JPH04206837A - Manufacture of semiconductor device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing a semiconductor device in which a thin film transistor (hereinafter referred to as TPT) is formed on a transparent substrate at a low temperature (<600° C.).

Conventional technology The method for forming polycrystalline silicon in an iF T using polycrystalline silicon as the conductor layer includes applying L P -CV D (Low Pressure) to a substrate such as quartz.
-Chemical Vapor Deposition
A method of directly depositing a thin polycrystalline silicon film at a temperature of 600°C or higher using a low-pressure chemical vapor deposition method, etc., and a method of melting a hydrogenated amorphous silicon thin film using an energy source such as a laser beam.

There is a method of forming a polycrystalline silicon nitride film by polycrystallization.

In addition, when producing polycrystalline silicon TPT by melting and crystallizing using laser light, the device configuration is a forward starga type in which the gate electrode is formed on the top of the semiconductor layer (the channel region is on the top of the semiconductor layer). Alternatively, the coplanar type is the mainstream because it allows easy 1-ping to the semiconductor layer.

Problems to be Solved by the Invention However, when manufacturing a polycrystalline silicon TPT using the above-mentioned conventional method of directly depositing a polycrystalline silicon thin film on a substrate, it is necessary to heat the substrate to at least 600'C. However, the number of substrates that can be used for TFTs is limited.

In addition, in the conventional polycrystalline silicon TPT device configurations, which are the mainstream type and the coplanar type, the gate insulating film is formed on the -L part of the semiconductor layer, so the gate insulating film is deposited after the semiconductor layer is deposited. become. However, when manufacturing TPT using a low-temperature process, it is not possible to use a high-temperature process such as a thermal oxide film that causes less damage. Therefore, if a silicon nitride film is deposited as the gate insulator Q by plasma CVD, for example, the plasma will damage the surface of the underlying hydrogenated amorphous silicon thin film, making it difficult to form a good channel. I had an issue. The same thing can be said when silicon dioxide (SiO□), quantal oxide (Ta20x), or the like is deposited as a dielectric film by sputtering or the like.

On the other hand, current TPTs using hydrogenated amorphous silicon as the semiconductor layer are mainly manufactured using an inverted staggered type. Silicon TPT and hydrogenated amorphous silicon TFT
When considering the case of configuring the same MW on the same MW, the staggered type and coplanar type have problems such as inability to maintain consistency with the current process.

Furthermore, when manufacturing n-channel or p-channel transistors using polycrystalline silicon TPT using laser light irradiation, the film formation process becomes complicated when conventional methods introduce a step of doping the channel region with impurities after depositing the semiconductor layer. Therefore, there was a problem in that the number of masks was considerably increased compared to the current inverted staggered hydrogenated amorphous silicon TPT process.

The present invention solves the above-mentioned conventional problems, and consists of TPT using polycrystalline silicon through a low-temperature process (<600°C).
An object of the present invention is to provide a method for manufacturing a semiconductor device.

Means for Solving the Problem In order to achieve this object, the present invention adopts an inverted staggered structure, sequentially deposits a gate insulating film and a semiconductor thin film (such as a hydrogenated amorphous silicon thin film), and further forms a polycrystalline film. Regarding silicon thin film formation, hydrogenated amorphous silicon thin films are melted and crystallized by laser beam irradiation.

Furthermore, the semiconductor thin film to be deposited on top of the gate insulating film is doped with impurities at a low concentration in advance, and then, with the channel region masked by the thin film, high concentration impurity elements are doped onto the surface of the semiconductor thin film or into the semiconductor thin film. After injecting the mask, the mask thin film is etched and laser light is irradiated.

Effect As in the above structure, by forming a polycrystalline silicon thin film by irradiating laser light, the polycrystalline silicon thin film can be formed at a low temperature (<600° C.), which widens the range of substrate selection.

In addition, by adopting an inverted staggered structure, the semiconductor thin film can be formed on the gate insulating film, so the channel region is located below the semiconductor layer, making it possible to form a good channel without being damaged by plasma. .

Furthermore, impurities are pre-doped at a low concentration into the semiconductor thin film deposited on the -1- side of the gate insulating film, and then high-concentration impurity elements are deposited or implanted in areas other than the channel region. It is possible to easily form a low-concentration channel region and high-concentration source and l-rain regions by melting and crystallization by laser beam irradiation.In addition, the impurity concentration of the channel region can be controlled by controlling the impurity concentration of the deposited semiconductor thin film. This can be easily done by changing the concentration.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a process sectional view showing a method of manufacturing a semiconductor device in an embodiment of the present invention. This is an n-channel polycrystalline silicon nitride film. As shown in FIG. 1(a), a thin metal film is deposited on a transparent substrate 1 by sputtering or the like, and then etched into a predetermined shape to form a gate. Electrode 2 is formed. Glass, quartz, or the like is used for the transparent substrate 1, and chromium (Cr) or the like is used for the metal thin film forming the gate electrode 2.

Next, as shown in FIG. 2B, after insulating films 3a and 3b and semiconductor thin film 5 are deposited on transparent substrate 1, masking thin film 5 is formed in the channel region.

The insulating film 3a includes Ta20X formed by sputtering or anodic oxidation, and 5i02 formed by atmospheric pressure CVD.
etc. are used. The insulating film 3b and the semiconductor thin film 5 are formed by plasma CV
Silicon nitride film and holon (B) are 10+1 using D equipment.
-107 cm' A low concentration p-type hydrogenated amorphous silicon thin film (hereinafter denoted by reference numeral 5) doped with 5 is formed by successive deposition. Here, the thickness of the p-type hydrogenated amorphous silicon thin film 5 is 300 to 3000. By continuously forming the hydrogenated amorphous silicon thin film 5 on the silicon nitride film 3b in this way, the interface between the silicon nitride film 3b and the hydrogenated amorphous silicon thin film 5 can be formed without exposing it to the atmosphere, resulting in natural oxidation. No influence of membrane. Furthermore, when depositing the silicon nitride film 3b and the hydrogenated amorphous silicon thin film 5 using the normal plasma CVD method, the high frequency power density is higher when depositing the silicon nitride film 3b than when depositing the hydrogenated amorphous silicon thin film 5. Because it is about 10 times larger, the film surface is larger when the hydrogenated amorphous silicon thin film 5 is deposited on the silicon nitride film 3b than when the silicon nitride film 3b is deposited on the second part of the hydrogenated amorphous silicon thin film 5. There is little damage to the plasma caused by the plasma, and a good interface can be formed. Further, by changing the hydrogenated amorphous silicon thin film 5OBfi degree, the impurity concentration in the channel region can be controlled. mask m1
For the film 4, a silicon nitride film or the like is used.

Next, as shown in FIG. 4C, impurity ions 6 are implanted into the hydrogenated amorphous silicon thin film 5 using the masking thin film 4 as a mask and using an impurity element supply gas. For example, PH8 (0.1 to 10% hydrogen dilution) is used as the source of this impurity element. Furthermore, this PH3 is ionized by plasma decomposition and then implanted into the hydrogenated amorphous silicon thin film 5.

The hydrogenated amorphous silicon thin film 5 into which phosphorus (P) ions have been implanted in this way has a P concentration of 10" to 10" cm-
'It becomes a highly doped n-type.

Here, the impurity element may be attached to the surface of the semiconductor thin film by a method other than ion implantation. Next, as shown in FIG. 7(d), the semiconductor thin film 5 is melted by irradiation with laser light 7.
crystallize. The laser beam 7 includes excimer laser and A
r laser etc. is used. Here, before irradiating the laser beam 7, the transparent substrate 1 is held in a vacuum container and is heated to 300 to 500° C. without evacuation, thereby dehydrating the hydrogenated amorphous silicon thin film 5. It is necessary to perform basic processing. This is because when a hydrogenated amorphous solicon thin film 5 that is not subjected to dehydrogenation treatment is melted using Rayleigh's light 7, the hydrogen in the film is heated rapidly and released from the film, causing great damage to the film. This is to give Also, the polycrystalline silicon thin film 8a after being irradiated with the radar light 7
A does not show good electrical properties because there are many dangling bonds in the formed grain boundaries. Therefore, after irradiating the laser beam 7, the transparent substrate 1 was
It is treated in a hydrogen atmosphere or a hydrogen plasma atmosphere while being heated to 0.degree. C. to reduce dangling spots and improve electrical characteristics. By performing the above-described processing, a highly doped n-type polycrystalline silicon thin film (source or train region) 8 and a lightly doped p-type subcrystalline silicon thin film (channel region) 9 can be formed. Next, as shown in FIG. 3E, an insulating film 10 is formed in a predetermined shape on the channel region 9. For this insulating film, a silicon nitride film or the like deposited using a plasma CVD apparatus is used. Next, as shown in FIG. 2F, after forming a metal thin film, the metal thin film and polycrystalline silicon nitride films 8 and 9 are etched into a predetermined shape to form a source electrode 11 and a train electrode 12. These electrodes 11 and 12 are made of aluminum (Δ° C.), molybdenum silicide (MoSi), titanium (Ti), or the like.

Next, the manufacturing process of Pchal Z·l polycrystalline silicon TPT will be explained. The fabrication process of the p-channel TPT is not shown in Fig. 1. (10''~]0'cm3 of P (phosphorous) instead of the conductor 3IN9.5) A low concentration n-type hydrogenated amorphous silicon thin film doped with 0'cm3 is used. , and can be manufactured by using B2H6 (0.1 to 10% diluted with hydrogen) as a source of impurity ions 6 and performing the same process as shown in FIG.

Effects of the Invention As described above, the process for manufacturing polycrystalline silicon TPT according to the present invention has the following effects.

(]) Semiconductor thin film (hydrogenated amorphous silicon thin film)
By melting and crystallizing polycrystalline silicon using laser light to form a thin film of polycrystalline silicon, a low-temperature (<600° C.) process becomes possible, expanding the range of substrate selection.

(2) By making the element structure inverted staggered, it is possible to form a good interface between the gate insulating film and the semiconductor thin film.

(3) After attaching or implanting an impurity element to a predetermined area on a semiconductor thin film (hydrogenated amorphous silicon thin film) containing impurities using a FIIIR mask, it is irradiated with laser light to melt and crystallize it. Polycrystalline silicon 'rI?' having a channel region, source, and drain regions with a predetermined impurity concentration. T can be easily formed.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(f) are process cross-sectional views showing a method of manufacturing a semiconductor device according to an embodiment of the present invention. 1... Transparent substrate, 2... Gate electrode (electrode), 3a, 3b... Insulating film [insulating aT film], 4
... Thin film for mask (thin film), 5... Hydrogenated amorphous silicon thin film (semiconductor 7! IJ film),
6...Impurity number 7...Laser light. Name of agent: Patent attorney Yoshiaki Ogata and 2 others A

Claims (7)

[Claims] (1) A first step of forming an electrode in a predetermined shape on a transparent substrate, a second step of depositing an insulating thin film on the transparent substrate and the electrode, and a step of depositing an insulating thin film on the transparent substrate and the electrode. a third step of depositing a semiconductor thin film on the thin film; a fourth step of forming a thin film on a partial region on the semiconductor thin film; and a third step of depositing an impurity element on the surface of the semiconductor thin film or in the semiconductor thin film. A method for manufacturing a semiconductor device, the method comprising at least a fifth step of injecting laser light into a region of the transparent substrate, and a sixth step of irradiating a partial region of the light-transmitting substrate with a laser beam. (2) Silane (SiH_4), disilane (Si_2H_
6) A claim characterized in that a semiconductor thin film is deposited using any one of plasma decomposition, thermal decomposition, or photodecomposition of a mixed gas in which a main source gas such as the above and a gas containing an impurity element are mixed. Item 1. A method for manufacturing a semiconductor device according to item 1. (3) The gas containing impurity elements is phosphine (PH
_3) or diborane (B_2H_6) and H_
3. The method of manufacturing a semiconductor device according to claim 2, wherein the gas is a mixture of 2 and 3. (4) The method according to claim 1, characterized in that the impurity concentration in the region where the impurity element is attached to the surface or implanted in the fifth step is higher than the impurity concentration in the semiconductor thin film deposited in the third step. A method for manufacturing a semiconductor device. (5) The method of manufacturing a semiconductor device according to claim 1, wherein the second step and the third step are performed in a vacuum. (6) After depositing the semiconductor thin film or after attaching an impurity element to the surface of the semiconductor thin film or implanting the impurity element into the semiconductor thin film, it is heated for 200 minutes in a vacuum, in a nitrogen atmosphere, or in a hydrogen atmosphere. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the heat treatment is performed in a temperature range of 600 DEG C. (7) After irradiating the laser beam, hydrogen treatment is performed in a hydrogen atmosphere or a hydrogen plasma atmosphere at a temperature of 100 to 400° C. and 10^3 to 10 Torr of the transparent substrate. A method of manufacturing the semiconductor device described above.