JP3800336B2 - Crystal method of polycrystalline silicon layer - Google Patents

Description

  The present invention relates to a method for crystallizing polycrystalline silicon, and more particularly, to provide a seed for the crystallizing process of polycrystalline silicon to increase the crystal grain size of the polycrystalline silicon layer and to achieve a uniform distribution (High Uniformity). It relates to a crystal method to obtain.

  In general, Poly Silicon Thin Film Transistor is applied to Active Matrix Liquid Crystal Display (AMLCD) and Active Matrix Organic Light Emitting Display (AMOLED). It is used as a basic electronic component for controlling the luminance of each pixel (Pixel) and as an electronic component for a peripheral drive circuit or a control circuit.

  In fabricating a polycrystalline silicon thin film transistor, the crystal of the polycrystalline silicon layer is the most important step. The electrical properties and uniformity of polycrystalline silicon thin film transistors are usually determined by this step.

1A and 1B show the production of a polycrystalline silicon layer in a conventional thin film transistor manufacturing process. In this conventional example, an amorphous silicon layer 104 is first formed on a glass (or plastic) substrate 100, and the amorphous silicon layer 104 is irradiated with an excimer laser to irradiate the amorphous silicon layer 104. The crystalline silicon layer 104 is melted. Then, the first amorphous silicon layer 104 is changed to the polycrystalline silicon layer 104 by cooling and recrystallization.
JP 58-206163 A JP 60-245124 A

  FIG. 2 shows the energy density of a conventional excimer laser and the electrical characteristics of polycrystalline silicon. As shown in the figure, even if the irradiation time is the same, the density control range of the output energy for the excimer laser to irradiate the amorphous silicon layer 104 and change it to the polycrystalline silicon layer is very narrow. In other words, if the energy density of the excimer laser is too high, the amorphous silicon layer 104 is completely melted, and after cooling and crystallization, microcrystalline silicon (Microcrystalline Si) with low electrical properties (eg, electronic transition rate) is obtained. End up. On the contrary, if the energy density of the excimer laser is too low, the amorphous silicon layer 104 remains almost undissolved, and even after cooling and crystallization, the amorphous silicon has low electrical characteristics.

  Further, since the excimer laser itself has variability, the polycrystalline silicon layer 104 formed after the irradiation with the excimer laser has a non-uniform distribution because the size of the polycrystalline silicon particles is too small. As a result, the electrical characteristics of the finally formed thin film transistor vary greatly.

  That is, the background of the present invention is as follows. That is, since the conventional excimer laser for forming the polycrystalline silicon layer is difficult to control, the crystal grain size of the polycrystalline silicon becomes non-uniform. The present invention has been made in view of the above-mentioned problems. By providing a method for crystallizing polycrystalline silicon, the problem is that the crystal grain size of polycrystalline silicon is too small and the distribution is nonuniform. Try to solve.

  As described above, the present invention provides a method for crystallizing a polycrystalline silicon layer. In this method, a seed crystal is formed on the surface of the substrate, an amorphous silicon layer is formed so as to cover the surface of the substrate and the seed crystal, and the amorphous silicon layer is irradiated with a laser to be amorphous. Melting the quality silicon layer.

  The method for crystallizing a polycrystalline silicon layer according to the present invention includes defining a first area and a second area on the surface of the substrate, forming a seed crystal in the first area, and forming the first area and the second area. Forming an amorphous silicon layer to cover the area, and irradiating the amorphous silicon layer with a laser to melt the amorphous silicon layer.

  3A to 3I show the production of a polycrystalline silicon layer in the thin film transistor production process of the present invention. First, as shown in FIG. 3A, a silicon nitride (SiNx) layer 204 is formed on a glass (or plastic) substrate 200. (In addition, a metal layer may be formed instead of the silicon nitride layer.)

  Next, as shown in FIG. 3B, a predetermined pattern is formed on the silicon nitride layer 204 using a mask 206, and the silicon nitride layer 204 is etched. When the mask 206 is transferred after the etching process, a silicon nitride layer 204 having a predetermined pattern appears on the glass substrate 200 as shown in FIG.

  Then, an amorphous silicon layer 208 as shown in FIG. 3D is formed on the silicon nitride layer 204 having a predetermined pattern. Thereafter, an etching process (non-isotropic etching) is performed on the amorphous silicon layer 208. After such an etching process, the remaining amorphous silicon 210 has a spacer structure and is attached to the side surface of the silicon nitride layer 204 as shown in FIG.

  Further, as shown in FIG. 3F, the silicon nitride layer 204 having a predetermined pattern is completely removed by performing the etching process again. Thus, what is left on the glass substrate 200 is the amorphous silicon 210 attached to the side surface of the silicon nitride layer 204. These residual silicons are referred to herein as seeds.

  Next, as shown in FIG. 3G, an amorphous silicon layer 212 is formed again so as to cover the glass substrate 200 and the seed crystal 210. Thereafter, as shown in FIG. 3H, the amorphous silicon layer 212 is completely melted by irradiating the amorphous silicon layer 212 with a pulse laser (usually, an excimer laser). Then, the first amorphous silicon layer 212 is changed to a polycrystalline silicon layer 212a by cooling and recrystallization.

  As described above, the amorphous silicon layer 212 is completely melted by controlling the energy density of the pulse laser, but the seed crystal 210 still remains on the glass substrate 200. Accordingly, the polycrystalline silicon layer 212a in the crystal starts to crystallize in the vicinity of the seed crystal 210 and condenses in the lateral direction on both sides (the direction indicated by the arrow). After being completely crystallized in this way, as shown in FIG. 3 (i), a crystal boundary (Grain Boundary) 214 is generated in the polycrystalline silicon layer 212a.

  FIG. 4 (a) is a front view showing a polycrystalline silicon layer according to the present invention. The broken portion indicates the position of the seed crystal 210. FIG. 4B is a front view of the thin film transistor completed according to the polycrystalline silicon layer of the present invention. A description of the manufacturing process of the polycrystalline silicon thin film transistor is omitted here.

  Since the characteristics of a conventional pulse laser (for example, excimer laser) are difficult to control, the distribution of microcrystalline silicon layers or crystal particles becomes non-uniform due to an excessive or excessive laser energy density. In contrast, in the present invention, since the seed crystal is provided between the substrate and the amorphous silicon layer prior to the formation of the amorphous silicon layer, even if the conditions such as the irradiation time are the same. As shown in FIG. 5, the controllable range of the output energy density of the excimer laser is widened. Note that when the amorphous silicon layer is completely dissolved, the seed crystal is not completely dissolved yet, so that both sides of the seed crystal start to crystallize first. Therefore, a thin film of a polycrystalline silicon layer in which the growth and distribution of crystal grains are uniform (High Uniformity) can be formed.

  A thin film transistor formed on a conventional glass substrate requires a gate channel composed of a polycrystalline silicon layer and a gate channel composed of a microcrystalline silicon layer. Therefore, each of the double-type thin film transistors must be formed on a glass substrate, which complicates the manufacturing process and lowers the product acceptance rate. On the other hand, in the present invention, the same double thin film transistor can be manufactured and completed at the same time. And as shown in FIG. 6, a glass substrate is divided into the distribution area of a double-type thin-film transistor. According to the present invention, since a polycrystalline silicon layer must be formed in the first area 220, it is necessary to form a seed crystal (not shown) in the first area 220. Since the microcrystalline silicon layer is formed in the second area 240, it is not necessary to form a seed crystal in the second area 240. Then, an amorphous silicon layer is formed in these two areas 220 and 240 and irradiated with a pulse laser. Thus, since the seed crystal is formed in the first area 220, a polycrystalline silicon layer is formed in the first area 220 after crystallization, and a microcrystalline silicon layer is formed in the second area 240. Has been. Finally, thin film transistors are formed simultaneously in these two areas.

  Thus, according to the present invention, a method for crystallizing a polycrystalline silicon layer is provided. Before forming the amorphous silicon layer on the substrate, a seed crystal is provided to start the crystal. At this time, the condensed polycrystalline silicon layer is crystallized outward from both sides of the seed crystal, and a thin film of a polycrystalline silicon layer having a large crystal grain size and a uniform distribution can be formed.

  The foregoing is only a preferred embodiment of the present invention and is not intended to limit the scope of the claims of the present invention. All changes or modifications made without departing from the spirit of the invention are within the scope of the following claims.

It is explanatory drawing which shows manufacture of the polycrystalline silicon layer in the manufacturing process of the conventional thin-film transistor. It is explanatory drawing which shows manufacture of the polycrystalline silicon layer in the manufacturing process of the conventional thin-film transistor. It is a graph which shows the energy density of the conventional excimer laser, and the electrical property of a polycrystalline silicon. It is explanatory drawing which shows manufacture of the polycrystalline silicon layer in the thin-film transistor manufacturing process based on this invention. It is explanatory drawing which shows manufacture of the polycrystalline silicon layer in the thin-film transistor manufacturing process based on this invention. It is explanatory drawing which shows manufacture of the polycrystalline silicon layer in the thin-film transistor manufacturing process based on this invention. It is explanatory drawing which shows manufacture of the polycrystalline silicon layer in the thin-film transistor manufacturing process based on this invention. It is explanatory drawing which shows manufacture of the polycrystalline silicon layer in the thin-film transistor manufacturing process based on this invention. It is explanatory drawing which shows manufacture of the polycrystalline silicon layer in the thin-film transistor manufacturing process based on this invention. It is explanatory drawing which shows manufacture of the polycrystalline silicon layer in the thin-film transistor manufacturing process based on this invention. It is explanatory drawing which shows manufacture of the polycrystalline silicon layer in the thin-film transistor manufacturing process based on this invention. It is explanatory drawing which shows manufacture of the polycrystalline silicon layer in the thin-film transistor manufacturing process based on this invention. It is a front view which shows the polycrystalline silicon layer based on this invention, and a front view which shows the structure after forming a thin-film transistor in this silicon layer. It is a front view which shows the polycrystalline silicon layer based on this invention, and a front view which shows the structure after forming a thin-film transistor in this silicon layer. It is a graph which shows the relationship between the energy density of the excimer laser which concerns on this invention, and the electrical property of a polycrystalline silicon. It is explanatory drawing which shows distribution of the double type thin-film transistor manufactured by this invention.

Explanation of symbols

100 Glass substrate 104 Amorphous silicon layer or polycrystalline silicon layer 200 Glass substrate 204 Silicon nitride layer 206 Mask 208 Amorphous silicon layer 210 Seed crystal 212 Amorphous silicon layer 212a Polycrystalline silicon layer 214 Crystal contact surface 220 First Zone 240 Zone 2

Claims (7)

Forming a coating layer on the surface of the substrate;
Forming a predetermined pattern on the covering layer;
Forming a sidewall structure of amorphous silicon on a side surface of the predetermined pattern of the covering layer;
Forming at least one seed crystal on the surface of the substrate by removing a predetermined pattern of the coating layer;
Forming an amorphous silicon layer so as to cover the surface and at least one seed crystal;
Irradiating the amorphous silicon layer with a laser to melt the amorphous silicon layer;
Crystallizing the melted amorphous silicon layer by the seed crystal so as to become a polycrystalline silicon layer, and a method for crystallizing the polycrystalline silicon layer. 2. The method for crystallizing polycrystalline silicon according to claim 1, wherein the substrate is a glass substrate or a plastic substrate. 2. The method for crystallizing polycrystalline silicon according to claim 1, wherein the laser is an excimer laser. The method for crystallizing a polycrystalline silicon layer according to claim 1, wherein the covering layer is a silicon nitride layer or a metal layer. 2. The method for crystallizing a polycrystalline silicon layer according to claim 1, wherein a first area and a second area are partitioned on the surface of the substrate. 6. The method for crystallizing a polycrystalline silicon layer according to claim 5, wherein the amorphous silicon layer melted in the first zone is crystallized by the seed crystal so as to become a polycrystalline silicon layer. 6. The method for crystallizing a polycrystalline silicon layer according to claim 5, wherein the amorphous silicon layer melted in the second zone is crystallized to become a microcrystalline silicon layer.

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