JPH021366B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a semiconductor device such as a field effect thin film transistor, and more particularly to a semiconductor device whose main portion is composed of a polycrystalline silicon thin film semiconductor layer. Recently, scanning circuit parts of image reading devices such as long one-dimensional photo sensors and large-area two-dimensional photo sensors, liquid crystals (abbreviated as LC), and electrochromic materials (abbreviated as EC) have recently been developed for image reading. ) Alternatively, as the area of image display devices using electroluminescent materials (abbreviated as EL) becomes larger, it is becoming possible to form the drive circuit portion of an image display device using a silicon thin film formed on a predetermined substrate. Proposed. It is desired that the silicon thin film to be fitted be polycrystalline rather than amorphous in order to realize larger image reading devices and image display devices with higher speed and higher functionality. One of the reasons for this is that, for example, the value representing the performance of the silicon thin film, which is the material for forming the scanning circuit section of the high-speed, high-performance reading device and the drive circuit section of the image display device, is as follows.
effective carrier mobility of TFT
(mobility) μeff is required to be large, but in amorphous silicon thin films obtained by ordinary discharge decomposition methods, it is at most about 0.1 cm ² /V・sec, and when made from single crystal silicon. They are far inferior to MOS transistors and do not meet the desired requirements. This small mobility μeff is due in part to the small Hall mobility, which is a characteristic unique to amorphous silicon thin films. It has the inherent inconvenience that it cannot be cut. Furthermore, amorphous silicon inherently suffers from changes over time and is inferior to single crystal silicon. On the other hand, the Hall mobility of polycrystalline silicon thin films is larger than that of amorphous silicon thin films based on actual measured data, and the mobility μeff when made into a thin film transformer is much larger. Specifically, there is a possibility that a device having a mobility μeff even larger than the value currently obtained can be created. It is also expected to be stable with respect to changes over time. CVD (Chemical Vapor Deposition) method,
LPCVD (Low Pressure Chemical Vapor)
Deposition method, MBE (Molecular Beam)
Epitaxy) method, IP (Ion Plating) method, GD (Glow
Discharge) law etc. are known. In either method, although the substrate temperature is different, it is known that a polycrystalline silicon thin film can be produced on a large-area substrate. However, the current situation is that semiconductor elements or semiconductor devices whose main parts are formed from polycrystalline silicon thin film semiconductor layers conventionally produced by these methods cannot sufficiently exhibit desired characteristics and reliability. The present invention has been made in view of the above points, and as a result of intensive studies, the stability of the performance and characteristics of a semiconductor element or semiconductor device whose main part is composed of a polycrystalline silicon thin film semiconductor layer is as follows: (1) Polycrystalline silicon This is based on the finding that the amount of hydrogen atoms contained in a thin film (2) and the etching speed of the film are correlated.
In other words, it is important that the formed semiconductor layer contains hydrogen atoms in a certain amount range, and that the etching rate for a specific etching solution is below a certain value, which improves the stability of device characteristics, μeff, and characteristics over time. improved, exhibiting extremely excellent usage characteristics in practical use,
It has been discovered that when designing a device, variations in the characteristics of each element can be substantially eliminated, and practicality can be dramatically improved. The object of the present invention is to improve the device characteristics, μeff
The technology has been dramatically improved compared to conventional semiconductor devices whose main parts are made of polycrystalline silicon thin-film semiconductor layers, and the device characteristics have virtually no change over time, resulting in semiconductor devices that exhibit extremely excellent usage characteristics. It is to provide. The semiconductor device of the present invention contains hydrogen atoms of 3 atomic% or less, and has a mixing ratio of hydrofluoric acid (50 vol% aqueous solution):nitric acid (d=1.38, 60 vol) at a volume ratio of 1:3:6.
% aqueous solution): The main part thereof is composed of a polycrystalline silicon thin film semiconductor layer having a characteristic that the etching rate with an etching solution consisting of glacial acetic acid is 20 A°/sec or less. In addition, the diffraction intensity of the X-ray diffraction pattern or electron beam diffraction pattern (220) of the polycrystalline silicon thin film is 30% or more of the total diffraction intensity, or the average crystal grain size (average grain size) of the polycrystalline silicon thin film is ) is 200A° or more, the object of the present invention can be achieved even more effectively. A field effect thin film transistor (FE-TFT) is an example of a semiconductor device manufactured using a polycrystalline silicon thin film having such H content and surface roughness. hold voltage,
LC, EL or
Scanning circuits and drive circuits for display or image devices using EC or the like can be stably provided. In the present invention, various transistor characteristics can be improved by controlling the amount of H contained in the polycrystalline silicon thin film to 0.01 atomic % or more. The H contained in the polycrystalline silicon thin film is
It mainly exists in polycrystalline silicon grain powder and is bonded to Si atoms in the form of Si-H, but Si=
It is expected that it also contains bonded forms such as H ₂ and Si≡H ₃ as well as free hydrogen, and due to these hydrogens contained in an unstable state, their properties change over time. However, based on the inventors' many experimental facts, at an H amount of 3 atomic% or less, there is almost no deterioration of transistor characteristics over time, and the characteristics are stably maintained. It has been observed that this is possible. That is,
For example, when the H amount exceeds 3 atomic%, when the transistor is operated continuously as described above, the effective carrier mobility decreases, the output drain current decreases over time, and the threshold voltage changes. A change over time was observed. In the present invention, the amount of H is 0.01 to 3 atomic%
However, it is preferably about 0.5 to 2 atomic %, most preferably about 0.1 to 1 atomic %. The amount of hydrogen contained in the polycrystalline silicon thin film specified in the present invention can be measured by using a hydrogen analyzer (Model-240 elemental analyzer manufactured by Perkin Elmer), which is normally used for chemical analysis. total)
I went there. In each case, 5 mg of the sample was loaded into an analyzer holder, the hydrogen weight was measured, and the amount of hydrogen contained in the film was calculated in atomic %. Micro-quantity analysis of 0.1 atomic% or less is performed using a secondary ion mass spectrometer - SIMS - (Model IMS - manufactured by Cameca).
3t). This analytical method followed a conventional method. That is, gold was deposited to a thickness of 200 Å on the thin film to prevent charge up, the ion energy of the primary ion beam was 8 KV, the sample current was 5 × 10 ^-10 A, the spot size was 50 μm in diameter, and the etching area was 250 × 250 μm. Find the detection intensity ratio of H ⁺ ions to ⁺ and calculate the hydrogen content.
Calculated as atomic%. Conventionally, when polycrystalline silicon thin films are formed at low temperatures below 700°C, desired performance such as μeff and stability as a TFT has not been achieved.
It was found that high-performance TFTs can be provided if the film satisfies the hydrogen content and etching rate. Desirable substrate materials include polycrystalline silicon thin films for forming the semiconductor layer of TFT elements that constitute the scanning circuit section, drive circuit section, and front section of the image reading device or display device, as well as inexpensive materials such as glass and ceramics. The polycrystalline silicon thin film according to the present invention satisfies this requirement and has been highly desired industrially.
It provides TFT. In the present invention, as disclosed, in particular, a method of glow discharge decomposition of gases of hydrogenated silicon compounds;
In the silicon sputtering method, ion plating method, and ultra-high vacuum evaporation method in an H ₂ atmosphere, polycrystalline silicon that can meet the purpose of the present invention when the substrate surface temperature is 500°C or less (in the range of about 350 to 500°C) is used. It is possible to form silicon thin films. This fact is not only advantageous in terms of uniform heating of the substrate and inexpensive large-area substrate materials in the production of large-area drive circuits and scanning circuits for large-area devices, but also in the production of large-area drive circuits and scanning circuits for large-area devices. Transparent glass substrates are often desired in image device applications such as substrates and substrate-side incident type photoelectric conversion light-receiving elements, and are important as they can meet this demand. Therefore, according to the present invention, since it is possible to operate in a lower temperature range compared to the conventional technique, heat-resistant glasses such as high melting point glass and hard glass, heat-resistant ceramics, Sahuaiyah,
In addition to spinel, silicon wafers, etc., general low-melting glass, heat-resistant plastics, etc. may also be used. Examples of the glass substrate include ordinary glass with a softening point of 630°C, ordinary hard glass with a softening point of 780°C, and superhard glass (JIS 1st grade superhard glass) with a softening point of 820°C. In the examples of the present invention, Corning #7059 glass among ordinary glass (soda glass) with a low softening point was used as the substrate glass, but it is also possible to use quartz glass or the like with a softening point of 1500°C as the substrate. . However, from a practical point of view, using ordinary glass is advantageous in manufacturing thin film transistors over a large area at low cost. Although the amount of hydrogen contained in the polycrystalline silicon thin film semiconductor layer formed in this way varies depending on the formation conditions, formation procedure, and formation method, the amount of hydrogen contained in the polycrystalline silicon thin film varies. In order to clarify the relationship between this and the characteristics of a TFT as an example of a semiconductor device, we measured the amount of hydrogen contained in polycrystalline silicon thin films formed under various production conditions, and compared samples with different amounts of hydrogen. As a result of fabricating and examining TFTs each having a semiconductor layer, it was found that the amount of hydrogen in the thin film is particularly preferably 3 atomic % to 0.01 atomic %. In the X-ray diffraction or electron diffraction pattern of the polycrystalline silicon thin film semiconductor layer constituting the main part of the semiconductor device of the present invention, the diffraction intensity from the (220) plane is different from the diffraction intensity from all plane indices (total diffraction intensity). )
By setting the average grain size to 30% or more and having an average crystal grain size of 200 Å or more, the object of the present invention can be achieved more effectively. According to the present inventors, it has been confirmed that the amount of hydrogen contained in a polycrystalline silicon thin film varies greatly depending on the film formation method and film formation conditions. For example, when creating a film by glow discharge of silane,
The amount of hydrogen contained in the film varies depending on discharge power, pressure, substrate temperature, gas flow rate, degree of dilution of source gas such as silane, type of diluent gas, and the like. Next, we will discuss in detail the correlation between the etching rate of polycrystalline silicon thin films and the characteristics of TFTs. The present inventors have confirmed that the film etching rate used to evaluate the polycrystalline silicon thin film that constitutes the main part of the semiconductor device of the present invention is an important measurement quantity that indicates film quality and film density. It was done. The etching solution used to define the etching rate in the present invention is a typical etching solution for silicon crystals. A mixed solution of hydrofluoric acid, nitric acid, and acetic acid was used. The mixed solution is hydrofluoric acid (50 vol% aqueous solution), nitric acid (d=1.38,
The etching rate when etching a silicon wafer with a composition ratio of 1:3:6 and ρ = 0.3Ω cm is 15 Å/sec. (However,
Etching temperature is 25℃). The above acids are commonly commercially available chemicals for the electronic industry and are easily available. It is known that the etching rate of a polycrystalline silicon thin film varies depending on film formation conditions, and the inventors have confirmed that the etching rate of the above-mentioned etching composition varies over a range of 15 Å/sec to 80 Å/sec. Therefore, we fabricated TFTs using various polycrystalline silicon thin films with different etching rates as semiconductor layers, and investigated the correlation with the etching rate, and found that the preferable film etching rate for TFT characteristics is 20 Å/sec or less. found. The crystallinity of polycrystalline silicon thin films depends on the film preparation method,
It is known that various films can be obtained depending on the film formation conditions. In the present invention, the orientation was examined using X-ray diffraction and electron beam diffraction. The X-ray diffraction intensity of each polycrystalline silicon film created
Measurements were made using an X-ray diffractometer manufactured by Rigaku Electric Co., Ltd. (copper tube 35 kV 10 mA), and comparisons were made.
The diffraction angle 2θ was varied from 20° to 60° (111),
The diffraction peaks of (220) and (311) were detected, and the ratio was determined from the diffraction intensity and used as an index. At the same time, the electron beam diffraction intensity was measured using a JEOL microscope (JEM-
100U) was read from the difference in diffraction intensity in the electron beam diffraction pattern, and the ratio of the diffraction intensities was determined. According to the ASTM card (No. 27-1402, JCPDS1977), in the case of a polycrystalline silicon thin film with no orientation, the surfaces (h, k, l) with high diffraction intensity are expressed as (111): (220): (311). = 100:55:30 (220)
The ratio to the total diffraction intensity, that is, the diffraction intensity of (220)/(total diffraction intensity) is approximately (55/250) x 100 = 22%. Based on this value, those with a large value of good orientation, especially those with a value of 30% or more, exhibit better transistor characteristics, while those with a value of less than 30% are undesirable because of large changes over time. In the present invention, the optimum ratio is preferably 50% or more. Furthermore, it was found that as the H content and surface roughness of the polycrystalline silicon thin film were satisfied and the average crystal grain size (average grain size) increased, transistor characteristics, particularly effective carrier mobility, improved. The value of the average grain size was determined from the half-value width of the (220) peak of the above-mentioned X-ray diffraction pattern by the commonly used Scherrer method. Effective carrier mobility is particularly improved when the average grain size is 220 Å or more. Particularly optimally, 300 Å or more is desirable. In the present invention, as described above, in the case of a film thickness of about 3.000 Å to 1 μm, information can be properly obtained at this thickness. The grain size of the polycrystalline silicon thin film was determined from the half width of the diffraction peak of X-ray diffraction, and at the same time, films with a thickness of 3000 Å or less were also examined using a transmission electron microscope. Next, a process for manufacturing a TFT as an example of the semiconductor device of the present invention will be explained with reference to FIG. The TFT includes a semiconductor layer 101, an electrode layer 107, ohmic contact layers 103 and 104, and an insulating layer 4.
05, a source electrode 108 and a drain electrode 109 are adjacent to the semiconductor layer 101 and have an ohmic contact formed therein.
A voltage is applied between the insulating layer 1 and the current flowing therein.
05 (the structure is shown in step (g) of FIG. 1). First, after cleaning the substrate 100, a polycrystalline silicon thin film 101 is deposited thereon [step (a)]. Details of the deposition method will be described in each example. After that, as an ohmic layer
After an n ⁺ (P-doped silicon) layer 102 is deposited and a source and drain are formed by etching [step (c)], an insulating layer 105 is deposited thereon [step (a)]. The insulating layer is made of a material such as silicon nitride SiO ₂ or Al ₂ O ₃ formed by CVD or LPCVD. Next, contact holes 106 for the source and drain electrodes are opened [step (e)], and the upper electrode gate, source and drain are wired [step (f) and
(g)〕Complete. The following method was used to measure changes over time to determine the stability of the polycrystalline silicon thin film transistor of the present invention. A TFT with the structure shown in the following figure 2 was fabricated, and the gate 20
1, a gate voltage, V _D = 40 V, and a drain voltage, V _D = 40 V, are applied between the source 203 and the drain 202, and the drain current I _D flowing between the source 203 and the drain is measured using an electrometer 208 (Keithley).
610C electrometer) to measure the temporal change in drain current. The rate of change over time is
The amount of variation in drain current after 500 hours of continuous operation was divided by the initial drain current, multiplied by 100, and expressed as a percentage. The threshold voltage of the TFT was defined by the point where the straight line portion of the V _D −√ _D curve, which is usually done for MOSFETs, was extrapolated and intersected with the horizontal axis. Changes in V _TH before and after the change over time were also examined, and the amount of change was expressed in volts. Next, examples of the present invention will be described. Example 1 In this example, a polycrystalline silicon thin film was formed on a substrate by a glow discharge decomposition method, and a TFT was created using it.
The device shown in the figure was used. Board 300
Corning glass #7059 (0.5 mm thick) was used. First, after cleaning the substrate 300, HF/HNO ₃ /
After lightly etching the surface with a CH ₃ COOH mixture and drying, a substrate heating holder (area
452cm ² )302. Thereafter, the Belgear 301 was evacuated to a background vacuum of 2.0×10 ^-6 Torr or less using a diffusion pump 309. At this time, care must be taken because if the degree of vacuum is low, not only will the reactive gas not work effectively for film deposition, but also O and N will be mixed into the film, significantly changing the resistance of the film. Next, the temperature of the substrate 300 was maintained at 500℃ by increasing T _s (the substrate temperature was
3). Next, while controlling the H ₂ gas with the mass flow controller 308,
1 to clean the surface of the substrate 300, and then the reactive gas was introduced. Substrate temperature
T _s was set at 350°C. Belgear 30 during discharge
The pressure inside 1 was maintained at Torr. In this example, the reactive gas introduced was diluted to 3 vol% with easily handled _H2 gas.
SiH ₄ gas (abbreviated as SiH ₄ (3)/H ₂ ) was used.
The gas flow rate was controlled by a mass flow controller 304 so that it was 5 SCCM.
The pressure inside the bell gear 301 was set to a desired pressure by adjusting the pressure regulating valve 310 on the exhaust side of the bell gear 301 and using the absolute pressure gauge 312. After the pressure inside the bell jar 301 stabilizes, a 13.56MHz high frequency electric signal is applied to the cathode electrode 313 from the power source 314.
was added to start a glow discharge. At this time, the voltage was 0.7KV, the current was 60mA, and the RF discharge power was 20W. Under these conditions, the discharge was continued for 60 minutes, and after the formation of the polycrystalline silicon film was completed, the discharge was stopped and the inflow of the source gas was also stopped. Next, the substrate temperature was lowered to 180°C and maintained in preparation for the next process. The silicon film deposition rate under this condition is 0.9
It was Å/sec. The thickness of the formed film is 3000Å
When a circular ring-shaped outlet was used, the uniformity was within ±10% for a substrate size of 3 inches by 3 inches. Further, this polycrystalline silicon film was of n-type and had a resistance value of ~10 ⁷ Ω·cm. Next, using this film, a thin film transistor (TFT) was fabricated according to the process shown in Figure 1. In order to achieve good ohmic contact between the source and drain of the TFT, the n ⁺ silicon layer was formed as follows while keeping the substrate temperature at 180°. 100vol with hydrogen gas
PH ₃ gas diluted to ppm (PH ₃ (100ppm)/
(abbreviated as _H2 ) was diluted to 10 vol% with _H2 .
For SiH ₄ (abbreviated as SiH ₄ (10)/H ₂ ) gas,
Bergier 301 at a mol ratio of 5×10 ^-3
The pressure inside the bell gear 301 is
Step (b) in which the P-doped n ⁺ layer 102 was formed to a thickness of 500 Å by performing glow discharge at a pressure of 0.12 Torr. Next, Al was deposited, and then, as in step (c), Al and the n ⁺ layer 102 were removed by photoetching except for the source electrode 103 region and the drain electrode 104 region. Next, in order to form a gate insulating film, the above-mentioned substrate was again loaded into the heating holder 302 on the anode side inside the bell jar 301. As in the case of manufacturing polycrystalline silicon, the Bergier 301 was evacuated and the substrate temperature _T3 was set at 250°C.
Introduce 20 SCCM of NH ₃ gas and 5 SCCM of SiH ₄ (SiH ₄ (10)/H ₂ ) gas to generate glow discharge.
The SiNH film 105 was deposited to a thickness of 2500 Å. Next, the source electrode 1 is etched by a photo-etching process.
03. Drill contact holes 106-1 and 106-2 for the drain electrode 104, and then SiNH
After forming an electrode film 107 by vapor depositing Al on the entire surface of the film 105, the Al electrode film 107 is processed by a photoetching process to form the source electrode extraction electrode 10.
8. A drain electrode extraction electrode 109 and a gate electrode 101 were formed. After this, in _H2 atmosphere
Heat treatment was performed at 250℃. TFT formed according to the above conditions and process (channel length L = 20μ,
The channel width W = 650 μ) was stable and showed good characteristics. Figure 4 shows an example of the characteristics of the TFT prototyped in this manner. Figure 4 shows the relationship between drain current I _D and drain voltage V _D using gate voltage V _G as a parameter.
Examples of TFT characteristics are shown. The gate threshold voltage is as low as 5V, and V _G = 0 at V _G = 20V.
The ratio of current values is said to be three digits or more. TFT
The results of measuring the amount of hydrogen in the polycrystalline silicon thin film used to create the polycrystalline silicon thin film and the mixed solution (mixing ratio,
Table 1 shows the results of examining the etching rate using hydrofluoric acid: nitric acid: glacial acetic acid = 1:3:6). Regarding the substrate temperature Ts, the results are shown when only the substrate temperature was changed between 500° C. and 450° C. and 400° C., and other conditions were kept the same. The effective mobilities (μeff) of TFTs fabricated using these polycrystalline silicon thin films are also shown in the table. A film with a high substrate temperature of Ts = 500°C has a small hydrogen content of 0.5 atomic% and an etching rate of 15 Å/sec, and the μeff of a TFT made using this film is 8 cm ² /v.sec. Good characteristics with no change over time were obtained. In this example, Corning #7059 glass was used as the substrate, but similar characteristics could be achieved by using ultra-hard glass or quartz glass as the substrate even if the heat treatment temperature and substrate temperature were increased. Therefore, according to the present invention, the substrate temperature Ts can be freely selected from a wide range from a low temperature side to a high temperature side, depending on the substrate material, and because there is a remarkable degree of freedom in selecting the substrate material, it is possible to achieve excellent characteristics. A TFT storage circuit can be easily produced at a lower cost and using a simpler device.

[Table] Example 2 Using the same procedure as in Example 1, the substrate temperature Ts for glow discharge decomposition of a polycrystalline silicon film was set to 400, 450,
500℃, RF discharge power 50W, silane gas (SiH ₄ (3)/H ₂ ) flow rate 10SCCM, and pressure
Table 2 shows the relationship between the characteristics (μeff) of the TFT made from the TFT after forming it at a constant value of 0.05 Torr, the amount of hydrogen in the material, the etching rate, and the orientation.

[Table] Example 3 Using the same procedure as in Example 1, a polycrystalline silicon film was decomposed by glow discharge at a substrate temperature Ts of 400, 450,
The temperature was changed to 500℃, the discharge power was 100W, the silane gas (SiH ₄ (3)/H ₂ ) flow rate was 10SCCM, and the pressure was
Table 3 shows the relationship between the characteristics (μ _eff ) of the TFT made from the TFT formed at a constant 0.05 Torr, the hydrogen content of the material, the etching rate, and the orientation.

[Table] The characteristics of the above transistor are as follows:
℃ (sample No. 3-3), μ _eff = 5.5, showing good characteristics with no change over time. Example 4 An equivalent Corning glass substrate 300 prepared in the same manner as in Example 1 is tightly fixed to the substrate heating holder 302 on the upper anode side in the bell gear 301, and placed on the electrode plate of the lower cathode 313 facing the substrate. Polycrystalline silicon plate (not shown:
99.99%) was allowed to stand still. The bell jar 301 was evacuated to 2×10 ^-6 Torr using a diffusion pump 309, and the substrate heating holder 302 was heated to maintain the surface temperature of the substrate 300 at 450°C. Next, high-purity _H2 gas was introduced into the 0.5SCCM bell jar using the mass flow meter 308, and then Ar/He gas was introduced into the 0.5SCCM bell gear.
A mixed gas (5/95 ratio by volume) was introduced into the bell gear 301 at a flow rate of 50 SCCM by the mass flow meter 307, and the main valve 310 was throttled to set the internal pressure of the bell gear to 0.05 Torr. After the internal pressure of the bell gear is stabilized, 1.5VK is applied to the lower cathode electrode 313 by the 13.56MHz high frequency power supply 314 to connect the crystal silicon plate on the cathode 312 and the anode (substrate heating holder) 3.
Glow discharge was generated during 02 hours. The RF discharge power (forward wave - reflected wave) was 120. Under these conditions, the growth rate of the silicon film is 0.2 Å/sec, which is 4
A film of approximately 0.3μ was formed by growing for a period of time. The amount of H contained in the silicon layer was 0.5, and the etching rate was 19 Å/sec. Subsequently, a TFT was produced by the same steps ((a) to (g)) as in Example 1. The effective mobility of this element is 1.0 (cm ² /v.sec), V _G = 40V, V _D =
The changes in I _D and V _th were measured under the condition of 40V, but the
I _D was 0.1% or less, V _th remained unchanged over time, and the DC operating characteristics over time were good. Example 5 A Corning 7059 glass substrate 500 prepared in the same manner as in Example 1 was loaded into a substrate holder 502 in an ultra-high vacuum chamber 501 whose pressure was reduced to 2×10 ^-11 Torr, and the pressure in the vacuum chamber was reduced to 5×10 After reducing the pressure to ^-11 Torr or less, the substrate temperature was set at 350°C using a tantalum heater 503 (see Figure 5). Next, the electron gun 504 is operated at an accelerating voltage of 8KV,
The emitted electron beam is irradiated onto the silicon evaporator 405 to evaporate the silicon evaporator, and then the shutter 507 is opened and the film is controlled by the crystal oscillator film thickness meter 506 so that the film thickness is 0.5μ on the substrate 500. A crystalline silicon film was formed. At this time, the pressure during deposition was 1×10 ^-9 Torr, and the deposition rate was 1.4
Å/sec (Sample No. 5-1). On the other hand, the cleaned Corning 7059 glass substrate is again fixed on the substrate holder 502, and after the pressure inside the vacuum chamber 501 is reduced to 5×10 ^-11 Torr or less, high purity hydrogen gas (99.9999%) is pumped through a variable leak valve. 508 into a vacuum chamber, and the pressure inside the chamber 501 was set to 5×10 ⁻¹¹ Torr. The substrate temperature was set at 400°C, and the electron gun 504 was controlled so that the deposition rate was 1.0 Å/sec to form a 0.5 μ thick polycrystalline silicon thin film (Sample No. 5-
2). Table 4 shows the amount of hydrogen, etching rate, orientation, and effective mobility μ _eff of TFT prepared by the same process as in Example 1 for Samples No. 5-1 and No. 5-2. .

[Table] As can be seen from Table 4, both sample Nos. 5-1 and 5-2 had almost the same etching rate and orientation, and were good. The effective mobility (μ _eff ) is more than one order of magnitude larger in sample No. 5-2 than in sample No. 5-1.
It was found that the thin film of sample No. 5-2 was more preferable as a semiconductor layer for TFT. Example 6 An example in which a polycrystalline silicon thin film was produced using the ion plating deposition apparatus shown in FIG. 6 of the present invention, and a thin film transistor was produced using the thin film as a material will be described below. First, a non-dope is placed in the deposition chamber 603 which can be depressurized.
A silicon evaporator 606 of polycrystalline silicon is placed within the board 207, a Corning #7059 substrate is mounted on the support, and a base pressure of approximately 1 is maintained in the deposition chamber.
After exhausting to a pressure of ×10 ⁻⁷ Torr, H ₂ gas with a purity of 99.999% was introduced into the deposition chamber through the gas introduction pipe 505 so that the hydrogen partial pressure P _H became 1×10 ⁻⁴ Torr. The gas introduction pipe 505 used has an inner diameter of 2 mm.
There is a 2cm gas outlet in the loop-shaped part at the end.
I used one with holes of 0.5 mm at intervals. Next, the high frequency coil 610 (diameter 5 mm)
A high frequency of 13.56 MHz was applied and the output was set to 100 W to form a high frequency plasma atmosphere inside the coil. On the other hand, while the supports 611-1 and 611-2 are being rotated, the heating device 612 is put into operation and the heating device 612 is turned on.
It was heated to 475°C. Next, the evaporator 606 was irradiated with an electrogun 608 to cause the heated silicon particles to fly.
The power of the electrogun at this time is approximately 0.5KW
It was hot. In this way, a 5000 Å thick polycrystalline silicon thin film was formed in 50 minutes. Using this thin film, a thin film transistor was fabricated using the same process as in the previous example. The table below shows the amount of hydrogen contained in the film, the etching rate of the film, and the effective mobility of the thin film transistor in this example. At the same time, data for the case where the hydrogen partial pressure was 4×10 ^-4 Torr and the case where the film was formed without introducing hydrogen were also shown.

[Table] Current change (change over time) after continuous application of drain voltage V _D and gate voltage V _G of 40 V in a transistor formed with a hydrogen partial pressure of P _H2 = 1 × 10 ^-4 Torr
It exhibited excellent transistor characteristics with no loss of energy and a mobility of 2.4. On the other hand, when the amount of hydrogen is large, the change over time is large, and when the amount of hydrogen is small, the mobility is small.

[Brief explanation of drawings]

FIG. 1 is a schematic process diagram illustrating the steps for manufacturing the semiconductor device of the present invention, and FIG. 2 is an explanatory diagram schematically showing a circuit for measuring the characteristics of the semiconductor device of the present invention. FIG. 3, FIG. 5, and FIG. 6 are schematic explanatory diagrams for explaining an example of the semiconductor film manufacturing apparatus according to the present invention, and FIG. 4 is a diagram showing the V _D -I _D characteristics of the semiconductor element of the present invention. It is an explanatory diagram showing an example. 100...Substrate, 101...Semiconductor layer, 102
... Electrode layer, 105 ... Insulating layer.

Claims (1)

[Claims] Hydrofluoric acid (50 vol% aqueous solution): Nitric acid (d=1.38, 60 vol% aqueous solution): Ice, containing 1.3 atomic% or less hydrogen atoms and having a mixing ratio of 1:3:6 by volume. The etching speed with etching solution consisting of acetic acid is
A semiconductor device characterized in that its main part is composed of a polycrystalline silicon thin film semiconductor layer having a characteristic of 20 A°/sec or less. 2. The semiconductor device according to claim 1, wherein the ratio of the diffraction intensity of (220) to the total diffraction intensity according to the X-ray diffraction pattern or the electron beam diffraction pattern of the semiconductor layer is 30% or more. 3. The semiconductor device according to claim 1, wherein the average crystal grain size of the semiconductor layer is 200 A° or more. 4. The semiconductor device according to claim 1, wherein the semiconductor layer is formed on a glass substrate.