JP3269734B2 - Semiconductor device and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device which is used, for example, in an active matrix type liquid crystal display device, in which a thin film transistor is provided on an insulating substrate such as glass, and a method of manufacturing the same. The present invention relates to a semiconductor device having a thin film transistor having a crystalline silicon film obtained by crystallizing a crystalline silicon film as an active region, and a method for manufacturing the same.

[0002]

2. Description of the Related Art As the semiconductor device, an active matrix type liquid crystal display device and an image sensor using a thin film transistor (TFT) for driving a pixel are known. In general, a thin silicon semiconductor film is used for a TFT used in these devices.

[0003] Silicon semiconductor films are roughly classified into those made of an amorphous silicon (a-Si) semiconductor and those made of a crystalline silicon semiconductor. The former amorphous silicon semiconductor is most commonly used because it has a low manufacturing temperature and can be manufactured relatively easily by a gas phase method, and has high mass productivity. However, since the physical properties such as conductivity are inferior to the latter crystalline silicon semiconductor, in order to obtain higher speed characteristics in the future, there is a strong need to establish a method of manufacturing a TFT made of a crystalline silicon semiconductor. Was sought. In addition, as a silicon semiconductor having crystallinity,
Polycrystalline silicon, microcrystalline silicon, amorphous silicon containing a crystalline component, semi-amorphous silicon having an intermediate state between crystalline and amorphous are known.

The following methods are known as methods for obtaining these crystalline silicon thin films.

(1) A method of directly forming a film having crystallinity at the time of film formation. (2) A method of forming an amorphous semiconductor film in advance and imparting crystallinity by the energy of laser light. (3) A method in which an amorphous semiconductor film is formed and crystallinity is imparted by applying thermal energy. However, in the method (1), since crystallization proceeds simultaneously with the film formation step, a large particle size is required. In order to obtain crystalline silicon, it is indispensable to increase the thickness of the silicon film, and it is technically difficult to form a film having good semiconductor properties uniformly over the entire surface of the substrate. Further, since the film formation temperature is as high as 600 ° C. or more, there is a problem in cost that an inexpensive glass substrate cannot be used.

Further, in the method (2), since the crystallization phenomenon in the melting and solidification process is used, the grain boundaries are favorably treated with a small grain size, and a high-quality crystalline silicon film can be obtained. However, taking the excimer laser, which is currently most commonly used, as an example, there is a problem that the irradiation area of the laser beam is small and the throughput is low. The stability is not enough, and the feeling of next-generation technology is strong.

The method (3) has an advantage that it can cope with a large area as compared with the methods (1) and (2). However, the crystallization requires a heat treatment at a high temperature of 600 ° C. or more for several tens of hours. is necessary. That is, considering the use of an inexpensive glass substrate and the improvement in throughput, it is necessary to simultaneously solve the conflicting problems of lowering the heating temperature and crystallizing in a shorter time. Also, in order to utilize the solid-phase crystallization phenomenon, crystal grains spread parallel to the substrate surface and even appear with a grain size of several μm, but since the grown crystal grains collide with each other to form a grain boundary, The grain boundaries serve as trap levels for carriers, and are a major cause of lowering the mobility of the TFT.

Therefore, in order to solve all of the various problems described above, in the above method (3), both lowering of the temperature required for crystallization and shortening of the processing time are achieved, A method for producing a crystalline silicon thin film in which the influence of the field is minimized has been proposed (Japanese Patent Application No. 5-218156). In this method, by introducing an impurity metal element such as Ni into the amorphous silicon film as a nucleus for crystal growth, the nucleus generation rate at the initial stage of crystallization and the subsequent nucleus growth rate can be remarkably improved. Sufficient crystallinity can be obtained by a heat treatment for about 4 hours at a temperature of 580 ° C. or lower, which was not attained. This mechanism is understood from the fact that crystal nucleus generation with an impurity metal element as a nucleus occurs at an early stage, and then the impurity metal element serves as a catalyst to promote crystal growth, and crystallization proceeds rapidly. In this sense, these impurity metal elements are hereinafter referred to as catalyst elements in the present specification.

The crystalline silicon film crystallized by the catalysis promoted by the above-mentioned catalytic element has a twin structure, whereas the amorphous silicon film crystallized by the ordinary solid phase growth method has a twin structure. Each of the needle crystals or columnar crystals is in an ideal single crystal state. In addition, by selectively introducing a catalytic element into a part of a substrate, a crystalline silicon film and an amorphous silicon film can be selectively formed in the same substrate. Further, when the heat treatment is continued thereafter, a crystal growth portion is formed in a lateral direction (a direction parallel to the substrate surface) from a portion where the catalytic element is selectively introduced and crystallized to an amorphous portion in a peripheral portion thereof. A prolonged phenomenon occurs. This lateral crystal growth portion is referred to as a lateral growth portion in the present specification.

In the lateral growth portion, needle-like or columnar crystals extend along the growth direction in parallel with the substrate.
No grain boundaries exist in the growth direction. Therefore, by forming a channel portion of the TFT using the lateral growth portion, a high-performance TFT can be realized.
When a TFT is manufactured using such a laterally grown portion as an active region, the field-effect mobility is improved about twice as compared with a case where a crystalline silicon film formed by a normal solid-phase growth method is used. Further, after that, the difference becomes more remarkable by irradiating laser light or strong light to promote the crystallinity. That is, when the lateral growth portion is irradiated with laser light or strong light, the crystal grain boundary portion is intensively treated due to the difference in melting point between the crystalline silicon film and the amorphous silicon film. In a crystalline silicon film formed by the phase growth method, the crystal structure is in a twin state, so that the inside of a crystal grain boundary remains as a twin defect even after laser irradiation. On the other hand, the lateral growth part where the catalyst element is introduced and crystallized is formed of needle-like crystals or columnar crystals, and the inside is a single crystal state, so that the crystal grain boundary part is irradiated by laser light or strong light. Is treated, a crystalline silicon film almost in a single crystal state is obtained.

[0011]

The above-mentioned selective introduction of the catalytic element into the amorphous silicon film is carried out by using a mask made of silicon dioxide or the like. It will be expensive. Therefore, the introduction section
Although it is necessary to separate them from the TFT channel region and the source / drain regions so that they do not overlap with each other, there is a limit to the lateral growth distance.
Is provided in the vicinity of.

As shown in FIG. 2, when the introduction portion is irradiated with a laser beam or an intense light in order to promote crystallinity, a catalytic element is deposited on the surface of the introduction portion 205 or the crystalline silicon film is formed. A large amount of the catalyst element is diffused into the portion of the base film 202 below the polycrystallized region 208 to form a deposition / diffusion region 218. As a result, the catalyst element is present on the substrate 201 in a large amount. TF on such a substrate
When a semiconductor device is obtained by forming an element such as T, there has been a problem that the reliability and electrical stability of the semiconductor device are impaired by the presence of the catalytic element.

SUMMARY OF THE INVENTION The present invention has been made to solve such problems of the prior art, and has as its object to provide a semiconductor device capable of improving reliability and electrical stability and a method of manufacturing the same.

[0014]

According to the present invention, there is provided a semiconductor device comprising:
A semiconductor device having an active region made of a crystalline silicon film, wherein the active region is formed by heat-treating an amorphous silicon film into which a catalytic element that promotes crystallization is selectively introduced. A lateral growth portion, wherein the lateral growth portion is formed in the amorphous silicon film.
After removing the catalyst element introduction portion, the lateral growth portion is removed.
The laser beam or the intense light is applied to the laser beam , so that the above object is achieved.

In the semiconductor device of the present invention, Ni, Co, Pd, Pt, Cu, Ag, A
A structure using one or more elements selected from u, In, Sn, P, As, Sb, and Al can be employed.

In the semiconductor device according to the present invention, the concentration of the catalytic element in the active region is 1 × 10 ¹⁴ atoms.
/ Cm ³ to 1 × 10 ¹⁸ atoms / cm ³ .

According to the method of manufacturing a semiconductor device of the present invention, there is provided a step of forming an amorphous silicon film on a substrate, and a step of forming a catalyst element for promoting crystallization of the amorphous silicon film on a part of the amorphous silicon film. a step of obtaining a step of introducing into the inlet portion, the in the periphery of the inlet portion to the surface of the substrate is heated to cause the crystal growth in a direction substantially parallel to the crystalline silicon film is, the object to be removing the introduction, in order to promote the crystallization of the crystalline silicon film in the peripheral portion of the removed said the introduction, by irradiating a laser beam or an intense light, lateral growth
Forming a portion, whereby the above object is achieved.

[0018]

According to the present invention, an amorphous silicon film into which a catalyst element for promoting crystallization is selectively introduced is heated, and lateral growth is carried out in a peripheral portion of a portion to which the catalyst element is introduced. Then, before the entire surface is irradiated with the laser light or the intense light, the above-described introduced portion is removed. Therefore, even if the entire surface is irradiated with laser light or strong light, the above-mentioned introduced portion does not exist at that time, so that the deposition of the catalytic element on the surface of the introduced portion and the diffusion of a large amount of the catalytic element into the underlayer film occur. Does not happen. Also, only the laterally grown region can be used for the channel region and the source / drain region of the TFT,
The reliability and electrical stability of the semiconductor device can be improved. In addition, when the catalyst element is introduced, even if the addition amount of the catalyst element varies in the part to be introduced, the variation in the addition amount of the catalyst element does not affect the TFT characteristics.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below.

FIG. 1 is a cross-sectional view showing an outline of a manufacturing process when the present invention is applied to manufacturing of a TFT.
The manufacturing process sequentially proceeds in the order of (A) → (H).

First, as shown in FIG. 1A, a base film 102 made of silicon oxide having a thickness of 50 to 200 nm, for example, 100 nm is formed on a cleaned glass substrate 101 by, for example, a sputtering method. The required thickness of the silicon oxide film varies depending on the surface state of the glass substrate 101, is sufficiently flat, and has an impurity (sodium ion).
If the substrate has a sufficiently low concentration of ions that adversely affect the semiconductor characteristics such as, it is possible to omit it. Conversely, if the surface state is severely scratched or uneven, the film thickness is greater than the above film thickness. It needs to be deposited thick. Instead of the glass substrate 101, a substrate of another material can be used in the present invention.

Next, a low pressure CVD method or a plasma CV
25 to 100 thicknesses by D method, sputtering method, etc.
An intrinsic (I-type) amorphous silicon film (a-Si film) 103 having a thickness of, for example, 50 nm is formed.

Next, a mask 1 is formed on the amorphous silicon film 103.
04 is formed with a thickness of about 100 nm using silicon oxide or the like. This mask 104 is for selectively introducing an element that promotes crystallization into the amorphous silicon film 103.

Next, in this state, as an element promoting the crystallization, for example, nickel is introduced into the doped portion 10 which is the portion of the amorphous silicon film 103 not covered with the mask 104.
Introduce to 5. For this introduction, a method such as vapor deposition, sputtering, plasma treatment, or solution coating can be used.

Next, in this state, the entire substrate is heated. Then, polycrystallization occurs first in the portion to be introduced 105. When the heat treatment is further continued, as shown in FIG. 1B, the heat treatment is directed outward from the portion to be introduced 105, that is, toward the crystal growth direction 106 indicated by the arrow, and in a direction substantially parallel to the surface of the substrate 101. Crystallization proceeds. When the heat treatment is sufficiently performed, the state shown in FIG.
That is, the crystal growth end 107 is present outside the polycrystallized region 108 connected to the portion 105 to be introduced. The crystal growth end 107 is a crystal growth end when polycrystallization progresses in a direction substantially parallel to the substrate surface, and is a polycrystallized region 108.
This is a region where the concentration of nickel is higher than that of the region. As a specific example of the heat treatment, crystallization is performed by annealing at a heating temperature of 520 to 580 ° C. for several hours to several tens of hours, for example, 550 ° C. for 8 hours under a hydrogen reducing atmosphere or an inert atmosphere. Note that the actual nickel concentration in FIG. 1 (C) is 1 × 10 ^19-
About 1 × 10 ²⁰ atoms / cm ³ , polycrystalline region 10
8 is about 1 × 10 ¹⁴ to 1 × 10 ¹⁸ atoms / cm ³ .

Next, as shown in FIG. 1D, the mask 104 and the crystalline silicon film 105 of the portion 105 to be introduced are removed. As a result, isolation between the two TFTs described below is performed.

Next, as shown in FIG. 1E, an island-shaped crystalline silicon film 109 to be an active region (source / drain region, channel region) of the TFT is formed using the polycrystallized region 108. I do.

Next, laser light is irradiated to promote the crystallinity of the crystalline silicon film 109. The laser light at this time is a XeCl excimer laser (wavelength 308 nm)
Was used. The irradiation conditions of the laser beam are as follows.
It is heated to 00 to 450 ° C., for example, 400 ° C., and has an energy density of 200 to 400 mJ / cm ² , for example, 300 mJ /
Irradiated in cm ² .

Next, as shown in FIG. 1F, a silicon oxide film having a thickness of 20 to 150 nm, here 100 nm, is formed as the gate insulating film 110 so as to cover the crystalline silicon film 109. For the formation of the silicon oxide film, TE
Substrate temperature 150 to 600 with OS as raw material together with oxygen
C, preferably 300-450 ° C., RF plasma CV
Decomposed and deposited by D method. Alternatively, reduced pressure CVD or normal pressure CVD using TEOS as a raw material together with ozone gas
Depending on the method, the substrate may be formed at a substrate temperature of 350 to 600C, preferably 400 to 550C.

Next, in order to improve the bulk characteristics of the gate insulating film 110 itself and the interface characteristics between the crystalline silicon film 109 and the gate insulating film 110, a process under an inert gas atmosphere is performed.
Annealing was performed at 0 to 600 ° C. for 30 to 60 minutes.

Next, a thickness of 4
An aluminum film having a thickness of 00 to 800 nm, for example, 600 nm is formed, and the aluminum film is patterned to form a gate electrode 111.

Next, the gate electrode 111 is anodized to form an oxide layer 112 on the surface. The anodization is performed in an ethylene glycol solution containing tartaric acid at 1 to 5%, and the voltage is first increased to 220 V at a constant current, and the state is maintained for 1 hour to complete the process. Obtained oxide layer 112
Has a thickness of 200 nm. Note that this oxide layer 112
Becomes the thickness for forming the offset gate region in the subsequent ion doping step, so that the length of the offset gate area can be determined in the anodic oxidation step.

Next, as shown in FIG. 1G, the gate electrode 11 is formed in the active region 113 by ion doping.
1. Impurities (phosphorus or boron) are implanted using the oxide layer 112 as a mask. Phosphine (PH ₃ ) and diborane (B ₂ H ₆ ) are used as the doping gas. In the former case, the acceleration voltage is 60 to 90 kV, for example, 80 kV,
In the latter case, it is 40 kV to 80 kV, for example, 65 kV, and the dose is 1 × 10 ¹⁵ to 8 × 10 ¹⁵ cm ⁻² , for example, phosphorus is 2 × 10 ¹⁵ cm ⁻² , and boron is 5 × 10 ¹⁵ cm ⁻² . I do. By this step, the gate electrode 111, the oxide layer 1
The region which is masked by No. 12 and into which impurities are not implanted
The channel region 114 becomes T. At the time of doping, each element is selectively doped by covering a region not requiring doping with a photoresist. As a result, an N-type impurity region (source / drain region) 114A or a P-type impurity region (source / drain region) 114A is formed in the active region 113.
An N-channel TFT or a P-channel TFT can be formed.

Next, annealing is performed by irradiating a laser beam to activate the ion-implanted impurities, and at the same time, to improve the crystallinity of the portion where the crystallinity has deteriorated in the impurity introducing step. At this time, a XeCl excimer laser (wavelength 308 nm) was used as a laser,
Irradiation was performed at an energy density of 150 to 400 mJ / cm ² , preferably 250 mJ / cm ² . The sheet resistance of the impurity region 114A into which the impurity (phosphorous or boron) thus formed was introduced was 200 to 800 Ω / □.

Next, as shown in FIG.
A silicon oxide film or a silicon nitride film having a thickness of about 0 nm is formed as the interlayer insulating film 115. When a silicon oxide film is used, if TEOS is used as a raw material and formed by a plasma CVD method with oxygen, a reduced pressure CVD method with ozone, or a normal pressure CVD method, a good interlayer having excellent step coverage can be obtained. An insulating film is obtained. When a silicon nitride film formed by a plasma CVD method using SiH ₄ and NH ₃ as a source gas is used, hydrogen atoms are supplied to the interface between the active region and the gate insulating film, and the unpaired bonding that deteriorates the TFT characteristics is provided. It has the effect of reducing hands.

Next, a contact hole is formed in the interlayer insulating film 115, and the electrode / wiring 116, 1
17 is formed.

Finally, at 350 ° C. in a hydrogen atmosphere of 1 atm.
Anneal for 30 minutes to complete the TFT.

When the TFT thus manufactured is used as an element for switching a pixel electrode,
One of the electrodes / wirings 116 and 117 is connected to a pixel electrode made of a transparent conductive film such as ITO, and a signal is input from the other electrode / wiring. When the present TFT is used for a thin film integrated circuit, a contact hole may be formed also on the gate electrode 111 and a necessary wiring may be provided.

The TFT manufactured as described above has an n-ch
In the case of a TFT, the field-effect mobility is 120 to 150 cm ²
/ Vs, S value is 0.2 to 0.4 V / digit, threshold voltage is 2 to 3
V showed good characteristics. The variation in the TFT characteristics within the substrate was within ± 12% in the field effect mobility and within ± 8% in the threshold voltage. In the case of the p-ch TFT, favorable characteristics such as a field-effect mobility of 100 to 140 cm ² / Vs, an S value of 0.3 to 0.5 V / digit, and a threshold voltage of −2 to −3 V were exhibited. Variations in TFT characteristics within the substrate are ± 10% in field effect mobility and approximately ± 5 in threshold voltage.
%.

As described above, one embodiment according to the present invention has been specifically described. However, the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible. .

For example, in the above-described embodiment, the impurity metal element that promotes crystallization is not only nickel but also cobalt, palladium, platinum, copper, silver, gold, indium, and the like.
Similar effects can be obtained by using tin, phosphorus, arsenic, antimony, and aluminum.

In this embodiment, as a means for promoting the crystallinity of the crystalline silicon film, a heating method by irradiating an excimer laser which is a pulse laser is used, but other lasers (for example, a continuous oscillation Ar laser) may be used. Similar processing is possible. In addition, an infrared light or a flash lamp is used in place of the laser light to shorten the time from 1000 to 1
The temperature is raised to 200 ° C. (temperature of the silicon monitor) and the sample is heated. Intense light equivalent to so-called laser light such as so-called RTA (rapid thermal annealing) or RTP (rapid thermal process) is also used. Good.

Further, the TFT of this embodiment can be used not only as a driver circuit and a pixel portion of an active matrix type liquid crystal display device but also as an element constituting a CPU on the same substrate.

Further, as an application of the present invention, in addition to an active matrix type substrate for liquid crystal display, for example, a contact type image sensor, a driver built-in type thermal head, a driver built-in type light using an organic EL or the like as a light emitting element. A writing element, a display element, a three-dimensional IC, and the like can be considered. By using the present invention, high performance such as high speed and high resolution of these elements is realized. Further, the present invention is not limited to the MOS transistors described in the above embodiments,
The present invention can be widely applied to semiconductor processes including a bipolar transistor and an electrostatic induction transistor using a crystalline semiconductor as an element material.

[0045]

As described above in detail, in the case of the present invention, when the entire surface is irradiated with laser light or intense light, there is no part to be introduced. , A large amount of catalyst element does not diffuse into the underlayer,
Further, only the laterally grown region can be used for the channel region and the source / drain region of the TFT, so that the reliability and the electrical stability of the semiconductor device can be improved.

When the active region, which is a feature of the present invention, is applied to a thin film transistor, a semiconductor device having a high performance thin film transistor having uniform and stable characteristics over a large area substrate can be obtained by a simple manufacturing process. it can. In particular, when applied to a liquid crystal display device, the pixel switching TFT required for an active matrix substrate
Realization of a driver monolithic type active matrix substrate, which comprises the active matrix section and the peripheral drive circuit section on the same substrate, while at the same time satisfying the uniformity of the characteristics of the TFT and the high performance required for the TFTs constituting the peripheral drive circuit section. It is possible to reduce the size, performance and cost of the module.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an outline of a manufacturing process when the present invention is applied to the manufacture of a TFT.

FIG. 2 is a view for explaining a problem in the related art, and is a cross-sectional view showing the vicinity of a part to be introduced.

[Explanation of symbols]

 101 Glass substrate 201 Substrate 102, 202 Base film 103 Amorphous silicon film 104 Mask 105, 205 Introduced part 106 Crystal growth direction 107 Crystal growth end 108, 208 Polycrystallized region 109 Crystalline silicon film 110 Gate insulating film 111 Gate Electrode 112 oxide layer 113 active region 114A impurity region (source / drain region) 114 channel region 115 interlayer insulating film 116, 117 electrode / wiring 218 deposition / diffusion region

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-140915 (JP, A) JP-A-5-82442 (JP, A) JP-A-4-22120 (JP, A) JP-A-7- 153689 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/20

Claims (4)

(57) [Claims] 1. A semiconductor device having an active region made of a crystalline silicon film, wherein the active region is formed by heating an amorphous silicon film into which a catalytic element for promoting crystallization is selectively introduced. process has become the lateral growth part formed by, the lateral growth
Part is the part to which the catalyst element is introduced in the amorphous silicon film.
Is removed to form an active region, and then the lateral growth is performed.
A semiconductor device formed by irradiating a part with laser light or strong light . 2. The catalyst element according to claim 1, wherein the catalyst element is Ni, Co, P
d, Pt, Cu, Ag, Au, In, Sn, P, As,
2. The semiconductor device according to claim 1, wherein one or more elements selected from Sb and Al are used. 3. The method according to claim 1, wherein the concentration of the catalyst element in the active region is 1 × 10 ¹⁴ atoms / cm ³ to 1 × 10 ¹⁸ atom.
2. The semiconductor device according to claim 1, wherein the rate is ms / cm ³ . 4. A step of forming an amorphous silicon film on a substrate, and introducing a catalyst element which promotes crystallization of the amorphous silicon film into a portion to be introduced which is a part of the amorphous silicon film. a step, the heating to cause the crystal growth in a direction substantially parallel to the surface of the substrate at the periphery of the inlet portion, a step of obtaining a crystalline silicon film, and removing the object inlet portion, in order to promote the crystallization of the crystalline silicon film in the peripheral portion of the removed the object inlet portion, irradiating a laser beam or an intense light
Forming a lateral growth portion .