ENHANCING THE WIDTH OF POLYCRYSTALLINE GRAINS WITH MASK
A system, method and masking arrangement are provided of enhancing the width of polycrystalline grains produced using sequential lateral solidification using a modified mask pattern is disclosed. One exemplary mask pattern employs rows of diamond or circular shaped areas in order to control the width of the grain perpendicular to the direction of primary crystallization.
This application is a divisional of 12/644,273, filed Dec. 22, 2009 which is a continuation of Ser. No. 11/373,773, filed Mar. 10, 2006, and granted under U.S. Pat. No. 7,638,728, issued Dec. 29, 2009 which is a continuation of International Application Serial No. PCT/US04/030326, filed Sep. 16, 2004, published Mar. 31, 2005, and which claims priority to U.S. Provisional Application No. 60/503,437, filed on Sep. 16, 2003, each of which are incorporated by reference in their entireties herein and from which priority is claimed.
FIELD OF THE INVENTIONThe present invention relates to semiconductor processing techniques, and more particularly, techniques for fabricating semiconductors suitable for use as thin-film transistor (“TFT”) devices.
BACKGROUND INFORMATIONDuring the past several years, sequential lateral solidification (“SLS”) techniques have been developed to generate quality large grained polycrystalline thin films, e.g., silicon films, having a substantially uniform grain structure. For example, in U.S. Pat. No. 6,322,625, issued to Im and U.S. patent application Ser. No. 09/390,537 (the “537 application”), the entire disclosures of which are incorporated herein by reference, particularly advantageous apparatus and methods for growing large grained polycrystalline or single crystal silicon structures using energy-controllable laser pulses and small-scale translation of a silicon sample to implement sequential lateral solidification have been described. As described in these patent documents, at least portions of the semiconductor film on a substrate are irradiated with a suitable radiation pulse to completely melt such portions of the film throughout their thickness.
In order to increase throughput, continuous motion SLS processes have been proposed. Referring to FIG. 1., such system preferably includes an excimer laser 110, an energy density modulator 120 to rapidly change the energy density of a laser beam 111, a beam attenuator and shutter 130, optics 140, 141, 142 and 143, a beam homogenizer 144, a lens and beam steering system 145, 148, a masking system 150, another lens and beam steering system 161, 162, 163, an incident laser pulse 164, a thin film sample on a substrate 170 (e.g., a silicon thin film) a sample translation stage 180, a granite block 190, a support system 191, 192, 193, 194, 195, 196, and a computer 100 which manages X and Y direction translations and microtranslations of the film sample and substrate 170. The computer 100 directs such translations and/or microtranslations by either a movement of a mask within masking system 150 or by a movement of the sample translation stage 180. As described in U.S. Pat. No. 6,555,449 issued to Im, the entire disclosure of which is incorporated herein by reference, the sample 170 may be translated with respect to the laser beam 149, either by moving the masking system 150 or the sample translation stage 180, in order to grow crystal regions in the sample 170.
As noted above, the aforementioned SLS techniques typically employ a straight slit mask pattern. This allows for the ease of control of the grain length (in the direction of the primary crystallization). In such case, the perpendicular grain spacing may be dependent on the properties of the film, and thus is not very easily manipulated. While the tailoring of the shaped areas to manipulate the microstructure has been employed in other SLS methods and systems, such as with the use of chevron-shaped openings in a mask, the techniques associated therewith may produce narrow grain areas. Accordingly, there is a need to control grain length in the thin film, as well as increase the area in which a smaller number of grains are present.
SUMMARY OF THE INVENTIONThe present invention overcomes the above-mentioned problems by providing a mask having a row of point-type areas (e.g., diamond and/or dot patterned opaque regions) provided thereon. Such mask pattern that uses closely spaced circular or diamond-shaped areas is utilized in lieu of the straight slits in at least a portion of the mask in order to produce a microstructure with wider grain areas. Using the mask of this configuration according to the present invention advantageously affects a melt interface curvature on the evolution of grain boundaries to favorably increase the perpendicular grain boundary spacing.
According to one exemplary embodiment of the present invention, a masking arrangement, system and process are provided for processing a thin film sample, e.g., an amorphous silicon thin film, into a polycrystalline thin film. In particular, a mask can be utilized which includes a first section having at least one opaque areas arranged in a first pattern, e.g., diamond areas, oval areas, and/or round areas. The first section may be configured to receive a beam pulse thereon, and produce a first modified pulse when the beam pulse is passed therethrough. The first modified pulse may include at least one first portion having a pattern that corresponds to the first pattern of the first section. When the first portion is irradiated on the sample, at least one first region of the sample is prevented from being completely melted throughout its thickness. The mask may also includes a second section associated with the first section, with the second section including a further area arranged in a second pattern. The second section may be configured to receive a further beam pulse thereon, and produce a second modified pulse when the further beam pulse is passed therethrough. The second modified pulse can include at least one second portion having a pattern that corresponds to the second pattern of the second section. When the second portion is irradiated on the sample, at least one second region of the sample irradiated by the second portion is completely melted throughout its thickness. In addition, when the first region is irradiated by the second modified pulse, the second portion of the second modified pulse completely melts the first region throughout its thickness.
The accompanying drawings, which are incorporated and constitute part of this disclosure, illustrate preferred embodiments of the invention and serve to explain the principles of the invention.
Throughout the Figs., the same reference numerals and characters, unless otherwise stated, are used to denote like features, elements, components or portions of the illustrated embodiments. Moreover, while the present invention will now be described in detail with reference to the Figs., it is done so in connection with the illustrative embodiments.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTSReferring to
Referring to
Referring to
Referring next to
Next, the shutter maybe opened 1035 to expose the sample to a single pulse of irradiation through a masking arrangement including at least one of diamond shaped areas, oval shaped areas, and round shaped areas, and accordingly, to commence the sequential lateral solidification process. The sample may be translated in the horizontal direction 1040. The shutter is again opened 1045 exposing previously unmelted regions to a single pulse of irradiation. The process of sample translation and irradiation 1040, 1045 may be repeated 1060 to grow the polycrystalline region.
Next, if other regions on the sample have been designated for crystallization, the sample is repositioned 1065, 1066 and the crystallization process is repeated on the new region. If no further regions have been designated for crystallization, the laser is shut off 1070, the hardware is shut down 1075, and the process is completed 1080. Of course, if processing of additional samples is desired or if the present invention is utilized for batch processing, steps 1005, 1010, and 1035-1065 can be repeated on each sample.
The foregoing merely illustrates the principles of the invention. Various modifications and alterations to the described embodiments will be apparent to those skilled in the art in view of the teachings herein. It will thus be appreciated that those skilled in the art will be able to devise numerous systems and methods which, although not explicitly shown or described herein, embody the principles of the invention and are thus within the spirit and scope of the invention.
Claims
1. A masking arrangement for processing a thin film sample comprising:
- a first section which includes at least one opaque area arranged in a first pattern, the first section is configured to receive at least one beam pulse thereon, and produce at least one first modified pulse when the at least one beam pulse is passed therethrough, the at least one first modified pulse including at least one first portion having a pattern that corresponds to the first pattern of the first section, wherein, when the first portion is irradiated on the sample, at least one first region of the sample is prevented from being completely melted throughout its thickness; and
- a second section associated with the first section, the second section including a further area arranged in a second pattern, the second section being configured to receive at least one further beam pulse thereon, and produce at least one second modified pulse when the at least one further beam pulse is passed therethrough, the at least one second modified pulse including at least one second portion having a pattern that corresponds to the second pattern of the second section, wherein, when the second portion is irradiated on the sample, at least one second region of the sample irradiated by the second portion is completely melted throughout its thickness, wherein when the first region is irradiated by the at least one second modified pulse, the second portion of the at least one second modified pulse completely melts the at least one first region throughout its thickness.
2. The masking arrangement as in claim 1, wherein at least one of the first pattern and the second pattern comprises at least one of diamond areas, oval areas, dot areas and round areas.
3. The masking arrangement as in claim 1, wherein,
- the first pattern extends approximately along a first horizontal axis, the first pattern having a width measured along the vertical axis,
- a second area of the second section extends approximately along the first horizontal axis, the second section being configured to permit the at least one first region to be completely melted throughout its thickness by the second modified pulse, the second area being offset horizontally from the first pattern, the second area having a width measured in the vertical axis that is at least equal to the width of the first pattern, and
- the second pattern extends approximately along a second horizontal axis and vertically offset from the first horizontal axis, wherein the second pattern is configured to prevent at least one third region of the sample from being completely melted throughout its thickness.
4. A masking arrangement as in claim 3, wherein the first section includes
- at least one further opaque area arranged in a third pattern extending approximately along a third horizontal axis,
- wherein the third horizontal axis is vertically offset from the first horizontal axis,
- wherein the third pattern is substantially aligned vertically with the first pattern,
- wherein the third pattern is configured to prevent at least one fourth region of the sample from being completely melted throughout its thickness,
- wherein a position of the third horizontal axis is such that the second horizontal axis is between the first horizontal axis and the third horizontal axis.
5. The masking arrangement as in claim 4, wherein the third pattern comprises at least one of diamond areas, oval areas, dot areas and round areas.
6. The masking arrangement of claim 3, wherein the second horizontal axis extends approximately along a centerline in between the first and third horizontal axes.
7. The masking arrangement of claim 4, wherein,
- elements of the first pattern are approximately equidistant from other elements of the first pattern, and
- elements of the third pattern are approximately equidistant from other elements of the third pattern.
8. The mask arrangement of claim 1, wherein the second pattern comprises one or more substantially parallel lines.
9. A method for processing a thin film sample, comprising the steps of:
- providing at least one beam on a first section of a masking arrangement to produce at least one first modified pulse when the at least one beam is passed therethrough, the first section which includes at least one opaque area arranged in a first pattern, the at least one first modified pulse including at least one first portion having a pattern that corresponds to the first pattern, wherein, when the first portion is irradiated on the sample, at least one first region of the sample is prevented from being completely melted throughout its thickness;
- based on the dimensions of the masking arrangement, translating at least one of the thin film sample and the beam relative to the other one of the thin film sample and the beam; and
- providing at least one further beam on a second section of a masking arrangement to produce at least one second modified pulse when the at least one further beam is passed therethrough, the second section associated with the first section, the second section including a further area arranged in a second pattern, the at least one second modified pulse including at least one second portion having a pattern that corresponds to the second pattern, wherein, when the second portion is irradiated on the sample, at least one second region of the sample irradiated by the second portion is completely melted throughout its thickness; wherein, when the first region is irradiated by the at least one second modified pulse, the second portion of the at least one second modified pulse completely melts the at least one first region throughout its thickness.
10. The method of claim 9, wherein at least one of the first pattern and the second pattern comprises at least one of diamond areas, oval areas, dot areas and round areas.
11. The method of claim 9, wherein,
- the first pattern extends approximately along a first horizontal axis, the first pattern having a width measured along the vertical axis,
- a second area of the second section extends approximately along the first horizontal axis, the second section being configured to permit the at least one first region to be completely melted throughout its thickness by the at least one second modified pulse, the second area being offset horizontally from the first pattern, the second area having a width measured in the vertical axis that is at least equal to the width of the first pattern, and
- the second pattern extends approximately along a second horizontal axis and vertically offset from the first horizontal axis, wherein the second pattern is configured to prevent at least one third region of the sample from being completely melted throughout its thickness.
12. The method of claim 11, wherein the first section includes
- at least one further opaque area in a third pattern extending approximately along a third horizontal axis,
- wherein the third horizontal axis is vertically offset from the first horizontal axis,
- wherein the third pattern is substantially aligned vertically with the first pattern,
- wherein the third pattern is configured to prevent at least one fourth region of the sample from being completely melted throughout its thickness,
- wherein a position of the third horizontal axis is such that the second horizontal axis is between the first horizontal axis and the third horizontal axis.
13. The method of claim 12, wherein the third pattern comprises at least one of diamond areas, oval areas, dot areas and round areas.
14. The method of claim 11, wherein the second horizontal axis is approximately along a centerline in between the first and third horizontal axes.
15. The method of claim 12, wherein,
- elements of the first pattern are approximately equidistant from other elements of the first pattern, and
- elements of the third pattern are approximately equidistant from other elements of the third pattern.
16. The method of claim 9, wherein the second pattern comprises one or more substantially parallel lines.
17. A system for processing a thin film sample, comprising:
- a mask,
- a processor to activate a device to irradiate through the mask, the processor being configured to perform the steps of: providing at least one beam on a first section of a masking arrangement to produce at least one first modified pulse when the at least one beam is passed therethrough, the first section which includes at least one opaque area arranged in a first pattern, the at least one first modified pulse including at least one first portion having a pattern that corresponds to the first pattern, wherein, when the first portion is irradiated on the sample, at least one first region of the sample is prevented from being completely melted throughout its thickness, based on the dimensions of the masking arrangement, translating at least one of the thin film sample and the beam relative to the other one of the thin film sample and the beam, and providing at least one further beam on a second section of a masking arrangement to produce at least one second modified pulse when the at least one further beam is passed therethrough, the second section associated with the first section, the second section including a further area arranged in a second pattern, the at least one second modified pulse including at least one second portion having a pattern that corresponds to the second pattern, wherein, when the second portion is irradiated on the sample, at least one second region of the sample irradiated by the second portion is completely melted throughout its thickness; wherein, when the first region is irradiated by the at least one second modified pulse, the second portion of the at least one second modified pulse completely melts the at least one first region throughout its thickness.
18. The system of claim 17, wherein at least one of the first pattern and the second pattern comprises at least one of diamond areas, oval areas, dot areas and round areas.
19. The system of claim 17, wherein,
- the first pattern extends approximately along a first horizontal axis, the first pattern having a width measured along the vertical axis,
- a second area of the second section extends approximately along the first horizontal axis, the second section being configured to permit the at least one first region to be completely melted throughout its thickness by the at least one second modified pulse, the second area being offset horizontally from the first pattern, the second area having a width measured in the vertical axis that is at least equal to the width of the first pattern, and
- the second pattern extends approximately along a second horizontal axis and vertically offset from the first horizontal axis, wherein the second pattern is configured to prevent at least one third region of the sample from being completely melted throughout its thickness.
20. The system of claim 19, wherein the first section includes
- at least one further opaque area extending in a third pattern approximately along a third horizontal axis,
- wherein the third horizontal axis is vertically offset from the first horizontal axis,
- wherein the third pattern is substantially aligned vertically with the first pattern,
- wherein the third pattern is configured to prevent at least one fourth region of the sample from being completely melted throughout its thickness,
- wherein a position of the third horizontal axis is such that the second horizontal axis is between the first horizontal axis and the third horizontal axis.
21. The system of claim 20, wherein the third pattern comprises at least one of diamond areas, oval areas, dot areas and round areas.
22. The system of claim 20, wherein the second horizontal axis is approximately along a centerline in between the first and third horizontal axes.
23. The system of claim 22, wherein,
- elements of the first pattern are approximately equidistant from other elements of the first pattern, and
- elements of the third pattern are approximately equidistant from other elements of the third pattern.
24. The system of claim 19, wherein the second pattern comprises one or more substantially parallel lines.
Type: Application
Filed: Oct 14, 2011
Publication Date: Feb 9, 2012
Applicant: THE TRUSTEES OF COLUMIBA UNIVERSITY IN THE CITY OF NEW YORK (New York, NY)
Inventor: James S. Im (New York, NY)
Application Number: 13/273,687
International Classification: H01L 21/26 (20060101); B23K 15/00 (20060101);