JP2652369B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulated gate type semiconductor device used for a driving element of an active matrix type liquid crystal display device or the like.

[0002]

2. Description of the Related Art Conventionally, a silicon oxide film formed by a sputtering method using Ar atoms as a sputtering gas has been used as a gate insulating film of an insulating gate type semiconductor device used as a thin film transistor.

[0003]

In the conventional method, atoms contained in the material used and also present during the reaction are used.
(E.g., Ar, etc.) is incorporated in the gate insulating film in large numbers,
This has caused the generation of fixed charges in the film. Furthermore, ionic species of atoms present during the reaction collide with the active layer surface of the thin film transistor and cause damage, resulting in the formation of a mixed layer of the active layer and the gate insulating film near the interface between the gate insulating film and the active layer. As a result, an interface state was formed, and good characteristics of the thin film transistor could not be obtained in any case.

[Object of the Invention] An object of the present invention is to invent a configuration which solves the problem of the interface characteristics which is a problem of the conventional insulating film.

[0005]

SUMMARY OF THE INVENTION The present invention relates to an insulated gate field effect transistor provided on an insulating substrate, characterized in that a halogen element is mixed in a silicon oxide film. 3 illustrates a method for manufacturing a semiconductor device.

A glass substrate is typically used as the insulating substrate. Conventionally, there is an example in which a semiconductor layer is directly formed on a glass substrate which is an insulating substrate. However, there are problems such as diffusion of impurities (especially sodium) from the glass substrate and poor interface characteristics between the glass substrate and the semiconductor layer. When a silicon oxide film is provided over a glass substrate to prevent a problem and a semiconductor device is formed thereover, a highly reliable device can be obtained.

[0007] By mixing a halogen element into at least one of the silicon oxide film on the insulating substrate and the gate insulating film of the insulating gate type field effect transistor provided on the silicon oxide film, the semiconductor layer and the silicon oxide film are formed. Can be obtained in which there is almost no localized level at the interface between.

As a method for forming the silicon oxide film, a sputtering method, a photo CVD method, a PCVD method, a thermal CVD method or the like can be used.

[0009]

【Example】

[Embodiment 1] In this embodiment, a semiconductor film is formed by sputtering on a substrate in an atmosphere of hydrogen or an inert gas containing hydrogen, and fluoride is formed before and after the formation of the semiconductor film obtained by the sputtering. A silicon oxide film is formed by a sputtering method in an atmosphere of an inert gas containing a gas and an oxide gas or a fluoride gas and an oxide gas, and a part of the semiconductor film is formed as a channel formation region of an insulating gate semiconductor device. Part of the silicon oxide film is a gate insulating film.

As an example of a technique for forming a part of the semiconductor film as a channel formation region, an amorphous material (amorphous or extremely amorphous) obtained by sputtering in an atmosphere of hydrogen or an inert gas containing hydrogen is used. By providing a semiconductor film (hereinafter referred to as a-Si) at a temperature of 450 ° C. to 700 ° C., typically 600 ° C., and typically at least 600 ° C. to crystallize at least the channel formation region, the insulating gate type semiconductor device of the present invention can get.

The semiconductor film after this crystallization has an average crystal grain size of about 5 to 400 ° and the hydrogen content in the semiconductor film is 5 atomic% or less. In addition, the semiconductor film having this crystallinity has lattice distortion, and the interfaces of the crystal grains are in close contact with each other microscopically, and have an effect of eliminating a barrier for carriers at the crystal grain boundaries. For this reason, impurity atoms such as oxygen segregate and form barriers (barriers) at the polycrystalline grain boundaries having no lattice distortion and hinder the movement of carriers, but have lattice distortion as in the present invention. In this case, a barrier was not formed or its existence was negligible, so that the electron mobility also had very good characteristics of 5 to 300 cm ² / V · S.

Further, the semiconductor film obtained by the plasma CVD method has a large proportion of an amorphous component, and the amorphous component portion is naturally oxidized to form an oxide film to the inside. On the other hand, the sputtered film is dense and naturally oxidized. Does not proceed to the inside of the semiconductor film, and is oxidized only in the vicinity of the surface. Due to this denseness, crystal grains having lattice distortion strongly push each other, and an energy barrier against carriers near the crystal grain interface. Is not formed.

FIG. 1 shows a manufacturing process of the thin film transistor manufactured in this embodiment. First, on the glass substrate (11)
An SiO ₂ film (12) was formed to a thickness of 200 nm by magnetron RF sputtering under the following conditions. Reaction gas O ₂ 95% by volume NF ₃ 5% by volume Deposition temperature 150 ° C RF (13.56MHz) output 400W Pressure 0.5 Pa Silicon is used as target

Further, an a-Si film (13) serving as a channel forming region is further deposited on the film by a magnetron type RF sputtering apparatus.
A film was formed to a thickness of 0 nm to obtain the shape shown in FIG.

The deposition conditions are as follows: H ₂ / (H ₂ + Ar) = 80% (partial pressure ratio) in an atmosphere of argon and hydrogen, which are inert gases, deposition temperature 150 ° C. RF (13.56 MHz) output 400 W total pressure The pressure was 0.5 Pa, and a single crystal silicon target was used as the target.

Thereafter, the temperature range of 450 ° C. to 700 ° C., especially 600 ° C.
At a temperature of 10 ° C. for 10 hours in hydrogen or an inert gas, in this embodiment, in a 100% nitrogen atmosphere.
The i-film (13) was thermally crystallized to produce a silicon semiconductor layer having high crystallinity. Note that the a-Si film (1
3) When a film is formed by a sputtering method, when a non-single-crystal silicon target is used and the input power is reduced, a dense crystal state having a small particle size that can be ignored and having lattice distortion can be obtained.

The amount of oxygen impurities present in the semiconductor film formed by such a method is 2 × by SIMS analysis.
10 ²⁰ cm ^-3 , carbon was 5 × 10 ¹⁸ cm ^-3 , and the content of hydrogen was 5% or less. Since the value of the impurity concentration using the SIMS changes in the depth direction in the semiconductor film, the concentration in the depth direction was examined and described with the minimum value. This is because a natural oxide film exists near the surface of the semiconductor film. Further, the value of the impurity concentration did not change even after the crystallization treatment.

Obviously, the lower the impurity concentration is, the more advantageous it is when used as a semiconductor device, but the semiconductor film of the present invention has both crystallinity and lattice distortion. Therefore, no barrier is formed at the crystal grain boundary, and even if an oxygen impurity concentration of about 2 × 10 ²⁰ cm ⁻³ exists, the degree of hindering the movement of carriers is low, and a practical problem occurs. Did not.

As can be seen from the data of the laser Raman analysis shown in FIG. 9, the position of the peak indicating the presence of a crystal in this semiconductor film has a lower wave number than the position of the peak (520 cm ^-1 ) of normal single crystal silicon. To the side, confirming the existence of lattice distortion.

In the present embodiment, the present invention is described using a silicon semiconductor. However, a germanium semiconductor or a semiconductor in which silicon and germanium are mixed can be used. It was possible to reduce the temperature added during crystallization by about 100 ° C.

In the case of sputtering in the above-mentioned hydrogen atmosphere or an atmosphere of hydrogen and an inert gas in order to form a still more dense semiconductor film or silicon oxide film, the substrate or the sputtered target particles in flight are sputtered. 1000nm
The following intense light or laser irradiation may be applied continuously or in pulses.

The thermally crystallized silicon semiconductor film is subjected to device isolation patterning to obtain the shape shown in FIG.
A part of this semiconductor film was formed as a channel formation region of an insulating gate type semiconductor device.

Next, a silicon oxide film (SiO ₂ ) (15) was formed to a thickness of 100 nm by magnetron RF sputtering under the following conditions. Oxygen 95% by volume NF ₃ 5% by volume Pressure 0.5pa Film formation temperature 100 ° C RF (13.56MHz) output 400W A silicon target or a synthetic quartz target was used as a target.

Also in this case, when the input power of the amorphous silicon target is reduced, a dense silicon oxide film in which fixed charges do not easily exist can be obtained.

When a silicon oxide film such as a gate insulating film in the structure of this embodiment is formed by a sputtering method, a gas containing a halogen element and an oxide gas are within 50% of an inert gas, preferably an inert gas. It is preferable to form a film under a condition without using a gas.

Further, by mixing a gas containing a halogen element with 2 to 20% by volume of the oxide gas at the same time, neutralization of alkali ions simultaneously and reluctantly introduced into the silicide oxide, Sum can also be possible.

As a sputtering method used to obtain the structure of this embodiment, any method such as RF sputtering and DC sputtering can be used. However, when the sputtering target is an oxide having low conductivity, for example, SiO ₂ or the like, stable sputtering is performed. It is preferable to use the RF magnetron sputtering method to maintain the generated discharge.

The oxide gases include oxygen, ozone,
Although nitrous oxide and the like can be mentioned, particularly when ozone or oxygen is used, since there is no unnecessary atom taken into the silicon oxide film, a very good insulating film such as a gate insulating film can be obtained. Was.

As the gas containing a halogen element, nitrogen fluoride (NF ₃ , N ₂ F ₄ ), hydrogen fluoride (HF), fluorine (F ₂ ), or Freon gas can be used as the fluoride gas. NF ₃ which is easily decomposed chemically and easy to handle is easy to use. As chloride gas, carbon tetrachloride (CCl ₄ ), chlorine (Cl ₂ ), hydrogen chloride (H
Cl) can be used. Also, for example, the amount of nitrogen fluoride is
The content was set to 2 to 20% by volume relative to the oxide gas, for example, oxygen.

[0030] Neutralization with alkali ions such as sodium, these halogen element in silicon oxide by heat treatment, if it is effective in neutralizing the unpaired bonds of silicon is too large amount at the same time, the SiF ₄ such as silicon main component It is not good because there is a possibility of gas. In general, a halogen element of 0.1 to 5% by volume with respect to silicon was mixed in the film.

The use of ozone as a gas for sputtering has a tendency that ozone is easily decomposed into O radicals, the amount of O radicals generated per unit area is large, and it has been possible to contribute to the improvement of the film forming speed.

In the conventional production of a gate insulating film by a sputtering method, an inert gas is used.
Ar was larger than oxygen gas, and oxygen was usually produced at about 0 to 10% by volume. That is, in the conventional sputtering method, it was naturally considered that Ar hits the target material and the resulting target particles are formed on the surface on which the target material is to be formed. This is because the probability that an inert gas such as Ar will strike the target material (sputtering
Was high.

The present inventors have conducted intensive studies on the characteristics of the gate insulating film formed by the sputtering method. As a result, the interface state between the active layer and the gate insulating film, which shows the performance of the gate insulating film, and the state of the gate insulating film. It has been found that the deviation of the flat band voltage from the ideal value reflecting the number of fixed charges greatly depends on the ratio of Ar gas during sputtering.

The flat band voltage is a voltage required to cancel the effect of fixed charges in the insulating film, and the lower the flat band voltage, the better the characteristics of the insulating film.

In FIG. 2, a silicon oxide film (15) is formed on the polycrystalline silicon semiconductor (13) manufactured in this embodiment by the method shown in this embodiment (the state of FIG. 1A). Flat band voltage and volume% of (Ar gas / oxidizing gas) as a result of electron beam evaporation and examination of 1 mmφ aluminum electrode
The relationship is shown below.

It can be seen that, when the amount of Ar gas is smaller than the amount of oxidizing gas (oxygen in FIG. 2) compared to 100% of Ar gas, and 50% or less, the deviation of the flat band voltage is reduced. The deviation of the flat band voltage from the ideal voltage largely depends on the ratio of the Ar gas, and when the ratio of the Ar gas is 20% or less, the value is almost close to the ideal voltage.

From these facts, the activated Ar atoms present in the reaction atmosphere at the time of film formation by sputtering affect the film quality of the gate insulating film. It turned out to be desirable.

It is considered that the reason is that Ar ions or activated Ar atoms collide with the interface and form damage or defects at the interface, causing fixed charge generation.

FIG. 3 shows a silicon oxide film in which a halogen element is mixed on the polycrystalline silicon semiconductor (13) manufactured in this embodiment.
(15) Aluminum electrode (1mmφ) on (state of Fig.1 (a))
The characteristics of a sample annealed at 300 ° C. after formation are shown.

FIG. 3 shows that a BT (bias-temperature) process is performed and a negative bias voltage is applied to the gate electrode side at 2 × 10 ⁶ V / cm.
, A positive bias voltage was applied under the same conditions, and the difference between them, that is, the measured value of the flat band voltage deviation (ΔF _FB ), and the oxidation value of the gate oxide film in this embodiment were measured. (Oxygen / NF ₃ ) in the atmosphere when producing the silicon film (15) by the sputtering method
4 is a graph showing the relationship between the volume% and the volume%.

As is apparent from FIG. 3, when the silicon oxide film was formed by magnetron type RF sputtering in an atmosphere containing NF ₃ of 0% by volume, (ΔF _FB ) was as high as 9V. However, even if a small amount of fluorine as a halogen element was added during the film formation, the value sharply decreased.

[0042] This is by what was contamination of positive ions such as sodium during deposition is added ^{fluorine, Na + + F - → NaF} Si - + F - → Si-F becomes electrically Medium It is estimated that they will be summed.

Since the positive ions of sodium also diffuse from the glass substrate, it is effective to provide a silicon oxide film containing fluorine atoms on the glass substrate.

Regarding the neutralization of silicon, a method of adding hydrogen is also known. However, the neutralized Si-
The H bond is re-separated by a strong electric field (BT treatment), becomes a dangling bond of Si again, and causes an interface state to be established. Therefore, it is preferable to neutralize the H bond with fluorine.

In addition, Si—H bonds always exist in the silicon oxide film, and when the Si—H bonds are separated again, the fluorine atoms actively neutralize the separated hydrogen to establish an interface state. There is also the effect of preventing. Further, the presence of fluorine causes H bonded to Si to form a hydrogen bond with fluorine, preventing Si from becoming a fixed charge.

FIG. 4 shows the breakdown voltage when the fluoride gas is further increased. The withstand voltage was a voltage when the leak current exceeded 1 μ１ using an Al electrode of 1 mm φ.

Since there is variation among samples, the values are shown as X and σ (dispersion sigma value) in the figure. This withstand voltage becomes lower when it exceeds 20%, and the σ value also becomes larger. For this reason, the addition of the halogen element should be set to 20% by volume or less, and generally, 0.2 to 10% should be used. By the way, when the amount of fluorine was examined by SIMS (Secondary Ion Mass Spectrometer), 1% by volume was
× 10 ²⁰ cm ^-3 . That is, it was found that the element is extremely easy to be taken into the film when added simultaneously during the film formation by sputtering. However, when the amount is too large (20% by volume or more), the silicon oxide film tends to be distorted, and as a result, the withstand voltage is poor and the dispersion is increased.

Further, it is preferable that all materials used for sputtering have high purity. For example, sputtering
The getter is most preferably made of synthetic quartz of 4N or more, or silicon of high purity enough to be used for an LSI substrate. Similarly, the gas used for sputtering was of high purity (5N or more), and the contamination of the silicon oxide film with impurities was avoided as much as possible.

The silicon oxide film, which is a gate insulating film formed by a sputtering method in an oxygen atmosphere containing a fluoride gas as in this embodiment, is irradiated with excimer laser light.
It is effective to perform flash annealing to activate halogen elements such as fluorine introduced into the film, to neutralize it with incomplete bonds of silicon, and to remove the cause of generation of fixed charges in the film.

At this time, the activation of the halogen element and the activation of the semiconductor layer under the gate insulating film can be simultaneously performed by appropriately selecting the power and the number of shots of the excimer laser.

In this embodiment, a semiconductor layer mixed with phosphorus as an impurity imparting one conductivity type is formed on the silicon oxide film (15) by a CVD method, and photolithography is performed using a predetermined mask pattern. Then, the doped semiconductor film is formed as a gate electrode (20), and FIG.
Was obtained.

As a method for forming the semiconductor layer into which the impurity imparting one conductivity type is mixed, a film forming method such as a sputtering method or a CVD method can be used.

The gate electrode is not limited to the doped semiconductor layer, and other materials can be used.
Next, using the gate electrode (20) or the mask used for etching the gate electrode (20) as a mask, the impurity regions (14) and (14 ′) were formed in a self-aligned manner using ion implantation technology. .

As a result, the semiconductor layer (17) under the gate electrode (20) was formed as a channel region of the insulated gate type semiconductor device.

Next, an interlayer insulating film is formed covering all of these upper surfaces.
After forming (18), a hole for contact of the source and drain electrodes is made, metal aluminum is formed on the upper surface by sputtering, and predetermined patterning is performed, and the source and drain electrodes (16) and (16 ′) To complete an insulated gate semiconductor device.

In the case of this embodiment, the semiconductor layer (17) forming the channel region and the semiconductor layer forming the source (14) and the drain (14 ^, ) are made of the same material. To be peeled off. In addition, since the same semiconductor layer is used, the source and drain semiconductor layers also have crystallinity and the mobility of carriers is high, so that an insulated gate semiconductor device having higher electric characteristics can be realized.

Finally, at 375 ° C. in a 100% hydrogen atmosphere.
At this temperature, hydrogen thermal annealing was performed for 30 minutes to complete this example. This hydrogen thermal annealing is for reducing the grain boundary potential in the polycrystalline silicon semiconductor and improving the device characteristics.

The size of the channel portion (17) in the thin film transistor shown in FIG.
It has a size of μm.

The above is the method for manufacturing a thin film transistor using the polycrystalline silicon semiconductor layer manufactured in this embodiment.
The formation of the semiconductor layer ((13) in FIG. 1A) and its thermal recrystallization will be described.

FIG. 1 (a) showing a channel forming region will now be described.
Reference Example 5 in which the hydrogen concentration, which is the condition for forming the a-Si layer (13) by the magnetron RF sputtering method, was changed.
An example is shown below.

[0061] (Reference Example 2) This reference example of the channel forming region in the production process FIGS. 1 (a) the partial pressure ratio of the atmosphere during sputtering of making the (13) H ₂ / Example 1 ( (H ₂ + Ar) = 0% (partial pressure ratio), and the others were produced in the same manner as in Example 1.

[0062] (Reference Example 3) this reference example of the channel forming region in the production process FIGS. 1 (a) the partial pressure ratio of the atmosphere during sputtering of making the (13) H ₂ / Example 1 ( (H ₂ + Ar) = 5% (partial pressure ratio), and the others were produced in the same manner as in Example 1.

[0063] (Reference Example 4) This example of a channel forming region in the production process FIGS. 1 (a) the partial pressure ratio of the atmosphere during sputtering of making the (13) H ₂ / Example 1 ( (H ₂ + Ar) = 20% (partial pressure ratio), and the others were produced in the same manner as in Example 1.

[0064] (Reference Example 5) This reference example of the channel forming region in the production process FIGS. 1 (a) the partial pressure ratio of the atmosphere during sputtering of making the (13) H ₂ / Example 1 ( (H ₂ + Ar) = 30% (partial pressure ratio), and the others were produced in the same manner as in Example 1.

[0065] (Reference Example 6) the partial pressure ratio of the atmosphere during sputtering of making the (13) of the present embodiment is a channel formation region in the fabrication method in the Embodiment 1 FIG. 1 (a) H ₂ / ( (H ₂ + Ar) = 50% (partial pressure ratio), and the others were produced in the same manner as in Example 1.

The results of comparison of the electrical characteristics of the above examples are shown below. FIG. 5 shows the carrier mobility μ (FIELD) in the completed channel section (FIG. 1 (d) (17)).
MOBILITY) and the hydrogen partial pressure ratio ratio during sputtering (P _H / P _{TO TA}
= H ₂ / (H ₂ + Ar)) in a graph. FIG.
Table 1 below shows the correspondence between the plot points and the respective examples.

[0067]

[Table 1]

FIG. 5 shows that a remarkably high mobility μ (FIELD MOBILITY) is obtained at a hydrogen partial pressure of 20% or more.

FIG. 6 is a graph showing the relationship between the threshold voltage and the hydrogen partial pressure ratio during sputtering (P _H / P _TOTAL = H ₂ / (H ₂ + Ar)) as a curve A.

The curve B is a graph curve corresponding to the curve A of the comparative example in which a gate oxide film in which fluorine atoms are not mixed in the present embodiment for comparison with the structure of the present invention.

The correspondence between the hydrogen partial pressure ratio (P _H / P _TOTAL = H ₂ / (H ₂ + Ar)) and each of the above example numbers is the same as in Table 1.

FIG. 6 shows that the adoption of the gate oxide film containing fluorine atoms according to the present invention has a lower threshold voltage (threshold) than that of the conventional insulated gate type field effect transistor employing the gate oxide film. Voltage) can be obtained.

Considering that the lower the threshold voltage, the lower the operating voltage for operating the thin film transistor, that is, the lower the gate voltage, the better the characteristics of the device can be obtained. A normally-off state with a threshold voltage of 2 V or less can be obtained by a sputtering method under a high condition.

That is, FIG. 1 showing a channel forming region
(a) Obtaining the a-Si film shown in (13), a device using a semiconductor layer having crystallinity obtained by thermally crystallizing this a-Si film shows good electrical characteristics You can see that. FIG. 3 also shows that the higher the hydrogen partial pressure ratio, the lower the threshold voltage. From this, it can be seen that when the a-Si film serving as the channel formation region in each of the above examples is manufactured by the sputtering method, increasing the partial pressure ratio of hydrogen tends to increase the electrical characteristics of the device.

FIGS. 7 to 11 show that the hydrogen partial pressure ratio = H ₂ / (H ₂ + Ar) when the a-Si film of FIG. 0%, 5%, 20%, 30
5 is a graph showing a change in the value of the drain current when the drain voltage and the gate voltage are used as parameters in the cases of% and 50%. Table 2 shows the relationship between the numbers in the drawings and the hydrogen partial pressures and the numbers in the above examples.

[0076]

[Table 2]

(71), (72), and (73) in FIG. 7 show the relationship between the drain current (ID) and the drain voltage (VD) when the gate voltage is 20, 25, and 30 volts, respectively. FIG.

Table 3 below shows the relationship between the notation of the curve in FIG. 7 and the gate voltage.

[0079]

[Table 3]

The correspondence between the display symbols of the curves showing the relationship between the gate voltage, the drain current and the drain voltage in FIGS. 8 to 11 can be obtained by converting the second digit of the display symbol into the number of the drawing in Table 3 above. Can be obtained.

For example, the curve (83) in FIG. 8 corresponds to the display symbol (73) in Table 3 above. In this case, FIG.
It can be seen from FIG.

The remarkable effect in the present embodiment becomes clear by comparing FIG. 8 and FIG.

That is, a curve (83) showing the relationship between the drain voltage and the drain current at a gate voltage of 30 V in FIG. 8 and a curve (93) showing the relationship between the drain voltage and the drain current at a gate voltage of 30 V in FIG. By comparison, it can be seen that FIG. 9, that is, Reference Example 4 (see Table 2) has a drain current 10 times or more that of FIG. 8, that is, Reference Example 3 (see Table 2).

Considering the difference between Reference Example 3 and Reference Example 4, this fact indicates that in this embodiment, the amount of hydrogen added at the time of sputtering when forming an a-Si film ((13) in FIG. 5% pressure ratio
It can be seen that the electrical characteristics of the completed thin film transistor are significantly improved when the ratio becomes 20%.

This can be confirmed by the following measurement results. FIG. 12 shows Examples 2 and 3 of the present invention.
A-Si films to be channel forming regions 4 and 5 (FIG. 1)
The crystallinity obtained by thermally crystallizing this a-Si film when the partial pressure ratio of hydrogen at the time of sputtering for producing (13)) of (a) was set to 0%, 5%, 20%, and 50%. 3 shows a Raman spectrum of a silicon semiconductor layer having the following. Table 4 shows the relationship between the display symbols shown in FIG. 12 , the example numbers, and the hydrogen partial pressure ratio during sputtering.

[0086]

[Table 4]

Referring to FIG. 12, the curve is compared with the curve (122).
(123), that is, the channel formation region ((17) in FIG. 1 (d))
When the partial pressure ratio of hydrogen at the time of sputtering at the time of producing the a-Si semiconductor layer becomes 5% and 20%,
When thermal crystallization, the partial pressure ratio of hydrogen during sputtering is
It can be seen that the Raman spectrum at 20% remarkably shows the crystallinity of the semiconductor silicon.

The average crystal grain size is 5 to 5 from the half width.
400 ° typically 50 to 300 °. The position of the peak of the Raman spectrum is shifted to a lower wavenumber side than the position of the peak of single crystal silicon, 520 cm ⁻¹ ,
Clearly had lattice strain.

This clearly shows the features of the present invention. In other words, the effect of producing an a-Si film by a sputtering method to which hydrogen is added appears only when the a-Si film is thermally crystallized.

As described above, if there is lattice distortion, each of the fine crystal grains is in a state of being forcibly shrunk to each other. There is no energy barrier for carriers in
In addition, segregation of impurities such as oxygen hardly occurs, and as a result, high carrier mobility can be realized.

As a result, even if the impurity concentration existing in the semiconductor film is about 2 × 10 ²⁰ cm ^−3, no barrier to carriers is formed, and the channel region of the insulated gate type semiconductor device is not formed. It can be used as However, this impurity concentration has never been lower.

Referring to Table 2, FIG. 9, FIG.
It can be seen from the comparison that the drain current increases as the ratio of the partial pressure of hydrogen at the time of sputtering when producing the a-Si film increases. This is clear from the comparison between the curves in FIGS. 9 (93), 10 (103) and 11 (113).

In general, when the drain voltage VD is low in a thin film transistor which is a field effect transistor, the relationship between the drain current ID and the drain voltage VD is expressed by the following equation.

ID = (W / L) μC (VG-VT) VD (a) (Solid.State electronics.Vol.24.No.11.pp.1059.198
1.Printed in Britain)

In the above equation (A), W is the channel width, L is the channel length, μ is the carrier mobility, C is the capacitance of the gate oxide film, VG is the gate voltage, and VT is the threshold voltage. is there. The vicinity of the origin of the curves shown in FIGS. 7 to 11 is expressed by the equation (A).

FIGS. 7 to 11 correspond to Examples 2 to 6 as apparent from Table 2, and FIGS.
Numeral 6 indicates a change in the hydrogen partial pressure ratio when the a-Si film serving as the channel formation region is formed by the sputtering method.

If the partial pressure ratio of hydrogen is determined, the mobility μ of the carrier and the threshold voltage VT are determined, and W, L, and C are constants determined by the structure of the thin film transistor. , VD. Since the variable VG is fixed near the origin of the curves shown in FIGS. 7 to 11, it can be seen that the variable VG is eventually expressed by the equation (16-1). In addition,
Equation (a) can only represent the vicinity of the origin of the curves shown in FIGS. This is because this equation is only an approximate equation that holds when the drain voltage VD is low.

According to the equation (A), the lower the threshold voltage VT and the higher the mobility μ, the more the curve of the graph, that is, FIGS.
It is shown that the slope near the origin of the curve shown in FIG. 11 increases.

This means that μ, p in each example of FIGS.
It is clear from comparing the curves shown in FIGS. 7 to 11 based on the difference in the value of VT.

According to the equation (a), it is found that the electrical characteristics of the thin film transistor depend on μ and VT. Therefore, the characteristics of the device cannot be determined independently from each of FIGS. Therefore, comparing the slopes of the origins of the curves shown in FIGS. 7 to 11, the hydrogen partial pressure ratio at the time of sputtering when forming an a-Si film which clearly becomes a channel formation region is at least 20% or more, if possible. Ten
It can be concluded that 0% is better.

This can be understood from the following considerations. Comparing FIGS. 7 to 11, a larger drain current is obtained as the a-Si film of (13) in FIG. You can see that there is. This is a curve
It is clear from comparing (73), (83), (93), (103) and (113).

Table 5 below shows data showing the effects of the present invention.

[0103]

[Table 5]

In Table 5, the hydrogen partial pressure ratio means that the a-Si film ((13) in FIG. 1 (a)) which becomes the channel forming region ((17) in FIG. 1 (d)) in this embodiment is a magnetron. It is the condition of the atmosphere when producing by the type RF sputtering method.

The S value is the value of [d (ID) / d (VG)] ⁻¹ at the rising portion of the curve in the graph showing the relationship between the gate voltage (VG) and the drain current (ID) showing the characteristics of the device. The smaller the value, the sharper the slope of the curve showing the (VG-ID) characteristic and the higher the electrical characteristics of the device. VT indicates the threshold voltage. μ indicates the carrier mobility, and the unit is (cm ² / V · s). The on / off characteristic is a logarithmic value of a ratio between an ID value and a minimum ID value at VG = 30 volts in the curve showing the (VG-ID) characteristic.

From Table 5, it can be seen that, in order to obtain a higher performance semiconductor device comprehensively by the method of this embodiment, it is appropriate to adopt the condition that the hydrogen partial pressure ratio is 80% or more. .

[Embodiment 2] In this embodiment, FIG.
1 shows an insulating gate type semiconductor device having the structure shown in FIG. Coating a silicon oxide film on an insulating substrate is the same as in Example 1, but in this example, a manufacturing method in which formation of a gate insulating film is completed before manufacturing a semiconductor layer forming a channel region is described. ing. Metal molybdenum was formed to a thickness of 3000 ° on the insulating film (12) by a sputtering method, and was subjected to predetermined patterning to form a gate electrode (20).

Next, a gate oxide film (SiO ₂ ) (15) was formed to a thickness of 100 nm by magnetron type RF sputtering under the following conditions. Oxygen 95% NF ₃ 5% Pressure 0.5pa, Film formation temperature 100 ° C RF (13.56MHz) output 400W A silicon target or a synthetic quartz target was used.

An a-Si film (1) serving as a channel formation region is formed on this silicon oxide film by a magnetron type RF sputtering apparatus.
3) is deposited to a thickness of 100 nm.

The film formation conditions are as follows: H ₂ / (H ₂ + Ar) = 80% (partial pressure ratio) under an atmosphere of argon and hydrogen, which are inert gases, film formation temperature 150 ° C. RF (13.56 MHz) output 400 W total pressure The target was 0.5 Pa, and a polycrystalline or non-single-crystal Si target was used.

Thereafter, a temperature range of 450 ° C. to 700 ° C., particularly 600 ° C.
At a temperature of 10 ° C. for 10 hours in hydrogen or an inert gas, in this embodiment, in a 100% nitrogen atmosphere.
The i-film (13) was thermally crystallized to produce a silicon semiconductor layer having high crystallinity. The amount of oxygen impurities present in the semiconductor film formed by such a method was 1 × by SIMS analysis.
10 ²⁰ cm ^-3 , carbon was 4 × 10 ¹⁸ cm ^-3 , and the content of hydrogen was 5% or less. As a result, a channel region (17) could be formed on the gate electrode (20).

Next, an n ⁺ a-Si film (14) was formed to a thickness of 50 nm by magnetron type RF sputtering under the following conditions.

The film forming conditions are as follows: an atmosphere having a hydrogen partial pressure ratio of 10 to 99% or more (80% in this embodiment) and an argon partial pressure ratio of 10 to 99% (19% in this embodiment), a film forming temperature of 150 ° C. RF (13.56 MHz) output 400 W Total pressure 0.5 Pa, and single crystal silicon doped with phosphorus was used as a target.

Next, an aluminum film for source and drain electrodes is formed on the semiconductor layer (14) and patterned, and the source and drain impurity regions (14) (1) are formed.
4 ′) and source and drain electrodes (16) and (16 ′) were formed to complete the semiconductor device.

In this embodiment, since the gate insulation is formed before the formation of the semiconductor layer in the channel formation region, the vicinity of the interface between the gate insulation film and the channel region is appropriately subjected to thermal annealing during the thermal crystallization process. And has the characteristic that the interface state density can be reduced. Although an a-Si film is used as a semiconductor layer to be thermally crystallized in the present example and the like, it goes without saying that the present invention is also effective when thermally crystallizing another non-single-crystal semiconductor. .

Although Ar is used as the inert gas at the time of the above-mentioned sputtering, a halogen gas such as He or a reactive gas such as SiH ₄ or Si ₂ H ₆ which is turned into plasma may be used. . In addition, the magnetron type of this embodiment
In forming an a-Si film by RF sputtering, the hydrogen concentration
5 ~ 100%, deposition temperature range 50 ~ 500 ℃, RF output 500Hz
It can be arbitrarily selected in the range of 1 W to 10 MW in the range of up to 100 GHz, and may be combined with a pulse energy source.

By using more powerful light irradiation (wavelength of 1000 nm or less) energy or electron cyclotron resonance (ECR) conditions, sputtering may be carried out by increasing hydrogen to a higher plasma.

This is because micro atoms in a film formed by sputtering by making light atoms of hydrogen into plasma to efficiently generate positive ions necessary for sputtering, and in the case of this embodiment, an a-Si film This is to prevent the generation of microstructures inside. Further, the other reactive gas may be applied to the above means.

In this embodiment, the amorphous semiconductor film is simply formed by a-
It was described as a Si film. This usually indicates a silicon semiconductor, but may be germanium or a mixed Si _x Ge _1-x (0 <X <1) of silicon and germanium.

It is needless to say that the configuration of the present invention can be applied to a staggered type, a coplanar type, an inverted staggered type, and an inverted coplanar type insulated gate field effect transistor.

[0121]

According to the present invention, a halogen element is added.
To form a base insulating layer by sputtering.
The base insulating layer formed between the plate and the non-single-crystal semiconductor layer
Acts as a blocking layer to prevent unwanted substances from entering
A non-single-crystal semiconductor layer with high carrier mobility.
A method for manufacturing a semiconductor device having pneumatic characteristics was realized.
According to the present invention, a halo formed by a sputtering method
The base insulating layer to which the gen element is added is formed densely
Therefore, crystal grains with lattice distortion push strongly against each other.
And the carrier interacts with the carrier near the crystal grain interface.
Energy barrier is not formed.

[Brief description of the drawings]

FIG. 1 shows a manufacturing process of Example 1.

FIG. 2 shows the relationship between the flat band voltage and (Ar gas / oxidizing gas)% in the silicon oxide film of the present embodiment.

FIG. 3 is a graph showing the relationship between ΔF _FB in the silicon oxide film of the present example and the volume% of NF _{3 in} an oxygen atmosphere.

FIG. 4 is a graph showing the relationship between the breakdown voltage of the silicon oxide film of this example and the volume% of NF _{3 in} an oxygen atmosphere.

FIG. 5 shows a relationship between a hydrogen partial pressure ratio and carrier mobility.

FIG. 6 shows a relationship between a partial pressure ratio of hydrogen and a threshold value.

FIG. 7 shows the relationship between the drain voltage and the drain current when the value of the gate voltage is fixed.

FIG. 8 shows the relationship between the drain voltage and the drain current when the value of the gate voltage is fixed.

FIG. 9 shows the relationship between the drain voltage and the drain current when the value of the gate voltage is fixed.

FIG. 10 shows the relationship between the drain voltage and the drain current when the value of the gate voltage is fixed.

FIG. 11 shows the relationship between the drain voltage and the drain current when the value of the gate voltage is fixed.

FIG. 12 shows a Raman spectrum of a semiconductor film having crystallinity of the present invention.

FIG. 13 shows another embodiment of the present invention.

[Explanation of symbols]

(11) ・ ・ ・ Glass substrate (12) ・ ・ ・ SiO ₂ film (13) ・ ・ ・ a-Si active layer (14) ・ ・ ・ Semiconductor layer in source region (14 ^, ) ・ ・ ・ Semiconductor in drain region Layer (15) ・ ・ ・ Gate oxide film (SiO ₂ ) (16) ・ ・ ・ Source electrode (16 ^, ) ・ ・ ・ Drain electrode (17) ・ ・ ・ Channel formation region (18) ・ ・ ・ Interlayer insulator ( 20) ・ ・ ・ Gate electrode

Claims (4)

(57) [Claims] An underlayer to which a halogen element is added on a substrate
A step of forming an insulating layer by a sputtering method, and a semiconductor device comprising a non-single-crystal semiconductor on the base insulating layer
The method for manufacturing a semiconductor device which comprises forming an active layer of a. 2. An underlayer to which a halogen element is added on a substrate
A step of forming an insulating layer by a sputtering method, and a semiconductor device comprising a non-single-crystal semiconductor on the base insulating layer
Forming an active layer of a method for manufacturing a semiconductor device characterized by comprising the a step of crystallizing the non-single-crystal semiconductor layer. 3. An underlayer to which a halogen element is added on a substrate
A step of forming an insulating layer by a sputtering method, and a semiconductor device comprising a non-single-crystal semiconductor on the base insulating layer
Forming an active layer, and connecting the non-single-crystal semiconductor layer with heat or laser light.
The method for manufacturing a semiconductor device which comprises the steps of crystallization, the. 4. Oxidation wherein a halogen element is added onto a substrate
Forming a base insulating layer consisting of a silicon film by sputtering
And a non-single-crystal semiconductor on the base insulating layer comprising the silicon oxide film.
Forming an active layer of a semiconductor device composed of: and connecting the non-single-crystal semiconductor layer with heat or laser light.
The method for manufacturing a semiconductor device which comprises the steps of crystallization, the.