JP2002280561A - Manufacturing method for semiconductor element, semiconductor element manufactured by the same manufacturing method, and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the gettering of catalyzer elements, by performing heat treatment at a low temperature in a short time. SOLUTION: By introducing the catalyzer elements into an amorphous silicon semiconductor film 3, the crystallization of the amorphous silicon semiconductor film 3 is promoted. Thereafter, a glass substrate 1 is heat-treated under a high- pressure condition which is not lower than at least the atmospheric pressure, so as to activate an ion-injected impurity and at the same time enable the gettering of the catalyzer elements by the ion-injected impurity. Therefore, since the efficiency of the gettering of the catalyzer elements can be increased and at the same time the silicon semiconductor layer containing the injected impurity can be activated, the productivity of a semiconductor element can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor element, a semiconductor element and a semiconductor device manufactured by the method, and more particularly, to a method for crystallizing an amorphous silicon semiconductor film. The present invention relates to a method of manufacturing a semiconductor element using a crystalline silicon semiconductor film as an active region, a semiconductor element manufactured by the method, and a semiconductor device.

[0002]

2. Description of the Related Art In recent years, high-performance semiconductor elements have been formed on an insulating substrate such as glass in order to realize a large-sized liquid crystal display device with high resolution, a high-resolution and high-speed contact image sensor, and a three-dimensional IC. Attempts have been made to do so. For such a semiconductor element, a thin silicon semiconductor film is usually used, and an amorphous silicon semiconductor film (a-S
i) and a crystalline silicon semiconductor film.

Since an amorphous silicon semiconductor film has a low manufacturing temperature and can be relatively easily formed by a gas phase method, it is excellent in mass productivity and is generally used more than a crystalline silicon semiconductor film. ing.

However, an amorphous silicon semiconductor film is different from a crystalline silicon semiconductor film in that:
Due to poor physical properties such as conductivity, there is a possibility that high-speed characteristics and the like of the semiconductor element cannot be improved. For this,
There is a strong demand for the establishment of a simple method of manufacturing a thin film semiconductor device having a crystalline silicon semiconductor film. Polycrystalline silicon, microcrystalline silicon, and the like are known as the crystalline silicon semiconductor film.

The following methods (1) to (4) are used to fabricate a thin silicon semiconductor film having such crystallinity.
The method shown in (3) is known. (1) A crystalline silicon semiconductor film is formed directly on an insulating substrate. (2) After the amorphous silicon semiconductor film is formed, the amorphous silicon semiconductor film is irradiated with strong light such as a laser beam, and the amorphous silicon semiconductor film is crystallized into a crystalline silicon semiconductor film by the light energy. (3) After the amorphous silicon semiconductor film is formed, it is heated and the amorphous silicon semiconductor film is crystallized into a crystalline silicon semiconductor film by the heat energy.

However, in the above method (1), crystallization proceeds simultaneously with the film formation step, so that a thick film must be formed in order to obtain a crystalline silicon semiconductor film having a large grain size. Therefore, it is technically difficult to form a film having good semiconductor properties over the entire surface of the substrate. Further, the film formation rate is as high as 600 ° C. or higher,
There is also a cost problem that an inexpensive glass substrate such as quartz which cannot withstand a high temperature of 00 ° C. or more cannot be used.

In the above method (2), since the crystallization phenomenon in the melting and singulation process is used, the crystal grains have a small grain size, but the grain boundaries formed by collision of the crystal grains are good. And a high quality crystalline silicon semiconductor film can be obtained.
However, for example, when using an excimer laser currently most commonly used as laser light,
Since the stability of laser light is not sufficient, it is not easy to perform uniform processing over the entire surface of a large-sized substrate, and a plurality of crystalline silicon semiconductor films having uniform characteristics are formed on the same substrate. May not be possible. Furthermore, since the irradiation area of the laser light is small, it is not easy to uniformly irradiate the entire substrate with the laser light, and there is a problem that a silicon semiconductor film cannot be efficiently manufactured.

The method (3) is more suitable for forming a large-area crystalline silicon semiconductor film than the methods (1) and (2). However, in order to crystallize an amorphous silicon semiconductor film, heat treatment for a long time under a high temperature condition of 600 ° C. or more is required. For this reason, there is a problem that an inexpensive glass substrate that cannot withstand a high temperature condition of 600 ° C. or more cannot be used, and that the throughput cannot be improved. Further, in the method (3), since the solid-phase crystallization phenomenon is used, the crystal grains become large, and the crystal grains having a diameter of several μm spread along the substrate surface, so that the grown crystal grains are separated from each other. When a grain boundary is formed by colliding with each other, the grain boundary acts as a trap level for carriers. As a result, in a manufactured semiconductor element such as a TFT, carrier mobility may be reduced.

A method of producing a high-quality and uniform crystalline silicon semiconductor film by lower-temperature and shorter-time heat treatment using the above method (3) is disclosed in Japanese Patent Laid-Open No. 6-33.
No. 3,824, JP-A-6-333825 and JP-A-8-330602, respectively.

In the film forming method described in these publications,
After introducing a trace amount of a metal element such as nickel to the surface of the amorphous silicon semiconductor film, the amorphous silicon semiconductor film is subjected to heat treatment at a low temperature of 600 ° C. or less and a short processing time of about several hours. Is being crystallized.

The metal element that promotes crystallization of the silicon semiconductor film acts catalytically in the amorphous silicon semiconductor film, and crystal nuclei having the introduced metal element as nuclei are generated at an early stage. Thereafter, it is considered that crystallization rapidly progresses around this crystal nucleus. For this reason, hereinafter, the metal element used for crystallization of the amorphous silicon semiconductor film is referred to as a catalyst element.

The introduction of such a catalytic element promotes the crystallization of the amorphous silicon semiconductor film. The crystalline silicon semiconductor film obtained by crystal growth has a structure composed of a plurality of columnar crystals, whereas a silicon semiconductor film crystallized by a normal solid-phase growth method has a twin structure. Is in a state close to a single crystal.

[0013]

In the method for producing a crystalline silicon semiconductor film which promotes crystallization by introducing a catalytic element described in the above publication, the catalytic element remains in the crystalline silicon semiconductor film. In such a case, the characteristics of the manufactured semiconductor element such as a TFT may be deteriorated.

JP-A-8-236471, JP-A-6-236471
JP-A-333824 discloses a method of providing a PSG (phosphorus silicide glass) film in contact with a silicon film containing a catalyst element, and a method of gettering a catalyst element in a silicon semiconductor film with phosphorus contained in the PSG film. A method has been proposed in which phosphorus ions are implanted into a silicon film containing an element by an ion doping method, and a catalytic element is gettered by the implanted phosphorus ions.

However, in these methods, in order to getter the catalytic element, a heat treatment at a high temperature of 500 ° C. or more and a long time of 4 hours or more is required.
For this reason, there is a problem that productivity is reduced and manufacturing cost is increased.

The present invention has been made to solve the above problems, and provides a method of manufacturing a semiconductor device capable of gettering a catalytic element by a heat treatment at a low temperature for a short time, and a semiconductor device thereof. The purpose is to:

[0017]

In order to solve the above-mentioned problems, a method of manufacturing a semiconductor device according to the present invention comprises a step of forming an amorphous silicon semiconductor film on a substrate having an insulating surface; Introducing a catalyst element to the semiconductor film to promote crystallization of the silicon semiconductor film, heating the amorphous silicon semiconductor film into which the catalyst element is introduced, and crystallizing the amorphous silicon semiconductor film; Forming a gate insulating film covering the semiconductor film, and forming a gate electrode on the gate insulating film;
A step of introducing an impurity into the crystalline silicon semiconductor film, and a step of subjecting the substrate into which the impurity is implanted to a heat treatment at a temperature of 600 ° C. or lower in an inert gas atmosphere of 1 atm or higher. It is characterized by the following.

In the method of manufacturing a semiconductor device according to the present invention, it is preferable that the impurities include P ions or B ions.

In the method for manufacturing a semiconductor device according to the present invention, the substrate is preferably a glass substrate.

In the method for manufacturing a semiconductor device according to the present invention, it is preferable that the heat treatment step is performed in a pressure range of 10 to 20 atm.

In the method of manufacturing a semiconductor device according to the present invention, the step of crystallizing the amorphous silicon semiconductor film preferably includes a laser annealing treatment after a heat treatment.

In the method of manufacturing a semiconductor device according to the present invention, the step of crystallizing the amorphous silicon semiconductor film preferably includes a heat treatment in a temperature range of 540 to 600 ° C.

In the method of manufacturing a semiconductor device according to the present invention, the amorphous silicon semiconductor film may have a thickness of 25 to 25.
It is preferable that the film is formed to have a thickness in the range of 80 nm.

In the method of manufacturing a semiconductor device according to the present invention, it is preferable that the catalytic element introduced into the amorphous silicon semiconductor film has a concentration of 1 × 10 ¹⁶ atm / cm ³ or less.

In the method for manufacturing a semiconductor device according to the present invention, the catalyst element may be one or more of nickel, cobalt, palladium, platinum, copper, silver, indium, tin, aluminum and antimony. preferable.

In the method of manufacturing a semiconductor device according to the present invention, the catalyst element preferably contains at least nickel.

In the method for manufacturing a semiconductor device according to the present invention, the inert gas is preferably one or more of nitrogen, argon and helium.

In the method of manufacturing a semiconductor device according to the present invention, the concentration of oxygen contained in the inert gas is 20 pp.
m or less.

The semiconductor device of the present invention is manufactured by the above-described manufacturing method of the present invention.

Further, in the semiconductor device of the present invention, a plurality of the semiconductor elements of the present invention are formed on the same substrate.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a semiconductor device according to an embodiment of the present invention will be described below with reference to the drawings.

The method of manufacturing a semiconductor device according to the present invention is applied, for example, for manufacturing an N-type TFT on a glass substrate. Such a TFT is applicable to a driver circuit and a pixel portion of an active matrix type, and can also be used as a constituent element of a thin film integrated circuit.

In this embodiment, a method of manufacturing hundreds of thousands to several millions of N-type TFTs to be used as pixel TFTs in an active matrix substrate for a liquid crystal display device will be described.

FIGS. 1A to 1D are cross-sectional views showing steps of manufacturing an N-type TFT as a semiconductor device according to the present invention. Although an active matrix substrate for a liquid crystal display device, which is a semiconductor device, is provided with hundreds of thousands or more TFTs, a method of manufacturing one TFT will be described in the drawings for easy understanding of the present invention. I do.

First, as shown in FIG. 1A, a plasma CVD method is performed on a glass substrate 1 which is an insulating substrate.
A base film 2 made of silicon oxide is formed to a thickness of 200 nm. Next, an intrinsic amorphous silicon semiconductor film 3 is formed by a plasma CVD method. If the amorphous silicon semiconductor film 3 has a thickness of less than 25 nm, sufficient crystal growth cannot be achieved even by the introduction of a catalyst element described later, and if it exceeds 80 nm, the introduction of the catalyst element in a later step will cause The resulting columnar crystals may have a two-layer structure and the crystallinity may be deteriorated, and the catalytic element may remain. Therefore, the thickness of the amorphous silicon semiconductor film 3 is preferably 25 to 80 nm. In this embodiment, the amorphous silicon semiconductor film 3 is formed to a thickness of 40 nm.

After the amorphous silicon semiconductor film 3 is formed, an unnecessary portion of the amorphous silicon semiconductor film 3 is removed to separate elements.

This amorphous silicon semiconductor film 3
Is an element formation film that will be a source region, a drain region, and a channel region in a later step, and forms a number of island regions by performing element isolation. In the present embodiment,
Since the present invention is applied to an active matrix type liquid crystal display device, the amorphous silicon semiconductor film 3 has island regions arranged in a matrix.

Next, Ni as a catalyst element is added to the amorphous silicon semiconductor film 3 by a sputtering method. Since the added catalytic element may remain in the active region of the TFT to be manufactured and cause an increase in leakage current or deterioration of characteristics, its surface concentration is
It is preferable that the concentration be 1 × 10 ¹⁵ atoms / cm ² or less. In this embodiment mode, 7 × 10 ¹³ atoms / cm ²
Ni as a catalyst element was added so that the surface concentration became.

The catalyst element to be added is Ni
In addition, one or more of metals such as cobalt, palladium, platinum, copper, silver, gold, indium, tin, aluminum, and antimony can be used. The crystallization of the silicon semiconductor film 3 can be promoted.

However, since the catalytic element promotes the crystal growth of silicon by being silicided in the amorphous silicon semiconductor film, the lattice constant of the silicide compound of the catalytic element becomes the lattice constant of the crystal structure of single crystal silicon. Preferably, they are similar. NiSi ₂ , a silicide compound of Ni, has the crystal structure most similar to that of single-crystal silicon among the silicide compounds of the catalyst element described above, and its lattice constant is also closest to the lattice constant of silicon. ing. Therefore, NiSi ₂ becomes the most excellent template for crystallization of the amorphous silicon semiconductor film, and crystallization of the amorphous silicon semiconductor film is most promoted. Therefore, Ni is suitable as a catalyst element.

The method of adding the catalytic element is not limited to the above-described sputtering method, but may be performed by using a coating liquid composed of a Ni compound to form the amorphous silicon semiconductor film 3.
A method of forming a coating film thereon may be used.

When the catalytic element is added to the amorphous silicon semiconductor film 3, the entire glass substrate 1 is heat-treated in an inert gas atmosphere at a temperature of 540 to 620 ° C. for several hours. The silicon semiconductor film 3 is crystallized. As described above, by performing crystallization with the catalyst element as a nucleus in a temperature range of 540 to 620 ° C., it is possible to prevent spontaneous generation of a crystal nucleus independent of the catalyst element in the amorphous silicon semiconductor film 3. it can. In this embodiment, the entire glass substrate 1 is heat-treated at 580 ° C. for 4 hours in a nitrogen atmosphere.

Next, by irradiating the silicon semiconductor film 3 with a laser beam, the crystallization of the silicon semiconductor film 3 is further promoted. In the present embodiment, a KrF excimer laser having a wavelength of 248 nm and a pulse width of 20 nsec is used as laser light to be applied to the silicon semiconductor film 3. However, not limited to such a KrF excimer laser, other laser light may be used.

The laser light irradiation conditions for the silicon semiconductor film 3 are as follows:
In the range of 00 to 400 mJ / cm ² , for example, 250 mJ
/ Cm ² , and 2 to 10 shots, for example, 2 shots of laser light are irradiated per spot. Simultaneously with the irradiation of the laser beam, the entire glass substrate 1
Heating to about ° C further promotes crystallization of the silicon semiconductor film 3.

Next, as shown in FIG. 1B, a silicon oxide film 4 as a gate insulating film is formed over the entire glass substrate 1 so as to cover the crystalline silicon semiconductor film 3 by a plasma CVD method. In the range of 50-250 nm,
For example, a film is formed to a thickness of 150 nm.

Next, as shown in FIG. 1C, an aluminum film is formed on the silicon oxide film 4 to a thickness of 400 to 800 nm, for example, 600 nm by a sputtering method. Is patterned into a predetermined shape to form a gate electrode 5 at the center of the crystalline silicon semiconductor film 3. Subsequently, the surface of the gate electrode 5 is anodized to form the oxide layer 6.
The anodic oxidation of the gate electrode 5 is performed in an ethylene glycol solution containing tartaric acid at 1 to 5%. The portion of the crystalline silicon semiconductor film 3 covered with the oxide layer 6 has a length corresponding to this anodic oxidation in order to form an offset gate region that is not ion-doped in a later ion doping step. It is determined by the thickness of the oxide layer 6 formed in the process. In the present embodiment,
The thickness of the oxide layer 6 was 200 nm.

Next, impurities such as phosphorus and boron are implanted into the crystalline silicon semiconductor film 3 by an ion doping method. In the present embodiment, phosphorus is used as an impurity, and its acceleration voltage is in the range of 60 to 90 kV, for example,
80 kV, phosphine (PH ₃ ) was used as the doping gas, and the dose of the phosphorus element was 1 ×.
In the range of 10 ¹⁵ to 8 × 10 ¹⁵ cm ⁻² , for example, 2 × 10 ¹⁵
cm ^-2 .

In this step, the gate electrode 5 and the oxide layer 6 formed on the silicon oxide film 4 function as a mask, and the crystalline silicon semiconductor film 3 on which the gate electrode 5 and the oxide layer 6 are not formed. The impurity is implanted into the region described above to form the source region 7 and the drain region 9 of the TFT through the steps described later (both refer to FIG. 1D).
On the other hand, the region of the crystalline silicon semiconductor layer 3 immediately below the gate electrode 5 is a region into which impurities are not implanted, and is subjected to a channel region 8 (FIG.
Reference).

It should be noted that an N-type TFT is replaced with a P-type TFT on the same substrate.
In the case of fabricating a semiconductor device in which the FT and the FT are configured in a complementary manner, a photoresist serving as a mask when each of the N-type or P-type impurities is implanted is formed.
If the respective photoresists are selectively doped with impurities, N-type and P-type impurity regions can be formed respectively.

Next, the entire glass substrate 1 is subjected to a heat treatment in an atmosphere of an inert gas under a temperature condition of about 50 to 600 ° C. under a pressure of at least atmospheric pressure. By performing such a heat treatment, it is possible to activate the ion-implanted impurities and to getter nickel, which is a catalytic element, by the injected impurities.

If the inert gas is selected from one or more of nitrogen, argon and helium, gettering of the catalytic element can be performed efficiently. Further, in order to prevent oxidation of the gate electrode during the heat treatment, the concentration of oxygen contained in the inert gas is 2
It is set to 0 ppm or less.

The pressure condition is preferably set to about 10 to 20 atm, since the temperature can be raised to a predetermined temperature in a short time and the temperature can be lowered to a predetermined temperature in a short time. Further, by setting the heating temperature to 600 ° C. or lower, an inexpensive glass substrate 1 can be used. In the present embodiment, at a temperature of 550 ° C. and a pressure of 10 atm, 1
The heat treatment was performed over time.

Next, as shown in FIG. 1D, a silicon oxide film 10 having a thickness of 600 nm is formed as an interlayer insulating film over the entire glass substrate 1 by plasma CVD over the entire surface of the substrate. A contact hole reaching the source region 7 and the drain region 9 of the silicon semiconductor layer 3 from the silicon oxide film 10 is formed. Thereafter, a TF is formed in each of the formed contact holes by a metal material, for example, a multilayer film of titanium nitride and aluminum.
A source electrode 11 and a drain electrode 12 that are conductive are formed in the source region 7 and the drain region 9 of T, respectively.

When the formed TFT is used as a pixel switching element of a liquid crystal display device or the like, a pixel electrode made of ITO or the like is formed instead of the source electrode 11 and the drain electrode 12 made of a metal electrode.

Finally, the TFT is completed by performing a heat treatment for 30 minutes under a steam atmosphere of 1 atm under a temperature condition of 350 ° C.

As described above, according to the method for manufacturing a semiconductor device of the present invention, the crystallization of the amorphous silicon semiconductor film 3 is promoted by introducing the catalytic element into the amorphous silicon semiconductor film 3. Thereafter, by heat-treating the substrate at least under high pressure conditions of atmospheric pressure or more, while activating the implanted impurities,
At the same time, nickel, which is a catalytic element due to the implanted impurities, can be gettered. Therefore, the efficiency of gettering of the catalytic element can be increased, and at the same time, impurities such as P ions and B ions can be implanted to activate the silicon semiconductor layer 3, thereby improving the productivity of semiconductor elements. be able to.

[0057]

According to the present invention, a crystallization of an amorphous silicon semiconductor film is promoted by introducing a catalytic element into the amorphous silicon semiconductor film, and then the substrate is subjected to a heat treatment under a high pressure condition of at least atmospheric pressure. By doing so, it is possible to activate the ion-implanted impurities and, at the same time, getter the catalytic element by the implanted impurities. Therefore, the efficiency of gettering of the catalytic element can be improved, and at the same time, the impurity can be implanted to activate the silicon semiconductor layer, so that the productivity of the semiconductor element can be improved.

[Brief description of the drawings]

FIGS. 1A to 1D are cross-sectional views illustrating a method for manufacturing a semiconductor device of the present invention for each process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Underlayer 3 Silicon semiconductor film 4 Silicon oxide film 5 Gate electrode 6 Oxide layer 7 Source region 8 Channel region 9 Drain region 10 Silicon oxide film 11 Source electrode 12 Drain electrode

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) NN23 NN35 NN72 PP01 PP03 PP10 PP13 PP34 QQ28

Claims (14)

[Claims] A step of forming an amorphous silicon semiconductor film on a substrate having an insulating surface; and a step of introducing a catalytic element that promotes crystallization of the silicon semiconductor film into the amorphous silicon semiconductor film. A step of heating and crystallizing the amorphous silicon semiconductor film into which the catalytic element has been introduced, a step of forming a gate insulating film covering the crystalline silicon semiconductor film, and a gate electrode on the gate insulating film. Forming an impurity on the crystalline silicon semiconductor film; and heating the substrate having the impurity implanted therein at a temperature of 600 ° C. or less in an inert gas atmosphere of 1 atm or more. A method for manufacturing a semiconductor device, comprising: 2. The method according to claim 1, wherein the impurities include P ions or B ions. 3. The method according to claim 1, wherein the substrate is a glass substrate. 4. The heat treatment step is performed at 10 to 20 atm.
The method for manufacturing a semiconductor device according to claim 1, wherein the method is performed in a pressure range of: 5. The method according to claim 4, wherein the step of crystallizing the amorphous silicon semiconductor film includes a laser annealing process after a heat treatment. 6. The method according to claim 1, wherein the step of crystallizing the amorphous silicon semiconductor film includes a heat treatment in a temperature range of 540 to 600 ° C. 7. The method according to claim 1, wherein the amorphous silicon semiconductor film is formed to have a thickness in the range of 25 to 80 nm. 8. The method according to claim 1, wherein the catalyst element introduced into the amorphous silicon semiconductor film has a concentration of 1 × 10 ¹⁶ atm / cm ³ or less. 9. The catalyst element is nickel, cobalt,
The method for manufacturing a semiconductor device according to claim 1, wherein the method is one or more of palladium, platinum, copper, silver, indium, tin, aluminum, and antimony. 10. The method according to claim 9, wherein the catalytic element contains at least nickel. 11. The method according to claim 1, wherein the inert gas is one or more of nitrogen, argon, and helium. 12. The method according to claim 11, wherein the concentration of oxygen contained in the inert gas is 20 ppm or less. 13. A semiconductor device manufactured by the manufacturing method according to claim 1. 14. A semiconductor device in which a plurality of the semiconductor elements according to claim 13 are formed on the same substrate.