicon material used in the first and second embodiments described above, but can be applied to other semiconductor materials such as germanium.

Although the semiconductor film containing the conductivity determining impurities is formed on the surface of the material to be doped in the above-mentioned embodiments, it is said that the semiconductor film may be formed first as the forming procedure. There is no end.

Further, the energy beam used in the present invention is not limited to the ArF excimer laser used in the embodiment, but other lasers such as XeCl, KrF and Ar ^+.
A laser or the like may be used.

[0062]

According to the method of manufacturing a semiconductor device of the present invention,
By forming a local change in the film thickness of the material to be doped in a pattern in advance, it is possible to provide a distribution of the conductivity type determining impurity concentration in the material to be doped.

In particular, according to the present invention, since a method by etching can be used as one of the means for changing the film thickness of the material to be doped, a pattern having a stable film thickness change can be formed and reproducibility is improved. An excellent semiconductor device can be obtained.

Further, a plurality of semiconductor films having different conductivity type determining impurity concentrations are superposed on the material to be doped, and an energy beam is applied to the semiconductor films, so that the portions of the material to be superposed formed on both semiconductor films. The included conductivity determining impurities diffuse into the material to be doped, and the concentration of the conductivity determining impurities in this portion is increased, resulting in a concentration distribution.

Therefore, according to the present invention, even in the formation of a semiconductor device which requires a relatively large concentration distribution, it is possible to easily adjust the concentration of the semiconductor film containing the conductivity determining impurity to be used. Can be done.

Further, by depositing a semiconductor film containing conductivity determining impurities having different film thicknesses on the material to be doped and irradiating it with an energy beam, the pattern corresponding to the change in the film thickness was dealt with. It will be possible to dope the material to be doped.

Therefore, conventionally, when the concentration is high or low, it is necessary to repeat the step of forming the semiconductor film and performing laser doping twice, but according to the present invention, only one step is required.

[Brief description of drawings]

FIG. 1 is a sectional view of an element structure for each step for explaining a method for manufacturing a semiconductor device according to the present invention.

FIG. 2 is a cross-sectional view of another element structure for each step for explaining the manufacturing method.

FIG. 3 is a sectional view of an element structure for each step for explaining the method for manufacturing the semiconductor device of the present invention.

FIG. 4 is a cross-sectional view of another element structure for each step for explaining the manufacturing method.

FIG. 5 is a sectional view of an element structure for each step for explaining a conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

(2)… Doped material (5)… Semiconductor film (6)… Energy beam

Front page continuation (72) Inventor Shigeru Noguchi 2-18 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd.

Claims (3)

[Claims] 1. A step of depositing a material to be doped having a different film thickness in a desired pattern and a semiconductor film containing a conductivity type determining impurity having a constant film thickness, and an energy beam on the semiconductor film. By irradiating the doped material with the conductive type determining impurity, and making the concentration distribution of the conductive type determining impurity in the doped material correspond to the change in the film thickness of the pattern. A method of manufacturing a semiconductor device, comprising: 2. A step of forming a material to be doped and a plurality of semiconductor films having different concentrations of conductivity determining impurities on at least a part of one surface of the material to be doped, and irradiating the semiconductor film with an energy beam. And a step of doping the conductivity determining impurity into the material to be doped, thereby manufacturing a semiconductor device. 3. A step of depositing a material to be doped and a semiconductor film containing a conductivity type determining impurity having different film thicknesses in a desired pattern; and irradiating the semiconductor film with an energy beam, A step of doping the material to be doped with the conductivity type determining impurities and associating a concentration distribution of the conductivity type determining impurities in the material to be doped with a change in the film thickness of the pattern. Device manufacturing method.