KR960008499B1 - Laser treatment method and laser treatment apparatus - Google Patents

Abstract

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Description

Laser processing method and laser processing apparatus

Fig. 1 is a production process diagram of the embodiment; Fig.

FIG. 2 is a manufacturing process diagram of the embodiment. FIG.

Fig. 3 is a production process diagram of the embodiment. Fig.

Fig. 4 is a production process diagram of the embodiment. Fig.

FIG. 5 is a conceptual diagram of a semiconductor processing (doping doping) apparatus of the present invention. FIG.

FIG. 6 is a conceptual diagram of a semiconductor processing (doping doping) apparatus of the present invention. FIG.

7 is an exemplary diagram of a semiconductor processing (doping doping) apparatus of the present invention;

Figure 8 is an illustration of an example of a semiconductor processing (doping doping) device of the present invention;

FIG. 9 is a depth distribution diagram of the impurity concentration in the semiconductor impurity region fabricated by the present invention and the conventional method. FIG.

FIG. 10 is a manufacturing process diagram of the embodiment; FIG.

FIG. 11 is a production process diagram of the embodiment; FIG.

12 shows CV characteristics and elemental distributions of the examples.

FIG. 13 is a distribution diagram of the depth direction of the impurity (boron) in the embodiment. FIG.

FIG. 14 is a longitudinal distribution diagram of the impurity (phosphorus) in practical examples. FIG.

FIG. 15 is a view showing a change in sheet resistance of a film in the embodiment; FIG.

FIG. 16 is a characteristic diagram of an inverter and a ring oscillator fabricated in the embodiment; FIG.

TECHNICAL FIELD [0001] The present invention relates to a technology for efficiently doping a semiconductor wafer in a low temperature process and performing other chemical and physical treatments.

Conventionally, as a technique for performing doping, a thermal diffusion method and an ion implantation method are known.

The thermal diffusion method is a method of diffusing an impurity into a semiconductor in a high-temperature atmosphere of 1,000 to 1,200 DEG C, and the ion implantation method is a method of accelerating ionized impurities to an electric field and putting them in a predetermined place.

However, the diffusion coefficient D of the impurity depends exponentially on the absolute temperature T, as indicated by D = D ₀ exp [-Ea / kT].

Where D ₀ is the diffusion coefficient at T = ∞, Ea is the activation energy, and k is the Boltzmann coefficient.

Therefore, in order to efficiently diffuse the impurities into the semiconductor, it is preferable to carry out the heat treatment at a high temperature as high as possible, and in the thermal oxidation method, the heat treatment is generally carried out at a high temperature process of 1,000 degrees or more.

Further, in the ion implantation method, a post heat treatment process at a temperature of 6000 to 950 ° C was required to activate impurities and to recover defects.

Recently, an active matrix type liquid crystal display device using a TFT (thin film transistor) provided on a glass substrate as a switching element of a pixel has been partly put to practical use. This is because the source and drain regions of the TFT are formed of amorphous silicon in an ohmic contact It is common.

In addition, since the structure of the TFT is of a reverse stagger type, it is easy to generate parasitic capacitance due to structural problems.

It has been studied to use a TFT that forms the source and drain regions in a self-aligning manner. However, in order to form the source and the drain regions in a self-aligning manner, the ion implantation method or the ion shower method must be used .

However, these methods require a post-heat treatment process at a temperature of 600 to 700 ° C to activate impurities and recover defects as described above. Considering that the heat-resistant temperature of general cheap glass substrates is 600 to 700 ° C, It was difficult to use it as an enemy.

As a method for solving the problem of thermal damage to such a glass substrate, a doping technique by irradiation of laser light is known.

One of these methods is a method of forming a thin film of an impurity on the surface of a semiconductor to be doped and melting the thin film of the impurity and the surface of the semiconductor by irradiation with laser light to dissolve the impurity.

The method of performing the doping by irradiation with the excimer laser light has the advantage of preventing the occurrence of defects due to thermal damage because it does not cause thermal damage to the glass substrate. However, it is necessary to carry out a step of forming a film of impurities .

Conventionally, a coating method such as a spin coating method is used to form an effervescent film.

However, in this process, if the uniformity of the film thickness is not good, the doping concentration of the impurity differs, which is not an ideal method.

In addition, the effervescent film is usually formed by using an organic solvent as a solvent. In such a case, undesirable elements such as carbon, oxygen, and nitrogen may be contained in the semiconductor, thereby deteriorating the characteristics.

The present invention has been made in view of the problem of the complication of the process and the intrusion of these elements, which has been a problem in the above-described laser light, in particular, in the doping technique using the excimer laser light.

The present invention aims at doping using a doping gas having a high purity in a gaseous state without using a doping material in a liquid state or a solid state and in order to simplify the process and to prevent intrusion of these elements do.

It is also an object of the invention to increase the doping efficiency.

The present invention also aims at doping various kinds of materials (insulators, conductors) and their surfaces in addition to doping with semiconductor materials, and also to improve the materials and surface of the doping.

For example, phosphorus doping is included in the silicon oxide film.

In order to solve the above-described problems, the present invention provides a method for manufacturing a semiconductor device, which comprises irradiating a surface of a sample semiconductor with laser light in a highly pure reactive gas atmosphere containing an impurity imparting a conductivity, Doping in the sample semiconductor.

However, according to the experience of the present inventors, if the sample semiconductor is at a low temperature such as room temperature, the diffusion of elements is not sufficient.

One of the present invention is to heat the sample and maintain the temperature at least 200 캜 or more during the laser irradiation so as to promote the diffusion of the impurity element and also to perform the dopant doping at a high concentration.

The heating temperature of the substrate varies depending on the kind of the semiconductor, but in the case of polysilicon (polycrystalline silicon) and semiamorphous silicon, 250 to 500 deg. C, preferably 300 to 400 deg.

Thus, when the sample is heated and irradiated with a laser, impurities are easily diffused, and a semiconductor in which the crystallinity is temporarily deteriorated by laser irradiation is thermally sufficiently relaxed, so that crystallinity is easily recovered.

In the case of laser irradiation, particularly in the case of pulsed laser irradiation, when the sample is not heated to an appropriate temperature, the semiconductor is likely to exhibit an amorphous state because of the typical rapid heating and quenching.

That is, the temperature is instantaneously heated to 1,000 ° C or higher, but falls to room temperature after several hundreds of milliseconds.

If the sample is heated to the above-mentioned range in silicon, it is calculated that the time required for the temperature to drop to about 500 deg. C, which is the lower limit of the crystallization temperature of silicon, is 10 times or more as compared with room temperature. At this stage, when the irradiation period of the laser is continued for a certain period of time, the silicon is melted and the impurities penetrate into the inside by the convection of the solution.

Further, when the pulse does not continue for a certain period of time, the silicon crystallizes in solid phase to form so-called semi-amorphous, but the impurity is solidly diffused therein.

It is not desirable that the temperature is too high.

This is because, at a high temperature, the reactive gas itself is decomposed and attached not only to the sample but also to the holder and the like, and the utilization efficiency of the gas is lowered.

Also, it is not preferable to maintain the temperature higher than the crystallization temperature of the semiconductor.

Particularly, this is not preferable for polycrystalline semiconductor, amorphous semiconductor, semi-amorphous semiconductor or the like.

When the doping is performed with respect to the crystalline semiconductor while the temperature is higher than the crystallization temperature, there arises a difficulty in controlling the electromagnet due to the generation of the level. Since it is said that amorphous silicon changes into polysilicon thermally at 500 to 550 캜, it is preferable that the amorphous silicon is performed at this temperature or lower, preferably 100 캜 or lower (that is, 400 to 450 캜 or lower) .

Further, in the case of using the structure of the present invention in a TFT (a-Si: TFT) using amorphous silicon, when the a-Si: TFT is heated to a temperature of 350 캜 or higher, the device is broken. Is suitably heated to a temperature of 350 DEG C or less.

This is the same for other semiconductors.

Another aspect of the present invention resides in the fact that, in a doping technique in a gaseous state using the laser light, particularly excimer laser light, when a plurality of dopings are to be performed using different doping gases, The characteristics are different from each other, and the doping efficiency is reduced due to the change in the decomposition characteristics depending on the kind of the gas.

In order to do so, electron energy is applied to decompose the reactive gas during laser irradiation in a reactive gas atmosphere containing an impurity imparting uniformity.

At this time, when the laser beam is irradiated again, the doping rate can be further increased by heating the semiconductor to be doped as a sample at a suitable temperature in the same manner as in the first invention.

In the present invention, in the case of using a silicon semiconductor (silicon) as the semiconductor, the impurity imparting the heat conduction type may be doped with a trivalent impurity, typically boron (B) or the like, (P), arsenic (As), or the like can be used as long as it can be used as the n-type impurity.

As the reactive gas containing these impurities, AsH 3, PH 2, BF 3, BCI 3, B (CH 3) ₃ and the like can be used.

As a semiconductor, an amorphous silicon semiconductor thin film formed by a vapor deposition method or a sputtering method is generally used as long as the TFT is manufactured.

In addition, the present invention can be applied to a polycrystalline or single crystal silicon semiconductor fabricated by liquid phase growth.

Further, it is needless to say that the present invention is not limited to the silicon semiconductor, and other semiconductors may be used.

As the laser light, it is useful to use a pulse oscillation type excimer laser device. This is because, in the pulse oscillation laser, the heating of the sample is instantaneous, and is limited to the surface only, and does not affect the substrate. In the continuous oscillation laser (argon ion laser or the like), the heated portion may be peeled off due to a significant difference in thermal expansion between the heated portion and the substrate, while the laser is heated locally. In this regard, in a pulsed laser, the thermal relaxation time is overwhelmingly shorter than the reaction time of mechanical stress such as thermal expansion, and does not cause mechanical damage. Of course, the impurities of the substrate rarely thermally diffuse.

Particularly, the liquid crystal laser has already been used in an experiment in which an amorphous silicon thin film is crystallized by laser irradiation to obtain a highly crystalline polycrystalline silicon thin film. As a specific type of laser, ArF excimer laser (wavelength: 193 nm), XeCl excimer laser (wavelength: 308 nm), XeF excimer laser (wavelength: 351 nm), KrF excimer laser (248 nm)

In the constitution of the present invention, as the means for heating the substrate, a conduction type in which a nichrome wire, a bent wire or other heating element is directly embedded in the holder may be used, but a radial type other than an infrared lamp may be used.

However, since the substrate temperature has a large influence on the impurity doping concentration and depth, it is preferable that the control is performed precisely. Therefore, a temperature sensor such as a thermocouple is indispensable as a sample.

In the constitution of the present invention, high frequency energy of 13.56 MHz is generally used as the electron energy applied to decompose the reactive gas for doping (referred to as doping gas). By the decomposition of the doping gas by the electron energy, the doping can be efficiently performed even when the laser light which can not directly decompose the doping gas is used. The kind of the electron energy is not limited to the frequency of 13.56 MHz. For example, the ECR condition generated by the interaction between the microwave of 2.45 GHz and the magnetic field of the magnetic field of 875 Gauss may be used. It is also effective to use light energy capable of directly decomposing the doping gas.

Although the above description has described the doping technique in semiconductors, the present invention is not limited thereto, and a wide variety of applications are possible. For example, it is possible to use the present invention even in the case of adding several percent of a trace element for improving the surface material to a specific thickness portion of the surface of the metal. For example, the present invention may be carried out on the surface of iron and ammonia, and nitrogen may be doped so that the surface to several hundreds nm of the surface may be nitrided.

Alternatively, the present invention can be applied to an oxide to obtain an effect.

For example, it is also possible to increase the superconducting critical temperature by making the Bismuth-based oxide high-temperature superconductor thin film contain lead in the lead chloride vapor. Conventionally, it has been known that several kinds of Bismuth-based oxide high-temperature superconductors exist, and the highest critical temperature is about 110K. Such an image having a critical temperature exceeding 100 K was difficult to obtain.

It is known that when lead is added, an image exceeding 100 K can be easily obtained. However, in the thin film manufacturing process, there is a tendency that the influence of substrate heating is increased to the outside of lead. However, since the present invention is a non-thermal equilibrium reaction, lead can be effectively included as a thin film forming material. Likewise, the present invention can be applied to PZT (lead zirconia titanium oxide), which is a ferroelectric material containing lead, which has recently attracted attention as a functional material of a semiconductor integrated circuit, particularly a semiconductor memory.

In addition, it can be used also in insulators such as silicon oxide when adding trace impurities. As silicon oxide has already been used in semiconductor processing, phosphorus glass is often made into phosphorus glass by containing phosphorus in a percentage. Of course, it is also possible to use phosphorus in silicon oxide by using the present invention. For example, phosphorus may be diffused at a concentration of 1 × 10 ²⁰ to 3 × 10 ²⁰ cm ^-3 .

Glass is known to prevent the penetration of mobile ions of sodium from the outside into the semiconductor. Conventionally, the film is formed by a CVD chamber dedicated to phosphorus glass (PSG). However, since a dedicated device must be prepared, the unit price rises. In the case of using the present invention, the laser doping apparatus can be used for the doping of the impurities of the semiconductor and the phosphorus formation, and the silicon oxide film formation apparatus can be widely used for other purposes, to be.

In particular, the practice of the present invention has been effective in improving the properties of silicon oxide films formed at relatively low temperatures (600 DEG C or less) using various organosilanes (tetra $ ethoxysilane (TEOS), etc.). That is, in such a film, the raw material contains a large amount of carbon, and the insulating property is not good. When the film is used as an insulating film such as a MOS structure, the trap level is too large and is not a good material.

However, according to the present invention, when phosphorus doping is performed by phosphorus, these carbons are removed from the film by the heating of the laser irradiation, and the trap level is remarkably reduced to improve the insulating property. As described above, it is possible to control the distribution of impurities in the depth direction by changing the substrate temperature at the time of laser doping. Therefore, in order to distribute phosphorus deeply in the silicon oxide film, the substrate may be maintained at room temperature or below in order to maintain the substrate temperature at 200 ° C or higher, preferably 350-450 ° C, and only the depth is 100 nm or less.

Further, when the semiconductor film such as silicon of amorphous silicon is deposited on the base film at the time of laser doping, the crystallinity is improved because these semiconductor materials are not simultaneously formed. That is, the silicon oxide film has a low absorption rate with respect to ultraviolet rays, and most of the laser light is absorbed by the underlying semiconductor material. Therefore, the two processes can be performed at the same time, which is effective for improving the mass productivity.

A conceptual diagram of the apparatus of the present invention is shown in FIGS. 5 and 6. FIG. 5 shows a substrate heating apparatus, and FIG. 6 shows an electronic apparatus for generating plasma in addition to the substrate heating apparatus.

Since these drawings are conceptual, it is a matter of course that, in an actual apparatus, other components can be provided as necessary. Hereinafter, how to use it will be outlined.

In FIG. 5, the sample 24 is placed on the sample holder 25.

First, the chamber 21 is evacuated by an evacuation system 27 connected to the evacuation apparatus. In this case, it is preferable to exhaust as high a vacuum as possible. That is, carbon, nitrogen and oxygen, which are atmospheric components, are generally not preferable for semiconductors. Such an element is included in the semiconductor, and at the same time, the activity of the added impurities may be lowered.

Further, the crystallinity of semiconductors is deteriorated and causes unsaturated bonds in the grain boundaries. Therefore, it is preferable to evacuate the inside of the chamber to 10 ^-6 otrr or less, preferably 10 ^-8 torr or less.

It is also preferable to operate the heater 26 before and after the exhaust to discharge the atmospheric component adsorbed in the chamber. It is also preferable to provide a spare chamber other than the chamber as in the present vacuum apparatus so that the chamber does not directly come into direct contact with the vacuum chamber. Naturally, it is preferable to use a turbo molecular pump or a cryo pump which is less contaminated with carbon or the like, as compared with a rotary pump or an oil diffusion pump.

If sufficiently exhausted, the reactive gas is introduced into the chamber by the gas system 28. The reactive gas may be composed of a single gas, or may be converted to sorbent, argon, helium, neon, or the like. The pressure may be at or below atmospheric pressure. These are selected in consideration of the kind of the intended semiconductor, the impurity concentration, the depth of the impurity region, the substrate temperature, and the like.

Then, the laser light 23 is irradiated to the sample through the window 22. At this time, the sample is heated to a constant temperature by the heater. The laser beam is normally irradiated at about 5 to 50 pulses in one place. The deviation of the energy of the laser pulse is sufficiently large, and therefore, when the number of pulses is too small, the probability of occurrence of defects is large. On the other hand, it is not preferable in terms of mass production (throughput) to irradiate too many pulses at one place. According to the inventor's experience, the above-mentioned number of pulses was valid in terms of mass productivity and manufacturing efficiency.

In this case, for example, when the pulse of the laser has a rectangular shape with a characteristic of 10 mm (x direction) x 30 mm (y direction), 10 pulses of laser pulse are irradiated to the same area, However, the laser may be moved by 1 mm in the x direction for one pulse.

When the laser irradiation is completed, the inside of the chamber is evacuated, and the sample is cooled to room temperature to take out the sample. Thus, in the present invention, the doping process is extremely simple and high speed. That is, in the conventional ion implantation process,

(1) Formation of a doping pattern (resist coating, exposure, development)

(2) ion implantation (or ion doping)

(3) Recrystallization

(Solid phase dispersion) by conventional laser irradiation,

(1) Formation of a doping pattern (resist coating, exposure, development)

(2) Impurity film formation (other than spin coating)

(3) Laser irradiation

I also needed three processes. However, in the present invention,

(1) Formation of a doping pattern (resist coating, exposure, development)

(2) Laser irradiation

. ≪ / RTI >

5, the inside of the chamber 31 is first evacuated by the evacuation system 37, and the reactive gas is introduced from the gas system 38. In this case, Then, the sample 34 on the sample holder 35 is irradiated with the laser light 33 through the window 32. At this time, the sample 39 is irradiated from the high frequency or alternating current (or DC) ), And generates plasma or the like in the chamber to activate the reactive gas. In the drawing, the electrodes are shown as capacitive coupling type, but they may be inductive (inductance) coupling type. [0154] Also in the capacitive coupling type, the sample holder may be used as one electrode. Further, at the time of laser irradiation, the sample 36 may be heated by the heater 36.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples.

[Example 1]

This embodiment is an example in which the doping method of the present invention is applied to manufacture an N-channel thin film insulated gate field effect transistor (hereinafter referred to as NTFT) provided on a glass substrate. In this embodiment, a glass substrate or a quartz substrate is used as the substrate. This is because the TFT manufactured in this embodiment is intended to be used as a switching element or a driving element of an active matrix type liquid crystal display device or an image sensor. Of course, the structure of the present invention may be applied to another semiconductor device, for example, a P-type semiconductor layer or an N-type semiconductor layer of a photoelectric conversion device, or a doping technique for manufacturing a single crystal semiconductor integrated circuit. Therefore, as the substrate, a single crystal or polycrystal of silicon or other semiconductor may be used, or another insulator may be used.

First, in FIG. 1, a SiO 2 film or a silicon nitride film on a glass substrate 11 as a substrate is formed as a protective film 12 of a base film. In the present embodiment, the SiO 2 film 12 was formed to a thickness of 200 nm by RF sputtering in an oxygen atmosphere of 100%. The deposition conditions are as follows.

O2 flow rate 50 sccm

Pressure 0.5 Pa

RF power 500W

Substrate temperature 150 ° C

Next, a hydrogenated amorphous silicon semiconductor layer 13 of intrinsic or substantially intrinsic (meaning that no artificial impurities are added) is formed to a thickness of 100 nm by the plasma CVD method. The hydrogenated amorphous silicon semiconductor layer 13 becomes a semiconductor layer constituting a channel forming region and a source and a drain region. The deposition conditions are as follows.

Atmosphere Silane (SiH4) 100%

Film forming temperature 160 캜 (substrate temperature)

Film forming pressure 0.05 Torr

Input power 20 W (13.56 MHz)

In this embodiment, although silane is used as a raw material gas for forming an amorphous silicon film, disilane or trisilane may be used in order to crystallize amorphous silicon polycrystallized by thermal crystallization .

The film forming atmosphere is performed at 100% silane because the amorphous silicon film formed in a 100% silane atmosphere is easier to crystallize than an amorphous silicon film formed in a hydrogen-diluted silane atmosphere in general . The low film forming temperature is intended to contain a large amount of hydrogen in the amorphous silicon film to neutralize the bonding number of silicon as much as possible with hydrogen.

In addition, the input power of the high-frequency energy (13.56 MHz) is as low as 20 W to strongly prevent the generation of clusters of silicon, that is, the formation of portions at the time of film formation. This is also based on the experimental fact that if the amorphous silicon film has a slight crystallinity in the amorphous silicon film, the crystallization is adversely affected at the subsequent laser irradiation.

Next, device separation pannings were performed to obtain the shape of FIG. 1. Then, the sample was heated under vacuum (10 ^-6 Torr or less) at 450 ° C. for 1 hour to thoroughly remove hydrogen, thereby forming a dangling bond in the film at a high density.

The sample was transferred to a laser irradiation apparatus shown in FIG. 5, and an excimer laser was irradiated to polycrystallize the sample. This process uses a KrF excimer laser (wavelength: 248 nm). The conditions are as follows.

Laser irradiation energy density 350 mJ / cm 2

Number of pulses 1 to 10 shots

Substrate temperature 400 ° C

After the laser irradiation, the temperature was raised to 100 DEG C in a hydrogen decontamination atmosphere (about 1 Torr).

In the present embodiment, crystallization of the amorphous silicon film by irradiation with laser light is shown, but it goes without saying that this may be replaced by a process by heating. This heating step is a step of crystallizing an amorphous silicon semiconductor film provided on a glass substrate by heating for 6 to 96 hours at a temperature of about 450 ° C. to 700 ° C. (generally 600 ° C.), which is a temperature lower than the heat resistance temperature of the glass Process.

5, reference numeral 21 denotes a vacuum chamber 21, 22 denotes a quartz for irradiating a laser from the outside of the vacuum chamber 21 (in the case of an excimer laser, in particular, anhydrous quartz) (Sample), (25) a sample holder, (26) a sample heating heater, (27) an exhaust system , And (28), the raw material gas is an introduction system of the incompressible gas and the carrier gas, and only one is shown in the drawing, but actually, a plurality of them are provided.

Further, in the exhaust system, the residual concentration of impurities (particularly oxygen) in the chamber was extremely reduced by using a rotary pump for low vacuum and a turbo molecular pump for high vacuum. The exhaust performance is set to 10 ^-6 torr or less, preferably 10 ^-8 torr or less.

After crystallization by an excimer laser using a vacuum chamber in FIG. 5, a SiO 2 film 14 to be a gate insulating film was formed to have a thickness of 100 nm by a PF sputtering method to obtain a second figure. And phosphorus (P) was added to form an amorphous silicon semiconductor layer or a polycrystalline silicon semiconductor layer (thickness: 150 nm) to be a Geff electrode 15 into an N-type conductivity type.

Then, a gate region was formed by patterning to obtain a shape in FIG. 3. As the gate electrode, a metal material such as aluminum, chromium, or tantalum may be used. In the case of using aluminum or tantalum, if the surface is anodically oxidized, the gate electrode is not damaged even in the subsequent laser irradiation. The planer TFT in which anodic oxidation is performed on the gate electrode is described in Japanese Patent Application No. 3-238713 (Japanese Patent Application).

Here, the apparatus shown in FIG. 5 is used again to perform doping of the impurity by the laser beam, which is a constitution of the present invention. In the apparatus shown in FIG. 5, phosphor (P) was doped by heating a sample (having a shape shown in FIG. 3) under a PH 3 atmosphere and irradiating laser light.

At this time, phosphorus is doped in the source and drain regions (131 and 133 shown in FIG. On the contrary, in the channel forming region (132 shown in FIG. 4), the gate insulating film 14 and the gate electrode 15 become masks, so that no laser is irradiated and the temperature of the portion does not rise. Do not. The doping conditions are as follows.

Atmosphere PH₂ 5% concentration (H2 dilution)

Sample temperature 350 ℃

Pressure 0.02 to 1.00 Torr

Laser KrF excimer laser (wavelength 248 nm)

Energy density 150 to 350 mJ / cm 2

Number of pulses 10 Shorts

After the source and drain regions were formed, as shown in FIG. 4, an SiO 2 film 16 having a thickness of 10 nm was formed as an insulating film by RF sputtering. Film forming conditions are the same as those of the gate oxide film.

Thereafter, a contact hole punching pane is performed, aluminum to be an electrode is adhered to form a source electrode 17 and a drain electrode 18, and hydrogen annealing is performed at a temperature of 350 ° C in a hydrogen atmosphere I completed the NTFT. Similarly, by setting the atmosphere to B ₂ H ₆ , a P-channel TFT (PTFT) could be formed.

Particularly, in order to compare the effects of the present invention, the laser was irradiated with completely the same intensity without heating the sample at the time of laser irradiation. In the case where the sample was not heated as shown in FIG. 9 (b) And the distribution of impurities was limited to the vicinity of the surface. On the other hand, in the present embodiment, as shown in FIG. 9 (a), the doping concentration of the impurity is large and the diffusion reaches the deep portion.

As described above, NTFT and PTFT were fabricated. As a result of constructing a CMOS inverter by combining these TFTs, good characteristics as shown by the graph in the upper part of FIG. 14 were obtained. Further, as a result of constituting a ring oscillator by connecting a plurality of these CMOS circuits, good characteristics were obtained as shown by the lower graph in FIG. 14.

[Example 2]

This embodiment is an example in which the doping method of the present invention is applied to the fabrication of an NTFT provided on a substrate. In this embodiment, a glass substrate or a quartz substrate was used as the substrate in the same manner as the first embodiment. First, a SiO 2 film or silicon nitride film is formed as a protective film 12 of a base film on a glass substrate 11, which is a substrate of FIG. 1, similarly to Embodiment 1.

Next, an intrinsic or substantially intrinsic hydrogenated amorphous silicon semiconductor layer 13 is formed to a thickness of 100 nm by a plasma CVD method. Next, device separation patterning was performed to obtain the shape of FIG. 1. Then, the sample was heated under vacuum (10 ^-6 Torr or less) at 450 ° C. for 1 hour to thoroughly remove hydrogen, thereby forming unsaturated bonds in the film at high density.

In the chamber where hydrogen was removed, an excimer laser was irradiated while maintaining the vacuum state, and polycrystallization of the sample was carried out under the same conditions as in Example 1. After laser irradiation, the temperature was raised to 100 DEG C in a hydrogen reduced pressure atmosphere (about 1 Torr).

In this embodiment, crystallization by irradiation of excimer laser light and doping of impurities by a heating process for removing hydrogen from the sample using the apparatus shown in FIG. 6 was also performed by a vacuum chamber. By using such a vacuum chamber, it is easy to maintain the vacuum state during the crystallization process by laser irradiation in the heating process, and a film in which impurities (particularly oxygen) are not mixed in the film can be obtained. This vacuum chamber is equipped with an electrode for applying electron energy to the atmosphere, and also serves as a PCVD apparatus. But. It is needless to say that each process may be performed in a separate reaction furnace by using an apparatus constituted by successive processes in a multi-chamber type. The reaction furnace shown in FIG. 6 is of a positive column type, but may be of other types and the method of applying the electron energy is not particularly limited. Also, it is useful to use an ECR-type device, especially if it is desired to obtain a high activation rate.

In FIG. 6, reference numeral 31 denotes a vacuum chamber, 32 denotes a quartz window for irradiating the laser outside the vacuum chamber 31, 33 denotes laser light in the case of laser irradiation, Reference numeral 35 denotes a sample holder, reference numeral 36 denotes a heater for heating the sample, reference numeral 37 denotes an evacuation system, reference numeral 38 denotes an introduction system of a raw gas, an inert gas or a carrier gas, It is not shown, but it is actually installed in plural. In addition, the residual concentration of impurities (particularly oxygen) in the chamber was extremely reduced in the exhaust system by using a rotary pump for low vacuum and a turbo molecular pump for high vacuum. Reference numeral 39 denotes a parallel plate electrode, which supplies 13.56 MHz of electron energy supplied from the high-frequency oscillator 40 into the chamber.

6, the SiO 2 film 14 to be a gate insulating film was formed into 100 nm by using an RF sputtering method to obtain a second figure. Phosphorus (P) was added to the amorphous silicon semiconductor layer or the polycrystalline silicon semiconductor layer (thickness: 150 nm) to be the gate electrode 15 in order to make the N type conductivity type. The gate region was then formed by patterning to obtain the shape of FIG.

Here again, the device shown in FIG. 6 is used to perform doping of the impurity by the laser light, which is a constitution of the present invention. In the apparatus shown in Fig. 6, phosphor (P) was doped by irradiating laser light to the specimen (shape of FIG. 3) under an atmosphere of PH 3 decomposed by applying electron energy. At this time, phosphorus is doped in the source and drain regions (131 and 133 shown in FIG. In contrast to this, the gate insulating film 14 and the gate electrode 15 are masked in the channel forming region (132 in FIG. 4) and the laser is not irradiated, so that the temperature of the portion is not increased. Do not. The doping conditions are as follows.

Atmosphere PH3 5% concentration (H2 dilution)

Sample temperature 350 ℃

Pressure 0.02 to 1.00 Torr

Input power 50 ~ 200W

Laser KrF excimer laser (wavelength 248 nm)

Energy density 150 to 350 mJ / cm 2

Number of pulses 10 Shorts

After forming the source and drain regions, an SiO 2 film 16 as an insulating film was formed to have a thickness of 100 nm by an RF sputtering method as shown in FIG. 4 in the same manner as in Example 1, and hole punching for contact was performed And the source electrode 17 and the drain electrode 18 were formed by vapor-depositing aluminum as an electrode, and hydrogen annealing was performed at 350 DEG C in a hydrogen atmosphere to complete the NTFT.

In this doping process, a P-channel TFT (PTFT) can be formed by setting the atmosphere to B ₂ H ₆ . Conventionally, the decomposition situation of the doping gas differs depending on the wavelength of the laser light, and the problem of non-uniformity of doping due to this point is considered. However, in the case of adopting the constitution of the present invention, the doping gas is decomposed by the electron energy Even with PTFT or NTFT, doping can be performed without being limited by the wavelength of laser light.

[Example 3]

FIG. 7 shows the shape of the doping treatment apparatus of the present invention. That is, a window 72 of a silt type made of anhydrous quartz glass is provided in the chamber 71. The laser light is shaped into an elongated shape conforming to the window. The beam of the laser was, for example, 10 mm in length and 300 mm in length. An evacuation system 77 and a gas system 78 for introducing a reactive gas are bended in the chamber. A sample holder 75 is provided in the chamber, and a sample (Functioning as a heater) 76 is provided under the sample holder. The sample holder is operated, and the sample can be operated in accordance with the shot of the laser.

In this way, when the mechanism for moving the sample is combined in the chamber, it is necessary to pay close attention to the temperature control because an abnormality of the mechanism occurs due to the thermal expansion of the sample holder by the heater. Maintenance in the chamber is troublesome.

[Example 4]

8 (A) shows the shape of the doping treatment apparatus of the present invention. That is, the chamber 81 is provided with a window 82 made of anhydrous quartz glass. This window is wide enough to cover the entire surface of the sample 84, unlike the case of the third embodiment. To the chamber, an exhaust system 87 and a gas system 88 for introducing a reactive gas are connected. A sample holder 85 is provided in the chamber, a specimen 84 is mounted on the specimen holder 85, and a heater is embedded in the specimen holder. The sample holder is fixed to the chamber. A pedestal 81a of the chamber is provided at the bottom of the chamber, and laser irradiation is performed by moving the entire chamber in accordance with the pulse of the laser. The laser beam has an elongated shape as in the case of the third embodiment. For example, a rectangular shape of 5 mm x 100 mm. The position of the laser beam is fixed in the same manner as in the third aspect. In this embodiment, a structure in which the entire chamber is moved is employed, unlike the third embodiment. Therefore, there is no mechanical part in the chamber, and dust is not generated, so maintenance is easy. In addition, the transfer mechanism is rarely affected by the heater row.

The present embodiment is superior not only to the above-described third embodiment but also to the following points. That is, in the method of the third embodiment, laser irradiation can not be performed until the sample is put in the chamber and vacuum exhausted to a sufficient degree of vacuum. In other words, there was a lot of non-operating time. However, in this embodiment, when a plurality of chambers as shown in FIG. 8 (A) are prepared and sequentially advanced in the form of sample advancement, vacuum exhaustion, laser irradiation, sample removal, I never do that. Such a system is shown in Fig. 8 (B).

That is, the chambers 97, 96 containing the untreated sample are directed to the pedestal 99 having a system capable of precise movement by the continuous transport mechanism 98 during the evacuation process. In the chamber 95 on the stage, laser light emitted from the laser device 91 and processed into suitable optical devices 92 and 93 is irradiated to the sample through the window. By moving the stage, the chamber 94 in which the necessary laser irradiation is performed is sent again to the next stage by the continuous transport mechanism 100, and the heater in the chamber is turned off, exhausted and sufficiently cooled down, .

As described above, in the present embodiment, continuous processing can be performed, the time required for exhausting can be reduced, and the throughput can be increased. Of course, in the case of this embodiment, although the throughput is improved, since more chambers are required than in the case of the third embodiment, the mass production scale and the investment scale must be considered.

[Example 5]

This embodiment is an example in which the doping method of the present invention is applied to the manufacture of an NTFT provided on a glass substrate. In the present embodiment, a glass substrate or a quartz substrate was used as the substrate in the same manner as in Example 1. First, a SiO 2 film is formed as a protective film 102 of a base film on a glass substrate 101 which is a substrate of the first embodiment, and then a substantially hydrogenated amorphous silicon semiconductor layer 103 ) Is formed with a thickness of 100 nm. Subsequently, device separation patterning was performed. Then, the sample was heated under vacuum (10 ^-6 Torr or less) at 450 ° C. for 1 hour to thoroughly remove hydrogen, thereby forming unsaturated bonds in the film at a high density. Thereafter, an SiO 2 film 104 was formed to a thickness of 100 nm by RF sputtering to obtain the shape of FIG. 10 (A). Then, a silicon oxide mask 105 is left only in the channel portion.

Here, the device shown in FIG. 6 is used to perform doping of the impurity by the laser light, which is a constitution of the present invention. In the apparatus shown in FIG. 6, the sample (having the shape of FIG. 10 (B)) was heated under an atmosphere of PH 3 decomposed by applying electron energy, and phosphorus (P) did. At this time, since phosphorus is doped in the source and drain regions (106 and 108 in the figure), N type is formed. On the other hand, in the channel forming region (107 in the figure), silicon oxide is masked by the mask 105, and the laser is irradiated and crystallized, but since the mask material exists, doping is not performed. That is, in this step, crystallization by laser and doping are simultaneously performed. The conditions at this time were the same as those in Example 2.

After the source and drain regions are formed, a gate oxide film 110 and a gate electrode 109 are formed, and an SiO 2 film 111 is formed to a thickness of 100 nm as an interlayer insulating film. Then, perforation punching for contact is performed, In addition, the source electrode 112 and the drain electrode 113 are formed by depositing aluminum to be an electrode, and thermal annealing is performed at 350 DEG C in a hydrogen atmosphere. As shown in FIG. 10C, , And NTFT.

In this embodiment, a self-aligned source and drain can not be formed. However, when the gate electrode is formed on the gate insulating film in the same manner as in Embodiment 1 and the backside is irradiated on the back surface of the gate insulating film, The crystallization of the channel region and the doping of the source and the drain can be performed at the same time.

[Example 6]

An example in which an active matrix is formed on a glass substrate of Corning 7059 (product name) is shown in FIG. As shown in Fig. 11 (A), a Corning 7059 glass substrate (1.1 mm in thickness, 300 x 400 mm) was used as the substrate 201. A silicon nitride film 202 having a thickness of 5 to 50 nm, preferably 5 to 20 nm was formed on the entire surface by plasma CVD so that impurities such as sodium contained in the Corning 7059 glass would not diffuse into the TFT. The technique of coating a substrate with a coating of silicon nitride or aluminum oxide and using it as a blocking layer is described in Applicant's Japanese Patent Application No. 3-238710 and No. 3-238714.

Subsequently, a silicon film 204 (30 to 150 nm in thickness, preferably 30 to 50 nm in thickness) is formed by LPCVD or plasma CVD after the formation of the basic oxide film 203 (silicon oxide), and tetraethoxy A gate insulating film (thickness: 70 to 120 nm, typically 100 nm) 205 of silicon oxide was formed by plasma CVD in an oxygen atmosphere using silane (TEOS) as a raw material. The substrate temperature was set at 400 DEG C or less, preferably 200 to 350 DEG C, in order to prevent atrophy or warping of the glass. However, at such a substrate temperature, a large amount of recombination centers exist in the oxide film, and for example, the interface level density is a level that can not be used as a gate insulating film at 10 ¹² cm ^-2 or more.

As shown in FIG. 11 (A), KrF laser light is irradiated from the hydrogen dilution phosphine PH (5%) to improve the crystallinity of the silicon film 204, and the gate oxide film 205 (The center of the trap). At this time, the energy density of the laser beam was set to 200 to 300 mJ / cm ² . In addition, the number of shots was 10 circuits. Preferably, the temperature is maintained at 200 to 400 캜, typically 300 캜. As a result, the silicon film 204, the crystallinity is improved, and also the gate oxide film (205) is nd, 1 × 10 ²⁰ ~ 3 × 10 ²⁰ cm ^-3 of phosphorus is doped, the interface state density of 10 ¹¹ cm ^{- 2} or less.

Next, as shown in FIG. 11 (B), a gate electrode 206 made of aluminum was formed and its periphery was covered with an anodic oxide 207.

Thereafter, boron is implanted into the silicon layer in a self-aligning manner as a P-type impurity by ion doping to form source / drain regions 208 and 209 of the TFT, and as shown in FIG. 11C, Was irradiated with KrF laser light to improve the crystallinity of the silicon film whose crystallinity was deteriorated due to the ion doping. At this time, however, the energy density of the laser light was set to be as high as 25 to 300 mJ / cm ² . Therefore, the sheet resistance of the source / drain of this TFT is 300 to 800 ?.

Thereafter, as shown in FIG. 11 (D), interlayer insulating material 210 was formed by polyimide and the pixel electrode 211 was formed by ITO. As shown in FIG. 11E, contact holes are formed to form chromium electrodes 212 and 213 in the source / drain regions of the TFT, and one of the electrodes 213 is also connected to the ITO. Finally, the hydrogen was not hydrogenated at 300 DEG C for 2 hours in hydrogen, completing the pixel of the liquid crystal display device.

[Example 7]

11 shows an example in which a silicon oxide film is doped with phosphorus and a TFT is formed as a gate insulating film in the same manner as in Embodiment 6. FIG. A silicon nitride film 202 having a thickness of 5 to 50 nm, preferably 5 to 20 nm, was formed on the entire surface of the substrate 201 as shown in FIG. 11 (A) by plasma CVD. A silicon oxide film 204 (thickness of 30 to 150 nm, preferably 30 to 50 nm) is formed by an LPCVD method or a plasma CVD method after forming the basic oxide film 203 (silicon oxide) A silicon film (thickness: 70 to 120 nm, typically 100 nm) 205 was formed. This process may be carried out by plasma CVD in an oxygen atmosphere using tetraethoxy silane (TEOS) as a raw material as in the sixth embodiment. The substrate temperature was set at 400 DEG C or less, preferably 200 to 350 DEG C, in order to prevent atrophy or warping of the glass.

As shown in FIG. 11 (A), KrF laser light is irradiated from hydrogen dilution phosphine PH (5%) to improve the crystallinity of the silicon film 204, and the gate oxide film 205 (The center of the trap). At this time, the energy density of the laser beam was set to 200 to 300 mJ / cm ² . It also had 10 circuits for the shot. The substrate temperature was set to room temperature. For this reason, phosphorus doping was limited to 70% or less of the surface of the silicon oxide film.

Next, as shown in FIG. 11 (B), a gate electrode 206 made of aluminum was formed and its periphery was covered with an anodic oxide 207. After the anodic oxidation process was terminated, negative (-) voltage was applied. For example, a voltage of -100 to -200 V is applied for 0.1 to 5 hours. Preferably, the substrate temperature is 100 to 250 캜, typically 150 캜. By this process, the movable ions in the silicon oxide or silicon oxide and the silicon interface are attracted to the gate electrode AI, and trapped in the region (presumed to be vitrified) having a large concentration of phosphorus present therein. A technique of applying a negative voltage to the gate electrode after the anodic oxidation or during the anodic oxidation is described in Japanese Patent Application No. 4-115503 (filed on April 7, 1992) by the inventors of the present invention.

Thereafter, phosphorus is implanted into the silicon layer in a self-aligning manner by a known ion doping method as an N-type impurity to form source / drain regions 208 and 209 of the TFT, and as shown in FIG. 11 (C) This was irradiated with KrF laser light to improve the crystallinity of the silicon film with deteriorated crystallinity due to the ion doping. Then, as shown in FIG. 11 (D), interlayer insulating material 210 was formed by polyimide and the pixel electrode 211 was formed by ITO. As shown in FIG. 11E, contact holes are formed to form electrodes 212 and 213 with chromium in the source / drain regions of the TFT, and one of the electrodes 213 is also connected to the ITO. Finally, the hydrogen was not hydrogenated at 300 DEG C for 2 hours in hydrogen to complete the TFT.

[Example 8]

In this embodiment, a silicon oxide film is formed on a single crystal substrate, phosphorus doping is performed on the silicon oxide film, and a MOS capacitor having the gate oxide film is removed therefrom, and the characteristics (CV characteristics) thereof are measured.

A gate insulating film of silicon oxide (thickness of 70 to 120 nm, typically 100 nm) was formed on the single crystal silicon (100) surface by using plasma of tetraethoxy silane (TEOS) as a raw material in an oxygen atmosphere. The substrate temperature was 400 占 폚 or less, preferably 200 to 350 占 폚. However, at such a substrate temperature, the s oxide film has a large number of clusters containing carbon and a large amount of recombination centers. For example, the interface state density can be used as a gate insulating film at a concentration of 10 ¹² cm ^-2 or more There was no level.

From this point, the recombination center (trap center) of the silicon oxide film was reduced by irradiating KrF laser light from hydrogen dilution phosphine PH (5%) using the apparatus used in Example 1. At this time, the energy density of the laser beam was set to 200 to 300 mJ / cm ² . In addition, the number of shots was 10 circuits. Preferably, the temperature is maintained at 200 to 400 캜, typically 300 캜. As a result, phosphorus of 1 x 10 ²⁰ to 3 x 10 ²⁰ cm ^-3 was doped into the oxide film, and the interfacial level density also decreased to 10 ¹¹ cm ^-2 or less. Next, a gate electrode of aluminum was formed.

For example, if the laser doping process is not performed, the CV characteristic of the obtained MOS capacitor becomes large as shown in FIG. 12 (A). Here, the abscissa represents the voltage, and the ordinate represents the electrostatic capacity. However, good CV characteristics as shown in Fig. 12 (b) can be obtained by the laser doping treatment as in this embodiment.

The distribution of each element in the film is as shown in FIG. 12 (C). In other words, phosphorus was doped to the middle of the silicon oxide film by the laser doping of this embodiment. It can be seen from this that the sodium element is removed by phosphorus. Carbon was also present in only a small fraction of all areas of the oxide film because it was emitted outside the film by laser irradiation. Also in this embodiment, as in the seventh embodiment, when negative (-) voltage is applied to the gate electrode AI and the movable ion such as sodium existing in the film is attracted to the region where the phosphorus is extremely phosphorous An even greater effect can be obtained.

[Example 9]

Examples 13 to 15 show examples in which the dopant is doped in the amorphous silicon thin film having a thickness of 500 nm formed on the glass substrate and the characteristics thereof are investigated. As the excimer laser, a KrF laser (wavelength: 248 nm) was used. The chamber also has the shape shown in FIG. In this chamber, it was tested to change the type of doping doped by changing the type of glass. That is, when doping the N-type impurity, hydrogen gas containing 5% of phosphine is introduced into the chamber, and a laser is irradiated. When the P-type impurity is doped, hydrogen gas containing 5% .

The pressure in the chamber was set at 100 Pa. The energy density of the laser was 190 to 340 mJ / cm < ² > The substrate temperature was room temperature or 300 占 폚.

13 and 14 show the substrate temperature dependency of the impurity diffusion. Here, the laser has an energy density of 300 mJ / cm ² and a shot number of 50. FIG. 13 shows the diffusion pattern of boron in the depth direction. Data were obtained by secondary ion mass spectrometry. As apparent from the drawing, when the substrate temperature is room temperature, the impurity concentration is higher by one digit or more and the diffusion depth of the impurity is twice as large when the substrate is heated to 300 占 폚.

FIG. 14 shows the diffusion pattern of phosphorus in the depth direction, showing the same tendency as boron. In particular, in the case of phosphorus, the effect of heating the substrate was more remarkable than boron.

FIG. 15 shows the relationship between the energy density of the laser, the shot number and the sheet resistance of the film. Boron was used as an impurity. As can be seen from the figure, it is presumed that the sheet resistance decreases and the impurity concentration increases as the energy density increases. However, the sheet resistance appears to converge to a certain value.

Further, as the number of shots of the laser increases, the sheet deterioration decreases. However, when the energy density of the laser is 220 mJ / cm ² or more, no remarkable decrease in sheet resistance is found even at 50 shots or 100 shots. However, since there was a big difference between 1 shot and 5 shot, we confirmed that laser irradiation of at least 5 shots is necessary.

By irradiating the semiconductor with laser light in the state of heating the sample or in the atmosphere containing the impurity which gives decomposition of decomposition by giving the electron energy to the reactive gas, which is the constitution of the present invention, It was possible to effectively dope the impurity imparting the conductivity. Particularly, it is possible to obtain an effect that doping can be performed without giving heat damage to the glass substrate and without depending on the wavelength of the laser beam or the kind of the doping gas.

Further, as described above, the present invention can be applied not only to the limited purpose of impurity doping in semiconductors, but also to the modification of the surfaces of metal materials and ceramic materials, the broadening of the metal thin films, the ceramic thin films, It is an industrially advantageous invention.

Claims (7)

The impurities may be physically or chemically modified by irradiating laser light in a reactive gas atmosphere containing an impurity by heating an object made of a semiconductor or a metal insulator doped with impurities or a combination thereof to a temperature not higher than the melting point thereof, Wherein the laser light is chemically diffused, recombined, and intruded. A method for doping an impurity imparting a uniform conductivity to a semiconductor by irradiating laser light onto a semiconductor surface in a reactive gas atmosphere containing an impurity imparting conductivity, , The temperature is higher than the room temperature, the reactive gas is not decomposed, and the temperature is maintained at a temperature not exceeding the crystallization temperature of the semiconductor. A chamber in which a sample holder and a sample function as a heating element, a chamber which is made of a material transparent enough to transmit laser light, a vacuum exhausting device, and an apparatus for introducing a reactive gas containing an impurity element, And a means for moving the chamber in synchronism with the irradiation of the laser beam. At least two chambers provided with a storage made of a material transparent enough to transmit laser light and a device for introducing a reactive gas containing an impurity element and a second chamber in which a pulsed laser beam is irradiated to the first chamber And means for moving said first chamber in synchronism with irradiation of laser light and means for conveying at least one chamber of another chamber of said chamber. Characterized in that phosphorus is doped in the silicon oxide by irradiating the surface of the silicon oxide with a laser beam in a reactive gas atmosphere containing phosphorus so that the silicon oxide is heated during the laser irradiation Method of laser treatment of silicon oxide. A method for doping phosphorus in a silicon oxide film produced by a gas phase reaction method at a substrate temperature of 600 DEG C or less using an organosilane gas as a material, characterized in that, in a reactive gas atmosphere containing phosphorus, Wherein the phosphor is doped in the silicon oxide by irradiating the phosphor with light. The method according to claim 6, wherein a silicon film is present under the silicon oxide coating.