JPS622531A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enable to simultaneously execute impurity doping in the semiconductor layer and heat treatment of the semiconductor layer including the impurity- undoped region of the semiconductor layer, in one process by a method wherein the semiconductor layer is irradiated with an energy beam (a) from the back side of the transparent substrate at the time of doping of an impurity. CONSTITUTION:A poly Si film 2 is formed on the surface of a glass substrate 1, then an Si oxide film 3, which is used as the gate insulating film, is formed, then a gate electrode 4 consisting of Al is formed and a part other than the part, located under the gate electrode 5, of the Si oxide film 3 is removed. After that, a PSG film 5 is formed on both the poly Si film 2 and the gate electrode 4 and a laser beam [energy (a)] is projected on the back surface of the glass sbstrate 1, hereby the interface between the PSG film 5 and the poly Si film 2 is heated. An N-type impurity, phosphorus P, is diffused in the poly Si film 2 from the PSG film 5, and an N<+> source region 6 and an N<+> drain region 7 are formed, but the doping of the impurity into the channel part can be interrupted by the gate electrode 4. As a result, the poly Si film 2 is heated over the whole and is crystallized.

Description

DETAILED DESCRIPTION OF THE INVENTION A method of manufacturing a semiconductor device according to the present invention will be explained according to the following items.

A. Industrial application field 33 Summary of the invention C1 Prior art [Figure 4] 00 Problems to be solved by the invention [Figure 4] E1 Means for solving the problems F. Examples [Figure 1] [FIGS. 1 to 3] a. Manufacturing method [FIGS. 1 to 3] b0 Effects of the invention (A. Field of industrial application) The present invention relates to a method for manufacturing a semiconductor device in which a semiconductor layer is selectively doped with conductive impurities in an impurity-containing layer formed on the surface of the semiconductor layer by heating with an energy beam.

(B. Summary of the Invention) A method for manufacturing a semiconductor device of the present invention is to remove conductive impurities in an impurity-containing layer formed on the surface of a semiconductor layer formed on a transparent substrate by heating with an energy beam such as a laser beam. In a method for manufacturing a semiconductor device to be doped, in order to simultaneously perform doping of the semiconductor layer with an impurity and heat treatment of the semiconductor layer including the region not doped with the impurity in one step, a transparent substrate is By forming a semiconductor layer and a mask layer on the surface, further forming an impurity-containing layer on the semiconductor layer and the mask layer, and then irradiating the semiconductor layer with an energy beam such as a laser beam from the back side of the transparent substrate. The semiconductor layer is heated, including regions to which impurities are doped and regions not to be doped.

(C, Prior Art) [Figure 4] An impurity doping method using ion implantation is generally used to form a self-alignment gate for reducing parasitic capacitance in devices such as MOS transistors.

However, in order to simplify the manufacturing process, it is necessary to form an impurity-containing layer such as PSGll [or BSG film containing conductive impurities] on the semiconductor substrate, and conductive impurities such as phosphorus P or boron B in the impurity-containing layer. It can be said that a doping method in which the oxide is diffused into the surface of the silicon semiconductor substrate is desirable. By the way, in order to diffuse phosphorus P, boron B, etc. into a silicon semiconductor substrate, it is necessary to heat the substrate at a temperature of 800° C. or higher. Therefore, it is difficult to use such an impurity doping method for doping for manufacturing a device (polycrystalline 5i TFT, SOI device, amorphous Si TFT, etc.) in which a semiconductor element is formed on a low melting point glass substrate.

However, a technique has been developed in which the impurity doping method is applied to devices by locally heating the device with a laser beam, and is introduced, for example, in Japanese Patent Application Laid-Open No. 52-36468. FIGS. 4A to 4D are cross-sectional views showing a method for manufacturing a MOS transistor using the impurity doping method in the order of steps.

(A) After forming a polycrystalline silicon film on the surface of a glass substrate a and converting the polycrystalline silicon film into a single crystal, a gate insulating Mc and a gate electrode d made of aluminum are formed on the surface of the silicon film. Form. FIG. 4(A) shows the state after forming the gate insulating film C and the gate electrode d.

(B) Next, for example, PSGII is placed on the surface of the glass substrate a.
(For N channel) Coat e. FIG. 4(B) shows the state after coating with PSG Me.

(C) Next, as shown in FIG. 4(C), by irradiating the surface of the substrate 8 with a laser beam and heating the PSG Ille, the phosphorus P, which is a conductive impurity in the PSG He, is converted into silicon. Diffuse into the membrane. Then.

Using the gate electrode d as a mask, phosphorus P is diffused into the surface area of the silicon film excluding the area under the gate electrode d.
A source region f and a drain region g are formed.

(D) After that, contact holes h and h are formed in the PSG film e, and then a source electrode l made of aluminum is formed.
and form a drain electrode j.

FIG. 4(D) shows the state after the source electrode I and drain electrode J are formed.

According to such a method of manufacturing a MOS transistor, the PSG film e and the semiconductor layer btt on the surface of the glass substrate 8 can be heated extremely locally and at a high temperature, so that the glass substrate a, which is a low melting point substrate, can be melted. The source region f and the drain region g can be formed by diffusing impurities by raising the temperature of the semiconductor layer to a temperature necessary for diffusion.

Therefore, a doping method in which an impurity-containing layer such as a PSG film or a BSG film is formed and a conductive impurity is diffused from the impurity-containing layer into a semiconductor layer to form a necessary semiconductor region is used for low-melting-point materials such as polycrystalline Si TFTs. It can be applied to manufacturing devices using the material as a substrate.

(D. Problem to be Solved by the Invention) [Figure 4] By the way, according to the conventional doping method shown in Figure 4 for manufacturing a device using a low melting point material as a substrate, the laser beam is Since the laser beam is irradiated from the surface side of the polycrystalline silicon film, the laser beam directed toward the channel of the polycrystalline silicon film (i.e., the region below the gate electrode d) is blocked by the gate electrode d, and the channel portion is heated during diffusion. Therefore, after forming a polycrystalline silicon film on a glass substrate a and before forming a gate electrode d and a gate insulating film C, the above-mentioned step [step ( (See A).However, the number of manufacturing steps can be reduced.

Although there is a need to reduce the manufacturing cost of devices such as MOS) transistors, polycrystalline silicon l! formed on a glass substrate a! It is not preferable to provide a special process just to achieve single crystallization of Jb.

The present invention has been made to solve these problems, and it combines doping of an impurity into a semiconductor layer on a transparent substrate and heat treatment of the semiconductor layer including areas not doped with impurities in one process. It is an object of the present invention to provide a novel method for manufacturing a semiconductor device that can be performed at the same time and requires fewer manufacturing steps.

(E. Means for Solving the Problems) In order to solve the above problems, the method for manufacturing a semiconductor device of the present invention includes forming a semiconductor layer and a mask layer on the surface of a transparent substrate, and further forming an impurity-containing layer on the semiconductor layer. After forming the semiconductor layer on the layer and the mask layer, the semiconductor layer is heated by irradiating the semiconductor layer with an energy beam such as a laser beam from the back side of the transparent substrate, including the regions to be doped with impurities and the regions not to be doped. be.

Therefore, according to the method for manufacturing a semiconductor device of the present invention, since the semiconductor layer is irradiated with an energy beam from the back side of the transparent substrate during impurity doping, the semiconductor layer has areas corresponding to the mask layer as well as areas not corresponding to the mask layer. is heated and heat treated. Therefore, impurity doping and heat treatment for the semiconductor layer can be performed simultaneously in the same process. Therefore, there is no need to provide a special process just to heat-treat the semiconductor layer on the transparent substrate for crystallization, and it is possible to reduce the number of manufacturing steps for devices such as MOS transistors formed on the transparent substrate. can.

(F. Embodiment) [Figures 81 to 3] A method for manufacturing a semiconductor device of the present invention will be described in detail below according to an embodiment shown in the accompanying drawings.

(a. Manufacturing method) [Figures 1 to 3] Figures 1 (A) to (C) show in order of steps one embodiment in which the method for manufacturing a semiconductor device of the present invention is applied to the manufacture of a MOS transistor. It is something.

(A) A polycrystalline silicon film 2 is formed on the surface of a glass substrate 1, and then a silicon oxide film 3 forming a gate insulating film is formed on the polycrystalline silicon film 2. Next, an aluminum film is formed on the silicon oxide film 3. A gate electrode 4 is formed, and a portion of the silicon oxide film 3 other than under the gate electrode 5 is removed. Thereafter, a PSG film 5 is formed on the polycrystalline silicon JII 2 and the gate electrode 4. In addition, the above glass substrate 1
An amorphous silicon film may be formed instead of a polycrystalline silicon film on top of the PSGjI5.
The state after formation is shown.

(B) The interface between the PSG film 5 and the polycrystalline silicon film 2 is heated by irradiating the back surface of the glass substrate l with a laser beam. To do this, the wavelength of the laser beam is set to 700 nm or less, where the light absorption coefficient of silicon is large (103 cm' or more). As a result, the glass substrate 1 is heated to its melting temperature (80
0℃) or lower (e.g. 700℃)
Conductive from FIN 5 to polycrystalline silicon film 2 (N type)
Phosphorus P, which is an impurity, is diffused to form N medium-sized source region 6 and drain region 7. However, impurity doping into the channel portion can be blocked by the gate electrode 4, and the source region 6 and drain region 7.
When forming the polycrystalline silicon sI2, the whole is, i.e.
Regardless of whether it is under the gate electrode 4 or not, it is heated by the laser beam and crystallized.

Here, test results have been obtained that support the fact that impurity doping and activation can be achieved by heating using a laser beam, so the test results will be explained. FIG. 2 is a sectional view showing the test object, in which 11 is a glass substrate, 12 is a 7-t-Jtz77 Sushiri° core FI4 (a
-5i mH, film thickness: 1000 mH), and is formed by plasma CVD. 13 is a PSG film (II!, thickness 3000A, concentration of phosphorus P as an N-type impurity 1 ato+wic%) formed on silicon 1llZ, and amorphous silicon [II!] on this glass substrate itt.
12. When PSGlfi 13 is irradiated with XeCL excimer laser (wavelength 308 nm, irradiation time 35 nsec, laser energy L 80 mJ/cm2), the change in electrical conductivity of the amorphous silicon film 12 is shown in FIG. 3, and the test results are shown. , the conductivity is 104Ωc' to 0
．． 5c+s-', the amorphous silicon film 1
2 is made into PS by impurity doping with a laser beam.
It has been found that conductivity is imparted by the conductive impurities diffused from the G film 13.

Thus, the source region 6 and the drain region 7 can be formed by self-alignment using the gate electrode 4 as a mask by impurity doping performed by heating with this laser beam, and the polycrystalline silicon 112 forms the channel portion. The entire structure, including the parts, is heated by a laser beam and crystallized. FIG. 1(B) shows the formation of the source region 6 and drain region 7 and the formation of the silicon film 2.
This shows the state when crystallization of is completed.

(C) After that, a contact hole 8.8 is formed by selective etching with respect to the PSG Ill 5, and then a source electrode 9 and a drain electrode 10 made of, for example, aluminum are formed. 11th m (C) shows the state after the source electrode 9 and drain electrode 10 are formed.

In the above embodiment, a PSG film is formed as the impurity-containing layer, but in the case of manufacturing a P-channel MOS transistor, an insulating film such as a silicon oxide film containing P-type impurities such as a BSG film may be used as the impurity-containing layer. A film must be formed.

The impurity concentration of phosphorus P or boron B in the PSG film or BSG film is 0.01 A/10 atomic.
% is preferable, and as a heating energy beam
e CL excimer laser beam is used,
Instead, for example, an argon laser beam (concentration 480
n layer) may be used, or an electron beam may be used, and various energy beams may be used as long as the beam passes through a transparent substrate, and the present invention is not limited to the above embodiments.

(b. Effect) According to the method for manufacturing a MOS transistor described above, conductive impurities are diffused from the PSG film 5 to the surface portion of the polycrystalline silicon film 2 by laser beam irradiation using the gate electrode 4 as a mask. Therefore, the source regions 6 and 7 can be formed in cell alignment by diffusion of the conductive impurity using the gate electrode 4 as a mask. Since the laser beam irradiation is performed from the back side of the glass substrate 1, the source region 6, drain region 7, and channel region of the polycrystalline silicon film 2 are not blocked by the gate electrode 4 and are entirely irradiated with the laser beam. The silicon is heated and then crystallized to form single-crystal silicon [2]. Therefore, there is no need to provide a special heat treatment process just for crystallization, and the doping and activation of conductive impurities for forming the source region 6 and drain region 7 and the formation of the polycrystalline silicon film can be performed in one heat treatment process. Crystallization including two channel portions can be performed simultaneously, and the number of manufacturing steps for a MOS transistor formed on a glass substrate can be reduced.

(G. Effects of the Invention) As is clear from the above description, the method for manufacturing a semiconductor device of the present invention includes the steps of forming a semiconductor layer on the surface of a transparent substrate, and selectively masking the semiconductor layer. forming a layer, forming an impurity-containing layer covering the surfaces of the mask layer and the semiconductor layer, and heat-treating the semiconductor layer by irradiating the semiconductor layer with an energy beam from the back side of the transparent substrate. and a step of diffusing impurities contained in the impurity-containing layer into the semiconductor layer.

Therefore, according to the method for manufacturing a semiconductor device of the present invention, since the semiconductor layer is irradiated with an energy beam from the back side of the transparent substrate during impurity doping, the semiconductor layer has areas corresponding to the mask layer as well as areas not corresponding to the mask layer. is heated and heat treated. Therefore, impurities and heat treatment on the semiconductor layer can be performed simultaneously in the same process. Therefore, there is no need to provide a special process just to heat-treat the semiconductor layer on the transparent substrate for crystallization, etc., which reduces the number of manufacturing steps for devices such as MOS transistors formed on the transparent substrate. can be done.

[Brief explanation of the drawing]

1(A) to CC> are cross-sectional views showing an example of the implementation of the method for manufacturing a semiconductor device of the present invention in the order of steps, FIG. 2 is a cross-sectional view showing a test target for impurity doping using an energy beam, and FIG. 3 is a test Figures showing the results, Figures 4 (A) to (D
) is a sectional view showing - in the conventional example in the order of steps. Code explanation 1. Fist transparent substrate, 2.O semiconductor layer, 3.4.@
Φ mask layer. 5.-Fist impurity-containing layer Figure 1 Kinjingun 1,000 nCm4

Claims (1)

[Claims] (1) A step of forming a semiconductor layer on the surface of a transparent substrate, a step of selectively forming a mask layer on the semiconductor layer, and a step of forming an impurity-containing layer on the surface of the mask layer and the semiconductor layer. and a step of heat-treating the semiconductor layer by irradiating the semiconductor layer with an energy beam from the back side of the transparent substrate and diffusing impurities contained therein from the impurity-containing layer into the semiconductor layer. A method for manufacturing a semiconductor device characterized by