JP2588446B2 - 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 a method for producing a film having a low oxygen content and excellent electrical characteristics.

[0002]

2. Description of the Related Art In general, silanes having extremely intense oxidizing power include lower oxides (SiOx is hereinafter referred to as silicon oxide) as impurities in reaction products due to their oxidizing power.
Is easily mixed.

In particular, since water as an impurity remains in silane, oxygen reacts to silicon oxide in a plasma CVD (PCVD) method in which only electric energy is applied to a reactive gas, and is mixed directly into a coating film. The concentration of oxygen in the coating is 1 × 10 ¹⁸ cm ⁻³ or more (generally, 2 × 10 ^{19 to} 3 × 10 ²⁰ cm ⁻³ ).
Will remain.

[0004] Therefore, it is necessary to provide a selectivity for forming an active state with respect to silicide while being inactive with respect to this oxide to form a film having silicon as a main component of extremely high quality. It was important.

[0005]

Conventionally, oxygen is contained in a silicide film in an amount of 2 × 10 ¹⁹ cm ⁻³ or more, and a high quality insulator is contained in a silicon film which should be a semiconductor. Due to the presence of certain silicon oxide, there were problems in electrical characteristics and reliability as a semiconductor.

An object of the present invention is to provide a semiconductor device having a high quality intrinsic semiconductor film having a low oxygen concentration in the film.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a hydride or a halide of silicon, comprising Si-H, Si-
A reactive gas having a bond of F, Si—Cl, Si—Br, and Si—I is used, and a continuous infrared (hereinafter, referred to as FIR) of 1500 to 300 cm ⁻¹ is applied to the reactive gas. substrate with a non-single crystal silicon film of conductivity type intrinsic oxygen obtained is not only incorporated an amount of less than 1 × 10 19 ^{atom /} cc by performing gas phase reactions by the addition of electrical energy for emitting light Fabricated on
Is what you do.

As non-single-crystal silicon provided on a substrate, there is amorphous silicon, semi-amorphous silicon, or microcrystalline silicon. In addition, the non-single-crystal silicon film has Si _X C _1-X (0.5 <X <1) and Si ₃ N
_4-X (2 <X <4) may be added.

The present invention provides a light plasma gas phase using a reactive gas having a Si—H bond, typically silane (SiH ₄ , Si ₂ H ₆ ), which is purified by removing oxygenates contained in silane. By a method (referred to as PPCVD), a semiconductor film containing silicon as a main component and having an oxygen concentration of 1 × 10 ¹⁹ atoms / cc or less is obtained.

For this purpose, the Si—H bond is 200
0 to 2200 cm ^-1 (peak value 2100 cm ^-1 ) and 1100 to 800 cm ^-1 (peak value 950 cm
^A gas phase reaction was performed by utilizing the characteristic of selectively absorbing light energy at a wavelength (far infrared light) that resonantly absorbs light at −1,830 cm ⁻¹ ) to provide an amorphous silicon film on the substrate.

Considering that the absorption peak of OH of the oxide gas, water, is in the range of 3000 to 3800 cm ^-1 , the absorption of far-infrared light further includes the largest amount of water as an impurity in silane. It was very effective to make the selection reaction take into account.

For this purpose, far-infrared light having a wavelength of 1500 cm ^-1 or less (1500 to 300 cm ^-1 ) is used for 5 m.
Since a luminous body (ceramic heating element) that emits strong light on W / cm ³ is used, 1100 to 700 c of Si—H is used.
Irradiate light energy with a strong absorption peak of m- ¹ .

Since the Si—H bond cannot be decomposed only by adding the above-mentioned FIR (far infrared light),
In addition, electric energy is added to the reactive gas to generate a plasma reaction by glow discharge. Further, by simultaneously performing the FIR and the plasma reaction, it is possible to form a film with low electric energy, which cannot be conventionally performed by the PCVD method, and therefore, it is possible to reduce spatter (damage) on the surface on which the film is formed. It became. Impedance matching can be achieved even in a wider pressure range, so that the active reactor pressure can be increased in a space where plasma is generated at a higher pressure (1 to 10 torr) and a lower pressure in a space where plasma is generated. have.

More importantly, when the same film growth rate is to be obtained, the plasma energy can be reduced to 1/3 or less of the conventional value, so that the water is hardly decomposed,
As a result, the mixing of oxygen into the silicon film can be reduced to 1/5 or less as compared with the conventional case.

As a result, the deterioration of the electric conductivity, which is called the so-called Steplaronsky effect due to the light irradiation caused by the mixing of oxygen, is reduced, and a high quality coating can be formed.

However, the present inventor has determined that the amount of silicon oxide as an impurity is not sufficient for P or N type using this silane.
PPCVD without addition of pure substance ([photo-plasma gas phase or Photo-Plasma Chemical Va
This is achieved by forming a semiconductor film containing silicon as a main component by a por dipos-tion method, and detecting and identifying the formed silicon film by SIMS (ion micro analyzer). did it. When such identification is performed, a conventionally known PC
In the silicon film obtained by the VD method, oxygen is 2 × 10 ¹⁹ to 1
It contained a concentration of × 10 ²¹ atoms / cc. That is, since the concentration of silicon was 2 × 10 ²² atoms / cc, it was found that oxygen was contained as much as 0.1 to 5%.

Further, the typical bond of Si
Regarding O ₂ , SiO, and SiOH, the ionic strength (count / sec) of the SIMS is, for example, Si
O ₂ 1 × 10 ⁴ , SiO 2 × 10 ² , SiOH 3
× 10 ³ and SiO ₂ were found to be contained in an extremely large amount.

The present invention removes the silicon oxide and reduces the oxygen concentration in the formed semiconductor to a non-crystalline, semi-amorphous (semi-amorphous semiconductor) or non-crystalline containing semi-amorphous structure. 1 × 10 ^{19 in} single crystal silicon
atom / cc or less, preferably 5 × 10 ¹⁷ atom / cc
The purpose is to obtain a semiconductor of less than cc.

On the other hand, a photo CVD method using only discrete light of a 10.6 μm CO ₂ laser is known.
However, while active species can be generated only by light, the reaction space cannot be 100 cm ³ or more, and the formation surface cannot be 1 cm ² or more. The photo-CVD method performed by applying only such a light energy of 10 W / cm ³ or more effectively increases the power consumption ratio required for forming a film, and is not effective in terms of energy saving. Not yet in a very small area such above, the present invention 4225cm is at least a 100-fold or more 100 cm ² or more (Example ²
Of the area), is characterized in that space also 1000 cm ² or more (in this embodiment 105625Cm ²⁾ greatly proposes industrial mass production possible way.

[0020]

[Embodiment 1] This embodiment is particularly applicable to monosilane (SiH ₄ ).
Although the semiconductor device of the present invention is obtained by using only the polysilane, the case where polysilane is used is also possible.

FIG. 1 shows that the reaction system is a CVD method (here, PP is a film forming method for obtaining a semiconductor device of the present invention).
CVD or conventional PCVD is generally referred to as CVD.
This is an outline of an apparatus for performing the method of the present invention.

FIG. 1 shows a reaction system (10) and a doping system (2
0) It has an exhaust system (30). The reaction system (10) has a reaction vessel (2) inner volume (width 90 cm, height 60 cm, depth 90 cm) reaction space (65 cm × 65 cm × 25 cm,
105625 cm ³ ) has a substrate (1) having a surface to be formed.
Is held by the quartz holder (31). Although this holder has a size of 65 cm, it has a size of 20 cm in the flow direction of the reactive gas, and 20 substrates (20 cm × 60 cm) (total area of the formation surface: 24000 cm ² ) were simultaneously inserted.

The substrate is heated to, for example, 200 to 500 ° C. by a halogen auxiliary heater (7). In addition, 110
^{0cm -1 (9.3μm) ~700cm -1 (} 14.3
At the same time, a lamp (9) (maximum 3 KW) for photochemical reaction that emits at an FIR wavelength of μm) is provided. The reactive gas reaches the reaction space (32) from the inlet (11) via the nozzle (3), and reaches the exhaust system (30) from the outlet (12) via the outlet (8). The exhaust system (30) discharges unnecessary substances to the outside from the pressure adjusting valve (13), the stop valve (14), the mechanical booster pump (17), and the rotary pump (18). Further, a back pressure having a system for exhausting by a stop valve (15) and a turbo molecular pump (19) is evacuated by using a turbo molecular pump to make a high vacuum, thereby removing residual oxygen. It was effective to reduce the amount of oxygen in the coating to 1 × 10 ¹⁹ / cc or less. During film formation, the gas may be exhausted by a turbo molecular pump.

The substrate is first placed in the preliminary chamber (16) by a holder, and the vacuum is evacuated by the valve (22) and the vacuum pump (2).
After performing the process in 3), the gate (37) was opened and moved to the reaction space (32). The reactive gas is a doping system (2
In (0), the silane is changed from (26) to other diborane (B ₂
H-type reactive gas such as H ₆ ), N-type gas (24) such as phosphine (PH ₃ ), ammonia or methane for adding nitrogen or carbon to silicon, CF ₃ , B
a gas (25) such as r, CF ₃ H, etc. Hydrogen or helium (27) as a carrier gas is supplied to a flow meter (29), respectively.
And controlled by a valve (28).

FIG. 1 Especially reacts only silane which is a silicide
When it is used as a neutral gas, it reaches the valves (35) and (36) via the pressure adjusting valve (32).

The reactive gas having a Si—H bond for semiconductors made of silane reaches the reaction system (10) via the flow meter (29) via (26). 100 to 5
00 ° C, preferably 200-350 ° C, typically 250
A surface to be formed maintained at a temperature of 0 ° C. was provided. The reaction pressure was set to 0.01 to 10 torr, for example, 1 torr, and the silane flow rate was supplied to 1 to 200 cc / min, for example, 60 cc / min. Irradiation is performed by using six lamps (length: 680 mm, diameter: 11 mm, maximum output: 500 W) (9) (maximum total 3 KW) which emit light energy of FIR (far infrared light) by a ceramic heating element such as zircon ceramic (ZrSiO). Was done.

FIG. 2 shows the emission characteristics (50) of this ceramic heating element. This graph shows that the surface temperature is 510 ° C
However, by setting the temperature higher than that, continuous light having a wave number of 1100 to 700 cm ^-1 could be further emitted. At 200 to 350 ° C., the peak emission shifted to a wave number of 700 cm ⁻¹ or less. Si-
The H bond is 1100-700 cm in this emission spectrum.
^-1 It was found that the wave number of (51) can be completely absorbed to cause infrared excitation of FIR.

Next, electric energy is supplied from a high frequency oscillator (frequency 13.56 MHz) (4) to a pair of electrodes (5),
For example, a power of 180 W was applied to (6) to cause plasma glow discharge to perform a PPCVD reaction.

The substrate position was disposed parallel to the irradiation light, and the photochemical reaction was performed on the reactive gas in flight rather than on the substrate surface. Thus, PPCVD capable of mass production could be performed. Further, when a simple PCVD is performed using this apparatus for comparison, heat energy for heating only electric energy was applied without applying light energy by a FIR lamp. In an embodiment of the device, the substrate is arranged in a positive column region in the generated glow discharge plasma,
For example, a silicon film is formed on a glass substrate by a reaction formula of SiH ₄ →
It was formed on the basis of Si + 2H _2.

This growth rate is 1 in PCVD only.
Å3Å / sec, for example, 1.6Å / sec. Also PPCV
In D, it was 2 to 6 ° / sec, for example, 4 ° / sec.

In the case of PPCVD, the damage caused by plasma is PCV.
When the same electric energy was applied, the film growth rate was 6 to 15 ° / sec, which was lower than that of D, which was 2 to 4 times higher than that of the PCVD method. This P
In the PCVD method, it is extremely important that light irradiation is performed in the process, and thereafter, electric energy is applied to generate plasma. By doing so,
It has the advantage that damage to the substrate surface due to plasma shock waves at the start of discharge can be prevented, and that plasma damage can be substantially prevented electrically.

As described above, the concentration of oxygen containing silicon as a main component shown by the method of the present invention is 1 × 10 ¹⁸ cm ⁻³ or less, that is, less than 1 × 10 ¹⁹ cm ⁻³ , preferably 5 × 10 ¹⁷ cm ^−3.
A non-single-crystal semiconductor having a size of cm ⁻³ or less can be formed over a surface over which a non-single-crystal semiconductor is formed, so that a high-quality semiconductor device can be obtained.

Examination of the film quality of the silicon film revealed that the SIMS measurement showed that the oxygen concentration was 1 × 10 ¹⁸ atom / cc or less (light output: 3.0 kW, discharge output: 180 W). In general, when a silicon film is provided on a glass substrate, oxygen is mixed in from the atmosphere near the surface of the silicon film, so that the oxygen concentration is higher as the surface is closer to the surface. Since oxygen present therein diffuses into the silicon film, the oxygen concentration in the silicon film becomes higher nearer the glass substrate as a result. Therefore, the oxygen concentration in the silicon film has a so-called U-shaped distribution, which is the lowest at the center in the thickness direction of the silicon film and increases toward both ends (the interface between the silicon film surface and the glass substrate).

When the emission power is 180 W, the oxygen concentration is 1 ×
10 ¹⁸ atom / cc or less which was, but when further discharge output to 30 W, and further reduced to 1/3 and 3 × ¹⁰ 17 atom / cc, a PCVD method which is conventionally known, 3 × ¹⁰ 19 atom / Cc or more, and it has been found that this value is reduced to 1/10 or less.

[0035] I was even able to make at 300 ° C. The non-single crystal silicon semiconductor that oxygen can be less than 1 × ¹⁰ 19 ^{cm -3} as nuclear. The substrate temperature is set to 350 ° C.
By setting the temperature to 00 ° C., the crystallinity further advanced.
The temperature for producing this reaction product is not 300 ° C but 150-
It was possible even at 300 ° C.

As the silane, polysilane (for example, Si ₂ H ₆ ) can be used instead of the above-mentioned monosilane.
This polysilane, especially disilane, is at least partially (SiH
₄ / (SiH ₄ + Si ₂ H ₆ ) 5-30%, for example, 15
%), The semiconductor film is formed by the above-mentioned PPCVD method using the silane contained in the film.
/ Sec and about 10 times that of monosilane. Of course, when the polysilane was present at a concentration of 90% or more, the growth rate could be further increased. FIG. 3 shows that a 0.5 μm silicon semiconductor layer is formed on a glass substrate by the PPCVD method (light output: 3.0 kW, discharge output: 30 W), and then an ohmic contact electrode is formed on this portion. Are provided as parallel electrodes, and the electrical conductivity characteristics are examined.

FIG. 3 shows that oxygen of the present invention is 1 × 10 ¹⁹
(56) (64) (65) Electrical characteristics of silicon semiconductor using intrinsic (I-type) silane with only contamination of not more than / cc
(66) (68) Characteristics of Conventional PPCVD Method (5
7) (63), (58), (67), and (69). In the drawing, the region (59) shows the dark electric conductivity (57) in the conventional example and is 3 × 10 ⁻⁸ (Ωcm ⁻¹ ).
Has the value of Here, AM1 (100 mW / c
m ² ) in the region (60), the conventional method has 1 × 10 ⁻⁴ (Ωcm) ^{−1 as} shown by the curve (58), and the value is approximately one digit after continuous irradiation for 2 hours. Had deteriorated.

On the other hand, the oxygen of the present invention is not more than 1 × 10 ¹⁹ / cc.
In the lower silicon semiconductor film , the dark conductivity (56)
5 × 10 ⁻¹¹ (Ωcm) ⁻¹ , and its photoconductivity (64) is 6 × 10 ⁻⁵ (Ωcm) ⁻¹ and 10 ^{6 in} photosensitivity. It turned out to be an order of magnitude larger . This dark conductivity is small and photoconductive
The greater the degree that this semiconductor is extremely resistant to light irradiation
Indicates that electron-hole pairs can be formed with high efficiency.
You. That is, the semiconductor film has high photosensitivity.
Recognize. Further, upon irradiation with continuous light, almost no deterioration of the electric conductivity was observed as shown by a curve (65). As a result, the light degradation is reduced to AM1 (100 mw / c
m ² ), and this oxygen is remarkably bad for property deterioration.
Was found to have a significant effect. Further area (6
In (1), the dark conductivity after the irradiation was the same in the present invention within the range of error as compared with (66) and (56). This means that light irradiation creates new recombination centers.
This indicates that it is unlikely that any 150 ° C
Is performed, the curve (67) changes to (69) in the conventional example, and there is an apparent characteristic change.
When light irradiation was performed again, the deterioration characteristics were observed again. That is, in the conventional example, as described above, the electrical conductivity shows degradation characteristics due to light irradiation. However, in the present invention, the presence or absence of electrical conductivity irradiation, changes in the properties with and without thermal annealing, deterioration was hardly observed, and (the proportion of photoconductivity with respect to dark conductivity) photo sensitivity is 10 ⁶ or more and <br/> could be large. The absolute value of the dark conductivity was small. This
Low dark conductivity of insulating gate type field effect semiconductor
Off current of ^10--11 A or less in equipment
It is important to lower it.

As described above, it has been found that the semiconductor device of the present invention has a highly reliable silicon semiconductor film. This is because the concentration of oxygen as an impurity has decreased,
It is determined that the characteristic deterioration of the PIE has been reduced.

The PIE promoted a decrease in industrial reliability in semiconductor electronics and was extremely harmful. The present invention, in which such deterioration characteristics have been clarified and countermeasures have been taken, can be applied to photoelectric conversion devices, optical sensors, electrostatic copying machines, insulated gate type field effect semiconductors and their integrated devices, and industrially It is determined to be extremely effective. Further, a comparison of characteristics with a conventional example obtained by the apparatus shown in FIG. 1 used for manufacturing the present invention is shown.

FIG. 4 (A) shows a substrate temperature of 250 ° C., a discharge output of 180 W, and a reactive gas introduction amount of 1.
0cc / min (41) (43) 60cc / min (42) (4
0). Curves (43) and (42) are conventional PCV
It was obtained by Method D. FIG. 1 (40) (4)
1) was obtained by a PPCVD method to which FIR (output 3 kW, 28 mW / cm ³ ) was added. This output is 5
When it is set to mW / cm ³ or less, the effect of photoexcitation is reduced, and therefore, it is preferable that it is at least 5 mW / cm ³ or more.

As apparent from the drawing, in the PCVD method, the film growth rate was increased, and as a result, the effective utilization rate of the reactive gas was improved. Furthermore, the region where the pressure is high (1 to
(rr or more), a film cannot be formed by the conventional PCVD method. On the other hand, in the PPCVD method used in this example, a sufficient film growth rate could be obtained even at 1 to 10 torr.

FIG. 4 (B) shows the relationship between the discharge output and the pressure inside the reactor (areas surrounded by curves) (44), (45) and 4 ° / The portion where the second film (46) is formed is shown. Drawing of conventional PCVD
The curve (44) is obtained by the method.
In the PCVD method, as shown in the curve (45), even more importantly on the high pressure side, a sufficient film could be obtained even at a low discharge output. In addition, a region (4) of 4 ° / sec or more, which cannot be obtained by the PCVD method, can be obtained in a large range. It was possible to reduce the amount and increase the effective utilization rate of the reactive gas introduced into the reactor (yield, ie, silicon adhered to the coating / silicon introduced). And, it is possible to increase from 2 to 5% in the PCVD method to 10 to 20%. The output of the FIR used in this example was 3 KW, which was 28 mW / cm ³ per unit space. However, it is effective to increase the output to 50 to 500 mW / cm ³ to further enhance the effect of FIR and reduce the plasma reaction as silicon so as not to damage the surface to be formed. In the examples in this specification, a non-single crystal formed at 100 to 350 ° C., particularly an amorphous or silicon semiconductor mixed with hydrogen or a halogen element is described. However, if this temperature is 400-60
Needless to say, the temperature may be set to 0 ° C. and a polycrystalline silicon semiconductor may be used for a VLSI (Large Area Integrated Circuit).

When a film is formed by the method of the present invention, Mo
In Example 1, it is possible to simultaneously add Cl ₅ and WF ₅ to produce a texture metal containing silicon as a main component such as MoSi ₂ or WSi ₂ .

In this specification, a semiconductor film containing silicon as a main component is shown. Since this semiconductor film has a strong absorption peak of amine (NH ₂ ) at 700 to 900 cm ⁻¹ , methane or ammonia is simultaneously introduced, and Si _X C _1-X (0.5 <x <
_{1), Si 3 N 4-} X (2 < making a non-single-crystal semiconductor carbon or nitrogen is added represented by x <4) is effective.

In the description above, Si-H is mainly shown. However, Si-F is 900 to 1150 cm ^-1 and Si
-Cl is 900 to 750 cm ^-1 , Si-Br is 500
750 cm ^-1 , Si-I 500-300 cm ^-1
Each have a strong absorption peak. Therefore, needless to say, PPCVD can be performed very effectively even when these silicon halide gases are used in the method of the present invention.

[0047]

According to the present invention, the oxygen concentration in the semiconductor film is reduced to 1
By setting it to less than × 10 ¹⁹ / cc, a semiconductor device excellent in electrical stability and reliability could be obtained.

[Brief description of the drawings]

FIG. 1 shows an outline of a gas phase chemical reaction apparatus used to obtain the present invention.

FIG. 2 shows the far-infrared light emission characteristics and S used in the present invention.
It is an infrared absorption characteristic of iH bond.

FIG. 3 shows electrical conductivity characteristics obtained by the present invention and a conventional example.

FIG. 4 shows characteristics of a film formed by a conventionally known plasma vapor deposition method and a light plasma vapor deposition method used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Reaction system 20 Doping system 30 Exhaust system 9 Lamp for photochemical reaction 5, 6 A pair of electrodes 32 Reaction space 1 Substrate 31 Substrate holder

Claims (1)

(57) [Claims] 1. The method of claim 1 wherein the hydride or halide of silicon
Responsive gas having a wave number of 1500 to 300 cm ^-1
Irradiates continuous light and supplies electrical energy to
Producing a film containing silicon as the main component by causing a zuma reaction
A method for producing a coating film, comprising: