JPH0396279A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a simple method which completely eliminates a defect due to damage by a plasma and whose mass production operation is easy while an effect to enhance a TFT characteristic is being secured by a method wherein a semiconductor device in which at least one part of a channel region of a field-effect transistor is composed of a non-single-crystal semiconductor is put in an atmosphere in which hydrogen gas has been decomposed by an optical pumping method. CONSTITUTION:In a manufacturing method of a semiconductor device in which at least one part of a channel region of an insulated-gate field-effect transistor is composed of a non-single-crystal semiconductor, at least a process to put the semiconductor device in an atmosphere in which hydrogen gas has been decomposed by an optical pumping method is included. For example, a non-singlecrystal silicon thin film 1-2 is formed on an insulating amorphous material 1-1 ; a gate oxide film 1-4 is formed by a thermal oxidation method; after that, a gate electrode 1-5 is formed; a source region 1-6 and a drain region 1-7 are formed. Then, an interlayer insulating film 1-8 is deposited; a heat treatment is executed; after that, hydrogen gas is decomposed by an optical pumping method; a hydrogen radical 1-9 whose activity is high is formed; a hydrogenation treatment is executed; then, contact electrodes 1-10 in the source region and the drain region are formed.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a thin film transistor manufactured using a non-single crystal semiconductor thin film formed on a non-quality insulating substrate or insulating film such as an insulating transparent substrate. Related to methods for manufacturing thin film semiconductor devices such as. [Prior Art] Many dangling bonds exist in non-single crystal semiconductor thin films such as amorphous silicon thin films or polycrystalline silicon thin films. For example, in polycrystalline silicon thin films, defects such as dangling bonds that exist at grain boundaries become trap levels for carriers and act as barriers to carrier conduction. (J.Y.W.
Se. to, J. AppI. Phys.
, 46, p5247 (1975)). Therefore,
In order to improve the performance of polycrystalline silicon thin film transistors, it is necessary to reduce the defects mentioned above. (J.
Appl. Phys. , 53 (2
), pll93 (1982)). For this purpose, the defects are terminated with hydrogen, and the main methods include hydrogen plasma treatment, hydrogen ion implantation,
Alternatively, a method of hydrogen diffusion from a plasma nitride film is known. [Problem M to be solved by the present invention] However, the hydrogen ion implantation method has the drawback of requiring an expensive device called an ion implanter, and the hydrogen ion diffusion method from the plasma nitride film However, this method has the disadvantage that an unnecessary nitride film is deposited. Furthermore, the hydrogen plasma treatment method causes damage due to plasma damage, making mass production difficult. Therefore, the present invention secures the effect of improving TPT characteristics while
The purpose is to eliminate the defects caused by the plasma damage mentioned above, and to provide a simple method that can be easily mass-produced. [Means for Solving the Problems] The semiconductor device of the present invention has the following features. (1) A method for manufacturing a semiconductor device in which at least a portion of the channel region of an insulated gate field effect transistor is made of a non-single crystal semiconductor, including at least the step of immersing the semiconductor device in an atmosphere in which hydrogen gas is decomposed by a photoexcitation method. have. (2) In a method for manufacturing a semiconductor device in which at least a part of the channel region of an insulated gate field effect transistor is semi-exclusively made of a non-single crystal, the method includes immersing the semiconductor device in an atmosphere in which a gas containing hydrogen atoms such as ammonia is decomposed by a photoexcitation method. It has at least a process. (3) Mercury is used as a sensitizing material in the step of decomposing a predetermined gas by the photoexcitation method. [Example] Example 1 of the present invention will be explained according to the process diagram of a thin film transistor shown in FIG. Figure (a) shows a non-monocrystalline silicon thin film on an insulating amorphous material 1-1 such as an insulating non-quality substrate such as glass or quartz or an insulating amorphous material layer such as Si02. In this step, a non-single crystal silicon thin film 1-2 is formed using a photolithography method. The following methods are available for forming the silicon thin film. (1) Low pressure CVD method, MBE method (M
o1ecular beam epitaxy),
A polycrystalline silicon thin film is deposited using the following method. (2)E
B (Electron Beam) evaporation method, sputtering method, plasma CVD method, photoexcitation CVD method, low pressure CVD
An amorphous silicon thin film or a microcrystalline silicon thin film is deposited by a method such as a method such as a method, an MBE method, or the like. For example, reduced pressure CV
In method D, an amorphous silicon thin film can be deposited by setting the debo temperature to about 550°C or less. FIG. 2B shows a step of forming a gate oxide film 1-4 by a thermal oxidation method. Using the dry oxidation method, a high-quality gate oxide film with high breakdown voltage can be obtained by heat treatment at approximately 1150°C in an oxygen atmosphere. If a wet oxidation method is used, an oxide film can be formed even at a low temperature of about 900°C, but the breakdown voltage is lower and the film quality is inferior to that of a film formed by a dry oxidation method. Through this oxidation step, the non-single crystal silicon thin film 1-2 progresses in crystal growth due to heat treatment, and becomes a polycrystalline silicon thin film 1-3. When a polycrystalline silicon thin film is used as the non-single crystal silicon thin film 1-2,
The crystal grain size of the polycrystalline silicon thin film 1-3 after the oxidation process is about 2000A to 3000A. When an amorphous silicon thin film or a microcrystalline silicon thin film is used as the non-single crystal silicon thin film 1-2, the crystal grain size grows from 5000A to several μm.
Figure (C) shows the step of forming the gate electrode 1-5 and forming the source/drain regions. Polycrystalline silicon is generally used as the gate electrode material. Using the gate electrode 1-5 as a mask, impurity elements are ion-implanted to form a source region 1-6 and a drain region 1-7. Phosphorus, arsenic, boron, etc. are used as the impurity element. In the same figure (d), an interlayer insulating film 1-8 is deposited at 600°C for the purpose of activating impurities in the source region 1-6 and drain region 1-7 and densifying the interlayer insulating film 1-8. ~1
．． This is a process that involves heat treatment at approximately 000°C. Figure (e) shows a step in which a gas containing hydrogen such as hydrogen gas or ammonia gas is decomposed by a photoexcitation method to form highly active hydrogen radicals 1-9, and hydrogenation treatment is performed.
The photoexcitation method includes (1) a method of directly exciting and decomposing hydrogen gas, etc., (2) a method of using a sensitizer such as mercury, first exciting the sensitizer by light irradiation, and decomposing the excited sensitizer. There is a method for decomposing hydrogen gas etc. An example of a mercury sensitization method using mercury as a sensitizing material is described below. As a device,
A normal optical CVD device or the like can be used. First, a substrate is set in a reaction chamber, and hydrogen gas or the like is introduced into the reaction chamber. Furthermore, mercury is introduced as a sensitizing material. (The internal pressure should be approximately 0.1 to 2 Torr.) Next, light is irradiated using a light source such as a low-pressure mercury lamp, a Xe lamp, or a deuterium lamp to excite the mercury. The excited mercury is
Hydrogen gas is decomposed to generate hydrogen radicals according to the reaction formula below. Hg hy + Hg
“Hg” 10 H2 → 2H
+Hg In this way, highly active hydrogen radicals are introduced into the substrate, terminating defects existing at the grain boundaries of polycrystalline silicon. Incidentally, in order to increase the diffusion rate of hydrogen radicals and shorten the processing time, it is appropriate for the substrate temperature to be about 200°C to 400°C. Example: 35
2. When processed at about 0°C to 400°C. 0 minutes to 3
Sufficient improvement in properties was observed after approximately 0 minutes of treatment. FIG. 5(f) shows a step of forming contact electrodes 1-10 in the source and drain regions. A metal material such as aluminum, chromium, or nickel is used as the contact electrode material. In addition, although the example shows the case where mercury is used as a sensitizer (mercury sensitization method), the present invention is not limited to this. For example, there is a method of directly decomposing hydrogen gas using ultraviolet light, but since decomposing hydrogen gas by direct photoexcitation requires ultraviolet light of about 100 nm, it is not recommended to use light of about 250 nm. The mercury sensitization method is preferable in terms of equipment configuration. Also,
There is also a method of using a gas containing hydrogen atoms, such as ammonia, instead of hydrogen gas. For example, when ammonia is used, it absorbs light of 210 nm or less and has an absorption peak at about 190 nm, so unlike when hydrogen gas is used, mercury can be Lamp, Xe
It has the characteristic that it can be easily decomposed using light sources such as lamps and deuterium lamps. Embodiment 2 of the present invention will be explained according to the process diagram of a thin film transistor shown in FIG. Figure (a) shows a non-monocrystalline silicon thin film 2 on an insulating amorphous material 2-1 such as an insulating non-quality substrate such as glass or quartz or an insulating amorphous material layer such as Si02. This is the process of depositing -2. The deposition method has been described previously, so it will be omitted here. 2-
3 indicates the grain boundary, a s - d e p
O. The crystal grain size of the film is small and there are many defects. In addition, figure (a
) describes the case where a polycrystalline silicon thin film is deposited, but an amorphous silicon thin film or a microcrystalline silicon thin film may also be deposited. FIG. 2B shows a step of crystal-growing the silicon thin film 2-2 to grow a polycrystalline silicon thin film 2-4. If the silicon thin film 2-2 is of poor quality or microcrystalline, solid phase growth is effective. When a substrate is placed in an inert gas atmosphere such as nitrogen gas and crystallized annealed at a low temperature of 500°C to 700°C for several hours to hundreds of hours, solid phase growth occurs and the crystal grain size increases to several thousand nanometers. It grows to a size of several micrometers. Further, if the silicon thin film 2-2 is polycrystalline, silicon ions are implanted into the polycrystal to make the polycrystalline amorphous, and then the solid phase growth method described above is performed to grow the crystal. As the crystal grain size increases, Figure 2(b)
As shown in , the interval between grain boundaries 2-3 becomes larger. Other crystal growth methods include laser annealing recrystallization, electron beam annealing recrystallization, and melt recrystallization using a carbon strip heater. The solid-phase method is an extremely effective method that can be applied to low-temperature processes below about 700°C. FIG. 2C shows a step of forming a gate oxide film 2-5. In the plasma CVD method, the gate oxide film is deposited at a temperature of about 200"C, and in the CVD method, it is deposited at a temperature of about 400"C.In addition, by the sputtering method, it can be formed at a low temperature of about room temperature to about 300"C.In addition, the plasma oxidation method, high pressure Gate oxide films can be formed at low temperatures using methods such as oxidation and laser oxidation.It goes without saying that ordinary thermal oxidation may also be used. Example 1
Since it was mentioned in the previous section, it will be omitted here. In the same figure (d), a gate electrode 2-6 is formed, and then an impurity element is ion-implanted using the gate electrode 2-6 as a mask to form a source region 2-6.
-7 and drain region 2-8 are formed, and hydrogenation treatment is performed. Phosphorus, arsenic, boron, etc. are used as the impurity elements. The interlayer insulating film 2-9 is
Deposition is performed by a method such as a PCVD method, an AP CVD method, a sputtering method, an ECR plasma CVD method, or a photoCVD method. Thereafter, heat treatment is performed at approximately 600° C. to 1000° C. for the purpose of activating the source region and drain region and densifying the interlayer insulating film. Next, hydrogenation treatment is performed. 2-10 shows highly active hydrogen radicals. Since the hydrogenation treatment was described in the section of Example 1, it will be omitted here.
FIG. 4(e) shows a step of forming contact electrodes 2-11 with the source and drain regions. In addition, Fig. 1 and No. zl! I is an example of a manufacturing process, and the hydrogenation process can be performed before forming the gate electrodes 1-5 and 2-6, or after forming the electrodes 1-10 and 2-11. Also, by doping impurities into the channel region, vt
It is also possible to control h (L, threshold voltage). When hydrogenation treatment is performed, the N-channel transistor shifts vth in the depletion direction, and the P-channel transistor shifts in the enhancement direction, but by doping the channel region with impurities of about 1015 to 10"/cm", Vth can be controlled. For example, in FIG. 1, before forming the gate electrode, an impurity such as B (boron) is added to the
There are methods such as implanting with a dose of about 0.013/Cm2. Particularly, if the dose amount is about the above value, vth can be controlled so that the off-state currents of both the P-channel transistor and the N-channel transistor are minimized. Therefore, even when forming a CMOS type TPT element, the entire surface can be channel doped in the same process without selectively channel doping Pch and Nch. As mentioned above, conventional hydrogen plasma processing frequently causes defects due to plasma damage, making it difficult to put it into practical use. The reason for this is that immersion in the plasma atmosphere causes charge-up and voltage is applied to the gate film, and furthermore, the substrate temperature is relatively high at around 300°C, which is a type of BT (Bias- Tempe
It is thought that TPT failure occurred due to stress. Therefore, measures to prevent charge-up are expected to be particularly effective in reducing defects. It has been found that in the method of decomposing hydrogen gas etc. using the photoexcitation method of the present invention, damage is significantly reduced because charge-up by ion species hardly occurs. As described above, by applying the present invention, it is possible to manufacture a highly reliable thin film transistor with a large ON current, a small OFF current, a steep rise in the subthreshold region, and no defects due to plasma damage or the like. Can be done. For example, when the present invention is applied to an active matrix substrate, a high-definition panel with a built-in driver can be realized. In addition, if it is used in an image sensor that integrates a shift register circuit and a photoelectric conversion element on the same substrate, it can be used for high-speed reading, large size such as A3 size, or
It can be expected to have a great effect on colorization, etc. Since the drive voltage can be reduced, it also helps reduce power consumption and improves reliability. Furthermore, as explained in Example 2, by applying the present invention to a low-temperature process of about 700° C. or less, a large-area, high-performance semiconductor device can be realized. As an example of the application of the present invention, FIG. 3 shows a cross-sectional view of an image sensor in which a shift register circuit and a photoelectric conversion element are integrated on the same substrate. In Figure 3, 3-1 is glass;
Amorphous insulating substrate such as quartz, 3-2 is gate insulating film, 3-
3 is a gate electrode, 3-4 is a source/drain region, 3-
5 is an interlayer insulating film, 3-6 is a lower transparent electrode of the photoelectric conversion element, 3-7 is an amorphous silicon layer, and 3-9 is an upper electrode and wiring of the photoelectric conversion element. In addition, in Figure 3, for simplicity,
Only a cross-sectional view of the photoelectric conversion element and the TPT that forms one gsw of the photoelectric conversion element is shown.The details of the method for forming the TPT have been described in FIGS. 1 and 2, so they are omitted here. After the hydrogenation treatment, a transparent electrode that will become the lower electrode of the charge conversion element is formed on the interlayer insulating film 3-5. The transparent electrode is made of ITO, Sn
It is formed by forming 02 etc. by sputtering method etc. and patterning it. Next, an amorphous silicon layer forming a photoelectric conversion layer is formed using a plasma CVD method or the like, and after patterning, contact holes are formed in the interlayer insulating film 3-5, and wiring and charge conversion are performed using a metal material such as A1 or Cr. The upper electrode of the device is formed in the same process. By applying the hydrogenation treatment of the present invention, the TPT characteristics were improved as described above, and the scanning speed of the shift register was improved. The conventional image sensor is A4 200D
What was 5ms/line with PI has been reduced to 1ms/line with A4200DPI by the present invention.
We were able to increase the speed to ne. In this way, the present invention has great effects on increasing the length of image sensors and realizing color image sensors. Although FIGS. 1 to 3 show an example in which the present invention is applied to a poly-SiTFT manufacturing process, the present invention is not limited to this. The present invention is effective for all insulated gate field effect transistors in which at least a portion of the channel region is polycrystalline. The present invention is also effective in transistors in which at least a portion of the channel region is made of microcrystals, or in transistors in which a portion of the channel region is made of a poor-quality semiconductor that is insufficiently hydrogenated and formed by sputtering or vapor deposition. be. Moreover, even if the channel region is single crystal, three-dimensional IC
When a device is formed in a silicon layer that has been recrystallized or grown in a solid phase, defects such as sub-grain boundaries are likely to occur within the crystal.
In this case, the characteristics can be effectively improved by terminating defects using the semiconductor device manufacturing method according to the present invention. Furthermore, the present invention is also effective in reducing the defect density at the heterojunction interface of HBTs (hetero-bibolar transistors) and the like. In particular, when at least one of the two semiconductor layers forming a heterojunction is made of a non-single crystal semiconductor, the hydrogenation treatment according to the present invention can simultaneously reduce defects in the film and at the interface. Furthermore, the present invention can be widely applied to semiconductor processes in general, including solar cells, optical sensors, bibolar transistors, and static induction transistors that use non-single crystal semiconductors as element materials. [Effects of the Invention] As described above, according to the present invention, poly-SiTF
It is possible to improve the performance of an insulated gate field effect transistor in which at least a portion of the channel region, such as T, is made of a non-single-crystal semiconductor without causing defects such as plasma damage. Further, the present invention can be widely applied not only to insulated gate field effect transistors but also to semiconductor processes in general, and its effects are extremely large.

[Brief explanation of drawings]

FIGS. 1(a) to 1(f) are process diagrams of a thin film transistor according to the present invention. FIGS. 2(a) to 2(e) are process diagrams of the thin film transistor according to the present invention. FIG. 3 is a cross-sectional view of the image sensor according to the present invention. 1-1. 2-1. 3-1; Insulating amorphous material 1-2. 2-2; Non-single crystal thin film 1-9
．． 2-10; Hydrogen radical 2-3
; Above the grain boundary

Claims (3)

[Claims] (1) A method for manufacturing a semiconductor device in which at least a portion of the channel region of an insulated gate field effect transistor is made of a non-single crystal semiconductor, including at least the step of immersing the semiconductor device in an atmosphere in which hydrogen gas is decomposed by a photoexcitation method. A method for manufacturing a semiconductor device, comprising: (2) In a method for manufacturing a semiconductor device in which at least a portion of the channel region of an insulated gate field effect transistor is made of a non-single crystal semiconductor, the step of immersing the semiconductor device in an atmosphere in which a gas containing hydrogen atoms such as ammonia is decomposed by a photoexcitation method is performed. A method for manufacturing a semiconductor device, comprising at least the following. (3) The method of manufacturing a semiconductor device according to claim 1 or 2, wherein mercury is used as a sensitizing material in the step of decomposing a predetermined gas by the optical excitation method.