JPH03283611A - Method for laser anneal - Google Patents

Abstract

PURPOSE:To improve throughput of a manufacture process by radiating laser light after forming a reflection preventing film whose thickness is different from that of a treated body. CONSTITUTION:A source region coated part 4a and a drain region coated part 4b of a reflection preventing film 4 are formed to have a film thickness which realizes maximum absorption rate of laser light, for example. LDD region coated parts 4c, 4d are formed thinner than source/drain coated parts 4a, 4b. After the reflection preventing film 4 is formed to have different film thicknesses for each part of a P-type Si substrate 1 in this way, boron ion is activated, which is implanted irradiating an entire region of the substrate 1 with laser light 5 wherein energy is set to a specified value. Thereby, it is possible to change an annealing temperature of the substrate 1 in accordance with a film thickness, to change activation rate of implanted ion and to control a film thickness of the reflection preventing film 4 readily. Throughput of a manufacture process can be improved in this way.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a laser annealing method.

[Summary of the Invention] The present invention provides a laser annealing method used in the manufacturing process of semiconductor devices, etc., in which antireflection is achieved by forming antireflection films with different thicknesses on an object to be processed and then irradiating the object with laser light. The effective annealing temperature of the object to be processed can be changed depending on the film thickness, which varies depending on the location of the film.

[Prior Art] For heat treatment of semiconductor devices such as thin film transistors (TPT), techniques have been developed to make the energy distribution within a spot beam uniform.
Improvement of crystallinity of type polysilicon (hereinafter simply referred to as r'ff2si) thin film, aluminum glue flow, titanium (1
For the practical application of 'i) to silicide, nitride, and formation of ultra-shallow pn junctions, laser annealing methods such as irradiation with 308 nm short wavelength laser (XeCl excimer laser) have been used. ing.

Among this type of laser annealing methods, for example,
As disclosed in Japanese Patent No. 8-116730, when a P-type Si substrate or a P-type Si thin film is irradiated with a laser beam as an object to be processed, the laser beam is reflected by the surface of the object to be processed.
% of the energy is absorbed, therefore, a method is known in which an antireflection film is formed on the object to be processed to increase its absorption efficiency.

[Problems to be Solved by the Invention] In the laser annealing method described above, since the antireflection film is formed between the paths over the entire area of the object to be irradiated with the laser beam, the laser energy If the object to be processed is irradiated with a laser beam while keeping the value set at a predetermined value, the entire area of the object will be at the same annealing temperature. Therefore, even if there is a region in the object to be treated that is not desired to be heat-treated, that region is also heat-treated, resulting in undesirable results such as redistribution of impurities. For this reason, the energy density of laser light is irradiated to each part of the object to be processed while controlling it, and each part is heat-treated to the required annealing temperature, so there is a limit to increasing throughput. was there.

In addition, since the thickness of the anti-reflection film is uniform across the entire area of the object to be processed, lightly doped drain-source (LiG) is used to prevent TPT leakage current.
When forming a doped drain-9source (hereinafter simply referred to as an LDD), the source and drain regions are highly doped during ion implantation.
The source and drain regions and L
Since the dose of ion implantation is different between the DD region and the DD region, there is a disadvantage that workability is poor.

[Means for Solving the Problems] Accordingly, in the present invention, antireflection films having different thicknesses are formed on an object to be processed, and then laser light is irradiated.

[Function] For example, the thickness of the antireflection film is varied for each part of the object to be processed, within the range from the minimum thickness to the maximum thickness for laser beam reflectance. Then, when the entire area of the object to be processed is irradiated with a laser beam whose energy is set to a predetermined value, the annealing temperature changes depending on the thickness of the antireflection film, which differs from part to part.

[Example] Figure 1 shows a TPT LDD, in which summer shows a Py11Si substrate implanted with boron ions (B'''), 2 a gate oxide film, 3 a gate electrode, 4 is an anti-reflection film. This anti-reflection film 4 is formed of, for example, 5 tot, and has a portion 4a covering the source region 1a of the P-type Si substrate l (hereinafter simply referred to as the source region covering portion) and a portion 4a of the P-type Si substrate l. A portion of the substrate l that covers the drain region 1b (hereinafter simply referred to as a drain region covering portion) 4
b, and portions 4c and 4d of the P-type Si substrate l that cover the LDD regions 1c and ld (hereinafter simply referred to as LDD region covering portions).
It is divided into two parts. The source region covering portion 4a and the drain region covering portion 4b have a thickness such that, for example, the reflectance of the laser beam is at a minimum, that is, the absorption rate of the laser beam is at a maximum. The LDD region covering portions 4c and 4d are the source and drain region covering portion 4a.

The film thickness is thinner than that of 4b. After forming the anti-reflection film 4 in different thicknesses for each part of the P-type Si substrate 1 in this way, a short wavelength laser (XeCl excimer laser) light 5 of, for example, 308 nm with energy set to a predetermined value is applied to the anti-reflection film 4. By irradiating the P-type Si substrate 1 with heat treatment, the boron ions implanted into the I)-type Si substrate 1 are activated.

Here, the film thickness of SiOx as the antireflection film 4 and the XeC
When the relationship with the reflectance of the excimer laser beam 5 was measured, the results shown in FIG. 2 were obtained. From the measurement results shown in Figure 2, the reflectance varies from 65% to 65% depending on the SiOx film thickness.
It is possible to change the absorption rate up to 33%, that is, from 35% to 67%, and when the film thickness is 500, the reflectance is the minimum value of 33% (the absorption coefficient is the maximum value of 67%), and the film thickness is 0. and 100
It can be seen that the reflectance reaches a maximum value of 65% (the absorption coefficient reaches a minimum value of 35%) when there is no person.

In addition, an anti-reflection film f1 of S i O * with a film thickness of 500
When a p-type St film with no boron ion implantation was laser annealed with XeC1 excimer laser light and its sheet resistance was measured, the results shown in FIG. 3 were obtained. These measurement results show that by forming an anti-reflection film to lower the reflectance of the P-type Si film surface, the activation rate of implanted ions becomes higher than when there is no anti-reflection film. .

Based on the measurement results shown in FIGS. 2 and 3, the structure of the embodiment shown in FIG. 1 will be considered. Source region covering portion 4a, drain region covering portion 4b and L
5 having different film thicknesses consisting of DD region covering portions 4c and 4d
When laser annealing is performed by irradiating the boron ion-implanted P-type Si substrate 1 with XeCl excimer laser light 5 whose energy is set to a predetermined value through the antireflection film 4 formed with ins, the source and drain regions 1a and lb and the LDD are
In the regions 1c and ld, depending on the thickness of the antireflection film 4,
Effective annealing temperature changes. Specifically, the source and drain region covering portions 4a of the antireflection film 4,
4b and the LDD region covering portions 4c and 4d, the annealing temperature of the source and drain la and lb is set to LD.
Since the annealing temperature is higher than that of D regions Ic and ld, the source.

The activation rate of implanted ions is high in the drain regions 1a and lb, and the activation rate of implanted ions is low in the LDD regions 1c and ld. Therefore, source and drain regions 1a, l
Even if ions are implanted at the same concentration into both the LDD region 1c and Id and the laser beam is irradiated with energy set to a predetermined value, the implanted ion concentration will vary depending on the difference in the thickness of the anti-reflection film 4. Concentration source and drain regions 1a
.

LDD region 1c with low concentration of Ib and implanted ions.

ld can be formed.

Note that the present invention is not limited to the above embodiments,
For example, as shown in FIG. 4, the film thickness of the source and drain region covering portions 4a and 4b is set to 500, which has the minimum reflectance, and the film thickness of the LDD region covering portions 4e and 4f is set to the source and drain region covering portion. As is clear from the measurement results in FIG. 2, it is also possible to make the film thicker than those of 4a and 4b in the same manner as in the above embodiment.

Further, the antireflection film 4 is made of silicon nitride (SiN) or silicon oxynitride (SiN) other than 5iOz.
It is also possible to configure it using SiON) or the like.

Furthermore, the present invention can be applied to semiconductor devices other than TPT or devices other than semiconductor devices.

[Effects of the Invention] As described above, according to the present invention, even if the entire area of the object to be processed is irradiated with a laser beam whose energy is set to a predetermined value, the annealing temperature of the object to be processed may be lowered by the anti-reflection film. It can be changed according to the different film thickness for each part. Therefore, even if ion implantation is performed at the same concentration, as in the manufacturing process of semiconductor devices, irradiation with laser light with a predetermined energy level is performed through anti-reflection films with different thicknesses, so the thickness of the anti-reflection film may vary. The activation rate of the implanted ions can be changed depending on the difference in the ions, and the thickness of the anti-reflection film can also be easily controlled, making manufacturing easier than controlling the ion implantation concentration or laser beam energy. Process throughput can be improved.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, FIG. 2 is a measurement result chart showing the relationship between the film thickness of 5iOy and the reflectance of XeCl excimer laser light as an antireflection film of the same embodiment, and FIG.
The figure is a measurement result diagram showing the sheet resistance when laser annealing is performed using a XeCl excimer laser on a P-type Si film implanted with boron ions with and without an anti-reflection 1L SiOx film of the same example. It is a sectional view showing an example. DESCRIPTION OF SYMBOLS 1... P-type Si substrate (processed object), 4... Antireflection film, 4a... Source region covering part, 4b... Drain region covering part, 4c, 4d... LDD region covering part , 5...Laser light. Outside I 6

Claims (1)

[Claims] (1) A laser annealing method characterized by forming anti-reflection films of different thicknesses on an object to be processed and then irradiating the object with laser light.