JP3587083B2 - Method for manufacturing semiconductor device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for processing a thin film semiconductor, and more particularly to a semiconductor processing method for forming a concentration gradient of an impurity element inside a thin film semiconductor, and a semiconductor device using the concentration gradient.
[0002]
[Prior art]
Generally, in order to secure the reliability of an insulated gate field effect transistor (MOSFET), it is effective to reduce the electric field at the drain end.
[0003]
2. Description of the Related Art A lightly-doped drain (LDD) MOSFET that realizes electric field relaxation by providing a low-concentration impurity region at a drain end has been known.
[0004]
Similarly, various LDD structures have been proposed for thin film transistors (TFTs) using polycrystalline silicon (poly-Si) obtained by subjecting amorphous silicon (a-Si) or the like to laser annealing.
[0005]
Further, J.I. R. Ayres et al., "Analysis of drain field and hot carrier stability of poly-Si Thin film transformers," (Jpn. J. Appl. Phys. As described in 1998.), the effect of relaxing the electric field is greater when the spatial distribution of the impurity concentration at the boundary between the drain region and the LDD region gradually changes. Here, a method of processing a thin film semiconductor that changes the spatial distribution of the impurity concentration is required.
[0006]
A conventional method for processing such a thin film semiconductor is described in, for example, the above-mentioned paper.
[0007]
Here, a method for forming an n-type poly-Si TFT having an LDD structure will be described as an example and described with reference to FIGS.
[0008]
First, an oxide film (SiO 2) is formed on an insulating substrate 110 such as glass by a plasma CVD method or the like. ₂ ) Is deposited to form a barrier layer 120 for preventing diffusion of impurities from the insulating substrate 110.
[0009]
Second, a thin-film semiconductor such as a-Si is formed on the entire surface of the barrier layer 120 by, for example, a low pressure chemical vapor deposition (LPCVD) method. To remove a-Si.
[0010]
Third, a region is limited by photolithography, and a high-concentration impurity (such as phosphorus in the case of n-type) is selectively introduced into this region by ion implantation or ion doping.
[0011]
Further, a similar process is used to selectively introduce impurities at a low concentration into another region.
[0012]
Thus, the region 130 into which the impurity is not introduced, the region 140 into which the low concentration impurity is introduced, and the region 150 into which the high concentration impurity is introduced are formed at the positions shown in the drawing.
[0013]
The photolithography process required so far is three times. Fourth, when the entire surface is irradiated with pulsed ultraviolet light 160 from an excimer laser such as XeCl at an appropriate intensity, the amorphous silicon (a-Si) in the semiconductor regions 130, 140, and 150 is almost instantaneously changed. Is melted.
[0014]
The semiconductor layer in the melted region is crystallized and reformed into poly-Si when the stored heat escapes to the surroundings and is cooled. At this time, in the semiconductor regions 140 and 150, the introduced impurities such as phosphorus are taken into the lattice of Si and activated electronically, that is, the low-concentration and high-concentration n-type poly-Si regions It is formed.
[0015]
Here, almost all the energy of the laser beam 160 is absorbed by the a-Si, and the pulse width of the laser beam is very short, several tens of nanoseconds, so that the substrate 110 is not damaged by heat.
[0016]
In addition, due to the presence of the barrier layer 120, there is no diffusion of impurities from the substrate 110 to these semiconductor regions 130, 140, and 150. Lastly, an insulating layer 170 serving as a gate insulating film is deposited on such a structure by a plasma CVD method or the like, and a metal layer serving as a gate electrode is further formed thereon by a method such as sputtering and the like. Perform patterning.
[0017]
After forming an interlayer insulating film thereon, a contact hole is formed by a photolithography process, a metal thin film is formed and patterned by a photography process, and an n-type poly-Si TFT having an LDD structure is formed.
[0018]
Here, the distribution of the impurity concentration will be considered. At the stage where the ion implantation or ion doping process is completed, the impurity distribution inside the thin film semiconductor becomes almost stepwise.
[0019]
Next, when the laser beam is absorbed and the semiconductor layer is melted, the impurity atoms diffuse from the high-concentration region to the low-concentration region because the difference in impurity concentration is large in the boundary region between the semiconductor regions 130 and 140. After being cooled and solidified, the impurity atoms are hardly taken into the Si lattice and diffused.
[0020]
The same applies to the boundary between the regions 140 and 150. As a result, the impurity concentration after the laser light irradiation changes gently at the boundary of each region, and becomes a distribution as shown in FIG.
[0021]
In the case where a circuit is formed only with the n-type TFT having the LDD structure described above, the number of necessary photography steps is six. If it is desired to form a CMOS circuit, it is necessary to add a p-type impurity before laser irradiation, so that a total of eight photolithography steps are required.
[0022]
[Problems to be solved by the invention]
A conventional method of processing a thin film semiconductor by laser light irradiation utilizes a phenomenon in which an impurity element is diffused in a short time during which the semiconductor light is instantaneously irradiated with the laser light and the semiconductor is melted.
[0023]
The diffusion phenomenon depends on the material, concentration distribution, and time. It is possible in principle to design the spatial distribution of impurities by extracting the diffusion coefficient by experiments and solving the diffusion equation, but the time factor is determined by the shape of the laser pulse, and there is little room for material selection. There are many limiting factors such as this, and such control is practically difficult. However, for example, in a TFT having an LDD structure, the impurity concentration distribution is an important design parameter for exhibiting the effect of relaxing the electric field at the drain end, and it is desirable that the TFT can be controlled as freely as possible.
[0024]
In the conventional method of forming a TFT having an LDD structure as described above, in order to introduce impurities at different concentrations into the source / drain region and the LDD region, two steps of introducing impurity ions and two steps of introducing impurity ions are performed. Photolithography steps (photoresist application, exposure, etching) are required.
[0025]
The increase in the number of steps may cause not only a problem of an increase in labor but also problems such as a pattern defect due to dust, a photoresist residue due to uneven etching, and the like.
[0026]
Therefore, in order to secure the reliability of the TFT and suppress the increase in the manufacturing cost, the increase in the number of steps should be minimized.
[0027]
Japanese Unexamined Patent Publication No. Hei 4-254335 describes a semiconductor device and a method of manufacturing the same. However, an LDD is only provided between a first conductivity type channel region and a second conductivity type drain region by an ion implantation operation. Only a transistor structure in which a structure is formed and an LDD structure is not formed between a source region and a channel region is shown, and there is no disclosure of a semiconductor device manufacturing technique using light energy.
[0028]
Japanese Patent Application Laid-Open No. 9-27624 describes a technique for forming an LDD structure using a double side wall structure as a mask, but only uses an ion implantation operation and uses light energy. There is no disclosure about the semiconductor device manufacturing technology described above.
[0029]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to improve the above-mentioned drawbacks of the prior art and to provide a high-performance thin-film semiconductor device by controlling the spatial distribution of impurity concentration inside a thin-film semiconductor with a high degree of freedom. Another object of the present invention is to reduce the number of manufacturing steps of a TFT having an LDD structure.
[0030]
[Means for Solving the Problems]
The present invention employs the following technical configuration to achieve the above object.
[0031]
That is, as a first aspect according to the present invention, When a transistor is formed, a first semiconductor region containing almost no impurities, and second and third semiconductor regions containing impurities having a predetermined impurity concentration are formed on a substrate in phase with each other. A step of arranging and forming the second semiconductor region and the third semiconductor region so as to be in contact with two boundaries that are not in contact with each other; and including a boundary in which the second semiconductor region and the first semiconductor region are in contact with each other. Supplying light energy having an irradiation width smaller than a desired width of the LDD region to all or a part of the semiconductor region in which the LDD region included in the transistor is formed, thereby supplying the light energy. Diffusing impurities present in the first semiconductor region and the second semiconductor region in the region to form the LDD region having a desired impurity concentration distribution; and A light energy having an irradiation width smaller than a desired width of the LDD region is applied to all or a part of the semiconductor region including the boundary where the region and the first semiconductor region are in contact with each other and where the LDD region constituting the transistor is formed. To diffuse the impurities present in the first semiconductor region and the third semiconductor region in the region to which the light energy has been supplied, thereby providing a desired impurity concentration distribution. Forming a LDD region. It is.
[0032]
Further, as a second aspect according to the present invention, On a substrate, a first semiconductor region containing almost no impurities and second and third semiconductor regions containing high-concentration impurities are formed on two non-adjacent boundaries of the first semiconductor region by the second semiconductor region. Forming the semiconductor region and the third semiconductor region so as to be in contact with each other; and selectively supplying light energy to the second semiconductor region to modify the semiconductor in the second semiconductor region. Modifying the semiconductor of the third semiconductor region by selectively supplying light energy to the third semiconductor region; and modifying the second semiconductor region and the first semiconductor region. Selectively supplying light energy to the vicinity of the boundary region where the first and second semiconductor regions are in contact with each other, and modifying the boundary region where the third semiconductor region and the first semiconductor region are in contact with each other. Is selectively supplied with light energy in the vicinity of The method of manufacturing a semiconductor device including the step of modifying the semiconductor forming the neighborhood It is.
[0033]
[Embodiment of the present invention]
Since the method for processing a semiconductor and the method for manufacturing a semiconductor device according to the present invention employ the above-described technical configuration, the spatial distribution of the impurity concentration in the semiconductor can be controlled with a high degree of freedom.
[0034]
That is, in a region where a steep impurity concentration distribution is desirable, the irradiation width or the overlap width of the laser light is reduced, or in a region where a gentle distribution is desirable, the irradiation width or the overlap width is set to be large, respectively. Thus, a desired impurity concentration distribution can be formed.
[0035]
Therefore, in the present invention, since the degree of freedom in controlling the impurity concentration distribution inside the thin film semiconductor is high, the electric field inside the thin film semiconductor can be controlled with a high degree of freedom according to the type and purpose of the semiconductor element formed of such a thin film semiconductor. There is an effect that it can be controlled in degrees.
[0036]
【Example】
Hereinafter, a configuration of a specific example of a semiconductor processing method and a semiconductor device manufacturing method according to the present invention will be described in detail with reference to the drawings.
[0037]
That is, FIG. 1 is a view for explaining a configuration procedure of a specific example of a semiconductor processing method according to the present invention. In the drawing, a semiconductor processing method in which light energy is supplied to the semiconductor 1 to modify the semiconductor 1 In the method, the light energy 30 is selectively supplied to at least one of the semiconductor regions 10 and / or 20 having a predetermined impurity concentration, so that the semiconductor region having an impurity concentration different from that before the light energy 30 is supplied. A semiconductor processing method for forming 40 is shown.
[0038]
To describe a more detailed configuration of the semiconductor processing method according to the present invention, for example, in a semiconductor processing method in which light energy 30 is supplied to the semiconductor 1 to modify the semiconductor 1, the impurity concentration is reduced. The light energy 30 is supplied to the vicinity 3, 3 ′ of the junction 2 of the plurality of types of semiconductor regions 10, 20 in the semiconductor 1 in which the plurality of types of semiconductor regions 10, 20 different from each other are arranged adjacent to each other. Accordingly, before the supply of the light energy 30, a new semiconductor region 40 having an impurity concentration N3 different from the impurity concentrations N1 and N2 of the semiconductor regions 10 and 20 adjacent to each other is arranged adjacent to the semiconductor region. Processing is performed so as to form between the semiconductor region groups 10 and 20.
[0039]
In the semiconductor processing method according to the present invention, the impurity concentration N3 of the new semiconductor region 40 depends on the region of each of the plurality of types of semiconductor regions 10 and 20 that are adjacently joined. However, it is desirable to perform processing so as to show a certain value N3 within a concentration range determined by the upper and lower limits of the impurity concentrations N1 and N2 individually held before the supply of the light energy 30.
[0040]
Furthermore, in the present invention, the plurality of semiconductor regions 10 and 20 arranged adjacent to each other before the light energy 30 is supplied and the plurality of semiconductor regions 10 and 20 after the light energy 30 is supplied. The semiconductor including the new semiconductor region 40 formed between the regions 10 and 20 can be processed so that an impurity concentration gradient is formed in a predetermined direction without using an ion implantation method.
[0041]
Therefore, in the semiconductor processing method according to the present invention, the first semiconductor region 10 having the first impurity concentration N1 which is a certain impurity concentration and the second semiconductor region 10 having a certain impurity concentration different therefrom are provided. The light energy 30 is selectively supplied to the vicinity 3, 3 'of the boundary region 2 where the second semiconductor region 20 having the impurity concentration N2 contacts the first and second semiconductor regions 10, 20. The third impurity concentration N3 of the third semiconductor region 40 formed after the light energy 30 is supplied in the vicinity 3, 3 ′ of the joint boundary region 2 between the first and second junction boundary regions 2 is determined by the first and second impurity concentrations. It is possible to set a certain value within a range limited by the first and second impurity concentrations N1 and N2 of the semiconductor regions 10 and 20, respectively.
[0042]
Further, in the present invention, in the semiconductor processing method, the impurity concentration N3 of the newly formed semiconductor region 40 may be different from that of the plurality of types of semiconductor regions 10 that are adjacently joined. , And 20 groups, it is also preferable to set the average value of the impurity concentrations N1 and N2 individually provided before the supply of the light energy.
[0043]
An example of the procedure of another specific example of the semiconductor processing method according to the present invention described above is as follows. For example, a first semiconductor region 80 containing almost no impurities and a predetermined impurity concentration are provided on a substrate. The second and third semiconductor regions 70 and 70 ′ containing impurities are placed at two boundaries 4 and 5 where the first semiconductor region 80 is not in contact with the second semiconductor region 70 and the third semiconductor region 70 ′. 70 'are arranged so as to be in contact with each other, and the light energy 30 is selectively supplied to a portion near a boundary region where the second semiconductor region 70 and the first semiconductor region 80 are in contact with each other. Modifying a semiconductor in a semiconductor region forming a predetermined range sandwiching the boundary region; and applying light energy 30 to a portion near the boundary region where the third semiconductor region 70 'and the first semiconductor region 80 are in contact with each other. To selectively sandwich the boundary region. A step of modifying the semiconductor of the semiconductor region forming the predetermined range but may be configured processing method of a semiconductor device as including.
[0044]
In the semiconductor processing method according to the present invention, it is preferable that the light energy 30 is obtained by a slit-shaped laser beam having a predetermined width.
[0045]
Further, in the semiconductor processing method according to the present invention, the slit-shaped laser light 30 is continuously connected to a plurality of semiconductor regions having different impurity concentrations at a predetermined pitch. It is preferable that the scanning is performed sequentially.
[0046]
On the other hand, in the semiconductor processing method according to the present invention, the slit-shaped laser light 30 is moved by a predetermined scanning amount, and is then irradiated onto a predetermined portion of a predetermined semiconductor region. It is preferable that the irradiation operation is intermittently repeated.
[0047]
Further, in the present invention, in performing the above-described scanning and irradiation operations, at least one of the irradiation ranges of the slit-shaped laser light to be irradiated on a predetermined portion of the semiconductor region in one irradiation operation. It is also preferable that the processing is performed so that the portion overlaps at least a part of the irradiation range of the slit-shaped laser beam irradiated to a predetermined portion of the semiconductor region in another irradiation operation.
[0048]
Further, in the semiconductor processing method according to the present invention, the width of the laser beam for irradiating one semiconductor region and the width of the laser beam for irradiating another semiconductor region can be different from each other.
[0049]
That is, the above-described semiconductor processing method of the present invention selectively supplies and reforms light energy to a plurality of semiconductor regions having different impurity concentrations at the same time, so that the impurity concentration different from that before the supply of the light energy is obtained. It is characterized by forming a region having the same.
[0050]
Further, in the above-described method for processing a semiconductor according to the present invention, the first semiconductor region having a certain impurity concentration and the second semiconductor region having a certain impurity concentration different from the first semiconductor region are in contact with each other. By selectively supplying light energy to the region, the impurity concentration of the boundary region is set to a certain value within a range limited by the respective impurity concentrations of the first and second semiconductor regions. It is a feature.
[0051]
Next, more specific examples of the above-described semiconductor processing method according to the present invention will be described below in the form of embodiments.
[0052]
(First specific example)
FIG. 1 is a cross-sectional view of a semiconductor 1 for describing an operation procedure in a first specific example of the semiconductor processing method of the present invention.
[0053]
The operation principle of the semiconductor forming method of the present invention will be described below with reference to FIG.
[0054]
That is, although not shown in FIG. 1, first, an oxide film serving as a barrier layer is formed on an insulating substrate such as glass, and the semiconductor 1, for example, the thin film semiconductor 1 is formed on the entire upper surface thereof. Is the same as the prior art.
[0055]
The thin film semiconductor 1 is formed so as to contain no impurity or to intentionally contain an impurity of a certain concentration N1 by introducing an impurity gas during film formation by LPCVD.
[0056]
That is, the impurity concentration N1 naturally includes the case where the impurity concentration is zero.
[0057]
To this, an impurity such as phosphorus is selectively introduced into a specific region of the thin film semiconductor 1, for example, 20 by a single photolithography process and an ion implantation process or an ion doping process.
[0058]
Thus, as shown in FIG. 1A, one region 10 containing an impurity of a certain concentration N1 and a second region 20 containing an impurity concentration N2 different from that are formed.
[0059]
Second, as shown in FIG. 1 (B), the first laser beam 30 is applied to the portion 2 where the first region 10 and the second region 20 are in contact with each other and the nearby portions 3 and 3 ′. Melts and crystallizes. During melting, the impurities in the region 10 diffuse into the region 20. As a result, as shown in FIG. 1, when the volume of the thin film semiconductor melted in the first region 10 and the volume of the thin film semiconductor melted in the second region 20 are equal, as shown in FIG. The impurity concentration N3 of the region forming the portion 2 and the neighboring portions 3, 3 ', that is, the third region 40 has an average value of the first and second regions.
[0060]
Generally, when V1 and V2 are the volumes of the first and second regions to be melted, respectively, the impurity concentration N3 of the third region 40 is given by the following equation.
[0061]
N3 = (N1 · V1 + N2 · V2) / (V1 + V2) (1)
Next, as shown in FIG. 1D, a region where the third region 40 and the second region 20 are in contact with each other (referred to as a fourth region 60) is irradiated with a second laser beam 50. Thereby, this region is melted and crystallized.
[0062]
As a result, as shown in FIG. 1E, the impurity concentration of the fourth region 60 becomes an intermediate value between the second and third regions for the above-described reason.
[0063]
By repeating this process, a distribution in which the impurity concentration monotonously decreases along the direction in which the laser light irradiation is repeated can be formed. Thus, a step-like impurity distribution as shown in FIG. 1F can be formed.
[0064]
In the drawings used in the above description, for convenience of explanation, the irradiation of the laser beam is illustrated as being repeated with a constant irradiation width and a moving amount, but the semiconductor processing method of the present invention imposes restrictions on these parameter settings. is not.
[0065]
For example, when forming an LDD structure having a length of 5 μm, the irradiation width of the laser beams 30 and 50 is 1 μm, and the overlap width of two consecutive laser beam irradiations is 0.5 μm. The irradiation width of the laser light may be appropriately set according to the distribution.
[0066]
Further, the irradiation width and the overlap width of the laser beams 30 and 50 can be changed according to the region on the substrate. For example, in a region where a steep impurity concentration distribution is desired, the irradiation width or the overlap width may be reduced.
[0067]
Conversely, in a region where a gentle distribution is desirable, the irradiation width and the overlap width may be set large. As described above, by controlling the width of the irradiation region of the laser beams 30 and 50 and the overlap width of the irradiation region of two or more consecutive times, the “stair” shown in FIG. Width and height can be adjusted.
[0068]
That is, the impurity concentration distribution inside the thin film semiconductor can be controlled with a high degree of freedom.
[0069]
(Second specific example)
In the first specific example, the irradiation and the movement of the laser light were repeated from the region with a high impurity concentration to the region with a low impurity concentration. Irradiation and movement of the laser beams 30, 50 toward the region may be repeated.
[0070]
FIG. 2 schematically shows such an example as a second specific example of the present invention. In FIG. 2, the components corresponding to those in FIG. The operation of this example is exactly the same as that of the first example, except that the change in density is reversed.
[0071]
(Third specific example)
As a third specific example of the present invention, an example in which the semiconductor processing method of the present invention is applied when forming a two-dimensionally arranged TFT having an LDD structure is shown in FIG.
[0072]
That is, FIG. 3 is a plan view schematically showing a region where a TFT is to be formed on the substrate 100 and a region irradiated with the first laser light 90.
[0073]
A semiconductor region 70 containing a high concentration of impurities and a region 80 containing a low concentration of an impurity or not intentionally introducing an impurity are formed over a substrate 100.
[0074]
The semiconductor region 70 is a region serving as a source or a drain of the TFT, and the impurity concentration may be constant. Later, since a contact hole is formed in a part of this region to connect this TFT to an external circuit, the distance in the direction of the arrow is about several μm.
[0075]
The semiconductor region 80 is a region serving as a channel of the TFT, and does not contain impurities or contains a certain low concentration of impurities. The width in the direction of the arrow is the channel width, which is usually about several μm in many cases.
[0076]
Next, the operation of the third specific example of the present invention will be described with reference to FIG.
[0077]
First, as shown in FIG. 3, one end of the semiconductor region 70 is irradiated with a laser beam 90 formed into a slit and having a linear shape having a predetermined width. At this time, the laser light is applied only to the inside of the semiconductor region 70, and when the semiconductor region 70 uses amorphous silicon, the light by the laser light is used. By selectively supplying energy to the semiconductor region 70, the semiconductor region 70 is transformed into polysilicon and is electrically activated.
[0078]
That is, in this specific example, by irradiating the laser light 90 while scanning the inside of the semiconductor region 70 with the laser light 90, the amorphous silicon in the semiconductor region 70 is changed to polysilicon and activated. Become.
[0079]
In addition, the laser light is applied across the boundary between the semiconductor region 70 and the semiconductor region 80, and the laser light 90 is continuously scanned by the laser light 90 while sequentially scanning the inside of the semiconductor region 80. By irradiating, the semiconductor region where the impurity concentration changes stepwise from the semiconductor region 70 to a predetermined region of the semiconductor region 80 and from the predetermined region of the semiconductor region 80 to the semiconductor region 70 Are formed continuously, and an LDD structure in the semiconductor device is formed.
[0080]
The width of the laser irradiation area of the laser beam 90 used in this specific example was 1 μm. Next, after the laser beam 90 is scanned and the irradiation position is adjusted so that the first irradiation region of the laser beam partially overlaps with the first irradiation region, the second irradiation is performed with the same irradiation width.
[0081]
At this time, the overlapping width of the laser beams was 0.5 μm. By repeating this process in the direction indicated by the arrow, it is possible to form a semiconductor region having a desired impurity concentration distribution consisting of monotonically decreasing and monotonically increasing, especially at the end of the channel region where the TFT is to be formed. it can.
[0082]
If a laser beam having a shape that is long in the lateral direction as shown here is used, it is possible to simultaneously modify the semiconductor in a region to be a plurality of TFTs by such a series of laser light irradiations.
[0083]
In this specific example, the number of laser light irradiations necessary for modifying all the semiconductor regions corresponding to the TFTs arranged in one horizontal row is 15 / 0.5 = 30. However, the width of each of the semiconductor regions 70 and 80 in the direction of the arrow was 5 μm.
[0084]
As an application example of the TFT having a plurality of LDD structures formed in this way, for example, an analog switch of a plurality of pixels arranged two-dimensionally, such as a TFT substrate of a liquid crystal display, or a liquid crystal display, a plasma display, Driving integrated circuits for driving devices such as printer engines and the like.
[0085]
(Fourth specific example)
In the specific example of FIG. 3, the laser light 90 used has the same irradiation width, but the irradiation width of the laser light 90 is not necessarily the same irradiation width, from one end of the substrate to the other end. It is not necessary to repeat laser light irradiation in the direction of the arrow.
[0086]
The fourth specific example of the present invention shows an example in which a semiconductor is treated with at least two types of laser beams 91 and 92 having different irradiation widths of laser beams. FIG. 4 is an explanatory view showing the procedure. .
[0087]
The same components as those in FIG. 3 are given the same numbers.
[0088]
Hereinafter, the operation of the fourth specific example will be described.
[0089]
That is, first, as shown in FIG. 4A, all the semiconductor regions 70 and the semiconductor regions 80 on the substrate 100 are irradiated using a laser beam 91 having a wide width of about several μm.
[0090]
However, here, it is assumed that the laser beam is not irradiated on the boundary 95 between the two regions 70 and 80 and at a predetermined width on the semiconductor region 80 side.
[0091]
That is, in this specific example, the semiconductor region 70 forming the drain region and the source region in the transistor, and the semiconductor region 80 forming the channel region are irradiated with the laser light 91 once, respectively. An activation process is performed.
[0092]
Accordingly, the irradiation width of the laser light 91 in this specific example is set so as to coincide with the width of the semiconductor region 70 and is set to have a width smaller than the width of the semiconductor region 80. Things are desirable.
[0093]
That is, it is desirable that the laser beam 91 is not irradiated to the boundary between the semiconductor region 70 and the semiconductor region 80 and the semiconductor region 95 extending from the boundary to the inside of the semiconductor region 80.
[0094]
Second, in the transistor, as shown in FIG. 4B, the irradiation width of the laser light 92 is reduced to about 1 μm to irradiate over the boundary between the semiconductor region 70 and the semiconductor region 80. By irradiating the semiconductor region portion 95 extending from the boundary to the inside of the semiconductor region 80, the impurity concentration of this region is stepwise between the impurity concentrations of both regions for the same reason as in the first specific example. It will take a changed configuration.
[0095]
Further, the value can be controlled by equation (1), that is, which area is included in the laser light irradiation area more widely.
[0096]
In this specific example, the number of times of irradiation can be reduced as compared with the case where laser light is repeatedly irradiated with the same narrow irradiation width as in the third specific example. In this example, the number of times of laser light irradiation necessary for modifying all the semiconductor regions corresponding to the TFTs arranged in one horizontal row is 3 + 2 = 5.
[0097]
However, the width of each of the semiconductor regions 70 and 80 in the direction of the arrow was 5 μm. Further, in order to change the irradiation width of the laser beam, it is necessary to change the optical system, which usually takes time and is not suitable for mass production.
[0098]
However, in this specific example, the change in the irradiation width of the laser beam can be minimized. As described above, according to the procedure of this specific example, the throughput of the semiconductor element manufacturing process is improved, and the manufacturing cost can be reduced.
[0099]
(Fifth specific example)
The fifth embodiment of the present invention also processes the semiconductor 1 with two types of laser beams 91 and 92 having different widths, and FIG. 5 is an explanatory view showing the procedure.
[0100]
The same components as those in FIG. 3 are given the same numbers. The operation of the fifth specific example will be described below.
[0101]
First, as shown in FIG. 5A, all the semiconductor regions 70 on the substrate are irradiated by using a laser beam 91 having a wide width of about several μm. However, here, it is assumed that the boundary with the semiconductor region 80 is not irradiated with the laser light 91.
[0102]
Second, as shown in FIG. 5B, the irradiation width of the laser light 92 is reduced to about 1 μm, and irradiation is performed across the boundary between the semiconductor region 70 and the semiconductor region 80. Third, the irradiation of the laser beam 92 with the same narrow irradiation width is repeated in all the regions of the semiconductor region 80, and reaches the boundary with the semiconductor region 80 and is completed.
[0103]
The overlap width of the laser light irradiation area is 0.5 μm. Here, the reason why the impurity concentration in this region monotonically decreases and then monotonically increases is the same as in the third specific example.
[0104]
In this specific example, the semiconductor region 80 is irradiated while partially overlapping a narrow laser beam. Since the next crystal grows in the laser scanning direction using the crystal formed by the first irradiation as a seed, a crystal having a larger grain size can be obtained as compared with the fourth specific example.
[0105]
However, the number of laser beam irradiations is smaller than that of the third specific example, but larger than that of the fourth specific example. In this example, the number of laser light irradiations necessary for modifying all the semiconductor regions corresponding to the TFTs arranged in one horizontal row is 2 + 5 / 0.5 = 12.
[0106]
However, the width of each of the semiconductor regions 70 and 80 in the direction of the arrow was 5 μm.
[0107]
(Sixth specific example)
In the first to fifth specific examples described above, two regions having different impurity concentrations are formed in advance before laser light irradiation.
[0108]
At least one photolithography step is required to selectively introduce impurities. When a CMOS circuit is formed by forming an n-type TFT and a p-type TFT on the same substrate, different types of impurities are introduced into different regions, so that two photolithography steps are required.
[0109]
On the other hand, the sixth example of the present invention is an example in which the number of steps can be reduced by using a laser doping technique from a gas phase.
[0110]
That is, laser doping from the gas phase is conventionally known, for example, as described in A. Crowder et al., "Low-temperature single-crystal Si-TFT's fabricated on Si films processed via sequential lateral sol. −308).
[0111]
That is, when a substrate on which a thin film semiconductor is formed is placed in a vacuum vessel and irradiated with laser light, for example, phosphine (PH) ₃ ), Diborane (B ₂ H ₆ This is a technique in which a gas containing impurities is introduced as in the above, and the impurities are introduced from the gas phase into the molten semiconductor.
[0112]
FIG. 6 is an explanatory diagram showing the procedure of the sixth specific example of the present invention.
[0113]
The same components as those in FIG. 5 are given the same numbers.
[0114]
The operation of the sixth specific example will be described below. First, the substrate 100 in which the region 80 which does not contain impurities or into which a certain amount of impurities is intentionally introduced is formed on the entire surface is placed in a vacuum vessel and phosphine (PH ₃ ) Is introduced into the gas phase.
[0115]
Here, as shown in FIG. 6A, when a specific semiconductor region 70 on the substrate 100 is irradiated with a laser beam 91 having a wide width of about several μm, the region that has been melted and solidified has a high concentration of n-type. It becomes the semiconductor region 75.
[0116]
Second, phosphine (PH ₃ ) Instead of diborane (B ₂ H ₆ ) Is introduced into a vacuum vessel, and another area 85 on the substrate 100 is irradiated with a laser beam 91 having a wide irradiation width as shown in FIG.
[0117]
The region 85 irradiated with the laser light 91 becomes a high-concentration p-type semiconductor region 76. Third, as shown in FIG. 6C, the irradiation width of the laser light 91 is reduced to about 1 μm, and the entire region of the semiconductor region 80 sandwiched between the semiconductor region 75 and the semiconductor region 76 is reduced to the first region. The irradiation of the laser beam 92 with the same narrow irradiation width as in the specific example 5 is repeated.
[0118]
Finally, by removing the thin film semiconductor in the other region by a photolithography process except for the region to be the TFT, semiconductor regions to be the source, drain, and channel of the n-type TFT and the p-type TFT are formed on the substrate 100. be able to.
[0119]
Further, after a gate oxide film is formed thereon, a gate electrode is formed by a second photolithography step. Thereafter, after forming an interlayer insulating film, a contact hole is formed by a third photolithography step, and finally, a wiring is formed by a metal thin film.
[0120]
Therefore, a CMOS circuit can be formed by four photolithography steps.
[0121]
In the specific example of the present invention described above, the case where amorphous silicon (a-Si) formed on a glass substrate as a thin film semiconductor is modified into polysilicon (poly-Si) is described. Are not limited to these.
[0122]
For example, even when polysilicon (poly-Si) is formed on a thermally oxidized silicon wafer and modified by laser irradiation, the present invention can be applied to control the impurity distribution with a high degree of freedom. Therefore, such a specific example is also regarded as a modified specific example of the present invention.
[0123]
As is clear from the specific examples described above, by using the semiconductor processing method according to the present invention, it is possible to efficiently manufacture a semiconductor device including a transistor and the like by a completely different method from the related art. It becomes.
[0124]
That is, specifically, for example, by forming a source or drain diffusion layer region in a transistor using each of the above-described methods, the semiconductor device can be manufactured.
[0125]
Further, specific procedures for manufacturing a semiconductor device using the present invention include, for example, a first semiconductor region containing almost no impurities on a substrate, and a second and a second semiconductor regions containing impurities having a predetermined impurity concentration. A first semiconductor region and a third semiconductor region, wherein the second semiconductor region and the third semiconductor region are arranged so as to be in contact with two boundaries of the first semiconductor region that are not in contact with each other; Light energy is selectively supplied to a portion near a boundary region where the second semiconductor region and the first semiconductor region are in contact with each other to reform a semiconductor in a semiconductor region forming a predetermined range sandwiching the boundary region. And a third step of moving the light energy supply region in the direction of the third semiconductor region to modify even the semiconductor region portion including the boundary region. A method of manufacturing the device is possible.
[0126]
Similarly, as another specific example of the method for manufacturing a semiconductor device according to the present invention, a first semiconductor region containing almost no impurities and a second and third semiconductor regions containing a high concentration of impurities are formed on a substrate. A first step of arranging the second semiconductor region and the third semiconductor region so as to be in contact with two boundaries of the first semiconductor region that are not in contact with each other; A second step of selectively supplying light energy to the semiconductor region to modify the semiconductor in the second semiconductor region; and selectively supplying light energy to the third semiconductor region to A third step of reforming the semiconductor in the third semiconductor region; and selectively supplying light energy to the vicinity of the boundary region where the second semiconductor region and the first semiconductor region are in contact with each other. A fourth step of modifying the semiconductor constituting the vicinity of the third semiconductor, and the third semiconductor A step of selectively supplying light energy to the vicinity of a boundary region where the region and the first semiconductor region are in contact with each other to modify a semiconductor constituting the vicinity of the boundary region. Is possible.
[0127]
As still another specific example of the method for manufacturing a semiconductor device according to the present invention, for example, a film formation step of forming a first semiconductor containing almost no impurity element on a substrate, Forming a second semiconductor containing the impurity element by selectively supplying light energy while supplying the impurity onto the substrate and reforming a part of the first semiconductor; Forming a third semiconductor region by selectively supplying light energy to the vicinity of a boundary region where the first semiconductor region contacts the semiconductor region of the first semiconductor region to modify a semiconductor in the vicinity including the boundary region; And a method for manufacturing a semiconductor device.
[0128]
Further, as another specific example of the method for manufacturing a semiconductor device according to the present invention, a plurality of the first, second, and third semiconductor regions are formed on the substrate in a regular array, and the light energy is reduced. The supply region includes a plurality of the first, second, or third semiconductor regions.
[0129]
【The invention's effect】
The method for processing a semiconductor and the method for manufacturing a semiconductor device according to the present invention employ the technical configuration as described above, so that the spatial distribution of the impurity concentration in the semiconductor can be controlled with a high degree of freedom.
[0130]
That is, in a region where a steep impurity concentration distribution is desirable, the irradiation width or the overlap width of the laser light is reduced, or in a region where a gentle distribution is desirable, the irradiation width or the overlap width is set to be large, respectively. Thus, a desired impurity concentration distribution can be formed.
[0131]
Therefore, in the present invention, since the degree of freedom in controlling the impurity concentration distribution inside the thin film semiconductor is high, the electric field inside the thin film semiconductor can be controlled with a high degree of freedom according to the type and purpose of the semiconductor element formed of such a thin film semiconductor. There is an effect that it can be controlled in degrees.
[0132]
Next, in the present invention, the number of times of irradiation can be reduced by irradiating a region where the impurity concentration may be constant with a wide laser beam. As a result, there is an effect that the throughput of the manufacturing process is improved.
[0133]
Further, in the present invention, since the polysilicon in the region serving as the channel can be made large in grain size, there is an effect that a high-performance TFT can be formed.
[0134]
Further, in the present invention, since the CMOS circuit can be formed by four photolithography steps, the number of steps can be reduced to reduce the manufacturing cost, and the reliability of the TFT circuit can be ensured. There is.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a configuration of a first specific example of a semiconductor processing method according to the present invention, in which a region from a region with a high impurity concentration to a region with a low impurity concentration is melted by irradiation with a narrow laser beam; 2 shows a state in which crystallization forms a monotonously decreasing impurity concentration distribution.
FIG. 2 is an explanatory view showing a configuration of a second specific example of the semiconductor processing method according to the present invention. 1 shows a state in which crystallization causes a monotonically increasing impurity concentration distribution to be formed.
FIG. 3 is an explanatory view showing a configuration of a third specific example of the semiconductor processing method of the present invention, in which a plurality of regions arranged on the same line are formed by using a narrow and long laser beam; The state where a plurality of semiconductor regions of a TFT having an LDD structure are formed on a substrate by simultaneous irradiation and melting and crystallization is shown.
FIG. 4 is an explanatory view showing a configuration of a fourth specific example of the semiconductor processing method of the present invention. A region having a constant impurity concentration is collectively irradiated with a wide laser beam, By irradiating the area that needs to have a gradient with a narrow laser beam, the number of laser beam irradiations when forming semiconductor regions of multiple LDD TFTs on the substrate is greatly reduced. It is shown.
FIG. 5 is an explanatory view showing a configuration of a fifth specific example of the semiconductor processing method of the present invention. A region serving as a source / drain is collectively irradiated with a wide laser beam, and a channel is irradiated to the channel. By irradiating narrow areas of laser light while overlapping in some areas, the number of laser light irradiations when forming semiconductor regions of a plurality of LDD TFTs on a substrate is reduced to some extent. And a method for improving the quality of the semiconductor in the channel region.
FIG. 6 is an explanatory view showing a sixth embodiment of the semiconductor processing method of the present invention, in which an impurity-containing gas is introduced into a semiconductor by irradiating the substrate with a gas containing the impurity and irradiating the substrate with a laser beam; Is shown, and a large number of LDD-structured TFTs are arranged and formed.
FIG. 7 is an explanatory view showing a procedure of one specific example of a conventional semiconductor forming method.
[Explanation of symbols]
1: Semiconductor film
2. Joint boundary area
3, 3 '... near the boundary area
4, 5 ... junction boundary
10 first semiconductor region
20: second semiconductor region
30, 50: Light energy, laser light
40, 60 ... semiconductor region
70: Thin film semiconductor region containing high concentration impurity
70 '... third semiconductor region
80, 85 ... thin-film semiconductor regions containing low-concentration impurities or intentionally not introducing impurities
75 ... n-type thin film semiconductor region containing high concentration impurity
76 ... p-type thin film semiconductor region containing high concentration impurity
90, 91, 92 ... laser beam
100 ... substrate
110 ... substrate
120 ... Barrier layer
130 ... Thin film semiconductor (intrinsic region)
140 ... Thin film semiconductor (low concentration n-type region)
150: thin film semiconductor (high concentration n-type region)
160 ... Laser light
170 ... Insulating film
180 ... Gate electrode

Claims (6)

When a transistor is formed, a first semiconductor region containing almost no impurities, and second and third semiconductor regions containing impurities having a predetermined impurity concentration are formed on a substrate in phase with each other. A step of arranging and forming the second semiconductor region and the third semiconductor region so as to be in contact with two boundaries that are not in contact with each other; and including a boundary in which the second semiconductor region and the first semiconductor region are in contact with each other. Supplying light energy having an irradiation width smaller than a desired width of the LDD region to all or a part of the semiconductor region in which the LDD region included in the transistor is formed, thereby supplying the light energy. Diffusing impurities present in the first semiconductor region and the second semiconductor region in the region to form the LDD region having a desired impurity concentration distribution; and A light energy having an irradiation width smaller than a desired width of the LDD region is applied to all or a part of the semiconductor region including the boundary where the region and the first semiconductor region are in contact with each other and where the LDD region constituting the transistor is formed. To diffuse the impurities present in the first semiconductor region and the third semiconductor region in the region to which the light energy has been supplied, thereby providing a desired impurity concentration distribution. Forming a LDD region.   On a substrate, a first semiconductor region containing almost no impurities and second and third semiconductor regions containing high-concentration impurities are formed on two non-adjacent boundaries of the first semiconductor region by the second semiconductor region. Forming the semiconductor region and the third semiconductor region so as to be in contact with each other; and selectively supplying light energy to the second semiconductor region to modify the semiconductor in the second semiconductor region. Modifying the semiconductor of the third semiconductor region by selectively supplying light energy to the third semiconductor region; and modifying the second semiconductor region and the first semiconductor region. Selectively supplying light energy to the vicinity of the boundary region where the first and second semiconductor regions are in contact with each other, and modifying the boundary region where the third semiconductor region and the first semiconductor region are in contact with each other. Is selectively supplied with light energy in the vicinity of The method of manufacturing a semiconductor device which comprises a step of modifying the semiconductor forming the neighborhood.   A film forming step of forming a first semiconductor region containing almost no impurity element on the substrate, and selectively supplying light energy while supplying a gas containing the impurity element onto the substrate; Forming a second semiconductor region containing the impurity element by modifying a part of the semiconductor region, and forming a second semiconductor region containing the impurity element near a boundary region where the second semiconductor region and the first semiconductor region are in contact with each other. Forming a third semiconductor region by selectively supplying light energy to modify a semiconductor in the vicinity including the boundary region.   4. The method according to claim 1, wherein the light energy is obtained by a slit-shaped laser beam having a predetermined width.   The width of the slit-shaped laser light applied to a predetermined portion of the semiconductor region is different from the width of the slit-shaped laser light applied to a predetermined portion of another semiconductor region. Item 5. The method for manufacturing a semiconductor device according to Item 4.   A plurality of the first, second, and third semiconductor regions are formed on the substrate so as to be regularly arranged, and a plurality of the first, second, or third semiconductor regions are formed in a region in a direction in which the light energy is supplied. 4. The method for manufacturing a semiconductor device according to claim 1, wherein the semiconductor region includes:

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